摘要:

Undesirable noise in the radio‐interferometer tracking system (General ElectricMod III) at Cape Kennedy during the Mercury‐Atlas and Ranger‐Atlas orbit series is alleged to have resulted from stochastic refractive ray bending and associated multipath conditions. Surface‐to‐16,000‐foot meteorological data for eight to nineteen shots were examined, using various functions of water vapor‐related parameters and temperature as noise predictors. Spearman rank correlations, significant at the 1% level, were found between all the water vapor‐related measurements tried and a measure of tracking noise. A threshold level of 370N‐units surface value was found (corresponding to about 19 gm‐m−3of water vapor), beyond which tracking problems are likely to develop. Results of earlier investigators are confirmed, and the present investigation strongly implies that the source of the noise problem indeed lies in the lowest layers of the atmosphere. Limited attempts to correlate noise with atmospheric inhomogeneit

ISSN:0048-6604    

DOI:10.1029/RS006i012p01021

年代:1971

数据来源: WILEY

摘要:

Beyond‐the‐horizon 2‐GHz radio paths in the Mekong Delta have shown large diurnal and seasonal propagation variations, which sometimes resulted in serious degradation of system performance. Measurements of refractivity gradients, in January and February 1970, using a high‐resolution radiosonde technique showed a higher incidence of subrefraction than was indicated by the available climatological statistics. Low‐based elevated layers with extreme superrefractive gradients were occasionally observed over w

ISSN:0048-6604    

DOI:10.1029/RS006i012p01027

年代:1971

数据来源: WILEY

摘要:

From the monthly average values of radiorefractivity near the ground surface and at the 850‐mb level (approximately 5000 ft above sea level), values of refractive index gradient have been computed between ground surface and 5000 ft above sea level for the 12 Indian radiosonde stations. These values ofNgradients have been examined to estimate super‐refraction of radio waves in the lower troposphere over India. Maps showing isopleths of refractive index gradient over the country during different seasons are also presen

ISSN:0048-6604    

DOI:10.1029/RS006i012p01033

年代:1971

数据来源: WILEY

摘要:

The reflection of a horizontally polarized, impulsive plane wave by a weakly perturbed ionosphere model is considered. A linear electron density profile and a constant collision frequency are assumed for the unperturbed model, and magnetic field effects are neglected. The transient response is formulated as an inverse Fourier transform of the first‐order frequency domain solution. For the special case of a thin‐layer irregularity, a numerical inverse transform is used to obtain responses that satisfy causality. It is shown that the presence of the thin‐layer irregularity is to modify the waveform of the reflected tran

ISSN:0048-6604    

DOI:10.1029/RS006i012p01039

年代:1971

数据来源: WILEY

摘要:

A determination, in geometric optics approximation, of the forward and backscatter characteristics of spherical overdense clouds having (1) a Gaussian decrease with distance from the center, (2) a sech2, or exponential, decay, and (3) an inverse‐square decrease, showed that the backscatter cross section for the inverse‐square distribution is always larger than for the other two distributions. As the center‐point density increases, the backscatter cross section obtained with the Gaussian sphere most rapidly takes on the characteristics of a conducting sphere, that of the sech2distribution lags slightly behind, but that of the inverse‐square sphere never gets close to the result for a conducting sphere. In forward scatter, the inverse‐square distribution shows the largest cross section and a fairly rapid increase with center‐point density, the sech2distribution has an essentially constant cross section, and the Gaussian, which has the lowest forward scatter cross section, shows a slight decrease with center‐

ISSN:0048-6604    

DOI:10.1029/RS006i012p01045

年代:1971

数据来源: WILEY

摘要:

Cross‐correlation and ‘similar fades’ time delays obtained on widely spaced aerial pairs in the north‐south direction have been used in investigating north‐south ionospheric motion at the low‐latitude station of Ibadan (magnetic latitude, 3°S), and a north‐south velocity of considerable magnitude is revealed. It is also found that, if an aerial spacing of at least one‐half kilometer is used at this latitude, systematic diurnal and seasonal variations of this velocity can be detected. The procedure of the analysis is briefly outlined, and the reliability of the resu

ISSN:0048-6604    

DOI:10.1029/RS006i012p01051

年代:1971

数据来源: WILEY

摘要:

Spectra of amplitude and amplitude‐difference fluctuations have been obtained over a millimeter‐wave propagation path, demonstrating substantial aperture‐filtering ef

ISSN:0048-6604    

DOI:10.1029/RS006i012p01059

年代:1971

数据来源: WILEY

摘要:

H. G. Booker's (1956) theory of the radio aurora as a random assembly of field‐aligned irregularities has been unsuccessful in explaining many observations, and this lack of success has led to the application of plasma instability theory to the phenomenon. The ion‐acoustic instability theory of D. T. Farley (1963) has had some success, and evidence is rapidly accumulating that the ion‐acoustic instability is an important mechanism in the production of radio aurora. A second theory, originally developed by A. Simon (1963), is currently being applied to the radio aurora. This theory involves another type of plasma instability, which is here called the ‘drift‐gradient instability.’ Both instabilities require the presence of an electric field directed perpendicular to the ambient magnetic field. For the ion‐acoustic instability the critical condition is that the electric field exceeds a threshold value of the order of 30 mv m−1. The drift‐gradient instability, however, requires a positive gradient of ionization density in the direction of the electric field. The growth of this drift‐gradient instability is dependent on the condition that electron‐ion drift velocity divided by the scale length of the plasma density exceeds a value such that damping due to diffusion is overcome. Experimental data are reviewed in the light of the two theories. It is shown that all the major features of the so‐called diffuse radio aurora (typeB1in the provisional nomenclature of the International Association of Geomagnetism and Aeronomy, IAGA, 1968) can be explained by the ion‐acoustic instability theory if account is taken of the nonlinear production of secondary irregularities discussed by J. P. Dougherty and D. T. Farley (1967). Progress to date in applying the drift‐gradient instability theory suggests that most features of the discrete radio aurora (typeB2andB3in the IAGA classification) may be explained. No attempt is made at this stage to relate the theories to forward scatter observations of the radio aurora. The theories suggest that appropriate observation of the radio aurora may be used as a powerful ground‐based tool for quantitative studies of electric fields in the ionosphere. Existing experimental data are discussed from this point of view, attention being paid in particular to substorms and pulsations of theB1type radio aurora in the Pc 5 frequency range. Results suggest that Pc 5 magnetic pulsations are associated with standing hydromagnetic waves in the magnetosphere with, contrary to some currently held assumptions, an antinode of electric field and field line displacement in the ionosphere. Progress in relatingB1‐type radio auroral events to IPDP micropulsation events is reviewed. If a relation can be established, it will allow further deductions to be made concerning the electric field in the magnetosphere. The aspects of the ionospheric electric field that can be monitored by an auroral radar system and the specifications

ISSN:0048-6604    

DOI:10.1029/RS006i012p01061

年代:1971

数据来源: WILEY

摘要:

During the summer of 1968, two‐beam, incoherent‐scatter radar measurements were made at Arecibo. The two beams were formed by two separate feeds for the Arecibo reflector, one a line feed which illuminated essentially all of the reflector, and the other a horn feed which effectively illuminated about 500 feet of the reflector. A by‐product of this experiment was the calibration of the near‐field correction to the backscatter gain of the line‐feed system. This was obtained by comparing the power received as a function of range in the two radar systems. The measured loss of gain in the near field for the line feed was about 1.5 db at a height

ISSN:0048-6604    

DOI:10.1029/RS006i012p01079

年代:1971

数据来源: WILEY

摘要:

The Radio Astronomy Explorer satellite (RAE‐1) is the first spacecraft designed exclusively for radio astronomical studies. It is a small, but relatively complex, observatory including two 229‐meter antennas, several radiometer systems covering a frequency range of 0.2 to 9.2 MHz, and a variety of supporting experiments such as antenna impedance probes and TV cameras to monitor antenna shape. Since its launch in July, 1968, RAE‐1 has sent back some 1010data bits per year on measurements of long‐wavelength radio phenomena in the magnetosphere, the solar corona, and the galaxy. In this paper we describe the design, calibration, and performance of the RAE‐1 experiments

ISSN:0048-6604    

DOI:10.1029/RS006i012p01085

年代:1971

数据来源: WILEY