Construction of fast dynamos using unsteady flows and maps in three dimensions

Bruce J Bayly, S. Childress

Research output: Contribution to journalArticle

52 Citations (Scopus)

Abstract

Unsteady fast dynamos are constructed using a sequence of rapid movements separated by periods of diffusion of the magnetic field. Motivated by the physical mechanism described by Zel'dovich and by Soward, we examine the effect of single-mode Beltrami waves applied sequentially, and show that they can be approximated by a simple “stretch-fold-shear” (SFS) map of the unit cube onto itself. In the SFS map, the field points in a fixed direction and diffusion is easily computed. The numerical results indicate that fast dynamo action occurs for sufficiently large shear, and that the process is primarily a coherent feature of the larger magnetic scales. Similar results are obtained for smooth flows. Some preliminary analysis of the SFS map using a decomposition method is described.

Original languageEnglish (US)
Pages (from-to)211-240
Number of pages30
JournalGeophysical and Astrophysical Fluid Dynamics
Volume44
Issue number1-4
DOIs
StatePublished - 1988
Externally publishedYes

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DC generators
rotating generators
unsteady flow
Unsteady flow
shear
Magnetic scales
fold
Magnetic fields
Decomposition
decomposition
magnetic field
magnetic fields

Keywords

  • : Kinetic dynamos
  • fast dynamos

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Geophysics
  • Computational Mechanics
  • Astronomy and Astrophysics
  • Mechanics of Materials

Cite this

Construction of fast dynamos using unsteady flows and maps in three dimensions. / Bayly, Bruce J; Childress, S.

In: Geophysical and Astrophysical Fluid Dynamics, Vol. 44, No. 1-4, 1988, p. 211-240.

Research output: Contribution to journalArticle

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