Sub-Auroral Polarization Streams: A complex interaction between the magnetosphere, ionosphere, and thermosphere

We use a novel coupled model of the magnetosphere-ionosphere-thermosphere system consisting of the OpenGGCM magnetosphere model, the CTIM ionosphere- thermosphere model, and the RCM model for the drift physics of the inner magnetosphere to study Sub-Auroral Polarization Streams (SAPS). We use the model to simulate the March 17, 2013 "St. Patrick's day" geomagnetic storm. It had been previously established that SAPS occur during this storm. We demonstrate that the model can reproduce the salient features of SAPS. In particular, the model reproduces the strong northward electric field associated with westward flows, well equatorward of the convection cells. The flows are located just equatorward of the lower boundary of electron precipitation and thus in a region of low ionosphere conductance. Associated with the flows is a deepening through in electron density. The SAPS extend from post-noon to post-midnight, and with increasing local time they extend to lower and lower latitudes. This had been previously fond in a statistical sense, but the model finds that this behavior is also true at given times. We thus conclude that self-consistent modeling of SAPS is now possible, which enables us to study their properties in more detail.