Observations of high-velocity SAPS-like flows with the King Salmon

Abstract. In this study, a focused investigation of the po-tential for the King Salmon (KS) SuperDARN HF radar to monitor high-velocity flows near the equatorial edge of the auroral oval is undertaken. Events are presented with line-of-sight velocities as high as 2 km/s, observed roughly along the L-shell. Statistically, the enhanced flows are shown to be typical for the dusk sector (16:00–23:00 MLT), and the average velocity in this sector is larger (smaller) for winter (summer) conditions. It is also demonstrated that the high-velocity flows can be very dynamical with more localized enhancements existing for just several minutes. These short-lived enhancements occur when the luminosity at the equa-torial edge of the auroral oval suddenly decreases during the substorm recovery phase. The short-lived velocity enhance-ments can be established because of proton and ion injec-tions into the inner magnetosphere and low conductance of the ionosphere and not because of enhanced tail reconnec-tion. This implies that some KS velocity enhancements have the same origin as subauroral polarization streams (SAPS)