SPATIOTEMPORAL EVOLUTION OF PARAMETRIC-INSTABILITIES DRIVEN BY SHORT LASER-PULSES - ONE-DIMENSIONAL ANALYSIS

The spatiotemporal evolution of parametric instabilities such as stimu lated Raman scattering and stimulated Brillouin scattering is studied analytically, within the framework of a one-dimensional model. New sol utions of the model equations are found that illustrate the evolution of forward, sideward, and backward instabilities. The evolution of ins tabilities that are initiated by fluctuations within the plasma has tw o distinct phases. The first phase is characterized by exponential fun ctions, whereas the second phase is characterized by Bessel functions. For times that are shorter than the time taken for the leading edge o f the laser pulse to cross the plasma, near-forward instabilities domi nate. For longer times near-sideward instabilities dominate. (C) 1996 American Institute of Physics.