基于北斗GEO卫星观测的桂林地区TEC空间梯度研究

Research on TEC spatial gradient in Guilin areabased on BeiDou GEO satellites observation

小尺度的总电子含量(TEC)梯度异常会显著影响区域电离层模型以及地基增强系统(GBAS)的精度。因此,为了提高区域电离层模型的准确性和GBAS导航定位的精度,深入研究小尺度的TEC空间梯度显得尤为重要。为了研究中小尺度的空间梯度,利用2019—2022年间桂林地区全球卫星导航系统(GNSS)接收机的北斗地球静止轨道(GEO)卫星数据,对中国低纬地区(23°N 107.9°~113.1°E)电离层的TEC空间梯度进行研究分析。根据3颗北斗GEO卫星对地形成的3个相邻穿刺点(从西至东,依次编号为C02,C03,C01)的TEC观测值,构成C02-C03与C03-C01两个约为300 km尺度区域(107.9°~110.3°E,110.3°~113.1°E)的TEC梯度观测。统计结果显示,C02-C03区域的空间梯度基本为西向;而C03-C01区域的空间梯度在1~4月与9~12月为东向,5~8月为西向。这表明2个相邻区域的空间梯度在季节变化上存在差异,揭示了中小尺度空间梯度具有显著的局地效应。此外,地方时差并非空间梯度事件的主要原因。在太阳活动高年,背景TEC较高,空间梯度事件更易发生。梯度事件发生率的半年变化是TEC半年异常的体现。空间梯度事件在不同地磁条件下的发生率相似。

Small-scale anomalies in total electron content(TEC)gradients can significantly affect the accuracy of regional ionospheric models and ground-based augmentation systems(GBAS).Therefore,to improve the accuracy of regional ionospheric modeling and GBAS navigation and positioning,further study on small-scale TEC spatial gradients is crucial.To investigate these gradients,data from the BeiDou geostationary Earth orbit(GEO)satellites collected by global navigation satellite system(GNSS)receivers in the Guilin area from 2019 to 2022 are used for the analysis,focusing on the TEC spatial gradients of the low-latitude region of China(23°N 107.9°~113.1°E).Based on the TEC observations from three adjacent BeiDou GEO satellite puncture points on the ground(numbered sequentially from west to east as C02,C03,and C01),two TEC spatial gradient observation areas of about 300 km in scale(107.9°~110.3°E and 110.3°~113.1°E)are established for C02-C03 and C03-C01.Statistical results show that the spatial gradient in the C02-C03 area is predominantly westward;whereas in the C03-C01 area,the spatial gradient is eastward from January to April and from September to December,and westward from May to August.This indicates that there are seasonal variations in the spatial gradients between adjacent areas,revealing a significant local effect on medium-and small-scale spatial gradients.Furthermore,local time differences are not the main cause of spatial gradients.In years of high solar activity,when the background TEC is higher,spatial gradient events are more likely to occur.The biannual variation in the occurrence rate of gradient events reflects the biannual anomaly of the TEC.The frequency rate of spatial gradient events is similar under different geomagnetic conditions.