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Dynamics of decaying two‐dimensional magnetohydrodynamic turbulence

 

作者: D. Biskamp,   H. Welter,  

 

期刊: Physics of Fluids B: Plasma Physics  (AIP Available online 1989)
卷期: Volume 1, issue 10  

页码: 1964-1979

 

ISSN:0899-8221

 

年代: 1989

 

DOI:10.1063/1.859060

 

出版商: AIP

 

数据来源: AIP

 

摘要:

High‐resolution numerical studies of decaying two‐dimensional magnetohydrodynamic turbulence were performed with up to 10242collocation points in general periodic systems using various initial states, but restricting consideration to weak velocity‐magnetic field correlation &rgr;. The global evolution is self‐similar with constant kinetic to magnetic energy ratioEV/EM, macro‐ and microscale Reynolds numbers, and correlation &rgr;, while the total energy decays asE(t)∝(t+t0)−1. As in three dimensions, dissipative small‐scale turbulence adjusts in such a way as to make the energy dissipation rate &egr; independent of the collisional dissipation coefficients. Normalized energy spectra are also invariant. The spectral index in the inertial range is, in general, close to 3/2 in agreement with Kraichnan’s Alfve´n wave argumentEk=DB1/2&egr;1/2k−3/2,B=(EM)1/2,D&bartil;1.8±0.2, but may be close to 5/3 in transient states, in which turbulence is concentrated in regions of weak magnetic field. In the dissipation range, intermittency gives rise to a modified dissipation scaleleff=(l2&lgr;)1/3, withl=Kolmogorov scale and &lgr;=Taylor microscale. This reflects the intermittency of the dissipation process, which is consistent with the picture of current microsheets of thicknessland width and spacing &lgr;.

 

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