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Two-scale Analysis of Solar Magnetic Helicity
Stockholm University, Nordic Institute for Theoretical Physics (Nordita). Stockholm University, Faculty of Science, Department of Astronomy. University of Colorado, USA.
Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
Number of Authors: 3
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 a 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 approximate to 0.06 Mm(-1) (scales around 100 Mm). There is no evidence of bihelical magnetic fields that are found in three-dimensional turbulence simulations of helicity-driven a effect-type dynamos.

Place, publisher, year, edition, pages
2017. Vol. 836, no 1, 21
Keyword [en]
dynamo, magnetohydrodynamics (MHD), Sun: magnetic fields, turbulence
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:su:diva-142511DOI: 10.3847/1538-4357/836/1/21ISI: 000397299000004OAI: oai:DiVA.org:su-142511DiVA: diva2:1094699
Available from: 2017-05-10 Created: 2017-05-10 Last updated: 2017-05-10Bibliographically approved

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Brandenburg, AxelSingh, Nishant K.
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Nordic Institute for Theoretical Physics (Nordita)Department of Astronomy
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Citation style
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  • Other locale
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