Astron. Astrophys. 326, 860-869 (1997)

The three-fluid structure
of the particle modulated solar wind termination shock

S.V. , Chalov ¹, H.J. and Fahr <sup>2

1</sup> Institute for Problems in Mechanics of the Russian Academy of Sciences, Prospect Vernadskogo, 101, 117526 Moscow, Russia
² Institut für Astrophysik und Extraterrestrische Forschung der Universität Bonn, Auf dem Hügel 71, D-53121 Bonn, Germany

Received 12 December 1996 / Accepted 22 May 1997

Abstract

In this paper we have improved our earlier physical concept to theoretically describe the particle-modulated solar wind termination shock by three dynamically interacting hydrodynamic fluids, i.e. the solar wind, the pick-up ion, and the anomalous cosmic ray (ACR) plasmas. In this earlier concept we have introduced a parametrized form to describe the injection of Fermi-I energized pick-up ions into the ACR regime in the precursor and the subshock region. With this parametrization it was possible to give solutions for the upstream-to-downstream transition of all thermodynamic fluid properties on the basis of two undefined parameters, i.e. the total injection efficiency of pick-up ions and the mean energy of post-shock ACR particles. Making use of the pick-up ion transport equation we now obtain a parameter-free description of the injection process. In addition we obtain the energy-averaged spatial diffusion coefficient as function of the upstream distance from the subshock by use of an approximated ACR energy spectrum. As a consequence of these improvements we now can give solutions for the spatial structure of the three-fluid system in the precursor and the subshock region in terms of bulk velocity, fluid pressures, and compression ratio, without undefined parameters. We discuss the observability of the derived multifluid post-shock plasma conditions by energetic neutral atoms (ENA's) and emphasize the fact that ENA's may be the best tracers to the physics of the particle-modulated solar wind termination shock.

Key words: solar system: multi-fluid shocks -- cosmic rays -- heliospheric termination shock -- pick-up ions

Send offprint requests to: H.J. Fahr

Contents

• 1. Introductory sketch of the shock scenario
• 2. Basic theoretical approach
  • 2.1. Governing equations
  • 2.2. The precursor flow
  • 2.3. Subshock transition relations
• 3. Numerical results and conclusions
• Acknowledgements
• Appendix A
  • Appendix A: evaluation of the injection efficiency
  • Appendix B: determination of the local diffusion coefficient
  • References

© European Southern Observatory (ESO) 1997

Online publication: October 15, 1997
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