bluuebunny/crossref_metadata_2025_split huggingface dataset:
Measurement of the Total Electron Content With the Differential Faraday Effect Using the Satellite Explorer 22
Authors: Munther Christian 
Published: November 2015

The signals of the American satellite Explorer 22 on 20, 40, 41 Mc/s have been received and their amplitudes recorded. The records show the Faraday effect when a fixed linearly polarized antenna is used. Using the Faraday effect, the total electron content can be computed, the total number of rotations being determined by comparing records of 40 and 41 Mc/s.The considerations of this paper are based upon the period January‐April 1965. Total electron content decreasing to the north prevail. In addition, a comparison of the Faraday effect on 20 and 40 Mc/s was performed. At small zenithal distances the Faraday periods on both frequencies (reduced to the same frequency) become equal; at larger distances typical deviations are observed.
Middle‐Latitude Ionospheric Total Electron Content: Summer 1965
Authors: Klobuchar J. A. , Whitney H. E. 
Published: November 2015

The total electron content of the ionosphere’ was measured continuously from a northern midlatitude station during the summer of 1965 by monitoring the polarization twist of VHF radio signals from the Early Bird synchronous satellite. The ambiguity in the total amount of polarization twist of the Early Bird signal was resolved by measurinj!; the total polarization twist of a lunar reflected radio wave at a time when the moon coincided in dirertion with Early Bird. Large day‐to‐day differences in electron content were seen. The late afternoon maximum value of electron content was not well related to magnetic activity. Many small, irregular changes in electron content were observed. Diurnal values of electron content were much lower than those observed during 1961.Observations of polarization twist of VHF radio waves from synchronous satellites provide a simple, accurate means of measuring diurnal, seasonal, and anomalous changes in ionospheric total electron content.
High‐Latitude Radio Star Scintillation Measurements at 68 Mc/s Made With a Phase‐Sweep Interferometer System
Authors: Lansinger John M. 
Published: November 2015

A quantitative evaluation and comparison are made of independent 68 Mc/s angular and amplitude scintillation data received at the College, Alaska, experimental station. A phase‐sweep interferometer system is employed and the outputs are digitized for subsequent analyses.A correlation analysis is made between ionospheric absorption, magnetic variation, and the angular and amplitude scintillation data. Some results are presented which show an association between short‐term absorption events and the enhancement of scintillation activity.Power spectral analysis and cross‐correlation analysis are made of the experimental data. Given theoretical ionization models, the computed ground diffraction patterns are compared with experimental data. The majority of the observations are consistent with an ionospheric model comprised of kilometer‐scale electron density gradients in combination with random scatterers.
Technique of Observing the 5‐mm Self‐Emission From the Oxygen of the Earth's Atmosphere to Obtain a Vertical Sense
Authors: Taylor H. P. , Campbell J. A. 
Published: November 2015

The results of previous calculations have shown that, due to the heavy absorption of the atmospheric oxygen, the resultant radiation both in the wells and in the cores of the 60‐Gc/s spectral complex provides a radiometrically bright mantle surrounding the earth. It becomes evident when viewed from space that this oxygen mantle could supply a uniform, nonftuctuating signal for radiqmetric sensing.This paper presents a quantitative expression of a technique of observing the 5‐mm self‐emission from the oxygen of the earth's atmosphere in order to obtain a vertical sense. The choice of operating frequency is a selection process in which a frequency is determined for which the atmospheric opacity is great enough to reject the radiation from the lower atmosphere, and at the same time have sufficient transmissivity in the upper atmosphere to allow predominance of radiation from the 15‐ to 32‐km region. Under these conditions a uniform and well‐defined radiating disk should be seen. To the degree that the observed disk exhibits circularly uniform emission and the mantle possesses spherically homogene US density, the line through its center of brightness may be defined as the direction corresponding to the local vertical at the spacecraft. This may be determined as the boresight axis of a lobe comparison antenna system.
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.
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.
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.
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 theoryAs 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.
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.
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.
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.
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.
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.
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.
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.
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.
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)