Sun-as-a-star Analysis of Hα Spectra of a Solar Flare Observed by SMART/SDDI: Time Evolution of Red Asymmetry and Line Broadening

Namekata, Kosuke; Ichimoto, Kiyoshi; Ishii, Takako T.; Shibata, Kazunari

doi:10.3847/1538-4357/ac75cd

Cited by 20 publications

(29 citation statements)

References 65 publications

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“…The time evolution of the ∆EW Hα±3.0 Å is similar to the GOES SXR light curve; for example, their time scales are comparable in each of the impulsive rising and gradual decay phases and their peaks are almost simultaneous [Figure 4 (b)]. The similarity of the Hα and the GOES SXR light curves is also reported in the Sun-as-a-star analysis of a flare by Namekata et al (2022c). Figure 6 shows the result of the Sun-as-a-star analysis of the Hα spectra of this M8.1 flare.…”

Section: Resultssupporting

confidence: 70%

“…(i) Flares (≥ C8.0) show emission near the Hα line center, with red asymmetry and/or line broadening in their Sun-as-a-star Hα spectra. Namekata et al (2022c) also reported that the Sun-as-a-star Hα spectrum of an M4.2 solar flare near the disk center showed red asymmetry and line broadening, and they thus suggested that the nature of the chromospheric condensation can be seen even in the Sun-as-a-star spectra. We note that, although event (2) and event (3) are especially energetic events in our study, red asymmetry is not very clear in them.…”

Section: Summary and Implications To Stellar Observationsmentioning

confidence: 95%

“…Since both solar and stellar spectra have similar characteristics, the authors concluded that a stellar filament eruption associated with a superflare had been detected. In addition, Namekata et al (2022c) analyzed the Sun-as-a-star Hα spectrum of an M-class solar flare that exhibited dominant emission from flare ribbons, and they showed that red asymmetry and line broadening can be seen even in a Sun-as-a-star spectrum, providing evidence of chromospheric condensation. This is how Sun-as-a-star analyses of Hα spectra are useful for investigating the dynamics of flares and plasmas on a stellar surface.…”

Section: Introductionmentioning

confidence: 99%

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

Takato¹,

Asai²,

Ichimoto³

et al. 2022

Preprint

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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 Hα 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 Hα spectral images taken by the Solar Magnetic Activity Research Telescope / Solar Dynamics Doppler Imager (SMART/SDDI) at Hida Observatory, Kyoto University. All the analyzed events show emission relative to the pre-event state and the changes in their Hα equivalent widths are all on the orders of 10 −4 Å. Sun-as-a-star Hα spectra exhibit different features depending on the causes of the emission: (i) Flares show emission at the Hα 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 Hα line center, accompanied by blue-/red-shifted absorption. Notably, disappearance of dark filaments leads to the apparent enhancement of the Hα line center emission. (iii) Eruptions of off limb prominences show blue-/red-shifted 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 red-shifted absorptions in Sun-as-a-star Hα spectra lead to coronal mass ejections (CMEs). This result suggests that even if the falling components of stellar filament eruptions are detected as red-shifted absorptions in Hα spectra, such stellar filament eruptions may also develop into CMEs.

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Section: Resultssupporting

confidence: 70%

Section: Summary and Implications To Stellar Observationsmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

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

Takato¹,

Asai²,

Ichimoto³

et al. 2022

Preprint

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show abstract

“…Since both solar and stellar spectra have similar characteristics, the authors concluded that a stellar filament eruption associated with a superflare had been detected. In addition, Namekata et al (2022c) analyzed the Sun-as-a-star Hα spectrum of an M-class solar flare that exhibited dominant emission from flare ribbons, and they showed that red asymmetry and line broadening can be seen even in a Sunas-a-star spectrum, providing evidence of chromospheric condensation. This is how Sun-as-a-star analyses of Hα spectra are useful for investigating the dynamics of flares and plasmas on a stellar surface.…”

Section: Introductionmentioning

confidence: 99%

“…So far, Sun-as-a-star analyses of Hα spectra have been performed for only three solar active events (flares and filament eruptions/surges; Namekata et al 2022aNamekata et al , 2022c. In this paper, we report the results of Sun-as-a-star analyses of Hα spectra for various active events on the Sun.…”

Section: Introductionmentioning

confidence: 99%

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

Takato

Asai

Ichimoto

et al. 2022

ApJ

Self Cite

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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 Hα 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 Hα 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 Hα equivalent widths are all on the orders of 10−4 Å. Sun-as-a-star Hα spectra exhibit different features depending on the causes of the emission: (i) flares show emission at the Hα 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 Hα line center, accompanied by blueshifted/redshifted absorption; notably, the disappearance of dark filaments leads to the apparent enhancement of the Hα 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 Hα 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 Hα spectra, such stellar filament eruptions may also develop into CMEs.

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Stellar flares

Kowalski

2024

Living Rev Sol Phys

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Magnetic storms on stars manifest as remarkable, randomly occurring changes of the luminosity over durations that are tiny in comparison to the normal evolution of stars. These stellar flares are bursts of electromagnetic radiation from X-ray to radio wavelengths, and they occur on most stars with outer convection zones. They are analogous to the events on the Sun known as solar flares, which impact our everyday life and modern technological society. Stellar flares, however, can attain much greater energies than those on the Sun. Despite this, we think that these phenomena are rather similar in origin to solar flares, which result from a catastrophic conversion of latent magnetic field energy into atmospheric heating within a region that is relatively small in comparison to normal stellar sizes. We review the last several decades of stellar flare research. We summarize multi-wavelength observational results and the associated thermal and nonthermal processes in flaring stellar atmospheres. Static and hydrodynamic models are reviewed with an emphasis on recent progress in radiation-hydrodynamics and the physical diagnostics in flare spectra. Thanks to their effects on the space weather of exoplanetary systems (and thus in our search for life elsewhere in the universe) and their preponderance in Kepler mission data, white-light stellar flares have re-emerged in the last decade as a widely-impactful area of study within astrophysics. Yet, there is still much we do not understand, both empirically and theoretically, about the spectrum of flare radiation, its origin, and its time evolution. We conclude with several big-picture questions that are fundamental in our pursuit toward a greater understanding of these enigmatic stellar phenomena and, by extension, those on the Sun.

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Sun-as-a-star Analysis of Hα Spectra of a Solar Flare Observed by SMART/SDDI: Time Evolution of Red Asymmetry and Line Broadening

Cited by 20 publications

References 65 publications

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

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

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

Stellar flares

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