AAS 204th Meeting, June 2004
Session 37 Solar Magnetic Fields and the Photosphere
SPD Poster, Tuesday, June 1, 2004, 10:00am-7:00pm, Ballroom

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[37.06] IR Vector Magnetic Fields I: Instrumental Polarization Correction

S. A. Jaeggli (University of Arizona), M. J. Penn (National Solar Observatory)

Instrumental polarization is evident in the spectra of active region 10008 taken with the CSUN-NSO IR camera at the McMath-Pierce telescope on June 24, 2002. Several iron lines near 15650 in the spectra exhibit Zeeman splitting. Using a technique described by Kuhn et. al. (1994) the original polarization is restored. For all Zeeman split lines in the spectra the corrected Stokes profiles for the Q and U components show symmetry, while Stokes V is made antisymmetric with no central component.

The observed Stokes vector is related to the true Stokes vector through the formula Strue = M-1 Sobs where M-1 is the inverse Mueller matrix. The correction coefficients from the Kuhn method are used to compute the inverse Mueller matrix for light path of the entire system. The expected inverse Mueller matrix is computed for the telescope at each scan time using a simple model described by Bernasconi (1997) but assuming the n and k values of the index of refraction are the same for each mirror surface. A least squares technique is used to fit this telescope model to the measured inverse Mueller matrix for the system. The telescope model can account for most of the measured cross-talk except for the observed Stokes Q to Stokes V cross-talk which is thought to occur in the polarimeter.

The author(s) of this abstract have provided an email address for comments about the abstract: jaeggli@noao.edu

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