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Disk accretion onto a magnetized star occurs in a variety of astrophysical contexts, from young stars to X-ray pulsars. The magnetohydrodynamic interaction between the stellar field and the accreting matter can have a strong effect on the…

Astrophysics · Physics 2009-10-31 Dmitri A. Uzdensky , Arieh Konigl , Christof Litwin

Models of planet-disk interaction are mainly based on 2D and 3D viscous hydrodynamical simulations. Accretion is classically prescribed by an alpha parameter which characterizes the turbulent radial transport of angular momentum (AM) in the…

Solar and Stellar Astrophysics · Physics 2023-05-22 Gaylor Wafflard-Fernandez , Geoffroy Lesur

Strongly magnetized accretion discs around black holes have attractive features that may explain enigmatic aspects of X-ray binary behaviour. The structure and evolution of these discs are governed by a dynamo-like mechanism, which channels…

High Energy Astrophysical Phenomena · Physics 2016-02-03 Greg Salvesen , Jacob B. Simon , Philip J. Armitage , Mitchell C. Begelman

Stellar atmosphere models of ionized accretion disks have generally neglected the contribution of magnetic fields to the vertical hydrostatic support, although magnetic fields are widely believed to play a critical role in the transport of…

Astrophysics · Physics 2009-11-11 O. M. Blaes , S. W. Davis , S. Hirose , J. H. Krolik , J. M. Stone

We present the first results of a global axisymmetric simulation of accretion onto rotating magnetized stars from a turbulent, MRI-driven disk. The angular momentum is transported outward by the magnetic stress of the turbulent flow with a…

Solar and Stellar Astrophysics · Physics 2015-05-27 Marina M. Romanova , Galina V. Ustyugova , Alexander V. Koldoba , Richard V. E. Lovelace

We have extended our previous mean-field galactic dynamo model which included algebraic and dynamic alpha nonlinearities (Kleeorin et al., A&A, v. 387, 453, 2002), to include also a quenching of turbulent diffusivity. We readily obtain…

Astrophysics · Physics 2014-10-13 N. Kleeorin , D. Moss , I. Rogachevskii , D. Sokoloff

Large-scale magnetic fields are key ingredients of magnetically driven disk accretion. We study how large-scale poloidal fields evolve in accretion disks, with the primary aim of quantifying the viability of magnetic accretion mechanisms in…

Earth and Planetary Astrophysics · Physics 2015-06-17 Satoshi Okuzumi , Taku Takeuchi , Takayuki Muto

We investigate the significance of large scale azimuthal, magnetic and velocity modes for the MRI turbulence in accretion disks. We perform 3D global ideal MHD simulations of global stratified proto-planetary disk models. Our domains span…

Solar and Stellar Astrophysics · Physics 2015-05-30 M. Flock , N. Dzyurkevich , H. Klahr , N. Turner , Th. Henning

The aim of this paper is to investigate the properties of accretion disks threaded by a weak vertical magnetic field, with a particular focus on the interplay between MHD turbulence driven by the magnetorotational instability (MRI) and…

High Energy Astrophysical Phenomena · Physics 2015-06-11 Sebastien Fromang , Henrik N. Latter , Geoffroy Lesur , Gordon I. Ogilvie

We present a systematic, analytical study of geometrically thin, optically thick accretion disc solutions for magnetized turbulent flows, with an alpha-like viscosity prescription. Under the only assumptions that (1) Magneto-Rotational…

Astrophysics · Physics 2009-11-07 A. Merloni

Giant planets embedded in protoplanetary disks (PPDs) can create annulus density gaps around their orbits in the type-II regime, potentially responsible for the ubiquity of annular substructures observed in PPDs. Despite of substantial…

Earth and Planetary Astrophysics · Physics 2024-07-23 Yuhiko Aoyama , Xuening Bai

A new theory of eccentric accretion discs is presented. Starting from the basic fluid-dynamical equations in three dimensions, I derive the fundamental set of one-dimensional equations that describe how the mass, angular momentum and…

Astrophysics · Physics 2009-11-06 G. I. Ogilvie

We present analytical and numerical solutions for accretion discs subject to a non-zero central torque. We express this in terms of a single parameter, $f$, which is the ratio of outward viscous flux of angular momentum from the inner…

High Energy Astrophysical Phenomena · Physics 2020-12-16 C. J. Nixon , J. E. Pringle

We perform local, vertically stratified shearing-box MHD simulations of protoplanetary disks (PPDs) at a fiducial radius of 1 AU that take into account the effects of both Ohmic resistivity and ambipolar diffusion (AD). The magnetic…

Earth and Planetary Astrophysics · Physics 2015-06-12 Xue-Ning Bai , James M. Stone

We propose that the accretion disks fueling active galactic nuclei are supported vertically against gravity by a strong toroidal ($\phi-$direction) magnetic field that develops naturally as the result of an accretion disk dynamo. The…

High Energy Astrophysical Phenomena · Physics 2016-10-12 Mitchell C. Begelman , Joseph Silk

(Abridged) Based on the rapidly increasing all-sky data of Faraday rotation measures and polarised synchrotron radiation, the Milky Way's magnetic field is now modelled with an unprecedented level of detail and complexity. We aim to…

Astrophysics of Galaxies · Physics 2015-06-17 Oliver Gressel , Detlef Elstner , Udo Ziegler

The final architecture of planetary systems depends on the extraction of angular momentum and mass-loss processes of the discs in which they form. Theoretical studies proposed that magnetized winds launched from the discs (MHD disc winds)…

Earth and Planetary Astrophysics · Physics 2021-12-15 Benoît Tabone , Giovanni P. Rosotti , Giuseppe Lodato , Philip J. Armitage , Alexander J. Cridland , Ewine F. van Dishoeck

Hydrodynamics and magnetohydrodynamic simulations of hot accretion flow have indicated that there is an inward decreasing of mass accretion rate with decreasing radius. Consequently, we have a flatter density profile ($\rho \propto r^{-p}$…

High Energy Astrophysical Phenomena · Physics 2017-06-12 Maryam Ghasemnezhad

The dynamics and structure of accretion disks, which accumulate the vertical magnetic field in the centers, are investigated using two- and three-dimensional MHD simulations. The central field can be built up to the equipartition level and…

Astrophysics · Physics 2009-11-13 Igor V. Igumenshchev

We review the current theoretical models of the inward advection of the large scale external magnetic fields in accretion discs. The most plausible theories for launching astrophysical jets rely on strong magnetic fields at the inner parts…

High Energy Astrophysical Phenomena · Physics 2019-04-24 Amir Jafari
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