External Sq currents in the West African region

Abstract

The external Sq currents for quiet days in 1993 were studied for the West African re- gion using the magnetic data obtained in the course of the French participation in the International Equatorial Electrojet Year (IEEY). Spherical Harmonic Analysis technique was used to separate the internal and external contributions of the quiet field variations. The external current range provided a simple way of viewing a full year’s change in the external Sq current system. The maximum range was found in March with a value of 34.4 × 106 A and the minimum found in December with a value of 1.7 × 106 A. The seasonal variation was found highest in March (equinox) with a value of 16.6 × 106 A followed by June (summer solstice) 9.42 × 106 A; the least was found in December (Winter solstice) 7.76 × 106 A.