Response of solar and stellar atmospheric heating to the surface magnetic flux
Abstract
Atmospheres of the Sun and stars, i.e., the coronae, transition regions, and chromospheres, are heated up and brightened in response to the appearance of active regions, the home to flares and coronal mass ejections (CMEs). Therefore, in order to understand the transient radiations and impacts associated with solar/stellar flares and CMEs, it is crucial to clarify the quasi-stationary radiations caused by the active regions. In this study, we analyze the Sun-as-a-star multi-wavelength observations over 10 years to investigate proportionalities between the surface magnetic flux and the irradiances of various wavelengths from X-ray to radio bands. As a result, the irradiances of X-ray, EUV, and radio fluxes corresponding to the coronal temperatures (logT=6-7) show power-law relationships with exponents of 1.1 to 1.4 with respect to the magnetic flux, while the power-law exponents are less than unity for NUV and visible lines corresponding to the chromospheric temperatures (logT=4). Moreover, in any wavelengths, i.e., in any temperature ranges, these scaling laws can be extended to G-type dwarf stars. By expanding the present analysis, we may empirically derive the XUV spectrum for a given stellar magnetic flux (see the presentation by Namekata et al.). Our study shows that the response of the atmospheres to the photospheric magnetic flux is universal among the Sun and sun-like stars, regardless of age or activity.
- Publication:
-
44th COSPAR Scientific Assembly. Held 16-24 July
- Pub Date:
- July 2022
- Bibcode:
- 2022cosp...44.2475T