scholarly journals 8.10. Three-dimensional global MHD simulations of jet formation in active galactic nuclei

1998 ◽  
Vol 184 ◽  
pp. 363-364
Author(s):  
R. Matsumoto ◽  
K. Shibata
Keyword(s):  
Active Galactic Nuclei ◽  
Accretion Disks ◽  
Three Dimensional ◽  
Galactic Nuclei ◽  
Equatorial Region ◽  
Astrophysical Jets ◽  
Magnetorotational Instability ◽  
Jet Formation ◽  
Mhd Simulations ◽  
Avalanche Flow

Magnetically driven jets from accretion disks are considered to be the most promising models of astrophysical jets. Uchida & Shibata (1985) and Shibata & Uchida (1986) first carried out two-dimensional nonlinear MHD simulations of jet formation from a magnetized disk. Matsumoto et al. (1996) applied the Uchida-Shibata model to a gas torus in active galactic nuclei and showed that the surface layer of the torus accretes faster than the equatorial region like an avalanche because magnetic braking most effectively extracts angular momentum from that layer. A magnetized torus subjects to global non-axisymmetric instabilities (Curry & Pudritz 1996) and local magnetorotational instability (Balbus & Hawley 1991). We carried out three-dimensional global MHD simulations to show the non-axisymmetric effects on the torus, avalanche flow and jet formation.

scholarly journals Three-Dimensional Global MHD Simulations of Magnetised Accretion Disks and Jets

1997 ◽  
Vol 163 ◽  
pp. 443-447 ◽  
Author(s):  
R. Matsumoto ◽  
K. Shibata
Keyword(s):  
Surface Layer ◽  
Magnetic Fields ◽  
Accretion Disks ◽  
Large Scale ◽  
Three Dimensional ◽  
Maximum Speed ◽  
Jet Formation ◽  
Mhd Simulations ◽  
Avalanche Flow ◽  
Magnetic Braking

AbstractWe carried out three-dimensional global MHD simulations of jet formation from an accretion disk threaded by large-scale magnetic fields. Numerical results show that bipolar jets with maximum speed υjet ~ υKepler are created. The surface layer of the disk accretes faster than the equatorial part because magnetic braking most effectively affects that layer. Accretion proceeds along spiral channels which correspond to the surface avalanche flow appearing in previous axisymmetric simulations. Spirally shaped low β (= Pgas/Pmag < 1) regions appear in the innermost part of accretion disks where toroidal magnetic fields become dominant.

scholarly journals Magnetically Driven Jets from Accretion Disks: Comparison Between 2.5D Nonsteady Simulations and 1.5D Nonsteady/Steady Solutions

1997 ◽  
Vol 163 ◽  
pp. 753-753 ◽  
Author(s):  
T. Kudoh ◽  
R. Matsumoto ◽  
K. Shibata
Keyword(s):  
Magnetic Field ◽  
Active Galactic Nuclei ◽  
Accretion Disks ◽  
Galactic Nuclei ◽  
Astrophysical Jets ◽  
Initial Value ◽  
Mhd Simulations ◽  
Current Belief ◽  
Steady Solutions ◽  
The Magnetic Field

We have performed 1D(1.5D) and 2D(2.5D) nonsteady MHD numerical simulations of astrophysical jets which are magnetically driven from Keplerian disks, in order to clarify the origin and structure of jets ejected from protostars and active galactic nuclei. The initial and boundary conditions are similar to those of 2D(2.5D) nonsteady MHD simulations of Shibata and Uchida (1986) and Matsumoto et al. (1996); there is initially a Keplerian disk with a nonrotating corona outside, both of which are penetrated by vertical magnetic fields. The subsequent interaction between the disk/corona and the vertical fields are studied as an initial value problem. Against the current belief that this kind of simulations show simply a transient jet caused by nonsteady interaction between the disk/corona and the magnetic field, we have found that the jets ejected from the disk in this way have the same properties of the steady magnetically driven jets that were investigated by using ID steady wind solution (Kudoh & Shibata 1995), even if the jets are not exactly in steady state.

scholarly journals Sweeping-Magnetic-Twist Mechanism and Molecular Bipolar Flows

1987 ◽  
Vol 115 ◽  
pp. 385-387
Author(s):  
Kazunari SHIBATA ◽  
Yutaka UCHIDA
Keyword(s):  
Magnetic Field ◽  
Black Hole ◽  
Active Galactic Nuclei ◽  
Accretion Disks ◽  
Large Scale ◽  
Galactic Nuclei ◽  
Main Mechanism ◽  
Astrophysical Jets ◽  
Centrifugal Effect ◽  
Poloidal Magnetic Field

Uchida and Shibata have proposed the “sweeping-magnetic-twist” mechanism for the formation of astrophysical jets in relation to the accretion disks (disks around protostars, around black hole in the center of active galactic nuclei, and so on) in which a jet is accelerated by thejxBforce in the relaxing magnetic twist created in the winding-up of the poloidal magnetic field by the rotation of the contracting disk (Uchida and Shibata 1985a, b; Shibata and Uchida 1986a, b; Uchidaet al.1985). In this mechanism, a jet is collimated also by thejxBforce due to the large scale poloidal magnetic field whose footpoints are squeezed in the contracting disk. The main mechanism involved is different from that of centrifugal wind models (Blandford and Payne 1982, Pudritz and Norman 1983) and worked out indepentently, but the centrifugal effect itself is automatically built-in.

scholarly journals Supernova Explosions in Accretion Disks in Active Galactic Nuclei: Three-dimensional Models

2020 ◽  
Vol 906 (1) ◽  
pp. 15
Author(s):  
A. Moranchel-Basurto ◽  
F. J. Sánchez-Salcedo ◽  
Raúl O. Chametla ◽  
P. F. Velázquez
Keyword(s):  
Active Galactic Nuclei ◽  
Accretion Disks ◽  
Three Dimensional ◽  
Galactic Nuclei ◽  
Supernova Explosions ◽  
Dimensional Models ◽  
Three Dimensional Models

scholarly journals Symmetry and the Arrow of Time in Theoretical Black Hole Astrophysics

2015 ◽  
Vol 2015 ◽  
pp. 1-5
Author(s):  
David Garofalo
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Active Galactic Nuclei ◽  
Accretion Disks ◽  
Time Reversal ◽  
Large Scale ◽  
Galactic Nuclei ◽  
Arrow Of Time ◽  
Time Symmetry ◽  
The Universe

While the basic laws of physics seem time-reversal invariant, our understanding of the apparent irreversibility of the macroscopic world is well grounded in the notion of entropy. Because astrophysics deals with the largest structures in the Universe, one expects evidence there for the most pronounced entropic arrow of time. However, in recent theoretical astrophysics work it appears possible to identify constructs with time-reversal symmetry, which is puzzling in the large-scale realm especially because it involves the engines of powerful outflows in active galactic nuclei which deal with macroscopic constituents such as accretion disks, magnetic fields, and black holes. Nonetheless, the underlying theoretical structure from which this accreting black hole framework emerges displays a time-symmetric harmonic behavior, a feature reminiscent of basic and simple laws of physics. While we may expect such behavior for classical black holes due to their simplicity, manifestations of such symmetry on the scale of galaxies, instead, surprise. In fact, we identify a parallel between the astrophysical tug-of-war between accretion disks and jets in this model and the time symmetry-breaking of a simple overdamped harmonic oscillator. The validity of these theoretical ideas in combination with this unexpected parallel suggests that black holes are more influential in astrophysics than currently recognized and that black hole astrophysics is a more fundamental discipline.

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