[P-AE17] Exoplanets

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

*Shin Toriumi¹, Kosuke Namekata², Vladimir S. Airapetian^3,4, Yuta Notsu^5,6,7 (1.Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 2.National Astronomical Observatory of Japan, 3.NASA Goddard Space Flight Center, 4.American University, 5.University of Colorado Boulder, 6.National Solar Observatory, 7.Tokyo Institute of Technology)

Keywords:Sun and sun-like stars, Atmospheric heating, XUV radiations

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.