Journal Article

Calibration of a full-disc longitudinal magnetogram at the Huairou Solar Observing Station

Xiaofan Wang, Jiangtao Su and Hongqi Zhang

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 406, issue 2, pages 1166-1176
Published in print August 2010 | ISSN: 0035-8711
Published online July 2010 | e-ISSN: 1365-2966 | DOI:
Calibration of a full-disc longitudinal magnetogram at the Huairou Solar Observing Station

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Based on a spectral profile analysis of a filter magnetograph and the application of the astronomical data analysis technique, a full-disc distribution of Stokes I-to-V crosstalk in the solar magnetism and activity telescope (SMAT) has been acquired quantitatively. We produce a correction template to remove the full-disc Stokes I-to-V crosstalk. This template is important for the accuracy of the full-disc longitudinal magnetogram. Then, we propose an observational calibration method under the weak-field approximation on the basis of the scanning spectrum of the filter magnetograph. The following main results have been obtained. (i) For the original Stokes V images, there is about −1.67 × 10−3 of Stokes I crosstalk into V at all wavelength positions, and this crosstalk presents itself as a horse-saddle surface distribution on the full disc. (ii) A sample of the calibration curve at different wavelength positions is given. (iii) After being calibrated into magnetic flux density, the Stokes I-to-V crosstalk has an amplitude of about 50 G, but introduces negative and positive spurious magnetic fields into the blue and red wing magnetograms, respectively.

Keywords: techniques: polarimetric; Sun: photosphere; Sun: surface magnetism

Journal Article.  7337 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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