Scattering of Supraluminous Plasma Waves by Inhomogeneities

The far‐field electromagnetic radiation produced when a field of supraluminous longitudinal plasma oscillations is incident on a localized inhomogeneity in the thermal plasma density is calculated. The plasma is assumed collisionless and is composed of stationary ions and thermal electrons. The calculation makes use of the thermal equilibrium spectrum of supraluminous waves (with phase velocities greater than the speed of light), which do not Landau damp. The generation and maintenance of this supraluminous spectrum is discussed elsewhere. Upon inserting numerical values for typical laboratory plasmas and also for a typical astrophysical radio source, such as the Crab nebula, it is demonstrated that the phenomenon is completely negligible in the laboratory but can be important in astrophysical systems.