Modeling large scale leader discharges in presence of a laser-created plasma channel

Summary form only given, as follows. In a laboratory study of the feasibility of the triggering and guiding of lightning by an ultrashort pulse laser, we have shown that a plasma channel produced by such a laser can guide the propagation of a positive leader on a distance of up to 4 m, with a tenfold increase of its velocity. We have made a theoretical study of the results of these experiments with a numerical model of the positive leader propagation. Previously developed by ONERA and the University of Padova for discharges occurring in ambient air, we have adapted this model to take into account the presence of a laser-created plasma channel. We found that this could be done simply by modifying a key parameter for the leader propagation, called qL, which is the amount of charge, flowing through the leader tip from its corona, required to heat up by Joule effect a unit length of leader channel. By correctly modifying qL, the results of the numerical simulations of the laser-guided discharges were in good agreement with the experiments. The nearly correct increased leader velocity and current, as well as reduced qL and breakdown voltage have been computed. We also propose a model linking the value of qL with the negative oxygen ions density in front of the leader tip, which leads to a direct relation between the negative ions left in the laser-created plasma channel and the accelerated leader velocity.