Publications (17)
Core-surface kinematic control of polarity reversals in advanced geodynamo simulations
Julien Aubert, Maylis Landeau, Alexandre Fournier +1
The geomagnetic field has undergone hundreds of polarity reversals over Earth's history, at a variable pace. In numerical models of Earth's core dynamics, reversals occur with incr…
Online learning of subgrid-scale models for quasi-geostrophic turbulence in planetary interiors
Hugo Frezat, Thomas Gastine, Alexandre Fournier
Machine learning approaches to subgrid-scale (SGS) modelling are now well established in atmospheric and oceanic applications. Among these, online end-to-end learning, where the di…
Turbulent geodynamo simulations: a leap towards Earth's core
Nathanaël Schaeffer, Dominique Jault, Henri-Claude Nataf +1
We present an attempt to reach realistic turbulent regime in direct numerical simulations of the geodynamo. We rely on a sequence of three convection-driven simulations in a rapidl…
Hydromagnetic quasi-geostrophic modes in rapidly rotating planetary cores
Elisabeth Canet, Chris Finlay, Alexandre Fournier
The core of a terrestrial-type planet consists of a spherical shell of rapidly rotating, electrically conducting, fluid. Such a body supports two distinct classes of quasi-geostrop…
Variational estimation of the large scale time dependent meridional circulation in the Sun: proofs of concept with a solar mean field dynamo model
Ching Pui Hung, Allan Sacha Brun, Alexandre Fournier +3
We present in this work the development of a solar data assimilation method based on an axisymmetric mean field dynamo model and magnetic surface data, our mid-term goal is to pred…
Spherical convective dynamos in the rapidly rotating asymptotic regime
Julien Aubert, Thomas Gastine, Alexandre Fournier
Self-sustained convective dynamos in planetary systems operate in an asymptotic regime of rapid rotation, where a balance is thought to hold between the Coriolis, pressure, buoyanc…
Dynamo-based limit to the extent of a stable layer atop Earth's core
Thomas Gastine, Julien Aubert, Alexandre Fournier
The existence of a stably stratified layer underneath the core-mantle boundary (CMB) has been recently revived by corroborating evidences coming from seismic studies, mineral physi…
A mean-field Babcock-Leighton solar dynamo model with long-term variability
Sabrina Sanchez, Alexandre Fournier, Katia Pinheiro +1
Dynamo models relying on the Babcock-Leighton mechanism are successful in reproducing most of the solar magnetic field dynamical characteristics. However, considering that such mod…
End-effects in rapidly rotating cylindrical Taylor-Couette flow
Rainer Hollerbach, Alexandre Fournier
We present numerical simulations of the flow in a rapidly rotating cylindrical annulus. We show that at the rotation rates relevant to the magneto-rotational instability, the flow…
Spherical Couette flow in a dipolar magnetic field
Rainer Hollerbach, Elisabeth Canet, Alexandre Fournier
We consider numerically the flow of an electrically conducting fluid in a differentially rotating spherical shell, in a dipolar magnetic field. For infinitesimal differential rotat…
Forward and adjoint quasi-geostrophic models of the geomagnetic secular variation
Elisabeth Canet, Alexandre Fournier, Dominique Jault
We introduce a quasi-geostrophic model of core dynamics, which aims at describing core processes on geomagnetic secular variation timescales. It extends the formalism of Alfvén to…
Geomagnetic semblance and dipolar-multipolar transition in top-heavy double-diffusive geodynamo models
Théo Tassin, Thomas Gastine, Alexandre Fournier
Convection in the liquid outer core of the Earth is driven by thermal and chemical perturbations. The main purpose of this study is to examine the impact of double-diffusive convec…
Can one use Earth's magnetic axial dipole field intensity to predict reversals?
Kyle Gwirtz, Matthias Morzfeld, Alexandre Fournier +1
We study predictions of reversals of Earth's axial magnetic dipole field that are based solely on the dipole's intensity. The prediction strategy is, roughly, that once the dipole…
Motional induction in Ganymede's ocean
Simon Cabanes, Thomas Gastine, Alexandre Fournier
We investigate the magnetic signature of oceanic circulation in Ganymede's subsurface ocean using kinematic induction modeling. Our approach couples zonal jet flows from rotating t…
The predictability of advection-dominated flux-transport solar dynamo models
Sabrina Maite Sanchez, Alexandre Fournier, Julien Aubert
Space weather is a matter of practical importance in our modern society. Predictions of forecoming solar cycles mean amplitude and duration are currently being made based on flux-t…
Estimating the deep solar meridional circulation using magnetic observations and a dynamo model: a variational approach
Ching Pui Hung, Laurène Jouve, Allan Sacha Brun +2
We show how magnetic observations of the Sun can be used in conjunction with an axisymmetric flux-transport solar dynamo model in order to estimate the large-scale meridional circu…
A case for variational geomagnetic data assimilation: insights from a one-dimensional, nonlinear, and sparsely observed MHD system
Alexandre Fournier, Céline Eymin, Thierry Alboussière
Secular variations of the geomagnetic field have been measured with a continuously improving accuracy during the last few hundred years, culminating nowadays with satellite data. I…