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Downward pumping of magnetic flux as the cause of filamentary structures in sunspot penumbrae

Thomas, J.H., Weiss, N.O., Tobias, S.M. and Brummell, N.H. (2002) Downward pumping of magnetic flux as the cause of filamentary structures in sunspot penumbrae. Nature, 420 (6914). pp. 390-393. ISSN 0028-0836

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The structure of a sunspot is determined by the local interaction between magnetic fields and convection near the Sun's surface. The dark central umbra is surrounded by a filamentary penumbra, whose complicated fine structure has only recently been revealed by high-resolution observations. The penumbral magnetic field has an intricate and unexpected interlocking-comb structure and some field lines, with associated outflows of gas, dive back down below the solar surface at the outer edge of the spot. These field lines might be expected to float quickly back to the surface because of magnetic buoyancy, but they remain submerged. Here we show that the field lines are kept submerged outside the spot by turbulent, compressible convection, which is dominated by strong, coherent, descending plumes. Moreover, this downward pumping of magnetic flux explains the origin of the interlocking-comb structure of the penumbral magnetic field, and the behaviour of other magnetic features near the sunspot.

Item Type: Article
Copyright, Publisher and Additional Information: © 2002 Nature Publishing Group
Institution: The University of Leeds
Academic Units: The University of Leeds > Faculty of Maths and Physical Sciences (Leeds) > School of Mathematics (Leeds) > Applied Mathematics (Leeds)
Depositing User: Repository Officer
Date Deposited: 20 Sep 2004
Last Modified: 08 Jun 2014 17:41
Published Version: http://www.nature.com/nature/
Status: Published
Refereed: Yes
Identification Number: 10.1038/nature01174
URI: http://eprints.whiterose.ac.uk/id/eprint/72

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