Date of Graduation

1997

Document Type

Dissertation/Thesis

Abstract

Important aspects of the generation and propagation of Inhomogeneous Energy-Density Driven (IEDD) waves are reported. Some aspects confirm significant and detailed predictions from theory and some aspects reveal significant and unexpected behavior. The IEDD instability requires an inhomogeneous profile of plasma flow, which is created in these experiments by producing a radially localized radial electric field in the magnetized plasma column of the WVU Q machine. The {dollar}{lcub}\\bf E{rcub}x{lcub}\\bf B{rcub}{dollar} speed resulting from this electric field will consequently have a radial profile whose maximum velocity and radial dimension are controlled by adjusting the biases applied to the segmented disk end electrode used to produce the electric field. Mode characteristics are measured for a variety of plasma conditions, ion species, bias potential configurations, and magnetic field strengths. Multiple, simultaneous spectral features, at large and comparable amplitudes are identified with specific eigenstates of the theoretical model. These eigenmodes are Doppler-shifted by the azimuthal flow such that eigenmode frequencies range from above the ion cyclotron frequency to low frequencies typically associated with ion acoustic waves. Cases in which the parallel component of the wavenumber is parallel and anti-parallel to the magnetic-field-aligned current are documented. A discussion is included on the revelance of these laboratory results to recent SCIFER and AMICIST experiments in the Earth's ionosphere where broadband, low frequency, electrostatic waves are observed in strong correlation to transverse ion acceleration events at values of magnetic field-aligned current that are marginal for the well-known ion acoustic and current-driven ion cyclotron instabilities.

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