Geomagnetic and geoelectricvariations in the West African longitudes of the equatorial electrojet (EEJ)

Abstract

Ten electromagnetic stations were set up as a coordinated programme for the International Equatorial Electrojet Year (IEEY) between November 1992 and November 1994 by a French Team. The stations occupied covered a distance of 1200 km from Lamto 6.2°N, 5.02°W in the South to Tombouctou 16.7°N, 3°W in the North. The stations are listed in Table 1 and Fig .1a. Similar experimentations were carried out in American and Asian sectors and over 200 stations were occupied across the dip equator. Simultaneous recordings of H, D, Z, E_x and E_y for the quiet days of May 1^st and 2^nd 1993 (A_p<7) have been analyzed for: The solar quiet daily variations Sq (H), Sq (D) and Sq (Z); Day to day variability of hourly amplitudes. Crustal and mantle MT-resistivity for SAN and NIE stations. Results show an abnormal Sq (H) variation for MOP station which has a higher Sq(H) hourly values than those closest the dip equator. Sq (H) should be maximum at the dip equator and decreases on either side progressively. Day to day variability of hourly amplitudes in H is higher in the African longitude when compared with the results of the Indian sector. Z variation has lower day to day variability than the results of the Indian sector. The MT-resistivity reveals a conductive sedimentary top layer with a highly resistive material, presumably crystalline basement rocks at depths of 1305 km and above.

Global Journal of Pure and Applied Sciences Vol. 12(2) 2006: 251-258