Sun-as-a-star Analyses of Various Solar Active Events Using Hα Spectral Images Taken by SMART/SDDI

Sun-as-a-star analyses in which observational data is spatially integrated are useful for interpreting stellar data. For future applications to stellar observations, we performed Sun-as-a-star analyses of H α spectra for various active events on the Sun, not only for flares and filament eruptions/surges on the solar disk, but also for eruptions of off-limb prominences using H α spectral images taken by the Solar Magnetic Activity Research Telescope/Solar Dynamics Doppler Imager at Hida Observatory, Kyoto University. All the analyzed events show emission relative to the pre-event state and the changes in their H α equivalent widths are all on the orders of 10 −4 Å. Sun-as-a-star H α spectra exhibit different features depending on the causes of the emission: (i) flares show emission at the H α line center, together with red asymmetry and line broadening, as reported in a previous study, (ii) filament eruptions with and without flares show emission near the H α line center, accompanied by blueshifted/redshifted absorption; notably, the disappearance of dark filaments leads to the apparent enhancement of the H α line center emission, and (iii) eruptions of off-limb prominences show blueshifted/redshifted emission. These spectral features enable us to identify the active phenomena on Sun-like stars. We have also found that even the filament eruptions showing redshifted absorptions in Sun-as-a-star H α spectra lead to coronal mass ejections (CMEs). This result suggests that even if the falling components of stellar filament eruptions are detected as redshifted absorptions in H α spectra, such stellar filament eruptions may also develop into CMEs.