bluuebunny/crossref_metadata_2025 huggingface dataset:
Atmospheric sciences in Antarctica
Authors: Meriwether John W.
Published: February 2008

The Antarctic is an interesting land that has become the focus of much attention in the last decade. Its undisturbed geological record dating back to the last interglacial period, a locale with seas and lakes populated with interesting organisms, a land with beautiful twilights and lovely cirrus and stratospheric cloud formations, a whole continent dedicated by international treaty to scientific research–these factors provide good reasons for the renewed interest. A recent review by Weller et al. [1987] explores in more detail the many scientific ideas that make Antarctica an attractive laboratory. Studies relating to sundry aspects of the Earth's geosphere‐biosphere system draw scientists from the whole spectrum of scientific disciplines.
Introduction to “Magma Genesis, plate tectonics, and chemical differentiation of the Earth” by Peter J. Wyllie
Authors: Lal D.
Published: February 2008

One of the fundamental problems in geophysics is the chemical differentiation of the Earth, which is accomplished through magmatic processes, which in turn are a direct manifestation of convection within the mantle. The framework of plate tectonics is as yet the best model for explaining the different types and styles of magmatic activity.

Experimental petrology calibrates the conditions for partial melting of various rock types and defines the conditions of magma crystallization under varied conditions. Laboratory data provide phase boundaries constraining the sites of partial melting in the Earth's interior.
Alternative theories of atmospheric teleconnections and low‐frequency fluctuations
Authors: Frederiksen Jorgen S. , Webster Peter J.
Published: February 2008

Observational studies have revealed a rich low‐frequency structure in the atmosphere. A review of the theories, observations, and model studies of this low‐frequency atmospheric variability is presented. On time scales of weeks or longer the atmosphere appears to possess distinct oscillatory behavior in well‐defined and persistent “centers of action.” This behavior is also an endemic feature of surrogate atmospheric data sets emerging from experiments with complicated climate models. Many theories have attempted to determine the dominant physical processes responsible for the low‐frequency variance but have usually failed when compared carefully with observations. For example, simple linear steady state and Rossby wave dispersion theories have been used in an attempt to explain the observed global response to low‐latitude perturbation. However, the observed structures of mature anomalies are often quite distinct from the vertical structures of disturbances predicted in these theories. Also, in general circulation and model studies, the sign of the nonlinear response is not simply related to the sign of the forcing as predicted by linear steady state theories. It is argued that the theories fail because either the full three‐dimensional complexity of the basic state is not considered or its inherent instability structure is not recognized or is, in fact, ignored. It is shown that three‐dimensional instability theory provides a natural generalization and marriage of the zonally averaged instability theory of Charney and Eady and the Rossby wave dispersion theory of Rossby and Yeh. As such, it provides a formalism which may be used to understand a wide variety of atmospheric fluctuations including the locations of eddy flux covariance maxima and storm tracks in both the tropics and extratropics and the generation of blocking, teleconnection patterns, and other quasi‐stationary anomaly features. Attention is focused on two particular mechanisms within this formalism for the formation of quasi‐stationary low‐frequency fluctuations. One of these is the baroclinic‐barotropic dipole instability mechanism in which the formation of quasi‐stationary mature anomalies is initiated by the upstream development of mid‐latitude eastward propagating dipole wave trains which arise through the combined baroclinic‐barotropic instability of the three‐dimensional atmospheric flow. The other is the westerly duct mechanism in which the initiation of low‐frequency variability is caused by tropical disturbances. According to this hypothesis, the longitudinal variation of the basic state flow near the equator causes a ducting of wave energy generated in the tropics to specific zones in the upper tropospheric westerlies; these zones then act as source regions for the emanation of waves into the extratropics. Furthermore, this duct also acts as a waveguide for extratropical modes propagating into or through the tropics.
Phanerozoic paleomagnetic poles from Europe and North America and comparisons with continental reconstructions
Authors: Van der Voo Rob
Published: February 2008

In over 30 years of paleomagnetic research, the available paleomagnetic pole determinations from North America and Europe have become much more abundant and, especially, more reliable. While it was still possible in the mid 1960s to conclude that the scatter in paleomagnetic poles made tests of continental reconstructions dubious and inconclusive at best, the data base now allows a much better resolution. For this study, paleomagnetic poles from the stable interiors of North America and Europe have been compiled with a quality index (0 ≤ Q ≥ 7) based on seven reliability criteria, with the purpose to test continental reconstruction parameters for closing the North Atlantic Ocean. An appropriate geographic and temporal data selection (with Q ≥ 3) allows a direct comparison of mean paleopoles for the entire interval of Ordovician through Early Jurassic with various Europe‐North America continental reconstructions published by Bullard and colleagues, Herron and colleagues, Le Pichon and colleagues, Sclater and colleagues, Srivastava and Tapscott, Savostin and colleagues, and Rowley and Lottes. The European set of mean paleopoles compares most favorably with those of North America in the fit of Bullard and colleagues. Using the best fit reconstruction, a common apparent polar wander path has been constructed for Europe and North America, which can serve as a reference path for analysis of displaced terrane motions. I conclude from this study that for the continents bordering the North Atlantic the paleopole data base has become fairly robust, that tight fits such as those by Bullard and colleagues are in superior agreement with the paleomagnetic data, and that the combined paleomagnetic North America‐Europe data set is apparently not affected by significant long‐term, nonzonal, nondipole fields.
Ocean flux studies: A status report
Authors: Jahnke Richard A.
Published: February 2008

Marine biogenic cycles play a key role in controlling atmospheric CO2 concentrations. To predict future atmospheric CO2 levels and to interpret past changes that may have been associated with global climatic events, it is necessary to determine on a global scale the rates at which carbon is cycled through the ocean and the factors that may alter the rates of transfer. Because of uncertainties and limitations in existing measurement techniques and the extreme spatial and temporal variability of ocean properties and processes, studies have not yet produced an accurate, comprehensive description of the marine carbon cycle. While some advances in the measurement of specific components of the carbon cycle have been made, the fundamental problem of undersampling an extremely heterogeneous ocean has remained. Recently, satellite‐deployed sensors have provided large‐scale, nearly synoptic images of ocean surface water properties, such as temperature and color, which have revealed mesoscale features not observed previously. In addition, moored and free‐drifting observation systems are being developed to determine directly the temporal variability of surface and subsurface water characteristics. With these remotely sensed properties to provide the space and time framework by which individual measurements of ocean processes and material fluxes can be extrapolated throughout ocean basins and over decadal time scales, we are poised to make a fundamental improvement in our understanding of ocean elemental cycles.
On the space‐frequency equivalence of a correlator interferometer
Authors: Swenson, Jr. G. W. , Mathur N. C.
Published: February 2008

It is shown that an exact equivalence exists between a monochromatic correlator interferometer using directional antennas and a wideband correlator interferometer using isotropic antennas. The necessary relationship between the frequency response function of the receiving system and the aperture illumination of the antennas to achieve the equivalence is derived.
Number Density Determination in the Atmosphere of O2, H2O, and CO2 Gas Constituents by Use of a High Intensity Laser Beam
Authors: Dobbins D. L. , LaGrone A. H.
Published: February 2008

A method is developed whereby number densities of several of the atmospheric gas constituents can be determined as a function of altitude. The method employs two laser signals of different wavelengths, one occurring in an absorption region of the gas in consideration and one occurring in a spectral region where no absorption takes place. Returned scattered signals are collected and used along with absorption line strength and line width to determine the number density. The method described affords an indirect way of determining number densities of a specific constituent of the atmosphere by electromagnetic probing.
Radiation From Circular Arc Antenna Arrays
Authors: Butler J. K.
Published: February 2008

The properties of radiation from circular arc antennas are discussed by using an asymptotic expansion method. Approximate pattern calculations of these antennas have usually been made by employing related techniques, such as the method of stationary phase. However, the stationary phase method has certain limitations, and it is not as accurate as the method presented here. The asymptotic expansion gives relatively accurate results when the radius of the arc source is large with respect to the wavelength. This requirement is usually satisfied if the antenna is to have a high directivity. The asymptotic expansion converges rapidly for observation angles away from the broadside direction, so that it is easy to determine the sidelobe energy distribution. The results given here can easily be applied to circular arc arrays with either uniform or nonuniform spacings of the elements along the arc by applying the Poisson sum formula. This is true because the resulting integrals governing the radiation fields from a circular arc array are similar to the ones discussed here.
HF Radar Signatures of Traveling Ionospheric Irregularities, 3D Ray‐Tracing Simulation
Authors: Georges T. M. , Stephenson Judith J.
Published: February 2008

A technique is described for automatically simulating a multitude of ground‐backscatter displays with information supplied by three‐dimensional computer ray tracing. Model ionospheres containing realistic wavelike traveling disturbances are used to produce representative displays and to correct some misconceptions about the interpretation of backscatter signatures.
Foreword
Authors: Wright R. W. H. , Matsushita S.
Published: February 2008

The papers in this issue are based upon some of the contributions presented at the Third International Symposium on Equatorial Aeronomy held at the Physical Research Laboratories, Ahmedabad, India, February 3‐10, 1969. Previous meetings of the Symposia had been held in Huaychulo, Peru, in 1962, and in Sao José dos Campos, Brazil, in 1965.

The earlier meetings had started cooperative work among workers in equatorial regions, initiating a breakdown of the tendency for the worker in equatorial regions to feel himself an ‘out‐station’ from one of the metropolitan countries. The conferences had also served the purpose of bringing some degree of unification among the areas of research that had tended to be pursued in isolated channels. Aeronomy is taken to include all studies of the earth's atmosphere above 60 km. Equatorial aeronomy restricts the interest to the vicinity of the equator and to effects that originate at the equator.
Equatorial Atmosphere Measurements Obtained With the Sounding Rocket Grenade Experiment
Authors: de Mendonça F. , Sobral J. H. , Rai D. B.
Published: February 2008

Under a grenade series of experiments with sounding rockets made at Barreira do Inferno, Natal (5.6°S, 35°W), 19 successful launchings have yielded useful data on the upper stratosphere and the mesosphere during the period August 7, 1966, to March 5, 1968. These experiments covered the height range of about 35‐95 km and were supplemented by radiosonde data from 19 balloons that provided data up to approximately 35 km. Also, data from 29 meteorological rockets with an upper limit of 60 km are available for the period September 14, 1966, to July 24, 1968. Only 2 of these 29 launchings were instrumented for temperature measurements. Data on winds, temperatures, and densities have been obtained and analyzed from the rocket‐grenade and balloon experiments. Some features of the wind and temperature distributions in the upper stratosphere and mesosphere are discussed. Extremely low mesopause temperatures of the order of 130°K were noticed in early summer at about 90 km. The temperature at this height was found to be higher in winter than in summer. A correlation between temperature at 40 km and absorption of cosmic noise at 30 MHz is also presented as a probable evidence of stratosphere‐ionosphere coupling.
On Diurnal Variation of Geomagnetic Pulsations Pc at M'Bour (West Africa)
Authors: Barsczus Hans G.
Published: February 2008

Six years of magnetic quick‐run records made at the low‐latitude M'Bour Observatory have been analyzed. It was found that the frequency of occurrence of pulsations Pc 3 and 4 presents a marked diurnal variation characterized by two principal maxima, at sunrise and around local noon. The curves of occurrence are compared with the diurnal variation of the critical frequency of the ionospheric F2 layer at Dakar. The morning maximum of pulsations corresponds to low values of foF2 which contrasts with high values corresponding to the noon maximum. In conclusion the frequency of occurrence of the geomagnetic pulsations Pc does not appear to be directly related to the critical frequency of the F2 layer.
Derivation of Closed Functions to Compensate Range and Angle Errors in an Exponential Atmosphere
Authors: Rowlandson L. G. , Moldt R. G.
Published: February 2008

It was shown by G. D. Thayer and J. J. Freeman that corrections to refraction‐induced errors can be expressed in terms of error functions for propagation in an exponential model atmosphere. Using Freeman's equations as an example, we replace the error functions by their asymptotic expressions, thereby giving closed form equations. To extend the usefulness of these functions for short ranges and small elevation angles, an empirical adjustment is made.
Small‐Aperture Measurements of the Shape of the Received Cone of Rays in Long‐Distance Ionospheric Propagation
Authors: Whale H. A.
Published: February 2008

The way in which a mechanical lock‐on type of direction finder of small aperture can be used for recording the variations of incoming wave‐normal direction in both the vertical and horizontal planes is discussed. The limitations arising from the inertia of the system are considered. It is shown that, in the case of near‐antipodal short‐wave ionospheric propagation (Great Britain to New Zealand), the received cone of rays usually contains two or more main groups displaced in angle in a plane that is nearly vertical.
The High‐Frequency Fluctuation of the Wind in the First Kilometer of the Atmosphere
Authors: Readings C. J. , Rayment D. R.
Published: February 2008

This paper describes some preliminary experiments made at Cardington during 1968 to measure the fluctuations of wind inclination in the frequency range 0.1–3 Hz. The measurements were made at heights up to about 1 km by using a tethered balloon. The results illustrate the intermittency of atmospheric turbulence and show the way in which the implied average rate of dissipation of turbulent kinetic energy varies with height under different daytime stability conditions including overhead inversions. The results are also broadly consistent with a buoyancy production that is roughly constant with height in the convective layer (and is the dominant contribution at the greater heights) and a mechanical production that falls off roughly as 1/z.
An Energy Budget for a Layer of Stratospheric CAT
Authors: Dutton John A.
Published: February 2008

The energy budget of a patch or layer of severe CAT encountered on one ofthe HICAT flights is analyzed. The shear feeding of energy, the buoyant extraction of energy, and the frictional dissipation are considered, and it is found that the budget balances within about 8% of the total rate of shear production. The cospectra that reveal the wavenumber decomposition of the rates of energy exchange are compared with the spectra for each component.The marked lapses from the spectral behavior expected in isotropic turbulence are in agreement with the calculated spectral fluxes of energy.
Anisotropy of the Fine Structure
Authors: Kaimal J. C. , Borkowski J. , Panchev S. , Gjessing D. T. , Hasse L.
Published: February 2008

Kolmogorov's theory postulates that the very small scales of motion in a turbulent fluid are isotropic. At the large end of these scales (inertial subrange) the spectral energy would be expected to fall off as the
power of wave number. Although it has been generally recognized that the
slope in the one‐dimensional spectrum extends to wave numbers well below the limits predicted for the three‐dimensional spectrum and cannot therefore be considered a sufficient condition for isotropy, it was assumed that local isotropy could be found if the measurements went far enough into the
region. Evidence presented at this meeting suggests that in the first few meters above the ground isotropy may never be reached even at scales small enough to be dominated by viscous dissipation. Above a height of approximately 20 meters, isotropy may be observed at wavelengths smaller than
the height above ground (i.e. a nondimensional frequency f > 10). In the free atmosphere, radio propagation experiments indicate that isotropy exists only at wavelengths of the order of 10 meters or less.
Heat, Moisture, and Momentum Fluxes in the Boundary Layer
Authors: Readings C. J. , Businger J. , Coantic M. , Mahoney A. R. , Naito K.
Published: February 2008

As there are many techniques available for measuring these fluxes in the boundary layer, the group considered that it would be useful to start by discussing seven principal ones in turn.

The vertical flux (or eddy transport) F of any atmospheric parameter ψ may be represented by

urn:x-wiley:00486604:media:rds178:rds178-math-0001
where w is the wind's vertical component, and the prime denotes the instantaneous deviation of the quantity from its mean value (e.g. w″ = w″ −
[Priestley, 1959]. It is important to choose the sampling rate and the observational period so that the required parts of the total flux spectrum are measured [Pasquill, 1962].
Budgets of Turbulent Fluctuations
Authors: Panofsky Hans A. , Atlas D. , Fehlhaber L. , Cermak J. E.
Published: February 2008

The propagation of electromagnetic or acoustic waves through a turbulent, locally isotropic medium is prescribed, provided we know the coefficient of k−5/3 in the Kolmogorov law. This coefficient is the product of b, a universal constant; N, the dissipation rate of the fluctuations of refractive index; and ϵ−1/3, where ϵ is the rate of dissipation of turbulent velocity fluctuation into heat. We might consider two kinds of problems:

How can electromagnetic or acoustic propagation information be used to get information about various meteorological properties?

How can meteorological data be used to estimate the propagation of waves?
Loop Impedance in Magnetoplasma: Theory and Experiment
Authors: Duff Graham L. , Mittra Raj
Published: February 2008

The impedance of a small loop in magnetoplasma is derived for the cases of magnetic field normal to and parallel to the plane of the loop. The quasi‐static and uniaxial approximation methods are used, and an argument is given to justify the uniaxial approximation as the more desirable method. The results of the theory are given in analytic form and are evaluated numerically and presented graphically. The loop impedance is seen to be much less plasma‐dependent than the impedance of a short electric dipole. It is shown that the small loop can be an efficient radiator under certain plasma conditions. The results of laboratory measurement of loop impedance in magnetoplasma are also given for the cases of normal and parallel orientation of the magnetic field with respect to the plane of the loop. The laboratory plasma is generated by using a brush‐electrode configuration. The measured impedance is compared with the theoretical predictions, and good agreement is shown for the perpendicular orientation. Quantitative agreement with the theory is not as good for the case of parallel orientation, but much of the gross impedance behavior is verified for this orientation, particularly the fact that the impedance is relatively plasma‐dependent.
Foreword
Authors: Evans J. V.
Published: February 2008

The Symposium on Planetary Atmospheres and Surfaces, held at Woods Hole, Massachusetts, August 11–15, 1969, was the successor to an earlier symposium held in May 1965 in Puerto Rico, whose proceedings were published in vol. 69D, no. 12 (1965) of Radio Science. Both meetings were organized through the initiative of Commission II of URSI (Radio Propagation in Non‐Ionized Media), who secured the sponsorship of URSI (International Union of Radio Science), the IAU (International Astronomical Union), and, in the case of this Symposium, of COSPAR (Committee on Space Research). Financial support for the Symposium was provided by URSI.

Whereas the earlier symposium dealt almost exclusively with the results of radar and radio astronomy, the most exciting new results since then have been obtained by space research. Thus, in planning the new symposium the organizers sought to bring together workers in the two fields. This was deemed particularly important in the study of the moon, since it is now possible to determine how well radio and radar astronomy succeeded in describing the properties of the lunar surface prior to its physical investigation by use of landed vehicles. Based on such a comparison, one may be able to apply the radio techniques to planetary surface investigations with greater confidence. Accordingly, four sessions of the symposium were devoted to the moon, permitting extensive reviews of the results secured by the Ranger, Orbiter, and Surveyor vehicles. The organizers and chairmen of these sessions were: Dr. H. Masursky, U. S. Geological Survey; Dr. G. H. Pettengill, Arecibo Ionospheric Observatory; Dr. L. D. Jaffe, Jet Propulsion Laboratory; and Prof. Z. Kopal, University of Manchester. A highlight of the meeting was some preliminary reports on the results of the Apollo experiments. From the talks and lively discussion it would seem that, although there are matters of detail to be ironed out, we now have a good physical description of the surface properties of the moon and recognize that both external and internal processes have played a part in shaping them. However, considerable work has to be done before we may hope to understand the full history of the moon and its origin.
Interferometric Investigations of The Atmosphere of Venus
Authors: Muhleman Duane O.
Published: February 2008

The determination of the opacity law as a function of wavelength for the Venus atmosphere is discussed. Interferometric and integrated brightness temperature observations are compared to model calculations for atmospheres of CO2, N2, and H2O which are consistent with the radar opacity law. If the atmosphere of Venus is essentially pure CO2, a surface pressure of 78 atm with a surface temperature of 725°K is obtained. The total CO2 in the atmosphere of Venus is estimated to be 4×1023 grams, which is in fair agreement with the amount of CO2 that has escaped from the interior of the earth since its formation.
First Results of the Mariner‐6 Radio Occultation Measurement of the Lower Atmosphere of Mars
Authors: Kliore Arvydas , Fjeldbo Gunnar , Seidel Boris
Published: February 2008

As the radio signal of Mariner 6 was intercepted by the surface of Mars near Meridiani Sinus, the presence of an atmosphere caused small changes in the frequency of the received signal. Analysis of these changes indicates that the pressure at the surface of Mars at that point is about 6.6 mb and the temperature approximately 276°K. Data taken as the radio beam emerged from behind Mars in the vicinity of the north pole indicate a surface pressure of approximately 6.4 mb and a temperature of about 158°K. Extrapolation of the 6.6‐mb pressure measurement at the point of entry over the 12—km range of topological variation measured by earth‐based radars indicates that the surface pressure in the near north equatorial regions of Mars may vary from about 3 to about 8 mb.
Preliminary Radar Results of Mars
Authors: Goldstein R. M. , Melbourne W. G. , Morris G. A. , Downs G. S. , O'Handley D. A.
Published: February 2008

Radar studies of Mars during the 1969 opposition (not yet completed) have yielded preliminary results. Elevation and radar brightness is presented as a function of longitude for areas between 3° and 12° north latitude.
Thermal Radio Emission From the Major Planets
Authors: Kellermann K. I.
Published: February 2008

Measurements of the thermal radio emission from all major planets have been reported at millimeter and centimeter wavelengths, and from Jupiter and Saturn at decimeter wavelengths as well. The measured brightness temperatures deduced from these measurements generally exceeds the expected equilibrium temperature calculated from solar heating. The highest temperatures are generally those measured at the longer wavelengths, which are thought to refer to the deeper, presumably hotter layers in the atmosphere. At least for Jupiter and Saturn the high flux measured at infrared wavelengths implies an internal source of heat comparable with solar heating.
The Twelve‐Year Periodicities of the Decametric Radiation of Jupiter
Authors: Carr Thomas D. , Smith Alex G. , Donivan Frank F. , Register Henry I.
Published: February 2008

Three parameters of Jupiter's decametric radiation which apparently undergo cyclic variations with periods of the order of a decade are the mean occurrence probability for an apparition, the central meridian longitude of the main source, and the effective width of the main source (or Source A). Observational results indicate that the oscillation in each parameter is caused by the apparent change in Jupiter's aspect as it orbits the sun and that the period in each case is therefore 11.86 yr. It was found that the average rotation period over an 11.86 year interval is 9h 55m 29.73s±0.04s. This is probably the rotation period of Jupiter's magnetic field.
Plasma Moment Equations in a Dipole Field
Authors: Grebowsky J. M.
Published: February 2008

A coordinate system is defined with respect to a magnetic dipole field configuration by unit vectors in the direction of the field, in the azimuthal direction, and along the line of intersection of the local magnetic meridian plane with the local equipotential surface of the magnetic dipole. The velocity terms of the continuity and momentum equations pertinent to plasma motion are expressed in terms of variations along these coordinate directions.
On VLF Radiation Resistance of an Electric Dipole in a Cold Magnetoplasma
Authors: Wang T. N. C. , Bell T. F.
Published: February 2008

By using full‐wave theory, an analysis is made of the radiation resistance of a short filamentary electric dipole, oriented with an arbitrary angle with respect to the static magnetic field, in a cold, uniform magnetoplasma. The frequency range considered lies below the local lower hybrid resonance frequency and above the proton gyrofrequency, and in this range approximate closed‐form expressions for the radiation resistance are obtained by using a plasma model appropriate to the magnetosphere. These closed‐form expressions are valid for dipoles of moderately restricted length, and the physical implications of this length restriction are discussed. It is found that the radiation resistance R increases rapidly as ф0, the angle of dipole orientation with respect to the magnetic field, varies from 0° to 30° but only gradually as ф0 varies from 30° up to 90°. The ratio of R(ф0 = 90°)/R(ф0= 0°) is approximately equal to (ƒHe/ƒ)2. Except for the case of parallel orientation and ƒ < 10−2 ƒHe, the radiation resistance of an electric dipole in the magnetoplasma is ∼ 102 to 105 times larger than that in free space. Thus, for the low frequency range considered, an electric dipole in the magnetoplasma is generally much more efficient that it would be in free space.
Radiation Characteristics of Longitudinal Waves From an Antenna in a Plasma
Authors: Shen K. , Aksornkitti S. , Hsuan H. C. S. , Lonngren K. E.
Published: February 2008

This paper describes experiments designed to measure the radiation patterns of a longitudinal wave excited in a warm plasma by both monopole and dipole antennas. The longitudinal wave used in this experiment is the low‐frequency ion acoustic wave that propagates with a phase velocity [γkTe/M/i]½. Experimental results agree well with the theoretical predicted radiation pattern.
Electromagnetic Scattering From a Finite Tubular Cylinder: Numerical Solutions
Authors: Kao Cheng C.
Published: February 2008

The method of approximate product integration is applied to solve numerically the integral equations of the total currents on the surfaces of the finite tubular cylinder with complete generality both in radius and length. Procedures have been devised to take care of the squareroot singularity of the transverse total current at the end of the cylinder. Both total currents and scattering cross sections are presented for three special cases with ka = 1.0 and kh = 0.5π, 1.0π, and 1.5π. A complete set of the computer program in Fortran 4 has been prepared for the IBM 7094 at Harvard Computing Center. It can solve simultaneously for cylinders of the same radius but discrete and different lengths.
Impedance of Antennas in a Warm Isotropic Plasma: A Comparison of Different Models
Authors: Schiff M. L. , Fejer J. A.
Published: February 2008

The impedance of a sphere in a plasma is calculated for four different models. There are important differences between the four results. In particular, the real part of the impedance is shown to vanish at several frequencies above the plasma frequency for a spherical grid if the plasma is described by hydrodynamic equations. If the kinetic (Vlasov) equation is used, the nulls are changed into minima that are only noticeable if the radius is much greater than the Debye length and the frequency is not too far above the plasma frequency. If the hydrodynamic equations are used but the normal component of the fluid velocity is assumed to vanish on the (solid) sphere, there are no nulls or minima. The relationship of these results to previous work on antennas in plasmas is considered.
Latitudinal Variation of Total Electron Content in the Winter at Middle Latitudes
Authors: Bertin F. , Lepine J. Papet
Published: February 2008

Studies of total electron content (TEC) have been made by using data obtained during three winter solstices in Paris, France, and Kiruna, Sweden. A nocturnal winter maximum is clearly shown by these data, and an effort is made to hypothesize its cause. A two‐fold hypothesis is offered; the increase in TEC is attributed to an electron flux descending from the protonosphere. This flux is linked to lowering electron temperatures in the force tube after sunset in the conjugate hemisphere. In addition to this production process, a regulatory process is invoked to reconcile the observed values with the maximum flux intensity compatible with the theory. The regulatory process is attributed to an interaction betweenthe neutral winds and the ionospheric plasma in the presence of the earth's magnetic field.
Influence of Solar Activity on the Total Electron Content of the Ionosphere Over Tortosa
Authors: Galdón Eduardo , Alberca Luis F.
Published: February 2008

Through the use of the data obtained from the BE‐B satellite, the effect of the solar cycle and the seasonal variation of the total electron content of the ionosphere are separated and evaluated. The results are compared with those of other authors.
Scintillation Studies of a Synchronous Satellite's Radio Signals at a Low‐Latitude Station
Authors: Houminer Zwi
Published: February 2008

Scintillation observations at 136 MHz were made with the Canary Bird synchronous satellite during the winter of 1967–1968 and the spring and early summer of 1968. The diurnal pattern of scintillations is similar for the two periods. The mean scintillation index is higher during the spring and early summer, however, because of the increase in the percentage of occurrence of mild scintillations during this period. There is a positive correlation between nighttime scintillations and magnetic activity. On the other hand, daytime scintillations are only slightly dependent on magnetic activity.
Results of the OV4‐1 Dual Satellite Experiment on Guided Ionospheric Propagation
Authors: Barker James I. , Grossi Mario D.
Published: February 2008

The OV4‐1 (orbiting vehicle 4, experiment 1) dual satellite guided ionospheric propagation experiment has confirmed the existence of long‐range, low‐loss, earth‐detached propagation paths in the bottomside ionosphere with mean path losses smaller than equivalent multihop and, in some instances, smaller than free‐space propagation. Satellite‐to‐satellite signals at 34.3 MHz were received from 56 to 100% of the five‐minute samples taken in real time by the ground telemetry network while the orbits of the two satellites were decaying from 300 to 250 km. Measured values of path losses range from between 124 and 159 db. Multipath spread was never found larger than 550 μsec, and there is some evidence that Doppler spread was less than 0.012 Hz. Signals at 20.75 and 46.8 MHz in the satellite‐tosatellite link were rarely received beyond the line of sight.
Faraday Rotation in Media Stratified Parallel to the Direction of Propagation
Authors: Datta A. N. , Nag B. R.
Published: February 2008

The effect on Faraday rotation of stratification in an ionized medium parallel to the direction of propagation is examined. An expression suitable for a general inhomogeneity profile is obtained in a series form. A closed‐form solution is also discussed with reference to a lens‐like medium described by a parabolic inhomogeneity profile. The departure of rotation from the first‐order value is shown to have a strong dependence on the nature of the inhomogeneity distribution. Near the focal points within a focusing medium, the Faraday effect is found to exhibit an anomalous behavior in that rotation changes sign through a large swing in amplitude.
The Brightness Temperature of a Vertically Structured Medium
Authors: Stogryn A.
Published: February 2008

Exact equations are derived for calculating the brightness temperature of a medium that is bounded by a plane surface and whose properties (dielectric constant and thermometric temperature) vary only with depth. Although no approximations are made in the development of the principal results, the final equations are presented in a form most convenient for use in the area of microwave radiometry (that is, in the limit where the Rayleigh‐Jeans approximation to the Planck blackbody radiation law is valid). Some special cases in which the differential equations arising in the theory can be solved analytically are presented as examples. A practical numerical method for evaluating the exact equations by use of a digital computer is also discussed.
A Vector Solution for Electromagnetic Wave Scattering From a Rough Surface of Arbitrary Dielectric Constant
Authors: Kaufman D. E.
Published: February 2008

A vector solution for electromagnetic wave scattering from a rough surface of arbitrary dielectric constant is developed through the use of the Stratton‐Chu integral under the assumption that the horizontal extent of the surface irregularities (and possibly the vertical extent also) is large compared with the incident wavelength. Other assumptions implicit in this solution are that the incident wave is a plane wave of arbitrary polarization, that the observation point is at any arbitrary direction in the far field zone of the scattering surface, and that the rough surface can be represented by a stationary random process with normal height distribution and Gaussian correlation function, the mean value of the surface being a plane. For a rough surface of lossless dielectric, plots showing the effects of dielectric constant, angles of incidence and scattering, and the statistical parameters of the rough surface are presented for the special cases of backscattering and bistatic scattering in the plane of incidence. For bistatic scattering the scattering behavior near the Brewster angle is clearly shown; the results for backscattering indicate the need for a more general rough surface model incorporating surface structure both large and small with respect to the incident wave‐length.
HF Backscatter From High‐Latitude, Ionospheric Barium Releases
Authors: Bates Howard F.
Published: February 2008

Of the six barium releases made in Alaska in March 1969, two gave good amplitude data from the 4‐ to 64‐MHz step‐frequency radars installed near Kodiak and Homer, Alaska. The effective cross section for isotropic scatter exceeded 1000 km2, whereas the projected area of the cloud was less than 100 km2; this indicates that the scatter was directive, not isotropic. The echoes were found to have an aspect sensitivity of 10 to 20 decibels per degree of off‐perpendicularity from the magnetic field. The backscatter cross section apparently had a maximum in the 15‐to 30‐MHz range; this indicates that transverse irregularity sizes of 5 to 10 meters were dominant n the clouds. At early times the length of the irregularities was of the order of a kilometer. Pronounced optical striation was accompanied by a decrease in aspect sensitivity; no other correlation was found between the optical and radar data. This indicates that the changes affecting the radar cross section were invisible. When all the available radio data are considered, the cloud at early times acts as if it were an over‐dense ball (not necessarily spherical) embedded in a field‐aligned cloud that is thin perpendicular to the direction of ion drift and that contains weak‐scattering field‐aligned irregularities. After striation the cloud acts as if it were a group of weak‐scattering, field‐aligned irregularities. The radar behavior of the clouds appears to be strongly dependent on ionospheric conditions.
Impedance of Cylindrical and Helical Antennas in Lossy Magnetoplasma Including Conditions of Refractive Index Resonance
Authors: Lafon Jean‐Pierre , Weil Herschel
Published: February 2008

A method is given to evaluate the input impedance of cylindrical and helical antennas immersed in cold lossy magnetoplasma. The impedance is shown to split into the sum of three terms associated, respectively, with the longitudinal current component, the circumferential current component, and the interaction between the two components of current. The procedure involves use of an assumed current density distribution for which necessary and sufficient conditions are obtained in order that the impedance will be finite for all frequencies including those for which there are refractive‐index resonances. The method is applied to obtain extensive numerical results for a specific choice of current distribution for the special case when the antenna is aligned parallel to the static magnetic field. Indications of the sensitivity of the results to choice of current distribution for cylindrical antennas (longitudinal current only) are obtained by comparison of the present numerical results with numerical results in the literature based on other current distributions.
Longitude and Seasonal Variations of the Sq Current System
Authors: Stening R. J.
Published: February 2008

The ‘equivalent circuit method’ of deriving electric currents in the ionosphere from assumed values of conductivities and emf's has been described earlier. The ionosphere is represented as a large circuit network, with the Hall effect included, and this network is solved by an iterative procedure on a computer. A single tidal wind system, the ‘1—2’ mode, is used as the driving force of the dynamo. The winds are converted from the geographic to the geomagnetic coordinate system. The international geomagnetic reference field (IGRF) is used to provide magnetic field values for calculating the dynamo emf's and the conductivities. The agreement between the calculated and observed positions of the focuses of the current system is remarkable when we consider that no seasonal variation of the wind was included. Seasonal variations of the reversal times of the equatorial electrojet are obtained in rough agreement with observation, whereas the calculated variations of the intensity of the electrojet do not agree so well.
Gq, a Galactic Component of the Geomagnetic Field Variation
Authors: Campbell W. H. , Matsushita S. , Bender B. K.
Published: February 2008

A quiet time galactic component, Gq, of the geomagnetic field variations has been extracted from observatory data of San Juan, Puerto Rico, and Honolulu, Hawaii, for the quiet sun years of 1965 and 1966. In the search for this effect, days of active solar‐terrestrial disturbances ere excluded, and the contributions of the solar quiet current (Sq) and the lunar tidal current (L) were first removed. Nighttime data show the Gq most effectively as a 1.5‐gamma variation that is diurnal in H with an increase at about 2200 sidereal time (SiT). The D and Z sidereal variations are less clear in the present data sample
E × B Drifts at Midlatitudes
Authors: Carpenter L. A. , Bowhill S. A.
Published: February 2008

At midlatitudes, vertical transport of ionization in the topside F region results from three mechanisms: first, ambipolar diffusion along the magnetic field, second, interaction between the ionization and the wind in the neutral atmosphere, and third, E × B drifts perpendicular to the magnetic field. The vertical velocity resulting from these three mechanisms was measured by determining the Doppler shift in the Thomson‐scattered power spectrum at altitudes between 450 and 900 km (Evans et al., 1970). Drift measurements were made at Millstone Hill Ionospheric Observatory. Electron‐density profiles and electron‐ and ion‐temperature profiles were made also. Drifts for the 24‐hour period of September 11–12, 1968, are examined for an altitude of 450 km. The diffusion velocity is calculated from the electron density and the thermal structure; the ion temperature at 300 km is taken as the neutral gas temperature for determination of the atomic oxygen density. With this diffusion velocity calculated and the vertical velocity measured, the combined effect of interaction with the neutral winds and E × B drifts can be determined. Through use of a model of the diurnal neutral wind behavior (Cho and Yeh, 1970), the effective E × B drift in the topside F region is estimated at midlatitudes. East‐west electric fields in the dynamo region that generate such E × B drifts are calculated from these results.
Atmospheric Emission and Absorption at Millimeter Wavelengths
Authors: Falcone Vincent J. , Wulfsberg Karl N. , Gitelson Samuel
Published: February 2008

We simultaneously measured atmospheric emission and absorption under clear sky conditions at frequencies of 15 and 35 GHz and compared the values with those calculated from the radiative transfer equation. The measurements show that atmospheric attenuation determined from emission and absorption measurements agree within experimental error and that the calculated values of attenuation agree with the measurements on a statistical basis when the Gross form factor is used with the model of a plane stratified atmosphere.
Nonlinear Longitudinal Waves in a Hot, Collisional Magneto Plasma with Applications to Ionospheric Irregularities
Authors: Sen Hari K. , Dubs Charles W. , Prasad Balram
Published: February 2008

Nonlinear differential equations are derived for a plane, longitudinal steady‐state wave propagating perpendicularly to a magnetic field in a thermal, collisional, weakly ionized plasma in the two‐fluid approximation. They describe the variation along the propagation direction of the longitudinal electric field and the two components of velocity of each species. In the limit of small amplitude of oscillation, the equations lead to the dispersion relation obtained by Kato and Hirata (1967). Numerical solutions for various possible values of parameters in the ionospheric E layer are obtained with a computer. When the electron jet velocity is larger than the ion thermal velocity, primarily ion waves of a few tens of khz frequency and a few cm wavelength are obtained. The amplitude of the waves has a maximum value and it decays in the laboratory frame with an e‐folding distance of a fraction of a meter. Radar backscatter observations (with metric wavelengths) seem to be from the envelope of the wave. The electric field of the maximum amplitude is 1–2 v/m, which is ∼105 times the microfield energy density and a few per cent of the kinetic energy density of the ion motion relative to the wave. It increases with wave velocity but not with electron jet velocity.
A Note on the Deterioration of the Coherence Properties of a Laser Beam by Molecular Scattering
Authors: Brookner Eli
Published: February 2008

A loss in monochromaticity, or equivalently coherence, occurs when a laser beam is propagated through the atmosphere. One factor causing the loss in coherence is the scattering from the randomly moving atmosphere molecules. In this short note, the effect on a communications system's performance of the loss of coherence arising from molecular scattering is studied. The results are given for the propagation, over a horizontal path of length L, of an ideal‐monochromatic, collimated laser beam with a radius R with L ≫ R and with the geometric optics condition (λ L)½ ≪ R satisfied (where λ is the laser wavelength). For the examples studied, it is shown that molecular scattering gives rise to only an inconsequential background noise in the receiver for typical communication systems. In particular, for λ = 1 μm and R = 5 cm and 5 m, the background noise is 74 and 54 db down, respectively. It will be necessary, however, for the communications engineer (and the radar engineer as well) to examine his particular case to ensure that the effects of molecular scattering are negligible or, if they are not negligible, that they are accounted for.
Errors in the Computation of Mean Monthly Values of Radio Refractive Index
Authors: Rao K. N. , Srivastava H. N.
Published: February 2008

An expression is derived for the difference between the atmospheric refractive index calculated from the monthly averages of pressure, dry bulb temperature, and vapor pressure and as the average of the corresponding daily values. It is shown that the order of differences between them is negligible. The orders of errors introduced in the computed values of refractive index by rounding off the temperature and the pressure values to the nearest integral values are shown to be 2 to 3 N units.
Analysis of a Backscatter Signature Obtained with a High‐Resolution HF Radar System
Authors: Hunsucker Robert D.
Published: February 2008

One particular backscatter signature obtained with an HF narrow‐beam scan backscatter sounder system is analyzed by considering its behavior statistics and applying a three‐dimensional computer ray‐tracing technique. Other simultaneous radio data are used to modify the theoretical model. Results of this investigation indicate that this particular signature probably is the result of medium‐scale traveling ionospheric disturbances which are the ionospheric manifestations of internal atmospheric gravity waves.