一次人工触发闪电通道光谱结构分析

用无狭缝光谱仪获得了广东地区一次人工触发闪电首次回击过程的发射光谱,同时测量了回击电流峰值为18.3kA,回击持续时间为4.5ms。发现导线部分通道的发射谱线中存在407.5,419.0,425.3和517.9nm等激发能比较高的谱线,具有强闪电通道发射光谱的谱线结构,空气部分则具有弱闪电通道的谱线结构;导线部分与空气部分的基本谱线的相对强度差别较小,强闪电特征谱线相对强度相差非常大。通过对导线部分与空气部分谱线激发能等参数的分析,发现回击开始时,导线部分先导通道还未完全消失,回击脉冲电流对先导闪电通道等离子体进行了进一步激发,增加了等离子体的温度和密度,使得导线部分具有较高激发能的谱线被完全激发,相对于空气部分407.5,419.0,425.3和517.9nm等谱线的强度有较大程度的增加,造成导线部分通道与空气通道两种不同的光谱结构。通过光谱分析,获得了闪电通道不同部分的温度、电子密度等参数,发现导线部分通道的辐射特性不同于空气通道是导线部分通道发光亮度与电流相关性较差的原因。

The Spectra Structure Characteristic of Triggered Lightning Channel

The spectra of artificially triggered lightning have been investigated by employing Slit-less Spectrograph in Guangdong region with the peak value of return stroke current was 18.3 kA,and the duration of return stroke was 4.5 ms.Through compared the spectrum of the metal and the air portion of the lightning channel,it was found the spectral line 425.3,419.0,407.5,517.9 nm of the metal channel emission had high excitation energy,which had spectrum structure of the strong lightning channel,while the air portion had the weak lightning channel spectral structure.Through compared the relative intensity of the lines,we found the difference of relative strength of the basic lines between the metal portion and air portion is small,but relative intensity of characteristic lines of strong lightning difference was very larger.Through analyzed the excitation energy and other parameters of spectral line of the metal and the air part,the reasons of different spectral structure of the metal and air part were given.When return stroke starting,the leader channel of wire portion had not completely disappeared leading to it was further stimulated by the pulse current of the return stroke.This increased the temperature and density of plasma channel,such that the spectral line of wire portion had completely excitation by higher excitation energy.Compared with air portion,the intensity of 407.5,419.0,425.3,517.9 nm had a greater increase.This result in the wire portion of the channel and the air channel had different spectral structure.Through analysis of the temperature and electron density of different channel portion which were calculated according to the information of lightning spectra,the reason why emission luminance of metal portion was different from the air portion is the radiation characteristics between the wire portion and air channel are different.