2018年8月磁暴期间北斗GEO卫星电离层TEC时空变化分析

基于北斗GEO卫星独有的静地特性，本文利用其观测数据提取电离层TEC进行磁暴期间电离层TEC时空变化研究。同时利用全球电离层格网图GIM值进行试验对比，结果表明：北斗GEO卫星提取的TEC与GIM模型值变化趋势一致，并且前者可更有效地监测电离层的细微扰动变化。在此次磁暴发生期间，亚太地区电离层TEC变化及扰动响应特征在纬度方向差异明显。其中南北半球较高纬度区域，电离层TEC在磁暴主相阶段主要表现为正响应扰动，而赤道及北半球较低纬度区域，电离层TEC在磁暴主相及恢复相阶段均产生了强度更大、持续时间更长的正响应扰动。结合现有研究，认为造成此次电离层异常扰动的激励因素主要为东向快速穿透电场的增强及热层中性成分的变化。试验结果也证明了GEO卫星可以精准有效地监测在磁暴发生时电离层TEC的变化规律及不同空间位置处TEC产生的扰动响应特征。

Spatial-temporal variations of the ionospheric TEC during the August 2018 geomagnetic storm by BeiDou GEO Satellites

Considering the unique geostationary characteristic of the Beidou GEO satellites, the spatial-temporal variations of ionospheric TEC during the geomagnetic storm are studied by using GEO Satellites. The global ionospheric map (GIM) is adopted as an experimental comparison. The results show that the TEC derived from the GEO satellite observations is consistent with the GIM model. Moreover, the GEO TEC can more effectively reflect subtle variations of the ionosphere. The variation and disturbance response characteristics of the ionospheric TEC are significantly different in the latitude direction during the geomagnetic storm in the Asia-Pacific region. The ionospheric TEC mainly presents positive response disturbance during the main phase of the storm in the higher latitudes of the northern and southern hemispheres, while the equatorial and lower latitude areas in the northern hemisphere both produce positive response disturbance with greater intensity and longer duration during the main phase and the recovery phase of the storm. Based on the existing studies, we think that the excitation factors of the anomalous ionospheric disturbance are the enhancement of the eastward prompt penetration electric field and neutral composition change of the thermosphere. In this paper, the experimental results suggest that GEO satellite observations can accurately and effectively monitor the anomalous variation of ionospheric TEC and the disturbance response characteristics generated by TEC at different space locations during geomagnetic storms.