Global simulations of axisymmetric radiative black hole accretion discs in general relativity with a mean-field magnetic dynamo

By A. Sa̧dowski, Ramesh Narayan, A. Tchekhovskoy, D. Abarca, Yucong Zhu, J. McKinney. 2014

160 citations recorded by the source corpus.

We present a sub-grid model that emulates the magnetic dynamo operating in magnetized accretion disks. We have implemented this model in the general relativisic radiation magnetohydrodynamic (GRRMHD) code \koral, using results from local shearing sheet simulations of the magnetorotational instability to fix the parameters of the dynamo. With the inclusion of this dynamo, we are able to run 2D axisymmetric GRRMHD simulations of accretion disks for arbitrarily long times. The simulated disks exhibit sustained turbulence, with the poloidal and toroidal magnetic field components driven towards a state similar to that seen in 3D studies. Using this dynamo code, we present a set of long-duration global simulations of super-Eddington, optically-thick disks around non-spinning and spinning black holes. Super-Eddington disks around non-rotating black holes exhibit a surprisingly large efficiency, $\eta\approx0.04$, independent of the accretion rate, where we measure efficiency in terms of the total energy output, both radiation and mechanical, flowing out to infinity. Super-Eddington disks around spinning black holes are even more efficient, and appear to extract black hole rotational energy through a process similar to the Blandford-Znajek mechanism. All the simulated models are characterized by highly super-Eddington radiative fluxes collimated along the rotation axis. We also present a set of simulations that were designed to have Eddington or slightly sub-Eddington accretion rates ($\dot{M} \lesssim 2\dot M_{\rm Edd}$). None of these models reached a steady state. Instead, the disks collapsed as a result of runaway cooling, presumably because of a thermal instability.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/b3c3bcc055d701ad27c0ec618a513999b77652f8

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Citations in the corpus

The Event Horizon General Relativistic Magnetohydrodynamic Code Comparison Project (2019, methodology): “In fact, a large simulation library comprising 43 well-resolved GRMHD simulations has been created for comparison to the observations, using iharm3D, KORAL, H-AMR, and BHAC (Event Horizon Telescope Collaboration et al. 2019b).”
Three-dimensional simulations of supercritical black hole accretion discs - luminosities, photon trapping and variability (2015, methodology): “In addition, we compare the properties of our fiducial three-dimensional model with an equivalent axisymmetrical twodimensional run which is simulated using the mean-field dynamo model described in Sądowski et al. (2015a).”
Hyper-Eddington accretion flows on to massive black holes (2015, methodology): “…break the hyper-Eddington accretion solution (e.g. Begelman 2002; Ohsuga et al. 2005, 2009; Dotan & Shaviv 2011; Li, Ostriker & Sunyaev 2013; Jiang, Stone & Davis 2014; McKinney et al. 2014; Sa̧dowski et al. 2015; Takahashi & Ohsuga 2015; McKinney, Dai & Avara 2015; King & Muldrew 2016).”
Three-dimensional GRMHD Simulations of Neutrino-cooled Accretion Disks from Neutron Star Mergers (2017, background): “6 shows that 〈 pB pf 〉 D̂ ' 0.1, (61) which is also characteristic of such a steady turbulent state (e.g., Jiang et al. 2014b; Sa̧dowski et al. 2015).”