Honors Theses and Capstones
Date of Award
Spring 2018
Project Type
Senior Honors Thesis
College or School
CEPS
Department
Physics
Program or Major
Physics
Degree Name
Bachelor of Science
First Advisor
Benjamin Chandran
Second Advisor
Harald Kucharek
Abstract
Energetic particles accelerated by large solar flares and coronal mass ejections (CMEs) are a threat to astronauts, global positioning systems (GPS), radio communications, and power grids. It is therefore vital that scientists be able to predict how such particles move and gain energy within the interplanetary medium in order to forewarn society impending hazards so that mitigating actions can be taken. In this work, I take a step towards this goal, using the Energetic Particle Radiation Environment Module (EPREM) code, which is used by UNH's radiation-dosage predictions website, I model interstellar-pickup ions (PUIs). I add to the model by including a momentum-diffusion term which contributes to the change in the distribution as it evolves in time. Here, I investigate how the given model of momentum diffusion affects the energetic PUI population ($v>u_{sw}$). This analysis focuses on the power-law spectra of the suprathermal tail of the PUI distribution. When the velocity dependence of the diffusion coefficient is normalized to the local solar-wind velocity, I have found little to no change in the spectra of the suprathermal ion tails when momentum-diffusion is included; however, when the velocity dependence of the diffusion coefficient is not normalized, hardening of the spectra of the suprathermal ion tail is observed. It is possible that the effect of momentum-diffusion and particle acceleration in CIRs is the source of the energetic seed particle population, which makes up the available particles to be accelerated by a shock. In order to understand these potentially dangerous seed particles, we hope to use new observations from Parker Solar Probe to determine the acceleration processes, such as momentum-diffusion, that yield the observed spectra.
Recommended Citation
O'Shea, Evin C., "Modeling Momentum-Diffusion in the Solar Wind" (2018). Honors Theses and Capstones. 431.
https://scholars.unh.edu/honors/431