Year

2021

Degree Name

Bachelor of Science (Honours)

Department

School of Earth, Atmospheric and Life Sciences

Advisor(s)

Dr Nicolas Flament

Abstract

The magnetic field of Earth and its behaviour over time is linked to its origin within Earth’s liquid outer core. Complex internal processes that operate within the outer core are not only responsible for the creation of the geomagnetic field, but also the magnetic field’s strength, stability, and position on Earth. The magnetic field acts as a critical barrier of protection, shielding Earth from harmful solar radiation from the sun and confining Earth’s atmosphere beneath the exosphere. As Earth’s core evolves and cools over time, it releases heat at the core-mantle boundary (CMB), the magnetic field reflects this evolution by weakening, strengthening, and reversing in polarity over time. It is important to study and form a better understanding of the behaviour of the magnetic field and its intensity over time, as its ability to weaken may give rise to biological and technological damage to Earth and its inhabitants. Variation in magnetic field behaviour over time is preserved in the geologic record, but data is scarce and poorly constrained, thus, numerical modelling solutions remain an essential aspect of paleo-geomagnetic field analysis. In this study, we analyse model-predicted core-mantle boundary heat flux as a proxy indicator of the dynamic evolution of the magnetic field, from 1 Ga to present for four model cases. We do this in aim of including periods known to exhibit the weakening of the magnetic field (superchrons, hyperactive periods and periods of biological extinction), and also investigate the spherical harmonics and Pearson correlation between these data and the current paleo-geomagnetic reversal rate data of two previous studies (Hounslow et al. 2018), Olson et al. 2013). Results conclude that CMB heat flux correlates weakly with the geomagnetic reversal rates, with equatorial CMB heat flux variability (q* equatorial) correlating the greatest of all quantities investigated. Spherical 3 harmonics analysis reveals a 200 Myr cycle in magnetic field intensity that may correlate with Earth’s 200 Myr deep mantle convection cycle.

FoR codes (2008)

040401 Electrical and Electromagnetic Methods in Geophysics

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Unless otherwise indicated, the views expressed in this thesis are those of the author and do not necessarily represent the views of the University of Wollongong.