Modified two-stream instability at perpendicular collisionless shocks: Full particle simulations

Abstract

A full particle simulation study is carried out for studying microinstabilities generated in self-consistently excited perpendicular collisionless shocks. The present two-dimensional simulation with a high ion-to-electron mass ratio shows that the modified two-stream instability can be generated by the interaction of incoming and reflected ions with electromagnetic whistler mode waves propagating in the direction quasi-perpendicular to the ambient magnetic field. Properties of the excited whistler mode waves are consistent with the linear dispersion analysis based on the simulated velocity distribution functions. It is also found that the excited waves have an electron-scale wavelength in the shock-normal direction and an ion-scale wavelength in the shock-tangential direction, suggesting that the electron-scale microturbulences and the ion-scale shock structures are coupled with each other through the modified two-stream instability. Copyright 2012 by the American Geophysical Union.