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Two-scale Analysis of Solar Magnetic Helicity
KTH, Centres, Nordic Institute for Theoretical Physics NORDITA. University of Colorado, USA.
2017 (English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 836, no 1, 21Article in journal (Refereed) Published
Abstract [en]

We develop a two-scale formalism to determine global magnetic helicity spectra in systems where the local magnetic helicity has opposite signs on both sides of the equator, giving rise to cancellation with conventional methods. We verify this approach using first a synthetic one-dimensional magnetic field and then two-dimensional slices from a three-dimensional α effect-type dynamo-generated magnetic field, with forced turbulence of opposite helicity above and below the midplane of the domain. We then apply this formalism to global solar synoptic vector magnetograms. To improve the statistics, data from three consecutive Carrington rotations (2161-2163) are combined into a single map. We find that the spectral magnetic helicity representative of the northern hemisphere is negative at all wavenumbers and peaks at (scales around ). There is no evidence of bihelical magnetic fields that are found in three-dimensional turbulence simulations of helicity-driven α effect-type dynamos.

Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP), 2017. Vol. 836, no 1, 21
Keyword [en]
dynamo, magnetohydrodynamics (MHD), Sun: magnetic fields, turbulence
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:kth:diva-208117DOI: 10.3847/1538-4357/836/1/21ISI: 000397299000004ScopusID: 2-s2.0-85014350712OAI: oai:DiVA.org:kth-208117DiVA: diva2:1106137
Funder
Swedish Research Council, 621-2011-5076
Note

QC 20170607

Available from: 2017-06-07 Created: 2017-06-07 Last updated: 2017-06-07Bibliographically approved

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CiteExportLink to record
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Citation style
  • apa
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  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
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  • de-DE
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  • en-US
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  • nn-NO
  • nn-NB
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  • Other locale
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Output format
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