Parametric instability of the helical dynamo

We study the dynamo threshold of a helical flow made of a mean plus a fluctuating part. Two flow geometries are studied: (i) solid body and (ii) smooth. Two well-known resonant dynamo conditions, elaborated for stationary helical flows in the limit of large magnetic Reynolds numbers, are tested agai...

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Bibliographic Details
Published in:Physics of fluids (1994) 2007-05, Vol.19 (5), p.054109-054109-14
Main Authors: Peyrot, Marine, Plunian, Franck, Normand, Christiane
Format: Article
Language:English
Subjects:
Exact sciences and technology
Fluid Dynamics
Fundamental areas of phenomenology (including applications)
Magnetohydrodynamics and electrohydrodynamics
Physics
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Summary:We study the dynamo threshold of a helical flow made of a mean plus a fluctuating part. Two flow geometries are studied: (i) solid body and (ii) smooth. Two well-known resonant dynamo conditions, elaborated for stationary helical flows in the limit of large magnetic Reynolds numbers, are tested against lower magnetic Reynolds numbers and for fluctuating flows with zero mean. For a flow made of a mean plus a fluctuating part, the dynamo threshold depends on the frequency and the strength of the fluctuation. The resonant dynamo conditions applied on the fluctuating (respectively, mean) part seems to be a good diagnostic to predict the existence of a dynamo threshold when the fluctuation level is high (respectively, low).
ISSN:1070-6631
1089-7666
DOI:10.1063/1.2734118