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The internal structure of alpha-accretion discs

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posted on 15.12.2014, 10:40 by Daniel Anthony Westwood. Heron
In this thesis we develop a mathematical model to describe the internal structure of an -accretion disc. The method is to consider the standard thin disc as a zero order approximation to a disc with vertical structure. The order of the approximation is controlled by the parameter 1/M2, where M is the Mach number of the azimuthal flow is a fiducial point. The theory is developed analytically as far as possible, using numerical solutions for the final system of ordinary differential equations only.;The model expands upon the work of other authors by assuming a disc surface defined by the condition of pressure balance between the disc and its environment. Vertically transported angular momentum is extracted by coupling to these surroundings. In the absence of an external couple, the vertical transport of angular momentum is ignored, as in the standard thin disc.;The internal structure and stability of the disc is investigated in both the gas and radiation pressure dominated regions, and the effects of including advection and the vertical transport of angular momentum is discussed. An application of the disc model is presented whereby external heating from X-rays associated with a radio jet are shown to induce mass loss from the disc surface. Such a configuration may undergo symmetry breaking to an asymmetric state in which one jet dominates. This is therefore a possible model for intrinsically one-sided radio sources.


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University of Leicester

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