Investigation of Solar Eclipse-induced Variations in Total Electron Content over Ethiopia During 26 January 2009 and 20 March 2015

Solar eclipses provide unique opportunities to study how the ionosphere responds to rapid changes in the ionization rate. The partial solar eclipse of January 26, 2009, and the partial solar eclipse of March 20, 2015, offered opportunities to understand ionospheric electron density variations along the annularity path during solar minimum and geomagnetic quiet periods. For this analysis, various ground-based GPS stations located along the annularity line were selected and divided into three major regions: namely, Bahir Dar, Arbaminch, and Robe stations. We analyzed the temporal and spatial vertical total electron content (VTEC) variations before, during, and after these events, while comparing the observed changes between the two eclipse periods. On January 26, the eclipse day, a noticeable depression in VTEC is observed during the eclipse interval, which began at 04: 57 UT, reached its maximum obscuration (55 - 65% coverage) at 07: 59: 44 UT, and ended around 09: 55 UT. This reduction corresponds to the temporary decrease in solar radiation reaching the Earth’s ionosphere. The VTEC variations observed over the Bahir Dar station during January 25-27, 2009, clearly demonstrate the ionospheric response. On the non-eclipse days (January 25 and 27, 2009), the TEC followed a normal diurnal trend, increasing after sunrise, peaking around midday, and decreasing toward night. In contrast, on the eclipse day, the TEC curve shows a pronounced depression during the eclipse interval. The comparison of TEC variation on consecutive days reveals that, on the reference day of 19 March 2015 (before the eclipse), the maximum VTEC was approximately 26 TECU. In contrast, on 20 March 2015 (the eclipse day), the maximum VTEC was approximately 24 TECU. This clearly demonstrates the effect of the partial solar eclipse on March 20, 2015, over BDR. The VTEC variations observed at the BDR station on 20 March 2015 show an approximate 20% reduction, corresponding to the temporary decrease in solar radiation reaching Earth's ionosphere.