HARM: A Numerical Scheme for General Relativistic Magnetohydrodynamics

Gammie, Charles F.; McKinney, Jonathan C.; Tóth, G.

doi:10.1086/374594

Cited by 736 publications

(1,156 citation statements)

References 38 publications

(50 reference statements)

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“…We developed H-AMR based on a 2D serial open-source code HARM2D (Gammie et al 2003;Noble et al 2006). H-AMR performs 10 times faster on a GPU than on a 16-core CPU.…”

Section: H-amr ("Hammer") Codementioning

confidence: 99%

Formation of precessing jets by tilted black hole discs in 3D general relativistic MHD simulations

Liska

Hesp

Tchekhovskoy

et al. 2017

Monthly Notices of the Royal Astronomical Society: Letters

304

334

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Gas falling into a black hole (BH) from large distances is unaware of BH spin direction, and misalignment between the accretion disc and BH spin is expected to be common. However, the physics of tilted discs (e.g., angular momentum transport and jet formation) is poorly understood. Using our new GPU-accelerated code H-AMR, we performed 3D general relativistic magnetohydrodynamic simulations of tilted thick accretion discs around rapidly spinning BHs, at the highest resolution to date. We explored the limit where disc thermal pressure dominates magnetic pressure, and showed for the first time that, for different magnetic field strengths on the BH, these flows launch magnetized relativistic jets propagating along the rotation axis of the tilted disc (rather than of the BH). If strong large-scale magnetic flux reaches the BH, it bends the inner few gravitational radii of the disc and jets into partial alignment with the BH spin. On longer time scales, the simulated disc-jet system as a whole undergoes LenseThirring precession and approaches alignment, demonstrating for the first time that jets can be used as probes of disc precession. When the disc turbulence is well-resolved, our isolated discs spread out, causing both the alignment and precession to slow down.

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“…We developed H-AMR based on a 2D serial open-source code HARM2D (Gammie et al 2003;Noble et al 2006). H-AMR performs 10 times faster on a GPU than on a 16-core CPU.…”

Section: H-amr ("Hammer") Codementioning

confidence: 99%

Formation of precessing jets by tilted black hole discs in 3D general relativistic MHD simulations

Liska

Hesp

Tchekhovskoy

et al. 2017

Monthly Notices of the Royal Astronomical Society: Letters

304

334

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“…Our basic model is thus to take a single-fluid GRMHD solution (e.g., Komissarov 1999;Gammie, McKinney & Tóth 2003;De Villiers & Hawley 2003) as an accurate description of the total fluid (composed of both the electron and proton gas) dynamics and thus the accretion flow density, magnetic field strength, and velocity field. We evolve the electrons as a second fluid on top of this background solution.…”

Section: Electron Thermodynamicsmentioning

confidence: 99%

“…We implemented the model described in §2 and §3 into the conservative GRMHD code, HARM2D (High-Accuracy Relativistic Magnetohydrodynamics; Gammie, McKinney & Tóth 2003;Noble et al 2006). To speed up the computations, we parallelised the code using OpenMP and MPI via domain decomposition.…”

Section: Tests Of Numerical Implementationmentioning

confidence: 99%

“…For this spin the last stable circular orbit is ≈ 2.04r g and the thin disc radiative efficiency is ≈ 0.18 (Novikov & Thorne 1973). We use the conservative code HARM (Gammie, McKinney & Tóth 2003) as our background GRMHD solution. Our initial conditions for the total fluid are the Fishbone & Moncrief (1976) equilibrium torus solution (see Appendix D) with inner radius r in = 6r g and with the maximum density of the disc occurring at r max = 12r g .…”

Section: Application To An Accreting Black Hole In 2d Grmhd Simulationsmentioning

confidence: 99%

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Electron thermodynamics in GRMHD simulations of low-luminosity black hole accretion

Ressler

Tchekhovskoy

Quataert

et al. 2015

Mon. Not. R. Astron. Soc.

162

238

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Simple assumptions made regarding electron thermodynamics often limit the extent to which general relativistic magnetohydrodynamic (GRMHD) simulations can be applied to observations of low-luminosity accreting black holes. We present, implement, and test a model that self-consistently evolves an entropy equation for the electrons and takes into account the effects of spatially varying electron heating and relativistic anisotropic thermal conduction along magnetic field lines. We neglect the back-reaction of electron pressure on the dynamics of the accretion flow. Our model is appropriate for systems accreting at ≪ 10 −5 of the Eddington accretion rate, so radiative cooling by electrons can be neglected. It can be extended to higher accretion rates in the future by including electron cooling and proton-electron Coulomb collisions. We present a suite of tests showing that our method recovers the correct solution for electron heating under a range of circumstances, including strong shocks and driven turbulence. Our initial applications to axisymmetric simulations of accreting black holes show that (1) physically-motivated electron heating rates that depend on the local magnetic field strength yield electron temperature distributions significantly different from the constant electron to proton temperature ratios assumed in previous work, with higher electron temperatures concentrated in the coronal region between the disc and the jet; (2) electron thermal conduction significantly modifies the electron temperature in the inner regions of black hole accretion flows if the effective electron mean free path is larger than the local scale-height of the disc (at least for the initial conditions and magnetic field configurations we study). The methods developed in this work are important for producing more realistic predictions for the emission from accreting black holes such as Sagittarius A* and M87; these applications will be explored in future work.

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“…The initial mass distribution is an isentropic hydroequilibrium torus (Fishbone & Moncrief 1976;Gammie et al 2003) with the inner edge at r r 10 g = and pressure maximum at r r 100 g = .…”

Section: Grmhd Simulationmentioning

confidence: 99%

Jet Signatures in the Spectra of Accreting Black Holes

Riordan¹,

Pe’er²,

McKinney³

2016

ApJ

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Jets are observed as radio emission in active galactic nuclei and during the low/hard state in X-ray binaries (XRBs), but their contribution at higher frequencies has been uncertain. We study the dynamics of jets in XRBs using the general-relativistic magnetohydrodynamic code HARM. We calculate the high-energy spectra and variability properties using a general-relativistic radiative transport code based on grmonty. We find the following signatures of jet emission: (i) a significant γ-ray peak above ∼10 22 Hz, (ii) a break in the optical/UV spectrum, with a change from L 0 n ñ n to L n ñ n , followed by another break at higher frequencies where the spectrum roughly returns to L 0 n ñ n , and (iii) a pronounced synchrotron peak near or below ∼10 14 Hz indicates that a significant fraction of any observed X-ray emission originates in the jet. We investigate the variability during a large-scale magnetic field inversion in which the Blandford-Znajek (BZ) jet is quenched and a new transient hot reconnecting plasmoid is launched by the reconnecting field. The ratio of the γ-rays to X-rays changes from L L 1 X > g in the BZ jet to L L 1 X < g during the launching of the transient plasmoid.

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HARM: A Numerical Scheme for General Relativistic Magnetohydrodynamics

Cited by 736 publications

References 38 publications

Formation of precessing jets by tilted black hole discs in 3D general relativistic MHD simulations

Formation of precessing jets by tilted black hole discs in 3D general relativistic MHD simulations

Electron thermodynamics in GRMHD simulations of low-luminosity black hole accretion

Jet Signatures in the Spectra of Accreting Black Holes

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