HEAVY ION EFFECTS ON MAGNETOPAUSE TRANSPORT

Recent ion composition measurements near the magnetopause have shown that heavy ionospheric ions can dominate the mass density as much as 30 percent of the time. Magnetopause transport processes, such as reconnection, Kelvin-Helmholtz instability, and kinetic-scale Alfvenic fluctuations, can all be significantly affected by the presence of heavy ions. We examine these effects using MHD and hybrid simulations. Heavy ions modify the onset and growth of the tearing mode as well as reduce the steady state reconnection rate by lowering the Alfven speed. Increased mass density reduces the effect of magnetic tension and therefore lowers the Kelvin-Helmholtz instability threshold and increases the growth rate. In 3D simulations, reconnection of the Kelvin-Helmholtz interchanged flux can lead to mass transport, but the reduced Alfven speed is compensated by increased shear in the boundary regions so that the reconnection rate adjusts as necessary to reconnect the interchanged flux. The presence of heavy ions can also increase the efficiency of mode conversion of compressional Pc3 waves to transverse, field-aligned Alfven modes with small-scale structure perpendicular the the magnetopause. We examine this process with hybrid simulations including heavy ions. We examine whether nonlinear heating and transport associated with mode converted waves will preferentially affect the heavy ions. Because heavy ions can significantly influence physical processes at the magnetopause associated with mass, momentum, and energy transport; we discuss how they could be used as a tool to probe those physical processes responsible for the transport.