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EP: Extraterrestrische Physik

EP 18: Sonne: Energetische Teilchen, Sonnenwind und CMEs

EP 18.2: Fachvortrag

Thursday, March 16, 2006, 11:30–11:45, B

Velocity ditribution functions of solar wind ions from ACE/SWICS using a maximum likelihood analysis technique — •Lars Berger¹, Muharrem Köten¹, Jim Raines², Robert F. Wimmer-Schweingruber¹, and Thomas H. Zurbuchen² — ¹Institut für Experimentelle und Angewandte Physik, University of Kiel, D-24098 Kiel, Germany — ²University of Michigan, Atmospheric, Oceanic, and Space Sciences 2455 Hayward St., Ann Arbor, MI 48109, USA

By studying the velocity distribution of solar wind ions we can learn a lot about the acceleration processes in the inner heliosphere. The shape of the distribution can help us to distinguish between heating by coulomb-interaction and wave-heating. Previous studies have shown that the velocity distribution of solar wind ions follows a thermal(maxwellian) distribution extended with a superthermal tail. These superthermal ions are rare and former analysis techniques have great uncertainties applied to them. We have analysed data from the solar wind ion spectrometer(SWICS) on the advanced composition explorer(ACE) using a maximum likelihood analysis technique based on poissonian statistics, to improve the results especially for low count rates. We present results for different solar wind types.