bluuebunny/crossref_metadata_2025 huggingface dataset:
Status of the geopotential
Authors: Rapp Richard H.
Published: February 2008

In the past 4 years the determination of the gravitational field of the earth has taken evolutionary steps. The main emphasis has been in the determination of potential coefficients. The Standard Earth (SE) II solution [Gaposchkin and Lambeck, 1971] was updated to the SE III solution [Gaposchkin, 1973] by the addition of new satellite and terrestrial data with improved analytic techniques. The SE III solution gave potential coefficients complete to degree 18, while the SEII solution had coefficients complete to degree 16. Work at the Goddard Space Flight Center progressed through a state of three basic solutions, each basic solution being composed of a set of coefficients based on satellite data alone and on a combination solution with terrestrial gravity data. In this sequence of solutions we had Goddard Earth Model (GEM) 1 and 2 [Smith et al., 1973], GEM 3 and 4 [Lerch et al., 1972], and GEM 5 and 6 [Richardson and Lerch, 1974]. The satellite alone solution (GEM 5) is complete to degree 12, while the combination solution is complete to degree 16. In these solutions the satellite data most strongly determine the potential coefficients up to about degree 12 plus resonance terms, while the terrestrial data are most strongly felt in the other coefficients. In the SE and GEM solutions the combination procedures use normal equations formed in terms of potential coefficients from the terrestrial gravity material, which are then added to the normal equations formed from the other data. In contrast to a strict least squares adjustment procedure, Rapp [1973a] determined a set of potential coefficients complete to degree 20 based on the method of least squares collocation by using the satellite alone solution of GEM 3 and 5° anomalies [Rapp, 1972]. A comparison of some combination techniques may be found in a paper by Hopkins [1972].
Geodesy by very long base line interferometry
Authors: Counselman C. C.
Published: February 2008

Important advances were made between 1971 and 1974 in the development of very long base line interferometry (VLBI) techniques for precision geodesy, including repeated determinations of the length of a transcontinental base line within 5 parts in 108, accurate measurements of polar motion and the variation of universal time, and the establishment of a catalog of extragalactic radio sources with positional uncertainties smaller than 0.1 arc sec.

An introduction to VLBI and an account of its early development have been given by Cohen [1973]. Counselman [1973] has reviewed applications of VLBI to geodesy and astrometry prior to 1973, and recently, Moran [1975a] has described the geodetic and astrometric results which have been obtained by VLBI through June 1974. Moran's review is particularly timely because he discusses important unpublished data, preliminary results, and work now in progress or being planned by the major VLBI groups in the United States.
Planetary geodesy
Authors: Anderson John D.
Published: February 2008

The last report on planetary geodesy in the United States was prepared by Kaula [1971] for the period 1967–1971. The purpose of this report is to review additional work for the period 1971–1975 and to present a corresponding bibliography as of November 1974. We restrict the discussion to the traditional subjects of geometrical and physical geodesy, with particular emphasis on the size and shape of the planets and on their masses and gravity fields.
Structure of the mantle
Authors: Anderson Don L.
Published: February 2008

This review and the accompanying references will be concerned mainly with the global and large‐scale seismic structure of the earth's mantle. Regional studies and data relevant to the uppermost mantle are thoroughly discussed in other reviews in this volume. For convenience the references are divided into separate categories. Emphasis in the last 4 yr has been placed on the determination of radially symmetric reference earth models from gross earth data, the increase and improvement of the gross earth data set including free oscillations and differential travel times, the search for lateral variations at all depths in the mantle and the development of regional earth models, the refinement of shear wave models, improvements in body wave, free oscillation, and inversion theory, and the attenuation of body waves.
Groundwater
Authors: Johnson A. I. , Meyer Gerald
Published: February 2008

The attitude toward groundwater changed during the period 1971–1974, with all phases of the water‐interested community, i.e., the general public, local, state, and federal governmental bodies, and the scientific and engineering professions, seeing groundwater from new perspectives. Water resource problems became more complex and demanding of attention, and population growth and industrial and irrigation requirements placed greater emphasis on groundwater, both as a source of water supply and as a disposal medium. New instruments of groundwater management were sought, and groundwater studies shifted from the qualitative to the quantitative. Ground‐water became more generally recognized during the past quadrennial as an important natural resource in the United States, a resource worthy of formal management, regulation, and realistic conservation.
Interactions of sea and atmosphere
Authors: Businger J. A.
Published: February 2008

Since the previous review of this subject by Pond [1971], a lively activity in air‐sea interaction research has been displayed. A number of large‐scale experiments have been and will be carried out since the Barbados Oceanographic and Meteorological Experiment (Bomex, 1968), notably: Joint North Sea Wave Project (Jonswap, 1968,1969,1973, and probably 1975), Atlantic Trade Wind Experiment (Atex, 1969), International Field Year of the Great Lakes (IFYGL, 1972), Joint Air‐Sea Interaction (Jasin, 1972 and probably 1977), Garp Atlantic Tropical Experiment (Gate, 1974) and Air Mass Transformation Experiment (Amtex, 1974, 1975) and others. It will be some time before all the information from these field experiments will have been digested, and so we may look forward to continued active reporting in this area for the coming years.

Numerous publications carrying articles in this area have appeared recently. The new Journal of Physical Oceanography has given ample space to air‐sea interaction topics as have the almost equally new journals, Geophysical Fluid Dynamics and Boundary Layer Meteorology. In 1974 this last journal devoted a special double issue to air‐sea interactions in memory of the German scientist Karl Brocks. Furthermore, the first textbook in the English language has appeared [Kraus, 1972].
Ionosphere‐magnetosphere coupling: 3. A review of the role of wave‐particle interactions
Authors: Thorne Richard Mansergh
Published: February 2008

Resonant interactions between waves and particles in the magnetosphere can cause a violation of the three adiabatic invariants µ, J, and Φ. Third‐invariant violation by fluctuating long‐period electric and magnetic fields acts as a major source for the inner radiation zone. Precipitation into the atmosphere induced by pitch angle diffusion associated with a violation of either of the first two invariants provides a major loss mechanism for geomagnetically trapped particles. Our understanding of such processes has advanced considerably over the last 4 years. Detailed models have been proposed to describe the nonadiabatic transfer of particles and energy from the magnetosphere and their effect on the upper atmosphere. This review will be limited to a discussion of recent advances in our understanding of four areas: auroral zone precipitation, relativistic electron precipitation events, the proton ring current and stable auroral red arcs, and middle‐latitude electron precipitation.
Solar wind‐magnetosphere coupling
Authors: Crooker Nancy Uss
Published: February 2008

During the past 4 years the interplanetary magnetic field (IMF) has been firmly established as a major influence in interactions between the solar wind and the magnetosphere. Evidence of its control over magnetospheric processes provides the thread of continuity in the following sections of this report: merging, polar cap disturbances and sector polarity, geomagnetic activity and solar wind structure, periodicities in geomagnetic activity, access of solar wind particles to the magnetosphere, the magnetopause, and the bow shock. A brief listing of references on aerodynamics is also included as a final section. The topic of tracing of magnetic field lines by solar particles has not been covered. The reader is referred to recent reviews by Morfill and Scholer [1973] and Paulikas [1974].

The references listed in each section are meant to be examples. More exhaustive listings covering the period fromlate 1970 through late 1974 are included in the bibliography.
Interplanetary gas of nonsolar origin
Authors: Thomas Gary E.
Published: February 2008

Beginning in 1970 a series of detailed sky maps of the extraterrestrial H I Lyman alpha (Ly α 1216 Å) and He I (584 Å) lines have become available. The observed spatial and temporal properties of the sky brightness provide unambiguous evidence of substantial quantities of neutral gas within the solar system. The view that the majority of these atoms are of interstellar origin is firmly supported by the success of the ‘interstellar wind’ model in explaining the essential features of the maps in terms of backscattering of solar chromospheric 1216‐Å and 584‐Å emission lines. The often hypothesized galactic 1216‐Å emission can now be discounted as a minor, if not negligible, component. These advances have turned attention to such questions as: What are the physical and kinematic properties of the nearby interstellar medium? Is the average solar wind emitted isotropically from the sun? What is the nature and location of the termination region of the solar wind in the interstellar medium? How important is the interstellar gas in heating the solar wind? Reviews of this new field of interplanetary studies were given by Tinsley [1971], Axford [1972], Fahr [1974], Thomas [1974], and Holzer [1974]. This will be a brief summary of some of the most significant advances for the years 1970–1974, and the summary is followed by a personal view of how future advances might be made.
Stratospheric aerosol particles and their optical properties
Authors: Cadle R. D. , Grams G. W.
Published: February 2008

This review emphasizes those aspects of aerosol particles in the stratosphere that have not been covered by other reviews. This approach is not severely limiting because of the almost explosive increase in our knowledge of such particulate matter during the last few years. Furthermore, this review places special emphasis on the optical properties of the particles. Stratospheric particles have been investigated by remote optical means for at least 80 years, but not until about 1960 were such particles collected and examined. The particles consist largely of volcanic ash for periods of possibly a few months following major explosive volcanic eruptions, but at other times they consist largely of impure sulfuric acid which may be in the form of droplets or crystals. The sulfuric acid is believed to be formed largely by the oxidation and hydration of sulfur dioxide, much of which is introduced into the stratosphere by volcanic eruptions. There is considerable uncertainty as to whether the particle size distributions are unimodal or polymodal or whether the nature of the distribution varies markedly with time and space. The mixing ratio of the particles, at least of the larger ones in the 0.1‐ to 1µm‐radius interval, is almost always greatest a few kilometers above the tropopause. However, this ‘layer’ is often highly structured. The particles may serve as catalysts for, or otherwise participate in, stratospheric chemical reactions. Stratospheric particles, by absorbing and scattering radiation from the sun and earth, can affect the atmosphere's radiation balance, thereby affecting the climate. Some numerical results concerning the amount of energy lost from an incident light beam as it propagates through a layer of uniformly distributed particles are presented. The results are shown as contours of constant values of the total percentage loss of energy due to extinction, scattering, and absorption for a vertically incident solar beam over a wide range of particle radii and imaginary refractive indices for real refractive indices of 1.4 and 1.5. The application of Mie scattering theory to the use of laser radar (lidar) is also described. Another major effect of the stratospheric aerosols is the denial of radiation to the region below the stratosphere. At the same time, they add energy to the stratosphere by the absorption of radiation. Various types of analytical models of climate change due to aerosols are discussed, and the energetic equilibrium of small particles in the atmosphere is also considered in some detail.
Interaction of solar wind with Mars as seen by charged particle traps on Mars 2, 3, and 5 satellites
Authors: Gringauz K. I.
Published: February 2008

The near‐Martian plasma measurements carried out by means of charged particle traps aboard the Mars 2, 3, and 5 satellites are reviewed. The planetary bow shock was observed; in a number of satellite passes near the planet the boundary of the obstacle that causes the bow shock was crossed. Arguments supporting the existence of an intrinsic magnetic field of Mars and of the possible existence of a quasi‐isotropic plasma zone in the Martian magnetic tail are given. The behavior of the plasma and magnetic field at the obstacle boundary gives evidence favoring a magnetic nature for the obstacle (i.e., favoring the existence of a Martian magnetosphere).
Strain heating and creep instability in glaciers and ice sheets
Authors: Clarke Garry K. C. , Nitsan Uzi , Paterson W. S. B.
Published: February 2008

Creep instability, the runaway increase of internal temperature and deformation rate, may affect the boundary condition at the base of glaciers and ice sheets and thus influence their flow and dimensions. We consider a simple slab model of heat transport in which three dimensionless parameters determine the relative importance of strain heating, ice advection normal to the surface, and boundary conditions. We find that an ice mass will be unstable if the strain‐heating parameter exceeds a critical value which depends strongly on advection and boundary conditions. Critical values over the range of parameters appropriate to natural ice masses are presented. Accumulation (downward advection) or ablation (upward advection) affects the critical value by up to 5 orders of magnitude: ablation tends to reduce stability, and accumulation increases it. For an ice mass frozen to its bed, instability eventually raises the basal ice to melting point. This can restore thermal stability, but the ice mass will start to slide over its bed. If the strain‐heating parameter exceeds a second, higher critical value, a layer of basal ice at melting point will form. We find that the conditions for instability are likely to exist in the accumulation and ablation zones of certain glaciers and ice sheets. However, times calculated for instability to develop are in the range 102–103 yr for glaciers and 103–104 yr for ice sheets. As these times exceed the normal residence time for ice in the ablation zone, it appears that instability is most likely to develop in the accumulation zone. This conclusion is reinforced by the fact that ablation increases the growth time for instability, whereas accumulation decreases it. The growth times quoted above are longer than the periods of most glacier surges, and thus creep instability is an unlikely surge mechanism. Unstable conditions may, however, obtain in East Antarctica and may have existed in the central part of ice age ice sheets. Surges of ice sheets triggered by creep instability may be possible.
Neutral hydrogen in interplanetary space
Authors: Holzer Thomas E.
Published: February 2008

The theory and observations relevant to the problem of neutral hydrogen in interplanetary space are reviewed. Emphasis is placed on those theoretical problems whose treatment in the existing literature is not entirely satisfactory, but discussion of all significant observational and theoretical aspects of the interplanetary H problem is provided. Attention is also given to other neutral constituents (particularly He) that are relatively abundant in interplanetary space and in the local interstellar medium, which is the primary source of the interplanetary neutral gas. Some consequences of the passage of the solar system through an interstellar cloud are also briefly considered.
The driving force for magnetospheric convection
Authors: Johnson Francis S.
Published: February 2008

The most popular concept for the driving force for magnetospheric convection has been that merging of the interplanetary magnetic field with the geomagnetic field at the front of the magnetosphere establishes a good electrically conducting path between the solar wind and the polar ionosphere; the flow of electrical energy then provides the driving force. This model has had impressive success in predicting some phenomena, but it also has some serious defects. The alternative view for the driving force has been that a viscous interaction exists between the solar wind and the outer layer of the magnetosphere. Although mechanisms of viscous interaction have been recognized, they have proved quantitatively inadequate to provide the required driving force. This concept has experienced a recent resurgence of support based on observation, but the conceptual problem in understanding the magnitude of the effect remains. A third possibility suggested by recent observations is that solar wind plasma enters the magnetosphere rather readily around the neutral points, where the flow is turbulent and the geomagnetic field is weak, and then spreads throughout a boundary layer covering virtually the entire inner surface of the magnetopause. This plasma can expand and drive magnetospheric convection by moving tailward around the flanks of the magnetosphere until it escapes out the open tail. The picture is rather similar to the viscously driven magnetosphere, but the driving force is different.
Empirical models of global thermospheric composition and temperature during geomagnetically quiet times compared with Esro 4 gas analyzer data
Authors: von Zahn U. , Fricke K. H.
Published: February 2008

Mass spectrometric composition measurements in the thermosphere form the basis for three global models of upper air composition and temperature: the Ogo 6, the Esro 4, and the MSIS model. The comparison of model predictions reveals differences of up to 25% with respect to mean absolute number densities. In the prediction of thermospheric variations there exists good agreement for the major constituents, but there are notable differences for the minor constituents. A comparison of individual Esro 4 density measurements with the Esro 4 and MSIS models indicates that the observed number density variations are, on the average, equally well represented by either model.
The signature of H+ in the equatorial anomaly: An empirical model
Authors: Taylor Harry A. , Mayr Hans G. , Hsieh Shiew‐Luan , Cordier Guy R.
Published: February 2008

The task of developing empirical models of the thermal ion composition is complicated by the presence of both short‐term temporal and localized spatial variations in the constituents. The requirements of a detailed numerical representation of variable composition patterns such as those detected in the zone of the equatorial anomaly (EA) may exceed either the statistical data available or the numerical modeling resolution, or both. As an illustrative example a correlative test of a parameterized spherical harmonic expansion model of Ogo 6 dayside measurements of n(H+) is performed, particular characteristics of the observations being used as a basis for comparison. Whereas a review of other research confirms that the Ogo 6 observations of EA variability in longitude and local time are generally consistent with independent experimental and theoretical results, the model reproduces the observed broad‐scale longitudinal behavior but falls short of representing some details of these features. Specifically, the model depicts the persistent prominence of the EA development in the eastern Asian longitude zone relative to the eastern American longitude zone, as Well as the longitudinal shift in the hemispheric asymmetry in EA crests, although the amplitudes of some observed features are not precisely modeled. These results emphasize (1) the limitation in statistical coverage from a single satellite for identifying complex localized and short‐term ionospheric variations and (2) the need for integrating dynamic parameters, e.g., neutral wind and electric field‐ion drift terms, to produce a hybrid empirical‐analytical model.
The Jovian spectrum in the region 0.4–1.1 µm: The C/H ratio
Authors: Wallace L. , Hunten D. M.
Published: February 2008

A review is presented of the interpretations of CH4 and H2 absorptions in the Jovian spectrum from ∼0.4 to 1.1 µm, which provide the only direct source of information on the CH4/H2 ratio in the Jovian atmosphere. The point of view is that of an interpreter rather than of an observer. A historical review of the identification of the absorbers is followed by discussions of laboratory spectroscopy and the representation of such results by curves of growth and band models. Next are a survey of radiative transfer methods and a discussion of the various representations of the Jovian atmosphere and cloud structure. Though the reflecting layer model is popular, it is known to be at odds with observation, and conclusions based on it must be viewed with suspicion. The same is true of the homogeneous scattering model, though a seldom used combination (the reflecting‐scattering model) has much to recommend it. Various versions of two‐cloud models have been used; their special problem is how to find enough data to pin down the multitude of parameters. Despite the various difficulties the best determinations of CH4/H2 have not been grossly disparate. The reflecting layer model consistently gives ∼7 × 10−4 by number, while the scattering models range upward to ∼30 × 10−4, 20'30 × 10−4 being preferred. At the same time the ratio of CH4/H2 expected for solar composition, once thought to be 7 × 10−4 also, has recently been suggested to be as low as 3.4 × 10−4. A carbon enrichment on Jupiter of as much as a factor of 5–10 must therefore be seriously considered.
Magnetic polarity stratigraphy
Authors: Butler Robert F. , Opdyke Neil D.
Published: February 2008

Our task of reviewing magnetic polarity stratigraphic research was made considerably easier by the publication of several recent review articles on various facets of the subject. Reviews of paleomagnetism of deep‐sea sediments have been presented by Opdyke (1977) and Harrison (1974). Larson and Helsley (1975) reviewed the Mesozoic geomagnetic reversal sequence. A rather exhaustive review of land‐based polarity stratigraphy was published by Irving and Pullaiah (1976).
Elastic and anelastic structure of the Earth
Authors: Dziewonski Adam M.
Published: February 2008

The objective of this review is to outline the progress made in the last four years in studies of global or large scale properties of the Earth. Work related to strictly regional structure of the crust and the uppermost mantle is described in other reports in this volume.

During the previous reporting period 1971–1974 (Anderson, 1975) there was a large increase in the data base relevant to the average structure of the Earth. The number of normal modes for which eigenfrequencies have been measured increased by an order of magnitude; observations of travel times of body waves (differential travel times, in particular) were reported for several phases of key importance in constraining the core radii as well as distribution of the seismic velocities in the core and lower mantle. Quite naturally, the emphasis has been placed on construction of Earth models that would be consistent with this substantially enlarged data set.
Modulation of relativistic galactic cosmic rays
Authors: Owens A. J.
Published: February 2008

This paper reviews the progress in our understanding of the solar modulation of relativistic galactic cosmic rays during the years 1975 to 1978. The contributions of U.S. authors are emphasized, although all major results published in English‐language journals are discussed. Topics reviewed include the microscale theory of particle scattering, steady‐state modulation models, particle drifts and effects due to the three‐dimensional nature of the solar modulation region, discrete periodicities and hysteresis in the cosmic‐ray intensity‐time profile, and aperiodic temporal variations and Forbush decreases. Prospects for improving our understanding of these phenomena in the near future are briefly discussed.
Energetic particles of planetary origin in interplanetary space
Authors: Pyle K. R.
Published: February 2008

It is the purpose of this review article to desscribe the progress that has been made over the past four years in a new field of space physics. The wealth of new observations by Pioneers 10 and 11, and Mariner‐10—as well as more sensitive instruments aboard Earth orbiters—has expanded the field dramatically. [In this article, the wealth of experimental and theoretical results obtained over the past 4 years in and near the Earth's solar wind cavity will be examined only cursorily.] This article will concentrate on propagation in the interplanetary medium, and acceleration and escape mechanisms in the regions near the planets other than Earth.
Auroral mechanisms and morphology
Authors: Swift Daniel W.
Published: February 2008

This past quadrennium has witnessed a considerable expansion of our knowledge and understanding of processes responsible for the aurora. Because of the number and diversity of contributions, a complete description is difficult, and many topics are presented here in summary form only. Instead, this review will emphasize the major accomplishments and outline the major problems that should be addressed during the next quadrennium.

The scope of this review includes observations, analysis of observations and theoretical work which are likely to be relevant to the understanding of the aurora. Ground‐based observations reviewed include (l) auroral imagery, both by television and all‐sky camera, (2) gross magnetic variations indicative of ionospheric currents, (3) VLF hiss observations, and (4) effects of high‐energy electron impact measured through cosmic radio noise absorption and by observations of bremsStrahlung x‐rays from balloons. Not included in this review are spectroscopic observations, observation of micropulsation activity and auroral radar observations, as these observations seem to provide less direct diagnostic information on the basic auroral mechanism. However, incoherent scatter radar observations are utilized to the extent they provide information on ionospheric currents and electric fields.
Eddies and the general circulation of numerical model gyres: An energetic perspective
Authors: Harrison D. E.
Published: February 2008

Energy budgets for the long‐time‐averaged circulation of mesoscale resolution numerical ocean circulation model (EGCM) experiments are the only widely used analysis methods that permit investigation into the eddy‐mean flow interaction of these model oceanic systems. All published energy results from the closed basin EGCM experiments are presented here in nondimensional form to facilitate comparison of the various types of behavior. The ubiquitous basin‐averaged energy analysis method is necessarily sensitive to changes in model forcing and dissipative processes, and it is shown that several natural energy measures of eddy‐mean flow interaction are strongly correlated with forcing and dissipation choices. In particular, it is found that by these energy measures, eddies are relatively unimportant in the mean flow when the horizontal momentum subgrid scale process corresponds to constant coefficient viscosity, but they are much more important when this process is modeled by a constant coefficient biharmonic operator. Energy budgets over subrogions of the full domain should offer increased insight into model mechanisms, but the use of quasi‐geostrophic dynamics can severely limit the number of independent energy pathways in the flow. Owing to these constraints the published regional two‐layer quasi‐geostrophic energy budgets offer information beyond that of the basin budgets. It is suggested that the assumptions of these quasi‐geostrophic models also limit the generality of inferences about the role of vertical processes based on these calculations. In none of the energy budgets reported is there significant direct driving of a mean flow by Reynolds stress work, and in only one case does mean buoyancy work act to try to increase mean flow kinetic energy. From these budgets it appears that if eddies are energetically important in the model flows, their only unambiguous role is as a pathway to dissipation. Further more detailed regional analysis is necessary to see if this result continues to hold when smaller horizontal subregions of the domain are analyzed. Such analysis activity, as well as more attention to alternative means of investigating eddy‐mean flow interaction, appears to be needed.
Review of major problems in sedimentation 1975–1978
Authors: Shen Hsieh Wen
Published: February 2008

Most early civilizations were cradled in river valleys because rivers are key sources of water. Since sediment is an integral part of the flow in a large majority of rivers, a great deal of research has been conducted on sedimentation. The purpose of this paper is to review major problems and advances in sedimentation from 1975 through 1978. Although there have been many significant foreign papers published, this review is mainly restricted to U.S. contributions.
Control surveys
Authors: Dracup Joseph F.
Published: February 2008

The progress of geodetic control surveys in the United States has been enhanced by the increased use of sophisticated instrumentation during 1975 to 1978. Although this report summarizes only the national and international activities of the several Federal agencies that establish geodetic surveys, significant accomplishments have also been made by state, county, and private organizations. Many of these organizations submit their observational data or adjusted results to the National Ocean Survey (NOS) for adjustment and/or publication in accordance with the detailed instructions provided for such submissions. As a result, more control of acceptable accuracy is being made available to the user.
Recent advances in shelf wave dynamics
Authors: Mysak Lawrence A.
Published: February 2008

A theoretical discussion is presented of the propagation, stability, generation, scattering, interactions, and dissipation of low‐frequency waves trapped along continental shelves. Brief accounts of laboratory and oceanic evidence of these ‘shelf’ waves are also given. The emphasis is on those aspects of shelf wave dynamics that have been published during the past 5 years. Several theoretical and observational questions that deserve attention in the future are raised.
Precipitation‐powered mechanisms of cloud electrification
Authors: Mathpal K. C. , Varshneya N. C. , Dass Narsingh
Published: February 2008

This article reviews those mechanisms of cloud electrification which are based on gravitational separation of precipitation particles and examines at some length the inductive charging mechanism. It is concluded that through the inductive mechanism, glaciated clouds can develop a maximum current density Jmax of 0.1 µA m−2 with a maximum field Emax of about 3.5 × 105 V m−1 (which values are necessary for the occurrence of lightning flashes in them) within a time of 1000 s provided that the precipitation intensity in them is greater than 1.39 × 10−5 m s−1 (50 mm hr−1). For precipitation intensities less than 8.33 × 10−6 m s−1 (30 mm hr−1), Jmax and Emax cannot develop to such high values. By its inherent nature this mechanism does not work in warm clouds.
Ionospheres of the terrestrial planets
Authors: Schunk R. W. , Nagy A. F.
Published: February 2008

The theory and observations relating to the ionospheres of the terrestrial planets Venus, the earth, and Mars are reviewed. Emphasis is placed on comparing the basic differences and similarities between the planetary ionospheres. The review covers the plasma and electric‐magnetic field environments that surround the planets, the theory leading to the creation and transport of ionization in the ionospheres, the relevant observations, and the most recent model calculations. The theory section includes a discussion of ambipolar diffusion in a partially ionized plasma, diffusion in a fully ionized plasma, supersonic plasma flow, photochemistry, and heating and cooling processes. The sections on observations and model calculations cover the neutral atmosphere composition, the ion composition, the electron density, and the electron, ion, and neutral temperatures.
General relationships between wave amplification and particle diffusion in a magnetoplasma
Authors: Gendrin Roger
Published: February 2008

The general conditions for wave generation (γ > 0) or wave absorption (γ < 0) by a given distribution of energetic particles are discussed in the case of electromagnetic waves propagating along the dc magnetic field. It is shown that the nature of the interaction (γ > 0 or γ < 0) can be easily determined by considering the relative position of three curves in the υ∥, υ⊥ plane (where υ∥ and υ⊥ are the parallel and perpendicular velocity of the particle): the isodensity curve, the constant energy curve, and the diffusion curve. For ‘regular’ distribution functions (i.e., distributions which are concave around the origin and for which there are less particles of high energy than particles of low energy) a necessary and sufficient condition for positive growth rate is that the third curve be situated within the area delineated by the other two curves. This geometrical formalism is extended to other kinds of distributions (field‐aligned beams or ring distributions). It is also applied to wave‐particle interactions in multicomponent plasmas. The conclusions which we arrive at are in agreement with previous findings. The analytical demonstration of this geometrical property is given. It is linked with the fact that the equations which govern the wave amplification and the particle diffusion involve the same operator, which is the derivative of the distribution function taken along the diffusion curve. The origin of this property lies in the special form of the Boltzmann‐Vlasov equation.
Electromagnetic kinetic instabilities in multicomponent space plasmas: Theoretical predictions and computer simulation experiments
Authors: Cuperman Sami
Published: February 2008

A review is presented of the status of our knowledge of electromagnetic cyclotron instabilities in multi‐component magnetosphericlike plasmas consisting of a hot anisotropic population and of additional cold plasma components, with special emphasis on the nonlinear phenomena. To achieve this, the results of a large number of computer simulation experiments are considered. While the paper deals primarily with naturally occurring magnetospheric phenomena, implications for the active space (seeding) experiments aimed at producing artificial auroras and consequently the verification of magnetospheric theories are also discussed.
Sedimentary processes in the Great Lakes
Authors: Rea David K. , Owen Robert M. , Meyers Philip A.
Published: February 2008

Sediments in the Great Lakes are subject to four general categories of processes: input, transport, deposition, and postdepositional alteration. Sedimentary input is from coastal erosion (64%), riverine input (26%), atmospheric transport (3%), and several lesser sources (7%). Once in the lake, sediments are transported to their place of deposition along the bottom and/or in suspension depending upon grain size and density. The rate of deposition in the Great Lakes is variable and ranges from zero in some areas to over 6000 g m−2 yr−1 in the eastern basin of Lake Erie. After deposition, sediments undergo bioturbation, dissolution of carbonate and opal, remobilization of many metals followed by reprecipitation within the surficial oxidized layer, and degradation of organic compounds.
ULF/lower‐ELF electromagnetic field measurements in the polar caps
Authors: Fraser‐Smith A. C.
Published: February 2008

A review is given of the known properties of naturally occurring ULF/lower‐ELF (0.022–100 Hz) electromagnetic pulsations in the polar caps. Because polar cap measurements by Western scientists in this particular frequency range have been surprisingly limited (even when allowance is made for the logistical difficulties), emphasis is given in the review (1) to a description of the gaps in our knowledge of the properties of the pulsations and (2) to the uniqueness of the geomagnetic field configuration in the polar caps and its implications. Given the gaps in knowledge and the unique field configuration, the opportunities for innovative research on ULF/lower‐ELF electromagnetic pulsations in the polar caps appear to be particularly promising.
Earth's radiation belts
Authors: Schulz Michael
Published: February 2008

This paper reviews the status of radiation belt science at the close of the data acquisition phase (1976–1979) of the International Magnetospheric Study. The purpose is to place recent discoveries in context with respect to long‐standing problems and to indicate possible directions for future research in radiation belt physics. The review includes a synopsis of results achieved on topics related to the source, energization, transport, and loss processes for geomagnetically trapped radiation, as well as results concerning certain subtle consequences of adiabatic charged particle motion. Major areas of interest include the effects of charge exchange and radial transport on the ion composition of the ring current and radiation belts, the measurement of ion distributions in all three dimensions of velocity space, and the evolution of radiation belt particle intensities as a consequence of temporal variations of transport coefficients and boundary conditions over the solar cycle and over the course of a magnetic storm. The realization is gradually developing that the major uncertainties in radiation belt physics lie beyond the radiation belts themselves. These uncertainties include (1) the problem of particle energization in the plasma sheet, which defines an outer boundary condition for the ring current and radiation belts, (2) the problem of particle energization in solar flares and in Jupiter's magnetosphere, both of which constitute possible sources for the earth's radiation belts, and (3) the relationship of large‐scale electric and magnetic field fluctuations across the magnetosphere to interplanetary parameters and geomagnetic indices that vary with time.
Scientific results of the U.S. IMS Ground‐Based Program
Authors: Rees M. H.
Published: February 2008

The scientific results of the U.S. International Magnetospheric Study (IMS) ground‐based program available to the author up to February 1982 are summarized. Included are results derived from (1) magnetometers of the IMS meridian chains, (2) incoherent scatter radars, (3) a balloon campaign, and (4) optical spectroscopic observations. A large body of data obtained during the IMS remains to be analyzed and published.
Magnetosphere‐ionosphere coupling: Contributions from IMS satellite observations
Authors: Burke William J.
Published: February 2008

This paper provides a preliminary review of International Magnetospheric Study (IMS) period advances in our understanding of how the magnetosphere and ionosphere act as an electrically coupled system. Emphasis is placed on particle and electric field observations from the AE, S3‐2, S3‐3, and DMSP satellites. Field‐aligned current measurements are reviewed by Saflekos and co‐workers. An overview of pre‐IMS measurements provides the point of departure. The capabilities of the various satellite instrumentation packages are then critically summarized. Measurements are divided according to their auroral oval or polar cap origins. The systematics of auroral boundary variations, large‐scale precipitation, and subauroral rapid convection are discussed with reference to their magnetospheric sources. The wave, electric field, and particle environment of inverted‐V structures have been given detailed study during IMS. The direct observation of parallel electric fields that accelerate electrons earthward to form discrete arcs and ion beams upward into the magnetosphere is a contribution whose analysis will continue strongly into the post‐IMS period. Studies of satellite measurements show that the cross‐polar cap potential is quantifiably related to solar wind/IMF parameters. The detection of sun‐aligned arcs as well as extensive regions of sunward convection in the polar cap suggests that the magnetosphere/solar wind coupling is radically different during periods of northward and southward IMF orientations.
Earth tides
Authors: Goad Clyde C.
Published: February 2008

In 1979, Farrell (1979) pointed out that investigators in all areas of earth tide studies were recognizing the importance of the inherent connection between the solid tidal response and that of the oceans to the same solar and lunar gravitational attractions. Since then, the use of ocean tide models determined from solutions of Laplace tidal equations (Parke and Hendershott, 1979) and solutions which incorporate a global distribution of tide gauge results (Schwiderski, 1979a, 1979b, 1980, 1982e) in the analysis of earth tide gravity data and satellite perturbations in the semi‐diurnal and diurnal bands have become a common operation. Results are available for most major semi‐diurnal, diurnal, and long period tidal constituents. Studies of the response of the earth's rotation to the long period tides have also been performed (Yoder et al. 1981a,b).
Hydrology 1979–1982
Authors: Wood Eric F.
Published: February 2008

The quadrennium 1979–1982 produced notable advances in surface water and groundwater hydrology, as well as important trends towards a more scientific basis for engineering hydrology. Examples of these developments will be given below, as well as an assessment of current trends.

One of the most significant areas to emerge during the last quadrennium is stochastic groundwater analysis. The basis for the conceptualization of groundwater flow and transport as a stochastic process is two‐fold: 1) the realization that hydrologeological environments are extremely heterogeneous, regardless of the scale of modeling or data collection and 2) the use of groundwater flow and transport modeling results within broader water resources or hazardous waste management studies where risk analysis requires and incorporates groundwater uncertainty.
Progress in weather modification research: 1979–1982
Authors: Dirks Richard A.
Published: February 2008

The 1979–1982 period began with the optimism of the Weather Modification Advisory Board (WMAB) Report (1978a) “that a useable technology for significantly enhancing rain and snow and ameliorating some weather damage is scientifically possible and within sight” and laid plans for implementing a national weather modification program. The Report also contained an important caveat “The experimental evidence for cloud‐seeding has not yet reached the levels of objectivity, respectability, and predictability required to establish new knowledge and techniques.” This warning came as a harsh reminder at the end of the quadrennium with the disappointing conclusions of such experiments as the Florida Area Cumulus Experiment (FACE) on rainfall enhancement and the Grossversuch IV hail suppression experiment in Switzerland, which were unable to demonstrate statistically significant cloud seeding effects. Finally, this period ended with national and international economic hardships bringing austerity to weather modification research programs.
Marine chemistry and paleoceanography in the United States — 1978–1982 — An overview
Authors: Schink David R.
Published: February 2008

The last four years have brought exciting advances in oceanography within the U.S. The traditional research approach of a modest program built around a single investigator was supplemented during the International Decade of Ocean Exploration in the United States by a series of large‐scale cooperative programs involving many investigators, often from a multitude of institutions. Continuing with this approach has allowed us to attack otherwise intractable problems. The broad range in program scales, from small to rather large, utilizes both individual creativity and the synergism of many observations focused on a single process; it continues to produce rich returns.
Deep earth structure
Authors: Cormier Vernon F.
Published: February 2008

Major developments in earth structure in the last four years have been concentrated in the description of the earth's lateral heterogeneity: the regions that are heterogenous and the per cent variation of velocity and density in each region. Most studies find that lateral variation is concentrated in the upper 400 and lower 200 km. of the mantle.

A radially symmetric earth model has been defined that represents the best average fit to seismic data in a broad frequency band, sampling many regions. P and S velocity is found to increase in zones of 50 km. or less at 400 and 650 to 700 km. depth. The model is transversely anisotropic in the upper mantle. It possesses a vertical axis of symmetry such that the elastic constants are different for vertical propagation than for horizontal and intermediate angles of propagation. The real earth generally exhibits azimuthal anisotropy as well, but the azimuthal anisotropy cannot be resolved by a global average of data. The nature and magnitude of the anisotropy agrees with that found in ultramafic samples of the upper mantle.

In attenuation, models of intrinsic attenuation have included the dispersive properties of intrinsic anelasticity and constructed relaxation models consistent with an observed frequency dependence of Q in the body wave band. There has been progress in mapping the scattering properties of the lithosphere. Attenuation due to scattering in the crust and lithosphere has been shown to have strong effects on the amplitudes of seismic waves at local and teleseismic distances.
Static ultrahigh‐pressure research
Authors: Bell Peter M.
Published: February 2008

Research in geophysics has advanced so that calibrated experiments can be done to static pressures as high as 1.7 Mbar at 4000 K. Part of this review references new experimental techniques to generate ultrahigh pressures, to calibrate the pressures, and to conduct in situ physical measurements. The other part lists geophysically relevant research results. Most of the references are related to research done in the United States during the past four years.