Axial dipolar dynamo action in the Taylor-Green vortex.
We present a numerical study of the magnetic field generated by the Taylor-Green vortex. We show that periodic boundary conditions can be used to mimic realistic boundary conditions by prescribing the symmetries of the velocity and magnetic fields. This gives insight into some problems of central interest for dynamos: the possible effect of velocity fluctuations on the dynamo threshold, and the role of boundary conditions on the threshold and on the geometry of the magnetic field generated by dynamo action. In particular, we show that an axial dipolar dynamo similar to the one observed in a recent experiment can be obtained with an appropriate choice of the symmetries of the magnetic field. The nonlinear saturation is studied and a simple model explaining the magnetic Prandtl number dependence of the super- and subcritical nature of the dynamo transition is given.
Laboratoire de Physique Statistique de l'Ecole Normale Supérieure, Associé au CNRS et aux Universités Paris VI et VII, 24 Rue Lhomond, F-75231 Paris, France.
Giorgio
G
Krstulovic
Gentien
G
Thorner
Julien-Piera
JP
Vest
Stephan
S
Fauve
Marc
M
Brachet