The structure and dynamics of the near-sun solar wind
File(s)
Author(s)
Woolley, Thomas
Type
Thesis
Abstract
The solar wind is a collisionless plasma that flows at hundreds of km/s away from the Sun into interplanetary space. Despite over half a century of solar wind research many questions remain unanswered. To address these questions, in situ data from small heliocentric distances is required. To date, Parker Solar Probe (PSP) is the only spacecraft to measure data within 0.29 au. Therefore, the PSP data set offers a unique opportunity to study the near-Sun solar wind.
The data from the Solar Probe Cup instrument are fitted to extract bulk solar wind parameters. These parameters are used in conjunction with data from the SPAN and MAG instruments to analyse three structures found in the solar wind: switchbacks, patches and quiet periods.
The ion velocity distribution functions within full-reversal switchbacks are shown to be consistent with a velocity-space rotation of the background plasma. This suggests that the proton core parallel temperature is the same inside and outside of full-reversal switchbacks despite the enhanced plasma velocity above the background.
The solar wind associated with two switchback patches is found to be consistent with slow Alfv\'enic solar wind from near the boundary of the southern polar coronal hole. A patch is also found to have a particularly low $\alpha-$particle abundance which is in contrast to a subsequent study, suggesting that $\alpha-$particle abundance within patches is variable.
Quiet periods are found to be consistent with longitudinal solar wind streams in close proximity to the heliospheric current sheet (HCS). The typical longitudinal scale size of these quiet periods is $\sim$2$^{\circ}$. However, most quiet period durations are not consistent with this scale, as they are modulated by PSP's orbital trajectory and the HCS dynamics.
The data from the Solar Probe Cup instrument are fitted to extract bulk solar wind parameters. These parameters are used in conjunction with data from the SPAN and MAG instruments to analyse three structures found in the solar wind: switchbacks, patches and quiet periods.
The ion velocity distribution functions within full-reversal switchbacks are shown to be consistent with a velocity-space rotation of the background plasma. This suggests that the proton core parallel temperature is the same inside and outside of full-reversal switchbacks despite the enhanced plasma velocity above the background.
The solar wind associated with two switchback patches is found to be consistent with slow Alfv\'enic solar wind from near the boundary of the southern polar coronal hole. A patch is also found to have a particularly low $\alpha-$particle abundance which is in contrast to a subsequent study, suggesting that $\alpha-$particle abundance within patches is variable.
Quiet periods are found to be consistent with longitudinal solar wind streams in close proximity to the heliospheric current sheet (HCS). The typical longitudinal scale size of these quiet periods is $\sim$2$^{\circ}$. However, most quiet period durations are not consistent with this scale, as they are modulated by PSP's orbital trajectory and the HCS dynamics.
Version
Open Access
Date Issued
2022-09
Date Awarded
2023-02
Copyright Statement
Creative Commons Attribution NonCommercial Licence
License URL
Advisor
Matteini, Lorenzo
Horbury, Timothy
Sponsor
Science and Technology Facilities Council (Great Britain)
Grant Number
ST/T506151/10
Publisher Department
Physics
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)