Honors Theses and Capstones

Date of Award

Spring 2020

Project Type

Senior Honors Thesis

College or School

CEPS

Department

Physics and Astronomy

Program or Major

Physics

Degree Name

Bachelor of Science

First Advisor

Jonathan Niehof

Second Advisor

Nathan Schwadron

Abstract

Results from the Advanced Composition Explorer (ACE) and the Ulysses spacecraft suggested the existence of a pervasive power-law spectrum of suprathermal ions in the solar wind with a spectral index of -3/2. This distribution is of particular interest to humanity because the suprathermal ions it describes can serve as the seed population for large, destructive events that can harm ground- and air-based equipment. It has been suggested that various statistical mechanisms can produce the observed spectrum, however the underlying physical phenomena are not yet known. The spectrum of suprathermal ions is relatively unstudied closer to the Sun than 1 au. I investigate the first year and a half of Parker Solar Probe's data to find evidence of this spectrum in this previously unstudied region. I find weak evidence to suggest the existence of a common spectrum of protons from 60 to 200 keV inside the region being studied. Naive fits to all of the events fail to produce the expected -3/2, yet some relationship between magnetic turbulence and spectral index is found, as is an apparent relationship between radial distance and spectral index, suggesting some type of asymptotic approach to index -3/2 as radial distance increases. Additionally, my results are not incompatible with recent adaptations to some statistical models that yield softer spectra. Further work is required to uncover the phenomena in this region that determine the shape of the solar wind spectrum.

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