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OSUG - Terre Univers Environnement OSUG

Séminaire du Jeudi 2 Octobre 2014

Tidally driven flows and magnetic fields due to the elliptical instability

David Cebron (ISTERRE) Thursday October 2nd - 11am IPAG Seminar Room - IPAG

Tidally driven flows have been suggested to play a role in different fields of planetary and stellar dynamics, namely their surface patterns ans shapes (e.g. Jupiter stripes), their rotational dynamics (e.g. synchronization), and the processes of dynamo generation. However, the nature of the driven flows remains uncertain. In this talk, I propose that the so-called elliptical instability can be a key ingredient to drive these flows. This hydrodynamic instability, arising in rotating flows with elliptical streamlines, is suggested in tidally deformed planets and stars. To investigate its features, I present the first simulations of the elliptical instability in an ellipsoidal geometry, relevant for planets and stars. These simulations allow to quantify the influence of different natural complexities, and to derive the scaling laws needed to bridge the gap between numerics and planetary or stellar applications. I will then consider magnetic field (dynamo) generation by using suited magnetohydrodynamic simulations. Finally, the obtained results are used to study the presence of the instability in known planets, moons, and stars. Telluric bodies are first considered, and a stability analysis adapted to this context shows that the instability can be expected in the Early Earth, the Early Moon, Europa and three exoplanets (55CnCe, CoRoT-7b et GJ1214b). To conclude, the possible presence of the instability in extra-solar Hot-Jupiters systems is considered, showing its possible relevance for some of them, such as the system of Tau-boo.

Sous la tutelle de:


Sous la tutelle de:

CNRS Université Grenoble Alpes