Stationary axisymmetric configuration of the resistive thick accretion tori around a Schwarzschild black hole

Shaghaghian, Mahboobeh

doi:10.1093/mnras/stv2639

Cited by 3 publications

(6 citation statements)

References 26 publications

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“…That is, the flow restricted to the azimuthal component only, with assumption that the radial and meridional components are negligible in comparison with the azimuthal one (Banerjee et al 1997; Kovar et al 2011; Trova et al 2018). Similar to our idea, both in Newtonian regime (Tripathy, Prasanna, & Das 1990) and in relativistic regime for a non-rotating Schwarzschild black hole without the vertical component for the magnetofluid velocity (Shaghaghian 2016), already have been done. It is known that almost all of the celestial bodies have a non-zero spin, and thus, the Schwarzschild geometry does not tell the whole story.…”

Section: Introductionsupporting

confidence: 63%

“…wherein k and B 1 are constants and b 2 (θ) and f (r) are the unknown functions that must be determined. It is valuable to mention that, this model is inspired us by the self-consistent solution for poloidal magnetic field in the Schwarzschild metric (Shaghaghian 2016). Substituting this model in equation (39), we have…”

Section: Disc Magnetic Field Modelmentioning

confidence: 99%

“…Now, if their radial dependencies are presumed to be similar [i.e. ], then the term is a function only of as and equation (32) is rewritten as In fact, the term in bracket can be interpreted as mass accretion rate (Shaghaghian 2016) Thus, equation (34) leads to wherein is an integration constant and is an unknown function that will be determined. We prefer a sub-Eddington regime.…”

Section: General Formalismmentioning

confidence: 99%

“…To this aim, we presume the following model for the poloidal component of the disc’s magnetic field here wherein k and are constants and and f ( r ) are the unknown functions that must be determined. It is valuable to mention that this model is inspired us by the self-consistent solution for poloidal magnetic field in the Schwarzschild metric (Shaghaghian 2016). Substituting this model in equation (39), we have As seen, functions of the variables r and have been separated.…”

Section: General Formalismmentioning

confidence: 99%

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Resistive accretion flows around a Kerr black hole

Shaghaghian

2020

Publ. Astron. Soc. Aust.

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In this paper, we present the stationary axisymmetric configuration of a resistive magnetised thick accretion disc in the vicinity of external gravity and intrinsic dipolar magnetic field of a slowly rotating black hole. The plasma is described by the equations of fully general relativistic magnetohydrodynamics (MHD) along with the Ohm's law and in the absence of the effects of radiation fields. We try to solve these two-dimensional MHD equations analytically as much as possible. However, we sometimes inevitably refer to numerical methods as well. To fully understand the relativistic geometrically thick accretion disc structure, we consider all three components of the fluid velocity to be non-zero. This implies that the magnetofluid can flow in all three directions surrounding the central black hole. As we get radially closer to the hole, the fluid flows faster in all those directions. However, as we move towards the equator along the meridional direction, the radial inflow becomes stronger from both the speed and the mass accretion rate points of view. Nonetheless, the vertical (meridional) speed and the rotation of the plasma disc become slower in that direction. Due to the presence of pressure gradient forces, a sub-Keplerian angular momentum distribution throughout the thick disc is expected as well. To get a concise analytical form of the rate of accretion, we assume that the radial dependency of radial and meridional fluid velocities is the same. This simplifying assumption leads to radial independency of mass accretion rate. The motion of the accreting plasma produces an azimuthal current whose strength is specified based on the strength of the external dipolar magnetic field. This current generates a poloidal magnetic field in the disc which is continuous across the disc boundary surface due to the presence of the finite resistivity for the plasma. The gas in the disc is vertically supported not only by the gas pressure but also by the magnetic pressure.

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Section: Introductionsupporting

confidence: 63%

Section: Disc Magnetic Field Modelmentioning

confidence: 99%

Section: General Formalismmentioning

confidence: 99%

Section: General Formalismmentioning

confidence: 99%

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Resistive accretion flows around a Kerr black hole

Shaghaghian

2020

Publ. Astron. Soc. Aust.

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“…Some of them (e.g. Shadmehri 2004, Ghanbari et al 2007, Shaghaghian 2011, 2016) studied purely poloidal magnetic fields and many concentrated only toroidal fields (Akizuki & Fukue 2006, Khesali & Faghei 2008, Mosallanezhad et al 2014, 2016, Sarkar & Das 2016) and a few theoritical works have been recently done with the global magnetic field (Samadi & Abbassi 2016, Mosallanezhad et al 2016, Samadi et al 2017.…”

Section: Introductionmentioning

confidence: 99%

Anchoring Polar Magnetic Field in a Stationary Thick Accretion Disk

Samadi

Abbassi

2017

ApJ

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We investigate the properties of a hot accretion flow bathed in a poloidal magnetic field. We consider an axisymmetric viscous resistive flow in the steady state configuration. We assume the dominant mechanism of energy dissipation is due to turbulence viscosity and magnetic diffusivity. A certain fraction of that energy can be advected towards the central compact object. We employ self-similar method in the radial direction to find a system of ODEs with just one varible, θ in the spherical coordinates. For the existence and maintaining of a purely poloidal magnetic in a rotating thick disk, we find the necessary condition is a constant value of angular velocity along a magnetic field line. We obtain an analytical solution for the poloidal magnetic flux. We explore possible changes in the vertical structure of the disk under the influences of even symmetric and asymmetric magnetic fields. Our results reveal that a polar magnetic field with even symmetry about the equatorial plane makes the disk vertically thin. Moreover, the accretion rate decreases when we consider a strong magnetic field. Finally, we notice hot magnetized accretion flows can be fully advected even in a slim shape.

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Dynamical evolution of the resistive thick accretion Tori around a Schwarzschild black hole

Shaghaghian

2023

Monthly Notices of the Royal Astronomical Society

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To study time-dependent phenomena of plasma surrounding a non-rotating black hole with a dipolar magnetic field, we have developed a fully set of 3+1 formalism of generalised general relativistic magnetohydrodynamic (GRMHD) equations. The general relativistic phenomena, in particular, have been investigated with respect to the Ohm law. Magnetofluid is supposed to flow in three directions and forms a thick disc structure around the central black hole. All physical quantities of the system are functions of three variables: radial distance r, polar angle θ and time t. The radial, meridional and time behaviors of all these quantities have been investigated. It has been shown that the electrical conductivity of the fluid is not constant and may be both positive and negative depending on the values of some free parameters. The initially purely rotating non-magnetized plasma in the presence of an external magnetic field gives rise to an azimuthal current density and a charge density measured by the comoving observer. This current generates an electromagnetic field inside the disc which has both poloidal and toroidal components. The dipolar magnetic field lines of the central black hole is able to penetrate the plasma disc, due to the presence of a finite resistivity for the plama. The accreting plasma pushes them outwards and makes them parallel to the rotation axis of the disc in the meridional plane.

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Stationary axisymmetric configuration of the resistive thick accretion tori around a Schwarzschild black hole

Cited by 3 publications

References 26 publications

Resistive accretion flows around a Kerr black hole

Resistive accretion flows around a Kerr black hole

Anchoring Polar Magnetic Field in a Stationary Thick Accretion Disk

Dynamical evolution of the resistive thick accretion Tori around a Schwarzschild black hole

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