Revisiting the relationship between full sun X-ray irradiance and total magnetic flux using Hinode/XRT and SDO/HMI

Pevtsov et al.(2003) studied the relationship between total unsigned magnetic flux and X-ray spectral irradiance over 12 orders of magnitude, from quiet region of the Sun through T Tauri stars, and found that power-law (index = 1.15) could well express the relationship for the whole range. The solar portion of their study was based on the X-ray data from Yohkoh/SXT and magnetic flux data from NSO/KP and they reported that the power-law index for the full disk integrated flux changes from the low magnetic flux end (index ~2) to high end (index ~1), which forms a “knee” in the plot of X-ray irradiance vs magnetic flux.

We used more recent data set, Hinode/XRT and SDO/HMI magnetograms, to see if we can confirm the same change of the power-law index for the full Sun data. We derived the X-ray irradiance from thin filter pairs of XRT full sun images corrected by the latest calibration methods, and the total unsigned magnetic flux from HMI magnetograms by integrating positive and negative flux which has larger value than the noise level.

Our results show that the relationship can be well fitted by single power-law with the index ~1.15 without a significant change of the index. We will discuss the cause of the difference from Pevtsov et al (2003).