Role of helicities for the dynamics of turbulent magnetic fields

Abstract

Investigations of the inverse cascade of magnetic helicity are conducted with pseudospectral, three-dimensional direct numerical simulations of forced and decaying incompressible magnetohydrodynamic turbulence. The high-resolution simulations which allow for the necessary scale-separation show that the observed self-similar scaling behavior of magnetic helicity and related quantities can only be understood by taking the full nonlinear interplay of velocity and magnetic fluctuations into account. With the help of the eddy-damped quasi-normal Markovian approximation a probably universal relation between kinetic and magnetic helicities is derived that closely resembles the extended definition of the prominent dynamo pseudoscalar $\alpha$. This unexpected similarity suggests an additional nonlinear quenching mechanism of the current-helicity contribution to $\alpha$.

7 pages, 4 figures, This is an Author's Accepted Manuscript of an article published in Geophysical \& Astrophysical Fluid Dynamics, First Published online : 01 Jun 2012. [copyright Taylor \& Francis]

References in corpus (4)

• Nonlinear current helicity fluxes in turbulent dynamos and alpha quenching
• Test-field method for mean-field coefficients with MHD background
• The inverse cascade of magnetic helicity in magnetohydrodynamic turbulence
• Advances in theory and simulations of large-scale dynamos

Cited by in corpus (1)

• Additivity of relative magnetic helicity in finite volumes