Mapping Ethiopian ionosphere using ground-based GPS TEC.

The objective of this paper is to map regional ionospheric Total Electron Content (vTEC) using Global Positioning System (GPS) data from 10 different GPS receiver sites in Ethiopia, to capture ionospheric phenomena (such as storm effect, Equatorial Ionization Anomaly (EIA) distribution) and to see the hourly evolution of the ionosphere for a single stormy day. GPS based TEC data acquired on 17 March 2013 was used for diurnal and anomaly observations and 17 March 2015 storm-day (storm intensity, Dst = −222nT) data was used for storm-time vTEC mapping. For regional ionosphere characterization, we converted slant TEC (sTEC) to equivalent vTEC. This is done by applying the ionospheric thin shell model. For smooth latitude and longitude boundary interpolation inverse distance weighted (IDW) interpolation technique was used. The map was produced with spatial resolution of 0:80 by 0:80 latitude and longitude, respectively. The result shows significant diurnal dependence of TEC. It also exhibits an equatorial ionospheric anomaly, characterized by minimum vTEC associated to lower latitudes and maximum vTEC over the higher latitude in the region. We noted that the equatorial anomaly distribution is pronounced during several of the early afternoon hours (13:00Lt, 14:00 LT and 15:00LT). The maps showed the enhancement of vTEC up to 85TECU during 17 March 2015 storm compared to the depletion up to 40TECU on 19 March 2015. [ABSTRACT FROM AUTHOR]