We submitted the above letter to Dr. Hawley, who writes:

Hawley, George

doi:10.1001/jama.1906.02520090053013

Cited by 3 publications

(10 citation statements)

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“…We note that results recently released by Hawley & Krolik (2000) and Hawley (2000b) show similar behaviour close to the inner edge of an accretion disk. Their numerical setup is much more complex than ours, and describes a 3D MHD model of the inner region of an accretion disk around a black hole with a pseudo-Newtonian potential.…”

Section: Time Analysis Of the Development Of The Instabilitysupporting

confidence: 82%

“…Brandenburg et al 1995, Hawley et al 1995, Stone et al 1996, Hawley 2000b. These all show that turbulent transport is indeed generated through a local instability.…”

Section: Introductionmentioning

confidence: 72%

“…More recently Hawley (2000a) and Machida et al (2000) describe simulations of accretion disks starting from toroidal configurations (i.e. a departure from Keplerian thin disks); at the time of preparation Hawley & Krolik (2000) and Hawley (2000b) have published numerical simulations of full accretion disk models.…”

Section: Introductionmentioning

confidence: 99%

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Numerical simulations of the accretion-ejection instability in magnetised accretion disks

Caunt

Tagger

2001

A&A

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Abstract. The Accretion-Ejection Instability (AEI) described by Tagger & Pellat (1999, hereafter TP99) is explored numerically using a global 2d model of the inner region of a magnetised accretion disk. The disk is initially currentless but threaded by a vertical magnetic field created by external currents, and frozen in the flow. In agreement with the theory a spiral instability, similar in many ways to those observed in self-gravitating disks, develops when the magnetic field is, within a factor of a few, at equipartition with the disk thermal pressure. Perturbations in the flow build up currents and create a perturbed magnetic field within the disk. The present non-linear simulations give good evidence that such an instability can occur in the inner region of accretion disks, and generate accretion of gas and vertical magnetic flux toward the central object, if the equilibrium radial profiles of density and magnetic flux exceed a critical threshold.

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Section: Time Analysis Of the Development Of The Instabilitysupporting

confidence: 82%

“…Brandenburg et al 1995, Hawley et al 1995, Stone et al 1996, Hawley 2000b. These all show that turbulent transport is indeed generated through a local instability.…”

Section: Introductionmentioning

confidence: 72%

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Numerical simulations of the accretion-ejection instability in magnetised accretion disks

Caunt

Tagger

2001

A&A

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“…Results of global 3D MHD simulations including vertical gravity were reported by and Hawley (1999). By adopting an initially gas pressure dominated torus threaded by toroidal magnetic fields, showed that magnetic energy is amplified exponentially owing to the growth of the Balbus & Hawley instability and that the system approaches a quasi-steady state with β ∼ 10. assumed β = constant in the torus at the initial state.…”

Section: Introductionmentioning

confidence: 94%

Global Simulations of Differentially Rotating Magnetized Disks: Formation of Low-β Filaments and Structured Coronae

Machida

Hayashi

Matsumoto

2000

The Astrophysical Journal

149

139

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We present the results of three-dimensional global magnetohydrodynamic simulations of the Parker-shearing instability in a differentially rotating torus initially threaded by toroidal magnetic fields. An equilibrium model of a magnetized torus is adopted as an initial condition. When beta0=Pgas&solm0;Pmag approximately 1 at the initial state, magnetic flux buoyantly escapes from the disk and creates looplike structures similar to those in the solar corona. Inside the torus, the growth of nonaxisymmetric magnetorotational (or Balbus & Hawley) instability generates magnetic turbulence. Magnetic field lines are tangled on a small scale, but on a large scale they show low azimuthal wavenumber spiral structure. After several rotation periods, the system oscillates around a state with beta approximately 5. We found that magnetic pressure-dominated (beta<1) filaments are created in the torus. The volume filling factor of the region in which beta

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“…This article presents results from simplified MHD simulations [9,10] of black hole accretion that focus on the first of these questions. We outline the numerical approach, and discuss our results and how they compare with those of other groups [11][12][13]. Our conclusion from work to date is that MHD effects in the plunging region can have an important influence on the dynamics of the inner disk flow, provided that the magnetic fields in the disk are already moderately strong.…”

Section: Runmentioning

confidence: 82%

Magnetohydrodynamic simulations of black hole accretion

Reynolds¹,

Armitage²,

Chiang³

2001

AIP Conference Proceedings

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We discuss the results of three-dimensional magnetohydrodynamic simulations, using a pseudo-Newtonian potential, of thin disk (h/r ~ 0.1) accretion onto black holes. We find (i) that magnetic stresses persist within the marginally stable orbit, and (ii) that the importance of those stresses for the dynamics of the flow depends upon the strength of magnetic fields in the disk outside the last stable orbit. Strong disk magnetic fields (alpha > 0.1) lead to a gross violation of the zero-torque boundary condition at the last stable orbit, while weaker fields (alpha ~ 0.01) produce results more akin to traditional models for thin disk accretion onto black holes. Fluctuations in the magnetic field strength in the disk could lead to changes in the radiative efficiency of the flow on short timescales.Comment: 6 pages, to appear in proceedings, 20th Texas Symposium on Relativistic Astrophysics, eds J.C. Wheeler and H. Marte

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We submitted the above letter to Dr. Hawley, who writes:

Cited by 3 publications

References 0 publications

Numerical simulations of the accretion-ejection instability in magnetised accretion disks

Numerical simulations of the accretion-ejection instability in magnetised accretion disks

Global Simulations of Differentially Rotating Magnetized Disks: Formation of Low-β Filaments and Structured Coronae

Magnetohydrodynamic simulations of black hole accretion

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