Dynamo action at low magnetic Prandtl numbers: mean flow vs. fully   turbulent motion
  We compute numerically the threshold for dynamo action in Taylor-Green swirling flows. Kinematic calculations, for which the flow field is fixed to its time averaged profile, are compared to dynamical runs for which both the Navier-Stokes and the induction equations are jointly solved. The kinematic instability is found to have two branches, for all explored Reynolds numbers. The dynamical dynamo threshold follows these branches: at low Reynolds number it lies within the low branch while at high kinetic Reynolds number it is close to the high branch. 
Yannick Ponty (OCA), Pablo Mininni (NCAR), Jean-Fran\c{c}ois Pinton   (Phys-ENS), H\'el\`ene Politano (OCA), Annick Pouquet ...