Turbulent dynamo at very low and high magnetic Prandtl numbers

E. Buchlin, Institut d'astrophysique Spatiale, Orsay, France.

We use local and non-local shell-models of MHD turbulence to simulate the dynamo at magnetic Prandtl numbers between 10^-11 and 10¹¹. We give support numerically to the conjecture that the critical magnetic Reynolds number tends to a finite value when Re tends to infinity. We show that the limit of the magnetic energy growth rate for Re\rightarrow\infty scales approximately as Rm^1/2 at large Rm, indicating that the dynamo is driven by inertial-range motions at the resistive scale.