An empirical method to correct the saturation seen in the SOHO/MDI magnetograms

作者：Gao, George Zhendong^*; Zhao, Yong-Heng; Liu, Yang

来源：Research in Astronomy and Astrophysics, 2010, 10(10): 1041-1048.

DOI：10.1088/1674-4527/10/10/007

• Sun: solar magnetic field
• Sun: MDI magnetograms
• Sun:Saturation

The magnetic field of the umbrae is sometimes found to be saturated in the magnetograms taken by the Michelson Doppler Imager (MDI) onboard the Solar and Heliospheric Observatory (SOHO). It is suggested that the combination of the low intensity of sunspot umbrae and the limitation of the 15-bit onboard numerical data acquisition leads to this saturation. In this paper, we propose to use the MDI's intensity data to correct this saturation. This method is based on the well-established relationship between the continuum intensity and the magnetic field (the so-called I-B relationship). A comparison between the corrected magnetic field and the data taken by the Stokes-Polarimeter of the Solar Optical Telescope (SOT/SP) onboard Hinode shows a reasonable agreement, suggesting that this correction is effective.

• 出版日期2010-10
• 单位中国科学院国家天文台