Absorption of Radiation in the Emission Line Regions

Inverse bremsstrahlung or the free-free absorption is believed to be the main mechanism of absorption of the nonthermal quasar radiation in the emission line regions. The absorption rate is found to change significantly when the inhomogeneous nature of the plasma and the nonlinear effects associated with the high intensity of the electromagnetic radiation are taken into account. A new process of resonance absorption comes into play when the electromagnetic radiation obliquely incident on a plasma density gradient excites plasma oscillations at the critical density surface.