African Equatorial GPS Scintillations during the Minimum and Ascending Phases of Solar Cycle 24

Abstract

This study characterizes African equatorial scintillations at L-band frequency during the minimum and ascending phases of solar cycle 24. Three years' (2009-2011) of amplitude scintillation data from three African equatorial GPS stations namely; Lagos (3.48oN, 3.27oE, mag. lat: 3.04oS), Nigeria; Nairobi (1.30oS, 36.80oE, mag. lat: 8.03oS), Kenya; and Kampala (0.30oN, 32.50oE, mag. lat: 9.26oS), Uganda were used for the investigation. We grouped the data on daily, monthly, seasonal, and yearly scales at three levels of scintillation (weak (0.3<=S4<0.4), moderate (0.4<=S4<0.7), and intense (S4>=0.7)), and adopted three data cut-off criteria. Scintillations exhibit daily trend of occurrence during the hours of 1900 LT-0200 LT, with higher levels being localized within the hours of 2000-2300 LT. Generally, highest scintillation occurrences were recorded during the equinoxes, and the trend increased with solar activity. Specifically, scintillations were almost absent during June Solstices of the period under investigation, and it appears as if January is a non-scintillation month over equatorial Africa. On a scintillation active day, the number of satellites available to the receiver's view reduces as the duration of observation reduces. These results may support the development of future models that could provide real-time predictability of African equatorial scintillations, with a view to supporting the implementation of GNSS-based navigation in Africa.