A unifiedmodel of auroral arc growth and electron acceleration in themagnetosphere-ionosphere coupling

Abstract

A unified physical model of auroral arc growth and electron acceleration is constructed from the gyrokinetic and two-fluid equations for the magnetosphere-ionosphere (M-I) coupling system. The present theory describes destabilization of kinetic Alfvén waves (KAWs) in the M-I coupling, where development of upward and downward field-aligned currents carried by the KAWs leads to ionospheric density enhancement and depletion, respectively. The feedback M-I coupling through KAWs elucidates growth of auroral arcs and field-aligned acceleration of electrons self-consistently and provides a possible explanation to the Alfvénic auroras observed by the FAST spacecraft.