Empirical Model of Subauroral Polarization Streams (SAPS) During Geomagnetic Storms

Abstract:

Subauroral Polarization Streams (SAPS) are important electromagnetic phenomena associated with geomagnetic storms that affect the inner magnetosphere and ionosphere. They are characterized by strong sunward plasma flows caused by poleward-directed electric fields in the region of the ionosphere equatorword of the auroral zone. To examine the effects subauroral electric fields have on ITM coupling and magnetospheric-ionospheric convection we are developing an empirical model of SAPS using data acquired by the Defense Meteorological Satellite Program (DMSP) spacecraft which have made decades of in-situ measurements of ionospheric ion drifts, composition, and precipitating auroral particles. These measurements are used to characterize the subauroral electric fields relative to the location of the auroral boundary at varying magnetic local times and magnetic activity levels. As a critical component of this model, we have developed a model of the nightside zero energy electron precipitation boundary equatorward of the auroral oval parameterized by AE and MLT, using boundary identifications derived from DMSP data. We will use this model to create a global subauroral potential model and perform a superposed epoch study of SAPS fields in relationship to the auroral boundary during selected geomagnetic storms as a function of storm phase. A global empirical model of SAPS electric fields of this kind is required to realistically model thermosphere-ionosphere coupling and inner-magnetospheric convection.