MMS Examination of FTEs at the Earth's Subsolar Magnetopause

Determining the magnetic field structure, electric currents, and plasma distributions within flux transfer event (FTE)-type flux ropes is critical to the understanding of their origin, evolution, and dynamics. Here the Magnetospheric Multiscale mission's high-resolution magnetic field and plasm...

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Bibliographic Details
Published in:Journal of geophysical research. Space physics 2018-02, Vol.123 (2), p.1224-1241
Main Authors: Akhavan-Tafti, M., Slavin, J. A., Le, G., Eastwood, J. P., Strangeway, R. J., Russell, C. T., Nakamura, R., Baumjohann, W., Torbert, R. B., Giles, B. L., Gershman, D. J., Burch, J. L.
Format: Article
Language:English
Subjects:
cluster
coalescence
Electric currents
Evolution
Field strength
Fluctuations
flux transfer events
force‐free
Geophysics
Instability
Ion velocity
Magnetic fields
Magnetic flux
Magnetism
Magnetopause
Magnetospheres
MMS
Plasma
Plasma density
Spacecraft
Spacecraft trajectories
Stability
Statistical analysis
subsolar magnetopause
Trajectory analysis
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Summary:Determining the magnetic field structure, electric currents, and plasma distributions within flux transfer event (FTE)-type flux ropes is critical to the understanding of their origin, evolution, and dynamics. Here the Magnetospheric Multiscale mission's high-resolution magnetic field and plasma measurements are used to identify FTEs in the vicinity of the subsolar magnetopause. The constant-alpha flux rope model is used to identify quasi-force free flux ropes and to infer the size, the core magnetic field strength, the magnetic flux content, and the spacecraft trajectories through these structures. Our statistical analysis determines a mean diameter of 1,700 ± 400 km (~30 ± 9 d(sub i)) and an average magnetic flux content of 100 ± 30 kWb for the quasi-force free FTEs at the Earth's subsolar magnetopause which are smaller than values reported by Cluster at high latitudes. These observed nonlinear size and magnetic flux content distributions of FTEs appear consistent with the plasmoid instability theory, which relies on the merging of neighboring, small-scale FTEs to generate larger structures. The ratio of the perpendicular to parallel components of current density, R(sub J), indicates that our FTEs are magnetically force-free, defined as R(sub J) < 1, in their core regions (
ISSN:2169-9380
2169-9402
DOI:10.1002/2017ja024681