Reconstruction of the Electron Diffusion Region with Inertia and
Compressibility Effects
Abstract
A method based on electron magnetohydrodynamics (EMHD) for the
reconstruction of steady, two-dimensional plasma and magnetic field
structures from data taken by a single spacecraft, first developed by
Sonnerup et al. (2016), is extended to accommodate inhomogeneity of the
electron density and temperature, electron inertia effects, and guide
magnetic field in and around the electron diffusion region (EDR), the
central part of the magnetic reconnection region. The new method assumes
that the electron density and temperature are constant along, but may
vary across, the magnetic field lines. We present two models for the
reconstruction of electron streamlines, one of which is not constrained
by any specific formula for the electron pressure tensor term in the
generalized Ohm’s law that is responsible for electron unmagnetization
in the EDR, and the other is a modification of the original model to
include the inertia and compressibility effects. Benchmark tests using
data from fully kinetic simulations show that our new method is
applicable to both antiparallel and guide-field (component)
reconnection, and the electron velocity field can be better
reconstructed by including the inertia effects. The new EMHD
reconstruction technique has been applied to an EDR of magnetotail
reconnection encountered by the Magnetospheric Multiscale spacecraft on
11 July 2017, reported by Torbert et al. (2018) and reconstructed with
the original inertia-less version by Hasegawa et al. (2019), which
demonstrates that the new method better performs in recovering the
electric field and electron streamlines than the original version.