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  Evershed and Counter-Evershed Flows in Sunspot MHD Simulations

Siu-Tapia, A. L., Rempel, M., Lagg, A., & Solanki, S. K. (2018). Evershed and Counter-Evershed Flows in Sunspot MHD Simulations. The Astrophysical Journal, 852(2): 66. doi:10.3847/1538-4357/aaa007.

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Item Permalink: http://hdl.handle.net/21.11116/0000-0000-601C-5 Version Permalink: http://hdl.handle.net/21.11116/0000-0004-B075-1
Genre: Journal Article

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 Creators:
Siu-Tapia, Azaymi Litzi1, Author              
Rempel, M., Author
Lagg, Andreas1, Author              
Solanki, Sami K.1, 2, Author              
Affiliations:
1Department Sun and Heliosphere, Max Planck Institute for Solar System Research, Max Planck Society, ou_1832289              
2ERC Advanced Grant: Solar magnetic field and its influence on solar variability and activity (SOLMAG), Max Planck Institute for Solar System Research, Max Planck Society, ou_3164813              

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 MPIS_GROUPS: Solar Lower Atmosphere and Magnetism
 Abstract: There have been a few reports in the literature of counter-Evershed flows observed in well-developed sunspot penumbrae, i.e., flows directed toward the umbra along penumbral filaments. Here, we investigate the driving forces of such counter-Evershed flows in a radiative magnetohydrodynamic simulation of a sunspot, and compare them to the forces acting on the normal Evershed flow. The simulation covers a timespan of 100 solar hours and generates an Evershed outflow exceeding 8 km s−1 in the penumbra along radially aligned filaments where the magnetic field is almost horizontal. Additionally, the simulation produces a fast counter-Evershed flow (i.e., an inflow near $\tau =1$) in some regions within the penumbra, reaching peak flow speeds of ~12 km s−1. The counter-Evershed flows are transient and typically last a few hours before they turn into outflows again. By using the kinetic energy equation and evaluating its various terms in the simulation box, we found that the Evershed flow occurs due to overturning convection in a strongly inclined magnetic field, while the counter-Evershed flows can be well-described as siphon flows.

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Language(s): eng - English
 Dates: 2018-02-022018
 Publication Status: Published online
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: DOI: 10.3847/1538-4357/aaa007
 Degree: -

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Project name : ERC-2015-AdG - SOLMAG
Grant ID : 695075
Funding program : Horizon 2020 (H2020)
Funding organization : European Commission (EC)

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Title: The Astrophysical Journal
Source Genre: Journal
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Publ. Info: Chicago, IL : University of Chicago Press for the American Astronomical Society
Pages: - Volume / Issue: 852 (2) Sequence Number: 66 Start / End Page: - Identifier: ISSN: 0004-637X
CoNE: https://pure.mpg.de/cone/journals/resource/954922828215_3