Core Density

Introduction

Knowledge of the density distribution inside the core is of interest for several reasons. Perhaps most importantly, the size of the density jump at the inner core boundary controls how important inner core growth is for powering the dynamo. Also of interest is the presence or otherwise of anomalous (e.g., convectively stable) regions in the outer core. This latter problem is more difficult as it requires an evaluation of the density gradient and how much this deviates from the Adams‐Williamson equation (see below), which is expected to control the density gradient in a vigorously convecting outer core.

The main constraints on density in the core come from measurements of the frequencies of free oscillations of the Earth (Masters and Gubbins, 2003). However, it is also possible to use the sensitivity of reflected body waves to impedance contrasts to infer the density jump at the ICB from the amplitudes of the seismic phase PKiKP (Koper and Pyle, 2004; Cao and Romanowicz, 2004...