# On the distribution function of H-atoms in the problem of
the solar wind interaction with the local interstellar
medium (LISM)

*V.B. Baranov, V.V. Izmodenov, Yu.G. Malama*

Institute for Problems in Mechanics, Russian Academy of
Science, Prospect Vernadskogo 101, Moscow, 117526, Russia
### Abstract:

The models of the solar wind interaction with the supersonic
flow of the local interstellar medium (LISM) self-
consistently taking into account mutual influence of plasma
(electrons and protons) and neutral (H atoms) components
of the LISM are analyzed. The flow of the neutral component
cannot be described in the framework of hydrodynamical
equations, because the mean free path of H atoms is
comparable with the characteristic length of the problem
(for example, with the size of the interface region).
That is why Baranov and Malama (JGR,1993,v.98, N A9)
constructed the model where only plasma component
is described by hydrodynamical equations and the motion
of H atoms is considered on the basis of kinetic
approximation. Later Zank et al. (JGR, 1996, 101, N A10)
used a multifluid model.
The last model is based on the main assumption that
the distribution functions of the all H atom populations
are Maxwellian.
On the basis of the model by Baranov and Malama [1993]
we show here that the distribution functions of the all
H atom populations are significantly not Maxwellian.
The comparisons of the results obtained on the basis
of the kinetic model by Baranov and Malama [1993]
and multifluid model by Zank et al. [1996] show that
the distributions of H atom parameters have large
quantitative as well as qualitative distinctions.
A number of theoretical predictions and relevant,
experimental data are analyzed.

**AGU Index Terms: **2124; 2144 Interstellar gas; 2151 Neutral particles; 7843 Numerical simulation studies

**Keywords/Free Terms: **heliosphere, solar wind, interstellar medium, interstellar atoms

*JGR-Space* 97JA03662

* Vol. 103
, No. A5
, p. 9575
*

*© 1998 AGU*