The influence of the heterogeneity (stratification) of the outer core fluid on the variation of the geomagnetic field

The Earth's magnetic field is divided into internal and external sources, with the internal field including the main magnetic field, the crustal magnetic field, and the induced magnetic field. Among these, the main magnetic field accounts for approximately 95% of the Earth's total magnetic field. Data from paleomagnetic records in rocks, various geomagnetic observatories, and satellites indicate that the main magnetic field exhibits westward drift, polarity reversals, intensity decay, and brief geomagnetic excursions at the core-mantle boundary. To explain these phenomena, several models have been proposed in previous studies. The prevailing view is that the outer core is composed of liquid metal, and the Earth's main magnetic field is generated by the turbulent fluid motion of this liquid metal, influenced primarily by factors such as its composition and properties, thermal convection, Lorentz force, and Coriolis force. Considering the strong Coulomb forces between electrons and ions, previous research has usually treated the electrons and ions in the outer core's metallic fluid as a unified component, greatly simplifying the study and achieving satisfactory results. However, existing studies have not taken into account the differences in motion between ions and electrons under the dynamics of the outer core, the resulting spatial distribution differences of electrons and ions in the outer core, or the impact of these differential distributions on the Earth's main magnetic field. In view of this, This paper studies the effect of the factors generating outer core dynamics on the distribution of electrons and ions in the outer core. It examines the distribution of electrons and ions in the outer core space under equilibrium conditions and estimates their contribution to Earth's main magnetic field. Then, by changing parameter conditions (such as temperature gradients) and adding convective terms (non-equilibrium state), the calculations are redone. These results are used to explain changes in Earth's magnetic field.