Abstract. In this study, velocities of E-region HF echoes observed by the Stokkseyri HF radar are compared with E×B plasma drifts in the F-region measured by the DMSP satellites. Events were selected for which the DMSP track projected to the height of 110 km was almost perpendicular to the central beams of the radar, resulting in a direct comparison of the cross-track component of the E×B 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 0-1700 m/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 E×B flow.

Abstract. Data collected by the Stokkseyri SuperDARN HF radar simultaneously at short and far ranges are used to investigate the relationship between the velocity of E-region HF echoes, E × B electron drift and the isothermal ionacoustic speed C S . The work targets large E × B drifts of >1000 m s −1 and observations predominantly along the flow. By considering the EISCAT temperature and electric field data, an empirical relationship between the E ×B drift velocity and C S is established for a number of ionospheric heights. For the Stokkseyri HF radar beams oriented roughly along the E × B direction, the observed E-region HF velocities are consistent with the C S values at the bottom of the electrojet but not at its center. For a subset of the data with smooth and consistent velocity variation with the beam azimuth at both short and far radar ranges the velocity varies according to the cosine law. For the E-region echoes, the proportionality coefficient in the cosine law is consistent with the C S values at the bottom of the electrojet. For these events, the E-region velocity maximum is shown to be between the E × B and electric field directions. The statistically average shift is ∼20 • and it increases slightly with the E × B magnitude.