Vladimir B. Baranov

Model of the solar wind interaction with the local interstellar medium: Numerical solution of self-consistent problem

A self-consistent gasdynamic model of the solar wind interaction with the local interstellar medium (LISM), which took into account the mutual influence of the plasma component (electrons and protons) of the LISM and the LISM H atoms that penetrate into the heliosphere was constructed by Baranov et al. (1981) in the approximation of axial symmetry. This model, however, had a number of defects. In particular, the motion of the H atoms was described by hydrodynamical equations, although the mean free path of the H atoms and the characteristic length of the problem were comparable. An iterative method, that used a Monte Carlo simulation of H atom motion in the field of the plasma component hydrodynamic parameters, was suggested by Baranov et al. (1991) and only the first step of the iteration was realized (non-self-consistent problem solution). In this paper the results of the self-consistent problem solution for a single set of the undisturbed solar wind and LISM parameters are presented. The structure of the upwind as well as wake regions of the flow is calculated. The geometrical pattern of the flow (bow shock, heliopause, termination shock, Mach disc, etc), the bulk velocity and the number densities of H atoms and plasma component are obtained and analyzed as a function of the distance from the Sun for different values of the polar angle. The effects of resonance charge exchange of the LISM H atoms as well as energetic H atoms “born” in the solar wind are taken into account. It is interesting to note that the effect of H atoms penetrating the solar wind results in the disappearance of the complicated flow structure as well as the supersonic regions between the heliopause and termination shock in the downwind region. In future we are going to compare our theoretical results with the results of Voyager 1/2, Pioneer 10/11, Ulysses spacecraft, and other experiments.

On the distribution function of H Atoms in the problem of the solar wind interaction with the local interstellar medium

This paper is devoted to the analysis of the models of the solar wind interaction with 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. The axisymmetric interaction model of Baranov and Malama [1993], that used the kinetic description of H atoms motion together with the hydrodynamic approximation for the plasma component, showed that the distribution functions of the all H atom populations are essentially not Maxwellian. The hydrodynamic model by Zank et al. [1996] is based on the Maxwellian distribution functions of the LISM and solar wind hydrogen atoms. 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.

An axisymmetric magnetohydrodynamic model for the interaction of the solar wind with the local interstellar medium

We numerically analyze a magnetohydrodynamic, steady-state model for the interaction of a spherically symmetric solar wind with a three-component local interstellar medium (LISM), which is composed of plasma, hydrogen atoms, and a magnetic field. The magnetic field is assumed to be parallel to the velocity in the LISM. In this case, the model is axisymmetric. We study the effects of magnetic field on the plasma-flow geometry and on the distribution of hydrogen-atom parameters. In particular, we show that the presence of hydrogen atoms does not affect the qualitative change in the shape of the bow shock, the heliopause, and the solar-wind shock with increasing strength of the interstellar magnetic field. The presence of a magnetic field in the LISM can strongly affect the parameters of the energetic hydrogen atoms originated in the solar wind, although its effect on the “hydrogen wall” observed with the GHRS instrument onboard the HST spacecraft (Linsky and Wood 1996) is marginal.

Axisymmetric self-consistent model of the solar wind interaction with the LISM: Basic results and possible ways of development

We analyze the main results of the axisymmetric self-consistent model of the solar wind (SW) and supersonic local interstellar medium (LISM) interaction proposed by Baranov and Malama (1993, hereafter BM93, 1995) for an interstellar flow assumed to be composed of protons, electrons and hydrogen atoms. Here, in addition to the resonant charge exchange we also take into account the photoionization and the ionization by electron impact. The characteristics of the plasma in the interface region and inside the heliosphere depend strongly on the ionization degree of the LISM. The distribution function of the H atoms which penetrate the solar system from the LISM is non-Maxwellian, which implies that a pure hydrodynamic description of their motion is not appropriate. The H atom number density is a non-monotonic function of the heliocentric distance and the existence of a “hydrogen wall” in the vicinity of the heliopause is important for the interpretation of solar Lyman-alpha scattering experiments.The influence of the interface plasma structure on the interstellar oxygen penetration into the solar system is also illustrated. Possible ways of development of the model are analyzed.

Interaction of interplanetary shocks with the heliospheric termination shock: Two‐dimensional magnetohydrodynamic model

The two-dimensional problem of the oblique interaction between an interplanetary shock (IPS) and the termination shock (TS) with allowance for the effect of the interplanetary magnetic field is studied within the framework of the ideal magnetohydrodynamic model and a steady model of the solar wind interaction with the local interstellar medium. The self-consistent axisymmetric model proposed by Baranov and Malama, which takes into account the processes of resonant charge exchange between H atoms and protons, is used. The electron number density and the solar wind velocity VSW ahead of TS depends on the parameters of this model. The postinteraction configuration consists of a new moving TS′, a transmitted IPS′, a set of Alfven and slow magnetohydrodynamic waves, and a contact discontinuity which can change as functions of five dimensionless governing parameters and the specific heat ratio γ. The maximum electron number density ne is usually reached behind the new termination shock TS′ for an oblique (θ ≠ 0) impingement of IPS on TS rather than for the head-on collision (θ = 0). Nevertheless, the maximum calculated values of ne are lower than those corresponding to plasma frequencies ωp ≅ 2 kHz observed by the Voyager spacecraft. It is found that all the quantities considered depends radically on the angle ψTS between the front of TS and the vector of the interplanetary magnetic field strength BSW.