Anomalous Short Period Geomagnetic Variations at Two Stations in Sri Lanka

摘要

An analysis of the rates of change in the geomagnetic field components in the period range 20-600 sec recorded at Kondavil and Hikkaduwa, two stations in the equatorial electrojet belt near the northern and southwestern coasts respectively of Sri Lanka, shows anomalous variations. The results confirm induced current concentration in the Palk Strait and deflection of induced currents around the southern coast of Sri Lanka postulated by earlier workers from observations of SSC and Bay events at Indian stations and from analogue and numerical model studies. At Kondavil, which is situated close to the geomagnetic equator, no appreciable difference in the night-time and day-time values of delta Z/ delta H and delta D/ delta H ratios was noticed, while at Hikkaduwa, a station situated under the edge of the equatorial electrojet belt, a day-time enhancement of delta Z/ delta H ratios was found at all periods in the observed range. An enhancement of the H component at Colombo over that at Hikkaduwa was also found at short periods, the enhancement being greater at day-time. The day-time enhancement in the delta Z/ delta H ratios at Hikkaduwa and in the ratio of the H components at Colombo and Hikkaduwa could be due to the effect of the equatorial electrojet on the short period variations. 11 refs, 8 figs. (Atomindex citation 18:017992)