2000/10/20 by Nir J. Shaviv · 1 citation
Engineering · Physics and Astronomy · #Boundary (topology) #Boundary value problem #Cosmology and Gravitation Theories #Eddington luminosity #Electron #Instability #Plane (geometry) #Radiative transfer #Scattering #Solar and Space Plasma Dynamics #Thermal Radiation and Cooling Technologies #astro-ph
paper · pdf · doi:10.1086/319428
18 Pages, 7 figures, uses emulateapj5.sty, accepted to ApJ
arxiv created 2000/10/20 · openalex publication_date 2001/03/10 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/06
Atmospheres having a significant radiative support are shown to be intrinsically unstable at luminosities above a critical fraction Γ crit ≈ 0.5-0.85 of the Eddington limit, with the exact value depending on the boundary conditions. Two different types of absolute radiation-hydrodynamic instabilities of acoustic waves are found to take place even in the electron scattering-dominated limit. Both instabilities grow over dynamical timescales and both operate on nonradial modes. One is stationary and arises only after the effects of the boundary conditions are taken into account, while the second is a propagating wave and is insensitive to the boundary conditions. Although a significant wind can be generated by these instabilities even below the classical Eddington luminosity limit, quasi-stable configurations can exist beyond the Eddington limit due to the generally reduced effective opacity. The study is done using a rigorous numerical linear analysis of a gray plane-parallel atmosphere under the Eddington approximation. We also present more simplified analytical explanations.