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Origin of Electron‐Scale Magnetic Fluctuations Close to an Electron Diffusion Region
Author(s) -
Hoilijoki S.,
Pucci F.,
Ergun R. E.,
Schwartz S. J.,
Wilder F. D.,
Eriksson S.,
Chasapis A.,
Ahmadi N.,
Webster J. M.,
Burch J. L.,
Torbert R. B.,
Strangeway R. J.,
Giles B. L.
Publication year - 2021
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1029/2020ja029046
Subject(s) - magnetopause , physics , magnetic reconnection , electron , magnetic field , instability , diffusion , computational physics , geophysics , magnetosphere , mechanics , quantum mechanics , thermodynamics
During a dayside magnetopause crossing, the Magnetospheric Multiscale (MMS) mission observed a series of magnetic depletions in the total magnetic field, mainly due to the fluctuation of the component normal to the magnetopause. These fluctuations are adjacent to signatures suggesting that the MMS is at, or close to (< d i ), a magnetic reconnection electron diffusion region (EDR). The temporal and spatial scales of the fluctuations are too short for the ions to be affected. In this paper we investigate the origin of these fluctuations, finding that they can develop from temporal variations of the reconnection rate at the nearby EDR. Indeed asymmetric reconnecting current sheets, and the nearby regions, are subject to multiple different instabilities, and may be affected by waves and turbulence activity. Here we suggest such oscillations in the normal component of the magnetic field can be interpreted either as i) electron‐scale structures, forming due to changes in the outflow speed and the corresponding changes in the angle between the separatrices, causing magnetic field to pile up or ii) electron vortices generated by enhanced sheared electron outflows, driving electron‐scale Kelvin–Helmholtz instability.