Solar activity and geomagnetic storm e ects on GPS ionospheric TEC over Ethiopia

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Addis Ababa University


Ionospheric GPS total electron content (TEC) is an important parameter to monitor for possible Space Weather impacts. The e ects of solar activity on TEC at low latitude stations with geographic locations (latitude, longitude) of Addis Ababa (9:040 N, 38:770 E) and Bahir Dar (11:60 N, 37:360 E) in Ethiopia, East Africa in the year of 2015 around peak of solar cycle 24 has been carried out. The data from the two stations were used to study the diurnal, monthly and seasonal variations of TEC and its dependence with solar activity and space weather e ects. The results of the analysis reveal that TEC undergoes diurnal and seasonal variations. From the daily variation analysis, the TEC value at both stations sharply increases to its peak value from 0900 �� 1500 UT and decreases around 1600 �� 0700 UT. Seasonal variations showed that TEC maximizes during the equinoctial months and least in summer, over the two stations. In all seasons the maximum value of TEC leads rst in Addis Ababa. These observations were investigated and further discussed with an analysis of Disturbance Storm Time (Dst) and Ap indices, solar radio ux (F10.7 cm) and sunspot number during the period of 2015. During the period of low or high sunspot number, the provided GPS ionospheric TEC builds up slowly or quickly. As a typical case of storm-time behavior, a geomagnetic storm of June 23, 2015 is considered in this study. The Dst values for the period shows that it is an intense intensity geomagnetic storm. The e ects of geomagnetic storms on TEC values have been found negative and positive output. Keywords: Solar activity, GPS, Ionosphere, TEC, Geomagnetic storm, Ethiopia.



Solar activity, GPS, Ionosphere, TEC, Geomagnetic storm, Ethiopia