UCLA

This dissertation presents a comprehensive investigation into chorus-wave-driven relativisticelectron precipitation in Earth’s outer radiation belt through a newly-developed numerical model, emphasizing the microscopic to macroscopic characteristics of relativistic microbursts. We initially develop the Chorus Induced Particle Precipitation (CIPP) model, designed to simulate detailed precipitation signatures on arbitrary magnetic field lines resulting from equatorially generated chorus waves. The modeling approach accurately captures the spatial and temporal precipitation dynamics and demonstrates robust predictive capability. We then model the spatial scales of chorus-driven relativistic electron microbursts, finding a typical scale size of approximately 60 km, consistent with observational data. Our results show that the spatial scale of microbursts primarily depends on wave propagation rather than source dimensions. Additionally, microbursts exhibit substantial poleward displacement from chorus wave source regions, challenging the traditional assumption of strict magnetic conjunction and highlighting the importance of non-conjugate geometries. Extending our framework globally, we simulate chorus sources distributed across various L-shells and magnetic local time sectors. Results demonstrate sector-dependent variations in precipitation, with noon-sector microbursts significantly stronger and broader than those in dawn or midnight sectors, primarily due to reduced Landau damping. These findings highlight the controlling role of ∼ keV electron populations in relativistic precipitation processes and provide a quantitative basis for estimating global radiation belt losses. Subsequently, we estimate relativistic electron lifetimes within the outer radiation belt under chorus-driven precipitation, finding lifetimes ranging from tens of hours in the core belt (L = 5–6.5) to significantly longer durations at lower L-shells. Our results confirm that chorus-driven microbursts can efficiently deplete relativistic electron populations on timescales of days, verifying their critical role in radiation belt electron dynamics. Finally, we demonstrate that efficient night-side relativistic precipitation requires chorus wave ducting by cold plasma density structures. Using multi-spacecraft observations coupled with event-specific modeling informed by ELFIN measurements, we show that ducted waves retain an amplitude sufficient for resonant interactions at high latitudes, with relativistic energies, approaching the strong diffusion limit. Our findings imply that plasma density ducts may be a common and essential feature for relativistic electron precipitation on the night-side, significantly affecting radiation belt dynamics. We conclude that chorus driven relativistic microbursts have unique and complicated spatiotemporal characteristics, and play an important role in the global radiation belt dynamics.