Abstract. We report on the longitudinal, local time and seasonal occurrence of equatorial plasma bubbles (EPBs) and L band (GPS) scintillations over equatorial Africa. The measurements were made in 2010, as a first step toward establishing the climatology of ionospheric irregularities over Africa. The scintillation intensity is obtained by measuring the standard deviation of normalized GPS signal power. The EPBs are detected using an automated technique, where spectral analysis is used to extract and identify EPB events from the GPS TEC measurements.Overall, the observed seasonal climatology of the EPBs as well as GPS scintillations in equatorial Africa is adequately explained by geometric arguments, i.e., by the alignment of the solar terminator and local geomagnetic field, or STBA hypothesis (Tsunoda, 1985(Tsunoda, , 2010a. While plasma bubbles and scintillations are primarily observed during equinoctial periods, there are longitudinal differences in their seasonal occurrence statistics. The Atlantic sector has the most intense, longest lasting, and highest scintillation occurrence rate in-season. There is also a pronounced increase in the EPB occurrence rate during the June solstice moving west to east. In Africa, the seasonal occurrence shifts towards boreal summer solstice, with fewer occurrences and shorter durations in equinox seasons. Our results also suggest that the occurrence of plasma bubbles and GPS scintillations over Africa are well correlated, with scintillation intensity depending on depletion depth. A question remains about the possible physical mechanisms responsible for the difference in the occurrence phenomenology of EPBs and GPS scintillations between different regions in equatorial Africa.

[1] The International Reference Ionosphere (IRI) model has been widely adopted as the international standard for specifying ionospheric parameters. An evaluation on the performance of the IRI model (version 2007) over Nsukka, Nigeria (Geographic: 6.87 N, 7.38 E; Geomagnetic: 8.47 N, 81.07 E) is presented in this work. We compare Total Electron Content (TEC) values for year 2010 from the IRI model with corresponding TEC data from the SCINDA (Scintillation Network Decision Aid) GPS receiver installed at Nsukka so as to evaluate the performance of the model over the Nsukka region. Given the proliferation of dual-frequency GPS receivers over the African continent, data from these equipment is proposed for use in TEC modeling over the continent together with the IRI model. Knowledge on the performance of the IRI over various regions of the continent will inform the extent to which the model will be used. The development of more accurate TEC maps find useful applications in enhancing the extent to which ionospheric influences on radio signals (as in single frequency GPS receivers) are corrected. Our results show very good diurnal correlations (above 0.88) between the IRI-TEC predictions and the GPS-TEC measurements for the days examined, and so reveal the potential of the IRI model as a good candidate for an enhanced TEC modeling over the African region.

The development of astronomy and space science in Africa has grown significantly over the past few years. These advancements make the United Nations Sustainable Development Goals more achievable, and open up the possibility of new beneficial collaborations.

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