Variability of Ionospheric Total Electron Content over some American, Asian and African Equatorial Stations

Abstract

Abstract The Earth’s ionosphere is a highly dynamic region, which interferes with radio wave propagation in the shortwave and L-band frequency. In this study, total electron content (TEC) data derived from the International Global Navigation Satellite System (GNSS) Service (IGS) over four stations were used to investigate the diurnal, seasonal and solar activity effects on ionospheric TEC variability. The stations with their respective geomagnetic latitudes are: DGAR (-16.89o), MBAR (-10.22o), BOGT (-3.80o) and AHUP (12.23o). Analysis of the diurnal variation showed that, across all the stations for all seasons, the nighttime values (ranging between 13 and 143%) are higher than the daytime values (ranging between 7 and 60%). The nighttime values showed two peaks in the range 35–143% during the post-midnight hours and 36–74% during the post-sunset hours. The diurnal-seasonal variation does not exhibit a regular pattern in any station. At three of the four stations considered, highest TEC variability was observed during low solar activity and lowest during high solar activity, particularly during the nighttime. On the average, considering all the seasons together, minimum TEC variability (7%) was observed at MBAR during March Equinox of the year of moderate solar activity and maximum (143%) was observed at AHUP during December Solstice of the year of low solar activity.