Author ORCID Identifier

https://orcid.org/0009-0005-4311-1215

Date of Award

Spring 6-8-2026

Document Type

Thesis (Undergraduate)

Department

Physics and Astronomy

First Advisor

Robyn Millan

Second Advisor

Kristina Lynch

Third Advisor

Ryan C. Hickox

Abstract

Wave-particle interactions play a central role in transferring energy between different particle populations in space plasmas. In the radiation belts, these interactions govern the acceleration, scattering, and loss of energetic particles to Earth’s atmosphere. Understanding the drivers of these energetic particle losses is essential, as these particles can collide with satellites and contribute to ozone depletion as they enter the atmosphere. Developing a clearer picture of these processes will improve our ability to predict radiation belt variability and quantify the impacts, ultimately allowing us to mitigate the adverse effects.

Previous research has identified wave modes important for scattering electrons into the atmosphere. For example, electromagnetic ion cyclotron (EMIC) waves are a key driver of very high-energy (>1 MeV) electron scattering and impulsive precipitation. EMIC waves have characteristic frequencies of 0.1-5 Hz and typically occur at low- and mid-latitudes during storm main phases. EMIC waves have been linked to duskside relativistic electron precipitation which are energetic and intense bursts of precipitation. However, there are also other processes that can scatter energetic electrons, and open questions remain regarding which processes dominate, under varying geomagnetic conditions, locations, and times. The role of broadband waves, in particular, has been suggested as important for scattering electrons with energies from hundreds of keV to multi-MeV, but supporting observations are limited. Moreover, their impact on electrons with energies < 100 keV has been less studied. These waves may play a significant role in driving the more extended < 100 keV scattering activity, observed by stratospheric balloon experiments in 2013.

In this thesis, we examine two conjunctions between GOES satellites and BARREL (Balloon Array for Radiation-belt Relativistic Electron Loss) to assess the relationship between broadband wave activity in the radiation belts and electron precipitation < 100 keV in Earth’s stratosphere. Motivated by the apparent co-occurrence of broadband waves and energetic precipitation during a 2013 event, we extend this analysis across multiple days of conjunction to better define the relationship. Ultimately, we find a statistically significant association between broadband waves and electron precipitation < 100 keV.

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