Magneto-Fluid Dynamics Seminar

A systematic approach to identify subcritical dynamo instabilities

Speaker: Florence Marcotte, INRIA / Laboratoire J.A. Dieudonné, Université Côte d'Azur

Location: Warren Weaver Hall 905

Date: Tuesday, December 7, 2021, 11 a.m.


Subcritical dynamo instabilities are widely assumed to explain the generation of long-lived magnetic fields in many astrophysical flows, where they can trigger magnetohydrodynamic turbulence and transport angular momentum. Yet, their modeling is challenging due in particular to the difficulty of assessing flow stability with respect to magnetic perturbations of arbitrary amplitude. Using transient growth analysis, we will show how the nonlinear optimisation of a finite-amplitude initial condition over a freely evolving (and possibly turbulent) flow can identify stable subcritical dynamo solutions, as well as the amplitude and spatial structure of critical dynamo perturbations.