Ionospheric TEC variations during the ascending solar activity phase at an equatorial station, Uganda

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 inefficient 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 diurnal, seasonal and solar activity dependence of TEC at the GPS-SCINDA (SCIntillation Network Decision Aid) station in Kampala, Uganda (geographic coordinates: latitude 0.3°N, longitude 32.6°S; and geomagnetic coordinates: latitude -9.3°, longitude 104.2°) for the years 2010 and 2011. The results obtained show that the diurnal variability in TEC at this station has a pre-dawn minimum followed by an early morning steady increase, an afternoon maximum and then a post sunset gradual reduction in TEC, with the equinoctial months depicting nighttime enhancements more prominently at around 2000 hrs UT (2300 hrs LT). Scintillation occurrence, a consequence of TEC fluctuations, was observed from about 1800 hrs UT (2100 hrs LT) to local midnight giving S4 index values above 0.4, with the equinox months recording higher occurrences than other seasons. TEC variations were also seen to exhibit solar activity dependence. The sunspot numbers and the F10.7 solar flux exhibited a good correlation with TEC recorded over the two years.

[1]  J. Mubiru,et al.  Total electron content variations in equatorial anomaly region , 2012 .

[2]  S. Radicella,et al.  Variability of total electron content over an equatorial West African station during low solar activity , 2012 .

[3]  I. Adimula,et al.  Variability of Electrojet Strength along the Magnetic Equator Using MAGDAS/CPMN Data , 2012 .

[4]  K. Groves,et al.  Study of Equatorial Ionospheric Scintillation and TEC characteristics at Solar minimum using GPS-SCINDA data , 2011 .

[5]  Bruno Bougard,et al.  Low latitude scintillations: A comparison of modeling and observations within the CIGALA project , 2011, 2011 XXXth URSI General Assembly and Scientific Symposium.

[6]  G. Seemala,et al.  Statistics of total electron content depletions observed over the South American continent for the year 2008 , 2011 .

[7]  S. Thampi,et al.  Toward prediction of L band scintillations in the equatorial ionization anomaly region , 2011 .

[8]  O. P. Singh,et al.  Diurnal and seasonal variation of GPS-TEC during a low solar activity period as observed at a low latitude station Agra , 2011 .

[9]  P. K. Purohit,et al.  Ionospheric time delay variations in the equatorial anomaly region during low solar activity using GPS , 2009 .

[10]  M. Ismail,et al.  Model validation for total Electron Content (TEC) at an equatorial region , 2009 .

[11]  D. Prasad,et al.  Temporal and spatial variations in TEC using simultaneous measurements from the Indian GPS network of receivers during the low solar activity period of 2004-2005 , 2006 .

[12]  S. Maus,et al.  Evidence for short spatial correlation lengths of the noontime equatorial electrojet inferred from a comparison of satellite and ground magnetic data , 2006 .

[13]  N. Dashora,et al.  Observations in equatorial anomaly region of total electron content enhancements and depletions , 2005 .

[14]  L. C. Gentile,et al.  Longitudinal variability of equatorial plasma bubbles observed by DMSP and ROCSAT‐1 , 2004 .

[15]  Cesar E. Valladares,et al.  Latitudinal extension of low-latitude scintillations measured with a network of GPS receivers , 2004 .

[16]  David L. Hysell,et al.  Effects of large horizontal winds on the equatorial electrojet , 2002 .

[17]  J. Klobuchar,et al.  Ionospheric electron content depletions associated with amplitude scintillations in the equatorial region , 1982 .

[18]  R. J. Moffett,et al.  lonization transport effects in the equatorial F region , 1966 .

[19]  R. Moffett,et al.  The F-layer at sunrise , 1961 .