The relation between the occurrence of ionospheric irregularities and the spatial gradient of TEC derived from two closely located stations, located within the equatorial region over Ethiopia, was investigated. The relationship between σ(∆TEC/∆long) and ROTI_ave correlate linearly with correlation coefficients of C = 0.7975 and C = 0.7915 over ASAB and DEBK, respectively. In addition to latitudinal gradients, the longitudinal gradient of TEC has a significant contribution to the TEC fluctuations.

Many studies carried out for model validation are realised under geomagnetically quiet conditions. For climatological models this is not an issue. But for models like NeQuick, which plays a crucial role in daily human activities, it has to be evaluated under different conditions. Our study, which is probably a preliminary study, shows the advantage of the ingestion of ionospheric data. Thus, through this technique, a model could be assessed regardless of the geomagnetic activity.

We have established that, over the East African region, the trough of the equatorial ionisation anomaly (EIA) during high solar activity and quiet geomagnetic conditions lies slightly south of the magnetic equator. During the equinox and December solstice seasons, and a local time interval of 13:00–15:00, the probability of observing the EIA on days with daytime equatorial electrojet (EEJ) strength ≥ 40 nT was mostly > 80 %.

An unusual geomagnetic storm effect on the ionosphere in the form of localized enhancement of total electron content southward of South Africa is investigated using data from different ionosphere sounding facilities. Global ionospheric maps allow us to get the occurrence rate of such irregularities over the period of 2002–2016 and to see its correlation with solar cycle. The events we detected occur during geomagnetic storms, but not every geomagnetic storm produces such an effect.