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Ion demagnetization in the magnetopause current layer observed by MMS
Author(s) -
Wang Shan,
Chen LiJen,
Hesse Michael,
Gershman Daniel J.,
Dorelli John,
Giles Barbara,
Torbert Roy B.,
Pollock Craig J.,
Lavraud Benoit,
Strangeway Robert,
Ergun Robert E.,
Burch Jim,
Avanov Levon,
Moore Thomas E.,
Saito Yoshifumi
Publication year - 2016
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2016gl069406
Subject(s) - physics , magnetopause , current sheet , ion , magnetic field , line (geometry) , demagnetizing field , outflow , magnetic reconnection , current (fluid) , computational physics , atomic physics , geophysics , magnetosphere , magnetohydrodynamics , magnetization , geometry , meteorology , quantum mechanics , mathematics , thermodynamics
We report ion velocity distribution functions (VDFs) observed by Magnetospheric Multiscale Mission (MMS) and present evidence for demagnetized ion Speiser motion during magnetopause reconnection. The demagnetization is observed in the vicinity of the X line, as well as near the current sheet midplane about tens of ion skin depths ( d i ) away from the X line. Close to the X line before the outflow is built up, the VDFs are elongated, and the elongated part of VDFs rotates from the out‐of‐plane current direction toward the outflow directions downstream from the X line. Farther downstream, demagnetized ions exhibit a characteristic half‐ring structure in the VDFs, as a result of the mixture of ions that have experienced different amounts of cyclotron turning around the magnetic field normal to the current sheet. Signatures of acceleration by electric fields are more pronounced in the VDFs near the X line than downstream.