A two-dimensional MHD model of the solar wind interaction with Mars

Abstract

The ionosphere of Mars is expected to be significantly affected by the solar wind because Mars does not possess a significant intrinsic magnetic field which deflects the solar wind. Despite a number of plasma measurements made near Mars, the nature of the solar wind-Mars interaction has not yet been fully understood. In order to self-consistently study the solar wind interaction with the ionosphere of Mars, a two-dimensional MHD model has been developed with an emphasis placed on the structure of the ionosphere of Mars. It is found that the modeled electron density profile in the upper ionosphere strongly depends on the solar wind dynamic pressure as well as the solar zenith angle. The ionosphere in the model tends to have an ionopause-like sharp drop of the electron density at some altitude for realistic solar wind dynamic pressures. Such behavior is not consistent with most of the observed electron density profiles, which exhibit relatively large and constant scale height in most of the dayside region. While the observed electron density profiles of the Venus ionosphere have been reproduced reasonably well by ionospheric models as well as recent three-dimensional MHD models, the electron density profiles of the Martian ionosphere have not been successfully reproduced by theoretical models including this study. This fact implies that processes not present in the Venus ionosphere, such as crustal magnetic fields and the rotation of the planet, may have significant effects on the structure and the dynamics of the ionosphere of Mars.

Global hybrid model of the solar wind interaction with the Venus ionosphere: ion escape processes

“…The magnetic field enhancement at the thick ionopause region of Fig. 1 results mainly from the kinetic energy loss of magnetosheath protons through chemical reactions and ion-neutral drag force (Shinagawa and Bougher, 1999).…”

Solar EUV and Electron-Proton-Hydrogen Atom-Produced Ionosphere on Mars: Comparative Studies of Particle Fluxes and Ion Production Rates Due to Different Processes

“…These processes are reported to be important in the martian ionosphere above ∼180 km (cf. Shinagawa and Bougher 1999). …”

Surface Waves along the Martian Ionopause

“…We also assume that the plasma is magnetic eld-free and incompressible (∇·v = 0). The former assumption is quite restrictive, but it gives a realistic approximation of plasma behaviour at the ionopause, where magnetic eld is negligibly small [13]. The later assumption complies well with surface gravity waves which are essentially incompressible, e.g.…”

“…A large amount of data collected by this mission [12] stimulated a number of numerical simulations. For instance, Shinagawa [13] developed the two--dimensional (2D) magnetohydrodynamic model to analyse the electron mass density prole vs. the solar wind gas pressure [13]. He studied inuence of the Martian crustal magnetic eld by comparing the electron mass density proles of Venus and Mars.…”