March 1, 2021 Poster Open Access

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

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{
  "description": "<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>", 
  "license": "https://creativecommons.org/licenses/by/4.0/legalcode", 
  "creator": [
    {
      "affiliation": "National Solar Observatory", 
      "@id": "https://orcid.org/0000-0002-4525-9038", 
      "@type": "Person", 
      "name": "Criscuoli, Serena"
    }, 
    {
      "affiliation": "Goddard Space Flight Center", 
      "@type": "Person", 
      "name": "Marchenko, Sergey"
    }, 
    {
      "affiliation": "Goddard Space Flight Center", 
      "@type": "Person", 
      "name": "DeLand, Matthew"
    }, 
    {
      "affiliation": "San Fernando Observatory", 
      "@type": "Person", 
      "name": "Choudary, Debi"
    }, 
    {
      "affiliation": "LASP", 
      "@type": "Person", 
      "name": "Kopp, Greg"
    }
  ], 
  "url": "https://zenodo.org/record/4570266", 
  "datePublished": "2021-03-01", 
  "@type": "CreativeWork", 
  "keywords": [
    "Balmer lines", 
    "Stellar variability", 
    "Stellar Chromosphere", 
    "Solar Irradiance variability", 
    "Magnetic activity", 
    "Activity Indices"
  ], 
  "@context": "https://schema.org/", 
  "identifier": "https://doi.org/10.5281/zenodo.4570266", 
  "@id": "https://doi.org/10.5281/zenodo.4570266", 
  "workFeatured": {
    "url": "http://coolstars20.cfa.harvard.edu/cs20half/index.html", 
    "location": "Online", 
    "@type": "Event", 
    "name": "Cool Stars 20.5"
  }, 
  "name": "Understanding variability of solar Balmer lines"
}