Equatorial electrojet in the African sector

Abstract

Hourly values of the deviations in the geomagnetic X and Y field for the three years 1962-64 are studied at two equatorial electrojet stations in Africa, Freetown (FTN) on the eastern part and Addis Ababa (AAE) on the western part. The declination is almost along the geographic N-S at AAE and 14^o towards west of the geographic N-S at FTN. The annual mean daily range in X is around 80 nT at FTN and 70 nT at AAE with peak around 11 hrs. Deviations in Y at FTN show peak of about -20 nT around noon. Seasonal mean variations of the daily range in X show almost equal peaks during D and E-months at FTN but at AAE it is highest during equinoctial months and lowest during J-months. The peak in February-March is higher than the peak in September-October at both the stations. Another notable feature at FTN is the steady increase in deviation in X from about -10 nT at 18 hrs to 10 nT at 06 hrs. Vector plots of ΔX versus ΔY show daytime points along a straight line aligned almost along the geographic N-S for D and E-months at AAE and along 12^o W of north during J-months. At FTN points lie along an elongated ellipse pointing to about 5^o W of north during D and E-months and to about 20^o W of north during J-months.