Browsing by Author "Hadley, Kathryn Z., 1955"
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Hadley, Kathryn Z., 1955 (University of Oregon, March , 2011)[more][less]Hadley, Kathryn Z., 1955 20110613T16:58:48Z 20110613T16:58:48Z 201103 http://hdl.handle.net/1794/11253 xvii, 371 p. : col. ill. An important problem in astrophysics involves understanding the formation of planetary systems. When a starforming cloud collapses under gravity its rotation causes it to flatten into a disk. Only a small percentage of the matter near the rotation axis falls inward to create the central object, yet our Sun contains over 99% of the matter of our Solar System. We examine how global hydrodynamic instabilities transport angular momentum through the disk causing material to accrete onto the central star. We analyze the stability of polytropic disks in the linear regime. A power law angular velocity of power q is imposed, and the equilibrium disk structure is found through solution of the timeindependent hydrodynamic equations via the Hachisu selfconsistent field method. The disk is perturbed, and the timedependent linearized hydrodynamic equations are used to evolve it. If the system is unstable, the characteristic growth rate and frequency of the perturbation are calculated. We consider modes with azimuthal e im[varphi] dependence, where m is an integer and [varphi] is the azimuthal angle. We map trends across a wide parameter space by varying m , q and the ratios of the startodisk mass M * /M d and innertoouter disk radius r  /r + . We find that low m modes dominate for small r  /r + , increasing to higher r  /r + as M * /M d increases, independent of q . Three main realms of behavior are identified, for M * << M d , M * [approximate] M d and M * >> M d , and analyzed with respect to the I, J and P mode types as discussed in the literature. Analysis shows that for M * << M d , small r  /r + disks are dominated by low m I modes, which give way to high m J modes at high r  /r + . Low m J modes dominate M * [approximate] M d disks for small r  /r + , while higher m I modes dominate for high r  /r + . Behavior diverges with q for M * >> M d systems with high q models approximating M * [approximate] M d characteristics, while low q models exhibit m = 2 I modes dominating where r  /r + < 0.60. Committee in charge: Raymond Frey, Chairperson; James Imamura, Advisor; Robert Zimmerman, Member; Paul Csonka, Member; Alan Rempel, Outside Member en_US University of Oregon University of Oregon theses, Dept. of Physics, Ph. D., 2011; Hydrodynamics Stability Polytropic disks Astrophysics Astronomy Linear stability analysis of nonaxisymmetric instabilities in selfgravitating polytropic disks Thesis
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