Harmonic Analysis of World-wide <i>f</i>_oF2 Data

Abstract

The harmonic analysis of published <i>f</i>_oF2 data for the year 1969 is done for 36 stations distributed all over the world. The variations of the constant, the diurnal and the semi-diurnal components with the time of the day and season have been studied. It is found that the behaviour of the stations in the northern hemisphere differs markedly from those of the southern hemisphere. The diurnal component shows a maximum in local winter for the northern hemispheric stations, while in the southern hemisphere the maximum occurs in equinoxes. It is found that the diurnal component variation is more pronounced for the high latitude stations. The equatorial stations do not show significant seasonal variations. A marked diurnal variation of the ionization occurs for the polar stations in local winter, suggesting sources of ionization other than solar radiations which are under direct solar control. These findings have been discussed in the light of the available information.