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KIEPENHEUER-INSTITUTFÜR SONNENPHYSIK2003 - 2005


Titelbild/Front cover:Modell laminarer KonvektionModel of laminar convection(S. Brun, M. Roth)Dopplerkarte der GranulationDoppler map of granulation(K. Mikurda, W. Schmidt)Polarisation eines SonnenflecksPolarization of a sunspot(C. Beck, R. Schlichenmaier)Modell der SonnenkoronaModel of solar corona(H. Peter)Hintergrund: Bild der Chromosphäre, aufgenommen durch einLyot-Filter bei einer Wellenlänge von 393.3 nm (CaII K)Background: Image of the chromosphere observed with a Lyot filterat a wavelength of 393.3 nm (Ca IIK)Kiepenheuer-Institut für SonnenphysikStiftung des öffentlichen Rechts des LandesBaden-WürttembergSchöneckstraße 679104 FreiburgTel: +49-(0)761-3198-0Fax: +49-(0)761-3198-111E-mail: secr@kis.uni-freiburg.deURL: www.kis.uni-freiburg.deISSN: 1612 - 6130Editors:O. von der Lühe, W. SchmidtSection editors:J. BrulsH. PeterM. RothR. SchlichenmaierO. SteinerS. Wedemeyer-Böhm


KIEPENHEUER-INSTITUTFÜR SONNENPHYSIK2003 - 2005Mitglied der Wissenschaftsgemeinschaft Gottfried Wilhelm LeibnizInternationales Mitglied der Association of Universities for Research in Astronomy (AURA)1


StiftungsratFoundation CouncilDr. Claus Fröhlich, DavosRD Dr. Jan Grapentin, Bundesministerium für Bildung und Forschung, BonnProf. Dr. Dr. h.c. mult. Wolfgang Jäger, Rektor der Universität FreiburgMinisterialdirigent Dr. Heribert Knorr, Ministerium für Wissenschaft, Forschungund Kunst Baden-Württemberg, Stuttgart (Vorsitzender)Konstanze Pistor, Ministerium für Wissenschaft, Forschung und Kultur des LandesBrandenburgPD Dr. Wolfgang Schmidt, Kiepenheuer-Institut für Sonnenphysik, FreiburgWissenschaftlicher BeiratScientific Advisory CommitteeProf. Dr. Mats Carlsson, OsloDr. Claus Fröhlich, Davos (chair)Prof. Dr. Thomas Henning, HeidelbergProf. Dr. Michael Kühne, BraunschweigProf. Dr. Fernando Moreno Insertis, La LagunaProf. Dr. Hanns Ruder, TübingenProf. Dr. Klaus Strassmeier, PotsdamVorstandBoardProf. Dr. Oskar von der LüheProf. Dr. Michael Stix (bis 31.8. 2004)2


VorwortPrefaceDieser Bericht ist die zweite umfassende Darstellung der wissenschaftlichenArbeit der 2002 gegründeten Stiftung Kiepenheuer-Institut für Sonnenphysik. Wie der erste richtet er sich an die Führungsgremiendes Instituts, an die Partner aus Wissenschaft undIndustrie und an alle, die sich für die Arbeit des Institutes interessieren.Der Berichtszeitraum umfasst wiederum zwei Jahre vonMitte 2003 bis Mitte 2005. Wie bisher ergänzt er den jährlichenBericht des Instituts in den Mitteilungen der Astronomischen Gesellschaftum eine ausführlichere Darstellung der wissenschaftlichenErgebnisse und der Projektarbeit.Wichtige, für die Zukunft des Instituts entscheidende Entwicklungenfanden in den vergangenen zwei Jahren statt. Die Entscheidung,die Stelle des zweiten Vorstandsmitglieds als Stiftungsprofessurfür Theoretische Astrophysik an der Albert-Ludwigs-Universitätauszugestalten, stärkt die theoretische Abteilung des Kiepenheuer-Institutsund festigt seine Verbindung mit der Universität.Nicht zuletzt deswegen wird ein wichtiger Aspekt unserertheoretischen Arbeiten – die numerischen Simulationen physikalischerProzesse auf der Sonne und auf Sternen – als eigener Beitragin diesem Bericht herausgestellt. Er beleuchtet eindrucksvolldas Wirken des bisherigen Leiters der Theoretischen Abteilung,Prof. Michael Stix, welcher vergangenes Jahr in den Ruhestandging und welchem ich an dieser Stelle für seine Arbeit sehrherzlich danken möchte.Die großen instrumentellen Projekte des Kiepenheuer-Institutshaben in den vergangenen zwei Jahren erhebliche Fortschrittegemacht. Das neue Sonnenteleskop GREGOR nähert sich seiner Fertigstellung.Die Entwicklung des Ballonteleskops Sunrise schreitetvoran. Deswegen fasst das Institut neue Herausforderungen insAuge, welche die experimentelle Arbeit im nächsten Jahrzehnt beherrschenwerden: ATST und Solar Orbiter. Das Advanced TechnologySolar Telescope wird mit einer Öffnung von vier Metern fundamentaleErkenntnisse über magnetohydrodynamische Prozessenicht nur in der Sonnenatmosphäre, sondern auch im Kosmos ermöglichen;Solar Orbiter wird die Sonne aus größter Nähe beobachten.An beiden internationalen Projekten will sich das Institutbeteiligen, die Vorarbeiten dazu sind bereits begonnen worden.Dadurch steigt nicht zuletzt immer mehr das internationaleGewicht, wie es sich in der Aufnahme des KIS als internationalaffilliate member der Association of Universities for Researchin Astronomy (AURA, USA) – als bislang einziges deutsches Institut– zeigt.Ein Abschnitt mit einer Übersicht der Arbeiten zu den im For–schungsplan dargestellten Schwerpunkten ist in diesem Berichtneu hinzugekommen, hier wird auch der Kontext zu den Publikationenim Anhang hergestellt. Einen detaillierten Blick auf wichtigeErgebnisse des Berichtzeitraums ermöglichen die Kurzberichteaus der Forschungs- und Projektarbeit der Mitarbeiter, welcheim Vergleich zum vorherigen Bericht deutlich zugenommen haben.Ich darf noch einmal allen, deren Sachverstand und Einsatzdas Zustandekommen dieses Berichts ermöglichten, sehr herzlichdanken.This document is the second comprehensive report about the scientificwork at the Kiepenheuer-Institut für Sonnenphysik. Likethe first one, it is directed at its governing bodies, at its scientificand economic partners, and at all those who are interested in theinstitute’s work and progress. The report covers the two-year periodfrom mid 2003 to mid 2005. It supplements the report issuedannually in the Mitteilungen der Astronomischen Gesellschaft bya comprehensive account of the scientific results and the progressmade in the development of instrumental projects during thelast two years.The evolution during the past two years has been decisive for thefuture of the institute. The decision to combine the vacant positionof the second member of the institute’s board with a sponsoredprofessorship for theoretical astrophysics strengthens boththe theoretical department of the institute and its links with theAlbert-Ludwigs-Universität Freiburg. This has not been the onlyreason to put an emphasis on an important aspect of the institute’swork into this report – a special feature on numerical simulationof physical processes in the Sun and in stars. The featurealso shines a light on the impressive accomplishments of Prof. MichaelStix who retired last year. I would like to take this opportunityto express my sincerest gratitude for his impressive contributionto the institute and to the community.There has also been a substantial progress of the institute’s largeinstrument development projects in the past two years. The newsolar telescope GREGOR is nearing completion. The development ofSunrise moves ahead. Therefore, the institute heads on towardsnew challenges which will shape its future in the next decade:ATST and Solar Orbiter. The 4m aperture Advanced Technology SolarTelescope will enable new insights in magneto-hydrodynamicalprocesses which are fundamental not only to the Sun, but also tothe cosmos as a whole. Solar Orbiter will provide a vantage pointto observe the Sun close-by. The institute will participate in thesetwo international projects and has already started with preliminaryactivites. These endeavours raise the international visibilityof the Kiepenheuer-Institut, which has just been appointed internationalaffiliate member of the Association of Universities for Researchin Astronomy (AURA) as the first German institution.There is a new section with an overview of the work in the researchfoci of the Research Plan which also puts the list of publicationsin the annex into context. An ever increasing portion ofthis report, however, is devoted to short reports on recent scientificresults and project developments which display the institute’sstrength and vigour. I would like to thank the staff ofthe Kiepenheuer-Institut for their dedication and skill which hasmade it possible to put this report together.Freiburg, im Juli 2005Oskar von der Lühe, Direktor3


InhaltVorwortContentsPreface3Situation des Kiepenheuer-InstitutsWissenschaftliche ArbeitLehre und AusbildungÖffentlichkeitsarbeitAbout the Kiepenheuer-InstitutProgress in ResearchTeaching and EducationPublic Outreach6Computer-Simulationen der SonneComputer simulations of the Sun24ForschungsschwerpunkteResearch Foci38Instrumentelle ProjekteTechnical Developments & Projects44Aktuelle Forschungsergebnisse und InstrumenteProgress in Science and Instrumentation51Veröffentlichungen seit 2003Publications since 20031135


ÜBER DAS KISZur Situation des KISVorbemerkungenDas Institut hat in den Jahren 2003 bis 2005 in vielen Bereichenerfreuliches, kontinuierliches Wachstum gesehen.Diese Zeit ist von der Umsetzung der Rechtsformänderungvon 2002 geprägt, welche das Institut in eine Stiftung öffentlichenRechts verwandelt hat. Damit verbunden sindgrundlegende Änderungen der Wirtschaftsform, durch dieEinführung der Kosten-Leistungsrechnung, sowie der Entwicklungvon Programmbudgets ab 2006. Die Zahl derMitarbeiter hat weiter zugenommen, vor allen Dingen imtechnischen Bereich. Hiermit wurde eine weitere Empfehlungdes Wissenschaftsrats, aufgrund der Evaluierung desInstituts im Jahre 1999, umgesetzt. Das Institut ist an großenProjekten beteiligt – die Entwicklung des 1.5m - SonnenteleskopsGREGORnähert sich dem Abschluss, das BallonteleskopSunrise macht gute Fortschritte. Am Horizonterscheinen die Projekte Advanced Technology Solar Telescope(ATST) des National Solar Observatory, USA, sowieder Solar Orbiter der ESA. Nationale und internationaleKooperationen werden ausgebaut.Rechtsform und StrukturSeit 2002 ist das Kiepenheuer-Institut eine rechtlich selbständigeStiftung des öffentlichen Rechts. Die Satzung derStiftung formuliert als Zweck der Stiftung die „Grundlagenforschungin der Astronomie und Astrophysik mit besonderemSchwerpunkt in der Sonnenphysik“. Dazu betreibtdas Institut selbst und zusammen mit Dritten Beobachtungseinrichtungenfür eigene und fremde Forschungsarbeiten.Darüber hinaus kann es weitere Aufgaben übernehmen,insbesondere in der Aus- und Weiterbildung, undder Förderung des wissenschaftlichen Nachwuchses.Die Struktur des Instituts hat sich im Berichtszeitraumnicht verändert. Das Organigramm ist in Abbildung 1 dargestellt.Organe der Stiftung sind Stiftungsrat (Vertreterder Mittelgeber, Rektor der Universität Freiburg und eingewählter Institutsmitarbeiter), der Wissenschaftliche Beirat(bestellte nationale und internationale Wissenschaftler)und der Vorstand. Das Institut besteht aus zwei WissenschaftlichenAbteilungen, Theoretische Sonnenphysik undExperimentelle Sonnenphysik. Daneben gibt es die nichtwissenschaftlichenQuerschnittsgruppen Verwaltung, Datenverarbeitungund Technische Dienste. Bei Bedarf könnendem Stiftungsvorstand unterstellte Projektgruppeneingerichtet werden. Zurzeit betrifft dies die Projekte GRE-GOR und Sunrise.About the KISIntroductionThe institute has experienced continuous growth in manyareas in the 2003 – 2005 time frame. This period is characterizedby putting into action the change of legal statusof 2002 which converted the institute into a foundation ofpublic law. A fundamental change of corporate status, theintroduction of cost-performance accounting, and the preparationof program plans as of 2006 accompanies this development.The number of staff has increased steadily, inparticular in the technical areas, thereby implementing anotherrecommendation of the Wissenschaftsrat which isbased on its 1999 evaluation. The institute participates inlarge development projects – the construction of the 1.5msolar telescope GREGOR is nearing completion, and the bal-loon borne telescope Sunrise moves ahead steadily. TheAdvanced Technology Solar Telescope (ATST) of the NationalSolar Observatory, USA, as well as ESA’s missionSolar Orbiter appear at the horizon. National as well as internationalcollaborations are being extended.Legal Status and StructureSince 2002, the legal status of the Kiepenheuer-Institut hasbeen that of a legally independent public foundation . Thestatutes of the foundation formulate its purpose as “basicresearch in astronomy and astrophysics with particular emphasison solar physics”. The institute shall operate on itsown and together with third parties, observatories to supportthe research work of its own and of others. It assumesadditional duties, in particular in the areas of education andthe advancement of young scientific talent.The organizational structure has remained unchangedwithin the period covered by the report (Fig. 1). Governingbodies are the Foundation Council with members fromstate and federal funding authorities, the Rektor of the university,and a staff representative, the Scientific AdvisoryCommittee (SAC) with national and international scientistsas members, and the Board of the institute. There are twoscience departments, experimental and theoretical solarphysics. Three support groups, administration, informationtechnology, and technical services, were established.In addition, independent project groups of temporary nature,which are supervised by the board, can be establishedas need arises. Presently this applies to the GREGOR andSunrise projects.6


ABOUT THE KISFigure 1: Organigramm des KIS (Stand: Mai 2005) Figure 1: Structure of the KIS (as of May 2005)ProgrammbudgetAuf der Grundlage des Beschlusses der Bund-Länder-Kommission (BLK) vom 19.6.2000, welcher die Einführungvon Programmbudgets für die Institute der Leibniz –Gemeinschaft bis 2006 verbindlich vorsieht, hat das Institutim Frühjahr 2004 den Entwurf eines Programmbudgetsfür das Jahr 2006 zusätzlich zum Entwurf des Wirtschaftsplansvorbereitet. Der Entwurf wurde gemäß den Richtliniender BLK und basierend auf der zusammen mit demForschungsplan vorgelegten Finanzplanung erarbeitet. Einvollständiger Entwurf lag zu den Sitzungen des WissenschaftlichenBeirats und des Stiftungsrats im Herbst 2004vor.Wesentliche Elemente des Programmbudgets des Kiepenheuer-Institutssind• die Einrichtung von zwei Programmbereichen, welchesich an den Kostenträgern der KLR orientieren,• die Formulierung von Leitzielen für das Institut und fürdie Programmbereiche, sowie die Formulierung von Strukturzielen,Financial program planIn spring 2004, the institute has developed tthe draft of afinancial program plan for 2006, in addition to the draftbudget. This action is based on the decision of the Bund-Länder-Kommission (BLK) of June 19, 2000, making financialprogram plans obligatory for institutes belongingto the Leibniz Society. The draft plan is based on BLK requirementsand on the financial plan which has been developedearlier together with the research plan. The completedraft was presented at the Research and Foundation Councilmeetings in fall of 2004.Essential elements of the draft financial program plan are• establishment of two program areas which are alignedwith cost objectives of the cost performance accountingsystem,• formulation of mission statements for the institute andthe program areas, as well as the formulation of structuralgoals,• establishment of metrics that represent the performanceof the institute during execution of the budget.7


ÜBER DAS KISZur Situation ... About ...• die Einrichtung von Leistungsindikatoren, mit welchendie Ergebnisse der Institutsarbeit im Zuge der Durchführungdes Budgets erfasst und dargestellt werden können.Kosten-LeistungsrechnungDie wesentlichen Schritte zur Einführung der Kosten-Leistungsrechnungist mit der Kostenträgerbezogenen Erfassungder Personalkosten ab Herbst 2004 abgeschlossen. AnSchulungen in den jeweiligen Kompetenzbereichen nahmenauch 2003 und 2004 Mitarbeiter/innen der Wissenschaft,der Verwaltung und des Technischen Dienstes, sowieder Vorstand teil.Personelle EntwicklungIm wissenschaftlichen Bereich verfügt das Institut währenddes Berichtszeitraums über 14.7 Planstellen. Drei dieserStellen waren zu Beginn befristet besetzt. Nach positiveninternen und externen Evaluierungen der wissenschaftlichenLeistungen wurden zwei Verträge unbefristetverlängert.Im Jahre 2003 waren im wissenschaftlichen Bereich 7.5Vollzeitäquivalente (9 Mitarbeiter) über Drittmittel finanziert,im Folgejahr 9.5 Vollzeitäquivalente (12 Mitarbeiter).Während des Berichtszeitraums erhielten weitere Gäste Stipendiender Alexander von Humboldt – Stiftung oder wurdenüber die Universität Freiburg im Rahmen einer Mercator-Professurvon der DFG gefördert. Mehrere Doktorandenwurden aus Mitteln des Instituts finanziert. Ein Doktoranderhält ein Stipendium nach dem Landesgraduiertenförderungsgesetz.Ein weiterer Doktorand arbeitete am Institutmit eigenem Stipendium.Im Januar 2003 hatte das Institut 26, im Januar 2004 28wissenschaftliche Mitarbeiter. In beiden Jahren arbeiteten7 Doktoranden und 5 Postdoktoranden am Institut. DreiDoktoranden haben während des Berichtszeitraums ihreDissertationen abgeschlossen. Sie haben Postdoktorandenstellenan astronomischen Forschungseinrichtungen imAusland angetreten. Während der Jahre 2003 und 2004 erhieltensechs Studenten für mehrere Wochen Verträge alswissenschaftliche Hilfskräfte im Rahmen des Leibniz-Forschungspraktikums.Der Stellvertretende Direktor des Instituts, Prof. Dr. MichaelStix, ging Ende August 2004 in den Ruhestand. Mitder Universität Freiburg wurde die Wiederbesetzung derStelle des Zweiten Vorstands des Instituts durch eine Berufungals Universitätsprofessor für Theoretische Astrophysikverhandelt. Dabei wird eine Berufung nach dem „JülicherModell“ zugrunde gelegt, deren Personalkosten vomCost Performance AccountingThe essential steps to introduce cost performance accountingwere concluded with the cost objectives oriented accountingof personnel cost as of fall 2004. Members of administrative,scientific and technical staff participated intraining courses specializing in the respective competenceareas.Development of PersonnelThe institute had 14.7 institutional scientific staff positionsat its disposal during the period covered by the report.Three positions were filled with term contract staff atfirst, two of which were awarded an indefinite contract aftera positive evaluation.7.5 full-time equivalents (FTEs) for scientists (staff of 9)were funded through third-party funds in 2003. 9.5 scientistFTEs corresponding to a staff of 12 were third-partyfunded in 2004. Several guest scientists received grantsfrom the Alexander von Humboldt-Foundation or throughthe German Science Foundation (DFG). Several PhD studentsreceived support through the institute’s payroll; onePhD student receives a State stipend, another one a grantfrom his home institution.The institute had 26 scientists in January 2003, and 28 scientistsin January 2004, including 7 PhD students and 5scientists at the postdoctoral level. Three PhD students finishedtheir theses and moved on to postdoctoral positionsabroad. Six undergraduate students worked for severalweeks as research assistants in the framework of the LeibnizSummer Research Program.The deputy director of the institute, Prof. Dr. Michael Stix,retired end of August 2004. An agreement has been foundwith the Albert-Ludwigs-Universität Freiburg to fill thevacancy with a joint professor’s appointment dedicated totheoretical astrophysics with a focus on solar physics. TheKiepenheuer-Institut für Sonnenphysik bears the full costfor this appointment. The agreement was signed by the rectorof the university and the institute’s director on Feb. 11,2005. The position was announced in March 2005, the appointmentprocedure has been initiated.The non-scientific staff amounts to 20.75 positions in 2003and 27.15 positions in 2004. Most of these positions are allocatedfor technical services, where two additional positionshave been created in 2004, in accordance with recommendationsof the Wissenschaftsrat, and filled in 2005.Two positions were improved in grade by internal reorganization,in order to account for the increasing need for high-8


ABOUT THE KISInstitut getragen werden. Der Vertrag über die gemeinsameBerufung wurde am 11. Februar 2005 vom Rektor der Universitätund vom Direktor des KIS unterzeichnet. Die Professurwurde im März 2005 ausgeschrieben und das universitäreBerufungsverfahren in Gang gesetzt.Der nichtwissenschaftliche Bereich ist 2003 mit 20,75 Stellen,im Jahre 2004 mit 27,15 Stellen ausgerüstet gewesen.Der überwiegende Teil der nichtwissenschaftlichen Mitarbeiterarbeitet im Technischen Dienst, welcher im Zusammenhangmit einer vom Wissenschaftsrat geforderten Verstärkungzu Beginn 2004 zwei zusätzliche Technikerstellenerhielt. Nach Ablauf der Wiederbesetzungssperre wurdendiese Stellen Anfang 2005 besetzt. Außerdem wurdendurch Umschichtungen im Stellenplan zwei Technikerstellenaufgewertet und somit wichtige Entwicklungskapazitätengeschaffen. Von den fünf im Haushaltsplan vorgesehenenStellen für Auszubildende sind zurzeit drei besetzt.ly qualified technical staff. Three of the existing five apprenticeshippositions are presently filled.The institute receives funding from DLR for technical staffin the framework of the Sunrise project. The position of aphysicist was filled in spring 2004 in addition to the existingpositions for an engineer and a draughts person.Für das Projekt „Sunrise“ werden im technischen BereichDrittmittelstellen vom DLR finanziert. Zusätzlich zu denbisher vorhandenen Stellen (Ingenieur und TechnischerZeichner, 1.7 VZE) ist im Rahmen der Fertigungsphaseeine weitere Stelle für einen Physiker hinzugekommen,welche im Frühjahr 2004 besetzt wurde.9


ÜBER DAS KISSchwerpunkte, Projekte undPublikationenDer wissenschaftliche Arbeitsplan des Kiepenheuer-Institutsist in die Bereiche wissenschaftliche Projekte, instrumentelleProjekte, Tagungen und Publikationen gegliedert.Die wissenschaftlichen Projekte sind in den im Forschungsplanbeschriebenen Schwerpunkten erfasst. Die instrumentellenProjekte unterstützen die wissenschaftlichen Projektean bodengebundenen und weltraumgestützten Observatorien.Diese Arbeiten sind in dem Abschnitt Forschungsplanausführlich beschrieben. Neuere Ergebnisse sind in den Abschnitten„Aktuelle Forschungsergebnisse“ und „Instrumente“dargestellt.Eine Liste der 2003 und 2004 erschienenen, sowie der 2005erschienenen und im Druck befindlichen Veröffentlichungenist im Abschnitt Veröffentlichungen seit 2003 enthalten.Eine Übersicht über die Publikationen seit 2001 ist in Tabelle1 und Abb. 2 gegeben.Scientific Foci, Projects andPublicationsThe scientific program of the Kiepenheuer-Institut containsthe sections scientific projects, instrument developmentprojects, conferences and publications. The scientificprojects are organized in four research foci. Instrumentdevelopment programs support the research projects by assuringadequate facilities at ground-based observatoriesand through participation in space experiments. Researchwithin the foci and instrument developments are describedin the section on The Research Plan. A collection of recentscientific results is provided in the sections “Progress inScience and Instrumentation”.The list of publications that appeared in 2003 and 2004 aswell as those which have appeared in 2005, are submittedor in press, are provided in chapter “Publications since2003”. The Figure 2 and Table 1 summarize the evolutionof publications in different categories since 2001.Publikationen10090807060504030201002001 2002 2003 2004 2005JahrRef. Fachzeitschriften Eingel. Vorträge etc. Konferenzbeiträge Abstracts, techn. Documente Bücher, PatenteRef. Fachzeits. (2005) Eingel. Vorträge (2005) Konferenzbeiträge (2005) Abstracts, etc. (2005) Bücher, Patente (2005)Fig. 2: Publikationen 2001 bis 2005 Fig. 2: Publications 2001 to 2005Publikationen 2001 - 2005Jahr/Year 2001 2002 2003 2004 2005 1referierte Fachbeiträge 23 39 37 31 33Übersichtsvorträge, Monografien 12 6 5 4 2Tagungabeiträge 29 26 56 43 171 bis 30. 6. 200510


ABOUT THE KISKonferenzenAG – Jahrestagung 2003Die Internationale WissenschaftlicheJahrestagung 2003 der AstronomischenGesellschaft fandvom 15. bis zum 20. Septemberunter dem Motto The Sunand Planetary Systems - Paradigmsof the Universe in Freiburgstatt. Vorbereitet wurdedie Veranstaltung von den Mitarbeiterinnenund Mitarbeiterndes Kiepenheuer-Instituts in engerZusammenarbeit mit der Albert-Ludwigs-UniversitätFreiburg,welche die Räumlichkeitenzur Verfügung stellte. Etwa 250 Wissenschaftler aus allerWelt, vorwiegend aus dem deutschsprachigen Raum, nahmenan der Jahrestagung teil, die zum dritten Mal in Freiburgveranstaltet wurde. Das Programm umfasste Plenarsitzungenmit Review- und Highlightvorträgen, zehn teilweiseparallele Splintertreffen zu verschiedenen astrophysikalischenThemen, sowie die Verleihung des SchwarzschildundBiermann-Preises. Begleitet wurde die Tagung von Sitzungendes Rats Deutscher Sternwarten und des Vorstandesder Astronomischen Gesellschaft, vom MHD-Tag und demHistorischen Astronomischen Kolloquium. Eine Veranstaltungzur Lehrerfortbildung auf dem Schauinsland schlossdie Veranstaltung ab.ConferencesAnnual Meeting of theAstronomische Gesellschaft2003The international Scientific AnnualAssembly of the AstronomischeGesellschaft with themotto The Sun and PlanetarySystems – Paradigms of theUniverse took place in Freiburgfrom September 15 to 20, 2003.It was prepared by the staff ofthe Kiepenheuer-Institut inclose collaboration with and onthe premises of the Albert-Ludwigs-Universität.Some 250 scientistsfrom all over the world, mostly from German-speakingcountries, participated in the assembly which was hostedin Freiburg for the third time. The program included plenarysessions with invited reviews and highlight presentations,ten splinter meetings covering a variety of astrophysicaltopics in partially parallel sessions, and the award of theKarl Schwarzschild- and Ludwig Biermann prizes. The assemblywas accompanied by meetings of the Rat DeutscherSternwarten and of the board of the Astronomische Gesellschaft,by the MHD day and the Historical AstronomicalColloquium. A seminar for school teachers at the SchauinslandObservatory concluded the event.Dynamo – Tagung 2004Das Kiepenheuer-Institut veranstaltete eine internationaleTagung zum Thema „Dynamos of the Sun, Stars & Pla-Dynamo Workshop 2004The Kiepenheuer-Institut has organized an internationalworkshop on the topic “Dynamos of the Sun, Stars & Planets”which took place on the premises of the Institute ofPhysics of the Albert-Ludwigs-Universität from October 4 to6, 2004. The program includedeight invited and 15 contributedtalks as well as eight posters.The event whose purpose wasto celebrate the scientific accomplishmentsof Prof. Stix hasbrought together some 50 scientistsfrom all over the world, includingmany collaborators andformer students of Prof. Stix.11


ÜBER DAS KISnets“ vom 4. bis 6. Oktober 2004 imHochhaus des Physikalischen Institutsder Albert-Ludwigs-Universität.Das Programm umfasste achteingeladene Vorträge, 15 Kurzvorträgesowie acht Posterbeiträge. DieVeranstaltung, mit welcher der wissenschaftlicheWerdegang von Prof.Stix gewürdigt wurde, wurde vonetwa 50 Wissenschaftlern aus allerWelt, darunter viele Kollegen undSchüler von Herrn Stix, besucht.Weitere VeranstaltungenDas Frühjahrstreffen des deutschenFRINGE-Konsortiums wurde am 3.3. 2003 in den Institutsräumen veranstaltet.Der GREGOR Design Review fand am 26. und 27. März 2003am Kiepenheuer-Institut statt. Vertreter der am Projekt GRE-GOR beteiligten Institute und der Industrie stellten das Designeiner internationalen Gutachterkommission vor.Das Solar Orbiter / Visible Imager Magnetograph Meetingfand vom 31. 8. bis 1. 9. 2004 im Institutsgebäude mit einerBeteiligung von etwa einem Dutzend Wissenschaftlern ausdem europäischen Raum statt.Albert-Ludwigs-Universität &Kiepenheuer-Institut für SonnenphysikFreiburg im Breisgau, Germany4. – 6. October 2004International meeting onDynamos of the Sun, Stars & Planetstopicssolar dynamo and activity cyclerole of flux tubes and the tachoclinedynamos of the Earth and other planetsstellar dynamos and cyclesdeadline for abstract submission:22. August 2004invited speakersNigel WeissAxel BrandenburgPeter GilmanManfred SchüsslerUlrich ChristensenFriedrich BusseWolfgang DoblerKlaus StrassmeierKiepenheuer-Institut für Sonnenphysik, Schöneckstr. 6, 79104 Freiburg, GermanyTel.: ++49/(0)761/3198-0, Fax: ++49/(0)761/3198-111Email: dynamo@kis.uni-freiburg.dehttp://www.kis.uni-freiburg.de/dynamo2004/Other EventsThe spring 2003 meeting of theGerman FRINGE consortium tookplace at the institute on March 3,2003.The design review for the Gregortelescope took place at the instituteon March 26 and 27, 2003. The designwas presented to an internationalreview team by members ofthe participating institutes and industry.The Solar Orbiter / Visible ImagerMagnetograph meeting took placeat the institute with participation ofabout a dozen European scientistson Aug. 31 and Sept. 1, 2004.The 4th annual International Sunrise Team Meeting hasbeen organized by the Kiepenheuer-Institut from Sept. 1to 3, 2004. Some 50 scientists and technicians of the MPS,Lindau, the HAO, Boulder and the Spanish IMAX consortiumvisited the meeting to discuss the progress of the Sunriseproject. The event took place on premises of the Univerity.Das 4. jährliche International Sunrise Team Meeting wurdevom Kiepenheuer-Institut vom 1. bis 3. 9. 2004 ausgetragen.An dieser Veranstaltung nahmen etwa 50 Wissenschaftlerund Techniker des MPS, Lindau, des HAO, Boulder, unddes spanischen IMAX-Konsortiums teil, um die Fortschrittebei dem Ballonteleskop Sunrise zu beraten. Auch diese Veranstaltungwurde in den Räumen der Albert-Ludwigs-Universitätdurchgeführt.Kiepenheuer-Institut für Sonnenphysik, FreiburgSchöneckstraße 6, D-79104 FreiburgTel. 0761-3198-04. International Sunrise Technical Meeting1 - 3 September 2004FreiburgThe Sunrise project:•1m balloon-borne optical solar telescope• presently under development• long duration balloon flight in Antarctica in 2007Kiepenheuer-Institut für Sonnenphysik, FreiburgMax-Planck-Institut für Sonnensystemforschung, LindauHigh Altitude Observatory, BoulderIMAX-Consortium, La Laguna, Granada, Madrid, Valencia12


ABOUT THE KISTeilnahme an TagungenParticipation in conferences• SUNRISE-IMaX Interface Meeting (Lindau, 25.-26.2. 2003).• Jahrestagung der Schweizerischen Physikalischen Gesellschaft (Basel, 20.-21.3. 2003).• Project meeting on solar variability and the Earth‘s climate (ETH Zürich, 17.4. 2003).• Pueo Nui Adaptive Optics Workshop (Grenoble, 22.–23.5. 2003).• Workshop Geodynamo (Lindau, 26.–27.5. 2003).• European Solar Magnetism Network Summer School: Radiative Transfer and Numerical MHD (Oslo, 2.–13.6. 2003).• AAS Solar Physics Division Meeting (Columbia, Md. USA, 16.–20.6. 2003).• CIAS Workshop: Convection and turbulence in the Sun and other stars (Meudon, 16.–20.6. 2003).• XXVth IAU General Assembly (Sydney, 13.–26.07. 2003).• SPIE Symposium: Optical Science and Technology (San Diego, 3.–28.8. 2003).• ATST Conceptual Design Review (Sunspot, USA, 24.–29.8. 2003).• Advances in IR Interferometry (Schloss Ringberg, 1.–5.9. 2003).• Jahrestagung der Schweizerischen Gesellschaft für Astronomie und Astrophysik (Bern, 12.9. 2003).• Numerical methods for multidimensional radiative transfer problems (Heidelberg, 24.–26.9.).• SOHO 13: Waves, oscillations and small–scale transient events in the solar atmosphere (Mallorca, 29.9.–3.10. 2003).• First Central European Solar Physics Meeting (Bairisch Kölldorf, Österreich, 23.–25.10. 2003).• Solar Image Recognition Workshop (Brüssel, 23.–24.10. 2003).• 3. Sunrise Workshop (Granada, 22.–24.10. 2003).• Kolloquium: Theory and Observations of Chromospheres and Coronae (Heidelberg, 7.11. 2003).• ATST Science Working Group Meeting (Tucson, USA, 17.–20.11.2003).• XVth Canary Islands Winter School: Payload & Definition of Space Sci. (17.–28.11.2003, Pto. de la Cruz, Tenerife)• Frühjahrstagung der DPG (Kiel, 8–11.3.2004).• 34th Saas–Fee Advanced Course, “The Sun, Solar Analogs and the Climate“ (Davos, 15.–20.3. 2004).• IAU Symposium 223 “Multi-wavelength investigations of solar activity” (St. Petersburg, 14.–19.6. 2004).• SPIE Conference “Astronomical Telescopes” (Glasgow, 21.–25.6. 2004).• Cool Stars, Stellar Systems and the Sun 13 (Hamburg, 5–9.7. 2004).• Thinkshop “Robotic Telescopes” (Potsdam, 12.–15.7. 2004).• 35th COSPAR Scientific Assembly (Paris, 18.–25.7. 2004).• Europ. Interferometry Initiatives Wkshp. “Science for Next Gen. Interferometr. Facilities” (Liège, 23.–25.8. 2004).• Workshop on Cosmic Ray Dynamics (Kopenhagen, 2.–4.9. 2004).• SoHO XV (St Andrews, 6–9.9. 2004).• Magnetohydrodynamics of Stellar Interiors (Cambridge, 6.–17.9. 2004).• JENAM 2004 (Granada, 13.–17.9. 2004).• Tagung der Deutschen Gesellschaft für Klinische Neurophysiologie (Jena, 13.–17.9. 2004).• 7th Hvar Astrophysical Colloquium (Hvar, 20.–24.9. 2004).• Jahrestagung der Astronomischen Gesellschaft (Prag, 20.–25.9. 2004).• Jahrestagung der Schweizerischen Gesellschaft für Astronomie und Astrophysik (Versoix, 15.10. 2004).• Four Solar Cycles of Space Instrumentation (Orsay, 17–18.11. 2004).• Graduiertenkolleg Nichtlineare Differentialgleichungen, Abschlusskolloquium (Freiburg, 18.–19.11. 2004).• Stellar dynamos (Leeds, England, 13.–17.12. 2004).• European Interferometry Initiatives Workshop „Radiative Transfer” (Nizza, 15.-16.12. 2004).13


ÜBER DAS KISKooperationenGREGOR– Kooperation des KIS (50%) mit dem AstrophysikalischenInstitut Potsdam und dem Institut für AstrophysikGöttingen (Bezeichnung bis 31.5.2005: Universitäts-Sternwarte) (je 25%) zum Bau eines 1.5 m-Sonnenteleskopsauf den Kanarischen Inseln.SUNRISE – Kooperation mit dem MPI für Sonnensystemforschung,Lindau, dem High Altitude Observatory, USA,dem Instituto de Astrofísica de Canarias, Spanien, und demLockheed Martin Solar and Astrophysics Laboratory zumBau eines ballongetragenenen 1 m-Sonnenteleskops.ATST – Memorandum of Understanding bezüglich einer-Kooperation mit dem National Solar Observatory (NSO)zur Entwicklung eines 4m-Sonnenteleskops.POLIS – Kooperation mit dem High Altitude Observatory,USA, zum Bau und Betrieb eines Spektropolarimetersfür das VTT.ChroTel – Kooperation mit dem High Altitude Observatory,USA, zum Bau eines full disk –Teleskops am VTT zurBeobachtung der Chromosphäre.Sol-Aces – Sonnenphotometer des Fraunhofer-Instituts fürPhysikalische Messtechnik, Freiburg, für die internationaleWeltraumstation. Beteiligung des KIS als Co-Investigator.MIDI – Kooperation des MPI für Astronomie, Heidelberg(PI), mit deutschen, holländischen und französischen Instituten,zum Bau eines Instruments für den Mittel-Infrarotbereichfür das VLT Interferometer. Beteiligung des KISals Co-Investigator.OPTICON – KIS ist Vertragspartner von OPTICON undbeteiligt sich an verschiedenen Aktivitäten, insbesondeream OPTICON Transnational Access Programme.Verschiedene institutionell begründete wissenschaftlicheKollaborationen mit Österreich (IGAM), Kroatien (HO),der Tschechischen Republik (Ondrejov) und der Slowakei(AISA).Beteiligung am DFG-Graduiertenkolleg „Nichtlineare Differentialgleichungen:Modellierung, Theorie, Numerik, Visualisierung“mit dem Institut für Angewandte Mathematikder Universität Freiburg.Seit dem Frühjahr 2005 ist das Kiepenheuer-Institut alsbislang einzige deutsche Forschungs-einrichtung internationalesMitglied der Association of Universities for Researchin Astronomy (AURA), welche im Auftrag der USamerikanischenNational Science Foundation mehrere großeObservatorien sowie das Space Telescope Science Institutebetreibt.CooperationsGREGOR– Cooperation of the KIS (50%) with the Astro-physikalisches Institut Potsdam (25%) and the Institut fürAstrophysik Göttingen (former name, until 31-05-2005:Universitäts-Sternwarte)(25% each) for the construction ofa 1.5 m solar telescope on the Canary Islands.SUNRISE – Cooperation with the MPI für Sonnensystemforschung,Lindau, the High Altitude Observatory, USA,the Instituto de Astrofísica de Canarias, Spain, and LockheedMartin Solar and Astrophysics Laboratory, USA forthe construction of a balloon borne 1 m solar telescope.ATST – Memorandum of Understanding with the Nation-al Solar Observatory (NSO), USA for a participation in thedevelopment of a 4 m solar telescope.POLIS – Cooperation with the High Altitude Observatory,USA, fort the construction and operation of a spektropolarimeterfor the VTT.ChroTel – Cooperation with the High Altitude Observatory,USA, fort he construction and operation of a full disk telescopeat the VTT for chromospheric observations.Sol-Aces – solar photometer of the Fraunhofer-Institut fürPhysikalische Messtechnik (IPM), Freiburg, for the InternationalSpace Station. KIS participation as co-investigator.MIDI – Cooperation of MPI für Astronomie, Heidelberg(PI), with German, Dutch and French institutes to build amid-infrared instrument for the VLT Interferometer. Participationof the KIS as co-investigator.OPTICON – KIS is contractual partner of OPTICON andparticipates in various activities, in particular in the OPTI-CON Transnational Access Programme.Various institutional collaborations with Austria (IGAM),Croatia (HO), the Czech Republic (Ondrejov) and Slowakia(AISA).Participation in the DFG-Graduiertenkolleg „NichtlineareDifferentialgleichungen: Modellierung, Theorie, Numerik,Visualisierung“ with the Institut für Angewandte Mathematikof the Universität Freiburg.The Kiepenheuer Institut was admitted as an internationalaffiliate member of the Association of Universities for Researchin Astronomy (AURA) as the only German institutionin spring 2005. AURA operates several observatoriesand the Space Telescope Science Institute under contract ofthe National Science Foundation.14


ABOUT THE KISForschungsaufenthalteund VorträgeFolgende Mitarbeiter des Instituts verbrachten in den Jahren2003 und 2004 Forschungsaufenthalte an anderen Einrichtungenoder wurden zu Vorträgen eingeladen:Visits and presentationsThe following members of the KIS undertook research visitsand/or were invited to presentations and talks in 2003and 2004:Aiouaz FOM-Institute for Plasma Physics, Nieuwegein (4.11. 2004)Bellot Rubio Instituto de Astrofísica de Andalucía, Granada (15.-28.6. und 22.10.-16.11. 2003)Brandt Sonnenobservatorium Kanzelhöhe (19.1.-2.2. und 12.-28.2. 2003)Bruls MPS, Katlenburg-Lindau (18.-19.8. 2004)Dobler Kolloquiumsvortrag an der Fakultät f. Mathematik und Physik der Universität Freiburg (21.7.)Nordic Institute for Theoretical Physics, NORDITA, Kopenhagen (24.1.-7.2. 2003)Friedlein HAO, Boulder, auf (26.07.-20.08. 2004)Kalkofen Vortrag am MPAE Lindau (5.5. 2003)von der Lühe Vortrag im Astrophysikalischen Kolloquium, Heidelberg (20.1. 2004)Vortrag am LMSAL (3.12. 2004)Vortragbeim NSO (8.12. 2004)Vortrag an der Universitätssternwarte Göttingen (16.12. 2004)Müller Institut for teoretisk astrofysikk, Oslo (31.5.-24.6. 2003)Nesis Vortrag an der Universitätssternwarte Göttingen (5.2. 2003)Ossendrijver Institut für Orientalistik, Wien (8.-12.11. 2004)Peter Vortrag am Institutt for teoretisk astrofysikk, Oslo (16.-21.6. 2003)Vortrag am Institut für Geophysik, Astrophysik und Meteorologie, Graz (17.12. 2003)Vorträge am MPS u. Seminar der Max Planck Res. School, Katlenburg-Lindau (22.1. 2004)AIP, PotsdamSchlichenmaier Vorträge am IAC, Teneriffa (6.8.2003 und 9.11.2004)Vortrag an der USG (20.11. 2003)Vortrag bei der International University of Bremen (11.3. 2004)Vortrag bei den Sternfreunden Breisgau, Freiburg (24.11. 2004)Schmidt Sunrise Team Meeting in Granada (22.-24.10. 2003)Sunrise Co-I-Treffen am MPS, Katlenburg-Lindau (11.-12.2. 2004)AIP, Potsdam (7.-8.9. 2004)StixVortrag am Laboratorio de Astrofísica Espacial y Física Fundamental in Villafranca del Castillo(Madrid, 17.3. 2003)Vortrag an der Universidad de Vigo, Facultad de Ciencias, Orense (18.-22.3. 2003)Vortrag in Würzburg (7.6. 2004)Volkmer Vortrag am Big Bear Observatory, USA (29.7-1.8. 2003)Festvortrag zum 60. Geburtstag von Prof. F. Kneer (Göttingen, 24.4. 2003)Wedemeyer-Böhm Sterrekundig Instituut, Universität Utrecht (5.-6.5. 2004)15


ÜBER DAS KISGästeZu kürzeren Forschungsaufenthalten oder zu Vorträgen besuchtendas Institut die folgenden Personen:2003:GuestsThe following researchers visited the institute for shorttermcollaborations and/or talks at the institute:S. Bingert (Karlsruhe), J. Brestensky (Bratislava, Slovakische Republik), K.R. Briggs (Zürich, Schweiz), J. Dreher (Bochum),C. Durrant (Sydney, Australien), A. Ferriz Mas (Orense, Spanien), A. Gabriel (Paris, Frankreich), H.-H. Gander(Freiburg), A. Getling (Moskau, Russland), M. Güdel (Zürich, Schweiz), E. Guenther (Tautenburg), A. Hanslmeier (Graz,Österreich), V. Hansteen (Oslo, Norwegen), S.S. Hasan (Bangalore, Indien), M.J. Korpi (Oulu, Finland / Toulouse, Frankreich),A. Lagg (Lindau), J. Leenaarts (Utrecht, Niederlande), M. Leitzinger (Graz, Österreich), T. Preibisch (Bonn), W.Rammacher (Heidelberg), A. Reiners (Hamburg), I. Roussev (Ann Arbor, USA), G. Rüdiger (Potsdam), W. Schaffenberger(Potsdam), R. Sridharan (Rajasthan, Indien), R. Stepanov (Perm, Russland), S. Tagare (Hyderabad, Indien), P. Ulmschneider(Heidelberg), G. Villanueva (Lindau), T. Wang (Lindau).2004:J.M. Borrero (Lindau), D. Cabrera-Solana (Granada), W. Dobler (Calgary), I. Dominguez Cerdenña (Göttingen), A. FerrizMas (Orense), A. Getling (Moskau), T. Granzer (Potsdam), E. Grebel (Basel), B. Gudiksen (Oslo), H. Holweger (Kiel),S.S. Hasan (Bangalore), M. Huber (Zürich), W. Kalkofen (Cambridge), J. Koza (Tatranska Lomnica), A. Kosovichev(Stanford), A. Kuçera (Tatranska Lomnica), K. Langhans (Stockholm), J. Linsky (Boulder), B. Lites (Boulder), S. Massaglia(Turin), D. Müller (Oslo), J.-U. Ness (Hamburg), T. Neukirch (St. Andrews), O. Okunev (Göttingen), W. Rammacher(Heidelberg), H. Rauer (Berlin), T. Rimmele (Sac Peak), W. Schaffenberger (Potsdam), H. Spruit (München), A. Tritschler(Big Bear), P. Ulmschneider (Heidelberg), R. Wachter (Davos), R. Wehrse (Heidelberg), E. Wiehr (Göttingen), Y.D.Zhugzhda (Moskau).GremientätigkeitFolgende Mitarbeiter des Instituts wirkten in den Jahren2003 und 2004 in Gremien mit:Participation in CommitteesIn 2003 and 2004 the following staff members participatedin committees:Bellot Rubio:Spanish Time Allocation Committee for solar telescopes (Repräsentant des CCI).Brandt: Mitglied der ATST Site Survey Working Group (bis August 2004).von der Lühe:Rynarzewski:Kuratorium des MPAE (Lindau); Comité Científico Internacional (CCI); VLTI Implementation Com–mittee der ESO; Solar Observatory Committee der AURA (Tucson); Wissenschaftlicher Beirat derLandessternwarte Tautenburg, Thüringen; Mitglied des FRINGE-Konsortium; Mitglied desOPTICON Board.Arbeitskreis Recht der WGL (Sprecherin).Schlichenmaier: Mitglied des Telescope Director’s Forum (OPTICON Access Program).Schmidt:Sigwarth:Finance Subcommittee des CCI (Vors.); Gutachterausschuss Extraterrestrik des DLR; Editor beiAstronomy & Astrophysics.ATST Science Working Group; Solar Orbiter Payload Working Group; Teide Observatory OperationSubcommittee des CCI.Soltau: Mitglied der ATST Site Survey Working Group (ab Sept. 2004).Stix:Wissenschaftlicher Beirat des AIP (bis Sept. 2004), Editorial Board Solar Physics, Auswahl-Komiteefür eine Nachwuchsgruppe am MPS, Lindau.16


ABOUT THE KISBeobachtungen am Vakuum-TurmteleskopWegen der Bauarbeiten am Gregory-Turm konnte ab demJahr 2003 nur noch mit dem Vakuum-Turm-Teleskop beobachtetwerden. Aufgrund der eingegangenen Anträge legtedas aus je einem Vertreter des AIP, KIS, MPG and USGund dem IAC bestehende Time Allocation Committee denBeobachtungsplan für das VTT in den Jahren 2003 und2004 fest. Die Zahl der Beobachtungstage ist in der letztenSpalte der folgenden Tabellen angegeben. Es ist nur derHauptantragsteller mit Heimatinstitut genannt. Ein „S“ beiden Beobachtungstagen von 2004 bezeichnet eine Kampagne,welche parallel zu einer anderen durchgeführt wurde.Observing programs at the VacuumTower TelescopeAs of 2003, observing campaigns were supported only atthe Vacuum Tower Telescope because the Gregory CoudéTelescope was dismantled to make room for GREGOR.Based on the proposals received the time allocation committeewhich consists of a representative each of the participatinginstitutes AIP, KIS, MPG and USG, as well as theIAC assembled the observing program for the years 2003and 2004, which are summarized in the tables below. Theprincipal investigator and her/his home institute, the campaigntitle, and the awarded observing days are provided inthe tables. Campaigns which are identified by an “S” in thelast column shared observing time with other campaigns.2003Principal Investigator Institute Subject DaysBello González IAC Magnetic field and velocity in umbra 3Kneer USG Supra resolution 3Sailer USG G-band with MCAO 3Okunev USG 2D Polarimetry of facular points 2Puschmann USG C-L variation of granulation 3Puschmann USG Polarimetry of small-scale features 3Soltau KIS Mercury transit AO 5Berkefeld KIS Multi-conjugate AO 12Mikurda KIS G-band bright points 8Schleicher KIS Velocity field in complex sunspots 5Nesis KIS 2D dynamics of granulation 5Ceppatelli THEMIS Sources of solar oscillations 1Tritschler KIS Prominences and filaments 4Peter KIS Blinkers 4Bellot Rubio KIS Spectropolarimetry of sunspots 2Briand IAC Magnetic field in active regions 13Collados Vera IAC Waves in magnetic regions 7Eibe García IAC Emerging flux regions 7Beck KIS Polarimetry with POLIS 7Collados Vera IAC Combination of TIP and POLIS 5Bellot Rubio KIS Moving magnetic features 7Collados Vera IAC Magnetic field in the quiet Sun 7Lagg MPAE Magnetic coupling in solar atmosphere 11Balthasar AIP Magnetic field of sunspots 10Trujillo Bueno IAC He I 1083 polarimetry 817


ÜBER DAS KISWiehr USG Penumbral fine structure 10Bello González IAC Magnetic field and velocity in penumbra 4Puschmann USG CL variation of granulation 4Andjiç USG Short-period waves 2Kalkofen KIS Chromospheric bright points 5Beck KIS 3D model of sunspot magnetic field 9Balthasar AIP Magnetic structure of sunspots 9von der Lühe KIS Fine structure connections 20Wöger KIS Ca and G-band bright points 6Zakharov MPAE Magnetic coupling in solar atmosphere 6Total Science Time 2202004Principal Investigator Institute Subject DaysSanchez AIP Chromospheric features of sunspots 7Hofmann AIP 3D-Magnetic topology of active regions 5Berkefeld KIS MCAO tests 42 SSchmidt KIS Venus transit 4 SKalkofen KIS Chromospheric bright points 6Beck KIS Sunspot atmospheric structure 6Beck KIS High resolution penumbral dynamics 6Mikurda KIS Spectropolarimetry of small structures 7Bellot KIS TESOS as a polarimeter 7Wöger KIS Photosph./chromosph. fine structure 10Soltau KIS Running penumbral waves 7Schlichenmaier KIS Height dependence of penumbr. flow field 10Wöhl KIS Spectroscopy of the solar photosphere 10Staiger KIS Speckle imaging with VTT and MSDP 5Nesis KIS Dynamics of the granulation 7Lagg MPS Photosph./chromosph. magnetic fields 16Andjic USG Short periode waves in solar atmosphere 9Bello Gonzalez USG Velocity and magn. fields in umbrae 7 SKneer USG Fabry-Perot spectrometer for GREGOR 5Kneer USG Supra Resolution 1 SPuschmann USG Magnetic fields in the intra-network 12Rauer DLR Venus-Transit und Moleküllinien 5 SSailer USG AO/MCAO supported G band observations 7 SPuschmann USG Evolution of exploding granules 10Khomenko MAO CLV variation of Mn I line profiles 4Khomenko MAO Fine structure of convective motions 4Dominquez Cerdena IAC Quiet Sun magnetic fields 518


ABOUT THE KISCenteno Eliot IAC Propagation of waves in magnetic regions 6Martinez IAC Magnetic field distribution in the quiet Sun 6Cabrera Solana IAC Temporal evolution of the Evershed flow 4Merenda IAC Spectropolarimetry of prominences (He, Na) 6Lopez Ariste THEMIS Spectropolarimetry of prominences (Paschen) 6Collados IAC Test of the new infrared camera for TIP II 3Balthasar AIP 3D structure and dynamics of sunspots 6Sütterlin SIU CLV of G-Band Bright Points 6Hirzberger IGAM Dynamics of Small Scale Magnetic Structures 7Arnaud OME Study of the Sunspot Atmosphere 5Total Science Time 244Beteiligte InstituteParticipating institutionsAIPAstrophysikalisches Institut PotsdamSIUSterrekundig Instituut, UtrechtASOCzech Academy of Sciences, Ondrejov ObservatoryHAOHigh Altitude ObservatoryIAC Instituto de Astrofísica de CanariasIGAM Institut für Geophysik, Astrophysik und Meterologie, GrazKISKiepenheuer-Institut für SonmnenphysikMPAE Max-Planck-Institut f. AeronomieNSO National Solar ObservatoryOME Observatoire Paris-MeudonTHEMIS Themis S.A, TenerifeUSGUniv.-Sternwarte Göttingen19


ÜBER DAS KISLehre und AusbildungVorlesungen und SeminareMitarbeiter des Kiepenheuer-Instituts beteiligen sich imRahmen des Kooperationsabkommens mit der UniversitätFreiburg an der Lehre in der Fakultät für Mathematik undPhysik. Sie vertreten insbesondere das Fach Astronomieund Astrophysik, welches ein Wahlpflichtfach des DiplomstudiengangsPhysik ist. Seit dem Wintersemester 2002/03wird in diesem Wahlpflichtfach ein Curriculum angeboten,welches trotz der sonnenphysikalischen Ausrichtung desInstituts eine breite astrophysikalische Ausbildung der Studentensichern und den Absolventen ein Promotionsstudiumin der allgemeinen Astrophysik ermöglichen soll.Die unten aufgeführten Lehrveranstaltungen wurden imBerichtszeitraum angeboten.Die Übungen zu diesen Vorlesungen, sowie weitere Übungenzu Vorlesungen und Praktika der Fakultät für Mathematikund Physik der Universität Freiburg, wurden von denDoktoranden des KIS betreut.Teaching and EducationLectures and seminarsInstitute staff participates in the teaching at the faculty formathematics and physics in the framework of the cooperationof the institute and the University of Freiburg. In particular,institute staff represents astronomy and astrophysics,which has become a part of the facultative curriculumof the diploma degree in physics. A curriculum that providesa broad education in astrophysics, despite the institute’sorientation towards solar physics, is offered sincewinter semester 2002/03. This curriculum should enablethe successful student to resume graduate studies anywherein the field of astrophysics.The following courses, seminars and practical exerciseswere offered in the reporting period:Additional exercises for the courses above as well as ofthe physics curriculum of the Faculty of Mathematics andPhysics were supported by doctorate students of the institute.SS 2003Einführung in die Astronomie und Astrophysik II (Dobler, Peter, 2st.) mit Übungen (1st.)Angewandte Optik (von der Lühe; 2st.)Magnetohydrodynamik (Schlichenmaier, Stix, 2st.) mit Übungen (1st.)Astronomisches Praktikum (Schmidt, Wöhl, 4st.)WS 2003/2004Einführung in die Astronomie und Astrophysik I (Schmidt, Schlichenmaier; 2st.) mit Übungen (1st.)Galaktische und Extragalaktische Physik (Dobler, von der Lühe; 2st.) mit Übungen (1st.)Astronomie: Alte Geschichten und neue Physik (Peter, Stix, 2st.)Oberseminar Astrophysik: Instabilitäten (Dobler, von der Lühe, Peter, Schmidt, Stix; 2st.)SS 2004Einführung in die Astronomie und Astrophysik II (Schlichenmaier, Schmidt, 2st.)mit Übungen (1st.)Adaptive Optik (von der Lühe; 2st.)Plasmaphysik (Dobler, Peter, 2st.) mit Übungen (1st.)Astronomisches Praktikum (von der Lühe, Schmidt, Wöhl, 4st.)WS 2004/2005Einführung in die Astronomie und Astrophysik I (von der Lühe; 2st.) mit Übungen (1st.)Physik der Sonne (Schmidt; 2st.) mit Übungen (1st.)Hydrodynamik (Peter, Schlichenmaier, 2st.)Astronomie für alle Fakultäten (von der Lühe und weitere Mitarbeiter des KIS; 1st.)Oberseminar Astrophysik (von der Lühe, Peter, Schmidt, Stix; 2st.)20


ABOUT THE KISDarüber hinaus hielten Mitarbeiter des Instituts weitereLehrveranstaltungen, meist an auswärtigen Einrichtungen,ab. H. Peter war Lecturer der Sommerschule Theory, Observationsand Simulation of Space Plasmas (Paris, F, 28.-30.9. 2003). M. Ossendrijver veranstaltete ein Seminar ander Universität Tübingen mit dem Thema „Astronomischeund astrologische Texte Mesopotamiens“. R. Schlichenmaierhielt eine Gastvorlesung an der International Universityof Bremen über „Magnetic fields in the photosphere“.M. Stix besuchte die Universidad de Vigo, Facultad deCiencias, Orense (8.-19.3. 2004) und hielt dort Vorlesungenüber Aufbau und Entwicklung der Sterne.PrüfungenVon der Lühe und Stix führten mehrere universitäre Prüfungen(Experimentalphysik und Wahlpflichtfach I Astronomie)durch. Beide waren Mitglieder von Prüfungskommissionenauswärtiger Promotionen.Several scientists gave additional courses on specializedtopics in astrophysics, mainly at external institutions. H.Peter was lecturer of the summer school Theory, Observationsand Simulation of Space Plasmas (Paris, F, 28.-30.9.2003). M. Ossendrijver held a seminar on “Astronomicaland astrological texts of Mesopotamia” at the University ofTübingen. R. Schlichenmaier gave a lecture on „Magneticfields in the photosphere“ at the International University ofBremen. M. Stix visited the Universidad de Vigo, Facultadde Ciencias, Orense (8.-19.3. 2004) and gave a lecture onstellar structure and evolution.ExaminationsVon der Lühe and Stix carried out several university examinationsin experimental physics und astronomy. Bothof them served as co-referees on several external doctorateexaminations.Staatsexamens-, DiplomarbeitenFolgende Staatsexamens- und Diplomarbeitsthemen werden2005 bearbeitet:Staatsexamen, Diploma thesesThe following Stattsexamen- and diploma theses are inprogress in 2005:Graves, S.:Jendersie, S.:Schmidt, D.:Zacharias, P.:Simulations of coronal stellar spectra (master thesis)Expansion des chromosphärischen Netzwerkes in die KoronaWellenfrontsensor für die solare Adaptive OptikUntersuchung der Längenskalen in stellaren KoronenDissertationenFolgende Dissertationen wurden während des Berichtszeitraumsam Institut abgeschlossen:DissertationsThe following dissertations have been completed since2003:Müller, D. A. N.: Catastrophic Cooling in Solar Coronal Loops, Dissertation, Freiburg (2004).Aiouaz, T: Koronale Trichter in koronalen Löchern, Dissertation, Freiburg (2005).Folgende Dissertationsthemen werden 2005 bearbeitet: The following dissertations are in progress in 2005:Beck, C.:Mikurda, K.:Hupfer, C.:Käpylä, P:Wöger, F.:3D-Beobachtung von Magnetfeld und Strömung in Sonnenflecken.Zur Entwicklung der G-band bright points.Magnetokonvektion in der Penumbra von Sonnenflecken.Numerical MHD-modelling of convective envelopes of late-type stars.Zusammenhang von photosphärischen und chromosphärischen bright points.21


ÜBER DAS KISForschungspraktikaWährend der Jahre 2003–2005 waren Studenten, zum Teilvon Universitäten außerhalb Freiburgs, für insgesamt 22Monate als WGL-Forschungspraktikanten oder als wissenschaftlicheHilfskräfte am Institut beschäftigt.Einmal im Jahr finden am Institut Berufserkundungstagefür Schüler von weiterbildenden Schulen statt, an welchenetwa ein halbes Dutzend Schüler teilnimmt.Berufliche AusbildungDas Kiepenheuer-Institut bietet im technischen Bereichund im Verwaltungsbereich Ausbildungsplätze der FachrichtungenIndustrieelektronik (Gerätetechnik) und Feinmechanik,sowie Verwaltungsfachangestellte(r) an. In denJahren 2003 und 2004 haben drei Auszubildende ihre Lehrenabgeschlossen. Zwei Mitarbeiter des Instituts sind Mitgliedervon Prüfungsausschüssen der Industrie- und HandelskammerFreiburg.Berufliche WeiterbildungDas Kiepenheuer-Institut unterstützt die Fortbildung seinerMitarbeiter im nichtwissenschaftlichen Bereich. Währenddes Berichtszeitraums fanden z. T. mehrtägige Fortbildungsmaßnahmenim Zusammenhang mit der Einführungder Kosten-Leistungsrechnung statt. Mehrere Mitarbeiternehmen an mehrjährigen berufsbegleitenden Fortbildungenin den Bereichen Informations- und Kommunikationstechnologieund Konstruktion teil. Ein Mitarbeiterabsolviert ein berufsbegleitendes Fachhochschulstudium.Mehrere Mitarbeiter aus dem administrativen und technischenBereich nahmen an Fortbildungsveranstaltungenteil.Research LabsDuring 2003–2005 several students, partially from otheruniversities, participated in the WGL summer student programat the Kiepenheuer-Institut for a total of 22 months.Once per year the institute organizes “days of professionalexploration” for the pupils of local high schools, which areattended by typically half a dozen persons.ApprenticeshipsThe Kiepenheuer-Institut offers apprenticeships for professionaleducation in several technical areas including industrialelectronics, precision mechanics, and business administration.Three apprentices completed their educationin 2003 and 2004. Two technical-staff members participatein examination boards of the Chamber of Commercein Freiburg.Continuing EducationThe Kiepenheuer-Institut supports continuing education ofits non-scientific staff through a number of measures. Numerouscourses, often covering several days, were attendedin the context of the introduction of cost performance accounting.Several technical-staff members receive continuingeducation in the areas of IT and mechanical design lastingseveral years. One staff member is enrolled in an advancedtechnical college with the aim of earning a degreein engineering. Several members of the technical and administrativestaff attended short-term training courses.22


ABOUT THE KISÖffentlichkeitsarbeitPublic OutreachDie Öffentlichkeitsarbeit desKiepenheuer-Instituts umfasstFührungen am ObservatoriumSchauinsland, Beantwortungvon Anfragen, dieBereitstellung der Institutsseitenim world wide web, sowieöffentliche Vorträge. DasInstitut arbeitet mit den lokalenAmateurastronomen, denSternfreunden Breisgau, undmit dem Planetarium Freiburgzusammen.Das Observatorium Schauinslandhat eine lange Traditionin der Öffentlichkeitsarbeit(siehe Bild); hier findenjedes Jahr am letzten Sonntagdes Monats öffentliche Führungen von Mai bis Septemberstatt. Die Besucher erhalten Information über die Geschichtedes Instituts und über die Astronomie des Sonnensystems,sowie einen Einblick in die Forschungsarbeit.Weitere Führungen, z.B. von Schulklassen, finden auf Anfragestatt. Bei besonderen Anlässen, wie Sonnen- oderMondfinsternissen, finden ebenfalls öffentliche Veranstaltungenoder Praktika statt. Ein Beispiel war der Durchgangder Venus vor der Sonne am 8. 6. 2004, der viele Menschenauf den Schauinsland lockte (s. Bilder unten). Ein Fernsehteamberichtete von diesem Ereignis in mehreren Nachrichtensendungen,darunter in der Tagesschau. Im Jahr 2003besuchen etwa 850 Personen das Observatorium auf demSchauinsland, im Jahr 2004 waren es 1278 Personen.60 Jahre Öffentlichkeitsarbeit am Observatorium Schauins–land: der damalige Direktor des Fraunhofer-Instituts, K. O.Kiepenheuer (halb verdeckt links vom Bild der Sonne), zeigtBesuchern die partielle Sonnenfinsternis am 9. Juli 1945.Führungen im Sonnenobservatorium auf Teneriffa werdenvom IAC in Absprache mit den deutschen Betreibern organisiert.Im world wide web erscheint das “Bild des Monats”auf der home page des Kiepenheuer-Instituts. Hier werdenwissenschaftliche Ergebnisse oder das Institut betreffendeEreignisse für die Öffentlichkeit dargestellt. Gegebenenfallswerden aktuelleErgebnisse als“Bild der Woche”präsentiert. Bilderder Vormonatesind archiviert undebenfalls über daswww zugänglich.Public outreach at theKiepenheuer-Institut involvesguided tours of the SchauinslandObservatory, answers toquestions from outside and thepresentation of the institute inthe world wide web, as well aspublic talks on various occasions.The institute collaborateswith local amateur astronomersand with the Freiburg planetarium.There is a long tradition of givingguided public tours of theSchauinsland observatory, onevery last Sunday of the monthsMay to September. The visitorsare informed about the historyof the institute and solar-system astronomy, and get an ideaabout the odds and ends of research work. Guided tours arealso organized upon request for, e.g., school classes. Thereare public events or student exercises on special occasionslike lunar or solar eclipses. For example, the Venus transiton June 8, 2004, has attracted many spectators to visit theSchauinsland observatory, which also received substantialcoverage in the nation-wide news that day. About 850 personsvisit the Schauinsland observatory in 2003 and 1278persons in 2004.Guided tours of the solar facilities on Tenerife are organizedby the Instituto de Astrofísica de Canarias (IAC) incoordination with the German operating staff. The mostprominent means of public outreach on the world wide webis the “Picture of the Month”, featured by the home page ofthe Kiepenheuer-Institut (http://www.kis.uni-freiburg.de).In these pictures scientific results of the institute or importantevents are being presented to the public. Occasionally,a “Picture of the Week” features a particularly interestingrecent result. The earlier pictures of the month have beenarchived and arealso available onthe web. Theyform a recordof the institute’sscientific work.Astronomen, Amateure und Interessierte beobachten den Transit der Venus am Observatorium Schauinsland am 8. Juni 2004.23


COMPUTER-SIMULATIONENComputer-Simulationender SonneWie können wir das Schicksal der Sonne Milliarden vonJahren vorhersagen? Warum glauben wir die Topologie derkonvektiven Strömungen unter der Sonnenoberfläche zukennen, obwohl diese Schichten der Beobachtung verborgenbleiben? Warum sprechen wir wie selbstverständlichüber Schockfronten in der Chromosphäre oder über magnetischeRekonnektion in der Korona, obwohl diese bisheute nicht beobachtet wurden? Die Antwort lautet immergleich: Auf Grund von Computersimulationen, die auf wenigenphysikalischen Grundgesetzen basieren, die überallim Universum gültig sind.Numerische ExperimenteMit Himmelskörper kann man nicht im Labor experimentieren.Um Sterne und die Sonne genauer zu untersuchen,bauen wir sie nach – in einem virtuellen Laboratorium, womit ihnen experimentiert werden kann. ComputergestützteAstrophysik beinhaltet das Experimentieren mit astrophysikalischenSystemen in einem virtuellen Laboratorium,vergleichbar dem Manipulieren mit realen Proben imklassischen Physikexperiment. Computersimulationen gehenüber das bloße Integrieren von partiellen Differentialgleichungenunter gegebenen Randbedingungen hinaus.Simulationen zielen meist auf die Frage „Was geschiehtwenn?“ und nicht nur „Was ist die Lösung dieser Gleichungen?“.(M. L. Norman, Computational Astrophysics,ASP Conference Series Vol. 123, 1997). Zum Beispiel wurdenam KIS numerische Experimente mit folgender Fragestellungausgeführt: Wie beeinflusst die Anfangsfeldstärkeden Pfad von magnetischen Flussröhren, die durchdie Konvektionszone aufsteigen? Was geschieht mit einemkoronalen Bogen, wenn der räumliche Bereich der Energiezufuhran den Fußpunkten verändert wird? Was geschieht,wenn in einer Simulation der Konvektionszone das Magnetfeldberücksichtigt wird und was, wenn die chemischeZusammensetzung des Plasmas um Kohlenmonoxid erweitertwird? Durch Ein- und Ausschalten verschiedener physikalischerProzesse lässt sich physikalische Intuition bezüglichdes simulierten Systems gewinnen, die zur Verbesserungdes theoretischen Modells und zu neuen Ansätzenfür die Beobachtungen führt. In einer ersten Phase der Simulationgeht es darum, gesicherte Eckdaten aus Beobachtungenzu reproduzieren, um in einer zweiten Phase beobachtbareVoraussagen zu machen, welche neuen Beobachtungenstandhalten müssen. Schließlich können Simulationen,die alle beobachtbaren Größen richtig wiedergeben,über Zeiträume und Regionen informieren, die der Beobachtungverborgen bleiben; zum Beispiel über die Entwicklungder Sonne in Milliarden von Jahren, die konvektiveStrömung unterhalb der Sonnenoberfläche, Schockfrontenin der Chromosphäre oder Rekonnektion in der Korona.Computer simulationsof the SunHow do we know about the evolution of the Sun, billions ofyears into the future and back in the past? How about theconvective flow topology below the solar surface where nobodycan look at? Why do we naturally speak about shocksin the chromosphere or magnetic reconnection in the coronaalthough these have not been observed yet? The answeris always the same: Because of computer simulationsthat are based on a few basic physical laws which are validthroughout the universe.Numerical ExperimentsBecause celestial bodies are not amenable to laboratory experimentslike the probes of a solid state physicist, we cannottake them to pieces nor experiment with them. All weknow from stars and the Sun is from remote sensing. In orderto have a closer look at stars and the Sun we take theminto the theoretical laboratory for experimenting. Computationalastrophysics is to experiment with virtual astrophysicalsystems in a virtual laboratory, comparable to themanipulation with real probes in classical physics experiments.Computer simulations are more than just the integrationof partial differential equations under given boundaryconditions. They are generally motivated by the question“What happens if” more so than “What is the solutionto these equations?”. (M. L. Norman, Computational Astrophysics,ASP Conference Series Vol. 123, 1997). For example,simulations at the KIS address the questions: Whathappens to the travel path of magnetic flux tubes that risethrough the convection zone if we change their initial fieldstrength? What happens to a coronal loop if varying thespatial extent of the energy deposition at its foot points?What happens if introducing magnetic fields into a relaxedstate of convective flow, or what if introducing the moleculeCO to the solar plasma mixture? By means of experimentingwe gain physical intuition with respect to the systemunder investigation, for example by switching on andoff process ingredients. This may lead to the improvementof theoretical models and to new approaches for observations.In an early phase, the simulation shall reproduce keydata from observations leading to the prediction of observationsin a second phase, which must be checked againstnew observations. Finally, if the simulation reproduces allobserved data correctly it can confidently inform us onphysical processes that are not accessible to direct observations:For example about the evolution of the Sun billionsof years from now, the topology of convective flow beneaththe solar surface, shocks in the solar chromosphere or magneticreconnection in the corona.24


COMPUTER SIMULATIONSTheorie – Simulation – BeobachtungNumerische Astrophysik steht in enger Wechselbeziehungmit Theorie und Beobachtung und kann als eigene Disziplinangesehen werden, angesiedelt zwischen theoretischerund experimenteller Forschung. Zuerst stellt die Theoriedie physikalischen Gleichungen zur Verfügung, welche daszu simulierende System beschreiben. Zweitens werden theoretischeKonzepte wie Erhaltungssätze bei der Konstruktionnumerischer Algorithmen verwendet. Drittens dienenanalytische Lösungen zur Überprüfung der Genauigkeitvon numerischen Lösungen (code validation). Schließlichmöchte man komplexe Simulationsresultate auf ein einfaches,leicht verständliches, analytisches Modell zurückführen,welches die essentielle Physik der Simulation beinhaltet.Eine Simulation liefert den Zustand des physikalischen Systemsan diskreten Stellen (Zellen) des Berechnungsgebietszu jedem Zeitschritt. Dadurch fällt eine enorme Datenmengean, welche aber auf beobachtbare physikalische Größenreduziert werden kann. Zum Beispiel kann aus einem dreidimensionalenWürfel, in welchem Granulation an der Sonnenoberflächesimuliert wird, die austretende Intensität invertikaler Richtung, entsprechendder Intensität inder Mitte der Sonnenscheibe,berechnet werden. Dadurchkann kann eine Simulationauf eine virtuelle„Beobachtung“ reduziertwerden, die nun mitrealen Beobachtungen verglichenwerden kann. Fallsdie Simulation die Beobachtungnicht reproduzierenkann, deutet dies daraufhin, dass wesentlichephysikalische Phänomeneunberücksichtigt blieben,numerische Schwierigkeitenauftraten, die Beobachtungenungenau sind,oder aber eine Kombinationdieser Probleme vorliegt.403020100Fe I 1564.8 nm10MeasurementTheory – Simulation – ObservationsComputational Astrophysics is in close interaction withtheory and observation; it can be considered as an owndiscipline between theoretical and experimental research.Theory, firstly, provides the physical equations that describethe system to be simulated. Secondly, concepts oftheoretical physics enter the construction of numerical algorithms,e.g. conservation laws. Thirdly, analytical solutionsserve for code validation. Finally, for a conceivableexplanation, one often seeks to recast complex simulationresults into a simple, analytical textbook model that encompassesthe relevant physical processes. The output of sucha simulation generally consists of a time sequence of tablesthat give the physical condition of the system at discretelocations (grid cells) of the computational domain.These, usually large data sets, can be reduced to observablequantities. For example, having obtained density, velocity,and temperature for each grid cell of the three-dimensionalsimulation box of granular flow at the solar surface,we can compute the outward intensity into the verticaldirection, corresponding to the intensity emanating fromthe solar surface at disk center. In this way the simulationsθ =30Theoretical prediction−0.6 −0.2Fig. 1: Polarisation eines Sonnenflecks. Beobachtungen (links) werden mit synthetischen Daten verglichen.Polarization of a sunspot. Observations (left) are compared to synthetic data.(Schlichenmaier, Müller & Beck, 2005)0.2θ =300 20 30 0 10 20 30−0.3 −0.1 0.1 0.3403020100Fe I 1564.8 nm0.625


COMPUTER-SIMULATIONENSynthetische BeobachtungenDie Berechnung synthetischer Beobachtungsdaten erfordertgewöhnlich das Lösen der Strahlungstransportgleichung,oft unter Berücksichtigung der Polarisation. SolcheBerechnungen sind manchmal so aufwändig bezüglichProgrammierung und Berechnung wie die Simulationselbst. Zum Beispiel wurde für die Analyse von Simulationenvon penumbralen Filamenten die Strahlungstransportgleichungfür polarisiertes Licht längs einer großen Anzahlvon Sichtlinien integriert, welche das Berechnungsgebietan verschiedenen Stellen durchlaufen. Dadurch erhält manPolarisationskarten als einer Funktion von Ort, Neigungswinkelund Wellenlänge. Der Vergleich mit beobachtetenSonnenfleckenpenumbren zeigt, dass solche Karten Auskünfteüber die Diskontinuität des Magnetfeldes zwischenFilament und penumbralem Hintergrundfeld geben.Methoden der ComputersimulationUm eine Simulation auszuführen wird das Rechengebiet inkleine, diskrete Zellen unterteilt (Rechengitter), in denen,stellvertretend für die ganze Zelle, jeweils ein Wert fürphysikalische Größen wie Dichte, Geschwindigkeit oderTemperatur steht. Ausgehendvon einem bestimmtenAnfangszustand dieserGrößen, lässt sich derenEntwicklung in derZeit darstellen, indem dieGrundgleichungen, die dasastrophysikalische Systembeschreiben, Zeitschrittfür Zeitschritt und für jedeZelle mit dem Computerintegriert werden. SolcheGrundgleichungen bildentypischerweise das Systemder magneto-hydrodynamischenGleichungen,wobei die Komplexitätaus verschiedenenQuelltermen in der Energie-und Impulsbilanzherrührt, etwa aus Strahlungsverlusten,Gravitations- und Corioliskräften usw.can be reduced to “observations” of the virtual system thatnow can be compared to observations of the real Sun. This“reality check” tells us how good the simulation is and howwell we have understood the physical system under investigation.A mismatch between virtual and real observationindicates that either essential physical processes were notor erroneously taken into account, that numerical problemsoccurred, that the observations are inaccurate, or a combinationthereof.Synthetic ObservationsFig. 2: Simulation eines Ausschnitts der Konvektionszone.Simulation of a piece of convection zone.(Ossendrijver, Stix & Brandenburg, A&A 376 (2001), 713)Gewöhnlich umfasst das berechnete Gebiet nur einen Teildes kompletten astrophysikalischen Systems; zum Beispieleinen kleinen Ausschnitt aus der Konvektionszone odereinige Granulen an der Sonnenoberfläche. Deshalb sindRandbedingungen notwendig, welche die Wechselwirkungdes Berechnungsgebietes mit dessen Umgebung beschrei-The production of virtual observations, like the intensitymaps mentioned above, mostly proceeds by radiative transfer,often taking polarization into account. It can take asmuch effort in programming and computing time as thesimulation itself. For example, for the analysis of simulationsof penumbral filaments we integrated the equationsof radiative transfer for polarized light along linesof sight traversing the computational domain under variousangles and at various locations. This results in polarizationmaps. Comparing to measured ones of sunspot penumbraewe found that these maps bear information on thetangential discontinuity between the magnetic field of thefilaments and the penumbralbackground field. Differentfrom inversion techniques bywhich one tries to infer theunderlying physical systemdirectly from observed quantities,the here described technique,sometimes called forwardmodelling, aims at derivingthe underlying physicalsystem from first principles,checking it against the realworld by comparing syntheticwith real observations. It isbelieved that forward modellingis less vulnerable to ambiguitiesthan inversions are.Methods of ComputerSimulationsIn order to carry out the computation, the domain of simulationis subdivided into small, discrete cells. To each cellassociated are physical quantities that represent its averagestate like density, velocity, temperature, magnetic field, etc.Starting from a given, prescribed initial state, one can computethe evolution of these quantities with time by integratingthe basic equations that describe the astrophysical systemto be simulated time step by time step for each cell.26


COMPUTER SIMULATIONSben, die nicht Teil der Simulation ist. Das Stellen von Randbedingungenerfordert deshalb gute physikalische Intuitionund oft müssen diese in einer Simulation variiert werden,um deren Einfluss auf die Lösung besser kennen zulernen. Je feiner Raum und Zeit in Zellen unterteilt sind,desto genauer die Rechnung, um so größer aber auch derRechenaufwand. Während früher die Rechnungen auf einigenhundert bis tausend Gitterzellen ausgeführt wurden,umfassen heutige Simulationen bis zu 1024 x 1024 x 1024räumliche Zellen. Der enorme Fortschritt der rechnergestütztenAstrophysik beruht einerseits auf der Entwicklungimmer schnellerer Computer, deren Rechenleistungsich über die letzten 30 Jahre alle 18 Monate verdoppelt hat(Gesetz von Moore), andererseits auf der Entwicklung undVerbesserung von Algorithmen, deren Effizienz ebenfallszunimmt. Manche moderne Methoden der numerischenFluiddynamik schließen physikalische Gesetze wie Erhaltungssätzeoder die Sprungbedingungen für Schockfrontendirekt mit in die diskrete Formulierung der Gleichungenein. Gitteradaptionstechniken erhöhen die Anzahl derGitterpunkte im Rechengitter automatisch dort, wo einegrößere Genauigkeit erforderlich ist und tragen so zu einerFig. 3: Simulation einer magnetischen Flussröhre welche durch die Konvektionszone an dieSonnenoberfläche steigt, um dort als Sonnenfleckenpaar zu erscheinen.Simulation of a magnetic flux tube rising through the convection zone, leading to asunspot pair at the solar surface. (From Caligari, Moreno-Insertis & Schüssler, ApJ 441(1995), 886)These basic equations are typically the system of magnetohydrodynamicequations, where complexity enters fromdifferent kinds of source and sink terms in the energy andmomentum equation, such as radiative losses, gravitationalor Coriolis force, etc.Usually the computational domain encompasses only partof the complete astrophysical system: for example a smallpiece of the convection zone, or a few granules at the solarsurface. Therefore, boundary conditions specify the interactionof the simulation domain with the environmentthat is not part of the simulation. It requires good physicalintuition to specify reasonable boundary conditions andsometimes they need to be varied over several simulationruns in order to acquire better knowledge on their influenceon the solution. The finer the subdivision of spacetimein cells, the more accurate is the computation, but alsothe more computationally expensive. While early simulationswere carried out with a few hundred to thousands ofcomputational cells, today’s simulations encompass up to1024 x 1024 x 1024 spatial cells. The enormous progressof computational astrophysics over the past few decadesis based on the development of everfaster computers whose computingpower doubled every 18 months overthe past 35 years (Moore’s law). Onthe other hand it is also due to theinvention and development of evermore efficient numerical algorithms.Many modern methods of computationalfluid dynamics directly includephysical laws in the finite differenceformulation of the equations, such asconservation laws or the jump conditionsfor shock fronts. A techniquethat substantially increases the computationalefficiency is the automaticadaptive mesh refinement: use of acloser mesh at locations in the computationaldomain where an accuracylimit calls for. Progresses in computationalpower and algorithmic efficiencyhave considerably enlargedthe simulation opportunities with respectto dimensionality, spatial andtemporal resolution, and physicalcomplexity. Yet, compromises mustbe made: If the dimensionality is increased,the physical complexity of aformerly one-dimensional simulationmay have to be reduced and vice versa.27


COMPUTER-SIMULATIONENMagnetic flux tubes occur at the solar surface also in theform of tiny, bright “points” and “crinkles” with a spatialextension of around 100 km. Unlike sunspots, they are exposedto the buffeting by granules so that they are constantlypushed along the intergranular space. Early computersimulations at the KIS treated these objects, oftencalled magnetic elements. Radiative transfer was fully takeninto account, showing that extra radiation is escapingmagnetic elements, which act like radiation leaks. Todayit is clear that this property of magnetic elements substanenormenEffizienzsteigerung bei. Fortschritte in Rechenleistungund Effizienz von Algorithmen haben die Simulationsmöglichkeitenbeträchtlich erweitert – bezüglich Dimensionalitätdes Berechnungsgebiets, räumlich-zeitlicherAuflösung und physikalischer Komplexität. Kompromissemüssen jedoch noch immer eingegangen werden. Wirdzum Beispiel die Dimensionalität erhöht, so muss möglicherweisedie physikalische Komplexität der Simulationreduziert werden.Entwicklungen bis 2003Seit 1980 werden am KIS mit dem Programm SONNE Simulationender zeitlichen Entwicklung der Sonne durchgeführt,mit dem Ziel einer stetigen Verbesserung des Standard- Sonnenmodells. Zu den damit untersuchten Themengehören das solare Neutrino-Problem, Abweichungen vonder idealen Gasgleichung, konvektive Strömungen an derSonnenoberfläche und am unteren Rand der Konvektionszone,die Ausdünnung von Lithium und Beryllium, die Stabilitätdes Kerns der Sonne und das gravitationsbedingteAbsinken von Helium. Dieses Programm diente auch zurBeschreibung der Entwicklung von magnetischen Struktureninnerhalb der Konvektionszone.Erste Magnetische FlussröhrenDiese magnetischen Flussröhren – das sind Konzentrationenvon Magnetfeldern in röhrenähnlichen Formen – tretenin sehr verschiedenen Größen und Anordnungen aufder Sonne in Erscheinung. So sind auch Sonnenflecken dieAustrittsstellen großer magnetischer Flussröhren auf dersichtbaren Sonnenoberfläche. Man nimmt an, dass solcheFlussröhren ihren Ursprung am unteren Rand der Konvektionszonehaben und von dort innerhalb etwa eines Monatsan die Oberfläche aufsteigen. Dieser Prozess war Gegenstandintensiver numerischer Simulationen am KIS in derersten Hälfte der neunziger Jahre. Simuliert wurden dabeidie Bewegungen einer eindimensionalen (dünnen) Flussröhrein der Konvektionszone (als Schale um die Sonne modelliert,siehe Fig. 3) unter dem Einfluss von Auftriebskräften,magnetischer Spannung sowie der Corioliskraft. DieseRechnungen konnten eine Verbindung zwischen den magnetischenFeldern, die in der „overshoot-layer“ erzeugt undgespeichert werden, und ihrem Erscheinen in der Form vonSonnenflecken an der Oberfläche etablieren. Ein Ergebnisdieser Untersuchungen war, dass magnetische Flussröhrenam unteren Rand der Konvektionszone eine Feldstärke von10 Tesla haben müssen, damit die Verteilung der Sonnenfleckenüber die Breitengrade sowie der Winkel zwischenvorauslaufenden und nachfolgenden Flecken korrekt wiedergegebenwerden können. Fig. 3 zeigt einen Schnapp-Development until 2003Since 1980 computer simulations of the solar evolution,aiming at a steady improvement of the standard solar modelhave been performed at the KIS with the code SONNE.Questions relating to the neutrino problem, deviations fromthe perfect-gas state, convective overshooting at the solarsurface and at the base of the convection zone, the depletionof lithium and beryllium, the stability of the solar core, andthe gravitational settling of helium were addressed. Thiscode served also to describe the background of the evolutionof magnetic structures in the solar interior.Pioneering magnetic flux tubesThese magnetic flux tubes or ropes – the concentrationof magnetic field in a tube-like form – occur on differentscales and locations on the Sun. Sunspots are a manifestationof magnetic flux tubes intersecting the visible surface.These flux tubes are thought to originate from the basis ofthe convection zone from where they rise within one monthto the solar surface. This process was the subject of intensenumerical simulations at the KIS. The movement of a onedimensional(thin) magnetic flux tube in the three-dimensionalspace of the convection-zone shell, subjected to theforces of buoyancy, drag, magnetic tension, and to the Coriolisforce that act on each mass element of the tube, wassimulated. Here we established the connection between themagnetic field generated and stored in the overshoot layerand its appearance in the form of sunspots at the solar surface.By numerical experimentation it was found that themagnetic flux tubes must have a field strength of 10 Tesla atthe base of the convection zone in order that the latitudinaldistribution of sunspots and the inclination angle betweenleading and following spot were correctly reproduced. Fig.3, which shows a snapshot of a rising flux tube, became anicon of computational solar physics and the correspondingpublication was heavily cited according to the Smithsonian/NASAAstrophysics Data System (ADS). These simulationswere later extended to cool stars which led to an explanationof the “coronal dividing line” in the Hertzsprung-Russell-diagram.28


COMPUTER SIMULATIONSYet another highlight of numerical simulations at the KISin the late nineties was devoted to the sunspot penumbra –a complicated structure that radially extends from the sunspotumbra, consisting of magnetic flux tubes. Again, radiativelosses play a crucial role, this time driving a flowalong and in the outward direction of the flux tubes, knownas the Evershed flow. These simulations helped to exschusseiner solchen aufsteigendenFlussröhre; dieses Bild wurdezu einem Sinnbild der numerischenSonnenphysik und derFachartikel, in dem es erschien,wurde laut Smithsonian/NASAAstrophysics Data System (ADS)sehr zahlreich von anderen Arbeitenzitiert. Diese Simulationenwurden später dann ausgedehntauf kühle Sterne und führten zueiner Erklärung der sogenannten„koronalen Trennlinie“ im Hertzsprung-Russell-Diagramm.Magnetische Flussröhren erscheinenauf der Sonnenoberflächeauch in Form von relativkleinen aber hellen „Punkten“und „Falten“ mit einer räumlichenAusdehnung von lediglich rund 100 km. Im Unterschiedzu Sonnenflecken sind sie jedoch den Stößen durchGranulen ausgesetzt, so dass sie permanent hin und her geschobenwerden. Diese kleinräumigen magnetischen Elementewaren Gegenstand früher numerischer Rechnungenam KIS; der Strahlungstransport wurde dabei berücksichtigtund es zeigte sich, dass diese magnetischen Elementeerhöht Strahlung emittieren und damit wie Strahlungsleckswirken. Heute ist es klar, dass diese erhöhte Emissionder magnetischen Elemente wesentlich zur Variabilitätder solaren Strahlung beiträgt und sogar das durch Sonnenfleckenverursachte Strahlungsdefizit überkompensiert.Die numerischen Simulationen sagen auch voraus, dassdieser Strahlungsverlust eine Plasmaströmung in Richtungder magnetischen Elemente verursacht. Eine ähnliche Strömungbei Poren ist kürzlich entdeckt worden, aber die Beobachtungsolcher Strömungen bei magnetischen Elementenliegt noch jenseits des Auflösungsvermögens heutigerInstrumente. Die Simulationen zeigten außerdem, wie diedynamische Wechselwirkung zwischen konvektiven Strömungenund dem Magnetfeld die Bildung von Schockwelleninitiiert an den Stellen der Photosphäre, wo sich der magnetischeFluss konzentriert. Aus einer dieser Rechnungenzeigt Fig. 4 einen Schnappschuss, der nach seiner Veröffentlichung1994 schnell populär wurde, und so in vielen internationalenProjektanträgen und als Titelbild eines Konferenzbuchsund einer Sonnenphysik-Zeitschrift benutztwurde; auch in Fachbüchern und Dissertationen über Sonnenphysiksowie in einem Lehrvideo über die Sonne fanddiese Abbildung Verwendung. In der Folge wurde derselbeCode erfolgreich benutzt, um die Bildung magnetischerElemente durch konvektiven Kollaps, die polarimetrischenFig. 4: Konvektive Strömung in Wechselwirkung mit einer magnetischen Flussschicht. Standbildaus einer zweidimensionalen magnetohydrodynamischen Simulation.Convective flow interacting with a magnetic flux sheet. Snapshot of a two-dimensional magnetohydrodynamicalsimulation. (Steiner, Grossmann-Doerth, Knölker & Schüssler, ApJ (1998),495)tially contributes to the solar radiance variability, in fact itovercompensates the radiative deficit of sunspots. The numericalsimulations also predicted that this radiative lossdrives a plasma flow convergent on the magnetic element.A similar convergent flow on pores was recently discovered,but a detection in the case of magnetic elements isyet beyond the resolution capabilities of present-day measurementtechniques. The simulations showed that the dynamicinteraction of convective motion with the magneticfield spurs the formation of shock waves in the photosphericlayers in and around the flux concentration. Fig. 4 showsa snapshot from one of these simulations that, after its publicationin 1994, became quickly popular and appeared inmany international project proposals, as frontispiece of aconference proceeding and a solar physics journal, in textbooks and theses of solar physics, and in an educationalvideo on the Sun. Subsequently, the same code with whichthese simulations were carried out was successfully usedto study the formation of magnetic elements by the convectivecollapse, the polarimetric signature of pores, andmore recently, the appearance of faculae, and wave excitationby magnetic elements. Many of these simulations werecarried out at the High Performance Computing Center inStuttgart (HLRS).29


COMPUTER-SIMULATIONENKennzeichen von Poren sowie – ganz aktuell – dasAuftreten von Fackeln und die Wellenanregungdurch magnetische Elemente zu untersuchen. Vieledieser Rechnungen wurden am Hochleistungs-Rechenzentrum in Stuttgart (HLRS) ausgeführt.Eine weitere numerische Simulation, die nachhaltigeAufmerksamkeit erregt hat, widmete sich derPenumbra von Sonnenflecken - ein komplexer feinstrukturierterRing, der die Umbra umgibt, undaus magnetischen Flussröhren besteht. Auch hierspielen Strahlungsverluste in der Photosphäre diewesentliche Rolle, indem durch sie eine auswärtsgerichteteStrömung entlang von Flussröhren getriebenwird – Beobachter kennen diese Strömungals Evershed-Strömung. Diese Simulationen habendazu beigetragen, dass eine Reihe von Beobachtungsbefundenerklärt werden können, wie dieUrsache der Evershed-Strömung, die Eigenbewegungund Form der penumbralen „grains“, die Topologiedes Magnetfeldes, der Energietransport in der Penumbra,und die Existenz magnetischer Phänomene in derSuperpenumbra. Mit diesen Modellen kann die beobachtetePolarisation im Sichtbaren und im Infraroten reproduziertwerden (s. Fig. 1).Dynamos im Weltall und im Labor10 km/sFig. 6: Ein M-Zwergim numerischenLabor. In diesemvollkonvektivenStern bildetsich ein grossskaligesMagnetfeld.An M-dwarf inthe virtual Lab. Alarge-scale magneticfield forms inthis fully convectivestar. (Dobler,Astron. Nachr. 326(2005), 254)4000 kmFig. 5: Flussröhre in der Penumbra eines Sonnenflecks. Die schweifförmigenpenumbralen Körner und die Strömung ergeben sich aus der Simulation.Magnetic flux tube in the penumbra of a sunspot. The cometary-tail like penumbralgrains and the flow derive from the simulation (From Schlichenmaier(1999), ASP Conference Series, Vol. 183)Nach den frühen Dynamo-Rechnungen in den 80er Jahrenbeschäftigten sich viele numerische Simulationen imKIS mit der Erzeugung kosmischer Magnetfelder – demDynamoproblem. Vergleichende Beobachtungsdaten gibtes hierzu nur wenig, eigentlich nur das Schmetterlingsdiagramm,das die Breitengrade der Sonnenflecken im 11-jährigen Zyklus zeigt. Deshalb ist es sinnvoll, Ergebnisplaina number of observed features of the penumbra includingthe origin of the Evershed flow, the movement andshape of penumbral grains, the interlacement of the penumbralmagnetic field, the energy transport in the penumbra,and even the existence of moving magnetic features inthe super-penumbra. The net circular polarization of spectrallines in the visible and infrared, synthesized from thismodel agrees well with measured narrow band circular polarizationmaps of penumbrae (Fig. 1).Cosmic and Experimental Dynamos6 10 14Temperatur (1000 K)After the early dynamo calculations in the 1980s, a numberof numerical simulations at the KIS were devoted to the dynamoproblem. In this field, observations are rather sparse,basically restricted to the butterfly diagram, which displaysthe location of sunspots on the solar globe as a function oftime. Therefore, other ways for information are sought, forexample from stellar observations or from laboratory experiments.The fact that fully convective stars like manyM-dwarfs, brown dwarfs, or T-Tauri stars are known topossess a rather strong magnetic field poses a riddle to solarphysicists who believe that the interface where the convectionzone adjoins the stably-stratified core plays a decisiverole for dynamo action. Therefore, a fully convective,self-gravitating star was simulated in a box-shaped computationaldomain running the PENCIL code on the then newlyinstalled Linux-cluster at the KIS. It was found that magneticfield generation on large scales quickly takes place.The strong magnetic flux is mostly concentrated in longbent tubes. Even in the absence of rotation, magnetic fieldgeneration takes place although on a slower growth rate.30


COMPUTER SIMULATIONSse mit Daten stellarer Beobachtungen und von Laborexperimentenzu vergleichen. Man beobachtet, dass voll-konvektiveSterne wie M-Zwerge, braune Zwerge, und T-TauriStern starke Magnetfelder besitzen, obwohl sie im Gegensatzzur Sonne voll konvektiv sind. Bei der Sonne spielendie Scherströmungen am unteren Rand der Konvektionszoneeine entscheidende Rolle bei der Verstärkung von Magnetfeldern.Um zu verstehen, wie der Dynamo bei Sternenfunktioniert, die einen solchen unteren Rand nicht haben,wurde am KIS mithilfe des eigenen LINUX-Clustersein voll konvektiver, selbst-gravitierender Stern mit demPENCIL Code simuliert. Diese Simulationen haben gezeigt,dass auch in diesem Stern aufgrund der Konvektiongroßskalige Magnetfelder erzeugt werden, selbst wenn derStern nicht rotiert.Um ein laborgestütztes Dynamo-Experiment zu verstehen,wurde der Aufbau und die Funktionsweise des Apparatesim russischen Perm durch kinematische Rechnungen simuliert.Dieses numerische Experiment hat zur Optimierungdes Laborexperimentes beigetragen.Numerische Simulationen können aber auch dazu verwendetwerden, um makroskopische Konstanten der Dynamotheorie,die auf dem Konzept der mittleren Felder basiert,zu bestimmen: Die hochgradig nicht-linearen Prozesse einesDynamos lassen sich durch Mittelung auf großen Skalendurch Parameter für mittlere Felder beschreiben.Bei derartigen Simulationen bettet man dienumerische Box in verschiedene Regionen derSonne und bestimmt abhängig von der Positionmakroskopische Parameter, wie den α− und denβ-Tensor, welche beschreiben, wie poloidales Magnetfeldverstärkt wird. Durch diese Experimentekonnten Erkenntnisse gewonnen werden überdie Änderung des α-Tensors und über die Magnetfeldstärkebei welcher der Dynamo-Effekt sättigt.Der antisymmetrische Anteil des α-Tensorsbeschreibt die Effekte des Transports von Magnetfeld,dem magnetischen Pumpen. Es hat sich gezeigt,dass dieser Transport sowohl vertikal wiehorizontal stattfindet. Der horizontale Transportvon Magnetfeld kann mit dem Schmetterlingsdiagrammverglichen werden. Diese Simulationenhaben entscheidend zu unserem Verständnis dessolaren Dynamos beigetragen, weil es gelungenist, die Prozesse der kleinen Skalen mit großskaligenEffekten auf mittlere Felder zu verknüpfen.Numerical experiments have been performed for predictingthe growth rate in a helical flow of liquid sodium through atorus-shaped tube. These kinematic simulations helped tooptimize the experimental apparatus of the Perm dynamolaboratory experiment in Russia.Numerical simulations also serve to constrain the macroscopicconstants of the mean field dynamo – a model of thesolar dynamo, based on first principles. In this way, informationof highly non-linear processes can enter a more abstractparametric model. Magneto-convection in a box thatis positioned at different places in the rotating convectionzone is numerically simulated. This yields fluctuations ofthe velocity and magnetic field as a function of position andorientation of the box from where the coefficients of the socalled α- and β-tensor can be derived. The depth dependencyof the component of the a tensor that takes care ofthe generation of a mean poloidal from the mean toroidalmagnetic field could be determined and it was found that itchanges sign near the transition from the convection zoneproper to the adjacent stably stratified layer. The scalingfor the magnetic quenching (the saturation of the dynamoeffect imposed by the magnetic field) with magnetic fieldstrength was determined. The asymmetric part of the αtensor bears information on the magnetic pumping, whichwas found to act not only in the vertical but also in the horizontaldirection, a fact that can be related to the butterflyFig. 7: Vertikaler Schnitt durch eine dreidimensionale magnetohydrodynamischeSimulation der atmosphärischen Schichten von der Konvektionszonebis in die Chromposhäre.Vertical section through a threedimensional magnetohydrodynamic simulationof the atmospheric layers from the convection zone to the chromosphere.(Schaffenberger, Steiner, Wedemeyer-Böhm)31


COMPUTER-SIMULATIONENFig. 8: Synthetische Intensitätskartebei 1 mmWellenlänge, berechnetaus einer dreidimensionalenSimulation derChromosphäre.Intensity map at 1 mmwavelength, synthesizedfrom a three-dimensionalsimulation of thechromosphere.(Wedemeyer-Böhm, Ludwig,Steffen, Freytag &Holweger: Cool Stars,Stellar Systems and theSun 13, (2005))y [km]50004000300020001000Die Dynamische Korona1000 2000 3000 4000 5000x [km]In den letzten Jahren wurden am KIS numerische Simulationender Millionen Grad heißen Korona begonnen, diewährend einer Sonnenfinsternis mit dem bloßen Auge zusehen ist. Um die augenfälligsten Strukturen – koronaleBögen – zu modellieren, haben wir eindimensionale Rechnungeneiner von halbkreisförmigen magnetischen Feldlinienbegrenzten Atmosphäre durchgeführt.Um den steilen Temperaturgradienten in dieKorona aufzulösen und zeitlich zu verfolgen,wurde ein adaptives Rechengitter benutzt.Es zeigte sich, dass diese koronalen Bögenthermisch instabil werden und sich dynamischentwickeln können, wenn man denEnergieverlusten durch Strahlung angemessenRechnung trägt. Mathematisch gesprochenist dies durch die Nichtlinearität der zuGrunde liegenden physikalischen Gesetzegegeben, was zu einem chaotischen Verhaltenführt, vergleichbar der Entwicklung desWetters auf der Erde.Um die Wechselwirkung der verschiedenenmagnetischen Strukturen in der Korona realistischzu beschreiben, muss man allerdingszwei- oder besser dreidimensionale Modellebetrachten. In einem ersten Schritt haben wir die Expansionvon magnetischen Strukturen in die Korona in zwei Dimensionenstudiert, wobei man einen Teil der Selbstkonsistenzdes Modells gegen die räumliche Komplexität eintauschenmuss. Diese Rechnungen können gut auf dem Linux-Cluster(34 Prozessoren) des KIS durchgeführt werdenund dienen als Vorbereitung für komplexere dreidimensionaleModelle, um Rechenzeit an Super-Computer-Zentren,diagram of solar activity. These simulationsgreatly advanced our understanding of thesolar dynamo and contributed to the foundationsof the mean field theory.The Dynamic CoronaMore recent numerical simulations at theKIS focussed on the million degrees hot coronaof the Sun, visible to the naked eye duringa solar eclipse. To study the most prominentstructures, coronal loops, we appliedone-dimensional models of an atmospherechanneled by semi-circular magnetic fieldlines. To resolve and follow the steep temperature gradientinto the corona, we are using a numerical code with anadaptive mesh refinement. When properly accounting forthe energy losses through radiation we find that the loopscan become unstable and evolve very dynamically. Mathematicallyspeaking this is because of the highly non-linearcharacter of the governing physical laws, leading to a chaoticevolution, similar to the weather on Earth.Fig. 9: Zwei Momentaufnahmen der Emission aus einem thermisch instabilen koronalenBogen in einem Abstand von 45 Minuten zeigen helles abströmendesPlasma.Two snapshots of the emission from a thermally instable coronal loop 45 minutesapart show bright down-moving plasma. (Müller, PhD-Thesis)In order to realistically simulate the interaction of variousmagnetic structures in the corona, it is essential to moveto two- or better three-dimensional space. As a first stepwe modeled the expansion of magnetic structures into thecorona in two dimensions, trading some of the self-consistencyof the model for spatial complexity. Such simulationscan well be run on the KIS Linux cluster (34 processors).This paved the road to more complex three-dimen-32


COMPUTER SIMULATIONSwie dem High-Performance Computing Center in Stuttgartoder dem John von Neumann Institute for Computing inJülich zu beantragen.Entwicklungen 2004 - 2005Kopplung an die ChromosphäreMit dem CO 5 BOLD - 3D-Code konnten wir in jüngsterZeit die Simulationen der solaren Oberflächenschichtenbis in die Chromosphäre hinein ausdehnen, unter Einbeziehungvon chemischen Reaktionsnetzwerken, Magnetfeldernund zeitabhängiger Ionisation des Wasserstoffs. Dieseseinzigartige Werkzeug ermöglicht es uns deshalb, einenbisher nur schlecht verstandenen, dafür aber um so heftigerdiskutierten Sachverhalt gründlich zu untersuchen: dieKopplung der Konvektionszone und der Photosphäre an diedarüberliegende Chromosphäre. Unsere Simulationen dersolaren Chromosphäre sagen voraus, dass man in ruhigen,magnetfeldfreien Gebieten der Sonne ein Netzwerk aus heißemGas und davon eingeschlossenen kühlen Gebieten sehensollte. Fig. 8 zeigt die aus unseren Rechnungen gewonneneIntensität bei 1 mm Wellenlänge. Das geplante AtacamaLarge Millimeter Array (ALMA), dessen Fertigstellungfür 2012 projektiert ist, sollte diese Strukturen dann beobachtenkönnen. Eine weitere mit Hilfe von CO 5 BOLD gewonneneVorhersage betrifft die lange schon diskutiertenKohlenmonoxid-Wolken in der Sonnenatmosphäre. DerenExistenz ist schon lange bekannt, aber die räumliche Auflösungder Beobachtungen war bisher nicht ausreichend, dieseWolken wirklich zu lokalisieren. Unseren Berechnungennach sollte das Kohlenmonoxid (CO) in den kühlen Gebietender mittleren Photosphäre zu finden sein. Diese Simulationenzeigen zudem, dass die Rolle von CO bei der Strahlungskühlungder Chromosphärevernachlässigbar istund es deshalb nicht für diegroßen Temperaturfluktuationen,die in der Chromosphäreauftreten, verantwortlichsein kann, so wie esfrüher angenommen wurde.Die neueste Entwicklungim CO 5 BOLD - Code ist dasHinzufügen von Magnetfeldernund die Berechnung damitverbundener magnetohydrodynamischerEffekte.Erste Rechnungen mit einemin allen Höhenschichten homogenenvertikalen Magnetfeldals Anfangszustand zei-sional models, for which our in-house computing powerserves for test runs of the simulations in order to apply forsuper-computing time at, e.g., the High Performance ComputingCenter in Stuttgart or the John von Neumann Institutefor Computing in Jülich.Development 2004–2005Connecting to the ChromosphereWith the CO 5 BOLD code we recently achieved to extendsimulations of the solar surface layers into the chromosphere,accounting for chemical reaction networks, magneticfields, and even for the time-dependent ionization andlevel population of hydrogen. This unique tool enables usto focus research on the poorly understood but fiercely debatedcoupling of the convective zone and the photosphereto the chromosphere. Our simulations of the solar chromospherepredict that the future Atacama Large MillimeterArray (ALMA) – to be finished in 2012 – will see a networkof hot gas and enclosed cool regions if directed inquiet, field-free regions of the Sun. Fig. 8 shows the correspondingsynthetic observation from our simulations. Likewise,we predict that the elusive carbon monoxide cloudsin the solar atmosphere that were since long detected butnot spatially resolved are located in the cool regions of thereversed granulation pattern at mid-photospheric heights.The simulations also show that the role of carbon monoxideas a cooling agent is a minor one and that it is not responsiblefor the large thermal fluctuation in the chromosphere,as was previously thought. Recently we finished afirst MHD-simulation run of the integral layers from theconvection zone to the chromosphere with an initially homogeneousvertical magnetic field. Surprisingly, we findFig. 10: Magnetfeldstärke in drei Horizontalschnitten von 4800 x 4800 km durch eine magnetohydrodynamischeSimulation in der Konvektionszone (links) an der Sonnenoberfläche (Mitte) und inder Chromosphäre (rechts).Horizontal sections of 4800 x 4800 km through a magnetohydrodynamic simulation showing themagnetic field strength in the convection zone (left), the solar surface (middle), and the chromosphere(right). (Schaffenberger, Steiner, Wedemeyer-Böhm)33


COMPUTER-SIMULATIONENThe correlation time of the velocity field and the turnovertime of convection was determined from numerical simulationsof convection. The ratio of these quantities, the Strouhalnumber, is the decisive number for the applicability ofthe first order smoothing approximation in the mean fielddynamo theory. The Strouhal number was found to be largeenough to suggest that higher than first order contributionsmight be important. Convection simulations in a rotatingframe of reference were carried out to gain a better understandingof the angular momentum transport in the convectionzone and hence of differential rotation. The main resultwas that the turbulent angular momentum transport dimingenüberraschenderweise, dass ein Zusammenschluss derFeldlinien zu einem mehr oder weniger horizontalen Magnetfeld(der sog. „magnetic canopy“) etwa in der Höhe erfolgt,in der die Chromosphäre gerade beginnt. Diese „magneticcanopy“ war schon aufgrund von Beobachtungen inden 70er Jahren postuliert worden, war aber in den letztenJahren dann wieder zunehmend in Zweifel gezogen worden.Das sehr dynamische Magnetfeld in der Chromosphäreweist außerdem noch zarte Filamente mit übernormalstarken Magnetfeldern aus, die in den Kompressionszonenvon durchwandernden Schockwellen entstehen. Die Simulationenmit CO 5 BOLD wurden bisher hauptsächlich aufdem KIS-eigenen 8-Prozessor SUN-Computer ausgeführt.Für umfangreichere Rechnungen soll der NEC SX-8 Supercomputerdes HLRS in Stuttgart benutzt werden – entsprechendeComputerzeit wurde bereits bewilligt.Um die benötigte Rechenzeit nicht zu groß werden zu lassenund trotzdem möglichst viel an physikalischer Komplexitätund Genauigkeit beizubehalten, ist es zuweilen sinnvoll,auf die volle mehrdimensionale Behandlung zu verzichtenund stattdessen nur 1D-Simulationen auszuführen.Genau dies geschieht in einigen die Ausbreitung von Wellenin stellaren Chromosphären simulierenden Programmen:Non-LTE Strahlungstransport und die Benutzung vonMulti-Level-Atommodellen für Wasserstoff, Kalzium undMagnesium sind nun möglich. Diese Simulationen wurdenausgeführt, um Skalierungsregeln für die Berechnung desgesamten Strahlungsverlustes der wichtigsten Emissionslinienin Chromosphären zu erhalten; solche Regeln sind unverzichtbar,will man mit vertretbarem Rechenzeitaufwandauch in 3D-Simulationen den auftretenden StrahlungsverlustenRechnung tragen.Fortschritte in der DynamosimulationEs wurde ein spezielles Verfahren zur Lösung der MHDGleichungen entwickelt in denen die Ausbreitung vonDruckwellen vernachlässigt wird – die anelastische Näherung.Mit dem entwickelten Algorithmus ist es möglichZeitschritte bis zu 100 Mal länger zu wählen als bei herkömmlichenVerfahren, so dass es möglich ist den unterenRand der Konvektionszone sehr viel realistischer als bisherzu simulieren. Hierbei konnte unter anderem gezeigtwerden, dass die Evakuierung die bei dem Ausbruch vonmagnetischem Fluss in der Dynamo-Schicht stattfindet einsehr wichtiger Mechanismus sein kann, um die Magnetfelderauf die extrem hohen Felder zu verstärken, die man dortvermuten muss.In einer weiteren Simulation wurden Eigenschaften derKonvektion bezüglich der Strouhal-Zahl untersucht, welchedas Verhältnis zwischen der Korrelationszeit des Ge-the formation of a canopy of more or less horizontal magneticfield at the base of the chromosphere, a structure thathas been inferred from observations in the seventies, butbecame very much doubted in more recent years. The verydynamic magnetic field in the chromosphere exhibits delicatefilaments of stronger than average field that form in thecompression zone of travelling shock waves. Simulationswith CO 5 BOLD were mainly carried out with the in-houseeight processor shared memory SUN computer. Large productionruns are planned to run on the NEC SX-8 computerof the HLRS in Stuttgart. Computing time has beengranted.Trading dimensionality for physical complexity and accuracywe performed one-dimensional simulations of wavepropagation in stellar chromospheres, taking full non-LTEradiative transfer and multi-level model atoms for hydrogen,calcium, and magnesium into account. Simulationswere carried out in order to derive scaling laws for the computationof the total radiation losses from major emissionlines in a highly dynamic chromosphere. Such scaling lawswill be indispensable if accounting for radiation losses inthree-dimensional simulations.Progress in Dynamo SimulationsA special code for the solution of a system of modifiedMHD-equations in which the propagation of pressurewaves is discarded (anelastic approximation) was developed.This approximation allows for up to 100 times largertime stepping than would be the case if information isallowed to propagate at the speed of sound. It enables thesimulation of a dynamo layer at the base of the convectionzone. The partial evacuation by disruption of field in thedynamo layer could be demonstrated to be a potentially importantmechanism of field amplification in stellar dynamos.Also the formation of flux tubes out of an initially homogeneousdynamo layer and their subsequent rise throughthe convection zone was for the first time simulated in threespatial dimensions.34


COMPUTER SIMULATIONSschwindigkeitsfeldes und der Zeitskala der Umwälzungmisst. Es hat sich gezeigt, dass die Strouhal-Zahl so großist, dass bei einer wesentlichen Näherung der Theorie dermittleren Felder, nicht nur die Terme 1. Ordnung wie normalerweiseangenommen, sondern auch die Terme höhererOrdnung beitragen können. Konvektionsrechnungen in rotierendenMedien wurden durchgeführt, um den Transportvon Drehimpuls beziehungsweise die differentielle Rotationder solaren Konvektionszone besser zu verstehen. DasHauptergebnis bestand darin, dass der turbulente Transportvon Drehimpuls mit der Erhöhung der Rotationsrate signifikantabnimmt, und dass die Rotationsrate einen wesentlichenEinfluss auf die Mischungsweglänge hat, mit welcherdie Effektivität der Konvektion parametrisiert wird. Inden tiefen Schichten der Konvektionszone ist diese um daszwei- bis fünffache erniedrigt.Wie wird die Korona geheizt?In den letzten beiden Jahren konzentrierten sich unsereBemühungen bei den Modellen der Korona insbesondereauf eine Beschreibung der dreidimensionalen Strukturund der Wechselwirkung der einzelnen Bausteine derKorona untereinander. Um die Korona zu untersuchen, habenwir Modelle betrachtet, in denen die Heizung durchein Verflechten der Magnetfeldlinien geschieht, was wiederumdurch horizontale Bewegungen an der Sternoberflächeverursacht wird. Zu diesemZweck haben wir den PEN-CIL-Code benutzt und diesendurch Physik-Module erweitert,insbesondere durch solche, dieWärmeleitung und Strahlungsverlustein das Modell einführen.Ebenso wurde eine zeitabhängigeRandbedingung implementiert,die es erlaubt, dieGeschwindigkeiten am unterenRand vorzugeben. Dies ermöglichtes, beobachtete Geschwindigkeitsfelderzu benutzen, sobaldsie in ausreichender Qualitätzur Verfügung stehen, etwamit Hilfe des neuen 1.5m-TeleskopesGREGOR. Derzeit benutzenwir unseren KIS-Linux-Cluster für Testrechnungen dieserSimulationen. In einem typischenLauf entwickeln wir die physikalischen Gleichungenmit Zeitschritten von etwa 0.02 Sekunden. Umeine halbe Stunde echte Zeit auf der Sonne abzudeckenmüssen wir somit etwa 100,000 Zeitschritte rechnen.Bei einer Rechnung auf einem Gitter mit 512 3 Zellenishes significantly as rotation is increased. It was also foundthat rotation has a profound effect on the mixing length ofconvection, in particular in deep layers of the convectionzone, where it is reduced by a factor of two to five.Heating the CoronaOver the last two years work on the simulation of coronalstructures concentrated on models that account for thefull three-dimensional structure, especially the interactionof different magnetic building blocks. Aiming at anunderstanding of the mechanism that heats the corona toa million degrees we account for the braiding of magneticfield lines induced by horizontal motions at the stellar surface.On the basis of the Pencil code we developed physicsmodules to include the relevant processes in the corona,especially heat conduction and radiative losses. Timedependentboundary conditions were implemented to prescribethe varying velocity and magnetic field at the lowerboundary. Once sufficiently accurate observations of thesolar surface fields that drive the corona become available,for example with the new 1.5m GREGOR telescope, they willserve as a constraint of the driving mechanism. Presentlywe use the in-house Linux cluster for test runs. In a typicalrun we evolve the physical equations on a time scaleof some 0.02 seconds. In order to advance half an hour ofreal time, which is desirable for an adequate simulation, weFig. 11: Momentaufnahme der Emission bei 10 6 K (in grün) und bei 10 5K (in rot) aus einer 3D-Simulation der Korona (60 Mm x 34 Mm)Snapshot of the emission at 10 6 K (in green) and at 10 5 K (in red) froma 3D simulation of the corona (60 Mm x 34 Mm).(Peter, Gudiksen & Nordlund)35


COMPUTER-SIMULATIONENentspricht dies etwa 10,000 Stunden auf einem modernenProzessor, entsprechend einigen Wochen auf dem 34-ProzessorKIS-Cluster. Für noch größere Simulationen werdenwir daher Rechenzeit an Super-Computer-Zentren beantragen.AusblickDa die numerischen Simulationen, die das Sonneninnereund ihre Atmosphäre beschreiben,zunehmend realistischerwerden, können wir hoffen, diese komplexen Systeme baldadäquat beschreiben zu können. Wie oben ausgeführt, beteiligtsich das KIS auf mehreren Gebieten an diesen Anstrengungen.Die neuen Simulationsrechnungen, die zu synthetischenBeobachtungsergebnissen führen, werden mithelfen, dieimmer umfangreicheren und hochwertigeren Beobachtungsergebnissezu verstehen. Diese werden beispielsweisevom neuen 1.5m-Teleskop GREGOR kommen, vom ballongetragenenSunrise-Teleskop mit 1m Öffnung, vom AdvancedTechnology Solar Telescope und von künftigen Weltraum-Missionenwie Solar-B, Solar Dynamics Observatoryund Solar Orbiter.Künftig werden Computersimulationen ein integraler Bestandteilder Datenauswertung sein, weil nur so die ganzeKomplexität der Sonne begriffen werden kann. Aufgrundder intensiven Zusammenarbeit zwischen den experimentellenund den theoretischen Gruppen ist das KIS bestensauf die neuen Herausforderungen der Sonnenphysik vorbereitet.would have to compute some 100,000 time steps. For simulationswith 512 3 grid-points, we will need approximately10,000 hours on a modern processor, which translates toa couple of weeks on our in-house 34 processor cluster. Foreven larger simulations we will therefore apply for computingtime at a super-computing center.OutlookAs the numerical simulations describing the physical processesin the Sun’s interior and atmosphere become moreand more realistic, we might hope to describe this verycomplex system adequately. As shown above, the KIS iscontributing to these efforts in various fields.The advanced simulations, providing synthetic observations,will help us to understand the increasing amountof high-quality observational data from new instruments,like the 1.5m ground-based telescope GREGOR, the 1m balloontelescope Sunrise, the 4m Advanced Technology SolarTelescope and future space missions like Solar-B, SolarDynamics Observatory or Solar Orbiter.Computer simulations will be an integral part of the dataanalysis process in the future, because only they can providethe complexity as found with the Sun. Through thevery intense interaction of its observational and theoreticalgroups, the Kiepenheuer-Institut is well prepared to facethese new challenges in solar physics.36


,n3m2,n2 COMPUTER SIMULATIONS1=m1,n1+1---State Computer averages codes presently (linear) used for simulations ---at the KISavg( i1,i2,i3)= wl(i1) * P( i1-1,i2,i• CANEM is a high-order finite-difference (1.0-wl(i1))* code for anelastic, compressible magnetohydrodynamics P(in i1Cartesi-,i2,ian geometry and three spatial dimensions. It is used for high-resolution local simulations of convection and dynamo-relatedprocesses in the lower half of the convection zone of the Sun and solar-type stars. Code development,M. Ossendrijver.--- Roe • CO---5BOLD averages: is a finite volume code for solving weightingthe hydrodynamic equations with in two or three sqrt(rho)spatial dimensions. It isbased on Riemann solvers and higher order reconstruction schemes, optionally including radiative transfer, magne-tic field, chemical networks, ionization in non-LTE, dust formation. This code, originally developed by B. Freytag,o_til(i1,i2,i3)=sqrt_rho(i1-1,i2,i3)*sqrt_rhois used for simulating processes from the convection zone to the chromosphere.www.astro.uu.se/co5bold/_main.htmlho=sqrt_rho(i1-1,i2,i3)/(sqrt_rh• DP is a finite difference code for astrophysical hydrodynamical simulations in 2D or 3D Cartesian and cylindrical_til(geometry, parallelized with MPI. The discretization is accurately up to 10th order (spatially) and 5th order in time.i1,i2,i3)=wrho*(v1(i1-1,i2,i3)-v1(This code is used for stellar convection including differential rotation. Code developed by Ch. Hupfer._til(••LOCOi1,i2,i3)=wrho*(v2(is a finite-difference code that works in Cartesian coordinates and i1-1,i2,i3)-v2(is used to simulate convection in localdomains including the effects of rotation and magnetic fields. The code is parallelized with MPI. The results of the_til(simulations are used to study the theories of convective turbulence and mean-field dynamos. Original code versioni1,i2,i3)=wrho*(v3(by S. E. Caunt and M. J. Korpi modified and extended by P. i1-1,i2,i3)-v3(Käpylä._til • MOVINGTUBE is a Lagrangian finite =wrho*(ei(difference code 2nd order accurate i1-1,i2,i3)-ei(for computing the dynamical evoluti-on of a one-dimensional magnetic flux tube in two-dimensional space. The tube is treated in either the thin-tubeor two-mode approximation. It is used for the simulation of penumbral filaments. Code authorship R. Schlichenmaierand K. Jahn.---Derived •PENCILis a high-order Roe finite-difference averagescode for compressible ---hydrodynamic flows with magnetic fields in threespatial dimensions. It is used for the simulation of stellar dynamos, dynamo experiments, magnetohydrodynamictil(i1,i2,i3)turbulence, and coronal magnetic = fields. rho_til(i1,i2,i3)/(sqrt_rho(i1Code developed by A. Brandenburg and W. Dobler, www.nordita.dk/data/brandenb/pencil-code/(P(i1-1,i2,i3)/sqrt_rho(i1• Re_6-6 is a magnetohydrodynamic code in two-dimensional Cartesian coordinates with a finite volume, flux cor-rected transport scheme, automatic adaptive mesh refinement, and constrained solenoidal magnetic field transport.It is used for the simulation of magneto-convective processes P(i1and flux-tube ,i2,i3)/sqrt_rho(i1wave interactions. Code developed byO. Steiner on the basis of the AMR-code (rho_til(i1,i2,i3)/(sqrt_rho(iof M. Berger.• SONNE is a descendant of the stellar evolution code of R. Kippenhahn et al., adapted to the special needs of theSun, with tables for the equation of state and the opacity, a mixing-length formalism of convection that permitsovershooting, the possibility of gravitational settling of helium, and a calculation of the neutrino emission. It can beused in combination with a code that calculates the frequencies of p-mode oscillations.( (v1(i1,i2,i3)-v1(i1-1,i2,i3)(v2(i1,i2,i3)-v2(i1-1,i2,i3)(v3(i1,i2,i3)-v3(i1-1,i2,i3)• TTRANZ is a code with an adaptive grid solving the one-dimensional equations of mass, momentum and energybalance together with the ionization rate equations for a given number of atomic species in an optically thin gas. Itis based on an implicit conservative upwind method. Code developed by Viggo Hansteen.• VAC is a versatile advection code for the integration of the system of hydro- and magnetohydrodynamic equati-ons. It uses different finite volume schemes including Riemann solvers. Parallelization with HPF. Code developmentby G. Tóth and R.Keppens, www.phys.uu.nl/~toth•WAVEis a 1-D code for time-dependent acoustic and MHD wave calculations, which is based on the method===Boundary of characteristics, treating conditions shocks as real discontinuities. Time-dependent III ===element ionization and NLTE radiativetransfer for the most important chromospheric lines and continua is included. WAVE is used for the simulation oftil(i1,i2,i3)=(1.0-mask_bound_l(i1)-mask_boundstellar atmospheres from the photosphere to the transition region. Code by W. Rammacher and P. Ulmschneider.mask_bound37


FORSCHUNGS-SCHWERPUNKTEDie Sonne verstehenUnderstanding the sunWith the most powerful solar telescopesand advanced computer simulations theKiepenheuer-Institut endeavors to unveil thepuzzles of the Sun‘s magnetism.Die Sonne ist der Schlüssel zum Verständnis der Sterne.Dank ihrer Nähe ist sie der einzige Stern, auf dessen OberfächeDetails erkennbar sind. Der Reichtum an Strukturund Aktivität, den wir auf der Sonne sehen, Übersteigt dieMöglichkeiten irdischer Labors bei weitem. Das Kiepenheuer-Institutfür Sonnenphysik führt experimentelle undtheoretische Grundlagenforschung in der Astrophysik mitbesonderemSchwerpunkt in der Sonnenphysik durch. Zusammenmit drei Partnerinstituten betreibt das Kiepenheuer-Institutdie deutschen Sonnenteleskope aufTeneriffa.Mit dem 1.5m-Teleskop GREGOR, das Ende 2005 fertiggestelltsein wird, wird dem Institut das leistungsfähigsteSonnenteleskop der Welt zur Verfügung stehen. Das Kiepenheuer-Institutkooperiert mit deutschen Partnerinstitutensowie mit führenden Forschungseinrichtungen in denUSA, Europa und anderen Teilen der Welt.Der Forschungsplan 2002–2007 des Kiepenheuer-Institutsträgt den Titel ,,Die Sonne verstehen‘‘. Darin sind diewissenschaftlichen Projekte des KIS in vier Forschungsschwerpunktenzusammengefasst. Darüber hinaus beschreibtder Forschungsplan die instrumentellen Projektedes Instituts.Understanding the Sun is the key to understanding the stars.Thanks to its vicinity to Earth, the Sun is the only star thatcan be scrutinized in detail. On the Sun we see a wealth ofstructure and activity, far beyond of the phenomena thatcan be studied in a laboratory on Earth. The Kiepenheuer-Institut für Sonnenphysik conducts experimental and theoreticalresearch in fundamental astronomy and astrophysics,with particular emphasis on solar physics. In cooperationwith three partner institutions the institute operates theGerman solar telescopes on the island of Tenerife, Spain.With the 1.5-m telescope GREGOR, to be completed in 2005,the Kiepenheuer-Institut will have the world’s most powerfulsolar telescope. The Kiepenheuer-Institut cooperateswith German partner institutions, as well as with leadingresearch institutions in the United States, Europe, and otherparts of the world. The Research Plan 2002 - 2007 of theKiepenheuer-Institut is entitled “Understanding the Sun”.The plan groups the scientific projects of the institute intofour research foci. In addition, the Research Plan describesthe development of instruments that will be used by the solarobservers in their experimental work.Dieses Kapitel enthält eine Zusammenfassung des aktuellen Forschungsplans2002-2007 des KIS, gefolgt von einer kurzen Übersichtder Aktivitäten in den vier Forschungsschwerpunkten. Diezugehörigen referierten Publikationen sind am Ende des jeweiligenAbschnitts aufgelistet. Die vollständige Publikationslistebefindet sich am Ende dieses Berichts.This chapter contains a summary of the present research plan2002-2007 of the KIS, followed by a brief description of our activitiesin the four research foci. The corresponding refereed publicationsare listed at the end of each section. The full list ofpublications is at the end of this report.38


RESEARCH FOCIDie Projekte des Kiepenheuer-Instituts sind in vier Forschungsschwerpunktenzusammengefasst. Das System dessolaren Magnetismus verbindet diese Schwerpunkte:Konvektion, Rotation,DynamoDieser Schwerpunkt befasst sich mit denMaterieströmungen der Konvektionszoneund mit dem Ursprung des solaren Magnetfelds.The research projects of the Kiepenheuer-Institut are organizedinto four main areas. The system of solar magnetismis the link between these research foci:Convection, Rotation,DynamoThis research focus deals with the materialflow in the convection zone, and with theorigin of the Sun‘s magnetic field.SonnenfleckenZiel der Erforschung dieses am besten bekannten,jedoch in vieler Hinsicht immernoch unverstandenen Phänomens des solarenMagnetismus ist ein konsistentes magnetokonvektivesSonnenfleckenmodell.SunspotsSunpots constitute the best known and yet,in many respects, little understood manifestationof solar magnetism. Research atKIS focuses at a consistent magneto-convectivesunspot model.Feinstruktur derPhotosphäreDie Feinstruktur gilt als Schlüssel zum Verständnismagnetischer Strukturbildung undder Wirkung des Magnetfelds auf den konvektivenEnergietransport.Fine structure of thephotosphereThis focus aims at understanding magneticstructure formation and convective energytransport in the presence of a magnetic field.Chromosphäre, Koronaund solar-stellareBeziehungenDie Erforschung der äußeren Atmosphäreder Sonne zielt auf deren Struktur und Dynamik,und den Heizungsmechanismus.Solar-stellare Beziehungen erhellen dieStellung der Sonne unter den Sternen.Chromosphere, Corona,and Solar-stellarConnectionsResearch on the outer atmosphere of theSun is directed towards its structure anddynamics, and the heating mechanism. Investigationof the solar-stellar connectionallows apprehending the Sun‘s positionamong the stars.39


FORSCHUNGS-SCHWERPUNKTEKonvektion, Rotation, undDynamoDie differentielle Rotation und die konvektive Strömungspielen eine Schlüsselrolle im Dynamoprozeß, der das solareMagnetfeld erzeugt. Auf der Oberfläche und in derKorona wurden die Entwicklung der solaren Granulationund die differentiellen Rotation durch die Untersuchungvon hochaufgelösten Spektrogrammen und Aufnahmender ganzen Sonnenscheibe im fernen Ultraviolett bestimmt[041, 045]. Anhand der Rotationsgeschwindigkeit konntenachgewiesen werden, dass wiederkehrende und nicht wiederkehrendeSonnenfleckengruppen bei ihrer Entstehungverschieden tief verankert sein müssen [055].Mit Hilfe des Virialtheorems konnte eine mögliche Verbindungzwischen der Variation der solaren Abstrahlungwährend des Sonnenzyklus und der zyklischen Erzeugungmagnetischer Energie durch den Interface-Dynamo hergestelltwerden.Um den Drehimpulstransport in der Sonne und in Sternenzu verstehen, befassten sich numerische Simulationen mitdem Reynoldschen Spannungstensors und weiterer Größenwie Rotation und Magnetfeld [048, 078]. Zur Erklärung derausgedehnten Minima in der langfristigen solaren Aktivitätkonnte anhand eines 2D Dynamomodells nachgewiesenwerden, dass durch die Ausdehnung des Attraktors solcheMinima intermittent ausgelöst werden [020].Es wurden numerische Simulationen der Prozesse, die amBoden der solaren Konvektionszone in engem Zusammenhangmit dem Dynamo stehen, mittels der anelastischenNäherung durchgeführt, so auch z.B. die Simulation dermagnetischen Feldverstärkung durch Evakuation [090].Simulationsrechnungen der solaren Granulation reproduzierenden Intensitätskontrast und die Zeitskalen von beobachtetenHelligkeitsmustern in den Flügeln von Ca II H.Daraus folgt, dass magnetische Einflüsse bei der Ausbildunginverser Granulation unbedeutend sind [083].Die Bestimmung der Eigenfrequenzen akustischer Schwingungsmodi,die durch Konvektionsrollen in einem durchdie Schwerkraft geschichteten Medium beeinflusst werden,bestätigte die Frequenzverringerung früherer ungeschichteterModelle [063]. Erste Ergebnisse helioseismischer Inversionen,die auf der Konvektions-Oszillations-Wechselwirkungberuhen, weisen auf eine sich mit dem Zyklus veränderndeStruktur der meridionalen Zirkulation hin.Convection, Rotation, andDynamoThe differential rotation and the convective flow play a keyrole in the dynamo process that generates the solar magneticfield. On the surface and in the corona, the evolutionof the solar granulation and the properties of the differentialrotation have been determined by the investigation ofhigh-resolution spectrograms and by full-disc solar imagesin the extreme ultraviolet, resp. [041, 045]. By determiningthe rotation velocity, recurrent and non-recurrent sunspotgroups were identified to have different anchoring depthsat their birth [055].With the help of the virial theorem, a possible connectionbetweenthe variation of the solar irradiance over the solarcycle and the cyclic generation of magnetic energy by theinterface dynamo has been established.For understanding the transport of angular momentum inthe Sun and the stars, numerical simulations dealt with therole of the Reynold stress tensor and further quantities,e.g. ,rotation and large-scale magnetic field [048, 078]. Explainingthe grand minima in long-term solar activity, evidencehas been given by a 2D non-linear mean field dynamomodel that such intermittent minima are due to changesin the dimension of the attractor [020].Furthermore numerical simulations of the dynamo relatedprocesses near the bottom of the solar convection zone usingthe anelastic approximation were carried out, e.g., simulationsof the magnetic field amplification by evacuation[090].Simulations of the solar granulation allowed reproducingthe intensity contrast and the time scales of subsonicbrightness patterns observed in the wings of Ca II H-K. Itwas concluded that the magnetic effects are not importantin the formation of reversed granulation [083].The calculation of the eigenfrequencies of acoustic wavemodes affected by a model that includes convection rollsand stratification due to gravity confirms the frequency decreaseof earlier non-stratified models [063]. First results ofhelioseismic inversion techniques based on the earlier studiesof convection-oscillation interaction indicate a varyingstructure of the meridional circulation with the solar cycle.Involved KIS staff: R. Brajsa, J. Bruls, W. Dobler, Ch. Hupfer, P. Käpylä, J. Leenaarts, M. Ossendrijver, A. Nesis, M. Roth, H. Schleicher,O. Steiner, M. Stix, S. Wedemeyer-Böhm, H. Wöhl, Y.D. ZhugzhdaStudents: L. KriegerReferences: 010, 011, 015, 020, 023, 024, 026, 036, 041, 042, 045, 046, 047, 048, 055, 061, 074, 078, 079, 080, 081, 083, 090,091, 097, 099, 103, 104, 108, 110, 11140


RESEARCH FOCISonnenfleckenBei der Erforschung der Sonnenflecken haben wir uns aufdie spektroskopischen und spektropolarimetrischen Eigenschaftenphotosphärischer Absorptionslinien konzentriert.Mit TESOS-Daten wurden mittels Vorwärtsmodellen neueErkenntnisse zur Geometrie des Strömungsfeldes gewonnen[058, 095]. Um den Informationsgehalt zu optimierenwurden mit TIP und POLIS [070] simultan die spektropolarimetrischenEigenschaften von verschiedenen magnetischempfindlichen Eisenlinien bei 1564.8 nm and 630.2nm vermessen. Da Zeeman- und Dopplereffekt in diesenbeiden Wellenlängenbereichen unterschiedliche Auswirkungenauf die Linienprofile haben und die Linien in unterschiedlichenSchichten enstehen, konnte der tiefenabhängigenVerlauf der Atmosphäre rekonstruiert werden [102].Wir haben neue Inversiontechniken entwickelt, die daraufbasieren, dass die Penumbra eine „ungekämmte“ Strukturhat und aus zwei magnetischen Komponenten besteht:eine vorwiegend horizontale Komponente, die die starkeEvershed-Strömung innerhalb einer Röhre beherbergt, undeine geneigtere Komponente die den strömungsfreien magnetischenHintergrund darstellt [001, 002, 003, 038, 040].Unter der Annahme, dass eine Sichtlinie beide Komponentendurchqueren kann, sind wir in der Lage, die beobachtetenLinienasymmetrien zu reproduzieren [107].Die Auswertung räumlich hochaufgelöster Bilder von Penumbrenhat sich mit den kürzlich entdeckten „dunklenKernen“ in penumbralen Filamenten beschäftigt. UnsereDaten haben gezeigt, dass deren Erscheinung mit einerunerwarteten Asymmetrie gekoppelt ist: Sie sind aufder zentrumsseitigen Penumbra deutlicher ausgeprägt alsauf der randseitigen Penumbra. Wir vermuten, dass eindunkler Kern zusammen mit den beiden lateralen hellenKanten eine magnetische Flussröhre manifestiert, die dieEvershed-Strömung trägt [064,065].Theoretische Arbeiten konzentrieren sich auf die Entwicklungeines neuen Konzeptes zur Beschreibung magnetischerFlussröhren. Es wurde die ‚two-mode‘-Näherungentwickelt und auf horizontale Flussröhren angewendet.Hierbei ergeben sich soliton-artige Lösungen, in denenStoßwellen durch Dispersion unterdrückt werden. Somitist es möglich Stoßwellen, z.B. in der Penumbra, zu beschreiben,was im Rahmen der Näherung dünner Flußröhrennicht möglich ist [062,068].SunspotsSunspot research focussed on the measurement and interpretationof spectroscopic and spectropolarimetric data ofphotospheric absorption lines. The interpretation was performedusing forward modelling and inversion techniques.While TESOS suited to investigate the flow configuration[058, 095], TIP and POLIS [070] were used simultaneouslyto optimize the amount of spectropolarimetric information.Measurements of neutral iron lines around 1564.8 nm and630.2 nm, provide information of different layers of the solarphotosphere and are differently affected by the Dopp–ler and Zeeman effects, allowing to retrieve the depth dependenceof the physical variables [102].New inversion techniques were developed that are basedon the assumption that the penumbra has an “uncombed”structure and consists of two components [001, 002, 003,038, 040]. Two component models were used to demonstratethat a more horizontal flow component and a less inclinedbackground component reproduce the measuredStokes profiles [107]. In an attempt to incorporate the scenarioof the uncombed penumbra, i.e. an essentially horizontalflux tube carrying the Evershed flow being embeddedin a less inclined background, a two-component techniquewas developed that mimics the inclined flow channelby a gaussian variation superimposed on the background.Thereby, discontinuities along the line-of-sight can be describedand first results show that such inversions can reproducethe properties of the line asymmetries.High spatial resolution observations concentrated on thenewly discovered ‘dark cores’ in bright penumbral filaments,which are thought to be the building blocks of thesunspot penumbra. Our measurements revealed an unexpectedasymmetry in the appearance of dark cores: theyare more prominent on the center-side penumbra than onthe limb-side penumbra. We speculate that dark-cored filamentsmanifest magnetic flux tubes that carry the Evershedflow [064, 065].Theoretical advances concentrate on the development of anew framework to describe magnetic flux tubes. Based onthe concept of thin flux tubes, the two-mode approximationwas developed and applied to horizontal flux tubes. It wasshown that the shock development is suppressed due to dispersionin the two-mode approximation leading to solitarylikewave solutions. Such waves are expected to be of relevancefor the sunspot penumbra [062, 068].Involved KIS staff: L. Bellot, C. Beck, R. Schlichenmaier, W. Schmidt, M.Stix, H. Schleicher, A. Tritschler, H. Wöhl, Y. ZhugzhdaStudents: G. Fritz, A. BitzerReferences: 001, 002, 003, 012, 016, 027, 028, 029, 030 038, 039, 040, 058, 059, 062, 064, 065, 070, 072, 095, 102, 105, 10741


FORSCHUNGS-SCHWERPUNKTEFeinstruktur derPhotosphäreDie Beobachtung und die theoretische und numerischeBehandlung der kleinskaligen Phänomene der Sonnenatmosphäresind wichtig für unser Verständnis der Wechselwirkungvon Konvektion, Strahlung und Magnetfeldan der Sonnenoberfläche. Die Beobachtungen umfassenspektropolarimetrische Messungen von magnetischenFlussröhren, Spektroskopie und Fotografie von „brightpoints“, Untersuchungen der allgegenwärtigen Granulationund schmalbandige Abbildungen der chromosphärischenDynamik. Mit numerischen Modellen werden Spektrallinienberechnet und Temperatur- und Geschwindigkeitskartenvon verschiedenen Schichten der Atmosphäre erstellt.Aus Serien von Spektren ermittelten wir Temperaturfluktuationen.Dabei fanden wir Hinweise auf einen hydrodynamischeSchock in der Granulation, der von überschallschnellerhorizontaler Bewegung herrührt, was mit einemnahegelegenen G-band bright point in Verbindung zu stehenscheint [017, 045, 056, 090]. Granulen, die kleiner sindals 1200 km zerfallen rasch mit der Höhe, während größereweiter aufsteigen können [087].Aus Intensitätsspektren fanden wir, dass es verschiedeneArten von bright points gibt, die unterschiedliche spektraleSignaturen haben. Wir fanden weiterhin, dass der zusätzlicheKontrast nur bei den bright points innerhalb von intergranularenBereichen durch die Schwächung der CH-Linienverursacht ist. Wir fanden bright points, die keine Bewegungrelativ zu ihrer umgebung zeigen, allerdings beobachtetenwir eine starke Abwärtsströmung während der Entstehungeines bright points [018, 049, 071]. Neuere hochaufgelösteBeobachtungen von Fackeln wurden auf der Basiseines Flussröhrenmodells interpretiert. Es wurde gezeigt,dass der Querschnitt, der für die Strahlung verantwortlichist, größer ist als die Flusskonzentration selbst. Das Modellerklärt die randseitige Ausdehnung von Fackeln ebensowie den zentrumsseitigen dunklen Bereich [034].Aus dreidimensionalen Simulationen mit dem MHD-codeCO 5 BOLD folgt, dass CO hauptsächlich in kühlen Zonender mittleren Photosphäre zu finden ist. Numerische Resultatemit diesem Programm wurden verglichen mit Beobachtungenvon inverser Granulation. Weiterhin wurden(Sub)-Millimeter-Bilder berechnet, wie sie künftigmit ALMA beobachtet werden könnten. Diese Berechnungenzeigen eine sehr inhomogene und dynamische Chromosphäre,als Folge der Ausbreitung und Wechselwirkungvon akustischen Wellen [067, 101, 222].Fine structure of thephotosphereThe observation and the theoretical and numerical treatmentof the small-scale phenomena in the solar photosphereare of key importance for our understanding of the interactionbetween convection, radiation and magnetic fieldat the solar surface. The observational work includes thespectropolarimetric measurements of magnetic flux tubes,spectroscopy and imaging of photospheric bright points,studies of the ubiquitous granulation and narrow-band imagingof the chromospheric dynamics. Numerical modellingis used to calculate spectral lines and synthetic temperatureand velocity maps of different layers of the solaratmosphere.From sequences of spectra of the granulation we derivedthe variation of the temperature. We found evidence for ahydrodynamic shock in the granulation caused by supersonichorizontal motion. The shock seems to be related to anearby G-band bright point [017, 045, 056, 090]. We showedthat granular structures smaller than about 1200 km decayrapidly with height, whereas larger ones penetrate moreeasily into higher layers [087].From intensity spectra we found that different kinds of G-band bright points exist that have different spectral signaturesand that the weakening of the CH-lines is responsiblefor the excess contrast only in those bright points that residein intergranular lanes. In several cases we found brightpoints that show no distinct motion relative to their surroundings,whereas during the formation of a bright pointa vigorous downflow is observed [018, 049, 071]. Recenthigh resolution white light observations of faculae were interpretedon the basis of a model of simple magnetic fluxconcentration with a „hot wall“. It is shown that the crosssectionalarea that effects radiative escape from faculae islarger than the magnetic field concentration. The model explainsthe observed limbward extent of facular brighteningand the centerward dark facular lane [034].From three-dimensional simulations using the (M)HD codeCO 5 BOLD we found that the CO molecule is mainly presentin the cool regions of the middle photosphere. The samecode was also used to compare numerical results with observationsof reversed granulation and to predict intensityimages at (sub-)millimeter wavelengths as they could beobserved by future instruments like ALMA. These calculationsare based on a 3D model that features a very inhomogeneousand dynamic chromosphere as result of acousticwave propagation and interaction [067, 101, 222].Involved KIS staff: C. Beck, L. Bellot Rubio, P. Brandt, J. Bruls, W. Kalkofen, K. Langhans, K. Mikurda, A. Nesis, M. Roth, R. Schlichenmaier,W. Schmidt, O. Steiner, M. Stix, A. Tritschler, S. Wedemeyer-Böhm, H. WöhlReferences: 006, 017, 018, 025, 034, 035, 044, 045, 049, 056, 057, 063, 066, 067, 068, 071, 077, 082, 084, 087, 088, 089, 098,101, 10642


RESEARCH FOCIChromosphäre, Korona undsolar-stellare BeziehungenSeit der Entdeckung vor über 60 Jahren, dass die Koronader Sonne über eine Million Grad heiss ist, liegt der Prozeßder koronalen Heizung im Dunkeln. Wir untersuchen diekomplexe schnell veränderliche Korona indem wir sowohleinzelne Bausteine der Korona wie auch die dreidimensionalemagnetische Struktur mit Hilfe von Modellen untersuchen.Dabei synthetisieren wir Profile von EUV-Emissionslinienaus den Modellen, um diese mit Beobachtungen zuvergleichen, wobei vor allem SUMER und CDS auf SOHObenutzt werden [069, 014, 043].Mit Hilfe von 1D-Modellen konnten wir zeigen, dasskoronale Bögen thermisch instabil sein können, was einenatürliche Erklärung für sog. koronalen Regen gibt [075,086]. Den Fingerabdruck des chromosphärischen magnetischenNetzwerkes in der oberen Korona konnten wir in 2D-Modellen koronaler Trichter zeigen [168].In einer neuen Zusammenarbeit haben wir die EUV-Emissionuntersucht, die wir aus einem 3D-MHD-Modell derKorona synthetisiert haben und eine gute Übereinstimmungmit Beobachtungen zeigt [053]. Dies favorisiert dieim Modell benutzte Heizung der Korona durch Verflechtenvon Magnetfeldlinien mit anschliessender Dissipationder resultierenden Ströme. Wir erweitern nun diese MHD-Modelle, inbesondere in Hinblick auf die räumliche Komplexität.Während in den Koronamodellen bisher die Chromosphärenicht ausreichend genau beschrieben wird, berücksichtigenwir Strahlungs- und Ionisationsprozesse in 1D Modellender dynamischen Chromosphäre [093, 100]. Hierbei wurdeuntersucht, in wie weit mittlere Temperaturen eine sinnvolleBeschreibung darstellen [092]. Das chromosphärischePhänomen der nadelartigen Spikulen wurde neuerlich untersuchtund ein Mechanismus basierend auf einem starkenAbfall des Drucks in der Korona vorgeschlagen [212].Zur Untersuchung der solar-stellaren Beziehungen habenwir zwei Projekte gestartet, in denen stellare Spektren basierendauf solaren Strukturen synthetisiert werden, umstellare EUV-Emissionslininen zu studieren. In einem anderemProjekt wurden anahnd von Radialgeschwindigkeitenund chromosphärischer Aktivität gezeigt, dass auf RiesensternenStrukturen existieren, die mit dem Very LargeTelescope Interferometer sichtbar sein sollten [060]. Dabeikonnten wir auch substellare Begleiter um G- und K-Riesensternenachweisen [032, 096].Chromosphere, corona andsolar-stellar connectionSince the discovery over 60 years ago that the corona ofthe Sun consists of a million degrees hot plasma , the physicalnature of the heating process remains elusive. We investigatethe spatially complex and highly dynamic coronaby studying individual structures, like loops or funnels,and by analysing the dynamics induced through the complexmagnetic structure via 3D models. Synthesizing EUVemission line profiles from these models allows us to comparethem in detail to observations, for which we primarilyutilized the SUMER and CDS spectrographs on-boardSOHO [069, 014, 043].Using 1D models we showed that loops are subject to thermalinstabilities, giving a natural explanation for observationssuch as catastrophic cooling and coronal rain [075,086]. In 2D models of coronal funnels we showed that thereis an imprint of the chromospheric magnetic network in thehigh corona.In a new collaboration we investigated the EUV emissionline spectra from a 3D MHD model of the corona. The derivedDoppler shifts and emission measures compare verywell to the observations [053]. This strongly favours theheating mechanism underlying the 3D MHD model, namelybraiding of magnetic field lines and subsequent dissipationof the induced currents. We are now pursuing to advancethese forward models, especially with respect to thespatial complexity.While in the coronal models there is, as yet, no propertreatment of the chromosphere included, we accountfor radiative and ionization processes in 1D time-dependentchromospheric models [093, 100]. We analysed underwhich circumstances mean temperatures and ionization degreesare useful [092]. The chromospheric phenomenon ofthe needle-shaped spicules was re-investigated to proposea new mechanism based on a strong decrease of coronalpressure [212].To study the connection between the Sun and solar-likestars we started two projects synthesizing stellar spectrabased on solar structures to investigate stellar EUV emissionlines. In another stellar project the observations of radialvelocities and chromospheric activity of red giant starsshowed that surface structures might be resolvable usingthe Very Large Telescope Interferometer [060]. These observationsalso gave evidence for substellar companionsaround G and K giants [032, 096].Involved KIS staff: T. Aiouaz, S. Bingert, A. Brkovic, R. Hammer, D. Müller, H. Peter, W. Rammacher, O. von der Lühe, H. WöhlStudents: S. Graves, S. Jenderie, C. Prahl, P. ZachariasReferences: 007, 008, 009, 013, 014, 019, 021, 022, 031, 032, 037, 041, 043, 052, 053, 060, 069, 073, 075, 076, 086, 092, 093,094, 096, 100, 10943


TECHNISCHE ENTWICKLUNGEN & PROJEKTEDie Sonnenforschung im Kiepenheuer-Institut beruht aufeiner engen Kooperation zwischen experimenteller undtheoretischer Arbeit, sowie auf der langjährigen Erfahrungin der Entwicklung von Instrumenten zur Sonnenbeobachtung.Die theoretische Arbeit, ebenso wie die Analyse derBeobachtungsdaten, stützt sich auf die leistungsfähigenComputer des Instituts. Ein Netz von Workstations undPCs und ein Linux-Cluster bieten die Grundlage zur Datenanalyseund zu umfangreichen magneto-hydrodynamischenRechnungen. Darüber hinaus werden externe Hochleistungsrechnereingesetzt. Schwerpunkt der instrumentellenEntwicklung sind bodengebundene Teleskope undderen Zusatzgeräte. Das KIS nimmt jedoch ebenfalls anBallon- und Weltraumprojekten teil. Die wichtigsten instrumentellenProjekte sind:• Das Vakuum-Turm-Teleskop (VTT) auf Teneriffa,mit Echelle-Spektrograph, Polarimetern und adaptiverOptik.• Das 1.5m-Teleskop GREGOR, ein offenes Teleskopmit gekühltem Hauptspiegel und adaptiver Optik. MitGREGOR wird das KIS das leistungsfähigste Sonnenteleskopder Welt besitzen.• Das 18cm-Teleskop ChroTel, welches die Chromosphäreder Sonne gleichzeitig in drei Spektralbereichenabbilden wird.• Das 1m-Ballon-Teleskop SUNRISE. Das KISliefert in diesem internationalen Projekt ein Gerät zur Bildstabilisierungund Fein-Nachführung, das auf einem Shack-Hartmann Wellenfrontsensor basiert.• Das 4m-Sonnenteleskop ATST. Mit der beiGREGORerworbenen Expertise wird das Kiepenheuer-Institutan diesem ambitionierten US-amerikanischen Projektmitarbeiten.• Das Weltraum-Projekt SOLAR ORBITER.Diese F2-Mission der ESA wird der Sonne näher kommenals alle bisherigen Raumsonden. Das KIS wird Beiträgeliefern zum Imager and Magnetograph.Research in the Kiepenheuer-Institut relies on the close cooperationbetween experimental and theoretical physicists,and on the expertise in the development of instrumentsused for solar observations. Theoretical research as well asdata analysis depends on the large computer facilities of theinstitute. A net of workstations andPCs, and a Linux cluster,provide the capacity that is required to analyze the observationalmaterial, and to perform the necessary magneto-hydrodynamicalcalculations. External computing centersare being used additionally. Instrument developmentat the Kiepenheuer-Institut focuses on ground-based telescopesand telescope equipment. In addition, the instituteparticipates in balloon and space projects. The main instrumentalprojects are:• The Vacuum-Tower-Telescope (VTT) on Tenerife,with Echelle spectrograph, polarimeters and adaptiveoptics.• The 1.5m-telescope GREGOR, an open telescopewith cooled primary mirror and adaptive optics. WithGREGOR, the KIS will have the most powerful solar telescopein the world.• The 18cm-telescope ChroTel, which will imagethe solar chromosphere simultaneously in three wavelengthbands.• The balloon-borne telescope SUNRISE. TheKIS develops for the 1m-telescope of this international projectthe image stabilization and tracking unit, based on aShack-Hartmann wavefront sensor.• The 4m solar telescope ATST. The expertisegained in the GREGORproject will be most useful in theplanned cooperation in this ambitious US project.• The space project SOLAR ORBITER. ThisF2-mission of ESA will get closer to the Sun than any previousspacecraft. The KIS will contribute to the VisibleImager and Magnetograph instrument.44


TECHNICAL DEVELOPMENTS & PROJECTSZeitplan der instrumentellenEntwicklungen am KISSchedule for the instrumentaldevelopments at the KIS200405060708091011122013VTTMCAO@VTTVTT OperationChroTelConstruction & AssemblyFirst LightChroTel OperationGREGORTelescope AssemblyFirst LightGREGOR OperationSUNRISESystem Test FlightConstructionGondola Test FlightMCAO@GREGORFirst Long−Duration FlightFollow−up FlightsSOLARORBITERATST / VTFPayload Definition & AssessmentAnnouncement of OpportunityDesign & ConstructionATST Concept & DesignVTF Design & PrototypingVTF Construction, Test, ImplementationLaunchATST First Light45


TECHNISCHE ENTWICKLUNGEN & PROJEKTE1.5m-Teleskop GREGORGREGORist ein neues Sonnenteleskop mit einer Öffnung von1.5 Metern, das derzeit im Observatorio del Teide auf Teneriffa,Spanien, installiert wird. Es ist ein gemeinsames Projektdes Kiepenheuer-Instituts für Sonnenphysik, des AstrophysikalischenInstituts Potdsam, des Instituts für AstrophysikGöttingen und internationalen Partnern. GREGORist ausgelegt für hochauflösende Beobachtungen der solarenPhotosphäre und Chromosphäre im sichtbaren und infrarotenSpektralbereich und einer Auflösung von 70 kmauf der Sonne. GREGOR ist auch für stellare Nachtbeobachtungenvorgesehen.GREGOR ist ein offenes Teleskop, um Windkühlung derStruktur und der Spiegel zu ermöglichen. Es ist deshalbmit einer abklappbaren Kuppel ausgestattet, die 2004 ander TU Delft gebaut und getest wurde. Im Sommer 2004wurde die Kuppel nach Teneriffa verschifft und auf demGebäude installiert.Die Herstellung der Teleskopstruktur wurde im Mai 2004abgeschlossen, und die Installation im Observatorium aufTeneriffa erfolgte im Herbst desselben Jahres. Erste Testszeigen, dass die Anforderungen an das Nachführsystem erfülltsind.Die Renovierung des Gebäudes wurde in 2004 fortgesetzt,einschließlich der Installationen für Kommunikation. DieLieferung der großen Spiegel (M1, M2 und M3) ist für diezweite Jahreshälfte von 2005 geplant. Das „Erste Licht“soll es Anfang 2006 geben. Daran wird sich eine Phase derInbetriebnahme anschließen, bei der die adaptive Optikund die Fokalinstrumente installiert und getestet werden.Eines der ersten Fokalinstrumente wird ein zweidimensionalesSpektro-Polarimeter sein, mit zwei Fabry-Perot Interferometern.Ein Prototyp dieses Instruments wurde imFrühjahr 2005 am VTT erfolgreich getestet. Das zweite Instrumentist ein Spalt-Spektrograph für den sichtbaren undden infraroten Spektralbereich, wobei das Beugungsgitterdes früheren Spektrographen des Gregory-Coudé-Teleskopswiederverwendet wird. Eine Strehl-Zahl von 0.8 belegtdie optische Qualität dieses Instruments. Das Detektor-Systementspricht demjenigen von TIP II am VTT.Für Nachtbeobachtungen ist ein Echelle-Spektrograph mitGlasfaser-Einkopplung vorgesehen. Dieses Instrumentwird fernbedient werden können und soll im Jahr 2007 inBetrieb gehen.1.5m-telescope GREGORGREGORis a new solar telescope with a 1.5 m aperture thatis presently being assembled at the Teide Observatory, Tenerife,Spain. It is a project of the Kiepenheuer Institut fürSonnenphysik, the Astrophysikalisches Institut Potsdam,the Institut für Astrophysik Göttingen, and other nationaland international partners. GREGORis designed for highprecisionobservations of the solar photosphere and chromospherein the visible and infrared wavelength regime,with a resolution of 70 km on the Sun. GREGOR is also de-signed for night-time stellar observations.GREGORis designed as a fully open telescope to allow forwind-cooling of the structure and the mirrors. Thereforeit is equipped with a completely retractable dome, whichwas manufactured and tested in early 2004 at the TechnicalUniversity of Delft. In summer 2004 the dome was shippedto Tenerife and erected on the building.The manufacturing of the telescope structure was finishedin May 2004, and its installation on Tenerife was completedin autumn of the same year. First tests show that the performanceof the telescope pointing system meets the requirements.The refurbishment of the building continued during 2004,including installations for communication. Delivery of thelarge-size optics (M1, M2 and M3) is planned for the secondhalf of 2005. First Light is expected for early 2006, followedby a commissioning phase during which the adaptiveoptics and the focal plane instruments will be installedand tested.One of the first-light focal plane instruments will be a twodimensionalspectro-polarimeter with two Fabry Perot interferometers.A prototype of this instrument has alreadybeen successfully tested at the VTT in spring of 2005. Thesecond instrument is a slit spectrograph for the visible andthe infrared wavelength range. The grating of the formerGregory Coudé spectrograph will be reused. The opticalperformance calculations show a Strehl ratio around 0.8.The camera system is similar to the TIP II instrument currentlyused at the VTT.For night-time observations, a high-resolution fibre-fedEchelle spectrograph is foreseen. This instrument shall beoperated under remote control. Its integration is plannedfor 2007.Involved KIS staff: T. Berkefeld, P. Caligari, C. Halbgewachs, W. Schmidt, M. Sigwarth, D. Soltau, R. Volkmer, O. von der LüheReferences: 004, 033,085, (conference contributions: 115, 133, 134, 163, 164, 165, 171, 186, 207)46


TECHNICAL DEVELOPMENTS & PROJECTSSunrise BallonteleskopSunrise ist ein ballongetragenes Sonnenteleskop mit einerÖffnung von 1 m, das Sonnenbeobachtungen im sichtbarenund ultravioletten Wellenlängenbereich durchführenwird. Im UV wird Sunrise eine Auflösung von 0.05 Bogensekundenerzielen und Strukturen bis zu einer Größe von35 km erkennen. Das Teleskop ist mit einem Spektro-Polarimeter,einem Magnetographen und einem Filtergraphenausgestattet. Der erste Langzeitflug über der Antarktis istfür Dezember 2008 geplant. Sunrise ist ein internationalesProjekt unter der Leitung des MPS in Lindau, mit Beteiligungdes HAO, Boulder, von LMSAL, Palo Alto, desIMAX-Konsortiums (La Laguna, Granada, Madrid) unddes KIS.Das KIS baut für Sunrise die Anlage zur Bildstabilisierungund Feinnachführung, verbunden mit einem Wellenfrontsensor,der zur automatischen Fokussierung und Justierungdes Teleskops während des Flugs vorgesehen ist (CorrelatingWavefront Sensor, CWS). Der Wellenfrontsensor verwendeteinen Shack-Hartmann-Sensor mit 18 Subaperturenzur Messung von Defokus und Koma. Die Korrekturdieser Aberrationen erfolgt durch Bewegung des Sekundärspiegelsbzw. eines Fokussierspiegels.Für die Bildstabilisierung wird ein zweistufiger Kippspiegelentwickelt, der gleichzeitig einen großen Verstellbereichvon ± 30 Bogensekunden und im Servobetrieb eine Bandbreitevon mindestens 30 Hz hat. Zu diesem Zweck wirdein piezogetriebener Spiegel eingebaut in einen Grobantrieb,der seinerseits motorisch um zwei zueinander senkrechteAchsen kippbar ist. Der Grobantrieb wird mit einerBandbreite von ca. 0.2 bis 1 Hz die systematischen Bildbewegungenausgleichen, die innerhalb eines Zeitintervallsvom Feinantrieb kumuliert wurden. Ziel ist es, eine Bildstabilitätvon 0.005 Bogensekunden zu erreichen.Eine wichtige Anforderung an das Gerät, und insbesonderean die Software ist der robotische Betrieb während desFlugs, wenn es keine oder nur sehr geringe Möglichkeitengibt, vom Boden aus in die Abläufe einzugreifen.Im Juli 2005 findet der erste Test des CWS am VTT aufTeneriffa statt. Dort werden mit Hilfe der adaptiven Optikbestimmte Aberrationen vorgegeben, die dann vom CWSermittelt werden. In ähnlicher Weise wird auch Bildbewegungunterschiedlicher Amplitude und Frequenz erzeugt,die dann vom CWS kompensiert werden soll.Sunrise balloon telescopeSunrise is a balloon-borne telescope with an aperture of 1mthat will observe the sun in the visible and ultraviolett wavelengthrange. In the UV, Sunrise will achieve a spatial resolutionof 0.05 arcs and detect structures with a size of 35km. The telescope is equipped with a spectro-polarimeter,a magnetograph and a filtergraph. The first long-durationflight above Antarctica is planned for December 2008. Sunriseis an international project led by the MPS in Lindau,with participation of the HAO in Boulder, LMSAL in PaloAlto, the Spanish IMAX consortium, and the KIS.The KIS develops a unit for image stabilization and fineguiding in combination with a wave-front sensor that willallow for automatic focussing and telescope alignment duringthe flight (Correlating wave-front sensor, CWS). Thewave-front sensor is based on the adaptive optics systemthat has been developed for the solar telescopes on Tenerife.It uses a Shack-Hartmann sensor with 18 sub-aperturesfor the measurement of defocus and coma. These aberrationsare corrected for by moving the secondary mirror ofthe telescope and a focus mirror stage.For the image stabilization we developed a dual-stage tiptiltmirror that has both a large tilt range of ± 30 arcs (onthe sky) and a high bandwidth which allows for a closedloopoperation of 30 Hz or more. To this end, a commerciallyavailable piezo-driven mirror (fine drive) has beenmounted inside a motorized coarse drive that can be tiltedaround two orthogonal axes. The coarse drive will operateat a bandwidth of 0.2 to 1.0 Hz and will compensate for allsystematic effects that have been accumulated by the finedrive during a specific time interval. We plan to achieve animage stability of 0.005 seconds of arc.A key requirement for the device and especially for the softwareis the robotic operation during the flight, when thereis little or no possibility to control the procedures from theground. This holds both for the regular operations, i.e. allobserving programs as well as for the handling of errorconditions.The first test at the VTT on Tenerife takes place in Julyof 2005. The adaptive optics of the VTT will be used togenerate known aberration states. These will then be measuredby the CWS. Similarly, image motion will be producedwith different amplitude and frequencies and thendetected and compensated by the CWSInvolved KIS staff: T. Berkefeld, B. Feger, R. Friedlein, K. Gerber, F. Heidecke, T. Kentischer, W. Schmidt, M. Sigwarth, D. Soltau, E.Wälde.References: 051, (conference contributions: 145, 153,154, 179, 201)47


TECHNISCHE ENTWICKLUNGEN & PROJEKTEVakuum-Turm-TeleskopDas VTT ist das wissenschaftliche Arbeitspferd des KISund seiner Partner. Die verfügbaren Instrumente des VTTsind leistungsfähige Werkzeuge für wissenschaftliche Beobachtungender Sonne.Adaptive Optik: Sie hat sich zu einem stabilen und benutzerfreundlichenSystem entwickelt, die praktisch bei jederBeobachtungskampagne eingesetzt wird. Zur einfacherenFokussierung wurden TESOS und POLIS mit einerVerstelleinrichtung längs der optischen Achse ausgestattet.Eine Scan-Einheit ermöglicht präzise Raster-Scansmit dem Spektrographen.Beobachtungen mit mehreren Instrumenten:Ein dichroitischer Strahlteiler und Software-Modifikationenermöglichen simultane Beobachtungen mit TIP undPOLIS oder TESOS.TESOS: Dieses Spektrometer wird derzeit zum Stokes-Vektor-Polarimeter erweitert. Es wird ein Flüssigkristall-Retarder eingebaut werden, mit dem die verschiedenen Polarisationszuständegemessen werden können. Die dazugehörigeKontroll-Elektronik ist eine Beistellung des Institutode Astrofísica de Andalucía.TIP: In Zusammenarbeit von MPS und IAC wurde dieInfrarot-Kamera durch ein Gerät mit 1024 2 Pixel ersetzt.Das verbesserte TIP wurde in die Teleskopsteuerung integriert.Neue DALSA CCD: Eine schnelle 1024 2 PixelDALSA1M40 CCD steht zur Verfügung. Die Steuerungs-Softwarewurde am KIS entwickelt. Es ist vorgesehen, vorhandeneCCDs mit derselben Soft- und Hardware zu betreiben, umdie Benutzung zu vereinfachen und zu verbessern.Sensor-System: Ein Ultraschall-Anemometer wurdeam VTT installiert, welches Windrichtung und -geschwindigkeitmit hoher Genauigkeit misst. Ein Beschleunigungsmesseram Coelostaten liefert Informationen über Vibra–tionen des Teleskops.Teleskop-Steuerung: Ein Teil der Teleskop-Steuerungwurde auf ein WINDOWS-XP-basiertes PC-Systemumgestellt. Die neue Steuerungs-Software bietet leichterenZugang zu Teleskop-Funktionen von anderen am VTT installiertenRechnern.Vacuum Tower TelescopeThe VTT is the scientific „work horse“ of the KIS and itspartners. The set of instrumentation available at the VTTprovides powerful tools for scientific investigations of theSun.Adaptive optics: It developed toward a very stable anduser friendly system that is used in almost every observingcampaign. In order to allow for a better focussing of theinstrumentation, TESOS and POLIS have been equippedwith a fine adjustment along the optical axis. A scan unit allowsfor precise scanning with the spectrograph.Multi-instrument observations: A dichroic beamsplitter and software modifications allow for simultaneousobservations of TIP with POLIS or TESOS.TESOS: This spectrometer is currently being upgradedto a full Stokes Polarimeter. A liquid crystal retarder (LCR)will be integrated to measure all polarization states. Thecontrol electronics for the LCR are contributed by the Institutode Astrofísica de Andalucía.TIP: The infrared camera was upgraded to 1024 2 pixels.This was a joint effort of the MPS and the IAC. The newTIP was then integrated into the VTT instrumentation andtelescope control system.New DALSA CCD: A fast 1024 2 Pixel DALSA 1M40CCD is available. The control software and graphical userinterface was developed at the KIS. It is planned to moveexisting CCDs to the same software and hardware platformin order to simplify and improve their operation.Sensor system: A new ultrasonic anemometer hasbeen installed outside the dome atop the VTT. It allows tomeasure the direction and the speed of the wind with highaccuracy. An accelerometer with micro-g sensitivity hasbeen installed on the coelostat’s secondary mirror to recordstructural vibrations.Telescope control system: Part of the telescope’sguiding system has been migrated from the VME-buscomputerto a WINDOWS XP-based PC-System. The newcontrol software allows easier access of telescope functionalityfrom other computing installations at the VTT.Dome maintenance: In 2005, the dome received itssecond major revision since its installation in 1987.Kuppel-Wartung: Im Jahr 2005 erfuhr die Kuppelihre zweite Generalüberholung seit 1987.48


TECHNICAL DEVELOPMENTS & PROJECTSNeue ProjekteAdvanced TechnologySolar TelescopeIm Herbst 2003 bildete sich ein europäisches Konsortiumunter der Führung des IAC, um mittels einer Förderungdurch die Europäische Gemeinschaft eine Beteiligung andem Design des amerikanischen „Advanced Technology SolarTelescope“ (ATST) zu erzielen. Das ATST hat einen Durchmesservon 4m und soll 2014 fertig gestellt werden. Es wirddann das weltweit größte Sonnenteleskop sein. Eine nennenswerteeuropäische Beteiligung würde Sonnenforschernin Europa einen angemessenen Zugang zu der dann wichtigstenbodengebundenen Beobachtungseinrichtung sichern.Einige Mitarbeiter des KIS wirken in Arbeitsgruppenan der Entwicklung des ATST mit. Anfang März 2004 wurdebei der EU ein gemeinsamer Antrag auf Förderung als Designstudieeingereicht. Wesentliche Beiträge des KIS wärenDesigns für einen Teil der Optik, basierend auf den Entwicklungenfür GREGOR, in Zusammenarbeit mit der Industrie gewesen.Der Antrag wurde im August 2004 abgelehnt.Anfang 2005 haben das Kiepenheuer-Institut und das NationalSolar Observatory (NSO) ein Memorandum of Understandingunterzeichnet. Inhalt des MoU ist die Zusammenarbeitbeim Projekt ATST, welche zunächst den Austauschtechnischer Informationen sowie den Zugang zu den Beobachtungseinrichtungenbetrifft. Das KIS bemüht sich umeine Beistellung zum ATST unter eigener Finanzierung, sehrwahrscheinlich in Form eines Post-Fokus-Instruments.ESA-Mission Solar OrbiterIn den Jahren 2004 und 2005 fanden mehrere Treffen einerinternationalen Arbeitsgruppe für die Entwicklung eines Instrumentesfür die Mission „Solar Orbiter“ (SolO) der ESAstatt. SolO soll sich ab 2013 in einem nahen Orbit der Sonnebis auf 1/5 des Abstands Erde-Sonne nähern. Das InstrumentVisible Imager Magnetograph (VIM) soll unter der Federführungvom MPS in Zusammenarbeit mit Forschern desKIS, des IAC sowie von den Universitäten Oslo und Stockholmund dem Observatoire de Paris, sowie mit amerikanischerBeteiligung entwickelt werden. Das KIS beabsichtigt,hierzu einen technischen Beitrag zu leisten und an der wissenschaftlichenArbeit mitzuwirken.New projectsAdvanced TechnologySolar TelescopeA European consortium was formed in fall 2003 under theleadership of the IAC to promote the funding of a Europeanparticipation in the design of the „Advanced TechnologySolar Telescope“ (ATST). The ATST is a 4m solar telescopewhich is currently in the design phase under the leadershipof the National Solar Observatory (NSO), USA. After completionin 2014, it will be the largest ground based solartelescope. A significant European contribution would secureaccess of European scientists to the then most importantground-based facility. Several scientists of the KIS alreadyparticipate in ATST working groups. A proposal for adesign study was submitted to the EC in March 2004. TheKIS contribution would have been designs of part of theoptics in collaboration with industry. The proposal was rejectedin August 2004.KIS and NSO signed a Memorandum of Understanding onthe collaboration for ATST early 2005. The MoU concernsthe exchange of technical information and the access toobserving facilities in the context of ATST development.KIS endeavours to secure additional funding for a significantcontribution to the ATST, most likely in the form of apost focus instrument.ESA mission Solar OrbiterIn 2004 and 2005, several meetings of an internationalworking group for the development of an instrument onboard of the upcoming ESA mission “Solar Orbiter”, whichwill approach the Sun at 0.2 AU, were held . The instrumentVisible Imager Magnetograph (VIM) will be built under theleadership of the MPS with participation from institutes inFrance, Norway, Sweden and the US. KIS intends to maketechnical contributions and to participate in the science.49


GREGOR-IMPRESSIONENGREGOR-Teleskop und neue KuppelGREGORtelescope structure and new domeOben: Kuppel offen, Teleskop zeigt zum ZenitTop: dome open, telescope pointing to zenithMitte: Oberer Gebäudeteil mit neuer kuppelMiddle: top part of building with new domeUnten links: Kuppel teilweise geöffnet, Teleskopin ParkpositionBottom left: dome partially open, telescope stowedUnten rechts: GREGOR und VTTBottom right: GREGORand VTT50


Aktuelle Forschungsergebnisseund technische EntwicklungenProgress in Science and InstrumentationInhalt — ContentsConvection, Rotation, DynamoDynamo action in fully convective stars . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53Reynolds stresses – dependence on latitude . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54Mixing length relations, rotation, and overshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55Evacuation and magnetic field amplification in a dynamo layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56Formation of buoyant magnetic structures in a dynamo layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57The meridional circulation determined by global helioseismology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .58Phase synchronization of solar oscillations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59Data analysis tools for the DIFOS experiment: filling data gaps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60The next solar cycle has its maximum in 2011 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61The deep roots of solar radiance variability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62Meridional motions in countercells on the Sun? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63SunspotsIntensity and flow properties of penumbral filaments in sunspots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64The 3-D topology of sunspots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65Asymmetrical appearance of dark-cored filaments in DOT images . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66Measurements of narrow band circular polarization of sunspot penumbrae confirms theoretical prediction . . . . 67Tube waves – two and more modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68Soliton-like perturbations on magnetic flux tubes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69Cycle-related variations of the solar rotation determined by sunspot groups . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70Magnetic flux cancellation in the solar photosphere . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .71Fine structure of the photosphereSignature of convective collapse during formation of a G-band bright point . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72Bisector of an isolated G-band bright point . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73Influence of image reconstruction on spectral line profiles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74Speckle imaging with the extended Knox-Thompson technique . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75Observations of the dynamics of abnormal granulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .76Understanding faculae . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .77First holistic magnetohydrodynamic simulation from the convection zone to the chromosphere . . . . . . . . . . . . . . 78Recent upgrades of CO 5 BOLD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79Development of CO 5 BOLD Analysis Tool . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .80Carbon monoxide in the solar atmosphere . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81Radiative line cooling of carbon monoxide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82Time-dependent hydrogen ionisation in simulations of the solar atmosphere . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83Observation and simulation of reversed granulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84Temporal evolution of physical parameters in the solar photosphere - results of inversion . . . . . . . . . . . . . . . . . . . . 85A new method for comparing spectroscopic observations with numerical simulations . . . . . . . . . . . . . . . . . . . . . . . 86Stellar surface imaging with interferometric instruments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8751


Chromosphere, Corona & Solar–stellar ConnectionsFirst Sun-as-a-star EUV spectra . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88EUV spectra from 3D MHD models of a coronal active region . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89Coronal heating trough braiding of magnetic field lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90Simulated SUMER/SOHO maps of an active region . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91The solar coronal structure from 3D MHD forward models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92The correlation between coronal Doppler shifts and the supergranular network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93Forward modeling of coronal funnels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94High-speed coronal rain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95Are spicules driven by oscillations? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .96Fast method for computing chromospheric Ca II and Mg II radiative losses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97The Sun at (sub-)millimeter wavelengths . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98High-resolution data of the solar chromosphere . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99Variations of the He I 1083 nm line on the Sun . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100Instrumental developmentsExpanding the corrected field of view with multi-conjugate adaptive optics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101Hunting multi–conjugate adaptive optics “flying shadows” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102Wavefront Sensor based on Liquid Crystal Arrays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103Modulation of the speckle transfer function by adaptive optics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .104Parallelized speckle image reconstruction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105Dual-stage tip-tilt mirror for the SUNRISE telescope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106Image Stabilization for SUNRISE with CWS – A high-precision testbed in the KIS lab . . . . . . . . . . . . . . . . . . . . . 107Wavefront Sensor for the SUNRISE telescope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108COSM interface for controlling the SUNRISE wavefront sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .109MiscellaneousSpectroscopic observations of the Venus transit in 2004 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .110Mercury Transit: First Detection of Excess Absorption produced by Mercury’s Exosphere . . . . . . . . . . . . . . . . . 11152


Dynamo action in fully convective starsW. Dobler (KIS & Univ. of Calgary), M. Stix (KIS) and A. Brandenburg (NORDITA, Copenhagen)Numerische Rechnungen zeigen, dass auch vollkonvektiveSterne einen Dynamo haben können. Wirfinden Magnetfelder, die nahe der Oberfläche Äquipartitionerreichen. Kleine Skalen dominieren im Sterninneren,außen sieht man das globale Feld.Numerical simulation shows that dynamo action infully convective stars is possible. The magnetic fieldsaturates at equipartition strength near the surface.Small scales dominate in the interior of the star, buta global field is visible outside.Stars that are fully convective exist, e.g., on the Hayashi track in the Hertzsprung–Russell diagram, and on the lowermain sequence. Many of these stars show strong magnetic activity. Dynamos in such stars should be different fromdynamos of solar type, where the transition region between convection zone and radiative core plays an importantrole.In this contribution, we present global dynamo simulations in a rotating sphere. We use a Cartesian grid, i.e.,the sphere is embedded in a rectangular box. Heating and cooling, with dependence on r = √ x 2 + y 2 + z 2 , isappropriately distributed within the box, inside and outside the star, respectively. The calculations are done bymeans of the PENCIL CODE, which uses a scheme that is of sixth order in space and third order in time.10 −310 −410 −5146012501050850650E B (k)10 −610 −710 −810 −910 −101 10kR/2πFigure 1: Left: Three-dimensional visualization of the magnetic field in the saturated phase. The green sphere isthe star in the box, yellow and blue are regions of strong positive and negative magnetic polarity. Right: Spectraof the magnetic energy at five epochs. The numbers in the window give the time in units of the dynamical scale[t] = (GM/R 3 ) −1/2 .Figure 1 shows typical results. For an initial phase the magnetic field grows exponentially. During this periodthe shape of the magnetic energy spectrum remains invariant; its peak is at intermediate scales. Later, saturationis reached, and the largest scales dominate. In most of our models, the large-scale field has a strong quadrupolarcomponent. We have not seen evidence of magnetic cycles. Differential rotation is a by-product of our dynamocalculations; the angular velocity shows a tendency to be constant along cylinders, with a slower-rotating equator(“anti-solar”).References:Dobler, W., Stix, M., Brandenburg, A.: Astrophys. J., submitted53


Reynolds stresses – dependence on latitudeC. Hupfer, P. Käpylä, and M. Stix, Kiepenheuer-Institut für Sonnenphysik, FreiburgDie Reynolds-Spannungen Q ij = 〈u ′ i u′ j 〉 sind derSchlüssel zum Verständnis der differentiellen Rotationder Sonne. Wir finden ein markantes Maximum vonQ θφ nahe am Äquator.The Reynolds stresses Q ij = 〈u ′ i u′ j 〉 are the key to theunderstanding of the Sun’s differential rotation. Wefind a strong peak of Q θφ at low latitude very closeto the equator.Hydrodydamic calculations in a limited spatial domain can be made with higher resolution than global calculationsin a sphere or a spherical shell. We simulate solar convection in a rectangular box that can be placed at any depthand latitude within the convection zone. The calculation is performed in a rotating frame, so that a Coriolis forceappears. The box consists of three layers: The main (middle) layer with an unstable stratification, a lower stablelayer into which an overshooting flow may penetrate, and a thin upper layer containing a sink for the heat flowthat enters at the lower boundary of the box. The aim is to let the flow develop for a sufficient period of timeso that a statistical equilibrium is established. Averaging over the horizontal coordinates and/or time then yieldsquantities that are important for global mean-field models. In particular, we are interested in the Reynolds stressesQ ij = 〈u ′ i u′ j 〉 that play a key role in the theory of the differential rotation of the solar convection zone.Q xy0.00040.0000-0.0004-0.0008-0.0012-0.0016-0.0020-0.00240 0.5 1 1.5 2Height z0.0000-0.0004θ90.0°92.5°95.0°97.5°100.0°102.5°105.0°120.0°135.0°150.0°165.0°172.5°180.0°zz = 0.68The calculations were carried outon the 16-processor Linux clusterKABUL of the Kiepenheuer-Institut. The component Q xy , whichin spherical geometry would correspondto the latitude–longitude correlationQ θφ , is shown in Fig. 1.This component is one of the maindrivers of differential rotation. Ithas been calculated before, but notwith sufficiently dense latitude positionsof the computational box toreveal the remarkable peak that occursvery close to the equator. Thepeak is positive in the northern andnegative in the southern hemisphere.The example shown in the figure hasbeen calculated for a Coriolis numberCo ≈ 4 that is representative ofthe deep part of the solar convectionzone.-0.0008z = 1.17Q xy-0.0012-0.0016-0.0020-0.002490 105 120 135 150 165 180Colatitude θz = 1.68z = 1.74Figure 1: Top: The component Q xyof the Reynolds stress tensor, as afunction of height z, for several positionsin the southern hemisphere.The vertical lines mark the layerboundaries. Bottom: The componentQ xy as a function of colatitude θ, forfour different heights z in the computationalbox (θ = 90 ◦ correspondsto the equator).References:Hupfer, C., Käpylä, P., Stix, M.: Astron. Nachr. 326 (2005), 223–22654


Mixing length relations, rotation, and overshootingP. J. Käpylä, Kiepenheuer-Institut für Sonnenphysik and the University of Oulu, FinlandM. Stix, Kiepenheuer-Institut für SonnenphysikM. J. Korpi, NORDITA, Copenhagen, DenmarkI. Tuominen, Observatory, Helsinki and the University of Oulu, FinlandDreidimensionale Konvektionsrechnungen deuten daraufhin, dass der Mischungsweg-Parameter α mit derRotation abnimmt. Im Sonnenmodell kann diese Variationvon α das konvektive overshooting so weit reduzieren,dass die Diskrepanz zum helioseismischenBefund verschwindet.Three-dimensional convection calculations indicatethat the mixing-length parameter, α, decreases as afunction of rotation. In a solar model such a variationof α can reduce the convective overshooting so that thedisagreement with helioseismic observations is cured.The mixing-length conceptIn stellar structure models convection is parameterized by the use of the mixing-length concept. In this formalismthe convective parcels lose their identity after rising or descending a certain distance, the mixing length. The mixinglength is usually assumed to be proportional to the local pressure scale height, l = αH p , where α is a constantO(1). With this assumption it is possible to derive relations between the temperature and velocity fluctuations andthe mean thermal stratification that allow the computation of the convective flux. However, important physicaleffects such as rotation and magnetic fields are disregarded in this parameterization. We have studied the formereffect in detail.Effects of rotationUsing data from a mixing-length model of the solar convection zone, and the known solar rotation rate, we determinethat the Coriolis number (the inverse of the Rossby number) is of the order 10 −3 near the surface andcan reach values in excess of ten near the base of the convection zone. We use a three-dimensional numericalconvection model to perform calculations in this parameter regime and find that α decreases monotonically as afunction of rotation, which can now be interpreted as depth dependence. Introducing a decreasing α into a solarmodel with a non-local mixing-length formalism shows that the overshooting below the convection zone decreasesapproximately in proportion to α. If the mixing-length parameter is decreased by a factor of 2.5 at the base (seeFig. 1) the discrepancy between helioseismic observations and the steep transition of the temperature gradient atthe bottom of the convection zone can be reconciled. Numerical calculations indicate a similar decrease of α.Figure 1: Temperature gradients ∇ = d ln T/d ln P near thebase of the convection zone. The actual gradient is denoted bythe heavy curve. A local model with no overshooting (lowercurve); non-local models with mean path l/2 (top curve), as assumedin local theory, and with mean path l/5 (middle curve).References:Käpylä, P. J., Korpi, M. J., Stix, M., & Tuominen, I., Astron. Astrophys. 438 (2005), 403, astro-ph/041058455


Evacuation and magnetic field amplification in a dynamo layerM. Ossendrijver, Kiepenheuer-Institut für SonnenphysikNumerische Simulationen von Evakuierung andVerstärkung des Magnetfeldes in einer Dynamoschichtam Boden der Konvektionszone eines sonnenähnlichenSterns werden vorgestellt.Numerical simulations of evacuation and magneticfield amplification in a dynamo layer at the base of theconvection zone of a solar-type star are presented.The magnetic field of the Sun is generated near the bottom of the convection zone, at a depth of about 200.000 km.In the ’dynamo layer’, just below the convection zone of a solar-type star, the magnetic field can be stably storedand amplified. Shear flows (’differential rotation’) are the main amplification mechanism, but probably not the onlyone. A recently proposed additional amplification mechanism is based on compression occurring in the dynamolayer when there is an outflow of matter into the convection zone due to an instability. The current simulationsprovide the first numerical demonstration of this mechanism in three dimensions. The simulation domain consistsof a convectively unstable zone in-between two stably stratified layers. In the beginning of the simulation thereis a homogeneous horizontal magnetic field in the dynamo layer and no convection in the unstable layer. Afterthe instability is triggered by introducing a weak random velocity field the dynamo layer is disrupted and partiallyevacuated. In the section of the dynamo layer that remains anchored in the stably stratified layer, the magnetic fieldis amplified accordingly, as can be seen on the left face of the cube. The maximal amplification achieved in thebox is a factor of 7.The computations were performed with an anelastic MHD code in Cartesian geometry developed at the KIS on thebasis of an existing MHD code. Due to the anelastic approximation the code is especially suitable for simulationsof the lower part of stellar convection zones. The Cartesian rather than spherical geometry enables the necessaryhigh spatial resolution.Figure 1: The color indicates the strength of the magnetic field (white=high); the arrows give the direction of theflow, projected on the faces of the cube. The top and bottom faces are inside the simulation domain, at z = −0.07and z = 1.53, respectively. The boundaries of the convectively unstable layer, indicated by the white horizontallines, are at z = 0 and z = 1.1. Depth is measured in units of d ≈ 10 5 km. The computational grid has 64 2 · 100points.References:M. Ossendrijver, Astron. Nachr. 326, 166-169 (2005)56


Formation of buoyant magnetic structures in a dynamo layerM. Ossendrijver, Kiepenheuer-Institut für SonnenphysikNumerische Simulationen von der Entstehung aufsteigendermagnetischer Strukturen in einer stabilgeschichteten Dynamoschicht unterhalb der Konvektionszoneeines sonnenähnlichen Sterns werdenvorgestellt.Numerical simulations of the formation of buoyantlyrising magnetic structures in a stably-stratified dynamolayer below the convection zone of a solar-type star arepresented.Below the convection zone of solar-type stars there is a ’dynamo layer’, where a magnetic field can be stably storedand amplified. If the strength of the magnetic field in the dynamo layer is sufficiently large, tube-like magneticstructures are formed and begin their buoyant rise through the convection zone. Understanding this process isan important goal of solar physics. Firstly, during their rise the magnetic structures acquire a systematic twistequivalent to an ’alpha effect’, for which reason they might play a role in the dynamo process by generating alarge-scale poloidal magnetic field. Secondly, some of them continue to the solar surface to produce sunspots. Theresults shown here provide a numerical illustration in three dimensions of the formation of such structures out of adynamo layer with an initially homogeneous magnetic field, and, for the first time, their buoyant rise through theconvection zone.Our anelastic MHD code is especially suitable for simulations of the lower part of stellar convection zones; here itallows for a time step that is about 110 times larger than the value allowed in an elastic MHD scheme.Figure 1: Left: The color indicates the strength of the magnetic field (white=high); the arrows give the directionof the flow, projected on the faces of the cube. The top and bottom faces are inside the simulation domain, atz = −0.04 and z = 1.24, respectively. The boundaries of the convection zone, indicated by the white horizontallines, are at z = 0 and z = 1.1. Depth is measured in units of d ≈ 10 5 km. Right: Isosurface of the magnetic fieldstrength. The computational grid has 64 2 · 80 points.References:M. Ossendrijver, Adv. in Space Res. (submitted)57


The meridional circulation determined by global helioseismologyM. Roth, Kiepenheuer-Institut für SonnenphysikAuf der Grundlage der quasi-entarteten Störungstheoriewird eine Inversionmethode globaler Eigenfrequenzender Sonne entwickelt, die sensitiv für die meridionaleZirkulation ist. Es ist das Ziel, mit dieser Inversionstechnikin die tiefen Bereiche der Konvektionszonevorzudringen. Erste Ergebnisse weisen daraufhin,daß sich die meridionale Zirkulation im Laufedes Zyklus merklich verändert.Based on quasi-degenerate perturbation theory an inversionmethod of global eigenfrequencies of the Sunis currently developed that is sensitive to the meridionalcirculation. It is the goal, to probe the deep layers in theconvection zone with this inversion technique. First resultsgive hints on significant changes in the structureof the meridional circulation during the solar cycle.As derived in prior investigations the meridional circulation is expected to affect the solar oscillations by shiftingthe frequencies ω nl according to the relation:δω nl (m) = ∑ n ′ l ′ ∑sc sll ′(ω 2 nl − ω2 n ′ l ′) ∣ ∣∣∣∣ ∫ R⊙0( ) ∣ s l lv s (r) s K nn′ ,ll ′ dr ′2∣∣∣0 m −mwhere s K nn′ ,ll ′ is an integral kernel containing the eigenfunctions of two coupled oscillations identified by thequantum numbers n, n ′ and l, l ′ ; v s (r) is the radial velocity component with degree s of the meridional circulationdecomposed into Legendre polynomials; and the arrays on the right-hand side are Wigner-3j symbols. This relationis inverted by using squared Wigner-3j symbols as basis functions for fits to solar oscillation multiplet frequencies.The result is an estimate for the meridional velocity components v s in the solar interior.,Figure 1: The meridional velocity component v 2 (r) used as input for the calculation of the forward problemaccording to the above equation (left) and as inverted from such artificial data (middle); red: up-flow, blue: downflow.Right: The relative strength of the meridional flow components with degrees s = 1–6 during the last solarcycle as derived from GONG data. The results for 2005–2014 are copies from the years 1995–2004.Inverting the numerically determined results of the forward problem for a model of a single meridional flowcomponent gives already reliable results. The investigation of the strength of the meridional flow components asthey are mirrored in annual frequency averages of oscillation multiplets over the last decade (GONG data from1995–2004) gives an indirect hint on a varying structure of the meridional circulation with the solar cycle. One ofthe next steps is a full inversion for the solar meridional circulation.58


Data analysis tools for the DIFOS experiment: filling data gapsM. Roth, Kiepenheuer-Institut für SonnenphysikY. Zhugzhda, IZMIRAN, MoscowDIFOS ist ein Multikanal-Photometer an Bord des russischenCORONAS-F-Satelliten. Dieses Instrument istder Untersuchung der globalen Oszillationen der Sonneals Stern gewidmet. Da der Satellit sich auf einem Orbitum die Erde befindet, treten in den Daten etwa alle90 min. Lücken von 30 min. Länge auf. Diese giltes zu füllen, bevor die Daten sinnvoll weiterverarbeitetwerden können.DIFOS is a multichannel photometer aboard the RussianCORONAS-F mission. This instrument is devotedto the investigation of the global oscillations of the Sunas a star. As the satellite is orbiting the Earth, gaps of30 min. length occur in the data every 90 min. Thesegaps need to be filled before the data processing continues.The development of data analysis tools for DIFOS data is currently concerned with the filling of gaps in thesedata. This step is crucial before the scientific processing of the data can start. One possible approach is themathematical description of the observed variations of the solar radiation due to the global eigenoscillations of theSun as a superposition of stochastically excited damped harmonic oscillators. These oscillators can be modeledwith autoregressive processes of second order (AR[2]). The estimation of the model parameters is carried out withthe expectation maximization (EM) algorithm. Once the process parameters are estimated the gaps are filled byforecasting the continuation of the process into the gaps. Subsequently, the process parameters are re-estimated,which then result in better predictions for the oscillation amplitudes during the gaps. In this way the gaps are fillediteratively.A first test of the gap-filling algorithm on data with artificially introduced gaps yields a promising outcome: withincreasing number of iterations the estimated course of the time series in the gap approaches the original timeseries better. Moreover side lobes in the power spectrum emerging due to the gaps are more and more reduced.Figure 1: Result of the gap-filling algorithm after 10(top) and 100 (bottom) iteration steps. Left: Section ofthe original time series (black curve) and the gap-filledtime series (red curve). The gap is indicated by thevertical lines. Right: Periodograms of the gap-filledtime series at the respective iteration steps.Figure 2: Periodogram of the original time series.Scientific Goal: The DIFOS’ photometers record the intensity variations on the Sun in six different wavelengthscorresponding to six different heights of the solar atmosphere. Therefore with these data and an appropriate datahandling seismology of the global properties of the solar atmosphere will be possible.60


The next solar cycle has its maximum in 2011M. Roth, Kiepenheuer-Institut für SonnenphysikStatistische Modelle erlauben die Vorhersage desVerlaufs der Sonnenfleckenrelativzahlen während desnächsten Sonnenzyklus.Statistical models allow a prediction of the course ofthe sunspot relative number during the next solar cycle.The recorded relative sunspot number is very often used in the literature as an example for modeling a timeseries with an auto regressive moving average (ARMA) model. ARMA models are based on statistical processes,whose current state depends on a certain number of realizations in the past and which is influenced by a movingaverage of noise terms. Therefore, the process recollects itself but loses this “self-memory” after some time.For the presented fit to the yearly averaged relative sunspot number we used an ARMA(4,5) model; i.e. therecollection reaches 4 years back in time, whereas the influence of the noise is an average effect of the last 5 years.However, the description of the relative sunspot number with a stationary ARMA model can only serve as a crudeapproximation, because the solar dynamo mirrored in the relative sunspot number is not a stationary process, i.e.,it is not unchanging. Anyway, we dare to predict the next solar cycle (the red colored region in the figure) on thestatistical basis of the years 1700 to 2003. According to this prediction, the next cycle (counted the 24th cycle)will set in in the year 2006. This is where the next minimum is expected. The next maximum of sunspots wouldbe in the year 2011. This maximum seems to turn out lower than in the preceding cycles.200Relative Sunspot Number1501005001970 1980 1990 2000 2010YearFigure 1: Yearly average of the relative sunspot number from 1965 to 2016. The prediction of the course of therelative sunspot number from 2004 to 2016 (marked red) was carried out on the basis of data from 1700 to 2003.61


The deep roots of solar radiance variabilityO. Steiner, Kiepenheuer-Institut für Sonnenphysik; A. Ferriz-Mas, Facultad de Ciencias de Orense, SpainDie Modulation der Sonnenleuchtkraft mit dem Sonnenzyklusbewirkt einen thermodynamischen Zykluswelcher die gesamte Konvektionszone umfasst. DasVirialtheorem erlaubt einen Zusammenhang zwischenVariation von Leuchtkraft und magnetischer Energieherzustellen.We show that the variability of the solar luminosity resultsin a thermodynamic cycle that involves the entireconvection zone. With the help of the virial theoremwe try to establish a connection between the variationsin luminosity and magnetic energy.The excess of radiative loss from solar faculae entails entropy-deficient material beneath plage and network regions.It drifts in the convective downdrafts to the deep convection zone and hence, communicates radiance variation atthe surface to the base of the convection zone on a hydrodynamical time scale. We identify a correspondingthermodynamic process with the rise of large-scale flux tubes from the base of the convection zone to the solarsurface. This process in turn transports entropy-rich material from the base into the middle and outer convectionzone. It entails a reduction in the superadiabaticity of the convection zone and hence throttles energy transportacross it.extra entropy−deficientdownflowconvectionzonethrottledenergy fluxconvectionzoneextraradiationcoreextra entropy−richupflowconvection zoneFigure 1: Left: The thermodynamic cycle, associated with the magnetic solar cycle. Right: Large-scale magnetic flux tube rising from thebase of the convection zone to the solar surface.From computer simulations Schüssler et al. (1994, A&A 282, L69) and others conclude that large-scale flux tubesat the base of the convection zone must have a flux density of approximately 10 T. Correspondingly, the magneticenergy produced there over half a solar cycle is M ≈ 5 × 10 32 J. Using the virial theorem for magnetohydrodynamics,1 d 2 J2 dt∫R2 = 2K + Ω + M + 3 pdV + S ,we first show that the second time derivative of the moment of inertia J, the kinetic energy K, and the surfaceterm S, are either negligible or constant, which leaves us with the equation Ω + M + 2U = 0 , where Ω is thegravitational binding energy and U the internal energy of the convection zone. At times of maximum solar activity,the magnetic energy is being reduced by flux-tube eruptions or Ohmic dissipation, so that it is turned into thermalenergy without change of Ω. Using in addition the total energy equation we conclude that this process implies anexcess of radiation from the Sun of 10 32 J, which agrees with the value from total solar irradiance measurements.The excess of radiation thus ultimately originates from the magnetic energy built up during one half-cycle, whichexplains the coincidence of equal magnetic and thermal energy change over a solar cycle.On the other hand, the intensification of the magnetic field by the dynamo process results according to the virialtheorem in an internal energy change of ∆U = −(1/2)(∆Ω + ∆M). From the fact that the flux tubes stored in theovershoot layer of the convection zone must be neutrally buoyant we conclude that ∆Ω = 0. In fulfillment of thetotal energy equation we thus conclude that this process implies a reduction of radiative loss from the surface of10 32 J over the other half-cycle.References:Steiner, O.: 2004, AN, 324 Suppl. Issue 3, 106–107Steiner, O.: 2005, IAU Symp. 223, 77–80Steiner, O. & Ferriz-Mas, A: 2004, AN, 326, 190–19362


Meridional motions in countercells on the Sun?H. Wöhl, Kiepenheuer-Institut für Sonnenphysik (KIS), FreiburgR. Brajša, B. Vršnak, V. Ruždjak, Hvar Observatory, Faculty of Geodesy, University of ZagrebF. Clette, J.-F. Hochedez, Observatoire Royal de Belgique, BruxellesKleinskalige helle koronale Strukturen in Bildernaufgenommen mit EIT/SoHO wurden verwendet, ummeridionale Bewegungen auf der Sonne zu bestimmen.Small-scale bright coronal structures in images takenwith EIT/SoHO were used to determine meridionalmotions on the Sun.Full-disc solar images obtained in 1998/99 with the Extreme ultraviolet Imaging Telescope (EIT) on board of theSolar and Heliospheric Observatory (SoHO) were used to analyse the solar large-scale motions by tracing coronalbright points. Their main advantage is the rather homogenous distribution in latitude. An interactive method andan automatic method to follow the structures in sequences of images taken mostly 6 hours apart were applied.Special methods were developed to correct the center of images and correct for the height of the structures in thesolar atmosphere.Details of the reductions and results of the differential rotation were given in the papers by Brajša et al. (2001,2002). Results of meridional motions and angular momentum transport are given by Vršnak et al. (2003) – fordetails on the meridional motions see their section 3.1.2. These results recently gained interest again, becauseby reductions of helioseismological data from GONG and MDI/SoHO different signatures of meridional motionswere found (Komm et al. 2004, ApJ 605, 554). One of the findings of a ’countercell’ in MDI data is similar to thatfound in our EIT data: there are equatorward motions near the equator and in higher latitudes, while the motionsare poleward around the mean latitude of activity.Figure 1: Meridional motion v mer in [m/s] as a function of heliographic latitude B in degrees. The velocity datastem from the interactive data reduction of the bright points in EIT images. Data from the northern and southernhemispheres are combined. Positive values represent motions towards the poles, negative towards the equator.Curves in grey color connect mean values from 5 and 10 degree latitude bins of the data. The full curve connectsthe mean values for 7 bins of 206 data points each. The vertical dashed line marks the mean latitide of activity.Acknowledgements: The project was performed with support of the Alexander von Humboldt Foundation to R.Brajša 2000/2003. SoHO is an international cooperation of ESA and NASA. Several research students in Zagreband Freiburg helped in the data reduction processes.References:Brajša, R., Wöhl, H., Vršnak, B. et al.: Astron. Astrophys. 374, 309 (2001)Brajša, R., Wöhl, H., Vršnak, B. et al.: Astron. Astrophys. 392, 329 (2002)Vršnak, B., Brajša, R., Wöhl, H. et al.: Astron. Astrophys. 404, 1117 (2003)63


Intensity and flow properties of penumbral filaments in sunspotsR. Schlichenmaier, Kiepenheuer-Institut für Sonnenphysik, FreiburgL.R. Bellot Rubio, Instituto de Astrofisica de Andalucia, Granada, SpainA. Tritschler, Big Bear Observatory, Big Bear City, USAWir untersuchen die Intensitäts- und Geschwindigkeitseigenschaftenpenumbraler Filamente und finden, dasses keinen eindeutigen Zusammenhang zwischen derEvershed-Strömung und der Helligkeit gibt. Füreinzelne Strömungsfilamente ist es sogar so, dassdie Helligkeit entlang des Filamentes von innen nachaußen abnimmt. Dies ist im Einklang mit dem ’movingtube’-Modell.We analyze the intensity and flow properties of penumbralfilaments and elaborate on the issue of correlationbetween dark filaments and the Evershed flow, findingthat the flow is present in bright and dark filaments dependingon the location within the penumbra. Individualcases show that bright and dark filaments are connectedthrough a flow channel, supporting the movingtube model.arcsecarcsecarcsec54321054321054321Doppler shift in line wing [km/s]Continuum imageEquivalent width [pm]00 2 4 6 8 10arcsec-0.2-0.4-0.6-0.8-1.0-1.215.014.514.013.513.012.5Bisector intensity levels0.80.40.00.80.40.00.80.40.00.80.40.0-1.0 -0.5 0.01234Doppler shift [km/s]Velocity mapIntensity mapFigure 1: Left: Disk center side of penumbra, displaying Doppler shift of line wing, intensity, and equivalentwidth. Co-spatial black and white lines mark inner and outer ends of individual flow channels. Right: Bisectorsof Fe I 557.6 nm at 4 positions (marked by the squares in the velocity and intensity maps) along one of the flowchannels.High spatial (≈ 0.5 arcsec) and high spectral (λ/δλ = 250 000) resolution observations of Fe I 557.6 nm taken withTESOS@VTT are used to analyse a sunspot at a heliocentric angle of 23 ◦ . From the left panel of the figure itis apparent that the correlation between Doppler shift and intensity changes along flow channels. The right paneldisplays the bisectors of Fe I 557.6 nm, demonstrating that the line wing shift increases along an intensity filamentfrom subpanel 1 to 3. The end of the filament (subpanel 4) is associated with a kink in the bisector, which can beinterpreted as a location of downflow. As such these observations are consistent with the moving tube model.References:R. Schlichenmaier, L.R. Bellot Rubio, A. Tritschler: 2005, AN 326, No. 3/4, 30164


The 3-D topology of sunspotsC. Beck, W. Schmidt, R.Schlichenmaier, Kiepenheuer-Institut für SonnenphysikAus der Inversion von simultanen Spektren im sichtbarenund infraroten Licht leiten wir die dreidimensionaleStruktur des Magnetfeldes eines Sonnenflecksab. Die Ergebnisse bestätigen das “Moving TubeModel” (Schlichenmaier et al. 1998, A&A 337, 897).From the inversion of simultaneous spectra in visibleand infrared spectral lines we derive the 3-D topologyof the magnetic field in a sunspot. The results supportthe “Moving Tube Model” (Schlichenmaier et al. 1998,A&A 337, 897).Left: intensity in the G-band. Right two panels: top view of the 3-D sunspot model and view from above atheliocentric angle 40 ◦ . The color of the drawn surface gives the field strength, the color of the elevated flux tubestheir temperature. The hot upstream points in the inner penumbra on the limb side of the spot (lower half) in theG-band image compare well to the flux tube temperatures in the top views.Infrared and visible spectra were spatially co-aligned and subjected to an inversion, i.e. a forward modelling ofthe solar atmosphere from an inital model stratification, with two magnetic atmosphere components (2C) in thepenumbra. The inversion components were separated by their respective inclination to the solar surface into a lessinclined “background field” (bg) and a more horizontal “flux tube” (ft) component.The 3-D topology has been derived twofold: Firstly, the inclination to the surface, γ, was integrated radially usingh(r i ) = ∑ 1j=0...i tan γ(r · ∆r , where ∆r is the step width in radius, and γ(r j) j) is the inclination at a given radiusr j . Note that the derived height has to be taken with care, it mainly serves as a tool to enable a better visualization.Secondly, the results of the 2C inversion were used as inital parameters for a so-called “Gaussian” inversion wherethe ft component is included in one of the model atmospheres as a disturbance with a Gaussian shape at a certainheight; the height is a free parameter in the inversion.optical thicknessThe final result using the 2C integration for r < 7 Mm and the Gaussian for larger radii is displayed in the upperimage: The ft component is an almost horizontal, slightly elevated flux channel with a flow velocity around6 km/s. The ft component has a weakerfield strength than the bg field, especiallyvisible at the hot upstream pointwhere the ft reaches the solar surface atz = 0 Mm. The results compare well tothe Moving Tube Model (lower image).The color gives the field strength from0 to 3500 G in both images, horizontaland vertical axis radial distance, respectively,height in Mm.65


Asymmetrical appearance of dark-cored filaments in DOT imagesL.R. Bellot Rubio 1,2 , R. Schlichenmaier 1 , 1 Kiepenheuer-Institut für Sonnenphysik, Freiburg2 Instituto de Astrofisica de Andalucia, Granada, SpainP. Sütterlin, Sterrekundig Instituut Utrecht, The NetherlandsDunkle Kerne in penumbralen Filamenten sind deutlicherzu sehen auf der zentrumsseitigen als auf derrandseitigen Penumbra von Sonnenflecken. DiesenBeobachtungsbefund kann man verstehen, wenn mandavon ausgeht, dass die Isothermen in der innerenPenumbra leicht geneigt sind.Dark-cored filaments in sunspot penumbrae are foundto appear more pronounced on the disk-center side ofa sunspot than on the limb side. We speculate that thisgeometric effect can be understood if the isotherms inthe inner penumbra are tilted.G bandarcsec3020100zz0 5 10 15 20 25arcseco27Limb−sidePenumbracoolLine of sightUmbraτ=0.1Line of sightCenter−sidePenumbracoolDark cores in penumbral filaments have beendiscovered for a sunspot at disk center withthe Swedish 1m Telescope by Scharmer et al.(2002). We confirm their existence using theDutch Open Telescope (DOT) for sunspots offdisk center, but find that they are more pronouncedon the center-side penumbra (upperleft in the image as indicated by the arrow)as compared to the limb-side penumbra (lowerright in the image). The spot shown here has aheliocentric angle of 27 ◦ .We speculate on the origin of this geometricaleffect using tilted isotherms in the innerpenumbra as sketched in the lower figure.This explanation relies on the assumption thatthe dark cores and the corresponding lateralbrightenings are partial aspects of a single essentiallyhorizontal magnetic flux tube, whichis cooler in the top part than on the deeper lyingsides.As the isotherms are tilted in the inner penumbra,the line of sight experiences an effect similarto the limb darkening, in the sense thatthe τ = 1 level is reached in different layers.With respect to the line of sight the isothermsare tilted more on the center-side as comparedto the limb side. Hence, higher layers of theflux tube are seen on the center-side penumbra.As a consequence the τ = 1 level probes thecooler, darker structure of the flux tube whileit is fully contained in the hot part of the tubeon the limb side penumbra.hothotτ = 1References:P. Sütterlin, L.R. Bellot Rubio, R. Schlichenmaier: 2004, A & A 424, 104966


Measurements of narrow band circular polarization of sunspot penumbraeconfirms theoretical predictionR. Schlichenmaier, G. Fritz, C. Beck, Kiepenheuer-Institut für Sonnenphysik, FreiburgD.A.N. Müller, Kiepenheuer-Institut für Sonnenphysik, Freiburg, and Institute of Theoretical Astrophysics, Oslo,NorwayErstmals wurden am VTT simultane spektropolarimetrischeMessungen in zwei Wellenlängenbereichen,bei 1564.8 nm und bei 630.2 nm, durchgeführt.Bei beiden Wellenlängen wurden neutrale, magnetischempfindliche Eisenlinien vermessen. Mit diesen Messungenkonnten theoretische Verhersagen des ’movingtube’-Modells bezüglich der schmalbandig integriertenNetto-Zirkular-Polarisation bestätigt werden.For the first time spectropolarimetric measurements inthe infrared (neutral iron line at 1564.8 nm observedwith TIP@VTT) and the visible (neutral iron line at630.2 nm observed with POLIS@VTT) could be performedsimultaneously. Thereby, theoretical predictionsfor the narrow band circular polarization of theso-called moving tube model for the sunspot penumbracould be confirmed.MeasurementTheoretical prediction40Fe I 1564.8 nmθ =3040Fe I 1564.8 nmθ =30303020201010000 10 20 30 0 10 20 30−0.3 −0.1 0.1 0.3 −0.6 −0.2 0.2 0.6MeasurementTheoretical prediction403020100Fe I 630.2 nm θ =300 102030−0.1 0 −0.1 0.2 0.34030201000−2Fe I 630.2 nm−11020θ =30300 1 2The narrow-band circular polarizationis the wavelength integral of asingle spectral line of the Stokes Vsignal (Stokes V being the differencebetween right and left circularly polarizedlight). The left panels showthe measurements, and the right panelsdisplay the theoretical predictionswhich are based on the uncombedscenario of the penumbra:a horizontal magnetic flow channelthat is embedded in an inclined magneticfield at rest. The arrow pointstowards the center of the solar diskand the narrow-band circular polarizationis given in pm.It can be seen that the measurementsconfirm the predicted symmetryproperties of the two maps. Differencesstill exist with respect to theamplitudes of the signals.References:R. Schlichenmaier, G. Fritz, D.A.N. Müller, C. Beck: to be submitted to A & A.67


Tube waves – two and more modesM. Stix, Kiepenheuer-Institut für Sonnenphysik, FreiburgWellen in einem magnetischen Zylinder werden mitHilfe der Entwicklung nach Potenzen des Abstandsvon der Achse dargestellt. Eine einzige Graphik liefertsämtliche Eigenfrequenzen.Magnetohydrodynamic body waves in a cylinder areanalyzed with the thin-tube expansion. For all levels oftruncation the mode eigenfrequencies are found from asingle graph.The variables v, B, etc., are expanded in terms of powers of the distance r from the axis of symmetry. Theexpansions are substituted into the equations of ideal magnetohydrodynamics, under the assumption of adiabaticperturbations. Comparing equal powers of r one obtains an infinite set of equations, which are linearized in orderto analyze tube waves of small amplitude. I neglect the coupling of the tube wave to the external medium, use anAnsatz exp[i(ωt − kx)] of harmonic solutions, and derive the dispersion relation. This has been done before, butit appears that it has not been realized that for all levels of truncation the normalized phase velocity Ω = ω/(kc T )depends only on the single parameter ε, viaΩ 2 = ε ± √ ε 2 − 2ε ,ε = c2 S + c2 A2c 2 T(1 + z2α 2 ), α = kR . (1)where α is a dimensionless wave number, and R the radius of the tube. The sound, Alfvén, and tube speeds aregiven byc 2 S = γP ρ ,c2 A = B2µρ , c2 T = c2 S c2 Ac 2 S + . (2)c2 AThe constant z depends on the level of truncation. For the two-mode approximation z = 2, for 4 modes z = √ 8; forthe infinite series, which represents a Bessel function, z is any zero of J 0 . Figure 1 shows the dimensionless phasevelocity Ω(ε), as well as the group velocities of the slow and fast modes. The phase and group velocities of theslow mode both approach c T for α → 0 (i.e., ε → ∞). For α ≫ 1 the two modes approach c S and c A , respectively.Figure 1: Phase velocity (blue) and group velocity (red) of the slow (dashed) and fast (solid) body waves in amagnetic flux tube, as functions of the parameter ε.References:Stix, M.: Astron. Astrophys. 415 (2004), 751–75468


Soliton-like perturbations on magnetic flux tubesM. Stix, Y.D. Zhugzhda, and R. Schlichenmaier, Kiepenheuer-Institut für Sonnenphysik, FreiburgWir untersuchen die Ausbreitung von Störungenendlicher Amplitude an magnetischen Flussröhren inder two-mode-Näherung. Es existieren solitonartigeLösungen, wobei Dispersion und die Tendenz zurStoßwellenbildung gegeneinander wirken.The propagation of finite-amplitude perturbationsalong magnetic flux tubes is studied numerically inthe two-mode approximation. We find solutions thatclosely resemble solitary waves, with shock formationand dispersion opposing each other.The two-mode approximationThe dynamics of magnetic flux tubes are conveniently described by means of an expansion in terms of the distancefrom the tube axis. Truncation in the second order yields the two-mode approximation, which is of second orderin the time derivative and therefore allows for a second (fast) wave mode, in addition to the slow tube wave thatalready exists in the leading-order truncation. But the slow mode is modified as well: instead of the constant phasevelocity which it has in the leading order, it now has a phase velocity that depends on wavelength. This dispersionentails an interesting behaviour, in particular since the truncated equations retain the non-linearity of the originalMHD equations.We solve the two-mode equations numerically by a two-step predictor-corrector method. At small amplitude, wereproduce the two wave modes that one finds analytically by linearization. At moderate amplitude, the systemof non-linear equations can be reduced approximately to a Korteweg–de Vries equation, as shown recently byY. D. Zhugzhda. In this case solitary waves (solitons) of the form B(z, t) = B a sech 2( (z − V t)/L ) exist, whereV is the travel velocity in a frame moving with the tube speed. Both V and the width L of the soliton depend onits amplitude B a ; the amplitude can be positive or negative. We use such perturbations, with t = 0, as an initialcondition.The numerical solution of the exact two-mode equations yields indeed traveling perturbations like solitons. Althoughthey do not keep their shape – mainly due to the presence of the fast wave mode – they are soliton-likein that dispersion works against the tendency of shock formation, cf. Fig. 1. This result will have implications toshocks that occur in the moving magnetic flux tubes of a sunspot penumbra.Figure 1: Large-amplitude wave packets on a magnetic flux tube: one mode, with shock formation (left), and twomodes, with soliton-like behaviour (right). In both cases the same magnetic signal starts at the left edge and isshown after 8 min (grey) and 16 min (black). The abscissa is in grid points, with grid constant 12.3 km.References:Stix, M., Zhugzhda, Y.D., Schlichenmaier, R.: Physics of Plasmas, submitted69


Cycle-related variation of the solar rotation determined from sunspot groupsH. Wöhl, Kiepenheuer-Institut für Sonnenphysik (KIS), FreiburgR. Brajša, D. Ruždjak, Hvar Observatory, Faculty of Geodesy, University of ZagrebDie erweiterten Greenwich Daten bestehend aus Positionenvon Sonnenfleckengruppen wurden verwendet,um zyklus-abhängige Variationen der Sonnenrotation1874-1981 zu untersuchen. Durch Anwendung derResiduenmethode wurde eine mögliche Abhängigkeitder Rotationsgeschwindigkeit von der Zyklusphase gefunden.The extended Greenwich data set consisting of positionsof sunspot groups is used for the investigationof cycle-related variations of the solar rotation in theyears 1874-1981. Applying the residual method a possibledependence of the rotation velocity residual on thephase of the solar cycle was found.Positions of sunspot groups were measured on photographic plates taken at the Royal Greenwich Observatory on adaily basis during the years 1874-1976. The results were published in the catalogue ”Greenwich PhotoheliographicResults” (GPR). We used the electronic version of the GPR and extended it with measurements for the years 1977-1981 provided by the Solar Optical Observing Network (SOON) of the US Air Force and the National Oceanicand Atmospheric Administration (NOAA).Rotation rates were determined with the daily shift method and sidereal values were calculated from the synodicones. The residual method (Gilman and Howard 1984, ApJ 283, 385) provides yearly deviations from the meanrotation velocity, averaged over all years, for each latitude band. These deviations are averaged over latitudes andyearly rotation rate residuals are determined yielding a single number for each year. A positive (negative) rotationrate residual indicates a higher (lower) velocity than the average.Rotation rates residuals were averaged for all years with the same solar cycle phase relative to the nearest sunspotminimum which occurred in the years 1878, 1889, 1901, 1913, 1923, 1933, 1944, 1954, 1964, 1976, and 1986. Ascan be seen in Fig. 1 the variation pattern reveals a higher rotation rate than the average in the minimum of activityand, to less extent, also around the maximum of activity. Preliminary results were published by Brajša et al. (2004)and the work is still in progress.Figure 1: Dependence of the rotation rate residual on the phase of the solar cycle for the years 1874-1981.References:Brajša, R., Wöhl, H., Ruždjak, D., Schawinski-Guiton, K.: Hvar Observatory Bulletin 28, 55 (2004)70


Magnetic flux cancellation in the solar photosphereL.R. Bellot Rubio, Instituto Astrofísica de AndalucíaC. Beck, Kiepenheuer-Institut für SonnenphysikIn zeitgleichen Beobachtungen am VTT auf Teneriffaund dem Dutch Open Telescope (DOT) auf La Palmahaben wir die Auflösung eines Netzwerkelementesdurch magnetische Rekonnektion mit einem “MovingMagnetic Feature” (MMF) von entgegengesetzterPolarität beobachtet. Das MMF wird durchden “moat flow” gegen ein isoliertes Netzwerkelementgetrieben, das im Laufe von 35 min. vollständigverschwindet. Die Rekonnektion wird von Aufströmungenund zeitlich versetzter Emission in derChromosphere begleitet.In simultaneous observations taken at the VacuumTower Telescope (VTT) on Tenerife and the DutchOpen Telescope (DOT) on La Palma we witness a cancellationevent between a network element and a “MovingMagnetic Feature” (MMF) of opposite polarity.The MMF is driven towards an isolated network elementby the “moat flow”. The reconnection event isaccompanied by upflows, and, with a time lag, an enhancedchromospheric emission at the cancellation sitethat persists after the network element has vanished.∆ t = −14 min −7 min 0 min 7 min 14 min 21 min 28 min 35 minFigure 1: Top to bottom: Signed flux, G-band, Calcium II H line core, inclination, field strength, filling fraction,LOS velocity, temperature. The time is given at the top.The MMF (white patch in 1st row) collides with a non-moving network element (black patch). At t = 0 min(3rd column) the net magnetic flux starts to decrease. The network element completely disappears around t = 28min. The chromospheric emission in the Ca II H line core is first centered on the two patches, but in the last maps(t>14 min) it appears above the magnetic neutral line where the two patches meet. The emission persists evenafter the 2nd patch is gone at t = 35 min. The network element shows upflows of about 1 km/s. The observationis compatible with a reconnection scenario depictured in Ryutova et al. (2003, SP 213, 231). We observe onlyone half of their predicted up- and downflows, but the later appearance of the chromospheric emission over thereconnection site supports the picture of an upwards oriented energy transport, presumably by an upward movingshock front.References:Bellot Rubio, L.R. & Beck, C., 2005, ApJ 626, L12571


Signature of convective collapse during formation of a G-band bright pointC. Beck, W. Schmidt, R.Schlichenmaier, Kiepenheuer-Institut für SonnenphysikL.R. Bellot Rubio, Instituto Astrofísica de AndalucíaP. Suetterlin, Sterrekundig Instituut UtrechtIn zeitgleichen Beobachtungen am VTT auf Teneriffaund dem Dutch Open Telescope (DOT) auf La Palmahaben wir die Entstehung eines “G-band Bright Points”(GBP) aus einem Gebiet mit diffusem magnetischenFluss verfolgt. Die Beobachtungen zeigen die Signaturdes “convective collapse”: das Feld wird im Verlaufevon mehreren Minuten von 400 auf ca. 900 Gaussverstärkt, begleitet von Abströmungen von 1–2 km/s.Der GBP erscheint dann innerhalb einer Minute.In simultaneous observations taken at the VacuumTower Telescope (VTT) on Tenerife and the DutchOpen Telescope (DOT) on La Palma we witness theformation of a G-band bright point (GBP) from apatch of diffuse magnetic flux. The observations showthe signature of the “convective collapse”: the fieldstrength increases from 400 to around 900 G duringsome minutes in the presence of downflowns of 1–2 km/s. The GBP appears within less than 1 minuteafter the field concentration has reached 800 G.Figure 1: Temporal evolution of observation and inversion parameters with 7 min cadence. From left to right:Calcium, G-band, IR intensity, magnetic flux, integrated polarization level, field strength, magnetic filling fraction,line-of-sight velocity . The GBP is visible at t = 14 min. The line-of-sight velocity (last column, upper two rows)shows very localized downflows around 2 km/s at the later location of the BP. The field strength (6th column)increases from 400 G at t = 0 min to 900 G at t = 14 min at the GBP position; it reaches already 800 G at t = 7 min,but with a low magnetic flux value (4th column). The time scale of the field concentration and the rapid appearanceof the GBP afterwards are in agreement with the C1 model in the numerical simulations of Grossmann-Doerth etal. (1998, A&A 337, 928) where a 1 kG flux tube is formed from an inital seed field around 100 G in 5 minutes.References:Beck et al., 2005, A&A, submitted72


Bisector of an isolated G-band bright pointK. Mikurda, W. Schmidt, Kiepenheuer-Institut für SonnenphysikA. Tritschler, Big Bear Solar ObservatoryAus simultanen G-Band-Filtergrammen und zweidimensionalenSpektren wird die Sichtliniengeschwindigkeiteines isolierten “G-band brightpoints” bestimmt. Die Geschwindigkeit innerhalb desbright point unterscheidet sich praktisch nicht von derintergranularen Strömung in der unmittelbaren Umgebung.Simultaneous G-band filtergrams and two-dimensionalspectra are used to analyze the line-of-sight velocity ofan isolated G-band bright point. The flow within thebright point does not differ from the downflow of thesurrounding intergranular lane.The observations presented here were taken at the German Vacuum Telescope on Tenerife, Canary Islands usingthe two-dimensional Fabry-Perot interferometer TESOS, a 1k×1k Dalsa camera and the adaptive optics system.2D spectra were taken in the Fe I line at 557.6 nm and imaging was performed with a 1.0 nm wide interferencefilter centered around 430.3 nm in the G band. We observed two small pores with surrounding granulation in theactive region AR 10180 located at θ = 16 ◦ (µ = 0.96) in the southern hemisphere [2].For this analysis we chose an isolated G-band bright point (GBP) located in the abnormal granulation region. Fig. 1shows the bisectors of the investigated GBP and its surroundings.The GBP is located in the intergranular downflow region, but no line-of-sight motion relative to the surroundingscan be seen and the velocity gradient is about the same inside and outside the GBP. This result can hardly beexplained by the presence of the scattered light, because the bisector of the nearby granule is quite different andscattering from the dark intergranular area to the bright point is not sufficient.2D simulations of the solar magnetoconvection often predict a strong downflow relative to the surroundings whena flux tube is formed. Such an effect was observed by Beck et al. [1]. In 3D MHD simulations [3] in mostcases there is almost no difference between the flow inside the magnetic flux concentration and the intergranularlanes, although some magnetic flux concentrations show a strong downflow or upflow in respect to their immediatesurroundings.Our result and that of Beck et al. may be explained by the life history of bright points and it will be addressed in adetailed study of bright point development.0.8line depth0.60.40.20.0x xFigure 1: Bisectors of an isolated G-band brightpoint and its surroundings. Thick solid line: G-band bright point. Solid curve: immediate surroundingsof the GBP (upper cross in the inlay).Dashed curve: intergranular lane at 0.6 ′′distance (lower cross in the inlay). Dotted curve:bright granule at 0.5 ′′ distance. The inlays showthe analysed GBP and its surroundings (left toright): G-band image, broad-band continuum image,line-wing velocity. The FOV is 2.2 ′′ ×2.2 ′′ .0.0 0.5 1.0LOS velocity [km/s]References:[1] Beck, C., Schmidt, W., Bellot Rubio, L. R., Schlichenmaier, R., Sütterlin, P., 2005, A&A., submitted[2] Mikurda, K., Tritschler, A., Schmidt, W., 2005, A&A., submitted[3] Shelyag, S., Schüssler, M., Solanki, S. K., Berdyugina, S. V., Vögler, A., 2004, A&A., 427, 33573


Influence of image reconstruction on spectral line profilesK. Mikurda, W. Schmidt, Kiepenheuer-Institut für SonnenphysikA. Tritschler, Big Bear Solar ObservatoryDer Einfluss von Bildrekonstruktion auf die photometrischeQualität von 2D-Spektren wird untersucht.Linienpositionen und Asymmetrien werdendurch den angewandten Entfaltungsprozess praktischnicht verändert.We investigate the influence of image reconstruction onthe photometric quality of 2D spectral data. Line positionsand aysmmetries are not altered by the deconvolutionprocess applied.The observations presented here were taken at the German Vacuum Telescope on Tenerife, Canary Islands usingthe two-dimensional Fabry-Perot interferometer TESOS. 2D spectra (TESOS narrow-band channel) were taken ata heliocentric angle of 16 ◦ in the Fe I line at 557.6 nm and imaging (broad-band channel) was performed with a10 nm wide interference filer centered around 550 nm.In a first step, a speckle reconstruction is computed by applying an extended Knox-Thompson algorithm to thebroad-band data. Then the narrow-band images are reconstructed from the following expression:〈InŌj n j (Ij b = 〈 )∗〉|Ibj | 2〉 + 〈 |Nj b ,|2〉Ōbwhere ∗ is the complex conjugate, and O b , Ij n, Ib j denote, in Fourier domain, the speckle-reconstructed broadbandimage and the instantaneous narrow- and broad-band images, respectively. The index j denotes the differentwavelength positions in the narrow-band channel as well as the corresponding frames in the broad-band channelthat are taken strictly simultaneously.The result of the deconvolution process is demonstrated in Fig. 1 (lower row). For comparison, the un-restored butaveraged corresponding filtergrams are shown in the upper row. In the right panel of Fig. 1 we display spatiallyand temporally averaged profiles (upper row) and the corresponding bisectors (lower row) of the brightest granulesand the darkest intergranular lanes. To demonstrate the effect of the reconstruction process, the correspondingdata before (dotted) and after the deconvolution (solid) are plotted. The reconstructed mean line profile for thebrightest granules in the FOV shows an enhanced continuum intensity, narrower wings, and a slightly higher linecore intensity. For the darkest intergranular lanes, the deconvolution leads to a decrease of the continuum intensity,broader wings, and a slightly lower line core intensity. Thus, bright structures become brighter and dark structuresbecome darker by the deconvolution process, as expected. The close correspondence of the of bisector shapesbefore and after the deconvolution proves that line asymmetries are preserved.Figure 1: Left panel: Narrow-band filtergrams before (top row) and after (bottom row) reconstruction. From left to right weshow images in the line core, red line wing, and red continuum, respectively. One minor tick mark corresponds to one arcsec.Right panel: Averaged line profiles (top row) and bisectors (bottom row) before (dotted) and after (solid) the deconvolutionprocess. In addition we show bisectors for selected regions of interest in normal granulation (dashed curves) and abnormalgranulation (solid curves) before (thin) and after (thick) the deconvolution process.References:Mikurda, K., Tritschler, A. and Schmidt, W., 2005, A&A., submitted74


Speckle imaging with the extended Knox-Thompson techniqueK. Mikurda, O. von der Lühe, Kiepenheuer-Institut für SonnenphysikWir zeigen Ergebnisse von Tests des erweiterten Knox–Thompson Speckle-Abbildungsalgorithmus.The application of the extended Knox-Thompson(EKT) speckle reconstruction algorithm to a simulateddata set is presented.The extended Knox–Thompson (EKT) speckle imaging algorithm produces a diffraction-limited image of the solarsurface from a sequence of short-exposures distorted by seeing. The reconstructed Fourier phases of the result areestimated from the average Knox-Thompson cross spectrumN∑NF i (s)Fi ∗ (s − δ) = F 0(s)F0 ∗ (s − δ) ∑S i (s)Si ∗ (s − δ),i=1where F i (s) and F 0 (s) are the Fourier transforms of the i-th frame in the sequence and of the undisturbed objectintensity, and S i (s) is the instantaneous optical transfer function. The parameter δ corresponds to a shift in thefrequency domain. The average cross spectrum encodes information on the object phase gradient from which theobject phase can be recovered. The EKT algorithm uses the information of many cross spectra, typically morethan a dozen, to estimate the reconstructed Fourier phase. The Fourier amplitudes are estimated using the Labeyriealgorithm for which δ = 0.To test the performance of our implementation of the EKT algorithm we created simulated sets of 100 frames ofseeing degraded solar granulation images affected by high-level photon noise. A speckle reconstructed G-band(430.5 nm) image taken at the Vacuum Tower Telescope, Tenerife was used as an input “true” scene. We usedKolmogrov statistics for modeling atmospheric turbulence. The telescope diameter was assumed to be 700 mm.Figure 1 shows examples of speckle reconstruction of such bursts of 100 images with r 0 = 5, 10 and 15 cm,corresponding to seeing conditions ranging from mediocre to excellent. The reconstructed images are consistentin structure and photometry, despite the large variance of simulated seeing conditions. The reconstructions areessentially indistinguishable from the original image.i=1Figure 1: Speckle reconstructionof the simulated image bursts with(from the top to the bottom row)r 0 = 5, 10, 15 cm. From left toright: the best single rame fromthe burst, mean of all frames (’longterm exposure’), raw recontructedimage (without amplitude calibration),seeing and noise calibratedreconstructed image. The left halfof each subframe is displayed in acommon greyscale to show the differencesin the contrast. The fieldof view is 12 ′′ ×12 ′′ .References:Mikurda, K., von der Lühe, O., 2005, Solar Phys., in prep75


Observations of the dynamics of abnormal granulationA. Nesis, R. Hammer, H. Schleicher, Kiepenheuer-Institut für SonnenphysikEs wird untersucht, wie die Anwesenheit von Magnetfelddie Struktur und Dynamik der Granulation ändert.The change of both structure and dynamics of the granulationin the presence of magnetic field is investigated.Abnormal granulation is characterized by a reduction of its intensity contrast and geometric scales, which accordingto Dunn and Zirker (1973) has to be attributed to neighboring magnetic field. Thus, observations of anabnormal granulation area over time are an appropriate means of studying the behavior of convection in the presenceof magnetic field.In the figure we display the dynamical history of abnormal granulation. The left panel shows an abnormal granulationarea embedded in a region of undisturbed granulation, half surrounded by pores, which indicate concentrationsof strong vertical magnetic field. The absence of structuring in the anomalous area is obvious. The same abnormalregion is presented 22 min later in the middle panel. It shows a tri-level display of the velocity field, from bottomto top as a 2D image, a surface plot, and a contour plot. The structuring of the velocity field is evident. In the centerof the abnormal area, for example, we observe an upward flow similar to regular granulation. The correspondingintensity image also shows granular-like structures (Nesis et al., 2005). Changes in the structuring of the abnormalgranulation are accompanied by changes in the morphology of the pores.The change of the intensity structuring of the abnormal granulation over time was already reported by Dunn andZirker (1973, SP 14, 98). In the present work we were able to show for the first time that this change is alsoassociated with a change of the dynamical state of the abnormal area. Assuming that the reduction of the granularcontrast and geometric scales of the abnormal granulation is due to the interruption of the convective transport bythe action of subsurface magnetic field, we calculated the correlation between the velocities in the abnormal field inthe higher and deeper layers. This correlation as a function of time is presented in the right panel. By comparison,for undisturbed granulation with its coherent flow the correlation is nearly 1.Figure 1: Left: Intensity map, with the abnormal area indicated. Middle: Line-center velocity 22 min later for thearea of abnormal granulation, shown as 2D map (bottom), surface plot (middle), and contour plot (top). Right:Correlation between the velocities at two different heights, as a function of time, for the entire area of abnormalgranulation.References:Nesis, A., Hammer, R., & Schleicher, H. 2005, Astron. Nachr., 326, 30576


Understanding faculaeO. Steiner, Kiepenheuer-Institut für SonnenphysikDas Fackelmodell, bestehend aus einer Magnetflussröhreeingebettet in eine planparallele Atmosphäre,reproduziert das beobachtete Kontrastprofil vonSonnenfackeln. Insbesondere wird damit die sonnenrandseitigeAusdehnung des Kontrastprofils und derzentrumsseitige dunkle und schmale Saum negativenKontrasts verständlich.The simple facular model, consisting of a magneticfield concentration embedded in a plane parallel atmospherereproduces the observed contrast profile of solarfaculae. In particular it renders the limbside extensionof the contrast enhancement and the recently discoveredcenter-side dark, narrow lane understandable.Faculae appear as bright granules (facular granules) near the solar limb when observed in white-light. They play acrucial role for the solar radiance variability–by their brightness they slightly overcompensate the radiation deficitof sunspots. Recent high-resolution observations and models have brought us now to a new level in understandingfaculae. A basic model that captures the essential properties of faculae is illustrated in Fig. 1.Figure 1: Left:a) Magnetic flux concentration (blue) with surfaces of optical depth τ = 1 (red) for vertical lines of sight (heavy red curve)and inclined ones (light red curve). b) Corresponding contrast curves. Black dot corresponds to lines of sight indicated in panel a). Right: a)Surfaces of optical depth τ = 1 and 5 (red) for lines of sight inclined by 50 ◦ to the vertical together with isotherms. b) Contrast profile. Theregion of negative contrast is bounded by the two lines of sight (blue) indicated in panel a).Accordingly, faculae are vertically-oriented magnetic flux concentrations (blue field lines in the lower left panel)embedded in a field-free, plane parallel atmosphere. When looking straight down on the flux concentration (observationat disk center) light comes from around the heavy, red surface (optical depth unity) and gives rise to thedouble humped red contrast profile shown on top. The surface depression is due to the magnetic tension forces ofthe flux concentration. Observing near the solar limb when seeing the flux concentration from a direction indicatedby the black line of sight, we obtain the surface and contrast shown in orange red. The steep contrast increase at theright flank (disk center side) comes from the “hot wall” of the surface depression. The gentle decreasing extensionof the contrast enhancement on the limb side is due to the rarefied, thus more transparent atmosphere of the fluxconcentration. A plasma parcel on the solar surface sideways of the flux concentration “sees” a more transparentsky, leading to enhanced photon escape, in the direction towards the magnetic field compared to a direction awayfrom it. This effect makes the “hot wall” to extend in a more horizontal direction far outside the flux concentrationproper, exactly as is observed. The indicated line of sight gives rise to the contrast marked by the black dot. Itdivides the contrast profile into a “hot wall” and a “hot surface” regime.A dark narrow lane centerward of the facular brightening is another observed feature of many faculae. The twopanels to the right show a similar situation as before but for a broader magnetic flux concentration. The blue linesof sight bound a region for which the corresponding contrast is negative, forming a dark lane. One sees in this lanethe deep layers of the flux concentrations that are cool (dark), while the “wall” of the depression is yet hidden fromsight at larger optical depths.A self-consistent, non-stationary simulation that takes the energy and radiation transfer equation fully into accountconfirms the properties of the present basic model.References:Steiner, O.: 2005, A&A, 430, 691–70077


First holistic magnetohydrodynamic simulation from the convection zoneto the chromosphereW. Schaffenberger, O. Steiner, S. Wedemeyer-Böhm, Kiepenheuer-Institut für SonnenphysikEine erste MHD-Simulation, welche Schichten vonder Konvektionszone bis in die Chromosphäre umfasst,zeigt ein überraschend dynamisches chromosphärischesMagnetfeld. Dieses besitzt groß- undkleinskalige Struktur, welche sich schnell verändert.A first holistic MHD simulation from the convectionzone to the chromosphere reveals a surprisingly dynamicchromospheric magnetic field. It shows largeand small-scale structure on a short dynamic timescale.We have carried out a three-dimensional magnetohydrodynamic simulation of the integral layers from the convectionzone to the chromosphere. The simulation starts with a homogeneous vertical magnetic field of a fluxdensity of 10 G superposed on a previously computed, relaxed model of thermal convection. This flux densityought to mimic magnetoconvection in a network-cell interior. The three-dimensional computational domain extendsfrom 1500 km below the surface of optical depth unity to 1500 km above it and it has a horizontal dimensionof 2500 × 2500 km. Thus, for the first time it became possible to extend simulations of magnetoconvection of thesurface layers into the chromosphere.Figure 1: Three horizontal sections through the three-dimensional computational domain. Left: bottom layer, Middle: layer near opticaldepth τ c = 1, Right: Top, chromospheric layer. The color coding displays absolute magnetic field strength, with individual scaling for eachpanel. Red indicates high, blue low or zero flux density.The magnetic field concentrates in narrow sheets near the surface of optical depth unity with field strengths up toapproximately 1 kG. Below the surface the field disperses again but partially remains concentrated in flux tubeswith a strength of a few hundred Gauss. The chromospheric magnetic field is marked by strong dynamics with acontinuous reshuffling of magnetic flux on a time scale much shorter than in the photosphere or in the convectionzone. The formation of weak flux tubes prevails again but on a spatial scale much larger than the width of the sheetsnear the surface and with a slight tendency to be located in between the flux concentrations at the surface. Highlydynamic filaments of stronger than average magnetic field are a ubiquitous phenomenon in the chromosphere.They form in the compression zone behind and along propagating shock fronts, that continue to be an integral partof chromospheric dynamics as already seen in the hydrodynamic simulations of the chromosphere by Wedemeyeret al. (2004). These magnetic filaments that have a field strength of not more than a few tens of Gauss, rapidlymove with the shock fronts and quickly dissolve or form with them. Overall, the picture of flux concentrations thatstrongly expand through the photosphere into a more homogeneous chromospheric field remains valid. That fieldfills the entire chromosphere and leads to a surface of plasma β = 1 around a height of 1000 km. However, thechromospheric magnetic field experiences a much more vigorous dynamics than previously thought.References:Wedemeyer S., Freytag, B., Steffen, M., Ludwig, H.-G., Holweger, H.: 2004, A&A, 414, 1121–113778


Recent upgrades of CO 5 BOLDSven Wedemeyer-Böhm, Kiepenheuer-Institut für SonnenphysikBernd Freytag, Department for Astronomy and Space Physics, Uppsala, SwedenWerner Schaffenberger, Astrophysikalisches Institut Potsdam/Kiepenheuer-Institut für SonnenphysikMatthias Steffen, Astrophysikalisches Institut PotsdamJorrit Leenaarts, Utrecht University, The NetherlandsOskar Steiner, Kiepenheuer-Institut für SonnenphysikInga Kamp, Space Telescope Division of ESA, STScI, Baltimore, USADas Strahlungshydrodynamikprogramm CO 5 BOLDwurde um die Behandlung von Magnetfeldern, chemischerReaktionsnetzwerke und zeitabhängiger Wasserstoffionisationerweitert.The radiation hydrodynamics code CO 5 BOLD hasbeen supplemented with the treatment of magneticfields, chemical reaction networks, and time-dependenthydrogen ionisation.The code CO 5 BOLD is designed for simulating hydrodynamics and radiative transfer in the outer and inner layersof stars. Additionally, it can treat dust formation in stellar atmospheres. The code has been extended to a magnetohydrodynamics(MHD) version recently. Moreover, the time-dependent treatment of chemical reaction networks(CHEM) has been implemented. The changes of number density of chemical species due to chemical reactions andthe advection with the hydrodynamic flow field are taken into account. A simplified method of radiative coolingdue to carbon monoxide infrared spectral lines is also available. Time-dependent hydrogen ionisation (HION) isnow included, too, though hydrogen is treated as a minority species so far.The upgraded code now offers a large range of possible applications. For instance, it has been used for 2D and 3Dsimulations of the formation and destruction of carbon monoxide in the non-magnetic solar photosphere and lowchromosphere. First simulations with the MHD version and the HION extension are currently in progress. Thespecial design of the code even allows the simulation of magnetic fields in the solar chromosphere and will help togain insight in the dynamic and inhomogeneous structure of the solar chromosphere.Figure 1: Exemplary applications of CO 5 BOLD: 2D and 3D models for different stellar types, including the Sun,and the optional extensions.References:Freytag, B., Steffen, M., & Dorch, B. 2002, Astron. Nachr., 323, 213Wedemeyer, S., Freytag, B., Steffen, M., Ludwig, H.-G., & Holweger, H. 2004, A&A, 414, 1121Wedemeyer-Böhm, S., Kamp, I., Bruls, J., & Freytag, B. 2005, A&A, 438, 104379


Development of CO 5 BOLD Analysis ToolSven Wedemeyer-Böhm, Kiepenheuer-Institut für SonnenphysikFür die Auswertung der mit CO 5 BOLD berechnetenSimulationen wurde ein auf IDL basierendes Analyseprogrammentwickelt.An IDL-based software package has been developedfor the analysis of simulations computed withCO 5 BOLD.The simulations done with the radiation hydrodynamics code CO 5 BOLD result in a large amount of data thatrequire extensive data analysis. In particular the visualisation and quantitative examination of 3D models is aninvolved task that can be made much more efficient by means of a comprehensive tool. CO 5 BOLD Analysis Toolwas developed in the interactive data language IDL that is widely used for astrophysical applications. It providesa graphical user interface (GUI, Fig. 1) so that even an unexperienced user can easily browse through the resultsof numerical simulations. The main tool is the display of 2D slices for a large number of physical quantities.Number densities for chemical species, hydrogen population numbers, and also magnetic field components arenow included to account for the newest upgrades of CO 5 BOLD. The view plane and its direction can be changedby simple mouse-clicks, enabling the user to easily “walk” through the model. Additionally 1D profiles canbe plotted and even a 3D visualisation is possible. Many other features like, e.g., contours and streamlines areavailable. Next to visualisation the tool offers the output of images, movies and model data for external usage.CO 5 BOLD Analysis Tool was developed to make the numerical simulations accessible in an easy way for thegrowing CO 5 BOLD user community.Figure 1: Screen-shot of CO 5 BOLD Analysis Tool showing the gas temperature in a horizontal cross-section inthe model chromosphere by Wedemeyer et al. (2004).References:Wedemeyer, S., Freytag, B., Steffen, M., Ludwig, H.-G., & Holweger, H. 2004, A&A, 414, 112180


Carbon monoxide in the solar atmosphereSven Wedemeyer-Böhm, Kiepenheuer-Institut für SonnenphysikInga Kamp, Space Telescope Division of ESA, STScI, Baltimore, USAJo Bruls, Kiepenheuer-Institut für SonnenphysikBernd Freytag, Department for Astronomy and Space Physics, Uppsala, SwedenMit dem StrahlungshydrodynamikprogrammCO 5 BOLD gerechnete zwei- und dreidimensionaleSimulationen zeigen, dass Kohlenstoffmonoxid (CO)in der Sonnenatmosphäre hauptsächlich in den kühlenRegionen der mittleren Photosphäre zu finden ist.Two- and three-dimensional simulations calculatedwith the radiation hydrodynamics code CO 5 BOLDshow that the bulk of carbon monoxide (CO) is foundin the cool regions of the middle photosphere.Two- and three-dimensional simulations of carbon monoxide (CO) in the non-magnetic solar photosphere and lowchromosphere were carried out with an extended version of the radiation hydrodynamics code CO 5 BOLD. Achemical reaction network has been constructed that takes into account the reactions which are most importantfor the formation and dissociation of CO under the physical conditions of the solar atmosphere. It consists of 27reactions, involving the chemical species H, H 2 , C, O, CO, CH, OH, and a representative metal.The highest absolute CO number density is found in the cool regions of the reversed granulation pattern at midphotosphericheights and decreases strongly above. But the relative abundance of CO remains high in the atmosphereabove, indicating that a large fraction of carbon atoms is bound in CO in and above the middle photospherewith exception of the hot propagating shock waves which are a ubiquitous phenomenon of the model atmosphere.For a large part of the atmosphere, in particular in the lower layers, the chemical timescales are short. There, thesimplifying assumption of instantaneous chemical equilibrium is valid but it fails near and in chromospheric shockwaves where a time-dependent approach is mandatory. Furthermore, simulations with altered reaction networkshow that the formation channel via hydroxide (OH) is the most important one under the conditions of the solaratmosphere.Figure 1: Carbon monoxide “clouds” in the middle photosphere: Iso-surfaces for CO number density n CO =4 · 10 12 cm −3 (blue) and gas temperature T = 7000 K (red).References:Wedemeyer-Böhm, S., Kamp, I., Bruls, J., & Freytag, B. 2005, A&A, 438, 104381


Radiative line cooling of carbon monoxideSven Wedemeyer-Böhm, Kiepenheuer-Institut für SonnenphysikMatthias Steffen, Astrophysikalisches Institut PotsdamSimulationen der Sonnenatmosphäre mit zeitabhängigerStrahlungskühlung durch Kohlenmonoxidlinien zeigenkeine thermische Bifurkation der Atmosphäre, sondernnur eine Senkung der mittleren Gastemperatur um etwa100 K.Simulations of the solar atmosphere with timedependentradiative cooling due to carbon monoxidelines do not show a thermal bifurcation of the atmospherebut only a reduction of the average gas temperatureby 100 K.In addition to the treatment of chemical reaction networks the radiative cooling by carbon monoxide (CO) lineshas been implemented in the radiation chemo-hydrodynamics code CO 5 BOLD. The radiation transport is nowsolved in a Rosseland mean opacity band and an additional band with CO opacity. The latter is calculated from thetime-dependent CO number density via approximate opacity distribution functions (ODFs). The number densityis derived from the solution of a chemical reaction network that was already used by Wedemeyer-Böhm (2005). Itconsists of 27 reactions and involves the chemical species H, H 2 , C, O, CO, CH, OH and a representative metal.z [km]z [km]10005000-500-100010005000-500-10001000 2000 3000 4000x [km]-5 0 5Q rad, R [10 9 erg g -1 s -1 ]1000 2000 3000 4000x [km]-0.6 -0.4 -0.2 0.0∆Q rad [10 9 erg g -1 s -1 ]A direct comparison of simulations withand without CO line cooling shows that theinclusion of CO line cooling causes additionalcooling in the fronts of propagatingshock waves in the chromosphere. There,the time-dependent approach results in ahigher CO number density compared to theequilibrium case and with that in a largernet radiative cooling rate. But since the effectis much smaller outside shock wavesthe average gas temperature stratification ofthe model atmosphere is only reduced byroughly 100 K. Also the temperature fluctuationsand the CO number density areonly affected to a small extent. The relatedhydrodynamical timescales are muchtoo small to allow for the radiative relaxationto localised cool structures. Consequently,there is no thermal bifurcation ofthe solar atmosphere due to carbon monoxideas cooling agent.Figure 1: Net radiative heating rate Q rad in a2D model. Top: grey continuum band. Bottom:heating rate due to CO opacity; the curvesrepresent Q rad = 0 (dotted), optical depth unity(solid), and temperature T = 5000 K (dashed).The strongest radiative emission (white colour)in the continuum band is found near opticaldepth unity (the “surface”) and in the hot chromosphericshock waves. The CO band causesadditional emission at the fronts of the shockwaves.References:Wedemeyer-Böhm, S., Kamp, I., Bruls, J., & Freytag, B. 2005, A&A, 438, 1043Wedemeyer-Böhm, S., Steffen, M., A&A, in prep82


Time-dependent hydrogen ionisation in simulations of the solar atmosphereJorrit Leenaarts, Utrecht University, The NetherlandsSven Wedemeyer-Böhm, Kiepenheuer-Institut für SonnenphysikDie zeitabhängige Behandlung von Wasserstoff wurdeim Strahlungshydrodynamikprogramm CO 5 BOLDimplementiert.The time-dependent treatment of hydrogen ionisationhas been implemented in the radiation hydrodynamicscode CO 5 BOLDThe ionisation degree of hydrogen (H) and the electron density are essential for describing the gas by means of anequation of state. In the radiation hydrodynamics code CO 5 BOLD the equation of state has been treated under theassumption of instantaneous local thermodynamic equilibrium (LTE) in the form of a precomputed look-up tableso far. The thereby assumed instantaneous ionisation equilibrium is valid as long as the timescales for ionisationand recombination are shorter than the dynamical timescales. However, in the chromosphere, which is the maintarget of this project, this assumption is no longer valid. Rather, the finite ionisation and recombination rates haveto be taken into account (cf. Carlsson & Stein 2002, ApJ 572, 626).Following the work by Sollum (1999, Master thesis, University of Oslo), we implemented the time-dependenttreatment of a simplified model atom of hydrogen. This model atom consists of six energy levels, includingthe ionised state. To render this approach feasible, a constant radiation field is assumed. This assumption isjustified by the fact that the bulk of the relevant radiation is indeed emitted in the photospheric layers well belowthe chromosphere. The rates are calculated from the new level populations similar to the treatment of chemicalreaction networks (see Wedemeyer-Böhm et al. 2005). With that the ionisation degree is retrieved. The advectionof the level populations and of the free electrons is done with the same routines as for the chemistry case.The final step will be the feedback of the time-dependent hydrogen ionisation to the general equation of state thatis used in CO 5 BOLD so far and with that to the internal energy of the gas and to the radiative transfer term in thetotal energy equation.15001500instantaneous ionisation (NLTE)1500time-dependent ionisation (NLTE)100010001000z [km]5000z [km]5000z [km]5000-500-500-500-1000-1000-10001000 2000 3000 4000x [km]1000 2000 3000 4000x [km]1000 2000 3000 4000x [km]4 6 8 10 12 14 16log. gas temperature (cgs)-7 -6 -5 -4 -3 -2 -1 0log. ion. frac. log n HII / n HI-7 -6 -5 -4 -3 -2 -1 0log. ion. frac. log n HII / n HIFigure 1: Snapshot from a 2-D model after 27 min simulation time: logarithmic gas temperature (left), logarithmicionisation fraction for instantaneous ionisation (middle) and time-dependent ionisation (right). For both casesdeviations from local thermodynamic equilibrium (LTE) are taken into account. The dashed curves representcontours for a constant gas temperature of T = 5000 K.References:Wedemeyer-Böhm, S., Kamp, I., Bruls, J., & Freytag, B. 2005, A&A, 438, 104383


Observation and simulation of reversed granulationJorrit Leenaarts, Utrecht University, The NetherlandsSven Wedemeyer-Böhm, Kiepenheuer-Institut für SonnenphysikInverse Granulation kann bereits sehr realistisch durchhydrodynamische Simulationen wiedergegeben werden,wie ein detaillierter Vergleich mit Beobachtungenzeigt.Reversed granulation can be reproduced quite realisticallyby hydrodynamic simulations as can be seen froma detailed comparison with observations.High-quality image sequences from the Dutch Open Telescope (DOT) are compared with synthetic image sequencesobtained from 3D radiation hydrodynamics simulations of the solar granulation by Wedemeyer et al.(2004). The simulation was carried out with the radiation hydrodynamics code CO 5 BOLD without the new MHDextension and thus refer to non-magnetic internetwork regions only. Based on this simulation, synthetic intensityimages are calculated with the SPANSAT radiative transfer code by V. A. Sheminova.The emphasis of this work is on the brightness pattern observed in the wings of CaII H. We compared auto- andcross-correlations, different Fourier properties, and intensity contrast and found that the simulations reproduce theobserved intensity contrast, time scales, and Fourier behaviour rather well. Most of the remaining differences canbe attributed to the lower resolution of the observations and to the small geometrical extent of the simulation.But in general observations and simulations agree very well, indicating that the basic mechanism for formationof reversed granulation is already included in the simulations. We conclude that the reversed granulation patternis mostly produced by convection reversal and that magnetic fields play no or at least only a minor role in theformation of the pattern in internetwork areas.500050005000400040004000y [km]3000y [km]3000y [km]300020002000200010001000100000 1000 2000 3000 4000 5000x [km]00 1000 2000 3000 4000 5000x [km]00 1000 2000 3000 4000 5000x [km]500050005000400040004000y [km]3000y [km]3000y [km]300020002000200010001000100000 1000 2000 3000 4000 5000x [km]00 1000 2000 3000 4000 5000x [km]00 1000 2000 3000 4000 5000x [km]Figure 1: Simulated and observed intensity images of the blue continuum (upper row) and CaII H wing (lowerrow). Left: synthetic image from simulation. Middle: synthetic image convoluted with the best fit telescopepointspread function. Right: DOT observations of June 18, 2003.References:Leenaarts, J., Wedemeyer-Böhm, S., 2005, A&A, 431, 687-692Wedemeyer, S., Freytag, B., Steffen, M., Ludwig, H.-G., & Holweger, H. 2004, A&A, 414, 112184


Temporal evolution of physical parameters in the solar photosphere –results of inversionH. Wöhl, Kiepenheuer-Institut für SonnenphysikJ. Koza, A. Kučera, J. Rybák, Astronomical Institute of the Slovak Academy of SciencesZeitliche und räumliche Entwicklung physikalischerParameter in der Photosphäre wurden in einer nichtmagnetischenRegion und in einer kleinen Regionerhöhter magnetischer Aktivität im Sonnenscheibenzentrumbestimmt. Die angewandte Methode nutzt dieSIR (Stokes Inversion basierend auf Responsefunktionen)Programme.The temporal and spatial evolution of the physical parametersin the solar photosphere was inferred in anon-magnetic region and in a small region of enhancedmagnetic activity at disk center. The method applieduses the SIR code (Stokes Inversion based on Responsefunctions).Time series of spectrograms obtained at the German Vacuum Tower Telescope were interpreted by the inversioncode SIR. Profiles of five spectral lines of different atomic species and ionization stages were inverted simultaneously.The resulting models exhibit increasing temperature variations with height especially in a non-magneticregion. While 5 min oscillations induce conspicuous oscillatory variations of the temperature and the line-of-sightvelocity in the non-magnetic region, no obvious oscillatory-like behaviour of the physical parameters was foundin the magnetic region.Generally, the magnetic region is well identifiable as the hottest part of the middle photosphere with a featurelessevolutionary track of the temperature. The mean temperature model of the non-magnetic region is in satisfactoryagreement with the classical 1D model HOLMUL as well as with the horizontally and temporally averaged modelarising from 3D numerical simulation of the solar granulation (Asplund et al. 2004, A&A 417, 751, and Asplundet al. 2005, A&A 435, 339). In addition the line-of-sight velocity shows increasing variations with height considerablyamplified in the upper photosphere. In agreement with 3D numerical simulations (Stein and Nordlund1998, ApJ 499, 914), a certain fraction of the granules in the magnetic region possesses downflows and oppositely,the upflows were detected in the abundant clump of the intergranular spaces both in the non-magnetic and in themagnetic region. This feature has a physical as well as an observational origin. The reversal of the flow directioncan be ascribed partly to the turbulence and partly to the influence of stray light. In conclusion: well-defined rangesof temperature and line-of-sight velocity are characteristic at least for some layers of the solar photosphere.spatial direction [arcsec]100806040200T [K], log τ = -1.90 2 4 6 8 10 12 14time [min]5150505049504850475046504550v LOS [km s -1 ]v LOS [km s -1 ]86420-2-486420-2-4log τ = 0.70 log τ = 0.00log τ = 0.70 log τ = 0.00log τ = - 0.70log τ = - 0.70non-maglog τ = - 1.50maglog τ = - 1.509000 8000 7000 6000 5000T [K]Figure 1: Left: Space-time evolution of the temperature at the optical depth log τ = −1.9. The non-magnetic andmagnetic region are ranging from 0 to 55 ′′ and from 60 to 95 ′′ , respectively, in spatial direction. Right: Scatterplot of the line-of-sight velocity and temperature at selected optical depths in the non-magnetic (upper panel) andmagnetic region (lower panel). Negative velocities indicate upflows.85


A new method for comparing spectroscopic observations with numericalsimulationsH. Wöhl, S. Wedemeyer-Böhm, O. Steiner, Kiepenheuer-Institut für SonnenphysikJ. Rybák, A. Kučera, Astronomical Institute of the Slovak Academy of SciencesEine einfache Methode wurde entwickelt, umErgebnisse von hochaufgelösten spektroskopischenBeobachtungen der solaren Photosphäre - wie etwasolchen vom VTT - mit Resultaten aus numerischenSimulationen der Konvektion in der Sonnenatmosphärezu vergleichen.A simple method was developed for comparing resultsderived from high-resolution spectroscopic observationsof the solar photosphere - like those taken atthe Vacuum Tower Telescope (VTT) - with results obtainedfrom numerical simulations of convection in thesolar atmosphere.The method is based on the comparison of the granular continuum contrasts obtained from both, the observationsand the synthetic spectra, calculated from numerical simulations. It can be used post factum, especially whenno auxiliary measurements on instrumental characteristics of the telescope/spectrograph and on seeing conditionsare available. The procedure consists in degrading the synthetic spectra using a point spread function roughlyknown for the atmosphere and telescope/spectrometer and finally tune the free parameters of the function until thedegraded synthetic spectra matches the granular continuum contrasts of the observed spectra.The method is very convenient for the investigation of statistical relations between different physical parameterscoming from simulations and from spectroscopic observations. It was tested by comparing results of numericalsimulations computed with the CO 5 BOLD code (Wedemeyer et al., 2004) to VTT/Tenerife high-resolution spectroscopicechelle observations (Rybák et al., 2004). In particular it was used in a search for shock waves in thesolar photosphere.1.41.441.241.2SLIT POSITION [arc sec]321.00.8SLIT POSITION [arc sec]321.00.810.610.60−0.2 −0.1 −0.0 0.1 0.2WAVELENGTH [Å]0.40−0.2 −0.1 −0.0 0.1 0.2WAVELENGTH [Å]0.4Figure 1: Left: Synthetic spectrum of the FeII 6454 Å line at heliocentric angle µ = 0.65 originating from thesimulations. Right: Same spectrum, degradated using the new method. The shock event at the slit position 2.8 arcsec is visible as an extremely broadened profile in the original synthetic spectrum. In the degradated spectrum theeffect is very weak only.References:Rybák, J., Wöhl, H., Kučera, A., Hanslmeier, A., Steiner, O.: Astron. Astrophys. 420, 1141 (2004)Wedemeyer, S., Freytag, B., Steffen, M., Ludwig, H.-G., Holweger, H.: Astron. Astrophys. 414, 1121 (2004)86


Stellar surface imaging with interferometric instrumentsJ. Bruls, O. v.d. Lühe, J. Sahlmann, Kiepenheuer-Institut für SonnenphysikWir untersuchen die Signaturen von Oberflächenströmungenund Magnetfelder in synthetischen interferometrischenBeobachtungen von nahen K-Riesensternen.By means of synthetic interferometric observations in aclean near-infrared spectral line we investigate the signaturesof differential rotation, surface flows and magneticfields on a nearby K-giant star.Only a handful of stars with very large apparent diameters are accessible to direct surface imaging with currentinterferometric instruments; signatures of differential rotation, surface flows and various manifestations of surfacemagnetic fields should be detectable in the interferometric signal of many resolved stars.We first perform the radiative transfer at various wavelengths in a clean near-infrared spectral line and for a suitableset of ray directions for a snapshot of a hydrodynamic simulation of a K-giant, comprising just a handful ofgranules. From those results we synthesize stellar disk images at all wavelengths (Fig. 1, left panel) by patchingthe intensities computed for the simulation box over the entire stellar surface taking into account all angle dependencesand center-to-limb variation. Some radial stretching is applied in order to obtain a seamless transitionbetween neighboring patches, resulting in a rather regular, towards the limb slightly curved, appearance of the stellardisk. These images are then subjected to a simulated VLTI observation procedure. Afterwards we investigatethe interferometric signals for various wavelengths (Fig. 1, right panel) and search for features that are related to(convective) surface flows.Figure 1: Left: simulated stellar disk image in the infrared spectral line. Clearly visible is the inverse granulationpattern. Right: the corresponding visibility amplitudes (fringe contrast) as a function of spatial frequencies, hereexpressed in terms of the equivalent baseline length, for the pure convection case (no surface flows, differentialrotation or magnetic fields added).We find that a convective star has a higher visibility than a featureless star, both in the continuum and in the line.The left part of the visibility curves results from the center-to-limb variation, the lack of features in the middle partof the curves results from the absence of structures larger than the simulation box size, and the strongest featuresin the right parts of the curves for a convective star are the dips in the visibility due to the regular patching ofthe simulation box across the stellar surface. The visibility in the line is enhanced w.r.t. the continuum; it is stillunclear whether the limb effect plays a role here. We conclude that existing baselines (up to about 200 meters)should suffice to resolve convection on a handful of giants with large apparent diameters — a resolution of only afew inverse stellar radii is sufficient since these stars have only few and very large granules — but that substantiallylonger baselines are needed to resolve convection on other stars.87


First Sun-as-a-star EUV spectraHardi Peter, Kiepenheuer-InstitutErstmalig wurden Spektren der Sonne als Stern gewonnen,die es erlauben, die Profile der Emissionslinenim Extrem-Ultravioletten spektral aufgelöst zuanalysieren. Diese Spektren sind für vergleichendeStudien der Sonne und anderer Sternen von großerWichtigkeit.The first Sun-as-a-star spectra allowing to resolve detailsof emission line profiles in the extreme ultraviolethave been calculated from full-disk rasters of theSun. These spectra are of vital importance to relate thecorona of our Sun to other stars.Observations in the extreme ultraviolet (EUV) show a star only as a single point, and the spectra we see are theintegral from the whole visible hemisphere. In solar observations we usually concentrate on a small region withthe highest possible spatial resolution, at the cost of the field of view. As the spectrograph slit will cover only asmall fraction of the solar disk (with SUMER/SOHO 0.01%), one has to scan the area of interest. To account forthe instrumental drifts occurring during the up to 24 hours long SUMER full-disk raster scans, all spectral profilesare fitted by Gaussians, and the resulting line profile parameters corrected (Peter 1999, ApJ 516, 490). Based onthese corrected data at each location of the original raster a now corrected spectrum is calculated and all spectraare then integrated over the whole disk.1.0α Cen A C IV (1548 Å)Sun−as−star spectrumrelative intensity0.80.60.42.5 km/s0.27.5 km/sblue−60 −40 −20 0 20 40 60Doppler shift [km/s]redThe figure shows the resulting Sun-as-star spectrum of the C IV (1548 Å) line formed at some 10 5 K in the transitionregion from the chromosphere to the corona (grey histogram) the red curve shows the excellent double Gaussianfit with the narrow and broad component shown in green and blue.The Sun-as-a-star spectrum is clearly non-symmetric, but very well described by a double Gaussian fit. Theproperties of this spectrum are very similar to those of the “solar twin” αCen A (see inlet showing the sameemission line with the same range in wavelength; Pagano et al. 2004, A&A 415, 331).The asymmetry of the Sun-as-a-star spectrum as well as the relative strength of the two Gaussian componentsdiffer significantly from the average spectrum near the disk center, which indicates that the two components asseen in the Sun-as-a-star spectrum are a result of the center to limb variation of line intensity and shift, andprobably contain only limited (direct) information on the coronal heating process. If further studies will confirmthis, studies of stellar coronae can utilize these results to extract information on the center-to-limb variation of lineintensity and shift, and through this might open the possibility to study the spatial extent of the transition regionfrom the chromosphere to the corona, which contains indirect information on the heating mechanism.88


EUV spectra from 3D MHD models of a coronal active regionHardi Peter, Kiepenheuer-Institut; Boris Gudiksen, Univ. Oslo; Åke Nordlund, Univ. CopenhagenAuf der Basis eines 3D-MHD-Modells der Korona synthetisierenwir die Profile von Emissionslinien in einemTemperaturbereich von 20 000 K bis 10 6 K. Die resultierendenKarten der Korona erlauben einen detailliertenVergleich mit den Beobachtungen und stellenein neues Hilfsmittel zur Untersuchung der Korona dar.Based upon a 3D MHD model of a coronal active regionwe derived the profiles of a number of emissionlines spanning temperatures from 20 000 K to 10 6 K.The resulting synthesized images of the corona allow adetailed comparison to observation and provide us witha new tool for coronal studies.Doppler shift [km/s]−20 −10 0 10 20C IV (1548 Å)relative intensity I / 0.01 0.10 1.00 10.00 100.00logT=5.02Z [Mm]302010horizontal coordiante Y [Mm]504030201000 10 20 30 40 50horizontal coordiante X [Mm]Y [Mm]504030201000 10 20 30 40 50X [Mm]vertical coordinate Z [Mm]030201000 10 20 30 40 50Y [Mm]0 10 20 30 40 50X [Mm]The 3D MHD model is solving the mass, momentum and energy balance along with the evolution of the magneticfield in a 3D box (60×60×37Mm 3 including the whole atmosphere from the photosphere to the corona. Theheating is due to braiding of the magnetic field lines due to footpoint motions in the photosphere as suggested byParker (Gudiksen & Nordlund 2005, ApJ 618, 1020 & 1031)Based on the MHD model results we calculate the spectral profile at each grid point under the assumption ofionization equilibrium. By integrating along a line of sight and taking the moments of the line profile we obtain2D maps in line intensity, shift and width, which can be analyzed in the same way as observations.The figures show maps in line shift and intensity when viewing from above (left panels) and side views of thecomputational box (right panels) for a snapshot from the simulation for a C IV line from the transition region(10 5 K) and a Mg X line from the corona (10 6 K). The transition region shows much finer structures than thecorona and especially the Doppler shifts in the corona have a more complex structure than the emissivity. Alsonote the presence of small cool loops in the transition region when looking at the box from the side (top right).Doppler shift [km/s]−20 −10 0 10 20Mg X (625 Å)relative intensity I / 0.1 1.0 10.0logT=6.01Z [Mm]302010horizontal coordiante Y [Mm]504030201000 10 20 30 40 50horizontal coordiante X [Mm]Y [Mm]504030201000 10 20 30 40 50X [Mm]vertical coordinate Z [Mm]030201000 10 20 30 40 50Y [Mm]0 10 20 30 40 50X [Mm]References:Peter H., Gudiksen B., Nordlund Å. (2004): ApJ 617, L85; ApJ submitted, astro-ph/050334289


Coronal heating through braiding of magnetic field lines:comparison of a forward model to observationsHardi Peter, Kiepenheuer-Institut; Boris Gudiksen, Univ. Oslo; Åke Nordlund, Univ. CopenhagenEs werden mittlere Doppler-Verschiebungen und Emissivitätenaus einem 3D-MHD-Modell der Koronaberechnet und mit Beobachtungen verglichen. Die guteÜbereinstimmung stützt eine Koronaheizung durchVerflechten von Magnetfeldlinien.We derive average Doppler shifts and emission measuresfrom a 3D MHD coronal model and comparethem to observations. The good match gives furthersupport for coronal heating being due to braiding ofmagnetic field lines.To account for the complex structure and to describe the heating and dynamics of the corona we use a forwardmodel consisting of a 3D MHD model and a code to compute the resulting emission line spectra. The line profileproperties can then be compared to observations, and here we concentrate on the average variation of Dopplershifts and the emission measure as a function of temperature in the corona.The average Doppler shifts are displayed as a function of line formation temperature in the top panel; the bars indicatethe scatter in the modeled volume. The observed trend is shown as a thick dashed line.The overall match is very good, especially the peak atDoppleraround 200 000 K. Only at the high temperatures theshift C III C IVobserved blueshifts are not well reproduced, probablydue to imperfections of the treatment of the upper10boundary.Doppler shift [km/s] → redlog DEM [cm −5 K −1 ]50−5272625242322Si IIC IISi IVobservationsO IVO VO VIline shifts from averagesynthetic spectraNe VIII4.0 4.5 5.0 5.5 6.0log 10 line formation temperature [K]Si IIC IIC IIIdifferentialemissionmeasure (DEM)Si IVCHIANTI inversion fitof synthetic spectra2 x observed QS DEM4.0 4.5 5.0 5.5 6.0log 10 line formation temperature [K]Mg XC IVO IVO VINe VIII Mg XO VNevertheless, it should be stressed that for the firsttime this model provides an overall match to the lineshifts observed in the transition region without anyfine-tuning or special assumptions on the geometry ofthe relevant coronal structures.The lower panel shows the emission measure as derivedfrom the synthesized spectra as a solid red curve. Thelines used in the inversion and the scatter are indicatedby the bars. The emission measure as inverted fromobservations is shown as a thick dashed curve.The match is remarkably good. We find a minimumaround 200 000 K and an increase towards lower temperatures,where previous 1D and 2D models failedbadly. This shows that the corona is made up by ahierarchy of structures, where hot large loops dominatethe emission above some 400 000 K and coolsmall low transition region loops dominate below some200 000 K. It has to be stressed that the cool transitionregion structures are highly intermittent.This forward-modeling approach shows that the flux-braiding mechanism is a prime candidate for the coronalheating process. The spectra derived from a complex 3D MHD model show properties very similar to thoseobserved with the Sun and solar-like stars. Especially the Doppler shifts and the emission measure as a function oftemperature match the observations very well. For the first time this match was achieved without any fine tuningor special assumptions. The model shows that the whole corona is very intermittent with large fluctuations in timeand space.This type of forward modeling is also of vital interest to understand stellar coronae. Other stars exhibit a quitedifferent structure of the photospheric magnetic fields and of convection patterns. This type of forward model is avaluable tool to study the relevant processes in these coronae in detail and to compare the results for the spectrallines synthesized from the model directly to stellar observations. Further progress in numerical forward modelingwill open a new path to study stellar coronae.References:Peter H., Gudiksen B., Nordlund Å. (2004): ApJ 617, L8590


Simulated SUMER/SOHO maps of an active regionHardi Peter, Kiepenheuer-Institut; Boris Gudiksen, Univ. Oslo; Åke Nordlund, Univ. CopenhagenAnhand der aus 3D-MHD-Modellen synthetisiertenProfile von Emissionslinien erstellen wir Karten derKorona in Intensität und Doppler-Verschiebung — geradeso, wie ein modernes EUV-Spektrometer die Sonnesehen würde.Based upon the emission line spectra derived from a3D coronal model we constructed maps of line intensityand shift as they would be acquired by raster scansusing a current EUV spectrometer.A slit spectrometer has to perform a raster scan to produce a map of an area on the Sun in line intensity or shift,which currently can only be done on time scales longer than those in the low corona. Therefore we simulated whatSUMER/SOHO would see of the coronal emission line profiles as derived from a 3D MHD coronal model. Weconcentrate on results for the Mg X (625 Å) line formed at about 10 6 K, i.e. at a similar temperature as representedby the 171 Å passband of TRACE or EIT, dominated by Fe IX/X.We produce two consecutive raster scans of a 20 minutes series of spectra computed from the 3D coronal MHDmodel, in the same fashion as SUMER on-board SOHO would see the corona, i.e. we have reduced the spatialresolution with “pixels” of a bit less than 1 Mm squared and assumed an (optimistically short) exposure time foreach slit position of 10 s.first map − simulated SUMER rasters (10 min apart) − second map10relative intensity I/1horizontal coordinate Y [Mm]504030201000 10 20 30 40 50horizontal coordinate X [Mm]Doppler shift [km/s]3020100−10−20−30Mg X (625 Å) − 10 6 KThe figure shows the resulting ∼60×60 Mm 2 maps in line intensity (top panels) and Doppler shift (bottom panels)for the two rasters taken some 10 minutes apart (the left panels show the first raster, the right panels the second one).The intensity maps are quite similar (correlation coefficient of ∼0.85), which is because of the small variability inline intensity. The Doppler maps, however, differ significantly and have a correlation coefficient of only ∼0.25.This shows that in order to study the response of the corona to the heating process, one needs a fast scanningspectrometer, largely exceeding the capabilities of present instrumentation. Basically the scanning process wouldhave to be fast enough to resolve the time scale of the driving forces — in the case of the flux braiding mechanismsome minutes to resolve the response to the photospheric driver.The simulation of spatial maps as they would be observed with a future EUV spectrometer is another potential forthe forward modeling technique. On the one hand this shows the limitations of current instrumentation, especiallywith respect to the time it takes to raster a sufficient area on the Sun. On the other hand the forward modelingstudies, i.e. the 3D coronal models including spectral synthesis, can be used to help in defining requirements forfuture instrumentation.References:Peter H., Gudiksen B., Nordlund Å. (2005): SOHO 16 proceedings, ESA SP-59291


The solar coronal structure from 3D MHD forward modelsSven Bingert, Hardi Peter, Kiepenheuer-Institut; Boris Gudiksen, Univ. Oslo; Åke Nordlund, Univ. CopenhagenMit Hilfe eines 3D-MHD-Modells der Korona zeigenwir, dass große koronale Bögen einen kontinuierlichenÜbergang von der Photosphäre zur Korona besitzen.Unter diesen heissen Bögen befinden sichkühlere Strukturen, die keine Verbindung zum heisserenPlasma besitzen.Using a 3D forward model of a part of the solar coronawe show that in large coronal loops a continuous connectionfrom the photosphere into the corona is found,while also cool transition region structures exist belowhot loops, which are not reaching coronal temperatures.There is a long-standing debate whether the transition region and the corona form a continuous structure or aredisconnected regions. It was suggested in the mid 1980s that the corona and transition region are composed ofcoronal funnels as well as large hot and smaller cooler loops. Utilizing the transition and coronal emission lines asfollowing from an 3D MHD model and the modeled magnetic field structure, we can now investigate this problemin detail.The small panels at the top right show a top view on the computational box showing the emission in C IV and inMg X. The white lines in these panels indicate the position of a vertical cut through the box shown in the overviewpanel below. One can identify large hot coronal loops in Mg X (red) as well as the transition region as seen in C IV(green). The panels (1) and (2) zoom into the regions outlined in the overview panel along with the magnetic fieldlines derived from the MHD model.12Mg X21C IVThis investigation shows that there are regions on the sun with a continuous vertical connection from the photosphereto the corona, which are to be found at the base of active region loops (panel 1). In more quiet regions thereare cool structures that are disconnected from the coronal plasma directly above them (panel 2), but of course thatcoronal plasma is also connected to the solar surface. It should be emphasized here that both the transition region atthe feet of large loops and the cool loops contribute to the emission measure below 10 5 , but that the emission fromthe cool low lying structures is responsible for the increase of the emission measure towards lower temperatures.References:Bingert S., Peter H., Gudiksen B., Nordlund Å. (2005): SOHO 16 proceedings, ESA SP-59292


The correlation between coronal Doppler shiftsand the supergranular networkTayeb Aiouaz, Hardi Peter, Kiepenheuer-Institut für SonnenphysikPhilippe Lemaire, Institut d’Astrophysique Spatial, Orsay, FranceWir analysieren EUV-Spektren von ruhiger Sonne undkoronalem Loch nahe der Scheibenmitte. Hierzu untersuchenwir Doppler-Verschiebungen von Emissionslinienaus der Übergangsregion zur Korona. Wir stellenfest, daß der maximale Ausfluss nicht in der Mitte derNetzwerkelemente, sondern eher nahe der Netzwerkgrenzenerscheint.We analyze EUV spectra near disk center includingquiet Sun and coronal hole regions. We use Dopplershifts and intensities to search for line shift profilesacross the network. We establish that the maximumoutflow (blueshift) at low coronal temperatures doesnot appear in the center of the network but rather nearnetwork boundaries.We examine properties of line profiles as found with large raster scans of the solar corona acquired by the EUVspectrometer SUMER on board SOHO. The observed regions include an equatorial coronal hole, a polar coronalhole, as well as surrounding quiet Sun areas. In order to reveal the network and remove strong local brightenings,a filter is applied to a continuum map originating from the chromosphere. The resulting filtered continuum map(right panel), the intensity map (left panel) and the Doppler map (middle panel) are shown in the figure below.We find correlations between the chromospheric network, the Ne VIII (770 Å) intensity as well as the Ne VIIIDoppler shifts in quiet Sun areas and in coronal holes. We establish that the maximum outflow (blueshift) at lowcoronal temperatures does not appear above the center of the network but rather near the boundaries from the brightnetwork elements to the inter-network. In order to get a visualize this finding we over-plot areas of stong outflowon top of the filtered continuum image in white (right panel).The maximum blueshift seems to appear in the dark regions in Ne VIII line intensity, as already shown in previousstudies. Furthermore we find the the opposite correlation for the lowest intensities, revealing a lack of energy inthese very dark regions to either accelerate the solar wind or to produce any detectable coronal radiation. Theabsence of magnetic field concentrations in these regions in a reconstructed magnetogram from a MDI/SOHOseries confirms this interpretation.log of relative intensity−0.6 −0.3 0.0 0.3 0.6Doppler shift [km/s]−10 −5 0 5 10log of filtered continuum−0.2 −0.1 0.0 0.1 0.2 0.3250250250coordinate Y [arcsec]200150100coordinate Y [arcsec]200150100coordinate Y [arcsec]20015010050505000 50 100 150 200coordinate X [arcsec]00 50 100 150 200coordinate X [arcsec]00 50 100 150 200coordinate X [arcsec]Right: Ne VIII line intensity image observed on March 7, 1997. Middle: Corresponding Doppler map of the Ne VIIIline. Left: Filtered continuum intensity image on a logarithmic scale with white patches showing regions with thehighest blueshifts — regions with blueshifts larger than 9 km/s for the quiet Sun, and larger than 15 km/s for thecoronal hole. The coronal hole is outlined by a thick solid curve.References:Aiouaz T., Peter H., Lemaire P. (2005): A&A 435, 71393


Forward modeling of coronal funnelsTayeb Aiouaz, Hardi Peter, Kiepenheuer-Institut für SonnenphysikRony Keppens, FOM Institute for Plasma Physics, Nieuwegein, NetherlandsUm die Eigenschaften koronaler Trichter und dieRolle der koronalen Heizung zu studieren, benutzenwir ein neues 2D zeitabhängiges magnetohydrodynamishesModell der Sonnenatmosphäre. Die Resultatezeigen eine systematische Veränderung derDoppler-Verschiebungen in den Linien der unteren Koronaan, je nach verwendeter Heizungsfunktion.To study the properties of magnetic funnels and the roleof the coronal heating, we employed a new 2D MHDtime dependent model of the solar atmosphere. Theresults indicate a systematic variation of the Dopplershifts in lines formed in the low corona depending onthe heating function used.A possible scenario for the structure of the transition region above the quiet Sun suggests that coronal funnels canbe viewed as the base of the corona, either of large coronal loops, or of magnetically open structures connectedto the solar wind. We propose a forward modeling approach of such coronal funnels to investigate the outerlayers of the solar atmosphere with respect to their thermodynamical properties and resulting emission line spectra.We investigate the plasma flow through funnels with a new 2D MHD time-dependent model including the solaratmosphere all the way from the chromosphere to the corona.The plasma in the funnel is treated in the single fluid MHD approximation including radiative losses, thermal conduction,and two different parameterized heating functions. We obtain plasma properties (e.g. density, temperatureand flow speed) within the funnel for each heating function. From the results of the MHD calculation we derivespectral line profiles of a low corona emission line (Ne VIII at 770 Å).The results indicate that the line shift above the magnetic field concentration in the network is stronger than inthe inter-network in both cases. However, for the heating function which decreases exponentially with height, themaximum blue-shift (outflow) is not to be found in the very center of the funnel but in the vicinity of the center(left panels of the figure below). This is not the case when using a heating function proportional to the square ofthe magnetic field strength, where the maximum Doppler shift is well aligned with the center of the funnel (rightpanels). This model directly relates for the first time the form of the heating function to the thermodynamic andspectral properties of the plasma in a funnel.exponential decrease2proportional to B−10−10−8−8Doppler shift [km/s]−6−4Doppler shift [km/s]−6−4−2−2vertical direction z [10Mm]001.0−1.0 −0.5 0.0 0.5 1.0horizontal direction x [10Mm]1.00.80.60.4vertical direction z [10Mm]0.80.60.42.01.81.61.41.21.00.8log of relative emissivity−0.5 0.0 0.5horizontal direction x [10Mm]2.01.81.61.41.21.00.8log of relative emissivity0.20.20.60.6−0.5 0.0 0.5horizontal direction x [10Mm]−0.5 0.0 0.5horizontal direction x [10Mm]The upper panels show the line shifts of Ne VIII line across the funnel calculated for the resulting synthetic spectraintegrated along the line of sight (z-direction) when the funnel is viewed from above. The lower panels show thecorresponding emissivity of Ne VIII calculated from the MHD results using the CHIANTI database. The contourlines show magnetic field lines.References:Aiouaz T., Peter H., Keppens R. (2004): ESA SP-575, p. 337 and A&A, submitted94


High-speed coronal rainDaniel Müller, Kiepenheuer-Institut für Sonnenphysik & Institute of Theoretical Astrophysics, OsloAnik De Groof, Centrum voor Plasma-Astrofysica, K.U. Leuven, BelgiumViggo Hansteen, Institute of Theoretical Astrophysics, Oslo, NorwayHardi Peter, Kiepenheuer-Institut für SonnenphysikDie thermische Instabilität in koronalen Bögen lieferteine gute Erklärung für “koronalen Regen”, d.h. kühlePlasmablasen in der heissen Korona, die entlang vonmagnetischen Bögen auf die Sonne zurückfallen.The thermal instability in coronal loops offers an explanationfor the “coronal rain”, i.e. cool plasma blobsin the hot corona sliding down magnetic loops back tothe Sun.At high spatial and temporal resolution, coronal loops are observed to have a highly dynamic nature. Recentobservations with SOHO, TRACE, and ground-based telescopes frequently show localized brightenings “raining”down towards the solar surface. What is the origin of these features? We present the first comparison of intensityenhancements observed with the Extreme ultraviolet Imaging Telescope on SOHO (in shutterless mode) with non–equilibrium ionization simulations of coronal loops in order to reveal the physical processes governing fast flowsand localized brightenings.The figure above shows part of the solar atmosphere above the limb as seen in the blue wing of the Hα line at6563 Å (data taken with the Swedish Vacuum Solar Telescope). The on-disk part is over-exposed here (yellow)in order to show the structures in the corona. The regions of strong emission above the solar limb correspond todense, cool plasma clumps embedded in the hot corona. A chain of condensations along a coronal magnetic loop(indicated by the white lines) is seen while raining down.Based on the self-consistent 1D loop model including non–equilibrium ionization processes we show that catastrophiccooling around the loop apex as a consequence of footpoint–concentrated heating offers a simple explanationfor these observations. An advantage of this model is that no external driving mechanism is necessary as thedynamics result entirely from the non-linear character of the problem.References:Müller D., Hansteen V., De Groof A., Peter H. (2005): A&A 436, 106795


Are spicules driven by oscillations?R. Hammer, Kiepenheuer-Institut für SonnenphysikZ. E. Musielak, Univ. Texas at ArlingtonA. Nesis, Kiepenheuer-Institut für SonnenphysikIn geneigten magnetischen Flussröhren können Oszillationenvon der Photosphäre leicht in die höherenSchichten vordringen. Dieser Effekt kann allerdingsnicht alle Eigenschaften von Spikulen erklären.In inclined magnetic flux tubes, the energy of photosphericoscillations can leak into the upper atmospheremore efficiently than previously thought. Thiseffect cannot, however, explain all observed propertiesof spicules.The Sun is constantly ejecting spicules, visible as thin plasma jets protruding out of the solar limb. It has beensuggested that their on-disk counterparts are the mottles seen in magnetically quiet regions; perhaps the fibrils inactive regions are also related. Spicule plasma shoots up at speeds of 20–30 km s −1 , reaching heights of 5–10 Mmwithin a few minutes. All these jets appear to be confined by magnetic field.Recently De Pontieu, Erdélyi & James (2004, Nature 430, 536) suggested a new mechanism for driving theseflows. They had observed remnants of the photospheric 5-min p-mode oscillations in the upper parts of fibrils.This is surprising since in the cool temperature minimum region the cut-off frequency ω c for longitudinal wavesexceeds the frequency ω of these oscillations, so they should not be able to pass that forbidden zone. De Pontieuet al. showed, however, that due to the strong inclination of the flux tubes in the outer parts of active regions thecut-off frequency ω c ∝ γg/c = γg 0 cos θ/c (where θ is the inclination angle to the vertical, γ the ratio of specificheats, and c the sound speed) becomes smaller, so that waves can penetrate more easily into the upper atmosphere,where they produce fibril-like dynamic events.We have shown that the transmission of p-mode energy into the upper atmosphere should be even more efficientthan envisioned by De Pontieu et al., for two reasons: First, flux tubes are generally thought to be warmer thanthe environment, so that c is larger and (because of enhanced ionization) γ is smaller. Second, p-mode oscillationsinject not only longitudinal waves into inclined flux tubes, but also transverse waves (see the figure). Theyhave milder cut-off restrictions and are thus barely hindered on their way into the chromosphere, where they areconverted to longitudinal waves by mode-coupling, in particular in the region where β ≈ 1 (dashed line), but alsoelsewhere through inclination and nonlinearity effects.However, we point out that this mechanism is much less efficient for spicules proper, which have smaller inclinationsthan fibrils. Moreover, it cannot explain several spicular properties that were sometimes observed, such asbipolar flows, twisting motions, or the occasional coherent motion of large groups of spicules. In fact, we argue thatno single mechanism can explain all observed spicule properties, so that most likely several driving mechanismsare operating.Figure 1: Magnetic flux tubes are rooted in the photosphere, which is essentially free of magnetic field (i.e., plasmaβ, the ratio of gas to magnetic pressure, is large). Due to the stratification of the atmosphere, the flux tubes expandwith height and fill all available space in the overlying chromosphere, where β < 1. In the photosphere, the mostlyvertical solar p-mode oscillations inject energy into the flux tubes – partially as longitudinal, but in inclined fluxtubes also significantly as transverse motions.References:Hammer, R., & Nesis, A.: 2005, in 13th Cambridge Workshop, eds. F. Favata et al., ESA SP-560, 61996


Fast method for computing chromospheric Ca II and Mg II radiative lossesW. Rammacher, Kiepenheuer-Institut für SonnenphysikD. Fawzy, Astronomy Department, Faculty of Science, Cairo University, Giza, EgyptP. Ulmschneider, Institut für Theoretische Astrophysik, Universität HeidelbergZ. Musielak, Department of Physics, University of Texas at ArlingtonWir entwickeln eine Methode, mit der man inzeitabhängigen numerischen Simulationen der Chromosphäreden gesamten Strahlungsverlust vonCa II- und Mg II-Ionen schnell und mit recht hoherGenauigkeit berechnen kann.We develop a fast and reasonably accurate method forcalculating the total radiative losses by Ca II and Mg IIions for time-dependent chromospheric wave calculations.In the process of constructing theoretical models of stellar chromospheres based on wave heating mechanisms, thetime-dependent energy balance between the wave dissipation due to shocks and the emitted radiative losses hasto be calculated many times at each height in a stellar atmosphere. From semiempirical solar modelling we knowthat the major sources of these chromospheric radiative losses are the H − and hydrogen continua as well as thehydrogen, Ca II, Mg II and Fe II lines. It is essential that these time-dependent radiative losses are be computedsimultaneously with the calculation of energy dissipation by acoustic and magnetic waves.Since the treatment of radiative losses requires a lot of computation time, it is necessary to develop a fast andreliable method to calculate the total radiation losses from the Ca II and Mg II ions. In our code WAVE, wecompute the radiative losses only in the Ca II K and Mg II k lines (which is very fast), and then scale up theseresults by correction factors to account for the full radiative losses. These correction factors are obtained by usingthe multi-level atom transfer code MULTI (Carlsson 1986, Uppsala Astron. Obs. Report 33): in a first step, wecalculate with WAVE a series of preliminary atmospheres (which represent different phases and times of our wavecalculation); in a second step, we apply MULTI to these atmospheres. Finally, we compare the Mg II and Ca IIcooling rates of MULTI and WAVE and deduce cooling rate correction factors for both elements. These factors arethen used in all further WAVE calculations.The relations between the multi-level and the two-level cooling rates are reliably stable as Fig. 1 shows for theexample of a calculation with a monochromatic wave of period P = 20 s: For Ca II (left panel), the rates of a 5-levelCa II atom are plotted versus the rates of a 2-level atom for all height points of a number of snapshots at differenttimes. The same is also done for Mg II. In case of a change of model parameters like effective temperature,gravity, metallicity, mechanical energy flux or wave period it is necessary to recalculate the correction factors. Theextension of the method to Fe II and other elements is the subject of further investigations.6*10 51*10 5Ca II, K = 7.08Mg II, K = 1.514*10 55*10 42*10 50*10 0Damping function MULTI0*10 0−2*10 5Damping function MULTI−5*10 4−1*10 5−2*10 5−4*10 5−2*10 5−6*10 5−3*10 5−8*10 5−7*10 4 −6*10 4 −5*10 4 −4*10 4 −3*10 4 −2*10 4 −1*10 4 0*10 0 1*10 4 2*10 4 3*10 4Damping function WAVE−3*10 5−2*10 5 −2*10 5 −1*10 5 −5*10 4 0*10 0 5*10 4 1*10 5Damping function WAVEFigure 1: Individual comparisons for CaII and MgII of the full MULTI and WAVE damping functions D for 1344height points of four wave phases at different times. Also shown are best-fit lines; their slopes K constitute thecorrection factors.References:Rammacher, W., Fawzy, D., Ulmschneider, P., Musielak, Z., Astrophys. J. (in press, 2005)97


The Sun at (sub-)millimeter wavelengthsSven Wedemeyer-Böhm, Kiepenheuer-Institut für SonnenphysikHans-Günter Ludwig, Lund Observatory, SwedenMatthias Steffen, Astrophysikalisches Institut PotsdamBernd Freytag, Department for Astronomy and Space Physics, Uppsala, SwedenHartmut Holweger, Institut für Theoretische Physik und Astrophysik, Universität KielAusgehend von einem zeitabhängigen 3D-Modell derSonnenatmosphäre wurden synthetische Intensitätsbilderbei (Sub-)Millimeterwellenlängen berechnet,wie sie mit zukünftigen Instrumenten wie ALMAbeobachtbar sein sollten.Based on a time-dependent 3D model of the solar atmospheresynthetic intensity images at (sub-)millimeterwavelengths are calculated as they should be observablewith future instruments like ALMA.Recent high-resolution observations of the solar chromosphere reveal its dynamic and inhomogeneous nature onsmall spatial and temporal scales. The internetwork regions are filled with a network-like structure of enhancedbrightness that is similar to the small-scale pattern seen in the three-dimensional radiation hydrodynamic simulationsby Wedemeyer et al. (2004). The model chromosphere consists of a network of hot gas and enclosed coolregions that are caused by the propagation and interaction of atmospheric shock waves. The spatial scales arecomparable to the granulation, i.e., of the order of only 1000 km. The whole pattern evolves on time scales ofonly 20-30 s. A detailed comparison of the model and observations would be very instructive but is hampered bydifficulties with the computation of synthetic intensity images so far. For many diagnostics it is necessary to takeinto account deviations from local thermodynamic equilibrium (LTE), making the task computationally infeasibleso far. The situation is much easier for the radio continuum at millimeter wavelengths which is formed in LTE andthus can serve as a rather direct measure of the thermal structure of the solar chromosphere. The involved time andlength scales are not accessible with today’s equipment for that wavelength range, but the next generation of instruments,such as the Atacama Large Millimeter Array (ALMA), will facilitate the wanted comparison. We used thespectrum synthesis code LINFOR3D to calculate intensity images at mm and sub-mm wavelengths with emphasison spatial and temporal resolution that are crucial for the ongoing discussion about the chromospheric temperaturestructure and for observational constraints of future radio instruments. Currently the influence of non-LTE electrondensities is under investigation.5000a7.05000c5.5y [km]40003000200010006.05.04.03.0temperature at z = 1000 km[1000 K]y [km]40003000200010005.04.54.03.53.0intensity at λ = 1.0 mm[10 −6 erg cm −2 s −1 Å −1 sr −1 ]1000 2000 3000 4000 5000x [km]1000 2000 3000 4000 5000x [km]Figure 1: Left: gas temperature in horizontal cross-section of the 3D model by Wedemeyer et al. (2004) at ageometrical height of z = 1000 km above optical depth unity. Right: synthesized intensity image at a wavelengthof λ = 1 mm at disk-center for the same model snapshot.References:Wedemeyer, S., Freytag, B., Steffen, M., Ludwig, H.-G., & Holweger, H. 2004, A&A, 414, 1121Wedemeyer-Böhm, S., Ludwig, H.-G., Steffen, M., Freytag, B., Holweger, H., 2005, Proc. of Cool Stars, StellarSystems and the Sun 13, eds. F. Favata et al., ESA SP-560, 103598


High-resolution data of the solar chromosphereFriedrich Wöger, Sven Wedemeyer-Böhm, Wolfgang Schmidt, Oskar von der LüheKiepenheuer-Institut für SonnenphysikWir haben im April 2005 am VTT, Observatorio delTeide, Spanien, die Sonne in der CaII K Linie (3933 Å)mit einem Lyot-Filter (0.3 Å FWHM) beobachtet undeine Zeitserie von hoch aufgelösten Filtergrammen mitca. 2 Std. Dauer erstellt.In April 2005 we have observed the Sun at the VTT,Observatorio del Teide, Spain, in the CaII K (3933 Å)line using a Lyot filter (0.3 Å FWHM) and obtained atime sequence of high resolution filtergrams of about2 h duration.We used a Halle Lyot filter to obtain a time series of high spatial and spectral resolution filtergrams. The filterwas tuned to the line core around the K 2V reversal peak to sample the chromosphere at high layers as they canbe modelled by Wedemeyer et al. (2004). The narrow filter width, a field of view of ≈ 48 ′′ and a plate scaleof 0.145 ′′ / px as well as the cadence of 10 s allow to resolve structure and dynamical behaviour of network andinternetwork. The Kiepenheuer-Institute Adaptive Optics System (KAOS) maintained the unprecedented highresolution even for exposure times of 2 s.Using this data we intend to evaluate the average evolution time scales of network and internetwork structureas well as their individual oscillatory behaviour. Future work will focus on the connection of photosphere andchromosphere using the simultaneously acquired G-Band (4305 Å) and Hα (6563 Å) data. In this regard we planto investigate the G-Band bright points and their influence on their counterparts in the chromosphere. We aim toanalyze their intrinsic size and proper motion to shed light on some of the basic properties of the chromosphere.Ca II K IntensityG-Band Intensity40403030arcsec20arcsec20101000 10 20 30 40arcsec00 10 20 30 40arcsecFigure 1: Sample images of the data acquired on 18.04.2005 at the VTT. The left image shows a sample of thesubsonically filtered Calcium series, the right displays a speckle-reconstructed G-Band image.References:Wedemeyer et al., A&A 414, 1121 (2004)99


Variations of the He I 1083 nm line on the SunH. Wöhl, Kiepenheuer-Institut für Sonnenphysik (KIS), FreiburgR. Brajša, Hvar Observatory, Faculty of Geodesy, University of ZagrebR. Jurdana-Šepić, Physics Department, Faculty of Philosophy, University of RijekaEs wurden Messungen der He I 1083 nm Spektralliniemit dem Vakuum-Turm-Teleskop in Teneriffa währendzweier Beobachtungskampagnen 1993 und 1995durchgeführt. Dabei wurden räumliche und zeitlicheVariationen der Spektrallinie auf der Sonnenscheibeanalysiert. Volle Bilder der Sonne in Mikrowellen, inder Hα Linie und in weichen Röntgenstrahlen sowieals Magnetogramme wurden zum Vergleich herangezogen.Measurements of the He I 1083 nm line were performedwith the Vacuum Tower Telescope (German Solar Telescopes,Teide Observatory, Izana, Tenerife, Spain) duringtwo observational campaigns in 1993 and 1995 andspatio-temporal variations of the line across the solardisc are analysed. Full-disc solar images in microwaves,in the Hα line and in soft X-rays, as wellas magnetograms are used for comparison.The role of the solar chromosphere and corona in the excitation of neutral helium atoms in the solar atmosphereis still not fully resolved, although the photoionization–recombination (PR) mechanism can explain many observationalphenomena. Observations were performed at the Vacuum Tower Telescope (German Solar Telescopes,Teide Observatory, Izana, Tenerife, Spain) using the Echelle spectrograph with a spectral resolution of 1.6 pm anda dispersion of 0.671 pm per pixel. 40 Solar scans were obtained during May 24–31, 1993 and 43 solar scansduring June 27–July 1, 1995. Preliminary results of this analysis were presented at the VIIth Hvar AstrophysicalColloquium ’Solar Activity Cycle and Global Phenomena’ which was held at Hvar, Crotia, September 20–24,2004.We inspect the average relative intensity in the He 1083 line (I λ ) devided by the relative intensity of the nearbyquasi-continuum (I C ), placed between the helium line and the telluric water-vapour line at 1083.21nm: I λC =I λ /I C . The solar scans are now represented by this line contrast vs. position on the solar disc. In all cases of ourobservations the He 1083 line was observed in absorption on the solar disc. Next we calculate the mean value ofI λC and corresponding standard error for each solar scan. As an example we present the results for the secondobserving campaign in 1995 in the Figure, where each of the 43 solar scans is represented by one data point. Scanswere performed parallel to the solar equator. A new observational campaign with the VTT of the He 1083 line onthe Sun is being planned and the line profiles observed at various solar phenomena will be compared to calculatedones.Preliminary results indicate a distinct dependence of the He I 1083 nm line contrast (measure of absorption) on thesolar latitude, a strong North-South asymmetry and a well-pronounced dependence on the solar-cycle phase. Adetailed comparison of all absorptive features discernable in He 1083 solar scans with various phenomena observedin microwaves (at 37 GHz), Hα and soft X-rays, as well as with solar magnetograms is under way.Figure 1: Mean values of the line contrast I λC vs. mean latitude relative to the solar equator for each of the 43 solarscans obtained in 1995. The northern (southern) solar hemisphere is represented by positive (negative) values.100


Expanding the corrected field of view with multi-conjugate adaptive opticsT. Berkefeld, D. Soltau, O. von der Lühe, F. Wöger, Kiepenheuer-Institut für SonnenphysikWir zeigen Ergebnisse der MCAO vom April 2005. We show MCAO results obtained in April 2005.In order to increase the relatively small corrected field of view (FOV) of an Adaptive Optics (AO) system, typicallyabout 10 ′′ in the visible, J.M. Beckers proposed to place deformable mirrors (DMs) in the image (conjugate)planes of the most turbulent atmospheric layers (Multi-Conjugate Adaptive Optics, MCAO). The MCAO presentlydeveloped at the 70 cm Vacuum Tower Telescope (VTT), Tenerife, is an extension of our conventional AO systemKAOS and acts mainly as a testbed for the MCAO of the 150 cm GREGOR telescope. The corrected FOV isincreased to 30-35 ′′ by using two DMs, one in the pupil conjugate plane and another one in the conjugate of alayer 13 km away (which is the tropopause at a zenith distance of 45 ◦ ). Observations with KAOS indicate a Friedparameter r 0 > 50 cm for high-altitude turbulence (usually the tropopause). Therefore a 70 cm telescope suffersmostly from differential tip-tilt.We use two Shack-Hartmann wavefront sensors (WFS). The high-order WFS is the sensor of the conventional AOsystem and measures the aberrations in the center of the corrected FOV with high accuracy. It has a FOV of about12 ′′ and consists of 36 subapertures, corresponding to a subaperture size of 10 cm. The other wavefront sensor hasonly seven subapertures, corresponding to a subaperture size of 23 cm, but covers a 35 ′′ FOV. It measures the loworder off-axis aberrations caused by the high altitude turbulence in the tropopause across the corrected FOV. Thecontrol loop frequency is 955 Hz.At this time the high altitude and the pupil DM handle the field-dependent and field-independent aberrations,respectively. A more efficient global 2 DM / 2 WFS reconstruction will be used in the future. The accuracy ofthe off-axis correction is limited to about five corrected off-axis modes. This is due to the the lack of stroke ofthe high-altitude DM. By using a DM whose parameters have been optimized for MCAO, this problem will beovercome at the GREGOR MCAO.Figure 1: Local Fried parameter r 0 across the 50 ′′ FOV for uncorrected (left), AO-corrected (center) and MCAOcorrectedimaging. r 0 has been determined by speckle reconstruction.Fig. 1 shows the local Fried parameter r 0 across the 50 ′′ FOV for uncorrected (left, mean of 200 exposures),AO-corrected (center, mean of 100 exposures), and MCAO-corrected (right, mean of 600 exposures) imaging.Although a seeing of r 0 = 6 cm is well outside the operational regime of both AO and MCAO, the correction effectof AO and MCAO is obvious.The intensity fluctuations that we first saw in May 2003 have also been present. The relative RMS within theMCAO-corrected field was of the order of 2%. Because of the D −7/3 law of the variance of scintillation we expectit not to exceed 1% for the GREGOR telescope.101


Hunting multi–conjugate adaptive optics “flying shadows”O. von der Lühe, Th. Berkefeld, D. Soltau, Kiepenheuer-Institut für SonnenphysikWir haben feldabhängige Fluktuationen der Beleuchtungsstärkein der korrigierten Fokalebene während unsererersten Experimente mit multi-konjugierter AdaptiverOptik (MCAO) im Jahre 2003 am VTT entdeckt.Wir erklären diesen Effekt mit Hilfe von geometrischerOptik und schlagen Korrekturmaßnahmen vor.We discovered field-dependent irradiance fluctuationsin the compensated focal plane of a multi–conjugateadaptive optics (MCAO) system during first tests at theVTT in 2003. We offer an explanation based on geometricaloptics and offer remedies.The first attempt to close the loop with the multi-conjugate extension of the solar adaptive optics system KAOS atthe VTT took place in May 2003. The system’s second deformable mirror follows the original science focus at aconjugate of a plane about 13 km in front of the telescope. We noticed unexpected fluctuations of intensity at thecorrected focus as soon as an attempt to close the loop was made. These fluctuations were prominently visible onthe video monitor which showed the corrected focus at high contrast, and they were evidently related to the actionof the second deformable mirror. The intensity fluctuations appeared with a spatial scale that is consistent with theactuator dimensions and varied with frequencies of a few Hz.It occurred to us that the origin of the observed fluctuations must be the local curvature of the second deformablemirror which changes the image scale and hence the effective focal length in the MCAO-compensated focal plane.Such a change should be accompanied by an anti-correlated change in focal plane irradiance. Since the purpose ofthe MCAO system is to render undone the field-dependent aberrations of the atmosphere, including field-dependentdistortion which is the manifestation of a spatially variable effective focal length, we investigated why the MCAOcompensatedfocal plane shows irradiance fluctuations instead of the primary focal plane by means of a detailedparaxial ray tracing analysis. We conclude that an image compensated by MCAO shows fluctuations of irradianceof a few percent of the mean, with frequencies of up to a few Hz, which are caused by field-dependent fluctuationsin the radius of the entrance pupil due to high-altitude turbulence. This is a purely geometric effect.The fluctuation may become intolerable for wide-field solar observations with exposures of typically a few seconds.Introducing an aperture stop at the position of the exit pupil in front of the compensated science focus, which isa few percent smaller than the diameter of the exit pupil with the MCAO system turned off, should effectivelyremove the fluctuations. Subsequent experiments at the VTT confirmed this hypothesis (Fig. 1).Figure 1: Irradiance variations in the MCAO-compensated focal plane before (left) and after (right) applying anintermediate aperture stop.References:O. von der Lühe (2004), “Photometric Stability of Multi-Conjugate Adaptive Optics,” in Proc. of the SPIE Proc.5490, 617–624102


Wavefront Sensor based on Liquid Crystal ArraysO. von der Lühe, D. Schmidt, Kiepenheuer-Institut für SonnenphysikWir stellen ein Konzept für einen neuartigen Wellenfrontsensorfür solare adaptive Optik vor, welcherfür Aberrationen bei der Abbildung von ausgedehntenQuellen empfindlich ist. Der Sensor benutzt eineFlüssigkristall-Matrix als optischen Modulator in einerBildebene und misst den Gradienten des Wellefrontfehlersin einer darauffolgenden Pupillenebene.We introduce a novel concept for a solar adaptive opticswavefront sensor which detects aberrations whenimaging extended sources. The sensor uses an opticalmodulator based on a liquid crystal matrix in an imageplane conjugate and detects wavefront error gradientsin a subsequent pupil conjugate.Today’s solar adaptive optics systems use exclusively Shack-Hartmann (SH) type wavefront sensors. Their limitationis mainly the size of a subaperture, which cannot be reduced arbitrarily and therefore dominates the wavefrontmatching error, rendering the AO system ineffective in conditions of bad seeing. We investigate the viability ofa concept for a different wavefront sensor which was proposed by von der Lühe (1988). It is based on opticalmodulation of the light in an aberrated image plane of the solar surface. The light transmitted by the modulator isthen used to form an image of the telescope entrance aperture. Given a suitable modulation, wavefront gradientsappear as fluctuations of intensity in those images, which are captured by a fast camera and transmitted to thecontrol system. In principle, the sensor should be capable to adapt wavefront error resolution to a wide range oferrors, offering more flexibility than conventional SH wavefront sensors.¡¡¡¡¢¡¢¡¢¡¢¡¢¡¢¡¡¡¡¢¡¢¡¢¡¢¡¢¡¢¡¡¡¡¢¡¢¡¢¡¢¡¢¡¢¡¡¡¡¢¡¢¡¢¡¢¡¢¡¢¡¡¢¡¢¡¢¡¢¡¢¡¢¡¡ ¢¡¢¡¢¡¢¡¢¡¢ ¡ ¡ ¡ ¡¢¡¢¡¢¡¢¡¢¡¢ ¡ ¡ ¡ ¡ Lens 3Wollaston 2¡¡¡¡¢¡¢¡¢¡¢¡¢¡¢¨¡¨¡¨¡¨¡¨¡¨¡¨§¡§¡§¡§¡§¡§¡§¡§Detector§¡§¡§¡§¡§¡§¡§¡§¨¡¨¡¨¡¨¡¨¡¨¡¨¨¡¨¡¨¡¨¡¨¡¨¡¨§¡§¡§¡§¡§¡§¡§¡§¡¡¡¡¢¡¢¡¢¡¢¡¢¡¢¨¡¨¡¨¡¨¡¨¡¨¡¨§¡§¡§¡§¡§¡§¡§¡§¤¡¤¡¤¡¤¡¤¡¤¡¤£¡£¡£¡£¡£¡£¡£¡££¡£¡£¡£¡£¡£¡£¡£¤¡¤¡¤¡¤¡¤¡¤¡¤£¡£¡£¡£¡£¡£¡£¡£¤¡¤¡¤¡¤¡¤¡¤¡¤¤¡¤¡¤¡¤¡¤¡¤¡¤£¡£¡£¡£¡£¡£¡£¡£LCDLens 2Wollaston 1¥¡¥¡¥¡¥ ¦¡¦¡¦¥¡¥¡¥¡¥ ¦¡¦¡¦¦¡¦¡¦ ¥¡¥¡¥¡¥¥¡¥¡¥¡¥©¡©¡©¡© ¦¡¦¡¦¡¡¡¡ ©¡©¡©¡© ¥¡¥¡¥¡¥Lens 1¦¡¦¡¦¡¡ ©¡©¡©¡©¦¡¦¡¦ ¥¡¥¡¥¡¥¥¡¥¡¥¡¥¡¡ ©¡©¡©¡©¦¡¦¡¦¡¡ ©¡©¡©¡©¡¡ ©¡©¡©¡©Figure 1: Principle of the proposed wavefront sensor.FieldstopThe reason why this concept has not been realised up to now was the lack of suitable optical modulators at areasonable cost. The success of digital projectors as mass market items has advanced the development of smallformat liquid crystal displays (LCDs) and deformable mirror devices (DMDs) which can be used as modulators.Fig. 1 shows the concept of a wavefront sensor based on a liquid crystal array. A small section of the solarsurface, typically a 10 ′′ square, is selected by a field stop. A video camera (not shown) collects images of thefield to produce an average image for further processing and control of the LCD. A reimaging system with anintermediate Wollaston prism produces two side-by-side, linearly polarized images of the field on top of the naked(polarizers stripped) LCD. Voltages that correspond to the image gradients in horizontal and vertical directionsare applied to the illuminated regions of the LCD. The transmitted light is analyzed by a second Wollaston prism.A lens generates four images of the telescope’s entrance aperture, showing the wavefront aberration gradients inhorizontal and vertical directions encoded as intensity patterns, where they can be detected by a fast camera andprocessed further to control the AO system. We are working on a laboratory test setup of the wavefront sensor.References:O. von der Lühe (1988), “A Wavefront Error Measurement Technique using Extended, Incoherent light sources,”Opt. Engin. 27, 1078-1087103


Modulation of the speckle transfer function by adaptive opticsFriedrich Wöger, Kiepenheuer-Institut für SonnenphysikOskar von der Lühe, Kiepenheuer-Institut für SonnenphysikWir modellieren den Einfluss eines adaptiven optischenSystems (AO) auf die Speckle Transfer Funktion,welche eine wesentliche Rolle in der solaren Speckle–Interferometrie spielt.We model the influence of an adaptive optics system(AO) on the speckle transfer function which plays a vitalrole in solar speckle interferometry.The calibration of the Fourier amplitude in solar speckle interferometry requires the knowledge of the speckletransfer function (STF), which can be estimated from the data (von der Lühe 1984, OSAJ 1, 510). We extend thewell known analytical model by Korff (1973, JOSA 63, 8, 971) for the STF to take into account the correction ofan arbitrary number of Zernike modes by an AO system (Wang & Markey 1978, JOSA 68, 1, 78). The residualvariance of each mode can be adjusted to the performance of a specific AO system. The analytical expression forthe STF takes on the form of the integral∫ ∫〈|S(⃗s )| 2 〉 = d⃗r dr ⃗′ W (⃗r + 1 2 ⃗s ) W (⃗r − 1 2 ⃗s ) W (⃗ r ′ + 1 2 ⃗s ) W (⃗ r ′ − 1 2[⃗s ) ·}exp − D(⃗s ) − D(∆⃗r ) + 2{ 1 D(∆⃗r + ⃗s ) + D(∆⃗r − ⃗s ) +]K(⃗r, ⃗s ) + L(⃗r, ⃗s ) + K(⃗r ′ , ⃗s ) + L(⃗r ′ , ⃗s ) − ˜K(⃗r, ⃗r ′ , ⃗s ) − ˜L(⃗r, ⃗r ′ , ⃗s ) − ˜K(⃗r ′ , ⃗r, ⃗s ) − ˜L(⃗r ′ , ⃗r, ⃗s ) .The 4D integral is performed in the plane of the entrance pupil described by the function W (⃗r). The function D isthe structure function accounting for atmospheric turbulence. The terms K, ˜K, L and ˜L describe the modificationof the incoming wavefront due to the correction of an arbitrary number of Zernike modes by an AO system. Wesolve this integral with a parallelized Monte-Carlo integration algorithm provided by the GNU Scientific Library(GSL).The modelled STFs (Fig. 1) allow the reconstruction of speckle data acquired using an AO system to a highphotometric accuracy.Figure 1: Left: STFs at r 0 /D = 0.12 for different correction levels – solid: Korff model without correction, dotted:modified Korff with 98% tip/tilt, 90% defocus and 60% astigmatism error corrected, dashed: additionally 30%coma and trefoil error corrected, dot-dashed: additionally 50% primary spherical and 20% secondary astigmatismand tetrafoil error corrected. Right: STFs with 98% tip/tilt, 90% defocus, 60% astigmatism and 30% comaand trefoil error corrected at different seeing conditions – solid, dotted, dashed and dot-dashed correspond tor 0 /D = 0.10, 0.14, 0.18, and 0.22, respectively.104


Parallelized speckle image reconstructionFriedrich Wöger, Oskar von der LüheKiepenheuer-Institut für SonnenphysikWir haben zwei verschiedene Algorithmen zur Berechnungvon Speckle Rekonstruktionen (extended Knox-Thompson & iterative weighted least squares specklemasking) parallelisiert und auf ihre Leistung in verschiedenenMulti-Prozessor Umgebungen hin untersucht.We have parallelized two different algorithms for thecomputation of speckle recontructions (extended Knox-Thompson & iterative weighted least squares specklemasking) and evalutated their performance on differentmulti-processor environments.Within the last decades several techniques for post-facto image reconstruction to reach the diffraction limit of earthboundtelescopes have evolved and gained popularity as the computer technology advanced. We have implementedtwo methods for the reconstruction of solar images by means of speckle interferometry: an extended algorithmbased on Knox-Thompson (KT) using cross-spectra and an iterative weighted least squares speckle masking (SM)algorithm using bispectrum values.Both algorithms have been parallelized using MPI which allows us to run the code on different cluster systems aswell as chip architectures. We have compared the performance in speed with• a SUN SunFire V880 with eight 1.2 GHz Ultra3 processors and 16 GB RAM,• a Linux Cluster with 8 nodes, each equipped with two 1.6 GHz AMD Athlon processors and 1 GB RAM, connectedvia Gbit LAN and• a 3.06 Ghz Pentium 4M with HyperThreading technology and 512 MB RAMusing different parameter sets which control the complexity of the calculation. These are either the number of shiftsused for the computation of the cross-spectra (KT) or the number of bispectrum values evaluated (SM). The figurebelow shows the results of our tests. The surprising fact that the SM algorithm is faster than the KT algorithm isexplained by the restriction to a fraction of the available number of bispectrum values. Hence, the SM algorithmuses only a small amount of system and swap memory leading to a faster computation. Nevertheless, the SMmethod is robust enough to produce comparable reconstructions even when the bispectrum is strongly delimited.2000extended Knox-Thompson6609 sec2000Speckle Maskingcomputational time [s]15001000500computational time [s]15001000500012 54 124number of shifts used086747 234366 374190number of bispectrum values usedFigure 1: Bar diagram of the computational time for different environments. Blue represents the cluster, yellowthe SunFire and red the Pentium 4M environment.References:Mikurda & von der Lühe, in preparation105


Dual-stage tip-tilt mirror for the SUNRISE telescopeW. Schmidt, T. Berkefeld, B. Feger, R. Friedlein, K. Gerber, F. Heidecke, T. Kentischer, M. Sigwarth, D. Soltau,E. Wälde, Kiepenheuer-Institut für SonnenphysikFür die Feinnachführung und Bildstabilisierung fürSUNRISE wurde ein zweistufiges Kippspiegelkonzeptentwickelt. Ein Piezo-Antrieb mit einer Bandbreite bis3 kHz und einem Stellbereich von ±6 ′′ ist eingebettetin einen Grobantrieb, der mit einer Bandbreite bis 1 Hzarbeitet und einen Winkelbereich von ±30 ′′ abdeckt.For the fine guiding and image stabilization of SUN-RISE we developed a dual-stage tip-tilt mirror design.A commercial piezo-drive with a bandwidth of 3 kHzand a range of ±6 ′′ is embedded into a motor-drivencoarse drive that operates below 1 Hz and has an angularrange of ±30 ′′ .SUNRISE is a balloon-borne telescope that will carry out high-resolution observations of the sun. The telescopehas an aperture of 1 m and is equipped with several focal plane instruments. The first long-duration stratosphericballoon flight of the telescope in Antarctica is planned for 2008. The specified spatial resolution and polarimetricaccuracy imply a tracking precision in the order of 0.005 ′′ . In order to achieve this ambitious goal, the KIS developsa tracking system, based on a tip-tilt mirror and a correlation tracker and wavefront sensor (CWS).The tip-tilt mirror unit is designed as a dual-stage device: the coarse drive (cf. Fig. 1) with an angular range of±30 ′′ and a dynamic range of about 1 Hz and the fine drive with a range of a few arcseconds and a high bandwidththat allows for a closed-loop operation of at least 30 Hz. The large angular range is needed to compensate anylarge-scale excursion of the telescope, while the high bandwidth is important to guarantee the tracking precision,even in the presence of high-frequency disturbances that may arise during the flight. Since a single tip-tilt mirrorcannot fulfill both requirements at the same time, we designed this dual-stage solution. The high-speed drive is acommercial piezo-driven unit, with an open-loop bandwidth of 3 kHz. The specified closed-loop bandwidth of thesystem is 30 Hz. The fine drive is integrated in the coarse drive which uses motorized actuators for the tip and tiltmotion in two orthogonal axes.SpringMotorEncoderMotorsSpringMirrorEncoderFine DriveHousingSpringCoarseDriveFine DriveFigure 1: Mechanical design of the tip-tilt mirror. The left panel shows the rear side with the motors of the coarsedrive and the housing of the fine drive. The sectional cut in the right panel shows the mirror (30 mm diameter), themotors and the springs that move the mirror back to its zero position.SUNRISE is an international collaboration, led by the Max-Planck Institut für Sonnensystemforschung (Lindau, D) and withthe High Altitude Observatory in Boulder (Colorado, U.S.A.), the IMAX team (Spain) and the Kiepenheuer-Institut für Sonnenphysikas partners.References:W. Schmidt et al., Proceedings of the SPIE, Volume 5489, pp. 1164-1172 (2004)106


Image Stabilization for SUNRISE with CWS – A high-precision testbed inthe KIS labD. Soltau, Th. Berkefeld, B. Feger, R. Friedlein, K. Gerber, Th. Kentischer, F. Heidecke, M. Sigwarth, E. Wälde,Kiepenheuer-Institut für SonnenphysikFür das SUNRISE Projektes entwickelt dasKiepenheuer-Institut ein System zur Bildstabilisierung(CWS). Es ist so ausgelegt, dass Bildbewegungen, diewährend des Fluges von SUNRISE auftreten können,auf besser als 0.005 ′′ ausgeregelt werden. Um einsolches System auch testen zu können, wurde imFreiburger Optiklabor des KIS ein Messaufbau realisiert.Die Messgenauigkeit beträgt weniger als1 µm auf dem Empfänger bei einer Zeitauflösung von0.001 s.For SUNRISE KIS develops an image stabilization systemCWS. The system shall be able to compensate imagemotion during the flight down to a level of 0.005 ′′ .In order to be able to test such a system in the lab inFreiburg we built a test setup that allows analysis ofimage motion of less than 1 µm (on the detector) and atime resolution of 0.001 s.The demanding goal of image motion control down to 0.005 ′′ requires a suitable testbed where such a performancecan be measured and verified. Therefor an optical setup (Fig. 1) has been constructed in the lab in Freiburg thatsimulates the telescope enviroment to a certain extent.Science cameraerror compensatingCWS tip tilt mirror M6imaginglensWFS cameraM6Science cameraError creatingtip tilt mirrorBeamsplitterTo WFSerror creatingtip tilt mirrorbeam expanderLaserFigure 1: Test setup for the SUNRISE CWSA laser point source acts as the optical object and the expanded and collimated beam illuminates a piezo-driventip-tilt mirror. This mirror limits the beam diameter (pupil) and is used to create tip-tilt error signals. Close tothis mirror follows the SUNRISE tip-tilt mirror M6 which is the one under investigation. A lens reimages the pointsource. Part of the light is used for a Shack-Hartmann type wave front sensor after passing a beam splitter cube.The reflected light produces an image of the pinhole on a high-speed science camera. This camera is read out 1000times per second and is used to analyze the residual image motion.In this configuration a number of measurements have been performed that yielded information about the stabilityof the setup, performance characteristics of the servo and dynamic charcteristics of the coarse tip-tilt mirror drive.The results are given in milli-arcseconds as measured on the sky.It turns out that in the current version the setup is stable down to the 15 milli-arcsecond level. When the controlloop is switched on the image is stable down to 9 milli-arcseconds. That means that although the servo has not yetbeen optimized we are already close to the desired performance level. Measurements of the system´s step responseand it´s dynamical behaviour can now be performed in a standardized way and are part of the development process.107


Wavefront sensor for the SUNRISE telescopeE. Wälde, T. Berkefeld, B. Feger, R. Friedlein, K. Gerber, T. Kentischer, F. Heidecke, W. Schmidt, D. Soltau, M.Sigwarth, Kiepenheuer-Institut für Sonnenphysik, FreiburgFür das ballon–getragene SUNRISE–Teleskop wirdein Shack–Hartmann Wellenfrontsensor eingesetzt, umwährend des Fluges die Bildberuhigung und Optimierungzu steuern. Koma–Fehler werden durch Verschiebendes Sekundärspiegels minimiert.The balloon–borne SUNRISE telecope features aShack–Hartmann wavefront sensor to drive image stabilisationand optical alignment during flight. Comaaberrations will be reduced by correcting the positionof the secondary mirror.The SUNRISE telescope features a Shack–Hartmann wavefront sensor as seen in the field of Adaptive Optics. Itwill be used to measure low-order aberrations (image shift, focus, coma) of the image produced by the telescopeand its motion. The image shift will be compensated using a dual stage tip-tilt mirror.Minimizing coma will be achieved by optimizing the alignment of the secondary (M2) and primary mirrors (M1).The mount of M2 will allow for small corrections (some 10 µm) of M2s position in three axes. Changing M2sposition can reduce coma at the expense of some additional image shift, which is easily corrected with the tip-tiltmirror. Focus will be corrected with M2. It’s range can be supplemented by moving the position of the foldingmirrors M3 and M4.The figure below provides an overview of the wavefront sensor’s main components and their communication paths.The light path is unfolded for simplicity. Images will be aquired by a CMOS camera and read through a C–Linkconnection. Correlation of the new image with a reference will generate new values to be issued to adjust thepositions of M6 and M2.Since the wavefront sensor will lock to the observed feature on the sun, it will follow its motion across the sun’sdisk. Therefore the wavefront sensor will also provide offset corrections to the azimuth and elevation drives toprevent exhaustion of the tip-tilt mirrors range.SUFISUPOSIMAXEPM1F1M2M4M5BS1BS3M3 F2 M6 BS2L5M19M18F6L6 LL L7 L8M20M21CMOScameraAzimuthElevationPointingsystemalignment, focusfocusTelescopeControllerPinholecoarsefineHK data sensorsserialCoSM field busCoSM BuscontrollerCW Com(ARM)PinholeserialND wedgeCoSM BuscontrollerFramegrabberPCICW AOCamera LinkEthernetICU &Data StorageFigure 1: Overview of the image stabilisation and wavefront correction system for the SUNRISE telescope.SUNRISE is an international collaboration, led by the Max–Planck Institut für Sonnensystemforschung (Lindau, D) and withthe High Altitude Observatory in Boulder (Colorado, U.S.A.), the IMAX team (Spain) and the Kiepenheuer-Institut für Sonnenphysikas partners.References:W. Schmidt et al., Proceedings of the SPIE, Volume 5489, pp. 1164-1172 (2004)108


COSM interface for controlling the SUNRISE wavefront sensorF. Heidecke, T. Berkefeld, B. Feger, R. Friedlein, K. Gerber, T. Kentischer, W. Schmidt, D. Soltau, M. Sigwarth,E. Wälde, Kiepenheuer-Institut für Sonnenphysik, FreiburgFür die Steuerung des SUNRISE Wellenfrontsensorswurde eine Feldbusschnittstelle entwickelt, welche inzwei Applikationen eingesetzt wird.A fieldbus interface has been developed to control theSUNRISE wavefront sensor, which is used by two differentapplications.COSM fieldbus interfaceThe Communication of Short Messages (COSM) has been developed to deal withthe control and monitor tasks of the SUNRISE wavefront sensor. This means to controlmotor mechanisms with off the shelf motor controllers and data aquisition ofphysical values like temperature, voltage and current. Using COSM reduces thecomplexity of the system substantially when compared to common fieldbus systemslike CAN–bus. Furthermore the interface to host systems is transparent and easyto use. The SUNRISE wavefront sensor contains CW–AO and CW–COM as hostsystems. Cell of the COSM fieldbus interface is a 8–bit microcontroller and a differentialfieldbus driver IC. This hardware is available at a low price of 5 EUR. Onthe software side the whole fieldbus interface is implemented in a single C–routinein two variations. This COSM communication driver is located in program memoryof the 8–bit microcontroller. The COSM cell containing the root–communicationroutine is connected to the host system. This cell also generates the 33-bit longmessage frame. All other COSM cells must synchronize with the given messageframes using their cell–communication routine. The COSM communication driverFigure 1: COSM cellprovides data exchange and error detection of single messages, but there is no protocol.This job has to be done by the application software at the same 8–bit microcontroller. So far there are twodifferent protocols using the COSM fieldbus interface, which are optimized for their purposes.COSM fieldbus protocol: Housekeeping dataThe cell with the root–communication routine in this relationship is called the COSM Bus Controller. The cell’smicrocontroller is connected to the CW–COM host system via an additional RS232 driver IC. All other cells areused as sensor modules, which provide the aquisition of the Housekeeping data.COSM motor terminal protocol: motor controllersThis protocol manages up to 9 COSM servers and one COSM client, which are connected to each other via theCOSM bus. All COSM cell’s microcontrollers have an additional RS232 driver IC in this application. The root–cell in this protocol is the COSM client, which is connected to the host. The host system CW–AO has in theend access to every connected motor controller. Each motor controller has also one RS232 interface and each isconnected to one COSM server. The host system has the possibility to create a point–to–point connection to oneserver via the client. This provides a transparent RS232 connection to the motor controller and allows to use itsoriginal instruction set by CW–AO.SUNRISE is an international collaboration, led by the Max–Planck Institut für Sonnensystemforschung (Lindau, D) and withthe High Altitude Observatory in Boulder (Colorado, U.S.A.), the IMAX team (Spain) and the Kiepenheuer-Institut für Sonnenphysikas partners.109


Spectroscopic observations of the Venus transit in 2004W. Schmidt, H. Schleicher, Kiepenheuer-Institut für SonnenphysikT. Brown, High Altitude ObservatoryR. Alonso, Instituto de Astrofísica de CanariasWährend des Venus-Transits im Juni 2004 wurdenSpektren von dem von der Sonne kommenden Licht,das den Rand der Venus passierte, aufgenommen.Dabei wurde hauptsächlich nach Absorptionslinien vonCO, O 2 und CO 2 gesucht.The transit of Venus in June of 2004 was used to observethe atmosphere of the planet, by measuring thelight from the sun passing along the Venusian limb. Themain goal was the search for absorption lines of certainmolecules, mainly CO, O 2 and CO 2The transit of Venus in 2004 was used by a team of German, American and Spanish scientists to observe theatmosphere of the planet, by measuring the light from the sun passing along the Venusian limb. The goals were thesearch for certain molecules, mainly CO, O 2 and CO 2 , and the measurement of gas motion in the atmosphere ofVenus. To this end, we have carried out two different spectroscopic measurements at the Vacuum tower Telescopeon Tenerife with the filter spectrometer TESOS and with the Tenerife Infrared Polarimeter. We took 2D-spectraof an O 2 -line at 628 nm and of an atomic oxygen line at 777 nm with TESOS. The left panel of Fig. 1 shows aTESOS filtergram with Venus in the center of the field, surrounded by solar granulation. We derived an upperlimit for the presence of O 2 in the atmosphere above Venus: any additional absorption in the O 2 line is less than0.05 pm (for comparison: during the transit of Mercury in 2003, we detected an additional absorption in the NaD2 line up to 1.5 pm). The Tenerife Infrared Polarimeter was used for the observation of CO and CO 2 lines at awavelength of 1.597 µm. The presence of CO 2 in the atmosphere of Venus is quite obvious, as shown in the lowerright panel of Fig. 1. It shows the difference of a spectrum taken near the limb of Venus and the solar spectrum,thereby eliminating the solar line profiles. The contrast has been enhanced for better visibility of the spectral linesin the Venus atmosphere. The grey area at the bottom is part of the Venus disk. The location of the atmosphere ofVenus is indicated by horizontal lines; the arrows mark the CO 2 lines. The top right panel shows a slit jaw imageof Venus near the solar limb. A detailed analysis of the spectra is presently carried out at the IAC.Spectrograph slitVenus limbWavelengthCO2 lines at Venus limbFigure 1: Left: Filtergram of Venus, surrounded by solar granulation, observed with a filter spectrometer (TESOS).Bottom right: slit spectrum of the Venus limb and the solar photosphere. The slit is positioned perpendicular tothe Venus limb, as shown in the upper right panel of the figure. The spectrum shown is the difference between themeasured one and a solar spectrum, in order to enhance the visibility of the Venusian absorption lines.110


Mercury transit May 7, 2003: First detection of excess absorptionproduced by Mercury’s exosphereH. Schleicher, Kiepenheuer-Institut für Sonnenphysik; G. Wiedemann, Hamburger Sternwarte;H. Wöhl, T. Berkefeld, D. Soltau, Kiepenheuer-Institut für SonnenphysikWährend des Transits am 7. Mai 2003 konnte zum erstenMal die Exosphäre von Merkur als zusätzlicheAbsorption in der Na D 2 Linie außerhalb der Planetenscheibenachgewiesen werden. Die Beobachtungenwurden mit dem 2–D Spektrographen TESOS amVTT auf Izaña gemacht.On occasion of the transit of Mercury on 2003-May-07, absorption of solar light in the Na D 2 line producedby Mercury’s exosphere could be detected outside theplanet’s disk for the first time. The observations werecarried out with the 2–D spectrograph TESOS of theVTT at Izaña.The exosphere of Mercury is known since the fly–by of Mariner 10 and ground–based detection of narrow emissionlines superimposed on the solar resonance lines of sodium and potassium at the sun–illuminated part of Mercury’sdisk. The atoms of the latter elements are sputtered off the planet surface by the solar wind and/or by bombardmentof micro–meteorites.During the Mercury transit, a narrow absorption line, superimposed on the blue flank of the solar Na D 2 linecould be detected outside Mercury’s disk, see the left panel of the Figure. The absorption feature was blue–shiftedrelative to the center of the solar line because of the negative radial velocity of Mercury at that time. As shownin the right panel of the Figure, the absorption, and hence the sodium atoms of the exosphere, are concentrated atthe two polar regions and can be traced up to ≈ 700 km above the planet’s surface. Attempts by other groups todetect such absorption on occasion of former transits had failed. We succeeded thanks to the combination of a 2–DFabry–Perot spectrograph (TESOS) and adaptive optics (KAOS).counts30002500200015001000500∆λ 0Mercury∆λ 0SunNW1 Mm(2.5")00 20 40 60 80∆λ [pm]W λ0.0 1.0 2.0 [pm]Figure 1: Left panel: Comparision of two Na D 2 profiles, scanned by TESOS during the transit of Mercury. The redprofile is obtained in the north polar region, 214 km above Mercury’s limb; the green profile is a reference profileobtained ≈ 10 ′′ away from the planet. The absorption feature from Mercury’s exosphere is seen as a depressionof the red profile relative to the green one (brown color). The feature is located at the predicted wavelength. Rightpanel: the spatial distribution of the absorption (in terms of equivalent width) around the planet.From the strength of the absorption along the radial direction the surface density, column density, and the scale–height of the neutral sodium atoms can be derived in a straight–forward way (Schleicher et al. 2004). Theseobservations are complementary to the investigations of emission lines seen projected at the illuminated part ofMercury’s disk which lack of the height information. The determination of the amount of absorption by theexosphere is also of interest for projects to find extra–solar planets with the occultation method.References:H. Schleicher, G. Wiedemann, H. Wöhl, T. Berkefeld, D. Soltau, Astronomy & Astrophysics, 425, 1119 (2004)111


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Veröffentlichungen seit 2003Publications since 2003In referierten Zeitschriften – In refereed Journals2003001 Balthasar, H., Bellot Rubio, L.R., Collados, M.: Thestructure of the penumbra, Astron. Nachr./AN, 324,390–390 (2003)002 Bellot Rubio, L.R., Balthasar, H., Collados, M.,Schlichenmaier, R.: Field-aligned Evershed flows inthe photosphere of a sunspot penumbra, Astron. Astrophys.403, L47–L50 (2003)003 Bellot Rubio, L.R., Collados, M.: Understanding internetworkmagnetic fields as determined from visibleand infrared spectral lines, Astron. Astrophys. 406,357–362 (2003)004 Berkefeld, T., Soltau, D., Lühe, O. von der: MulticonjugativeAdaptive Optics for the 1.5 m GREGORtelescope, Astron. Nachr./AN 324, 296–296 (2003)005 Bird, A.J., Barlow, E.J., Bazzano, A., Blondel, C.,Del Santo, M., Di Cocco, G., Gabriele, M., Laurent,P., Lebrun, F., La Rosa, G., Malaguti, G., Quadrini,E., Segreto, A., Tikkanen, T., Ubertini, P., Volkmer,R.: IBIS ground calibration, Astron. Astrophys. 411,L159–L166 (2003)006 Borrero, J.M., Bellot Rubio, L.R., Barklem, P.S., delToro Iniesta, J.C.: Accurate atomic parameters fornear-infrared spectral lines, Astron. Astrophys. 404,749–762 (2003)007 Brčeková, K., Kučera, A., Hanslmeier, A., Rybák,J., Wöhl, H.: Dynamics and turbulence of the chromosphericlayers of a flaring atmosphere, Astron.Nachr./AN 324, 366–366 (2003)008 Brković, A., Peter, H., Solanki, S.K.: Variability ofEUV-spectra from the quiet upper solar atmosphere:Intensity and Doppler shift, Astron. Astrophys. 403,725–730 (2003)009 Brković, A., Peter, H.: Relation of transition regionblinkers to the low chromosphere, Astron. Astrophys.406, 363–371 (2003)010 Dobler, W., Frick, P., Stepanov, R.: Screw dynamo ina time-dependent pipe flow, Phys. Rev. E 67, 056309,1–10 (2003)011 Dobler, W., Haugen, N.E.L., Yousef, T.A., Brandenburg,A.: The bottleneck effect in three-dimensionalturbulence simulations, Phys. Rev. E, 68, 026304, 1–8(2003)012 Eker, Z., Brandt, P.N., Hanslmeier, A., Otruba, W.,Wehrli, C.: Deriving effective sunspot temperaturesfrom SOHO/VIRGO irradiance measurements - Astarspot modelling approach, Astron. Astrophys. 404,1107–1115 (2003)013 Gontikakis, C., Peter, H., Dara, H.C.: Sizes of quietSun transition region structures, Astron. Astrophys.408, 743–753 (2003)014 Harrison, R.A., Harra, L.K., Brković, A., Parnell,C.E.: A study of the unification of quiet-Sun transienteventphenomena, Astron. Astrophys. 409, 755–764(2003)015 Haugen, N.E.L., Brandenburg, A., Dobler, W.: Thespectrum of nonhelical hydromagnetic turbulence, Astrophys.J. 597, L141–L144 (2003)016 Khomenko, E.V., Collados, M., Bellot Rubio, L.R.:Magnetoacoustic waves in sunspots. Astrophys. J.588, 606–619 (2003)017 Koza, J., Bellot Rubio, L.R., Kučera, A., Hanslmeier,A., Rybák, J., Wöhl, H.: Evolution of temperature ingranule and intergranular space, Astron. Nachr./AN324, 349–351 (2003)018 Langhans, K., Schmidt, W., Tritschler, A.: Observationsof G-band bright structures with TESOS, Astron.Nachr./AN 324, 354–354 (2003)019 Müller, D.A.N., Hansteen, V.H., Peter, H.: Dynamicsof solar coronal loops I. Condensation in cool loopsand its effect on transition region lines, Astron. Astrophys.411, 605–613 (2003)020 Ossendrijver, M., Covas, E.: Crisis-induced intermittencydue to attractor-widening in a buoyancy-drivensolar dynamo, Internat. J. of Bifurcation and Chaos13, No.8, 2327–2333 (2003)021 Peter, H., Brković, A,: Explosive events and transitionregion blinkers: Time variability of non-Gaussianquiet Sun EUV spectra, Astron. Astrophys. 403, 287–295 (2003)022 Peter, H., Vocks, C.: Heating the magnetically openambient background corona of the Sun by Alfvénwaves, Astron. Astrophys. 411, L481–L485 (2003)023 Rekowski, B. von, Brandenburg, A., Dobler, W.,Shukurov, A.: Structured outflow from a dynamo activeaccretion disc, Astron. Astrophys. 398, 825–844(2003)024 Roth, M., Stix, M.: Time-dependent coupling of solaroscillations, Astron. Astrophys. 405, 779–786 (2003)025 Roudier, T., Lignières, F., Rieutord, M., Brandt, P.N.,Malherbe, J.M.: Families of fragmenting granules andtheir relation to meso- and supergranular flow fields,Astron. Astrophys. 409, 299–308 (2003)026 Rüdiger, G., Elstner, D., Ossendrijver, M.: Do sphericalα 2 -dynamos oscillate?, Astron. Astrophys. 406,15–21 (2003)113


027 Schleicher, H., Balthasar, H., Wöhl, H.: Velocity fieldof a complex sunspot with light bridges, Solar Phys.215, 261–280 (2003)028 Schlichenmaier, R., Solanki, S.K.: On the heat transportin a sunspot penumbra, Astron. Astrophys. 411,257–262 (2003)029 Schmidt, W.: Material flow in sunspots, Astron.Nachr./AN 324, 374–375 (2003)030 Schmidt, W., Beck, C., Kentischer, T., Elmore, D.,Lites, B.: POLIS: A spectropolarimeter for the VTTand for GREGOR, Astron. Nachr./AN 324, 300–301(2003)031 Setiawan, J., Pasquini, L., Silva, L. da, Lühe, O. vonder, Hatzes, A.: Precise radial velocity measurementsof G and K giants - First results, Astron. Astrophys.397, 1151–1159 (2003)032 Setiawan, J., Hatzes, A.P., Lühe, O. von der, Pasquini,L., Naef, D., Silva, L. da, Udry, S., Queloz, D., Girardi,L.: Evidence of a sub-stellar companion aroundHD 47536, Astron. Astrophys. 398, L19–L23 (2003)033 Soltau, D., Berkefeld, T., Hofmann, A., Lühe, O. vonder, Schmidt, W., Volkmer, R., Wiehr, E.: GREGOR- Optical Design Considerations, Astron. Nachr./AN324, 292–295 (2003)034 Steiner, O.: Distribution of magnetic flux density atthe solar surface. Formulations and results from simulations,Astron. Astrophys. 406, 1083–1088 (2003)035 Steiner, O., Hauschildt, P., Bruls, J.: The contrast ofmagnetic elements across the solar spectrum, Astron.Nachr./AN 324, 398–398 (2003)036 Stix, M.: On the time scale of energy transport in thesun, Solar Phys. 212, 3–6 (2003)037 Vršnak, B., Brajša, R., Wöhl, H., Ruždjak, V., Clette,F., Hochedez, J.-F.: Properties of the solar velocityfield indicated by motions of coronal bright points, Astron.Astrophys. 404, 1117–1127 (2003)2004038 Bellot Rubio, L.R., Balthasar, H., Collados, M.: Twomagnetic components in sunspot penumbrae, Astron.Astrophys. 427, 319–334 (2004)039 Bonet, J.A., Márquez, I., Muller, R., Sobotka, M.,Tritschler, A.:. Phase diversity restoration of sunspotimages I. Relations between penumbral and photosphericfeatures, Astron. Astrophys. 423, 737–744(2004)040 Borrero, J.M., Solanki, S.K., Bellot Rubio, L.R.,Lagg, A., Mathew, S.K.: On the fine structure ofsunspot penumbrae: I. A quantitative comparison oftwo semiempirical models with implications for theEvershed effect, Astron. Astrophys. 422, 1093–1104(2004)041 Brajša, R., Wöhl, H., Vršnak, B., Ruždjak, V., Clette,F., Hochedez, J.-F., Roša, D.: Height correction inthe measurement of solar differential rotation determinedby coronal bright points, Astron. Astrophys.414, 707–715 (2004)042 Brandenburg, A., Käpylä, P.J., Mohammed, A.: Non-Fickian diffusion and tau approximation from numericalturbulence, Physics of Fluids 16, 1020–1027(2004)043 Brković, A., Peter, H.: Statistical comparison of transitionregion blinkers and explosive events, Astron. Astrophys.422, 709–716 (2004)044 Bruls, J.H.M.J., Solanki, S.K.: Apparent solar radiusvariations: The influence of magnetic network andplage, Astron. Astrophys. 427, 735–743 (2004)045 Hanslmeier, A., Kučera, A., Rybák, J., Wöhl, H.: Twodimensionalspectroscopic time series of solar granulation,Solar Phys. 223, 13–26 (2004)046 Haugen, N.E.L., Brandenburg, A., Dobler, W.: Simulationsof nonhelical hydromagnetic turbulence, Phys.Rev. E 70a, 016308, 1–14 (2004)047 Haugen, N.E.L., Brandenburg, A., Dobler, W.: Highresolutionsimulations of nonhelical MHD turbulence,Astrophys. Space Sci. 292, 53–60 (2004)048 Käpylä, P.J., Korpi, M.J., Tuominen, I.: Local modelsof stellar convection: Reynolds stresses and turbulentheat transport, Astron. Astrophys. 422, 793–816(2004)049 Langhans, K., Schmidt, W., Rimmele, T.: Diagnosticspectroscopy of G-band brightenings in the photosphereof the sun, Astron. Astrophys. 423, 1147–1157(2004)050 Leinert, Ch., Boekel, R. van, Waters, L.B.F.M.,Chesneau, O., Malbet, F., Köhler, R., Jaffe, W.,Ratzka, Th., Dutrey, A., Preibisch, Th., Graser, U.,Bakker, E., Chagon,G., Cotton, W.D., Dominik, C.,Dullemond, C.P., Glazenborg-Kluttig, A.W., Glindemann,A., Henning, Th., Hofmann, K.-H., Jong, J.de,Lenzen, R., Ligori, S., Lopez, B., Meisner, J., Morel,S., Paresce, F., Pel, J.-W., Percheron, M.E., Perrin, G.,Przygodda, F., Richichi, A., Schöller, M., Schuller, P.,Stecklum, B., Ancker, M.E. van den, Lühe, O. von der,Weigelt, G.: Mid-infrared sizes of circumstellar disksaround Herbig Ae/Be stars measured with MIDI onthe VLTI,, Astron. Astrophys. 423, 537–548 (2004)051 Lühe, O. von der: Adaptive optics for robotic telescopes,Astron. Nachr./AN 325, 613–618 (2004)052 Müller, D.A.N., Peter, H., Hansteen, V.H.: Dynamicsof solar coronal loops: II. Catastrophic cooling andhigh-speed downflows, Astron. Astrophys. 424, 289–300 (2004)053 Peter, H., Gudiksen, B.V., Nordlund, Å.: CoronalHeating through Braiding of Magnetic Field Lines,Astrophys. J. 617, L85–L88, (2004)054 Rekowski, B. von, Brandenburg, A., Dobler, W.,Shukurov, A.: Outflows from dynamo-active protostellaraccretion discs, Astrophys. Space Sci. 292,493–500 (2004)055 Ruždjak, D., Ruždjak, V., Brajša, R., Wöhl, H.: Decelerationof the rotational velocities of sunspot groupsduring their evolution, Solar Phys. 221, 225–236(2004)056 Rybák, J., Wöhl, H., Kučera, A., Hanslmeier, A.,Steiner, O.: Indications of shock waves in the solarphotosphere, Astron. Astrophys. 420, 1141–1152(2004)057 Schleicher, H., Wiedemann, G., Wöhl, H., Berkefeld,T., Soltau, D.: Detection of neutral sodium above114


Mercury during the transit on 2003 May 7, Astron. Astrophys.425, 1119–1124 (2004)058 Schlichenmaier, R., Bellot Rubio, L.R., Tritschler,A.: Two-dimensional spectroscopy of a sunspot II.Penumbral line asymmetries, Astron. Astrophys. 415,731–737 (2004)059 Schmidt, W., Fritz, G.: On the geometry of sunspotpenumbral filaments, Astron. Astrophys. 421, 735–739 (2004)060 Setiawan, J., Pasquini, L., Silva, L. da, Hatzes, A.P.,Lühe, O. von der, Girardi, L., Medeiros, J.R. de,Guenther, E.: Precise radial velocity measurements ofG and K giants. Multiple systems and variability trendalong the Red Giant branch, Astron. Astrophys. 421,241–254 (2004)061 Solanki, S.K., Preuss, O., Haugan, M.P., Gandorfer,A., Povel, H.P., Steiner, P., Stucki, K., Bernasconi,P.N., Soltau, D.: Solar constraints on new couplingsbetween electromagnetism and gravity, Phys. 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089 Odert, P., Hanslmeier, H., Rybák, J., Kučera, A.,Wöhl, H.: Influence of the 5-min oscillations on solarphotospheric layers: I. Quiet region, Astron. Astrophys.(submitted, March 2005)090 Ossendrijver, M.: The magnetic layer in solar-typestars, Astron. Nachr./AN 326, 166–169 (2005)091 Ossendrijver, M.: Approaching the solar dynamo, Adv.Space Res. (submitted, 2005)092 Rammacher,W., Cuntz, M.: Definition and significanceof average temperatures in time-dependent solarchromosphere models, Astron. Astrophys. 438, 721–726 (2005)093 Rammacher, W., Fawzy, D., Ulmschneider, P.,Musielak, Z.: Fast method for calculating chromosphericCa II and Mg II radiative losses, Astrophys.J. (in press, 2005)094 Ruždjak, D., Brajša, R., Sudar, D., Wöhl, H.: The influenceof the evolution of sunspot groups on the determinationof the solar velocity field, Solar Phys. (inpress, 2005)095 Schlichenmaier, R., Bellot Rubio, L.R., Tritschler, A.:On the relation between penumbral intensity and flowfilaments, Astron. Nachr./AN 326, 301–304 (2005)096 Setiawan, J., Rodmann, J., da Solva, L., Hatzes, A.P.,Pasquini, L., Lühe, O. von der, Medeiros, J.R. de,Döllinger, M.P., Girardi, L.: A substellar companionaround the intermediate-mass giant star HD 11977,Astron. Astrophys. 437, L31–L34 (2005)097 Setiawan, J., Weise, P., Roth, M.: Multi-periodic oscillationsof α Hya, Astron. Astrophys. (submitted,2005)098 Steiner, O.: Radiative properties of magnetic elementsII. Center to limb variation of the appearance of photosphericfaculae, Astron. Astrophys. 430, 691–700(2005)099 Steiner, O., Ferriz-Mas, A.: Connecting solar radiancevariability to the solar dynamo with the virial theorem,Astron. Nachr./AN 326, 190–193 (2005)100 Ulmschneider, P., Rammacher, W., Musielak, Z.,Kalkofen, W.: On the validity of acoustically heatedchromosphere models, Astrophys. J. Letters (submitted,2005)101 Wedemeyer-Böhm, S., Kamp, I., Bruls, J., Freytag,B.: Carbon monoxide in the solar atmosphere I. Numericalmethod and two-dimensional models, Astron.Astrophys. 438, 1043–1057 (2005)Übersichts-Artikel – Review Articles2003102 Bellot Rubio, L.R.: The fine structure of the penumbra:From observations to realistic physical models,in: Trujillo Bueno, J., Sánchez Almeida, J. (eds.): SolarPolarization 3, Astron. Soc. Pac. Conference Series307, 301–323 (2003)103 Ossendrijver, M.: The solar dynamo, The Astron. Astrophys.Rev. 11, 287–367 (2003)104 Ossendrijver, M.: The solar dynamo: A challengefor theory and observations, in: Pevtsov, A.A., Uitenbroek,H. (eds.): Current Theoretical Models and FutureHigh-Resolution Solar Observations, Preparingfor ATST, Astron. Soc. Pac. Conf. Ser. 286, 97–112(2003),105 Schlichenmaier, R.: The sunspot penumbra: newdevelopments, in: Pevtsov, A.A., Uitenbroek, H.(eds.), Current Theoretical Models and Future High-Resolution Solar Observations, Preparing for ATST,Astron. Soc. Pac. Conf. Ser. 286, 211–226 (2003)106 Steiner, O.: Photospheric magnetic field at smallscales, in: Erdélyi, R. et al. (eds.): Turbulence, Waves,and Instabilities in the Solar Plasma, NATO AdvancedResearch Workshop, held 16–20 September 2002 inBudapest, Hungary, 117–141, (Kluwer, 2003)2004107 Bellot Rubio, L.R.: Sunspots as seen in polarized light,in: Schielicke, R.E. (ed.): Reviews in Modern Astronomy17, 21–50 (Wiley-VCH, 2004)108 Brandenburg, A., Sandin, C., Käpylä, P.J.: Helicalcorona ejections and their role in the solar cycle,in: Stepanov, A.V., Benevolenskaya, E.E., Kosovichev,A.G. (eds.): Multi-wavelength investigations of solaractivity, Proceedings of IAU Symposium 223, 57–64(2004)109 Peter, H.: Structure and dynamics of the low corona ofthe Sun, in: Schielicke, R.E. (ed.): Reviews in ModernAstronomy 17, 87–110 (Wiley-VCH, 2004)110 Stix, M.: Helioseismology, in: Schielicke, R.E. (ed.):Reviews in Modern Astronomy 17, 51–67 (Wiley-VCH, 2004)2005111 Dobler, W.: Stellar dynamos – theoretical aspects, Astron.Nachr./AN 326, 254–264 (2005)112 Lühe, O. von der: Interferometry - an introductionto multiple telescope array interferometry at opticalwavelengths, in: Foy, R. (ed.): Optics in Astrophysics,Cargése, Corse, Workshop held in September 2002,(in press, 2005)116


Konferenzbeiträge – Conference Contributions2003113 Aiouaz, T., Peter, H., Lemaire, P., Keppens, R.:Dynamics and Properties of Coronal Funnels, Astron.Nachr./AN324 Suppl. Issue 3, 7–8 (2003)114 Bellot Rubio, L.R., Schlichenmaier, R., Tritschler, A.:Thermal and Kinematic Structure of a Sunspot at 0.5arcsec Resolution, Astr.Nachr. / AN 324 Suppl. Issue3, 104–105 (2003)115 Berkefeld, T., Soltau, D., Lühe, O. von der: Multiconjugateadaptive optics at the Vacuum Tower Telescope,Tenerife, in: Wizinowich, P.L., Bonaccini,D.(eds.): Adaptive Optical System Technologies II,SPIE 4839, 544–553 (2003)116 Borrero, J.M., Bellot Rubio, L.R.: Two-componentmodeling of convective motions in the solar photosphereand determination of atomic parameters, in:Piskunov, N.E., Weiss, W.W., Gray, D.F. (eds.): Modellingof Stellar Atmospheres, IAU Symp. 210 , PosterC9, http://www.astro.uu.se/ iau210 (2003)117 Borrero, J.M., Lagg, A., Solanki, S.K., Frutiger, C.,Collados, M., Bellot Rubio, L.R.: Modeling the finestructure of a sunspot penumbra through the inversionof Stokes profiles, in: Pevtsov, A.A., Uitenbroek, H.(eds.): Current Theoretical Models and Future High-Resolution Solar Observations, Preparing for ATST,Astron. Soc. Pac. Conference Series 286, 235–242(2003)118 Brajša, R., Wöhl, H., Vršnak, B., Ruždjak, V., Clette,F., Hochedez, J.-F., Roša, D., Hržina, D.: Solar rotationvelocity determined by coronal bright points,Hvar Observatory Bulletin 27, 13–23 (2003)119 Brandenburg, A., Haugen, N.E.L., Dobler, W.: MHDsimulations of small and large scale dynamos, in :Fay-Siebenbürgen, R.v., Petrovay, K., Roberts, B., Aschwanden,M. 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F., Hochedez, J.-F., Dibos, F., Brajša, R.,Jacques, L., Berghmans, D., Zhukov, A., Clette, F.,Wöhl, H., Antoine, J.-P.: Extracting the apparent motionfrom two successive EIT images, in Wilson, A.(ed.): Solar Variability as an Input to the Earth’s Environment,proceedings of the ISCS symposium 2003held at Tatranska Lomnica, Slovakia, 23 – 28 June2003, ESA SP-535, 853–856 (2003)125 Gömöry, P., Rybák, J., Kučera, A., Curdt, W., Wöhl,H.: Transition region eruptive event observed withSOHO/CDS in the quiet sun network, Hvar ObservatoryBulletin 27, 67–74 (2003)126 Hammer, R., Nesis, A.: A New Class of DrivingMechanisms for Solar Spicules, Astron.Nachr./AN 324Suppl. Issue 2, 56–56 (2003)127 Hammer, R., Nesis, A.: Equipartition in Spicules, Astron.Nachr./AN324 Suppl. Issue 3, 100–101 (2003)128 Hammer, R., Nesis, A.: What controls spicule velocitiesand heights? in: Brown, A., Ayres, T.R.,Harper, G.M. (eds.): The future of cool-star astrophysivs,Cool Stars, Stellar Systems, and the Sun, Proceedingsof the 12th Cambridge Workshop, held inBoulder, USA, 30 July – 3 August 2001, 613–618,http://origins.colorado.edu/cs12/proceedings/poster/hammer.ps (2003)129 Kalkofen, W., Hammer, R.: The Filling Factor of SolarInternetwork Grains, Astr.Nachr. / AN 324 Suppl.Issue 3, 101–102 (2003)130 Käpylä, P.J., Korpi, M.J., Ossendrijver, M., Stix, M.:What can we learn from Local Convection Simulationsin the Context of Mean Field Models of StellarRotation and Magnetism?, Astr. Nachr./AN 324 Suppl.Issue 3, 63–63 (2003)131 Kučera, A., Rybák, J., Hanslmeier, A., Wöhl, H.:Observational evidence for a shock event in the solargranulation, Hvar Observatory Bulletin 27, 25–37(2003)132 Langhans, K., Schmidt, W., Tritschler, A.: TwodimensionalSpectroscopy of G-band Bright Structuresin the Solar Atmosphere, Astr. Nachr./AN 324Suppl. Issue 2, 54–54 (2003)133 Lühe, O. von der, Soltau, D., Berkefeld, T., Schelenz,T.: KAOS – Adaptive optics system for the VacuumTower Telescope at Teide Observatory, in: Keil,S.L., Avakyan, S.V. (eds.), Innovative Telescopes andInstrumentation for Solar Astrophysics, SPIE 4853,187–193 (2003)134 Lühe, O. von der: Sensitivity of Active and PassiveHigh Resolution Techniques, Astr. Nachr./AN 324Suppl. Issue 3, 23–23 (2003)135 Mikurda, K., Lühe, O. von der, Schmidt, W.: Dynamicsof the G-band Bright Points, Astr. Nachr./AN 324Suppl. Issue 3, 24–24 (2003)136 Mikurda, K., Lühe, O. von der, Wöger, F.: Solar Imagingwith an Extended Knox-Thompson Technique,Astr. Nachr./AN 324 Suppl. Issue 3, 112–112 (2003)137 Müller, D.A.N., Hansteen, V.H., Peter, H.: Dynamicsof Coronal loops: Catastrophic Coolingänd HighspeedDownflows, Astr. Nachr./AN 324 Suppl. Issue3, 13–13 (2003)117


138 Müller, D.A.N., Hansteen, V.H., Peter, H.: Condensationin Cool Coronal Loops and its Effect on TransitionRegion Lines, Astr. Nachr./AN 324 Suppl. Issue3, 108–109 (2003)139 Nesis, A., Hammer, R., Schleicher, H.: Evolution ofthe granular dynamics and energy transport, in: Abstractsof the 34th Solar Physics Division Meeting ofthe American Astronomical Society, 34.0702N (2003)140 Nesis, A., Hammer, R., Schleicher, H.: Time Variationof Statistical Properties of the Solar Granulation, Astr.Nachr./AN 324 Suppl. Issue 2, 55–55 (2003)141 Nesis, A., Hammer, R., Schleicher, H.: Mergingand Splitting Phenomena in the solar Granulation:A Spectroscopic Investigation, Astr.Nachr./AN 324Suppl. Issue 2, 55–55 (2003)142 Nesis, A., Hammer, R., Schleicher, H.: Dynamical Dichotomyof Granules Smaller and Larger than 1200km, Astron. Nachr./AN 324 Suppl. Issue 2, 102–103(2003)143 Nesis, A., Hammer, R., Schleicher, H.: Evolution ofthe Solar Granulation Dynamics, Astr. Nachr./AN 324Suppl. 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Issue 3, 23–23 (2003)149 Sankarasubramaniam, K., Elmore, D.F., Lites, B.W.,Sigwarth, M., Rimmele, T.R., Hegwer, S., Gregory,S., Streander, K.V., Wilkins, L., Richards, K., Berst,C.: Diffraction Limited Spectro-Polarimetrera - PhaseI, in: Fineschi, S. (ed.): Polarimetry in Astronomy,SPIE 4843, 414–424 (2003)150 Schleicher, H., Nesis, A., Hammer, R., Tritschler, A.:Long-Term Observation of Abnormal Granulation usingAdaptive Optics, Astr. Nachr./ AN 324 Suppl. Issue3, 24–25 (2003)151 Schleicher, H., Wöhl, H., Balthasar, H.: MercuryTransit Observed with TESOS at the VTT on Tenerife,Astr. Nachr./AN 324 Suppl. Issue 3, 114–114 (2003)152 Schlichenmaier, R., Bellot Rubio, L., Tritschler, A.:Penumbral Line Asymmetries of Fe I 557.6 nm: Implicationson the Flow Geometry of a Sunspot Penumbra,Astr. Nachr./AN 324 Suppl. 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Sonstige Veröffentlichungen – Other Publications2003225 Mattig, W.: Orbituary Anton Bruzek (1915–2003), SolarPhys. 216, 1–3 (2003)226 Mattig, W., Soltau, D.: Merkur vor der Sonne: EineFinsternis der besonderen Art, Sterne und Weltraum42 (April-Heft), 66–68 (2003)227 Peter, H.: Das Wetter auf der Sonne, in: Der heißeKosmos, Sterne und Weltraum Special 4, 44–61 (2003)2004228 Roth, M.: Neue Blicke in das Innere der Sonne, Sterneund Weltraum 43, Nr. 8, 24–32 (2004)229 Roth, M.: Helioseismologie am Südpol, Sterne undWeltraum 43, Nr. 12, 42–43 (2004)2005230 Wöhl, H.: Anzeigefehler bei Funkuhren (Leserbrief),Sterne und Weltraum 44, Nr.5, 6–6 (Mai 2005)122


ConDynReyMixEvaFormThePhasDataTheTheMerSunInteTheAsyMeaTubSoliCycMagFinSignBiseABKÜRZUNGENABBREVIATIONSAIP Astrophysikalisches Institut PotsdamATST Advanced Technology Solar TelescopeAURA Association of Universities for Research in Astronomy, USACCI Comité Científico InternacionalDLR Deutsches Zentrum für Luft-und RaumfahrtHAO High Altitude Observatory, BoulderHLRS Hochleistungsrechenzentrum StuttgartIAA Instituto de Astrofísica de Andaludía, GranadaIAC Instituto de Astrofísica de Canarias, La LagunaMPAE Max-Planck-Institut für Aeronomie, Lindau (= MPS ab 2004)MPS Max-Planck-Institut für Sonnensystemforschung, LindauNSO National Solar Observatory, USAPOLIS Polarimetric Littrow SpectrometerTESOS Telecentric Solar SpectrometerTIP Tenerife Infrared PolarimeterUSG Universitäts-Sternwarte GöttingenVTT Vacuum Tower TelescopeAunP

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