HR: 1340h
AN: NG23A-1183    [Abstracts]
TI: Characterising the Scaling Properties of the Local Rate of Dissipation in Incompressible Isotropic Three-Dimensional MHD Turbulence
AU: Merrifield, J
EM: merrifj@astro.warwick.ac.uk
AF: Space and Astrophysics, University of Warwick, Coventry, CV4 7AL United Kingdom
AU: * Chapman, S C
EM: sandrac@astro.warwick.ac.uk
AF: Space and Astrophysics, University of Warwick, Coventry, CV4 7AL United Kingdom
AU: Muller, W -
EM: Wolf.Mueller@ipp.mpg.de
AF: Center for Interdisciplary Plasma Science, Max Planck Institut fur Plasmaphysik, Garching, 85748 Germany
AU: Dendy, R O
EM: R.O.Dendy@ukaea.org.uk
AF: Euratom/UKAEA Fusion, Culham, Abingdon, Oxon, OX14 3DB United Kingdom
AB: Recent improvements in the scale and accuracy of direct numerical simulations (DNS) of three-dimensional incompressible isotropic MHD turbulence enable many of its fundamental properties to be investigated anew. Here we report progress on several questions, achieved using the DNS of Biskamp and Muller [Phys. Plasmas 7, 4889 (2000)]. This employs the incompressible resistive MHD equations to simulate decaying isotropic turbulence, with finite magnetic helicity and initially equal magnetic and kinetic energy densities. It has a spatial resolution of $512^3$ Fourier modes. Central questions include the nature, including dimensionality, of the localised turbulent structures that give rise to intermittency in the local rate of dissipation; and the relation of their role to that of less strongly dissipative turbulent structures that are more widely distributed. There is also the question of the extent and nature of any universal scaling properties of the turbulent fluctuations. Here the scaling of the local rate of dissipation (both viscous and Ohmic), and of its one-dimensional surrogate, are compared with the picture gained from the study of the Elsasser field variables. A range of techniques is used to characterise any universal scaling behaviour that arises from the relatively low Reynolds number flows obtainable by DNS. These include extended self-similarity (ESS), which extends a variant of inertial range scaling into the dissipative range. Intermittency in these measures is then analysed in the framework of the generalised theory of the intermittency correction proposed by She and Leveque [Phys. Rev. Lett. 72, 336 (1994)].
DE: 7863 Turbulence
DE: 2149 MHD waves and turbulence
DE: 2159 Plasma waves and turbulence
DE: 3210 Modeling
DE: 3250 Fractals and multifractals
SC: Nonlinear Geophysics [NG]
MN: 2004 AGU Fall Meeting