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P: Fachverband Plasmaphysik

P 18: Poster: Theorie/Modellierung

P 18.16: Poster

Wednesday, April 1, 2009, 17:30–19:30, Foyer des IfP

Modeling Lagrangian MHD fluctuations — •Thorsten Hater, Holger Homann, Martin Rieke, and Rainer Grauer — Theoretische Physik I, Ruhr-Universität Bochum

Understanding and modeling magnetic field fluctuations in turbulent flows like the solar wind is of fundamental importance. Modeling magnetic field fluctuations such that the higher order statistical features are correclty captured opens a way to efficiently study questions like cosmic ray transport properties. Here, we present a model based on the Recent Fluid Deformation closure (RFD) introduced by Chevillard and Meneveau (2006, 2007) for the incompressible Navier-Stokes equations. We extend this theory to include kinematic magnetic field fluctuations and fluctuations of the gradient of passively transported quantities. Comparison of the PDFs of these fluctuations gives insight into the influence of the relevant stretching processes. PDFs of the modeling are also compared with PDFs obtained from high-resolution direct spectral simulations of Lagrangian turbulence. The agreement between modeling and direct simulations exceeded our expectations.

In addition, we started using graphics cards for spectral simulations. As a first example, long time Lagrangian statistics of the 2D inverse cascade are simulated. Speed-ups of a factor 30 have been achieved compared to CPU computing.