Four-spacecraft measurements of the shape and dimensionality of magnetic structures in the near-Earth plasma environment

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Title: Four-spacecraft measurements of the shape and dimensionality of magnetic structures in the near-Earth plasma environment
Authors: Fadanelli, S
Lavraud, B
Califano, F
Jacquey, C
Vernisse, Y
Kacem, I
Penou, E
Gershman, D
Dorelli, J
Pollock, C
Giles, B
Avanov, L
Burch, J
Chandler, M
Coffey, V
Eastwood, J
Ergun, R
Farrugia, C
Fuselier, S
Genot, V
Grigorenko, E
Hasegawa, H
Khotyaintsev, Y
Le Contel, O
Marchaudon, A
Moore, T
Nakamura, R
Paterson, W
Phan, T
Rager, A
Russell, C
Saito, Y
Sauvaud, J-A
Schiff, C
Smith, S
Toledo Redondo, S
Torbert, R
Wang, S
Yokota, S
Item Type: Journal Article
Abstract: We present a new method for determining the main relevant features of the local magnetic field configuration, based entirely on the knowledge of the magnetic field gradient using four- spacecraft measurements. The method, named “Magnetic Configuration Analysis” (MCA), estimates the spatial scales on which the magnetic field varies locally. While it directly derives from the well-known Magnetic Directional Derivative (MDD) and Magnetic Rotational Analysis (MRA) procedures (Shi et al., 2005, doi:10.1029/2005GL022454; Shen et al., 2007, doi:10.1029/2005JA011584), MCA was specifically designed to address the actual magnetic field geometry. By applying MCA to multi-spacecraft data from the MMS satellites, we perform both case and statistical analyses of local magnetic field shape and dimensionality at very high cadence and small scales. We apply this technique to different near-Earth environments and define a classification scheme for the type of configuration observed. While our case studies allow us to benchmark the method with those used in past works, our statistical analysis unveils the typical shape of magnetic configurations and their statistical distributions. We show that small-scale magnetic configurations are generally elongated, displaying forms of cigar and blade shapes, but occasionally being planar in shape like thin pancakes (mostly inside current sheets). Magnetic configurations, however, rarely show isotropy in their magnetic variance. The planar nature of magnetic configurations and, most importantly, their scale lengths strongly depend on the plasma β parameter. Finally, the most invariant direction is statistically aligned with the electric current, reminiscent of the importance of electromagnetic forces in shaping the local magnetic configuration
Issue Date: 1-Aug-2019
Date of Acceptance: 10-Jun-2019
DOI: 10.1029/2019JA026747
ISSN: 2169-9380
Publisher: American Geophysical Union
Start Page: 6850
End Page: 6868
Journal / Book Title: Journal of Geophysical Research: Space Physics
Volume: 124
Issue: 8
Copyright Statement: ©2019. American Geophysical Union. All Rights Reserved.
Sponsor/Funder: Science and Technology Facilities Council (STFC)
Funder's Grant Number: ST/N000692/1
Publication Status: Published
Embargo Date: 2020-02-18
Online Publication Date: 2019-08-18
Appears in Collections:Space and Atmospheric Physics
Faculty of Natural Sciences

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