[P-EM14] Frontiers in solar physics

[PEM14-04] Sun-as-a-star Analysis of Hα Spectra for Various Active Events on the Sun

*Takato Otsu¹, Ayumi Asai², Kiyoshi Ichimoto², Takako T. Ishii², Kosuke Namekata³ (1.Department of Astronomy, Kyoto University, 2.Astronomical Observatory, Kyoto University, 3.National Astronomical Observatory of Japan)

Keywords:solar flares, filaments, prominences, stellar flares

Superflares are known as explosive phenomena on stars releasing the energy more than 10³³ erg (e.g., Maehara et al. 2012). In recent years, it has been studied whether superflares can also occur on the current Sun from the perspective of space weather (e.g., Shibata et al. 2013). In the study of stars, it is sometimes difficult to interpret observational data because the surfaces of distant stars cannot be spatially resolved. On the other hand, the surface of the Sun can be observed with high spatial resolution. From this background, detailed data of the Sun are utilized for analysis of stellar data (e.g., Toriumi et al. 2020, Namekata et al. 2021). For comparison with stellar data, solar data are spatially integrated and such an analysis is called Sun-as-a-star analysis. Namekata et al. (2021) carried out Sun-as-a-star analysis of the Hα spectra for solar flares accompanied by filament eruptions in order to interpret the Hα spectra for a stellar superflare. From a resemblance between them, the authors concluded that a stellar filament eruption associated the detected stellar superflare. In addition to flares, other various active events are also observed on the Sun and Sun-as-a-star analysis for such solar events are required for advanced understandings of stellar flares including superflares. Here we report a result of Sun-as-a-star analysis of Hα spectra for various solar active events, namely, flares, filament eruptions, and prominence eruptions. We used full-disk solar Hα spectral data observed by SMART/SDDI at Hida observatory, Kyoto University. SMART/SDDI can takes full-disk solar images in the wavelengths from Hα- 9.0Å to Hα+ 9.0Å with the spectral resolution of 0.25Å and the time cadence of 12-16 sec (Ichimoto et al. 2017). All analyzed events show brightening relative to pre-event and their changes in Hα equivalent width are the same orders of 10^-4Å. However, there are different features in Hα spectra depending on causes of brightening: brightening near Hαcenter with red asymmetry and line broadening due to flares, brightening near Hαcenter accompanied by shifted absorptions due to filament eruptions, and shifted brightening due to prominence eruptions. These spectral features can be used to diagnose the causes of brightening even though the changes in the Hα equivalent width are similar. Our result can be helpful in studying various active events on stars.