光谱学与光谱分析, 2018, 38 (12): 3673, 网络出版: 2018-12-16   

一次空中触发闪电通道光谱分析

The Spectra Characteristic of Altitude Triggered Lightning Channel
作者单位
1 中国气象科学研究院灾害天气国家重点实验室/雷电物理和防护工程实验室, 北京 100081
2 山西省气象灾害防御技术中心, 山西 太原 030002
3 复旦大学大气科学研究院, 上海 200438
4 新疆气象灾害防御技术中心, 新疆 乌鲁木齐 830001
摘要
利用无狭缝光谱仪获得了一次空中触发闪电过程中400~660 nm的发射光谱, 对空中触发闪电小回击和上行正先导通道的发射光谱进行了分析, 讨论了人工触发闪电导线通道与空气通道光谱的差异, 发现导线段通道光谱持续了约140 ms, 而空气段通道仅持续了0.167 ms; 结合Fe, N, O等元素的电离能、 激发能, 给出了导线通道亮度强、 持续时间长的原因。 在电流强度相同的情况下, 人工触发闪电通道的导线段有更多的粒子被激发, 能产生更多的光谱辐射, 导线段通道的亮度远强于空气段, 导线段通道的光谱强度也远强于空气段; 在随后的等离子体通道消散阶段导线段闪电通道的复合反应持续时间也更长。 通过对小回击以及上行正先导导线通道上部、 下部空气段光谱结构以及通道温度等参数与广东地区自然闪电特征谱线及温度等参数的比较, 发现小回击通道光谱主要由NⅡ离子低激发态之间的跃迁组成, 具有NⅡ 444.7 nm, NⅡ 517.9 nm, NⅡ 616.8 nm等广东地区一般强度自然闪电的特征谱线。 上行正先导下部空气段通道具有高激发能的谱线开始消失, 出现了Hα, Hβ, OⅠ 615.8 nm等激发能较低的谱线, 具有闪电回击后期的光谱结构。 小回击通道以及上行正先导通道下部空气段温度分别为21 000和20 000 K, 通道温度低于自然闪电温度。
Abstract
Spectra of altitude triggered lightning channel in the range of 400~660 nm had been obtained by Slit-less spectrograph. The spectra of mini-return stroke and upward positive leader channel were analyzed. The difference of the spectra between metal and air of the lightning channel was discussed. It is shown that duration of the spectra of metal channel was about 140 ms, while the air portion channel was only 0.167 ms. The reasons why the metal channel has high brightness and long duration were given through analyzing the excitation energy and ionization energy of Fe, N, O elements. When the current intensity is same, there are more excited particles in the metal than in the air channel which leads to trigger lightning channel to generate more radiation, brighter channel and stronger spectral intensities. And what is more, the duration of the recombination processes of metal channel was also longer in the subsequent phase of dissipating the plasma channel. Through comparing the spectra structure and temperature of mini-return stroke and lower and upper air portion of positive leader channel to the natural lightning in Guangdong, it depicted that the spectra of mini-return stroke channels were mainly composed of transitions between low excited states of NⅡ ions, and had NⅡ 444.7 nm, NⅡ 517.9 nm, NⅡ 616.8 nm which were the characteristic lines of the general intensity natural lightning in Guangdong area. The spectra with high excitation energy in the lower air portion channel of upper positive leader began to disappear. The spectral with low excitation energy such as Hα, Hβ, and OⅠ 615.8 nm appeared, and had spectral structure of the late stage of lightning return stroke. The temperature of the mini-return stroke and lower air portion upward positive leader channel were 21 000 and 20 000 K, lower than natural lightning temperature.

张华明, 张义军, 吕伟涛, 张阳, 齐奇, 钱勇, 樊艳峰. 一次空中触发闪电通道光谱分析[J]. 光谱学与光谱分析, 2018, 38(12): 3673. ZHANG Hua-ming, ZHANG Yi-jun, L Wei-tao, ZHANG Yang, QI Qi, QIAN Yong, FAN Yan-feng. The Spectra Characteristic of Altitude Triggered Lightning Channel[J]. Spectroscopy and Spectral Analysis, 2018, 38(12): 3673.

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