March 1, 2021 Poster Open Access

Criscuoli, Serena; Marchenko, Sergey; DeLand, Matthew; Choudary, Debi; Kopp, Greg

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{
  "publisher": "Zenodo", 
  "DOI": "10.5281/zenodo.4570266", 
  "title": "Understanding variability of solar Balmer lines", 
  "issued": {
    "date-parts": [
      [
        2021, 
        3, 
        1
      ]
    ]
  }, 
  "abstract": "<p>Precise, adequately high-cadence, long-term records of spectral variability at different temporal scales lead to better understanding of&nbsp; a wide variety of phenomena including&nbsp; 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&nbsp;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. &nbsp;In this study, we investigate the variability of solar Balmer lines (H-&alpha;, &beta;, &gamma; and &delta;) observed by space-borne radiometers, combining these precise, long-term observations with abundant, high-resolution data from&nbsp; 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&nbsp; 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 H&alpha;-index.</p>", 
  "author": [
    {
      "family": "Criscuoli, Serena"
    }, 
    {
      "family": "Marchenko, Sergey"
    }, 
    {
      "family": "DeLand, Matthew"
    }, 
    {
      "family": "Choudary, Debi"
    }, 
    {
      "family": "Kopp, Greg"
    }
  ], 
  "id": "4570266", 
  "event-place": "Online", 
  "type": "graphic", 
  "event": "Cool Stars 20.5"
}