Rate of change of TEC (ROT) and its index (ROTI) are considered a good proxy to characterize the occurrence of ionospheric plasma irregularities like those observed after sunset at low latitudes. SBASs (satellite-based augmentation systems) are civil aviation systems that provide wide-area or regional improvement to single-frequency satellite navigation using GNSS (Global Navigation Satellite System) constellations. Plasma irregularities in the path of the GNSS signal after sunset cause severe phase fluctuations and loss of locks of the signals in GNSS receiver at low-latitude regions. ROTI is used in this paper to characterize plasma density ionospheric irregularities in central–western Africa under nominal and disturbed conditions and identified some days of irregularity inhibition. A specific low-latitude algorithm is used to emulate potential possible SBAS message using real GNSS data in the western African low-latitude region. The performance of a possible SBAS operation in the region under different ionospheric conditions is analysed. These conditions include effects of geomagnetic disturbed periods when SBAS performance appears to be enhanced due to ionospheric irregularity inhibition. The results of this paper could contribute to a feasibility assessment of a European Geostationary Navigation Overlay System-based SBAS in the sub-Saharan African region.

Perturbations from thunderstorms can play a notable role in the dynamics of the ionosphere. In this work, ionospheric perturbation effects due to thunderstorms were extracted and studied. Thunderstorm-associated lightning activities and their locations were detected by the World-Wide Lightning Location Network (WWLLN). The mechanical components of ionospheric perturbations due to thunderstorms were extracted from the total electron content (TEC), which was measured at selected thunderstorm locations using the polynomial filtering method. Further analyses were conducted using wavelet analysis and Discrete Fourier Transform (DFT) to study the frequency modes and periodicities of TEC deviation. It was revealed that the highest magnitudes of TEC deviations could reach up to ~2.2 TECUs, with dominant modes of frequency in the range of ~0.2 mHz to ~1.2 mHz, falling within the gravity wave range and the second dominant mode in the acoustic range of >1 mHz to <7.5 mHz. Additionally, a 20–60 min time delay was observed between the sprite events, the other high-energy electrical discharges, and the time of occurrence at the highest peak of acoustic-gravity wave perturbations extracted from TEC deviations. The possible mechanism responsible for this phenomenon is further proposed and discussed.

Anomalous propagation conditions may cause multipath fading and strong signal enhancement on terrestrial line of sight links or interference on transhorizon paths. In detecting this conditions, spatial distribution of vertical refractivity gradient and ducting index were estimated across Nigeria using atmospheric data obtained from Era5 archive of European Centre for Medium‐Range Weather Forecasts (ECMWF). Refractivity and refractivity gradient were calculated from the obtained temperature, relative humidity, and pressure data using International Telecommunication Union (ITU) recommendation expression. Vertical refractivity gradient (VRG) and ducting index (D_i) were deducted from refractivity gradient and modified the refractivity gradient. Correlation between vertical refractivity gradient, D_i, and latitude were also computed. The result shows that the VRG values range between −5 and −65 N units/km in the Coastal and Guinea Savannah regions, and between −30 and −95 N units/km in the Midland and Sahelian regions. The D_i values range between 10 and 60 in the Coastal and Guinea Savannah regions, between −10 and 110 in Midland and Sahelian region. Likewise, superrefraction and ducting are more prominent in the northern part, while superrefraction with minor subrefraction were noticed in the south. The D_i performed better than VRG in detecting propagation conditions. Correlation between VRG and latitude ranges between −0.75 and −0.92. Correlation between D_i and latitude is between 0.84 and 0.95. The values of VRG decrease northward, while those of the D_i increase northward. Both VRG and D_i revealed high variability in the dry months than in the wet months.