MMS observation of asymmetric reconnection supported by 3-D electron pressure divergence
File(s)Genestreti_JGR_2018_accepted.pdf (14.18 MB)
Accepted version
Author(s)
Type
Journal Article
Abstract
We identify the electron diffusion region (EDR) of a guide field dayside reconnection site encountered by the Magnetospheric Multiscale (MMS) mission and estimate the terms in generalized Ohm's law that controlled energy conversion near the X-point. MMS crossed the moderate-shear (∼130°) magnetopause southward of the exact X-point. MMS likely entered the magnetopause far from the X-point, outside the EDR, as the size of the reconnection layer was less than but comparable to the magnetosheath proton gyroradius, and also as anisotropic gyrotropic "outflow" crescent electron distributions were observed. MMS then approached the X-point, where all four spacecraft simultaneously observed signatures of the EDR, for example, an intense out-of-plane electron current, moderate electron agyrotropy, intense electron anisotropy, nonideal electric fields, and nonideal energy conversion. We find that the electric field associated with the nonideal energy conversion is (a) well described by the sum of the electron inertial and pressure divergence terms in generalized Ohms law though (b) the pressure divergence term dominates the inertial term by roughly a factor of 5:1, (c) both the gyrotropic and agyrotropic pressure forces contribute to energy conversion at the X-point, and (d) both out-of-the-reconnection-plane gradients (∂/∂M) and in-plane (∂/∂L,N) in the pressure tensor contribute to energy conversion near the X-point. This indicates that this EDR had some electron-scale structure in the out-of-plane direction during the time when (and at the location where) the reconnection site was observed.
Date Issued
2018-03-06
Date Acceptance
2018-02-05
Citation
Journal of Geophysical Research: Space Physics, 2018, 123 (3), pp.1806-1821
ISSN
2169-9380
Publisher
American Geophysical Union
Start Page
1806
End Page
1821
Journal / Book Title
Journal of Geophysical Research: Space Physics
Volume
123
Issue
3
Copyright Statement
© 2018. American Geophysical Union. All Rights Reserved. An edited version of this paper was published by AGU. To view the published open abstract, go to: https://dx.doi.org/10.1002/2017JA025019
Sponsor
Science and Technology Facilities Council (STFC)
Grant Number
ST/N000692/1
Subjects
Science & Technology
Physical Sciences
Astronomy & Astrophysics
MAGNETOSPHERIC MULTISCALE OBSERVATIONS
MAGNETIC RECONNECTION
DIFFUSION REGION
MAGNETOPAUSE RECONNECTION
X LINE
PARALLEL
FIELD
TURBULENCE
WAVES
DRIFT
Publication Status
Published
Date Publish Online
2018-02-08