Collisionless relaxation of non-gyrotropic downstream ion distributions: dependence on shock parameters

Abstract

Upon crossing the shock front, ions begin to gyrate. The ion distribution just behind the ramp is manifestly non-gyrotropic. The gyration of the ion distribution as a whole results in spatially periodic oscillations of the ion pressure. The magnetic pressure must oscillate in the opposite phase to ensure the maintenance of the pressure balance throughout the shock front. The ion non-gyrotropy and the pressure oscillations gradually damp due to the collisionless gyrophase mixing. The rate of this relaxation depends on the basic shock parameters. The most influential are the angle between the shock normal and the magnetic field, the upstream ion temperature and the magnetic compression.