Browsing by Author "Spanswick, Emma Louise"

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    Characterization of Ionosphere-Thermosphere Coupling from the VISIONS-2 Mission
    (2023-08) Wilson, Kieran; Burchill, Johnathan Kerr; Knudsen, David J.; Harlick, Anna Maria; Spanswick, Emma Louise; Friesen, Timothy
    VISIONS-2 was a NASA sounding rocket mission consisting of two payloads flown on December 7th, 2018 from Svalbard, Norway. On board the first Visions-2 payload, electrostatic analyzers gathered data on low-energy ions throughout the flight. Existing in situ studies of the mechanics of ionosphere-thermosphere coupling within the undersampled E-region are limited. The present study aims to bolster these existing findings by characterizing the transition from collisionless to collision-dominated ionosphere-thermosphere interaction peaking near 120 km altitude, estimating the altitude at which friction balances the Lorentz force on ionospheric ions. For the purposes of this study, ion drift is estimated at regular altitude intervals throughout the transition region using two-dimensional images gathered by the electrostatic analyzers. In the absence of thermospheric wind measurements and low-altitude electric field measurements, the ion drift variation with altitude is used as a proxy measurement for neutral winds and the guiding centre drift. This approach prohibits the direct exploration of the effects of payload potential or ion species on the measured ion velocity. Study results place the collisional transition height below 120 km, corroborating previous research that constrains the collisional transition height, during quiet conditions, between 110 – 120 km.
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    Characterizing Energetic Electron Precipitation and Whistler-mode Waves during Electron Injection Events
    (2022-01) Ghaffari, Reihaneh; Cully, Christopher M; Jackel, Brian; Spanswick, Emma Louise; Gomes da Rocha, Claudia; Jaynes, Allison N
    Magnetically trapped particles in the magnetosphere can be lost and precipitate into the atmosphere. Precipitated particles deposit energy into the atmosphere and affect the atmospheric chemistry and ionization in the ionosphere. The change in the ionospheric charge density can disturb telecommunication on the Earth. The precipitated particles can also alter the density of substantial atmospheric components such as HOx and NOx which are critical catalysts in ozone destruction. Therefore, studying the causes and effects of energetic particle precipitation has great importance. One type of geomagnetic event that is associated with energetic particle precipitation is a substorm injection. Energetic electron precipitation associated with substorm injections typically occurs when magnetospheric waves, particularly whistler-mode waves, resonantly interact with electrons to affect their pitch angle and scatter particles into the loss cone through a diffusion process. In this thesis, I describe two studies about electron precipitation through wave-particle interactions during substorm injection events. The first study aims to quantitatively characterize energetic electron precipitations during injection events in the magnetosphere. This part uses in-situ measurements by the Van Allen Probes and presents the typical substorm-induced precipitation flux as 4×〖10〗^6 el/cm2.s.sr. The precipitation flux is estimated from characterizing the ground signatures of precipitated electrons on radio signal propagation in the ionosphere. The second study aims to investigate the physical drivers of electron precipitation during injections. This part investigates whistler-mode wave generation in conjunction with electron injections using in-situ wave measurements by the Time History of Events and Macroscale Interactions during Substorms (THEMIS) mission. This study indicates that only 5% of the injection events are associated with an order of magnitude wave power enhancement. Investigating diffusion rates due to the generated waves during the selected events states that strong scattering is not typically associated with injection events in the magnetosphere.
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    Event-Based Precipitation Patterns of Ring Current Electrons Observed by Riometers
    (2024-09-18) Keenan, Christian; Spanswick, Emma Louise; Donovan, Eric F; Knudsen, David J; Wieser, Michael E
    A primary loss mechanism for high-energy particles in the Earth’s ring current is precipitation into the ionosphere. Precipitation has been historically difficult to quantify since it is primarily studied with in situ satellites. With in situ approaches, it is difficult to understand the spatial-temporal nature of the precipitation. In this thesis, ground-based measurements of high-energy electron precipitation are used to characterize and classify ring current electron precipitation events based on their spatial extent and temporal behaviour. As will be shown, there are multiple types of events visible in the ground-based data. When separated in this manner, these event types display different characteristics that demonstrate they are likely connected to different precipitation mechanisms. These results are important because they shed light on dominant wave-particle interactions in the ring current region, and pave the way for more detailed studies of wave-particle coupling and quantifying ring current losses.