The average (onion-peel) structure of the earth has been known to a good first approximation since the middle of the 20th century. The following topical questions concerning the nucleus can be cited:
- Composition of the core and seed: which light elements make up the majority of the core and seed?
- What is the melting temperature of iron (and its alloys) at seed surface pressure?
- what is the origin of the seismic anisotropy observed in the seed?
- is there significant differential rotation of the seed in relation to the mantle?
- what is the morphology of convection currents in the outer core, and what is the heat flux across the core-mantle boundary?
These questions are important because they have implications for the Earth's thermal evolution (when did the seed form?) and, by extension, that of the magnetic field.
The first 5 lectures were devoted to the tools and results obtained from seismology, then we moved on to the constraints imposed by materials physics (lectures 6 and 7) and finally to core dynamics (lecture 8) and the generation of the Earth's magnetic field.