HAL will be down for maintenance from Friday, June 10 at 4pm through Monday, June 13 at 9am. More information
Skip to Main content Skip to Navigation
Journal articles

The decay of isotropic magnetohydrodynamics turbulence and the effects of cross-helicity

Abstract : Decaying homogeneous and isotropic magnetohydrodynamics (MHD) turbulence is investigated numerically at large Reynolds numbers thanks to the eddy-damped quasi-normal Markovian (EDQNM) approximation. Without any background mean magnetic field, the total energy spectrum E scales as k −3/2 in the inertial range as a consequence of the modelling. Moreover, the total energy is shown, both analytically and numerically, to decay at the same rate as kinetic energy in hydrodynamic isotropic turbulence: this differs from a previous prediction, and thus physical arguments are proposed to reconcile both results. Afterwards, the MHD turbulence is made imbalanced by an initial non-zero cross-helicity. A spectral modelling is developed for the velocity-magnetic correlation in a general homogeneous framework, which reveals that cross-helicity can contain subtle anisotropic effects. In the inertial range, as the Reynolds number increases, the slope of the cross-helical spectrum becomes closer to k −5/3 than k −2. Furthermore, the Elsässer spectra deviate from k −3/2 with cross-helicity at large Reynolds numbers. Regarding the pressure spectrum E P , its kinetic and magnetic parts are found to scale with k −2 in the inertial range, whereas the part due to cross-helicity rather scales in k −7/3. Finally, the two 4/3rd laws for the total energy and cross-helicity are assessed numerically at large Reynolds numbers.
Document type :
Journal articles
Complete list of metadata

Cited literature [73 references]  Display  Hide  Download

https://hal-amu.archives-ouvertes.fr/hal-02112143
Contributor : Olivier Boutin Connect in order to contact the contributor
Submitted on : Friday, April 26, 2019 - 2:37:13 PM
Last modification on : Tuesday, January 4, 2022 - 5:29:55 AM

File

briard2018.pdf
Files produced by the author(s)

Identifiers

Citation

Antoine Briard, Thomas Gomez. The decay of isotropic magnetohydrodynamics turbulence and the effects of cross-helicity. Journal of Plasma Physics, Cambridge University Press (CUP), 2018, 84 (1), ⟨10.1017/S0022377818000120⟩. ⟨hal-02112143⟩

Share

Metrics

Record views

114

Files downloads

331