Partial reflections from equatorial E region gradients

Anomalous narrow peaks in both daytime and nighttime equatorial E region VHF radar spectra observed when the electron drift is low appear to be explainable in terms of partial reflections from regions of sharp plasma density gradients. Both zero-order gradients and secondary gradients from incoherent returns. Some of the anomalous peaks have Doppler shifts which appear to be consistent with the ambient ion-neutral drifts and independent of the electrojet (electron drift) direction. This may be due to the fact that both the steep zero-order gradients and the large irregularities that produce the partial reflections tend to predominate at somewhat lower heights, where the plasma is strongly collision dominated