Hydromagnetics of Advective Accretion Flows around Black Holes: Removal of Angular Momentum by Large-scale Magnetic Stresses
Abstract
We show that the removal of angular momentum is possible in the presence of large-scale magnetic stresses in geometrically thick, advective, sub-Keplerian accretion flows around black holes in steady state, in the complete absence of α-viscosity. The efficiency of such an angular momentum transfer could be equivalent to that of α-viscosity with α = 0.01-0.08. Nevertheless, the required field is well below its equipartition value, leading to a magnetically stable disk flow. This is essentially important in order to describe the hard spectral state of the sources when the flow is non/sub-Keplerian. We show in our simpler 1.5 dimensional, vertically averaged disk model that the larger the vertical-gradient of the azimuthal component of the magnetic field is, the stronger the rate of angular momentum transfer becomes, which in turn may lead to a faster rate of outflowing matter. Finding efficient angular momentum transfer in black hole disks via magnetic stresses alone, is very interesting when the generic origin of α-viscosity is still being explored.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- July 2015
- DOI:
- 10.1088/0004-637X/807/1/43
- arXiv:
- arXiv:1505.01281
- Bibcode:
- 2015ApJ...807...43M
- Keywords:
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- accretion;
- accretion disks;
- galaxies: active;
- ISM: jets and outflows;
- magnetohydrodynamics: MHD;
- X-rays: binaries;
- Astrophysics - High Energy Astrophysical Phenomena;
- General Relativity and Quantum Cosmology;
- Physics - Fluid Dynamics
- E-Print:
- 14 pages including 8 figures