In Situ Observations of Outer Electron Diffusion Region in the Magnetotail

Le résumé fourni par la source

Abstract The electron diffusion region (EDR), which can be divided into inner and outer EDR, is the crucial region where the magnetic field topology changes and strong energy conversion between fields and plasmas occurs during magnetic reconnection. The outer EDR is characterized by energy conversion from the particles to the fields ( J · E ′ < 0) and can extend tens of ion inertial lengths as a single layer in the outflow direction. Using high‐resolution data from the Magnetospheric Multiscale (MMS) mission, we identified an outer EDR under a weak guide field in the Earth's magnetotail. However, J · E ′ within the outer EDR exhibits significant electron‐scale fluctuations, which may be caused by tearing mode instability. These observations provide new insights into the microphysics of magnetic reconnection in tearing unstable and weak guide field regime, manifesting the role of electron‐scale dynamics in mediating energy dissipation.

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