Coupling of Magnetohydrodynamic to Electromagnetic Waves at a Plasma Discontinuity. II. The Nonpropagating Field

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Abstract
The coupling of magnetohydrodynamic to electromagnetic waves at a plasma‐vacuum boundary is considered for the case in which the angle of incidence of the magnetohydrodynamic wave falls outside the cone for radiation. When this occurs, the electric and magnetic fields transmitted into the vacuum region decay exponentially in space in the direction of the normal to the boundary. The phase velocity in a direction parallel to the plane boundary has a value between the Alfvén velocity and the velocity of light, depending upon the angle of incidence of the magnetohydrodynamic wave. The magnitude, frequency, and angular dependence of the transmitted electric and magnetic fields are explored. In one situation a phenomenon called a transmission resonance is found to occur; i.e., the ratio of the transmitted to the incidence electric field becomes very large over a restricted range of angles of incidence.