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

Die vorliegende Arbeit beschäftigt sich mit zwei Aspekten der Gammastrahlungsastronomie. Einerseits studiert sie die Anforderungen an das zukünftige CTA-Observatorium für Gammastrahlung und präsentiert insbesondere Abschätzungen der Datenmengen, die während des Betriebs des Observatoriums anfallen werden. Für das größere CTA-Teleskopfeld auf der Südhalbkugel werden demnach eine Triggerate von 13 kHz und Datenraten von bis zu 2500 MB/s erwartet. Unter der Annahme, dass 15% der Zeit für Beobachtungen genutzt werden können, ergibt sich in 15 Jahren ein Datenvolumen von bis zu 165 PB. Die Implementation eines entsprechenden Systems zur Datenerfassung und -speicherung stellt eine Herausforderung dar, die jedoch mit existierenden Technik bewältigt werden kann. Andererseits befasst sie sich mit dem Supernovaüberrest RX J0852.0-4622 (auch bekannt als Vela Junior), präsentiert die Ergebnisse einer Analyse von Daten, die mit dem H.E.S.S.-Experiment genommen wurden, und geht der Frage nach, ob RX J0852.0-4622 ein kosmischer Teilchenbeschleuniger ist. Dabei erlauben die präzisen Messungen eine im Vergleich zu früheren Veröffentlichungen verbesserte Bestimmung der Eigenschaften der emittierenden Teilchenpopulation. Es ergibt sich, dass das Energiespektrum von RX J0852.0-4622 ein Potenzgesetz ist, das zu hohen Energien hin mit einer Abschneideenergie von 7.2 TeV exponentiell unterdrückt wird. Abschließend wird anhand von Simulation gezeigt, dass CTA die Abschneideenergie von RX J0852.0-4622 signifikant besser bestimmen können wird. Diese genauere Vermessung des Energiespektrums sollte dazu beitragen, den hadronischen oder leptonischen Charakter der Emission aufzuklären. / This work focuses on two different aspects of gamma-ray astronomy. On the one hand, it studies the instrumental challenge posed by the future CTA Observatory by estimating the amount of data to be collected. Based on an analysis of simulated data, the more demanding southern array is expected to have an array trigger rate of 13 kHz, a data rate of up to 2500 MB/s and a data volume after 15 yr of operation and assuming a duty cycle of 15% of up to 165 PB. The design of the data acquisition and storage systems will be a challenge but should be manageable with existing technologies. On the other hand, it studies supernova remnants, by presenting analysis results of the gamma-ray data of the RX J0852.0-4622 supernova remnant (commonly known as Vela Junior) measured with the operating H.E.S.S. experiment and interpreting them in order to check the plausibility of RX J0852.0-4622 being a cosmic ray accelerator. The more precise measurements permit a better determination of the parent particle population properties with respect to previous publications. More precisely, a clear curvature of the spectrum of RX J0852.0-4622 is measured with an exponential energy cut-off at 7.2 TeV. Finally, the analysis of simulated data shows that CTA should be able to significantly improve the determination of the spectral energy cut-off of RX J0852.0-4622, which should help in identifying the nature of the gamma-ray emission.

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