One more explanation of superluminal motion

Abstract

A model in which stimulated Raman scattering produces superluminal motion in extragalactic radio sources is examined. The scattering medium studied is a plasma whose position, density, and temperature determine the rate and angle of scattering. When the radiation from a stationary and constant source is scattered from a stationary plasma, a halo is formed around the source. It is found that the plasma must have the characteristics of the emission-line regions and the intercloud medium in order to Raman scatter the radiation. Because the scattering is dependent on polarization, the rotation of the electric vector along the direction of the apparent motion of a radio source may be estimated.