17 November 2026 | 16:15 - 19:15
Earth’s atmosphere is constantly struck by cosmic rays and, at times, by energetic particles from the Sun and from the radiation belts. These particles trigger cascades of secondary particles that ionize the air, deposit radiation dose, and can destroy ozone. Yet the computer models used to simulate this process usually assume one fixed, standard atmosphere, whatever the place or time.
This thesis asks how much that simplification matters, and how particle precipitation affects the upper atmosphere during an extreme space weather event.
Using a Monte Carlo simulation tool combined with empirical atmospheric models, three studies address these questions.
The first characterizes every major secondary particle species, validates the simulations against an independent model and aircraft measurements, and shows that latitude and season change particle fluxes by up to 80 percent below 20 kilometres, even with high geomagnetic shielding.
The second shows that ionization and radiation dose differ by up to 68 and 60 percent between equatorial and polar atmospheres, produces global maps that single-profile models cannot reproduce, and finds that this sensitivity reverses sign for solar proton spectra.
The third study examines the extreme geomagnetic storm of 11 May 2024 and the solar proton event of 8 June 2024. Satellite observations reveal ozone depletion of up to 60 percent in the polar upper atmosphere, lasting seven days in May and two days in June.
Overall, the state of the atmosphere is not a negligible input for simulating cosmic radiation, and its influence can grow under storm conditions.
Prof. Hugues Goosse (UCLouvain) (Supervisor)
Prof. Viviane Pierrard (UCLouvain/BIRA-IASB) (Supervisor)
Prof. Qiuzhen Yin (UCLouvain) (Chairperson)
Prof. Michel Crucifix (Secretary)
Prof. Fabio Bacchini (KULeuven)
Prof. Konstantin Herbst (University of Oslo, UiO)
Prof. Véronique Dehant (UCLouvain)
Dr. Edith Botek (BIRA-IASB)