A comparison of ionospheric scintillation proxy indices derived from low rate IGS data with the amplitude scintillation index, S4, in a low latitude region over Africa

Abstract

Ionospheric irregularities are of great concern to GNSS users due to the fact they can degrade navigation information. The detection and characterization of such irregularities has become a key research problem especially at the low latitude ionosphere where they are most abundant. In this work we make a comparison of ionospheric indices that can be used as proxies to conventional amplitude scintillation indices using data from the easily accessible IGS data network. The scintillation proxy indices are compared with the standard amplitude scintillation S4 from a dedicated scintillation receiver from a nearby station to evaluate the strengths and weakness of each proxy index.Our results show that the weaknesses and strengths of the amplitude scintillation proxies are as follows: ROTI, even though derived from GNSS phase information, corresponds well with the trend of the amplitude index S4 during the generation, evolution and decay phases of signal amplitude. The scintillation proxy derived from the L1 Signal to Noise ratio (S/N) observable (S1) is shown to have a useful correspondence with S4 index.