Issue |
A&A
Volume 433, Number 3, April III 2005
|
|
---|---|---|
Page(s) | 1117 - 1125 | |
Section | Stellar atmospheres | |
DOI | https://doi.org/10.1051/0004-6361:20041719 | |
Published online | 29 March 2005 |
Radiative transfer and Faraday effect in turbulent atmospheres
1
Instituto Nacional de Astrofísica, Óptica y Electrónica, Apartado Postal 51 y 216, Z.P. 72000, Pue. México, Mexico e-mail: silant@inaoep.mx
2
Main Astronomical Observatory of Russian Academy of Sciences, Pulkovo, St.-Petersburg, 196140, Russia
Received:
23
July
2004
Accepted:
30
November
2004
We investigated the system of transfer equations for the Stokes
parameters ,
and
in turbulent atmospheres. The extinction
coefficients
,
the number density of free electrons
and magnetic field
are considered as
stochastic values. The dependence of the averaged Stokes parameters
I0, Q0 and U0 on fluctuating parts
of these coefficients is investigated. It is found that the extinction coefficient
for the averaged Stokes parameters is smaller than the average value
.
The existence of magnetic and number density fluctuations gives rise to
an additional decrease of the magnitude of linear polarization.
These fluctuations also decrease the positional angle
of polarization compared with its mean value. We have found that it is
possible to write the radiative transfer equations for I0,
Q0 and U0 with the renormalized coefficients
(effective extinction coefficient, Faraday rotation parameter and additional
extinction coefficient for polarized radiation components). The only
condition for doing this is that the characteristic correlation
length R1 of turbulence should be small compared to the photon free path. The conservative
Milne problem is solved analytically for the case of large Faraday rotation
(mean or fluctuating) along the photon free path. The magnetic field
fluctuations change drastically the spectrum of linear polarization for large
wavelengths. The spectrum acquires the form
whereas the
atmospheres without magnetic fluctuations give
-dependence.
The
-dependence of the
positional angle
also changes considerably.
Key words: radiative transfer / turbulence / accretion, accretion disks / polarization / magnetic fields / stars: atmospheres
© ESO, 2005
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.