Daniel Proga and Mitchell C. Begelman 2003 ApJ 592 767 doi:10.1086/375773
Daniel Proga1 and Mitchell C. Begelman1,2
Show affiliationsWe report on the second phase of our study of slightly rotating accretion flows onto black holes. We consider magnetohydrodynamical (MHD) accretion flows with a spherically symmetric density distribution at the outer boundary but with spherical symmetry broken by the introduction of a small, latitude-dependent angular momentum and a weak radial magnetic field. We study accretion flows by means of numerical two-dimensional, axisymmetric, MHD simulations with and without resistive heating. Our main result is that the properties of the accretion flow depend mostly on an equatorial accretion torus that is made of the material that has too much angular momentum to be accreted directly. The torus accretes, however, because of the transport of angular momentum due to the magnetorotational instability (MRI). Initially, accretion is dominated by the polar funnel, as in the hydrodynamic inviscid case, where material has zero or very low angular momentum. At the later phase of the evolution, the torus thickens toward the poles and develops a corona or an outflow or both. Consequently, the mass accretion through the funnel is stopped. The accretion of rotating gas through the torus is significantly reduced compared with the accretion of nonrotating gas (i.e., the Bondi rate). It is also much smaller than the accretion rate in the inviscid, weakly rotating case. Our results do not change if we switch on or off resistive heating. Overall our simulations are very similar to those presented by Stone, Pringle, Hawley, and Balbus despite different initial and outer boundary conditions. Thus, we confirm that MRI is very robust and controls the nature of radiatively inefficient accretion flows. Although the time-averaged properties of our models approach a steady state, we find that the instantaneous mass-accretion rate in the latter stages of our simulations is highly time-dependent, with the inner flow displaying three generic flow patterns.
accretion, accretion disks; black hole physics; galaxies: active; galaxies: nuclei; methods: numerical; MHD
Issue 2 (2003 August 1)
Received 2003 February 20, accepted for publication 2003 April 7
Daniel Proga and Mitchell C. Begelman 2003 ApJ 592 767
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Ion I Cotaescu and Mihai Visinescu 2001 Class. Quantum Grav. 18 3383
T Palani Selvam et al 2003 Phys. Med. Biol. 48 N139
Akimasa Hirata et al 2008 Phys. Med. Biol. 53 7215
Shmuel Fishman et al 2009 Nonlinearity 22 2861
E Kolbe et al 2003 J. Phys. G: Nucl. Part. Phys. 29 2569
G Contopoulos et al 2003 J. Phys. A: Math. Gen. 36 8639
M H Annaby and Z S Mansour 2005 J. Phys. A: Math. Gen. 38 3775
Ilya Avdeev et al 2004 J. Micromech. Microeng. 14 1491