Numerical Simulation of Dynamo Model with the Earth's Axis Precession

  Objectives  The Poincaré force related to the precession of Earth's axis is usually omitted in the solution of the dynamo equations as its effects are minimal. But in fact, the period of Earth's axial precession is still a term that is worth considering compared to the period of Earth's magnetic field reversal.

  Methods  This paper compares and analyzes different dynamo models with Ekman number and Rayleigh number by introducing Earth's axis precession velocity with a period of 25 960 years.

  Results  It is found that Earth's axial precession stabilizes the kinetic energy and magnetic energy fluctuation of spherical shell magnetic fluid in a smaller range than the benchmark dynamo, and increases the toroidal kinetic energy of spherical shell magnetic fluid by more than 10%-20%, which leads to significantly accelerated westward drift rate of the magnetic field. Based on the magnetic field strength and magnetic Reynolds number at the core-mantle boundary of those dynamos, it is found that the introduction of the precession item of Earth's axis makes magnetic energy more tend to kinetic energy conversion. And by comparing the core-mantle boundary dipolarity, it is found that the introduction of the precession item will reduce the dipolarity. But for the dynamos in this article, the influence is not strong enough to make it become less Earth-like.

  Conclusions  From the comparison and analysis of the dynamo models, the introduction of Earth's axis precession would possibly change the dynamo model with a small Ekman number to a multipole dominant dynamo model. It can be inferred that the term of Earth's axis precession should be considered in more precise research of the numerical dynamo simulation for more.