Enhancement of Ionization in the E-Layer due to Solar Flares during the International Geophysical Year

Abstract

INCREASES in the ionization of the E-layer have been reported after the occurrence of individual major solar flares^1,2, and an analysis by Bibl³, for a three-month period in 1950, has shown that all increases in the critical frequency of the E-layer of more than about 0.2 Mc./s. above the monthly median value can be attributed to the effects of solar flares. Bibl considered only the deviations of the critical frequency from its monthly median value, and a similar analysis for 8 flares in the period 1951–56 has also been made by Taubenheim⁴. No detailed comparison has so far been made between the critical frequency after a flare and its value before the flare. Recently, in the course of other work, Minnis and Bazzard⁵ have examined the hour-to-hour changes in the values of the E-layer critical frequency (ƒoE) at Slough for the period of the International Geophysical Year. These data have been used to study the changes in ƒoE associated with the occurrence of all the flares of importance 2+ and 3 which were listed in the CRPL F-Series Bulletins (Part B) and which occurred during the period 0800–1500h. U.T.