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.

what (according to my computer) lies beneath our feet

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Gyres, jets and waves in the Earth's core

25/05/2023

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 taxonomy of simulated geomagnetic jerks

04/08/2022

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

A new category of waves identified in Earth's core

23/03/2022

Together with our colleagues at IsTerre and the Royal Observatory of Belgium, Nicolas Gillet has performed a reanalysis of satellite magnetic data over the past twenty years to reveal subtle fluctuations in Earth’s magnetic field that are caused by a previously overlooked category of magnetohydrodynamic waves, the rapid ‘Quasi-Geostrophic Magneto-Coriolis (QGMC) waves’. Such waves had been previously theoretically described but were thought to arise with long periods in Earth’s core. The study of Nicolas, published in PNAS, shows that these are present at interannual (about 7 years) periods. These waves, which we have worked upon from various (theoretical, numerical, observational) standpoints within the 4DEarth ESA project open the way to a better magnetic sounding of the core interior. 


Gillet, N., Gerick, F., Jault, D., Schwaiger, T., Aubert, J., Istas, M.: Satellite magnetic data reveal interannual waves in Earth’s core, PNAS 119, e2115258119, 2022, doi: 10.1073/pnas.2115258119