Constructing the magnetospheric model including pressure measurements

[1] We modeled the magnetotail configuration during a highly disturbed period on 19 April 1985 based on data from three magnetospheric spacecraft (Active Magnetospheric Tracer Explorers (AMPTE)/IRM, AMPTE/CCE, and ISEE 1) and proton precipitation measured by DMSP spacecraft. The goal was to test the procedure of including the plasma pressure as input data when constructing the magnetotail magnetic field model. On the basis of AMPTE/IRM data we confirm statistically a high degree of pressure isotropy at 8–17 RE distances in the tail plasma sheet, which allows computation of the plasma pressure from magnetospheric magnetic field model and easy mapping of the pressure along the corresponding flux tubes. The usage of pressure data not only increases the amount of data for event-oriented modeling but also imposes the nonlocal constraints on the configuration and mapping between magnetosphere and ionosphere to stabilize the solution of inverse problem and get it to be more realistic. Observational and modeling results indicate large systematic deviations of observed configuration from predictions of standard models (T89 or T96) [Tsyganenko, 1989, 1995] and reveal highly variable configurations, justifying a need for the development of event-oriented modeling. Indications of localized B minimum and current density maximum at around 12 RE have been obtained in the model with best data coverage, but precipitation from this region showed no signatures of discrete structures. The structured precipitation has been mostly seen in poleward half of the auroral zone precipitation, which is mapped to rather distant parts (>30 RE) of the plasma sheet.