电离层层析辅助等离子体泡的TEC空间梯度研究

TEC spatial gradient resulted from plasma bubbles with ionospheric tomography

在严重的电离层活动时,发生的极端电离层扰动会对GNSS地基增强系统(Ground-based Augmentation Systems, GBAS)的用户构成完好性威胁,例如中国低纬地区出现的等离子体泡现象。本文针对等离子体泡造成的TEC空间梯度展开研究,提出了一种电离层层析辅助研究等离子体泡造成的TEC空间梯度的方法。首先,通过多分辨率电离层层析成像技术重构中国及周边中低纬地区在2017-09-08T12:00—17:00UT扰动最强烈时段的电离层层析图像,发现该时段内中国低纬地区出现电子密度耗竭的等离子体泡现象;其次,利用短基线双站法和时间步长法两种方法计算等离子体泡附近区域TEC空间梯度;最后,结合两者进行比较研究,验证了较大的TEC空间梯度往往存在于等离子体泡的侧壁周围,如本文在14:06UT出现在香港空域附近的最大TEC空间梯度为133.16 mm/km。同时还可以看出:层析反演的电离层图像不仅能直观地分析等离子体泡的三维电子密度分布,还可以帮助发现TEC空间大梯度产生的原因。

Extreme ionospheric disturbances,such as plasma bubbles at low latitudes in China,pose an intact threat to GNSS Ground-based Enhancement System(GBAS)users during severe ionospheric activity.In this paper,the TEC spatial gradient caused by these plasma bubbles is studied,and an ionospheric tomography assisted method is proposed to study the TEC spatial gradient caused by plasma bubbles.Firstly,the multi-resolution ionospheric tomography technology is used to reconstruct the ionospheric tomography results of China and its surrounding middle and low latitudes during the strongest period of 12:00−17:00UT disturbance on September 8,2017.It is found that the plasma bubble phenomenon of depleted ionospheric electron density occurred in China’s low latitudes during this period.Secondly,the TEC spatial gradient caused by plasma bubble is calculated by short baseline station-pairs method and time step method according to the inversion TEC image.Finally,a comparative study is conducted combining the two to verify that a large TEC spatial gradient often exists around the side wall of the plasma bubble.For example,the maximum TEC spatial gradient near Hong Kong airspace at 14:06UT on September 8th is 133.16 mm/km.It is also found that the inverted images can not only provide 3D electron density distributions of the bubbles,but also help explore the underlying mechanism resulting in large TEC gradients.