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The Lyman-alpha Dayglow Emission on Uranus

Masters Thesis Presentation

Tid: Fr 2021-01-15 kl 12.30

Föreläsare: Jahangir Jazayeri

Plats: https://kth-se.zoom.us/j/64621436669

Uranus is one of the least explored planets in our solar system. The Uranian Lyman-alpha emission has been a subject of study for decades, with great advancements derived from ultraviolet observations of the International Ultraviolet explorer between 1982-1986 and Voyager 2's Ultraviolet Spectrometer in 1986. However there is not a complete consensus in regards to what the exact sources is and their respective contribution to the Uranian Lyman-alpha signal. This thesis aims to analyse the contribution from two sources to the Uranian Lyman-alpha dayglow through solving the radiative transfer equation for the atmosphere on Uranus. The sources are solar Lyman-alpha resonant scattering and Rayleigh scattering by atomic and molecular hydrogen respectively. The radiative transfer equations is solved using the Feautrier Method Program, a program written by Randall G. Gladstone that has previously been applied to the Jovian atmosphere. In this thesis the radiative transfer equation was solved for the Uranian atmosphere subjected to different variations in parameters, including the atmospheric temperature and particle density of Lyman-alpha scatterers and absorbers. The visualisation of the results showed a significant Lyman-alpha limb brightening with a maximum intensity located around 400 km outside one planetary radius as seen from the disk center. The contributions to the Lyman-alpha dayglow from Rayleigh scattering by \ce{H2} was calculated to be 160 R whereas the contribution from resonant scattering by \ce{H} was 550 R. From the simulated Lyman-alpha sources an intense limb brightening is expected while none of the current observations has indicated such a feature. A technical conclusion from this thesis is the efficiency of the Feautrier Method Program and how some Lyman-alpha sources and their contributions could easily be analysed and compared to observations.