Multiwavelength Sun-as-a-star Analysis of the M8.7 Flare on 2022 October 2 Using H$α$ and EUV Spectra Taken by SMART/SDDI and SDO/EVE

Abstract: This paper presents a multiwavelength Sun-as-a-star analysis of the M8.7 flare on 2022 October 2, which were associated with a filament eruption and the following coronal mass ejection. The Sun-as-a-star analysis was performed using H$\alpha$ data taken by Solar Dynamics Doppler Imager on board the Solar Magnetic Activity Research Telescope at Hida Observatory, Kyoto University and full-disk integrated extreme ultraviolet (EUV) spectra taken by the Extreme ultraviolet Variability Experiment (EVE) on board the Solar Dynamics Observatory. The Sun-as-a-star H$\alpha$ spectra showed blueshifted absorption corresponding to the filament eruption. Furthermore, the EVE O {\sc v} 629.7 {\AA} spectra showed blueshifted brightening, which can also be attributed to the filament eruption. Even when the blueshifted absorption became almost invisible in the Sun-as-a-star H$\alpha$ spectra, the O {\sc v} blueshifted brightening up to $-400$ km s$^{-1}$ was still clearly visible. This result indicates that even when the shifted components--which are expected to originate from stellar eruptions--become almost invisible in the spatially integrated stellar H$\alpha$ spectra, the erupting materials may still be present and observable in EUV spectra. Additionally, the Sun-as-a-star H$\alpha$ and O {\sc v} spectra exhibited redshifted absorption and brightening, respectively, during the decay phase of the flare. These components probably originate from the post-flare loops, providing clues for the multi-temperature nature of the post-flare loops in the spatially integrated observation. Our Sun-as-a-star results suggest that the combination of H$\alpha$ and EUV lines allows the investigation of the multi-temperature structure and temporal development of stellar active phenomena even in spatially integrated spectra.