scholarly journals On some direct evidence for downward atmospheric reflection of electric rays

1925 ◽  
Vol 109 (752) ◽  
pp. 621-641 ◽  
Keyword(s):  
Direct Evidence ◽  
Wireless Transmission ◽  
Long Distance ◽  
Wireless Receiver ◽  
Negative Results ◽  
The Earth ◽  
Apparent Direction ◽  
Distance Communication ◽  
The Waves ◽  
The Magnetic Field

In a recent paper in these Proceedings (Series A, vol. 107, p. 587) Smith-Rose and Barfield have called attention to the two outstanding problems of the propagation of wireless waves over the earth s surface. A complete theory of wireless transmission must explain ( a ), why long-distance communication is possible, and ( b ), why large and rapid variations of signal intensity and apparent direction of propagation of the waves are observed at night, and, to some extent, during daylight, particularly in winter. Smith-Rose and Barfield further point out that both phenomena can be explained to some extent by the well-known Kennelly-Heaviside layer theory, but that it is generally admitted that further evidence of the existence of the layer is needed. They also describe accurate experiments designed to detect the existence of waves arriving at a wireless receiver in a downward direction ( i . e ., inclined to the horizontal), such as must be present if the Heaviside layer theory is correct. In these experiments Smith-Rose and Barfield sought, by directional methods, to detect a departure of the electric field of the waves from the vertical by means of a large Hertzian oscillator, and a departure of the magnetic field from the horizontal by means of a rotating frame aerial. It was, however, found that the conductivity of the ground was sufficiently high to make it act very nearly as a perfect reflector, and, because of the presence of the reflected wave from the ground, none of the effects sought for could be detected even in conditions such as are normally associated with signal strength and directional variations. These authors therefore concluded that the results of their experiments could not be considered as evidence for or against the Heaviside layer theory. In a later paper, Smith-Rose and Barfield describe further experiments of this type, again with negative results, and state that “ adequate experimental evidence on the existence of the Heaviside layer is still lacking.”

scholarly journals On the determination of the directions of the forces in wireless waves at the earth's surface

1925 ◽  
Vol 107 (743) ◽  
pp. 587-601 ◽  
Keyword(s):  
Three Dimensions ◽  
Electric Force ◽  
Long Distance ◽  
Quantitative Measurements ◽  
The Earth ◽  
Apparent Direction ◽  
The Hours ◽  
Distance Communication ◽  
The Waves

There are two outstanding problems relating to the propagation of wireless waves over the earth’s surface which at present remain unsolved, viz.— What is the agency which causes the waves to follow the curvature of the earth, thus rendering long-distance communication possible ? And what is the cause of the large and rapid variations of the intensity and apparent direction of the waves, very commonly observed at the receiving station and confined almost entirely to the hours of darkness ? Both phenomena can be explained to some extent by the well-known Heaviide-layer theory, with the modifications proposed by Eccles, but it is generally admitted that further experimental evidence of the existence of the layer is needed. If the theory is correct and is sufficient, it follows that, a receiver experiencing either of the above phenomena, part of the energy must be arriving in a downward direction ( i. e ., inclined to the horizontal); and that during the occurrence of directional variations, this downcoming wave must have at horizontally polarised component ( i. e ., with its electric force horizontal). I has, therefore, been generally recognised for some time that a conclusive experimental demonstration of the presence or absence of such waves, by suit able quantitative measurements in three dimensions, would aid considerably in proving or disproving the Heaviside-layer theory.

Basic communication sciences

1969 ◽  
Vol 308 (1493) ◽  
pp. 183-198
Keyword(s):  
Long Distance ◽  
Earth Station ◽  
Early Communication ◽  
Technical Developments ◽  
Radiated Power ◽  
The Earth ◽  
Distance Communication ◽  
Quality Of Transmission ◽  
Communication Equipment

The feasibility and utility of long-distance communication via Earth-orbiting satellites has been demonstrated during recent years and it is appropriate therefore to focus attention on the more important scientific studies and technical developments that will be needed if full use is to be made of this valuable mode of communication in the future. The early communication satellites (the Telstar and Relay series) were pioneers in a relatively unknown propagation environment. The satellites themselves were conceptually simple and the communication equipment consisted essentially of a frequency-changing transponder with an r. f. power output of a few watts and a bandwidth some tens of megahertz. Carrier frequencies in the range 2 to 6 GHz were employed; typically either 2 or 6 GHz was used for transmission and 4 GHz for reception at the Earth station. To obtain an adequate signal/noise ratio at the output of the Earth station receiver, frequency modulation was employed, the frequency deviations being greater than those used on terrestrial microwave links. Launcher limitations and other factors meant that the satellites had to be placed in inclined elliptical orbits (see figure 1) with maximum heights of only a few thousand miles. Nevertheless, these satellites demonstrated that some hundreds of frequency-division multiplex telephony circuits, or a television channel, could be achieved with generally satisfactory quality of transmission. It is to be noted, however, that the satellite transponders accommodated only one, or at the most two, r. f. carriers at any time, and that the transmission performance was at times marginal due to limitations of the satellite effective radiated power. Furthermore, these relatively low orbit satellites provided communication in periods of generally less than an hour at a time and required continuous tracking by the Earth station aerials, due to movement of the satellites relative to the Earth.

scholarly journals How to determine the thermal electron density and the magnetic field strength from the Cluster/Whisper observations around the Earth

2001 ◽  
Vol 19 (10/12) ◽  
pp. 1711-1720 ◽  
Author(s):  
J. G. Trotignon ◽  
P. M. E. Décréau ◽  
J. L. Rauch ◽  
O. Randriamboarison ◽  
V. Krasnoselskikh ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Electron Density ◽  
Magnetic Field Strength ◽  
Density Ratio ◽  
Electron Velocity ◽  
Thermal Electron ◽  
The Earth ◽  
The Waves ◽  
The Magnetic Field

Abstract. The Wave Experiment Consortium, WEC, is a highly integrated package of five instruments used to study the plasma environment around the Earth. One of these instruments, the Waves of HIgh frequency and Sounder for Probing of Electron density by Relaxation, Whisper, aims at the thermal electron density evaluation and natural wave monitoring in the 4–83 kHz frequency range. In its active working mode, which is our primarily concern here, the Whisper instrument transmits a short wave train at a swept frequency and receives echoes after a delay. Incidentally, it behaves like a classical ground-based ionosonde. Natural modes of oscillations may thus be excited in the surrounding medium. This means that with suitable interpretations, the Whisper sounding technique becomes a powerful tool for plasma diagnosis. By taking into account the characteristic frequencies of the magnetoplasmas encountered by the Cluster spacecraft, it is indeed possible to reliably and accurately determine the electron density and, to a lesser degree, the magnetic field strength from the Whisper electric field measurements. Due to the predominantly electrostatic nature of the waves that are excited, observations of resonances may also lead to information on the electron velocity distribution functions. The existence of a hot population may indeed be revealed and the hot to cold density ratio can be estimated.Key words. Magnetospheric physics (plasma waves and instabilities). Space plasma physics (active perturbation experiments; instruments and techniques)

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