Reddy, Sachin Alexander; (2024) Ions, Irregularities, and Plasma Dynamics in Earth’s Equatorial Ionosphere. Doctoral thesis (Ph.D), UCL (University College London).

Text SachinReddy_Thesis_Accepted.pdf - Accepted Version Access restricted to UCL open access staff until 1 May 2025. Download (19MB)

Abstract

The ionosphere is a highly dynamic region that acts as the interface between Earth and space, generating a variety of intriguing and complex phenomena. Understanding it is crucial for mitigating the harmful effects of space weather on a wide range of technological and societal systems. Further exploration is especially needed in two key areas: in-situ observations and predicting ionospheric events and space weather effects. The first study assesses the impact of spacecraft charging on a CubeSat and its payload. The study reveals that charging adversely affects the measurements of plasma density, temperature, and bulk speed. This emphasises the necessity of correcting for charging and underscores the difficulty in conducting in-situ observations of the region. The second introduces VIPER, a machine learning model that can accurately predict vertical plasma drift in the equatorial latitudes. These drifts are responsible for the distribution of plasma and tell us how the ionosphere responds to space weather events. VIPER is the first model to produce a weather-like prediction whilst also providing bespoke errors on predictions. The final presents APE, an AI model which predicts equatorial plasma bubbles detected by the Swarm spacecraft. Plasma bubbles are a known cause of radio wave scintillations and predicting them has been a high priority for decades. Using cooperative game theory techniques, APE also sheds new scientific light on bubble climatology. Collectively, these studies also reveal that plasma dynamics play a fundamental role in the ionosphere, and enhancing our understanding of drifts is essential for improving the prediction of ionospheric phenomena and space weather effects.

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