SAPS in the 2013 March 17 Storm Event: Simulation Results of the Coupled LFM-TIEGCM-RCM Model

Subauroral polarization streams (SAPS) are latitudinally narrow flow channels of large westward plasma drifts in the subauroral ionosphere. The westward drifts are driven by the enhanced poleward electric field and typically occurs during geomagnetically active times. In this study, we make use of the coupled magnetosphere-ring current-ionosphere-thermosphere model, namely the LFM-TIEGCM-RCM (LTR) model, to study the SAPS structure, evolution and their driving mechanism during the 2013 St. Patrick's Day major storm event. Strong westward ion drift channel was formed equatorward of the aurora precipitation boundary the duskside after the storm started, which is identified as the SAPS structure. This SAPS channel corresponds to Region 2 field aligned currents (FAC). Model results are further analyzed to characterize the dynamic evolution of the SAPS as the driving conditions change. We also analyze the current loop in the magnetosphere-ionospheric coupling and investigate the role of the substorm current wedge and the FAC in the driving process of SAPS. The electrojet turbulence effects investigated by Wiltberger et al. [2017] with LFM-RCM will also be studied with regard to SAPS in the context of the fully coupled LTR model.