MICROWAVE PROPAGATION IN AN OVER-DENSE BOUNDED MAGNETOPLASMA

Thesis/Dissertation · Mon Jan 01 04:00:00 EST 1962

OSTI ID:4766692

Wieder, B

The magneto-ionic theory shows that for plane wave propagation along the direction of the magnetic field in a magnetoplasma, a mode of propagation exists when the frequency of the wave is smaller than the electron gyrofrequency of the medium. Electromagnetic waves will propagate in this mode regardless of the magnitude of the plasma frequency. It requires only that the collision frequency of the electrons in the plasma be sufficiently small so that collision damping does not excessively attenuate the waves. This mode of propagation has been used to explain very low frequency whistles'' associated with lightning discharges and very low frequency emissions in the earth's exosphere, and has been called the whistler mode'' by ionosphere physicists. This dissertation de- . scribes experiments which attempted to use the properties of this made of propagation as a diagnostic tool in the hot plasma of the magnetic field stabilized pinch discharges in ZETA. While the experiments succeeded in demonstrating that electromagnetic waves could be made to propagate through the overdense plasma, the detected signals exhibited properties that could not be completely accounted for in terms of the whistler mode theory. Further, wave propagation was detected during periods of the pinch discharge which in no way could be explained by the theory. Starting with basic principles, the wave equations which describe the propagation of the waves through the plasma are derived. The whistler mode properties result from the infinite plane wave solution to the wave equations. In a bounded plasma whose dimensions are large compared with the wavelength in the medium propagation modes exist for which the infinite plane wave solution is a valid approximation; other modes, however, are also allowed, which, if excited, can contribute significantly to the actual fields. To determine the nature of these modes, numerical solutions to a complicated transcendental dispersion relation involving Bessel functions of complex argument were required. These solutions show that a large number of discrete modes are allowed. All the qualitative features of the experimental data are easily explained in terms of these modes. The conclusion derived from the experimental results and the analysis developed to explain the results is that the detected microwave signals, transmitted through the dense ZETA plasma, are the resultant of a multitude of discrete modes. The whistler mode, defined for our purposes as the infinite plane wave solution to the wave equations for frequencies smaller than the gyrofrequency, can exist in the ZETA plasma only as an approximation to some of the modes of propagation. (Dissertation Abstr., 23: No. 3, 1982)

• Research Organization: Originating Research Org. not identified
• NSA Number: NSA-17-002410
• OSTI ID: 4766692
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

ATMOSPHERE
BESSEL FUNCTIONS
COLLISIONS
DENSITY
DISPERSION RELATIONS
ELECTRIC DISCHARGES
ELECTROMAGNETIC WAVES
ELECTRONS
ELEMENTARY PARTICLES
EMISSION
EQUATIONS
EXCITATION
FIELD THEORY
FREQUENCY
IONOSPHERE
IONS
LIGHT
LOSSES
MAGNETIC FIELDS
MAGNETOHYDRODYNAMICS
MATHEMATICS
MEASURED VALUES
MICROWAVES
MOTION
NUMERICALS
PHYSICS
PINCH
PLASMA
PLASMA DIAGNOSTICS
ROTATION
SHOCK WAVES
STABILITY
WHISTLERS