Magnetized Laser-Plasma Interactions in High-Energy-Density Systems: Parallel Propagation

Abstract: We investigate parametric processes in magnetised plasmas, driven by a large-amplitude pump light wave. Our focus is on laser-plasma interactions relevant to high-energy-density (HED) systems, such as the National Ignition Facility and the Sandia MagLIF concept. We derive dispersion relations for three-wave interactions in a multi-species plasma using Maxwell's equations, the warm-fluid momentum equation and the continuity equation. The application of an external B field causes right and left polarised light waves to propagate with differing phase velocities. This leads to Faraday rotation of the polarisation, which can be significant in HED conditions. Raman and Brilllouin scattering have modified spectra due to the background B field, though this effect is usually small in systems of current practical interest. We identify a scattering process we call stimulated whistler scattering, where a light wave decays to an electromagnetic whistler wave ($\omega \lesssim \omega_{ce}$) and a Langmuir wave. This only occurs in the presence of an external B field, which is required for the whistler wave to exist. We compute the scattered wavelengths for Raman, Brillouin, and whistler scattering.