Spatial variability of solar quiet fields along 96° magnetic meridian in Africa: Results from MAGDAS

We have used chains of Magnetic Data Acquisition System (MAGDAS) magnetometer records of the horizontal (H) and vertical (Z) magnetic field intensities during September 2008 to August 2009 (year of deep minimum) across Africa to study their variability during the quietest international days, which coincidently associated with the sudden stratospheric warming (SSW) event in January 2009. This selection of the most international quiet days is indicative of 80% that are strongly associated with days when unusually strong and prolonged sudden SSW event occurs in January 2009. Interestingly, in January, a significant magnitude depletion of solar quiet (S_q) equivalent current was observed near noon hours around the magnetic equator (Addis Ababa, ABB) compared to any other months along with a consistent significantly reduced value across the Northern Hemisphere and moderate decrease at the Southern Hemisphere. Also, we found that Nairobi and Dar es Salaam at the Southern Hemisphere, which are close to ABB (dip equator), are strongly prone to westward electric field compared to the magnetic equator and Khartoum at the Northern Hemisphere. Significant negative values of MS_q(Z) magnitudes observed near noon hours at Hermanus indicate the presence of induced currents that suggest ocean effects along with reversal to significant positive values in the afternoon, which subsided before 1800-LT in almost all the months, indicate stronger influence of ionospheric currents. On seasonal variability of S_q(H), a slight depression at ABB during September equinox is one of the evidences of seasonal S_q focus shift. Latitudinal variability of S_q near-noon hours was also investigated.