Poster Open Access

Modelling Solar Ca II H&K Emission Variations

Sowmya, Krishnamurthy; Shapiro, Alexander I.; Witzke, Veronika; Nèmec, Nina-E.; Chatzistergos, Theodosis; Yeo, Kok Leng; Krivova, Natalie A.; Solanki, Sami K.


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  <identifier identifierType="DOI">10.5281/zenodo.4564796</identifier>
  <creators>
    <creator>
      <creatorName>Sowmya, Krishnamurthy</creatorName>
      <givenName>Krishnamurthy</givenName>
      <familyName>Sowmya</familyName>
      <nameIdentifier nameIdentifierScheme="ORCID" schemeURI="http://orcid.org/">0000-0002-3243-1230</nameIdentifier>
      <affiliation>Max Planck Institute for Solar System Research</affiliation>
    </creator>
    <creator>
      <creatorName>Shapiro, Alexander I.</creatorName>
      <givenName>Alexander I.</givenName>
      <familyName>Shapiro</familyName>
      <nameIdentifier nameIdentifierScheme="ORCID" schemeURI="http://orcid.org/">0000-0002-8842-5403</nameIdentifier>
      <affiliation>Max Planck Institute for Solar System Research</affiliation>
    </creator>
    <creator>
      <creatorName>Witzke, Veronika</creatorName>
      <givenName>Veronika</givenName>
      <familyName>Witzke</familyName>
      <nameIdentifier nameIdentifierScheme="ORCID" schemeURI="http://orcid.org/">0000-0002-0929-1612</nameIdentifier>
      <affiliation>Max Planck Institute for Solar System Research</affiliation>
    </creator>
    <creator>
      <creatorName>Nèmec, Nina-E.</creatorName>
      <givenName>Nina-E.</givenName>
      <familyName>Nèmec</familyName>
      <nameIdentifier nameIdentifierScheme="ORCID" schemeURI="http://orcid.org/">0000-0001-6090-1247</nameIdentifier>
      <affiliation>Max Planck Institute for Solar System Research</affiliation>
    </creator>
    <creator>
      <creatorName>Chatzistergos, Theodosis</creatorName>
      <givenName>Theodosis</givenName>
      <familyName>Chatzistergos</familyName>
      <nameIdentifier nameIdentifierScheme="ORCID" schemeURI="http://orcid.org/">0000-0002-0335-9831</nameIdentifier>
      <affiliation>Max Planck Institute for Solar System Research</affiliation>
    </creator>
    <creator>
      <creatorName>Yeo, Kok Leng</creatorName>
      <givenName>Kok Leng</givenName>
      <familyName>Yeo</familyName>
      <nameIdentifier nameIdentifierScheme="ORCID" schemeURI="http://orcid.org/">0000-0003-3851-7323</nameIdentifier>
      <affiliation>Max Planck Institute for Solar System Research</affiliation>
    </creator>
    <creator>
      <creatorName>Krivova, Natalie A.</creatorName>
      <givenName>Natalie A.</givenName>
      <familyName>Krivova</familyName>
      <nameIdentifier nameIdentifierScheme="ORCID" schemeURI="http://orcid.org/">0000-0002-1377-3067</nameIdentifier>
      <affiliation>Max Planck Institute for Solar System Research</affiliation>
    </creator>
    <creator>
      <creatorName>Solanki, Sami K.</creatorName>
      <givenName>Sami K.</givenName>
      <familyName>Solanki</familyName>
      <nameIdentifier nameIdentifierScheme="ORCID" schemeURI="http://orcid.org/">0000-0002-3418-8449</nameIdentifier>
      <affiliation>Max Planck Institute for Solar System Research</affiliation>
    </creator>
  </creators>
  <titles>
    <title>Modelling Solar Ca II H&amp;K Emission Variations</title>
  </titles>
  <publisher>Zenodo</publisher>
  <publicationYear>2021</publicationYear>
  <subjects>
    <subject>The Sun and the Heliosphere</subject>
    <subject>Solar activity</subject>
    <subject>Solar chromosphere</subject>
    <subject>Stellar activity</subject>
  </subjects>
  <contributors>
    <contributor contributorType="Editor">
      <contributorName>Wolk, Scott</contributorName>
      <givenName>Scott</givenName>
      <familyName>Wolk</familyName>
    </contributor>
  </contributors>
  <dates>
    <date dateType="Issued">2021-02-26</date>
  </dates>
  <language>en</language>
  <resourceType resourceTypeGeneral="Text">Poster</resourceType>
  <alternateIdentifiers>
    <alternateIdentifier alternateIdentifierType="url">https://zenodo.org/record/4564796</alternateIdentifier>
  </alternateIdentifiers>
  <relatedIdentifiers>
    <relatedIdentifier relatedIdentifierType="DOI" relationType="IsVersionOf">10.5281/zenodo.4564795</relatedIdentifier>
    <relatedIdentifier relatedIdentifierType="URL" relationType="IsPartOf">https://zenodo.org/communities/coolstars20half</relatedIdentifier>
  </relatedIdentifiers>
  <rightsList>
    <rights rightsURI="https://creativecommons.org/licenses/by/4.0/legalcode">Creative Commons Attribution 4.0 International</rights>
    <rights rightsURI="info:eu-repo/semantics/openAccess">Open Access</rights>
  </rightsList>
  <descriptions>
    <description descriptionType="Abstract">&lt;p&gt;The emission in the near ultraviolet Ca II H&amp;amp;K lines, often quantified via the S-index, has been serving as a prime proxy of solar and stellar magnetic activity. Despite the broad usage of the S-index, the link between the coverage of a stellar disk by magnetic features and Ca II&amp;nbsp;H&amp;amp;K emission is not fully understood. In order to fill this gap we developed a physics-based model to calculate the solar S-index. To this end, we made use of the distributions of the solar magnetic features derived from the simulations of magnetic flux emergence and surface transport, together with the Ca II&amp;nbsp;H&amp;amp;K spectra synthesized using a non-local thermodynamic equilibrium (non-LTE) radiative transfer code.&lt;/p&gt;

&lt;p&gt;We show that the value of the solar S-index is influenced by the inclination angle between the solar rotation axis and the observer&amp;rsquo;s line-of-sight, i.e. the solar S-index values obtained by an out-of-ecliptic observer are different from those obtained by an ecliptic-bound observer. This is important for comparing the magnetic activity of the Sun to other stars. We computed time series of the S-index as they would be observed at various inclinations dating back to 1700. We find that depending on the inclination and period of observations, the activity cycle in solar S-index can appear weaker or stronger than in stars with a solar-like level of magnetic activity. We show that there is nothing unusual about the solar chromospheric emission variations in the context of stars with near-solar magnetic activity.&lt;/p&gt;</description>
  </descriptions>
  <fundingReferences>
    <fundingReference>
      <funderName>European Commission</funderName>
      <funderIdentifier funderIdentifierType="Crossref Funder ID">10.13039/501100000780</funderIdentifier>
      <awardNumber awardURI="info:eu-repo/grantAgreement/EC/H2020/797715/">797715</awardNumber>
      <awardTitle>Impact of Magnetic field on Emergent solar spectra</awardTitle>
    </fundingReference>
  </fundingReferences>
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