Three-dimensional Magnetohydrodynamical Simulations of Vertically Stratified Accretion Disks

Stone, James M.; Hawley, John F.; Gammie, Charles F.; Balbus, Steven A.

doi:10.1086/177280

Cited by 548 publications

(570 citation statements)

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“…In fact, stratified shearing box simulations have found that a mean toroidal field can be generated at the disk midplane and buoyantly rise out, to be replaced by a mean toroidal field of the opposite sign. This happens on 10 orbit timescale and is consistent with a simple α-Ω dynamo (Brandenburg et al 1995;Stone et al 1996;Hirose et a. 2006;Guan 2009;Shi et a.…”

Section: Radial Advection Of Fieldsupporting

confidence: 76%

Relativistic jets: Physics and simulations

Hawley

2010

Proc. IAU

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Abstract. Jets are one of the more dramatic and visible manifestations of black hole accretion. It is becoming increasingly accepted that magnetic fields underlie the mechanism behind the launching of relativistic jets. At the same time it is now appreciated that the fundamental driving mechanism behind accretion is due to magnetohydrodynamical processes and the stresses they engender. Global disk simulations in full general relativity have begun to reveal the radial dependence of disk stresses and the intimate connections between accretion and jet-launching. This talk will review the issues involved, the recent progress that has been made, and the challenges that remain.

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Section: Radial Advection Of Fieldsupporting

confidence: 76%

Relativistic jets: Physics and simulations

Hawley

2010

Proc. IAU

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“…In one case, it has been claimed that a rapidly rotating black hole (a ≡ cJ/GM 2 ≈ 1 is required to explain inferred values of inner radius r i < 2GM/c 2 (Iwasawa et al 1996). C) Another approach involves fits to the energy dependence of the continuum (X-ray) spectrum (Zhang et al 1997). A disk luminosity and maximum temperature is obtained for sources of known distance in which the non power-law component of the energy spectrum can be fit with a standard (diluted blackbody) optically thick accretion disk model.…”

Section: Introductionmentioning

confidence: 99%

Relativistic Diskoseismology

Wagoner

1997

International Astronomical Union Colloquium

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We will summarize results of calculations of the modes of oscillation trapped within the inner region of accretion disks by the strong-field gravitational properties of a black hole (or a compact, weakly-magnetized neutron star). Their driving and damping will also be addressed. The focus will be on the most observable class: the analogue of internal gravity modes in stars. Their frequencies which corrrespond to the lowest mode numbers depend almost entirely upon only the mass and angular momentum of the black hole. Such a feature may have been detected in the X-ray power spectra of two galactic 'microquasars', allowing the angular momentum of the black hole to be determined in one case.

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“…This effect is particularly dramatic in the recent simulations of Miller and Stone [61]. This distribution does not seem to be due to magnetic buoyancy [73], that is, the fields are mostly generated locally. The time averaged magnetic stress ( B r B θ ) is somewhat more uniform.…”

Section: Applying and Testing The Theorymentioning

confidence: 93%

“…These are the simulations of magnetized, ionized accretion disks (e.g. [36,39,40,73,14,15] see also [3,38] for a review) which are subject to the magneto-rotational instability. These simulations include extremely simplified physics and cover a limited set of spatial scales and geometries.…”

Section: Applying and Testing The Theorymentioning

confidence: 99%

“…In accretion disks the typical magnetic field energy density is probably an order of magnitude below the ambient gas pressure (e.g. [39,40,73,14,15]) but they play a critical role in the outward transfer of angular momentum and the dissipation of orbital energy. Moreover, in optically thin environments the presence of a strong magnetic field can have a dramatic effect on the luminosity and spectrum of an object.…”

Section: Introductionmentioning

confidence: 99%

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Problems and Progress in Astrophysical Dynamos

Vishniac

Lazarían²,

Cho³

Turbulence and Magnetic Fields in Astrophysics

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Abstract. Astrophysical objects with negligible resistivity are often threaded by large scale magnetic fields. The generation of these fields is somewhat mysterious, since a magnetic field in a perfectly conducting fluid cannot change the flux threading a fluid element, or the field topology. Classical dynamo theory evades this limit by assuming that magnetic reconnection is fast, even for vanishing resistivity, and that the large scale field can be generated by the action of kinetic helicity. Both these claims have been severely criticized, and the latter appears to conflict with strong theoretical arguments based on magnetic helicity conservation and a series of numerical simulations. Here we discuss recent efforts to explain fast magnetic reconnection through the topological effects of a weak stochastic magnetic field component. We also show how mean-field dynamo theory can be recast in a form which respects magnetic helicity conservation, and how this changes our understanding of astrophysical dynamos. Finally, we comment briefly on why an asymmetry between small scale magnetic and velocity fields is necessary for dynamo action, and how it can arise naturally.

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Three-dimensional Magnetohydrodynamical Simulations of Vertically Stratified Accretion Disks

Cited by 548 publications

References 0 publications

Relativistic jets: Physics and simulations

Relativistic jets: Physics and simulations

Relativistic Diskoseismology

Problems and Progress in Astrophysical Dynamos

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