Jeong, Seong-Yeop;
(2022)
The Kinetic Plasma Physics of Solar-Wind Electrons.
Doctoral thesis (Ph.D), UCL (University College London).
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Abstract
This thesis uses kinetic plasma physics to study the kinetic evolution of the electron velocity distribution function (VDF) in the solar wind. We propose an analytical model for resonant wave–particle instability in homogeneous plasma based on quasi-linear theory. By using this model, we confirm that the oblique fastmagnetosonic/whistler (FM/W) instability can scatter the electron strahl in the electron VDF. Following the study of the local scattering, we propose a global transport theory for the kinetic expansion of solar-wind electrons. We derive a gyro-averaged kinetic transport equation that accounts for the solar-wind expansion in the geometry of the Parker-spiral magnetic field. Our kinetic transport model shows the development of the core–strahl configuration in the electron VDF near the Sun. Applying fits to our numerical results, we compare our numerical results with data from Parker Solar Probe (PSP), and provide theoretical evidence that the electron strahl is not scattered by the oblique FM/W instability near the Sun. To confirm our theoretical results for strahl scattering, we analyse data from PSP and Helios. We compare the measured strahl properties with the analytical thresholds for the oblique FM/W instability in the low- and high-β∥c regimes, where β∥c is the ratio of the parallel core thermal pressure to the magnetic pressure, as functions of heliocentric distance. Our PSP and Helios data show that the electron strahl is stable against the oblique FM/W instability in the inner heliosphere. Our analysis suggests that this instability can only be excited sporadically, on short timescales. For the numerical evaluation of the kinetic equations in the research chapters, we develop a mathematical approach based on the Crank–Nicolson scheme. This approach numerically solves any kind of diffusion equations with any dimensions. We note that our mathematical approach is applicable to other complex diffusion equations.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | The Kinetic Plasma Physics of Solar-Wind Electrons |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Copyright © The Author 2021. Original content in this thesis is licensed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) Licence (https://creativecommons.org/licenses/by-nc/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request. |
| UCL classification: | UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Space and Climate Physics UCL > Provost and Vice Provost Offices > UCL BEAMS UCL |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10146798 |
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