bluuebunny/crossref_metadata_2025 huggingface dataset:
Lunar atmosphere
Authors: Johnson Francis S.
Published: February 2008

A rarified atmosphere should be present on the moon because of contributions from the solar wind, meteoric volatilization, and internal degassing. Transient contributions to the atmosphere must be produced by rocket gases during lunar missions. These gases may obscure the ambient atmosphere in the vicinity of the landing site for a period of several months after a lunar landing. Of the three natural sources, definite predictions can be made only on the basis of solar wind input. The lunar atmosphere of solar origin is expected to consist mainly of neon, lighter gases being less prevalent because of their more rapid thermal escape and leaves gases less prevalent because of their lesser concentrations in the solar wind. Daytime néon concentrations are expected to be near 6 × 104 cm−3, and nighttime concentrations are expected to be near 1.5 × 106 cm−3.
Crustal resistivity anomalies from geomagnetic deep‐sounding studies
Authors: Porath H. , Dziewonski A.
Published: February 2008

A number of magnetic variation anomalies observed in geomagnetic deep‐sounding studies can be attributed to inhomogeneities of electrical resistivity in the upper crust. The electromagnetic induction in isolated conductors is usually too small to explain anomalies associated with crustal inhomogeneities, and anomalous variation fields mainly arise from concentration and channeling of currents induced elsewhere. These systems of currents are induced over a large region of the earth and have dimensions comparable to those of the source field. Most of the crustal anomalies are associated with deep conducting sedimentary basins or with regions of rapid change of sedimentary conductivity.

Examples of anomalies of this origin are the North German basin, the Anadarko basin in Oklahoma and a region in north‐central Texas where more resistive paleozoic sediments are adjacent to conductive sediments in the Gulf coast plains. Other anomalies are related to currents concentrated in channels of conducting sea water located between two resistive continental blocks. Anomalous fields arising in this way have been observed on both sides of the Bonifacio Straits between Corsica and Sardinia. It is also thought that the Alert anomaly in the Canadian Arctic is closely related to the channeling of current through the Robeson Channel. An additional inland anomaly seems to be due to leakage of currents induced in the oceans into conductive structures in the upper crust. A magnetic variation anomaly with an amplitude larger than any other reported in the literature has been found in the northern Great Plains province of the United States. It extends along the eastern edge of the Black Hills north to the Williston basin. Higher conductivities than those characteristic of sediments are needed to explain this anomaly, which has been tentatively attributed to a zone of conducting graphite schists in the basement. Examples of magnetotelluric observations near current concentrations compared with two‐dimensional model calculations show that plane‐layered solutions are rarely adequate as representations of magnetotelluric resistivity curves in the vicinity of these features. In spite of these difficulties, the geomagnetic deep‐sounding technique can yield information about the lateral variations of resistivities of the upper mantle, providing that the conductivities at the surface are not too high or are relatively uniform, or both.
Ionospheric effects of Birkeland currents
Authors: Cloutier Paul A.
Published: February 2008

Since Birkeland's observations of high‐latitude magnetic perturbations led him to postulate the existence of geomagnetically aligned electric currents, theoretical studies have led to a general understanding of the mechanisms that are capable of driving such currents, and of the processes associated with formation and control of current configurations. Recent advances in experimental techniques have yielded information on the spatial and temporal behavior of such field‐aligned Birkeland currents and have established their association to an individual auroral arc and energetic precipitating particles. This paper gives a brief summary of ionospheric effects related to production, maintenance, and control of Birkeland current systems. Available experimental data are discussed in relation to some of these, effects.
Dynamics of submergence and uplift of a sedimentary basin underlain by a phase‐change boundary
Authors: O’Connell Richard J. , Wasserburg G. J.
Published: February 2008

A procedure is given for calculating the evolution of a sedimentary basin underlain by a phase‐change boundary that is in isostatic equilibrium. The equation of motion of the water depth w(t) as a function of the water depth and as a function of the sedimentation rate ds/dt is where l(t) is the lag of the phase boundary behind the transient equilibrium position. Numerically precise integrals of this equation are given for different time regimes by use of certain approximations for the temperature field that determine dl/dt. Solutions are demonstrated that are attenuated, explosive, or near periodic, depending on the physical parameters used. The results clearly show the possibility of depositing very thick sedimentary sections and the existence of self‐sustained oscillations (above and below sea level) for a sedimentary basin of this type.
Solar activity
Authors: Tandberg‐Hanssen E.
Published: February 2008

The changes in the sun's surface and atmosphere, normally referred to as solar activity, are intimately linked to the production, transport, and dissipation of magnetic fields. The most obvious manifestations of the changes are sunspots, flares, and the changing corona. The complex of solar activity can be divided into two parts: (1) the problem of the generation of magnetic fields and of the solar cycle (the 11‐year period) and (2) the surface manifestations of solar activity. The first problem concerns the solar dynamo, and we discuss in some detail dynamo maintenance. In particular, we show that a combination of differential rotation of the outer parts of the sun and cyclonic turbulence of the solar plasma constitutes a very efficient system for generation of magnetic fields. When these fields are transported to the sun's surface, they interact with the motions of the atmospheric plasma to produce the manifestation of solar activity: plages, sunspots, flares, prominences, and the active corona. Models of plages and several types of prominences are discussed, and the first steps toward theories for solar flares are indicated. The role of the magnetic fields, either as a supporting agent to store energy or as an energy source (field annihilation), cannot be overemphasized. Prominence formation and stability, as well as the occurrence of different types of flares, are treated in some detail. We close with a discussion of the active corona and interaction of the coronal plasma with other types of activity (flares and active prominences).
San Fernando Earthquake series, 1971: Focal mechanisms and tectonics
Authors: Whitcomb James H. , Allen Clarence R. , Garmany Jan D. , Hileman James A.
Published: February 2008

The largest events in the San Fernando earthquake series, initiated by the main shock at 14h 00m 41.8s UT on February 9, 1971, were chosen for analysis from the first three months of activity, 87 events in all. C. R. Allen and his co‐workers assigned the main shock parameters: 34°24.7′N, 118°24.0′W, focal depth h = 8.4 km, and local magnitude ML = 6.4. The initial rupture location coincides with the lower, northernmost edge of the main north‐dipping thrust fault and the aftershock distribution. The best focal mechanism fit to the main shock P wave first motions constrains the fault plane parameters to: strike, N67°(±6°)W; dip, 52°(±3°)NE; rake, 72° (67°−95°) left lateral. Focal mechanisms of the aftershocks clearly outline a down step of the western edge of the main thrust fault surface along a northeast‐trending flexure. Faulting on this down step is left lateral strike slip and dominates the strain release of the aftershock series, which indicates that the down step limited the main event rupture on the west. The main thrust fault surface dips at about 35° to the northeast at shallow depths and probably steepens to 50° below a depth of 8 km. This steep dip at depth is a characteristic of other thrust faults in the Transverse ranges and indicates the presence at depth of laterally varying vertical forces that are probably due to buckling or overriding that causes some upward redirection of a dominant north‐south horizontal compression. Two sets of events exhibit normal dip slip motion with shallow hypocenters and correlate with areas of ground subsidence deduced from gravity data. One set in the northeastern aftershock area is related to shallow extensional stresses caused by the steepening of the main fault plane. The other set is probably caused by a deviation of displacements along the down step of the main fault surface that resulted in localized ground subsidence near the western end of the main fault break. Several lines of evidence indicate that a horizontal compressional stress in a north or north‐northwest direction was added to the stresses in the aftershock area 12 days after the main shock. After this change, events were contained in bursts along the down step, and sequencing within the bursts provides evidence for an earthquake‐triggering phenomenon that propagates with speeds of 5–15 km/day. Seismicity before the San Fernando series and the mapped structure of the area suggest that the down step of the main fault surface is not a localized discontinuity but is part of a zone of weakness extending from Point Dume, near Malibu, to Palmdale on the San Andreas fault. This zone is interpreted as a decoupling boundary between crustal blocks that permits them to deform separately in the prevalent crustal shortening mode of the Transverse ranges region.
Photoelectrons in the ionosphere: Radar measurements and theoretical computations
Authors: Cicerone Ralph J.
Published: February 2008

Ionospheric photoelectrons may be studied by measuring the power returned in the plasma lines of the radar incoherent scatter spectrum. This paper reviews the type and quality of information about photoelectrons available from radar measurements. Distinctive capabilities and limitations of this ground‐based technique are discussed, and results are presented for a number of plasma line studies, mostly at Arecibo, Puerto Rico, and Millstone Hill, Massachusetts. These results are compared with measurements by satellite‐borne instruments and certain findings of theoretical studies of photoelectrons. It is noted that measured photoelectron escape fluxes generally exceed those predicted by current theories and that inadequate input data for theoretical computations are the likely cause of the discrepancy. Other outstanding problems involving photoelectrons require further research and are described here. One of these is the quantitative evaluation of photoelectron transport and energy degradation in the plasma contained in the magnetospheric field tubes. Experimental and theoretical work is needed on this problem to achieve quantitative understanding of protonospheric thermal structure and of predawn temperature and airglow enhancements in the F region of the ionosphere.
The electromagnetic pulse from nuclear detonations
Authors: Price Gary H.
Published: February 2008

Models of the processes whereby a nuclear detonation emits a coherent electromagnetic pulse fall into three classes: those involving Compton electron currents produced by interaction of prompt γ radiation from the detonation with the environment, those involving photoelectron currents produced by the similar interaction of primary X radiation from the detonation, and those involving perturbation of the ambient magnetic field by the expanding plasma surrounding the detonation point. For each model considered the cause of the asymmetry in the current system necessary for the radiation of a signal is discussed. These causes include the earth‐atmosphere interface, the atmospheric density gradient, anisotropy of the environment by virtue of the presence of the earth's magnetic field, nonuniform emission of the energetic radiation (γ and X rays) by the detonation, and asymmetries of the delivery vehicle and device case. The available experimental data are then examined in the light of the models. These data suffice to establish the models as probably being correct in their identification of the principal processes whereby the nuclear electromagnetic pulse is generated, but they are inadequate for a quantitative assessment of the accuracy of the models.
Climate modeling
Authors: Schneider Stephen H. , Dickinson Robert E.
Published: February 2008

Understanding and predicting climate change have recently acquired a sense of urgency with the advent of serious climate‐related food shortages and with the realization that human activities may have an influence on climate. Unfortunately, there is no comprehensive theory of climate to explain its variability, nor are there physical models that can adequately simulate the climate system. Hence there is a serious need for the development of quantitative mathematical models of climate, first to derive better understanding and ultimately to allow some degree of predictive capability. Many modeling approaches are available, ranging from simple one‐dimensional representation of the vertical radiative processes in the atmosphere up to very complex mathematical systems that describe the three‐dimensional behavior of the circulation of the atmosphere and ocean along with the chemical and thermodynamical processes that control the hydrological cycle and the existence of sea ice. Since the simpler models isolate the important physical processes that determine the climate, we weigh our discussion more heavily toward these but also discuss many aspects of the more complex models. We try to stress the fundamental physical basis of each kind of model and its contribution to the understanding of the simultaneous interactions (or feedbacks) of the many coupled processes that determine the climate. One difficulty in predicting climate change is the large degree of cancellation that occurs between many of the climatic feedback mechanisms. Considerable discussion is included of the applications of theories of baroclinic disturbances to the parameterization of eddy heat fluxes. Also stressed are basic energy balance approaches to the calculation of the surface temperature. Finally, we give our view of the future of climate modeling and argue that a flexible plan that vigorously pursues many avenues of approach is preferable. Although this review is often critical, we hope that it serves (1) to illustrate the multidisciplinary nature of climate simulation modeling and (2) to clarify the relative importance of individual contributions to the broader problems of understanding and (ultimately) predicting climate change.
Overt weather modification
Authors: Hosler C. L.
Published: February 2008

This review presents a short summary of the most often examined ideas about small‐scale overt weather modification and a subjective assessment of the progress that has been made. In addition, suggestions are made as to where the most fruitful avenues of investigation may lie in the future. Global weather modification and climatic change are not discussed, since the techniques employed thus far in overt weather modification present us with no physical reason for supposing that they affect anything on a grid larger than a few hundred kilometers. Nor is inadvertent modification discussed, even though it is the author's opinion that man's impact upon weather and climate is at the present time principally through this channel.
The impulse response of a Maxwell Earth
Authors: Peltier W. R.
Published: February 2008

An extended form of the correspondence principle is employed to determine directly the quasi‐static deformation of viscoelastic earth models by mass loads applied to the surface. The stress‐strain relation employed is that appropriate to a Maxwell medium. Most emphasis is placed on the discussion of spherically stratified self‐gravitating earth models, although some consideration is given to the uniform elastic half space and to the uniform viscous sphere, since they determine certain limiting behaviors that are useful for interpretation and proper normalization of the general problem. Laplace transform domain solutions are obtained in the form of ‘s spectra’ of a set of viscoelastic Love numbers. These Love numbers are defined in analogy with the equivalent elastic problem. An efficient technique is described for the inversion of these s spectra, and this technique is employed to produce sets of time dependent Love numbers for a series of illustrative earth models. These sets of time dependent Love numbers are combined to produce Green functions for the surface mass load boundary value problem. Through these impulse response functions, which are obtained for radial displacement, gravity anomaly, and tilt, a brief discussion is given of the approach to isostatic equilibrium. The response of the earth to an arbitrary quasi‐static surface loading may be determined by evaluating a space‐time convolution integral over the loaded region using these response functions.
Radiogenic isotope research
Authors: Church S. E.
Published: February 2008

The research effort in this field over the past 4 years has been exciting and extremely productive. The review of the literature presented here covers three main areas of research: extraterrestrial geochronology, terrestrial geochronology, and the rapidly growing field of isotopic tracer applications to problems of petrogenesis. Special emphasis is placed on a review of the lunar data. The literature cited covers most of the major English language journals from the period July 1970 through mid‐1974.
Analysis of marine magnetic data
Authors: Blakely Richard J. , Klitgord Kim D. , Mudie John D.
Published: February 2008

The general history of geomagnetic field reversals during the Cenozoic was well recognized by the beginning of this quadrennial period [Heirtzler et al., 1968]. During the last 4 years, analyses of marine anomalies have contributed not only to the refinement of this time scale but also to an understanding of its statistical importance and to an understanding of the processes with which reversals are recorded by the ocean crust, This report concentrates on the analyses of marine anomalies as directed to these ends and consequently ignores a large volume of work within the realm of its title, for example, the determination of seamount magnetization. Although not discussed in the text, these contributions are documented in the bibliography.
Magnetism of the moon and meteorites
Authors: Gose Wulf Achim , Butler Robert F.
Published: February 2008

One of the exciting results of the Apollo program is the observation that all returned lunar samples contain a remanent magnetization. This finding, together with the direct measurement of lunar surface magnetic anomalies [Dyal et al., 1970; Coleman et al., 1972] and the discovery of magnetic fields on Mars [Dolginov et al., 1973] and Mercury [Ness et al., 1974], has provided specific incentive for the study of planetary magnetic fields. The magnetic properties of meteorites attained special importance as the second source of extraterrestrial samples. The study of the remanent magnetization in these samples can provide important information about the role of magnetic fields in the evolution of planetary bodies and the solar system.
Crustal movement investigations
Authors: Savage J. C.
Published: February 2008

Studies of horizontal crustal movement using conventional geodetic methods have been considerably expanded in the quadrennium 1971–1974. The basic fault monitor Geodimeter network now covers most of the major faults in California as well as the zone of faulting that extends into Nevada. Isolated Geodimeter networks in seismic areas of Montana, New Mexico, Utah, and Washington are also monitored. Part of the Geodimeter network along the San Andreas fault has been monitored for over 15 yr, and there appears to be a systematic deviation from a linear trend for most of the lines [Greensfelder and Bennett, 1973; Savage et al., 1973]. However, this deviation may be an artifact of a change in survey procedures in mid‐1969. The conclusions that can be drawn from the Geodimeter observations at present are the following: (1) The present apparent interplate motion across the San Andreas fault in central California is only 30–40 mm/yr [Savage and Burford, 1973], in contrast to the average of 50–60 mm/yr as estimated from magnetic anomalies at the mouth of the Gulf of California. (2) Measurements of fault creep on the creeping segment of the San Andreas fault agree reasonably well with the plate movement indicated by geodetic measurements, this agreement suggesting that fault creep on this segment is the principal mode of accommodation [Savage and Burford, 1971]. (3) The rate of strain accumulation along the San Andreas fault is not well measured anywhere, but the overall tensor strain rate appears to be about 0.3 microstrain/yr or less [Savage et al., 1973]. A considerable effort has also been expended reanalyzing old triangulation data for networks that cross the San Andreas fault. In such a study, Thatcher [1974] deduced evidence for several meters of afterslip on the San Andreas fault at depths greater than 10 km following the 1906 earthquake. This appears at the surface as a very rapid accumulation of strain in the years immediately following the earthquake. Meade [1974] has called attention to a remarkably uniform change of the astronomic azimuth with time for a line that crosses the San Andreas fault about 35 km south of the southern terminus of the 1906 rupture. This change of azimuth implies a uniform right lateral motion across the fault amounting to 32 mm/yr in the period 1885–1962. By comparing a 1942 triangulation survey and a 1970 Geodimeter survey, Page [1972] found neither lateral slip nor shear strain accumulation consistent with lateral slip across the Denali fault in Alaska. He did observe a north‐south extension that was possibly an effect of strain release at the time of the 1964 Alaska earthquake.
Selenodesy
Authors: Kaula William M.
Published: February 2008

In the last 4 years, knowledge of the gravitational field and shape of the moon greatly improved through the Apollo 15–17 subsatellites, metric photography, and altimeter systems and the continued programs of laser ranging and radio interferometry from the earth. This summary is divided into three sections: gravity, rotational dynamics, and geometry. For a more detailed review, see Kaula [1975].

Of the global gravity field, only the second‐ and third‐degree harmonics are known reliably. The best determination was by Sjogren [1971], who used tracking of Lunar Orbiter 4, the 2700‐ to 6100‐km altitude of which effectively filtered out higher harmonics. Other solutions for higher‐degree harmonics [Liu and Laing, 1971; Michael and Blackshear, 1972] give severely distorted representations of the far side gravity field. Ferrari [1975a, b] and Ananda [1975] have recently obtained a more plausible result, using improved statistical techniques on Apollo 15 and 16 subsatellites plus Lunar Orbiter 5 data.
Structure of the Earth's core
Authors: Engdahl E. R. , Dziewonski A. M. , Flinn Edward A.
Published: February 2008

Recent advances in the identification of normal mode data [Dziewonski and Gilbert, 1972, 1973a, b; Gilbert and Dziewonski, 1975; Mendiguren, 1972, 1973] have allowed new constraints to be imposed on the distribution of elastic parameters within the earth's interior. In particular, the new overtone modes identified have an effective control over possible models of the structure of the inner and the outer core. Aniong recent studies using these new data, those of Gilbert et al. [1973], Jordan and Anderson [1974], and Gilbert and Dziewonski [1975] are the most relevant, since these workers made an attempt to invert simultaneously the entire available seismic data set to model the deep structure of the earth's interior.

Body wave studies have concentrated on the fine structure and the anelasticity of the core. Differential travel times (the difference between the arrival times of two body phases) have been used in inversion studies and in making independent estimates of the radii of the outer and the inner core. Differential travel times have the advantage of being independent of the base line bias always present in absolute travel times and of virtually eliminating the effects both of inhomogeneities in the upper mantle and of uncertainties due to source mislocation [Jordan, frequency waves near 1 Hz, Q ≥ 5000, P7KP being consistently higher in frequency than P4KP. This latter effect is likely to be caused by a PmKP tunneling phenomenon, discussed by Richards [1973], which predicts a frequency dependent transmission coefficient through the core that selectively removes low frequencies. Because of tunneling, the estimates of Q in the outer core from PmKP waves may be somewhat too high.
The driving mechanism of plate tectonics
Authors: Turcotte Donald L.
Published: February 2008

With the general acceptance of plate tectonics there is the question of its cause. An energy source is required which can account for the earth's heat loss, seismicity, volcanism, and tectonics. The probable energy source is the heat production due to radioactive decay of uranium, thorium, and potassium [Lliboutry, 1972; Turcotte and Oxburgh, 1972]. Alternative energy sources are differentiation processes in the core and mantle and solid earth tides.
Heat flow and shallow thermal regime
Authors: Diment W. H.
Published: February 2008

This subject is extremely broad and touches on many fields of geology and geophysics, some of which are covered in other sections of this report. Our focus is the measurement and interpretation of heat flow. However, information from other fields is noted where it appears to be of interest, but no attempt has been made to search these related areas. Blackwell's [1971a] report for the previous quadrennium is our point of departure.
Evapotranspiration
Authors: Federer C. A.
Published: February 2008

The principal goal of evapotranspiration (ET) research is to find methods for calculating the value of ET under any given conditions. Progress in the United States since 1970 has centered on understanding the water relations of plants, particularly the limitation of transpiration by variable stomatal aperture. Readers who compare this report with the preceding one [Ekern, 1971] will notice a change in emphasis from ET as a physically controlled process to ET as a physiologically controlled process. This is not due solely to the bias of the author but represents a real shift in ET research toward the stomata and their operation.
The Global Atmospheric Research Program
Authors: Perry John S.
Published: February 2008

While this report was in preparation an international force of about 40 ships, 13 aircraft, and 4000 scientists and technicians was engaged in measuring the atmosphere and ocean of the tropical Atlantic in unprecedented detail. This followed by a few months the efforts of a smaller armada in the China Sea which studied energy exchanges between the warm Kuroshio current and cold Asian air masses. These large field programs, Garp Atlantic Tropical Experiment (Gate) and Air Mass Transformation Experiment (Amtex), respectively, were visible manifestations of the Global Atmospheric Research Program (Garp), an international undertaking which has formed the unifying focus for a large fraction of the world's meteorological research during the past decade and a half.

The primary objective of this report is to highlight the activities and accomplishments of Garp—and among these, primarily the United States' contributions—during the last 4 years. These and their supporting rationale are familiar to most meteorologists. For the broader audience of this report, however, it is appropriate to begin by outlining the genesis and conceptual framework of Garp.
Cloud physics and radar meteorology
Authors: Cotton William R. , Jiusto James E. , Srivastava Ramesh C.
Published: February 2008

In recent years the specializations of cloud microphysics, cloud dynamics, laboratory and theoretical cloud modeling, and radar meteorology have become so interrelated that they can hardly be considered as separate disciplines. By combined use of these techniques and tools, the cloud physicist has made significant advances in our understanding of the complex physics and dynamics of clouds. The purpose of this report is to review major advances in laboratory and field observations of clouds, cloud modeling, and radar meteorology.
Planetary atmospheres
Authors: Gierasch Peter J.
Published: February 2008

The past 4 years have been marked by tremendous observational advances in the field of planetary atmospheres. A great deal of new information has been obtained by unmanned spacecraft, notably the Mariner 9 mission to Mars, the Pioneer 10 mission to Jupiter, and the Mariner 10 mission to Venus, all sponsored by the National Aeronautics and Space Administration. In this summary review we shall discuss only a few of the most exciting advances and the theoretical issues which as a consequence have been resolved or raised. The emphasis will be on dynamics, as it was in the previous quadrennial report. The field has been extremely active, and it would be impossible to touch on all areas. In the bibliography, however, a wide range of other work is referenced.
Research in magnetospheric wave phenomena
Authors: Barfield Joseph N.
Published: February 2008

During the last 4 years a number of developments have occurred which have led to an increased understanding of the role of wave phenomena in the physical processes of the magnetosphere. While the studies span the frequency regime from millihertz to the electron gyrofrequency, the developments to be discussed in this paper have in common that they have added substantially to the understanding of the controlling processes, regions, and boundaries in the magnetosphere. The topics discussed are the increased awareness and documentation of the role of the plasmapause in micropulsation generation and propagation; the establishment of the role of ion cyclotron waves in the wave‐particle interactions at the plasmapause; the discovery of magnetospheric electrostatic waves with ω = (3/2)Ω_; the discovery and preliminary identification of the source of plasmaspheric hiss; and the analysis of storm time Pc 5 waves as observed on the satellites ATS 1 and Explorer 45.
Coronal magnetic field models
Authors: Schatten Kenneth H.
Published: February 2008

A review of the development of coronal magnetic field models is presented. Each model's assumptions are discussed with reference to their validity within the solar corona. It is pointed out how remarkable it is that electrodynamics is applicable on a large scale as well as on the small scale from which it originated.
Electric currents in cosmic plasmas
Authors: Alfvén Hannes
Published: February 2008

Since the beginning of the century, physics has been dualistic in the sense that some phenomena are described by a field concept and others by a particle concept. This dualism is essential also in the physics of cosmic plasmas: some phenomena should be described by a magnetic field formalism, and others by an electric current formalism. During the first period of evolution of cosmic plasma physics the magnetic field aspect has dominated, and a fairly exhaustive description has been given of those phenomena, like the propagation of waves, which can be described in this way. We have now entered a second period, which is dominated by a systematic exploration of the particle (or current) aspect. A survey is given of a number of phenomena which can be understood only from the particle aspect. These include the formation of electric double layers, the origin of ‘explosive’ events like magnetic substorms and solar flares, and further, the transfer of energy from one region to another. A useful method of exploring many of these phenomena is to draw the electric circuit in which the current flows and to study its properties. A number of simple circuits are analyzed in this way.
The solubility of H2O and CO2 under predicted magma genesis conditions and some petrological and geophysical implications
Authors: Mysen Bjørn O.
Published: February 2008

Available data on the solubility of H2O and CO2 in silicate melts at high pressures and temperatures reveal that (1) the solubility of H2O is several times greater than that of CO2 and (2) the solubility of H2O depends strongly on pressure and, compared to that of CO2, depends only to a small extent on temperature. It has been suggested that the species in silicate melts can be chosen so that the molar solubility of H2O may not depend on the bulk composition of the melt. The solubility of CO2, on the other hand, varies significantly with pressure, temperature, and bulk composition of the melt. Solution of volatiles at high pressure affects the structure of the silicate melts. Water depolymerizes the melt, the result being lowered viscosity. The same depolymerization is manifested in the enhanced stability of silicate minerals on the liquidus, which are less polymerized than the minerals precipitating from the same melt composition at the same pressure under volatile‐free conditions. Carbon dioxide, on the other hand, enhances polymerization of the melt, the result being increased viscosity and increased stability of liquidus minerals which are more polymerized than those that would precipitate under volatile‐free conditions. Because of the large difference in the solubilities of CO2 and H2O in silicate melts, partial melting of an (H2O + CO2)‐bearing mantle results in enrichment of H2O in the liquid, whereas the residual mantle becomes, enriched in CO2. At P ≲ 20 at the CO2 may be retained in a vapor phase. At higher pressures, carbonate is likely to be the stable phase. Therefore it would be expected that as the result of partial melting throughout geological history the upper mantle would be heterogeneous with respect to vapor components.
A survey of Waterdrop Interaction Experiments
Authors: Abbott C. E.
Published: February 2008

The growth of waterdrops by inertial capture and coalescence induced by the size‐dependent terminal velocities in the earth's gravitational field is an important process in the formation of rain. The extensive experimental data on this fundamental process are reviewed and organized into a coherent summary of the collection efficiencies applicable to natural clouds, in the following circumstances: negligible effects of electric charges and fields, normal laboratory temperatures and pressures, and relative humidities between 50 and 100%. The judgments required to reduce the experimental data to the brief summary form are documented.
Space and time scales of mesoscale motion in the western North Atlantic
Authors: Richman James G. , Wunsch Carl , Hogg Nelson G.
Published: February 2008

From moored data, primarily temperature, of the Mid‐Ocean Dynamics Experiment (Mode I) and its successor experiments we find a statistical description of the mesoscale variability. In the Mode I area itself the spectral characteristics of the thermocline and the deep water are different. The thermocline is conveniently described as being made up of three spectral bands: a ‘low‐frequency’ band dominated by zonal velocity fluctuations, an ‘eddy‐containing’ band in which the velocity field is nearly isotropic, and a ‘high‐frequency’ band consistent with models of geostrophic turbulence. In the deep water the zonal dominance at low frequencies is not apparent, and there is enhanced energy at periods of 20–50 days. Vertical structure scales with WKBJ approximation in the high‐frequency band but not in the lower frequencies, where low vertical modes dominate the motion. Linear models do not adequately describe the data in the Mode I region. Differences between rough and smooth topography regions are clearly seen only at 1500 m, where there is a loss of energy consistent with a reduced barotropic motion. Other differences, while apparently real, are small. It is found, consistent with the results of Schmitz (1976a), that the Mode I region is atypical of the midocean in that large changes of energy level are found elsewhere. A region due east of Mode I has slightly reduced kinetic energy levels in the main thermocline, but deep energy levels are much lower. Potential energy is less variable than kinetic; in the eastern region the frequency spectra change structure slightly. Linear models may be more adequate there. With more than 2 years of data, no statistically significant heat flux was found in the Mode I area, except for a weak zonal flux in the deep water. There is no direct evidence for baroclinic instability as a significant mechanism of eddy generation; the Gulf Stream is a possible, if unconfirmed, source.
Electron density models of the ionosphere
Authors: Köhnlein W.
Published: February 2008

Electron density data show a strong variation in space, time, and geophysical conditions. Empirical models were established to describe this space‐time variation over an 11‐year solar cycle. The international reference profiles of URSI and COSPAR provide electron densities in the altitude range 54–1000 km at specific locations and times. Global variations of the F2, F1, and E layers were mapped for long‐term predictions of the ionospheric characteristics by the Comité Consultatif International des Radiocommunications and NOAA. On the basis of these analyses, several models of the bottomside ionosphere were constructed covering the whole altitude range down to the D layer. Since the advent of ionospheric satellites the models are being extended to higher altitudes. The Bent model, the model of Ching and Chiu, and the Nisbet model contain the height interval from approximately 100 to 1000 km. These models are presently among the most general setups available. A similar model was recently developed at the University of Bonn. It covers the altitude range from about 60 to 3500 km and is based upon rocket data, ionograms, and satellite observations. A comparison of the latter models shows a reasonable agreement despite their different analytical and observational foundations.
Stratospheric warmings: Observations and theory
Authors: Schoeberl Mark R.
Published: February 2008

Winter stratospheric warming observations and associated theories are reviewed. Historically, major warmings occur on the average every other year and may thus be considered an important climatological component of the winter stratosphere. The warming results from eddy heat transport from equatorial latitudes into the polar regions. The eddies chiefly responsible for the transport are the planetary scale waves which may attain amplitudes twice their monthly average values in the lower stratosphere prior to the warming. In the troposphere this amplitude increase is associated with the development of blocking patterns. The warming is shown to have a strong nonzonal component in the upper stratosphere, a feature not fully recognized by modelers. The critical level theory of the sudden stratospheric warming provides a simple dynamic explanation of the event. Yet mechanistic numerical models which have reproduced many features of the warming exhibit results which tend to indicate that the interaction of planetary waves and the mean flow occurs through a variety of mechanisms including transience and damping. The close connection between blocking in the troposphere and the development of the sudden warming is likely to be a result of resonance of free planetary waves in a stratospheric wind cavity.
Thermodynamics and lattice vibrations of minerals: 1. Mineral heat capacities and their relationships to simple lattice vibrational models
Authors: Kieffer Susan Werner
Published: February 2008

This is the first of a series of five papers in which the thermodynamic properties of minerals are interpreted in terms of lattice vibrational spectra. In this paper, measured heat capacities for minerals are examined in terms of the Debye theory of lattice vibrations, and it is demonstrated that heat capacities of silicates show large deviations from the behavior expected from Debye theory. The underlying assumptions of Debye theory are critically reviewed, and it is shown that the observed thermodynamic deviations in minerals probably arise from four effects not included in the Debye model: anisotropy of elastic parameters, dispersion of acoustic waves toward Brillouin zone boundaries, optic vibrations in excess of the Debye spectrum at low frequencies, and optic vibrations at frequencies much greater than the Debye cutoff frequency predicted by acoustic measurements. Each of the four effects influences the heat capacity in a particular temperature range: anisotropy, dispersion and low‐frequency optic vibrations are important at low temperatures (0°K to ∼100°K); high‐frequency vibrations are important at higher temperatures. It is necessary to include all four effects in a generalized lattice vibrational model for minerals; such a model is developed in papers 2‐5 of this series. The minerals included in this study are halite, periclase, brucite, corundum, spinel, quartz, cristobalite, silica glass, coesite, stishovite, rutile, albite, microcline, jadeite, diopside, enstatite, tremolite, talc, muscovite, forsterite, zircon, kyanite, andalusite, sillimanite, pyrope, grossular, andradite, spessartine, almandine and calcite.
Paleosecular variations from lake sediments
Authors: Lund S. P. , Banerjee S. K.
Published: February 2008

We have known since at least the 16th century that the Earth's magnetic field varies with time as well as geographic position. This secular variation (SV), which has been monitored instrumentally at various locations since that time, is fundamentally important to a complete understanding of the geomagnetic field and its origin. Unfortunately, the instrument record for SV is very short in duration and if we wish to extend this record backward through time we must use a very different recording process.

Paleomagnetists have considered this problem for well over 100 years, and have discovered two processes by which the SV may be commonly recorded. The first, thermoremanent magnetization (TRM), essentially causes a rock, which has been heated above a characteristic temperature, to acquire a remanent magnetization parallel to the field present when the rock cools. In this manner, lava flows and fired pottery or bricks record an instantaneous picture of the field during their cooling process.
Magnetotelluric and related electromagnetic investigations in geophysics
Authors: Filloux J. H.
Published: February 2008

A noticeable characteristic of the field of geophysical exploration of the earth through electromagnetic methods is the substantial degree of active and effective interaction presently achieved within the international community of its representative researchers, a growing group numbering two to three hundred. The “Workshop on Electromagnetic Induction in the Earth and Moon”, a program initiated by Working Group III of IAGA, constitutes the principal and indeed a powerful forum for this highly diversified scientific association. The latter, although largely elective in its constitution, is nevertheless tightly organized and meets regularly for weekly periods at the relatively frequent rate of once every two years. The program includes comprehensive and informative review papers on each one of a dozen of distinct and fundamental aspects of the main subject as well as numerous contributed papers.
Ionospheric chemistry
Authors: Torr D. G.
Published: February 2008

This report deals primarily with progress in the chemistry of minor neutrals and ionized constituents of the thermosphere. Significant progress was made over the last few years in quantitative studies of many chemical processes. This success was primarily due to the advent of multi‐parameter multi‐satellite programs which permitted accurate simultaneous measurements to be made of many important parameters. In many cases studies of chemical reactions were made with laboratory‐like precision. Rate coefficients have been derived as functions of temperature for a number of important reactions. New information has been acquired on nearly every major process which occurs in the thermosphere, including the recombination rates of all major molecular ions, charge transfer reactions, ion atom interchange reactions, and reactions of neutral and ionized metastable atoms and molecules.
Interplanetary magnetic fields
Authors: Smith Edward J.
Published: February 2008

Within the past four years, significant scientific progress has been possible as a result of improvements in observations of the interplanetary field. First, the range of radial distances over which observations are available has been greatly extended; measurements have been made as near the Sun as 0.3 AU and as far away as 8.5 AU. Second, the range of solar latitudes that have been studied by direct means has also been increased from 7 1/4 to 16°. Third, there have been many more opportunities to compare observations at two or more spacecraft including cases in which they are at widely separated locations.
The electric field and global electrodynamics of the magnetosphere: Review and Quadrennial Report to the IUGG
Authors: Stern David P.
Published: February 2008

When the radiation belt was discovered some 20 years ago, its very existence posed a fundamental problem. The way the geomagentic field managed to trap and to hold particles was readily explained—but what processes energized them in the first place, and how were they brought into their trapped orbits?

As our knowledge about the Earth's environment increased it became evident that similar questions also applied to other plasma populations such as those of the ring current and of the plasma sheet. In most cases, it turned out, both the particles' energization and their transport were provided by a large‐scale electric field
, permeating the magnetosphere. The “main” part of
, oriented roughly from dawn to dusk (near the equatorial plane), is the one responsible for a large‐scale sunward plasma flow (“convection”) found throughout most of the magnetosphere. In addition, the various sources of
accelerate charged particles in several distinct ways, maintain a global system of electric currents linking the magnetosphere with the ionosphere [Potemra, 1979] and transfer energy from the solar wind to the magnetosphere. For more complete details the reader is referred to a recent review by Stern [1977].
Genesis of metalliferous ore deposits
Authors: Beane Richard E.
Published: February 2008

During the quadrennial period beginning in 1975, the major topic of interest regarding genesis of metallic mineral deposits has been the extent and consequences of fluid flow within the shallow earth crust. Although certain advances have been made in understanding formation of metallic minerals from the liquid (magmatic) state (cf., Irvine, 1975a; Naldrett and Watkinson, 1978), the most abundant harvest of information concerning metal genesis has been derived from studies focusing on sources, compositions, and physico‐chemical characteristics of H20‐rich fluids, the nature of their movement, and the processes responsible for removal and localization of the materials which they transport. The extent and importance of hydrothermal fluid circulation relating to the formation of mineral deposits has been predicted and reasonably documented by complementary field and laboratory analyses of fossil and active geothermal systems. The following brief discussion will attempt to provide an overview of research efforts originating, for the most part, from centers within the USA as well as a summary of results and insights obtained which contribute to our understanding of the generation of metallic mineral deposits.