scholarly journals Accretion disks with a large scale magnetic field around black holes, and magnetic jet collimation

2011 ◽  
Author(s):  
Gennady Bisnovatyi-Kogan
Keyword(s):  
Magnetic Field ◽  
Black Holes ◽  
Accretion Disks ◽  
Large Scale ◽  
Large Scale Magnetic Field ◽  
Jet Collimation

scholarly journals ACCRETION DISKS WITH A LARGE SCALE MAGNETIC FIELD AROUND BLACK HOLES

2013 ◽  
Vol 53 (A) ◽  
pp. 677-682
Author(s):  
Gennady Bisnovatyi-Kogan ◽  
Alexandr S. Klepnev ◽  
Richard V.E. Lovelace
Keyword(s):  
Magnetic Field ◽  
Black Holes ◽  
Accretion Disk ◽  
Accretion Disks ◽  
Large Scale ◽  
Outward Diffusion ◽  
Large Scale Magnetic Field ◽  
Jet Collimation ◽  
The Magnetic Field ◽  
Inner Parts

We consider accretion disks around black holes at high luminosity, and the problem of the formation of a large-scale magnetic field in such disks, taking into account the non-uniform vertical structure of the disk. The structure of advective accretion disks is investigated, and conditions for the formation of optically thin regions in central parts of the accretion disk are found. The high electrical conductivity of the outer layers of the disk prevents outward diffusion of the magnetic field. This implies a stationary state with a strong magnetic field in the inner parts of the accretion disk close to the black hole, and zero radial velocity at the surface of the disk. The problem of jet collimation by magneto-torsion oscillations is investigated.

Large scale magnetic field and advection in accretion disks around black holes

2008 ◽  
Author(s):  
G. S. Bisnovatyi-Kogan ◽  
Felix A. Aharonian ◽  
Werner Hofmann ◽  
Frank Rieger
Keyword(s):  
Magnetic Field ◽  
Black Holes ◽  
Accretion Disks ◽  
Large Scale ◽  
Large Scale Magnetic Field

scholarly journals Magnetic Flux Transport in Protostellar Accretion Disks

1997 ◽  
Vol 163 ◽  
pp. 692-692
Author(s):  
John Contopoulos ◽  
Arieh Königl
Keyword(s):  
Magnetic Field ◽  
Angular Momentum ◽  
Accretion Disks ◽  
Large Scale ◽  
Turbulent Viscosity ◽  
Flux Transport ◽  
Disk Structure ◽  
Large Scale Magnetic Field ◽  
Field Lines ◽  
Open Magnetic Field

AbstractCentrifugally driven winds from the surfaces of magnetized accretion disks are a leading candidate for the origin of bipolar outflows and have also been recognized as an attractive mechanism for removing the angular momentum of the accreted matter. The origin of the open magnetic field lines that thread the disk in this scenario is, however, still uncertain. One possibility is that the field lines are transported through the disk, but previous studies have shown that this process is inefficient in disks with turbulent viscosity and diffusivity. Here we examine whether the efficiency can be increased if angular momentum is transported from the disk surfaces by large-scale magnetic fields instead of radially by viscous stresses. In this picture, the removal of angular momentum is associated with the establishment of a global poloidal electric current driven by the radial EMF in the disc, and it does not necessarily need to involve super-Alfvénic outflows. We address this problem in the context of protostellar systems and present representative solutions of the time evolution of a resistive disk that is initially threaded by a uniform vertical field anchored at a large distance from its surfaces. We assume that the angular momentum transport in the disk is controlled by the large-scale magnetic field and take into account the influence of the field on the disk structure.

scholarly journals Jet launching and field advection in quasi-Keplerian discs

2010 ◽  
Vol 6 (S275) ◽  
pp. 260-264 ◽  
Author(s):  
Jonathan Ferreira ◽  
Pierre Olivier Petrucci
Keyword(s):  
Magnetic Field ◽  
Black Holes ◽  
Large Scale ◽  
Accretion Disc ◽  
Total Power ◽  
State Problem ◽  
Confined Jets ◽  
Anomalous Viscosity ◽  
Large Scale Magnetic Field ◽  
Steady State Problem

AbstractThe fact that self-confined jets are observed around black holes, neutron stars and young forming stars points to a jet launching mechanism independent of the nature of the central object, namely the surrounding accretion disc. The properties of Jet Emitting Discs (JEDs) are briefly reviewed. It is argued that, within an alpha prescription for the turbulence (anomalous viscosity and diffusivity), the steady-state problem has been solved. Conditions for launching jets are very stringent and require a large scale magnetic field Bz close to equipartition with the total (gas and radiation) pressure. The total power feeding the jets decreases with the disc thickness: fat ADAF-like structures with h ~ r cannot drive super-Alfvénic jets. However, there exist also hot, optically thin JED solutions that would be observationally very similar to ADAFs.Finally, it is argued that variations in the large scale magnetic Bz field is the second parameter required to explain hysteresis cycles seen in LMXBs (the first one would be Ṁa).

scholarly journals Large-scale dynamo of accretion disks around supermassive nonrotating black holes

2006 ◽  
pp. 49-55
Author(s):  
A.L. Poplavsky ◽  
O.P. Kuznechik ◽  
N.I. Stetyukevich
Keyword(s):  
Magnetic Field ◽  
Black Holes ◽  
Active Galactic Nuclei ◽  
Accretion Disks ◽  
Large Scale ◽  
Temporal Distribution ◽  
Galactic Nuclei ◽  
Dynamo Action ◽  
Stable Circular Orbit ◽  
General Relativistic

In this paper one presents an analytical model of accretion disk magnetosphere dynamics around supermassive nonrotating black holes in the centers of active galactic nuclei. Based on general relativistic equations of magneto hydrodynamics, the nonstationary solutions for time-dependent dynamo action in the accretion disks, spatial and temporal distribution of magnetic field are found. It is shown that there are two distinct stages of dynamo process: the transient and the steady-state regimes, the induction of magnetic field at t > 6:6665 x 1011GM/c3 s becomes stationary, magnetic field is located near the innermost stable circular orbit, and its value rises up to ~ 105 G. Applications of such systems with nonrotating black holes in real active galactic nuclei are discussed.

Large-scale magnetic field of the accretion disks of T Tauri stars

2018 ◽  
Vol 14 (S345) ◽  
pp. 297-298
Author(s):  
Alexander E. Dudorov ◽  
Sergey A. Khaibrakhmanov ◽  
Sergey Yu. Parfenov ◽  
Andrey M. Sobolev
Keyword(s):  
Magnetic Field ◽  
Accretion Disks ◽  
Large Scale ◽  
Young Stars ◽  
T Tauri ◽  
Ionization Structure ◽  
Large Scale Magnetic Field ◽  
Field Geometry ◽  
Simulation Results

AbstractThe large-scale magnetic field in the accretion disks of young stars is investigated. Main features of our magnetohydrodynamical (MHD) model of the accretion disks and typical simulation results are presented. We discuss the role of MHD effects, ionization structure, magnetic field geometry and strength of the accretion disks.

scholarly journals The magnetic helicity density patterns from non-axisymmetric solar dynamo

2021 ◽  
Vol 87 (1) ◽  
Author(s):  
Valery V. Pipin
Keyword(s):  
Magnetic Field ◽  
Differential Rotation ◽  
Conservation Law ◽  
Large Scale ◽  
Solar Dynamo ◽  
Magnetic Helicity ◽  
Dynamo Model ◽  
Density Distributions ◽  
Large Scale Magnetic Field ◽  
Helicity Conservation

We study the helicity density patterns which can result from the emerging bipolar regions. Using the relevant dynamo model and the magnetic helicity conservation law we find that the helicity density patterns around the bipolar regions depend on the configuration of the ambient large-scale magnetic field, and in general they show a quadrupole distribution. The position of this pattern relative to the equator can depend on the tilt of the bipolar region. We compute the time–latitude diagrams of the helicity density evolution. The longitudinally averaged effect of the bipolar regions shows two bands of sign for the density distributions in each hemisphere. Similar helicity density patterns are provided by the helicity density flux from the emerging bipolar regions subjected to surface differential rotation.

scholarly journals Gaseous Disks in the Nuclei of Elliptical Galaxies

1997 ◽  
Vol 163 ◽  
pp. 620-625 ◽  
Author(s):  
H. Ford ◽  
Z. Tsvetanov ◽  
L. Ferrarese ◽  
G. Kriss ◽  
W. Jaffe ◽  
...  
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Angular Momentum ◽  
Accretion Disks ◽  
Large Scale ◽  
Elliptical Galaxies ◽  
Central Mass ◽  
Massive Black Holes ◽  
Radio Jets

AbstractHST images have led to the discovery that small (r ~ 1″ r ~ 100 – 200 pc), well-defined, gaseous disks are common in the nuclei of elliptical galaxies. Measurements of rotational velocities in the disks provide a means to measure the central mass and search for massive black holes in the parent galaxies. The minor axes of these disks are closely aligned with the directions of the large–scale radio jets, suggesting that it is angular momentum of the disk rather than that of the black hole that determines the direction of the radio jets. Because the disks are directly observable, we can study the disks themselves, and investigate important questions which cannot be directly addressed with observations of the smaller and unresolved central accretion disks. In this paper we summarize what has been learned to date in this rapidly unfolding new field.

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