In this report, we analyze general relativistic effects on celestial bodies, including gravitational strength in different metrics, gravitational radiation, and frame-dragging. We present simulation methods for classical and general relativistic motion, through the use of systems of equations that may be numerically integrated. The amount of energy leaving the system as gravitational radiation is approximated using the quadrupole formula, and by using a binary pair of planetary bodies as an approximation for orbital motion. Here we demonstrate that classical approximations may be suitable in low-mass high-distance scenarios. The eccentricity of an orbit also affects the gravitational radiation and would have to be much less than one for reliable results. It is concluded that frame-dragging effects are negligible for slowly rotating objects only, which is a well-known result.

It has been noted by several authors that General Relativistic frame dragging in rotating neutron stars is a first order effect which has to be included in a self-consistent model of pulsar magnetospheric structure and associated radiation and transport processes. To this end, I undertook the present study with the aim of investigating the effect of General Relativity (GR) on millisecond pulsar (MSP) visibility. I developed a numerical code for simulating a pulsar magnetosphere, incorporating the GR-corrected expressions for the electric potential and field. I included curvature radiation (CR) due to primary electrons accelerated above the stellar surface, as well as inverse Compton scattering (ICS) of thermal X-ray photons by these electrons. I then applied the model to PSR J0437-4715, a prime candidate for testing the GR-Electrodynamic theory, and examined its visibility for the H.E.S.S. telescope. I also considered the question of whether magnetic photon absorption would take place for this particular pulsar. In addition, I developed a classical model for comparison with the GR results. I found that the typical electron energies and associated CR photon energies are functions of position above the polar cap (PC). These energies are also quite smaller in the GR case than in the classical case due to the different functional forms of the GR and classical electric fields. I found the CR energy cut-off to be ~ 4 GeV compared to the well-known classical value of ~ 100 GeV. Since the H.E.S.S. energy threshold is ~ 100 GeV, it seems as though the CR component will not be visible, contrary to wide-held opinion. However, the ICS component seems to be well in excess of the H.E.S.S. energy threshold and is expected to be visible. I also found that no pair production will take place for PSR J0437-4715. Hopefully, forthcoming H.E.S.S. observations will provide validation of these results. KEY WORDS: General relativistic frame dragging, GR electrodynamics, millisecond pulsar visibility, non-thermal radiation processes, pair production, H.E.S.S., individual pulsars: PSR J0437-4715. / Thesis (M.Sc. (Physics))--North-West University, Potchefstroom Campus, 2004.

It has been noted by several authors that General Relativistic frame dragging in rotating neutron stars is a first order effect which has to be included in a self-consistent model of pulsar magnetospheric structure and associated radiation and transport processes. To this end, I undertook the present study with the aim of investigating the effect of General Relativity (GR) on millisecond pulsar (MSP) visibility. I developed a numerical code for simulating a pulsar magnetosphere, incorporating the GR-corrected expressions for the electric potential and field. I included curvature radiation (CR) due to primary electrons accelerated above the stellar surface, as well as inverse Compton scattering (ICS) of thermal X-ray photons by these electrons. I then applied the model to PSR J0437-4715, a prime candidate for testing the GR-Electrodynamic theory, and examined its visibility for the H.E.S.S. telescope. I also considered the question of whether magnetic photon absorption would take place for this particular pulsar. In addition, I developed a classical model for comparison with the GR results. I found that the typical electron energies and associated CR photon energies are functions of position above the polar cap (PC). These energies are also quite smaller in the GR case than in the classical case due to the different functional forms of the GR and classical electric fields. I found the CR energy cut-off to be ~ 4 GeV compared to the well-known classical value of ~ 100 GeV. Since the H.E.S.S. energy threshold is ~ 100 GeV, it seems as though the CR component will not be visible, contrary to wide-held opinion. However, the ICS component seems to be well in excess of the H.E.S.S. energy threshold and is expected to be visible. I also found that no pair production will take place for PSR J0437-4715. Hopefully, forthcoming H.E.S.S. observations will provide validation of these results. KEY WORDS: General relativistic frame dragging, GR electrodynamics, millisecond pulsar visibility, non-thermal radiation processes, pair production, H.E.S.S., individual pulsars: PSR J0437-4715. / Thesis (M.Sc. (Physics))--North-West University, Potchefstroom Campus, 2004.

Les jets sont des phénomènes d’éjection collimatée de plasma magnétisé. Ces ph́énomènes liés à l’accrétion d’un disque sur un objet central, sont relativement répandus dans l’univers : les environnement des étoiles jeunes (objets Herbig-Haro, étoiles T Tauri), des binaires X, des sursauts gamma et les noyaux actifs de galaxies... Les jets extra-galactiques sont issus des trous noirs super-massifs au centre de galaxies telles que les quasars ou les radiogalaxies. Ils sont caractérisés par leur taille, leur puissance et la vitesse du plasma.Les jets extragalactiques sont étudiés dans de ce travail de thèse, même si les outils et méthodes développés peuvent être utilisés pour les binaires X et les micro-quasars. Nous poserons en particulier les questions des mécanismes de lancement, d’accélération et de collimation de ces écoulements. Nous traiterons également de la source énergétique à l’origine de l’écoulement qui peut atteindre une puissance de l’ordre de 10^47 erg.s−1.Le liens avec l’accrétion, la proximité de la base des jets avec le trou noir central, les vitesses d’écoulement observées dans certains jets, montrent que le traitement de ces questions doit inclure les effets de la relativité générale. Nous étudierons donc des solutions de la décomposition 3+1 des équations de la magnéto-hydrodynamique en métrique de Kerr. Nous nous appliquerons au développement d’un modèle d’écoulement méridional auto-similaire avec un traitement consistant du cylindre de lumière. Ce modèle pouvant s’appliquer à la fois au jet et à l’accrétion. Nous explorons les mécanismes d’accélération et de collimation des solutions produites. Nous calculerons des solutions de l’écoulement entrant dans l’horizon et de l’écoulement sortant à l’infini incluant des termes d’injection de paires. Le rôle du mécanisme de création de paires et des processus d’extraction de l’énergie du trou noir sera exploré. / Jets are collimated ejection phenomena of magnetized plasma. These phenomena related to the accretion of a disk on a central object, are relatively common in the universe: the environment of young stars (Herbig- Haro Objects, T Tauri stars...), X-ray binaries, Gamma-ray-bursts, and active galactic nuclei... Extragalactic jets come from super-massive black holes in the center of galaxies such as quasars or radiogalaxies. They are characterized by their size, their power and velecity of the plasma.Extragalactic jets will be the subject of studies in this thesis work, although the tools and methods developed can be used for X-ray binaries and microquasars. In particular, we will ask questions about the mechanisms of launching, accelerating and collimating these flows, but also about the energy source at the origin of the flow that can reach a power in the order of 10^47erg.s−1.The links with the accretion, the proximity of the jet base to the central black hole, flow velocities observed in some jets, show that the treatment of these issues must include the effects of general relativity. We will therefore study solutions of the 3+1 decomposition of magneto-hydrodynamic equations in Kerr metric. We will apply ourselves the development of a meridional self-similar magnetized flow model with a consistent treatment of the light cylinder effect. This model can be applied to both spine jet and accretion. We explore the mechanisms of acceleration and collimation of the obtained solutions. We will calculate solutions of the incoming flow in the horizon and the outgoing flow reaching infinity including injection terms. The role of the pair creation mechanism and the processes of extracting energy from the black hole are explored.

Thesis (Ph.D. (Space Physics)--North-West University, Potchefstroom Campus, 2008.

Thesis (Ph.D. (Space Physics)--North-West University, Potchefstroom Campus, 2008.

Thesis (Ph.D. (Space Physics)--North-West University, Potchefstroom Campus, 2008.