bluuebunny/crossref_metadata_2025 huggingface dataset:
Spectral studies of tropospheric wave disturbances in the tropical western Pacific
Authors: Wallace J. M.
Published: February 2008

Tropospheric wave disturbances in the tropical western Pacific have been subjected to intensive analysis during three separate seasons. These all show evidence of spectral peaks in the 4‐ to 5‐day range and at periods longer than 10 days. In this review I attempt to synthesize the results for these three seasons, together with the analysis of a fourth season, into a tentative description of the various types of wave disturbances in this region. The conclusions are outlined below.

It appears that there are two types of tropical disturbances that contribute to the 4‐ to 5‐day peaks: synoptic‐scale, westward‐propagating waves with phase speeds on the order of 6‐7 degrees per day, and planetary‐scale equatorial waves that extend into the lower stratosphere. There are also one or more wave types associated with the low‐frequency spectral peaks.

All the tropical waves exhibit a similar vertical structure, with a phase reversal in the wind field between upper and lower troposphere. There are warm temperature anomalies at 300 mb, above the low‐level troughs, in qualitative agreement with the thermal‐wind equation. These warm anomalies coincide with the regions of maximum rising motion. As distinguished from tropical waves, the subtropical disturbances do not exhibit a phase reversal in the wind field between upper and lower tropospheric levels. The troughs of these waves appear to be colder than their surroundings at 300 mb.

The available potential energy the tropical waves derive from condensation heating is immediately converted into kinetic energy by the synoptic‐scale divergent wind field. This appears to be the dominant energy source for these waves. The leakage of wave energy upward through the tropopause appears to be at least an order of magnitude smaller than the rate of energy generation.

The spectral results indicate that most of the synoptic‐scale mass convergence into regions of disturbed weather takes place above the subcloud layer. Although the vertical distribution of latent heat release displays the same gross features in different regions, a simple linear proportionality between boundary‐layer convergence and condensation heating (as is usually assumed in the CISK hypothesis) does not appear to exist.
Bermuda sea level in relation to tides, weather, and baroclinic fluctuations
Authors: Wunsch Carl
Published: February 2008

The sea‐level record over an 8‐year period at the Biological Station, Bermuda, has been analyzed in an attempt to deduce the complete physics of sea‐level variations in the frequency band of 1 cycle per 8 years to 0.5 cycles per hour. The admittance of the linear tidal lines was calculated, and, on the basis of certain assumptions about a linear system, the Hilbert transform relation between real and imaginary parts of the admittance function was used to deduce the function between diurnal and semidiurnal tides. The North Atlantic appears to be resonant with a period of 14.8 hours having a Q exceeding 3.3. An overtone of the resonance is also possibly present. An examination of the overtides in the record indicates that the hydrodynamical regime plus measuring system is highly linear. The spectra of observed atmospheric pressure, temperature, and winds were calculated, and the transfer functions between atmospheric narrow‐band processes (tides) and the continuum with sea level were computed. The tidal constituent S2 is about 10 per cent radiational in nature. The continuum of sea level is found to be dominated by pressure in an inverted barometer sense for periods shorter than a year. At longer periods, the winds appear to dominate, but low‐frequency sea‐level power rises more rapidly than any other weather variable, so that the sea‐level spectrum essentially decouples from the atmosphere. The effect of atmospheric temperature is found to be negligible. A comparison between temperature measured in the main thermocline and the sea‐level record yielded no coherence in any part of the spectrum. Approximately 0.1 cm of the semidiurnal tide is attributed to motion of the sea surface by the baroclinic tide. Otherwise, the rest of the internal wave spectrum can be ignored. The Panulirus hydrographic station sequence shows coherence between dynamic heights and the residual (nonweather) sea‐level record for periods between 6 months and a year. At very low frequencies, the dynamic height spectrum tapers off, indicating that the lowest‐frequency energy in the sea‐level record is probably in barotropic motions. Examination of the coherence between the sea‐level record and another record made nearby on Bermuda indicates that the tide‐gage record used in this study is representative of sea‐level motion over a scale of a few miles. Approximately 87 per cent of the total sea‐level variance is explicitly accounted for. The remainder of the energy is in errors of the analysis and in barotropic motions.
Sky‐wave backscatter: A means for observing our environment at great distances
Authors: Croft Thomas A.
Published: February 2008

For 45 years, men have measured and studied echoes from the distant surface of the earth, obtained with high‐frequency signals (3 to 30 MHz) that travel to and from the scatterers via ionospheric refraction. During the last five years, much progress has been made in the understanding of this ‘sky‐wave backscatter.’ An explanation of the various interacting phenomena is presented, as is a review of the current state of knowledge reflecting recent advances in observational methods and analytic techniques. New narrow‐beam antennas, coupled with signal modulations that permit fine resolution in time delay, are beginning to yield information concerning the character of the scatterers, which now can be separately discerned. These narrow beams also permit study of polarization fading from small regions, and this shows promise as a means for learning the distant sea state. Doppler shifts of a fraction of a hertz on signals of tens of megahertz are separable, permitting isolation of sea returns from ground returns by virtue of the Doppler effect resulting from sea‐wave speed; this also suggests a potential sea‐monitoring principle. New modulation equipment permits short‐wave broadcast stations to make sky‐wave backscatter soundings with existing transmitters as an adjunct to normal operations, so that area coverage can be observed in real time. Despite these advances, there is little practical application of sky‐wave backscatter as a means of environmental monitoring. This lack is attributed to the large remaining gaps in our understanding of the echoes and our inability to interpret the forms of data that can be acquired with equipment of reasonable cost. It is still not possible to calculate ionospheric structure from an observation of sky‐wave backscatter although it is the opinion of many workers that this should be feasible. It is now at least possible to carry out the reverse process, calculating sky‐wave backscatter from an assumed ionosphere of much complexity. Study of such synthetic data is yielding additional insight into the causes of diverse forms of observed sky‐wave backscatter.
The general linear inverse problem: Implication of surface waves and free oscillations for Earth structure
Authors: Wiggins Ralph A.
Published: February 2008

The discrete general linear inverse problem reduces to a set of m equations in n unknowns. There is generally no unique solution, but we can find k linear combinations of parameters for which restraints are determined. The parameter combinations are given by the eigenvectors of the coefficient matrix. The number k is determined by the ratio of the standard deviations of the observations to the allowable standard deviations in the resulting solution. Various linear combinations of the eigenvectors can be used to determine parameter resolution and information distribution among the observations. Thus we can determine where information comes from among the observations and exactly how it constrains the set of possible models. The application of such analyses to surface‐wave and free‐oscillation observations indicates that (1) phase, group, and amplitude observations for any particular mode provide basically the same type of information about the model; (2) observations of overtones can enhance the resolution considerably; (3) the degree of resolution has generally been overestimated for many model determinations made from surface waves; and (4) computation of parameter and information resolution is such a simple extension of any inversion procedure based on perturbation parameters that such inversion studies are incomplete without considering resolution.
Late Quaternary vertical movements in eastern North America: Quantitative evidence of glacio‐isostatic rebound
Authors: Walcott R. I.
Published: February 2008

From 18,000 to 6500 years ago the ice sheets covering North America melted, and sea level rose almost 100 meters. Since that time, sea level has remained almost constant, but the earth has not yet completed its adjustment to the removal of the ice load. In the center of the uplifted region the ground has risen 138 meters in the last 6000 years and is rising at a rate of 2 ± 0.5 cm/yr today; there may be another 300 ± 120 meters of vertical motion left before isostatic equilibrium is reached. This review collects the evidence of vertical movements in northern and eastern North America from different sources and disciplines to provide in one publication the quantitative data important for geophysical analyses of glacio‐isostatic rebound. The paper covers evidence from the area of uplift and the peripheral zone of submergence and from the past movements and instrumentally recorded recent trends, provides a discussion of the eustatic rise in sea level, and gives an updated free‐air gravity anomaly map of the deglaciated region.
Early chemical history of the solar system
Authors: Grossman Lawrence , Larimer John W.
Published: February 2008

The extreme antiquity and lack of evidence for significant chemical processing of the chondritic meteorites since they were formed suggest the possibility that their chemistry and mineralogy may have been established during the condensation of the solar system. By using equilibrium thermodynamics, the sequence of condensation of mineral phases from a cooling nebula of solar composition has been calculated. Applying the predictions of these theoretical models suggests that (1) the chemistry and mineralogy of Ca‐Al‐rich inclusions in C2 and C3 chondrites were established during condensation at temperatures >1300°K; (2) fractionation of such inclusions is necessary to account for the refractory element depletions of ordinary and enstatite chondrites relative to the carbonaceous chondrites; (3) the metal‐silicate fractionation in ordinary chondrites took place in the nebula at T < 1000°K and Ptot ∼ 10−5 atm; (4) the volatile element depletion of C2 and C3 chondrites relative to C1 chondrites took place during chondrule formation; (5) the most volatile elements are depleted in ordinary chondrites because they accreted before these elements were totally condensed; and (6) many chemical features of planetary rare gases and organic material in carbonaceous chondrites could have been established during condensation. Chemical fractionation during condensation may also be responsible for the heterogeneous accumulation of the earth, the refractory element enrichment of the moon, and the varying Fe/Si ratios of the terrestrial planets.
The Sun and cosmic rays
Authors: Pomerantz M. A. , Duggal S. P.
Published: February 2008

Solar phenomena produce cosmic ray intensity variations over a wide range of time scales. The observed flux is modulated and rendered anisotropic as the particles propagate in the solar wind, and it is occasionally enhanced by the sporadic emission of solar cosmic rays. Both quasi‐static phenomena (the long‐term omnidirectional intensity variation and the steady state diurnal anisotropy) and transient fluctuations (disturbed daily variation and Forbush decrease) as well as the spatial distribution of solar flare particles are represented by a theoretical model that prescribes the role of the several solar‐controlled parameters that characterize the electromagnetic properties of the interplanetary medium. Considerable information concerning the ambient conditions has been obtained with spacecraft. However, the in situ measurements are confined to a limited region near the ecliptic plane. Consequently, in some cases, theoretical predictions based upon them are not in accord with observations of cosmic ray intensity variations. Thus the modulations and anisotropies must be treated in a three‐dimensional framework. It is therefore reasonable to attempt to deduce the properties of the relevant inaccessible regions of the heliosphere from observations of the sun itself. These properties can be determined by relating the various cosmic ray phenomena to changes during a solar cycle and from one cycle to another. To this end, data covering at least two solar cycles are studied to determine the solar cycle dependence of the following effects: long‐term variations in the omnidirectional intensity, Forbush decreases, solar diurnal variations, and solar cosmic ray events (ground level enhancement and polar cap absorption).
Waves and irregularities in the solar wind
Authors: Lee M. A. , Lerche I.
Published: February 2008

This review is not meant to be for the specialist who already knows the subject area but rather for the nonspecialist who wants a simple physical picture. Therefore some simple calculations are given to show why waves and irregularities in the solar wind are of importance in obtaining a physical understanding of the dynamical processes occurring in the interplanetary medium. The basic physics of divers phenomena observed in the heliosphere, resulting because of the presence of waves in the solar wind, is spelled out in some detail. The most fundamental point made in this review is that a considerable body of phenomena occurring in the solar wind are either caused directly or modified significantly by the turbulent waves that are always present in the solar wind. Spacecraft data indicate the essentially continuous presence of strong magnetic irregularities in the solar wind, which, apparently, are predominantly Alfvén waves being convected outward from the sun by the solar wind. The bulk dynamical properties of the wind are changed substantively by the waves and irregularities that the wind carries, this change leading, in particular, to higher solar wind speeds than occur in the absence of the waves. Also the observed spread of the ‘frozen‐in’ field lines in the solar wind can be traced back to the random wanderings of the photospheric ‘feet’ of field lines emanating from the sun. The observed variations in neutron monitor intensities and the low‐energy particle fluctuations observed on Explorer 34 are accountable in terms of a ‘slab’ of material containing an irregular frozen‐in magnetic field being convected past an observer. This field causes irregular fluctuations in the number of charged particles crossing the slab that are picked up by a detector. The detected irregularities are related to the irregularities in the ‘slab,’ which also are measurable. The agreement is surprisingly good. The presence of magnetic irregularities and waves in the solar wind also causes scattering of cosmic ray particles as they journey inward through the solar system from interstellar space. This leads to a modulation of the intensity of the cosmic rays seen at earth. The relevant diffusion coefficients, conventionally used to describe this process, are expressible in terms of both the power spectra of the waves present in the solar wind and the charged particle parameters, such as speed, charge, and pitch angle. Although the main physical ideas incorporated into this process seem to be reasonably well understood, there remain an embarrassingly large number of unanswered questions, concerning the details.
Chlorofluoromethanes in the environment
Authors: Rowland F. S. , Molina Mario J.
Published: February 2008

The molecules CF2Cl2 and CFCl3 are released into the atmosphere following their extensive use as propellants for aerosol spray cans and in refrigeration. Since they are chemically inert and have low solubility in water, these chlorofluoromethanes have very long atmospheric residence times and can be detected throughout the troposphere in amounts roughly corresponding to the integrated world industrial production to date. The most important sink for atmospheric CFCl3 and CF2Cl2 appears to be photolytic dissociation in the stratosphere by ultraviolet radiation around 2000 Å. Upon photolysis the chlorofluoromethanes release chlorine atoms, which initiate an extensive catalytic chain reaction

Cl + O3 → ClO + O2

ClO + O → Cl + O2

leading to the net destruction of O3 in the stratosphere. This chain reaction can be diverted through reaction of ClO with NO, which interconnects the NOx and ClOx catalytic cycles. The Cl‐ClO chain is interrupted by the reaction of Cl with methane or other hydrogenous species to form HCl, and it is renewed by reaction of OH with HCl. One‐dimensional diffusion calculations show that present O3 depletion levels resulting from the presence of the chlorofluoromethanes are of the order of 1%. This depletion would increase up to 15 or 20% if the chlorofluoromethane injection were to continue indefinitely at present rates. Furthermore, the calculations show that the full stratospheric effect of the photodissociation of CF2Cl2 and CFCl3 is not immediately felt after their introduction at ground level because of the delay required for upward diffusion to the 25‐ to 30‐km level. If the atmospheric injection of these compounds were to terminate only after causing an observable depletion of stratospheric ozone, the depletion would intensify for sometime thereafter and would remain significant for a period of a century or more.
Some basaltic and andesitic gases
Authors: Anderson A. T.
Published: February 2008

Igneous gases escape from igneous rocks and magmas. They may originate by effervescence or they may bubble through the melt from an external source. In this paper I review data (mostly post‐1963) on H2O, B, CO2, N2, O2, Ne, sulfur gases, Cl, Ar36, Ar40, Br, Kr, I, Xe, Hg, and Rn. The compositions of volcanic gases are compatible with solubility and melt composition for H2O, Cl, and possibly sulfur gases. For other gases there are either inadequate data or conflicting data (CO2). Volcanic gas emitted at surface pressure is generally very rich in H2O because H2O is the principal gas dissolved in most melts. CO2‐rich volcanic gases can be explained by separation of gas from melt at pressures of a few tens of atmospheres and by effervescence of magmas with high ratios of dissolved CO2/H2O (mostly alkaline basalts). There is no single magmatic gas phase. Glassy basalts from the sea floor have substantial concentrations of both active and noble gases. The concentrations of H2O and Cl correlate with the alkali concentration (especially K2O). The recorded concentrations of H2O and CO2 in sea floor basalts are far below saturation at 500 atm. Yet the basalts contain tiny vesicles. It appears likely that magmatic gas of basalts at sea floor pressure is 60% SO2, 20% H2O, 10% H2S, and 10% CO2 at 1200°C. The concentrations of Cl and H2O in basaltic and andesitic glasses trapped in large crystals in pumices from continental margins are about 10 times those of deep sea basalts. Detailed relationships suggest that at least some andesitic magmas develop in vapor‐saturated environments. The restored or potential concentrations of H2O and Cl in andesitic magmas I estimate by allowing for vapor loss during production of andesite from a basaltic precursor. I use the restored concentrations as a basis for estimating the rate of igneous outgassing in island arcs and continental margins. The inferred rates of outgassing are such that the present quantities of gaseous elements in seawater and sediment would be exhaled in 109 to 1010 years for H2O, Cl, Br, S, I, and Hg. The rates of outgassing of CO2 from Kilauea volcano and of SO2 from Pacaya exceed the rate which could be maintained by outgassing of erupted lava. These relations imply the existence of a larger source of these gases than that of the volcanic rocks. Apparently, large subsurface reservoirs of melt discharge gas out of the volcanic vents. It seems probable that volcanic rocks are generally volumetrically small portions of subsurface reservoirs which may be vapor‐saturated. Such a condition has major implications for crustal evolution, the origins of volcanic rocks, eruption mechanisms, and hydrothermal ore deposits.
Wave‐particle interactions in the magnetosphere and ionosphere
Authors: Thorne Richard Mansergh
Published: February 2008

Two distinct aspects of the interaction between waves and particles in the earth's magnetosphere and ionosphere were discussed at the Yosemite Conference on Magnetosphere‐Ionosphere Coupling; these will be briefly reviewed. Intense field‐aligned currents flow between the ionosphere and magnetosphere at auroral latitudes. Under certain conditions these currents can become unstable, permitting potential drops to be established along the field lines. The present status of experimental evidence favoring such parallel electric fields is somewhat controversial. Theoretical models for their origin invoke regions of anomalous resistivity or electrostatic double layers. To date it is impossible to distinguish between these alternatives on the basis of experimental data. The nonadiabatic behavior of magnetospheric ring current particles during geomagnetic storms is largely controlled by wave‐particle processes. During the storm main phase, intense fluctuating convection electric fields are responsible for injecting trapped particles into the outer radiation zone. The outer radiation zone also moves in closer to the earth following the storm time compression of the plasmapause. Simultaneous pitch angle scattering by higher‐frequency plasma turbulence causes precipitation loss near the strong diffusion limit throughout the outer magnetosphere. During the storm recovery phase the plasmapause slowly moves out toward its prestorm location; energetic particle loss at such times appears to be dominated by cyclotron resonant scattering from electromagnetic turbulence.
Theoretical models of magnetic field line merging
Authors: Vasyliunas Vytenis M.
Published: February 2008

Models of magnetic field line merging that consider processes in a limited region around the magnetic X line, within which the external magnetic fields are roughly uniform and antiparallel, are reviewed. Part 1 describes the concept of magnetic merging and then considers the models based on a hydromagnetic approach. The models developed by Sweet and Parker, by Petschek, and by Sonnerup and Yeh and Axford are shown to be fundamentally consistent, representing different aspects of the same problem. The model of Sweet and Parker describes the small region around the neutral line where magnetic field diffusion is the dominant process. The inclusion of inertial as well as finite resistivity effects allows an extension of their model to collisionless plasmas. Petschek's model represents a system with a boundary condition of uniform field at the sides; it has been extended and formulated in a mathematically precise manner. The nonsingular model of Sonnerup and of Yeh and Axford has special boundary conditions at the sides producing localized slow mode MHD expansion fans in the external flow; the singular models and the compressible similarity models are physically unrealizable. The maximum merging rate corresponds to flow into the diffusion region at the local Alfvén speed, which, however, can be made arbitrarily large by slow mode MHD expansion if suitable boundary conditions are present.
The continental tectosphere
Authors: Jordan Thomas H.
Published: February 2008

Studies of free oscillations and body wave travel times have established that the one‐way vertical S wave travel times through the upper mantle average about 5 s greater for oceans than for stable continental regions. This datum and the pure path dispersion data make it necessary to invoke significant differences between continental and oceanic shear velocity structures to depths exceeding 400 km. An analysis of the constraints on thermal profiles, including the constraints recently established by empirical geothermometry, indicates that temperature differences between the ancient shields and the ocean basins also extend deep into the mantle, with shields characterized by thermal gradients that are superadiabatic above 400 km. To at least 400‐km depth beneath shields the dominant mechanism of heat transport is conduction, not advection. It is concluded that this entire region, termed here the continental tectosphere, translates coherently during lateral plate motions. It is proposed that the superadiabatic vertical temperature gradients beneath shields and the horizontal temperature gradients within the transition from shield to oceanic structures are stabilized by compositional gradients, the subcontinental mantle consisting of intrinsically less dense material. The existence of deep continental structure is apparently consistent with the dynamics of plate motions. It suggests that convection is not confined to the earth's upper mantle.
Introduction to the Report on Geodesy
Authors: Mueller Ivan I.
Published: February 2008

The following articles summarize the achievements of the U.S. geodetic community during the years 1971–1974, between the General Assemblies of the IUGG. During this quadrennium, American geodesy made the first transition from meeting the traditional needs of surveying and mapping to catering to the geophysical and oceanographic communities, trying to satisfy their ever‐increasing appetite for ultraprecise surveys.

Major achievements included the completion of the National Geodetic Satellite Program, probably the largest single effort to establish a global network of satellite tracking stations and the determination of the earth's gravity field to an accuracy heretofore not available; the proliferation of Doppler satellite observations for control surveys and polar motion determination; the affirmation of lunar and satellite laser ranging and very long base line interferometry (VLBI) as the best available geodetic tools for global geophysical investigations, such as plate tectonics, polar motion, and the earth's rotation; the development of the satellite‐borne altimeter and the establishment of its feasibility for a better definition of the surface of the oceans; major improvements in the knowledge of the dynamics, size, shape, gravity field, and topography of the moon and some of the major planets; the extension of the high‐precision transcontinental traverse to a total of 9000 km, only 10% of the network remaining for completion in 1975; the start of the readjustment of the North American Datum, in collaboration with Canada, Mexico, and Denmark; and an unprecedented cross‐fertilization between geodesy, solid earth geophysics, oceanography, and dynamical astronomy.
Marine geodesy
Authors: Mourad A. G.
Published: February 2008

Marine geodesy is concerned primarily with the determination of geodetic positions, control at sea, and the ocean geoid. The determination of these parameters is not an end in itself but a means to solving various ocean‐related problems, e.g., surveying and mapping, environment, resources development, mean sea level, systems calibration, and evaluation and ocean physics applications. This report summarizes the marine geodetic activities in the United States since the 1971 International Union of Geodesy and Geophysics meeting. These activities are discussed under the following topics: (1) geodetic positions and control and (2) ocean geoid determination.
Effect of atmospheric nuclear explosions on total ozone
Authors: Bauer Ernest , Gilmore Forrest R.
Published: February 2008

This paper reviews the current knowledge of the depletion of stratospheric ozone due to the injection of oxides of nitrogen from thermonuclear explosions in the atmosphere, discussing the theoretical calculations, the ground‐based observations of global ozone after the 1961–1962 multimegaton test series, and the satellite observations of local effects following an individual French thermonuclear explosion in 1970. There is general agreement on the approximate NO production per megaton yield and on the subsequent ozone depletion expected to be associated with the various nuclear tests. The latter depletion, as calculated principally by Chang and Johnston, extending earlier work of Foley and Ruderman, is small—typically of the order of several percent during a reasonable observation interval—and lies within the probable error of available ozone measurements. Thus while there is no real disagreement between prediction and observations and no reason to doubt the validity of the predictions of ozone depletion, existing atmospheric data do not provide a statistically significant demonstration of the catalytic destruction of ozone by oxides of nitrogen.
Sources and sinks for atmospheric N2O
Authors: McElroy Michael B. , Elkins James W. , Wofsy Steven C. , Yung Yuk Ling
Published: February 2008

Observations of the temporal and spatial distribution of N2O in solution are not yet sufficient to permit quantitative assessment of the role of the ocean in the budget of atmospheric N2O. Consideration of the global nitrogen cycle suggests that the land should be the primary source of N2O. The gas is removed in the atmosphere by photolysis and by reaction with O(¹D), and there may be additional sinks in the ocean.
Atmospheric chemical kinetics data survey
Authors: Anderson Larry G.
Published: February 2008

Chemical kinetic data for more than 250 gas phase reactions of possible importance in the atmosphere have been reviewed. The results of available evaluations of the rate data are tabulated with selected recent experimental values. A preferred value for each reaction rate constant is indicated. A brief discussion of some of the experimental techniques that have been utilized is also given. This discussion emphasizes the capabilities and limitations of the individual techniques. The tables should be of use to those interested in modeling the complex chemical processes of the stratosphere, troposphere, or the urban atmosphere.
Secondary and tertiary creep of glacier ice as measured by borehole closure rates
Authors: Paterson W. S. B.
Published: February 2008

Published and previously unpublished measurements of closure rates of five boreholes in polar ice caps are reviewed. The data cover effective shear stresses between 0.15 and 1.0 MN m−2, temperatures between −16° and −28°C, and strains up to 2.2. Curves of strain at the borehole wall (logarithm of the ratio of hole diameter to its initial diameter) against time show a stage of constant closure rate corresponding to secondary (steady state) creep of the ice followed by accelerating closure rate attributed to recrystallization of the ice (tertiary creep). Curves for low stresses also show an initial transient stage of decreasing closure rate. The onset of tertiary creep is largely determined by the strain; critical values range from 0.03 to 0.10, and the lower the temperature, the higher the critical value. Secondary creep rates in the different boreholes are consistent with each other; the data yield a creep activation energy of 54 kJ/mol and a flow law index close to 3. The borehole data reduced to a common temperature of −22°C are compared with the results of two laboratory experiments at this temperature. For a given stress the strain rates measured by Steinemann (1958a, b) are 2–3 times those in the boreholes, and for the experiments of Barnes et al. (1971) the factor is about 8. Differences between laboratory and glacier ice, probably in grain size, may explain the differences between the borehole data and the results of Steinemann. Some evidence is presented that the creep rates measured by Barnes et al. at this temperature may contain a significant component of transient creep; this might account for the large difference between their results and those of Steinemann. The ratio of tertiary to secondary creep rate increases approximately linearly with the strain. No steady state tertiary creep rate is observed even at a strain of 1.5, at which point the ratio of tertiary to secondary creep rate is about 10. However, the ice is not strained uniformly during borehole closure. Even if recrystallization has been completed in the ice near the borehole wall, the ice further away, having been strained less, may still be recrystallizing. This may account for the failure to observe steady state tertiary creep. Near the bottom of one borehole, creep rates (tertiary) are about 4 times those in the ice immediately above. The boundary between the two deformation regions corresponds closely to the boundary between ice deposited during the Wisconsin glaciation and ice deposited since that time. The crystals in the Wisconsin ice are smaller, much less variable in size, and more nearly equidimensional than those elsewhere. Moreover, the Wisconsin ice has a much higher microparticle content and a much lower content of salts of marine origin. It is suggested that one or more of these differences make the Wisconsin ice ‘softer’ than the remainder of the ice. The decrease in grain size is considered to be the most likely factor.
Importance of physical dispersion in surface wave and free oscillation problems: Review
Authors: Kanamori Hiroo , Anderson Don L.
Published: February 2008

Physical dispersion resulting from anelasticity is investigated from the point of view of linear viscoelastic models and causality relations. It is concluded that inasmuch as Q in the earth's mantle is nearly independent of frequency, at least in the seismic frequency band, a dispersion relation in the form of C(ω) = C(ωr)[1 + (1/πQm) In (ω/ωr)] must be used for correcting the effect of physical dispersion arising from anelasticity. (Here C(ω) is the phase velocity of either body waves, surface waves, or free oscillations, ω is the angular frequency, ωr is the reference angular frequency, and Qm is the path average Q for body waves or Q of a surface wave or a mode of angular frequency ω; for surface waves and free oscillations, C(ωr) should be understood as the phase velocity at ω computed by using the elastic moduli at ω = ωr.) The values of Q outside the seismic frequency band affect mainly the absolute value of the phase velocity but do not affect significantly the relative dispersion within the seismic frequency band. Even if the microscopic mechanism of attenuation is nonlinear, this dispersion relation can be used if departure from elasticity is relatively small, so that the signal can be approximated by a superposition of propagating harmonic waves. Since surface wave and free oscillation Q is 100–500 for fundamental modes, a correction of 0.5–1.5% must be made for joint interpretation of body wave and surface wave data. This correction is nearly 1 order of magnitude larger than the uncertainties associated with these data and are therefore very significant. When this correction is made, the discrepancy between the observed surface wave phase velocities and free oscillation periods and those predicted by the Jeffreys or Gutenberg model becomes much smaller than has previously been considered.
Satellite observations of polar, magnetotail lobe, and interplanetary electrons at low energies
Authors: Mizera P. F. , Fennell J. F.
Published: February 2008

Low‐altitude satellite observations of the low‐energy electron fluxes that populate the polar regions are summarized and classified into two groups: class 1, the very low intensity distributions, and class 2, the more intense, often structured distributions observed during magnetically disturbed conditions. High‐altitude observations of electron fluxes, including the solar wind and the tail lobes, are presented to suggest that class 1 observations are the result of direct access of interplanetary electrons through the lobes into the polar regions. Class 2 observations may be due in part to magnetospheric processes.
Goals and status of the International Reference Ionosphere
Authors: Rawer K. , Bilitza D. , Ramakrishnan S.
Published: February 2008

Under the supervision of an international steering committee, basic data for establishing ionospheric profiles were gathered, critically reviewed, and used for establishing vertical profiles of the most important parameters of the ionosphere, namely, electron density, electron and ion temperature, and (positive) ion composition. The data sources used are described in detail, their reliability and coverage is discussed, and remaining problems are reviewed. The International Reference Ionosphere (1978) is to be published soon by URSI in the form of computer programs.
Dynamics of the thermosphere at high latitudes
Authors: Straus Joe M.
Published: February 2008

In contrast with the low‐latitude thermosphere, which derives most of its energy from the absorption of solar extreme ultraviolet radiation (EUV), the energy balance of the high‐latitude thermosphere is dependent on processes of magnetospheric origin. Particles precipitating from the magnetosphere deposit energy in the lower thermosphere throughout the high‐latitude region. Processes such as magnetospheric convection drive bulk motions of charged particles; both energy and momentum are transferred to the neutral atmosphere by collisions between neutral constituents and these charged particles. The present paper presents a review of both observational and theoretical investigations of the response of the neutral upper atmosphere to processes which are unique to high latitudes. It also describes in some detail recent three‐dimensional model calculations dealing with the effects of magnetospheric convection on thermospheric dynamics. The three‐dimensional calculations, which treat the effects of viscosity, ion drag, the Coriolis force, thermal conduction, and solar EUV heating, as well as Joule and particle precipitation heating, allow an assessment of the relative importance of processes characteristic of high latitudes.
The origin of KREEP
Authors: Warren Paul H. , Wasson John T.
Published: February 2008

KREEP is a lunar material having very high concentrations of incompatible elements; its name is an acronym for the incompatibles K, rare‐earth elements (REE), and P. Although a few pristine (endogenously igneous) KREEPy samples were returned from the Apollo 15 and 17 sites, most KREEPy samples are polymict breccias. Most models of KREEP petrogenesis have been based on partial melting of a variety of sources. Such models fail to explain the veritable absence of variations in incompatible element patterns over the sampled portion of the moon. We have defined a KREEP component based on the average composition of Apollo 14 breccias having extremely high concentrations of incompatible elements. Normalization of accurate incompatible data for KREEPy samples from the Apollo 12, 14, 15, 16, and 17 sites to this component virtually always shows no resolvable fractionation (e.g., <10% variation in the La/Lu ratio), whereas partial melting models typically produce larger fractionations (±20–25% in La/Lu) from a factor of 2 difference in degree of partial melting. Required is a single major source that could provide KREEP to widely separated locations on the nearside of the moon. The anorthositic crust of the moon is commonly attributed to the flotation of plagioclase on a deep, moon‐wide magma ocean. Fractional crystallization of this magma ocean would have produced large enrichments of incompatibles in a residual liquid. No other plausible major source of incompatibles has been proposed. We borrow the German prefix ur—meaning primeval and designate this residual liquid ‘urKREEP.’ We propose that all KREEPy rocks originated by dilution of urKREEP with crustal or mantle materials during assimilation, or zone‐refining (pristine samples), or impact‐induced brecciation (breccias and melt rocks). The formation of urKREEP cannot be dated precisely. Correction of breccia Rb‐Sr model ages for Rb loss or gain during the early intense bombardments yields ages that cluster in the range 4.4–4.5 Gy. This implies that crystallization of the magma ocean was essentially complete at this time and is in general agreement with U‐Pb evidence indicating crustal formation at 4.4 Gy. Assuming that the moon had the composition of an H‐group chondrite depleted in Fe‐Ni and FeS and that half the incompatibles fractionated into materials other than urKREEP, the thickness of a moon‐wide urKREEP layer was <2 km. Thorium concentrations determined by gamma ray spectroscopy indicate that about 4% of the incompatibles in an H chondritic moon are now in the outermost kilometer.
Paleomagnetic records of geomagnetic field reversals and the morphology of the transitional fields
Authors: Fuller M. , Williams I. , Hoffman K. A.
Published: February 2008

The reversal of polarity of the earth's magnetic field is one of the most remarkable features of our planet's magnetism. A proper documentation of reversal phenomena may therefore be expected to yield useful ideas about the generation of the field. Reversals are also of interest to geologist; they have given rise to a new stratigraphy, allowed us to map the history of the ocean basins and to trace the movement of plates. The subject of reversals was comprehensively reviewed by Bullard (1968) and again more recently by Jacobs (1976). In this paper, we review paleomagnetic records of reversals and attempts to determine the geometry of transitional fields.
Double layers and electrostatic shocks in space
Authors: Goertz C. K.
Published: February 2008

In recent years, much evidence has been accumulated which supports the existence of spatially limited regions of strong electric fields (>100 mV/m) parallel to the magnetic field. Evidence which will be reviewed comes from rocket measurements, satellite observations, and plasma cloud releases above the polar ionosphere. The most plausible explanation of such structures is provided by the concept of double layers or electrostatic shocks, which are double layers moving in relation to the plasma. We also review some recent laboratory investigations of double layers which show that double layers can exist for long periods of time. The production of these structures requires large currents. The theory of double layers has so far concentrated on the nature of stationary double layers, and theoretical proof is now available that the Vlasov equation allows for stationary double layer solutions in one or two dimensions. A full three‐dimensional treatment is not available. Necessary conditions for the existence of double layers (generalized Bohm criterion), relations between thickness and strength of the layer, and the field signature are studied. Comparison with observations reveals many similarities, but major problems (e.g., lack of magnetic field alignment of accelerated particles and particle heating in contrast to free acceleration) remain. All double layers observed so far are parts of a large‐scale electric circuit carrying a current driven by a generator and dissipated in a load. Thus the whole circuit must be analyzed in order to understand properly the generation and nature of double layers.
Minor constituents in the stratosphere and mesosphere
Authors: Hudson R. D.
Published: February 2008

This paper is a brief survey of the research on the role of the trace constituents in the stratosphere and mesosphere that was published between 1975 and 1979. During this period of time the emphasis shifted away from the role of the nitrogen oxides in the stratosphere to the role of the chlorine oxides and the hydrogen oxides. A great deal of progress was reported in the understanding of the natural stratosphere and its response to anthropogenic perturbations.

This is but a brief review of that portion of the research carried out in the stratosphere and mesosphere which dealt with the role of the trace constituents. The years between 1971 and 1974 were reviewed by Cicerone (1975). This review is limited to the years 1975 to 1978. The increase in interest in research in the stratosphere noted by Cicerone has continued, spurred by the public concern on the effects of the chlorofluoromethanes on stratospheric ozone. Changes in reaction rates have tended to alleviate concerns over increases in the nitrogen oxides, but not, it should be noted, removed them completely.
Active experimentation with the ionospheric plasma
Authors: Walker James C. G.
Published: February 2008

Considerable effort in recent years has been directed towards experiments that actively perturb the ionospheric plasma, producing a measure of control over its properties (locally and ephemerally) and also exciting a variety of plasma instabilities. Space vehicles have been used for the release in the ionosphere of exotic chemicals and for the operation in the ionosphere of charged particle accelerators. Ground based radio transmitters at VHF perturb the magnetosphere, while transmitters at HF and higher frequencies perturb the ionosphere. This paper discusses the last technique, often called ionospheric heating, which uses powerful transmitters to change electron densities and temperatures and to excite a variety of parametric instabilities in the ionospheric plasma. Recent work in this area is cited and a qualitative description is given of the physical mechanisms that underlie many of the observed phenomena. Bibliographies of recent work are included for the other three techniques of active experimentation.
Current systems in the Earth's magnetosphere: A Review of U.S. Progress for the 1975–1978 IUGG Quadrennial Report
Authors: Potemra T. A.
Published: February 2008

Electric currents play a fundamental role in a variety of magnetospheric phenomena and a system of large‐scale currents defines the shape of the magnetosphere itself. Currents are believed to drive a variety of complicated plasma instabilities, both in the near‐earth auroral region and in distant magnetospheric regions. The purpose of this report is to identify and summarize the significant contributions to the understanding of electric currents during the years 1975–1978. Although this is intended to be a report of US achievements, the contributions of researchers from other countries are frequently cited, because they are tightly interwoven with research done in this country.
Computer modeling in low temperature geochemistry
Authors: Potter Robert W.
Published: February 2008

During the 1975–78 quadrennium, the field of low‐temperature geochemistry advanced greatly from a synergistic relation combining increasing utilization of computer science with other endeavors in geochemistry. The rapid growth in computer programming and its applications to modeling and predictions of natural phenomena has generated a rapid growth of sophisticated experimental methods to check the validity of the computer models and increased the data base necessary for calculation and comparison of the models. Evolution of this relation can be seen as an extension of trends that had been developing during the past decade. Application of thermodynamics to the interpretation of natural geochemical systems (Garrels and Christ, 1965) was enhanced by use of computers, enabling more complex and relevant systems to be investigated.