Dissertation
Methods for isolation and phase-space energization analysis of instabilities in collisionless shocks with applications
University of Iowa
Doctor of Philosophy (PhD), University of Iowa
Spring 2024
DOI: 10.25820/etd.007389
Abstract
Particle heating and acceleration can be done by many mechanisms in collisionless shocks and have been a topic of uncertainty due to the strong dependence on the parameters of the system. Above the critical Mach number, due to the abundance of free energy, kinetic instabilities are excited which can interact with particles through wave-particle interactions. Moreover, it has been difficult to causally match proposed mechanisms/ instabilities to observed and simulated phenomena due to the non-linear and non-homogeneous nature of the system and the limited ways to measure real shocks in the heliosphere. In-situ spacecraft measurements are limited to single line(s) in space and time which makes it difficult to study shocks as they evolve rapidly spatially and temporally. Here, we propose a new technique to study instabilities, the instability isolation method, to be used with the Field-Particle correlation technique, to solve these issues. We determine how to linearly separate fields such that terms containing the instability physics can be isolated. We apply these methods to study two energy-transferring phenomena commonly found in Heliospheric shocks, shock ripple and the non-adiabatic heating of electrons. We are able to find distinct signatures that can be used to identify the presence of these mechanisms in shocks using velocity-space information. Furthermore, we use linear kinetic theory to predict the velocity-space signatures produced by the Field-Particle correlation technique for fundamental wave-particle interactions, which are prevalent in the precursor of many shocks and abundant in the solar wind in general.
Details
- Title: Subtitle
- Methods for isolation and phase-space energization analysis of instabilities in collisionless shocks with applications
- Creators
- Collin R Brown
- Contributors
- Gregory G Howes (Advisor)Jasper Halekas (Committee Member)Allison Jaynes (Committee Member)Colby Haggerty (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.007389
- Number of pages
- xx, 179 pages
- Copyright
- Copyright 2024 Collin R Brown
- Comment
- This thesis has been optimized for improved web viewing. If you require the original version, contact the University Archives at the University of Iowa: https://www.lib.uiowa.edu/sc/contact/
- Language
- English
- Date submitted
- 04/22/2024
- Description illustrations
- illustrations, tables, graphs
- Description bibliographic
- Includes bibliographical references (pages 150-162).
- Public Abstract (ETD)
- The sun emits a steady stream called the solar wind comprised of plasma that interacts non-trivially with itself and the planets. One key interaction is collisionless shocks, where the energy of the supersonic flow is rapidly converted into heating and particle acceleration on a length scale much shorter than the collisional path. This process of plasma, the fourth state of matter where electrons and ions are separated and electromagnetic effects are significant, requires new methods to study, as much of our knowledge is from linear theory and verified through measurements by spacecraft limited to single lines in space, despite shocks having strong spatial dependence and evoking instabilities to dissipate surplus energy. These instabilities are especially challenging to study as they are convoluted with the main non-linear shock process(es). Here, we develop two methods to analyze the mechanisms and instabilities that transfer energy within shocks. We create the novel Instability Isolation Method to isolate these instabilities. Also, we develop the Field-Particle Correlation technique, a diagnostic that shows the gain of energy of particles in velocity-space, for use with the isolated instabilities. Furthermore, we use kinetic theory to predict the Field-Particle Correlation diagnostic. Together, these are used to identify the energy transfer caused by individual mechanisms in collisionless shocks and space plasmas. We apply these methods to understand two significant effects on shock systems, the rippling of the shock surface and the extra, non-adiabatic heating of electrons. These techniques develop our ability to diagnose and understand the complex behavior of plasma systems.
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9984647255802771
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