Synthetic substorm expansion model

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.EI02-3193-2003