The Effects of Toroidal Magnetic Field on the Vertical Structure of Hot Accretion Flows

Zeraatgari, Fatemeh Zahra; Mosallanezhad, Amin; Abbassi, Shahram; Yuan, Ye‐Fei

doi:10.3847/1538-4357/aa9ffd

Cited by 10 publications

(9 citation statements)

References 68 publications

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“…So there is a possibility that the disk thickness can matched with previous studies for some suitable flow parameters. If we compare results for 2D disk structure with no outflow (Narayan & Yi 1995a;Zeraatgari et al 2018) then the our disk vertical thickness is low since the integration is terminated at the sonic surface. For no outflow disk structure (Figure 2f), the thickness increased with the increasing viscosity.…”

Section: Inflow-outflow Solutionsmentioning

confidence: 99%

The 2D Disk Structure with Advective Transonic Inflow–Outflow Solutions around Black Holes

Kumar

2018

ApJ

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We solved analytically viscous two-dimensional (2D) fluid equations for accretion and outflows in spherical polar coordinates (r, θ, φ) and obtained explicitly flow variables in r− and θ−directions around black holes (BHs). We investigated global transonic advection-dominated accretion flow (ADAF) solutions in r−direction on an equatorial plane with using Paczyński-Wiita potential. We used radial flow variables of ADAFs with symmetric conditions on the equatorial plane, as initial values for integration in θ−direction. In the study of 2D disk structure, we used twoazimuthal components of viscous stress tensors namely, τ rφ and τ θφ . Interestingly, we found that the whole advective disk is not participating in outflow generation and the outflows form close to the BHs. Normally, outflow strength increased with increasing viscosity parameter (α 1 ), mass-loss parameter (s) and decreasing gas pressure ratio (β). Outflow region increased with increasing s, α 1 for τ rφ and decreasing α 2 for τ θφ . The τ θφ is effective in angular momentum transportation at high latitude and outflows collimation along an axis of symmetry since it changes polar velocity (v θ ) of the flow. The outflow emission is also affected by the ADAF size and decreased with decreasing it. Transonic surfaces formed for both inflows (v r < 0, very close to BH) and outflows (v r > 0). We also explored no outflows, outflows and failed outflows regions, which mainly depend on the viscosity parameters.

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Section: Inflow-outflow Solutionsmentioning

confidence: 99%

The 2D Disk Structure with Advective Transonic Inflow–Outflow Solutions around Black Holes

Kumar

2018

ApJ

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“…Since these flows, such as ADAFs, have the mean free path for Coulomb interactions larger than the typical size of the system, they are effectively collisionless (Quataert 1998), and the ideal MHD approximation may not be sufficient to study their properties. The recent studies have shown that the resistive dissipation in hot accretion flows around black holes can modify the amount of magnetic field, and the role of magnetic field in transferring the angular momentum (Zahra Zeraatgari et al 2018). Zahra Zeraatgari et al (2018) suggested that the magnetic dissipation heating in regions of disc where outflows may be important is comparable to the viscous heating.…”

Section: Introductionmentioning

confidence: 99%

Self-similar structure of resistive ADAFs with outflow and large-scale magnetic field

Ghoreyshi

2020

Publ. Astron. Soc. Aust.

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The observations and simulations have revealed that large-scale magnetic field and outflows can exist in the inner regions of an advection-dominated accretion disc where the resistive diffusion may also be important. In the present paper, the roles of large-scale magnetic field and outflows in the structure of resistive advection-dominated accretion discs are explored by assuming that the accretion flow is radially self-similar. In the non-ideal magnetohydrodynamic (MHD) approximation, the results show that the angular velocity is always sub-Keplerian when both the outflow and the large-scale magnetic field are taken into account. A stronger toroidal field component leads to faster rotation, while the disc rotates with faster rate if the vertical field component is weaker. The increase of magnetic diffusivity causes the infall velocity to be close to Keplerian velocity. Although the previous studies in the ideal MHD approximation have shown that the disc temperature decreases due to the vertical field component, we find that the effect of vertical field component on the temperature of a resistive disc depends on the magnetic diffusivity. When the magnetic diffusivity is high, the more efficient mechanism for decreasing the disc temperature can be the outflows, and not the large-scale magnetic field. In such a limit of the magnetic diffusivity, the components of the large-scale magnetic field enhance the gas temperature. The increase of temperature can lead to heating and acceleration of the electrons and help us to explain the origin of phenomena such as the flares in Sgr A*. On the other hand, the infall velocity in such a limit rises as the temperature increases, and therefore the surface density falls to too low values. Any change in the density profile can alter the structure and the emitted spectrum of disc.

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“…The self-similar solutions are qualitatively good with ADAFs (Narayan & Yi 1994;Narayan et al 1997). They are used to simplify partial differential equations (PDEs) into ordinary differential equations (ODEs) of the fluid for the studies of two-dimensional (2D) disk structures, with and without outflows, by many authors (Narayan & Yi 1995a;Xu & Chen 1997;Blandford & Begelman 1999Xue & Wang 2005;Xie & Yuan 2008;Gu et al 2009;Jiao & Wu 2011;Gu 2012Gu , 2015Jiao et al 2015) for HD flows and MHD flows (Samadi & Abbassi 2016;Mosallanezhad et al 2016;Habibi et al 2017;Zeraatgari et al 2018;Ghasemnezhad & Samadi 2018;Bu & Mosallanezhad 2018), and also for the investigation of disk nonthermal radiation (Narayan & Yi 1995b). These authors have used the self-similar solution of the first kind, and all the three-velocities ∝ r 0.5 .…”

Section: Introductionmentioning

confidence: 91%

“…In the present study, we have defined general self-similar solutions (power index rule, p) of the second kind with the help of different sized ADAFs. So, these kinds of self-similar solutions can give an easier understanding of the two-zone radial theory, when one can reproduce results of Narayan & Yi (1995b); Esin et al (1997), and the outflows (Narayan & Yi 1995a;Jiao & Wu 2011;Zeraatgari et al 2018) with changing only p, which changed the energy and transition radius of the flow. This study lacks two things; First, in the sense of quantitative ways because we have not considered explicitly relevant cooling in the fluid, and we will leave it for future studies.…”

Section: Introductionmentioning

confidence: 99%

Self-similar Solutions for Finite Size Advection-dominated Accretion Flows

Kumar

2019

ApJ

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We investigated effects on flow variables of transonic advection-dominated accretion flows (ADAFs) for different outer boundary locations (BLs) with a changing energy constant (E) of the flow. We used the ADAF solutions and investigated a general power index rule of a radial bulk velocity (v r ∝ r −p ) with different BLs, but the power index with radius for a rotation velocity and sound speed is unchanged. Here, p ≥ 0.5 is a power index. This power rule gives two types of self-similar solutions; first, when p = 0.5 gives a self-similar solution of a first kind and exists for infinite length, which has already been discovered for the ADAFs by Narayan & Yi, and second, when p > 0.5 gives a self-similar solution of a second kind and exists for finite length, which corresponds to our new solutions for the ADAFs. By using this index rule in fluid equations, we found that the Mach number (M ) and advection factor (f adv ) vary with the radius when p > 0.5. The local energies of the ADAFs and the Keplerian disk are matched very well at the BLs. So, this theoretical study is supporting a two-zone configuration theory of the accretion disk, and we also discussed other possible hybrid disk geometries. The present study can have two main implications with a variation of the p; first, one that can help with the understanding of outflows and non-thermal spectrum variations in black hole candidates, and second, one that can help with solving partial differential equations for any sized advective disk.

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The Effects of Toroidal Magnetic Field on the Vertical Structure of Hot Accretion Flows

Cited by 10 publications

References 68 publications

The 2D Disk Structure with Advective Transonic Inflow–Outflow Solutions around Black Holes

The 2D Disk Structure with Advective Transonic Inflow–Outflow Solutions around Black Holes

Self-similar structure of resistive ADAFs with outflow and large-scale magnetic field

Self-similar Solutions for Finite Size Advection-dominated Accretion Flows

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