scostep 2010 (stp12) - Leibniz-Institut für Atmosphärenphysik an der ...

STP12 Abstracts
Berlin, 12 - 16 July 2010
SCOSTEP Symposium 2010
On the Importance of the Local Interstellar Spectrum for the Solar Modulation
Parameter
Herbst Klaudia 1 , Kopp Andreas 1 , Heber Bernd 1 , Steinhilber Friedhelm 2 , Fichtner Horst 3 , Scherer
Klaus 3 , Matthiä Daniel 4
1 Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel,
Germany, 2 Swiss Federal Institute of Aquatic Science and Technology, Eawag, 8600 Dübendorf,
Switzerland, 3 Theoretische Physik IV, Ruhr-Universität Bochum, Germany, 4 Institut für Luft- und
Raumfahrtmedizin, Deutsches Zentrum für Luft- und Raumfahrt, Köln, Germany
Here we compare several local interstellar proton spectra often used in literature, and show
that the modulation parameter $\phi$, which parametrizes the modulation of the local
interstellar spectrum (LIS) in the heliosphere, strongly depends on the LIS itself. Taking the
LIS dependency of $\phi$ into account, we first derive linear equations to convert the
modulation parameter between the different LIS and afterwards apply these conversions to a
long-term reconstruction of $\phi$ from a derived cosmogenic nuclide 10 Be record. For some
LIS models occasionally negative values are obtained, a fact which is impossible from the
physical point of view. Despite inner-heliospheric effects such as uncertainties in the
geomagnetic field and climate influences on the 10 Be production, one possible reason may
also be the choice of the LIS. We show that the reconstruction of $\phi$ provides the potential
to derive the lower intensity limit of the LIS, keeping in mind that first the inner-heliospheric
effects have to be removed from the data.