Issue |
A&A
Volume 407, Number 2, August IV 2003
|
|
---|---|---|
Page(s) | 403 - 421 | |
Section | Astrophysical processes | |
DOI | https://doi.org/10.1051/0004-6361:20030868 | |
Published online | 17 November 2003 |
Extending the Shakura-Sunyaev approach to a strongly magnetized accretion disc model*
1
Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627, USA
2
P.N. Lebedev Physical Institute, Leninsky Prospect 53, Moscow 117924, Russia
3
Department of Astronomy and Astrophysics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637, USA
Corresponding author: V. I. Pariev, vpariev@pas.rochester.edu
Received:
6
March
2003
Accepted:
3
June
2003
We develop a model of thin turbulent accretion discs supported
by magnetic pressure of turbulent magnetic fields.
This applies when the turbulent kinetic and magnetic energy
densities are greater than the thermal energy density
in the disc. Whether such discs survive in nature or not
remains to be determined, but here we simply
demonstrate that self-consistent solutions
exist when the α-prescription for the viscous stress,
similar to that of the original
Shakura–Sunyaev model, is used.
We show that for the strongly
magnetized case and we calculate the radial structure
and emission spectra from the disc in the regime when it is optically
thick.
Strongly magnetized optically thick discs can
apply to the full range of disc radii for objects
10-2 of the
Eddington luminosity or for the outer parts of discs in higher luminosity
sources.
In the limit that the magnetic pressure is equal to the thermal
or radiation pressure, our strongly magnetized disc
model transforms into the Shakura–Sunyaev model with
.
Our model produces spectra quite similar to those of standard
Shakura–Sunyaev models. In our comparative study, we also
discovered a small discrepancy in the spectral calculations
of Shakura & Sunyaev (1973).
Key words: accretion: accretion disks / turbulence / magnetohydrodynamics (MHD) / plasmas
© ESO, 2003
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