Astronomy and Astrophysics – Astronomy
Scientific paper
Aug 2011
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011apj...737...95a&link_type=abstract
The Astrophysical Journal, Volume 737, Issue 2, article id. 95 (2011).
Astronomy and Astrophysics
Astronomy
3
Line: Formation, Magnetic Fields, Polarization, Scattering, Sun: Atmosphere
Scientific paper
Coherent scattering of limb-darkened radiation is responsible for the generation of the linearly polarized spectrum of the Sun (the Second Solar Spectrum). This Second Solar Spectrum is usually observed near the limb of the Sun, where the polarization amplitudes are largest. At the center of the solar disk the linear polarization is zero for an axially symmetric atmosphere. Any mechanism that breaks the axial symmetry (like the presence of an oriented magnetic field, or resolved inhomogeneities in the atmosphere) can generate a non-zero linear polarization. In the present paper we study the linear polarization near the disk center in a weakly magnetized region, where the axisymmetry is broken. We present polarimetric (I, Q/I, U/I, and V/I) observations of the Ca I 4227 Å line recorded around μ = cos θ = 0.9 (where θ is the heliocentric angle) and a modeling of these observations. The high sensitivity of the instrument (ZIMPOL-3) makes it possible to measure the weak polarimetric signals with great accuracy. The modeling of these high-quality observations requires the solution of the polarized radiative transfer equation in the presence of a magnetic field. For this we use standard one-dimensional model atmospheres. We show that the linear polarization is mainly produced by the Hanle effect (rather than by the transverse Zeeman effect), while the circular polarization is due to the longitudinal Zeeman effect. A unique determination of the full \bm {B} vector may be achieved when both effects are accounted for. The field strengths required for the simultaneous fitting of Q/I, U/I, and V/I are in the range 10-50 G. The shapes and signs of the Q/I and U/I profiles are highly sensitive to the orientation of the magnetic field.
Anusha L. S.
Bianda Michele
Frisch Henry
Holzreuter R.
Nagendra K. N.
No associations
LandOfFree
Analysis of the Forward-scattering Hanle Effect in the Ca I 4227 Å Line does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Analysis of the Forward-scattering Hanle Effect in the Ca I 4227 Å Line, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Analysis of the Forward-scattering Hanle Effect in the Ca I 4227 Å Line will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1741745