The nonuniform laser heating of a plasma has been identified as contributing to a source of enhanced ion acoustic fluctuations that occur during the initial phase of the laser plasma interaction process. The resulting temperature gradient creates a heat flux that is responsible for the excitation of unstable ion waves, which propagate predominantly in a plane perpendicular to the laser beam axis. We have used the results of weak turbulence theory to estimate the stationary level and the angular distribution of these fluctuations. These are shown to have a dramatic effect on the Brillouin scattering reflectivity. The importance of this ion waves enhancement mechanism for the short (10 ps) laser pulse interaction experiments is discussed.

• Received 14 July 1994

DOI:https://doi.org/10.1103/PhysRevE.50.4005