On the stability and evolution of relativistic radiation tori: equations and speculations

Abstract

Equations describing the general relativistic evolution of hypothetical radiation-supported tori in active galactic nuclei are presented and discussed. Equations describing global, non-axisymmetric perturbations of radiation tori are also given. The role of instabilities in transporting angular momentum and heat is examined and some simple prescriptions for use in numerical calculation of the secular evolution of these structures are suggested. In particular, if a sufficiently optically thick torus evolves to become dynamically unstable then a gyrotropic, marginally stable convection zone with angular momentum constant on isentropes may be established. Goldreich–Schubert–Fricke instability should be adequate to maintain a radiative zone in a barotropic state.