bluuebunny/crossref_metadata_2025 huggingface dataset:
Some new thoughts on magnetospheric substorms
Authors: Akasofu S.‐I. , Kan J. R.
Published: February 2008

Several important new observations of magnetospheric substorms now allow us to examine many substorm features in terms of the solar wind‐magnetosphere dynamo and of four rates, the merging rate M of the interplanetary and geomagnetic field lines, the transport rate T of the merged field lines from the dayside magnetosphere to the magnetotail, the reconnection rate R of the transported field lines and the return rate R of the reconnected field lines to the dayside magnetophere. It is shown that magnetospheric observations of great variety are consistently explainable by the deduced result that the expansive phase of a typical intense substorm occurs when the combination of the four rates is such that

urn:x-wiley:00486604:media:rds769:rds769-math-0001

while a weak substorm occurs when the combination of the four rates is such that

urn:x-wiley:00486604:media:rds769:rds769-math-0002

where an upward‐pointing arrow denotes an increasing rate. The first combination corresponds to a negative Bz component of the interplanetary magnetic field, while the second one to a positive Bz component. Thus, the Bz component does not control triggering mechanisms of substorms, but does control the intensity of substorms. Indeed, there are also periods in which the combination may be such that M(∼T)↑, ℜ = const., R = const., which does not consistently result in substorm activity.
Recent developments and outstanding problems in the theory of the D region
Authors: Thomas L.
Published: February 2008

The present understanding of the ionization processes, and of the positive and negative ion chemistry of the D region, is reviewed with particular attention being given to outstanding problems.

Rocket‐borne mass spectrometer observations carried out in the past decade have shown that the change in positive ion composition with height (from NO+, O2+ and metallic ions above to water cluster ions H+· (H2O)n below) is a general feature of the D region at all latitudes and under all geophysical conditions. Furthermore, these observations indicate that this change occurs over a very small range of heights, between 82 and 86 km under normal conditions and at lower heights during auroral or Polar Cap Absorption conditions. These results are discussed in terms of current ideas concerning the formation of water cluster ions from O2+ and NO+ ions.

Mass spectrometer observations by two experimental groups have provided conflicting results concerning the negative ion composition in the D region and cannot be used to test theoretical models. Such models have been derived from laboratory measurements, and involve reaction schemes leading from O2− ions, formed by electron attachment, to ions O3−, O4−, CO3−, CO4−, NO2− and NO3−. The effect on these models of including recent laboratory measurements of negative ion hydration is considered, and the importance of photodetachment is also mentioned.
Normal and abnormal E‐region electron density profiles at a midlatitude station
Authors: Taylor G. N.
Published: February 2008

The problems of measuring reliable E‐region electron density vs. height profiles with a vertically pointing, pulsed incoherent scatter radar are discussed, and profiles from heights of 90 km upward observed at Malvern are presented. The minimum above hmaxE is more pronounced in winter than in summer, and the overall average density in the minimum is 92% of NmaxE. From the observational point of view, profiles showing an unresolved sporadic‐E layer seem merely to be an extreme case of the normal type. Many layers are present in the E region at night; the behavior of these is erratic except for the principal layer centered just below 100 km, which may be meteoritic in origin. Incoherent scatter offers a new method of investigating the effects of solar flares in the 100 to 130 km range; observations taken during a flare, and also during a partial solar eclipse and on a magnetically disturbed day, are described.
Reflection and transmission of obliquely incident electromagnetic waves by an inhomogeneous plasma slab moving parallel to the magnetostatic field
Authors: Seikai S. , Tanaka K. , Shiozawa T.
Published: February 2008

The problem of the reflection and transmission of obliquely incident electromagnetic waves by an inhomogeneous plasma slab moving parallel to the magnetostatic field is discussed. For the analysis of the problem, an inhomogeneous plasma slab is subdivided into a number of thin homogeneous layers, and the easier problem of the reflection and transmission by the stratified plasma slab is solved instead of directly treating the wave equations for an inhomogeneous plasma slab. For linear and parabolic electron density profiles, the reflection properties of the moving inhomogeneous magnetoplasma slab are investigated quantitatively with the aid of numerical examples.
Reflection of optimum pulses from the ionosphere
Authors: McIntosh Robert E. , Paroline Richard J.
Published: February 2008

The reflection of RF pulses having linear frequency variation off an inhomogeneous, anisotropic, dispersive, and absorbing ionospheric layer is considered in this paper. It is found that moderate pulse compression (10 to 20 db) can be achieved by utilizing the intrinsic dispersive properties of this transmission channel. Results are presented which indicate how this compression varies with magnetic dip angle, solar zenith angle, transmitter‐receiver separation distance, and propagation direction with respect to a magnetic meridian.
TEM reflection from a flanged and dielectric‐filled parallel‐plate waveguide
Authors: Itoh Tatsuo , Mittra Raj
Published: February 2008

A new semianalytical method has been developed which allows efficient numerical solution for radiation from a flanged waveguide filled with a dielectric material. Some numerical results are presented and compared with other available data.
Radio frequency scattering from a heated ionospheric volume: 3, Cross section calculations
Authors: Minkoff J.
Published: February 2008

The proper normalization procedure for determining per‐unit‐volume properties of aspect‐sensitive scattering media from experimental measurements is discussed. This is complicated by the fact that, because of the aspect sensitivity, it is not clear a priori what the per‐pulse scattering volume actually is. In general, the correct normalization requires quantitative knowledge of the aspect sensitivity which may not be possible to determine because of fundamental limitations imposed by the spatial‐resolution capability of the measurement system on the extent to which this property of the scattering medium can actually be determined. The identical problem exists in radio‐auroral measurements. This problem is considered here, and an exact expression from which the desired per‐unit‐volume quantities of interest can be obtained from measurements is given. It is shown that proper choice of the experimental parameters leads to a simplification whereby the normalization can be carried out without knowledge of the aspect sensitivity being necessary. The results are applied to calculating from experimental data the per‐unit‐volume scattering properties of a heated ionospheric volume as a function of frequency, from which a transverse scale size for the scattering medium of 3 m is estimated. For these experiments, under maximum heating conditions, a representative value of 1% for the rms fractional electron density deviation is calculated; an upper bound is also established, showing that values as large as 4 or 5% were probably never achieved. It is shown that, for an electron density distribution axially symmetric with respect to the geomagnetic field, B, the cross section for backscatter within a plane containing B uniquely determines the cross section for bistatic scattering axially around B. Experimental results for small axial‐bistatic angles are presented showing good agreement between calculated and measured values.
Generation of large‐scale field‐aligned irregularities in ionospheric modification experiments
Authors: Cragin Bruce L. , Fejer J. A.
Published: February 2008

The threshold of the purely growing mode of stimulated Brillouin scattering is exceeded in ionospheric modification experiments for horizontal wave‐lengths longer than about half a km. The “beat wavelength” along the field lines is a few km long and increases with decreasing height. The irregularities are therefore not purely field aligned initially although diffusion across the field lines could, over longer periods of time, produce purely field‐aligned irregularities which persist after the heating transmitter is switched off.
Propagation regimes for turbulent atmospheres
Authors: de Wolf D. A.
Published: February 2008

Although much progress has been made in the subject of propagation through random media recently, the average user of the results could be bewildered by the large number of governing parameters and conditions of validity of diverse scintillation statistics. Continuing from previous work summarizing a state of affairs of some years ago, we present some graphical representations of parameter regimes and discuss typical propagation links in nonionized media at optical and at radio wave frequencies, as well as microwave links through an ionized atmosphere. One useful graphical representation defines parameter regimes defined by a coordinate system that uses the number of mean free paths as one axis and the number of Fresnel radii as another. It is sketched for a medium defined by Kolmogorov turbulence laws in the inertial subrange.
Electron density profiles from ionograms: Underlying ionization corrections and their comparison with rocket results
Authors: Wright J. W. , Paul A. K. , Mechtly E. A.
Published: February 2008

Electron density profiles from nine daytime rocket flights at Wallops Island, Va., conducted by the University of Illinois at high and low levels of solar activity, are compared with profiles calculated by inversion of ionograms obtained at the same times and location. Sources of error and uncertainty in the ionogram inversion are discussed, as are means for their amelioration. In most cases, agreement between the two kinds of measurement within a few percent in electron density and within a few percent of a scale height can be achieved.
Ionizing nightglow: Sources, intensity, and spatial distribution
Authors: Young J. M. , Troy B. E. , Johnson C. Y. , Holmes J. C.
Published: February 2008

Photometers carried aboard an Aerobee rocket mapped the ultraviolet night sky at White Sands, New Mexico. Maps for five 300 Å passbands in the wavelength range 170 to 1400 Å reveal spatial radiation patterns unique to each spectral subregion. The major ultraviolet features seen in these maps are ascribed to a variety of sources: 1) solar Lyman α (1216 Å) and Lyman β (1026 Å), resonantly scattered by geocoronal hydrogen; 2) solar HeII (304 Å) resonantly scattered by ionized helium in the Earth's plasmasphere; 3) solar HeI (584 Å) resonantly scattered by neutral helium in the interstellar wind and Doppler shifted so that it penetrates the Earth's helium blanket; and 4) starlight in the 912 to 1400 Å band, primarily from early‐type stars in the Orion region. Not explained are the presence of small, but measurable, albedo signals observed near the peak of flight. Intensities vary from several kilorayleighs for Lyman α to a few rayleighs for HeII.
Tidal effects in the E region from incoherent scatter radar observations
Authors: Salah J. E. , Wand R. H. , Evans J. V.
Published: February 2008

Measurements of the neutral temperature in the altitude region 100 to 130 km during the past several years at Millstone Hill (42°N) and St. Santin (45°N) have revealed that, on the average, there exist strong semidiurnal tidal effects which can be identified with the (2,4) tidal mode propagating from the stratomesosphere. The average amplitude of the temperature oscillation reaches a maximum of about 35 K at 116 km with maxima at 0630 and 1830 hr LT. At each station, large variability is found in amplitude and phase from one observing period to another, particularly during winter. From classical tidal theory, the average temperature behavior implies a semidiurnal zonal wind oscillation with an amplitude of about 45 m sec−1 at 110 km having eastward maxima at about 0500 and 1700 hr LT, and a meridional component with similar amplitude having southward maxima at 0800 and 2000 hr LT. The downward phase velocity is about 4 km hr−1. These results are in good agreement with direct wind measurements at St. Santin, and with some recently reported characteristics of the height variations of sporadic‐E at midlatitudes.

At Arecibo (18°N), semidiurnal oscillations have also been found to dominate the E‐region temperature and wind structure with similar amplitude and phase velocities as above; however, the observed phase behavior is more variable than at midlatitudes and the average results do not allow reliable mode identification. Some results of recent simultaneous observations at low and midlatitudes are presented which imply that during any particular observing period, the E‐region structure must be controlled by local effects.
Current and future trends in ionospheric research
Authors: Bowhill S. A.
Published: February 2008

In the early days of upper atmosphere research, radio signals were the most useful diagnostic for studying ionospheric processes. During the space era, it has become possible to measure directly solar radiations that are screened from reaching the surface of the Earth, to measure the structure and composition of the upper atmosphere directly with in situ sensors, to conduct plasma experiments in space, to carry out remote sensing of the atmosphere from space, and to measure directly transionospheric radio propagation properties of the ionosphere. This recent dominance of space research methods in ionospheric research is becoming less marked as satellite opportunities diminish and greater emphasis is placed on studies of the ionosphere using new types of ground‐based instrumentation. Looking to the 1980s, the principal space flight opportunities will be associated with Spacelab, and new initiatives in ionospheric research will depend on a combined approach using all available methods for studying the dynamics and structure of the ionosphere. Future possibilities are outlined, with particular reference to new radio experiments on the ionosphere.
MHD gravity waves
Authors: Perona Giovanni E.
Published: February 2008

The dispersion relation of gravity waves propagating in a conducting atmosphere in the presence of a magnetic field has been evaluated. Extreme simplifying assumptions have been adopted in an effort to reach simple results. In this way, the applicability of the results to any real situation is highly doubtful. However, a qualitative and intuitive understanding of the influence of conductivity and magnetic field on the dispersion relation of gravity waves is more easily reached.
A reliable ionosonde for continuous automatic operation
Authors: Morgan M. G. , Pratt B.
Published: February 2008

Combining time‐tested techniques with modern electronic components, an inexpensive ionosonde producing high quality records and capable of unattended automatic operation for extended periods has been designed. Four instruments were built at a cost in 1967, exclusive of labor, of $2000 apiece. Three have been operated continuously for five years at a rate of one ionogram every two minutes, being attended but once a week to change the film. One of these ran 23 months with no maintenance whatsoever.
Propagation in random media with stationary temporal fluctuations
Authors: Gardner C. S. , Kavala F. , Plonus M. A.
Published: February 2008

Born's method is applied to the time‐dependent wave equation. Exact solutions, valid for all wavelengths, are obtained for the first‐order perturbation terms for monochromatic plane and spherical waves propagating in random media with stationary temporal fluctuations. It is shown that the temporal fluctuations of the medium can be neglected if the temporal frequencies of the fluctuations are much less than the frequency of the propagating wave and if the propagation time from the transmitter to receiver is much less than the coherence time of the medium. In the atmosphere for the case where (λ30/l40)L≪ 1, where l0 is the inner scale of turbulence, log‐amplitude and phase covariance functions were calculated for the polarized and depolarized fluctuations of plane waves propagating in slightly different directions. Numerical evaluation revealed that the polarized log‐amplitude fluctuations decorrelate for angular separations on the order of tan−1 [(λ0/L)1/2] while phase fluctuations decorrelate for angular separations on the order of tan−l(L0/L), where L0 is the outer scale of turbulence.
The brightness temperature of a half‐space random medium with nonuniform temperature profile
Authors: Tsang L. , Kong J. A.
Published: February 2008

The problem of microwave thermal emission from a half‐space random medium is solved. We consider a laminar structure which has a nonuniform temperature distribution in the vertical direction. A radiative transfer approach is applied. For constant absorption and scattering coefficients, the brightness temperature is determined by a simple closed‐form formula. Physical interpretations and numerical results are illustrated and discussed for the various cases.
The physical significance of the correlation ellipse in ionospheric drift analysis
Authors: Burke M. J.
Published: February 2008

It is shown that the correlation ellipse bears no relationship to the “average” shape of irregularities in the amplitude pattern formed at the ground from the interference of radio waves reflected or scattered from the ionosphere. The concept that the correlation ellipse should be related to the average shape arose because it was considered that the cross‐correlation coefficient for zero delay between two fading records (with spatial separation r) was related to the average normalized amplitude of the irregularities at a displacement r from the center of the average irregularity. As shown in this paper, the cross‐correlation coefficient for zero delay depends only on the mean fading period and the mean and variance of the time delays between corresponding fades. It retains its usual significance only if r is in the direction of drift.
Radiation from a line source carrying a traveling wave in a magnetoplasma
Authors: Pridmore‐Brown D. C.
Published: February 2008

A modulated beam of charged particles is represented as an infinite line antenna carrying a current distribution traveling along it at a prescribed speed. The radiation from such an antenna is calculated theoretically, and typical patterns are presented for conditions appropriate to the ionosphere and magnetosphere.
Excitation of cylindrical electron Bernstein waves by modulated thin electron beams
Authors: Ohnuma Toshiro , Shibata Kan , Adachi Saburo
Published: February 2008

When cylindrical electron beams, density modulated at a prescribed repetition frequency (f ≈ 3 to 6 MHz), are injected into plasmas along a magnetic field, cylindrical electron Bernstein waves are found to be launched nearly perpendicular to the electron beams. The wave amplitude and frequency are controlled easily. The mechanism of the excitation of cylindrical electron Bernstein waves by electron beams is investigated theoretically to explain the experimental results.
Spreading of waves emitted from an ELF/VLF source in the magnetosphere
Authors: Kelly Francis J. , Baker Dennis J. , Chayt Gerald A.
Published: February 2008

Electromagnetic waves from an ELF/VLF source in the magnetosphere may be propagated through the ionosphere to receiving antennas on the earth's surface. Among many factors important in estimating the received signal strength is the geometric spreading factor, dΩ'dAE, measuring the area, dAE, of the earth's surface intercepting the power radiated into the solid angle, dΩ from the source. The spreading factor has been isolated and accurately estimated by a ray‐tracing computer program. Calculations have been performed for transmissions at 3 and 10 kHz and for three different ionospheric models using source altitudes ranging between 300 and 8000 km for some representative receiver point locations. Spreading factors were calculated both for direct and multiple hop waves in the earth‐ionosphere waveguide. For low source altitudes (below about 2200 km) the coverage patterns of spreading‐factor versus the receiver's geographic position showed well‐defined peaks, indicating locally high radio fields. For higher altitudes the coverage patterns were broader but showed weaker maximum field strengths. A comparison was made with a simply estimated factor employed by Smith and Rorden, and quantitative and qualitative differences are noted.
On wavelike perturbations in the F region
Authors: Toman Kurt
Published: February 2008

Characteristics of wavelike perturbations in the F region are deduced from Doppler measurements made on CW transmissions between time station CHU, Ottawa, Canada, and AFCRL, Bedford, Massachusetts. For periods ranging from 5 to 100 min, occurrence frequencies and phase‐path amplitudes of F‐region perturbations are obtained for the years 1968–1970. While shorter periods are observed to occur more frequently than longer periods, peaks in the distribution are sometimes observed between 10 and 20 min. Amplitude distributions derived from phase‐path undulations, which usually reveal an increase of amplitude with period, are at times found to fluctuate, indicating preferred bands of quasiperiodic activity in the Fregion. For selected ionospheric undulation events, ratios of phase‐path amplitude to wavelength are estimated to be usually less than 0.02, but sometimes 0.05. The spectra of time series, derived from ionospheric Doppler measurements, are obtained by means of Fourier‐analysis and maximum‐entropy methods. These spectra are isometrically displayed using overlapping data windows while advancing in the time domain to observe the dynamics of ionospheric waves. Comparisons are made with comparable data samples derived from random numbers. While both spectral analyses show similar results, the maximum‐entropy method appears to make it more certain that temporal changes of the spectra result from actual changes in the periods of wavelike ionospheric perturbations. For estimating the propagation effects resulting from the overhead passage of several traveling waves, mirrorlike reflection surfaces are synthesized computationally through the superposition of cylindrical waves of different characteristics. For a bistatic radar configuration, their effects on changing ray‐azimuth deviations and Doppler shifts are illustrated.
Wave propagation in a one‐dimensional random inhomogeneous medium
Authors: Ryzhov Yu. A.
Published: February 2008

The problem of wave propagation in a medium with random one‐dimensional inhomogeneities of dielectric permittivity is considered in the approximation of a Markov random diffusion process. The solution of the diffusion equation for the distribution function of the reflection coefficient from the inhomogeneous slab is obtained. Some statistical moments of the solution are investigated. It is shown that the reflection coefficient has equally probable distribution of phase if the regular reflection at the boundaries of the layer vanishes. For this reason there is no regular component in a random reflected wave. Expressions are obtained for the intensity of the transmitted and reflected waves. A sufficiently thick layer reflects the whole energy of an incident wave in the form of the random scattered field energy. Also found are the formulas for the mean field inside the layer and behind it and for the effective permittivity of a one‐dimensional random inhomogeneous medium. The problem is considered for two limiting cases of a small‐scale (kl « 1) and a large‐scale (kl » 1) inhomogeneous medium.
Remote temperature profiling in the lower troposphere
Authors: Frankel Michael S. , Peterson Allen M.
Published: February 2008

Remote probing of atmospheric phenomena has become an area of intense research during the past decade. One result of this research is a technique for remote measurement of temperature profiles in the lower troposphere, which was developed and is being tested at Stanford University. This technique is based on the concept of Doppler‐tracking an acoustic pulse by an electromagnetic radar; hence the name radio‐acoustic sounding system (RASS). With this system, real‐time temperature profiles from near ground level to 1 to 3 km have been obtained. These data compare in accuracy with those obtained from radiosondes; however, use of the RASS is a much more cost‐effective procedure.
Theory and experiment of a mobile radio communication in tunnels by means of a leaky braided coaxial cable
Authors: Degauque P. , Demoulin B. , Fontaine J. , Gabillard R.
Published: February 2008

To realize a radio wave communication along mine galleries a few kilometers long without repeater, we show that it is possible to use a leaky braided coaxial cable, with an inductive coupling to the tranceivers. By using the transmission line theory, we determine the optimal electrical and geometrical constants of the cable. A communication 2 km long has been demonstrated for a total transmission loss along the line of about 70 dB. We also account for the possibility in which the cable is situated close to the wall along a short distance and we show that the increase in attenuation of the monofilar mode does not have a great influence on the performance of the cable. The theoretical approach is confirmed by experimental data for a number of specific cases.
ANNOUNCEMENT AND CALL FOR PAPERS
Authors: Fante R. L.
Published: February 2008

The 1976 International Symposium sponsored by the IEEE Antennas and Propagation Society (AP‐S) and a meeting of URSI sponsored by the US National Committee of URSI (USNC) will be held jointly at the University of Massachusetts on the Amherst Campus. The technical sessions for IEEE/AP‐S and URSI will be coordinated to provide a well integrated program. Authors are invited to submit papers on all topics of interest to the AP‐S and URSI memberships. The topics listed below are intended as suggestions and consideration will be given to papers covering other subjects. Inquires for information may be directed to R. Fante and C. Sletten, Technical Program Committee, AFCRL(LZ), Hanscom AFB, Massachusetts 01731, (617)861‐3683.
Oblique propagation of electron plasma waves in a magnetoplasma
Authors: Ohmori S. , Ohnuma T. , Adachi S.
Published: February 2008

The electron plasma waves which are radiated from a point source and propagate in an oblique direction with respect to an applied static magnetic field are investigated both theoretically and experimentally. The observed phase velocities and wave amplitudes in the oblique directions are explained by considering anisotropic characteristics of a magnetoplasma in which the directions of phase and group velocities are different. The observed phase velocity in the radial direction was found to agree with the theoretical ray velocity.
Intensity fluctuations due to an incoherent extended source seen through extended strong turbulence
Authors: Rumsey V. H.
Published: February 2008

The intensity correlation function for an extended incoherent source seen through strong turbulence is worked out assuming that the intensity randomization U≫ 1. The scintillation index is found as a function of source angular size θ0, path length z, wave number k, strength of turbulence A, and slope of the assumed power law turbulence spectrum α (α = 11/3 for the Kolmogoroff case). The scintillation index drops to about 0.5 when Ak2 Zαθ0α−2 ≈ 1.
Doppler shift formulas for waves in the ionosphere
Authors: Bennett J. A.
Published: February 2008

Ray techniques are used to examine the range of validity of the Doppler shift formula Δƒ = (−ƒT/c) dP/dt where ƒT is the transmitter frequency and P the phase path. The simple formula may be used when the time scale of changes in the medium and transmitter and receiver positions is sufficiently large. However, it may fail for quite moderate rates of change. For a moving transmitter a more accurate analysis shows that there may be additional solutions, associated with the complex and “faster than light” Doppler effects, which it does not predict. Space‐time rays are used to obtain formulas valid in the case where the time scale of the changes, though still large in comparison to the reciprocal of the wave frequency, is not large compared with the time characterizing the wave propagation from transmitter to receiver.
A comparative study of three techniques for using the spectral matrix in wave analysis
Authors: Arthur C. W. , McPherron R. L. , Means J. D.
Published: February 2008

Digital power spectral analysis and coherency analysis are powerful techniques for studying ultra‐low‐frequency (ULF) waves in the earth's magnetosphere. Wave polarization parameters provided by these techniques are important in the development of theoretical models for wave generation. Because of this, it is important to understand the capabilities of the digital analysis techniques. Three different techniques of using the spectral matrix to do wave analysis have been presented in the literature. Because data for wave studies involve measurement in arbitrary coordinate systems, it is necessary to transform the spectral matrix to the principal plane of the wave before coherency analysis can be performed. The fundamental differences in the three techniques lie in how they determine the transformation to the principal plane. A comparative study of these three techniques was done using simulated data involving known wave and noise properties and real ULF wave event data from the geosynchronous satellites ATS 1 and ATS 6. In general, the quality of performance of the three different techniques on both simulated and real wave events was approximately the same.
Measurements of rain effects on an 18‐GHz dual‐polarized propagation link
Authors: Bostian C. W. , Stutzman W. L. , Wiley P. H. , Marshall R. E.
Published: February 2008

This paper presents the results of rain attenuation and depolarization measurements made at 17.65 GHz along a 1430‐m terrestrial path. The experimental observations agree well with theory.
The reconciliation of an F‐region irregularity model with sunspot cycle variations in spread‐F occurrence
Authors: Singleton D. G.
Published: February 2008

A recently proposed means of combining models of ionospheric F‐layer peak electron density and irregularity incremental electron density (ΔN) so as to simulate the global occurrence probability of the frequency‐spreading component of spread‐F is discussed. This procedure is then used to model experimental spread‐F occurrence results. It is found possible to readily simulate the sunspot‐maximum results, independently of season, with only small adjustments to the amplitudes of the empirical expressions used to model ΔN in the several latitude regimes. However, at sunspot minimum and for each season, the ΔN model requires modification in the equatorial and midlatitude regions of high irregularity incidence, before successful simulations of the spread‐F data can be obtained. These modifications, which include a broadening of the equatorial region and a poleward shift of the midlatitude region with decreasing sunspot number, are discussed in detail. It is concluded that the scintillation data base, from which the original ΔN model derives, is not sufficiently representative with regard to sunspot number and magnetic index. The use of the spread‐F adaptation of the ΔN model, as well as its original scintillation version, to rectify these failings of the ΔN model are also discussed.
A method for inverting oblique sounding data in the ionosphere
Authors: Chuang S. L. , Yeh K. C.
Published: February 2008

We have developed in this paper a method of inverting backscatter leading edge ionograms and fixed distance oblique ionograms to obtain ionization profiles. The problem of ionogram inversion is first formulated in such a way that the Backus‐Gilbert technique can be applied. This inversion technique starts by assuming an initial profile based on available knowledge. Oblique group paths are computed by using this initial profile and are compared with the experimental data. The discrepancy in group path is used as a basis for improving the profile and thus an iterative procedure is developed. This iteration is continued until an optimum solution is found. As is well known, when ionograms are given at discrete frequencies there may exist an infinite number of profiles that will yield the observed group path data. Among this infinite number of solutions there is an optimum one in the sense that its fractional departure from the initially assumed profile is a minimum in terms of value at boundaries and in terms of the profile curvature. The method is then applied to the special vertical incidence case and reasonably fast convergence is obtained. This success demonstrates the promise of this method in inverting oblique sounding data.
On auroral electrojet curvature and the interpretation of azimuth‐scan, radar Doppler data
Authors: Brekke A. , Tsunoda R. T. , Baron M. J.
Published: February 2008

In this paper we show that the geometrical configuration of the auroral electrojet is of great importance in the interpretation of Doppler velocity data obtained by auroral backscatter radars operated close to the auroral oval at low elevation angles. We show that some of the characteristic features in the azimuthal dependence of the radar Doppler velocity can be explained by accounting for the auroral electrojet curvature produced by (1) the shape of the auroral oval, (2) the altitude variation of the Hall and Pedersen currents, and (3) other local variations in current flow. An important application of the geometrical considerations described in this paper is the estimation of the ionospheric electric field from Doppler‐velocity variations observed in the diffuse radar aurora.
On the relativistic invariance of the complex phase of plane waves
Authors: Ko H. C.
Published: February 2008

Using the covariance of Maxwell's equations, the complex phase of plane waves in lossy media is shown to be invariant under Lorentz transformations. The complex wave vector k = kr + iki and the complex frequency ω = ωr + iωi form two four‐vectors, (kr, iωr/c) and (ki, iωi/c). In a lossy medium a homogeneous plane wave in one inertial frame will appear in general as an inhomogeneous plane wave in another moving inertial frame. The general relativistic disperison relation for a moving lossy medium is derived.
The input admittance and near‐field coupling of a TEM‐driven concentric annular slot array
Authors: Irzinski E. P.
Published: February 2008

A theoretical study of a pair of TEM‐driven concentric annular slot antennas radiating through a perfectly conducting ground plane is described. The problem solution is accomplished in the rigorous Maxwell equation‐boundary value sense. Closed‐form solutions are obtained for the annular slot admittance and mutual coupling. These expressions include the effects of higher‐order TM modes which exist only in the evanescent state. Approximate solutions are obtained to a number of infinite coupling‐type integrals which are subsequently employed for numerical evaluation of the admittance and mutual coupling for several annular slot configurations. The effects to the annular slot admittance and mutual coupling are separable into those that are purely TEM induced and those that result from the presence of the beyond‐cutoff higher‐order TM modes. The analysis shows that the higher‐order mode perturbations are relatively minor provided that the width of the annular slots is less than one half wavelength. The method of analysis presented can be readily extended to multiple annular slot ring arrays under any set of TEM‐driven conditions.
Variations of atmospheric radio noise at Ping‐Cheng, Taiwan, China
Authors: Huang Yinn‐Nien
Published: February 2008

The observation of atmospheric radio noise by use of the ARN‐2 recorder has been carried out since June 1967 at Ping‐Cheng. Using the data obtained from June 1967 to December 1972, the diurnal, seasonal, and solar cycle variations of the atmospheric noise power were investigated. The seasonal and solar cycle variations of the diurnal amplitude of the noise levels were also investigated. At 5 MHz, the diurnal amplitude of the noise power as well as the noise power at noon were found to be slightly dependent on the sunspot number. Comparison between the CCIR atmospheric noise predictions for Ping‐Cheng and the present observed results shows some differences.
A quasi‐optical approximation for absorbing media having dispersion relations with repeated solutions
Authors: Bennett J. A.
Published: February 2008

A quasi‐optical approximation is constructed for waves in media for which the dispersion relation has repeated solutions, the order of repetition being constant throughout the medium. By a suitable choice of the basis vectors representing the polarizations corresponding to the repeated solution, the equations for the amplitude may sometimes be uncoupled. An important application is to radio waves in an isotropic absorbing medium.
System considerations and design
Authors: Goell J. E. , Kao C. K.
Published: February 2008

The advantages of optical fiber transmission make its use attractive for a host of applications. The requirements of fiber systems are discussed in general and design concepts and approaches are given to provide an overall appreciation of system design.
An experimental 400 Mb/s optical transmission system using SELFOC® fibers
Authors: Shimodaira M. , Hiramatsu T. , Honma K.
Published: February 2008

As a result of recent progress in the glass refining process and index profile control technique, it is possible to get a very low loss and wide band SELFOC fiber which is made of multicomponent glass. For experiments of high bit‐rate PCM transmission using this fiber, a compact 400 Mb/s repeater has been developed. Transmission of a 400 Mb/s PCM signal has been achieved at an error rate of less than 1×10−9 with 5.2 km repeater spacing. Experiments on two repeater links showed no significant degradation in error rate characteristics. It is the purpose of this paper to describe the low loss SELFOC fiber, the design concept of the repeater, and the results of the experiment.
Two‐dimensional analysis of the GaAs double hetero stripe‐geometry laser
Authors: Rozzi T. , Itoh T. , Grun L.
Published: February 2008

The double hetero stripe‐geometry laser is analyzed using a technique which has recently been referred to as the effective dielectric constant (EDC) method. Unlike previously reported techniques, the EDC method allows both vertical and horizontal directions in the cross section of the laser to be taken into account in analyzing the field confinement mechanism. Computed data on field concentrations and cutoff behaviors of the fundamental mode are presented for both single and coupled structures.
An alternative expression for the curvature loss of a dielectric waveguide and its application to the rectangular dielectric channel
Authors: Kuester Edward F.
Published: February 2008

An alternative expression for the radiative attenuation coefficient of a surface wave propagating along a curved dielectric waveguide of arbitrary cross section is derived, which contains integrals of the fields inside the guide rather than those outside, as in previous formulas. This is especially suitable for application to guides for which the exterior fields are not known accurately, but reasonable approximations exist for the internal fields. As an example the expression is applied to the case of a rectangular dielectric channel waveguide, and a comparison made with a previous result of Marcatili.
A new technique for the determination of modal characteristics of optical waveguides
Authors: Daniele V. , Zich R. , Montrosset I.
Published: February 2008

The evaluation of the modes into a guiding structure for integrated optics is successfully approached with a suitable formulation of the problem. The actual guide is considered as a perturbation of a simpler structure (unperturbed guide) with known modal characteristics. By coupling the continuous and discrete modes of the unperturbed structure, an integral equation is obtained which can be handled numerically through the alternative use of the moment method or of continuous spectrum discretization. Numerical results are presented for some one‐dimensional problems and successfully compared with those obtained with different theoretical approaches.
Prediction of slant path rain attenuation statistics at various locations
Authors: Goldhirsh Julius
Published: February 2008

A method is described here for predicting attenuation statistics as a function of frequency and elevation angle at various locations. This method uses median reflectivity factor‐height profiles as measured with radar. The zenith attenuations for each profile are calculated assuming a Laws and Parsons drop size distribution. These attenuations are tied to the ground point rain rate and the corresponding probability exceedance levels as measured using long term raingauge data for the particular region in which statistics are to be predicted. The slant path attenuations at other elevation angles, θ (θ ≥ 20°), are arrived at using the csc θ factor. The attenuation contribution of clouds which occur in the presence of rain is also considered using model liquid water content‐height profiles. Eight comparisons of absolute probability fade distributions are made of the measured and predicted cases, namely, for Maryland (15 GHz), Texas (30 GHz), Slough, England (19 and 37 GHz), Fayetteville, N.C. (13 and 18 GHz), and Cambridge, Mass. (13 and 18 GHz). In comparing the measured and predicted cases, the overall average of the probability ratios was 1.4.
A pulse synthesis technique for improving ionosonde resolution
Authors: Devlin J. C. , Dyson P. L. , Hammer P. R.
Published: February 2008

When an ionosonde sweeps through a given frequency range, the transmitted pulses may be regarded as the frequency components of a synthesized pulse. If measurements are made of the phase and amplitude of the ionospheric echoes observed over this frequency range they may be regarded as the frequency spectrum of the echo of the synthesized pulse. The range of the echo of the synthesized pulse is therefore given by the Fourier transform of the phase and amplitude measurements. Using a frequency range of 128 kHz gives a range quantization of 586 m so that echoes separated by about 1 km in range can be resolved. This paper discusses the principles of the method and presents examples of results obtained using the method.
Energy transfer in macroscopic plasma
Authors: Unz Hillel
Published: February 2008

The energy balance equation is derived for macroscopic, single fluid plasma from the general electromagnetoplasma‐gas‐dynamics nonlinear equations. The electromagnetic, mechanical and internal energies of the plasma are defined and the transfer of these energies is given.
Dual‐beam TEM applicator for direct‐contact heating of dielectrically encapsulated malignant mouse tumor
Authors: Cheung A. Y. , Dao T. , Robinson J. E.
Published: February 2008

A microwave heating technique, a direct parallel to the parallel‐opposed treatment field that is used in therapeutic ionizing radiation, has been developed. The sources of radiation are two oppositely directed TEM applicators that operate at 2450 MHz. The applicator's design consists of an open‐ended rectangular waveguide that is partially loaded with low‐loss dielectric slabs. Such a structure can support a TEM mode of propagation. On direct contact with a tissue‐equivalent slab, the TEM applicator heats uniformly in the transverse plane. Exposed C3H mouse tumors, 1 cm in diameter and transplanted to grow on the flank of mice, were encapsulated within simulated phantom materials with dielectric properties that are similar to that of the tumor to form a rectangular slab. The TEM applicators were used to heat from opposite sides at alternating intervals of 5 to 50 seconds. The technique is capable of producing a uniform temperature of 42 (±0.25) °C over the entire tumor.
Microwave irradiation of the isolated rat heart after treatment with ANS blocking agents
Authors: Reed James R. , Lords James L. , Durney Carl H.
Published: February 2008

Microwave irradiation (960‐MHz CW) at a specific absorption rate (SAR) near 1.5 W/kg induced bradycardia in isolated rat heart as reported earlier. When parasympathetic and sympathetic nerves were simultaneously blocked, respectively, by atropine and by propranolol, no significant effect of irradiation was observed. Previous experiments have revealed that atropine plus irradiation produces tachycardia and propranolol plus irradiation produces bradycardia. The results may indicate a microwave neuron or microwave‐synapse interaction by a mechanism other than generalized heating of tissues.
Theoretical calculation of frequencies and thresholds of microwave‐induced auditory signals
Authors: Lin James C.
Published: February 2008

Previously developed thermoelastic models of microwave‐induced auditory sensations are applied to calculate the frequency and amplitude of the acoustic signals that are generated in human beings and laboratory animals. Graphs of computed displacement and pressure as a function of time are presented for several species.
Properties of joint gaussian statistics
Authors: Knepp Dennis L. , Valley George C.
Published: February 2008

In this paper joint‐ or complex‐gaussian statistics are assumed to apply to the in‐phase and quadrature components of an electromagnetic wave which has propagated through a turbulent medium, and the consequences of this assumption are compared to tropospheric, ionospheric, and laboratory propagation experiments. New curves for the cumulative probability distribution of intensity and for the variance of intensity versus the variance of the logarithm of intensity are presented. Joint‐gaussian statistics are shown to fit the total set of turbulence propagation results better than the log‐normal, Rice‐Nakagami, or Nakagami‐m distributions. However, a major feature of optical observations cannot be fit by joint‐gaussian statistics: the straight‐line cumulative intensity distributions in the saturation regime that reflect a large probability of occurrence of high intensity spikes.
A generalized method for environmental surveillance by remote probing
Authors: Gjessing Dag T.
Published: February 2008

New components and methods in the field of microwave techniques, electrooptics, computer technology, statistics, and electromagnetics open new and very interesting possibilities with regard to detection and identification problems. The current contribution suggests with varying degrees of substantiation a set of unified detection methods which may conceivably have an impact on several application areas (environmental surveillance, detection/identification of specific objects). The basic principle is the following. Most of the existing detection/identification systems do not make optimum use of all the a priori information that one generally is in possession of with regard to the target of interest. Knowing the geometrical shape of the target of interest and its molecular surface structure (e.g., structure of paint), an illumination function can be structured (matched filter concept) which gives optimum system sensitivity (minimum receiver bandwidth) with respect to the target of interest at the expense of the sensitivity for background objects (interferents). Theoretical results are given in the paper for a limited number of geometrical objects and for two different molecular surface compositions. It is shown that the system sensitivity and identification capability can be improved considerably using the suggested matched filter illumination technique.