Building a regime diagram for the Earth’s inner core

A number of geodynamical mechanisms have been proposed to explain the origin of the structure of the inner core. Our goal here is to compare quantitatively mechanisms involving deformation of the inner core and build a regime diagram giving the dominant mechanism as a function of key control parameters. A meaningful comparison between the different mechanisms requires the definition of a measure of the strength of the flow, and we choose here to compare this mechanisms in terms of the instantaneous strain rate, and consider that the dominant mechanism is the one which induces the highest strain rates at a given time. Using scaling laws for all proposed mechanisms, we build regime diagrams giving the dominant mechanisms as a function of control parameters including the sign and strength of the density stratification in Earth’s inner core, its viscosity, and magnetic field strength. We find that only specific regions of the diagram have a dominant regime potentially consistent with the seismological observed geometry and strength of the inner core anisotropy.