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The dynamics of Wolf numbers based on nonlinear dynamos with magnetic helicity: comparisons with observations
KTH, Centres, Nordic Institute for Theoretical Physics NORDITA.
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2016 (English)In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 460, no 4, 3960-3967 p.Article in journal (Refereed) Published
Abstract [en]

We investigate the dynamics of solar activity using a nonlinear one-dimensional dynamo model and a phenomenological equation for the evolution of Wolf numbers. This system of equations is solved numerically. We take into account the algebraic and dynamic nonlinearities of the alpha effect. The dynamic nonlinearity is related to the evolution of a small-scale magnetic helicity, and it leads to a complicated behaviour of solar activity. The evolution equation for the Wolf number is based on a mechanism of formation of magnetic spots as a result of the negative effective magnetic pressure instability (NEMPI). This phenomenon was predicted 25 yr ago and has been investigated intensively in recent years through direct numerical simulations and mean-field simulations. The evolution equation for the Wolf number includes the production and decay of sunspots. Comparison between the results of numerical simulations and observational data of Wolf numbers shows a 70 per cent correlation over all intervals of observation (about 270 yr). We determine the dependence of the maximum value of the Wolf number versus the period of the cycle and the asymmetry of the solar cycles versus the amplitude of the cycle. These dependences are in good agreement with observations.

Place, publisher, year, edition, pages
Oxford University Press, 2016. Vol. 460, no 4, 3960-3967 p.
Keyword [en]
Sun: activity, dynamo
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
URN: urn:nbn:se:kth:diva-193208DOI: 10.1093/mnras/stw1267ISI: 000381711100042Scopus ID: 2-s2.0-84980385967OAI: oai:DiVA.org:kth-193208DiVA: diva2:1033642
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QC 20161007

Available from: 2016-10-07 Created: 2016-09-30 Last updated: 2017-11-30Bibliographically approved

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Kleeorin, NathanRogachevskii, Igor
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CiteExportLink to record
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Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
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  • Other locale
More languages
Output format
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  • asciidoc
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