Abstract
The study investigates the relationship between SuperDARN HF radar
velocities detected at intermediate ranges of 600-100 km from the radar
and the plasma drift. Two approaches are implemented. First, a
three-hour interval of SuperDARN Rankin Inlet (RKN) radar measurements
and Resolute Bay incoherent scatter radar RISR-C measurements in nearly
coinciding directions are investigated to show that 1) HF echoes with
low velocities (less than 200 m/s) are often detected when drifts are in
excess of 1000 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 velocity does not show a tendency for an
increase at the largest drifts, 3) for E region echoes, 12 MHz
velocities are slightly larger than those at 10 MHz, and 4) It often
occurs that 12 MHz echoes are 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
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 flows are fast.
Under this condition, the SuperDARN cross polar cap potential is
underestimated by ~4 kilovolts.