Current distribution on a thin cylindrical antenna immersed in an isotropic compressible plasma

1968 ◽  
Vol 46 (8) ◽  
pp. 1013-1017 ◽  
Author(s):  
Richard L. Monroe
Keyword(s):  
Current Distribution ◽  
Integrodifferential Equation ◽  
Free Space ◽  
Plasma Frequency ◽  
Propagation Constant ◽  
Wave Number ◽  
Compressible Plasma ◽  
Cylindrical Antenna ◽  
Space Wave

An integrodifferential equation is derived for the current distribution along a thin, hollow, center-driven, cylindrical, perfectly conducting antenna immersed in an isotropic, compressible plasma. On the basis of this equation it is shown that the current distribution approaches sinusoidal form as the radius of the antenna approaches zero. The propagation constant for this current is approximately equal to the free-space wave number for most frequencies greater than the plasma frequency.

Admittance of an infinite cylindrical antenna immersed in a lossy, compressible plasma

1969 ◽  
Vol 47 (20) ◽  
pp. 2129-2135 ◽  
Author(s):  
Richard L. Monroe
Keyword(s):  
Plasma Frequency ◽  
Propagation Constant ◽  
Plasma Temperature ◽  
Particle Collision ◽  
Low Loss ◽  
Compressible Plasma ◽  
Cylindrical Antenna ◽  
Electroacoustic Wave ◽  
Gap Width ◽  
Good Agreement

An expression is derived for the driving point admittance of an infinite, perfectly conducting cylindrical antenna excited by a finite uniform gap and immersed in a lossy, compressible, isotropic plasma. This expression is based on the twin assumptions that the gap width is much smaller than the wavelength of the plasma (electroacoustic) wave and that the radius of the antenna is much smaller than the wavelength of the electromagnetic wave; it is similar in form to the corresponding expression for an infinite antenna in free space, and it is obtained in much the same manner. Conductance and susceptance curves computed from the admittance function are in good agreement with those obtained numerically by other authors for f ≥ 0.7 fP. The behavior of the admittance function at frequencies in the neighborhood of the plasma frequency depends mainly on the electron – neutral particle collision frequency, not the plasma temperature. In general, the effect of the temperature is quite small, although a temperature-related effect can produce large admittance values in very low-loss plasmas at frequencies well below the plasma frequency (f ~ 0.03 fP for T = 1500 °K). This investigation supports the view that the propagation constant of the current along a cylindrical antenna in a compressible plasma is nearly equal to the plane-wave propagation constant in an incompressible plasma.

THE ADMITTANCE OF AN INFINITE CYLINDRICAL ANTENNA IN A LOSSY INCOMPRESSIBLE, ANISOTROPIC PLASMA

1967 ◽  
Vol 45 (12) ◽  
pp. 4019-4038 ◽  
Author(s):  
Edmund K. Miller
Keyword(s):  
Magnetic Field ◽  
Free Space ◽  
Cyclotron Frequency ◽  
Plasma Frequency ◽  
Floating Potential ◽  
Space Layer ◽  
Cylindrical Antenna ◽  
Warm Plasma ◽  
Positive Ion ◽  
Uniform Plasma

A numerical investigation of the admittance of an infinite, circular cylindrical antenna excited at a circumferential gap of nonzero thickness, and immersed in a lossy incompressible magnetoplasma with the antenna parallel to the static magnetic field is described. A concentric free-space layer (the vacuum sheath) which separates the antenna from the external uniform plasma is included in the analysis to approximate the positive ion sheath which may form about a body at floating potential in a warm plasma. The numerical results for the antenna admittance show that: (1) in the absence of a sheath, a sharp admittance maximum is found at the electron cyclotron frequency, with the maximum more pronounced when the plasma frequency exceeds the cyclotron frequency than for the converse case; (2) the vacuum sheath shifts upward in frequency and reduces in amplitude the admittance maximum which occurs for the sheathless case at the cyclotron frequency; (3) a kink or minimum in the admittance is found at the plasma frequency.

Infinite cylindrical antenna in a uniaxial compressible plasma

1968 ◽  
Vol 46 (24) ◽  
pp. 2846-2849
Author(s):  
Edmund K. Miller
Keyword(s):  
Significant Influence ◽  
Plasma Frequency ◽  
Compressible Plasma ◽  
Cylindrical Antenna

Numerical values are given for the admittance of an infinite cylindrical antenna in a uniaxial plasma, taking into account both plasma compressibility and a vacuum sheath. The susceptance is found to exhibit no significant sheath or compressibility dependence above the plasma frequency (ƒp) and only a slight dependence on these factors below ƒp. The conductance behavior shows no significant influence of compressibility or sheath in the range centered about ƒp, in which it is relatively constant in value except for a slight minimum at ƒp.

SCATTERING BY A PERFECTLY CONDUCTING CYLINDER IN A COMPRESSIBLE PLASMA

1964 ◽  
Vol 42 (3) ◽  
pp. 465-476 ◽  
Author(s):  
S. R. Seshadri ◽  
I. L. Morris ◽  
R. J. Mailloux
Keyword(s):  
Cross Sections ◽  
Plasma Frequency ◽  
P Wave ◽  
Wave Number ◽  
Compressible Plasma ◽  
Backscattering Cross Section ◽  
Scattering Cross Sections ◽  
Physical Quantities ◽  
Wave Incidence ◽  
Quantities Of Interest

The scattering of a plane electromagnetic (EM) or plasma (P) wave by a perfectly conducting and rigid circular cylinder immersed in an isotropic compressible plasma is treated. Expressions for all the physical quantities of interest are obtained in the form of infinite series. For the case of a plane EM wave incidence, numerical results for the current induced on the surface of the cylinder, the total scattering cross sections, and the backscattering cross section are obtained as a function of ke0a for various values of the plasma frequency, where a is the radius of the cylinder and keo is the wave number of the EM wave in free space.

RADIATION FROM A PHASED LINE SOURCE IN A MAGNETOIONIC MEDIUM

1965 ◽  
Vol 43 (9) ◽  
pp. 1636-1648
Author(s):  
H. S. Tuan ◽  
S. R. Seshadri
Keyword(s):  
Electric Current ◽  
Current Distribution ◽  
Free Space ◽  
Line Source ◽  
Propagation Constant ◽  
Electron Plasma ◽  
Radiation Characteristics ◽  
Magnetostatic Field ◽  
Phase Constant ◽  
Special Case

The radiation characteristics of a phased line source of electric current immersed in a magnetoionic medium are analyzed. The line source is assumed to be parallel to the direction of the external magnetostatic field and the phase constant for the current distribution is assumed to be given by k0/β, where k0 is the propagation constant of free space and β is a dimensionless phase parameter. In general, it is found that two modes are excited. The frequency ranges of propagation of these so-called ordinary and extraordinary modes are examined by means of a construction in the Ω2–R2 parameter space for the case [Formula: see text], where Ω = ω/ωp, R = ωc/ωp, and ω, ωp and ωc are the source, the electron plasma, and the gyromagnetic frequency respectively. The dispersion relations and the frequency spectrum are evaluated. It is found that β = 1 is a special case for which only one mode is excited.

Determination of the velocity of short electromagnetic waves by interferometry

1952 ◽  
Vol 213 (1112) ◽  
pp. 123-141 ◽  
Keyword(s):  
Phase Velocity ◽  
Electromagnetic Radiation ◽  
Free Space ◽  
Electromagnetic Waves ◽  
Wave Beam ◽  
Wave Length ◽  
Wave Frequency ◽  
Space Wave

A new measurement of the velocity of electromagnetic radiation is described. The result has been obtained, using micro-waves at a frequency of 24005 Mc/s ( λ = 1∙25 cm), with a form of interferometer which enables the free-space wave-length to be evaluated. Since the micro-wave frequency can also be ascertained, phase velocity is calculated from the product of frequency and wave-length. The most important aspect of the experiment is the application to the measured wave-length of a correction which arises from diffraction of the micro-wave beam. This correction is new to interferometry and is discussed in detail. The result obtained for the velocity, reduced to vacuum conditions, is c 0 = 299792∙6 ± 0∙7 km/s.

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