Revues

We present a new web tool, Planetary Dynamo Simulation Explorer, to survey available published simulations of rapidly rotating spherical dynamos.With numerical codes and computers being increasingly efficient, recent years have seen a surge in the number of publications presenting such computations.Our tool comes as an interactive catalogue that allows exploring existing dynamos with respect to input and output dimensionless parameters, choosing from various dynamo setups (e.g. choice of boundary conditions, couplings at play, etc.), with the possibility to test scaling laws on a filtered set of simulations.It also links each dynamo to its associated publication and possibly to online datasets. Alongside the cataloguing work, and to enhance comparability across various setups, conversion rules are explicitly derived and aggregated from previous studies and applied on a broad scale for the first time.Thought of as a collaborative and scalable initiative, the web interface allows uploading new simulation metadata.The whole interface, displayed as a website, is designed for the community to have a better overview while driving transparency, open-source initiatives, and FAIR principles (Findable, Accessible, Interoperable, Reusable).We encourage the community to explore and contribute to it at https://geodyn.univ-grenoble-alpes.fr/explorer/

Claveau, Romain

Convection in Earth's outer core is driven by the release of heat and light elements at the inner core boundary. A key question is whether these buoyancy sources drive convection throughout the core, or whether a stable layer exists just below the core-mantle boundary (CMB). Recent simulations incorporating CMB heat flux heterogeneities propose locally stable ``regional inversion lenses'' (RILs) rather than a global layer, allowing stable and unstable regions to coexist. However, these simulations combine thermal and compositional anomalies, ignoring differences in diffusivities and boundary conditions. Here we simulate thermal, chemical, and thermochemical convection at Ekman number $E=10^{-5}$, with thermal and chemical flux Rayleigh numbers $\widetilde{Ra}_T=30-4000$ and $\widetilde{Ra}_ξ=30-100000$, and Prandtl numbers $Pr_T=1$ and $Pr_ξ=10$. Purely chemical simulations accumulate light elements below the CMB, forming locally stable regions near the poles or global layers, depending on $\widetilde{Ra}_ξ$. These chemically stratified regions persist in thermochemical simulations even when thermal forcing is destabilising. Introducing heterogeneous CMB heat flux produces thermally stratified RILs even with strongly destabilising compositional buoyancy. Our simulations reveal a diverse range of locations, properties, and morphologies of stable regions depending on $\widetilde{Ra}_T$ and $\widetilde{Ra}_ξ$, they can have a seismically detectable thickness and strength and might also have a signature in geomagnetic observations.

Naskar, Souvik