Nonlinear Mean-Field Dynamos With Magnetic Helicity Transport and Solar Activity: Sunspot Number and Tilt

Nathan Kleeorin, Kirill Kuzanyan, Igor Rogachevskii, Nikolai Safiullin

Research output: Chapter in Book/Report/Conference proceedingChapterpeer-review

Abstract

In this chapter, we discuss a mean field solar dynamo model with algebraic and dynamic nonlinearities, various mechanisms of sunspot formation, and prediction of solar activity. The algebraic nonlinearity describes the quenching of the alpha effect, turbulent magnetic diffusion, and the effective pumping velocity due to feedback from the growing large-scale magnetic field on the fluid motion. The dynamic nonlinearity is due to the evolution of the magnetic helicity of the small-scale magnetic field during the nonlinear stage of the dynamo; it is derived from conservation of the total (large-scale plus small-scale) magnetic helicity for very small microscopic magnetic diffusivity.We discuss observations of magnetic helicity in the Sun and their connection with the nonlinear mean field dynamo. We derive a budget equation for sunspot numbers taking into account sunspot formation mechanism due to the negative effective magnetic pressure instability. To predict solar activity, we use dynamo simulations as input to an artificial neural network that learns sunspot dynamics from available observations. Finally, we analyze the contribution of magnetic helicity transport to the formation of tilt in sunspot bipolar regions and compare the results with available observational data over the last 10 solar cycles (15-24).

Original languageEnglish
Title of host publicationHelicities in Geophysics, Astrophysics, and Beyond
Publisherwiley
Pages217-240
Number of pages24
ISBN (Electronic)9781119841715
ISBN (Print)9781119841685
DOIs
StatePublished - 1 Jan 2023

Keywords

  • Magnetic helicity
  • mean-field dynamo theory
  • Nonlinear dynamo
  • solar cycle prediction
  • solar dynamo
  • tilt of bipolar sunspots

ASJC Scopus subject areas

  • General Physics and Astronomy

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