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STP12 Abstracts Berlin, 12 - 16 July 2010 SCOSTEP Symposium 2010 Observations of tidal behavior in mesospheric water vapor at mid- and high latitudes. Hallgren Kristofer , Hartogh Paul Max Planck Institude for Solar System Researech Water vapor is a good tracer of the middle atmosphere dynamics due to its long chemical lifetime. Observed tidal variability in the amount of water vapor can therefore be assumed to be caused by different transport mechanisms. Gravity waves are known to be of importance for the momentum balance in the MLT region. However they can be affected by the tides. A comprehensive understanding of all aspects of tidal behavior in the upper mesosphere is therefore of importance. Tidal behavior in accordance with current models are regularly observed in the different wind-fields by radars. Satellites can readily detect water vapor in the MLT region with a high temporal resolution but are burdened by orbital constrains and the continuous observational record of tidal behavior in water vapor is small. Ground based detections of water vapor in the MLT region have until now been sparse due to the weak signal. In May 2008 we installed a microwave spectrometer sensitive enough to observe tidal behavior in the mesospheric water vapor on a monthly basis at ALOMAR (69 N, 16 E). A similar instrument was installed at Schneefernerhaus on Zugspitze (47 N, 10 E) in January 2009. We measure water vapor at 22.235 GHz which set the upper limit of the resolvable profile to approximately 80 km. We will here present observations of tidal behavior in mesospheric water vapor from two different measurement locations, one polar location (ALOMAR) and one mid-latitude location (Zugspitze). By applying a moving time-frame integration scheme where each month is integrated and rebinned to a monthly-mean represented by one day we are able to resolve variability within that day. The variability is fitted by a cosine function with two components, one diurnal and one semidiurnal. Both locations indicate tide-like behavior according to the fit-function. The behavior at each location will be described and compared to each-other. It will also be compared to models describing tidal effects in mesospheric water vapor. The daily variations in water vapor do not follow any single wind field, but is most probably the result of a superposition of the different mesospheric dynamical fields. The diurnal component above ALOMAR show a distinct behavior of amplitude maxima at the equinoxes, something which is not observed above Zugspitze. These equinoctial maxima show the largest amplitude of all components, although the diurnal component above Zugspitze do in general have a larger amplitude than the ALOMAR.
STP12 Abstracts Berlin, 12 - 16 July 2010 SCOSTEP Symposium 2010 Global study of CMEs and of their effects in the Earth environment Hanuise Christian 1 , GMI-PNST Group 2 1 LPC2E/CNRS, 2 PNST The aim of the GMI (Multi-Instrument Group) of the French National Solar-Terrestrial Physics program is to study the physical processes in, and the relations between, the various regions on the path from the Sun to the Earth. Are successively involved the formation mechanism of solar flares and CMEs, the propagation within the solar wind, the interaction with the Earth’s magnetosphere and the coupling between the magnetosphere, the ionosphere and the neutral atmosphere.To that effect, we use the CME database published at wwwsolar.mcs.st-and.ac.uk/~stephane/PNST/ and select several events chosen among the 233 halo CMEs in order to study their geoeffectiveness. We look successively at the origin of the CMEs at the Sun, at the characteristics of the associated ICMEs and of the solar wind, at the interactions between CMEs and the magnetosphere, as seen on the polar cap potential derived from SuperDARN radars and magnetic indices, and at the CMEs effects down in the thermosphere, as seen on a disturbance thermospheric coefficient. The variations of these parameters are studied during five-day intervals starting on the day of a CME. The polar cap potential, obtained from the APL database for the northern hemisphere radars, shows a noticeable response to the arrival of the CME only in a very limited number of cases (about 10% of the database). The other indices also show that there are some long periods without any geoeffective CME. For halo CMEs propagating backwards from the Sun or on the eastward limb of the Sun, the lack of terrestrial effect is quite normal. But, in addition, halo CMEs with a negative acceleration seem also to lack of effectiveness. Moreover, the direction of B and the orientation of Bz might play a role in the geoeffectiveness of a halo CME.
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scostep 2010 (stp12) - Leibniz-Institut für Atmosphärenphysik an der ...

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