LAUSR

Past experiments have shown an ionization front propagation in the millimeter-wave whose intensity was one order lower than the critical intensity of breakdown. Propagation in such a low-intensity region is inexplicable by past theories because no mechanism can enhance ionization sufficiently in the precursor region ahead of bulk plasma. This study examines a new propagation theory incorporating excited neutral particles. The excited neutral particles are carried to the precursor region repeating radiative decay and reabsorption of a photon created by that decay process. Ionization occur with collisions of an electron and that excited neutral particle. One-dimensional computations were conducted for various power densities of an incident beam to reproduce propagation. The obtained propagation velocities were around 50% of experimental values for quenching frequencies lower than 10^6 /s.