A study of the ionization crests detected by means of the Ariel I satellite

Abstract

An analysis of the Ariel I electron probe data shows that the satellite passed through 1577 significant crests during a period of 2 1 2 months after launch. A study of the magnetic L values at which these crests occurred shows that the structure in the topside ionosphere is irregular and complex and cannot be represented, as suggested in an earlier paper by one of the authors ( Sayers, 1965), by three discrete shell-aligned strata in addition to the equatorial anomaly. The crests observed during the day include features which may be identified with the equatorial anomaly together with further irregular structure at higher L-values. The night-time data show that, particularly in the southern hemisphere, the equatorial anomaly can persist into the night, but the most prominent night-time feature is the existence of many crests at L-values between 1.2 and 2.5; these are observed most frequently at L-values of about 1.7.