Fine Structures of the Electron Current Sheet in Magnetotail Guide-Field Reconnection

We investigate fine structures of the electron current sheet in magnetotail guide-field reconnection using Magnetospheric Multiscale observations. This current sheet, observed in the outer electron diffusion region (EDR) of reconnection, is featured by clear bifurcation and deflection, and also has complicated fine sublayers. The formation of these sublayers is closely related to streaming and meandering electrons, which are facilitated by the reconnection guide field. In particular, in the sublayer around the B_L reversal, the meandering electrons, which usually move along the out-of-plane (M) direction, are strongly distorted into the v_L-v_N plane due to the finite B_M component. The low frequency fluctuation of this current sheet is also revealed, contributing ∼3% of the reconnection electric field by the anomalous effect. We suggest that such current sheet fluctuations, possibly driven by the magnetic double-gradient instability, can be characteristic in the outer EDR.