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

Abstract

In this study, we compare the standard scintillation indices (S4 and σΦ) from a SCINDA receiver with scintillation proxies (S4p and sDPR||) derived from two IGSGPS receivers. Amplitude (S4) and phase (σΦ) scintillation data were obtained from the SCINDA installed at Makerere University (0.34°N, 32.57°E). The corresponding amplitude (S4p) and phase (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, σΦ and sDPR|| are in agreement .Amplitude scintillation occurrence estimated using the S4p are fairly consistent with the standard S4, mainlybetween17:00UT and 21:00UT, despite a few cases of over and underestimation of scintillation levels by S4p. Correlation coefficients between σΦ and the 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 PRN2, 15, 27 and11asobserved 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 scin-illation occurrence.TheoutcomeofthisstudyimpliesthatGPSderivedscintillationproxiescanbeused to quantifyscintillationlevelsintheabsenceofstandardscintillationdataintheequatorialregions