Erratum: Scattering of Radio Waves by an Ionized Gas in Thermal Equilibrium

1951 ◽  
Vol 29 (1) ◽  
pp. 86-86
Keyword(s):  
Thermal Equilibrium ◽  
Radio Waves ◽  
Ionized Gas

SCATTERING OF RADIO WAVES BY AN IONIZED GAS IN THERMAL EQUILIBRIUM

1960 ◽  
Vol 38 (8) ◽  
pp. 1114-1133 ◽  
Author(s):  
J. A. Fejer
Keyword(s):  
Incident Wave ◽  
Thermal Equilibrium ◽  
Debye Length ◽  
Density Fluctuations ◽  
Characteristic Scale ◽  
Radio Waves ◽  
Ionized Gas ◽  
Positive Ions ◽  
Frequency Power Spectrum ◽  
Frequency Power

A theory is developed for the scattering of radio waves by density fluctuations which exist in an ionized gas in thermal equilibrium.Expressions for the frequency power spectrum of the scattered waves are obtained. These expressions make it possible to interpret the results of observations of this type of scattering from the ionosphere in terms of electron density and temperature.It is shown that if the characteristic scale of the scattering irregularities (this scale depends on the wavelength of the incident radio wave and the scattering angle) is much greater than the Debye length then the width of the spectrum of the scattered signal is determined by the thermal velocities (and the collision frequencies if the latter are sufficiently high) of the positive ions, rather than of the electrons.If the characteristic scale is greater than the Debye length then for low collision frequencies the spectrum is flat-topped, with two slightly raised shoulders situated symmetrically above and below the frequency of the incident wave. For high collision frequencies the spectrum has only one maximum situated at the frequency of the incident wave.

SCATTERING OF RADIO WAVES BY AN IONIZED GAS IN THERMAL EQUILIBRIUM IN THE PRESENCE OF A UNIFORM MAGNETIC FIELD

1961 ◽  
Vol 39 (5) ◽  
pp. 716-740 ◽  
Author(s):  
J. A. Fejer
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Thermal Equilibrium ◽  
Uniform Magnetic Field ◽  
Debye Length ◽  
Density Fluctuations ◽  
Total Power ◽  
Radio Waves ◽  
Ionized Gas ◽  
The Magnetic Field

In an earlier paper (Fejer 1960) a theory was developed for the scattering of radio waves by the electron density fluctuations that exist in an ionized gas in thermal equilibrium. The theory treated only the extreme cases where the "characteristic scale" of the scattering irregularities is either very much larger or very much smaller than the Debye length. The presence of only one type of singly charged ion was considered and the ion and electron temperatures were assumed equal. The effects of an external magnetic field were not taken into account.These earlier limitations are removed in the present paper and the effects of an external magnetic field are taken into account.It is shown that the total power is independent of the magnetic field and an expression for the frequency spectrum of scattered power in the presence of a uniform magnetic field is obtained. Useful approximations to this expression are derived for various limiting cases of interest.It is concluded that the magnetic field need not be taken into account in the interpretation of past observations by Bowles (1958, 1959) and by Pineo, Kraft, and Briscoe (1960). In future experiments, however, particularly at great heights, the effect of the magnetic field could be considerable.

Note on an Ionized Gas Modulator for Short Radio Waves

1934 ◽  
Vol 22 (6) ◽  
pp. 791-793 ◽  
Author(s):  
E.G. Linder ◽  
I. Wolff
Keyword(s):  
Radio Waves ◽  
Ionized Gas

The use of satellite signals to investigate the polar ionosphere

Polar Record ◽  
1966 ◽  
Vol 13 (82) ◽  
pp. 7-15 ◽  
Author(s):  
J. E. Titheridge
Keyword(s):  
Electron Density ◽  
Maximum Density ◽  
Polar Ionosphere ◽  
Radio Waves ◽  
Ionized Gas ◽  
Direct Information ◽  
The Earth ◽  
The World ◽  
Thick Mantle

The ionosphere is a thick mantle of partly ionized gas surrounding the earth at heights between 80 and 800 km. It was discovered about fifty years ago, and during the last decade has been studied intensively at observatories all over the world. These studies consist primarily of observing the characteristics of radio waves reflected from the ionosphere. Since waves of different frequencies are reflected at different heights, it is possible to determine how the electron density varies with height, up to the height of maximum density at about 300 km. Radio waves which pass this height, however, continue into space and are not reflected. Consequently very little direct information can be obtained from the ground about the characteristics and behaviour of the ionized region above 300 km.

Radio Measurements of Coronal Magnetic Fields

1994 ◽  
Vol 144 ◽  
pp. 21-28 ◽  
Author(s):  
G. B. Gelfreikh
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Solar Corona ◽  
Active Regions ◽  
High Sensitivity ◽  
Coronal Magnetic Field ◽  
Transverse Magnetic ◽  
Radio Sources ◽  
Radio Waves ◽  
Solar Active Regions

AbstractA review of methods of measuring magnetic fields in the solar corona using spectral-polarization observations at microwaves with high spatial resolution is presented. The methods are based on the theory of thermal bremsstrahlung, thermal cyclotron emission, propagation of radio waves in quasi-transverse magnetic field and Faraday rotation of the plane of polarization. The most explicit program of measurements of magnetic fields in the atmosphere of solar active regions has been carried out using radio observations performed on the large reflector radio telescope of the Russian Academy of Sciences — RATAN-600. This proved possible due to good wavelength coverage, multichannel spectrographs observations and high sensitivity to polarization of the instrument. Besides direct measurements of the strength of the magnetic fields in some cases the peculiar parameters of radio sources, such as very steep spectra and high brightness temperatures provide some information on a very complicated local structure of the coronal magnetic field. Of special interest are the results found from combined RATAN-600 and large antennas of aperture synthesis (VLA and WSRT), the latter giving more detailed information on twodimensional structure of radio sources. The bulk of the data obtained allows us to investigate themagnetospheresof the solar active regions as the space in the solar corona where the structures and physical processes are controlled both by the photospheric/underphotospheric currents and surrounding “quiet” corona.

Radio Waves Kill Insect Pests

1933 ◽  
Vol 148 (5) ◽  
pp. 272-273 ◽  
Author(s):  
J. H. Davis
Keyword(s):  
Insect Pests ◽  
Radio Waves
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