Deep earth electrical conductivity-depth profiles around African geomagnetic equator using solar quiet currents

• Published in: Journal of the Geological Society of India 2017-03, Vol.89 (3), p.344-350
• Main Authors: Ugbor, D. O., Okeke, F. N.
• Format: Article
• Language: English
• Subjects: Conductivity; Depth profiling; Earth; Earth and Environmental Science; Earth Sciences; Electrical conductivity; Electrical resistivity; Equator; Geology; Geomagnetism; Geophysics; Harmonic analysis; Hydrogeology; Magnetic fields; Resistivity; Spherical harmonics; Transfer functions
• ISSN: 0016-7622; 0974-6889
• DOI: 10.1007/s12594-017-0609-8

Electrical conductivity structure of the Earth’s deep interior has been successfully mapped out down to approximately 1500 km around the geomagnetic dip equatorial regions of Africa using solar quiet-day ionospheric currents. Spherical harmonic analysis (SHA) was employed in separating the internal and external field contributions to the solar quiet variations. Transfer function was used for each of the external and internal pairs to compute the conductivity-depth profile for the region. Calculated average electrical conductivity values were evidently higher than obtained in other parts of the world farther away from the geomagnetic equator. Sq current vortex foci are observed very close to the geomagnetic equator. Depth of penetration was greatly enhanced. Stations on latitudes less than 1° from the geomagnetic equator show higher electrical conductivity when compared with that situated more than 4° away from it at various corresponding depths. Evidence of discontinuities in the earth layers were also noted at some depths. Highly conductive layers were delineated around 400 km depth and beyond 1200 km.