Volume 104, Number 6, December 2013
|Number of page(s)
|Geophysics, Astronomy and Astrophysics
|13 January 2014
Energy transfers during dynamo reversals
1 Laboratoire de Physique Statistique, Ecole Normale Supérieure, CNRS, Université P. et M. Curie, Université Paris Diderot - Paris, France
2 MAG(CNRS/ENS/IPGP), LRA, Ecole Normale Supérieure - Paris, France
Received: 19 September 2013
Accepted: 9 December 2013
Using direct numerical simulations of the equations of magnetohydrodynamics, we study reversals of the magnetic field generated by the flow of an electrically conducting fluid in a sphere. We show that at low magnetic Prandtl numbers, , the decrease of magnetic energy, ohmic dissipation and power of the Lorentz force during a reversal is followed by an increase of the power injected by the force driving the flow and an increase of viscous dissipation. Cross correlations show that the power of the Lorentz force is in advance with respect to the other energy flows. We also observe that during a reversal, the maximum of the magnetic energy density migrates from one hemisphere to the other and comes back to its initial position, in agreement with recent experimental observations. For larger magnetic Prandtl numbers , the magnetic field reversals do not display these trends and strongly differ one from another.
PACS: 91.25.Cw – Origins and models of the magnetic field; dynamo theories / 47.65.-d – Magnetohydrodynamics and electrohydrodynamics
© EPLA, 2013
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.