Modeling of Occurrence and Dynamics of Sub-Auroral Polarization Streams (SAPS) During Storm and Non-Storm Conditions

Occurrence and evolution of Sub-Auroral Polarization Stream, or SAPS, structures, defined here as latitudinally narrow channels of enhanced westward convection flows in the evening ionosphere equatorward of the auroral electron precipitation boundary, is the subject of the ongoing CEDAR-GEM focus study. In this paper, we present simulation results of several event intervals selected for the focus study, obtained with the SAMI3-RCM ionosphere-magnetosphere coupled model. We simulate intervals that include quiet-times, storm main phases, and storm recovery phases, as well as non-storm intervals with variations in the high-latitude convection. We compare simulation results with multi-instrument observations. In the ionosphere, these include mid-latitude SuperDARN Doppler flow velocities, DMSP topside ionospheric ExB drifts, Millstone Hill incoherent scatter flow velocities and F-region densities, and ground-based GPS Total Electron Content (TEC) maps. Magnetospheric data used for model comparison are electric field and cold plasma densities from Van Allen Probes and plasma and fields measurements by the Magnetospheric Multiscale Mission (MMS) probes. Through comparing modeling results and data, we address the following questions: (1) Can observed occurrence of SAPS be predicted by the model based on time history of magnetospheric activity? (2) To what extent does non-linear ionospheric feedback affect dynamics of SAPS? (3) How does the preconditioning of the background ionosphere (specifically, night-time main ionospheric trough) affect SAPS dynamics? (4) How does presence of SAPS structures in the global ionospheric convection pattern affect storm-time plasma re-distribution (e.g., storm-enhanced densities (or SEDs), plasmaspheric plumes, traveling ionospheric disturbances (or TIDs))?