TRANSIENT VARIATIONS OF IONOSPHERIC SCINTILLATIONS AND TOTAL ELECTRON CONTENT OVER A TERRESTRIAL POINT WITHIN EQUATORIAL ANOMALY REGION

Abstract

The monitoring of Ionospheric Scintillation and variability of Total Electron Content TEC over a terrestrial point within equatorial anomaly region has been achieved by using the NovAtel GSV 4000B GPS-SCINDA system at Akure (7.3°N, 5.2°E), Nigeria. This system is capable of tracking up to 14 GPS satellites simultaneously. The dual frequency signals obtained from the GPS satellites have been analyzed to study the ionospheric variations in terms of Total Electron Content (TEC) as well as the Scintillation index (S4) for the period from January 2007 to December 2009. Diurnal and seasonal variations of Total Electron Content as well as the ionospheric scintillation activity within the equatorial anomaly region were examined. The diurnal variation of TEC showed pre-dawn minimum for a short period of time, followed by a early morning increase and then reached maximum value between 14:00UT and 16:00 UT. TEC maximizes during Equinox months (March, April, September, October), and minimizes during the December Solstice (November, December, January, February), with intermediate values during June Solstice (May, June, July, August), showing a semiannual variation. The semiannual variation of TEC was asymmetry with maximum in Spring Equinox. The average value for TEC in 2007, 2008 and 2009 were 48.34, 42.89 and 45.64 TECU respectively while the average of Scintillation index (S4) for each of the years was 0.103. The influence of solar activity on VTEC was investigated by taking the correlation coefficients between VTEC, FI0.7cm radio flux index and sunspot numbers. The range of solar flux variation during the period of observation is very limited, there is high positive correlation (Correlation Coefficient 0.61) between daytime peak TEC and the solar FlO.7 flux.