The 30‐MHz radar interferometer studies of midlatitude E region irregularities

Abstract

The 30‐MHz radar observations of coherent scatter from midlatitude E region plasma irregularities are presented and interpreted. Our analysis indicates that quasiperiodic (QP) echoes can be interpreted as quasi‐point target scatterers drifting through the radar beam at approximately constant altitude. Interferometry data collected with multiple baselines show that the patchy scatterers are not organized along wave fronts but instead form drift and decay independently of one another. An analysis of the intensity of the echoes versus range reveals that the morphology of the QP echo striations is consistent with expectations for drifting field‐aligned irregularities with finite aspect angle sensitivity. An analysis of the effects of refraction, aspect sensitivity, and scattering geometry shows that the plasma irregularities in question reside at altitudes between 95 and 120 km. Type I echoes observed on one occasion imply the existence of strong zonal polarization electric fields with magnitudes of about 20 mV/m. A numerical model of the E region current system demonstrates how such electric fields can be generated by elongated, patchy sporadic E layers electrically coupled to the F region dynamo.