Séminaire ISTerre

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Modelling the large-scale dynamics of Jupiter: zonal jets and vortices

jeudi 2 décembre 2021 - 09h30

Daphné Lemasquerier - IRPHE
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The ongoing NASA's Juno mission is providing stunning observations of Jupiter, which underline the complex fluid dynamics involved on the gas giant. Among others, Jupiter's atmosphere exhibits multiple persistent vortices embedded within strong zonal jets, both features being part of an intense turbulent flow. I will present laboratory experiments complemented by numerical and theoretical analyses to better understand the emergence and properties of Jovian vortices and zonal jets. First, I will focus on large-scale Jovian vortices and more precisely on the equilibrium shape of anticyclones in a rotating, stratified shear flow. By taking advantage of their quasi-equilibrium state, we can predict the vertical extent of midlatitude anticyclones. We show that they are shallow structures, confined near the weather layer, as recently confirmed by the Juno data, and we predict that the Great Red Spot thickness has remained constant despite its horizontal shrinkage. Second, I will focus on the strong and deep east-west winds responsible for the banded aspect of Jupiter, the so-called zonal jets. We designed a setup where dominant zonal jets emerge spontaneously from a rapidly-rotating turbulent flow with a topographic beta-effect. Our experiments demonstrate the essential role of Rossby waves in the emergence and nonlinear saturation of the jets through a transition between two regimes involving hysteresis. We study the inhomogeneous and anisotropic properties of the associated turbulent flow in an extreme regime, relevant to the gas giants. Note that the presented features are not restricted to Jupiter. Hence, our results aim at being generic and applicable to other fluid systems subject to analogous physical effects, such as oceans, atmospheres an planetary liquid cores.

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Equipe organisatrice : Géodynamo

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