摘要:

Time‐ and frequency‐domain statistics are presented for multipath propagation in a suburban mobile‐radio environment for vehicle‐travel distances on the order of 30 m. These statistics were obtained by measuring the quadrature components of the bandpass impulse response for the medium as a measuring vehicle was driven along the streets. For suburban residentialand commercial areas on relatively flat terrain, the delay spread is generally less than 1/4 μsec, and the correlation bandwidth at .9 correlation is greater than 250 kHz. Some extreme areas exhibit multiple‐propagation paths with significant amplitudes at excess delays of 5 to 7 μsec, (delay spreads of 2 μsec) and associated correlation bandwidths as l

ISSN:0048-6604    

DOI:10.1029/RS007i012p01069

年代:1972

数据来源: WILEY

摘要:

Numerical solutions of the continuity equation for electrons are obtained for the purpose of testing the vertical‐drift effect on the plasma distributions in the equatorialFregion of the earth's ionosphere. The results have shown that the altitude profile of electron density and the accompanied vertical‐drift velocity measured at Jicamarca are consistent and confirmed that electromagnetic lifting is the major factor to cause the equatorial anomaly as suggested byMartyn[1955]. The calculated values are found to be in good agreement with the observations both in magnitudes and in distribution patte

ISSN:0048-6604    

DOI:10.1029/RS007i012p01079

年代:1972

数据来源: WILEY

摘要:

The day‐to‐day variability observed in the structure of the equatorial anomaly during a period of high solar activity is investigated. Using hourly values of ƒ0F2observed at a number of ionosonde locations in the American and Japanese longitude sectors during 1958, the structure of the equatorialF2region has been obtained on an hourly basis for an entire year. It is observed that the equatorial anomaly shows considerable day‐to‐day fluctuations in both its structure and its diurnal development.The anomaly is generally best developed in the evening hours, and day‐to‐day changes in the time of best development are typically on the order of 2 to 4 hr. It is observed that the time when the anomaly attains its maximum development is not the same on both sides of the magnetic equator, although this time is closer to coincidence during the equinoctial months than during the solstices. Also during the equinoctial months, the anomaly crests tend to be more symmetric about the equator than during the solstices. The relative magnitudes of the crests display a noticeable changeover with time during the northern solstice in both longitude sectors. The crest on the winter side of the magnetic equator is larger during the day, and the summer crest is larger at night. The exact time that this changeover occurs varies on the order of 5 to 7 hr on a day‐to‐day basis. During the southern solstice this crest changeover is observed only in the

ISSN:0048-6604    

DOI:10.1029/RS007i012p01085

年代:1972

数据来源: WILEY

摘要:

The fading characteristics of ionospheric amplitude scintillations can be described by a cumulative amplitude probability distribution function (cdf). The cdf expresses the probability (percentage of time) that the signal amplitude will equal or exceed a given amplitude. Distributions of amplitude variations are made with the use of ionospheric scintillations observed on beacon signals from synchronous satellites transmitting at 136 MHz. The resulting distributions are divided into six groups corresponding to ranges of the scintillation index, the predominant measure in scintillation studies. The model distributions are then combined with the occurrence of scintillations in various index ranges to produce cumulative amplitude probability distributions. These have been done for long‐term observations made at Hamilton, Massachusetts, Narssarssuaq, Greenland, and Huancayo, Peru. The results allow engineers to determine margins necessary for communication and navigation systems. Individual 15‐min distributions have been compared to the theoretical distributions obtained byNakagami[1960] in hism‐distribution method of characterizing amplitude scintillation and were found to be in good agreement. Themparameter is shown to be a measure of the frequency dependence of scintillations and can be used to determine a spectral index for interpolating the amplitude distributions to other frequencies of int

ISSN:0048-6604    

DOI:10.1029/RS007i012p01095

年代:1972

数据来源: WILEY

摘要:

This paper discusses the problem of remote probing and diagnostics of an inhomogeneous medium of which the properties vary only along a single dimension. The medium is described in terms of a set of unknowns that are determined via parameter optimization techniques such that the response of the trial medium agrees closely with that of the actual medium.

ISSN:0048-6604    

DOI:10.1029/RS007i012p01105

年代:1972

数据来源: WILEY

摘要:

We have derived tractable analytical results for a more complete understanding of the distortion of the amplitude, the pulse length, and the rate of frequency shift of an FM Gaussian pulse after it has undergone reflection from an ionospheric model with a linear electron‐density profile and constant collision frequenc

ISSN:0048-6604    

DOI:10.1029/RS007i012p01113

年代:1972

数据来源: WILEY

摘要:

The input resistance of a short dipole antenna immersed in a warm magnetoplasma is calculated on the basis of the kinetic theory (Boltzmann equation). The plasma is uniaxial; i.e., the cyclotron frequency is much larger than the operating frequency of the antenna and the plasma frequency. The plasma is homogeneous, and collisions are included although the sheath is neglected. The dipole is assumed to be infinitesimally thin (producing an infinite input reactance( except for the case in which the dipole axis is parallel to the static magnetic field when we allow the dipole to have a nonzero radius and calculate the input impedance. It is found that at frequencies much less than the plasma frequency the input resistance differs markedly from the hydrodynamic and cold‐plasma results because of collisionless absorption processes. The input resistance is generally smaller when the dipole axis is inside the resonance cone than when it is outside. The resonance cone anomaly in the input resistance is reduced in magnitude from that of the cold‐plasma theory and is shifted to a higher freque

ISSN:0048-6604    

DOI:10.1029/RS007i012p01117

年代:1972

数据来源: WILEY

摘要:

The net‐field polarization of a plane wave propagating in a magnetically biased cold plasma has been treated in a systematic fashion. Under quasi‐longitudinal conditions the polarization transformations are particularly simple and as such have been treated in the literature. However, under more general conditions the polarization transformations are relatively complex. The axial ratio, tilt angle, rotation rate, and polarization sense all become functions of the initial conditions and the constants of the medium. Under quasi‐longitudinal conditions the polarization ellipse rocks between two extremes, while the axial ratio also changes periodically between a minimum and a maximum value (Cotton‐Mouton effect). The wide variety of polarization transformations available suggests the usefulness of slabs of magnetically biased plasma to synthesize microwave polarizers and depolarizers. The theory of net‐field polarization when applied to data obtained during the 1968 solar occultation of Pioneer 6 verified that the usual quasi‐longitudinal approximation (Faraday rotation) is adequate to describe S‐band polarization in the

ISSN:0048-6604    

DOI:10.1029/RS007i012p01131

年代:1972

数据来源: WILEY

摘要:

The linearized, continuum fluid‐dynamical equations for a warm, collisional electron plasma with independent source terms are presented, and their applicability to boundary‐value problems is discussed. Boundary conditions are developed for a perfectly conducting cylindrical antenna immersed in the warm collisional plasma and excited by a delta‐function generator. An integral equation relating the antenna surface current and charge is derived based upon all the conventional boundary conditions and the requirement that proper continuity be maintained between the antenna and the plasma. The deficiency of other integral formulations, including the grid‐type dipole, is di

ISSN:0048-6604    

DOI:10.1029/RS007i012p01143

年代:1972

数据来源: WILEY

摘要:

The electric field at large distances from a moving test charge in a collisionless plasma is calculated. Significant differences from the well‐known inverse fourth‐power dependence of the electric field on the distance between the observer and the charged particle are obtai

ISSN:0048-6604    

DOI:10.1029/RS007i012p01151

年代:1972

数据来源: WILEY