Investigating the structure of the near-Sun solar wind
File(s)
Author(s)
Laker, Ronan Luke
Type
Thesis
Abstract
The recent launch of two flagship missions, Parker Solar Probe and Solar Orbiter, have ushered in an exciting new era for solar wind research.
This thesis uses this novel data to study structures in the solar wind, with the aim of elucidating how the solar wind is heated and accelerated.
First, a newly formed constellation of spacecraft was used to study the structure and dynamics of the solar wind from different perspectives.
This included the identification of small-scale ripples in the heliospheric current sheet, along with a study of a co-rotating interaction region in latitude.
Parker Solar Probe was then used to study small-scale switchbacks, which are folds in the magnetic field that dominate the near-Sun solar wind.
Since switchbacks are seen throughout the solar wind, it is important to characterise their properties to test against theoretical predictions.
In one of the first investigations of its kind, switchbacks were estimated to have a width of $\sim$50,000\,km and an aspect ratio of the order of 10.
It was also demonstrated that the magnetic field in switchbacks tended to deflect in certain directions, implying a systematic source closer to the Sun.
Finally, as Parker Solar Probe moved to only 13\,\solarradii{} from the Sun, a coherent pattern in the switchbacks was identified, which had a spatial scale comparable to bright points on the solar surface.
It was also found that switchbacks were associated with consistent temperature enhancements.
This feature, together with the newly identified systematic pattern in the switchback magnetic field, were used to propose a new switchback definition.
This provides a more robust way to identify switchbacks, which does not rely solely on the absolute magnetic field angle.
These observations were used to conclude that switchbacks represent the imprint of interchange reconnection on the solar wind.
This thesis uses this novel data to study structures in the solar wind, with the aim of elucidating how the solar wind is heated and accelerated.
First, a newly formed constellation of spacecraft was used to study the structure and dynamics of the solar wind from different perspectives.
This included the identification of small-scale ripples in the heliospheric current sheet, along with a study of a co-rotating interaction region in latitude.
Parker Solar Probe was then used to study small-scale switchbacks, which are folds in the magnetic field that dominate the near-Sun solar wind.
Since switchbacks are seen throughout the solar wind, it is important to characterise their properties to test against theoretical predictions.
In one of the first investigations of its kind, switchbacks were estimated to have a width of $\sim$50,000\,km and an aspect ratio of the order of 10.
It was also demonstrated that the magnetic field in switchbacks tended to deflect in certain directions, implying a systematic source closer to the Sun.
Finally, as Parker Solar Probe moved to only 13\,\solarradii{} from the Sun, a coherent pattern in the switchbacks was identified, which had a spatial scale comparable to bright points on the solar surface.
It was also found that switchbacks were associated with consistent temperature enhancements.
This feature, together with the newly identified systematic pattern in the switchback magnetic field, were used to propose a new switchback definition.
This provides a more robust way to identify switchbacks, which does not rely solely on the absolute magnetic field angle.
These observations were used to conclude that switchbacks represent the imprint of interchange reconnection on the solar wind.
Version
Open Access
Date Issued
2023-03
Date Awarded
2024-01
Copyright Statement
Creative Commons Attribution NonCommercial Licence
License URL
Advisor
Horbury, Timothy S.
Sponsor
Imperial College London
Publisher Department
Physics
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)