Global Variations of Ionospheric Total Electron Content (TEC) Derived from GPS Global Ionospheric Maps

This paper is aimed to investigate diurnal, monthly and seasonal variation of  ionospheric total electronic content (TEC) obtained from two GPS satellites IGS and COD and to inspect mean VTEC Correlation between the two satellites by the year  of 2008. TEC is defined by the integral of electron density in a 1 m 2 column along  the signal transmission path. It is an important parameter to monitor possible space weather impacts. The processed and archived data taken from IGS and COD  satellites has been imported in to a MATLAB code which gave us the results of the  value of VTEC. Results of the two satellites revealed that, Out of the selected  equinox and solstice day’s maximum value of TEC is recorded on March 20/2008  over North and South west equator due to the maximum solar radiation reaching to  the ionosphere of the Earth. On the contrary, the Minimum peak ionospheric TEC  value is recorded on June 21/2008 over south Asia particularly Srilanka and  Bangladesh due to emission of low solar radiation. As regards to monthly variations  of ionospheric TEC, results of IGS and COD satellites show that highest mean TEC  value is recorded on March and July recorded the least peak TEC value. Results  regarding to seasonal variation also revealed that E-Season recorded maximum  TEC value and least TEC value is recorded on J-Season. The observations of the two satellites also show that the mean TEC value presents stronger solar activity sensitivity at lower-latitude bands than the middle and high latitudes. In general,  there was a very high correlation between Mean TEC value recorded by IGS and COD satellites by the year of 2008 in all low, middle and high latitudes. Keywords : IGS and COD satellites, GPS, Ionosphere, Low, middle and  high-latitudes, TEC.