Scattering of quasar radiation in intercloud plasma

Three different levels of description are available to describe the interaction of electromagnetic radiation with electrons in a fully ionized plasma: when the scattering of radiation occurs by excitation of a plasmon, the collective plasma oscillation of the electrons, it is called stimulated Raman scattering; if it occurs by excitation of a heavily dampled plasmon, it is called stimulated Compton scattering, and if it occurs by excitation of individual electrons, it is called Compton scattering. The scattering rates in each case differ significantly. The physics of these mechanisms is illustrated by taking a quasar as the source of intense radiation and the hot plasma surrounding it as the scattering medium. It is concluded that, through Raman scattering, the non-thermal radio radiation equilibrates with the intercloud medium at much higher temperatures than are achievable through Compton processes. (author)