Electron crescent distributions as a manifestation of diamagnetic drift in an electron scale current sheet

TL;DR

This paper uses high-resolution electron measurements from MMS to identify electron crescent distributions caused by diamagnetic drift near magnetic reconnection regions, revealing detailed electron dynamics.

Contribution

It introduces a new technique for 7.5 ms electron moments and links electron crescent distributions to diamagnetic drift in reconnection diffusion regions.

Findings

Electron crescent distributions are observed near reconnection sites.

Diamagnetic drift explains deviations in electron velocity from E×B drift.

Electron momentum equation is not satisfied during current transition.

Abstract

We report Magnetospheric Multiscale observations of electron pressure gradient electric fields near a magnetic reconnection diffusion region using a new technique for extracting 7.5 ms electron moments from the Fast Plasma Investigation. We find that the deviation of the perpendicular electron bulk velocity from $E \times B$ drift in the interval where the out-of-plane current density is increasing can be explained by the diamagnetic drift. In the interval where the out-of-plane current is transitioning to in-plane current, the electron momentum equation is not satisfied at 7.5 ms resolution.