[P-EM14] Frontiers in solar physics

[PEM14-P03] Multiwavelength Sun-as-a-star Analysis of an M8.7 Flare on 2022 Oct. 2 with H-alpha and EUV Using SMART/SDDI and SDO/EVE

*Takato Otsu^1,2, Ayumi Asai² (1.Department of Astronomy, Kyoto University, 2.Astronomical Observatory, Kyoto University)

Keywords:Solar flare, Stellar flare, Coronal mass ejection

Solar flares are known as sudden energy release that occur in the solar atmosphere. In association with solar flares, plasma ejections into interplanetary space, called coronal mass ejections (CMEs), sometimes occur; accurate prediction of CMEs is important from the perspective of space weather forecasting, because the interaction of CMEs with planetary magnetospheres generates magnetic storms. In recent years, sudden brightening phenomena called stellar flares have been observed in stars other than the Sun. Especially, stellar flares that emit 10 times more energy than the largest solar flares are called superflares. By analogy with solar observations, superflares are thought to be accompanied by CMEs on a larger scale than in the case of the Sun, which are thought to have severe impacts on the exoplanets around the host stars (e.g., Airapetian+ 2020). However, stellar CMEs are difficult to detect because they cannot be spatially resolved unlike the solar case. Indirect evidence for stellar CMEs includes blue asymmetry of Balmer and UV lines (e.g., Maehara+ 2021, Leitzinger+ 2011), which is thought to be caused by prominence eruptions that form the core of the CME (Munro+ 1979), and coronal dimming in X-ray and Extreme Ultraviolet (EUV) due to the extraction of plasma in the corona by CME (e.g., Veronig+ 2021). Simultaneous detection and anaysis of these signals is expected to improve the reliability of stellar CMEs' detection. For future multiwavelength observations of stellar CMEs, it is necessary to clarify how the numerous signals associated with solar CMEs are observed in an analysis that deal with the Sun as if it were a distant star, i.e., the Sun-as-a-star analysis (e.g., Otsu+ 2022).
In this study, we performed a Sun-as-a-star analysis of an M8.7 flare and the associated eruption that occurred on 2022 October 2 in NOAA 13110 using SMART/SDDI (Hα imaging spectroscopy) at Hida observatory, Kyoto University and SDO/EVE (EUV full-disk integrated spectroscopy). As a result, a blueshifted absorption component of ∼300 km/s appeared in the spatially integrated Hα line spectra, although it is fainter than a slower component. In addition, blueshifted emissions were observed in the EUV spectra such as O V 62.97 nm (logT[K]~5.37) almost simultaneously with the absorption of the fast component in the Hα line. The results of this multiwavelength Sun-as-a-star analysis suggest that the multi-temperature structure of stellar eruptions can also be detected in spatially integrated spectra. With a view of the application to stellar research, we will report the details of the time evolutions of these blueshifted components in the Hα line and EUV lines and also discuss the occurrence of coronal dimming related to the CME.