中国地区电离层TEC暴扰动研究

Study on the ionospheric TEC storms over China

电离层总电子含量(TEC)是空间天气研究和监测预报的重要参量.本文引入了电离层TEC扰动指数DI,对青岛等6个台站的DI数据进行分析,选取DI>0.35(DI≤-0.30)作为正(负)相电离层TEC扰动的强度标准,并以连续6h及以上的DI满足该值来判定电离层TEC暴扰动事件.对电离层TEC暴扰动事件的统计分析表明,在地方时日落后至子夜前为发生高峰时段,正(负)相暴扰动事件平均持续时间约为10.9h(10.5h),正相暴发生率以冬季为多,夏季为少,而负相暴则以夏季略高.发现位于赤道异常驼峰区的广州站和位于高中纬度的海拉尔站比典型中纬地区的北京站电离层TEC暴扰动更易发生,且低纬地区以正相暴扰动为主.分析表明,约有70%的电离层TEC暴扰动伴随着有地磁扰动,但是电离层TEC暴扰动并不完全由地磁扰动所引起,强烈气象活动等局地环境因素也可能对电离层TEC暴扰动有着重要影响.

Ionospheric TEC is an important parameter for space weather research, monitoring and forecasting. This paper introduces the ionospheric TEC disturbance index （DI） that is the relative deviation of the vertical TEC. By investigating the DI data at Qingdao and other five GPS observations in China the value of DI〉0.35 （DI≤-0.30） has been selected as the criterion of positive （negative） ionospheric TEC disturbed state, and the ionospheric TEC storm event is identified when the DI values satisfy above criterion in six consecutive hours or more. Statistical analysis of the TEC storm events has shown that the section between sunset and midnight is the occurrence peak period of the TEC storm. The average duration is about 10.9 h （10.5 h） for the positive （negative） ionospheric TEC storm. For the positive storm, the occurrence is higher in winter and lower in summer. For the negative storm, the occurrence is highest in summer. The ionosphere at GUAN （lies in the ionospheric equatorial anomaly crest）and HLAR （a high-midlatitude station） are more disturbed than BJSH （a typical mid latitude station）. And the positive TEC storm event is dominant in low latitudes. It is shown that about 70% of TEC storm events accompany with the geomagnetic disturbances. But the ionospheric TEC storms are not entirely caused by the geomagnetic disturbances, and the intense weather events and other local environmental factors may also play important roles in the ionospheric TEC disturbances.