Structuring of high latitude plasma patches with variable drive

Abstract

Three-dimensional nonlinear simulations of the structuring of high-latitude patches with variable drive demonstrate the role of the gradient drift instability as the primary operative structuring mechanism. In this letter we show that by introducing a variable convective E × B drive obtained from the ionosphere module of a global MHD code simulation of a real substorm [Sojka et al., 1997], the nature of the structuring is strongly influenced by the drive. In fact, due to occasional reversal of the direction of the convection, the structuring from the gradient-drift instability takes place on both edges of the patch. Using different ion-neutral collisionality to account for the seasonal or solar cycle variability of the ionosphere, the four categories of structured patches identified by Kivanç and Heelis [1997] have been simulated.