bluuebunny/crossref_metadata_2025 huggingface dataset:
A Proposed Wide‐Band Satellite Transmission Experiment
Authors: Fremouw E. J. , Burns A. A.
Published: February 2008

An experiment has been proposed, for the early 1970's, for the purpose of obtaining data on ionospheric and tropospheric effects on wide‐band trans‐atmospheric transmission. It is desired to radiate three combs (each composed of seven to ten highly stable, phase‐coherent CW signals) from a geostationary satellite and to monitor the amplitude and phase of the signals in considerable detail. The tones would be grouped at S band, L band, and UHF, with group bandwidths and frequency spacings set to measure the mean dispersion and second‐order parameters of the random part of the channel. One CW signal would be transmitted at HF and one at VHF to provide a comparative link with the existing collection of scintillation data obtained by various workers. Some multiple‐antenna observations are desired so that spatial coherence questions can also be attacked. It is hoped that observations will be made through the equatorial, midlatitude, and auroral ionosphere.
40‐MHz Ionospheric Scintillation and the Sporadic‐E Layer
Authors: Anastassiadis Michael , Matsoukas Dimitris , Moraitis George
Published: February 2008

Simultaneous observation of minute‐by‐minute ionograms and signal‐amplitude recordings from Explorer 22 (BE‐B) have shown a marked coincidence of high scintillation indices and a height spreading of the sporadic‐E trace. These observations, made at Athens (37° 58′N, 23° 43′E) over a period of 18 months, lead to the conclusion that the existence of spreading is usually associated with strong scintillation.
Ionospheric Ducting of Radio Signals in the ORBIS CAL Experiment
Authors: Mullen John P. , Zuckerman Lawrence H.
Published: February 2008

ORBIS CAL is the mnemonic for Orbiting Radio Beacon Ionospheric Satellite for Calibration, which is an experiment in ionospheric ducting of satellite beacon signals that was performed March 19–24, 1969. Propagation ranges of 20,000 kilometers were recorded frequently at day and night hours at Thule and at Sagamore Hill, Massachusetts. The results of this experiment are compared with those of earlier ORBIS attempts, and the probable propagation mechanisms are discussed. Rough path‐loss calculations indicate that received levels exceed those of free‐space propagation by about 5 decibels.
Mode Conversion of Gaussian Light Beams Propagating Through a Random Medium
Authors: Imai Masaaki , Kikuchi Shoichi , Matsumoto Tadashi
Published: February 2008

Mode conversion of a Gaussian beam due to random fluctuations of a turbulent medium is discussed. The mean‐square value of the mode‐conversion coefficient (i.e., the power occupation of the higher mode in the perturbed field) is obtained by the perturbation technique. The results show that mode conversion decreases in the neighborhood of the focal point of a focused beam and that the decrease at that point becomes significant when the aperture size is large compared with the scale of the turbulence of the medium. The influence of the anisotropy of the fluctuations on mode conversion is also discussed.
D‐region Electron Temperatures at the Northern Auroral Zone
Authors: Lerfald G. M. , Little C. G.
Published: February 2008

To determine the approximate temperatures of free electrons in the sunlit ionospheric D region an experiment was conducted at a site near College, Alaska, during the summer and fall of 1960. A dual polarized antenna whose beam was directed at the zenith was used to observe alternately the incident radio noise fluxes in the ordinary and extraordinary polarizations at the frequency 2.89 MHz. The 2.89‐MHz radio noise flux measured on a vertical dipole antenna was used to check for propagated interference from low elevation angles. The results show that, during the five‐month observing period, the extraordinary‐mode antenna registered a median daytime temperature of 260°K, with a standard deviation of about ±23°K, which indicates that the electrons in the D region are approximately in thermal equilibrium with the neutral gas, even at the auroral zones. The theoretically anticipated antenna temperatures, based on assumed ionospheric parameters, agree fairly well with the observed experimental values. In particular, the observed variations of antenna temperature with solar zenith angle can be matched by use of reasonable theoretical models.
Electric Field Observations of Ionospheric Whistlers
Authors: Maynard N. C. , Aggson T. L. , Heppner J. P.
Published: February 2008

A Nike‐Tomahawk sounding rocket was launched near local noon on November 8, 1966, from Wallops Island with a triaxial electric field experiment using long cylindrical dipoles for sensors. Twenty ELF whistlers with dispersion constants ranging from 0.15 to 0.85 sec1/2 were detected and identified as having propagated up to the rocket through the E region from the earth‐ionosphere waveguide. The data extend to the smallest dispersion ever encountered and the lowest frequencies observed on ionospheric whistlers (60 Hz). The waves were eliptically polarized, becoming more nearly circular at higher altitudes. Analysis showed good agreement between the experimental results and quasi‐longitudinal (QL) propagation theory for amplitude, dispersion, and polarization characteristics of the wave once it is away from the D‐ to E‐region boundary. No appreciable effects of negative ions or protons were observed in the dispersion of the whistlers.
Scattering From a Turbulent Plasma
Authors: Guthart H. , Graf K. A.
Published: February 2008

The scattering of electromagnetic waves from a dense turbulent plasma has been examined experimentally. The experiments include measurements of bistatic radar cross section, Doppler frequency, backscattered cross‐polarized signals, and distribution of scattered power by a radar interferometer. Comprehensive diagnostic measurements were made on the plasma so that the radar measurements could be compared to a proposed scattering model. Using the model, the radar cross section of the inhomogeneous plasma can be calculated for peak electron densities well beyond critical. The agreement between calculations and experiments is excellent.
A Theoretical Study of Optical Wave Propagation Through Random Atmospheric Turbulence
Authors: Laussade Jean‐Pierre , Yariv Amnon
Published: February 2008

A new method for obtaining exact analytical expressions for some statistical functions of an optical wave propagating through a randomly turbulent medium is reported. A power‐series solution of the wave equation (∇2 + k2n2(x))u(x) = 0 is derived for a homogeneous random‐refractive‐index field n(x). Exact analytical expressions are obtained for the average wave function 〈u(x)〉 and the two‐point correlation function 〈u(L, r1)u*(L, r2)〉, with the added assumption that n(x) is a Gaussian random process always close to unity. The intensity correlation function 〈I(L, r1)I(L,r2)〉 is investigated, and recent experimental results regarding the behavior of the intensity fluctuations are discussed.
VLF Mode Propagation Across an Elevated Coastline
Authors: Wait James R. , Spies Kenneth P.
Published: February 2008

In this paper, we outline a derivation for and present calculations for the mode conversion at an elevated coastline between sea and land. It is shown that the land elevation above sea level will modify the conversion coefficients, particularly when the propagation is from land toward sea.
Phase‐Monopulse Tracking Errors Due to Mutual Scattering Effects in Phase‐Scanned Arrays
Authors: Lewis D. J. , Buck G. J.
Published: February 2008

The voltage at the terminal of each half of a phase‐monopulse antenna is induced by the incident wave and by the electromagnetic fields scattered from the other half of the antenna. In phase‐scanned arrays, the asymmetrical scattering by the antenna of the waves that are incident from a direction other than broadside introduces a tracking error into the system. A qualitative investigation of the cause of the pointing error indicates that the error is dependent on the spacing between the halves of the antenna and on the radiation and scattering patterns of the subarrays. Carter's formulas for mutual impedance are used to give a more accurate estimate of the magnitudes of the pointing error and error slope that are caused by the mutual scattering in arrays of dipoles. The results of the calculations for arrays of half‐wavelength dipoles can also be used to describe the pointing error in arrays of slots on an infinite planar conductor, which serve as an approximation to slot arrays on a finite planar conductor.
Using Loran‐C Transmissions for Long Baseline Synchronization
Authors: Shapiro L. D. , Fisher D. O.
Published: February 2008

The use of Loran‐C transmissions for time and frequency synchronization has been discussed in a number of recent publications. This paper presents further developments of the techniques of relating Loran‐C times of transmission with the universal time‐coordinated (UTC) second. In addition, it reports on the current synchronization status of Loran‐C transmissions and outlines typical instrumentation configurations for use with long baseline experiments as well as for other applications.
Hydrogen‐Maser Time and Frequency Standard at Agassiz Observatory
Authors: Levine Martin W. , Vessot Robert F. C.
Published: February 2008

A hydrogen maser was installed at the Harvard College Observatory‐Smithsonian 84‐foot radio telescope in Harvard, Massachusetts, for very long baseline interferometry (VLBI) experiments in October, November, and December of 1969. The maser is a compact unit (42 by 22 by 22 inches) of relatively low power consumption, designed specifically for field use; it is readily transportable. A precision 5‐MHz crystal oscillator that is phase locked to the maser provides all frequency and time references for the VLBI receivers, recorders, and clocks. The maser was tuned against a rubidium standard by a rapid flux‐switching technique; maser frequency resettability was estimated to be approximately ±3×10−13 with an over‐all accuracy of approximately ±1×10−12. Loran‐C was continuously monitored during the VLBI experiments, and the results of the Loran‐C maser comparisons are included.
Radio Reflectivity of Tropospheric Layers
Authors: Thayer G. D.
Published: February 2008

Radio reflection coefficients for tropospheric elevated layers are examined as functions of the ratio of layer thickness to the effective radio wavelength and the refractive index structure of the layers. The layer reflectivity is shown to be nearly independent of the refractive index structure for small values of the thickness‐wavelength ratio. Results for some layers observed with refractometers show that the reflectivities for large thickness‐wavelength ratios are generally larger than those given by the simple linear or constant‐gradient layer model.
Distributions of Nighttime F‐Region Molecular Ion Concentrations and 6300‐Å Nightglow Morphology
Authors: Brasher W. E. , Hanson W. B.
Published: February 2008

A numerical technique is employed in solving the coupled, nonlinear system of equations for the O+, NO+, and O2+ number densities in the nighttime F region, including the effects of diffusion, E×B drift, and neutral air motions. The best fits to the ‘sunset’ [Johnson, 1967] and ‘midnight’ [Holmes et al., 1965] rocket observations of the ion profiles obtained at White Sands, New Mexico, are achieved by iteratively varying the neutral wind, the electrodynamic drift, the neutral atomic nitrogen and nitric oxide concentrations, and the ion‐atom interchange and dissociative recombination rate coefficients. The best fit results for both sets of profiles with a Jacchia model atmosphere are achieved with the rate coefficients (cm3 sec−1) at 300°K given by γN2 = 1.1×10−12, γO2 = 2.0×10−11, αNO+ = 3.5×10−7, and αO2+ = 3.1×10−7, each with an assumed inverse temperature dependence. In addition, the ‘sunset’ best fit solutions require that the chemical time constant τ for reaction of O2+ with N and NO be 500 seconds at 200 km and that the net vertical plasma transport velocity wz due to E×B drift and a neutral wind be downward with a speed of 14 m sec−1. The midnight best fit solutions are achieved with τ = 2.5×103 at 200 km and wz = 10 m sec−1 upward. The 6300‐Å nightglow morphology in the inter‐tropical region is computed directly from the ion concentrations calculated for assumed drift and neutral wind models representative of equinoctial, sunspot‐minimum conditions. Isophote contours of zenith intensity are presented to illustrate the nightglow morphology associated with the decay of the Appleton anomaly. Calculated results are compared with the observations of Barbier [1964] to demonstrate the influence of electrodynamic drift on the morphology of nightglow enhancements. The results show that the electrodynamic drifts required to produce the observed enhancements are consistent with the drifts observed at Jicamarca.
A Unified Description of the Tidal Effects in ƒ0F2
Authors: Rush C. M. , St. John D. E. , Venkateswaran S. V.
Published: February 2008

The ionospheric spectrum of the critical frequency of the F2 region, ƒ0F2, is studied in detail at 35 locations during solar maximum and at 21 stations during solar minimum. The spectra contain prominent lines superposed on background continua. The most prominent lines correspond to solar periods of 24, 12, and 8 hours. Lines at half a lunar day (period of 12.48 solar hours) and at two lunisolar periods have also been detected in all the spectra investigated. The lunisolar lines have statistically significant amplitudes only at the low‐latitude stations. Our analysis indicates the influence in the F region of plasma transport processes such as E×B drift, ambipolar diffusion, and ion‐drag effects of the neutral air wind generated by the thermospheric diurnal density variations. An assessment of the roles of some of these processes is attempted in terms of the results obtained from our analysis.
A New Stable Capacitor and its Application to the Measurement of Angle
Authors: Makow David
Published: February 2008

A capacitor that consists of four suitably spaced rings is considered for use as a reference standard and as the main element of a device for precise measurement of angle. In this capacitor, the mean of the two values of capacitance between the diagonally opposite rings is a second‐order function of random variations of ring spacing and shape. This property promises good stability and leads to simplified construction. When used for angle measurement, a ratio of two capacitances defines the angle. This makes variations of supply voltages, temperature, humidity, and pressure of lesser concern. Possible applications are in the fields of astronomy, geodesy, space technology, and precision mechanics.
Simple Models of the Lower F2 Layer Near the Dip Equator
Authors: VanZandt T. E. , Clark W. L.
Published: February 2008

For the lower F2 layer very near the dip equator it is assumed that vertical electromagnetic drift is important but that other contributions to the divergence of the ionospheric plasma are not. By also assuming constant scale heights and by making other usual approximations, a continuity equation is obtained that can be solved in terms of tabulated transcendental functions, for both day and night. It is shown that these solutions fit very well to electron density profiles measured by the incoherent scatter technique near the dip equator; this fit suggests that the assumptions and approximations are suitable. From these fittings, reasonable estimates of the rates of photo‐ionization and recombination are obtained.
Hourly Changes in Conjugate Location Determined From Absorption and Field Data
Authors: Campbell W. H.
Published: February 2008

The ionospheric absorption detected by five‐riometer arrays and the concurrent magnetometer records from Great Whale River, Canada, and Byrd, Antarctica, were studied during mildly active periods of August 23, 1966, and April 24, 1967. Through use of the four methods of absorption gradient variation, correlated absorption region, triangulated current, and field pulsation patterns, evidence of hourly change in apparent conjugate location was sought. The riometer data showed analogous changes in the two hemispheres but rather random variations in conjugate position. The field pulsation patterns were not interpretable. The relative north‐south position of the auroral electrojets from the two stations indicated a regular change in the outer magnetosphere, which probably caused a variation in the conjugate location.
The Dungey Model of the Magnetosphere, and Astro‐Geophysical Current Sheets
Authors: Speiser Theodore W.
Published: February 2008

By the addition of an interplanetary magnetic field in various orientations to a closed magnetosphere model, the Dungey model was generated for all orientations other than a strictly northward interplanetary magnetic field. Particles can be accelerated in both the dayside magnetopause current sheet and in the tail current sheet, but there are inherent asymmetries. Particles may have asymmetric access to the north or the south polar caps, depending on the interplanetary field orientation. The breakdown of the usual adiabatic theory is discussed for a model current sheet.
A Model of the Geomagnetic Cavity
Authors: Coleman Paul J.
Published: February 2008

A heuristic model of the geomagnetic cavity is introduced. The model includes a unipolar induction current JU, that is driven by the solar wind. The current is generated by the solar wind plasma flowing in the magnetopause boundary layer. This current closes in the ionosphere. The electromagnetic forces associated with JU drive the magnetospheric convection. Even though the solar wind plasma at the magnetopause is basically collisionless, the plasma penetrates more deeply into the geomagnetic cavity than it would if the magnetopause were an ideal Chapman‐Ferraro sheath because the boundary layer flow is non‐adiabatic in the regions where JU is nonzero. Downstream from the earth the resulting expanded boundary layer forms the plasma sheet and the geomagnetic tail. Since the generation of JU does not depend on the existence of an interplanetary magnetic field, the geomagnetic cavity is closed when the interplanetary field is zero. The tangential drag is developed in the part of the boundary layer that lies forward of the midnight‐meridian intersection of the leading edge of the neutral sheet. The tail is produced by the inflation of the downstream part of the modified cavity that is formed by the superposition of the geomagnetic field and the magnetic field of JU. Transient phenomena produced by changes in JU include substorm expansions and injections of ring current particles which are initiated by decreases in JU. Changes in JU are caused by changes in the solar wind velocity (i.e., by changes in the unipolar emf) and by changes in the effective resistance to the flow of JU. If there is a critical value of |JU| above which the current is unstable, then there is a corresponding critical magnitude of the unipolar emf and therefore of the solar wind velocity. Such an instability in JU would account for the positive correlation between solar wind velocity and Kp. When the interplanetary magnetic field is greater than zero, shear stresses are set up between the solar wind plasma in the magnetopause boundary layer and that in the magnetosheath. The unipolar induction, i.e., the unipolar emf, and the resulting tangential drag then depend on the direction and magnitude of the interplanetary field as well as on the velocity of the solar wind and the electrical (Pedersen) resistivity of the magnetospheric plasma. The many attractive features of the model, especially the simplicity of the tangential drag mechanism, suggest that unipolar induction is a competitive alternative to magnetic field line reconnection and the other mechanisms that have been proposed to account for the tangential drag on the cavity and the various transient cavity phenomena.
Pulse Return from a Low‐Density Dielectric Cylinder
Authors: Plonus M. A.
Published: February 2008

A solution is presented for the backscattered field of plane‐wave pulse modulated carrier incident broadside on a low‐density dielectric circular cylinder. The pulse return is expressed in terms of the inverse Laplace transform of the CW backscattered fields. Finite cylinders are considered with use of the infinite cylinder fields in an approximation.
Radiation Patterns of Four Symmetrically Located Sources on a Perfectly Conducting Sphere
Authors: Du Li‐jen , Tai C. T.
Published: February 2008

The radiation field of dipoles or small apertures on a perfectly conducting sphere has been examined analytically with the aid of the dyadic Green's function technique. The patterns of four symmetrically located sources (dipoles or small apertures) on the sphere have been calculated to illustrate the diffraction phenomena due to spheres of various dimensions.
Midlatitude Auroral Arcs of 6300 Å (O I) and the Concurrent Ionospheric Current System
Authors: Okuda M. , Old T. , Kim J. S.
Published: February 2008

A multiple midlatitude 6300‐Å auroral arc occurred during the recovery phase of a geomagnetic storm on March 8/9, 1970. Variations of the arcs were characterized by a southward shift in position and by a diminution in intensity with time before midnight. During the recovery phase of the storm, well‐defined magnetic baylike disturbances occurred. The vairations in both position and brightness of the concurrent arc were strongly correlated with changes in the H and D components of these geomagnetic field deviations. An equivalent current system is determined from these baylike disturbance fields observed at twenty‐six magnetic observatories for periods when the correlation was strongest. The current system found is similar to that of the DP 1 field, with a superimposed DP 2 field. The changes in these fields that are associated with the bayklie disturbances are presented to account for the transient variations observed in the intensity and position of the midlatitude auroral arc.
Radiation From a Parallel‐Plate Waveguide into a Dielectric or Plasma Layer
Authors: Kostelnicek R. J. , Mittra R.
Published: February 2008

An analytical solution for radiation from a truncated parallel‐plate waveguide into a dielectric or plasma slab is obtained by solving the Hubert problem associated with a certain singular integral equation. The technique has the advantage that the edge condition is easily shown to be satisfied, and numerical results can be obtained with excellent accuracy. Numerical results are presented for a variety of dielectric and plasma slabs, parallel‐plate separations, and aperture‐to‐slab distances.
The Propagation of Electromagnetic Waves in Tubes with Large Wall Conductivity
Authors: Mann James E.
Published: February 2008

We solve for the fields in a waveguide with finitely conducting walls by a singular perturbation technique. The method provides a systematic procedure for finding higher‐order terms in the solution and also yields insight into the effects of conductivity on a waveguide whose cross section has degenerate eigenvalues. The problem is formulated in terms of the Hertz potential with the guide excited by an electric vector polarized longitudinally (TM case). Since the equations are similar for the case of the guide excited by a magnetic vector polarized longitudinally (TE case), the method developed may be easily extended to include that case.
Investigations of North‐South Ionospheric Movements at a Low‐Latitude Station
Authors: Bamgboye D. K.
Published: February 2008

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 results is discussed.
Radio Aurora and Electric Fields
Authors: Unwin R. S. , Knox F. B.
Published: February 2008

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 (type B1 in 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 (type B2 and B3 in 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 the B1 type 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 relating B1‐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 for such a system are outlined.
Nonlinear Whistler Propagation Through the Ionosphere
Authors: Buti B. , Tripathi V. K.
Published: February 2008

The field‐strength dependence of the damping coefficient of whistlers is studied in the geometrical optics approximation in the two limiting cases: (1) weak collisions where (ω ‐ ωe)2 » v2 (ω, ωe, and v being the wave, electron cyclotron, and electron‐neutral collision frequencies, respectively) but with no restriction on the nonlinearity parameter; (2) strong collisions where v2 » (ω ‐ ω)2 and the nonlinearity parameter is very high. The nonlinear effects are found to be very important at low frequencies as well as at frequencies near the electron cyclotron frequency.
Fifty‐Megahertz E89 1964–1970
Authors: Dyer Patrick J.
Published: February 2008

Using amateur signals in the 50‐MHz band to indicate the presence of oblique‐incidence E8 paths, the diurnal, seasonal, and magnetic relationships of the phenomena for the years 1964–1970 were examined. Summer double diurnal peaks were found along with ‘off‐season’ meteor shower influences.
Mode Coupling in Partial Reflections From the Ionosphere at Vertical Incidence
Authors: Connolly Denis J. , Tanenbaum B. Samuel
Published: February 2008

The effect of mode coupling has been calculated for radio waves partially reflected from the lower ionosphere at vertical incidence. Calculations were made for parameters appropriate to the partial reflection experiments [Belrose, 1970]. The four reflection coefficients (two direct and two coupled) are calculated for a plane discontinuity using a matrix perturbation analysis. The ratios of coupled to direct reflection coefficients are calculated for a general one‐dimensional reflecting layer using the coupled equations of Clemmow and Heading [1954]. At the highest electron density considered, 104 cm−3, about 10% of the reflected extraordinary wave amplitude might be due to coupling from the incident ordinary wave. The effect is smaller at lower electron density.
Amplitude Probability Distribution of Radio Waves Reflected From Traveling Ionospheric Disturbances
Authors: Srivastava S. K. , Pradhan S. M. , Tantry B. A. P.
Published: February 2008

In this paper, the amplitude distributions of the reflected radio waves, from various portions of the traveling ionospheric disturbances (TID) superimposed on small‐scale irregularities, have been studied with the help of simultaneous records of amplitude and phase patterns of vertically reflected echoes. Amplitude distributions of reflected waves, related to different small portions of TID are found to exhibit different types of well‐known distributions, like Rayleigh, Rice, and displaced Gaussian, while resultant distributions corresponding to two successive small portions of the TID may have different shapes, including the familiar M shape reported by many workers. Further, in some events, even three‐peaked amplitude distributions are observed depending upon the ratio of steady component to random component present in the received echo and the nature of the reflecting surface.
Instabilities and Turbulence: Summary Report
Authors: Vandenplas P. E.
Published: February 2008

R. J. Forrest (University College, London) examined the relation existing between various theories of helical propagation along a weakly ionized plasma column in an axial magnetic field. He showed that these particular theories are limiting cases of a general theory which includes both the effects of ion inertia and the influence of the magnetic field on the ions. The theory uses the first two fluid equations for the perturbed quantities of a warm plasma, i.e., the first two moments of the Boltzmann equation. For simplicity the model used is a planar one in which the perturbed densities and velocities for electrons and ions are introduced together with an electrostatic potential.
Review of Wave Excitation in Plasmas
Authors: Johnston Tudor Wyatt
Published: February 2008

The excitation of plasma waves is reviewed, organized according to the mode of excitation: linear wave coupling, use of exciters (such as antennas and probes), particle‐velocity anomalies (such as streams and loss cones) and wave‐wave stimulation (such as three‐wave and echoes).
Linear and Nonlinear Coupling of Waves in Plasmas
Authors: Larenz R. W.
Published: February 2008

A survey of wave‐coupling phenomena is given. Different physical influences are discussed from a rather general plasma‐wave equation displaying these influences. Nonlinear interaction is considered and some basic examples are given. Attention is called to certain physical points of view related to nonlinear analysis.
Focusing of Waves in Ducts
Authors: Sodha M. S. , Ghatak A. K. , Tewari D. P. , Dubey P. K.
Published: February 2008

This paper presents an investigation of the propagation of cylindrical waves (the field being independent of x) along the z direction inducts described by

urn:x-wiley:00486604:media:rds618:rds618-math-0001

where c(y, z) is the wave velocity, C0 and ϵ0 are constants, ϵ2(z) is an arbitrary function of z, and ϵ corresponds to the dielectric constant for electromagnetic waves.

It has been shown that the intensity A02 of the wave is in general given by

urn:x-wiley:00486604:media:rds618:rds618-math-0002

where E0 is a constant, yo is a constant, F is an arbitrary function of [y/yoƒ(z)L], and ƒ(z) is a dimensionless beam‐width parameter given by

urn:x-wiley:00486604:media:rds618:rds618-math-0003

in the geometrical optics approximation.

The nature of the variations of ƒ with z has been discussed for some simple profiles of ϵz(z) in the geometrical optics approximation; diffraction has also been taken into account when the beam (F) is Gaussian.
An Improved True‐Height Reduction Technique
Authors: Kantarizis E. , Whitehead J. D.
Published: February 2008

The advent of the phase ionosonde, which gives more precise experimental data than the conventional instrument, has made it necessary to seek improvement in the technique of true‐height reduction by reducing calculation errors. The method described here gives errors of approximately a few meters when the lowest observable frequency is 0.6 MHz and both magnetoionic modes are used.
Announcement USNC/URSI Meeting August 21–24, 1973
Authors: Wait James R.
Published: February 2008

The 1973 Main Meeting sponsored by the U.S. National Committee of URSI and the 1973 IEEE International Antennas and Propagation Symposium will be held jointly at the Engineering Center of the University of Colorado. URSI and IEEE/G‐AP technical programs will be arranged separately, except for the appropriate coordination.
On the Effect of the Vertical Drift in the Equatorial F Region
Authors: Wu Mao‐Fou
Published: February 2008

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 equatorial F region 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 by Martyn [1955]. The calculated values are found to be in good agreement with the observations both in magnitudes and in distribution patterns.
Transient radiation in homogeneous anisotropic cold plasmas
Authors: Chen Kenneth C. , Yen Jui Lin
Published: February 2008

A convenient ω‐θè plot for the group index of refraction is introduced for studying the radiated field from transient current sources of arbitary orientations in anisotropic cold plasmas. The plot is valid not only for the far zone, but also for the near zone with large time. Typical numerical examples are given to provide the quantitative insight of the transient response in anisotropic cold plasmas.
Eastern thunderstorms located by VLF atmospherics parameters
Authors: Harth W. , Pelz J.
Published: February 2008

Daily variations of spectral atmospherics parameters, as measured by the atmospheric analyzer of the Heinrich Hertz Institut in Berlin‐Charlottenburg, are analyzed over an eight day period for long lasting storm centers within the octant NE‐E (receiving station Stockert near Bonn). The delay‐time difference and the amplitude ratio of spectral groups at 6 and 8 kHz were measured alternatively every 5 min. Within the first‐mode approximation these parameters are proportional to the propagation distance. Storm centers located by these parameter measurements are compared with synoptical observations. As theory indicates, the strong directional dependence of the GDD (group delay‐time difference) and the SAR (spectral amplitude ratio) on the propagation direction relative to the earth's magnetic field is verified by these measurements.
High‐frequency radio‐wave propagation through plane‐stratified ionospheric models
Authors: Price Gary H.
Published: February 2008

The sensitivity of refractive effects to profile shape in the propagation of high‐frequency radio waves through the ionosphere is examined for a planar isotropic trapezoidal model of the electron‐density variation with height. For a family of trapezoidal profiles with constant peak density, fixed orientation relative to a straight‐line path from source to receiver, and constant integrated density along this path, the dependence of the group delay upon profile shape is found to involve only the ratio of the thickness of the peak‐density segment of the profile to that of the total profile. For thin profiles, the theory suggests an insensitivity of the group delay to the profile shape for frequencies near the peak plasma frequency divided by the cosine of the zenith angle of the straight‐line path, as well as in the familiar high‐frequency limit. Expressions for the group delay are also given for parabolic and more general linearly segmented profile models.
Spectra of short‐term fluctuations of line‐of‐sight signals: Electromagnetic and acoustic
Authors: Mandics P. A. , Lee R. W. , Waterman A. T.
Published: February 2008

Theoretical expressions for the spectral density of amplitude, amplitude‐difference, and phase‐difference fluctuations of waves propagating over a line‐of‐sight path in a weakly scattering turbulent medium are derived. Experimental observations made at radio (35 GHz) and acoustic (3 kHz) frequencies are in good agreement with the theoretical predictions under a variety of meteorological conditions. Comparison of experimental and theoretical spectra yields a measure of the average across‐the‐path wind velocity and the average refractive‐index structure constant Cn. In general, wind speeds and refractive‐index structure constants inferred from simultaneous meteorological measurements agree with those obtained from propagation data.
The imperfectly conducting circular‐loop antenna
Authors: Lin Juang‐Lu
Published: February 2008

The fundamental transmitting characteristics of an imperfectly conducting circular‐loop antenna are investigated theoretically. To obtain the antenna‐current distribution, a mathematically simpler method based on a differential equation for the loop current is first developed. Next, an existing, more general method based on an integral equation for the distribution of current is applied with modification and solved numerically with a digital computer. Knowing the current distribution, one can easily find the driving‐point impedance. The results of both methods are compared for the case of uniform resistive loading, and they are found to be in good agreement. Some additional numerical examples showing the effect of nonuniform reactive loading on the driving‐point impedance are also included. The outcome of this research should provide useful information for the design of broadband circular‐loop antennas.
A neutral‐atmosphere composition experiment for the Atmosphere Explorer‐C, ‐D, and ‐E
Authors: Pelz David T. , Reber Carl A. , Hedin Alan E. , Carignan George R.
Published: February 2008

The neutral‐atmosphere composition experiment instrumentation is designed to obtain in‐situ measurements of neutral thermosphere composition from Atmosphere Explorer‐C, ‐D, and ‐E. The system is based on previously flown OGO‐6 and San Marco‐3 composition instruments. The mass‐spectrometer sensor includes a gold‐plated thermalizing chamber and ion source, a hyperbolic rod quadrupole analyzer, and an off‐axis electron multiplier. Automatic ion‐source sensitivity control and pulse‐counting techniques provide density measurement capability from approximately 125 to 1000 km altitude. The normal operating mode includes measurement at all masses in the range 1 to 44 amu with emphasis on hydrogen, helium, oxygen, nitrogen, and argon. Additional operational modes are optimized for minor constituent studies of any individual gas in this mass range.
Phase‐difference distributions in a D‐region partial‐reflection experiment
Authors: Tanenbaum B. Samuel , Shapiro Jeffrey H. , Reed James E.
Published: February 2008

Histograms of phase‐difference data for ordinary‐ and extraordinary‐mode signals reflected from the D region of the ionosphere are compared with two phenomenological scattering models: (a) a small‐scale homogeneous turbulence model and (b) a single reflecting‐layer model. Although the turbulence model fits the data somewhat better than the single reflecting‐layer model does, the predictions of both models are in surprisingly close agreement on virtually all aspects of differential‐phase data. In particular, both models are shown to predict a broadening of the histograms with increasing altitude as found experimentally. This is attributed to the increasing difference between the differential phases of signals scattered from the top and bottom of the scattering volume. Thus, by operating at a higher frequency or using a shorter or a coded pulse, one should obtain useful differential‐phase data at higher altitudes.
Impedance of a short cylindrical dipole antenna in a hot uniaxial plasma
Authors: Singh N.
Published: February 2008

The impedance of a short cylindrical dipole antenna in a hot uniaxial plasma is calculated. The hot‐plasma effects are found to be specially important for very low frequencies. For these frequencies the results of the cold‐ and hot‐plasma theories differ appreciably. As ω → 0 the cylindrical dipole is found to be capacitive rather than inductive as predicted by the cold‐plasma approximation.
Commission 1. Radio measurement methods and standards
Authors: Altschuler H. M.
Published: February 2008

K. Evenson (USA) delivered the paper, ‘Stabilized laser‐frequency measurements: Methane‐stabilized HeNe 3.39 μm and CO2‐stabilized 9.3 and 10.2 μm.’

The most notable results reported were the measurements by the National Bureau of Standards (NBS), Boulder, Colorado of both the frequency and wave‐length of the HeNe laser stabilized on the 3.39‐µm saturated absorption in methane. By this means the velocity of light has been deduced with an estimated accuracy of about 3 parts in 109. This result is at least 100 times more accurate than previous determinations of the velocity of light and is in reasonable agreement with the previously adopted value published by Froome and Essen [1969]. The new value for the velocity of light determined by NBS with to the fundamental standards of time (cesium) and length (krypton) is:

urn:x-wiley:00486604:media:rds710:rds710-math-0001
Commission 2. Radio and nonionized media
Authors: Katz I.
Published: February 2008

The June 1972 Inter‐Union Commission on Radio Meteorology (IUCRM) colloquium, ‘Waves and turbulence and their interaction with EM waves,’ was reported by B. R. Bean (USA). The IUCRM is concerned with interdisciplinary problems related to the effects of the nonionized atmosphere on the propagation of electromagnetic waves and the use of remote‐probing techniques to study the atmosphere. Of particular interest to atmospheric scientists and fluid dynamicists on the one hand and to radio scientists on the other is the fine‐scale structure of stratified layers marked by strongly sheared flow. Such stratums are the seat of both stable gravity waves and unstable Kelvin‐Helmholtz waves; the breaking of the latter is responsible for clear‐air turbulence, among other things. The resulting refractively turbulent stratum is also responsible for the scatter of EM waves in tropospheric propagation and for backscatter in the case of microwave or acoustic radars. Recent studies with high‐resolution radars have cast new light on the mechanisms of waves and turbulence in hydrostatically stable layers, while fluid dynamicists have advanced this knowledge through theoretical and experimental research on the stability of such flows. Simultaneously, meteorologists have been making strides on the structure and prediction of clear‐air turbulence.
Commission 4. On the magnetosphere
Authors: Fejer J. A.
Published: February 2008

R. M. Thorne (USA) delivered the paper, ‘The need for measurements of plasma density in the outer magnetosphere.’ Inside the magnetopause one of the most important parameters to be measured is the flow of the plasma. These flows result from the electric fields that exist there. Measurement of the low‐density thermal (E < 1 kev) plasma can help provide the needed information about the plasma flow and, hence, the electric fields. The importance of the cold plasma is vividly displayed by the correlation of the location and presence of stable‐auroral‐red arcs with the location of the plasmapause. OGO‐5 data was used to show this correlation. The plasmasphere and plasmatrough are filled from the ionosphere during the daylight hours. Measurements of low‐density plasma are needed to study the details of the filling mechanisms.
On resonant interaction of atmospheric waves
Authors: Jurén C. , Stenflo L.
Published: February 2008

Resonance conditions concerning the nonlinear interaction of acoustic gravity waves are considered. It is shown that a resonant trio of waves with nonzero frequencies can be found in situations in which viscous damping has to be taken into account.
The ionosphere as the secondary conductor of a transformer for ELF
Authors: Booker Henry G.
Published: February 2008

A study is made of the physics of radiation into the guide between the earth and the ionosphere from a center‐fed antenna consisting of a long horizontal wire grounded at its two ends. The length of the wire and the height h of the ionosphere are short compared with the free‐space wavelength λ0. The antenna wire, together with its return path through the ground, constitutes the primary circuit of a transformer of which the ionosphere above the antenna to a distance of the order of λ0/2π is a part of the secondary circuit. This portion of the ionosphere, together with the corresponding portion of the ground, constitutes the secondary circuit of the transformer. This circuit applies voltage between the rest of the ionosphere and the rest of the ground, thereby launching a wave that propagates between the earth and the ionosphere towards the antipode. The coefficients of mutual and self‐impedance for the transformer are calculated and are used to relate the voltage at the terminals of the antenna to the wave that leaves the transformer for the antipode. The transformer action increases the radiated power by a factor of λ0/4h above that for the same antenna in the absence of the ionosphere.
Comments on “Radiation from a parallel‐plate waveguide into a dielectric or plasma layer”
Authors: Montgomery James P.
Published: February 2008

It is shown that in the above paper [Kostelnicek and Mittra, 1971] and also in previous work [Mittra and Bates, 1967], the solutions do not satisfy the edge condition due to an error in the asymptotic expansion of the infinite product employed in the solutions.
The ring current and magnetic storms
Authors: Coroniti F. V.
Published: February 2008

The ion‐cyclotron turbulent ring current precipitation model of magnetic storms is reexamined in light of recent experimental and theoretical developments. The ring current‐plasmapause spatial coincidence results from the proton Alfvén layer shielding of the convection electric field. Observations indicate that the dominant ring current precipitation occurs outside the plasmasphere in agreement with recent theories of the high beta, large anisotropy ion cyclotron and electrostatic ion loss cone waves. Hydrogen arc proton precipitation may be caused by parallel electric fields at the equatorward edge of the auroral oval. During the main phase, convection may be both the source and major sink of the asymmetric ring current. During the rapid recovery phase, neutral‐wind‐induced convection may be the dominant ring current loss process. At this time there is no definitive evidence that ion cyclotron turbulence inside the plasmapause constitutes a major sink for the ring current or generates a SAR arc by electron Landau damping.