Empirical Global Model of Subauroral Polarization Streams

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 ionosphere-thermosphere-magnetosphere coupling and magnetospheric convection we are developing an empirical model of the SAPS using data acquired by the Defense Meteorological Satellite Program (DMSP), Dynamic Explorer 2, and Atmospheric Explorer C spacecraft, which have made decades of in-situ measurements of ionospheric ion drifts, composition, and precipitating auroral particles. These measurements will be used to characterize the latitudinal drift profiles, 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 equatorword particle precipitation boundary of the auroral oval parameterized by AE and MLT, using boundary identifications derived from DMSP data. This will allow the incorporation of the empirical SAPS model into other global models, such as the Global Ionosphere Thermosphere Model. We will also use this model to 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 storm-time theremosphere-ionosphere coupling and inner-magnetospheric convection.