Strong and Weak Dynamo Regimes in Taylor-Couette Flows

We reveal a nonlinear magnetic dynamo in a Taylor-Couette flow at small magnetic Prandtl numbers <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mrow><a:mi>P</a:mi><a:mi>m</a:mi><a:mo>≤</a:mo><a:mn>1</a:mn></a:mrow></a:math>, which has been previously believed to exist only at higher <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:mrow><c:mi>P</c:mi><c:mi>m</c:mi><c:mo>≳</c:mo><c:mn>10</c:mn></c:mrow></c:math> in this flow. The amplitude of initial perturbations, <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"><e:mi>P</e:mi><e:mi>m</e:mi></e:math>, 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 <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"><g:mi>P</g:mi><g:mi>m</g:mi></g:math>.