Dissertation
Electron Measurements of the nascent solar wind with the Parker Solar Probe
University of Iowa
Doctor of Philosophy (PhD), University of Iowa
Spring 2021
DOI: 10.17077/etd.005830
Abstract
The in situ measurement of the velocity distribution function is the foundation from which many of the most important aspects of a plasma's kinetic properties can be determined. Properties such as the density, velocity, and temperature can be obtained by fitting models representing the physics of various populations in the plasma or by directly integrating the moments of the distribution. Parker Solar Probe (PSP), carrying a number of particle detecting instruments, extends measurements of the solar wind plasma to distances closer to the Sun than have been observed by any prior mission. The electron detectors of the Solar Probe Analyzer- Electron (SPAN-E) are poised to provide clues to answering many outstanding questions in space physics such as the heating and transport of energy in the solar wind. The electrostatic potential of the spacecraft and the magnetic fields produced by several spacecraft components interfere with the ability of the SPAN electron detectors to accurately measure the electron velocity distribution function (eVDF) by deflecting the trajectories of the measured electrons and altering their kinetic energies. By modeling the interaction of the spacecraft potential and magnetic fields with the electrons, it is possible to estimate the magnitude of the impact to the measurements. Furthermore, once this interaction is understood, it is possible to create a method of correcting the measurements in order to remove the effects of these fields. In this work, models of the PSP spacecraft and the electric and magnetic fields it produces are incorporated into an analysis of the electron trajectories measured by the SPAN electron detectors. Using this analysis, an estimation of the changes to the field of view (FOV) of the instruments and the effect on the determination of electron moments is obtained. Techniques for correcting the data in the context of model fitting and moment integration are also developed and their use is discussed. These correction techniques are applied to SPAN electron measurements taken over the first five orbits of PSP and a three component model representing the core, halo, and strahl electrons is fit to the resulting eVDFs. A bi-modal structure in the relative frequency of strahl drift is observed and discussed. Radial trends of the fitted parameters obtained over the range of 0.12 to 0.52 AU are placed in the context of previous measurements. Finally, the role of intra-particle collisions and plasma instabilities in the radial evolution of the suprathermal electron populations is quantified and evidence is presented for the relative importance of oblique whistler waves in the regulation of heat flux and the pitch-angle scattering of the strahl electrons.
Details
- Title: Subtitle
- Electron Measurements of the nascent solar wind with the Parker Solar Probe
- Creators
- Daniel J McGinnis
- Contributors
- Jasper Halekas (Advisor)Kenneth Gayley (Committee Member)Gregory Howes (Committee Member)Allison Jaynes (Committee Member)Kristopher Klein (Committee Member)
- Resource Type
- Dissertation
- Degree Awarded
- Doctor of Philosophy (PhD), University of Iowa
- Degree in
- Physics
- Date degree season
- Spring 2021
- DOI
- 10.17077/etd.005830
- Publisher
- University of Iowa
- Number of pages
- xi, 110 pages
- Copyright
- Copyright 2021 Daniel J. McGinnis
- Language
- English
- Description illustrations
- color illustrations
- Description bibliographic
- Includes bibliographical references (pages 95-110)
- Public Abstract (ETD)
The advent of the space age opened entirely new avenues of scientific investigation. The use of spacecraft has allowed us to greatly increase our understanding of the solar system by granting us the capacity to directly measure the heliospheric plasma. Despite our advancements, several fundamental problems remain unsolved, including the heating of the corona and the acceleration of the solar wind. Parker Solar Probe (PSP) was designed and launched with the mission of providing the electromagnetic field and particle measurements in the near-Sun environment that are vitally needed to answer these questions. Particular challenges are presented to the measurement of electrons by PSP, due to the unique and previously unencountered environment and the large spacecraft-produced magnetic fields. In this work, the degree to which the measurement of electron velocity distribution functions could be impacted is estimated by modeling the interaction of the solar wind electrons with the spacecraft and its associated electrostatic and magnetic fields. A method of correcting for these effects is presented and applied in the analysis of electron measurements from PSP's first five periods of nearest approach to the Sun. These measurements represent the closest taken from any space mission and provide important information on the formation and evolution of the young solar wind. The electrons in this environment are characterized by their bulk properties, radial variations, and relative instability to various plasma wave modes.
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9984097168502771
Metrics
6 File views/ downloads
32 Record Views