Radiation from a magnetic ring source encircling a drifting plasma column

The problem of radiation from a magnetic ring source encircling a plasma column drifting uniformly with a relativistic velocity is treated. In order to know the effect of the motion of the plasma on the radiation, first the radiation pattern for the ring source is investigated. From the numerical examples it is found that the lobe of the radiation pattern shifts in the direction of the plasma motion. Secondly the properties of the surface waves, which propagate along the plasma column, are investigated in detail. It is shown that the dispersion curve exhibits the characteristic natures which do not appear in the case of stationary plasma; in the case of drifting plasma the surface waves are generally excited to higher frequency extent, having no cut-off frequency.