The geomagnetic field is generated by a so-called `fluid dynamo'. This dynamo is driven by rapidly rotating, turbulent convection in Earth's molten metal core. Yet rapidly rotating core-style convective turbulence has not been accurately simulated. The goal of this project is to provide the first cross-disciplinary quantification of rapidly rotating, turbulent, core-style convection. In doing so, we will greatly strengthen our understanding of the core flows that turn Earth into a giant magnet.
We will develop next-generation models of turbulent convection in Earth's core to address significant limitations in current models of dynamo generation. These models will combine leading laboratory rotating convection experiments with state-of-the-art finite element models and with advanced, asymptotically reduced theoretical models of rotating convection systems. The data we will produce will be of fundamental importance to modelers of Earth's core and other planetary dynamos, as well as modelers of solar and stellar convection zones and dynamos, and modelers of Earth's climate and planetary atmospheres. The asymptotically reduced modeling tools will be made openly available through the Computational Infrastructure for Geosciences (CIG) website. Furthermore, we will develop a unique library of geoscience educational films, via an ongoing internship for students interested in combining science and documentary filmmaking.
The geomagnetic field is generated by convection-driven dynamo action in Earth's liquid metal outer core. With this CSEDI award, we have built the most advanced models to date of rapidly rotating convective turbulence, that likely simulates the large-scale convective motions in the core. Our collaboration brought together asymptotic theory (CU Boulder), direct numerical simulations (U. Muenster) and laboratory convection experiments (UCLA). In closely comparing the results from our three methods, we have been able to show both qualitative (Figure 1) and quantitative agreements. Greatly to our surprise, we have shown that mechanical boundary conditions are likely to affect the properties of rapidly rotating convection, likely even under extreme planetary core conditions. Further, we have demonstrated that rotating convection tends to generate strong large-scale turbulent vortices (schematic in Figure 2b) that likely help shape and generate the large-scale structure of the observed geomagnetic field. However, such turbulent vortices are not yet resolved in present day geodynamo models (schematic in Figure 2a). Towards this end, this award also supported the development of extreme numerical and laboratory tools to investigate the physics of strongly turbulent convection-driven dynamo action. In addition to the above studies, this award funded the construction of an optimally sparse, massively parallel numerical model of rotationg convection and dynamo action by the applied mathematics team at CU Boulder. This numerical model will be capable of carrying out both direct numerical simulations and theoretically reduced models of planetary core turbulence on the world's supercomputers, thus allowing us to investigate the properties of geodynamo action in the presence of large-scale turbulent vortices. Furthermore, this flexible model can simulate Cartesian boxes, cylinders or spherical geometries. In the planetary core dynamics laboratory at UCLA also supported the fabrication of one of the world's largest rotating convection experiments. With this device, we will greatly extend the data available on rotating convective turbulence. In addition, the UCLA team was also able to tripled the size of their rotating magnetoconvection experiment. The results of these laboratory experimental studies of rotating convective turbulence and magnetoturbulence will be directly compared with coupled simulations made using the new CU Boulder model, which will allow us to greatly extend our understanding of the essential outer core flows that generate Earth's magnetic field.
