Chapter 11 - Empirical Modeling of Extreme Events: Storm-Time Geomagnetic Field, Electric Current, and Pressure Distributions

Abstract

Recent advances in empirical modeling of the magnetospheric magnetic field and underlying electric currents, including reconstruction of the eastward current, make it possible to derive the distribution of the force-free isotropic storm-time plasma pressure. Here we consider such distributions for two extreme events, the July 2000 (Bastille Day) storm with Sym−Hmin ≃−300nT and the March 2015 event, the strongest storm in the Van Allen Probes era with Sym−Hmin ≃−200nT. We find that the main phase pressure distributions are strongly localized in radius and limited in local time with pressure peaking in the premidnight sector. More azimuthally symmetric distributions in the early main phase and in the recovery phase may still have pressure enhancements on the dayside and in the postmidnight sector. The degree of possible underestimation of current and pressure values in empirical modeling of extreme events is evaluated and attributed to limited representation of such events in historical records. A method of the model renormalization to mitigate this problem is described.