ERC project THEIA

THEIA team and collaborators, 2020–2026

David Cébron, CNRS researcher at ISTerre and principal investigator of ERC THEIA, led the project from September 2020 to August 2026. He built a group bringing together theory, numerical simulations and rotating-fluid experiments to investigate planetary core dynamics.

His collaborative research included ellipsoidal modes, forced flows and magnetic induction with Jérémie Vidal; topographic coupling with Rémy Monville and Dominique Jault; and semi-convective dynamos with Paul Pružina and Nathanaël Schaeffer. He also worked on inner-core coupling with Paolo Personnettaz and collaborators, and jointly conceived and designed the THEIA and mini-THEIA experiments with Max Solazzo.

Researchers

• Rémy Monville — doctoral researcher, October 2020–March 2024; thesis defended on 22 April 2024, followed by further research contributions, including a short research-fellow appointment in October–November 2024. He developed ToCCo and the local theory of topographic coupling, working with David Cébron and Dominique Jault. Research and software.
• Jérémie Vidal — research fellow, September 2020–January 2025. He developed and extended spectral methods for modes, forced flows, stability and magnetic induction in ellipsoidal cores, and subsequently became a permanent CNRS researcher. His numerical tools include SHINE, alongside the earlier SWAN and SIREN methods. Research and tools.
• Paul Pružina — research fellow, October 2024–September 2025. With Nathanaël Schaeffer and David Cébron, he studied semi-convection, layered flows and dynamo generation in rotating stratified shells. The resulting publications also received subsequent collaborative support, including ChEESE-2P.
• Paolo Personnettaz — contributor from December 2022, initially through complementary funding, with a project-team appointment from February 2025 to January 2026. He worked on XSHELLS developments and magnetohydrodynamic coupling, including inner-core translation and oscillating-sphere drag, with David Cébron, Nathanaël Schaeffer and collaborators. This work also involved ERC GRACEFUL.
• Baptiste Penlou — THEIA postdoctoral researcher, September 2025–August 2026. He developed PIV acquisition and analysis methods and spin-up protocols using the intermediate tank, providing the basis for comparisons between smooth and rough bottoms.
• Samuel Payen — doctoral researcher contributing to the experimental programme, January–April 2025.

Experimental engineering: design, construction and assembly

Max Solazzo, permanent CNRS engineer at ISTerre, jointly conceived and designed the THEIA and mini-THEIA experiments with David Cébron. He carried out their computer-aided design (CAD), mechanical construction and assembly.

The programme used mini-THEIA, approximately 50 cm across, and an intermediate tank approximately one metre across on the WEBER rotating platform. These devices supported the development of experimental procedures and the study of rotating flows over smooth and rough bottoms.

The Experiments page explains how the apparatus was used. The Gallery shows the assembled experiments, laser illumination and mechanical design. PIV acquisition, analysis and spin-up protocols were developed by Baptiste Penlou, following earlier experimental contributions including Samuel Payen’s work.

Scientific collaborations

ISTerre collaborators included Dominique Jault for topographic-coupling theory and doctoral supervision, Nathanaël Schaeffer for XSHELLS and rotating-fluid and dynamo simulations, Renaud Deguen for inner-core dynamics, and Henri-Claude Nataf for rotating-fluid experiments and acoustic diagnostics.

Collaborative publications also involved Jérôme Noir and Vadim Giraud at ETH Zürich, Yves Colin de Verdière in mathematical wave theory, Mioara Mandea in inner-core and magnetic studies, and the co-authors credited in the individual papers.

Other students and interns also contributed to THEIA. The Publications page provides the full scientific references and authorship, and the project homepage presents the main scientific results.