Open AccessObservational test of interchange instability associated with magnetic dipolarization in the near‐Earth plasma sheet of r < 12 R E
Author(s) -
Lee D.Y.,
Ohtani S.,
Kim H. S.,
Kim K. C.
Publication year - 2012
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2012ja017633
Subject(s) - instability , physics , ballooning , magnetic field , mode (computer interface) , plasma , plasma sheet , pressure gradient , mechanics , phase (matter) , magnetosphere , tokamak , quantum mechanics , computer science , operating system
Interchange instability is basically a pressure gradient‐driven mode, and therefore, it may naturally be expected to be triggered in the near‐Earth tail during the growth phase of magnetic dipolarization as the tail field lines become more stretched by an increasing radial pressure gradient. To examine this possibility, we have tested the classic interchange criterion by using the plasma and magnetic field observations from the THEMIS inner tail probes at r < 12 R E . Both the specific events and the statistical results of this study indicate that the stretched tail field configurations during the dipolarization growth phase are actually stable to the interchange mode. Considering that the interchange mode is formally regarded as a special case of the more general ballooning mode, our conclusion of the interchange mode stability prior to the dipolarization onset eliminates one family of the pressure gradient‐driven modes as a possible trigger of dipolarization at the near‐Earth tail. However, interestingly, we find the possibility that sometimes, the near‐tail field configurations can become less stable and even occasionally be unstable after they become rounder through the dipolarization process, although this possibility requires more rigorous test for a solid conclusion.