Space-weather impacts of the sub-auroral polarization stream

During the strongest geomagnetic storms of the last solar cycle, severe space-weather effects were observed at mid-latitudes. These effects included large-scale enhancements of the total electron content (TEC), steep spatial and temporal gradients in the TEC, and the associated scintillation in phase and amplitude of radio-wave signals. All of these space-weather events can affect the performance of ground and space-based technological systems. An underlying cause of these space-weather disturbances is a phenomenon known as the sub-auroral polarization stream (SAPS), first defined by [1] and characterized by [2]. SAPS is a direct result of magnetosphere-ionosphere (M-I) coupling associated with the enhancement of the storm-time ring current at the inward extent of the plasma sheet. SAPS electric fields erode the outer plasmasphere, producing plasma spheric plumes, detached plasmas, and large fluxes of cold plasma to the dayside magnetopause. These intense electric fields map between high and low altitudes along the magnetic field. These intense electric fields also drive plasma within the ionosphere, producing plumes of ionization, associated with steep gradients in the TEC, in the pre-midnight and afternoon sectors. This paper reviews the SAPS phenomenon, and describes its associated space-weather effects and their implications.