Solar activity dependence of total electron content derived from GPS observations over Mbarara

Vertical total electron content (VTEC) observed at Mbarara (geographic co-ordinates: 0.60 degrees S, 30.74 degrees E; geomagnetic coordinates: 10.22 degrees S, 102.36 degrees E), 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 (F-10.7) 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-F-10.7 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 F-10.7 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. (C) 2012 COSPAR. Published by Elsevier Ltd. All rights reserved.