Masao Sugawa

The effect of dust charge fluctuations on ion cyclotron wave instability in the presence of an ion beam in a plasma cylinder

An ion beam propagating through a magnetized dusty plasma cylinder drives electrostatic dust ion cyclotron waves to instability via Cerenkov interaction. The growth rate of the instability increases with the relative density δ (=n0i/n0e) of negatively charged dust. The growth rate scales as the one-third power of the beam density. The frequency of the unstable wave also increases with the relative density δ of negatively charged dust. The results of the theory are applied to explain some of the experimental observations of Barkan et al. [Planet. Space Sci. 43, 905 (1995)].

Nonlinear Landau damping of electrostatic waves in an electron beam‐plasma system

The nonlinear Landau damping and growth of electrostatic waves in an electron beam‐plasma system in a magnetic field has been observed experimentally. The space charge wave of the beam decays into the Trivelpiece mode, which is amplified exponentially by increasing the amplitude of the pump wave.

Absorption of far‐infrared radiation by alkali halide aqueous solutions

The absorption of radiation in the frequency range 10–80 cm−1 by 2 mol/l electrolyte solutions has been investigated. The absorption at low frequencies below 20 cm−1 is dominantly attributed to the dielectric relaxation of water dipole. At frequencies higher than 40 cm−1, resonance absorption by ion oscillation in a potential well formed by surrounding water molecules comes to contribute to the absorption.

Far infrared absorption by electrolyte solutions

The far infrared absorption spectra of aqueous solution of LiCl have been investigated in a frequency range 8–40 cm−1 at room temperature. In low frequency range (8–20 cm−1), the absorption is mainly controlled by Debye relaxation of the electric dipole rotation, and the absorption decreases with the increase of concentration.

Observation of Nonlinear Landau Damping of Electrostatic Waves in an Electron Beam-Plasma System

The nonlinear Landau damping and growth of electrostatic waves in an electron beam-plasma system in a magnetic field have been observed experimentally. The space charge wave of the beam decays nonlinearly into the Trivelpiece-Gould mode, satisfying the resonant condition ω 0 -ω 1 -( k //0 - k //1 )ν b = m ω c ( m is an integer). This decayed wave can be amplified exponentially by increasing the amplitude of the pump wave. Similarly, an externally launched small amplitude test wave, having the same frequency as the decayed wave, can be amplified at the comparable rate. The nonlinear Landau damping coupling coefficients measured experimentally are in good agreement with theory. The virtual wave has also been observed. The pump wave amplitude decays strongly by the presence of the large amplitude test wave.

Behaviors of electrostatic ion cyclotron waves excited in ion beam-plasma systems☆

Abstract Experimental results are presented for a behavior of the electrostatic ion cyclotron waves excited in an ion beam-plasma system. This wave appears as forward and backward waves with respect to the propagating component along the magnetic field.

Numerical Study of Ion Heating Due to Nonlinear Landau Damping in an Ion Beam-Plasma System

Ion heating due to nonlinear Landau damping in an ion beam-plamsa system is studied numerically by solving a set of equations representing the distortion of ion velocity distribution by this instability, where fast or slow space charge wave of an ion beam decays into Trivelpiece-Gould mode by nonlinear interaction with plasma ions and causes ion heating. A nonlinear Landau damping of a usual type by fast space charge wave shows that the ion temperature grows almost exponentially in initial time and saturates. A nonlinear Landau damping of an explosive type by slow space charge wave with negative energy exhibit an explosion of ion temperature and amplitude of all related waves at an explosion time. Considering effect of ion heating which makes nonlinear wave-particle coupling coefficients reduced, it is found that the explosion time of ion heating by slow space charge wave becomes several times larger than the original explosion time.

Excitation of electron cyclotron harmonic waves due to helical electron beams in a plasma

Abstract Instabilities of electron cyclotron harmonic waves due to the anisotropy of the velocity distribution of electrons which was produced by the injection of the electron beam perpendicular to the magnetic field have been observed.

Submillimeter spectroscopic study of concentrated electrolyte solutions as high density plasma

The transport property of ions in highly concentrated electrolyte solutions, which are governed by many body Coulomb interaction, are found to be well described by a model that ions behave as high density strongly coupled plasma irrespective of ion species. The frequency of plasma oscillation, which is the long-range collective motion of plasma, is estimated to be order of 1 THz for concentrated electrolyte solutions, and evidence of the plasma oscillation can be searched by submillimeter spectroscopy. Transmission and reflection spectra of the concentrated electrolyte solutions have been measured in the 10 to 50 cm−1 range, and the real and imaginary parts of refractive indices for the solutions are obtained. A close inspection of these spectral data suggests that the plasma oscillation is not excited in the highly concentrated electrolyte solutions. This is probably caused by that the long-range collective motion of ions is disturbed by short-range solute–solvent interaction.

Nonlinear Amplitude Oscillations of Obliquely Propagating Bernstein Waves in a Plasma

Electrostatic electron cyclotron harmonic waves are observed to executed amplitude oscillations. Observed results are consistent with the expected periodic energy exchanges between the wave and trapped electron particles.