UPPER MANTLE CONDUCTIVITY DETERMINED FROM THE SOLAR QUIET DAY IONOSPHERIC CURRENTS IN THE MID AND HIGH LATITUDES OF EUROPE

Abstract The mantle electrical conductivity-depth profile of mid and high latitudes of Europe have been determined using solar quiet day ionospheric current (Sq). The magnetometer data obtained for 2009 from geomagnetic stations installed across Europe by magnetic data acquisition set (MAGDAS) were employed in this study. Gauss spherical harmonic analysis (SHA) method was used to separate the internal and external field contributions to Sq current system. The result depicted that the conductivity values at DOU showed a sharp increase from 0.026791sm-1 at 103.38km to 0.129sm-1 at 137.24km, it increased to 0.142sm-1 at 160.84km and got to 0.178sm-1 at 203.61km. At HRN, the conductivity profile rose steadily from about 0.0179sm-1 at a depth of 140.42km and increased gradually until it got to 0.0245sm-1 at 206.34km. This high conductivity region agreed with the global seismic low velocity region, the asthenosphere. A discontinuity in the conductivity values was observed between 432.63 and 699.6km, this region corresponds to the mantle transition zone, which is part of the Earth’s mantle and located between the lower mantle and the upper mantle between depths of 410 and 660km.