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Substorm classification with the WINDMI model
1The University of Texas at Austin, Austin, TX 78712, USA
2NRC at NASA/GSFC, Greenbelt, MD 20771, USA
3USRA at NASA/GSFC, Greenbelt, MD 20771, USA
4Department of Physics, University of Colorado, Boulder, CO 80309, USA
Abstract. The results of a genetic algorithm optimization of the WINDMI model using the Blanchard-McPherron substorm data set is presented. A key result from the large-scale computations used to search for convergence in the predictions over the database is the finding that there are three distinct types of vx Bs -AL waveforms characterizing substorms. Type I and III substorms are given by the internally-triggered WINDMI model. The analysis reveals an additional type of event, called a type II substorm, that requires an external trigger as in the northward turning of the IMF model of Lyons (1995). We show that incorporating an external trigger, initiated by a fast northward turning of the IMF, into WINDMI, a low-dimensional model of substorms, yields improved predictions of substorm evolution in terms of the AL index. Intrinsic database uncertainties in the timing between the ground-based AL electrojet signal and the arrival time at the magnetopause of the IMF data measured by spacecraft in the solar wind prevent a sharp division between type I and II events. However, within these timing limitations we find that the fraction of events is roughly 40% type I, 40% type II, and 20% type III.
Full Article (PDF, 130 KB)
Citation: Horton, W., Weigel, R. S., Vassiliadis, D., and Doxas, I.: Substorm classification with the WINDMI model, Nonlin. Processes Geophys., 10, 363-371, 2003. Bibtex EndNote Reference Manager
