Solar activity dependence of total electron content derived from GPS observations over Mbarara
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Vertical total electron content (VTEC) observed at Mbarara (geographic co-ordinates: 0.60oS, 30.74oE; geomagnetic coordinates: 10.22oS, 102.36oE), Uganda, for the period 2001–2009 have been used to study the diurnal, seasonal and solar activity variations. The daily values of the 10.7 cm radio ﬂux (F10.7) and sunspot number (R) were used to represent Solar Extreme Ultraviolet Variability (EUV). VTEC is generally higher during high solar activity period for all the seasons and increases from 0600 h LT and reaches its maximum value within 1400 h–1500 h LT. All analysed linear and quadratic ﬁts demonstrate positive VTEC-F10.7 and positive VTEC-R correlation, with all ﬁts at 0000 h and 1400 h LT being signiﬁcant with a conﬁdence level of 95% when both linear and quadratic models are used. All the ﬁts at 0600 h LT are insigniﬁcant with a conﬁdence level of 95%. Generally, over Mbarara, quadratic ﬁt shows that VTEC saturates during all seasons for F10.7 more than 200 units and R more than 150 units. The result of this study can be used to improve the International Reference Ionosphere (IRI) prediction of TEC around the equatorial region of the African sector.
Total electron content , Solar ﬂux , Sunspot number , Equatorial region
Adewale, A.O., Oyeyemi, E.O., Cilliers, P.J., and Olwendo, J. Solar activity dependence of total electron content derived from GPS observations over Mbarara. Adv. Space Res., 50 (2012) 415–426. http://dx.doi.org/10.1016/j.asr.2012.05.006.