[P-AE17] 系外惑星

[PAE17-13] Universal Heating and Radiation Mechanism of the Sun and Sun-like Stars

*鳥海 森¹、行方 宏介²、Airapetian Vladimir^3,4、野津 湧太^5,6,7 (1.宇宙航空研究開発機構 宇宙科学研究所、2.国立天文台、3.NASA Goddard Space Flight Center、4.American University、5.コロラド大学ボルダー校、6.アメリカ国立太陽天文台、7.東京工業大学)

キーワード：太陽・太陽型星、大気加熱、XUV放射

The atmospheric heating and resulting XUV radiation of the Sun and stars have a profound impact on close-in exoplanets. While the planetary atmosphere helps protect surface life from harmful radiation, strong XUV radiation from stellar active regions and flares may promote ionization and the subsequent escape of the atmospheres, which can threaten the habitability. In the Sun, it is generally thought that the energy transported from the surface along magnetic fields dissipates to heat the atmospheres. However, it is unclear if the heating mechanism is common to the Sun and other stars. Therefore, in this study, by analyzing the multi-wavelength monitoring data of the Sun over 10 years, we investigate how the atmospheric layers of various temperatures (the corona, the transition region, and the chromosphere) respond to the surface magnetic flux. As a result, we find that the irradiances and magnetic flux show power-law relations with the exponent decreasing as the temperature drops from the corona to the chromosphere. It is also found that this atmospheric-heating relations can be extended to sun-like stars. That is, the heating/radiation mechanism is universal among the Sun and sun-like stars, regardless of age or activity. Using the scaling relations obtained in this study, the XUV radiation spectrum can be empirically reproduced for the magnetic flux of a given G-type star. It is expected that the synthesized XUV spectra are utilized as inputs for chemical calculations of exoplanetary atmospheres.