HYBRID SIMULATIONS OF INTERMEDIATE SHOCKS - COPLANAR AND NONCOPLANAR SOLUTIONS

The kinetic structure and stability of subfast intermediate shocks (IS) are investigated using a hybrid code. The shocks are formed dynamically by the interaction between a flowing plasma and a stationary piston. For theta(BN) = 60-degrees and plasma beta = 0.46, the strong IS is found to be stable with a width in the range of 10 to 20 ion inertial lengths (lambda(i)). The rotation of the transverse component of the magnetic field is in the ion sense. The weak IS has a more complex structure and consists of both Alfven and slow waves. The leading edge of the shock is dominated by the Alfven mode and is associated with a S-shape electron sense field rotation with a small decrease (increase) in the magnetic field (density) across it. Some of the ion dissipation occurs within this layer, which is relatively thin (approximately 17 - 20-lambda(i)). However, the transition to the downstream density and magnetic field occurs in the much wider (approximately 150-lambda(i)) trailing slow wave. The main heating associated with this trailing edge occurs in the direction parallel to the magnetic field. This slow wave has a phase velocity larger than the Alfven speed due to kinetic corrections to linear wave properties. As a result, the slow wave stays attached to the leading edge of the shock which remains time-stationary. The classification of IS's, based on phase velocity of MHD modes, becomes ambiguous in the kinetic limit. When the magnetic field is noncoplanar, the strong IS becomes time-dependent and expands self-similarly in time, whereas the weak IS disintegrates into an RD.