Volume 92, Number 3, November 2010
|Number of page(s)||6|
|Section||Electromagnetism, Optics, Acoustics, Heat Transfer, Classical Mechanics, and Fluid Dynamics|
|Published online||23 November 2010|
Long-term free decay of MHD turbulence
Institute of Continuous Media Mechanics - Korolyov str. 1, Perm, 614013, Russia
Accepted: 20 October 2010
The free decay of MHD turbulence at large Reynolds numbers is studied numerically using a shell model. We study the statistical properties based on a representative sample of realisations (128 realisations for each type of initial conditions) over a period of 105 large-scale turnover times. The performed simulations show that the free-decaying nonhelical MHD turbulence can demonstrate two different scenarios of evolution in spite of similar initial conditions. Within the first scenario, the cross-helicity accumulation is so fast that the energy cascade vanishes before significant magnetic energy dissipates. Then the system approaches the state of maximal cross-helicity. Within the second scenario, the cascade process continues to remain active until time 104 in units of large-scale turnover time. Then the magnetic field becomes vastly helical due to magnetic helicity conservation. Thus the magnetic energy does not dissipate with kinetic energy.
PACS: 47.27.E- – Turbulence simulation and modeling / 47.35.Tv – Magnetohydrodynamic waves
© EPLA, 2010
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