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  Normal and counter Evershed flows in the photospheric penumbra of a sunspot: SPINOR 2D inversions of Hinode-SOT/SP observations

Siu-Tapia, A. L., Lagg, A., Solanki, S. K., van Noort, M., & Jurčák, J. (2017). Normal and counter Evershed flows in the photospheric penumbra of a sunspot: SPINOR 2D inversions of Hinode-SOT/SP observations. Astronomy and Astrophysics, 607: A 36. doi:10.1051/0004-6361/201730647.

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Item Permalink: http://hdl.handle.net/21.11116/0000-0000-6011-0 Version Permalink: http://hdl.handle.net/21.11116/0000-0000-6012-F
Genre: Journal Article

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 Creators:
Siu-Tapia, Azaymi Litzi1, Author              
Lagg, Andreas1, Author              
Solanki, Sami K.1, Author              
van Noort, Michiel1, Author              
Jurčák, J., Author
Affiliations:
1Department 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 / Sun: general
 MPIS_GROUPS: Sun and Heliosphere: Solar Lower Atmosphere and Magnetism
 Abstract: Context. The Evershed effect, a nearly horizontal outflow of material seen in the penumbrae of sunspots in the photospheric layers, is a common characteristic of well-developed penumbrae, but is still not well understood. Even less is known about photospheric horizontal inflows in the penumbra, also known as counter Evershed flows. Aims. Here we present a rare feature observed in the penumbra of the main sunspot of AR NOAA 10930. This spot displays the normal Evershed outflow in most of the penumbra, but harbors a fast photospheric inflow of material over a large sector of the disk-center penumbra. We investigate the driving forces of both, the normal and the counter Evershed flows. Methods. We invert the spectropolarimetric data from Hinode SOT/SP using the spatially coupled version of the SPINOR inversion code, which allows us to derive height-dependent maps of the relevant physical parameters in the sunspot. These maps show considerable fine structure. Similarities and differences between the normal Evershed outflow and the counter Evershed flow are investigated. Results. In both the normal and the counter Evershed flows, the material flows from regions with field strengths of the order of 1.5–2 kG to regions with stronger fields. The sources and sinks of both penumbral flows display opposite field polarities, with the sinks (tails of filaments) harboring local enhancements in temperature, which are nonetheless colder than their sources (heads of filaments). Conclusions. The anti-correlation of the gradients in the temperature and magnetic pressure between the endpoints of the filaments from the two distinct penumbral regions is compatible with both the convective driver and the siphon flow scenarios. A geometrical scale of the parameters is necessary to determine which is the dominant force driving the flows.

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Language(s): eng - English
 Dates: 2018-02-022017
 Publication Status: Published online
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: DOI: 10.1051/0004-6361/201730647
 Degree: -

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Title: Astronomy and Astrophysics
  Other : Astron. Astrophys.
Source Genre: Journal
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Publ. Info: Berlin : Springer-Verlag
Pages: - Volume / Issue: 607 Sequence Number: A 36 Start / End Page: - Identifier: ISSN: 0004-6361
CoNE: https://pure.mpg.de/cone/journals/resource/954922828219_1