HR: 08:30h
AN: NG41A-03    [Abstracts]
TI: Large Scale Numerical Simulations of Compressible Isotropic 2D MHD Turbulence, Phenomenology and Scaling Laws
AU: * Merrifield, J
EM: J.A.Merrifield@warwick.ac.uk
AF: Space and Astrophysics and Centre for Scientific Computing, University of Warwick, Coventry, CV4 7AL United Kingdom
AU: Chapman, S C
EM: S.C.Chapman@warwick.ac.uk
AF: Space and Astrophysics and Centre for Scientific Computing, University of Warwick, Coventry, CV4 7AL United Kingdom
AU: Arber, T
EM: T.D.Arber@warwick.ac.uk
AF: Space and Astrophysics and Centre for Scientific Computing, University of Warwick, Coventry, CV4 7AL United Kingdom
AU: Dendy, R O
EM: R.O.Dendy@ukaea.org.uk
AF: Culham Science Centre, UKAEA Culham, Abingdon, OX12 8QU United Kingdom
AB: In many solar system, astrophysical and laboratory plasmas, the magnetic Reynolds number is large and the magnetohydrodynamic (MHD) approximation is valid. In these cases plasmas exhibit MHD turbulence. The 2D equations of MHD can be used to model plasma turbulence where the perturbed magnetic field is small when compared to the mean magnetic field and is essentially perpendicular to it, with particular relevance to solar system and astrophysical applications. In the present work we simulate the equations of isothermal compressible MHD directly in two spatial dimensions. Contrary to the case of hydrodynamic turbulence, absolute equilibrium theory shows that MHD turbulence is expected to display similar cascade properties in two and three dimensions, such as a direct cascade in total energy. However, recent numerical studies of isotropic incompressible MHD turbulence suggest that the cascade may be governed by different processes in 2D and 3D. It has been found previously that scaling laws derived after the phenomenology of Kolmogorov (K41) can be used to describe incompressible MHD turbulence in 3D. Numerical studies presented here, and those of other authors, suggest that the scaling properties of 2D MHD turbulence differ significantly from those found in 3D. It has been suggested that this difference stems from the fact that the energy cascade is modified by the presence of Alfven waves in 2D after the manner of Iroshnikov and Kraichnan(IK). However, we find that intermittency models based on the IK phenomenology do not fully describe the scaling properties of MHD turbulence in 2D. Here we evaluate the applicability of the K41 and IK phenomenologies by investigating the relevant scaling relations. We pay particular attention to the combined scaling properties of the Elsasser field variables and the local rate of dissipation which bear particular relevance to currently favoured models for intermittency.
DE: 2149 MHD waves and turbulence (2752, 6050, 7836)
DE: 4490 Turbulence (3379, 4568, 7863)
DE: 6050 Plasma and MHD instabilities (2149, 2752, 7836)
DE: 7836 MHD waves and instabilities (2149, 2752, 6050)
SC: Nonlinear Geophysics [NG]
MN: Fall Meeting 2005