Probing planetary cores with global magnetic fields

The global magnetic fields produced by terrestrial planets exhibit remarkable variability in both strength and structure. These fields are all generated by turbulent motions in liquid iron cores and thus provide a unique probe into the dynamics and evolution of planetary interiors. So why are the fields so different if they are all generated by the same basic process? This fundamental question in planetary science is still under debate. We hypothesise that a key factor is the way solids freeze from liquid iron inside terrestrial planetary cores. Freezing releases heat and light material that provide crucial power for global magnetic fields, but many different regimes are possible: depending on the size and thermal/chemical properties of the body, freezing can begin at the top, middle or bottom of the core and produce solid particles that "snow" into the deeper core or "float" to the core surface. While bottom-up freezing of heavy solid is well-studied, little is known about the other regimes and so fundamental questions remain: under what conditions can snow and floatation generate global magnetic fields? What are the characteristics of the generated fields? Do these characteristics differ between the different crystallization regimes? Are the fields compatible with observations?

We have recently developed a new model for studying iron snow, including its role in magnetic field generation. In this project you will extend this model, including developing the first model of the floatation regime, producing a unique tool for investigating the origin of global terrestrial magnetic fields. Through a systematic analysis you will establish whether differences in the magnetic fields of bodies including Earth, Mercury, Mars, Ganymede and The Moon reflect different crystallization regimes in their cores. The results will make new predictions regarding the interior structure and evolution of these bodies, constrained by and informing existing and forthcoming observational data.

You will join a team within the School of Earth and Environment at Leeds that is currently leading large NERC- and NSF-funded projects on solid-liquid interactions in planetary cores in collaboration with University College London and Scripps Institution of Oceanography. The School also hosts one of the largest deep Earth research groups in the world and has strong links to the astrophysical fluid dynamics research group in the School of Mathematics. Within this environment you will be trained in the skills that will enable you to develop the next generation of core crystallization models.