Coronae as Consequence of Large Scale Magnetic Fields in Turbulent Accretion Disks

Abstract

Non-thermal X-ray emission in compact accretion engines can be interpreted to result from magnetic dissipation in an optically thin magnetized corona above an optically thick accretion disk. If coronal magnetic field originates in the disk and the disk is turbulent, then only magnetic structures large enough for their turbulent shredding time to exceed their buoyant rise time survive the journey to the corona. We use this concept and a physical model to constrain the minimum fraction of magnetic energy above the critical scale for buoyancy as a function of the observed coronal to bolometric emission. Our results suggest that a significant fraction of the magnetic energy in accretion disks resides in large scale fields, which in turn provides circumstantial evidence for significant non-local transport phenomena and the need for large scale magnetic field generation. For the example of Seyfert AGN, for which of order 30 per cent of the bolometric flux is in the X-ray band, we find that more than 20 per cent of the magnetic energy must be of large enough scale to rise and dissipate in the corona.

submitted to ApJL, 2 figs

References in corpus (9)

• MHD simulations of the magnetorotational instability in a shearing box with zero net flux. II. The effect of transport coefficients
• Impact of dimensionless numbers on the efficiency of MRI-induced turbulent transport
• MHD simulations of the magnetorotational instability in a shearing box with zero net flux. I. The issue of convergence
• Angular Momentum Transport in Accretion Disks: Scaling Laws in MRI-driven Turbulence
• Aspect ratio dependence in magnetorotational instability shearing box simulations
• The signature of the magnetorotational instability in the Reynolds and Maxwell stress tensors in accretion discs
• Empirical relation between angular momentum transport and thermal-to-magnetic pressure ratio in shearing box simulations
• Toward Coupling Flow Driven and Magnetically Driven Dynamos
• MHD disc winds

Cited by in corpus (32)

• Sustained Magnetorotational Turbulence in Local Simulations of Stratified Disks with Zero Net Magnetic Flux
• Hidden Cores of Active Galactic Nuclei as the Origin of Medium-Energy Neutrinos: Critical Tests with the MeV Gamma-Ray Connection
• High-Energy Neutrinos from Magnetized Coronae of Active Galactic Nuclei and Prospects for Identification of Seyfert Galaxies and Quasars in Neutrino Telescopes
• Mass Transfer and Disc Formation in AGB Binary Systems
• Acceleration and collimation of relativistic MHD disk winds
• Turbulence in Global Simulations of Magnetized Thin Accretion Disks
• Characterizing the mean-field dynamo in turbulent accretion disks
• On the Observational Difference Between the Accretion Disk-Corona Connections among Super- and Sub-Eddington Accreting Active Galactic Nuclei
• Low-Frequency Oscillations in Global Simulations of Black Hole Accretion
• Revealing the accretion disc corona in Mrk 335 with multi-epoch X-ray spectroscopy
• Magnetic Helicity and Large Scale Magnetic Fields: A Primer
• The Nature of Soft Excess in ESO 362-G18 Revealed by XMM-Newton and NuSTAR Spectroscopy
• Testing the disk-corona interplay in radiatively-efficient broad-line AGN
• MRI channel flows in vertically-stratified models of accretion disks
• A Correlation Between the Ionization State of the Inner Accretion Disk and the Eddington Ratio of Active Galactic Nuclei
• Accretion Disks and Dynamos: Toward a Unified Mean Field Theory
• On Vertically Global, Horizontally Local Models for Astrophysical Disks
• Motivation and challenge to capture both large scale and local transport in next generation accretion theory
• Vertical Structure and Coronal Power of Accretion Disks Powered by MRI Turbulence
• Local models of two-temperature accretion disc coronae. I. Structure, outflows, and energetics
• On characterizing nonlocality and anisotropy for the magnetorotational instability
• Radially Dependent Large Scale Dynamos in Global Cylindrical Shear Flows and the Local Cartesian Limit
• Comparisons and Connections between Mean Field Dynamo Theory and Accretion Disc Theory
• Global simulations of magnetorotational turbulence II: turbulent energetics
• Persistent mysteries of jet engines, formation, propagation, and particle acceleration: have they been addressed experimentally?
• Turbulent Mixing in Stars: Theoretical Hurdles
• MRI turbulence in vertically stratified accretion discs at large magnetic Prandtl numbers
• Inconsistency in the Standard Model for Thin Accretion Disks
• The Accretion Disc Dynamo in the Solar Nebula
• The Low Temperature Corona in ESO 511$-$G030 Revealed by NuSTAR and XMM-Newton
• Helical and nonhelical large-scale dynamos in thin accretion discs
• Kelvin-Helmholtz Instability at the interface of a disc-corona system