In the present paper, we reviewed some linear and non-linear interactions which possibly occur when intense microwave beam emitted from Solar Power Satellite (SPS) propagates through the ionosphere down to the ground. In the linear regime, effects are discussed about the Faraday rotation, refraction, scintillation, and particle collision on the microwave beam propagation through the ionosphere. As to the non-linear interactions, three-wave coupling, self-focusing of microwave beam, and plasma perturbation by the Ponderomotive force are briefly reviewed. Since the theoretical analysis of these nonlinear phenomena is generally difficult, numerical simulations play an important role for the understanding of the interactions. In the present paper, we particularly focused on the three-wave coupling and the density perturbation by the Ponderomotive force by showing some simulation results obtained in computer experiments with plasma particle model.