Mantle electrical conductivity determination employing the ionospheric solar quiet day (Sq) currents in the Southern African regions

Abstract

Solar quiet (Sq) daily currents variation obtained in the Hermanus (34.34 o S, 19.22 o E), Tsumeb (19.24 o S, 17.72 o E), Hartebeesthoek (25.68 o S, 28.09 o E) and Maputo (25.97 o S, 32.57 o E), were employed in determining the mantle electrical conductivity depth profile of the Southern African region. The external and internal contributions in the solar quiet field were separated using the spherical harmonic analysis (SHA), after which, the transfer functions were used to compute the electrical conductivity depth profiles of the region. A downward increase was observed in electrical conductivities and deep depth of penetration within the Earth regions. In Hartebeesthoek, Hermanus, Maputo and Tsumeb, the evaluated average electrical conductivity values are 0.028 Sm -1 , 0.039 Sm -1 , 0.057 Sm -1 and 0.0.025 Sm -1 at depths of 76.4 km, 84.1 km,141.0 km and 111.5 km at the respective maximum depths of penetration of 1052.8 km, 1467.0 km, 1160.8 km and 1289.5 km in Hartebeesthoek, Hermanus, Maputo and Tsumeb, the calculated electrical conductivity reached the maximum values of 0.498 Sm -1 , 0.323 Sm -1 , 0.387 Sm -1 and 0.187 Sm -1 respectively. Discontinuities were observed in all the profiles but are more prominent in Tsumeb region near 390.0 -750.0 km, 820.0 -980.0 km and 200.0 -300.0 km. From these results, we are stating that the effects from the deeper 3-D structures (such as gold, copper etc), the hydrated transition zone and effect from the ocean contribute to the greater depth of Sq penetration.