Laser-triggeredlightning discharge

Abstract

Advances in ultrafast optics in recent years have revived a keeninterest in laser-induced dielectric breakdown study. While itis widely accepted that femtosecond laser pulses with peakpowers reaching gigawatts can propagate over tens of metresunder laboratory conditions, the dynamics underlying thishighly nonlinear phenomenon is yet not fully understood.Although initial research on laser-triggered lightning wasstarted with infrared lasers, it was found that they are notsuitable to initiate lightning. Recent published literature andexperimental work favour the use of ultraviolet (UV) laser pulses asthe appropriate means for laser-induced lightning discharge. Ananalytical solution based on Maxwell's equations has beendeveloped for UV filamentation in air, arising from adynamic oscillating balance between self-focusing, diffractionand plasma defocusing. This model suggests that UV(220-420 nm) 200 ps laser pulses with a peak power ofaround 50 MW (or 12.5 mJ input energy) and a beam size of100 µm are the optimal tool to trigger outdoor lightning.The laser beam size remains relatively small (less than 0.3 mm)after a propagation distance of 200 m up into the normallycloudy and damp atmospheric conditions.