We study the nonlinear evolution of mixing layers subject to the Kelvin-Helmholtz (KH) instability with MHD codes for large eddy simulation (LES). As the input for the numerical codes use physical conditions of special events at the Earth magnetosphere boundary layer recorded by spacecraft crossings. We describe features of large vortices development that influence the downstream growth of the boundary layer width. A prediction of theory is that for flows with constant density the presence of velocity gradient interferes with the tearing process when the Alfven Mach number, MA > 1. The tearing modes are absent in super-Alfvenic flows which are, instead, dominated by the KH instability. The opposition between tearing and KH instabilities is investigated by including the effect of resistivity on LES.
展开▼
