Diurnal & Semidiurnal Drifts in the E Region over a Low Latitude Station

Abstract

Ionospheric E region drift measurements at Udaipur (mag. lat. 18·2°N) have been reported using the closely spaced receiver technique at 2·5 and 3·0 MHz. Data of drift velocities obtained by the method of "similar fades" during 1972-74 were grouped season wise and subjected to harmonic analysis to investigate the contribution of different periodicities. When the data at 2·5 and 3·0 MHz for common days are analyzed separately, the average drift vectors (diurnal and semidiurnal) in different seasons showed the same sense of rotation at the two different heights. However, an analysis of all the available data at 2·5 MHz and data at 2·5 MHz on day’s common with 3'0 MHz observations gave a different nature of diurnal and semidiurnal vectors. Daily and weekly harmonic analysis of the data showed that the diurnal and semidiurnal drift vectors rotate clockwise on some days and anticlockwise on other days. The steady (prevailing) drift vector also shows gradual changes during the course of summer. Such behaviour of different drift components at this latitl.lde seems to be responsible for the observed day-to-day variation of E region ionospheric drifts.