A PRELIMINARY-STUDY ON LASER-TRIGGERED LIGHTNING

As a preliminary study on triggering lightning with a CO2 high-power l aser, we carried out laser-triggered discharge experiments to investig ate the necessary conditions for initiating and guiding an electrical streamer with a CO2 laser-produced plasma channel. We found the follow ing. (1) The necessary electric field for initiating a streamer with t he plasma channel depends closely on the absorbed energy for producing the plasma channel and not on the length of the plasma channel. The h igher the absorbed energy, the smaller the necessary electric field. T he minimum electric field is about 200 kV/m. (2) The necessary electri c field for guiding a streamer by the plasma channel is lower than tha t for initiating a streamer. The minimum electric field is about 170 k V/m. Furthermore, we observed the electric field at the top of a 50-m tower and the field on the ground simultaneously during 10 Japanese wi nter thunderstorms. The observed results agree with theoretical calcul ations showing that the field at the top of a 50-m tower is on average 2 orders larger than the field on the ground. We conclude that it is highly possible to trigger a lightning discharge if we shoot a CO2 las er-produced plasma channel upward through the top of a high grounded t ower under conditions of high thunderstorm electric fields.