Coherent Plasma Processes in Active Galactic Nuclei

Abstract

The physics of active galactic nuclei (AGN) and related objects is one of the most actively pursued areas of astrophysics. Their large inosities over the entire electromagnetic spectrum combined with extremely short time variability has stimulated a large number of astrophysicists to propose rather unconventional ideas. A variety of radiation mechanisms such as, thermal, synchrotron and Compton processes have been proposed to account for the complex continuum emission. It is only recently that the role of plasma radiation mechanisms has been shown to be of the utmost importance. It is demonstrated how a combination of the stimulated Raman and Compton scattering processes accounts for the major part of the spectrum, taking 3C273 as an example. In addition plasma mechanisms for, the heating of the emission line regions, absorption of 21 cm radiation,producing time variability on dierent time scales and pair production and annihilation are also discussed.