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Strong and Weak Dynamo Regimes in Taylor-Couette Flows
Ashish Mishra1, George Mamatsashvili1,2, Frank Stefani1
1Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstr. 400, D-01328 Dresden, Germany.
Physical Review Letters
|October 5, 2025
Summary
A nonlinear magnetic dynamo was discovered in Taylor-Couette flow at low magnetic Prandtl numbers (Pm≤1), challenging previous beliefs. This finding impacts understanding of astrophysical dynamos with low Pm.
Area of Science:
- Fluid dynamics
- Magnetohydrodynamics
- Astrophysics
Background:
- The existence of magnetic dynamos in Taylor-Couette flow was previously thought to require high magnetic Prandtl numbers (Pm≳10).
- Low magnetic Prandtl numbers (Pm≤1) are relevant for certain astrophysical environments.
Purpose of the Study:
- To investigate the possibility of a nonlinear magnetic dynamo in Taylor-Couette flow at small magnetic Prandtl numbers.
- To identify key parameters influencing the dynamo's onset and evolution.
Main Methods:
- Numerical simulations of Taylor-Couette flow.
- Analysis of the role of initial perturbation amplitude, magnetic Prandtl number, and domain aspect ratio.
Main Results:
- A nonlinear magnetic dynamo was revealed at small magnetic Prandtl numbers (Pm≤1).
- The dynamo's behavior is sensitive to initial perturbation amplitude, Pm, and domain aspect ratio.
- Two distinct dynamo states were observed: a weak state with large-scale modes and a strong, turbulent state with small-scale modes.
Conclusions:
- Nonlinear magnetic dynamos can occur in Taylor-Couette flow at low magnetic Prandtl numbers.
- These findings have implications for understanding dynamo processes in astrophysical objects with low Pm.
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