Abstract This study evaluates the performance of Ionospheric and Solar proxy indices for the International Reference Ionosphere extended to the Plasmasphere (IRI-Plas 2017/SPIM) model in predicting the Total Electron Content (TEC) over the East African equatorial region during the high (2014) and low (2018) solar activity periods of solar cycle 24. TEC is derived from Global Positioning System (GPS) installed at Addis Ababa (adis, Geog: 9.04° N; 38.77° E and Geom: 5.28° N; 112.6° E) and Ambo (aboo, 8.99° N; 37.81° E and Geom: 5.43° N; 111.6° E). The results show that the SPIM model with all options of proxies overestimates the observed TEC for all seasons at both stations during the low solar activity year of 2018. However, in some cases, the SPIM model with IG index option showed a better agreement during the low solar activity period, while it displayed poor performance at both stations during the high solar activity period. The SPIM model with SSN proxy option was better in estimating seasonal and annual VTECs during the high solar activity period, while it was poor during low solar activity period over the study region. Results also showed that the SPIM model with Lyman-α proxy option performed poor for the seasonal and annual prediction of VTECs with maximum RMSE of 19 TECU during the high and low solar activity years. A good agreement is observed between the observed-VTEC and SPIM model with SSN proxy option. The correlation coefficients (r) between observed-VTEC and model output using SSN as proxy was good (r = 0.9566 at adis and 0.9494 at aboo stations) during the high solar activity year of 2014. Moreover, the model with all proxy options displayed a strong correlation (r > 0.96 at adis and r > 0.95 at aboo stations) during low solar activity year. Overall, the results in this study revealed that the SSN proxy option of the SPIM model was better in estimating VTEC during high solar activity period, while SPIM with the IG index was better during low solar activity period over the East African equatorial region. Such performance evaluation of a global model for different inputs/options is important for the space weather community at the study region where little or no ground based instruments are found.

中文翻译：

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太阳活动周期 24 期间东非赤道地区 IRI-Plas 2017 模型的电离层和太阳代理指数评估

摘要 本研究评估了扩展到等离子层的国际参考电离层 (IRI-Plas 2017/SPIM) 模型的电离层和太阳代理指数在预测高 (2014) 期间东非赤道地区的总电子含量 (TEC) 方面的性能。 ) 和太阳活动周期的低 (2018) 太阳活动期 24. TEC 来自安装在亚的斯亚贝巴的全球定位系统 (GPS)（阿迪斯，Geog：9.04° N；38.77° E 和 Geom：5.28° N；112.6° E ) 和安博（阿布，北纬 8.99°；东经 37.81°，吉奥姆：北纬 5.43°；东经 111.6°）。结果表明，带有所有代理选项的SPIM模型高估了2018年低太阳活动年两个站点所有季节的观测TEC。但是，在某些情况下，带有IG指数选项的SPIM模型在2018年期间表现出更好的一致性。低太阳活动期，而在高太阳活动期间，它在两个站点都表现出较差的性能。带有SSN 代理选项的SPIM 模型在估计太阳高活动期的季节性和年度VTEC 方面较好，而在研究区域的低太阳活动期则较差。结果还表明，带有 Lyman-α 代理选项的 SPIM 模型在高太阳活动和低太阳活动年份对 VTEC 的季节性和年度预测表现不佳，最大 RMSE 为 19 TECU。观察到的 VTEC 和带有 SSN 代理选项的 SPIM 模型之间观察到了很好的一致性。在 2014 年高太阳活动年期间，观测到的 VTEC 与使用 SSN 作为代理的模型输出之间的相关系数 (r) 良好（在 adis 处为 0.9566，在 aboo 站处为 0.9494）。此外，在低太阳活动年期间，具有所有代理选项的模型显示出很强的相关性（adis 的 r > 0.96 和 aboo 站的 r > 0.95）。总体而言，本研究的结果表明，在东非赤道地区，SPIM 模型的 SSN 代理选项在估计太阳活动高期间的 VTEC 方面更好，而具有 IG 指数的 SPIM 在太阳活动低期间更好。对于不同输入/选项的全球模型的这种性能评估对于研究区域的空间天气界很重要，因为那里几乎没有或没有发现地面仪器。而在东非赤道地区太阳活动较低的时期，具有 IG 指数的 SPIM 更好。对于不同输入/选项的全球模型的这种性能评估对于研究区域的空间天气界很重要，因为那里几乎没有或没有发现地面仪器。而在东非赤道地区太阳活动较低的时期，具有 IG 指数的 SPIM 更好。对于不同输入/选项的全球模型的这种性能评估对于研究区域的空间天气界很重要，因为那里几乎没有或没有发现地面仪器。