Analysis of the transverse magnetic field in solar active regions by the Huairou vector magnetograph

Abstract

In this paper, we analyse Stokes parameters I,Q,U of the Fe i λ5324.19A line, calculated with radiative transfer equations in a solar model atmosphere with a magnetic field, and the influence of magneto-optical effects on the measurement of transverse magnetic field. It is found that the measurement of azimuthal angles of the transverse field is obviously disturbed by the magneto-optical effects. We compare with the observational Stokes images Q and U at different wavelengths from the center to the wing of the Fe i λ5324.19A line obtained at Huairou Solar Observing Station of Beijing Astronomical Observatory to confirm azimuthal angles of the transverse field, because the insignificant influence of magneto-optical effects in the far wing of the line was found by the theoretical analysis. The accuracy of azimuthal angles of the transverse field measured near the Fe i λ5324.19A line center has been estimated.