Missions

Over the past few years, the advent of continuous observation of the geomagnetic field from space on the one hand, and of advanced numerical simulations of the geodynamo on the other hand, have opened new avenues for our understanding of the dynamics at play in the Earth's outer core, with implications for deep Earth processes [1]. A variety of inverse methods (data assimilation, machine learning, etc.) has been employed to recover the fluid motions in the core [2-5]. Contrary to the geomagnetic inverse problem for which there exists an intercomparison in the context of the IGRF [6], and to the numerical simulation of the geodynamo for which benchmarks exist [7], no such community effort has been carried out regarding the estimation of core motions.
The main goal of the postdoc will consist in setting up a benchmark for the recovery of snapshot and transient motions at the top of Earth's core. The benchmark will be the subject of an international call to candidate models. It will lead to an evaluation of the various methods when applied to synthetic data from numerical geodynamo simulations, and to an intercomparison of the several candidate models in an application to the geomagnetic field as seen from satellite observations. These evaluations will be carried out by the post-doc, in collaboration with researchers from the 4D Earth Core+ consortium sponsored by ESA.
On top of this prime activity, the post-doc will also have time to develop a side collaborative research activity on an open topic (to be discussed) related to the issues addressed within the 4D Earth Core+ project.
References:
[1] Finlay et al. (2023). Gyres, jets and waves in the Earth's core. Nature Reviews Earth & Environment, 4(6), 377-392.
[2] Aubert (2023). State and evolution of the geodynamo from numerical models reaching the physical conditions of Earth's core. Geophys. J. Int., 235(1), 468-487.
[3] Gillet et al. (2024). Waves in Earth's core and geomagnetic field forecast. Phys. Earth Planet. Int., 357, 107284.
[4] Li et al. (2024). Dynamic mode decomposition of the core surface flow inverted from geomagnetic field models. Geophys. Res. Lett., 51(1), e2023GL106362.
[5] Shakespeare-Rees et al. (2025). Local Flow Estimation at the top of the Earth's Core using Physics Informed Neural Networks. arXiv preprint arXiv:2504.02566.
[6] Alken et al. (2021). Evaluation of candidate models for the 13th generation International Geomagnetic Reference Field. Earth, Planets and Space 73(1), 48.
[7] Christensen et al (2001). A numerical dynamo benchmark. Physics of the Earth and Planetary Interiors 128(1-4), 25-34.

Activités

- Get familiar with the literature regarding the core flow inverse problem.
- Creating, communicating and evaluating the core flow benchmark.
- Analysis and post-processing of geodynamo simulation outputs from various codes (e.g. XSHELLS , Parody_JA ), possibly running new simulations.
- Become at ease with the pygeodyn tool developed at ISTerre for geomagnetic data assimilation , in order to produce updated flow models.
- Participate to meetings within the geodynamo team of ISTerre, and to workshops within the 4D-Earth Core+ consortium.
- Collaborate with members of the 4D Earth Core+ consortium from Paris, Copenhagen and Leeds.

Compétences

The ideal candidate has a PhD in (geo)physics or applied maths, and combines many of the following characteristics:
- Scientific curiosity, creativity, pragmatism
- Experience in numerical modelling
- Experience in inverse modeling
- Knowledge of deep Earth geophysics
- Knowledge of geophysical fluid mechanics
- At ease with code versioning and collaborative tools (e.g. git)
- Ability to work in English, teamwork.

Contexte de travail

The National Center for Scientific Research (CNRS), a multidisciplinary public research organization under the supervision of the Ministry of Higher Education, Research, and Innovation, is one of the world's leading research institutions. To meet the major challenges of today and tomorrow, its scientists explore living organisms, matter, the universe, and the functioning of human societies. Internationally recognized for the excellence of its scientific work, the CNRS is a benchmark both in the world of research and development and for the general public.
The postdoctoral researcher will work at UMR 5275, the ISTerre laboratory at Grenoble-Alpes University in Saint Martin d'Hères (France), a member of the Grenoble Observatory of Universe Sciences (https://www.osug.fr/). ISTerre is a joint research unit under the supervision of six institutions (UGA, CNRS, IRD, Grenoble-INP, USMB, Université Gustave Eiffel). The laboratory's scientific objective is the physical and chemical study of planet Earth, focusing in particular on the links between observations of natural objects, experimentation, and modeling of the associated complex processes. The laboratory is made up of ~300 people and includes many nationally and Europeanly recognized experts in seismology and space geodesy.
The postdoctoral researcher will be part of the geodynamo team (8 permanent researchers).
The Swarm mission of ESA brings measurements of the Earth's magnetic field recorded onboard of a constellation of three satellites since 2013. In this context, ESA is financing the 4D Earth Core+ consortium for 2,5 years, starting from October 2025. This project, led within the geodynamo team of ISTerre in Grenoble, involves collaborations with colleagues at IPG Paris, DTU Copenhagen and the University of Leeds.
Employee benefits:
- Annual leave entitlement: 45 working days
- Inter-company restaurant
- Public transportation reimbursement (75%)
- Mutual insurance contribution
- Teleworking
- Cultural and sporting activities
- Sports facilities

Contraintes et risques

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Informations complémentaires

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