Can Paleomagnetism Be Used to Distinguish Between Changes in Core Structure and Mantle Convection?

The present-day geodynamo, generating Earth's magnetic field, is believed to be driven by the growth of the solid inner core due to the release of light elements and latent heat of crystallization. The magnetic field has been a feature of Earth for at least the past 3.5 billion years, however the timing of inner core nucleation is not well-constrained. It is assumed that the nucleation of the inner core affected Earth's magnetic field and should be recorded in the paleomagnetic record. Currently, the exact effects of inner core nucleation on Earth's magnetic field are unknown, however, and the issue is further confounded by other unknowns such as the influence of mantle convection on the magnetic field. Understanding the effects inner core nucleation had on Earth's paleomagnetic field will allow for a clearer understanding of the evolution of Earth's magnetic field and the deep interior.

This study aims at elucidating the evolution of the inner core and its influence on Earth's past magnetic field by investigating geodynamo simulations that successfully capture the long-term paleomagnetic field behavior, using core-mantle boundary heat flux patterns from state-of-the-art mantle convection models and varying inner core sizes. Models with ratios of the inner to outer core radii of 0.35, 0.20, 0.15, 0.10, and 0.05 have been run. Preliminary results suggest that inner core size has a significant effect on the stability of the magnetic field.