Issue |
A&A
Volume 383, Number 1, FebruaryIII 2002
|
|
---|---|---|
Page(s) | 326 - 337 | |
Section | Astronomical instrumentation | |
DOI | https://doi.org/10.1051/0004-6361:20011740 | |
Published online | 15 February 2002 |
Polarization from magnetized optically thick accretion disks
1
Instituto Nacional de Astrofísica, Óptica y Electrónica, Apartado Postal 51 y 216, Z.P. 72000, Pue. México
2
Main Astronomical Observatory of Russian Academy of Sciences, Pulkovo, 196140 St.-Petersburg, Russia
Corresponding author: silant@inaoep.mx
Received:
24
April
2001
Accepted:
25
October
2001
We present simple approximate formulae for intensity and the other Stokes
parameters of outgoing radiation for magnetized, plane-parallel optically
thick atmospheres. We assume that the polarization arises as a result of
the light scattering on free electrons in magnetized plasma of an atmosphere.
Our asymptotic formulae take place when the Faraday rotation angle ψ at
the optical length is large,
, and magnetic
field ≤
105 G, when the scattering cross-section has the Thomson value.
The formulae describe the radiation for an arbitrary direction of the
magnetic field. The Milne problem, the atmospheres with homogeneous and
linearly distributed thermal sources, as well as exponential sources are
considered. The superposition of these “standard" sources can represent
practically any real distribution of sources in optically thick accretion
disks. Polarization for some particular models of magnetic fields on the
surface of flat accretion disks are considered (chaotic fields in turbulent
plasma, axially symmetric plane magnetic fields and the field of the magnetic
dipole). The presented results allow us to calculate or estimate the
polarization for a large variety of optically thick magnetized
accretion disks.
Key words: accretion disks / polarization / magnetic fields / stars / quasars / galaxies: nuclei
© ESO, 2002
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