On the relationship between the velocity of E-region HF echoes and ExB plasma drift

Abstract. In this study, velocities of E-region HF echoes observed by the Stokkseyri HF radar are compared with ExB plasma drifts in the F-region measured by the DMSP satellites. Events were selected for which the DMSP track projected to the height of 110km was almost perpendicular to the central beams of the radar, resulting in a direct comparison of the cross-track component of the ExB drift and the line-of-sight HF velocity. We found that the typical ratio of HF velocity to the DMSP drift is ~0.35 in a range of DMSP drifts of 0-1700m/s. It is suggested that E-region HF velocities, observed both along the electrojet and at large flow angles, are significantly affected by scatter from the bottom of the electrojet layer where the irregularity phase velocity is expected to be strongly depressed with respect to the ExB flow.