Toshiro Ohnuma

Radiation Phenomena of Plasma Waves Part 1. Fundamental Radiation Theory

1. I. Preface Introduction Fundamentals for waves Il-1. Phase, group, and ray velocities 11-2 Phase velocity surface, group velocity surface, ray velocity surface, and refractive index surface 111. Fundamental radiation theory in an isotropic plasma 111-1. Radiation theory for electron plasma waves 111-2. Radiation theory for ion plasma waves 111-3. Generalized radiation theory in an isotropic plasma IV. Electromagnetic radiation from an electric dipole in a cold anisotropic plasma V. Quasi-static radiation from a point source in a warm anisotropic plasma V-1. General formula for quasi-static radiation field V-2. Radiation field in an electron plasma-high frequency resonance cone V-2-1. Radiation in a cold electron plasma V-2-2. Radiation in a warm electron plasma V-3 Radiation field in a two component (electron and ion) plasma low frequency resonance cone V-3-1. Radiation in a cold plasma V-3-2. Radiation in a warm prasma References

Instability of Three- or Four-Component (Electron, Ion and Beam) Plasma Systems

The instability of a beam-plasma system with no magnetic field is investigated mainly by means of the graphical analysis of the dispersion equation. Unstable regions are determined in detail in kinetic theory approach for three types of waves of electron beam-electron coupling, ion beam-electron (electron beam-ion) coupling and ion beam-ion coupling. The effect of the stationary electron appears in the region of the beam-ion coupling in a three-component plasma and in the region of all the waves except electron beam-electron coupling in a four-component plasma.

Self-oscillations excited by two stream ion-ion instability

In an ion beam-plasma system, low frequency self-oscillations are observed when an ion beam with a velocity near the ion acoustic velocity is injected into the plasma. This oscillation has a discrete spectral structure which results from the fact that the system is axially bounded. A real wave number for each discrete excited mode is determined by the bounded length. The self-oscillation frequency is approximately proportional to the wave number and to the ion beam velocity. These properties of the oscillation are quantitatively explained by the kinetic dispersion relation for the two stream ion-ion instability in the ion beam-plasma system.

Spatial change of ion beam by collisions

The probability of the collision of an ion with neutral‐gas atoms is obtained from the decay length of the ion‐beam intensity by an injection of an ion beam into a weakly ionized plasma. The damping of the ion‐beam intensity is compared with the collisional damping of an ion acoustic wave.

Oscillations in ion beam-plasma system

Abstract Low-frequency oscillations are observed when controlled ion-beams are injected into controlled plasmas.

Spatially growing waves in an ion beam‐plasma system

An externally excited ion wave in an ion beam‐plasma system was found to grow spatially in the case where the ion beam velocity is nearly equal to an ion acoustic velocity. The phase velocity and growth rate are in good agreement with the results based on the kinetic dispersion equation.

Radiation and reception characteristics of an electron plasma wave from grid antennas having a d.c. biased parasitic grid

The radiation and reception characteristics of an electron plasma wave from closely spaced double grids, one of which is a d.c. biased parasitic grid (unfed by r.f.-signal), are investigated experimentally. As a result, it is found that the radiation and reception with high efficiency of an electron plasma wave are enhanced by about 50% by the presence of the parasitic grid with a Floating d.c. potential. The directional radiation and reception patterns of this antenna can also be made unidirectional with an increased radiation and reception efficiency by about 20% by the appropriately biased parasitic grid.

Theoretical analysis on radiation and reception characteristics of an oblate spheroidal antenna for electron plasma waves

The radiation and reception characteristics of the oblate spheroidal antenna for electron plasma waves are theoretically investigated. The analysis is carried out as a boundary‐value problem. The formulas for the radiation and reception characteristics such as radiation impedance, electron charge distributions, radiated wave potential, directional properties, and receiving voltage of the oblate spheroidal antenna are analytically obtained. As a result, it is concluded that the radiation and reception characteristics of the antennas are not uniquely determined by kpa (kp is the wave number of an electron plasma wave, and a is the radius of the circular‐plate antenna), but are determined by two out of three factors, kpa, ζ (radius divided by Debye length), and ω/ωp (angular signal frequency to angular plasma frequency). This conclusion is in marked contrast to the conventional theory in which the charge distribution on the antenna is assumed a priori as uniform and, thus, the antenna characteristics are uni...

Wave-Wave Coupling in Ion Wave Propagation

Wave-wave coupling among ion waves is investigated, experimentally and theoretically. When two ion waves of different frequencies of f 1 and f 2 are excited by one grid, the signals of the harmonic (2 f 1 ) and f 1 – f 2 are detected by another grid. They are found to grow spatially in some region, on the contrary to those of f 1 and f 2 which decrease monotonously in the region. The growing regions of the harmonic and f 1 – f 2 are in accord with those obtained from the theory of the wave-wave coupling among ion waves. The propagation of small-amplitude wave under the large-amplitude wave and the propagation of ion wave with large-amplitude are also investigated.

Experimental investigations of a loop antenna as electron plasma wave radiator and detector

The radiation and reception characteristics of a circular loop antenna for an electron plasma wave are investigated experimentally. As a result, it is shown that the measured directional radiation and reception patterns agree well with the theoretically predicted ones, and that the quantitatively measured amplitude of the radiated wave potentials are also found to agree fairly well with the theoretically predicted values.