Influence of turbulence on the dynamo threshold

Jean-Philippe Laval (1) , Pierre Blaineau (2) , Nicolas Leprovost (2) , Bérengère Dubrulle (2) , François Daviaud (2)

1 LML - Laboratoire de Mécanique de Lille - FRE 3723
2 SPEC - UMR3680 - Service de physique de l'état condensé

We use direct and stochastic numerical simulations of the magnetohydrodynamic equations to explore the influence of turbulence on the dynamo threshold. In the spirit of the Kraichnan-Kazantsev model, we model the turbulence by a noise, with given amplitude, injection scale and correlation time. The addition of a stochastic noise to the mean velocity significantly alters the dynamo threshold. When the noise is at small (resp. large) scale, the dynamo threshold is decreased (resp. increased). For a large scale noise, a finite correlation time reinforces this effect.

Mots clés: Turbulence; Effet dynamo; Processus stochastiques

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

Jean-Philippe Laval, Pierre Blaineau, Nicolas Leprovost, Bérengère Dubrulle, François Daviaud. Influence of turbulence on the dynamo threshold. Physical Review Letters, 2006, 96, pp.204503. ⟨10.1103/PhysRevLett.96.204503⟩. ⟨hal-00016684⟩