Modeling the triggering of streamers in air by ultrashort laser pulses

The physical processes involved in the triggering of ionization waves (stre amers) by ultrashort laser pulses, focused in air at 350 Torr and in a unif orm electric field, are investigated by means of a one-dimensional (1-D) nu merical model. The model describes the interaction of the laser pulse with air and takes into account many of the reactions in the laser-created plasm a as well as the radial expansion of the plasma. Consequences of the model are that the threshold electric field for the appearance of streamers is an increasing function of the delay between the laser pulse and the electric field pulse and a decreasing function of the laser energy. Also, it appears that the electron temperature, the plasma density and radius, and the cond uction of heat across the plasma boundaries play major roles in the capacit y of the laser-created plasma to trigger streamers. The results of the mode l are compared with the available experimental data.