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PhD on Topographic coupling and wave dynamics in planetary cores

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Français - Anglais

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General information

Reference : UMR5275-FABCAR-037
Workplace : GRENOBLE
Date of publication : Monday, May 18, 2020
Scientific Responsible name : David Cébron
Type of Contract : PhD Student contract / Thesis offer
Contract Period : 36 months
Start date of the thesis : 1 October 2020
Proportion of work : Full time
Remuneration : 2 135,00 € gross monthly

Description of the thesis topic

Beyond magnetic observations, the dynamics of a planetary liquid core can be probed by measuring the planetary rotation. For instance, on certain timescales, the energy dissipation in the liquid cores of the Earth and the Moon are constrained by, respectively, VLBI measurements of the Earth's nutations and LLR measurements of the Earth-Moon distance. In both cases, the data do not agree well with our current models of core-mantle boundary couplings.
In order to interpret these data, this PhD proposal aims at developing a new kind of coupling models, where rotation, density variation, magnetic fields, and topographic effects are taken into account simultaneously to calculate the flow and the stress on the solid boundaries. These new coupling models will be studied at a local scale by going beyond the work of Jault (GJI, in press), but also at intermediate and global scales. In the latter case, the project will use quasi geostrophic approximations and will follow up the results obtained in a thesis currently in preparation in our group (collaboration Institute of Geophysics, ETH Zürich and ISTerre, Univ. Grenoble Alpes). Coordinate mappings will be used in order to remove the limitations of the perturbation approaches, which will also allow us to study the relevant limit where the topography is larger than the viscous boundary layer.
With these new tools at hand, we will study wave dynamics in the planetary cores, in particular the influence of the magnetic Prandtl number Pm, the torsional mode dynamics and the effect of a conducting lowermost mantle. Ultimately, our results should shed a new light on the interpretation of the energy dissipation data in the Earth and Moon liquid cores.

This PhD thesis is central to the THEIA project (Topographic effects in planetary fluid cores: application to the Earth Moon system) led by D. Cébron and funded by the European Research Council (ERC).

The candidate will have an excellent background in fluid mechanics, physics and/or applied mathematics. He or she will not fear programming in Python, perform physical analyses as well as visualizations. He or she will show a strong motivation, a good autonomy and team work skills. Knowledge in Earth sciences will be a plus.

Work Context

Organized in 10 research teams, the primary goal of our research unit is the physical and chemical study of the planet Earth through a combiniation of observations of natural objects, experimentation, and the modeling of complex processes.
The PhD student will work in the Geodynamo group, who studies the magnetic field of the Earth and the physics of the Earth core.

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