A Method to Correct the Intensity to Polarization Crosstalk in Measuring Full-Disk Solar Photospheric Vector Magnetic Fields

Abstract

Precise polarimetry is very important for studying the characteristics and evolution of solar magnetic fields. We focus on the intensity to linear and circular polarization crosstalk that affect polarimetric accuracy of full-disk vector magnetic-field measurements. An attempt is made to correct such crosstalk and to reconstruct full-disk vector magnetic fields from polarization data. By analyzing the data taken at 31 filter positions from −0.3 A to 0.3 A off the spectral line Fe i $\lambda $ 5324.19 A spaced by 0.02 A, we estimate that the intensity to linear and circular polarization crosstalks are less than 0.1% (≈ 10 G) of the quiet-Sun intensity. The method, which uses background maps obtained by averaging over many Stokes -Q, -U, and -V images to correct the crosstalks of I-to-Q, -U, and -V, is proved to be effective.