Séminaire IPAG

---

Tracking subcritical dynamo transitions and minimal dynamo seeds

jeudi 23 janvier 2025 - 11h00

Florence Marcotte - U. Côte d'Azur - INRIA
--- 
In some astrophysical flows known to be linearly stable, finite-amplitude perturbations with favourable spatial structure can nonlinearly 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 rates in stellar discs. I will first present numerical examples of nonlinearly-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 optimal control can identify stable MHD equilibria 'blindly', i.e. without requiring prior knowledge of the magnetic field amplification mechanisms.

---

Hôtes : Henri-Claude Nataf (ISTerre) & Isabelle Joncour

Salle Manuel Forestini, 414 rue de la piscine, 38400 Saint Martin d'Hères