Statistical Study of Nightside Quiet Time Midlatitude Ionospheric Convection

Previous studies have shown that F region midlatitude ionospheric plasma exhibits drifts of a few tens of meters per second during quiet geomagnetic conditions, predominantly in the westward direction. However, detailed morphology of this plasma motion and its drivers are still not well understood. In this study, we have used 2 years of data obtained from six midlatitude SuperDARN radars in the North American sector to derive a statistical model of quiet time midlatitude plasma convection between 52° and 58° magnetic latitude (MLAT). The model is organized in MLAT‐MLT (magnetic local time) coordinates and has a spatial resolution of 1° × 7 min with thousands of velocity measurements contributing to most grid cells. Our results show that the flow is predominantly westward (20–55 m/s) and weakly northward (0–20 m/s) deep on the nightside but with a strong seasonal dependence such that the flows tend to be strongest and most structured in winter. These statistical results are in good agreement with previously reported observations from Millstone Hill incoherent scatter radar measurements for a single latitude but also show some interesting new features, one being a significant latitudinal variation of zonal flow velocity near midnight in winter. Our analysis suggests that penetration of the high‐latitude convection electric fields can account for the direction of midlatitude convection in the premidnight sector, but postmidnight midlatitude convection is dominated by the neutral wind dynamo.

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