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Modeling geomagnetic storms on prompt and diffusive time scales / By Zhao Li

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Author	Li, Zhao
Title	Modeling geomagnetic storms on prompt and diffusive time scales / By Zhao Li
Date	2014
Abstract	The discovery of the Van Allen radiation belts in the 1958 was the first major discovery of the Space Age. There are two belts of energetic particles. The inner belt is very stable, but the outer belt is extremely variable, especially during geomagnetic storms. As the energetic particles are hazardous to spacecraft, understanding the source of these particles and their dynamic behavior driven by solar activity has great practical importance. In this thesis, the effects of magnetic storms on the evolution of the electron radiation belts, in particular the outer zone, is studied using two types of numerical simulation: radial diffusion and magnetohydrodynamics (MHD) test-particle simulation. A radial diffusion code has been developed at Dartmouth, applying satellite measurements to model flux as an outer boundary condition, exploring several options for the diffusion coefficient and electron loss time. Electron phase space density is analyzed for July 2004 coronal mass ejection (CME) driven storms and March-April 2008 co-rotating interaction region (CIR) driven storms, and compared with Global Positioning System (GPS) satellite measurements within 5 degrees of the magnetic equator at L-4.16. A case study of a month-long interval ii in the Van Allen Probes satellite era, March 2013, confirms that electron phase space density is well described by radial diffusion for the whole month at low first invariant ?400 MeV/G, but peaks in phase space density observed by the ECT instrument suite at higher first invariant are not reproduced by radial transport from a source at higher L. A 3D guiding center code with plasmasheet injection is used to simulate particle motion in time-dependent MHD fields calculated from the Lyon-Fedder-Mobarry global MHD code, as an extension of the Hudson et al. (2012) study of the Whole Heliosphere Interval of CIR-driven storms in March- April 2008. Direct comparison with measured fluxes at GOES show improved comparison with observations relative to the 2D guiding center test particle simulations and enhancement of flux at >0.6 MeV by an order of magnitude over 24 hours as observed.
Description	1 online resource (xi, 120 leaves) : illustrations (mostly color)
Format	application/pdf
College	Dartmouth College -- Department of Physics and Astronomy.
Issuing Body	Dartmouth Dissertations are made available through the Dartmouth Digital Library.
Degree	Thesis (Ph.D.)--Dartmouth College.
Copyright	All rights reserved. No part of this book may be reproduced in any form by any electronic or mechanical means without permission in writing from the author.
DOI	http://dx.doi.org/10.1349/ddlp.1609

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