摘要:

This paper describes a new theory of random surface scattering based on the group theoretic consideration of the stochastic homogeneity of the infinite random surface. To show the basic idea of the theory, we only discuss scalar wave scattering for one‐dimensional random surface that is described by a reactance boundary condition having a random reactance of a stationary random function. A form of the stochastic wave solution associated with the random boundary condition is determined by the group theoretic consideration. The wave solution is then written in terms of a stationary random function that is approximately solved as a stochastic functional of the random surface. The optical theorem, the angle dependence of the incoherent scattering, and the energy flow of the surface wave are calculated and are shown in the figure

ISSN:0048-6604    

DOI:10.1029/RS015i006p01049

年代:1980

数据来源: WILEY

摘要:

A second‐order renormalization theory is formulated to calculate the cross‐polarized backscattering cross sections from an isotropic half space random medium whose permittivity fluctuations are characterized by center‐valued Gaussian statistics. The results show that the second‐order theory predicts a significant level of depolarized backscatter, in contrast to the first‐order theory, which has been shown to contain no depolarized backscatter except from anisotropy effects in t

ISSN:0048-6604    

DOI:10.1029/RS015i006p01059

年代:1980

数据来源: WILEY

摘要:

The analysis for the circular loop antenna in a concentric insulating sphere is extended to the case where the loop is eccentrically located in the sphere, that is to say, coaxial with the sphere but not concentric. Both the transmitting and receiving antennas are treated. Parametric studies are used to determine the effect of the electrical size of the loop and sphere, the eccentricity, and the electrical properties of the media on the directivity of the antenna. The field pattern for the loop is found to be a vertical beam with approximately linear polarization when the electrical size of the loop is near that for resonance in the insulation, β1b≈ 1.0, the ratio of the permittivity of the surrounding medium to that in the insulation εer2/εer1is large, and when the eccentricityd/cis high. Measured driving point admittances and field patterns of model antennas are compared with theoretical calculations and found to be in good agreement. A limited experimental investigation indicates that the circular loop antenna with an eccentric cylindrical insulation will have directive properties similar to those obtained with a spherical insula

ISSN:0048-6604    

DOI:10.1029/RS015i006p01067

年代:1980

数据来源: WILEY

摘要:

The electron‐transparent and electron‐reflecting models of antennas in a warm isotropic plasma are reexamined. It is shown that a purely electrical treatment of both the models without an explicit use of the boundary condition on electron velocity yields the same results as those previously obtained through an electromechanical treatment. The essential difference between the two models is that for the electron‐reflecting model, fields are nonzero only in the exterior region, while for the electron‐transparent model, they are nonzero both in the exterior and interior regions of the antenna. This distinction helps in clarifying some misconceptions about these models of antennas in warm isotropic

ISSN:0048-6604    

DOI:10.1029/RS015i006p01083

年代:1980

数据来源: WILEY

摘要:

We present the first experimental characterization of the frequency spectra of first and subsequent stroke electric fields over a distance range from about 1 km, where the fields are primarily electrostatic, to 200 km, where they are primarily radiation. Spectra are presented to about 700 kHz for lightning within 12 km and to about 300 kHz for lightning at 50 and 200 km. We show that the return stroke ground wave spectrum beyond 50 km has a peak near 4 kHz but that within 10 km the spectrum shows a steady increase with decreasing frequency to 1 kHz. Subsequent strokes beyond 50 km contain more energy above 100 kHz relative to the peak spectral value than do first strokes. Frequency spectra at all ranges fall off roughly as 1/ƒ for frequencies between 5 and 100 kHz, whereas the falloff above 100 kHz is faster as the distance to the stroke increases. From this high‐frequency attenuation we determine an RF conductivity for central Florida of between 0.002 and 0.005 Ω

ISSN:0048-6604    

DOI:10.1029/RS015i006p01089

年代:1980

数据来源: WILEY

摘要:

The coupling between the lateral waves and the radiation field by rough surfaces is derived using a full‐wave approach. Both horizontally and vertically polarized waves are considered, and the solutions are shown to satisfy the reciprocity and duality relationships in electromagnetic theory. The slope of the rough surface is not restricted, shadowing effects are considered, and the solutions are also applied to random and periodic rough surfaces. Using stationary phase techniques, closed‐form solutions are also derived for high frequenc

ISSN:0048-6604    

DOI:10.1029/RS015i006p01095

年代:1980

数据来源: WILEY

摘要:

Determining electrical ground constants of the earth is an important problem in geophysical probing [Keller, 1971;Wait, 1979] and underground communication system design [Aldredge, 1973]. Several different methods are used to determine the relative permittivity εrand resistivity p or conductivity ó of a stratified earth. As noted in theInstitute of Electrical and Electronics Engineers(IEEE) [1974] Standard 356, techniques for determining the electrical constants of the earth are roughly divided into two categories: (1) methods where drill hole access into the earth does not exist or is not required, (2) techniques requiring drill hole access into the earth. Methods using drill holes are primarily for determining electrical ground constants in a local area.This article contains supplementary materia

ISSN:0048-6604    

DOI:10.1029/RS015i006p01105

年代:1980

数据来源: WILEY

摘要:

Initial attention is directed toward summarizing the finite element method (FEM) analysis technique. This is followed by a discussion of exact lossy offset sphere verification tests as well as comparisons with oblate spheroid scattering results, as presented in two previous independent publications. The FEM is then applied to the computation of scattering by the theoretical raindrop shapes as derived by Pruppacher and Pitter. Vertical and horizontal polarizations are considered for 30‐GHz plane waves, having both 90° broadside and 50° canted arrival angles. Tabulated and graphical bistatic scattering results are presented, comparing the Pruppacher and Pitter drops with equivolume oblate sphero

ISSN:0048-6604    

DOI:10.1029/RS015i006p01109

年代:1980

数据来源: WILEY

摘要:

The method of Jones used for the ray tracing of internal gravity waves has been applied to radio waves in the ionosphere. This method avoids problems usually encountered near a reflection point and, consequently, may be used to trace both reflected and refracted rays. The method is particularly efficient when the propagation effects of the magnetic field are neglected.

ISSN:0048-6604    

DOI:10.1029/RS015i006p01121

年代:1980

数据来源: WILEY

摘要:

Measurements made on board the orbiting Air Force meteorological satellite equipped with a high‐frequency (HF) receiver have been studied in order to describe the HF radio environment at the satellite height. The satellite is in a sun‐synchronous dawn‐dusk orbit at a height of nearly 500 nmi (860 km) above the surface on the earth. The receiver sweeps repeatedly through the band 1.2–13.9 MHz in 100‐kHz steps once every 32 s, providing observations at each frequency approximately every 200 km along the satellite orbit. Measurements from a 3‐month period early in the satellite lifetime—September, October, and November, 1977—have been grouped and analyzed by frequency to yield results that are consistent with the hypothesis that the primary source of the observations is emissions from terrestrial transmitters. The relative differences in the received signals vary with frequency in a manner that agrees with the allocation of

ISSN:0048-6604    

DOI:10.1029/RS015i006p01127

年代:1980

数据来源: WILEY