Space Science Reviews

, Volume 169, Issue 1, pp 123–157

Current Status of Turbulent Dynamo Theory

From Large-Scale to Small-Scale Dynamos
  • Axel Brandenburg
  • Dmitry Sokoloff
  • Kandaswamy Subramanian
Article

DOI: 10.1007/s11214-012-9909-x

Cite this article as:
Brandenburg, A., Sokoloff, D. & Subramanian, K. Space Sci Rev (2012) 169: 123. doi:10.1007/s11214-012-9909-x
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Abstract

Several recent advances in turbulent dynamo theory are reviewed. High resolution simulations of small-scale and large-scale dynamo action in periodic domains are compared with each other and contrasted with similar results at low magnetic Prandtl numbers. It is argued that all the different cases show similarities at intermediate length scales. On the other hand, in the presence of helicity of the turbulence, power develops on large scales, which is not present in non-helical small-scale turbulent dynamos. At small length scales, differences occur in connection with the dissipation cutoff scales associated with the respective value of the magnetic Prandtl number. These differences are found to be independent of whether or not there is large-scale dynamo action. However, large-scale dynamos in homogeneous systems are shown to suffer from resistive slow-down even at intermediate length scales. The results from simulations are connected to mean field theory and its applications. Recent work on magnetic helicity fluxes to alleviate large-scale dynamo quenching, shear dynamos, nonlocal effects and magnetic structures from strong density stratification are highlighted. Several insights which arise from analytic considerations of small-scale dynamos are discussed.

Keywords

Magnetic fieldsTurbulenceSun: Magnetic fields

Copyright information

© Springer Science+Business Media B.V. 2012

Authors and Affiliations

  • Axel Brandenburg
    • 1
    • 2
  • Dmitry Sokoloff
    • 3
  • Kandaswamy Subramanian
    • 4
  1. 1.NorditaRoyal Institute of Technology and Stockholm UniversityStockholmSweden
  2. 2.Department of AstronomyStockholm UniversityStockholmSweden
  3. 3.Department of PhysicsMoscow UniversityMoscowRussia
  4. 4.Inter-University Centre for Astronomy and AstrophysicsPuneIndia