Julien Aubert, CNRS, IPG Paris

I am a CNRS senior researcher working at the Institut de Physique du Globe de Paris (IPGP), within the Geological Fluid Dynamics team. 

I am interested in the interpretation of the geomagnetic signal emanating from Earth’s liquid outer core. Over a broad range of space and time scales, this signal is a powerful probe for investigating the structure, dynamics and geological history of our planet. Understanding the geodynamo is an outstanding fundamental challenge of Physical Sciences as well as Earth Sciences. 

To this end I develop and use direct numerical computer simulations of the dynamo process, as well as data assimilation algorithms aiming at forecasting the future evolution of the geomagnetic field. This has important societal impacts as the geomagnetic field interacts with life on Earth and with human technological activities.



In a new paper published in Geophysical Journal International, I present the first numerical geodynamo simulations that operate at the physical conditions of Earth’s core. Such simulations have been enabled by terminating the exploration of the theoretical parameter space ‘path’ that we designed in 2017. Here the simulations are furthermore constrained with the available geomagnetic data from the past 180 years by a data assimilation approach. This results in model trajectories that are both morphologically and dynamically relevant, and reproduce the details of observed geomagnetic variations over time scales of years to centuries. An interesting perspective of this work is the possibility to extract significantly more geophysical information on the structure and history of the Earth from the geomagnetic signal than was previously possible. 

Aubert, J.: State and evolution of the geodynamo from numerical models reaching the physical conditions of Earth’s core, Geophys. J. Int. 235, 468-487, 2023, doi: 10.1093/gji/ggad229


Together with myself and our colleagues of the ESA 4DEarth project, Chris Finlay has published a very informative and in-depth Nature Reviews paper of the recent community progress in identifying and explaining the features of the general circulation within Earth’s liquid core. There, we discuss the secular ‘eccentric gyre’ and ‘high-latitude’ jet flows, as well as the intriguing rapid (interannual) waves that have been recently discovered and characterised by joining our forces in geomagnetic observation, theory and numerical modelling. 

Finlay, C.C., Gillet, N., Aubert, J., Livermore, P. and Jault, D.: Gyres, jets and waves in the Earth’s core, Nature Rev. Earth. Environ. 4, 377–392, 2023, doi: 10.1038/s43017-023-00425-w


A collection of simulated geomagnetic jerk events has been built using a numerical model of the geodynamo that reaches closer to Earth’s core conditions than earlier models. This new paper presents a systematic analysis and categorisation of these events, according to the role played by rapid hydromagnetic waves in triggering these. We also characterise the (high) level of agreement between the signatures of these events in the magnetic field produced by the dynamo and their geomagnetic counterparts from historical and recent ground observatory and satellite records.

Aubert, J., Livermore, P., Finlay, C., Fournier, A. and Gillet, N.: A taxonomy of simulated geomagnetic jerks, Geophys. J. Int. 231, 650-672, 2022, doi:10.1093/gji/ggac212