Coherent Plasma Processes and the Continuum Emission in Active Galactic Nuclei

Abstract

Stimulated Raman scattering processes appear to be able to produce the typical electromagnetic continuum of an active galactic nucleus (AGN). Seed photons beat through Raman forward-scattering to create Langmuir plasma waves which can quickly accelerate electrons to Lorentz factors of 10^3^ to 10^4^. These electrons radiate their energy through Raman back- scattering off magnetic fields engendered by magnetic modulational instabilities afflicting the Langmuir waves. The frequency of emission is proportional to the square root of the ambient density, so γ-rays can be produced in the highest density regions near the central engine, with X-rays through to IR photons produced at greater distances. Both the high luminosity and broken power-law continuum characteristic of an AGN emerge from reasonable density distributions. Bremsstrahlung emission in the UV is a by-product of this mechanism and could explain the 'blue bump'. Because the electrons are continuously accelerated in this picture, a steady-state distribution arises naturally and a simple relation exists between the density of the relativistic particles which emit the radiation and the ambient plasma density which is involved in the acceleration.