Magnetically Driven Accretion Flows in the Kerr Metric. I. Models and Overall Structure

Villiers, Jean-Pierre De; Hawley, John F.; Krolik, Julian H.

doi:10.1086/379509

Cited by 350 publications

(401 citation statements)

References 23 publications

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“…The jet eventually evolving from these disks is not propelled by the Blandford & Payne (1982) mechanism, but driven by the toroidal magnetic pressure (Contopoulos 1996;De Villiers et al 2003;Kato et al 2004). These so-called Tower jets have initially been proposed by Lynden-Bell (1996) and directly extract Poynting flux from the disk rather than first converting rotational energy into the twisted magnetosphere that is present at the Alfvén surface.…”

Section: Poynting Dominated Flowsmentioning

confidence: 99%

Acceleration and Collimation of Relativistic Magnetohydrodynamic Disk Winds

Porth

Fendt

2010

ApJ

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We perform axisymmetric relativistic magnetohydrodynamic simulations to investigate the acceleration and collimation of jets and outflows from disks around compact objects. Newtonian gravity is added to the relativistic treatment in order to establish the physical boundary condition of an underlying accretion disk in centrifugal and pressure equilibrium. The fiducial disk surface (respectively a slow disk wind) is prescribed as boundary condition for the outflow. We apply this technique for the first time in the context of relativistic jets. The strength of this approach is that it allows us to run a parameter study in order to investigate how the accretion disk conditions govern the outflow formation. Substantial effort has been made to implement a current-free, numerical outflow boundary condition in order to avoid artificial collimation present in the standard outflow conditions. Our simulations using the PLUTO code run for 500 inner disk rotations and on a physical grid size of 100 × 200 inner disk radii. The simulations evolve from an initial state in hydrostatic equilibrium and an initially force-free magnetic field configuration. Two options for the initial field geometries are applied-an hourglass-shaped potential magnetic field and a split monopole field. Most of our parameter runs evolve into a steady state solution which can be further analyzed concerning the physical mechanism at work. In general, we obtain collimated beams of mildly relativistic speed with Lorentz factors up to 6 and mass-weighted half-opening angles of 3-7 deg. The split-monopole initial setup usually results in less collimated outflows. The light surface of the outflow magnetosphere tends to align vertically-implying three relativistically distinct regimes in the flow-an inner subrelativistic domain close to the jet axis, a (rather narrow) relativistic jet and a surrounding subrelativistic outflow launched from the outer disk surface-similar to the spine-sheath structure currently discussed for asymptotic jet propagation and stability. The outer subrelativistic disk-wind is a promising candidate for the X-ray absorption winds that are observed in many radio-quiet active galactic nuclei. The hot winds under investigation acquire only low Lorentz factors due to the rather high plasma-β we have applied in order to provide an initial force-balance in the disk corona. When we increase the outflow Poynting flux by injecting an additional disk toroidal field into the outflow, the jet velocities achieved are higher. These flows gain super-magnetosonic speed and remain Poynting flux dominated.

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Section: Poynting Dominated Flowsmentioning

confidence: 99%

Acceleration and Collimation of Relativistic Magnetohydrodynamic Disk Winds

Porth

Fendt

2010

ApJ

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“…Despite nearly 40 years of work on accretion disk physics, the simple Shakura & Sunyaev (1973) thin-disk model, its relativistic cousins (e.g., Page & Thorne 1974;Hubeny & Hubeny 1997;Hubeny et al 2001;Li et al 2005) and more sophisticated implementations (e.g., Narayan et al 1997;De Villiers et al 2003;Blaes 2007) remain the standard model despite some observational reservations (see Francis et al 1991;Koratkar & Blaes 1999;Collin et al 2002). Quasar accretion disks cannot be spatially resolved with ordinary telescopes, so we have been forced to test accretion physics through time variability (e.g., Vanden Berk et al 2004;Sergeev et al 2005;Cackett et al 2007) and spectral modeling (e.g., Sun & Malkan 1989;Collin et al 2002;Bonning et al 2007).…”

Section: Introductionmentioning

confidence: 99%

The Quasar Accretion Disk Size-Black Hole Mass Relation

Morgan

Kochanek

Morgan

et al. 2010

ApJ

350

484

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We use the microlensing variability observed for 11 gravitationally lensed quasars to show that the accretion disk size at a rest-frame wavelength of 2500 Å is related to the black hole mass by log(R 2500 /cm) = (15.78 ± 0.12) + (0.80 ± 0.17) log(M BH /10 9 M ). This scaling is consistent with the expectation from thin-disk theory (R ∝ M 2/3 BH ), but when interpreted in terms of the standard thin-disk model (T ∝ R −3/4 ), it implies that black holes radiate with very low efficiency, log(η) = −1.77 ± 0.29 + log(L/L E ), where η = L/(Ṁc 2 ). Only by making the maximum reasonable shifts in the average inclination, Eddington factors, and black hole masses can we raise the efficiency estimate to be marginally consistent with typical efficiency estimates (η ≈ 10%). With one exception, these sizes are larger by a factor of ∼4 than the size needed to produce the observed 0.8 μm quasar flux by thermal radiation from a thin disk with the same T ∝ R −3/4 temperature profile. While scattering a significant fraction of the disk emission on large scales or including a large fraction of contaminating line emission can reduce the size discrepancy, resolving it also appears to require that accretion disks have flatter temperature/surface brightness profiles.

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“…These codes have been used to study the structure of accretion flows onto Kerr black holes [31,32], the Blandford-Znajek effect in low-density regions near the hole [28,33], and the formation of GRB jets [34].…”

Section: Introductionmentioning

confidence: 99%

Relativistic magnetohydrodynamics in dynamical spacetimes: Numerical methods and tests

et al. 2005

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Many problems at the forefront of theoretical astrophysics require the treatment of magnetized fluids in dynamical, strongly curved spacetimes. Such problems include the origin of gamma-ray bursts, magnetic braking of differential rotation in nascent neutron stars arising from stellar core collapse or binary neutron star merger, the formation of jets and magnetized disks around newborn black holes, etc. To model these phenomena, all of which involve both general relativity (GR) and magnetohydrodynamics (MHD), we have developed a GRMHD code capable of evolving MHD fluids in dynamical spacetimes. Our code solves the Einstein-Maxwell-MHD system of coupled equations in axisymmetry and in full 3+1 dimensions. We evolve the metric by integrating the BSSN equations, and use a conservative, shock-capturing scheme to evolve the MHD equations. Our code gives accurate results in standard MHD code-test problems, including magnetized shocks and magnetized Bondi flow. To test our code's ability to evolve the MHD equations in a dynamical spacetime, we study the perturbations of a homogeneous, magnetized fluid excited by a gravitational plane wave, and we find good agreement between the analytic and numerical solutions.

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Magnetically Driven Accretion Flows in the Kerr Metric. I. Models and Overall Structure

Cited by 350 publications

References 23 publications

Acceleration and Collimation of Relativistic Magnetohydrodynamic Disk Winds

Acceleration and Collimation of Relativistic Magnetohydrodynamic Disk Winds

The Quasar Accretion Disk Size-Black Hole Mass Relation

Relativistic magnetohydrodynamics in dynamical spacetimes: Numerical methods and tests

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