The negative magnetic pressure effect in stratified turbulence

K. Kemel, A. Brandenburg, N. Kleeorin, I. Rogachevskii

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review


While the rising flux tube paradigm is an elegant theory, its basic assumptions, thin flux tubes at the bottom of the convection zone with field strengths two orders of magnitude above equipartition, remain numerically unverified at best. As such, in recent years the idea of a formation of sunspots near the top of the convection zone has generated some interest. The presence of turbulence can strongly enhance diffusive transport mechanisms, leading to an effective transport coefficient formalism in the mean-field formulation. The question is what happens to these coefficients when the turbulence becomes anisotropic due to a strong large-scale mean magnetic field. It has been noted in the past that this anisotropy can also lead to highly non-diffusive behavior. In the present work we investigate the formation of large-scale magnetic structures as a result of a negative contribution of turbulence to the large-scale effective magnetic pressure in the presence of stratification. In direct numerical simulations of forced turbulence in a stratified box, we verify the existence of this effect. This phenomenon can cause formation of large-scale magnetic structures even from initially uniform large-scale magnetic field.

Original languageEnglish
Title of host publicationThe Physics of Sun and Star Spots
EditorsDebi Prasad Choudhary, Klaus Strassmeier
Number of pages6
StatePublished - 1 Aug 2010

Publication series

NameProceedings of the International Astronomical Union
ISSN (Print)1743-9213
ISSN (Electronic)1743-9221


  • MHD
  • Sunspots
  • Turbulence

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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