J. Vaclavik

Spectrum of low-frequency, nonaxisymmetric oscillations in a cold, current-carrying plasma column

Reference CRPP-ARTICLE-1983-008View record in Web of Science Record created on 2008-04-16, modified on 2017-05-12

Dynamics of Coupled Solitons

Keywords: LRP 125 Reference CRPP-REPORT-1977-001 Record created on 2008-04-18, modified on 2017-05-12

Electromagnetic radiation from an inhomogeneous plasma: theory and experiment

The problem of the linear conversion of a Langmuir wave to a transverse electromagnetic wave in the presence of a density gradient has been solved numerically with appropriate boundary conditions. A reciprocity principle was found, allowing the deduction of solutions of this problem from those obtained from the transverse‐Langmuir conversion. This model has been applied to study the spectrum emitted from an inhomogeneous plasma, including the effect of the antenna radiation pattern. Experiments have been performed in a large unmagnetized dc discharge plasma (ne∼5×1010 cm−3, Te = 1.3 eV, gradient scale length L = 100−1000 cm). The shape of the spectrum observed with a horn antenna agrees with the theoretical one, but the deduced level of Langmuir fluctuations is much higher than the thermal level. This enhancement is due to the presence of primary energetic (E = 60 eV) electrons.

Cerenkov and anomalous Doppler effects in the relaxation of an electron beam

The interplay between the Cerenkov and anomalous Doppler interactions in the relaxation of a warm electron beam is investigated by numerical means. The most important feature in the interplay is found to be a nonelastic isotropization. A simple semianalytical model which allows one to estimate various quantities relevant to the relaxation process is also presented.

Quasisteady turbulence driven by runaway electrons

The evolution of the turbulence driven by runaway electrons has been followed by means of a computer code based on the quasilinear equations. The evolution is not characterized by periodic relaxations as claimed in previous works but ends in a quasisteady turbulent, yet very persistent state, accessible from different initial conditions. This discrepancy is clarified as being due to the excessive stiffness of the moment equations used to demonstrate the relaxations. Moreover, a theory is developed to interpret the quasisteady state found.

Adiabatic Interaction of Coherent Waves with Weak Turbulence in Plasmas

Reference CRPP-ARTICLE-1980-002doi:10.1063/1.863204View record in Web of Science Record created on 2008-04-16, modified on 2017-05-12

The ponderomotive force in a magnetized plasma: The effect of radio‐frequency‐induced magnetization

The ponderomotive force acting on a magnetized plasma resulting from a radio‐frequency (rf) electric field is studied both theoretically and experimentally. The fundamental difference between the predictions of the single‐particle and fluid approaches is emphasized and its origin elucidated. An experiment is described that illustrates the collective interaction of a fluid with an rf field. This collective behavior manifests itself in the perpendicular ponderomotive force by the interaction of the rf‐induced magnetization current with the magnetic field.

Quasi-linear theory without the random phase approximation

The system of quasi‐linear equations is derived without making use of the random phase approximation. The fluctuation quantities are described by the autocorrelation function of the electric field using the techniques of Fourier analysis. The resulting equations possess the necessary conservation properties, but comprise new terms which hitherto have been lost in the conventional derivations.

Quasilinear Theory of Inhomogeneous Magnetized Plasmas

Reference CRPP-ARTICLE-1983-030View record in Web of Science Record created on 2008-04-16, modified on 2017-05-12

Quasi‐linear theory of the current‐driven ion‐acoustic turbulence in a weakly ionized plasma

Saturation of the current‐driven ion‐acoustic instability in a weakly ionized plasma is investigated within the context of a quasi‐linear model that includes the effects of collisions. The turbulent wave energy is calculated under the assumption that the waves are excited within the cone of a small angle. The results obtained compare favorably with the recent experimental observations of Ilic.