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In this paper we review some aspects of the theory of magnetic threaded disks. We discuss in particular the equations that determine the position of the inner disk boundary by using different prescriptions for the neutron star-accretion…

Astrophysics · Physics 2009-11-13 E. Bozzo , L. Stella , M. Vietri , P. Ghosh

We use global magnetohydrodynamic simulations to study the influence of net vertical magnetic fields on the structure of geometrically thin ($H/r \approx 0.05$) accretion disks in the Newtonian limit. We consider initial mid-plane gas to…

High Energy Astrophysical Phenomena · Physics 2020-01-23 Bhupendra Mishra , Mitchell C. Begelman , Philip J. Armitage , Jacob B. Simon

We investigate the rotational dynamics of disk accretion around a strongly magnetized neutron star with an aligned dipole field. The magnetospheric field is assumed to thread the disk plasma both inside and outside the corotation radius. As…

Astrophysics · Physics 2009-11-10 M. Hakan Erkut , M. Ali Alpar

We performed 2D and full 3D magnetohydrodynamic simulations of disk accretion to a rotating star with an aligned or misaligned dipole magnetic field. We investigated the rotational equilibrium state and derived from simulations the ratio…

This paper studied the relativistic accretion thick disc model raised by a deformed compact object that slightly deviated from spherical up to the quadrupole moment by utilising $\rm q$-metric. This metric is the simplest asymptotically…

High Energy Astrophysical Phenomena · Physics 2025-02-14 Shokoufe Faraji , Audrey Trova

We present numerical solutions for stationary and axisymmetric equilibriums of compact stars associated with extremely strong magnetic fields. The interior of the compact stars is assumed to satisfy ideal magnetohydrodynamic (MHD)…

General Relativity and Quantum Cosmology · Physics 2025-12-22 Koji Uryu , Shijun Yoshida , Eric Gourgoulhon , Charalampos Markakis , Kotaro Fujisawa , Antonios Tsokaros , Keisuke Taniguchi , Mina Zamani

We present the results of numerical integrations yielding the structure of and meridional flow in axisymmetric thin viscous accretion disk models. The solutions are obtained by simplifying and approximating first the equations, using…

Astrophysics · Physics 2009-11-07 O. Regev , L. Gitalman

We present a set of three-dimensional, global, general relativistic radiation magnetohydrodynamic simulations of thin, radiation-pressure-dominated accretion disks surrounding a non-rotating, stellar-mass black hole. The simulations are…

High Energy Astrophysical Phenomena · Physics 2022-11-09 Bhupendra Mishra , P. Chris Fragile , Jessica Anderson , Aidan Blankenship , Hui Li , Krzysztof Nalewajko

An analytical model is developed for the screening of the external magnetic field of a rotating, axisymmetric neutron star due to the accretion of plasma from a disk. The decrease of the field occurs due to the electric current in the…

Astrophysics · Physics 2007-05-23 R. V. E. Lovelace , M. M. Romanova , G. S. Bisnovatyi-Kogan

We review observational evidence and open issues related to the process of magnetospheric accretion in T Tauri stars. Emphasis is put on recent numerical simulations and observational results which suggest that the interaction between the…

Astrophysics · Physics 2016-11-03 J. Bouvier , S. H. P. Alencar , C. Dougados

We use three dimensional magnetohydrodynamic simulations to study the structure of the boundary layer between an accretion disc and a non-rotating, unmagnetized star. Under the assumption that cooling is efficient, we obtain a narrow but…

Astrophysics · Physics 2009-11-07 Philip J. Armitage

A numerical model of a steady state, thin accretion disk with a constant effective speed of sound is presented. We demonstrate that `zero torque' inner boundary condition is a reasonable approximation provided that the disk thickness,…

Astrophysics · Physics 2009-09-02 Niayesh Afshordi , Bohdan Paczynski

I briefly review the theoretical models of radiatively efficient, geometrically thin and optically thick accretion disk spectra that currently exist for AGN. I then discuss three recent observational developments that have real potential to…

Astrophysics · Physics 2007-05-23 Omer Blaes

Applying the Horsk\'y-Mitskievitch conjecture to the empty space solutions of Morgan and Morgan due to the gravitational field of a finite disk, we have obtained the corresponding solutions of the Einstein-Maxwell equations. The resulting…

General Relativity and Quantum Cosmology · Physics 2015-05-20 Antonio C. Gutiérrez-Piñeres , Guillermo A. González

We perform resistive MHD simulations of accretion disk with alpha-viscosity, accreting onto a rotating star endowed with a magnetic dipole. We find backflow in the presence of strong magnetic field and large resistivity, and probe for the…

Solar and Stellar Astrophysics · Physics 2020-12-25 Ruchi Mishra , Miljenko Čemeljić , Wlodek Kluźniak

We describe three-dimensional general relativistic magnetohydrodynamic simulations of a geometrically thin accretion disk around a non-spinning black hole. The disk has a thickness $h/r\sim0.05-0.1$ over the radial range $(2-20)GM/c^2$. In…

The problem of the late accretion phase of the evolution of an axisymmetric, isothermal magnetic disk surrounding a forming star has been formulated in a companion paper. The "central sink approximation" is used to circumvent the problem of…

Astrophysics · Physics 2009-11-10 Konstantinos Tassis , Telemachos Ch. Mouschovias

We obtained thermal equilibrium solutions for optically thin, two-temperature black hole accretion disks incorporating magnetic fields. The main objective of this study is to explain the bright/hard state observed during the bright/slow…

High Energy Astrophysical Phenomena · Physics 2015-05-18 Hiroshi Oda , Mami Machida , Kenji E. Nakamura , Ryoji Matsumoto

A widely accepted picture of an accretion flow in the luminous soft spectral state of X-ray binary systems is a geometrically thin disc structure much like the classic analytic solution of Shakura \& Sunyaev. Although the analytic models…

We obtained steady solutions of optically thin, single temperature, magnetized black hole accretion disks assuming thermal bremsstrahlung cooling. Based on the results of 3D MHD simulations of accretion disks, we assumed that the magnetic…

Astrophysics · Physics 2015-06-24 H. Oda , M. Machida , K. E. Nakamura , R. Matsumoto