Multistep Electron Acceleration in Multiple Dynamic Electron‐Scale Current Sheets

Abstract We study multiple Electron‐scale Current Sheets (ECSs) formed in the Plasma Sheet (PS) perturbed by the propagation of ion Bursty Bulk Flows (BBFs) generated by the X‐line located downtail. The BBF arrival is followed by compression, magnetic flux pile‐up and an increase in the convection electric field. These phenomena supposedly trigger electron‐only Secondary Reconnection (SR) near the MMS location. We consider the accompanying physical effects as elementary bricks of the collisionless energy conversion in electron kinetic scales via generation of Cascading Electron Current Sheets (CECSs), which evolution leads to an additional electron acceleration and affects local electron anisotropy. The proposed scenario of CECS formation is as follows. The SR(s) accelerate field‐aligned electron jets, generating current filaments in the SR's outflow. The external drivers provided by the ion BBF force the filament merging and formation of quasi‐1D field‐aligned ECS(s). Further ECS thinning generates an inductive electric field directed along the current ( E J ). This field provides: (a) an additional energy gain to current‐carrying electrons up to ∼1 keV resulting in generation of new field‐aligned ECS; (b) contributes to drift of magnetized electrons generating a new electron jet and the related perpendicular ECS with . The J E × B increase generates a new inductive E J (1) directed along the J E × B . This field accelerates electrons in the direction perpendicular to B until the drift exists. Such cascade electron acceleration explains the appearance of ECSs with arbitrary current directions in different PS locations until the external drivers transfer the BBF's energy from the macroscale to the electron kinetic scales.