On-off intermittency in spherical Couette flow
Résumé
We perform 3D numerical simulations of dynamos in a Couette flow generated by two contra-rotating spheres. We show that the magnetic field may display on-off inter- mittency at relatively low magnetic Prandtl number, close to the onset of dynamo ac- tion. The basic signature of this phe- nomenon lies in series of short bursts of the magnetic energy (“on” phases) separated by low energy phases (“off” phases). The length of the “off” phases increases as the system gets closer to the threshold. We successfully compare our observations to predictions based on a canonical model and find it provides an accurate estimate of the threshold.
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