M. Berhanu et al 2007 EPL 77 59001 doi:10.1209/0295-5075/77/59001
M. Berhanu1, R. Monchaux2, S. Fauve1, N. Mordant1, F. Pétrélis1, A. Chiffaudel2, F. Daviaud2, B. Dubrulle2, L. Marié2,4, F. Ravelet2,5, M. Bourgoin3,6, Ph. Odier3, J.-F. Pinton3 and R. Volk3
Show affiliationsWe report the first experimental observation of reversals of a dynamo field generated in a laboratory experiment based on a turbulent flow of liquid sodium. The magnetic field randomly switches between two symmetric solutions B and –B. We observe a hierarchy of time scales similar to the Earth's magnetic field: the duration of the steady phases is widely distributed, but is always much longer than the time needed to switch polarity. In addition to reversals we report excursions. Both coincide with minima of the mechanical power driving the flow. Small changes in the flow driving parameters also reveal a large variety of dynamo regimes.
47.65.-d Magnetohydrodynamics and electrohydrodynamics
91.25.Cw Origins and models of the magnetic field; dynamo theories
Issue 5 (March 2007)
Received 22 December 2006, in final form 12 February 2007
Published 23 February 2007
M. Berhanu et al 2007 EPL 77 59001