Thesis and Dissertation Defenses
Understanding Solar Wind Formation by Identifying the Origins of In Situ Observations
Presented by Samantha Wallace (UNM)
Over the past century, significant progress has made on the subjects of two fundamental unresolved questions in Heliophysics, namely 1) how is the solar corona heated to multi-million-degree temperatures, and 2) how is the solar wind formed, from its origin, to its release and acceleration. While the two are in many ways intertwined, this dissertation focuses on the latter. Our current understanding of solar wind formation has developed largely through relating the general origins of the observed solar wind on global spatial scales to the corresponding observed speed at 1 au. However, we are now at a point where long-standing relationships and frameworks cannot account for all of the solar wind that has been observed. In order to make progress, in this work we exploit the rigorous capabilities of the Wang-Sheeley-Arge (WSA) model driven by Air Force Data Assimilative Photospheric Flux Transport (ADAPT) time-dependent photospheric field maps, and develop a methodology to derive the precise source locations of the in situ observed solar wind. This methodology is applied to three different studies with the goal of understanding the physical mechanisms involved in the release and acceleration of solar wind parcels from the same source. In the first study, we test the well-known inverse relationship between expansion factor (f_s) and observed solar wind speed (v_obs) for solar wind that emerges from a large sampling of pseudostreamers, to investigate if field line expansion plays a physical role in accelerating the solar wind from this source region. In the second study, we determine the source locations of the first identified quasiperiodic density structures (PDSs) inside 0.6 au in order to test the Separatrix-web (S-web) theory that slow solar wind can be formed via magnetic reconnection both near to and far from the heliospheric current sheet (HCS). In the final study, we apply our methodology to the first observations of the new Parker Solar Probe mission. Without the use of modeling capabilities such as those of ADAPT-WSA, it is not possible to determine if solar wind emerges from active regions, quiet Sun, near/far from coronal hole boundaries, or near/far from the HCS. This information is critical to interpreting in situ observations and making progress in our understanding of how the solar wind is released and accelerated.
2:00 pm, Thursday, September 24, 2020
Zoom,
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