The dynamics of Wolf numbers based on nonlinear dynamos with magnetic helicity: Comparisons with observations

Y. Kleeorin, N. Safiullin, N. Kleeorin, S. Porshnev, I. Rogachevskii, D. Sokoloff

Research output: Contribution to journalArticlepeer-review

16 Scopus citations

Abstract

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.

Original languageEnglish
Pages (from-to)3960-3967
Number of pages8
JournalMonthly Notices of the Royal Astronomical Society
Volume460
Issue number4
DOIs
StatePublished - 21 Aug 2016

Keywords

  • Dynamo
  • Sun: activity

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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