Abstract: Magnetic field configuration instability in regions near the inner edge of the near-Earth current sheet is further studied with the generalized progressing wave expansion method in the one-fluid MHD approximation. Previous work on drift ballooning instability in the equatorial region has been extended to include a decelerated non-stationary flow and to consider the off equator regions. It is found that the presence of a decelerated earthward flow causes the magnetic field configuration on a large portion of the field lines to be absolutely unstable and substantially reinforces the instability. A high level synthesis thus exists in global substorm initiation processes. An integral NENL-NECD model of substorm expansion onset is proposed which seems to be in agreement with a variety of satellite and ground-based observations at substorms. Different substorms may be initiated by different triggering processes.

Key words: magnetospheric substorm, substorm expansion phase, magnetic reconnection, configuration instability

摘要： 用一元磁流体力学广义行波展开法进一步研究了近磁尾内边界的位型不稳定性。将笔者以前关于近磁尾赤道面附近的漂移气球模不稳定性工作推广到非赤道区和存在非定常地向流的情形。论证了减切地向流将导致近磁尾内边界绝对不稳定，并使增长率显著增加。研究表明在亚暴电流楔的形成过程中，中磁尾磁重联和近磁尾位型不稳定性可能协同地起着重要作用。在此基础上提出了一个磁层亚暴膨胀相的中性线一电流中断协同模型。该模型能解释卫星和地面的许多亚暴观测结果。不同的亚暴可能有不同的触发过程。

关键词: 磁层亚暴, 亚暴膨胀相, 磁重联, 位型不稳定性