Steepening of Alfvén waves and its effect on the structure of slow shocks

Abstract

The interaction between Alfvén/ion cyclotron (A/IC) waves and a slow shock is examined by means of hybrid simulations. It is shown that for a rather general set of parameters, slow shocks can generate A/IC waves which become group standing within the shock transition layer, and steepen into thin structures (∼4 ion inertial lengths). Each front is shocklike with finite jumps in the plasma parameters across it. In such cases, the transition from upstream to downstream conditions across the slow shock occurs over a number of layers. Following the jumps over the steepened front(s), the final transition to downstream is made over a much broader region more typical of slow shocks (≳60 ion inertial lengths). Other important effects of the steepened front are the local trapping of the plasma, generation of a coherent wavetrain and changes in the polarization of the slow shock. In particular, the first simulations of slow shocks with a right‐handed polarization and an upstream wavetrain are shown. Due to the unusually complicated structures of these slow shocks much care must be taken in the search and identification of slow shocks in the observations.