This study focusses on modelling important aspects of the evolution of pulsar wind nebulae
using two different approaches. The first uses a hydrodynamic model to simulate the morphological
evolution of a spherically-symmetric composite supernova remnant that is expanding
into a homogeneous interstellar medium. In order to extend this model, a magnetic field is
included in a kinematic fashion, implying that the reaction of the fluid on the magnetic field
is taken into account, while neglecting any counter-reaction of the field on the fluid. This approach
is valid provided that the ratio of electromagnetic to particle energy in the nebula is
small, or equivalently, for a large plasma β environment. This model therefore allows one to
not only calculate the evolution of the convection velocity but also, for example, the evolution
of the average magnetic field.
The second part of this study focusses on calculating the evolution of the energy spectra of
the particles in the nebula using a number of particle evolution models. The first of these is
a spatially independent temporal evolution model, similar to the models that can be found
in the literature. While spatially independent models are useful, a large part of this study
is devoted to developing spatially dependent models based on the Fokker-Planck transport
equation. Two such models are developed, the first being a spherically-symmetric model that
includes the processes of convection, diffusion, adiabatic losses, as well as the non-thermal
energy loss processes of synchrotron radiation and inverse Compton scattering. As the magnetic
field geometry can lead to the additional transport process of drift, the previous model is
extended to an axisymmetric geometry, thereby allowing one to also include this process. / PhD (Space Physics), North-West University, Potchefstroom Campus, 2014
| Identifer | oai:union.ndltd.org:NWUBOLOKA1/oai:dspace.nwu.ac.za:10394/10861 |
| Date | January 2014 |
| Creators | Vorster, Michael Johannes |
| Source Sets | North-West University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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