Transient Convection in the Nightside Subauroral Ionosphere: Occurrence Statistics and Driving Influences

The expansion of the Super Dual Auroral Radar Network (SuperDARN) to middle latitudes in recent years provides new capabilities to investigate the electrodynamics of the subauroral ionosphere with unprecedented spatiotemporal resolution and coverage. At the present time there are four mid-latitude SuperDARN radars operational in the United States. During periods of quiet geomagnetic activity mid-latitude SuperDARN radars tend to see long-lived bands of ionospheric irregularities co-rotating or drifting slowly westward across the night side. Superposed on this average behavior are episodic events in which the convection velocities of the irregularities become enhanced for a period of a few tens of minutes. In this presentation we relate the occurrence of these convection transients to the location of the auroral oval, interplanetary parameters, and measurements of geomagnetic activity at high and middle latitudes. We discuss the extent to which the subauroral transients can be associated with direct penetration of the interplanetary electric field into the subauroral ionosphere and/or the ionosopheric impacts of substorm activity occurring at higher latitudes.