GPS derived amplitude scintillation proxy model: A case over a low latitude station in East Africa

Ionospheric scintillation is quite a common phenomenon over the low latitude regions and in East Africa it is often monitored using measurements from the SCIntillation Network Decision Aid (SCINDA) receivers. The SCINDA receivers over East Africa are characterized by long base lines and data paucity thus offering a huge challenge in the long term scintillation characterization over the region. To alleviate this challenge, we implemented the use of data from the dual frequency GPS receivers of the IGS network in combination with data from the SCINDA receiver at Nairobi, Kenya to model amplitude scintillation. The data from the SCINDA (geographic coordinates 36.808(o)E, -1.274(o)N) and GPS (geographic coordinates 36.893(o)E, -1.221(o)N) receivers were used to derive S4 index and its proxy respectively. Comparison of the S4 and its proxy revealed a high correlation coefficient between the two datasets. Scintillation occurrence was observed to peak during the equinox months of March-April and September-October. The vernal equinox was observed to have less frequent scintillation events than the autumnal equinox. The local time (LT) scintillation occurrence shows a peak between 20:00 LT and 23:00 LT. An empirical hybrid amplitude scintillation occurrence probability model was then developed. The results show that the model predicted values were in good agreement with the observed amplitude scintillation occurrence probabilities from the SCINDA receiver. This observation suggests that the model is a useful tool for approximating amplitude scintillation occurrence probabilities at L-band frequencies at African equatorial latitudes.