Gradient drift instability in high latitude plasma patches: ion inertial effects

Nonlinear simulations of the gradient drift instability with inertial effec ts for the high latitude plasma patches demonstrate that the initial cross- field elongated structures, driven by the gradient drift instability, are u nstable to the Kelvin-Helmholtz instability and to the generation of sheare d flows. The shear flow develops on the scale-length of the irregularities. Both these processes arise from the nonlinear inertial term. The computed density and velocity fluctuation levels are of the order of the observed va lues. The combined effect of parallel dynamics as well as secondary instabi lities prevent the patch from disintegrating for hours.