The reflection of the electromagnetic waves from the ionosphere with the impedance modified by internal gravity waves

We have studied the influence of a smoothly inhomogeneous disturbance of the impedance of the ionosphere caused by internal gravity waves present in the reflection zone of propagating VLF electromagnetic waves. The case has been considered when the amplitude of impedance disturbance is commensurable with its regular value. The problem is solved with an auxiliary function satisfying the Dirichlet zero condition at the boundary. The Hertz potential formula has been obtained for the grazing propagation of electromagnetic waves.