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Total electron content at equatorial and low-, middle- and high-latitudes in African longitude sector and its comparison with IRI-2016 and IRI-PLAS 2017 models
Advances in Space Research ( IF 2.6 ) Pub Date : 2020-07-22 , DOI: 10.1016/j.asr.2020.07.013
Aghogho Ogwala , Emmanuel Olufemi Somoye , Sampad Kumar Panda , Olugbenga Ogunmodimu , Eugene Onori , Sunil Kumar Sharma , Daniel Okoh , Oluwole Oyedokun

Ionosphere plays crucial role in satellite communication as well as the modern space-based positioning, navigation and timing applications. Progressive exploitation of ground and space-based observations across the African region has relatively strengthened the understanding and modeling of spatiotemporal ionospheric variations over the territory. However, it is also equally important to understand the latitudinal behaviour of ionosphere over the African longitude that would reinforce the ionospheric delay error modelling practices for an improved radio communication along the satellite pass. Hence, the aim of this research is to investigate the diurnal, seasonal and latitudinal variations of global positioning system derived total electron content (GPS-TEC) and to assess the performance of the recent version of empirical international reference ionosphere (IRI-2016) and plasmaspheric IRI (IRI-PLAS 2017) models during the ascending phase of solar cycle 24 (2012). The study is also supported by the integrated ionospheric TEC (IONO-TEC) extracted from the Digisonde observations in the vicinity of GPS receiver locations. The 3 GPS stations considered in this study are at a) an equatorial/ low-latitude location Federal University of Technology, Yola (FUTY; 9.35°N, 12.50°E, 4.91°S dip), b) a mid-latitude location Ankara (ANKR; 39.89°N, 32.76°E, 57.62°N dip), and a high-latitude location Tromso (TRO1; 69.66°N, 18.94°E, 78.17°N dip) in the northern hemisphere. Observations show the magnitude of TEC generally decreases with increasing latitude. While the average diurnal maximum of GPS-TEC at equatorial and low-latitude follow an almost equal level of magnitude during March and September equinoxes, the observations at middle and high latitude stations presents the highest magnitudes during the September equinox. Moreover, we noticed obvious higher magnitude of GPS-TEC than IONO-TEC at the three stations suggesting the discrepancies could be corresponding to the topside modeling and plasmaspheric contributions. The other prominent feature is the pattern of diurnal TEC being dome shaped at middle and high latitude locations whereas the equatorial and low latitude location manifested a noon bite-out characteristic in the IONO-TEC, IRI-2016, and IRI-PLAS outcomes. The comparative analysis of IRI-2016 and IRI-PLAS 2017 estimated TEC with the GPS-TEC show a clear overestimation of IRI-PLAS 2017 outcomes irrespective of seasons and latitudinal locations whereas the IRI-2016 outcomes either overestimated or underestimated the GPS-TEC. Hence, this study reveals that IRI-2016 performs better predictions compared to IRI-PLAS 2017 at all the three latitudinal locations. Such a latitudinal comparison across the African-European longitudinal sector may complement towards the efforts for improving the regional as well as global ionospheric model performances.



中文翻译:

赤道和低、中、高纬度非洲经度扇区的总电子含量及其与IRI-2016和IRI-PLAS 2017模型的比较

电离层在卫星通信以及现代天基定位、导航和授时应用中起着至关重要的作用。对整个非洲地区地面和天基观测的逐步开发,相对加强了对该地区时空电离层变化的理解和建模。然而,了解电离层在非洲经度上的纬度行为也同样重要,这将加强电离层延迟误差建模实践,以改进沿卫星通道的无线电通信。因此,这项研究的目的是调查昼夜,全球定位系统得出的总电子含量 (GPS-TEC) 的季节性和纬度变化,并评估最新版本的经验国际参考电离层 (IRI-2016) 和等离子体层 IRI (IRI-PLAS 2017) 模型在上升阶段的性能太阳周期 24 (2012)。该研究还得到了从 GPS 接收器位置附近的 Digisonde 观测中提取的综合电离层 TEC (IONO-TEC) 的支持。本研究中考虑的 3 个 GPS 站位于 a) 位于约拉联邦理工大学的赤道/低纬度位置(FUTY;北纬 9.35°,东经 12.50°,倾角 4.91°),b) 中纬度位置安卡拉(ANKR;39.89°N、32.76°E、57.62°N 倾角)和北半球的高纬度位置特罗姆瑟(TRO1;69.66°N、18.94°E、78.17°N 倾角)。观测表明,TEC 的大小通常随着纬度的增加而减小。虽然赤道和低纬度地区 GPS-TEC 的平均昼夜最大值在 3 月和 9 月的春分期间遵循几乎相同的震级水平,但中高纬度站的观测在 9 月的春分期间呈现出最高的震级。此外,我们注意到在三个站点上 GPS-TEC 的震级明显高于 IONO-TEC,这表明差异可能与上部建模和等离子层贡献相对应。另一个突出的特征是昼夜 TEC 在中高纬度地区呈圆顶状,而赤道和低纬度地区在 IONO-TEC、IRI-2016 和 IRI-PLAS 结果中表现出中午咬合特征。IRI-2016 和 IRI-PLAS 2017 估计的 TEC 与 GPS-TEC 的比较分析表明,无论季节和纬度位置如何,IRI-PLAS 2017 的结果都明显高估,而 IRI-2016 的结果要么高估了要么低估了 GPS-TEC。因此,这项研究表明,与 IRI-PLAS 2017 相比,IRI-2016 在所有三个纬度位置上的预测效果更好。这种跨越非洲-欧洲纵向部门的纬度比较可以补充改善区域和全球电离层模型性能的努力。这项研究表明,与 IRI-PLAS 2017 相比,IRI-2016 在所有三个纬度位置上的预测效果更好。这种跨越非洲-欧洲纵向部门的纬度比较可以补充改善区域和全球电离层模型性能的努力。这项研究表明,与 IRI-PLAS 2017 相比,IRI-2016 在所有三个纬度位置上的预测效果更好。这种跨越非洲-欧洲纵向部门的纬度比较可以补充改善区域和全球电离层模型性能的努力。

更新日期:2020-07-22
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