Analysis of ionospheric storm-time effects over the East African sector during the 17 March 2013 and 2015 geomagnetic storms

Abstract An analysis of the mechanisms that caused storm-time effects during two geomagnetic storms occurred on 17 March 2013 and 2015 is presented. We used Global Navigation Satellite System (GNSS) derived Total Electron Content (TEC) data over trough (Addis Ababa, ADIS, $$38.8^\circ$$ 38 . 8 ∘ E geographic longitude, $$0.18^\circ$$ 0 18 N latitude) near crest (Mbarara, MBAR, $$30.7^\circ$$ 30 7 $$10.22^\circ$$ 10 22 S regions East African sector. Magnetometer Addis Ababa (AAE) Mbour (MBO) were also to derive disturbance in ionospheric currents storm periods. The monthly median TEC values for a month within which under consideration as measure background variability analyse response ionosphere storms. considered be significant when magnitude deviation ( $$|\Delta TEC|$$ | Δ T E C ) $$\ge$$ ≥ 45%. During main phase, responded positively at 1800 UT, whilst regions, there was no St. Patrick’s day However, recovery phase storms, both stations Africa showed positive response. checked thermospheric [O]/[ $$\text {N}_2$$ N 2 ] changes result There appreciable this sector between 16 18 2013. observed an change 2015. increase more pronounced/obvious responses phases could not attributed because nighttime features. southward turning z component Interplanetary magnetic field (IMF Bz led enhanced eastward equatorial electric (EEF) 0725 UT (1025 LT) 0645 (0945 respectively. note IMF turned northward, EEF westward. turnings took place about 1435 (1735 2013, prompt penetration (PPEF) post-sunset period starting 1600 (1900 Prereversal enhancement (PRE). presence westward PPEF around 1500 (1800 acted suppress PRE may strong disturbed dynamo (DDEF), night. thus surmise low-latitude region combined effect equatorward neutral wind, DDEF. Graphical