Dissertation
Charged Particles in Magnetic Fields from Strongly Coupled Plasmas to Whistler-Mode Chorus Waves
University of Iowa
Doctor of Philosophy (PhD), University of Iowa
Spring 2024
DOI: 10.25820/etd.007390
Abstract
One of the most fundamental questions in physics is how do magnetic fields effect the motion of charged particles. Many applications from magnetically confined fusion devices to the dynamics of particles in the Van Allen Radiation Belts rely on the understanding of this basic question. In this thesis I present research that either directly relates to charged particle motion in a magnetic field or indirectly through possible wave-particle interactions that can occur. The first part of this thesis explores transport properties of strongly coupled plasmas when strong magnetic fields are applied. Molecular dynamics simulations were used to show that strong magnetization significantly increases the space and time scales associated with interparticle correlations. The physical mechanism responsible is a channeling effect whereby particles are confined to move along narrow cylinders with a width characterized by the gyroradius and a length characterized by the collision mean free path. The predominant interactions are the $180^\circ$ collisions at the ends of the collision cylinders, resulting in a long-range correlation parallel to the magnetic field. Its influence was demonstrated through the increase in the domain size and run time of the simulations of the one-component plasma in order to reach converged self-diffusion coefficients. The second part of this thesis explores the propagation properties of the whistler-mode chorus waves in the inner magnetosphere of Earth. Wave-particle interactions between chorus waves and electrons may lead to a host of physical phenomena and are important actors in the loss and enhancement of electrons in the outer radiation belt. Multipoint electric and magnetic field measurements aboard the Van Allen Probes, MMS, and Arase satellites were used to determine the power spectra, wave normal and Poynting vector angles, and phase and power spectra cross-correlations in several case studies. The case studies showed a wide range of wave normal angles at low and high magnetic latitudes. Cross-correlations between the MMS probes determined a chorus correlation length scale of 75-115 km transverse to the field and 35-80 km parallel to the field. Poynting vector angles show evidence of chorus waves traveling towards the equator from case studies on 4/14/2016 and 9/22/2018. In another case study on 4/11/2018, evidence of chorus propagating across the magnetic field is presented. Additionally, results from the case studies were compared to ray tracing simulations.
Details
- Title: Subtitle
- Charged Particles in Magnetic Fields from Strongly Coupled Plasmas to Whistler-Mode Chorus Waves
- Creators
- Keith R Vidal
- Contributors
- Allison N. Jaynes (Advisor)Jasper S. Halekas (Committee Member)Vincent G. J. Rodgers (Committee Member)Shea Brown (Committee Member)Christopher Colpitts (Committee Member)
- Resource Type
- Dissertation
- Degree Awarded
- Doctor of Philosophy (PhD), University of Iowa
- Degree in
- Physics
- Date degree season
- Spring 2024
- Publisher
- University of Iowa
- DOI
- 10.25820/etd.007390
- Number of pages
- xv, 117 pages
- Copyright
- Copyright 2024 Keith R. Vidal
- Language
- English
- Date submitted
- 04/22/2024
- Description illustrations
- illustrations, tables, graphs
- Description bibliographic
- Includes bibliographical references (pages 104-117).
- Public Abstract (ETD)
- One of the most fundamental questions in physics is how do magnetic fields effect the motion of charged particles. Many applications from magnetically confined fusion devices to the dynamics of particles in the Earth’s magnetic field rely on the understanding of this basic question. In this thesis I explored two drastically different systems related to this question. First, I present simulations of a dense collection of charged particles in a strong magnetic field. The strong magnetic field caused particles to be confined to move along the magnetic field. Because of this confinement, the particles travel exceeding long distances before encountering another particle and spread out at a slower rate than their non-magnetized counterparts. In the second part of this thesis, I present research into the propagation properties of a type of wave found in Earth’s magnetic field called the whistler-mode chorus wave. Like ocean waves affecting the motion of a surfer, these waves have the potential to influence electrons in Earth’s magnetic field and lead to whole host of observable phenomena. Studying the properties of chorus waves will elucidate their possible interactions with electrons.
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9984647354602771
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