Study of Total Electron Content Variations over the Ethiopia Region Using Kriging Technique

Abstract

This study investigates the vertical electron content (VTEC) variations and depletions using two years of Global Positioning System (GPS), Total Electron Content (TEC) data from 2012 and 2013. The data, gathered at altitudes between 5° and 15° and longitudes between 34° and 48°, was specifically focused on quiet days and analyzed from nine GPS stations. Employing a spherical model and standard kriging interpolation techniques, the research explored hourly, diurnal, and seasonal fluctuations of VTEC over the two-year period. The spherical model demonstrated high efficacy in estimating data with short lag distances, effectively capturing hourly and daily VTEC fluctuations. Diurnal VTEC variations showed a consistent pattern: increasing from dawn, peaking at 1200 UT, and declining to a minimum after 1800 UT. The peak in diurnal variation was most pronounced at Debark, with similar patterns observed at other stations, reflecting consistent ionospheric behaviors due to geomagnetic conjugcy. A strong correlation was observed between the alignment of the solar terminator and magnetic meridian during equinox seasons and VTEC variation and depletion, with the most significant effects during equinoctial seasons. The study identified a distinct north-south gradient in VTEC within the region, with levels exceeding 65 TECU in the north and around 40 TECU in the south, depending on ionospheric conditions. Nighttime VTEC levels typically decreased to approximately 5 TECU. The spatial distribution analysis of TEC revealed a pronounced maximum concentration in the northeastern sector, contrasting with a minimal concentration in the southwestern sector. This research provides valuable insights into the spatial and temporal behaviors of VTEC, enhancing our understanding of ionospheric dynamics within the specified region.