Statistical characterization of the large‐scale structure of the subauroral polarization stream

The subauroral polarization streams (SAPS) are latitudinally narrow regions of westward directed flows observed equatorward of the evening sector auroral oval. Previous studies have shown that SAPS generally occur during geomagnetically disturbed conditions and exhibit a strong dependence on geomagnetic activity. In this paper, we present the first comprehensive statistical study of SAPS using measurements from the U.S. midlatitude Super Dual Auroral Radar Network (SuperDARN) radars. The study period spans January 2011 to December 2014, and the results show that SuperDARN radars observe SAPS over a broad range of activity levels spanning storm time and nonstorm conditions. During relatively quiet conditions (−10 nT