Patterns of GPS-TEC variation over low-latitude regions (African sector) during the deep solar minimum (2008 to 2009) and solar maximum (2012 to 2013) phases

Yekoye Tariku

doi:10.1186/s40623-015-0206-2

Abstract

Due to the unique geometry of the geomagnetic fields near the magnetic equator and low-latitude regions, the satellite communication system in the African sector is strongly influenced by the effects resulting from the accumulation of electrons in their ionosphere. Hence, this paper investigates the patterns of the vertical total electron content (VTEC) variation detected by the Global Positioning System (GPS) over low-latitude regions during a very low (2008 to 2009) and a high solar activity (2012 to 2013) phases. The study has been carried out by considering eight ground-based dual-frequency GPS receivers installed recently at different regions in Ethiopia. In this work, the diurnal, monthly, and seasonal variations in the GPS-VTEC have been analyzed. It has been found that the diurnal variability of VTEC has shown minimum values at around 0300 UT (0600 local time (LT)) and maximum values nearly between 1000 and 1300 UT (1300 and 1600 LT) during both the low and the high activity phases. Moreover, the maximum and minimum of monthly mean hourly VTEC values are observed in October and July, respectively, during both the low (2009) and the high solar activity (2012) phases. It has also been depicted that seasonal mean hourly VTEC values have shown maxima and minima in the March equinox and the June solstice, respectively, during both the low and the high solar activity phases.

Highlights

Ionosphere is the ionized region of the Earth’s upper atmosphere where there are sufficient number of free electrons that can largely affect the propagation of radio waves
Diurnal variation of Global Positioning System (GPS)-vertical total electron content (VTEC) The results of the diurnal variation of GPS-VTEC are shown in Figures 2, 3, 4, and 5
We have described the diurnal, monthly, and seasonal VTEC variation over Ethiopia during both the low (2008 to 2009) and the high (2012 to 2013) solar activity phases by considering eight GPS receivers installed recently at different regions of the country

Summary

Introduction

Ionosphere is the ionized region of the Earth’s upper atmosphere where there are sufficient number of free electrons that can largely affect the propagation of radio waves. Acting as a dispersive medium, the ionosphere has great influence on the satellite navigation and communication This influence is directly proportional to the density of free electrons which could change the phase and strength of electromagnetic radio frequency waves. Due to the unique geometry of the geomagnetic fields, these effects are more pronounced near the magnetic equator and low-latitude regions such as the African regions In such regions, the satellite communication system is largely affected by the effects resulting from the accumulated electrons in their ionosphere. The African sector, in general, has the largest landmass under the equatorial anomaly strip, with an ionosphere that is characterized with complex electrodynamic structures that are not yet well understood Perhaps, this could be largely due to the sparse results of ionospheric studies from the continent

Methods

Results

Conclusion