Kinetic Alfven Wave Generation and Interaction with Electrons From Ion-Ion Streaming in a Non-uniform Slow Shock Geometry

Thin current sheets in the magnetotail lead to magnetic reconnection and a so-called Petschek-type geometry. In this geometry, slow shocks extend out from the reconnection site, where the incoming flow is diverted, accelerated and heated at the expense of the magnetic field energy. Slow shocks are occasionally observed in the magnetotail. They can be modeled in hybrid (particle ion, massless fluid electron) simulations at modest incident angles(θB n= 60° - 75°), but only at larger angles with a more sophisticated model for the electron fluid. To validate this improved model, we use particle-in-cell (1D) simulations of highly oblique slow-mode shocks (θB n=84° and β=0.1) [ Yin et al., JGR, in press, 2005] to show that the downstream electron temperature becomes anisotropic (Te∥ > Te∥) as observed in slow shocks in space. The electron anisotropy results, in part, from the electron acceleration/heating by the parallel electric field of very obliquely propagating kinetic Alfven waves excited by ion-ion streaming. Spiky structures in density in the shock ramp are also observed in these simulations. In this work, we present particle simulations of kinetic Alfven wave generation from ion-ion streaming in a non-uniform geometry relevant to the slow shocks.Both electron and ion dynamics in the wave fields are examined with respect to a broader range of plasma conditions. In particular, we study the electron heating parallel to the magnetic field direction as a function of various parameters and characterize the heating in terms of a polytropic relation