Date of Award
Doctor of Philosophy (PhD)
Physics and Astronomy
Dieter H Hartmann
When a high-mass star (& 4Msun) explodes at the end of its life, a supernova occurs, leaving its degenerate core and a fast-moving shell of matter, known as a supernova remnant (SNR). The SNR shell lasts for many thousands of years, generating emissions from low-frequency radio (~ 10-7 eV) up to γ-ray regime (~ 1015 eV). It is also believed that SNRs are the predominant source of galactic cosmic rays, accelerating a population of thermal ions, primarily protons, up to relativistic energies by means of the diffusive shock acceleration (DSA) mechanism. The small population of thermal (Boltzmann) particles, p ~ 10-3 eV, that are accelerated to relativistic energies, p ~ 1015 eV, extract a significant amount of energy from the SNR shell. The existence of a small but highly energetic population of non-thermal particles feeds back into the dynamic evolution of the SNR, which, in turn, affects the production of new particles and the continued acceleration of particles already swept up in the shock. Much research has been done in investigating the case of particles accelerated in spherically symmetric SNRs; we present here the first simulations of supernova remnant evolution with nonlinear cosmic ray feedback in multiple dimensions. The research here presents a new approach to an old problem, allowing for a deeper investigation into the role of cosmic ray production in supernova remnant environments. The findings here show that, at the early stages of SNR evolution, the presence of cosmic rays in the shocks modifies the growth of hydrodynamic instabilities; severely damping the Rayleigh-Taylor instabilities in particular. We also find that the young remnant produces a strong TeV population of CRs that can generate TeV emissions that could be observed with or without the SNR interacting with an adjacent molecular cloud. However, the GeV emissions that could distinguish between the hadronic and leptonic population of CRs could not be observed by Fermi-LAT without the interacting molecular cloud.
Wood, Joshua, "Multidimensional Simulations of Non-linear Cosmic Ray Production in Supernova Remnant Evolution" (2014). All Dissertations. 1515.