Relativistic effects in the parametric excitation of low-frequency electrostatic waves

The parametric excitation of low-frequency electrostatic waves in a homogeneous plasma is analyzed for the case in which the electrons can acquire relativistic velocities in the linearly polarized pump wave. A dispersion relation is derived for a homogeneous plasma. This relation is pertinent to both astrophysics and laser fusion. Analysis of the resulting relation shows that for power levels which are readily attained with modern lasers, relativistic effects can become governing and can lead to the excitation of new types of low-frequency (..omega..less than or equal to..omega../sub e/) waves.