bluuebunny/crossref_metadata_2025 huggingface dataset:
Reply to a Comment of J. R. Wait on Volland's “Remarks on Austin1S Formula”
Authors: Volland Hans
Published: November 2015

Wait [1965] has criticized my paper “Remarks on Austin's formula.” In that paper [Volland, 1964a] the mode theory of the ELF and VLF propagation within a flat waveguide has been extended into the LF region. It has been shown that the empirical Austin formula [Austin, 1915], the modified version due to Espenschied et al. [1926], and the relative attenuation maximum around 40 kc/s found by Anderson [1931] may be interpreted qualitatively by the flat model.
New Measurements of Phase Velocity at VLF
Authors: Kamas G. , Morgan A. H. , Jespersen J. L.
Published: November 2015

The purpose of this note is to describe some new phase velocity measurements using signals from the VLF stations NPG (18.6 kc/s) near Seattle, Wash., and WWVL (20.0 kc/s) near Fort Collins, Colo. Previous experimental results have been described by Wait [1961].
Excitation of Surface Currents on a Plasma‐ Immersed Cylinder by Electromagnetic and Electrokinetic Waves. Part II.; The Inhomogeneous Sheath
Authors: Miller E. K. , Olte A.
Published: November 2015

An investigation of the surface currents excited by plane electromagnetic (EM) and electrokinetic (EK) waves on a metal cylinder immersed in a uniform, collisionless isotropic plasma is described. The formulation is based on a linearized treatment which proceeds from velocity moments of the Boltzmann equation for electrons together with Maxwell's equations. The analysis includes the inhomogeneous sheath (assumed to be of finite thickness) which forms about the cylinder when at floating potential in the plasma, for an arbitrary angle of wave incidence.

Some results of numerical calculations carried out for normal wave incidence are presented. The effects of varying the sheath thickness and static potential are examined. In addition, numerical calculations are performed assuming either complete reflection or absorption of the electrons at the cylinder surface. It is found that the surface currents for EK wave incidence are substantially in agreement with results obtamed when the actual sheath is replaced by a free‐space region. In particular, the mhomogeneous sheath model which was used has the effect of decreasing the currents excited by the EK wave compared with the case where the plasma is uniform everywhere. For EM wave incidence on the other hand, the surface currents are found to be negligibly affected, both by the inhomogeneous sheath and plasma compressibility.
Summary of the 1965 URSI Symposium at Delft, Netherlands: Sessions on Nonlinear and Transient Phenomena
Authors: Cassedy E. S.
Published: November 2015

The 1965 symposium at Delft was the most recent of a series of triennial, international symposia on electromagnetic theory sponsored by URSI. Past meetings in this series have dealt largely with modern topics based on classical electromagnetic theory, such as boundary‐value problems, diffraction, scattering theory, antenna theory, microwave optics, propagation in various media. waveguides, surface waves, etc. As such, attention was focused almost exclusively on the behavior of electromagnetic waves propagating in, or in the presence of, media or structures which were linear, passive, and time‐invariant. The symposium at Delft, in contrast to the previous meetings in this series, had a significant number of contributions on problems involving either nonlinear, active, or time‐varying systems.
Linearly Polarized Characteristic Waves in a Magnetoplasma
Authors: Verdeyen Joseph T.
Published: November 2015

It is shown that linearly polarized electromagnetic waves can exist in a bounded magnetoplasma and propagate at an arbitrary angle with respect to the magnetic field lines. Although the Electric field of these waves is linearly polarized, the refractive mdex vector consists of real and Imagmary parts which are othogonal to each other in a collisionless plasma. The amplitude of the fields grow in direction of the imaginary part of the refractive index. and thus one surface must always be present to terminate and to guide the electromagnetic fields. Hence this theory is a generalization of surface‐wave phenomena occurring in magnetoplasmas. Expressions are developed which explicitly show the dependence of the real and imaginary parts of the refractive index upon the plasma parameters for an arbitrary angle of propagation with respect to the magnetic field. The special case of the propagation vector and the electric field oriented perpendicular to the magnetic field is discussed in detail. Experiments are presented which are in excellent agreement with the surface‐wave theory of this special case.
Radiation in Air Source Located in From an Electric Line Current an Ionospheric Halfspace
Authors: Wade H. D. , Williams R. H.
Published: November 2015

A uniform electric line current source is immersed a short distance into an ionospheric halfspace, the model of which is a homogeneous, linear, cold, lossy, single‐component magnetoplasma halfspace. Formal integral expressions for the electric fields radiated into the adjoining air halfspace are derived by a solution of Maxwell's equations in each region, using double Fourier transform techniques. The formal integral expressions for the radiation‐zone electric fields in air are evaluated asymptotically by the method of stationary phase. Radiation patterns are plotted for several combinations of polarization, frequency, depth of immersion, direction of magnetostatic field, and region of ionosphere. The field strength increases with frequency in the VLF spectrum, for a given strength of the line source. The field strengths are considerably larger for a magnetostatic field B0= 0.5 G than for B0= 0. There is a tendency for the vertical polarization to be enhanced in directions along B0 and reduced in directions perpendicular to B0. The horizontal polarization is affected less by B0 than the vertical polarization.
A Statistical Theory of Ridge Diffraction
Authors: Furutsu K.
Published: November 2015

The attenuation coefficient A is treated statistically when the radio wave is diffracted by a ridge whose height changes along the ridge around a mean value h0, by assuming a homogeneity of the height variation and its Gaussian multivariate distribution with an arbitrary correlation function. The mean values (A), (|A|2), and the correlation (A(x1)A*(x2)) at separate points are obtained exactly, including the case where the root mean square value of the height variation exceeds the magnitude of h0 (measured normally from the line connecting the transmitter and the receiver). The mean value (A) can be obtained by using the same formula as used for a smooth ridge, if the ridge height is replaced by an effective height of a complex value. While (A)|h0=0 = ½, which is the same as for a smooth ridge, the mean value (|A|2)h0=0 varies from ¼ to ½ as the variance of the height changes from 0 to ∞.
Some Introductory and Background Comments on Our State of Knowledge of Sporadic E
Authors: Smith E. K.
Published: November 2015

Some comments are offered as to the major types of sporadic E from the causal standpoint (e.g., plasma instabilities, precipitation of charged particles, and wind shear and turbulence).

The Cavendish Conference in 1958 on “sporadic E ionization” is reviewed, and extracts from the introductory and concluding statements of this conference are quoted with the thought that they are equally pertinent to the present conference.

Finally it is suggested that, from the scientific standpoint, the role of ground‐based radio experiments is to define the horizontal structure and height of sporadic E clouds.
Experimental Study of the Structure of Sporadic E (Summary)
Authors: Spizzichino A. , Giraud A.
Published: November 2015

Short‐term characteristics of sporadic E propagation were observed on a forward‐scatter radio link equipped with an angle‐of‐arrival measuring device. The evolution with time of the field intensity n, the fading rate N, and the width ∆α of the angular spectrum was studied in detail for several typical Es events. It reveals the coexistence of two distinct structural types of layers characterized as follows:
Prevailing and Tidal Wind Shears in the E Region
Authors: Hines C. O.
Published: November 2015

Winds revealed by 29 sodium vapor trails, as reported by Manring et al. [1964], have been analyzed to determine prevailing and tidal components at heights of 90–130 km. This was accomplished for each of several levels in turn, by averaging separately the winds observed at dawn and at dusk; the difference between the two average values was attributed to the diurnal component, which would be roughly in antiphase at dawn relative to dusk, while the mean of the two average values was attributed to a prevailing wind plus a semidiurnal component. The results of the analysis are depicted in the accompanying figure, which gives hodographs of the half‐difference and the half‐sum of the dawn and dusk averages. The probable errors of the averages are estimated to be about 12 m/s, and the probable errors of the points plotted in the hodographs are therefore about 17 m/s. The nature of the analysis and its limitations are discussed more fully in a paper now in press [Hines, 1966].
Some Rocket Results on Sporadic E
Authors: Aubry M. , Blanc M. , Clauvel R. , Taieb C. , Bowen P. J. , Norman K. , Willmore A. P. , Sayers J. , Wager J. H.
Published: November 2015

In 1964 several rockets were fired in Hammaguir, Algeria, in order to study the sporadic E region.
Mixtures of lons in the Wind‐Shear Theory of Sporadic E
Authors: Whitehead J. D.
Published: November 2015

The wind‐shear theory of sporadic E predicts that when only one ion species is present, and the peak electron density is a factor R times the ambient, the minimum electron density is 1/R of the ambient. With two species present, the minimum electron density is greater than this and approaches the ambient when the ratio of recombination coefficients is large and the more rapidly recombining ion predominates in the ambient ionsphere. The peak density depends only on the recombination coefficient of the slowly recombining ion and the gradient in the vertical drift motion. The problem of nighttime sporadic E is considered, but no satisfactory solution is offered.
Formation of Sporadic E Layers at Temperate Latitudes Due to Vertical Gradients of Charge Density
Authors: Tsuda Takao , Sato Tetsuya , Maeda Ken-ichi
Published: November 2015

Applying the method of instability analysis of weakly ionized plasmas, it is shown that the ionosphere at the height 100–120 km at temperate latitudes is capable of producing irregularities in charge density in the presence of vertical gradients of background charge density, external electric and geomagnetic fields. Worldwide distribution of local time versus geomagnetic latitudes where ƒ0Es exceeds 5 Mc/s is compared with that theoretically predicted. Results obtained seem to be an evidence that such a mechanism, other than that of wind shear, is also responsible for the formation of sporadic E at temperate latitudes.
5. Future Plans
Authors: Hines C. O.
Published: November 2015

Planning for the elucidation of the nature of sporadic E ionization must take into account the following factors:
Effects of Ions on Whistler‐Mode Ray Tracing
Authors: Kimura Iwane
Published: November 2015

Ray tracing for whistler‐mode propagation has been performed with the effects of ions included. The method is similar. to that employed by Yabroff but for the modification in the refractive index due to ions. Outstanding characteristics of the ray paths in such a medium result from the existence of purely transverse propagation at the lower frequencies. The main purpose of this study is to confirm the Smith interpretation of the “subprotonospheric” whistlers. It is found that an enhancement of electron density at the latitude of interest can support the ray path of the fractional hop as Smith suggested, as well as a possibility of successive echoes through a single path. The effect of collisions on propagation is also discussed.
Comparison of Time‐Delay Spread and Spatial Coherence for Ionospheric Propagation
Authors: Felperin Karl D.
Published: November 2015

This paper describes spatial selective fading (interference patterns due to modal arrival angle differences) as a homogeneous random process. It is shown that for ionospheric propagation, the power spectrum in vector wave number (wave number dispersion profile) should be of approximately the same shape as the power spectrum in time delay (time‐delay profile). On the basis of this similarity, it is suggested that the correlation between signals from spaced antennas (spatial coherence) should be inversely proportional to rms time‐delay spread.

An experiment was performed on a 4100‐km path at 7 and 14 Mc/s to verify this assumption. Results are generally in agreement with theory, and discrepancies that do exist are analyzed.
Boundary Scattering Effects In Underwater Sound Propagation
Authors: Marsh H. W. , Mellen R. H.
Published: November 2015

Signal scattering by rough boundaries is a phenomenon common to both radio and underwater sound propagation. A theory, supported by experimental evidence, is presented relating the angular scattering spectrum and the boundary roughness spectrum by first‐order diffraction. Accordingly, the Doppler. velocity for surface wave scatter is the phase velocity corresponding to wavelength resonance. Both radar and sonar backscatter measurements, however, show random velocity distributions except at long wavelengths, indicating that the wind‐driven sea surface is predominantly turbulent. Measurements of temporal coherence of forward‐scattered signal are also presented. In this case, the theoretical Doppler spectrum is dominated by motions of the longest waves.
The Electric Field Very Near a Driven Cylindrical Antenna
Authors: King Ronold W. P. , Wu Tai Tsun
Published: November 2015

A first‐order formula is derived for the component Ez(ρ, z) of the electric field very near to the surface and parallel to the axis of a perfectly conducting center‐driven cylindrical antenna with radius a and length 2h. It has the form Ez(ρ, z) = Ez(z) ln(ρ/a) where p is the radial distance from the axis of the antenna and Ez(z) is a complicated expression that involves generalized sine and cosine integral functions. Zero‐order results are compared with first‐order values for half‐and full‐wave dipoles with a/λ = 7.022 × 10∑3. It is shown that zero‐order values do not include large values of Ez(ρ, z) near the ends and near the driving point, so that a quantitative estimate of the field near a center‐driven cylindrical antenna requires a first‐order evaluation.
Radiation Impedance of a Dipole in an Infinite Planar Phased Array
Authors: Stark L.
Published: November 2015

The radiation impedance of a dipole in an infinite array phased for any angle of radiation is calculated. The calculation is made by means of plane wave expansions and gives a very simple result. The radiation resistance is the product of the broadside resistance times a scanning factor which is unity on broadside and changes the resistance as the beam is scanned. The scanning factor is identified as the product of the element pattern and a factor equal to the ratio of the broadside aperture to the projected aperture. The radiation reactance is also calculated and consists of a leading term due to reflection of the wave fronts from the ground plane plus an infinite series of higher order‐terms contributed by the cutoff wave. Results are plotted for the variation of radiation resistance and reactance with changes in radiation angle. A comparison is also made between results calculated by the method of plane wave expansions and those obtained from the method employing mutual impedance coefficients.
Vertical Magnetic Dipole Buried Inside a Homogeneous Earth
Authors: Sinha A. K. , Bhattacharya P. K.
Published: November 2015

The radiation characteristics of a low‐frequency vertical magnetic dipole antenna buried inside a semi‐infinite conducting medium have been investigated to determine the electric and magnetic fields at any point inside or outside the conducting medium. Some special cases of interest have been discussed. The results have been used to find the input impedance of the dipole inside the conducting medium.
Time History of the Magnetospheric Cavity
Authors: Osborne F. J. F. , Bachynski M. P. , Gore J. V. , Gore J. V.
Published: November 2015

Scale model laboratory experiments simulating the effect of the solar wind on the magnetosphere have shown the time history of the formation and breakup of the magnetospheric cavity. Time‐resolved (1 µsec) data on the visible “standoff” interaction show that the “quasi‐Van Allen belts” first become visible well within the cavity at the time the plasma wind encounters the fringing terrella field. The belts at this time show a definite structure with “ribbons” of plasma along the field lines. This structure is probably associated with oscillatory phenomena present in the belts and their excitation mechanism. The polar views show considerable asymmetry of both the internal and external phenomena throughout the interaction. The visual asymmetries indicate that the plasma in the tail of the dipole magnetic field “wags” as the interaction builds up and decays. Magnetic field measurements in the equatorial plane show a similar motion of the magnetic field in the tail.
Deterioration of the Coherence Properties of a Laser Beam by Atmospheric Turbulence and Molecular Scattering
Authors: Consortini A. , Ronchi L. , Scheggi A. M. , di Francia G. Toraldo
Published: November 2015

Turbulence and scattering can be considered as chiefly responsible for the deterioration of coherence properties of laser radiation when propagating through the atmosphere.

The effect of atmospheric turbulence as well as the effect of molecular scattering (in a quiet atmosphere) on the space and time coherence, respectively, have been theoretically investigated within the limits of ray theory

As a result we found that there is a limiting diameter for the beam cross section beyond which the advantages of the space coherence are largely offset by the intervention of turbulence. On the other hand, the thermal movements of molecules may affect the time coherence (that is, the monochromaticity) of a highly monochromatic beam.
Radiation From a Magnetic Line Source Located on a Conducting Plane Covered by a Warm Plasma Layer
Authors: Wenger Norman C.
Published: November 2015

A model of a re‐entry plasma layer is analyzed by using the linearized hydrodynamic equations for a single‐fluid warm plasma medium. The model consists of a perfectly conducting plane of infinite extent covered by a warm plasma layer of uniform density. The field excited by a magnetic line source located on the conducting plane is computed by Fourier transform techniques. Expressions are obtained for the far‐zone radiation field and for the surface waves guided by the plasma layer. Numerical results are presented that show the dependence of the energy transported by these waves on frequency and electron temperature. In addition, the radiation pattern of the far‐zone field is computed for various frequencies and electron temperatures.
Impedance of a Small VLF Dipole in the Ionosphere
Authors: deWolf D. A.
Published: November 2015

Previous workers have shown that by taking into account the nonzero dimensions of actual dipoles the infinity catastrophes of the impedance of VLF dipoles (X ≫ 1, Y ≫ 1) in a magneto plasma, as well as of the far fields, are eliminated. Nevertheless, the use of very small dipoles may still not lead to valid result if collisionless magneto‐ionic theory is utilized. Criteria are established for temperature and collision effects whiCh modify magneto‐ionic results, depending on the relative magnitudes of source dimensiOns, electron temperature, and collision frequency. Ion mobility effects are not taken into account. In the extreme case, radiation of very .small dipoles in a sparse low‐temperature plasma with high d‐c magnetic field cannot be predicted by lineanzed plasma‐kinetic theory.
Cavity Resonator Modes in a Cylindrically Stratified Magnetoplasma
Authors: Large David B. , Wait James R.
Published: November 2015

The exact harmonic series solution for the fields in a cylindrically stratified plasma is utilized to examine the cavity resonant frequencies. The prolilem is restricted to two‐dimensional geometry such that the d‐c magnetic field is parallel to the axis of the system. Some numerical results are given for the special case of an annular air region bounded by a perfectly conducting core and an homogeneous external plasma. It is shown that the d‐e magnetic field shifts the resonant frequencies from their isotropic values and causes certain “line‐splitting” effects.
Mode Propagation in Continuously Curved Waveguides
Authors: Cochran J. Alan , Pecina Robert G.
Published: November 2015

This paper presents the results of precise numerical computations and extensive analytical investigations of the angular propagation constants for the various electromagnetic modes which may exist in waveguide bends of rectangular cross section. Although the values of the several independent parameters have been chosen to be commensurate with microwave applications, the results are displayed and discussed in a manner which should be convenient for both the analysis and the design of such components in analogous problems in other and diverse practical situations. Moreover, special consideration is given to the relationship of this work to various efforts in the study of radio wave propagation.

Two important approximations, one for “high” frequencies and the other for gradual bends, are also considered as a part of the present inquiry. These approximations, especially the latter, turn out to be remarkably good, and rather accurate values of the propagation constants can be obtained with their use for wide ranges of parameter values.

The following are typical of the conclusions which can be drawn from this research: (1) cutoff frequencies for modes existing in continuously curved waveguides are curvature dependent; (2) there exist waveguide bends such that circularly polarized waves are undistorted by transmission along the curved section; (3) the angular propagation constants are generally monotonically increasing functions of the operating frequency f (for fixed mean radius) and of the mean radius R (for fixed frequency). Moreover, they vary linearly with f for frequencies far above cutoff and with R for small curvatures.
Preface to Special Issue on the Mode Theory of Wave Propagation
Authors: Wait James R.
Published: November 2015

The representation of the electromagnetic field as a sum of modes is very useful when dealing with propagation in stratified media. The term “mode of propagation” in this context refers to. a transverse field configuration which satisfies the required boundary conditions and does not vary along a coordinate which is normally parallel to the direction of propagation. A good example is the mode which may propagate in a metallic waveguide. In this case, the total fieid may be represented as a sum of such modes.

This issue of Radio Science contains a number of papers dealing with modal representations. While the emphasis is on electromagnetic fields, a number of examples of acoustic waveguides are also included. The August issue of the journal will contain additional mode theory papers.
Transhorizon Propagation Measurements From a Simultaneous; Frequency and and Angle Scan Experiment
Authors: Strohbehn J. W. , Waterman A. T.
Published: November 2015

An analysis of data from three sets of experiments in transhorizon microwave propagation is presented. In each set, a 3‐Gc/s signal was transmitted over a 163‐km path, and the wave arriving at the receiver was examined using a rapidly scanning phased‐array antenna. In one mode of operation, transmitter and receiver were synchronously swept over a 20‐Mc/s frequency band. The results show considerable variability in all quantities derived from the data.

Received power patterns on occasions were scarcely broader than the receiving antenna pattern and at other times showed considerable power arriving off the great‐circle bearing. A classification of such patterns into "stable” and “ unstable” showed no strong association with time of day. Signal level distributions were often, but by no means always, of the Rayleigh form. The time lag required for the signal autocorrelation to drop to 0.5 — indicative of fading period — varied from a half second to a few seconds. A similar measure of transmissable bandwidth — in terms of frequency correlation — showed a variability from 1 or 2 Mc/s to more than 20. The interrelationship between all these quantities, and their connection with meteorological parameters, showed interesting individual relationships but no clear‐cut overall pattern, except for a general increase in signal level associated with pronounced inversions.

In comparison with various atmospheric models, it becomes obvious that no single simple model is sufficient. On some occasions the received signal showed characteristics predicted from the theory of incoherent scatter by turbulent eddies: distorted angular response patterns with an average beam broadening, Rayleigh‐type signal level distribution, a modest fading rate, and limited transmissable bandwidth. On other occasions, the records showed evidence of marked atmospheric stability and stratification: unbroadened and undistorted antenna response patterns, a more restricted and non ‐ Rayleigh signal level distribution, variable fading rates, and extremely wide bandwidths. There are still other cases where these associations are not well defined.
The Angular Spread of Radio Waves in Long‐Distance Ionospheric Propagation
Authors: Whale H. A.
Published: November 2015

A simple solution of the problem of scattering of radio waves in successive encounters with a rough earth and an ionosphere which introduces irregularities into the phase is presented. This leads to calculated shapes of the incoming angular power spectrum and of the antipodal area and indicates that, under some special circumstances, an antipodal circle of enhanced signal strength may also be present. Some comparisons are made with a few experimental results.
A Comparison of Long‐Distance HF Radio‐Signal Reception at High and Low Receiving Sites
Authors: Epstein M. R. , Frank V. R. , Barry G. H. , Villard O. G.
Published: November 2015

High‐frequency radio signals transmitted over two separate 10,000‐km temperate‐zone paths were received over 1‐month periods at sea level and at elevated sites. Five frequencies were transmitted from Okinawa to Malta and one frequency from Puerto Rico to Hawaii. A comparison of the signal strengths indicates that antenna siting provides definite advantages over low siting for longdistance commumcation.

Antennas at the high sites, which were located an average of 700 ft above the low sites, received greater Signal strengths than those at the low sites, the amount of signal strength advantage (as much as 10 dB) decreasing with increasing frequency. The higher sites were also less susceptible to temporary signal‐strength reductions. When signal strengths were in the process of rising and falling as a result of the change of the MUF in the morning and evening, respectively, high antennas provided up to 1 1/2 hr more receiving time for a specified signal threshold.
Quasi#x2010;Oscillations of Cold, Sharply Bounded Plasmas
Authors: Leavens William M. , Leavens Ileana B.
Published: November 2015

The oscillatory modes of a sharply bounded plasma which involve surface charge are studied by a method which includes the behavior of the surface charge. It is found that these modes are “quasioscillations”—they do not persist indefinitely, eventually being destroyed by muliistreaming. They are inherently nonlinear, not even possessing a lineazeable limit if the density gradient is made finite. An important conclusion is that the surface charge modes probably play no role in laboratory experiments on the scattering and a‐c probe resonances. On the other hand, there may be situations in which the surface charge modes would contribute importantly to an experiment, but would not be predicted by a linearized theory.
Geometric Optics Investigation of HF and VHF Guided Propagation in the Ionospheric Whispering Gallery
Authors: Grossi M. D. , Langworthy B. M.
Published: November 2015

An investigation has been carried on, based on a geometric‐optics treatment, of HF and VHF propagation in the ionospheric whispering gallery, with emphasis on long‐range paths between terminal points both embedded in the lower ionosphere and not involving earth surface reflections.

The results of the investigation have proven that guided paths at HF and VHF are supported by the lower ionosphere despite sharp day‐to‐night transitions, refractive irregularities, and discontinuities, and have provided enough insight into their properties to allow the detailed design of a satellite‐to‐satellite experiment.
Propagation of VLF Radio Waves in a Model Earth‐Ionosphere Waveguide of Arbitrary Height and Finite Surface Impedance Boundary: Theory and Experiment
Authors: Bahar E.
Published: November 2015

This paper deals with propagation of radio waves in a model multimode waveguide with special applications to VLF propagation in the earth‐ionosphere waveguide. The effective height of the waveguide is assumed to be an arbitrary function of distance along the path of propagation. In this paper a finite surface impedance boundary is devised to simulate the ionosphere boundary. The quasi‐optical approach developed for perfectly reflecting boundaries is generalized to obtain the required solution. These theoretical solutions are compared with experimental data from the model waveguide in which a “day‐to‐night transition” and a localized depression in the effective height of the ionosphere are simulated.
Excitation of Surface Currents on a Plasma‐Immersed Cylinder by Electromagnetic and Electrokinetic Waves.: I. The Vacuum Sheath
Authors: Miller E. K. , Olte A.
Published: November 2015

The surface currents excited on an infinitely long. circular metal cylinder immersed in an isotropic compressible plasma by electromagnetic (EM) and electrokinetic (EK) plane waves are investigated. The formulation proceeds from velocity moments of the collisionless Boltzmann equation for the electrons. together with Maxwell's equations. and uses a linearized analysis. The sheath which forms about the cylinder is approximated by a free‐space layer between the cylinder and the uniform plasma, called the vacuum sheath. It is found from the numerical calculations that the vacuum sheath tends to screen the EK wave from the cylinder, and produces a large attenuation of the surface currents excited by the EK wave. The sheath and EK wave are found, on the other hand, to negligibly affect the currents excited by the EM wave.
Nonlinear Interaction of a Number of Electromagnetic Waves in a Magnetoplasma
Authors: Kaw Predhiman Krishan
Published: November 2015

Following the earlier treatments of Sodha and Palumbo, the author has investigated the mutual nonlinear interaction of a number of electromagnetic waves in a magnetoplasma. For simplicity in mathematical analysis, all the waves have been assumed to be moving in the same direction, viz, the direction of the magnetic field. The interesting phenomenon of resonances is discussed in detail.
Group Propagation in the Whistler‐Hydromagnetic Extension of Magnetoionic Theory
Authors: Kantor Gideon , Pivarunas Frank
Published: November 2015

This paper presents an exact formulation of the propagation of wave packets at whistler and hydromagnetic frequencies m a collisiOn‐free, electrically neutral mixture of electrons and ions of one type. Simple expressions are derived for µ', the group refractive index, and for α, the angle between the direction of propagation of a wave packet and the wave normal; µ' and α are explicit functions of X, Y, θ, the magnetmomc symbols, and R, the electron‐to‐ion mass ratio. Computed valuesof µ' and α for both a wave frequency f slightly above the proton gyrofrequency fMi [Y = (fMi/f) (1/R)=1500] and somewhat below it (Y=104) are plotted as a function of X for particular θ values; the µ' and α curves show how magnetoionic theory is modified at low frequencies by including proton motion. Group‐ray refractive index surfaces for the large X values which are applicable to whistler and hydromagnetic wave propagation in the magnetosphere are also presented.
Direct Use of the Phase Refractive Index for Reducing h'(f) Curves to N
Authors: Hoio H.
Published: November 2015

A method for obtaining N(h) profiles from h'(f) curves by the direct use of the phase refractive indices is developed for both the ordinary and extraordinary modes. The method is extended for solving the starting pmblem by the joint use of ordinary and extraordinary h'(f) curves and by assuming the Chebyshev expansion regarding the profile below fmin. It is pointed out that the phase height at fmin is useful for obtaining an accurate profile above fmin.

The profile is assumed to be a monotonic function of height, but the method can be extended to include the profile containing a valley. The effect of the earth's magnetic field is included without a height variation, and the method neglects the effect of electron collisions.
Use of Virtual‐Height Slopes for Determination of Electron‐Density Profiles
Authors: Paul Adolf K.
Published: November 2015

The relationship between the slope of an ionospheric virtual‐height curve and the higher derivatives of the N(h) profile is derived and discussed. The slope is found to depend mainly on the second‐height derivative at the reflection point of the probing wave. A method of ionogram analysis based upon this formulation is proposed. The appendix presents new forms of the phase refractive index and its derivatives.
Ten‐Point Method of lonogram Reduction
Authors: Schmerling E. R.
Published: November 2015

The “ten‐point” manual method of ionogram reduction provides true heights at selected frequencies. The method is especially convenient when only the height of maximum density is required, but it can also be used to obtain the complete profile. A single true height is obtained as the average of ten virtual heights sampled at fixed submultiples of the frequency. The sampling points, which depend on the geomagnetic parameters, may be rapidly selected by using the appropriate transparent overlay. A correction for underlying ionization may be incorporated by reading one virtual height from the extraordinary trace.
Direct Manual Calculations of Ionospheric Parameters Using a Single‐Polynomial Analysis
Authors: Titheridge J. E.
Published: November 2015

Two extensions of the basic polynomial analysis are described. Firstly the polynomial representation of the real‐height curve is modified to include a parabolic peak; this greatly increases the accuracy of calculations near the peak of the ionospheric layers. Secondly the analytic expression for the real‐height curve is used to obtain expressions for the height of the peak (hm) and the scale height at the peak (H). Integration of the real‐height curve also gives an expression for the effective subpeak thickness of the ionosphere (T), defined as the total amount of ionization below the peak divided by the density at the peak. These three expressions are then used to obtain coefficients relating hm, H, and T to the virtual heights at any required frequencies.

Eighty‐four sets of coefficients are given for analyzing h'(f) records taken anywhere in the world, with critical frequencies between 1.5 and 20 MHz. These coefficients give the values of hm, H, T, and the real heights of reflection directly in terms of the virtual heights at five or six different frequencies. For calculations on a single ionospheric layer the accuracy is extremely high, being equivalent to that obtained with a lamination analysis using more than 50 points. For calculations on the daytime F layer, coefficients are provided with alternative sampling points chosen to reduce the effects of the E and F1 layer cusps, so that the height, scale height, and total content of the F layer can be determined with an accuracy equivalent to a lamination analysis using more than 20 points. Finally, coefficients including an extraordinary‐ray correction for the underlying ionization are given, to enable accurate calculations for the nighttime F layer.
Field‐Strength Measurements in a Multipath Field Using Linear and Circular Probing
Authors: Mittra R. , Stearns C. O.
Published: November 2015

Techniques for resolving the components of a multipath field are investigated in this paper. Both linear and circular probing schemes are discussed. A method for analyzing the linearly probed data is given, which is considerably simpler than the procedure followed by Watterson in an earlier paper. The method is also extended to the circular case. It is found that the resolution in the cucular case is poorer than for the linear scheme.
Illumination of an Inhomogeneous Spherical Earth by an LF Plane Electromagnetic Wave
Authors: Wait James R.
Published: November 2015

Starting with a previous formalism, a method is developed for computing the tangential magnetic field on the surface of an inhomogeneous spherical earth for excitation by a plane wave. The model consists of a two‐section earth which is piecewise homogeneous. As has been shown before, the line integral approximation for the pattern function may be evaluated in terms of various representations for the pattern function and the groundwave attenuation functions for homogeneous earth. In the present paper, the results are cast in a form suitable for numerical work. This involves some nontrivial transformations of the relevant contour integral representations. Some specific examples for 50 and 100 kHz show that a marked recovery effect takes place as the receiving antenna is moved from land to sea.
Multiple Scattering in a Random Continuum
Authors: deWolf D. A.
Published: November 2015

The statistics of multiple‐scattering contributiona to the electric field received at a point beyond a layer containing a forward‐scattering random dielectric continuum are investigated. Specific Statistics such as first and second moments of the field are derived via high‐frequency approximations in all terms of the Born series, thus circumventing controversial derivations from an approximated wave equation. The results and their range of validity are compared to those predicted by Rytov't approximation.
Diurnal Changes of Phase and Group Velocity of VLF Radio Waves
Authors: Westfall W. D.
Published: November 2015

Very‐low‐frequency radio‐wave diurnal phase changes for frequencies between 10.2 and 26.1 kHz, inclusive, are tabulated and plotted as a function of frequency and path distance. Ninety measurements are listed, of which 25 are new data.

By using a daytime theoretical phase velocity for a homogeneous, sharply bounded ionosphere at 70 km which agrees well with experimental data, it is possible to obtain a nighttime first‐order‐mode phase‐velocity curve which does not change with frequency in a manner which is easy to predict.

First‐order‐mode phase velocity curves are used to obtain estimates of first‐order‐mode group velocity. These calculations suggest that for frequencies less than about 16kHz the nighttime group velocity is greater than the daytime group velocity. Above 16kHz it appears that the nighttime group velocity is less than the daytime group velocity. Calculated average group velocity is in agreement with a recent experimental measurement at 17.8 kHz within the experimental error.
Finite Scattering Matrix for an Infinite Antenna Array
Authors: Dufort E. C.
Published: November 2015

A finite scattering matrix, S, for a plane‐wave excited infinite array is developed for the purpose of relating a number of array and active‐element properties. The size of S depends on the polarization in space, the grating lobe locations, and the propagating modes in the feed. Array properties such as scattering on receive, transmission amplitude and phase, surface‐wave propagation, phase and amplitude of the active‐element pattern, etc., are described by this matrix. For the lossless array, the unitary conditions on S further relate the array properties. Some of the results are illustrated by the exact S matrix for an infinite TEM parallel‐plate array. The active element charactenst1cs, and the occurrence of surface‐wave‐type mutual admittances, are discussed in terms of S.
Coupled Equations for Electroacoustic Waves
Authors: Heading John
Published: November 2015

Further investigations are made into the forms of the coupled equations that govern the propagation of electroacoustic waves in an isotropic, stratified, compressible plasma. First‐order equations are considered in a more suitable notation than hitherto, and then the embedded form and the second‐order forms are derived that are valid throughout domains containing certain reflection and coupling points. Limitations of the W.K.B. solutions are pointed out, thereby correcting rather extravagant claims that have been made previously.
Propagation of VLF Waves Below Anisotropic Ionosphere Models With a Dipping Static Magnetic Field
Authors: Janis Galejs
Published: November 2015

A semi‐infinite homogeneous ionosphere with a dipping static magnetic field is used as an approximation to the upper region of a cylindrically stratified ionosphere model. The presence of a vertical static magnetic field component is neglected in the lower stratified regions. The presence of TM modes in the space between the earth and the ionosphere excites coupled TE and TM modes in the upper half space, and these TE fields also propagate in the cylindrically stratified region and in the space between the earth and ionosphere. The TE waves modify the effective surface impedance for the TM modes and the propagation parameters are determined by an iterative solution of the modal equation.

Propagation parameters are calculated numerically for a homogeneous sharply‐bounded ionosphere and also for stratified ionosphere models. The interference distance D of the two lowest waveguide modes is increased for propagation in the east‐to‐west (EW) direction relative to the west‐to‐east (WE) direction for frequencies less than 25 kHz and for the angles between the vertical and the direction of the static magnetic field in the range of 20° to 60°. These results are consistent with the recently reported measurements by Crombie (1966). The attenuation rates computed for the sharply bounded ionosphere model are in excess of 5 dB/1000 km for EW direction of propagation, but are lower in the stratified ionosphere models.
Effect of Thin Plasmas on an Aperture Antenna in an Infinite Conducting Plane
Authors: Fante R. L.
Published: November 2015

It is shown that for the plasmas present around a wide variety of reentry vehicles, it is acceptable to replace the plasma by an impedance sheet. Using this notion, a variational expression for the admittance of an arbitrary aperture (fed by a waveguide) in an infinite conducting plane covered by an impedance sheet is developed, and examined in some detail. We found that a purely real impedance sheet tends to suppress the higher‐order modes, while a purely imaginary sheet can enhance or suppress the higher modes, depending upon their nature.
Calculation of the Virtual Height and Absorption of Radio Waves in the Ionosphere
Authors: Titheridge J. E.
Published: November 2015

Calculations for the ordinary ray under different conditions show that the effect of collisions can considerably reduce the virtual heights given by ray theory. This reduction is, however, caused entirely by the errors inherent in ray theory. Phase mtegral calculations show that the simplest ray theory result, ignoring collisions, is accurate to within 0.1 percent except under those conditions which require a full wave treatment.

Calculations of absorption by integrating the absorption coefficient k up to the level X = 1 also give incorrect results, because of ray theory limitations. These errors are exactly counterbalanced by the errors in a commonly used approximation for k. The use of this approximation therefore gives results which are more accurate, by several orders of magnitude, than the use of the exact expression.
Cylindrical Antenna With Tapered Resistive Loading
Authors: Shen Liang-Chi , Wu Tai Tsun
Published: November 2015

The current, the input impedance, and the far field pattern of a cylindrical antenna with tapered resistive loading are determined. The distribution of the resistive loading along the antenna is a particular function multiplied by a constant positive parameter α. The current on the antenna and the field pattern are evaluated for a wide range oflengths with several different α's ranging from 0 to 1 and for positive integers. They are found not critically dependent on the parameter α. For α near or greater than 1, the antenna is nonreftecting.
A Rapid and Accurate Ray Tracing Algorithm for a Horizontally Stratified Atmosphere
Authors: Thayer G. D.
Published: November 2015

It is shown that the effective earth's radius technique may be applied to ray tracing through a horizontally stratified atmosphere over a smooth, spherical earth, where the refractive index profile consists of relatively thin layers of nearly‐constant n‐gradient. With this method the refraction (bending) of the radio ray becomes a closed form function of the elevation angle, which is itself a closed form function of the refractive index profile. This allows ray tracings to be performed with less computing time and with a much higher degree of internal precision than formerly. This latter advantage facilitates computation of small dispersive effects at optical wave lengths. It is shown that the radial distance power‐law model of n(r), inherent in the effective earth's radius approach, is nearly identical, for relatively thin layers, with the simple constant gradient model which has been widely used in the past, thus assuring compatibility with previous results.
Further Note on the Quasi‐Static Theory of a Cylindrical Impedance Probe for Magnetoplasma
Authors: Wait James R.
Published: November 2015

In a previous paper (Wait, 1966), an expression was derived for the fields of two parallel line charges in an anisotropic medium. A quasi‐static theory was used, and to facilitate the analysis, the line sources were encased in a cylindrical dielectric rod. An important conclusion was that the resonant frequencies of the driving point impedance did not depend on the geometry of the device; at least, this was true to within a first order. This is in contrast to many other plasma diagnostic devices (Heald and Wharton,. 1965).

It is the purpose of the present note to generalize the above‐mentioned derivation to include the effect of a sheath at the boundary of the plasma next to the probe. The influence of a cylindrical glass container for the dielectric rod is also considered. The situation is illustrated in figure 1 where the common z axis of the Cartesian (x, y, z) and the cylindrical coordinate system is normal to the paper. Two infinitesimally thin parallel wires are located at (ρ0, φ0) and (ρ0, φ0 + π), as indicated. For purposes of the quasi‐static analysis, these are assumed to have charges of q and −q coulombs per unit length, respectively. The thin wires are encased in a cylindrical rod of dielectric constant ε1 and radius c. The dielectric rod is enclosed by a cylindrical glass container of dieiectric constant ε2 and outer radius b. The sheath separating the plasma from the device is then regarded to be a cylindrical layer of vacuum of dielectric constant ε0 which has an outer radius a. The external medium is a homogeneous electron plasma and it is characterized by a (angular) plasma frequency ω0, collision frequency v, and (angular) cyclotron frequency ωc. If the d‐c magnetic field lies in the (x, z) plane and subtends an angle θ with the z axis, the relevant components of the dielectric tensor of the plasma are (Ratcliffe, 1959)