Degree Type

Dissertation

Date of Award

2010

Degree Name

Doctor of Philosophy

Department

Physics and Astronomy

First Advisor

Martin Pohl

Second Advisor

Frank Krennrich

Abstract

Cosmic rays, the product of natural extraterrestrial particle accelerators far more powerful than the LHC, were first detected a century ago. A "standard model" of cosmic-ray acceleration in supernova remnants has begun to emerge, but a number of questions still require satisfactory answers. The maximum particle energy attainable via the most favored mechanism, diffusive shock acceleration, is limited by the amplitude of magnetic-field turbulence in the unshocked interstellar or circumstellar medium, but cosmic rays are observed at high enough energies that some magnetic-field amplification is required. By what mechanisms might this amplification occur, and can it operate to a great enough extent to account for those cosmic rays thought to be of Galactic origin? A number of proposed solutions involve instabilities arising from interactions between cosmic rays and the upstream plasma, whose evolution becomes highly nonlinear. A related question explored is whether the presence of accelerated particles in the shock vicinity has any microscopic effect on the instabilities governing the shock itself. Particle-in-cell kinetic simulations allow us to investigate the growth and saturation of these instabilities at the (astrophysically) microscopic scale, providing valuable insights and important considerations for self-consistent macroscopic models of particle acceleration.

DOI

https://doi.org/10.31274/etd-180810-1843

Copyright Owner

Thomas Alan Stroman

Language

en

Date Available

2012-04-30

File Format

application/pdf

File Size

94 pages

Included in

Physics Commons

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