%0 Journal Article %T The signature of inner-core nucleation on the geodynamo %+ Morton K. Blaustein Department of Earth and Planetary Sciences [Baltimore] %+ Department of Applied Mathematics and Theoretical Physics (DAMTP) %+ Institut de Physique du Globe de Paris (IPGP (UMR_7154)) %A Landeau, Maylis %A Aubert, Julien %A Olson, Peter %Z National Science Foundation through Frontiers in Earth System Dynamics program EAR-1135382 %< avec comité de lecture %@ 0012-821X %J Earth and Planetary Science Letters %I Elsevier %V 465 %P 193-204 %8 2017 %D 2017 %R 10.1016/j.epsl.2017.02.004 %K geodynamo %K weak-field vs strong-field dynamo %K inner-core nucleation %K geomagnetic field on long time scales %K paleointensity %K Geocentric Axial Dipole %K geomagnetic field on long time scales %Z Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph]Journal articles %X Energy considerations indicate that the power delivered to the present-day geodynamo comes mainly from the growth of the solid inner core, through light element and latent heat releases. The nucleation of the inner core was, therefore, a major transition for the geodynamo. Here, we use numerical dynamo simulations linked by thermochemical evolution of the core to investigate the effects of inner-core nucleation (ICN) on the geodynamo, and identify possible ICN footprints in the palaeomagnetic field. Our results suggest that a strong-field dipole-dominated dynamo prior and after ICN (the uniformitarian scenario) is most likely. We predict little footprint of ICN on the surface field intensity, consistent with the observed lack of a long-term trend in paleointensity data. Instead, we find that the best proxy for inner-core growth is an increase in axial octupole strength with age, from present-day to ICN, which might be resolvable in the palaeomagnetic record. We confirm the existence of weak-field, multipolar dynamos prior to ICN, suggesting the dynamo might have transiently reached a weak-field state (the catastrophic scenario). The narrow stability domain of these weak-field dynamos implies that the catastrophic scenario is less probable than the uniformitarian scenario. %G English %2 https://insu.hal.science/insu-02918346/document %2 https://insu.hal.science/insu-02918346/file/S0012821X1730064X.pdf %L insu-02918346 %U https://insu.hal.science/insu-02918346 %~ INSU %~ AFRIQ %~ CNRS %~ IPGP %~ GENCI %~ USPC %~ UNIV-PARIS