Forces controlling the dynamics of planetary interiors

Hunter, Emma (2025) Forces controlling the dynamics of planetary interiors. PhD thesis, University of Glasgow.

Abstract

Convection occurs naturally in the atmospheres of giant planets and within electrically conducting regions of terrestrial planets, such as Earth’s outer core. Over time, increasing attention has been given to these conducting fluid regions in astrophysical and geophysical bodies, as they are believed to generate magnetic fields through dynamo action. Therefore, understanding convection and the dynamo process is fundamental to explaining how magnetic fields are sustained in astrophysical and geophysical bodies.

This thesis investigates convective fluid flows under the influence of rotation and magnetic fields. Numerical simulations are conducted using two models: an annulus model with an imposed magnetic field, and a spherical shell model that allows for the self-excitation of magnetic fields. Throughout this thesis, particular attention is given to the forces governing the flow dynamics. The first part presents a literature review of existing work and outlines the methods used in both models.

New results from nonlinear simulations of an annulus model with an imposed magnetic field are presented. The study examines how varying the strength of magnetic field and convection affects the prevailing force balances and flow patterns. Additionally, the characteristics of zonal flows and multiple jets within the annulus model are investigated, with particular emphasis on the influence of magnetic field strength and the force balances required to sustain these flows. Zonal flows and multiple jet solutions are typically found at weak magnetic field strength where a strong inertial force is present, although some cases of zonal flows and multiple jets are found at strong magnetic field strength where a strong Lorentz force is present. Force balances occur that are similar to those found in the main regimes of dynamo action.

Finally, spherical shell simulations are performed to investigate both forces and solenoidal forces, where flow lengthscales in two distinct directions are examined. Dynamically relevant flow lengthscales are identified by introducing a triple balance point involving key forces characteristic of the main dynamo regimes. These dynamically relevant lengthscales are then successfully compared with energetically dominant scales, highlighting how force balances at particular scales set the size of the flow. The forces and solenoidal forces across different regions of the spherical shell are further analysed. Transitions between the main dynamo regimes are examined, where solenoidal forces are used to explain the mechanisms driving these transitions

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Subjects: Q Science > QA Mathematics; Q Science > QC Physics
• Colleges/Schools: College of Science and Engineering > School of Mathematics and Statistics
• Funder's Name: Engineering and Physical Sciences Research Council (EPSRC)
• Supervisor's Name: Teed, Dr. Robert
• Date of Award: 2025
• Depositing User: Theses Team
• Unique ID: glathesis:2025-85593
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 21 Nov 2025 11:25
• Last Modified: 21 Nov 2025 11:34
• Thesis DOI: 10.5525/gla.thesis.85593
• URI: https://theses.gla.ac.uk/id/eprint/85593