CONSERVATIVE GRMHD SIMULATIONS OF MODERATELY THIN, TILTED ACCRETION DISKS

This paper presents our latest numerical simulations of accretion disks that are misaligned with respect to the rotation axis of a Kerr black hole. In this work, we use a new, fully conservative version of the Cosmos++ general relativistic magnetohydrodynamics (GRMHD) code, coupled with an ad hoc co...

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Bibliographic Details
Published in:The Astrophysical journal 2014-12, Vol.796 (2), p.1-13
Main Authors: Teixeira, Danilo Morales, Fragile, P Chris, Zhuravlev, Viacheslav V, Ivanov, Pavel B
Format: Article
Language:English
Subjects:
ACCRETION DISKS
Alignment
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
BLACK HOLES
COMPARATIVE EVALUATIONS
Computer simulation
COMPUTERIZED SIMULATION
COOLING
DESIGN
Disks
Fluid flow
INSTABILITY
KERR FIELD
MAGNETOHYDRODYNAMICS
Mathematical models
RELATIVISTIC RANGE
ROTATION
Scale height
Simulation
SPACE
SPIN
STRESSES
THICKNESS
TURBULENCE
Turbulent flow
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Summary:This paper presents our latest numerical simulations of accretion disks that are misaligned with respect to the rotation axis of a Kerr black hole. In this work, we use a new, fully conservative version of the Cosmos++ general relativistic magnetohydrodynamics (GRMHD) code, coupled with an ad hoc cooling function designed to control the thickness of the disk. Together these allow us to simulate the thinnest tilted accretion disks ever using a GRMHD code. In this way, we are able to probe the regime where the dimensionless stress and scale height of the disk become comparable.We present results for both prograde and retrograde cases. The simulated prograde tilted disk shows no sign of Bardeen-Petterson alignment even in the innermost parts of the disk. The simulated retrograde tilted disk, however, does show modest alignment. The implication of these results is that the parameter space associated with Bardeen-Petterson alignment for prograde disks may be rather small, only including very thin disks. Unlike our previous work, we find no evidence for standing shocks in our simulated tilted disks. We ascribe this to the black hole spin, tilt angle, and disk scale height all being small in these simulations. We also add to the growing body of literature pointing out that the turbulence driven by the magnetorotational instability in global simulations of accretion disks is not isotropic. Finally, we provide a comparison between our moderately thin, untilted reference simulation and other numerical simulations of thin disks in the literature.
ISSN:1538-4357
0004-637X
1538-4357
DOI:10.1088/0004-637X/796/2/103