The Study of TEC Variations on Some Special Days (Solstices, Equinoxes and Days When the Sun is Overhead) at Bahir Dar-Station

Abstract

The daily Total Electron Content (TEC) represents the highest TEC value recorded each day, crucial for understanding ionospheric fluctuations. This article examines the daily variations of TEC over a GPS station in Bahir Dar on specific dates including equinoxes, solstices, and the time of day when the Sun is directly overhead. We analyzed GPS TEC data from the Bahir Dar station, focusing on six selected days across three years (2013-2015). MATLAB software was used to create daily TEC plots and bar graphs that illustrate maximum TEC values for each chosen day. The study compares TEC measurements with International Reference Ionosphere model estimations, highlighting fluctuations in TEC from 2013 to 2015. Notably, elevated TEC values were recorded during winter solstice days compared to equinox days, with the highest TEC noted on the December solstice rather than the June solstice. This occurs due to increased solar radiation when the Earth is closest to the Sun (perihelion) in early January, leading to slightly more solar energy in December than in June. Additionally, the Equatorial Ionization Anomaly (EIA) significantly influences TEC by transporting plasma through the ionosphere. Its dynamics can hinder plasma movement toward the north, resulting in TEC variations due to enhanced ionization on the opposite side of the geomagnetic equator. Moreover, Bahir Dar's proximity to the magnetic equator contributes to lower TEC values observed during certain summer days. Overall, this study emphasizes the significant daily TEC variations over Bahir Dar, impacting satellite navigation and communication systems in the region.