Validating the use of scintillation proxies to study ionospheric scintillation over the Ugandan region

• Comparison of SCINDA S4 and σΦσΦ scintillation parameters with IGS derived S4pS4p and |sDPR|-proxies|sDPR|-proxies.
• Moderate and strong positive correlation was observed between S4 and σΦσΦ and the proxies.
• Equatorial plasma bubbles and large scale TIDs proposed as scintillation drivers.

In this study, we compare the standard scintillation indices (S4 and σΦσΦ) from a SCINDA receiver with scintillation proxies (S4p and |sDPR||sDPR|) derived from two IGS GPS receivers. Amplitude (S4) and phase (σΦσΦ) scintillation data were obtained from the SCINDA installed at Makerere University (0.34°N, 32.57°E). The corresponding amplitude (S4p) and phase (|sDPR||sDPR|) scintillation proxies were derived from data archived by IGS GPS receivers installed at Entebbe (0.04°N, 32.44°E) and Mbarara (0.60°S, 30.74°E). The results show that for most of the cases analysed in this study, σΦσΦ and |sDPR||sDPR| are in agreement. Amplitude scintillation occurrence estimated using the S4p are fairly consistent with the standard S4, mainly between 17:00 UT and 21:00 UT, despite a few cases of over and under estimation of scintillation levels by S4p. Correlation coefficients between σΦσΦ and the |sDPR||sDPR| proxy revealed positive correlation. Generally, S4p and S4 exhibits both moderate and strong positive correlation. TEC depletions associated with equatorial plasma bubbles are proposed as the cause of the observed scintillation over the region. These equatorial plasma bubbles were evident along the ray paths to satellites with PRN 2, 15, 27 and 11 as observed from MBAR and EBBE. In addition to equatorial plasma bubbles, atmospheric gravity waves with periods similar to those of large scale traveling ionospheric disturbances were also observed as one of the mechanisms for scintillation occurrence. The outcome of this study implies that GPS derived scintillation proxies can be used to quantify scintillation levels in the absence of standard scintillation data in the equatorial regions.