A systematic route to subcritical dynamo branches

TL;DR

This paper introduces a nonlinear optimization method to identify subcritical dynamo branches and their critical perturbations in turbulent flows without prior knowledge of amplification mechanisms.

Contribution

It presents a systematic approach to discover subcritical dynamo solutions and their structures, advancing understanding of magnetic field generation in complex flows.

Findings

Successfully identifies subcritical dynamo branches in turbulent flows.

Determines the structure and amplitude of critical perturbations.

Operates without prior knowledge of magnetic amplification mechanisms.

Abstract

We demonstrate that the nonlinear optimisation of a finite-amplitude disturbance over a freely evolving and possibly even turbulent flow, can successfully identify subcritical dynamo branches as well as the structure and amplitude of their critical perturbations. As this approach does not require prior knowledge of the magnetic field amplification mechanisms, it opens a new avenue for systematically probing subcritical dynamo flows.