Sun-as-a-star Analysis of the Solar Eruption Source Region Using H <i>α</i> Spectroscopic Observations of CHASE

Abstract Sun-as-a-star analyses serve as a bridge for comparative studies on solar and stellar activities. To investigate the typical Sun-as-a-star H α temporal spectral characteristics in solar eruption source regions, we analyzed five different types of solar eruptions, using spectroscopic data from the Chinese H α Solar Explorer. Because the spatially integral H α spectrum of the source region is mainly contributed to by emission from heated plasma in flare ribbons and absorption from cold plasma in evolving filaments, we separately analyze the subregions of the source region dominated by different dynamical processes. It is revealed that filament eruptions show emission near the H α line center, accompanied by blueshifted/redshifted absorption, while flare ribbons show H α line center emission with red asymmetry and line broadening. Moreover, a special spectral signature likely associated with coronal mass ejections (CMEs) is identified: prominent blueshifted absorption without a clear deceleration phase, along with redshifted absorption, which can be used as a probe when searching stellar CMEs. Furthermore, in the X9.0 flare (SOL2024-10-03T12:18) accompanied by a violent CME, the expected blueshifted signal is not visible in the spatially integral H α spectra. This suggests that filament-lifting signals associated with CMEs in the source region can be obscured by the simultaneous dominant flare-ribbon emission within the integration region, which may explain the relatively small number of confirmed stellar CMEs observed in H α . We also find that comparison between the H α and UV spectral observations can effectively reveal the velocity evolution of erupting filaments and the potential existence of associated CMEs.