全球电离层TEC格网时空变化特性分析

卫星导航定位中,电离层延迟是影响用户实时定位精度的重要因素之一。利用全球电离层格网(global ionosphere maps,GIM)提供电离层延迟改正是较为常用的方法,而GIM格网的精度受限于地面GNSS(global navigation satellite system)跟踪站的分布密度。利用区域内少量或1个GNSS跟踪站建立实时区域电离层总电子含量(total electron content,TEC)模型,生成高精度的实时区域电离层格网,为用户提供区域电离层延迟改正显得尤为重要。基于CODE(Center for Orbit Determination in Europe)分析中心2016-2018年995 d的GIM格网数据,分析了相邻格网点TEC的变化范围以及不同时间间隔同一格网点TEC的变化范围。结果表明,GIM在经度方向上分辨率为5°变化的均值范围为0.2~1.0 TECU,在纬度方向上分辨率为2.5°变化的均值范围为0.4~1.4 TECU,在经度和纬度分辨率均小于1°时,电离层TEC的变化小于1.0 TECU;1 h内同一格网点电离层TEC的变化均值约为1.28 TECU,30 min内同一格网点电离层TEC的变化小于1.0 TECU。该研究为小范围内(半径小于100 km)实时区域电离层TEC模型的建立及电离层格网的时间适用范围提供了有效的数据支撑和理论验证,同时对区域电离层TEC时空变化的研究、电离层TEC预报、电离层异常监测和磁暴监测等具有一定的参考意义。

Analysis of Temporal and Spatial Variation Characteristics of Global

The correction of ionospheric delay is one of the important factors affecting the real-time positioning accuracy of satellite navigation users. It is a common method to provide ionospheric delay correction by using global ionosphere maps(GIM). The accuracy of GIM is often limited by the distribution density of GNSS tracking stations on the ground. Hence, it is especially important to establish a real-time regional ionospheric total electron content(TEC) model by using one or few GNSS tracking stations, and to generate a real-time regional ionosphere map, which provides users with regional ionospheric delay corrections. In this contribution, GIM grid data of 995 days from 2016 to 2018 provided by the Center for Orbit Determination in Europe(CODE) is adopted to analyze the TEC variations between some adjacent grid points and the TEC variations after different time intervals at a same grid point. The results show that the mean value of GIM variations with a 5° longitude interval ranges from 0.2 to 1.0 TECU, and that with a 2.5° latitude interval ranges from 0.4 to 1.4 TECU. The variation of ionospheric TEC is less than 1.0 TECU when the variation of longitude and latitude is within 1°. The mean variation of ionospheric TEC at a same grid point within 1 hour is about 1.28 TECU, and that within 30 minutes is less than 1.0 TECU. This contribution provides effective experiment verification and data support of the establishment of real-time regional(within 100 km) ionospheric TEC model, along with its applicable temporal and spatial range. Furthermore, this contribution is also significant to the researches on temporal and spatial variations of ionospheric TEC, ionospheric TEC prediction and monitoring of ionospheric anomalies and magnetic storms.