Probing planetary cores with global magnetic fields

类地行星产生的全球磁场在强度和结构上都表现出显著的变化。这些场都是由液态铁核中的湍流运动产生的，因此为行星内部的动力学和演化提供了独特的探索。那么，如果这些场都是由相同的基本过程产生的，为什么它们会如此不同呢？行星科学中的这个基本问题仍在争论中。我们假设一个关键因素是固体从地球行星核心内的液态铁中冻结的方式。冻结释放热量和轻物质，为全球磁场提供关键动力，但许多不同的制度是可能的：根据身体的大小和热/化学性质，冻结可以开始在核心的顶部，中部或底部，并产生固体颗粒，“雪”到更深的核心或“漂浮”到核心表面。虽然重固体的自下而上的冻结已经得到了很好的研究，但对其他机制知之甚少，因此仍然存在一些基本问题：在什么条件下雪和漂浮物可以产生全球磁场？生成的字段有哪些特征？这些特性在不同的结晶状态之间是否不同？这些场与观测值是否一致？我们最近开发了一种新的模型来研究铁雪，包括它在磁场产生中的作用。在这个项目中，你将扩展这个模型，包括开发浮动制度的第一个模型，产生一个独特的工具，调查全球地球磁场的起源。通过系统的分析，您将确定包括地球，水星，火星，木卫三和月球在内的天体磁场的差异是否反映了其核心的不同结晶状态。这些结果将对这些天体的内部结构和演化做出新的预测，并受到现有和即将到来的观测数据的约束。您将加入利兹地球与环境学院的一个团队，该团队目前正在与伦敦大学学院和斯克里普斯海洋学研究所合作，领导大型NERC和NSF资助的行星核心固液相互作用项目。该学院还拥有世界上最大的地球深部研究小组之一，并与数学学院的天体物理流体动力学研究小组有着密切的联系。在这个环境中，您将接受技能培训，使您能够开发下一代核心结晶模型。

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.