Characterization of the effective height of the ionosphere using GPS data over East Africa, a low latitude region

Abstract

The ionospheric effective height is a very useful parameter in mapping the Total Electron Content (TEC) over a given region using the Single-Layer Model (SLM). The appropriate value of this height for East Africa that lies under low latitude region is not conclusive, and yet the SLM is continuously used in the region. This study determined the suitable height for the ever changing and dynamic ionosphere of the low latitude region of East Africa using Global Position System (GPS) data for 2014 from 10 receivers in the region. The suitable height was determined by a method that equates the TEC recorded by a satellite at an oblique elevation angle with the TEC recorded by satellite right at the zenith for a given epoch. This was supplemented with the method of coinciding pierce point. The study observed that the contribution of elevation angle of the satellite pass to the variation of mapping function value is negligible for elevation angle greater than 40o. It was observed that, the effective height of the ionosphere over the region is highly variable portraying diurnal and seasonal dependence, but also influenced by the fountain effect. The findings of the study suggest that, the suitable effective height of the ionosphere over low latitude region of East Africa ranges from 350 km to 600 km.