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Formation of a very thin current sheet in the near‐Earth magnetotail and the explosive growth phase of substorms
Author(s) -
Lee L. C.,
Zhang L.,
Choe G. S.,
Cai H. J.
Publication year - 1995
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 - 10.1029/95gl01033
Subject(s) - substorm , plasma sheet , current sheet , magnetosphere , explosive material , physics , magnetohydrodynamics , instability , magnetic reconnection , magnetic field , plasma , magnetohydrodynamic drive , geophysics , mechanics , chemistry , organic chemistry , quantum mechanics
A magnetofrictional method is used to construct two‐dimensional MHD equilibria of the Earth's magnetosphere for a given distribution of entropy function ( S = pV γ ), where p is the plasma pressure and V is the tube volume per unit magnetic flux. It is found that a very thin current sheet with B z < 0.5 nT and thickness < 1000 km can be formed in the near‐earth magnetotail ( x ∼ −8 to −20 R e ) during the growth phase of substorm. The tail current sheets are found to become thinner as the entropy or the entropy gradient increases. We suggest that the new “entropy anti‐diffusion instability” associated with plasma transport across field lines leads to magnetic field dipolarization and accelerates the formation of thin current sheet, which may explain the observed explosive growth phase of substorms.