A Resolution Study of Magnetically Arrested Disks

Abstract

We investigate numerical convergence in simulations of magnetically arrested disks around spinning black holes. Using the general-relativistic magnetohydrodynamics code Athena++, we study the same system at four resolutions (up to an effective 512 by 256 by 512 cells) and with two different spatial reconstruction algorithms. The accretion rate and general large-scale structure of the flow agree across the simulations. This includes the amount of magnetic flux accumulated in the saturated state and the ensuing suppression of the magnetorotational instability from the strong field. The energy of the jet and the efficiency with which spin energy is extracted via the Blandford-Znajek process also show convergence. However the spatial structure of the jet shows variation across the set of grids employed, as do the Lorentz factors. Small-scale features of the turbulence, as measured by correlation lengths, are not fully converged. Despite convergence of a number of aspects of the flow, modeling of synchrotron emission shows that variability is not converged and decreases with increasing resolution even at our highest resolutions.

19 pages, 18 figures, to be published in ApJ

References in corpus (3)

• Jet Launching Structure Resolved Near the Supermassive Black Hole in M87
• Magnetically Arrested Disks and Origin of Poynting Jets: Numerical Study
• The general relativistic thin disc evolution equation

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• Magnetic Reconnection in Black-Hole Magnetospheres: Lepton Loading into Jets, Superluminal Radio Blobs, and Multi-wavelength Flares
• The Effects of Resolution on Black Hole Accretion Simulations of Jets
• Constraining X-ray emission of magnetically arrested disk (MAD) by radio-loud AGNs with extreme ultraviolet (EUV) deficit