Evidence for a Geodynamo Driven by Thermal Energy in the Outermost Core and by Precession Deeper in the Outer Core

Fuller Michael D

doi:10.35840/2631-5033/1812

Abstract

VGP (Virtual Geomagnetic Pole) paths during reversals are preferentially located in roughly north south circum-Pacific arcs, where the temperature of the mantle at the core mantle boundary is lowest. This indicates that the movement of magnetic flux concentrations in the outermost core responds to thermal constraints during the reversal. Hence thermal energy plays a role in driving the geodynamo.

Highlights

It has long been held that thermal convection, or the rise of low density material released in the formation of the inner core, determine the motion of the fluid outer core and drive the geodynamo [1,2]
The primary purpose of this paper is to present evidence for roles of precession and thermal energy in driving the geodynamo, it seems appropriate to review briefly how precession might drive the dynamo because unlike the many models based on thermal effects precession based models are less well known
The evidence given here for a role of thermal energy in driving the dynamo during reversals has been in terms of VGP paths and their relation to interpreted temperatures on the core mantle boundary

Summary

Introduction

It has long been held that thermal convection, or the rise of low density material released in the formation of the inner core, determine the motion of the fluid outer core and drive the geodynamo [1,2]. Independent evidence of the role of thermal energy in constraining the outermost core flow during reversals is presented. Precession is less commonly held to play a role in the geodynamo, but has a long history stretching back to the classic studies of Poincaré [3]. Evidence is given here for precession energy contributing to driving the dynamo. A model based upon the combined effect of convection and precession, as the energy source of the geodynamo has already been proposed and suggests that neither source is adequate to drive the geodynamo alone [4].

Objectives

Discussion

Conclusion