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Topographic effects in planetary fluid cores: application to the Earth-Moon system

Project description

New models to understand planetary core flows

Many planets and their moons are partially or completely liquid at their cores. All this subsurface liquid sloshing around has important impact on the behaviour and characteristics of the planets and their moons, including their magnetic fields and rotations. The EU-funded THEIA project is utilising an experimental model system, a giant turntable-like structure, to study turbulent flows under various conditions. Scaling the resulting numerical models to the size of planets, scientists hope to elucidate the role of non-spherical topographies in modulating the effects of fluid flow on magnetic fields and rotation. The project is developing an innovative theoretical approach and numerical simulations using the fastest dynamo code. The project is rooted on thre well-documented geophysical observations within the Earth-moon system: energy dissipation in the Earth liquid core, energy dissipation in the lunar liquid core and magnetic field of the Early Moon.


Understanding planetary core flows is crucial as they generate planetary magnetic fields and modify planetary rotation. However, their study is an outstanding challenge involving geomagnetism, geodesy and fluid mechanics. Notably, present models fail to explain two puzzling observations. First, geodesy constrains the Earth and Moon core dissipations to values exceeding those of current theoretical models. Second, lunar paleomagnetism gives an early Moon magnetic field too intense for the current planetary dynamo paradigm, based on convection.

My project tackles these issues by going beyond the present planetary core simulations, performed in exact spheres. Planetary core boundaries are actually not spherical, being affected by large-scale and small-scale deformations. This topography, although advocated for a long time to play a role for the core dynamics, has been largely overlooked in core flow models.

I propose to investigate topographic effects in planetary fluid cores by combining theory, numerics and experiments. Using the largest turntable worldwide, I will build an experiment to study the dissipation of turbulent flows in the presence of rotation, density variations and topography. Building upon my recent advances in applied mathematics, I will develop new numerical models keeping only the relevant topographic effects. Using efficient spectral methods, I will reach unprecedented parameters, closer to planetary ones. Developing scaling laws, I will assess how planetary core dissipations and magnetic fields are modified by topographic effects. Beyond the Earth-Moon system, my models will also apply to fluid layers of other bodies, such as the subsurface oceans of the Jupiter icy moons, studied by future spatial missions (JUICE, Europa Clipper). This project is especially timely as the liquid core of Mars is studied by the on-going spatial mission InSight.

Host institution

Net EU contribution
€ 1 448 493,00
75794 Paris

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Ile-de-France Ile-de-France Paris
Activity type
Research Organisations
Total cost
€ 1 448 493,00

Beneficiaries (1)