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Statistics of the field‐aligned currents at the high‐latitude energetic electron boundaries in the nightside: Cluster observation
Author(s) -
Ren Jie,
Zong Q. G.,
Zhou X. Z.,
Zhang Hui,
Fu S. Y.,
Wang Y. F.,
Liu Yong C.M.
Publication year - 2016
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2015ja021754
Subject(s) - physics , plasma sheet , solar wind , ionosphere , magnetosphere , geophysics , latitude , magnetic field , current sheet , electron , interplanetary magnetic field , cluster (spacecraft) , field (mathematics) , current (fluid) , heliospheric current sheet , computational physics , astrophysics , astronomy , magnetohydrodynamics , mathematics , quantum mechanics , computer science , pure mathematics , thermodynamics , programming language
Magnetic field disturbances with a clear bipolar signature are frequently observed when the Cluster spacecraft fleet passes through both southern and northern high‐latitude energetic electron boundaries at the nightside magnetosphere. The dominant variation of the bipolar signature is in the azimuthal direction of the local mean field‐aligned coordinate, indicating a field‐aligned current. From 2001 to 2008, we have examined 110 events with the magnetic field and energetic electron measurements. The main results can be summarized as follows: (1) The density and thickness of the field‐aligned current, calculated under the assumption of the one‐dimensional sheet, are in order of tens of nA/m 2 and hundreds of kilometers, respectively. (2) Currents flowing into and away from the ionosphere tend to be observed in the postmidnight and premidnight sector, respectively, which have the same polarity as the region 1 current system. (3) These currents mainly distribute in the 60°–75° magnetic latitude region after mapping to the ionosphere. We also find that the current density and corresponding magnetic field variation are positively correlated with the K p index and solar wind pressure, but almost independent of the A E index.