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  Similarities of magnetoconvection in the umbra and in the penumbra of sunspots

Löptien, B., Lagg, A., van Noort, M., & Solanki, S. K. (2021). Similarities of magnetoconvection in the umbra and in the penumbra of sunspots. Astronomy and Astrophysics, 655: A61. doi:10.1051/0004-6361/202141440.

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 Creators:
Löptien, Björn1, Author              
Lagg, Andreas2, Author              
van Noort, Michiel2, Author              
Solanki, Sami K.2, Author              
Affiliations:
1Department Solar and Stellar Interiors, Max Planck Institute for Solar System Research, Max Planck Society, ou_1832287              
2Department Sun and Heliosphere, Max Planck Institute for Solar System Research, Max Planck Society, ou_1832289              

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Free keywords: sunspots / Sun: photosphere / Sun: magnetic fields
 Abstract: Context. It is unclear why there is a rather sharp boundary in sunspots between the umbra and the penumbra. Both regions exhibit magnetoconvection, which manifests in penumbral filaments in the penumbra and in umbral dots in the umbra. Aims. Here we compare the physical properties of umbral dots and penumbral filaments. Our goal is to understand how the properties of these convective features change across the boundary between the umbra and the penumbra and how this is related to the rapid increase in brightness at the umbra-penumbra boundary. Methods. We derived ensemble averages of the physical properties of different types of convective features based on observations of two sunspots with Hinode. Results. There are strong similarities between the convective features in the outer parts of the umbra and the ones in the penumbra, with most physical parameters being smooth and continuous functions of the length of the features. Conclusions. Our results indicate that the transition in brightness from the umbra to the penumbra is solely caused by an increased effectiveness of magnetoconvection within individual convective cells. There is no significant difference in the number density of convective elements between the outer umbra and the inner penumbra. Penumbral filaments exhibit a larger area and a higher brightness compared to umbral dots. It is still unclear how exactly the underlying magnetic field causes the increase in the size and brightness of convective features in the penumbra.

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Language(s): eng - English
 Dates: 2021
 Publication Status: Published in print
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: DOI: 10.1051/0004-6361/202141440
 Degree: -

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Title: Astronomy and Astrophysics
  Other : Astron. Astrophys.
Source Genre: Journal
 Creator(s):
Affiliations:
Publ. Info: Les Ulis Cedex A France : EDP Sciences
Pages: - Volume / Issue: 655 Sequence Number: A61 Start / End Page: - Identifier: ISSN: 1432-0746
ISSN: 0004-6361
CoNE: https://pure.mpg.de/cone/journals/resource/954922828219_1