Electrodynamics in a Very Thin Current Sheet: Comparison Between Cluster Observations and Simulations

Cluster observations have revealed that the current sheets (CSs) in the magneto-tail could thin to a few electron skin depth. Thinning of an initially broad CS, its re-widening and bifurcation are studied by means of 3D kinetic simulations. The evolution of the electrostatic potential structure (PS) associated with Hall electric fields is studied. When current-driven instabilities generate large-amplitude waves, which trap electrons causing current disruption and bifurcation of the CS, the PS develops fine structures. Ions are accelerated into the central region of the CS and appear as counter-streaming populations. We compare such CS features with those measured from Cluster. 1