Allen R.S., 1969, "Comparison of scintillation depths of radio star and satellite scintillations", Journal of Atmospheric and Terrestrial Physics, 31, pp 289-297.
A statistical comparison of the depth of scintillation of the 54 MHz beacon of satellite Transit 4A, to the depth consistent with 63 and 113 MHz observations of radio star, Cassiopeia A, indicates that (a) a thin screen of irregularities of height about 450 km and size somewhat greater than 1 km may represent weak scintillations during quiet geomagnetic periods but that (b) for scintillation indices above about 20 per cent or during periods with local magnetic K-index above 2, the analysis should be based on a thick layer of irregularities.
Briggs B.H. and Parkin I.A., 1963, "On the variation of radio star and satellite scintillations with zenith angle", Journal of Atmospheric and Terrestrial Physics, 25, pp 339-365.
The theory of the variation of the depth of amplitude scintillations with the zenith angle of the source is considered, for radio waves received from a star or satellite. It is assumed that irregular phase fluctuations are impressed on the wave in travelling through the ionosphere, and that the amplitude fluctuations develop by a diffraction process as the wave propagates in the free space beneath the ionosphere. Two effects are produced by an increase in the zenith angle of the source. The magnitude of the phase perturbations increases, because the thickness of the ionosphere along the line of sight increases, and the geometry of the diffraction process changes. Theoretical results are given, both for isotropic irregularities and for irregularities elongated along the earth's magnetic field. The advantages of observing simultaneously on two wavelenghts are stressed. Some comparisons with available experimental data are made, and suggestions are made for future experiments. Irregularities at different distances from the observer are not equally effective in producing amplitude scintillations, and some examples of the "weighting function" which determines their effectiveness are given. Various measures of "scintillation depth" are discussed and related to each other.
Briggs B.H., 1958, "A study of ionospheric irregularities which cause spread-F echoes and scintillations of radio stars", Journal of Atmospheric and Terrestrial Physics, 12, pp 34-45.
A study is made of the correlation between the occurrence of spread-F echoes at Slough, Inverness and Oslo. It is concluded that the ionospheric irregularities which cause the spreading occur in patches which have dimensions of the order of 500 km in the NS direction, and considerably greater in the EW direction. There is an indication that these "bands" of irregularities may lie along lines of magnetic latitude, and that they tend to occur in the same geographical position on successive nights. The correlation of the scintillations of the radio star in Cassiopeia with the occurrence of spread-F echoes at two places is investigated. The results are found to be consistent with the same picture of the spatial distribution of the irregularities. Some indirect arguments suggest that the irregularitites causing the scintillations are at heights near 300 km.
Briggs B.H., 1958, "The diurnal and seasonal variations of spread-F ionospheric echoes and the scintillations of a radio-star", Journal of Atmospheric and Terrestrial Physics, 12, pp 89-99.
A comparison is made of the spread-F ionospheric echoes oberved at Slough (52°N) and Inverness (57°N). It is found that the degree of spreading is greater at the station of the higher latitude. The diurnal and seasonal variations are similar at the two stations. The diurnal and seasonal variations of the scintillation index of the radio star Cassiopeia are explained in terms of the measured ionospheric parameters (spread- F index and critical frequency) together with the change of zenith angle of the source. A large seasonal anomaly which was previously thought to exist is found to be much reduced when all the relevant factors are taken into account.
Cappellini V. et. al., 1968, "Scintillation on S.Marco 1 satellite signals", Journal of Atmospheric and Terrestrial Physics, 30, pp 1581-1584.
An analysis is reported of the scintillation observed on the 20.005 MHz
signals from the S.Marco 1 satellite. The observations were made by six
stations situated at middle and low latitudes in both the north and south
hemispheres.
Results are presented of the scintillation occurrence and of the
geographical distribution of the scintillation index.
Chytil B., 1967, "The distribution of amplitude scintillation and the conversion of scintillation indices", Journal of Atmospheric and Terrestrial Physics, 29, pp 1175-1777.
The relationship between the most commonly used measures of scintillation depth is deduced assuming that the probability density of amplitude distribution is Nakagami's m-distribution.
Chytil B., 1968, "Amplitude and phase scintillations of waves scattered from ionospheric irregularities", Journal of Atmospheric and Terrestrial Physics, 30, pp 1687-1699.
The basic statistics of fluctuations of an electromagnetic wave after scattering from ionospheric irregularities are derived in this paper for the oblique incidence of a primary plane wave. The irregularities are assumed to be enclosed within a layer of finite thickness which is placed at a certain height above the ground. The spatial autocorrelation function of refractive index fluctuations is described by anisotropic Gauss and isotropic Bessel functions. The results obtained are compared with the conclusions of both diffraction and scattering theory so far achieved.
Chytil B., 1970, "Amplitude and phase scintillations of spherical waves", Journal of Atmospheric and Terrestrial Physics, 32, pp 961-966.
The formulae for variations of amplitude and phase fluctuations of a wave after scattering from ionospheric irregularities are derived for the oblique incidence of a spherical wave.
Dagg M., 1957, "Diurnal variations of radio-star scintillations, spread F, and geomagnetic activity", Journal of Atmospheric and Terrestrial Physics, 10, pp 204-214.
An equipment has been constructed to enable a long-term investigation to be made of the temporal variations of radio star-scintillations. A year's observations are presented in terms of the monthly average diurnal variations of scintillations which are compared with monthly average diurnal variations of spread F and geomagnetic activity.
Dagg M., 1957, "Radio-star ridges" Journal of Atmospheric and Terrestrial Physics, 11, pp 118-127.
The radio-star "ridge" effect has been investigated which is quite different in character from the usual radio-star scintillations. The occurrence of ridges correlates more closely with ionospheric inhomogeneities in the E region than in the F region. A divergent-lens mechanism for the production of the ridges is proposed which gives a qualitative explanation of the main features.
Dagg M., 1957, "The correlation of radio-star-scintillation phenomena with geomagnetic disturbances and the mechanism of motion of the ionospheric irregularities in the F region", Journal of Atmospheric and Terrestrial Physics, 10, pp 194-203.
The paper describes an experimental investigation of the relation between the phenomena of scintillations of the radio stars and geomagnetic disturbances. A close correlation is found between the magnitude of the variations in the earth's magnetic field and F-region drift velocities as determined by the radio-star scintillation method. There is also occassional correlation between the amplitude of the scintillations and the magnetic variations. These results and those concerned with the reversals in drift directions are shown to be in agreement with the predictions of MARTYN's theory, which ascribes the F-region phenomena to the interaction of the earth's magnetic field with an electric field communicated from the dynamo region.
Dagg M., 1957, "The origin of the ionospheric irregularities responsible for radio-star scintillations and Spread F I:Review of existing theories", Journal of Atmospheric and Terrestrial Physics, 11, pp 133-138.
The present state of knowledge about the irregularities responsible for radio-star scintillations is summarized, and the existing theories of the origin of these irregularities are discussed. All of the suggestions are shown to be inadequate to explain the observed features of scintillations and spread F. It is shown that any ionizing agent from outside the earth's atmosphere is unlikely to be responsible for the ionospheric irregularities that cause radio-star scintillations, and that the mechanism for their production must be sought in the terrestrial atmosphere.
Dagg M., 1957, "The origin of the ionospheric irregularities responsible for radio-star scintillations and Spread F II:Turbulent motion in the dynamo region", Journal of Atmospheric and Terrestrial Physics, 11, pp 139-150.
A theory is presented which attributes the occurrence of ionospheric irregularities in the F-region to turbulent wind motion in the dynamo region at a height of 110-150 km. The resulting turbulent component of the electric potential field produced is communicated to the F-region, as suggested by MARTYN (1955), where magneto-electric forces then cause the ionization to form eddies. It is suggested that the abscence of daytime scintillations is due to the inhibition of turbulent flow by large temperature gradients during the day. The theory is then compared in detail with observations and shown to be capable of explaining all the major features of radio-star scintillations, together with such diverse results as the long-term correlation of scintillation amplitude with magnetic activity and the variation in the occurrence of spread-F and scintillations at different parts of the earth over the sun-spot cycle.
Dyson P.L., 1967, "Magnetic field-aligned irregularities at mid-geomagnetic latitudes", Journal of Atmospheric and Terrestrial Physics, 29, pp 857-869.
The conditions are examined under which radio waves may be trapped and guided along magnetic field lines by irregularities in electron density. From the analysis of topside ionograms recorded by the Aloutte I satellite, it has been found that field-aligned irregularitites can exist in the form of sheets which may be up to 30 km in extent in the E-W direction. The results of ray tracing using simple models for the irregularities are also presented.
Elkins T.J. and Slack F.F., 1969, "Observations of travelling ionospheric disturbances using stationary satellites", Journal of Atmospheric and Terrestrial Physics, 31, pp 421-439.
Observations, at a sub-auroral zone site, of transmissions from certain geo-stationary satellites, have revealed an unusual regular type of fading, apparently due to diffraction from moving ionospheric formations. The velocity of movement of these electron density irregularities was measured by means of a spaced receiver network, which in turn, allowed their height to be computed, in several instances, as well as certain other parameters of interest. The fading is deduced to result from electron density discontinuities, with linear gradients ~700 cm-3m-1, and located usually near the F-region maximum, which travel in a generally equatorwards direction at ~50-120 m/sec. Apparent periodicity im many fading events, and an association with ionosonde-measured disturbance, suggest that the diffraction takes place at facets of travelling wavelike formations in the ionosphere. Additional observational evidence is presented to support a hypothesis of ducted acoustic-gravity waves, probably excited by impulsive auroral-zone events, and having horizontal wavelengths of ~50-100 km, with latitudinal extent, on occassion, exceeding 1500 km.
Goodman J.M., 1967, "Some evidence of Es-layer effects upon 137 MHz radio waves", Journal of Atmospheric and Terrestrial Physics, 29, pp 607-612.
The occurrence of pronounced scintillation of radio waves tarnsmitted from synchronous satellite Early Bird (1965-28A) appears to be correlated with the growth of the Es layer frequency f0 Es. The scintillation disturbances are usually short term but occasionally exist for as much as an hour. A number of the disturbances have well defined quasi-periodic edges although they generally exhibit a noisy spectrum.
Hooper A., 1968, "On the inversion phenomenom in radio star scintillation", Journal of Atmospheric and Terrestrial Physics, 30, pp 1823-1826.
Some observations of the phenomenon known as 'inversion' in records of
scintillation of signals from the sources Cassiopeia A and Cygnus A are
reviewed briefly. It is shown that the phenomenon is more likely to be
explained by the infinite angular diameters of these sources than, as
suggested by previous authors, by the aperture size of the antenna used
in making the observations.
An experiment is suggested which should distinguish between these and other
criteria which can bring about the observation of inversion.
Ireland W. and Preddey G.F., 1966, "Site effects in scintillations studies using satellite transmissions", Journal of Atmospheric and Terrestrial Physics, 28, pp 481-487.
Observation of radio signals from the satellites 1961 o 1 and 1964-64A at 20, 40, 54 Mc/s, made at New Zealand stations during 1964 and 1965 clearly show amplitude fading effects caused by ground-reflected waves. Regular fading, which has been named 'quasi-periodic', has been identified with reflection from a single reflecting area, whose position moves as the satellite position changes. A method of record analysis has been developed which allows the signal strength variations caused by the ground reflections to be identified. The sensitivity of receiving aerials at low elevations is shown to determine largely the incidence of "quasi-periodic" and site fading effects.
Ireland W. and Preddey G.F., 1967, "Regular fading of satellite transmissions", Journal of Atmospheric and Terrestrial Physics, 29, pp 137-148.
Fast regular scintillation of v.h.f. signals received from earth satellites
has been distinguished from scintillation often associated with an irregular
ionospheric diffracting screen. The appearance of such regular
scintillation is shown to correlate with the occurrence of sporadic-E.
Models consistent with its features are described, which attributes the
effects to the presence of sporadic-E patches.
Results show that scintillation should be further classified if
inconsistencies in interpretation are to be avoided.
Jones K.L., 1969, "Variation in the propeties of scintillation activity with the latitude of the observer", Panetary and Space Science, 17, pp 585-593.
Observations of scintillations of 40 Mc/s signals from satellites have been made at Brisbane (27°S) near sunspot minimum. The most notable feature of such observations is the way in which the scintillation index depends on the angle the radio ray makes with the magnetic field. This appears to be very different from what is observed at higher latitudes.
Kaiser A.B. and Preddey G.F, 1968, "Observations of transitions in satellite scintillation", Journal of Atmospheric and Terrestrial Physics, 30, pp 285-291.
A sub-auroral region of ionospheric irregularities with a well-defined equatorward boundary produces sharp transitions in the scintillation observed on VHF signals from the beacon satellite BE-B recorded at three New Zealand stations. Triangulation shows that the irregularities are located at heights between 240 km and 600 km, with about half of the values between 300 km and 400 km; the boundary tends to be aligned along geomagnetic latitude and lies in the range 50°-55°S geomagnetic latitude. Sharp boundaries are observed mainly between ground sunset and local midnight; their occurrence shows a minimum in winter and correlates weakly with magnetic activity.
Papagiannis M.D. and Elkins T.J., 1970, "Dispersive motions of ionospheric irregularities", Journal of Atmospheric and Terrestrial Physics, 32, pp 383-395.
Cross correlation functions for satellite scintillations at spaced receivers, show a systematic skewness, indicative of dispersive motions of ionospheric irregularities. Other features of the correlation functions, such as secondary pumps frequently present at large time lags and a very obvious change in shape of the curve over a long baseline are also suggestive of dispersive ionospheric wave motions. The fact that the skewness is found to be greater for a low elevation satellite than for one at higher elevation, suggests that these motions might contain a frequency dependent vertical component. The effects of a vertical velocity component upon the conventional horizontal spaced receiver measurements are carefully analyzed. Useful information, relating to velocity dispersion, was also obtained at a single location, by investigating the correlation between multi-frequency scintillation records of a radio star. Because of previous suggestions that apparent skewness of space receiver correlation functions was due merely to statistical sampling errors, the sationarity of the scintillation data is examined in considerable detail.
Parkin I.A., 1968, "The effects of field-aligned ionospheric irregularities on satellite scintillations", Journal of Atmospheric and Terrestrial Physics, 30, pp 1135-1142.
Observations of scintillations of radio signals from the satellites BEB and BEC made at Adelaide have been analysed to obtain information about the ionospheric irregularities which cause the scintillations. Observations of the radio diffraction pattern over the ground, made with three spaced receivers, indicate ionospheric irregularities aligned with their longer dimension along the Earth's magnetic field, and with axial ratios in the range 2-20. Observations of increases of scintillation depth when the direction of the radio ray is close to that of the magnetic field show effects in qualitative agreement with theory, but much larger in magnitude than would be expected on the basis of the above values of axial ratio. It is suggested that this result may indicate the presence of a new type of weakly ionized irregularities with very large values of axial ratio. However, further theoretical development appears to be necessary before a completely satisfactory model of such irregularities, consistent with all the observations, can be given.
Perona G., 1970, "On the theory of ionospheric scintillations of lunar radar echoes", Journal of Atmospheric and Terrestrial Physics, 32, pp 277-291.
Different components of lunar radar echoes can be isolated using Doppler shift techniques in conjunction with continuous wave transmissions. The shape of the region producing the echoes depends on the techniques used, which consequently should produce a definite, and possibly large, effect on the scintillations of ionospheric origin. If these scintillations can be seperated from the lunar-induced scintillations, it should be possible to derive useful information about ionospheric irregularities using a single antenna instead of groups of two or three antennas distributed at various distances on the ground.
Singleton D.G. and Lynch G.J.E., 1962, "The scintillation of the radio transmissions from Explorer VII-II. Some properties of the scintillation producing irregularities", Journal of Atmospheric and Terrestrial Physics, 24, pp 363-374.
Three months' observations, obtained at Brisbane of the scintillations of the 20 Mc/s transmissions from Explorer VII, have been analysed in order to discover the nature of the ionospheric irregularities responsible. The irregularities are found to be field-aligned and to have dimensionsof the order of 1 km. A considerable number of bursts of scintillation activity are found usually in association with the frequency-spreading type of spread-F but infrequently with the range-spreading type. This is interpreted as meaning that the irregularities associated with frequency-spreading have a more patchy horizontal distribution than those associated with range spreading. The horizontal dimensions of the patches are estimated to be of the order of 100 km or more.
Singleton D.G., 1970, "Dependence of satellite scintillations on zenith angle and azimuth", Journal of Atmospheric and Terrestrial Physics, 32, pp 789-803.
An analysis of experimental data is made to determine the nature of the variation of scintillation index with the zenith angle and azimuth of the direction of propagation at an observing point on the Earth's surface. Scintillation observations of the Beacon Explorer satellites are employed which were made at a number of sites throughout Australasia ranging in geomagnetic latitude from 25° to 50° South. At all sites strong evidence is found for the existence of field-aligned columns and indeed, such irregularities appear to be the main cause of scintillations throughout the latitude range regardless of season or time of day. At the high and low latitude stations, some of the field-aligned columns show signs of being spread laterally in a direction a little to the east of magnetic north in all seasons. In the middle latitudes this effect is present only in Summer and the equinoxes. During the Winter at these latitudes evidence for the existence of field-aligned sheets of large East-West extent is found. An improved understanding is obtained of the relationship between the occurrence of spead-F, deduced from bottomside and topside ionograms, and scintillations, in terms of the observed latitude variation in the shape of the irregularities which produce scintillations.
Singleton D.G., 1970, "The effect of irregularity shape on radio star and satellite scintillations", Journal of Atmospheric and Terrestrial Physics, 32, pp 315-343.
Current models of F-region irregularities include field-aligned columns, field-aligned sheets and frontal irregularities which extend many kilometers in the horizontal direction. An irregularity model is put forward which includes these shapes as special cases. Using this model and diffraction theory, a theoretical investigation is made of the effect these shapes have on (a) the nature of the variation of the scintillation index with the zenith angle and azimuth of the direction of propagation at a point on the ground and (b) the shape and orientation of the characteristic ellipse of the amplitude diffraction pattern observed at the ground. It is shown that there are characteristic differences in effects (a) and (b) for each type of shape considered. The possible detection of these differences experimentally and the consequent conclusions which could be drawn regarding the nature of the scintillation producing irregularities are also discussed.
Wild J.P., 1956, "The spectrum of radio-scintillations and the nature of irregularities in the ionosphere", Journal of Atmospheric and Terrestrial Physics, 8, pp 55-75.
An observational study of the spectrum of radio-star scintillations
has been made with a view to exploring the small-scale structure
ot the ionosphere. Observations of the intense source in Cygnus
were made near transit at an altitiude of about 15°. Three instruments
were used simultaneously:
(1) a swept frequency spectroscope to record the dynamic spectrum of
scintillations,
(2) a swept-frequency interferometer to study postional deviations
at different frequencies, and
(3) a triangular spaced-aerial system for studying the lateral size
and motion of the pattern on the ground.
The commonly occurring types of dynamic spectra are described, and their
interpretation in terms of ionospheric phenomena is discussed. From the
nature of the spectra it is inferred that most of the fluctuations are
due to focussing by single lens-like irregularities, rather than to
diffraction at a large number of irregularities. The spectra also show
that the scintillation patterns are often dipersed across the ground,
different frequencies being focused at different points. This is
tentatively attributed to ionospheric gradients which act like huge prisms.
Such "dispersing regions" may lie at different levels from the "focusing
regions".
The degree of fluctuation shows two maxima, one near midnight (winter) and
the other near midday (summer). The size, shape and motion of the pattern
on the ground, as well as the dispersion, also vary throughout the year.
In many cases the pattern on the ground is highly elongated, a feature which
complicates the determination of the direction and speed of motion. For
daytime conditions at least, this elongation indicates marked anisotropy in
the ionospheric irregularites.
Wright R.W., Koster J.R. and Skinner N. J., 1956, "Spread F-layer echoes and radio-star scintillation", Journal of Atmospheric and Terrestrial Physics, 8, pp 240-246.
Observations of radio-star scintillations made at University College of the Gold Coast, Achimota, and spread F-layers made at University College, Ibadan, Nigeria, have been compared. Considerable correlation is found, although there is 510km between the two stations, and the ionospheric observations are made at vertical incidence. The diurnal and seasonal variations of the presence of spread F-layers are examined. It is found that these depend considerably on the degree of magnetic disturbance. In particular, at Ibadan in winter on disturbed days there is only a quarter of the scatter that occurs on quiet days.
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Last updated 28/03/1997 by Mark Keir