Berlin 2005 – scientific programme

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EP: Extraterrestrische Physik

EP 1: Magnetosph
äre und Ionosph
äre

EP 1.2: Talk

Friday, March 4, 2005, 10:15–10:30, TU BH349

The Diffusion Mean Free Path Upstream of Earth’s Quasi-Parallel Bow Shock — •M. Scholer¹, A. Kis¹, B. Klecker¹, E. Möbius², E. A.. Lucek³, H. Reme⁴, J. M. Bosqued⁴, L. M. Kistler², and H. Kucharek² — ¹Max-Planck-Inst. extr. Physik, Garching, Germany — ²University of New Hampshire, Durham, USA — ³Imperial College, London, England — ⁴CESR, Toulouse, France

We have analyzed a number of diffuse upstream particle events observed by Cluster when the spacecraft separation was between 1 and 1.5 Earth radii. The spatial gradient of the partial ion densities parallel to the magnetic field has been determined in several energy bands as a function of distance from the bow shock. For the events investigated the e-folding distance increases with decreasing solar wind speed. Assuming that upstream diffusion is balanced by downstream convection we can determine the spatial diffusion mean free path as a function of energy. Since the mean free path is proportional to the e-folding distance and proportional to the solar wind speed the mean free path is approximately independent of solar wind velocity. We have also determined the magnetic field power spectra during these upstream events and compare the spatial development of the power spectra with distance from the shock with the spatial development of the energetic particle density.