Structuring of the Ampte magnetotail barium releases

Abstract

A new instability is proposed to explain the observed large‐scale structuring of the magnetotail AMPTE barium releases. The stability theory is based on a modified set of MHD equations which allows for large Larmor radius effects, i.e., ρ i ∼ R c which is typical of the AMPTE releases (here ρ i is the ion Larmor radius and R c is the transverse radius of the cloud). The mode is driven by the deceleration of the cloud and the density gradient at the edge of the cloud. The predicted linear growth rate and eigenmode structure are consistent with AMPTE observations.