Document Type


Publication Date


Publication Title

Physical Review Letters


Department of Physics and Astronomy


We present a three-pronged numerical approach to the dynamo problem at low magnetic Prandtl numbers PM. The difficulty of resolving a large range of scales is circumvented by combining direct numerical simulations, a Lagrangian-averaged model and large-eddy simulations. The flow is generated by the Taylor-Green forcing; it combines a well defined structure at large scales and turbulent fluctuations at small scales. Our main findings are (i) dynamos are observed from PM=1 down to PM=10−2, (ii) the critical magnetic Reynolds number increases sharply with P−1M as turbulence sets in and then it saturates, and (iii) in the linear growth phase, unstable magnetic modes move to smaller scales as PM is decreased. Then the dynamo grows at large scales and modifies the turbulent velocity fluctuations.



Original Citation

Ponty Y, Mininni PD, Montgomery DC, Pinton JF, Politano H, Pouquet A. Numerical study of dynamo action at low magnetic Prandtl numbers. Phys Rev Lett. 2005 Apr 29;94(16):164502. doi: 10.1103/PhysRevLett.94.164502. Epub 2005 Apr 27. PMID: 15904232.