Global GPS TEC Variability during the Solar Minimum 2008 Period

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Addis Ababa University


The International GPS Service (IGS) Working Group on Ionosphere was created in 1998. Since then, the Scienti c community behind IGS, in particular CODE, ESA, JPL and UPC, have been continuosly contributing to reliable IGS combined vertical total electron content (VTEC) maps in both rapid and nal schedules. The total electron content (TEC) is a vital and most dominant ionospheric parameter that can cause Global Positioning System (GPS) signal delays, signal degradation and in extreme cases loss of lock. This results into ine cient operations of ground and space based Global Navigation Satellite System (GNSS) applications. The study of TEC variability is, therefore, useful for GNSS users in order to minimize errors where high levels of accuracy in measurements are required. This paper presents the results of the Global GPS total electron content (TEC) variation to better understand its typical periodic variability. The Global positioning System (GPS) TEC data was obtained from the International GPS Service (IGS) station with the highest data availability in the country and used to study the diurnal, seasonal, latitudinal and longitudinal variability for 2008. The strength and characteristics of the EIA were equally analyzed. In general, the diurnal variation of TEC shows a short- lived pre-dawn minimum, a steady early morning increase, followed by an afternoon maximum and gradual fall after sunset. The seasonal variability was greatest during the equinox, moderate during the Winter solstices and least during the Summer solstices. Latitudinal study of TEC shows the clear e ect of EIA crest on the TEC variations in all the seasons. During this period of study, the so-called winter anomaly is seen near the equatorial and EIA crest region latitudes while it is found to be absent at low latitude outside the EIA crest. Evidences from our study show that the EIA was enhanced during the morning hours, suppressed during afternoon hours and a secondary enhancement was also noticed after sunset



The Solar Minimum 2008 Period