Instability of the current sheet in the Earth's magnetotail with normal magnetic field

Abstract

Instability of a current sheet in the Earth's magnetotail has been investigated by two-dimensional fully kinetic simulations. Two types of magnetic configuration have been studied; those with uniform normal magnetic field along the current sheet and those in which the normal magnetic field has a spatial hump. The latter configuration has been proposed by Sitnov and Schindler [Geophys. Res. Lett. 37, L08102 (2010)] as one in which ion tearing modes might grow. The first type of configuration exhibits electron tearing modes when the normal magnetic field is small. The second type of configuration exhibits an instability which does not tear or change the topology of magnetic field lines. The hump in the initial configuration can propagate Earthward in the nonlinear regime, leading to the formation of a dipolarization front. Secondary magnetic islands can form in regions where the normal magnetic field is very weak. Under no conditions do we find the ion tearing instability.