Effect of the Lorentz force on on-off dynamo intermittency

Alexandros Alexakis and Yannick Ponty
Phys. Rev. E 77, 056308 – Published 14 May 2008

Abstract

An investigation of the dynamo instability close to the threshold produced by an ABC forced flow is presented. We focus on the on-off intermittency behavior of the dynamo and the countereffect of the Lorentz force in the nonlinear stage of the dynamo. The Lorentz force drastically alters the statistics of the turbulent fluctuations of the flow and reduces their amplitude. As a result, much longer bursts (on phases) are observed than is expected based on the amplitude of the fluctuations in the kinematic regime of the dynamo. For large Reynolds numbers, the duration time of the on phase follows a power law distribution, while for smaller Reynolds numbers the Lorentz force completely kills the noise and the system transits from a chaotic state into a laminar time periodic flow. The behavior of the on-off intermittency as the Reynolds number is increased is also examined. The connections with dynamo experiments and theoretical modeling are discussed.

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  • Received 28 September 2007

DOI:https://doi.org/10.1103/PhysRevE.77.056308

©2008 American Physical Society

Authors & Affiliations

Alexandros Alexakis and Yannick Ponty

  • Université de Nice Sophia-Antipolis, France (UNS), Centre National de la Recherche Scientifique (CNRS), and Observatoire de la Côte d’Azur, Boîte Postale 4229, Nice Cedex 04, France

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Issue

Vol. 77, Iss. 5 — May 2008

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