Solar Activity And Geomagnetic Storm Effects On Gps Ionospheric Tec Over Ethiopia

Ionospheric GPS total electron content (TEC) is an important parameter to monitorrnfor possible Space Weather impacts. The e ects of solar activity on TEC at lowrnlatitude stations with geographic locations (latitude, longitude) of Addis Ababa (9:040rnN, 38:770 E) and Bahir Dar (11:60 N, 37:360 E) in Ethiopia, East Africa in thernyear of 2015 around peak of solar cycle 24 has been carried out. The data fromrnthe two stations were used to study the diurnal, monthly and seasonal variations ofrnTEC and its dependence with solar activity and space weather e ects. The resultsrnof the analysis reveal that TEC undergoes diurnal and seasonal variations. Fromrnthe daily variation analysis, the TEC value at both stations sharply increases to itsrnpeak value from 0900 À€€ 1500 UT and decreases around 1600 ð€€€ 0700 UT. Seasonalrnvariations showed that TEC maximizes during the equinoctial months and least inrnsummer, over the two stations. In all seasons the maximum value of TEC leads rstrnin Addis Ababa. These observations were investigated and further discussed with anrnanalysis of Disturbance Storm Time (Dst) and Ap indices, solar radio rnux (F10.7rncm) and sunspot number during the period of 2015. During the period of low orrnhigh sunspot number, the provided GPS ionospheric TEC builds up slowly or quickly.rnAs a typical case of storm-time behavior, a geomagnetic storm of June 23, 2015 isrnconsidered in this study. The Dst values for the period shows that it is an intensernintensity geomagnetic storm. The e ects of geomagnetic storms on TEC values havernbeen found negative and positive outputrnKeywords: Solar activity, GPS, Ionosphere, TEC, Geomagnetic storm,rnEthiopia

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