The Rate of Ionospheric Total Electron Content Index (ROTI) as a Proxy for Nighttime Ionospheric Irregularity Using Ethiopian Low-Latitude GPS Data

The correlation between the rate of TEC index (ROTI) and amplitude scintillation index S-4 for low-latitude region is analyzed using data collected from a Global Positioning System (GPS) scintillation monitoring receiver installed at Bahir Dar Ethiopia for the periods of 2012 and 2013. The analysis was done for selected quiet and disturbed days based on Kp and Dst values. Generally speaking, the ROTI and S-4 are nicely correlated almost in all cases we considered. It is also found that there is a good consistency between the temporal variations of ROTI with scintillation activity under different ionospheric conditions. ROTI has a high correlation with scintillation index on geomagnetically disturbed days. These results demonstrated the feasibility of using ROTI derived from GPS observations recorded by common non-scintillation GPS receivers to characterize ionospheric scintillation. Based on the correlation results, we have mapped the spatial variations of ionospheric scintillation over Ethiopia from a chain of ten non-scintillation GPS receivers. The mapped ROT index has clearly illustrated the spatial propagation of ionospheric scintillation over the considered area.