Séminaire ISTerre

The interplay between tidal flows and magnetic fields in stellar or planetary convective envelopes

jeudi 16 janvier 2025 - 11h00
Aurélie Astoul - University of Leeds
--- 
Tidal interactions are a key driver of orbital and rotational evolution in compact stellar and (exo-)planetary systems. In the convective envelopes of solar-like stars and giant gaseous planets, the tidal response takes the form of tidal flows, including (magneto-)inertial waves which are expected to be highly dissipative when they are excited. Convective envelopes are usually magnetised due to the dynamo effect, but the interactions between magnetic fields and tidal waves have not been well explored yet.
In this vein, I will present exploratory nonlinear MHD simulations of tidally-excited waves in spherical convective shells. In our model, wavelike tides are forced by an effective body force in an incompressible rotating fluid (as a first approach), harbouring an initially dipolar magnetic field. Simulations with weak magnetic fields exhibit tidally-generated differential rotation in the form of zonal flows as in the hydrodynamical case. This cylindrical-like differential rotation can substantially modify tidal dissipation rates from prior linear predictions. This is particularly true for thin shells, high tidal amplitudes, and low viscosities, for which non-linear effects (including wave-wave and wave-zonal flow interactions) are strong. Moreover, (non-)axisymmetric tidal flows affect the amplitude and structure of the magnetic field, notably through creation of toroidal fields via the omega effect. We also observe a strong quadrupolar poloidal magnetic response due to the type of forcing used. In contrast, simulations with strong magnetic fields feature inhibited zonal flows due to large-scale magnetic torques, possibly involving torsional waves at the transition between the two regimes for intermediate magnetic fields. For high magnetic Prandtl number, evidences of magnetic instabilities are observed, and I will discuss the possibility of magneto-rotational instabilities.

Equipe organisatrice : Géodynamo

Salle Dolomieu, Maison des Géosciences, 38400 Saint Martin d'Hères

Informations de visio :

https://univ-grenoble-alpes-fr.zoom.us/j/91690538748?pwd=buNDS0rAZw9rG4vS1rWxX53zHYdQaw.1

“Minimalist seismology”: studying earthquakes with sparse instrumentation

jeudi 17 septembre 2026 - 11h00

Mathieu Causse - ISTerre

Equipe organisatrice : Organisation labo

Amphithéâtre Killian, Maison des Géosciences, 38400 Saint Martin d'Hères

Lire la suite

Stable‑to‑dynamic expansion of fault slipping area through fluid injection observed in laboratory experiments using a sub‑meter scale specimen

vendredi 18 septembre 2026 - 14h00

Takatoshi Ito  - Université de Tohoku, Japan

Equipe organisatrice : Mécanique des failles

Amphithéâtre Killian, Maison des Géosciences, 38400 Saint Martin d'Hères

Lire la suite

Tectonics, Mantle Dynamics and Coupled Lithosphere-Mantle-Core Evolution of Earth and Other Rocky Worlds

jeudi 24 septembre 2026 - 11h00

Paul Tackley - ETH Zurich

Equipe organisatrice : Grands Séminaires ISTerre

Amphithéâtre Killian, Maison des Géosciences, 38400 Saint Martin d'Hères

Lire la suite

Tectonics, Mantle Dynamics and Coupled Lithosphere-Mantle-Core Evolution of Earth and Other Rocky Worlds

jeudi 24 septembre 2026 - 11h00

Paul Tackley - ETH Zurich

Equipe organisatrice : Grands Séminaires ISTerre

Amphithéâtre Killian, Maison des Géosciences, 38400 Saint Martin d'Hères

Lire la suite

Apport des expériences analogiques pour la modélisation et le suivi en temps réel de la propagation du magma en profondeur : Exemple du Rift Est Africain

jeudi 1er octobre 2026 - 11h00

Virginie Pinel - ISTerre

Equipe organisatrice : Organisation labo

Amphithéâtre Killian, Maison des Géosciences, 38400 Saint Martin d'Hères

Lire la suite

A t-on encore besoin de plaques pour expliquer la tectonique de la vallée du Rhône et des Alpes Occidentales ?

vendredi 2 octobre 2026 - 11h00

philippe VERNANT - Geosciences Montpellier

Equipe organisatrice : Tectonique active et sismicité

Salle Dolomieu, Maison des Géosciences, 38400 Saint Martin d'Hères

Lire la suite

TBA

vendredi 2 octobre 2026 - 14h00

Hugo Boulze - 

Equipe organisatrice : Cycle sismique et déformations transitoires

Amphithéâtre Killian, Maison des Géosciences, 38400 Saint Martin d'Hères

Lire la suite

TBA

vendredi 9 octobre 2026 - 11h00

Eric Beaucé - ISTerre

Equipe organisatrice : Cycle sismique et déformations transitoires

Salle Dolomieu, Maison des Géosciences, 38400 Saint Martin d'Hères

Lire la suite

TBA

vendredi 20 novembre 2026 - 11h00

Farzaneh Mohammadi - ENS Paris

Equipe organisatrice : Cycle sismique et déformations transitoires

Amphithéâtre Killian, Maison des Géosciences, 38400 Saint Martin d'Hères

Lire la suite