Coupling of Magnetohydrodynamic to Electromagnetic and Acoustic Waves at a Plasma-Neutral Gas Interface

Abstract

The coupling of magnetohydrodynamic waves to electromagnetic and sound waves at a plane interface between a plasma and a neutral gas is considered for arbitrary direction of the incident wave vector and for the constant external magnetic field lying either in the plane of incidence or perpendicular to it. The relations between the angle of incidence, reflection, and transmission, the ratio of the field amplitude transmitted or reflected to the corresponding amplitude incident, and the energy coupling coefficients are calculated. An incident fast magnetoacoustic mode generates a sound wave with energy coupling coefficient of the order of the ratio of the speed of sound to the Alfvén speed when this ratio is small. An incident slow magnetoacoustic mode generates a sound wave with energy coupling coefficient of the order of unity and an electromagnetic wave with energy coupling coefficient of the order of the ratio of the speed of sound to the speed of light.