On the Reflection and Refraction of Hydromagnetic Waves at the Boundary of Two Compressible Gaseous Media.

The reflection and refraction of a hydromagnetic plane wave at a plane boundary between two semi4nfinite homogeneous media of infinite electrical conductivity are discussed when a uniform magnetic field is present It is shown that, owing to the compressibility of the two media, one must expect any incident plane wave to give rise to three types of reflected waves and three types of refracted waves; these six waves can be either real or imaginary, depending on circumstances. In the particular case when the prevailing magnetic field is perpendicular to the plane boundary, a detailed analysis f the laws of reflection and refraction is given.