RESONANCE EXCITATION OF LINEAR AND NON-LINEAR SPIRAL DENSITY WAVES IN A GASEOUS DISK.
Item
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Title
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RESONANCE EXCITATION OF LINEAR AND NON-LINEAR SPIRAL DENSITY WAVES IN A GASEOUS DISK.
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Identifier
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AAI8801691
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identifier
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8801691
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Creator
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CHENG, YE.
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Contributor
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Chi Yuan
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Date
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1987
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Language
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English
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Publisher
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City University of New York.
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Subject
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Physics, Astronomy and Astrophysics
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Abstract
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This thesis develops the theory of linear and non-linear density and/or acoustic waves in a gaseous disk responding to a periodic perturbational force, such as that caused by a satellite in a ring system, or by a rotating mass distortion in the central region of a galaxy.;Based on the non-linear formulation devised by Shu, Yuan and Lissauer (1985), we rederive a fundamental integro-differential equation with the inclusion of all three factors: pressure, self-gravity and viscosity. To apply this equation, physical parameters used in various astrophysics problems are examined and approximations justified. The amplitude relation and the dispersion relation indicate the appropriate replacement for the integro-differential equation by a non-linear differential equation. These relations also describe the features of the excitation and propagation processes.;We work out a complete linear theory of density and/or acoustic waves with viscosity and self-gravity. We study the excitation mechanism by which the waves are generated in the gaseous disk. The asymptotic solutions to the linearized equation which are presented along with the numerical solutions help to clarify several important aspects concerning the nature of the waves in a disk system.;In an application to the 3-kpc arm problem in the Galaxy, we solve the non-linear differential equation numerically with the aid of the linear solutions. We find that an oval distortion of 5% of the mean gravitational field near the outer Lindblad resonance can generate a wave in a close resemblance to the observed 3-kpc arm.;The present theory has potential applications to astrophysical problems such as the proto-stellar disk of the solar nebula, the possible existence of the circumstellar disk of a binary, and the structure of barred galaxies.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
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Program
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Physics
