The Boundary Between The Northern And Southern Sq Current Loops Over The African Continent

Abstract

Geomagnetic declination variations of five quiet days in January, April, July and October 1969 are studied, based on observations from 11 African observatories. The variations are produced by electric current systems in the ionosphere together with their induced currents in the outer conducting layer of the earth. On the daylight side of the earth the ionospheric currents take the form of two large loops with currents flowing counterclockwise in the northern hemisphere and clockwise in the southern hemisphere. It is found that the boundary between the loops is much further south in South America than in Africa, comprising a difference in latitude of as much as 20 deg. This suggests that the dip equator position is important in influencing the boundary between the northern and southern current systems. Also, the trend in both continents is for the electrojet current to draw contributions from both the northern and southern current systems, thereby stabilizing the boundary close to the axis of the electrojet in the post midday period.