Structure of a hot accretion flow in the presence of outflow and convection with large ordered magnetic field

Ghasemnezhad, Maryam

doi:10.1093/mnras/stx1118

Cited by 12 publications

(4 citation statements)

References 44 publications

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“…We know that the ratio of the radial viscous force to the radial component of thermal pressure gradient for an accretion disc is proportional to (H/r) 2 in which H is the disc half-thickness (Frank et al 2002). Since the advectiondominated discs are geometrically thick, i.e., H/r ∼ 1, the radial viscosity may play a significant role in determining the properties of such discs (see also equation (32)).…”

Section: Introductionmentioning

confidence: 99%

The self-similar structure of advection-dominated discs with outflow and radial viscosity

Ghoreyshi

Shadmehri

2020

Monthly Notices of the Royal Astronomical Society

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Observational evidence and theoretical arguments postulate that outflows may play a significant role in the advection-dominated accretion discs (ADAFs). While the azimuthal viscosity is the main focus of most previous studies in this context, recent studies indicated that disc structure can also be affected by the radial viscosity. In this work, we incorporate these physical ingredients and the toroidal component of the magnetic field to explore their roles in the steady-state structure of ADAFs. We thereby present a set of similarity solutions where outflows contribute to the mass loss, angular momentum removal, and the energy extraction. Our solutions indicate that the radial viscosity causes the disc to rotate with a slower rate, whereas the radial gas velocity increases. For strong winds, the infall velocity may be of order the Keplerian speed if the radial viscosity is considered and the saturated conduction parameter is high enough. We show that the strength of magnetic field and of wind can affect the effectiveness of radial viscosity.

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Section: Introductionmentioning

confidence: 99%

The self-similar structure of advection-dominated discs with outflow and radial viscosity

Ghoreyshi

Shadmehri

2020

Monthly Notices of the Royal Astronomical Society

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“…The influence of poloidal field component in an ADAF in the absence of outflows has been examined by Zhang & Dai (2008). Adopting the ideal magnetohydrodynamic (MHD) approximation, they concluded that the poloidal field component can reduce the temperature (see also Ghasemnezhad 2017). But Bu, Yuan, & Xie (2009) showed that the role of poloidal field component in the temperature reduction can be more significant when the outflows are considered (see also Mosallanezhad, Khajavi, & Abbassi 2013).…”

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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“…Possibility of suppressing magnetic field reversals in accretion disks due to accretion was discussed in [42]. Also we mention works [43,44] devoted to modeling the relationship between convection and magnetic field in accretion disks. The effect of convective flows is essential for the evolution of magnetic fields in galaxies.…”

Section: Convection In Astrophysicsmentioning

confidence: 99%

Notes about collapse in magnetohydrodynamics

Kuznetsov,

Mikhailov

2022

Preprint

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We discuss a problem about magnetic collapse as a possible process for singularity formation of the magnetic field in a finite time within ideal magneto-hydrodynamics for incompressible fluids. This process is very important from the point of view of various astrophysical applications, in particular, as a mechanism of magnetic filaments formation in the convective zone of the Sun. The collapse possibility is connected with compressibility of continuously distributed magnetic field lines. A wellknown example of the formation of magnetic filaments in the kinematic dynamo approximation with a given velocity field, first considered by Parker in 1963 [1], rather indicates that the increase in the magnetic field is exponential in time. In the case of the kinematic approximation for the induction equation, the magnetic filaments formation is shown to occur in areas with a hyperbolic velocity profile.

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Structure of a hot accretion flow in the presence of outflow and convection with large ordered magnetic field

Cited by 12 publications

References 44 publications

The self-similar structure of advection-dominated discs with outflow and radial viscosity

The self-similar structure of advection-dominated discs with outflow and radial viscosity

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

Notes about collapse in magnetohydrodynamics

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