Seasonal, solar and magnetic activity effects on evening F region vertical plasma drifts

A study of the seasonal, solar, and magnetic activity dependence of the evening F region vertical plasma drifts using HF Doppler radar observations conducted during the period 1984-1989 at the equatorial station Trivandrum (dip. 0.5 deg N) is presented. The observations show that (1) during magnetically quiet days of moderate solar activity conditions, the characteristic prereversal enhancement in vertical plasma drift attains a maximum during equinox and is higher than the winter and summer values, which are not much different from each other, by about a factor of 2; (2) during equinox, the prereversal enhancement peak is sensitively dependent on solar activity for both magnetically quiet and disturbed conditions; and (3) magnetic activity does not seem to have a pronounced effect on the prereversal enhancement peak velocity. The results presented here are found to be in broad agreement with those reported for Jicamarca