EDP Sciences
Free access
Volume 445, Number 2, January II 2006
Page(s) 681 - 692
Section The Sun
DOI http://dx.doi.org/10.1051/0004-6361:20052822

A&A 445, 681-692 (2006)
DOI: 10.1051/0004-6361:20052822

Doppler redistribution of anisotropic radiation and resonance polarization in moving scattering media

Predicted results for the coronal O VI 1032 Å line
S. Sahal-Bréchot1 and N.-E. Raouafi2, 3

1  Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique (LERMA), Observatoire de Paris-Meudon, 92195 Meudon, France
    e-mail: sylvie.sahal-brechot@obspm.fr
2  Max-Planck-Institut für Sonnensystemforschung, 37191 Katlenburg-Lindau, Germany
3  National Solar Observatory, PO Box 26732 Tucson, AZ 85726-6732, USA

(Received 4 February 2005 / Accepted 11 June 2005)

The present paper puts the Doppler redistribution theory of anisotropic radiation and resonance polarization in moving scattering media into a predictive application following Sahal-Bréchot et al. (1998, A&A, 340, 579; P $_{\rm {II}}$), using the example of the $\ion{O}{vi}$ 1032 Å line of the corona. Numerical results are presented for different heights over the limb compatible with observations of different instruments on SOHO (SUMER, CDS, UVCS) but far from coronal holes in order to avoid inhomogeneities of the transition zone incident radiation. The orders of magnitude of our numerical results confirm the theoretical predictions of P $_{\rm {II}}$ and show that interpretation of polarimetric data of the $\ion{O}{vi}$ 1032 Å line of the corona, associated to the shift and the Doppler-dimming effect, offers a powerful diagnostic method of the complete velocity field vector, provided that the partial anisotropy of the incident radiation field be taken into account. These results also explain the precision of the diagnostic of interpretation polarimetric observations achieved by the ultraviolet spectrometer SUMER in the south polar coronal hole at 270'' above the solar limb; e.g. the solar wind acceleration region.

Key words: atomic processes -- line: formation -- line: profile -- polarization -- Sun: corona -- Sun: solar wind

© ESO 2005