Abstract
In this work we discuss the methods of bispectral analysis and their limitations. In order to study some special features, we will apply them to fluctuation data of the scrape-off-layer of the tokamak ASDEX. The fluctuations are monitored by the H{sub {alpha}}-diagnostic and by probes. The evaluation of the bispectrum is a statistical method to measure the phase-coherence between three Fourier components of the measured time series. This coherence can be discussed in terms of two different pictures: First the fluctuations can be regarded as a superposition of many independent waves, which can be identified with the Fourier components. The lowest order nonlinear interaction among them is the coupling of two waves to produce a new wave, either at the sum or at the difference frequency. These three waves have a fixed phase relation caused by the interaction, independent of the different realizations. On the other hand the plasma fluctuations can be regarded as a superposition of many independent plasma events. If most of the events are of the same shape, the Fourier components of any realization will show a strong relationship with each other. This paper interprets the results mostly in terms of the wave picture.
Citation Formats
Weinlich, M.
Study of the three-waves-coherence in fluctuations of the ASDEX scrape-off-layer; Untersuchung von Drei-Wellen-Kopplungen in den Fluktuationen der ASDEX-Abschaelschicht.
Germany: N. p.,
1992.
Web.
Weinlich, M.
Study of the three-waves-coherence in fluctuations of the ASDEX scrape-off-layer; Untersuchung von Drei-Wellen-Kopplungen in den Fluktuationen der ASDEX-Abschaelschicht.
Germany.
Weinlich, M.
1992.
"Study of the three-waves-coherence in fluctuations of the ASDEX scrape-off-layer; Untersuchung von Drei-Wellen-Kopplungen in den Fluktuationen der ASDEX-Abschaelschicht."
Germany.
@misc{etde_10136530,
title = {Study of the three-waves-coherence in fluctuations of the ASDEX scrape-off-layer; Untersuchung von Drei-Wellen-Kopplungen in den Fluktuationen der ASDEX-Abschaelschicht}
author = {Weinlich, M}
abstractNote = {In this work we discuss the methods of bispectral analysis and their limitations. In order to study some special features, we will apply them to fluctuation data of the scrape-off-layer of the tokamak ASDEX. The fluctuations are monitored by the H{sub {alpha}}-diagnostic and by probes. The evaluation of the bispectrum is a statistical method to measure the phase-coherence between three Fourier components of the measured time series. This coherence can be discussed in terms of two different pictures: First the fluctuations can be regarded as a superposition of many independent waves, which can be identified with the Fourier components. The lowest order nonlinear interaction among them is the coupling of two waves to produce a new wave, either at the sum or at the difference frequency. These three waves have a fixed phase relation caused by the interaction, independent of the different realizations. On the other hand the plasma fluctuations can be regarded as a superposition of many independent plasma events. If most of the events are of the same shape, the Fourier components of any realization will show a strong relationship with each other. This paper interprets the results mostly in terms of the wave picture.}
place = {Germany}
year = {1992}
month = {Jan}
}
title = {Study of the three-waves-coherence in fluctuations of the ASDEX scrape-off-layer; Untersuchung von Drei-Wellen-Kopplungen in den Fluktuationen der ASDEX-Abschaelschicht}
author = {Weinlich, M}
abstractNote = {In this work we discuss the methods of bispectral analysis and their limitations. In order to study some special features, we will apply them to fluctuation data of the scrape-off-layer of the tokamak ASDEX. The fluctuations are monitored by the H{sub {alpha}}-diagnostic and by probes. The evaluation of the bispectrum is a statistical method to measure the phase-coherence between three Fourier components of the measured time series. This coherence can be discussed in terms of two different pictures: First the fluctuations can be regarded as a superposition of many independent waves, which can be identified with the Fourier components. The lowest order nonlinear interaction among them is the coupling of two waves to produce a new wave, either at the sum or at the difference frequency. These three waves have a fixed phase relation caused by the interaction, independent of the different realizations. On the other hand the plasma fluctuations can be regarded as a superposition of many independent plasma events. If most of the events are of the same shape, the Fourier components of any realization will show a strong relationship with each other. This paper interprets the results mostly in terms of the wave picture.}
place = {Germany}
year = {1992}
month = {Jan}
}