Chaos and turbulence studies in low- plasmas (original) (raw)
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Drift waves and chaos in a LAPTAG plasma physics experiment
American Journal of Physics, 2016
In a project involving an alliance between universities and high schools, a magnetized plasma column with a steep pressure gradient was established in an experimental device. A two-dimensional probe measured fluctuations in the plasma column in a plane transverse to the background magnetic field. Correlation techniques determined that the fluctuations were that of electrostatic drift waves. The time series data were used to generate the Bandt-Pompe entropy and Jensen-Shannon complexity for the data. These quantities, when plotted against one another, revealed that a combination of drift waves and other background fluctuations were a deterministically chaotic system. Our analysis can be used to tell the difference between deterministic chaos and random noise, making it a potentially useful technique in nonlinear dynamics. V
Nonlinear Dynamics and Chaos in Gas Discharge Systems
Le Journal de Physique IV, 1995
This paper summarizes recent experimental work on nonlinear dynamical phenomena in gas discharge plasmas. As a relatively simple example, chaotic oscillations in low-pressure thermionic discharges are discussed in detail. Period doubling bifurcations and intermittency are clearly identified as standard routes to chaotic behaviour. Most of its dynamical features are well described by simple nonlinear oscillator models. In contrast, plasma waves are spatiotemporal phenomena and thus show a much richer dynamical behaviour. This is demonstrated for currentdriven drift waves in a linear magnetized plasma. Probe arrays provide the required information about the time evolution of the azimuthal wave structure.
Physics of Plasmas, 2014
Intermittent chaos was observed in a glow discharge plasma as the system evolved from regular type of relaxation oscillations (of larger amplitude) to an irregular type of oscillations (of smaller amplitude) as the discharge voltage was increased. Floating potential fluctuations were analyzed by different statistical and spectral methods. Features like a gradual change in the normal variance of the interpeak time intervals, a dip in the skewness, and a hump in the kurtosis with variation in the control parameter have been seen, which are strongly indicative of intermittent behavior in the system. Detailed analysis also suggests that the intrinsic noise level in the experiment increases with the increasing discharge voltage. An attempt has been made to model the experimental observations by a second order nonlinear ordinary differential equation derived from the fluid equations for an unmagnetized plasma. Though the experiment had no external forcing, it was conjectured that the intrinsic noise in the experiment could be playing a vital role in the dynamics of the system. Hence, a constant bias and noise as forcing terms were included in the model. Results from the theoretical model are in close qualitative agreement with the experimental results. V C 2014 AIP Publishing LLC. [http://dx.
Drift wave turbulence in low- plasmas
Plasma Physics, 1983
Experimental investigations of strong turbulence associated with the radial density gradient of a rotating magnetized plasma column are reported. The experiment is designed to make Taylor's hypothesis effective, in order to allow a simple interpretation of measured frequency spectra in terms of wavenumber spectra. The spectral index of the turbulent potential fluctuations is determined and the variation of the spectral intensity is investigated for varying magnetic fields. The results compare favourably with theoretical predictions. The importance of distinguishing subranges in the turbulent spectrum is demonstrated. Some aspects of the relative diffusion of a test-cloud of charged particles released in the turbulent field 2re discussed.
Spatiotemporal bifurcations in plasma drift-waves
Eprint Arxiv Chao Dyn 9510001, 1995
Experimental data from an experiment on drift-waves in plasma is presented. The experiment provides a space-time diagnostic and has a control parameter that permits the study of the transition from a stable plasma to a turbulent plasma. The biorthogonal decomposition is used to analyse the data. We introduce the notion of complex modulation for two-dimensional systems. We decompose the real physical system into complex modulated monochromatic travelling waves and give a simple model describing the speed doubling observed in the data as the control parameter increases.
Drift-Wave Turbulence in Low-β Plasmas
Physica Scripta, 1982
Experimental investigations of strong turbulence associated with the radial density gradient of a rotating magnetized plasma column are reported. The experiment is designed to make Taylor's hypothesis effective, in order to allow a simple interpretation of measured frequency spectra in terms of wavenumber spectra. The spectral index of the turbulent potential fluctuations is determined and the variation of the spectral intensity is investigated for varying magnetic fields. The results compare favourably with theoretical predictions. The importance of distinguishing subranges in the turbulent spectrum is demonstrated. Some aspects of the relative diffusion of a test-cloud of charged particles released in the turbulent field 2re discussed.
A model for the bifurcations in plasma drift-waves
Physica D: Nonlinear Phenomena, 1997
Spatiotemporal data from a plasma drift-wave experiment are analyzed by the biorthogonal decomposition (BOD). A description of the route to turbulence is given in terms of modulated monochromatic traveling waves. A low-dimensional dynamical system decribing some of the features of the route to the weak turbulence observed is presented.
CHAOS AND HYPERCHAOS IN A SYMMETRICAL DISCHARGE PLASMA: EXPERIMENT AND MODELLING
În această lucrare prezentăm rezultate experimentale şi modelări computaţionale ale tranziţiei haos-hiperhaos în plasma unui sistem format din două descărcări electrice care se produc în acelaşi tub de sticlă şi au geometrii şi parametri identici. Caracteristicile plasmei din spaţiul inter-anodic sunt controlate de o tensiune de polarizare aplicată pe cei doi anozi. Dinamicile plasmei sunt investigate prin intermediul fluctuaţiilor de curent. Pentru un anumit domeniu al polarizării inter-anodice continue, se observă o tranziţie haos-hiperhaos. Prezentăm un model computaţional constând din trei oscilatori neliniari cuplaţi care conduce la rezultate în bună concordanţă cu cele experimentale.
Resistive Drift-Alfven Instability in Cylindrical Plasma : Fluids, Plasmas, and Electric Discharges
Journal of the Physical Society of Japan, 2000
Linearized eigenmode equations governing resistive drift-Alfvén modes are derived by using the two-fluid model for a cylindrical plasma with a uniform longitudinal magnetic field. The local dispersion relation shows that the shear Alfvén wave couples with the unstable resistive drift wave due to the finite Larmor radius effect measured with the electron temperature. The eigenmode equations are solved by the shooting method in the cylindrical plasma. Generally growth rates decrease with the increase of electron pressure for the larger m mode. This behavior seems consistent with a theoretical model that stabilization of drift-Alfvén wave induces the L(Low confinement)-H(High confinement) transition at the edge of tokamak plasma.
Low-dimensional chaos and wave turbulence in plasmas
2008
We investigated drift-wave turbulence in the plasma edge of a small tokamak by considering solutions of the Hasegawa-Mima equation involving three interacting modes in Fourier space. The resulting low-dimensional dynamics presented periodic as well as chaotic evolution of the Fourier-mode amplitudes, and we performed the control of chaotic behaviour through the application of a fourth resonant wave of small amplitude.