Magnetic concentrations in stratified turbulence: the negative effective magnetic pressure instability

Abstract

In the presence of strong density stratification, hydromagnetic turbulence attains qualitatively new properties: the formation of magnetic flux concentrations. We review here the theoretical foundations of this mechanism in terms of what is now called the negative effective magnetic pressure instability. We also present direct numerical simulations of forced turbulence in strongly stratified layers and discuss the qualitative and quantitative similarities with corresponding mean-field simulations. Finally, the relevance to sunspot formation is discussed.

arXiv comment23 pages, 13 figures, special issue "Focus on Turbulence in Astrophysical and Laboratory Plasmas" of New Journal of Physics, published

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Cited by in corpus (17)

• Advances in mean-field dynamo theory and applications to astrophysical turbulence
• Varying the forcing scale in low Prandtl number dynamos
• Temporal and Periodic Variations of Sunspot Counts in Flaring and Non-flaring Active Regions
• Extended statistical analysis of emerging solar active regions
• The mean tilt of sunspot bipolar regions: theory, simulations and comparison with observations
• Nonlinear mean-field dynamo and prediction of solar activity
• $f$-mode strengthening from a localized bipolar subsurface magnetic field
• Sharp magnetic structures from dynamos with density stratification
• Magnetic fields in circumstellar envelopes of evolved AGB stars
• Large Scale Properties of Tilt of Sunspot Groups and Joy's Law Near The Solar Equator
• A new look at sunspot formation using theory and observations
• Spontaneous flux concentrations from the negative effective magnetic pressure instability beneath a radiative stellar surface
• Turbulent radiative diffusion and turbulent Newtonian cooling
• Cross-helically forced and decaying hydromagnetic turbulence
• Large-scale clustering of inertial particles in a rotating, stratified and inhomogeneous turbulence
• Estimates of current helicity and tilt of solar active regions and Joy's law
• Magnetic bipoles in rotating turbulence with coronal envelope