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  Magnetic bipoles in rotating turbulence with coronal envelope

Losada, I. R., Warnecke, J., Brandenburg, A., Kleeorin, N., & Rogachevskii, I. (2019). Magnetic bipoles in rotating turbulence with coronal envelope. Astronomy and Astrophysics, 621: A61. doi:10.1051/0004-6361/201833018.

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 Creators:
Losada, I. R., Author
Warnecke, Jörn1, 2, Author              
Brandenburg, A., Author
Kleeorin, N., Author
Rogachevskii, I., Author
Affiliations:
1Max Planck Research Group in Solar and Stellar Magnetic Activity (Mag Activity) – SOLSTAR, Max Planck Institute for Solar System Research, Max Planck Society, Justus-von-Liebig-Weg 3, 37077 Göttingen, DE, ou_2265638              
2Department Sun and Heliosphere, Max Planck Institute for Solar System Research, Max Planck Society, ou_1832289              

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Free keywords: magnetohydrodynamics (MHD) / turbulence / dynamo / Sun: magnetic fields / Sun: rotation / Sun: activity
 Abstract: Context. The formation mechanism of sunspots and starspots is not yet fully understood. It is a major open problem in astrophysics. Aims. Magnetic flux concentrations can be produced by the negative effective magnetic pressure instability (NEMPI). This instability is strongly suppressed by rotation. However, the presence of an outer coronal envelope was previously found to strengthen the flux concentrations and make them more prominent. It also allows for the formation of bipolar regions (BRs). We aim to understand the important issue of whether the presence of an outer coronal envelope also changes the excitation conditions and the rotational dependence of NEMPI. Methods. We have used direct numerical simulations and mean-field simulations. We adopted a simple two-layer model of turbulence that mimics the jump between the convective turbulent and coronal layers below and above the surface of a star, respectively. The computational domain is Cartesian and located at a certain latitude of a rotating sphere. We investigated the effects of rotation on NEMPI by changing the Coriolis number, the latitude, the strengths of the imposed magnetic field, and the box resolution. Results. Rotation has a strong impact on the process of BR formation. Even rather slow rotation is found to suppress BR formation. However, increasing the imposed magnetic field strength also makes the structures stronger and alleviates the rotational suppression somewhat. The presence of a coronal layer itself does not significantly reduce the effects of rotational suppression.

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Language(s): eng - English
 Dates: 2019
 Publication Status: Published online
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: DOI: 10.1051/0004-6361/201833018
 Degree: -

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Title: Astronomy and Astrophysics
  Other : Astron. Astrophys.
Source Genre: Journal
 Creator(s):
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Publ. Info: Les Ulis Cedex A France : EDP Sciences
Pages: - Volume / Issue: 621 Sequence Number: A61 Start / End Page: - Identifier: Other: 1432-0746
ISSN: 0004-6361
CoNE: https://pure.mpg.de/cone/journals/resource/954922828219_1