Anisotropic MHD model for the magnetosheath of Saturn

The ion temperature anisotropy in the magnetosheath of Saturn is estimated by three-dimensional MHD modelling using theoretical thresholds of the mirror and proton cyclotron instabilities obtained from kinetic theory. The calculation has been performed for typical parameters of the supersonic solar wind, and an angle between the interplanetary magnetic field and the solar wind velocity equal to 45°. It is found that in the Saturn's magnetosheath the plasma β is bigger and the ratio T ⊥/ T ∥ is less than in the Earth's magnetosheath. The maximum of T ⊥/ T ∥ at the subsolar point near the Saturn's magnetopause is about 1.5. The ion cyclotron instability is found to be the main source of the pitch-angle diffusion in the Saturn's plasma depletion layer, whereas the threshold of the mirror instability is lower in the magnetosheath proper.