Evolution of Dimensionless Numbers in Geodynamo Models

Abstract

The evolution of the dimensionless Ekman, Rossby, and Rayleigh numbers in the model of composite convection in the Earth’s, which that determine the force balance and magnetic field evolution, is considered on the basis of known estimates of the rate of solid core growth and variations in the day length. Various scenarios of this evolution, both in the past and future, are presented over time intervals comparable with the age of the core. It is shown, in particular, that the current intensity of convection in the fluid core continues to increase. This fact corresponds to the increase in the frequency of geomagnetic field inversions and the transition from a dipole field to a multipole one. A decrease in the volume of the liquid core leads to a decrease in the magnetic field strength.