Assessment of geomagnetic storm effects over Ethiopian ionosphere by using GPS measurements

In this paper we have investigated the effects of geomagnetic storm on the variation of interplanetary magnetic field(IMF Bz), disturbance storm time (Dst), solar wind speed and total electron content (TEC) over Ethiopian ionosphere. Atotal of 17 geomagnetic storms have analysed by using ground based Global Positioning System (GPS) stations at Bahir Dar(11o N, 38o E), Debark(4.32o N, 109.48o E), Armi (3.03o N, 109.29o E), Nazret (8.57o N, 39.29o E), Robe(7.60o N, 40oE),Assosa (1.14o N, 106.16o E), and Ambo( 8.59o N, 37.51o E) from the years 2010 to 2013. The results have revealed that thereis a mixed effect of geomagnetic storm on the variation of interplanetary magnetic field (IMF Bz), disturbance storm time(Dst), solar wind speed and total electron content (TEC), however, most of the effects were positive and might be attributedto the prompt penetration electric fields (PPEFs) and disturbed dynamo fields