Articles | Volume 10, issue 4/5
Nonlin. Processes Geophys., 10, 363–371, 2003
https://doi.org/10.5194/npg-10-363-2003

Special issue: Theory and Simulation of Solar System Plasmas, No.4

Nonlin. Processes Geophys., 10, 363–371, 2003
https://doi.org/10.5194/npg-10-363-2003

  31 Oct 2003

31 Oct 2003

Substorm classification with the WINDMI model

W. Horton1, R. S. Weigel2, D. Vassiliadis3, and I. Doxas4 W. Horton et al.
  • 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.