Inverse cascade of magnetic helicity in magnetohydrodynamic turbulence

Mueller, W.-C., Malapaka, S.K. and Busse, A. (2012) Inverse cascade of magnetic helicity in magnetohydrodynamic turbulence. Physical Review E, 85(1), 015302(R). (doi: 10.1103/PhysRevE.85.015302)

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The nonlinear dynamics of magnetic helicity HM, which is responsible for large-scale magnetic structure formation in electrically conducting turbulent media, is investigated in forced and decaying three-dimensional magnetohydrodynamic turbulence. This is done with the help of high-resolution direct numerical simulations and statistical closure theory. The numerically observed spectral scaling of HM is at variance with earlier work using a statistical closure model [ Pouquet et al. J. Fluid Mech. 77 321 (1976)]. By revisiting this theory, a universal dynamical balance relation is found that includes the effects of kinetic helicity as well as kinetic and magnetic energies on the inverse cascade of HM and explains the above-mentioned discrepancy. Consideration of the result in the context of mean-field dynamo theory suggests a nonlinear modification of the α-dynamo effect, which is important in the context of magnetic-field excitation in turbulent plasmas.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Busse, Dr Angela
Authors: Mueller, W.-C., Malapaka, S.K., and Busse, A.
College/School:College of Science and Engineering > School of Engineering > Systems Power and Energy
Journal Name:Physical Review E
Publisher:American Physical Society
ISSN (Online):1063-651X

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