Spread-F and ionization anomaly belt

Abstract

The present investigation attempts to bring out the dynamics of the F-region at magnetic equatorial and low latitudes in the American zone. Data are examined for two sets of nights, one with strong range-type spread at Huancayo another with complete absence of spread-F. A prominent bulge of the F-region was observed within and below a latitude 10°N in the evening hours of the spread-F nights. Contours of electron distribution during post-sunset hours at the equatorial latitude, Huancayo (Dip 2°N); low latitude, Talara (dip 13°N); and a location near the anomaly crest location, Panama (dip 38°N), indicated a much steeper gradient in electron density at fixed heights on spread-F nights compared to a rather low gradient on the nonspread-F nights. Enhanced concentration of electrons at the anomaly crest location Panama, and a lower density at the equatorial location Huancayo, were observed on spread-F present nights. This is attributed to the phenomena of an evening plasma fountain in operation at equatorial latitudes on spread-F nights.