Mean-field modes in a waveguide channel in the presence of vertical disturbances

An analysis is made of a situation in which random perturbations cause the natural modes of a regular waveguide channel to interact with one another and to produce only a slight change in the propagation characteristics; this is the case of vertical perturbations extending across the guiding layer. The mean field in the channel with the random perturbations is described by the Dyson equation, and the absorption of the normal modes due to scattering by the perturbations is examined. It is noted that this type of situation can arise in near-polar regions, where inhomogeneities extending along the magnetic field lines are practically vertical.