Modeling of remote sensing of thin current sheet

Abstract

Cluster encountered a thin current sheet in the magnetotail during a substorm on Oct. 1, 2001. The phase space distributions observed by Cluster CIS showed large gradients in the phase space with ions existing only in one hemisphere of the phase space. It has been suggested that these non-gyrotropic distributions come from remote sensing of a thin current sheet by spacecrafts outside the current sheet. We present the results of a test particle simulation that confirm non-gyrotropic distributions can arise from remote sensing of a thin current sheet. These non-gyrotropic distributions can yield large velocity moments even when the plasma is stationary. The large velocity moments are not in the convective flow direction that would be normal to the current sheet. Instead they are along the n x B direction where n is normal to the boundary. These modeling results reinforce the importance of examining full particle distributions when studying plasma sheet dynamics.