Global general relativistic magnetohydrodynamic simulations of black hole accretion flows: A convergence study

Hotaka Shiokawa, Joshua C. Dolence, Charles F. Gammie, Scott C. Noble

Research output: Contribution to journalArticlepeer-review

Abstract

Global, general relativistic magnetohydrodynamic (GRMHD) simulations of non-radiative, magnetized disks are widely used to model accreting black holes. We have performed a convergence study of GRMHD models computed with HARM3D. The models span a factor of four in linear resolution, from 96 × 96 × 64 to 384 × 384 × 256. We consider three diagnostics of convergence: (1) dimensionless shell-averaged quantities such as plasma β; (2) the azimuthal correlation length of fluid variables; and (3) synthetic spectra of the source including synchrotron emission, absorption, and Compton scattering. Shell-averaged temperature is, except for the lowest resolution run, nearly independent of resolution; shell-averaged plasma β decreases steadily with resolution but shows signs of convergence. The azimuthal correlation lengths of density, internal energy, and temperature decrease steadily with resolution but show signs of convergence. In contrast, the azimuthal correlation length of magnetic field decreases nearly linearly with grid size. We argue by analogy with local models, however, that convergence should be achieved with another factor of two in resolution. Synthetic spectra are, except for the lowest resolution run, nearly independent of resolution. The convergence behavior is consistent with that of higher physical resolution local model ("shearing box") calculations and with the recent non-relativistic global convergence studies of Hawley et al.

Original languageEnglish (US)
Article number187
JournalAstrophysical Journal
Volume744
Issue number2
DOIs
StatePublished - Jan 10 2012

Keywords

  • accretion, accretion disks
  • black hole physics
  • magnetohydrodynamics (MHD)
  • methods: numerical

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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