Cusp Type Anomalies in Variable Frequency Ionospheric Records

Abstract

Anomalous cusps which frequently appear at the high frequency end of ionosonde records of the F2. region are explained as the result of modification of the ion distribution during the passage of typical travelling disturbances. They indicate the presence, not of vertical stratification but of horizontal gradients of ionization causing oblique reflection. It is suggested that other anomalous cusps are of similar origin.