Study of the space weather effects during strong solar eruptions
Larsen, Nicholas Peter (2025-02-03)
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https://rightsstatements.org/vocab/InC/1.0/
https://urn.fi/URN:NBN:fi:oulu-202502031433
Kuvaus
Tiivistelmä
The Earth is constantly bombarded by high-energy particles originating from space, known as cosmic rays (CRs). CRs with enough energy penetrate the magnetosphere and enter the atmosphere. The byproducts of CR-induced atmospheric cascades can be detected at the Earth’s surface by ground-based detectors, e.g. neutron monitors (NMs). During strong solar eruptions large fluxes of CRs, known as solar energetic particles (SEPs), can be produced. Such eruptions directed at Earth can cause NMs to detect notable increases in CRs, an event called a ground-level enhancement (GLE). Arriving CRs determine the radiation environment at high altitudes, and during GLEs the flux of arriving CRs and radiation risk increase in tandem. This thesis investigates strong solar eruptions and their associated phenomena, including GLEs and magnetospheric disturbances, as well as their impact on the radiation environment at aviation altitudes.
Each GLE is unique and requires sophisticated analysis techniques to derive SEP spectra data necessary to assess GLE space weather effects. A much sought-after open-source tool for computing trajectories of CRs in the magnetosphere was developed, called OTSO, to aid GLE analysis. OTSO showed good agreement with similar older validated tools and was subsequently used to successfully analyse two GLE events.
A newly updated aviation dosimetry model, Cosmic Ray Atmospheric Cascade: Dosimetry Model (CRAC:DOMO), was validated by its application to GLE 60 (15 April 2001). The model radiation dose for an intercontinental flight from Prague to New York during GLE # 60 showed good agreement with in-situ radiation measurements taken by an onboard Liulin dosimetry device. The same methodology was applied to the Halloween GLE events, late October to early November 2003, which occurred during one of the strongest recorded geomagnetic storms. OTSO and an improved version of CRAC:DOMO, permitting greater computational resolution, successfully analysed these events and provided radiation estimates under extreme geomagnetic conditions, indicating the robustness of the GLE radiation analysis method outlined in this thesis. Additionally, comparisons between flight data during this period and CRAC:DOMO computations using anisotropic assumptions revealed a strong agreement.
Following the validation of CRAC:DOMO, the relationship between GLE characteristics and modelled radiation doses was investigated using unprecedented statistics offered by a database of historic GLEs analysed with a homogenous methodology. A statistically strong relationship was observed between the radiation doses and NM count rates for 21 analysed GLEs, leading to the proposal of NM count rates being used as a simple proxy for radiation dose at aviation altitude during strong SEP events.
Original papers
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Larsen, N., Mishev, A., & Usoskin, I. (2023). A new open‐source geomagnetosphere propagation tool (Otso) and its applications. Journal of Geophysical Research: Space Physics, 128(3), e2022JA031061. https://doi.org/10.1029/2022JA031061. https://doi.org/10.1029/2022JA031061
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Larsen, N., & Mishev, A. L. (2023). Analysis of the ground level enhancement gle 60 on 15 april 2001, and its space weather effects: Comparison with dosimetric measurements. Space Weather, 21(8), e2023SW003488. https://doi.org/10.1029/2023SW003488. https://doi.org/10.1029/2023SW003488
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Larsen, N., & Mishev, A. (2024). Relationship between nm data and radiation dose at aviation altitudes during gle events. Space Weather, 22(6), e2024SW003885. https://doi.org/10.1029/2024SW003885. https://doi.org/10.1029/2024SW003885
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Larsen, N., & Mishev, A. (2025). Radiation impact of the halloween gle events during the october–november 2003 period. Space Weather, 23(1), e2024SW004199. https://doi.org/10.1029/2024SW004199. https://doi.org/10.1029/2024SW004199
Osajulkaisut
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Larsen, N., Mishev, A., & Usoskin, I. (2023). A new open‐source geomagnetosphere propagation tool (Otso) and its applications. Journal of Geophysical Research: Space Physics, 128(3), e2022JA031061. https://doi.org/10.1029/2022JA031061. https://doi.org/10.1029/2022JA031061
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Larsen, N., & Mishev, A. L. (2023). Analysis of the ground level enhancement gle 60 on 15 april 2001, and its space weather effects: Comparison with dosimetric measurements. Space Weather, 21(8), e2023SW003488. https://doi.org/10.1029/2023SW003488. https://doi.org/10.1029/2023SW003488
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Larsen, N., & Mishev, A. (2024). Relationship between nm data and radiation dose at aviation altitudes during gle events. Space Weather, 22(6), e2024SW003885. https://doi.org/10.1029/2024SW003885. https://doi.org/10.1029/2024SW003885
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Larsen, N., & Mishev, A. (2025). Radiation impact of the halloween gle events during the october–november 2003 period. Space Weather, 23(1), e2024SW004199. https://doi.org/10.1029/2024SW004199. https://doi.org/10.1029/2024SW004199
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