Aspects of solar wind interaction with Mars: comparison of fluid and hybrid simulations

N V Erkaev,H K Biernat,A Bößwetter,U Motschmann

doi:10.5194/angeo-25-145-2007

Abstract

Abstract. Mars has no global intrinsic magnetic field, and consequently the solar wind plasma interacts directly with the planetary ionosphere. The main factors of this interaction are: thermalization of plasma after the bow shock, ion pick-up process, and the magnetic barrier effect, which results in the magnetic field enhancement in the vicinity of the obstacle. Results of ideal magnetohydrodynamic and hybrid simulations are compared in the subsolar magnetosheath region. Good agreement between the models is obtained for the magnetic field and plasma parameters just after the shock front, and also for the magnetic field profiles in the magnetosheath. Both models predict similar positions of the proton stoppage boundary, which is known as the ion composition boundary. This comparison allows one to estimate applicability of magnetohydrodynamics for Mars, and also to check the consistency of the hybrid model with Rankine-Hugoniot conditions at the bow shock. An additional effect existing only in the hybrid model is a diffusive penetration of the magnetic field inside the ionosphere. Collisions between ions and neutrals are analyzed as a possible physical reason for the magnetic diffusion seen in the hybrid simulations.

Highlights

Mars does not have a sufficient magnetic field to form its own magnetosphere, and the solar wind interacts directly with the ionosphere of the planet
The magnetic field has a jump at the bow shock and it becomes much stronger as the ionopause is approached, giving rise to the magnetic barrier with a distinct magnetic pile-up boundary (MPB), which is identified with the magnetic field rotation and the drop in the magnetic turbulence level
The calculated magnetosheath profiles corresponding to the ideal MHD model are shown in Fig. 2 along the subsolar line for y=0 and z=0, and in Fig. 3a and Fig. 3b in the two orthogonal planes: xy and xz, respectively

Summary

Introduction

Mars does not have a sufficient magnetic field to form its own magnetosphere, and the solar wind interacts directly with the ionosphere of the planet. Even though the planet is unmagnetized, the flow of the solar wind is strongly affected by the interplanetary magnetic field (IMF) which plays a crucial role in the interaction of the solar wind pro-. The magnetic field has a jump at the bow shock and it becomes much stronger as the ionopause is approached, giving rise to the magnetic barrier with a distinct magnetic pile-up boundary (MPB), which is identified with the magnetic field rotation and the drop in the magnetic turbulence level. As shown by Biernat et al (1999), the magnetic field profiles across the magnetosheath become steeper when the solar wind Alfven Mach number increases

Objectives

Results

Conclusion