Radiowave propagation in a statistically inhomogeneous plasma

The present work investigates the propagation of a radio pulse in an unmagnetized, statistically inhomogeneous plasma causing regular refraction and anisotropic scattering. Using the framework of geometrical optics, a Fokker-Planck equation is derived and integrated within a two-moment approximation. The method allows a continuous transition from weak to strong angular scattering and yields pulse shape, pulse delay and angular broadening detected by a distant observer. The results are compared to Monte Carlo simulations and the method is applied to coronal scattering of a burst emitted close to the local plasma frequency. It is shown that the two-moment approximation reproduces many of the features found in earlier simulations (Steinberg et al. \cite{Steinberg}, Riddle \cite{Riddle2}) within a small fraction of needed computation time. Although the method was developed for solar radio bursts, it can be applied to general transport-diffusion problems due to the equivalence of geometrical optics and Hamiltonian mechanics.