# The onset of turbulent rotating dynamos at the low $Pm$ limit

## TL;DR

This paper shows that global rotation significantly lowers the critical magnetic Reynolds number needed for turbulent dynamos at low magnetic Prandtl numbers, enabling more efficient dynamo generation in liquid metal experiments.

## Contribution

It reveals that rotation reduces turbulence and enhances dynamo onset, proposing a new approach for liquid metal dynamo experiments at low Pm.

## Key findings

- Rotation decreases critical magnetic Reynolds number by over 1000 times.
- Flow becomes more laminar-like under rotation, facilitating dynamo action.
- Dynamo behavior at low Pm can mimic high Pm laminar regimes due to rotation.

## Abstract

We demonstrate that the critical magnetic Reynolds number $Rm_c$ for a turbulent non-helical dynamo in the low magnetic Prandtl number $Pm$ limit (i.e. $Pm = Rm/Re \ll 1$) can be significantly reduced if the flow is submitted to global rotation. Even for moderate rotation rates the required energy injection rate can be reduced by a factor more than $10^3$. This strong decrease of the onset is attributed to the reduction of the turbulent fluctuations that makes the flow to have a much larger cut-off length-scale compared to a non-rotating flow of the same Reynolds number. The dynamo thus behaves as if it is driven by laminar behaviour (i.e. high $Pm$ behaviour) even at high values of the Reynolds number (i.e. at low values of $Pm$). Our finding thus points into a new paradigm for the design of new liquid metal dynamo experiments.