基于多分辨率GPS层析技术的电离层暴时LSTID特征研究

Ionospheric storm-time LSTID characteristics using multi-resolution GPS tomography

利用GPS电离层层析技术探测电离层已经有了数十年的发展,特别在电离层暴时有着独特的优势.文章基于一种多分辨率层析算法,并结合美国东西部地区部分GPS地面数据对2015年3月16日-17日出现的电离层暴进行重构.首先,借助独立的测高仪数据验证多分辨率层析技术对电子密度反演的精度结果,同时也证实了电离层暴时多分辨率层析算法的适用性.其次,通过对美国东部地区2015年3月17日磁扰动最强烈时段的电离层重构,检验由磁暴引起的大尺度电离层行扰(large-scale travelling ionospheric disturbance,LSTID)的存在,并利用总电子含量(total electron content,TEC)数据分析此次电离层行扰的水平特征.同时,通过与非相干散射雷达(incoherent scatter radar,ISR)观测值的对比,借助反演得到的电子密度剖面信息讨论电离层行扰在垂向上的特征.结果表明:此次LSTID的波长为1 200 km左右,周期为50~60 min,以350~400 m/s的波速向西南方向传播,并且电离层行扰(travelling ionospheric disturbance,TID)的垂向电子密度具有较可靠的精度.

The use of GPS ionospheric tomography to detect the ionosphere has been developed for decades, particularly during the period of ionospheric storms. In this paper, a multi-resolution tomographic algorithm based on GPS data is proposed to reconstruct the ionosphere over the eastern and western USA on March 16-17, 2015. First, the accuracy of inversions using the multi-resolution tomographic algorithm is analyzed by comparing with independent ionosonde data. It is confirmed the feasibility of the multi-resolution tomographic algorithm during the magnetic storm period. Secondly, the occurrence of a large-scale travelling ionospheric disturbance (LSTID) caused by the ionospheric storm is verified from the reconstructed ionospheric images in the eastern USA on March 17, 2015. The horizontal characteristic ofthis LSTID is also discussed with inverted TEC estimates. Finally, the vertical feature of the LSTID is studied by comparing the inverted electron density profile and the incoherent scatter radar (ISR) scan. The results show that the wavelength of LSTID is about 1 200 km, the period is 50-60 min, and it propagates to the southwest direction at a wave speed of 350-400 m/s, and the accuracy of the vertical electron density of the TID is reliable.