Research on laser triggered lightning for practical use

从1995年开始，在日本福井对冬季雷暴进行了激光触发闪电的实地实验。经过激光系统、雷暴监测装置和控制系统的多项技术发展后，第一次激光触发闪电在1997年实现。这是激光触发闪电原理实验的证明，随后是技术开发研究计划。本研究的目的是提高闪电触发的成功率。为了实现这一目标，本文提出了一种产生激光等离子体通道的新方案，并对该方案进行了研究，该方案通过产生强电离和弱电离等离子体通道来触发和引导闪电放电。该方法中使用的等离子体通道称为混合等离子体通道。该方法利用细长的弱电离等离子体通道，将触发的闪电放电引导到足够高的高度，使其能够自行延伸到云层。在本课题的研究过程中，明确了等离子体通道引导放电的条件。利用CO_2激光器、UV激光器（Nd: YAG激光辐射的四次谐波）和1 mv脉冲发生器进行了室内实验。结果表明，在雷雨云环境电场下，等离子体密度必须达到10^<13> cm^<-3>才能稳定地引导等离子体放电。这种等离子体状态可以通过IJV辐射电离大气来实现。根据研究结果，可以认为CO_2与紫外激光辐射和多聚焦反射镜的组合是下一代野外实验系统，有望成为实用系统。除了激光系统外，闪电预测和自动触发系统将提高系统性能，因为它们可以调整等离子体产生的时间窗口，从而有效地触发闪电。基于这些基本技术，可以设计一种新的激光触发闪电现场测试实验。少

Starting 1995 field experiments of laser-triggered lightning had been conducted on winter thunderstorms in Fukui, Japan. After a number of technical developments on laser system, thunderstorm monitoring devices and control system, the first laser-triggered lightning was achieved in 1997.This was a proof of the principle experiment of laser-triggered lightning which was followed by a technical development research program reported here. The target of the study was to improve success rate of triggering lightning. To approach the target, a new scheme of producing laser plasma channel for effective lightning induction was proposed and investigated in this study where strongly and weakly ionized plasma channels are generated to trigger and guide lightning discharges. The plasma channel used in the method is called Hybrid plasma channel. The method uses elongated weakly ionized plasma channel that guides the triggered lightning discharge high enough that it can extend to clouds by itself.In … More the course of the present research project, conditions for the plasma channel to guide discharge have been clarified. The laboratory experiments had been conducted with use of a CO_2 laser, an UV laser (the fourth harmonic of Nd : YAG laser radiation) and a 1-MV impulse generator. It was concluded that a plasma density of 10^<13> cm^<-3> was required to firmly guide an electrical discharge along the plasma under an ambient electric field of thunderclouds. This plasma condition can be achieved by ionizing atmosphere by the IJV radiation.Based on the results of the study, it can be considered that a combination of CO_2 and UV laser radiation and a reflecting mirror with multiple focusing points is a system for the field experiment of the next generation and hopefully a practical system.Beside the laser system, a lightning prediction and auto-triggering system would improve the system performance since they can adjust the temporal window for plasma generation to effectively trigger lightning. Based on these elemental technologies, a new experiments for field test of laser triggered lightning can be designed. Less