10.5281/zenodo.4564796
https://zenodo.org/records/4564796
oai:zenodo.org:4564796
Sowmya, Krishnamurthy
Krishnamurthy
Sowmya
0000-0002-3243-1230
Max Planck Institute for Solar System Research
Shapiro, Alexander I.
Alexander I.
Shapiro
0000-0002-8842-5403
Max Planck Institute for Solar System Research
Witzke, Veronika
Veronika
Witzke
0000-0002-0929-1612
Max Planck Institute for Solar System Research
Nèmec, Nina-E.
Nina-E.
Nèmec
0000-0001-6090-1247
Max Planck Institute for Solar System Research
Chatzistergos, Theodosis
Theodosis
Chatzistergos
0000-0002-0335-9831
Max Planck Institute for Solar System Research
Yeo, Kok Leng
Kok Leng
Yeo
0000-0003-3851-7323
Max Planck Institute for Solar System Research
Krivova, Natalie A.
Natalie A.
Krivova
0000-0002-1377-3067
Max Planck Institute for Solar System Research
Solanki, Sami K.
Sami K.
Solanki
0000-0002-3418-8449
Max Planck Institute for Solar System Research
Modelling Solar Ca II H&K Emission Variations
Zenodo
2021
The Sun and the Heliosphere
Solar activity
Solar chromosphere
Stellar activity
Wolk, Scott
Scott
Wolk
2021-02-26
eng
Poster
10.5281/zenodo.4564795
https://zenodo.org/communities/coolstars20half
https://zenodo.org/communities/eu
Creative Commons Attribution 4.0 International
The emission in the near ultraviolet Ca II H&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 H&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 H&K spectra synthesized using a non-local thermodynamic equilibrium (non-LTE) radiative transfer code.
We show that the value of the solar S-index is influenced by the inclination angle between the solar rotation axis and the observer’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.
European Commission
10.13039/501100000780
797715
Impact of Magnetic field on Emergent solar spectra