MHD ballooning instability in the plasma sheet

C. Z. Cheng, S. Zaharia

研究成果: Article同行評審

46 引文 斯高帕斯(Scopus)

摘要

Based on the ideal MHD model the stability of ballooning modes is investigated by employing realistic 3D magnetospheric equilibria for the substorm growth phase. Our results show that without making compressibility approximations the ballooning modes are unstable for the entire plasma sheet where the equatorial βeq ≥ 1, and the most unstable modes are located in the strong cross-tail current sheet region in the near-Earth plasma sheet, which maps to the initial brightening location of the breakup are in the ionosphere. However, the MHD βeq threshold is too low in comparison with observations by AMPTE/CCE, which show that prior to substorm onset a low frequency instability is excited only when βeq > 50. The difficulty can be mitigated by including kinetic effects, which greatly increase the stabilizing effects of field line tension and can enhance the βeq threshold to limit the unstable region to the cross-tail current sheet region.

原文English
頁(從 - 到)L06809 1-4
期刊Geophysical Research Letters
31
發行號6
DOIs
出版狀態Published - 2004 3月 28

All Science Journal Classification (ASJC) codes

  • 地球物理
  • 地球與行星科學(全部)

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