Structuring of high latitude plasma patches with variable drive

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.