Global GPS TEC Variability during the Solar Minimum 2008 Period
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Date
2015-07
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Addis Ababa University
Abstract
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
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The Solar Minimum 2008 Period