基于COSMIC数据开展全球电离层foF2建模及变化特征研究

电离层foF2是短波通信、天波超视距雷达系统所需的关键环境参数，使用2006—2014年COMSIC(constellation observing system for meteorology, ionosphere, and climate)掩星电离层数据和多项式方法，自主构建了高精度全球电离层foF2经验模型，并使用2015—2019年观测数据进行独立检验。本模型结果与建模及独立检验时段电离层foF2观测数据的相关系数分别为0.948和0.937,平均偏差分别为2.38%和3.08%,相对误差分别为11.72%和12.69%。利用该模型研究了电离层foF2时空变化特征，结果表明电离层foF2日夜变化幅度随纬度增加而变大，春秋分季期间南半球日夜变化幅度显著高于北半球，而夏季半球则远低于冬季半球。电离层foF2季节变化幅度随纬度增加而变大，夜间电离层foF2的季节变化以年特征为主，白天则包含了显著的年、半年特征，夜间季节变化幅度明显高于白天，南半球显著高于北半球。电离层foF2中纬槽现象主要出现在春秋分季夜间，经度方向四波结构主要出现在太阳活动低年和春秋分季期间。

Model and Investigate the Global Ionospheric foF2 based on the COSMIC observation

Ionospheric foF2 is great important for the short wave communication and over the horizon radar. In this study, an empirical ionospheric foF2 model was developed based on the polynomial method and the global ionospheric foF2, observed by COSMIC from 2006 to 2014. Meanwhile, the independent observations between 2015 and 2019 are used to test this empirical model. As a result, the correlation coefficients between this empirical model and the modeling and testing observations are 0.948 and 0.937. Meanwhile, the corresponding average deviations are about 2.38% and 3.08%, and the relative errors are 11.72% and 12.69%, respectively. The temporal and spatial variations of ionospheric foF2 are also comprehensively discussed by using this empirical model. The day-night variation of ionospheric foF2 increases with the increased latitude, and it is greater in the southern hemisphere than the northern hemisphere during the Spring and Autumn months. However, the diurnal variation of ionospheric foF2 in the summer hemisphere is much lower than that in the winter hemisphere. Significantly, the seasonal variation of ionospheric foF2 at night is mainly annual variation, but dominated by the annual and semiannual variations during the daytime. Moreover, the magnitude of seasonal variation is increasing with the increased latitude, with much greater values at nighttime and in the southern hemisphere. Noteworthy, the mid-latitude trough of ionospheric foF2 at nighttime usually occurs in the Spring and Autumn months, and the 4-waves structure in the longitude mainly occurs under the lower solar activity levels.