10.5281/zenodo.4570266
https://zenodo.org/records/4570266
oai:zenodo.org:4570266
Criscuoli, Serena
Serena
Criscuoli
0000-0002-4525-9038
National Solar Observatory
Marchenko, Sergey
Sergey
Marchenko
Goddard Space Flight Center
DeLand, Matthew
Matthew
DeLand
Goddard Space Flight Center
Choudary, Debi
Debi
Choudary
San Fernando Observatory
Kopp, Greg
Greg
Kopp
LASP
Understanding variability of solar Balmer lines
Zenodo
2021
Balmer lines
Stellar variability
Stellar Chromosphere
Solar Irradiance variability
Magnetic activity
Activity Indices
2021-03-01
Poster
10.5281/zenodo.4570265
https://zenodo.org/communities/coolstars20half
Creative Commons Attribution 4.0 International
Precise, adequately high-cadence, long-term records of spectral variability at different temporal scales lead to better understanding of a wide variety of phenomena including stellar atmospheres and dynamos, evolution of the magnetic fields on a stellar photosphere, convective motions, and rotational periods. These, in turn, are fundamental for the detectability of exoplanets, the characterization of their atmospheres and habitability, as well as characterization of stellar magnetospheres and winds. The Sun, viewed as a star via spectral irradiance measurements, offers a means of exploring such measurements while also having the imaging capability to help discern the causes of observed spectral variations. In this study, we investigate the variability of solar Balmer lines (H-α, β, γ and δ) observed by space-borne radiometers, combining these precise, long-term observations with abundant, high-resolution data from the ground-based NSO/ISS spectrograph. We relate the detected variability to magnetic features on the solar disk. We find that on solar-rotation timescales (~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 big sunspot groups) deviates from behavior of the line-activity indices that track chromospheric activity levels. At longer timescales (years), the correlation with chromospheric indices increases, with periods of low- or even anti- correlation found at intermediate timescales. Comparisons with Balmer-line variability patterns obtained from a semi-empirical model indicate the periods of low/anti correlations should be attributed to the increase of the relative abundance of network, which affects the Ca-index while leaving almost un-altered the Hα-index.