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Title: Solar wind particle populations at 1 au : examining their origins in advance of the Solar Orbiter mission
Author: Macneil, Allan Ross
ISNI:       0000 0004 7660 568X
Awarding Body: UCL (University College London)
Current Institution: University College London (University of London)
Date of Award: 2019
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The three studies presented in this thesis aim to understand the properties of solar wind particle populations in the context of their origins at the Sun. The observations used begin with in situ plasma measurements, and extend to remote sensing of solar wind sources. This approach is motivated by the upcoming Solar Orbiter mission, which will use similar techniques at < 0.3 au to address the question of how the Sun creates and controls the heliosphere. The first study compares energetic properties of suprathermal solar wind electrons, the 'halo' and 'strahl', against the inferred electron temperature of their source. From the weak nature of the resulting correlations we conclude, in contrast to earlier results, that a relationship with electron temperature may exist in the corona, but thatusually no strong signatures remain in these distributions at 1 au. The second study examines the origin of "intermediate" transitional heavy ion charge states in solar wind rarefactions. Linking in situ measurements of these regions with extreme ultraviolet solar observations, they are found to originate near trailing coronal hole boundaries. This result and a simple solar wind model suggest that it is the intrinsic properties at these boundaries which are the primary cause of the intermediate ionisation, as opposed to interplanetary mixing. The technique used to link these observations is also critically evaluated and improvements are suggested. The final study compares solar wind associated with a coronal hole-quiet Sun boundary, to solar wind associated with the same coronal hole later bordering an active region. Changing features found in a range of in situ parameters are compared in the context of source region mapping. We put forward suggestions for mechanisms of solar wind production which could produce such changes.
Supervisor: Owen, C. ; Wicks, R. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available