Bonn 2010 – scientific programme

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EP: Fachverband Extraterrestrische Physik

EP 3: Poster

EP 3.5: Poster

Monday, March 15, 2010, 17:45–19:00, AKM Foyer

On the importance of the Local Interstellar Spectrum for the Solar Modulation Parameter — •Klaudia Herbst¹, Andreas Kopp¹, Bernd Heber¹, Friedhelm Steinhilber², Horst Fichtner³, Klaus Scherer³, and Daniel Matthiä^4,1 — ¹IEAP, Christian-Albrechts-Universität zu Kiel, Kiel, Germany — ²Swiss Federal Institute of Aquatic Science and Technology, Dübendorf, Switzerland — ³Theoretische Physik IV, Ruhr-Universität Bochum, Bochum, Germany — ⁴Institut für Luft- und Raumfahrzmedizin, Deutsches Zentrum für Luft- und Raumfahrt, Köln, Germany

We compare several local interstellar proton spectra often used in literature. We show that the modulation parameter φ, which parametrizes the modulation of the local interstellar spectrum (LIS) in the heliosphere, strongly depends on the LIS itself. Taking the LIS dependency of the modulation parameter into account, we derive linear equations to convert φ between the different LIS. The conversions used are afterwards applied to a long-term reconstruction of φ derived from a record of the cosmogenic radionuclide, ¹⁰Be. For some LIS models occasionally negative φ values are obtained, a fact which is impossible from the physical point of view. Despite non-heliospheric effects such as uncertainties in the geomagnetic field and climate influences on the ¹⁰Be production, one possible reason may also be the choice of the LIS. We show that the reconstruction of φ provides the potential to derive the lower intensity limit of the LIS, keeping in mind that first the non-heliospheric effects have to be removed from the data.