Annual wave in the world-wide F-region ionization

Abstract

An analysis of squares of noon median F2 layer critical frequencies for a 3-year period has been made in order to derive the latitude variation of the annual effect in the electron densities and its relation to average F2 layer ionization. The results indicate that the annual component Rl varies with the latitude in a manner very nearly similar to that of the steady ionization Ro and that for a given value of Ro for any latitude, Rl can be derived approximately from a linear relationship of the type Rl = 0.3 Ro - 4.5. A similar analysis of 9-year data for precise phase and amplitude of the annual component for a pair of stations yields a value of Rl which is of the same order of magnitude as Ro and which attains a maximum around the epoch-of minimum sun earth distance.