title: Inverse cascade of magnetic helicity in magnetohydrodynamic turbulence.
abstract: 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.
authors.affiliation: Max-Planck-Institut für Plasmaphysik, 85748 Garching, Germany. wolf.mueller@ipp.mpg.de
authors.forename: Wolf-Christian
authors.initials: WC
authors.lastname: Müller
authors.forename: Shiva Kumar
authors.initials: SK
authors.lastname: Malapaka
authors.forename: Angela
authors.initials: A
authors.lastname: Busse