Fading characteristics and drift and anisotropy parameters of the ground diffraction pattern of the radio waves reflected from the equatorial ionosphere during spreadFconditions

1973 ◽  
Vol 78 (25) ◽  
pp. 5703-5709 ◽  
Author(s):  
R. K. Misra
Keyword(s):  
Diffraction Pattern ◽  
Equatorial Ionosphere ◽  
Radio Waves ◽  
Anisotropy Parameters

scholarly journals The Nature of D-region Scattering of Vertical Incidence Radio Waves. II. Experimental Observations Using Spaced Antenna Reception

1975 ◽  
Vol 28 (2) ◽  
pp. 171 ◽  
Author(s):  
BC Lindner
Keyword(s):  
Diffraction Pattern ◽  
Angular Spectrum ◽  
Statistical Properties ◽  
Angular Spread ◽  
Radio Waves ◽  
Reflected Waves ◽  
D Region ◽  
The Mean

Statistical properties of the ground diffraction pattern formed by ionospherically reflected radio waves are used to examine models of the angular spectra of reflections from the ionospheric D-region. In the daytime two distinct height regions characterized by differing reflection mechanisms are identified within the D-region. Below 85 km the angular spectrum of reflected waves frequently contains coherent components, whereas a spectrum of incoherent or randomly phased components is characteristic of reflections from the region above 85 km. There is evidence which suggests the presence on many occasions of isolated moving reflectors in the reflecting 'ionospheric screen' . . Both the mean angular spread and the fading speed of waves partially reflected from the D-region show an increase with increasing height of reflection.

The diffraction of radio waves in passing through a phase-changing ionosphere

1951 ◽  
Vol 209 (1096) ◽  
pp. 81-96 ◽  
Keyword(s):  
Wave Front ◽  
Diffraction Pattern ◽  
Wave Length ◽  
Ionospheric Irregularities ◽  
Phase Changes ◽  
Radio Waves ◽  
Phase Deviation ◽  
Lateral Extent ◽  
Radio Stars ◽  
The Way

The radio waves from ‘radio stars’ may suffer irregular phase changes in passing through the terrestrial ionosphere, so that when they reach the earth’s surface they produce a dis­turbance in which both amplitude and phase vary over the ground. In this paper it is assumed that the wave emerges from the ionosphere with amplitude constant but with phase varying across its wave-front, and deductions are made about the diffraction pattern produced at the ground. It is shown how, from a knowledge of the way in which phase and amplitude vary at the ground, it is possible to deduce the average magnitude of the phase deviations produced by the ionosphere and their lateral extent. It is also shown how an investigation of the diffrac­tion patterns produced by different wave-lengths may lead to an estimate of the distance of the effective diffracting screen from the plane of observation. Experiments to determine the diffraction pattern formed at the ground by waves emitted from a radio star are described in outline, and an application of the theory to some of the observations indicates that the ionospheric irregularities have a lateral extent of the order of 5 km. and are sufficient to cause a phase deviation of 1 to 2 radians for a wave-length of 6·7 m.

Diffraction from an irregular screen with applications to ionospheric problems

1950 ◽  
Vol 242 (856) ◽  
pp. 579-607 ◽  
Keyword(s):  
Diffraction Pattern ◽  
Angular Spectrum ◽  
Fresnel Diffraction ◽  
Radio Waves ◽  
Fraunhofer Diffraction ◽  
Related Method ◽  
Auto Correlation ◽  
Auto Correlation Function ◽  
Diffraction Patterns ◽  
Diffraction Effects

An analysis is made of the diffraction effects produced when a plane wave is incident upon an irregular diffracting screen, and the results are applied to the problem of the reflexion of radio waves from an ionosphere which is irregular in the horizontal plane. The nature of the irregular screen is assumed to be given in terms of the variation of electric wave-field in a plane just beyond the screen, and it is assumed that variations occur over the plane in one direction only. It is further assumed that the screen is 'random’ in the sense that it is one of an assembly all of which differ from each other, but have statistical properties in common, and deductions are made about the diffraction patterns averaged over the assembly. It is shown that many aspects of the problem can be investigated by use of the theory of ‘random’ electrical noise as developed by Rice and Uhlenbeck. The angular spectrum (Fraunhofer diffraction pattern) and the Fresnel diffraction pattern are described in terms of their spatial auto-correlation functions, and there is some discussion of a related method of dealing with Fresnel diffraction problems from completely determined screens. In part II of the paper the irregular ‘fading’ exhibited by a radio wave returned from the ionosphere is discussed in terms of two models in which the fading is assumed to be produced by movements of the diffracting centres in the ionosphere. The temporal auto-correlation function of the amplitude of the irregularly fading signal is related to the velocity of the ionospheric diffracting centres.

scholarly journals The Interstellar Medium as a Gravity Wave Detector

1997 ◽  
Vol 06 (01) ◽  
pp. 49-56 ◽  
Author(s):  
Redouane Fakir
Keyword(s):  
Interstellar Medium ◽  
Diffraction Pattern ◽  
Gravity Wave ◽  
Gravity Waves ◽  
Binary Star ◽  
Radio Pulsar ◽  
Radio Waves ◽  
Wave Effect ◽  
Wave Detector ◽  
Interstellar Scintillation

An observer, situated several thousand light-years away from a radio pulsar, finds himself embedded in the diffraction pattern resulting from the propagation of the radio waves through the irregular interstellar medium. The gravity waves produced by an intervening binary star cause the diffraction pattern to be displaced laterally in a manner familiar from refractive interstellar scintillation, except that this gravity wave effect is not dispersive. This periodic displacement can reach a few hundred kilometers. Thus, there seems to be a possibility that the exceedingly faint gravity waves can manifest themselves macroscopically.

Observations of Ionospheric Movements by the Use of a Large Aerial Array

1968 ◽  
Vol 1 (4) ◽  
pp. 150-151
Author(s):  
B. H. Briggs
Keyword(s):  
Radio Wave ◽  
Diffraction Pattern ◽  
Horizontal Velocity ◽  
Radio Waves

The ionosphere does not behave like a smooth mirror for radio waves, but more like an irregular diffracting screen. When a radio wave is reflected from it, a random diffraction pattern is formed over the ground. Simple arguments can be used to show that this pattern will move over the ground with a velocity which is twice the horizontal velocity of the ionosphere. This phenomenon can be used for the detection of movements taking place in the ionosphere.

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