Reconstruction of the electron diffusion region observed by the Magnetospheric Multiscale spacecraft: First results

We present first results of the reconstruction of the electron diffusion region (EDR) based on a two-dimensional, incompressible, and inertia-less version of the electron magnetohydrodynamics equations. The method is applied to 30 ms resolution magnetic field and electron moments data taken when the Magnetospheric Multiscale (MMS) spacecraft observed an EDR of near antiparallel magnetopause reconnection on 16 October 2015 [Burch et al., 2016b]. An X-type magnetic field configuration and quadrupolar Hall fields, consistent with the electron inflow and outflow, are successfully recovered. While MMS encountered a region of significant energy dissipation on the magnetospheric side of the sub ion-scale current sheet, the reconstructions show that the MMS tetrahedron missed the X-line by a distance of a few km (~2 electron inertial lengths). The estimated reconnection electric field is 0.42–0.98 mV/m, equivalent to the dimensionless reconnection rate of 0.11–0.25. Signatures of three-dimensional structures and/or time-dependent processes are also identified.