The Influence of Magnetic Field Geometry on the Evolution of Black Hole Accretion Flows: Similar Disks, Drastically Different Jets

Beckwith, Kris; Hawley, John F.; Krolik, Julian H.

doi:10.1086/533492

Cited by 263 publications

(332 citation statements)

References 23 publications

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“…Unlike the simulations in De , , Hirose et al (2004), Krolik et al (2005), Hawley & Krolik (2006), Beckwith et al (2008), McKinney &Gammie (2004), andMcKinney (2005) that considered a finite toroidal pool of gas, threaded by poloidal loops of like orientation, Igumenshchev (2008) considered an endless supply of gas from the outer boundary. This is a major fundamental distinction from the poloidal loop simulations.…”

Section: A Fundamental Topological Issuementioning

confidence: 99%

“…As a corollary to this, it customarily concluded that the accretion disk cannot maintain a strong magnetosphere and therefore the jet power would be quite small relative to Fanaroff-Riley type II (FRII) radio sources (Ghosh & Abramowicz 1997). 5 The only place in which a strong field can exist in this scenario is pinned against the event horizon, in the vortex of the accretion flow, and then only under a select set of circumstances (Beckwith et al 2008). Conversely, the second scenario implies that large-scale poloidal magnetic fields can be maintained by the accreting gas all the way down to the black hole (Bisnovatyi-Kogan & Ruzmaikin 1974Narayan et al 2003).…”

Section: Introductionmentioning

confidence: 99%

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Three-Dimensional Simulations of Vertical Magnetic Flux in the Immediate Vicinity of Black Holes

Punsly

Igumenshchev

Hirose

2009

ApJ

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This article reports on three-dimensional MHD simulations of non-rotating and rapidly rotating black holes and the adjacent black hole accretion disk magnetospheres. A particular emphasis is placed on the vertical magnetic flux that is advected inward from large radii and threads the equatorial plane near the event horizon. In both cases of non-rotating and rotating black holes, the existence of a significant vertical magnetic field in this region is like a switch that creates powerful jets. There are many similarities in the vertical flux dynamics in these two cases in spite of the tremendous enhancement of azimuthal twisting of the field lines and enhancement of the jet power because of an "ergospheric disk" in the Kerr metric. A three-dimensional approach is essential because two-dimensional axisymmetric flows are incapable of revealing the nature of the vertical flux near a black hole. Poloidal field lines from the ergospheric accretion region have been visualized in three dimensions and much of the article is devoted to a formal classification of the different manifestations of the vertical flux in the Kerr case.

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Section: A Fundamental Topological Issuementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Three-Dimensional Simulations of Vertical Magnetic Flux in the Immediate Vicinity of Black Holes

Punsly

Igumenshchev

Hirose

2009

ApJ

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“…Over the past years, the RIAF model has progressed from a simple semianalytical model to more complex time-dependent generalrelativistic magnetohydrodynamic (GRMHD) models. In these models relativistic jets are often produced (e.g., Beckwith et al 2008). The synchrotron emission from a GRMHD-RIAF can now be calculated with a high degree of precision using general relativistic radiative-transfer codes (e.g., Dolence et al 2009;Dexter & Agol 2009;Shcherbakov et al 2012).…”

Section: Introductionmentioning

confidence: 99%

Coupled jet-disk model for Sagittarius A*: explaining the flat-spectrum radio core with GRMHD simulations of jets

Mościbrodzka

Falcke

2013

A&A

122

146

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Context. The supermassive black hole in the center of the Milky Way, Sgr A*, displays a nearly flat radio spectrum that is typical for jets in active galactic nuclei. Indeed, time-dependent magnetized models of radiatively inefficient accretion flows (RIAFs), which are commonly used to explain the millimeter, near-infrared, and X-ray emission of Sgr A*, often also produce jet-like outflows. However, the emission from these models has so far failed to reproduce the flat radio spectrum. Aims. We investigate whether current accretion simulations can produce the compact flat spectrum emission by simply using a different prescription for the heating of the radiating particles in the jet. Methods. We studied the radiative properties of accretion flows onto a black hole produced in time-dependent general-relativistic magnetohydrodynamic (GRMHD) simulations. A crucial free parameter in these models has always been the electron temperature, and here we allowed for variations in the proton-to-electron temperature ratios in the jet and disk. Results. We found that the flat spectrum is readily reproduced by a standard GRMHD model if one has an almost isothermal jet coupled to a two-temperature accretion flow. The low-frequency radio emission comes from the outflowing sheath of matter surrounding the strongly magnetized nearly empty jet. The model is consistent with the radio sizes and spectrum of Sgr A*. Conclusions. Hence, GRMHD models of accreting black holes can in principle naturally reproduce jets that match observed characteristics. For Sgr A* the model fit to the spectrum predicts higher mass-accretion rates when a jet is included than without a jet. Hence, the impact of the recently discovered G2 cloud that is expected to be accreted onto Sgr A* might be less severe than currently thought.

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“…It is known that GRMHD simulation results depend on the initial magnetic field strength and topology (Beckwith et al 2008;Penna et al 2010;Tchekhovskoy et al 2011;McKinney et al 2012). The rotation rate of the initial torus may also be important.…”

Section: Introductionmentioning

confidence: 99%

A new equilibrium torus solution and GRMHD initial conditions

Penna

Kulkarni

Narayan

2013

A&A

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Context. General relativistic magnetohydrodynamic (GRMHD) simulations are providing influential models for black hole spin measurements, gamma ray bursts, and supermassive black hole feedback. Many of these simulations use the same initial condition: a rotating torus of fluid in hydrostatic equilibrium. A persistent concern is that simulation results sometimes depend on arbitrary features of the initial torus. For example, the Bernoulli parameter (which is related to outflows), appears to be controlled by the Bernoulli parameter of the initial torus. Aims. In this paper, we give a new equilibrium torus solution and describe two applications for the future. First, it can be used as a more physical initial condition for GRMHD simulations than earlier torus solutions. Second, it can be used in conjunction with earlier torus solutions to isolate the simulation results that depend on initial conditions. Methods. We assume axisymmetry, an ideal gas equation of state, constant entropy, and ignore self-gravity. We fix an angular momentum distribution and solve the relativistic Euler equations in the Kerr metric. Results. The Bernoulli parameter, rotation rate, and geometrical thickness of the torus can be adjusted independently. Our torus tends to be more bound and have a larger radial extent than earlier torus solutions. Conclusions. While this paper was in preparation, several GRMHD simulations appeared based on our equilibrium torus. We believe it will continue to provide a more realistic starting point for future simulations.

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The Influence of Magnetic Field Geometry on the Evolution of Black Hole Accretion Flows: Similar Disks, Drastically Different Jets

Cited by 263 publications

References 23 publications

Three-Dimensional Simulations of Vertical Magnetic Flux in the Immediate Vicinity of Black Holes

Three-Dimensional Simulations of Vertical Magnetic Flux in the Immediate Vicinity of Black Holes

Coupled jet-disk model for Sagittarius A*: explaining the flat-spectrum radio core with GRMHD simulations of jets

A new equilibrium torus solution and GRMHD initial conditions

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