Efficiency of Magnetized Thin Accretion Disks in the Kerr Metric

1999/06/14 by Charles F. Gammie · 5 citations
Earth and Planetary Sciences · Physics and Astronomy · #Accretion (finance) #Accretion disc #Astrophysical Phenomena and Observations #Astrophysics #Boundary value problem #High-pressure geophysics and materials #Inflow #Kerr metric #Magnetic field #Magnetohydrodynamic drive #Magnetohydrodynamics #Mechanics #Physics #Pulsars and Gravitational Waves Research #Quantum mechanics #Rotating black hole #Schwarzschild radius #Stars #Thermodynamics #Thin disk #Torque #astro-ph

paper · pdf · doi:10.1086/312207

11 pages, 3 figures, aastex, submitted to ApJ Letters

arxiv created 1999/06/14 · openalex publication_date 1999/09/01 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05

Abstract

The efficiency of thin disk accretion onto black holes depends on the inner boundary condition, specifically the torque applied to the disk at the last stable orbit. This is usually assumed to vanish. I estimate the torque on a magnetized disk using a steady magnetohydrodynamic inflow model originally developed by Takahashi et al. I find that the efficiency can depart significantly from the classical thin disk value. In some cases > 1, i.e., energy is extracted from the black hole.

Citations

• A powerful local shear instability in weakly magnetized disks. I - Linear analysis. II - Nonlinear evolution

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