Energy transfers in dynamos with small magnetic Prandtl numbers

Abstract

We perform numerical simulation of dynamo with magnetic Prandtl number Pm = 0.2 on 1024³ grid, and compute the energy fluxes and the shell-to-shell energy transfers. These computations indicate that the magnetic energy growth takes place mainly due to the energy transfers from large-scale velocity field to large-scale magnetic field and that the magnetic energy flux is forward. The steady-state magnetic energy is much smaller than the kinetic energy, rather than equipartition; this is because the magnetic Reynolds number is near the dynamo transition regime. We also contrast our results with those for dynamo with Pm = 20 and decaying dynamo.

Keywords:

• magnetic field generation
• dynamo
• energy transfers
• magnetohydrodynamic turbulence
• direct numerical simulation

Acknowledgements

We thank Emmanuel Dormy and Binod Sreenivasan for valuable discussions and comments. We are grateful to Madhusudhanan Srinivasan and Shuaib Arshad for helping us with visualisation plots. For computer time, this research used the resources of the Supercomputing Laboratory at King Abdullah University of Science and Technology (KAUST) in Thuwal, Saudi Arabia. This work was supported by a research grant SERB/F/3279/2013-14 from Science and Engineering Research Board, India. RS was supported through baseline funding at KAUST.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

Science and Engineering Research Board, India [grant number SERB/F/3279/2013-14] Ravi Samtaney was supported through baseline funding at KAUST.