Date of Graduation


Document Type


Degree Type



Eberly College of Arts and Sciences


Physics and Astronomy

Committee Chair

Richard Treat

Committee Member

Earl Scime

Committee Member

Mark Koepke


A program to implement a spectral analysis technique called the bispectrum was written and tested with computer generated time series data. The application of the algorithm to the study of nonlinear interactions was demonstrated by a comparison of computed quantities with results from model equations found in the literature. Specifically determined were: the amplitude and phase of coupling coefficients, the power transfer function, the fraction of power associated with nonlinear coupling, and the identification of waves involved in a quadratic coupling interaction. A method of distinguishing the two parent waves from the daughter wave in this three-wave interaction is proposed as a new application of the technique. These results, as well as the values computed from a Monte Carlo simulation of plasma turbulence were found to be consistent with expectations. Two experimental systems were investigated with the bispectrum. One was the periodically pulled time series data of a driven van der Pol oscillator (unijunction transistor circuit) which contained significant bispectral features but no real evidence of quadratic coupling. The other was plasma fluctuation data from the WVU-Q Machine, where the inhomogeneous energy-density driven mode exhibited a degree of coupling to lower frequencies that was absent in the case of the current driven mode.

Included in

Physics Commons