Strong and weak dynamo regimes in Taylor-Couette flows

Abstract

We reveal a nonlinear magnetic dynamo in a Taylor-Couette flow at small magnetic Prandtl numbers $Pm\le 1$, which has been previously believed to exist only at higher $Pm\gtrsim 10$ in this flow. The amplitude of initial perturbations, $Pm$ and domain aspect ratio play a key role in the onset and evolution of the dynamo. It exists in two main states -- a weak state dominated by large-scale modes and a strong, turbulent state with higher amplitude dominated by small-scale modes. These findings can be important for dynamo processes in various astrophysical objects with small $Pm$.

8 pages, 8 figures, accepted for publication in Physical Review Letters