Numerical Simulations of Mass Outflows Driven from Accretion Disks by Radiation and Magnetic Forces

By D. Proga. 2002

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We study the two-dimensional, time-dependent magnetohydrodynamics (MHD) of radiation-driven winds from luminous accretion disks initially threaded by a purely axial magnetic field. The radiation force is mediated primarily by spectral lines and is calculated using a generalized multidimensional formulation of the Sobolev approximation. We use ideal MHD to compute numerically the evolution of Keplerian disks, varying the magnetic field strengths and the luminosity of the disk, the central accreting object, or both. We find that the magnetic fields very quickly start deviating from purely axial because of the magnetorotational instability. This leads to fast growth of the toroidal magnetic field as field lines wind up because of the disk rotation. As a result the toroidal field dominates over the poloidal field above the disk and the gradient of the former drives a slow and dense disk outflow, which conserves specific angular momentum. Depending on the strength of the magnetic field relative to the system luminosity, the disk wind can be radiation or MHD driven. The pure radiation-driven wind consists of a dense, slow outflow that is bounded on the polar side by a high-velocity stream. The mass-loss rate is mostly due to the fast stream. As the magnetic field strength increases, first the slow part of the flow is affected; namely, it becomes denser and slightly faster and begins to dominate the mass-loss rate. In very strong magnetic field or pure MHD cases, the wind consists of only a dense, slow outflow without the presence of the distinctive fast stream so typical of pure radiation-driven winds. Our simulations indicate that winds launched by the magnetic fields are likely to remain dominated by the fields downstream because of their relatively high densities. The radiation force due to lines may not be able to change a dense MHD wind because the line force strongly decreases with increasing density.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/b3b74cdfebef11a71cdffe1b35537cc958c27b70

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Citations in the corpus

A unified model for AGN feedback in cosmological simulations of structure formation (2007, background): “Several numerical studies dealing with BH microphysics (e.g. Proga, 2003; McKinney, 2006) also predict existence of quasar outflows.”
Simultaneous Chandra and RXTE Spectroscopy of the Microquasar H1743–322: Clues to Disk Wind and Jet Formation from a Variable Ionized Outflow (2004, background): “However, recent simulations suggest that winds can be more equatorial (e.g., Proga 2003), and reasonable upper limits on themass outflow rate are likely only twice as high as the values given in Table 5.”
THE SDSS-IV EXTENDED BARYON OSCILLATION SPECTROSCOPIC SURVEY: OVERVIEW AND EARLY DATA (2015, background): “Highly ionized gas in the broadline region of quasars is subject to radiation-driven winds (e.g. Proga 2003).”
The nature and origin of Seyfert warm absorbers (2004, background): “This geometry is consistent with the radiatively driven accretion disc wind models of Proga (2003), where material is driven off the disc at a very low angle to the disc surface.”
The Accretion Disk Wind in the Black Hole GRO J1655–40 (2008, background): “Internal magnetic viscosity may drive disk accretion (e.g. Shakura & Sunyaev 1973, Balbus & Hawley 1991), and could give rise to slow, dense winds originating close to the black hole (e.g. Proga 2003).”
What broad emission lines tell us about how active galactic nuclei work (2009, background): “…the development of more sophisticated programs by several groups have allowed increasingly detailed magneto-hydrodynamic (MHD) simulations of accretion flows (e.g., Hawley & Krolik 2001; Proga 2003; Anninos, Fragile, & Salmonson 2005; Ohsuga et al. 2009; Shafee et al. 2008, and references therein).”
Short-hard gamma-ray bursts (2007, unknown): “…potentials (e.g., Hawley, 2000; Hawley & Krolik, 2002; Hawley & Balbus, 2002; Armitage, Reynolds & Chiang, 2001; Armitage & Reynolds, 2003; Proga, 2003; Proga & Begelman, 2003; Machida & Matsumoto, 2003; Kato, Mineshige & Shibata, 2004) to GR simulations using a Kerr metric in two…”
UNIFICATION OF LUMINOUS TYPE 1 QUASARS THROUGH C iv EMISSION (2010, background): “For example, radiation line driving may dominate in the “wind” objects, while the “disk” objects perhaps have MHD-driven winds (Proga 2003; Richards 2006).”
Chandra/High Energy Transmission Grating Spectrometer Spectroscopy of the Galactic Black Hole GX 339–4: A Relativistic Iron Emission Line and Evidence for a Seyfert-like Warm Absorber (2003, background): “Radiation pressure in spectral lines makes a large contribution to the acceleration of cataclysmic variable (CV) winds (e.g., Proga 2003), although it cannot account for all the driving force (Mauche & Raymond 2000).”
Modelling the behaviour of accretion flows in X-ray binaries (2007, background): “Proga (2000, 2003) make some calculations of magnetic winds from a geometrically thin disc, but imposed an external field geometry.”
Unification of X-ray winds in Seyfert galaxies: from ultra-fast outflows to warm absorbers (2012, background): “Some attempts in this direction have been reported in the literature (Proga 2000, 2003; Everett 2005; Ohsuga et al. 2009; Reynolds 2012).”