基于COSMIC掩星精密定轨数据的等离子体层电子含量研究

等离子体层是日地环境重要的组成部分.本文利用COSMIC掩星精密定轨数据经处理后得到的podTec文件获取等离子体层电子含量（PEC）对等离子体层进行研究.将podTec数据进行处理后获得的PEC（pod-PEC）和IRI-Plas经验模型提供的PEC （IRI-PEC）进行对比，发现pod-PEC与IRI-PEC符合得较好.在低（0°—20°）、中（20°—50°）、高（50°—90°）修正地磁纬度带下，分析了COSMIC在太阳活动极大年（2014年）3，6，9和12月的pod-PEC，得到如下结论:PEC随着纬度升高而逐渐减少，且3，9月PEC在中低纬关于磁赤道的南北对称性较好，6月北半球各纬度带的PEC明显高于南半球同一纬度带的值，而12月情况则完全相反，南半球中纬的PEC甚至会等于北半球低纬的PEC值；PEC在白天高而晚上低，高纬地区的PEC昼夜变化不明显；PEC具有明显的季节性.对于北半球，一年中PEC最大值出现在春季，冬秋季次之，夏季最低，具有明显的年度异常现象. 

Study of Plasmaspheric Electron Content Based on Precise Orbit Determination Data of COSMIC Radio Occultation

Plasmasphere is one of the most important parts in the solar-terrestrial environment. With the intention of plasmasphere study, podTec file from the satellite Precision Orbit Determination (POD) data of COSMIC (Constellation Observing System for Meteorology, Ionosphere, and Climate) occultation is used to obtain Plasmaspheric Electron Content (PEC). After data processing, PEC information from podTec (pod-PEC) is compared with the PEC provided by IRI-Plas model (IRI-PEC), and their values are found to have good consistency. pod-PEC data from COSMIC of March, June, September and December in 2014 of maximum solar activity are used to obtain PEC in low (0°—20°), middle (20°—50°) and high (50°—90°) modified dip (modip) latitude. Following conclusions are obtained. PEC decreases with the increase of latitude. The north-south symmetry of PEC about the magnetic equator in low and middle latitudes is better in March and September, and PEC in all latitudes of the northern hemisphere is significantly higher than that in the same latitudes of the southern hemisphere in June. However, even the PEC in the mid-latitudes of the southern hemisphere is equal to the PEC in the low latitudes of the northern hemisphere in December. The PEC value in the daytime is higher than that at night, and the diurnal variation of PEC in high-latitude area is not obvious. The PEC maximum value appears in the spring of the northern hemisphere, followed by winter and autumn, and the minimum occurs in summer, which shows an obviously annual anomaly.