Paper#: 127
Poster #: 30
Session Name: Poster Session 1
Room: East Ballroom
Day: Tuesday
Time: 10:10 a.m.-Noon
Abstract Title: A Substorm Sequence Studied with Automated Forward Modeling
PresentSurname: Connors, M.
All Authors: M. Connors, G. Rostoker
Abstract : Activity on April 10-11 1997 was observed by many instruments, and associated with a long period of generally southward IMF from 2030 UT April 10 ending with an abrupt northward turning at 0600 UT April 11. The new inversion technique of Automated Forward Modeling (AFM), based on optimizing parameters in a model computing magnetic perturbations from current systems, has been applied to ground magnetic data from this event. AFM has been applied to data both from meridian chains of magnetometers and from two-dimensional arrays. It leads to a simple characterization of the development of electrojets in particular. Notable in this event is the formation of a double auroral oval after poleward expansion of the westward electrojet following an initial onset at 2230 UT. A subsequent period of enhanced activity but without major substorm onsets resembles steady magnetospheric convection (SMC) and the current across meridians near the midnight sector remained close to 1 MA for about 4 hours during this period. Most activity was restricted to the poleward border of the double auroral oval at this time. This SMC episode ended with a major substorm expansive phase onset in the evening sector accompanied by the initiation of Ps 6 activity in the morning sector. This onset took place during steady southward IMF conditions similar to those during the entire SMC period. The AFM technique is shown to be a powerful tool in analyzing substorms.