bluuebunny/crossref_metadata_2025 huggingface dataset:
Production of carbon 14 by cosmic‐ray neutrons
Authors: Lingenfelter R. E.
Published: February 2008

The rate of production of carbon 14 by cosmic‐ray neutrons is calculated by multigroup diffusion theory as a function of altitude, latitude, and time, and it is normalized to absolute cosmic‐ray neutron flux measurements. The global average production rate over the last ten solar cycles is found to be 2.50 ± 0.50 carbon 14 atoms per square centimeter per second. This value is compared with recent estimates of the decay rate of 1.8 ± 0.2 and 1.9 ± 0.2, and some of the possible implications are discussed.
A discussion of Halphen's method of secular perturbations and its application to the determination of long‐range effects in the motion of celestial bodies
Authors: Musen Peter
Published: February 2008

The long‐range (secular) effects caused by the moon and the sun are of primary importance for establishing the stability of highly eccentric orbits of satellites. At present no complete analytical theory exists that can treat such orbits. In this paper Halphen's method of treating secular planetary effects is suggested also for the determination of long‐range lunar effects in the motion of artificial satellites, using step‐by‐step integration. Halphen's method permits the numerical integration of long‐range lunar effects over an interval of many years. The long‐range solar effects can be treated by averaging the disturbing function over the orbit of the satellite. Halphen's method is applicable to the determination of long‐range effects in the motion of minor planets over the interval of hundreds of thousands of years. We assume that no sharp commensurability between mean motions of the disturbed and disturbing bodies exists. A complete theory of Halphen's method is presented, using modern symbolics. Goursat transformations and a summability process are applied to speed up the convergence of series appearing in the theory.
Plasmas — Laboratory scale
Authors: Lehnert Bo
Published: February 2008

The present state of plasma physics research in the laboratory is reviewed. Important applications and related problems are summarized and are illustrated by a number of experimental results. Attempts to bring theory and experiments into quantitative agreement are especially emphasized.
Analytical calculation of the seismic travel‐time problem
Authors: Knopoff L. , Teng T. L.
Published: February 2008

A numerical scheme has been devised that permits calculation of the fit to seismic travel‐time data. The method involves the optimization of a multidimensional function of the parameters necessary to describe the segments of the curves used in the fit. In several examples it was found that (1) selective weights must be applied to avoid picking geophysically unreasonable solutions, and (2) many solutions exist. The results are in good agreement with those obtained by visual means.
On time‐dependent wave propagation in shadow zones caused by the inhomogeneity of the medium
Authors: Molotkov I. A.
Published: February 2008

A Heaviside unit pulse is applied to a point on the surface of a half‐space. The refractive index of the medium varies in such a manner that the surface casts a shadow. By means of complex contour integral representations of the solution, it is shown how to obtain the pulse shape within the shadow zone at times near the arrival of the diffracted pulse. Two‐dimensional and axisymmetric distributions of refractive index are considered, but it can be shown that the form of the expression for the diffracted pulse shape is valid in more general situations.
The work of the Leningrad School on seismic wave propagation
Authors: Petrashen G. I.
Published: February 2008

A historical and procedural outline is presented of several methods of solving problems of elastic wave propagation from impulsive sources. The methods include a summary of the formalism of the geometrical theory of diffraction, eigenvalue methods, and many others, all of which are used to solve the boundary value problems of elastic wave propagation. The mediums considered are homogeneous or inhomogenous in composition; the geometries are plane‐parallel and multilayered, or spherical (cylindrical) in analogy with the earth.
On changes in composition of the topside ionosphere
Authors: Rush Charles M. , Venkateswaran S. V.
Published: February 2008

The relative concentrations of the three ions O+, He+, and H+ in the topside ionosphere (ionosphere above the F2 maximum) are subject to variations of different periodicities. It would appear from previous work that the solar cycle variation can be described approximately in terms of models in which it is assumed that the ions and electrons are in a state of (ambipolar) diffusive equilibrium above a properly chosen reference level (∼500 km). One such model, considered to be particularly suitable for the period of the quiet sun, is discussed here. To specify the equilibrium state in this model it is proposed that the concentration ratios nH+/no+ and nHe+/no+ at the reference level are dependent only on the neutral particle temperature. The form of this dependence is established primarily from observations made over low latitudes and subsequently sought to be justified by chemical equilibrium theory. The published results from Ariel 1 for fairly low solar activity are shown to be consistent with the present model provided a latitudinal gradient of neutral temperature is postulated. The possibility of sounding the altitude at which He+ and H+ ions have equal concentrations (transition altitude) by means of subprotonospheric whistlers is mentioned.
Interpretation of heat flow anomalies 2. Flux due to initial temperature of intrusives
Authors: Simmons Gene
Published: February 2008

The interpretation of heat flow anomalies in terms of contrasts of heat sources was treated in part 1; the effect on surface heat flow of the initial temperature of intrusive bodies is treated here. From the solution for an instantaneous point source, expressions are obtained for a finite line source, strip source, rectangular parallelepiped, sill edge, horizontal rectangular cylinder, dipping dike, and a buried sphere. Solutions for two‐ and three‐dimensional bodies of arbitrary shape are derived in a form suitable for digital computation. The heat flow at the surface of the earth is obtained for each case.
Linear and nonlinear wave motion
Authors: Bourodimos E. L.
Published: February 2008

Wave motion is studied through the development of theoretical models of linear and nonlinear boundary value wave problems. Flow field characteristics and specific boundary conditions and assumptions are considered in each case. A general method for wave propagation over an uneven bottom is presented. The following conclusions may be stated:

1. The linear and nonlinear characteristics of gravity surface waves at discrete frequency were studied on the basis of relative amplitudea*, depthd*, and breaking parameterBr. Part of the breaking behavior has been confirmed experimentally.

2. An increase in energy dissipation up to 50% with increase of values of breaking parameter of the oncoming wave has been established experimentally.

3. The wave amplitude variation and wave energy transmission, unlimited by reflection and friction, are predicted theoretically to the first approximation for any form of channel geometry and type of wave motion.

4. For small‐amplitude waves in shallow water, Green's law has been found from the integral expression in the general case. For waves in intermediate depth or deep water an exponential formula applies.
Measurement of ionospheric movements
Authors: Kent G. S.
Published: February 2008

The methods of measuring movements in the upper atmosphere are subdivided according to the phenomena studied into three classes: (a) the methods that measure the motions of the neutral atmosphere; (b) those that measure the motions of the ionospheric plasma; and (c) those that measure the motions of the plasma irregularities. The methods within each class are described, special emphasis being placed on the nature and physical significance of the phenomena being studied. An outline is given of the expected behavior of the upper atmosphere, particularly of the interaction between the neutral atmosphere and plasma and of the motions of irregularities. The results obtained within each of the classes of methods are summarized and possible relationships between them discussed. In particular, the close‐spaced antenna method, as the most widely used method for ionospheric drifts, is discussed in some detail, together with the difficulties that occur in the interpretation of its results.
Extraterrestrial Lyman alpha
Authors: Tinsley B. A.
Published: February 2008

Theoretical work and observations on extraterrestrial Lyman α are reviewed. A source of extraterrestrial Lyman α near the solar apex is probably scattering of solar Lyman α on cold interplanetary hydrogen that has penetrated to the inner solar system. A minor source of interplanetary hydrogen comes from the breakup of comets. Galactic sources of Lyman α are probably also present, and such emission would tend to be rendered isotropic, depending on the amount of interstellar hydrogen in the near vicinity of the solar system.
A stochastic model for the occurrence of main‐sequence earthquakes
Authors: Knopoff L.
Published: February 2008

If a long earthquake sequence is considered to be a stationary stochastic process, the stored elastic energy of deformation can be shown to be an independent variable in the usual ‘backward’ equation. Three unknown probability functions are introduced: the probability that the stored energy of deformation is at a certain level; the probability that, if this energy is at a given level, an earthquake will occur; and the transition probability that, if the earthquake occurs, the final energy state will be at a certain level. It is assumed that the frequency‐energy distribution is known. The equations can be solved, if the transition probability is assumed to be known; and they have been solved for the model in which the transition probability is a function of the energy released in the shock but is not otherwise dependent on the final energy state. In this case, the results can be used to describe the earthquake history for some time after a great shock, and possibly for times just before a great shock. The results have some features of inconsistency with observations.
Geomagnetic models from satellite surveys
Authors: Cain Joseph C.
Published: February 2008

The use of satellite scalar magnetic field data to produce geomagnetic field models is reviewed. There have been nine separate spacecraft that have acquired observations of the geomagnetic field from low (<1500 km) satellite altitudes since 1958. The magnetic field models produced from such data have not been sufficiently compared with surface vector data to firmly, establish their validity. One comparison has indicated that satellite‐derived models are as valid over‐all as those produced from surface data. Variations in the field components are shown to be larger than those in scalar field by factors of 4–10. Recent satellite models indicate an increase in dipole decay to −27 γ/year, a value that may be plausible, judging from extrapolation of earlier surface‐derived models. Also noted is a recent slowing of eccentric dipole westward drift.
The patterns and sources of high‐latitude particle precipitation
Authors: Paulikas G. A.
Published: February 2008

We survey, in this paper, the properties of the zones of particle precipitation at high latitudes. We consider the average properties of particle influx from the outer magnetosphere as determined by satellite and rocket observations, as well as ground‐based techniques. The point of view of this paper is to try to associate source regions, and, if possible, precipitation mechanisms with each of the families of precipitating particles that collectively form the auroral zone. The precipitation patterns for both electrons and protons exhibit a diurnal variation. The several zones of particle precipitation can be placed in relationship to each other. The zone of electron precipitation is best described as consisting of a region at low latitudes (60° ⪝ Λ ⪝ 70° near local midnight) where electrons with characteristic energies of tens of kev precipitate; this region merges and overlaps at the higher latitudes with another region (70° ⪝ Λ ⪝ 80° near local midnight) characterized by precipitating electrons of ≈0.5 kev. The limited data available indicate that the zone of proton precipitation spatially overlaps the zone of electron precipitation. For example, the peak of precipitation of > 4‐kev protons near local midnight is found between Λ = 65° and Λ = 70°. Near local noon a separate region of very soft proton precipitation is found in the vicinity of Λ ≈ 80°, in addition to a region of proton influx at lower latitudes. We consider the plasma sheet, the extraterrestrial ring current, the polar cusp, and the outer radiation belt as source regions of precipitating particles. Brief surveys of the precipitation of helium ions and of possible means of artificially inducing particle precipitation are also included.
Description of solar structure and processes
Authors: Gibson Edward G.
Published: February 2008

A general introduction to solar structure and processes is presented. The sun is first viewed as a spherically symmetric steady‐state system, and the energy generated in the core is traced as it flows outward. The various forms and manifestations of this energy flow and the resulting uniquely defined characteristics of different atmospheric layers are described. The sources of solar activity are assumed to be differential rotation and solar magnetic fields. The interaction of these sources to produce the observed solar cycle, active regions, the active‐sun corona, and solar flares is discussed. In describing solar structure and processes, only elementary physical concepts are utilized. This allows people without advanced scientific training to appreciate the subject and provides a rapid orientation for those with more advanced backgrounds who are unfamiliar with solar phenomena.
The dissipation of kinetic energy in large‐scale atmospheric circulations
Authors: Smith Phillip J. , Adhikary Sharad P.
Published: February 2008

A concise review is given of the role of eddy processes in the dissipation of kinetic energy in large‐scale atmospheric circulations above the planetary boundary layer. A distillation of the more prominent works relevant to this problem is accomplished with the following two goals in mind: (1) to consolidate existing evidence for the presence of a dissipation maximum above the boundary layer in the so‐called ‘free’ atmosphere and (2) to provide new insight into the concept of dissipation as applied to large‐scale open atmospheric circulations.
Crystallography and mineralogy
Authors: Ghose Subrata
Published: February 2008

Significant advances in understanding the major rock‐forming silicates in the past 4 years have been achieved through theoretical and experimental studies of the thermodynamics of crystalline solutions, chemical bonding by molecular orbital calculations, and spectroscopic measurements and fine structure in minerals through high‐resolution and high‐voltage electron microscopy. Techniques of X ray diffraction and optical and Mössbauer spectroscopy of minerals under high pressure and temperature have opened up the possibility of studying crystal and electronic structures of minerals under mantle conditions. Significant advances have also been made in understanding the structures of nonsilicate minerals, particularly sulfides, borates, sulfates, and phosphates. Mineral descriptions, new or old, have been excluded from this review owing to space limitation.
Theoretical petrology
Authors: Luth W. C.
Published: February 2008

A discussion of significant advances in theoretical petrology is primarily a prediction of what the future holds in the way of application of ‘new’ approaches developed over the past quadrennium. Thompson [1970, p. 550] expressed the situation quite clearly:

My advice to those who wish to understand rocks more fully is to go ahead and experiment freely with new ways of doing things despite cries of ‘Who needs it!’ What is useless will be forgotten soon enough, what is not will stick and should.
Land gravimetry
Authors: Strange William E.
Published: February 2008

Activities of the following U.S. government organizations are covered: National Geodetic Survey (NGS), U.S. Geological Survey (USGS), Air Force Cambridge Research Laboratories (AFCRL), Army Engineering Topographic Laboratory (ETL), and the various components of the Defense Mapping Agency (DMA). The DMA components covered include the DMA Topographic Center (DMATC), DMA Aerospace Center (DMAAC), DMAAC Geodetic Survey Squadron (DMAAC/GSS), DMA Inter‐American Geodetic Survey (IAGS), and the U.S. Navy Oceanographic Office (NAVOCEANO). In addition, activities of universities, state organizations, and private industry were covered when these were of special interest. However, no attempt was made to include all of the voluminous activities of all university and state groups. The bulk of the land gravity taken, after being adjusted to a common datum by the DMAAC, is placed in the U.S. Land Gravity Data Bank of the National Geodetic Survey of the National Oceanic and Atmospheric Administration (Washington, D.C.).
Equations of state of the Earth
Authors: Ahrens Thomas J.
Published: February 2008

The major results of research in the United States for 1971–1974 in the areas of static, high‐pressure X ray, ultrasonic and shock wave measurements, and progress in theoretical equations of state are summarized. This 4‐year period has seen the massive accumulation of new data pertinent to describing the properties, and to some extent geodynamic processes, of the upper mantle as well as exposing the gauntlet of scientific challenge with regard to our lack of detailed understanding of the major changes in crustal seismic velocities, which seem to offer so much promise for earthquake prediction. In the area of very high pressure geophysics, another challenging problem uncovered is the question of explaining the low adiabatic gradient in the outer core, which seems to be required to retain liquid iron alloy material at the melting point. Important advances in what until recently has been quite empirical elastic moduli ‘systematics’ have demonstrated how ionic radii and ionic packing densities may be quantitatively employed to predict unmeasured equations of state as well as tie together an ever increasing body of data for the elasticity of compounds which are crystal‐chemical analogs of mantle minerals.
Our present view of Mercury and Venus
Authors: Danielson G. Edward
Published: February 2008

The discipline of planetology received a quantum jump in new information on the planets Mercury and Venus from the Mariner 10 spacecraft. A detailed look at the ultraviolet markings in the upper atmosphere of Venus and their attendant motion has stimulated a considerable reevaluation of theories concerning the circulation, composition, and nature of this planet's upper atmosphere. The geologic history of Mercury as revealed by Mariner 10's television science data, from two close flybys, has challenged the prevalent theories of planetary evolution. The Mercury surface morphology and optical properties resemble those of the moon and seem to record a similar sequence of events despite their differences in density and proximity to both the sun and the asteroid belt.
The outer solar system
Authors: Owen Tobias
Published: February 2008

During the last 5 years, our knowledge about the outer solar system has increased tremendously, owing largely to the application of increasingly sophisticated observational techniques with ground‐based and air borne telescopes. We have also witnessed the beginning of direct investigation with the successful Jupiter flybys of the U.S. spacecraft Pioneer 10 and 11. The first of these vehicles is on its way to solar system escape, while the second is targeted for Saturn. The next generation of missions will be twin Mariner‐class spacecraft to be launched in 1977 for further investigation of Jupiter (1979) and Saturn (1981) and their satellites. We may expect large gains in information from continued ground‐based studies during this same time period.
A review of lunar sample studies and their application to studies of the terrestrial planets
Authors: Albee Arden L.
Published: February 2008

During the last half decade, hundreds of scientists from many countries have been studying the samples, photographs, and instrumental data returned from the moon by the Apollo and Luna programs. These studies have placed significant limits on chemical, petrologic, and physical parameters, on the time of many events, and on the rate of many processes and are giving greater insight into the natural processes that formed the moon and shaped its surface. Increasingly, it is being recognized that very similar processes governed the origin and evolution of planetary bodies throughout the solar system. Spacecraft have extended our sensors to all the terrestrial planets, and the insights gained from Apollo dominate our interpretation of the photographic and instrumental data returned from these bodies.
Soil water
Authors: Amerman C. R. , Klute A. , Skaggs R. W. , Smith R. E.
Published: February 2008

Recent advances in developing methods to solve the equations governing combined saturated‐unsaturated flow in two and three dimensions [Freeze, 1971; Stephenson and Freeze, 1974] have focused attention on the need to determine effective field values of the hydraulic properties of the soil. Because of natural variation from point to point, hydraulic properties for field‐size units are difficult to characterize. A detailed field study was conducted by Nielsen et al. [1973] to determine the field variability of the hydraulic properties of the soil and to test various field methods of measuring these properties. They concluded that even seemingly uniform land areas manifest large variations in hydraulic conductivity. For a given point, methods for measuring the soil hydraulic properties will give values that are more accurate than those required to characterize an entire field because of the heterogeneity of the soil. Thus the ability to make predictions over a large area from soil properties determined at one location can range from good to unsatisfactory, depending on the prediction parameter of interest. Because of field variation in the hydraulic properties of the soil, simplified methods for calculating soil water flux and water contents during redistribution were found to be satisfactory when they were compared with more detailed numerical methods and with field measurements. Furthermore, when field variability is considered, simplified methods for measuring hydraulic conductivity or soil water diffusivity are sufficiently accurate for characterizing field conditions. The results of this study will have continued application in evaluating the worth of both simple and complex models for predicting water movement in the field.
Marine magnetics
Authors: Larson Roger L.
Published: February 2008

During this period, marine magnetic studies have generally concentrated on charting at various scales the lineated magnetic anomalies of the ocean basins that are characteristic of the sea floor spreading and magnetic field reversal processes during the past 160 m.y. These studies have yielded information about the time scale of magnetic reversals during that interval and the rates of directions of crustal generation at various places during various times and have constrained models of crustal generation processes at active ridge crests. Near‐bottom magnetometers have contributed considerable additional detail, and analysis techniques such as time series and stacking manipulations have been used to study in detail processes associated with the formation of magnetic anomalies. In addition, paleomagnetic results have been obtained by analyzing magnetic anomalies associated with seamounts, and inferences about crustal structure have been made from studies of magnetic anomalies associated with fracture zones.
Exploration seismology at sea
Authors: Shor George G.
Published: February 2008

When the previous one of these reports was written by Hales [1971], the use of reflection seismology at sea had just experienced a rapid proliferation, in the form of both continuous seismic profiling (CSP) by oceanographic institutions and ‘conventional’ multichannel reflection surveys of the continental shelves by petroleum exploration groups. Wide‐angle reflection studies were becoming more common, but seismic refraction work had decreased markedly from previous years. In the 4 years just past the use of CSP and wide‐angle reflection methods has continued to increase; more research (as distinguished from straight exploration) is being carried out with multichannel reflection systems, and seismic refraction work has been revived primarily because of an influx of new techniques, new instruments, and new ideas. The field has indeed been explosive in its expansion, even if the term ‘explosion seismology’ is no longer appropriate for a set of techniques that rely more on compressed air and electric sparks than on chemical explosives for sources of elastic waves. Because this is the U.S. report to the IUGG, the coverage has been limited chiefly to work in U.S. institutions and in cooperative programs.
Review of marine geochemistry
Authors: Spencer Derek W. , Farrington J. W.
Published: February 2008

In the period from January 1971 to December 1974, marine geochemical studies have progressed and expanded without major changes in direction from the previous half decade. One of the most significant aspects of this period is the establishment of some large cooperative international programs developed for the International Decade of Ocean Exploration.

The end of 1974 has seen the completion of much of the fieldwork of programs such as Geosecs (Geochemical Ocean Section Study), CUEA (Coastal Upwelling EcoSystems Analysis), and Climap (Climate/Long Range Investigation Mapping and Predictions). The accelerated rate of acquisition of data on many oceanic parameters, a direct result of these programs, has yet to have its full influence on the science, but it is already clear that a number of our concepts of factors controlling the distribution of various chemical species in the ocean are in need of revision.
Ocean sediment coring program and marine sedimentation
Authors: Peterson M. N. A.
Published: February 2008

During the past 4 years the work surrounding the National Science Foundation Ocean Sediment Coring Program Deep Sea Drilling Project has so dominated the field of marine sedimentation as to be virtually identical with it.

The Deep Sea Drilling Project (DSDP) is funded by the National Science Foundation under contract with the University of California; project management is delegated to the Scripps Institution of Oceanography at La Jolla, California. The University, in turn, subcontracts with Global Marine, Inc., of Los Angeles for the operation of the remarkable and specially designed drilling vessel Glomar Challenger. This fine relatively young offshore drilling and operating corporation is to be greatly complimented for the excellent and responsive manner in which they have carried out the needs associated with this unique and interesting project.
Oceanic micropaleontology: Progress and prospect
Authors: Berger W. H. , Roth P. H.
Published: February 2008

The seventies were marked by explosive development of oceanic micropaleontology and drastic changes in emphasis. The main impetus for expansion came from deep‐sea drilling. Global sampling made possible a global approach to paleoceanography and biostratigraphy. Scanning electron microscopy extended routine study to extremely small particles. The use of computers aided in quantifying paleoenvironmental reconstruction and in refining stratigraphic resolution. Integration of micropaleontologic information with physical and chemical oceanography has helped to make micropaleontology the mainstay of paleoceanographic research. The biogeography of planktonic foraminifera and of the paleontologically important coccoliths is now well documented. This is not yet true for radiolarians and diatoms. Much progress has been made in mapping distributions on the sea floor, in all groups, and in relating such distributions to supply, dissolution, and redeposition. Two major problems have been identified. One is the role of fecal pellets in the transfer of coccoliths and diatoms to the sea floor. The other is the relationship between preburial preservation states of microfossil assemblages and their postburial diagenesis (‘diagenetic potential’ of an assemblage). Important advances in Quaternary research include increased stratigraphic resolution, quantitative temperature determination (accuracy about 2°–3°C), and isotopic evidence for glacial‐interglacial fluctuations. Changes in productivity and preservation patterns remain major questions. Pre‐quaternary paleoceanography has largely been concerned with establishing biogeographic patterns through time and their correlation with changing geography due to plate tectonics. The mechanisms of cause and effect (surface currents, bottom water flow, water mass stratification, etc., versus biogeography and sedimentation patterns) remain speculative on the whole. The question of the origin of diversity and its variations through time continue to attract attention. There appears to be a positive correlation between diversity and isotopic temperature through time. Causes for major extinctions are unknown and are likely to remain so until the fundamental question of which processes control the overall productivity of the ocean is resolved. A model is developed, proposing a control of present microplankton assemblages by successive change of the limiting nutrient (silica‐bionitrogen‐phosphate). It is argued that a low‐fertility ocean should be characterized by high silica and phosphate concentrations and that this should be recognizable in the record. Stratigraphic work has greatly benefited from DSDP results, especially when care was taken to recover long sequences. Zonations, in part preliminary, are now available for all major groups, for Cretaceous and Cenozoic sequences. Attempts to correlate some of these sequences with the less complete standard sections reveal a fundamental weakness in the concept of stratigraphic standard.
Oceanography of the Arctic Seas
Authors: Aagaard Knut
Published: February 2008

Arctic oceanography has progressed during recent years in much the same manner as in the more temperate seas. There has been a great emphasis on current measurements [e.g., cf. Aagaard and Coachman, 1975], considerable interest in the upper boundary layer and in fine structure [e.g., cf. Smith, 1972; Neal and Neshyba, 1973], and notable expansion of and improved capability in field and measurement techniques. The frequent presence of an ice cover, while a major operational liability in certain respects, also proves a major asset in providing an extensive stable platform. While our understanding of the arctic seas has on the whole increased significantly in the last 4 years, a major gap exists in the Eurasian Basin of the Arctic Ocean; there we do not even have an adequate mapping of the large‐scale temperature and salinity fields, we have no current measurements, and we can only hypothesize the important processes. A recent summary of the physical oceanography of the arctic seas has been written by Coachman and Aagaard [1974].
Progress in research on boundary layers and atmospheric turbulences
Authors: Wyngaard J. C.
Published: February 2008

The potential of remote probing techniques, both acoustic and electromagnetic, for research in atmospheric turbulence has become apparent recently. Acoustic wind sounding devices, both one‐dimensional [Beran et al., 1971] and three‐dimensional [Beran et al., 1974; Mahoney et al., 1973] have been built. This ‘acoustic radar’ is sensitive to both temperature and velocity fluctuations [Cronenwett et al., 1972], and much of its early use has been for monitoring the height and structure of low‐level inversions [Wyckoff et al., 1973]. Early work has also dealt with measurements of temperature fluctuations and wind speed and direction profiles for use in gravity wave studies [Beran et al., 1973]. Emmanuel et al. [1972] observed breaking Helmholtz waves near an inversion, and Hooke et al. [1972] discussed planetary boundary layer (PBL) waves detected with an acoustic sounder and a microbarograph array. The performance of acoustic probes in turbulence is not yet fully understood but is under intensive investigation.
Radiation in the atmosphere
Authors: Coulson K. L. , Fraser Robert S.
Published: February 2008

Radiation in the atmosphere continues to be an area of intense research activity, as evidenced by the large number of publications which have appeared during the last 4 years and the several symposia which have been devoted either in large part or exclusively to atmospheric radiation. In the previous quadrennial report the authors of this section screened over 900 titles and listed about 750 in the bibliography; this time we have selected about 600 titles. The somewhat decreased number is probably due to our careful avoidance of papers dealing with satellite investigations and with the atmospheres of other planets, these subjects being covered in separate summaries. In addition, it would not be surprising if the tightening of research budgets were to somewhat dampen the burgeoning of research in general, and hopefully we may be becoming more selective in our headlong rush for publication.
Ionosphere‐magnetosphere coupling: 2. Electric fields
Authors: Banks Peter M.
Published: February 2008

The past 4 years represents an unprecedented period of scientific achievement with regard to advances made in our knowledge of electrodynamic processes acting within the magnetosphere and ionosphere. Perhaps the most impressive accomplishment has been the emergence of conceptual models that include dynamical links between the terrestrial upper atmosphere, the ionosphere, and the magnetosphere. It is now clear that the flow of the magnetized solar wind plasma past the magnetosphere establishes a permanent internal pattern of electric currents connecting the magnetopause with ionospheric regions at the inner peripheries of the auroral ovals. These currents, aligned in narrow longitudinal sheets, close through the ionosphere to create a global pattern of electric fields and currents. It should not be thought that the ionosphere and the upper atmosphere are simply passive receptors of these external influences, however, since they both exert important influences upon the magnetosphere through energy dissipation, variable electrical resistivity, and other processes. As a consequence it is no longer reasonable to consider separately the electrodynamic phenomena of the ionosphere or the magnetosphere. Instead, one must adopt a unified view based upon consideration of the full implications of magnetosphere‐ionosphere‐atmosphere (MIA) couplings and dynamics.
Ionospheric D and E regions
Authors: Sechrist C. F.
Published: February 2008

Several review papers on D and E region topics appeared during the quadrertnium as follows: the lower ionosphere [Thomas, 1971], theoretical models of the D region [Sechrist, 1972], the relationship of theory and experiment in the D region [Aikin, 1972], E region model parameters [Swider, 1972], progress in ionospheric research [Bowhill, 1973], chemistry of metallic elements in the ionosphere and mesosphere [Brown, 1973], theory of the D region [Thomas, 1974], physics and chemistry of the E region [Strobel, 1974], and lower ionosphere ion chemistry [Sechrist, 1974a].

Although D and E region research has made rapid progress in the past decade, it is evident that as knowledge expands, these regions become more complex physical and chemical systems, and our views appear to be less distinct than before; and aeronomers need to be reminded that the lower ionosphere is an ionospheric region that is hydrodynamically coupled to the lower atmosphere and electrodynamically coupled to the magnetosphere.
Minor constituents in the stratosphere and mesosphere
Authors: Cicerone Ralph J.
Published: February 2008

This paper is a brief survey of a portion of the research on trace constituents in the stratosphere and mesosphere between 1971 and 1974. A primary motivation for much of the stratospheric research came from the realization that man's activities may influence global climate and the atmospheric ozone content, our shield against certain UV wavelengths. A great deal of progress has been reported in understanding both the present background stratosphere and the responses to be expected from additions of nitrogen oxides, water, and chlorine oxides, especially with respect to ozone. Trace constituents in the mesosphere have been modeled and measured to increase our understanding of the physics and chemistry of the mesosphere but also to relate mesospheric composition and transport to ionospheric processes at higher altitudes, to D region ion chemistry, and to upper stratospheric composition.
Geodynamics Project: Initial developments in the U.S. Program
Authors: Drake Charles L. , Heirtzler James R. , Oliver Jack E.
Published: February 2008

The remarkable developments in geophysics and geology in the 1960's—the revolution in earth sciences—were the springboard of U.S. planning for the Geodynamics Project. The U.S. Geodynamics Committee was organized in the National Academy of Sciences under the Geophysics Research Board in collaboration with the U.S. National Committee for IUGG (International Union of Geodesy and Geophysics), IUGS (International Union of Geological Sciences), and SCOR (Scientific Committee on Oceanic Research). After 3 years of extensive consultation the U.S. Geodynamics Committee issued a report in 1973, U.S. Program for the Geodynamics Project: Scope and Objectives. In 1974 the Federal Council for Science and Technology established a committee on the International Geodynamics Project to coordinate activities of the federal agencies in the Geodynamics Project.
Sources of stratospheric gaseous chlorine
Authors: Ryan J. A. , Mukherjee N. R.
Published: February 2008

Interest in atmospheric gaseous chlorine (GCl) has been generated by its increasing anthropogenic introduction coupled with its reactivity with ozone. We describe present and anticipated future sources of GCl and derive an estimate of their stratospheric source strength. The stratospheric sources are transport of tropespheric GCl across the tropopause, direct stratospheric introduction by major volcanic eruptions, and anthropogenic emissions in the stratosphere. The mean source strengths are estimated to be, respectively, 4 × 1010, 1 × 1011, and 5 × 109 g GCl yr−1, the last figure representing a projection of anthropogenic emissions to include 50 space shuttle flights per year. Whereas the first source introduces GCl only at the base of the stratosphere, the other two can supply GCl directly to altitudes up to ≈50 km. The dominant, volcanic, source is highly variable, it being estimated that as much as 3 × 1013 g GCl can enter the stratosphere from a single eruption. Although major volcanic eruptions are indicated to be the dominant source, few ‘hard’ data are currently available.
Rocket‐borne measurements of auroral electrons
Authors: Boyd J. S.
Published: February 2008

Rocket measurements of the pitch angle and energy distributions of precipitated electrons in the 1‐ to 20‐keV range show a consistent and relatively simple pattern. Features such as ‘monoenergetic peaks’ and pitch angle distributions showing intense field‐aligned components, rather than being anomalous, are characteristic of bright well‐defined auroral forms. Presently available observations do not allow the identification of specific acceleration mechanisms, although they are consistent with several.
The dynamics of the littoral zone
Authors: Miller Christopher D. , Barcilon Albert
Published: February 2008

We review some of the properties of surface gravity waves and look at their modification as they enter the littoral zone. Theoretical and experimental modeling of processes pertaining to the near shore are discussed and compared with field observations. In particular we review the present knowledge pertaining to the dynamics of rip currents, longshore currents, and computer modeling of beach deformation due to wave‐induced erosion or accretion.
An evaluation of recent quantitative magnetospheric magnetic field models
Authors: Walker R. J.
Published: February 2008

Recent quantitative magnetospheric field models contain many features not found in earlier models. Magnetopause models which include the effects of the dipole tilt have been presented. More realistic models of the tail field include tail currents which close on the magnetopause, cross‐tail currents of finite thickness, and cross‐tail current models which model the position of the neutral sheet as a function of tilt. Finally, models have attempted to calculate the field of currents distributed in the inner magnetosphere. As the purpose of a magnetospheric model is to provide a mathematical description of the field that reasonably reproduces the observed magnetospheric field, several recent models have been compared with the observed ΔB(Bobserved ‐ Bmain field) contours. Models containing only contributions from magnetopause and tail current systems are able to reproduce the observed quiet time field only in an extremely qualitative way. The best quantitative agreement between models and observations occurs when currents distributed in the inner magnetosphere are added to the magnetopause and tail current systems. However, the distributed current models are valid only for zero tilt. Even the models which reproduce the average observed field reasonably well may not give physically reasonable field gradients. Three of the models evaluated contain regions in the near tail in which the field gradient reverses direction. One region in which all the models fall short is that around the polar cusp, though most can be used to calculate the position of the last closed field line reasonably well.
Linear inference and underparameterized models
Authors: Parker Robert L.
Published: February 2008

A version of Backus's theory of linear inference is developed by using a new finite‐dimensional space. This approach affords a clear geometric interpretation of the essential role played by a priori model smoothing assumptions and also facilitates the construction of a theory for the treatment of random data errors that is quite different from the treatment of Backus. When the unknown parameters form a (necessarily incomplete) description of the model, it is possible to formulate a special smoothing assumption that is particularly appropriate; in practical examples this strategy often leads to tighter bounds on the model uncertainty than those obtained with previous assumptions. An analysis of the numerical aspects of the problem forces one to the conclusion that the theory is not competitive numerically with conventional least squares parameter estimation, unless one of the large submatrices in the problem possesses a simple inverse. An example of this kind is discussed briefly.
The Earth's neutral upper atmosphere
Authors: King‐Hele D. G.
Published: February 2008

This paper was intended as an introductory and superficial survey of the earth's neutral upper atmosphere, mainly at heights between 100 and 1000 km, to prepare for the more specialized papers which followed. The density, temperature, and winds and their variations are briefly discussed.
Coastal current observations
Authors: Winant Clinton D.
Published: February 2008

A number of field observations of coastal currents have been recently reported. Using for the most part data acquired with moored current meters, these have allowed the determination of the spectrum of coastal currents in a broad frequency band, corresponding to periods ranging from 1 cycle/month to 1 cpm, in a wide variety of geomorphological settings and climates. In addition to such statistical descriptions of the current field, certain of these observations are such as to allow the effects of different driving forces, such as seasonal and short‐term meteorological forcing, adjoining ocean current systems, and tides, to be studied separately, providing required information for the development of reliable models of coastal currents.
Marine magnetic anomalies
Authors: Blakely Richard J. , Cande Steven C.
Published: February 2008

Marine magnetic data have been available for many years from all of the world's oceans, and their contribution to marine geophysics and geology is profound. These data, for example, have allowed charting the age of the ocean floor, reconstruction of the geologic history of the major ocean basins, development of a Cenozoic and Mesozoic timescale of geomagnetic reversals, and speculation on the processes of sea‐floor spreading. Research on these and similar problems actively continued during this quadrennial, but here we discuss only a few topics in which we believe the most significant advances have been made during the last four years: the source of marine magnetic anomalies, the geomagnetic time‐scale, high‐amplitude anomalies, and studies of back‐arc basins.

Source of Anomalies

Studies of magnetic surveys over continental areas can often be constrained by the magnetic properties of samples collected from below the survey. Until recently, model studies of marine magnetic anomalies have enjoyed the luxury of an inaccessible source. Except for samples scraped from the ocean floor by dredging [e.g., Irving, 1970] and inferences drawn from magnetic studies of ophiolite sequences [e.g., Vine and Moores, 1972], very little information was available for constraining studies of marine magnetic anomalies.
Continental magnetic anomalies
Authors: Hinze William J.
Published: February 2008

The mapping and interpretation of magnetic anomalies provide a useful and efficient method of studying crystalline basement rocks, igneous intrusions, and extrusive rocks of the continental crust. Accordingly, government, academic, and industrial efforts have been expended during the past four years in acquiring and interpreting new data, re‐interpreting old data, and developing new techniques for the analysis of magnetic anomaly data. Magnetic anomaly interpretation continues to be a major element in mineral exploration geophysics and a small but significant part of petroleum exploration. During the past several years these techniques have assumed increasing significance in basic geologic studies, geothermal investigations, and engineering studies related to seismic regionalization and site stability problems.
Earthquake prediction
Authors: Ward Peter L.
Published: February 2008

Earthquake prediction, hardly taken seriously as science in the United States before 1971, reached fledgling status in the period 1975 to 1978. By late 1974, most U.S. researchers in seismology were agreeing that earthquakes might be predictable on a scientific basis. Cautious optimism had in fact turned to rampant enthusiasm among some workers as evidence accumulated for many possible earthquake precursors and the theory of dilatancy seemed to explain most observations (see summaries by Bolt and Wang, 1975; Healy, 1975; Kisslinger and Wyss, 1975). Slower progress since 1974 has dampened the euphoria felt by some but a much more solid and broad foundation for a Prediction Program has now been constructed and a number of important cornerstones laid.