基于IGS电离层TEC格网的扰动特征统计分析

电离层总电子含量（TEC）是研究空间天气特性的重要参量，通过分析电离层TEC，可以了解空间环境的变化特征.利用IGS提供的1999—2016年全球电离层TEC格网数据，按照地磁纬度将全球划分为高、中、中低、低磁纬四个区域，计算不同区域的电离层扰动；利用大量统计数据选取电离层扰动事件的判定阈值，分析电离层扰动与太阳活动、时空之间的关系；计算电离层扰动指数与地磁活动之间的相关系数.结果显示:电离层扰动与太阳活动变化具有较强的正相关特性.在太阳活动低年，电离层扰动事件发生的概率约为1.79%，在太阳活动高年发生扰动的概率约为10.18%.在空间分布上，无论是太阳活动高年还是低年，高磁纬地区发生扰动事件的概率均大于其他磁纬出现扰动事件的概率.计算得到的中磁纬和中低磁纬地区电离层扰动指数与全球地磁指数Ap的相关系数分别为0.57和0.56，说明电离层扰动指数与Ap具有较好的相关关系；高磁纬电离层扰动指数与Ap的相关系数为0.44；低磁纬扰动指数与Ap的相关系数为0.39.以上结果表明，不同区域电离层扰动与全球地磁指数Ap的相关性不同，测定区域地磁指数可能会提高与电离层扰动的相关性. 

Statistical Analysis of the Ionosphere Disturbance Based on the IGS Global Ionosphere TEC Map

The ionospheric Total Electron Content (TEC) is an important parameter for space weather research and helps to understand the changes of space environment. In this paper, 18 years' IGS ionospheric TEC grid data from 1999 to 2016 are employed to calculate the ionosphere disturbance over four different areas, including high, middle, mid-low and low magnetic latitude. The thresholds of the ionosphere disturbance are selected according to the statistic results on different TEC grid point, and the relationship between ionosphere disturbance and other physical elements, such as solar activity, geomagnetic latitudes and geomagnetic activities, are studied. The results show that the ionosphere disturbances are closely related with the solar activities. The occurrence rate of TEC disturbance event's is about 1.79% at lower solar activity, while the rate increases to 10.18% at higher solar activity. The high latitude areas always have higher ionosphere disturbance rate than other areas. The correlation coefficient between TEC disturbance index of middle and mid-low magnetic latitude and geomagnetic index Ap are 0.57 and 0.56 respectively. The coefficients in high and low magnetic latitude are 0.44 and 0.39 respectively. There are different correlations between ionosphere disturbance of different areas and global geomagnetic index Ap, and using regional geomagnetic index could help improving the correlations between geomagnetic index and ionospheric disturbance.