Subcritical dynamo bifurcation in the Taylor Green flow

Yannick Ponty (1) , Jean-Phillipe Laval (2) , Bérengère Dubrulle (3) , François Daviaud (3) , Jean-François Pinton (4)

1 CASSIOPEE - Laboratoire de Cosmologie, Astrophysique Stellaire & Solaire, de Planétologie et de Mécanique des Fluides
2 LML - Laboratoire de Mécanique de Lille - FRE 3723
3 SPEC - UMR3680 - Service de physique de l'état condensé
4 Phys-ENS - Laboratoire de Physique de l'ENS Lyon

We report direct numerical simulations of dynamo generation for flow generated using a Taylor-Green forcing. We find that the bifurcation is subcritical, and show its bifurcation diagram. We connect the associated hysteretic behavior with hydrodynamics changes induced by the action of the Lorentz force. We show the geometry of the dynamo magnetic field and discuss how the dynamo transition can be induced when an external field is applied to the flow.

Mots clés: Dynamo; Subcritical Bifurcation; Taylor-Green; VKS

Domaines: Dynamique des Fluides [physics.flu-dyn]; Milieux fluides et réactifs; Astrophysique [astro-ph]; Cosmologie et astrophysique extra-galactique [astro-ph.CO]

Yannick Ponty, Jean-Phillipe Laval, Bérengère Dubrulle, François Daviaud, Jean-François Pinton. Subcritical dynamo bifurcation in the Taylor Green flow. 2007. ⟨hal-00163353v2⟩