云地闪电通道的径向结构及光辐射特征

Radial structure and optical radiation characteristics of the cloud-ground lightning channel

为揭示云地闪电通道形成和发展过程的微观物理机制,研究了云地闪电通道的径向结构及光辐射特征。利用无狭缝高速摄谱仪,在青海高原地区实施野外观测试验。在一次云地闪电中记录到了清晰可见的通道核心,而且在通道核心的外边缘和外部发光通道之间发现一个较弱的发光区。基于光谱观测结果,对比分析了首次回击和第三次继后回击的光辐射特征。实验验证了闪电通道电晕鞘模型,确定了连接点的位置,估算得到两个回击的闪击距离分别为57 m和53 m,并证实了回击放电最强的点在连接点处。由此可推断,在回击初期,云地闪电回击通道沿径向由内到外依次为通道核心-弱发光区-电晕鞘外层,即闪电通道内沿通道径向的电荷分布是不均匀的,闪电通道的光辐射特征与放电强度和持续时间密切相关。

For revealing the microphysical mechanism of the formation and development of the cloud-ground lightning channel,the radial structure and optical radiation characteristics of the cloud-ground lightning channel were studied.We carried out field observation experiments in the Qinghai Plateau region using a slit-less high-speed spectrograph.The clearly visible channel core was recorded in a cloud-ground lightning,and a weak luminescent region was found between the outer edge of the channel core and the external luminescent channel.Based on the spectral observation results,the optical radiation characteristics of the first return stroke and the third subsequent return stroke were compared and analyzed.The corona sheath model of the lightning channel was verified experimentally,the location of the connection point was determined.The estimated striking distance of the two return strokes is 57 m and 53 m respectively,and the strongest point of the return discharge is confirmed at the connection point.It can be inferred that in the initial stage of the return stroke,the cloud ground lightning return stroke channel consists of the channel core,the weak luminescence region and the outer corona sheath from the inside to the outside,that is,the charge distribution along the radial direction of the lightning channel is uneven.The light radiation characteristics of lightning channel are closely related to the intensity and duration of discharge.