Cross-helically forced and decaying hydromagnetic turbulence
Brandenburg, A., & Oughton, S. (2018). Cross-helically forced and decaying hydromagnetic turbulence. Astronomische Nachrichten, 339(9-10), 641–646. https://doi.org/10.1002/asna.201913602
Permanent Research Commons link: https://hdl.handle.net/10289/12818
We study the evolution of kinetic and magnetic energy spectra in magnetohydrodynamic flows in the presence of strong cross helicity. For forced turbulence, we find a weak inverse transfer of kinetic energy toward the smallest wavenumber. This is plausibly explained by the finiteness of scale separation between the injection wavenumber and the smallest wavenumber of the domain, which here is a factor of 15. In the decaying case, there is a slight increase at the smallest wavenumber, which is probably explained by the dominance of kinetic energy over magnetic energy at the smallest wavenumbers. Within a range of wavenumbers covering almost an order of magnitude, the decay is purely exponential, which is argued to be a consequence of a suppression of nonlinearity due to the presence of strong cross helicity.
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This is an author’s accepted version of an article published in the journal: Astronomische Nachrichten. © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim