Velocity of SuperDARN Echoes at Intermediate Radar Ranges

Abstract

AbstractThe study investigates the relationship between Super Dual Auroral Radar Network (SuperDARN) high‐frequency (HF) radar velocities measured at intermediate ranges of 600–1,000 km from the radar and the E × B plasma drift. Two approaches are implemented. First, a 3‐h interval of SuperDARN Rankin Inlet (RKN) radar measurements and Resolute Bay incoherent scatter radar RISR‐C measurements in nearly coinciding directions is investigated to show that (1) HF echoes with low velocities (less than 200 m/s) are often detected when E × B drifts are in excess of 1,000 m/s; (2) high‐velocity HF echoes from the E region have velocities somewhat below the expected values of the ion‐acoustic speed of the plasma and the HF line‐of‐sight velocity does not show a tendency for an increase at the largest E × B drifts; (3) for E region echoes, 12 MHz velocities are slightly larger than those at 10 MHz; and (4) 12‐MHz echoes are often received from the electrojet heights while 10‐MHz echoes are received from the F region heights so that the observed velocities are quite different with the latter reflecting the E × B drift of the plasma. In the second approach, velocities of 10‐ and 12‐MHz RKN echoes are compared for a large data set comprising several months of observations to show that occurrence of 12‐MHz low‐velocity echoes is fairly common (up to 25% of the time) whenever the plasma drifts are fast. Under this condition, the SuperDARN cross polar cap potential is underestimated, on average, by ~4 kV.