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Abstract: Magnetohydrodynamics MHD provides the simplest description of magneticplasma turbulence in a variety of astrophysical and laboratory systems. MHDturbulence with nonzero cross helicity is often called imbalanced, as itimplies that the energies of Alfv\-en fluctuations propagating parallel andanti-parallel the background field are not equal. Recent analytical andnumerical studies have revealed that at every scale, MHD turbulence consists ofregions of positive and negative cross helicity, indicating that suchturbulence is inherently locally imbalanced. In this paper, results from highresolution numerical simulations of steady-state incompressible MHD turbulence,with and without cross helicity are presented. It is argued that the inertialrange scaling of the energy spectra E^+ and E^- of fluctuations moving inopposite directions is independent of the amount of cross-helicity. When crosshelicity is nonzero, E^+ and E^- maintain the same scaling, but have differingamplitudes depending on the amount of cross-helicity.



Author: Jean Carlos Perez, Stanislav Boldyrev

Source: https://arxiv.org/







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