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Kinematic turbulent dynamo in the large Prandtl number regime

type de publication      article dans une revue internationale avec comité de lecture
date de publication 2004
auteur(s) West Robert J; Nazarenko Sergey V.; Laval Jean-Philippe; Galtier Sébastien
journal (abréviation) Astronomy & Astrophysics (A & A)
volume (numéro) 414 (3)
  
pages 807 – 824
résumé We present the results of a numerical investigation of the turbulent kinematic dynamo problem in a high Prandtl number regime. The scales of the magnetic turbulence we consider are far smaller than the Kolmogorov dissipative scale, so that the magnetic wavepackets evolve in a nearly smooth velocity field. Firstly, we consider the Kraichnan-Kazantsev model (KKM) in which the strain matrix is taken to be independent of coordinate and Gaussian white in time. To simulate the KKM we use a stochastic Euler-Maruyama method. We test the theoretical predictions for the growth of rates of the magnetic energy and higher order moments, the shape of the energy spectrum and the behaviour of the polarisation and spectral flatness. In general, the results appear to be in good agreement with the theory, with the exception that the predicted decay of the polarisation in time is not reproduced well in the stochastic numerics. Secondly, in order to study the sensitivity of the KKM predictions to the choice of strain statistics, we perform additional simulations for the case of a Gaussian strain with a finite correlation time and also for a strain taken from a DNS
mots clés MHD, Turbulence, Simulation
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