Effects of electron heating on the current driven electrostatic ion cyclotron instability and plasma transport processes along auroral field lines

Abstract

Fluid simulations of the plasma along auroral field lines in the return current region have been performed to show that the onset of electrostatic ion cyclotron (EIC) related anomalous resistivity and the consequent heating of electrons leads to much higher transverse ion temperature than the current driven EIC instability (CDICI) alone would produce. Anomalous resistivity enhances ion heating in two ways: (1) by inhibiting the growth of the critical electron‐ion drift velocity, V cH , which must be exceeded to excite the EIC instability and (2) by increasing the relative drift velocity between the electrons and the ions, V D , through the formation of density cavities due to increased ambipolar electric field. The anomalous resistivity associated with the turbulence is limited by electron heating, so that CDICI eventually saturates, but at a substantially higher transverse temperature than would be the case in the absence of resistivity. This process demonstrates a positive feedback loop in the interaction between CDICI, anomalous resistivity, and parallel large scale dynamics in the topside ionosphere.