Solar activity and responses observed in Balmer lines

Марченко, С. В.; Criscuoli, S.; DeLand, M. T.; Choudhary, Debi Prasad; Kopp, Greg

doi:10.1051/0004-6361/202037767

Cited by 11 publications

(7 citation statements)

References 36 publications

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“…The DPI describes the sunspot contribution to the TSI variability and is directly related to the sunspot area coverage. The relatively high correlation with this index in particular corroborates the conclusion drawn in Marchenko et al (2021) that on rotational timescales, the variability of Balmer lines is predominantly modulated by sunspots.…”

Section: Variability On Solar-rotational Timescalessupporting

confidence: 84%

Understanding Sun-as-a-Star Variability of Solar Balmer Lines

Criscuoli

Марченко

DeLand

et al. 2023

ApJ

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Precise, high-cadence, long-term records of stellar spectral variability at different temporal scales lead to better understanding of a wide variety of phenomena including stellar atmospheres and dynamos, convective motions, and rotational periods. Here, we investigate the variability of solar Balmer lines (Hα, β, γ, δ) observed by space-borne radiometers (OSIRIS, SCIAMACHY, OMI, and GOME-2), combining these precise, long-term observations with high-resolution data from the ground-based NSO/ISS spectrograph. We relate the detected variability to the appearance of magnetic features on the solar disk. We find that on solar-rotational timescales (about 1 month), the Balmer line activity indices (defined as line-core to line-wing ratios) closely follow variations in the total solar irradiance (which is predominantly photospheric), thus frequently (specifically, during passages of sunspot groups) deviating from behavior of activity indices that track chromospheric activity levels. On longer timescales, the correlation with chromospheric indices increases, with periods of low correlation or even anticorrelation found at intermediate timescales. Comparison of these observations with estimates from semiempirical irradiance reconstructions helps quantify the contributions of different magnetic and quiet features. We conclude that both the lower sensitivity to network and in part the higher sensitivity to filaments and prominences, may result in complex, time-dependent relationships between Balmer and other chromospheric indices observed for the Sun and solar-like stars. The fact that core and wings contribute in a similar manner to the variability, and current knowledge of Balmer-lines formation in stellar atmospheres, supports the notion that Balmer line core-to-wing ratio indices behave more like photospheric rather than chromospheric indices.

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Section: Variability On Solar-rotational Timescalessupporting

confidence: 84%

Understanding Sun-as-a-Star Variability of Solar Balmer Lines

Criscuoli

Марченко

DeLand

et al. 2023

ApJ

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“…Maldonado et al (2019) observed an anti-correlation when observing the Sun with HARPS-N, which nevertheless remains to be understood. Marchenko et al (2021) also found that the other Balmer lines, such as Hβ, Hγ, and Hδ, also do not trace the usual chromospheric activity indicators as well as expected on rotational timescales, possibly being more affected by photospheric variability due to spots. This was confirmed by Cincunegui et al (2007) who used simultaneous observations and a better temporal sampling, and found a correlation between averaged (overall values for each star) indexes in a large sample of F-G-K stars.…”

Section: Introductionmentioning

confidence: 76%

Relationship between Ca and Hα chromospheric emission in F-G-K stars: Indication of stellar filaments?

Meunier¹,

Kretzschmar

Gravet

et al. 2022

A&A

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Context. Different relationships between the Hα and Ca II chromospheric emissions have been reported in solar-type stars. In particular, the time-series of emissions in these two lines are clearly anti-correlated for a few percent of the stars, contrary to what is observed on the Sun. Aims. Our objective is to characterise these relationships in more detail using complementary criteria, and to constrain the properties of filaments and plages that are necessary to explain the observations. Methods. We analysed the average level and variability of the Hα and Ca II emission for 441 F-G-K stars, paying particular attention to their (anti-)correlations on both short and long timescales. We also computed synthetic Hα and Ca II time-series for different assumptions of plage and filament properties and compared them with the observations. Results. We were not able to find plage properties that, alone, are sufficient to reproduce the observations at all timescales simultaneously, even when allowing different Hα and Ca II emission relationships for different stars. We also specified the complex and surprising relationship between the average activity levels of both indexes, in particular for low-activity stars. Conclusions. We conclude that plages alone are unlikely to explain the observed variety of relationships between Ca II and Hα emission, and that the presence of other phenomena like filaments may help to reconcile the models with observations.

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“…The results from sophisticated quantum calculations are readily incorporated in stellar atmospheric modeling codes. "Quiet Sun" synthesis models have started to consider the advantages of these accurate, self-consistent hydrogen broadening profiles as well (Bjørgen et al 2019;Marchenko et al 2021). Here we describe the implementation of new line profile functions in the state-of-the-art RHD code RADYN, which is widely used for simulations of a wide variety of solar flare phenomena (Simões et al 2017;Polito et al 2019;Sadykov et al 2020;Monson et al 2021), Ellerman bombs (Hong et al 2017;Reid et al 2017), nanoflares (Testa et al 2014;Polito et al 2018), and chromospheric dynamics such as spicules and shocks (Carlsson & Stein 2002;Wedemeyer-Böhm & Carlsson 2011;Guerreiro et al 2013;Molnar et al 2021).…”

Section: Discussionmentioning

confidence: 99%

The Atmospheric Response to High Nonthermal Electron Beam Fluxes in Solar Flares. II. Hydrogen Broadening Predictions for Solar Flare Observations with the Daniel K. Inouye Solar Telescope

Kowalski,

Allred,

Carlsson

et al. 2022

Preprint

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Red-shifted components of chromospheric emission lines in the hard X-ray impulsive phase of solar flares have recently been studied through their 30 s evolution with the high resolution of IRIS. Radiative-hydrodynamic flare models show that these redshifts are generally reproduced by electronbeam generated chromospheric condensations. The models produce large ambient electron densities, and the pressure broadening of hydrogen Balmer series should be readily detected in observations. To accurately interpret upcoming spectral data of flares with the DKIST, we incorporate non-ideal, non-adiabatic line broadening profiles of hydrogen into the RADYN code. These improvements allow time-dependent predictions for the extreme Balmer line wing enhancements in solar flares. We study two chromospheric condensation models, which cover a range of electron beam fluxes (1 − 5 × 10 11 erg s −1 cm −2 ) and ambient electron densities (1 − 60 × 10 13 cm −3 ) in the flare chromosphere. Both models produce broadening and redshift variations within 10 s of the onset of beam heating. In the chromospheric condensations, there is enhanced spectral broadening due to large optical depths at Hα, Hβ, and Hγ, while the much lower optical depth of the Balmer series H12−H16 provides a translucent window into the smaller electron densities in the beam-heated layers below the condensation. The wavelength ranges of typical DKIST/ViSP spectra of solar flares will be sufficient to test the predictions of extreme hydrogen wing broadening and accurately constrain large densities in chromospheric condensations.

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Solar activity and responses observed in Balmer lines

Cited by 11 publications

References 36 publications

Understanding Sun-as-a-Star Variability of Solar Balmer Lines

Understanding Sun-as-a-Star Variability of Solar Balmer Lines

Relationship between Ca and Hα chromospheric emission in F-G-K stars: Indication of stellar filaments?

The Atmospheric Response to High Nonthermal Electron Beam Fluxes in Solar Flares. II. Hydrogen Broadening Predictions for Solar Flare Observations with the Daniel K. Inouye Solar Telescope

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