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SUMMARY:Tracking subcritical dynamo transitions and minimal dynamo seeds -
  Florence Marcotte (Université Côte d'Azur\, INRIA\, CNRS)
DTSTART:20251013T150000Z
DTEND:20251013T160000Z
UID:TALK237595@talks.cam.ac.uk
CONTACT:Mattias Brynjell-Rahkola
DESCRIPTION:In some astrophysical flows known to be linearly stable\, fini
 te-amplitude perturbations with favourable spatial structure can nonlinear
 ly trigger a transition from a non-magnetic\, non-turbulent state to self-
 sustained dynamo action and turbulence. Such transitions are suspected to 
 significantly impact spin-down in radiative stellar layers or accretion ra
 tes in stellar discs. I will first present numerical examples of nonlinear
 ly-triggered Tayler-Spruit dynamos in a spherical shell and zero-net-flux 
 MRI dynamos in a quasi-Keplerian plane flow. I will then discuss how optim
 al control can identify stable\, nontrivial (M)HD equilibria without requi
 ring prior knowledge of the transition mechanisms.
LOCATION:MR14 DAMTP and online
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