Resonant absorption in a self-consistent density profile at moderate intensities

A model for the nonlinear resonant absorption of an electromagnetic wave in an inhomogeneous collision-dominated plasma at moderate intensities is proposed. The wave propagation equations are numerically solved in the time-independent self-consistent density profile. A density step appears at the critical point, and a surface wave develops which tends to enhance the absorption. Extensions of the model to collisionless situations are given when the damping can be conveniently described by some phenomenological self-consistent collision frequency. Finally the effect of a plasma expansion across the critical density is briefly discussed.