Comparison of Digisonde derived ion drifts and SuperDARN line-of-sight velocities over Zhongshan Station, Antarctica

In this study, ion drift velocities measured by Digisonde instruments over Zhongshan Station (ZHS, geog. 69.38°S, 76.38°E), Antarctica, are compared with measurements from Super Dual Auroral Radar Network (SuperDARN) HF radars. For SuperDARN Syowa East (SYE) and Kerguelen (KER) radars that intersect with ZHS, a data set comprised of adjacent range gates from nearest radar beams is used. Digisonde ion drift measurements were projected onto the direction of co-located and concurrent line-of-sight SuperDARN velocities. A comparison of the velocities shows a clear correlation (R = 0.92) between the two data sets. Projected Digisonde velocity was found to be, on average, larger than the line-of-sight SuperDARN radar velocities by a factor of 1.7. Time dependence distributions of Digisonde-SuperDARN SYE radars showed that the larger velocity discrepancies are more located at the dawnside convection cell. Considering the known features of the high-latitude convection patterns at cusp latitude, the statistical results imply the velocity discrepancies are related to the differences in the temporal and spatial evolution of plasma structures.