Research on laser triggered lightning for practical use

从1995年开始，在日本福井的冬季雷暴上进行了激光触发闪电的野外试验。经过对激光系统、雷暴监测装置和控制系统的多次技术开发，1997年实现了第一个激光触发闪电。这是对激光触发闪电原理实验的证明，随后报道了一项技术开发研究计划。这项研究的目标是提高触发闪电的成功率。为了接近目标，提出并研究了一种产生有效雷电感应的激光等离子体通道的新方案，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。该方法使用细长的弱电离等离子体通道来引导触发的闪电放电到足够高的高度，使其能够自行延伸到云中。在…中进一步明确了等离子体通道引导放电的条件。实验采用CO_2激光器、紫外光激光器(四次谐波激光)和1 MV脉冲发生器进行。得出的结论是，在雷云环境电场下，需要10^&lt；13；cm；-3；-3的等离子体密度才能牢固地引导沿等离子体的放电。根据研究结果，可以认为CO_2和UV激光辐射相结合的多焦点反射镜是下一代野外实验的系统，有望成为一种实用的系统。除了激光系统外，闪电预报和自动触发系统还可以调整等离子体产生的时间窗口，从而有效地触发闪电。在这些基本技术的基础上，可以设计一种新的激光触发闪电现场测试实验。较少

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