Statistics – Computation
Scientific paper
Dec 2004
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004sf2a.conf..113d&link_type=abstract
SF2A-2004: Semaine de l'Astrophysique Francaise, meeting held in Paris, France, June 14-18, 2004. Edited by F. Combes, D. Barret
Statistics
Computation
Scientific paper
The installation of a new polarimeter at the Turret Dome of the Pic-du-Midi has permitted new observations of the "second solar spectrum" (which is the spectrum of the linear polarization observed near the solar limb), having a spatial resolution. On 2003 October 25, we have observed a quiet region located at the East limb equator, in the resonance line of neutral strontium at 4607 Å. The slit was positioned perpendicular to the limb: recording various limb distances provides a depth probing of the solar atmosphere. The intensity of the turbulent magnetic field has been derived from the Hanle effect interpretation, which is actually the only method for vectorial weak field determination. The theoretical profiles to be compared to the observed ones have been obtained by applying the atomic density matrix formalism (Landi Degl'Innocenti E., Bommier V., & Sahal-Bréchot S., 1990). The various collisional coefficients have been computed by applying semi-classical methods that are accurate to 20% or better: the one from Seaton (1962) and Sahal-Bréchot (1969a, 1969b) for the collisions with electrons, responsible for the inelastic transitions, and the one developed by Anstee & O'Mara (1991, 1995) for line broadening computations, generalized to the collisional depolarization by Derouich et al. (2003; see also Derouich, 2004), for the elastic collisions with neutral hydrogen atoms. The results have been found in full agreement with those previously obtained with THEMIS without any spatial resolution (at 9 limb distances). With the spatial resolution that we have now at the Pic-du-Midi (1 arcsec, 138 limb distances), it appears that the turbulent magnetic field intensity does not vary with depth, in the line formation region that ranges from ~200 to ~300 km above the tau5000=1 level.
Bommier Veronique
Derouich M.
Landi Degl'Innocenti Egidio
Malherbe Jean-Marie
Sahal-Bréchot Sylvie
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