Issue |
A&A
Volume 424, Number 1, September II 2004
|
|
---|---|---|
Page(s) | 263 - 278 | |
Section | The Sun | |
DOI | https://doi.org/10.1051/0004-6361:20035599 | |
Published online | 17 August 2004 |
A kinetic control of the heliospheric interface hydrodynamics of charge-exchanging fluids
1
Insitute of Astrophysics and Extraterrestrial Research, Bonn University, Auf dem Hügel 71, Bonn, Germany e-mail: hfahr@astro.uni-bonn.de
2
Space Research Centre PAS, Bartycka 18A, Warsaw, Poland
Received:
30
October
2003
Accepted:
4
May
2004
It is well known that the Solar System is presently moving through a
partially ionized local interstellar medium. This gives rise to a
counter-flow situation requiring a consistent description of behaviour
of the two fluids – ions and neutral atoms – which are dynamically
coupled by mutual charge exchange processes. Solutions to this problem
have been offered in the literature, all relying on the assumption that
the proton fluid, even under evidently nonequilibrium conditions, can be
expected to stay in a highly-relaxated distribution function given by
mono-Maxwellians shifted by the local proton bulk velocity. Here we
check the validity of this assumption, calculating on the basis of a
Boltzmann-kinetic approach the actually occurring deviations. As we
show, especially for low degrees of ionization, , both the
H-atoms and protons involved do generate in the heliospheric interface
clearly pronounced deviations from shifted Maxwellians with
asymmetrically shaped distribution functions giving rise to
non-convective transport processes and heat conduction flows. Also in
the inner heliosheath region and in the heliotail deviations of the
proton distribution from the hydrodynamic one must be expected. This
sheds new light on the correctness of current calculations of H-atom
distribution functions prevailing in the inner heliosphere and also of
the Lyman-α absorption features in stellar spectra due to the
presence of the hydrogen wall atoms. Deviations from LTE-functions would
be even more pronounced in magnetic interfaces, which via CGL-effects
cause temperature anisotropies to arise.
Key words: hydrodynamics / plasmas / Sun: solar wind / ISM: general / Galaxy: solar neighbourhood
© ESO, 2004
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