insu-03581751
https://insu.hal.science/insu-03581751
arxiv:1309.5062
doi:10.1209/0295-5075/104/69002
[INSU] INSU - Institut National des Sciences de l'Univers
[UNIV-PARIS7] Université Denis Diderot - Paris VII
[AFRIQ] HAL-Francophonie, Afrique et océan indien
[CNRS] CNRS - Centre national de la recherche scientifique
[IPGP] Institut de Physique du Globe de Paris
[SORBONNE-UNIVERSITE] Sorbonne Université
[UNIV-PARIS] Université Paris Cité
[SU-TI] Sorbonne Université - Texte Intégral
[ALLIANCE-SU] Alliance Sorbonne Université
Energy transfers during dynamo reversals
Mishra, Pankaj
Gissinger, Christophe
Dormy, Emmanuel
Fauve, Stephan
[SDU] Sciences of the Universe [physics]
ART
Physics - Fluid Dynamics
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, Pm=0.5 , 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 (Pm= 1, 2) , the magnetic field reversals do not display these trends and strongly differ one from another.
2013
en
Europhysics Letters