Generation of Langmuir turbulence and stochastic acceleration in laser beat wave process

Summary form only given. This paper investigates the filamentation (self-focusing) process of two co-axially propagating laser beams in a collisionless unmagnetized plasma. On account of the ponderomotive nonlinearity, two laser beams affect the dynamics of each other and cross-focusing takes place. We have derived the expressions for the laser beam intensities by using the eikonal method and the extended paraxial approximation. The initial Gaussian laser beams are found to have non-Gaussian structures in the plasma. Using the laser beam and the plasma parameters, appropriate for beat wave process, we have studied the filaments of the laser beams. Using these results, we have investigated the electron plasma wave (EPW) excitation at the beat wave frequency when the laser beams are having filamentary structures as discussed above. The excited EPW is not a plane wave; rather it has a turbulent structure. We have obtained the power spectrum of the excited beat wave (electron plasma wave) and studied the dependence of the spectral index on laser and plasma parameters. Different forms of collapsing Langmuir turbulence spectra have been observed. The stochastic electron acceleration has been studied in the presence of this Langmuir turbulence and relevance of these results to beat wave process has been pointed out.