Hybrid Input Algorithm: An event-oriented magnetospheric model

Abstract

We introduce and test a new approach suitable to model the magnetotail configuration during individual events. This Hybrid Input Algorithm (HIA) uses, in addition to spacecraft magnetic measurements in the tail, other complementary information (in this version, the isotropic boundaries of energetic particles observed at low altitudes), therefore increasing the amount of input data for the modeling and making models more accurate for mapping purposes as well as for evaluation of the current sheet thickness and current density. We test the HIA on two previously well-studied and modeled events, compare different models as well as the model-based and observation-based estimates for the plasma pressure and current density, and discuss the uncertainty in the resulting mapping. We apply the HIA-based models to evaluate the location of substorm onset in the tail during Coordinated Data Analysis Workshop 6A (CDAW-6A) substorm event and the characteristics of the current sheet at 7-15 RE just before the substorm onset obtained for several other events. We found moderate values for the maximal current densities in the thin current sheet region (10-35 nA/m2) and the minimal current sheet half thickness between 0.1 and 0.7 RE. The X scale of the thinning region was sim 5 RE. By assembling the modeling results for many events we found that the maximum current densities in the tail current sheet could be effectively predicted by taking into account the observed positions of isotropic boundaries and dipole tilt angle. We also briefly discuss possible future extension of the Hybrid Input Algorithm. Copyright 1999 by the American Geophysical Union.