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Astron. Astrophys. 353, L1-L4 (2000)

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Letter to the Editor

Ion acceleration in connection with a modulated solar wind termination shock: phase space propagation and complete energy spectra

Andreas Dworsky and Hans J. Fahr

Institut für Astrophysik und Extraterrestrische Forschung der Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany

Received 28 July 1999 / Accepted 17 November 1999


Using the general kinetic transport equation for cosmic ray particles the energization of heliospheric pick-up ions (PUI's) to Anomalous Cosmic Ray particles (ACR's) by means of non-linear wave-particle interactions is described. After creation of PUI's with initial energies of 1 keV/nuc they undergo phase space diffusion by Fermi-1 and Fermi-2 scattering processes in the heliosphere and at the termination shock and eventually appear as ACR's in the 10 MeV/nuc energy regime for which spatial diffusion becomes important. We present ion energy spectra derived from a fully consistent theoretical context and covering the range from 1 keV/nuc to 100 MeV/nuc. Our solutions of the kinetic transport equation reflect the effect of simultaneous operations of convective and diffusive transport processes in heliospheric phase space. As demonstrated in our calculations the kick-up from pick-up's to ACR's in our approach completely works on known physical grounds with no need to prescribe a specific injection of seed ACR's at the shock. The spectra resulting near the termination shock are far from being pure power-laws as is expected in classical shock acceleration theories. Thus the idea to start from measured VOYAGER ACR spectra and to apply a necessary demodulation up to a pure power-law cannot be used to find the shock location.

Key words: Sun: solar wind – inteplanetary medium – ISM: cosmic rays – acceleration of particles – shock waves – turbulence

Send offprint requests to: Hans J. Fahr

This article contains no SIMBAD objects.


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© European Southern Observatory (ESO) 2000

Online publication: December 8, 1999