Stratification in the Cores of Earth and other Planets

Based on mineral physics and seismic studies, it has been proposed that parts of the liquid outer core of the Earth and other terrestrial planets are stably stratified, in particular near the boundaries. Such stratification may have profound impacts on the convective state of these cores and the morphology of the magnetic field they generate. Stratification at the top of Earth’s core may have consequences for interpretations of the secular variation, including magnetic flux concentration, magnetic diffusion and dipole changes. It has also been suggested that a stratified layer prevails above the inner core boundary, possibly in the form of a slurry layer. Such a layer may be associated with the growth and/or internal dynamics of the inner core and the release of light elements to the outer core which is the primary source of energy for the geodynamo. Chemically stratified layers may be primordial or form slowly through differentiation, such as the solidification of the inner core or bulk precipitation of a minor species. Stratification may prevail in other planets as well. For example, the weak intensity of Mercury’s magnetic field and the axisymmetry of Saturn’s magnetic field may both be explained by a skin effect due to stratification at the top of the dynamo region of these planets.

The scope of this Research Topic encompasses evidence for (or against) stratification at the outer cores of Earth and other planets, and their dynamical consequences for core convection and the generated planetary magnetic fields. Such studies encompass multiple disciplines, including geomagnetism, dynamo simulations, mineral physics, seismology, thermal history models, and more. We welcome manuscripts dealing with all aspects of core stratification, including their observed magnetic signature and their dynamical implications, for Earth and for other planets.