An embedded electron current layer observed at the edge of the plasma sheet in the Earth’s magnetotail

The formation of an embedded electron current sheet within the magnetotail plasma sheet has been poorly understood. In this article, we present an electron current layer detected at the edge of the magnetotail plasma sheet. The ions were demagnetized inside the electron current layer, but the electrons were still frozen in with the magnetic field line. Thus, this decoupling of ions and electrons gave rise to a strong Hall electric field, which could be the reason for the formation of the embedded thin current layer. The magnetized electrons, the absence of the nongyrotropic electron distribution, and negligible energy dissipation in the layer indicate that magnetic reconnection had not been triggered within the embedded thin current layer. The highly asymmetric plasma on the two sides of the current layer and low magnetic shear across it could suppress magnetic reconnection. The observations indicate that the embedded electric current layer, probably generated by the Hall electric field, even down to electron scale, is not a sufficient condition for magnetic reconnection.