依据光谱研究闪电回击通道核心的特征参数

闪电回击通道核心中的大电流及其强电磁辐射是引发多种雷电灾害的主要根源。随着现代科技的飞速发展，闪电防护工作显得越为重要。为了完善闪电防护系统，需要从描述闪电回击通道核心的特征参数入手深入研究闪电通道形成和发展过程的微观物理机制。截至目前，光谱观测是获取闪电通道核心特征参数的最佳手段。2015年夏天在青海高原地区的野外试验中，利用由高速摄像机作为记录系统组装的无狭缝光栅摄谱仪，结合快天线地面电场测量仪，记录到一次包括四个回击的云地闪电放电过程的光谱以及与之同步的快电场变化信息。依据光谱，结合等离子体理论计算得到闪电回击通道核心的电导率。在此基础上，应用闪电电动力学模型计算了闪电回击速度、峰值电流、贯穿通道核心的电磁场以及通道核心单位长度的峰值功率等特征参数。结果表明，回击速度在(1.2～2.3)×108 m·s-1的范围内；贯穿回击通道核心的轴向电场、径向电场和磁感应强度的最大值分别在(1.42～1.74)×105 V·m-1，(8.22～9.99)×108 V·m-1和(1.51～2.83) T的范围内。当闪电回击的峰值电流在(7.52～24.05) kA的范围内时，回击通道核心的峰值功率在(0.63～1.92)×109 W·m-1的范围内。另外，分析了电导率、起始电场峰值、回击速度和峰值电流与峰值功率之间的相关性，结果发现峰值电流和峰值功率具有良好的线性关系。研究结果可为探索闪电回击通道形成和发展过程的微观物理机制提供参考依据。

Study on the Characteristic Parameters of Lightning Return Stroke Channel Core Based on Spectroscopy

High current and intense electromagnetic radiation in the lightning return stroke channel core are the leading causes of many lightning disasters. With the rapid development of modern science and technology, lightning protection is becoming more and more important. In order to perfect the lightning protection system, it is necessary to investigate the microscopic physical mechanism of the lightning channel formation and development from the characteristic parameters describing the channel core. Up to now, spectral observation is the most effective means to obtain the lightning channel core characteristic parameters. In a field experiment on the Qinghai Plateau in China in the summer of 2015, a slit-less grating spectrometer assembled by a high-speed camera as a recording system was used, combined with a fast antenna ground electric field measuring instrument, the spectra of a cloud-to-ground discharge process including four return strokes and the synchronous fast electric field change information were recorded. According to the spectrum and plasma theory, the conductivity of the lightning return channel core is calculated. On this basis, the lightning electrodynamics model is used to calculate the lightning return stroke velocity, peak current, electromagnetic field across the return stroke channel core and peak power per unit length of the channel core. The results show that the return stroke velocity is in the range of (1.2～2.3)×108 m·s-1, and the maximum values of the axial electric field, radial electric field and magnetic induction intensity across the return stroke channel core are in the range of (1.42～1.74)×105 V·m-1，(8.22～9.99)×108 V·m-1 and 1.51～2.83 T, respectively. When the peak current is in the range of 7.52～24.05 kA, the peak power of the return stroke channel core is in the range of (0.63～1.92)×109 W·m-1. In addition, the correlations between the electrical conductivity, the initial electric field peak value, the return stroke velocity and the peak current and the peak power are analyzed, it is found that the peak current and peak power has a good linear relationship. The results can provide a reference for further exploring the microscopic physical mechanism of the formation and development of the lightning return stroke channel.