World wide study of apparent horizontal movements in F2-region of the ionosphere

The paper presents the results of the study of latitude variation of apparent horizontal movements in the F2-region of the ionosphere using the data procured from the World Data Centre for the year 1958. The mean drift speed is found to decrease from equator and after reaching a minimum around a latitude of 40°, it increases. From the harmonic analysis of the NS and EW components the latitude variation of the prevailing 24-hourly and 12-hourly periodic components of the drifts has also been studied. The steady component is significant at all stations. The NS component of the steady drift is in general less than the EW component. The EW component of the steady drift is towards east at low latitudes and towards west at high latitudes, the changing over taking place at a geomagnetic latitude of about 30°N. The orientation of the steady drift vector changes systematically in a clockwise sense from low latitude to high latitude stations. The diurnal drift vector is very much larger than the semi-diurnal drift vector at low latitude stations whereas at middle and high latitude stations the semi-diurnal drift vector is greater than the diurnal drift vector. The 24-hourly drift vector which has a maximum value at the equator decreases with latitude and after reaching a minimum around 30° geomagnetic latitude it continues to increase. There is a systematic increase in the amplitude of the 12-hourly drift vector with increase of latitude. Both the 24- and 12-hourly drift vectors rotate clockwise in the northern hemisphere and anti-clockwise in the southern hemisphere