MHD modelling of the magnetosheath with anisotropic plasma pressure

Abstract

We study the solar wind flow in the Earth's magnetosheath using a three—dimensional, ideal magnetohydrodynamic (MHD) model with anisotropic plasma pressure. Four different closure relations are examined and compared with each other, i) The double adiabatic model; ii) the empirical relation with respect to the criterion of the anisotropic ion cyclotron instability; iii) the mirror instability criterion, and (iv) the combination of the mirror and the anisotropic ion cyclotron instability. Profiles of magnetic field strength and plasma parameters for the different closure relations are presented and compared with each other along the stagnation stream line between the shock and the obstacle. We find that the main body of the magnetosheath is mirror unstable. This is a reason to combine both, mirror and ion cyclotron instability criteria to close the ideal MHD model.