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Data collected by the CUTLASS Finland HF radar are used to illustrate the significant difference between the cosine component of the plasma convection in the F-region and the Doppler velocity of the E-region coherent echoes observed at large flow angles. We show that the E-region velocity is 5 times smaller in magnitude and rotated by 30 clockwise with respect to convection in the F-region. Also, measurements at flow angles larger than 90 exhibit a completely new feature: Doppler velocity increase with the expected aspect angle and spatial anticorrelation with the backscatter power. By considering DMSP drift-meter mea- surements we argue that the difference between F- and E- region velocities cannot be interpreted in terms of the con- vection change with latitude. The observed features in the ve- locity of the E-region echoes can be explained by taking into account the ion drift contribution to the irregularity phase ve- locity as predicted by the linear fluid theory.

Simultaneous HF measurements of E- and F-region Doppler velocities at large flow angles