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Astron. Astrophys. 341, 902-911 (1999)

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Continuum polarization in the solar spectrum

D.M. Fluri and J.O. Stenflo

Institute of Astronomy, ETH Zentrum, CH-8092 Zürich, Switzerland

Received 26 June 1998 / Accepted 2 October 1998


We present a theoretical study of the continuum polarization due to radiative scattering in the visible solar spectrum. The results from nine different solar model atmospheres are compared. The center-to-limb variation (CLV) as well as the wavelength dependence of the continuum polarization are determined, and the sources of the dependence on the model atmospheres are identified. The key physical quantities turn out to be the scattering coefficient and the temperature gradient in the layer where the polarization is formed.

A simple analytical function that approximates the CLV of the theoretical continuum polarization for every wavelength in the visible is found. This is based in first approximation on the assumption that the scattering layer producing the polarization is optically thin and lies above the layer of formation of the continuum intensity. Applications of the analytical function range from determinations of the instrumental zero-level of the polarization scale to diagnostic work using empirical center-to-limb curves to constrain the solar model atmospheres.

Key words: polarization – radiative transfer – scattering – Sun: atmosphere – Sun: photosphere

Send offprint requests to: D.M. Fluri (dfluri@astro.phys.ethz.ch)

© European Southern Observatory (ESO) 1999

Online publication: December 16, 1998