太阳活动下降年昆明地区TEC变化特征与IRI-2020模拟比较分析

Analysis of Variation Characteristic of TEC at Kunming Region and Comparison with IRI-2020 during Descending Phase of Solar Activity

利用昆明低纬度测站(24.7°N,102.9°E,磁纬15.1°N)2016-2019年的观测数据和最新版的国际参考电离层(IRI-2020)模拟结果,对昆明地区电离层总电子含量(TEC)在太阳活动下降年期间的变化特征及与模型输出进行对比研究。结果表明,昆明TEC存在明显的春秋高值、夏冬低值的半年异常;白天高值、夜间低值的日变化特点突出,日峰值出现在06:30-08:00 UT(约13:00-15:00 LT);TEC随太阳活动减弱而明显下降,年平均峰值在2016-2019年分别为48,33,27,24 TECU;日峰值TEC与F10.7存在显著相关,月均值相关系数达到0.86,而与Ap指数则表现为弱相关;IRI-2020能较好地模拟昆明地区TEC的季节变化,但与观测值存在较大差异;均方根偏差值多集中在2~15 TECU,相对偏差百分比值主要在–85%~50%范围变化。对比结果表明IRI-2020的预测精度仍有待提高。

The variation characteristics of ionospheric Total Electron Content(TEC)recorded at the low latitude station,Kunming(24.7°N,102.9°E,geomagnetic latitude 15.1°N)China,during the descending phase of solar activity in 2016-2019 and its comparison with the output by the latest version model of the International Reference Ionosphere(IRI-2020)have been studied and discussed in this paper.The results show that the TEC at Kunming has an obvious semi-annual anomaly,with the high values during the spring and autumn seasons while the low values during the summer and winter seasons.The diurnal variation of TEC is prominent with that the high value levels in daytime and the low value levels in nighttime,and the daily peak TEC at Kunming appears mainly between 06:30-08:00 UT(about 13:00-15:00 LT).The magnitudes of the average annual TEC decrease obviously as the solar activity weakens,with the values of 48,33,27 and 24 TECU during the year of 2016-2019,respectively.The correlation analysis results indicate that there is a significant correlation between the peak TEC and the F10.7,and with a correlation coefficient of 0.86 between the monthly value of peak TEC and F10.7,but shows weak correlation between the peak TEC and the Ap index during the descending phase of solar activity in 2016-2019.The comparative results reveal that the latest version of International Reference Ionosphere could simulate well the seasonal variation of TEC at Kunming.However,there is a big difference between the output value and the observed result.The values of the root mean square deviation from model prediction and observational results are mostly between 2~15 TECU,and the relative deviation percentage values are mainly between–85%and 50%,which manifest that the prediction accuracy of the model IRI-2020 still needs to be improved in the application of forecast.