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SYNS: Numerical Simulation of Hightemperature Plasmas

SYNS 2: Numerical Simulation II

SYNS 2.4: Talk

Thursday, April 2, 2009, 16:45–17:00, HS Biochemie (groß)

Lagrangian statistics and the phenomenological description of turbulence — •Angela Busse and Wolf-Christian Müller — Max-Planck-Institut für Plasmaphysik, Garching bei München

Various models have been proposed for the phenomenological description of the energy cascade in fully developed MHD turbulence. Based on the nonlinear interaction mechanism underlying the cascade process they can be divided into two main groups: Models of Iroshnikov-Kraichnan type which employ a weak interaction mechanism and the Goldreich-Sridhar phenomenology and its derivatives which propose a strong interaction mechanism. In the Eulerian reference frame it is difficult to distinguish between strong and weak interaction mechanisms since the same scaling laws for the energy spectrum can be derived using different cascade mechanisms. The Lagrangian frequency spectrum however, is sensitive to the time scales involved in the underlying cascade dynamics and different scaling laws in the inertial range are expected for weak and strong interaction mechanisms.

The Lagrangian frequency spectrum has been obtained by tracking fluid particles in direct numerical simulations of incompressible MHD turbulence for both the two- and three-dimensional cases. Results for the macroscopically isotropic MHD case as well as MHD turbulence under the influence of a strong mean magnetic field are presented.