Tangential stress due to Kelvin-Helmholtz instability at the magnetospheric boundary

A 2-dimensional MHD simulation of the Kelvin-Helmholtz instability at the terrestrial magnetospheric boundary shows that a finite thick velocity shear layer with super-Alfvenic velocity jump at the magnetospheric boundary is unstable no matter how large the magnetosheath sonic Mach number. For all magnetosheath sonic Mach numbers a velocity boundary layer is formed inside of the magnetospheric boundary due to tangential stress associated with the instability and a flow vortex is excited at the inner edge of the velocity boundary layer. The magnetospheric boundary is more highly nonlinearly corrugated by the instability for a smaller sonic Mach number. Tangential stress due to the instability at the boundary is mainly caused by Reynolds stress and is found to be large enough for exciting a residual plasma convection inside the terrestrial magnetosphere. (author) 26 refs., 6 figs