Analysis of Variation Characteristic of TEC at Kunming Region and Comparison with IRI-2020 during Descending Phase of Solar Activity
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摘要: 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。
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关键词:
- 电离层 /
- 总电子含量 /
- 变化特征 /
- 国际参考电离层-2020
Abstract: 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.-
Key words:
- Ionosphere /
- Total electron content /
- Variation characteristic /
- IRI-2020
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图 1 2016－2019年F10.7及Ap指数的变化情况
Figure 1. Variation conditions of F10.7 and Ap during 2016－2019
图 2 TEC在2016－2019年季节平均的日变化（虚线为各季节平均最高值对应的时间）
Figure 2. Diurnal variations of seasonal average of TEC during 2016－2019 (Dotted line is the time corresponding to the average maximum value of each season)
图 3 TEC日最大值和月均最大值与F10.7及Ap指数之间的相关系数（R为线性相关系数，红色直线是线性拟合结果）
Figure 3. Correlation coefficients among daily and monthly averaged peak TEC with F10.7 and Ap (R is linear correlation coefficient, and the red line is linear fitting result)
图 4 TEC观测值与IRI-2020模拟的季节平均值对比
Figure 4. Comparison of seasonal average of TEC from monitor and modeled by IRI-2020
图 5 IRI-2020对观测值的均方根偏差值在不同季节的变化
Figure 5. Variations of REMS for TEC from IRI-2020 with observation in different seasons
图 6 IRI-2020对观测值的相对偏差在2016－2019年中随季节和时间的分布
Figure 6. Daily and seasonal distributions of the relative difference of IRI-2020 with observation regardless seasons during 2016－2019
表 1 2016－2019年各季节及全年TEC最大 平均值（单位TECU）
Table 1. Seasonal and annually average peak value of TEC during 2016－2019 (unit TECU)
年 2016 2017 2018 2019 春 53.97 35.27 29.44 25.98 夏 38.36 25.35 25.02 19.7 秋 40.97 35.67 25.78 22.18 冬 41.86 23.05 21.52 16.99 全年 48.29 32.51 27.35 23.98 
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表 2 F10.7和Ap指数与峰值TEC 在不同年份 的相关系数统计值
Table 2. Statistical values of correlation coefficients among F10.7 and Ap with TEC in different years
年 F10.7与峰值TEC Ap与峰值TEC 每日 月均 每日 月均 2016－2017 0.61 0.83 0.09 0.39 2018－2019 0.08 0.04 0.19 0.62
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