A study of magnetic pulsations in the Indian equatorial region

Abstract

Magnetic pulsations in the period range 20–600 sec, are studied using quick-run magnetograms, taken simultaneously at Alibag, Annamalainagar and Trivandrum out of which the last two are in the electrojet belt. The magnetograms were taken on all ‘Regular World Days’ and ‘Regular Geophysical days’ during the period January 1964–December 1965. The main results are: 1. (1) Pc5 (150–600 sec) pulsations show an occurrence maximum during morning hours (0800–1100 hr LT), and during low to moderate magnetic activity. The difference between the maximum and the minimum period which varies from event to event is small (⩽100 sec) for 40% of the events and fairly large ( ⩾ 200 sec) for an equal number of events. 2. (2) A study of irregular pulsations associated with positive bays during night hours shows no correlation between their amplitudes. The pulsation period decreases with increase in Kp. 3. (3) The average pulsation amplitude ΔH increases with period. There is a clear evidence of equatorial enhancement due to the electrojet and this enhancement is more for large periods (⩾150 sec). 4. (4) The difference in ΔZ ΔH values noticed during night-time at the three stations for different periods can probably be attributed to the differences in local sub-surface electrical conductivity.