Hanle effect observations with the Ca I 4227 Å line

Content Provider	Semantic Scholar
Author	Bianda, Michele Stenflo, Jan Olof Solanki, Sami K.
Copyright Year	1999
Abstract	The Hanle effect in the Ca i 4227Å line has been explored through the analysis of a large number of Stokes profile recordings obtained on the quiet Sun with the beam-splitter polarimeter system at IRSOL (Istituto Ricerche Solari Locarno). In contrast to previous Hanle observations with this line, which were limited to the Stokes I andQ parameters, we are now in a position to study the combined effects of Hanle depolarization (via StokesQ) and rotation of the plane of linear polarization (via StokesU ) with the same methods that we recently applied to the Srii 4078Å line. The Hanle histograms for the distributions of the depolarization and rotation parameters are very similar for the two lines and show that there must be mixed contributions to the Hanle signals from spatially unresolved magnetic fields with random orientations (which do not contribute to Stokes U ) and partially resolved magnetic fields with a net orientation of the field vectors. Field strengths in the range 5–10 G are preferred. We also determine the “Hanle efficiency profile”, which shows how the Hanle effect is confined to the Doppler core but vanishes in the line wings. It is wider than the corresponding profile for the Sr line, as expected from the difference in atomic weight and wavelength between the two lines. The Q/I profiles of the Cai 4227Å line have minima around the Doppler core which turn negative (polarization perpendicular to the limb) for limb distancesμ = cos θ >∼ 0.2, a likely signature of partial redistribution effects.
Starting Page	1060
Ending Page	1070
Page Count	11
File Format	PDF HTM / HTML
Volume Number	350
Alternate Webpage(s)	http://aa.springer.de/papers/9350003/2301060.pdf
Alternate Webpage(s)	http://irsol.mobi/Papers/AA350_1060_1999.pdf
Language	English
Access Restriction	Open
Content Type	Text
Resource Type	Article