This paper examined the behavior of ionospheric irregularities over the African Equatorial Ionization Anomaly (EIA) during intense geomagnetic storms which occurred from 2012 to 2015. Total electron content (TEC) data was used to derive the rate of change of TEC index (ROTI). This was employed to monitor irregularities over the trough and crests of the EIA. Variations of the horizontal component of the Earth’s magnetic field (H) were examined. The H component was additionally used to compute ionospheric electric current disturbance (Diono). Prompt penetration electric field (PPEF) inferred from variations of Diono was compared with PPEF obtained from the Prompt Penetration Equatorial Electric Field Model (PPEFM). The PPEFM predicted accurately all PPEFs thus, was found to be valid over the African EIA. The local time of occurrence of interplanetary magnetic field (IMF ) dictated the behavior of irregularities. Eastward PPEF triggered short duration irregularities on 23 April 2012, 17 March 2013 and 20 February 2014 while westward disturbance dynamo electric field (DDEF) reduced them thereafter. During the storms recovery including the 15 July 2012 and 17 March 2015 events, irregularities were suppressed by westward DDEF. However, during the storms of 14 November 2012 and 29 June 2013 no irregularities were observed. Irregularities were always inhibited over the trough. The inhibition lasted longer during the super storm of March 2015. Over the crests, there were differences in their behavior on 16-17 July 2012, 15 November 2012 and 19 March 2013. These were however, not linked to storm-time electric field.

At the equatorial latitude of a West African station (8.50N, 4.68E), we have examined the slab-thickness (τ) relative to peak electron density height (hmF2) at F2 layer, employing Digisonde Portable Sounder τ (DPS-τ) and Global Positioning System τ (GPS-τ) during the low solar activity year 2010. Our observation revealed maximum and minimum τ during the daytime and nighttime respectively, which may indicate maximum and minimum scale height in τ through daytime and nighttime, respectively. The discrepancies between the together reversed signatures of DPS-τ and GPS-τ around 0100 - 0600 LT in June could indicate the failure to incorporate a reflection of the composition changes in the topside-DPS model. We have reported the pre-sunrise and post-noon peaks in GPS-τ and hmF2, which are contributions of plasmaspheric TEC and pre-reversal enhancement (PRE) velocity, respectively. Around 1100 - 1700 LT, the stability in hmF2 show that the interaction of neutral wind and eastward electric field could be employed to predict the τ. We also reported that the pre-sunrise increase in GPS-τ is not an indication of PRE velocity as observed during the nighttime. The relationship between τ and hmF2 gives a high correlation coefficient (CC), but CC during the daytime is higher than the nighttime values which suggest the constant diffusion state of plasmasphere during the daytime whereas the nighttime is a function of the plasmaspheric flow of electron content and PRE velocity. We compared the experimental hmF2 with IRI-2016 and found that the IRI-2016 model is incapable of capturing the post-sunset and pre-sunrise increases.