Comparing Observed with Simulated Solar-disk-center Scattering Polarization in the Sr i 4607 Å Line
Solar magnetic fields alter scattering polarization in spectral lines like Sr i at 4607 Å via the Hanle effect, making it a potential diagnostic for small-scale, mixed-polarity photospheric magnetic fields. Recently, observational evidence for scattering polarization in the Sr i 4607 Å line at the s...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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IOP Publishing
2024-01-01
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| Series: | The Astrophysical Journal |
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| Online Access: | https://doi.org/10.3847/1538-4357/ad26f9 |
| _version_ | 1797266086955057152 |
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| author | Franziska Zeuner Tanausú del Pino Alemán Javier Trujillo Bueno Sami K. Solanki |
| author_facet | Franziska Zeuner Tanausú del Pino Alemán Javier Trujillo Bueno Sami K. Solanki |
| author_sort | Franziska Zeuner |
| collection | DOAJ |
| description | Solar magnetic fields alter scattering polarization in spectral lines like Sr i at 4607 Å via the Hanle effect, making it a potential diagnostic for small-scale, mixed-polarity photospheric magnetic fields. Recently, observational evidence for scattering polarization in the Sr i 4607 Å line at the solar disk center was found. Here, we investigate the reliability of the reconstruction method that made possible this detection. To this end, we apply it to linear polarization profiles of the Sr i 4607 Å line radiation emerging at the disk center obtained from a detailed 3D radiative transfer calculation in a magneto-hydrodynamic (MHD) simulation snapshot with a small-scale dynamo contribution. The reconstruction method systematically reduces the scattering amplitudes by up to a factor of 2, depending on the noise level. We demonstrate that the decrease can be attributed to two systematic errors: first, the physical constraint that underlies our assumptions regarding the dependence of scattering polarization on the quadrupolar moment of the radiation field; and second, the limitations of our method in accurately determining the sign of the radiation field tensor from the observed intensity image. However, by consistently applying the reconstruction process and after taking into account image-degradation effects due to the temporally variable image quality, such as imposed by seeing, the observed and synthesized polarization signals show remarkable agreement. We thus conclude that the observed scattering polarization at the solar disk center is consistent with that emerging from a MHD model of the solar photosphere with an average magnetic field of 170 G at the visible surface. |
| first_indexed | 2024-04-25T00:55:06Z |
| format | Article |
| id | doaj.art-8309daa72ba24ae99cfaf5ecca9beda5 |
| institution | Directory Open Access Journal |
| issn | 1538-4357 |
| language | English |
| last_indexed | 2024-04-25T00:55:06Z |
| publishDate | 2024-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astrophysical Journal |
| spelling | doaj.art-8309daa72ba24ae99cfaf5ecca9beda52024-03-11T11:26:21ZengIOP PublishingThe Astrophysical Journal1538-43572024-01-0196411010.3847/1538-4357/ad26f9Comparing Observed with Simulated Solar-disk-center Scattering Polarization in the Sr i 4607 Å LineFranziska Zeuner0https://orcid.org/0000-0002-3594-2247Tanausú del Pino Alemán1https://orcid.org/0000-0003-1465-5692Javier Trujillo Bueno2https://orcid.org/0000-0001-5131-4139Sami K. Solanki3https://orcid.org/0000-0002-3418-8449Istituto ricerche solari Aldo e Cele Daccò (IRSOL), Faculty of Informatics, Università della Svizzera italiana , CH-6605 Locarno, Switzerland ; zeuner@irsol.ch; Max-Planck-Institut für Sonnensystemforschung , Justus-von-Liebig-Weg 3, D-37077 Göttingen, GermanyInstituto de Astrofísica de Canarias , E-38205 La Laguna, Tenerife, Spain; Departmento de Astrofísica, Facultad de Física, Universidad de La Laguna , E-38206 La Laguna, Tenerife, SpainInstituto de Astrofísica de Canarias , E-38205 La Laguna, Tenerife, Spain; Departmento de Astrofísica, Facultad de Física, Universidad de La Laguna , E-38206 La Laguna, Tenerife, Spain; Consejo Superior de Investigaciones Cientifícas , SpainMax-Planck-Institut für Sonnensystemforschung , Justus-von-Liebig-Weg 3, D-37077 Göttingen, GermanySolar magnetic fields alter scattering polarization in spectral lines like Sr i at 4607 Å via the Hanle effect, making it a potential diagnostic for small-scale, mixed-polarity photospheric magnetic fields. Recently, observational evidence for scattering polarization in the Sr i 4607 Å line at the solar disk center was found. Here, we investigate the reliability of the reconstruction method that made possible this detection. To this end, we apply it to linear polarization profiles of the Sr i 4607 Å line radiation emerging at the disk center obtained from a detailed 3D radiative transfer calculation in a magneto-hydrodynamic (MHD) simulation snapshot with a small-scale dynamo contribution. The reconstruction method systematically reduces the scattering amplitudes by up to a factor of 2, depending on the noise level. We demonstrate that the decrease can be attributed to two systematic errors: first, the physical constraint that underlies our assumptions regarding the dependence of scattering polarization on the quadrupolar moment of the radiation field; and second, the limitations of our method in accurately determining the sign of the radiation field tensor from the observed intensity image. However, by consistently applying the reconstruction process and after taking into account image-degradation effects due to the temporally variable image quality, such as imposed by seeing, the observed and synthesized polarization signals show remarkable agreement. We thus conclude that the observed scattering polarization at the solar disk center is consistent with that emerging from a MHD model of the solar photosphere with an average magnetic field of 170 G at the visible surface.https://doi.org/10.3847/1538-4357/ad26f9Quiet SunSolar magnetic fieldsRadiative transfer simulationsSpectropolarimetrySolar photosphere |
| spellingShingle | Franziska Zeuner Tanausú del Pino Alemán Javier Trujillo Bueno Sami K. Solanki Comparing Observed with Simulated Solar-disk-center Scattering Polarization in the Sr i 4607 Å Line The Astrophysical Journal Quiet Sun Solar magnetic fields Radiative transfer simulations Spectropolarimetry Solar photosphere |
| title | Comparing Observed with Simulated Solar-disk-center Scattering Polarization in the Sr i 4607 Å Line |
| title_full | Comparing Observed with Simulated Solar-disk-center Scattering Polarization in the Sr i 4607 Å Line |
| title_fullStr | Comparing Observed with Simulated Solar-disk-center Scattering Polarization in the Sr i 4607 Å Line |
| title_full_unstemmed | Comparing Observed with Simulated Solar-disk-center Scattering Polarization in the Sr i 4607 Å Line |
| title_short | Comparing Observed with Simulated Solar-disk-center Scattering Polarization in the Sr i 4607 Å Line |
| title_sort | comparing observed with simulated solar disk center scattering polarization in the sr i 4607 a line |
| topic | Quiet Sun Solar magnetic fields Radiative transfer simulations Spectropolarimetry Solar photosphere |
| url | https://doi.org/10.3847/1538-4357/ad26f9 |
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