Effect of magnetic activity on equatorial F region plasma drifts

Abstract

Effect of magnetic activity, caused by complex interaction of solar wind and magnetosphere, on night time equatorial F region plasma drifts is studied using scintillation data recorded using spaced receivers at Tirunelveli (dip 0.40), for a 251 MHz signal transmitted from a geostationary satellite. Once the perturbation electric field associated with plasma bubbles are eroded, about two hours after the initiation of bubble growth, the irregularities simply drift across the signal path along with background plasma. Hence irregularity drift speed estimated from spaced receiver scintillation data is very close to the drift speed of the background plasma during this period. In order to obtain monthly average quiet time plasma drift pattern in the nighttime equatorial F region, the drifts estimated from scintillation data are averaged after 22LT for all quiet days (Ap < 18) of a month. Quantitative estimate of the effect of a disturbance dynamo produced by enhanced geomagnetic activity, on the nighttime equatorial F region plasma drift is obtained by removing monthly quiet time plasma drift pattern from disturbed time plasma drift pattern. The maximum effect of disturbance dynamo on equatorial F region plasma drift is observed around midnight for most of the magnetically disturbed days considered in the present study. An attempt is made here, (i) to relate the maximum deviation of the disturbed nighttime equatorial F region plasma drifts from quiet time pattern, with an empirical measure of the Joule energy input at high latitudes during magnetically active periods (ii) to investigate the time delays, which are required for obtaining the maximum disturbance dynamo effects observed in the night time equatorial F region plasma drifts, based on AE and Kp indices.