Date of Award

Summer 2022

Project Type

Dissertation

Program or Major

Physics

Degree Name

Doctor of Philosophy

First Advisor

Marc Lessard

Second Advisor

Lynn Kistler

Third Advisor

Elena Long

Abstract

Ultra Low Frequency (ULF) waves are geomagnetic perturbations in the mHz to Hz range that contribute both directly and indirectly to particle losses in the radiation belts. Pi1B waves are ULF broadband bursts in the Pi1 range that are well correlated with substorm onset. Intervals of Pulsations of Diminishing Periods (IPDPs) are a sub-type of ULF Electromagnetic Ion Cyclotron (EMIC) waves that are characterized by an increase in frequency over time. IPDPs are thought to be generated by particles injected at substorm onset. One of the main instruments used to identify ULF waves is the searchcoil magnetometer. In this dissertation, hardware work related to searchcoil magnetometers as well as results from two studies that use searchcoil magnetometers to study substorm-driven ULF waves will be presented. The first uses a combination of case studies and simulations to examine the role that drift shell splitting plays in the generation and observation of IPDPs. This study finds that while the generation of IPDPs is dominated by injection boundary effects, the effects of drift shell splitting will influence the horizontal time-frequency characteristics of observed IPDP waves. The second involves a statistical study that compares substorm onsets identified using SuperMAG’s SML index and its derived substorm lists to IPDP observations. This statistical study uses Pi1B waves as a tool to filter the involved datasets, and finds that while there is little difference in SML trend for substorm onsets that occurred with and without correlated IPDP waves, there is some indication that not all IPDPs are generated by substorm onset.

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