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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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

Modelling the geodynamo, a strongly scale-separated MHD system

25/05/2021

I gave an invited talk at the UKMHD2021 conference - as is the case nowadays this was a fully virtual conference, and I wish to thank Céline Guervilly and the organisers at Newcastle University to have managed to create a stimulating and enjoyable experience amidst those difficult times for everybody, and also for research and the dissemination of scientific results. 


The good thing with virtual conference talks is that they are recorded, so the talk can be found by clicking on the image below. In this talk I summarise the recent work that my co-authors and myself have put out in an attempt to better understand and model the geodynamo in realistic physical conditions.