Pulsating Aurora: Optical observations and modelling of the time-variation of ionospheric response to precipitation of pitch-angle-scattered electrons from the magnetosphere

Abstract

This thesis explores the mechanisms governing pulsating auroras by combining observational analysis with theoretical simulations using the AURORA model. The AURORA model simulates electron transport and ionospheric responses, playing a key role in replicating the abrupt onset precipitation of electrons from source altitudes at 3RE, 4.4RE, 6.1RE, and 7.6RE. Eight events of pulsating aurora were selected between October 2006 and March 2007, with a focus on emissions at 4278 Å, 6730 Å, 7774 Å, and 8446 Å. The observational part of the thesis examines distinct pulsations, highlighting differences in intensity and noise levels across these eight events. The theoretical study aligns with observed pulsation characteristics, establishing a clear link when comparing observational results with theoretical findings. Furthermore, it emphasises the necessity of specific source altitudes for achieving abrupt onsets in the ionosphere. The research findings indicate that, for an abrupt pulsation onset in the ionosphere over Tromsø, the source altitude along the magnetic field line must fall within the range of 6.1RE and 7.6RE. The study highlights the importance of combining both observational and theoretical approaches to advance our understanding of the onset characteristics of pulsating aurora.