This study developed a model of total electron content (TEC) over the African region. The TEC data were obtained from radio occultation measurements done by the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) satellites. Data during geomagnetically quiet time (Kp < 3 and Dst > −20 nT) for the years 2008–2011 and 2013–2017 were binned according to local time, seasons, solar flux level, and geographic longitude and latitude. B splines were fitted to the binned data to obtain model coefficients. The model was validated using actual COSMIC TEC data of the years 2012 and 2018. The validation exercise revealed that approximation of observed TEC data by our model produces a root mean square error of 5.02 TECU (total electron content unit). Moreover, the modeled TEC data correlated highly with the observed TEC data (r=0.93). Due to the extensive input data and the applied modeling technique, we were able to reproduce well-known TEC features such as local time, seasonal, solar activity cycle, and spatial variations over the African region. Further validation of our model using TEC measured by ionosonde stations over South Africa at Hermanus, Grahamstown, and Louisville revealed r values > 0.92 and root mean square error (RMSE) < 5.56 TECU. These validation results imply that our model can estimate TEC fairly well that would be measured by ionosondes over locations which do not have the instrument. Another element of the significance of this study is the fact that it has shown the potential of using basis spline functions for modeling ionospheric parameters such as TEC over the entire African region.

中文翻译：

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模拟从非洲地区COSMIC卫星的无线电掩星测量得出的总电子含量

这项研究建立了非洲地区总电子含量（TEC）的模型。TEC数据是通过由气象，电离层和气候（COSMIC）星座星座观测系统进行的无线电掩星测量获得的。地磁静默时间内的数据（Kp <  3和Dst  >  -根据当地时间，季节，太阳通量水平以及地理经度和纬度对2008-2011年和2013-2017年的20 nT）进行了分类。将B样条拟合到合并的数据中以获得模型系数。该模型已使用2012年和2018年的实际COSMIC TEC数据进行了验证。验证工作表明，通过我们的模型对观测到的TEC数据进行近似，得出的均方根误差为5.02 TECU（总电子含量单位）。此外，建模的TEC数据与观测到的TEC数据高度相关（r = 0.93）。由于大量的输入数据和应用的建模技术，我们能够复制众所周知的TEC特征，例如当地时间，季节性，太阳活动周期以及非洲地区的空间变化。使用由南非赫曼努斯，格拉汉斯敦和路易斯维尔上的离子探空仪测得的TEC对我们的模型进行的进一步验证显示，r值>  0.92，均方根误差（RMSE） < 5.56 TECU。这些验证结果表明，我们的模型可以很好地估计TEC，这可以通过在没有仪器的位置上的离子探空仪来测量。这项研究意义的另一个要素是事实，它表明了使用基本样条函数来模拟整个非洲地区电离层参数（如TEC）的潜力。