Prof. Yan Xiaoli of the Chinese Academy of Sciences and Li Qiaoling, a postdoctoral researcher at Yunnan University, have discovered the bright-magnetic interaction between dying sunspots for the first time. The Astrophysical Journal reported related findings.
The brightness of sunspots is an essential metric in the study of total solar irradiance and a critical measure for verifying sunspot dynamics and magnetic characteristics. The bright-magnetic connection describes the link between the brightness of sunspots and the intensity of their magnetic fields.
The study of sunspot bright-magnetic relationships aids in understanding the brightness and atmospheric structure of sunspots and gives limitations to the theoretical model of the sunspot energy transfer process. Previous observational research on the bright-magnetic connection of sunspots has primarily focused on stable sunspots, with only a few focusing on fading sunspots.
Using stray light calibration data from the Solar Dynamics Observatory Helioseismic and Magnetic Imaging, the researchers examined the difference in the bright-magnetic connection between stable and decaying sunspots.
They discovered that the bright-magnetic connection difference between stable and decaying sunspots was most apparent in the continuous intensity (brightness) range of 0.35 Iqs to 0.65 Iqs (Iqs is the average continuum intensity of the quiet sun). The connection between the continuum intensity and the transverse magnetic field strength demonstrated a larger degree of dispersion in the declining sunspot.
Prof. Yan added that during the creation of the light bridge, they discovered a bifurcation pattern in the connection between the continuum intensity and the transverse magnetic field strength. This bifurcation pattern reveals that the thermodynamic parameters of the two regions of the umbra separated by the light bridge differ.
According to Li, the continuum intensity of the sunspot umbra in dying sunspots is brighter than in stable sunspots, and the mean continuum intensity of the sunspot umbra steadily increases as the sunspot decays. The mean continuous intensity of the penumbra, on the other hand, does not vary while the sunspot decays.
These findings suggest that when sunspots decline, the temperature of the umbra steadily rises while the temperature of the penumbra remains constant.
Journal Information: Qiaoling Li et al, Dependence of the Continuum Intensities on the Magnetic Fields at Different Evolution Phases of Sunspots, The Astrophysical Journal (2022). DOI: 10.3847/1538-4357/ac83b3