Orateur
Description
Dynamo action in a stably stratified environment has been observed
for the first time in global numerical simulations quite recently.
The so-called Tayler Spruit dynamo interestingly exhibits a strong
level of turbulent fluctuations, turbulence which can be maintained
up to very low levels of differential rotation. A systematic parameter
study shows that the relevant criterion for this dynamo is a constant
magnetic Reynolds number, compatible with previous predictions.
Besides this very general result, the simulations seem to suggest
that the mechanism at hand is a subcritical transition to turbulence,
relying on a possible α/Ω mechanism. This transition can be descri-
bed by a dynamical system involving only three modes. In very good
agreement with the direct numerical simulations, it offers a more ge-
neral scenario for a subcritical transition to turbulence, which could
also apply to other types of instabilities, such as magneto-rotational
instability.
| Affiliation de l'auteur principal | Laboratoire de physique de l'ENS |
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