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An Encounter With the Ion and Electron Diffusion Regions at a Flapping and Twisted Tail Current Sheet
Author(s) -
Farrugia C. J.,
Rogers A. J.,
Torbert R. B.,
Genestreti K. J.,
Nakamura T. K. M.,
Lavraud B.,
Montag P.,
Egedal J.,
Payne D.,
Keesee A.,
Ahmadi N.,
Ergun R.,
Reiff P.,
Argall M.,
Matsui H.,
Wilson L. B.,
Lugaz N.,
Burch J. L.,
Russell C. T.,
Fuselier S. A.,
Dors I.
Publication year - 2021
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1029/2020ja028903
Subject(s) - current sheet , substorm , physics , magnetic reconnection , electron , computational physics , magnetic field , field line , pitch angle , diffusion , ion , curvature , plasma sheet , heliospheric current sheet , flapping , atomic physics , magnetosphere , magnetohydrodynamics , geophysics , solar wind , interplanetary magnetic field , geometry , nuclear physics , quantum mechanics , wing , thermodynamics , mathematics
We analyze data returned by the Magnetospheric Multiscale mission (MMS) constellation during a rapid (∼1.5 s) traversal of a flapping and reconnecting current sheet (CS) in the near‐Earth magnetotail (X ∼−20 R E ). The CS was highly tilted, with its normal pointing strongly duskward. Its extreme thinness was confirmed by a curvature analysis of the magnetic field lines. The event was associated with a guide field of 8% of the reconnecting components. From the pitch angle distributions of low‐energy electrons we infer a crossing earthward of the X‐line. Traveling practically normal to the CS, MMS encountered an ion diffusion region (IDR) in which was embedded an electron diffusion region (EDR). IDR signatures included breaking of the ion frozen‐in condition in the presence of Hall B and E fields. EDR signatures included a strong out‐of‐plane current associated with a superAlfvénic electron jet, positive energy transfer, and a temperature anisotropy ( Te ∥ > Te ⊥ ) which disappeared at the field reversal. Derived scale sizes normal to the CS are: ∼6.9 d e (EDR) and ∼0.4 d i (IDR; 40 and 100 km). We estimate the average dimensionless reconnection rate as 0.077 ± 0.050. The observations and inferences are supported by particle‐in‐cell (PIC) numerical simulations. We find very good agreement in the reconnection rates. We also discuss the effects of asymmetries in the density, temperature and magnetic field strength on the Hall fields and length of the outflow jets. The event is associated with a substorm onset which began 7 min after the MMS observations.