Potential structures at the plasma sheet boundaries
Left: Symmetric electric current system (orange arrows) and U-shaped potential structure related to parallel electric fields in the acceleration region deduced from Cluster 1 (C1) measurements way above an auroral arc, at the boundary between the Plasma Sheet Boundary Layer (PSBL) and the Central Plasma Sheet (CPS). Electrons propagate in the direction opposite to the current directions (orange arrows).
Right: Asymmetric electric current system (orange arrows) and S-shaped potential structure found 16 minutes later by C2 due to the thinning and plasma density depletion in the PSBL.
Image courtesy of Prof. Göran Marklund, Alfvén Laboratory, Stockholm, Sweden, from [Marklund et al., 2007].