Global dynamics of advection-dominated accretion flows with magnetically driven outflow

Li, Shuang-Liang; Cao, Xinwu

doi:10.1111/j.1365-2966.2009.15595.x

Cited by 20 publications

(30 citation statements)

References 49 publications

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“…The structure of the disk will be altered in the presence of magnetic outflows (Li & Cao 2009;Cao & Spruit 2013;Li 2014;Li & Begelman 2014). The angular momentum equation for a steady ADAF with outflows is…”

Section: Criṫmentioning

confidence: 99%

An Accretion Disk-Outflow Model for Hysteretic State Transition in X-Ray Binaries

Cao

2016

ApJ

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We suggest a model of the advection-dominated accretion flow (ADAF) with magnetically driven outflows to explain the hysteretic state transition observed in X-ray binaries (XRBs). The transition from a thin disk to an ADAF occurs when the mass accretion rate is below a critical value. The critical mass accretion rate for the ADAF can be estimated by equating the equilibration timescale to the accretion timescale of the ADAF, which is sensitive to its radial velocity. The radial velocity of thin disks is very small, which leads to the advection of the external field in thin disks becoming very inefficient. ADAFs are present in the low/hard states of XRBs, and their radial velocity is large compared with the thin disk. The external field can be dragged inward efficiently by the ADAF, so a strong large-scale magnetic field threading the ADAF can be formed, which may accelerate a fraction of gas in the ADAF into the outflows. Such outflows may carry away a large amount of angular momentum from the ADAF, which significantly increases the radial velocity of the ADAF. This leads to a high critical mass accretion rate, below which an ADAF with magnetic outflows can survive. Our calculations show that the critical luminosity of the ADAF with magnetic outflows can be one order of magnitude higher than that for a conventional ADAF, if the ratio of gas to magnetic pressure 4 b~in the disk. This can naturally explain the hysteretic state transition observed in XRBs.

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Section: Criṫmentioning

confidence: 99%

An Accretion Disk-Outflow Model for Hysteretic State Transition in X-Ray Binaries

Cao

2016

ApJ

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“…This significant difference between the inner and outer mass accretion rates indicates mass loss from the accretion flow as a result of the outflow (Kawabata & Mineshige 2009). Thus, several authors have studied accretion discs in the presence of outflows (Knigge 1999; Fukue 2002, 2004; Shadmehri 2008; Xie & Yuan 2008; Bu, Yuan & Xie 2009; Kawabata & Mineshige 2009; Li & Cao 2009; Abbassi, Ghanbari & Ghasemnezhad 2010).…”

Section: Introductionmentioning

confidence: 99%

Viscous and resistive accretion flows with radially self-similar outflows

Faghei¹,

Mollatayefeh²

2012

Monthly Notices of the Royal Astronomical Society

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The existence of outflows in accretion flows has been confirmed by observations and by magnetohydrodynamics simulations. In this paper, we study the outflows of advection-dominated accretion flows (ADAFs) in the presence of resistivity and a toroidal magnetic field. The mechanism of energy dissipation in the flow is assumed to be the viscosity and the magnetic diffusivity as a result of turbulence in the accretion flow. It is also assumed that the magnetic diffusivity and the kinematic viscosity are not constant and that they vary by position, and the α-prescription is used for these. The influence of outflows emanating from an accretion disc is considered as a sink for mass, angular momentum and energy. The self-similar method is used to solve the integrated equations that govern the behaviour of the accretion flow in the presence of outflows. The solutions represent the disc that rotates faster and becomes cooler for stronger outflows. Moreover, by adding magnetic diffusivity, the surface density and rotational velocity decrease, while the radial velocity and temperature increase. A study of the present model with the magnitude of a magnetic field implies that the disc rotates and accretes faster and becomes hotter, while the surface density decreases. The thickness of the disc increases when adding a magnetic field or resistivity, while the disc becomes thinner for more mass and energy losses resulting from the outflows.

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“…In this work, we calculate the global structure of the accretion flows surrounding massive Schwarzschild BHs. Instead of using a constant accretion rate, we assume that the accretion rate is a function of radius, e.g.,Ṁ =Ṁ out (R/R out ) s (e.g., Blandford & Begelman 1999;Stone et al 1999;Igumenshchev & Abramowicz 1999;Stone & Pringle 2001;Li & Cao 2009;Yuan & Bu 2010), where R out is the outer radius of the RIAF andṀ out is the accretion rate at R out . The global structure of the RIAF can be calculated with proper outer boundaries, if the parameterṡ m, α, β, and δ are specified (see Manmoto 2000 for more details).…”

Section: Modelmentioning

confidence: 99%

Possible Origin of Radio Emission From Nonthermal Electrons in Hot Accretion Flows for Low-Luminosity Active Galactic Nuclei

Liu

2013

ApJ

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The two components of radio emission, above and below 86 GHz, respectively, from the Galactic center source Sgr A* can be naturally explained by the hybrid of thermal and nonthermal electrons in hot accretion flows (e.g., radiatively inefficient accretion flow; RIAF). We further apply this model to a sample of nearby low-luminosity active galactic nuclei (LLAGNs), which are also believed to be powered by RIAF. We selected LLAGNs with only compact radio cores according to high-resolution radio observations, and sources observed with jets or jet-like features are excluded. We find that the radio emission of LLAGNs is severely underpredicted by the pure RIAF model, but can be naturally explained by the RIAF model with a hybrid electron population consisting of both thermal and nonthermal particles. Our model can roughly reproduce the observed anticorrelation between the mass-corrected radio loudness and Eddington ratio for the LLAGNs in our sample. We further model the spectral energy distributions of each source in our sample and find that roughly all sources can be well fitted if a small fraction of the steady-state electron energy is ejected into the nonthermal electrons. The size of the radio emission region of our model is around several thousands of gravitational radii, which is also roughly consistent with recent high-resolution VLBI observations for some nearby LLAGNs.

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Global dynamics of advection-dominated accretion flows with magnetically driven outflow

Cited by 20 publications

References 49 publications

An Accretion Disk-Outflow Model for Hysteretic State Transition in X-Ray Binaries

An Accretion Disk-Outflow Model for Hysteretic State Transition in X-Ray Binaries

Viscous and resistive accretion flows with radially self-similar outflows

Possible Origin of Radio Emission From Nonthermal Electrons in Hot Accretion Flows for Low-Luminosity Active Galactic Nuclei

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