bluuebunny/crossref_metadata_2025 huggingface dataset:
Long‐range prediction of the zonal westerlies and some problems in data analysis
Authors: Brier Glenn W.
Published: February 2008

Long‐range weather forecasts, based on cycle analysis, have been attempted without much success. Recent research suggests the possibility of making use of lunar cycles or the quasi‐biennial oscillation (QBO) observed in atmospheric phenomena. Investigation of the sea‐level zonal index for the northern hemisphere, using monthly mean data, shows the existence of the QBO. But in addition to QBO, there is a more pronounced signal that can be interpreted in terms of a general soli‐lunar tidal framework. One reason this signal was not detected previously is due to the reduction in amplitude and the phase distortion produced by summarizing the data by monthly periods centered only at the midpoint of the calendar month. This phenomenon, referred to as the aliasing problem, should be considered in the analysis of all geophysical data (such as tide data) in which periodic components, even of low amplitude, can exist.
The geomagnetic tail
Authors: Ness Norman F.
Published: February 2008

The solar wind flows past the earth and stretches the geomagnetic field behind it, forming a tail to the magnetosphere. Magnetic‐field lines are directed toward the sun in the upper half of the tail and oppositely directed in the lower half. The separation region where the field reversal takes place is occupied by an enhanced plasma flux, which keeps the oppositely directed fields from annihilating themselves. Satellite observations have also found intense transient electron fluxes within the plasma sheet region. Although the role of the tail in the magnetic substorm phenomena is not yet clear, during the main phase of a magnetic storm the tail appears to contribute significantly to the dynamical distortion of the magnetosphere, the decrease of the horizontal geomagnetic field on the earth's surface, and the lowering of the latitude of the trapping boundary. Although the tail shows a well‐defined theta geometry at 80 RE, lunar orbit = 60 RE, it has not been clearly observed at 500 and 1000 RE. A radial gradient of the magnetic field magnitude is consistent with merging occurring at the neutral sheet and with the tail length being of the order of 100–200 RE. The basic mechanism for terminating the tail, as well as the means for momentum transfer on its boundary forming the tail, are not yet established. This paper reviews past experimental and theoretical models of the geomagnetic tail, outlines our present knowledge, and identifies the current major problems associated with its dynamics.
Particle fluxes in the outer geomagnetic field
Authors: Vernov S. N. , Gorchakov E. V. , Kuznetsov S. N. , Logachev Yu. I. , Sosnovets E. N. , Stolpovsky V. G.
Published: February 2008

The outer geomagnetic field comprises the outer radiation belt, consisting of electrons with energies of 104–107 ev, and the unstable radiation zone. The outer radiation belt is bounded on its inner side by a gap, which is at various times located at a distance of 2.2–3.5 RE and in which a considerable precipitation of electrons from radiation belts occurs, possibly owing to a high intensity of electromagnetic waves. The boundary separating the outer radiation belt from the unstable radiation zone is at λ ∼ 71° and ∼9 RE in the equatorial plane on the sunlit side, and at 7–8 RE in the equatorial plane on the nightside. Beyond this, the unstable radiation zone extends out to the magnetosphere boundary and up to λ ∼ 77° on the sunlit side, and out to 14–15 RE on the nightside. The relatively rapid electron intensity variations with periods of 1–7 days are essentially absent at distances less than that of the outer belt but are distinctly seen in the outer belt. In the unstable radiation zone the intensity of electrons with energies of the order of 105 ev changes by several times, and good correlation is observed with the increase in Kp. Analysis of the outer belt data shows that this belt is formed partly by electron diffusion into the magnetosphere (like the belt of protons with energies of 105–107 ev) and partly by the simultaneous acceleration of electrons at various distances from the earth.

A comparison of electron intensity changes with the solar activity cycle shows little or no correlation for electrons with Ee > 40 kev. The intensity of electrons with Ee > 500 kev has changed significantly; in 1964 it was 30 times lower than in 1959. The absence of significant dependence of the diffusion coefficients for electrons with E ∼ 104–105 ev on the phase of the solar activity cycle shows that the relatively weak magnetic disturbances that do not change with the phase of the cycle are of major importance in diffusion. This suggests that these magnetic disturbances appear at great distances from the sun because of the instabilities of plasma itself and, therefore, that they depend little on solar activity.
Interplanetary dust measurements near the Earth
Authors: Bandermann L. W. , Singer S. Fred
Published: February 2008

The impact of dust particles on space vehicles near the earth gives important information about interplanetary dust. Satellite impact measurements have been made with two types of detectors: acoustic and penetration detectors. These types of detectors correspond to momentum and energy restrictions, respectively, on the impact rate of dust. The early acoustic data showed a greatly enhanced rate near the earth, which suggested that there was a high concentration near the earth (‘dust belt’). Quite to the contrary, from theory no sensible enhancement in concentration can be derived but, instead, a moderate enhancement in impact rate, depending on the geocentric velocity of the particles. The dust belt would therefore exist only as a consequence of the measurement technique.

Here we review the theory that allows us to calculate the following, for a given geocentric velocity of dust particles and a distribution of velocities (all isotropic) : (1) the concentration; (2) the flux; and (3) the impact rate (momentum‐ and energy‐limited) at various distances from the earth and for various detector velocities so as to bracket all possible experimental situations. With the use of these results, it is then possible to analyze and compare results from different experiments. Of the experimental data reviewed, both U. S. and Russian, only certain are selected for a more detailed analysis. The theory accounts well for the observed penetration data in space vehicles flown near the earth and the moon; they lead to a zodiacal dust model similar to van de Hulst's model, having a particle population predominantly in the micron and decamicron size range (rather than submicron), with a flat (rather than steep) size distribution, and with geocentric velocities of 5 to 15 km/sec.

A theoretical analysis is also presented for a nonisotropic velocity distribution. This is of practical importance for very small particles, which are partly supported by solar radiation pressure and therefore develop a streaming velocity with respect to the earth; in addition, the earth itself introduces an asymmetry, since its orbital velocity varies throughout the year. Numerical results are given for predicted asymmetries in concentration, influx of dust into the atmosphere, and in the satellite impact rates. Impact rates from some satellites exhibited such asymmetries, and these cases support the hypothesis that the heliocentric dust orbits have small inclination and small eccentricity. These results are inconclusive because the data are scant; a systematic analysis of all available impact data with respect to asymmetries is needed.
Reflection of acoustic waves from a continuously varying interfacial region
Authors: Phinney Robert A.
Published: February 2008

Reflection‐transmission problems for plane waves can be analytically solved in a restricted number of special cases for which asymptotic connection formulas exist. The technique is demonstrated for the case of a parabolic barrier. A method of Epstein's, which makes use of the properties of hypergeometric functions, can be used to obtain solutions for a variety of transitional structures. This method is taken from the field of ionospheric radio‐wave propagation and is adapted to the acoustic problem without neglect of the density gradient. The solution for a monotonic transitional zone is obtained, and the behavior of the subcritical reflection is discussed, with reference to the inner core reflection as an example.
Contributions of theoretical seismograms to the study of modes, rays, and the Earth
Authors: Landisman M. , Usami T. , Satô Y. , Massé R.
Published: February 2008

Theoretical seismograms, for both simplified and realistic models of the earth, can be calculated and analyzed to learn the relations between free oscillations and traveling waves. These studies can help to clarify the influence of the physical properties of the earth upon the generation, propagation, attenuation, and dispersion of elastic waves. Principal results include the equivalence of mantle and crustal Rayleigh waves to the fundamental radial modes of spheroidal free oscillations and the equivalence of G waves and ordinary Love waves to the fundamental radial modes of torsional free oscillations. In contrast, the higher radial modes produce all the direct, reflected, refracted, and diffracted body phases, as well as the higher‐mode surface waves. Stoneley‐wave propagation along the core‐mantle boundary introduces a large number of interesting phenomena into the propagation of the spheroidal overtones. The confinement of the Stoneley modes to the vicinity of this boundary is responsible for the discontinuities in the spectra and the relative difficulty in the excitation of long‐period P and SV diffracted arrivals, as compared with the corresponding SH phases. The trapping of body‐wave energy for sources within a velocity inversion is demonstrated. The particle motion ratio at the surface may be as useful as phase velocity in the understanding of the physical properties beneath a recording site; realistic curves of this parameter are presented for a wide range of periods and radial orders.
Composition and dynamics of the solar wind plasma
Authors: Hundhausen A. J.
Published: February 2008

Although the coronal origin of the interplanetary plasma implies some general connection between solar and solar wind properties, strong evidence for specific relationships has emerged only recently. Three such relationships will be reviewed here; their observational and theoretical foundations will be discussed, as will their use in determining solar properties from solar wind observations. The first of these involves solar and interplanetary chemical compositions; emphasis will be placed on the implied concentration of helium (and other elements heavier than hydrogen) in the corona. The second relationship to be explored involves the effects of coronal and interplanetary dynamical processes on the properties of the undisturbed solar wind. Arguments for and against the extension of the basic coronal heating process well out into interplanetary space will be developed. The final relationship involves solar activity and properties of the disturbed solar wind. Attention will be focused on interplanetary shock waves produced by solar flares and on implications for the coronal deposition of energy released in flares.
Radial diffusion of trapped particles and some of its consequences
Authors: Walt Martin
Published: February 2008

The nonadiabatic motion of geomagnetically trapped particles across L shells has been inferred from the measured distributions of trapped particles and has also been observed directly in a number of cases. This type of motion has important influences on both the steady‐state structure and the dynamics of the radiation belts. The characteristics of the radial motion have been evaluated and are generally consistent (within an order of magnitude) with the radial diffusion expected from fluctuations in the magnetospheric electric and/or magnetic fields. However, the complexity and variability of the observed phenomena suggest that several basic processes are acting simultaneously, and further efforts are needed to identify specific mechanisms.
Large‐scale properties of the interplanetary magnetic field
Authors: Schatten Kenneth H.
Published: February 2008

Our knowledge of the large‐scale properties of the interplanetary magnetic field is reviewed. The early theoretical work of Parker is presented, along with the observational evidence supporting his Archimedes spiral model. The variations present in the interplanetary magnetic field from the spiral angle are related to structures in the solar wind. The causes of these structures are found to be either nonuniform radial solar wind flow or the time evolution of the photospheric field. The coronal magnetic models are related to the connection between the solar magnetic field and the interplanetary magnetic field. The direct extension of solar field‐magnetic nozzle controversy is discussed, along with the coronal magnetic models. The effect of active regions on the interplanetary magnetic field is discussed with particular reference to the evolution of interplanetary sectors. The variation of the interplanetary magnetic field magnitude is shown throughout the solar cycle. The percentage of time the field magnitude is greater than 10 γ is shown to closely parallel sunspot number. The suggested influence of the sun's polar field on the interplanetary field and alternative views of the magnetic field structure out of the ecliptic plane are presented. In addition, a variety of significantly different interplanetary field structures are discussed.
Seismological evidence for anomalous structure of island arcs with special reference to the Japanese region
Authors: Utsu Tokuji
Published: February 2008

Evidence indicating lateral heterogeneity in the deep structure of island arcs has been collected from seismological literature. Abundant evidence from seismological studies in Japan during the last fifty years generally supports the large‐scale anomalous structure beneath this typical island‐arc region, i.e., the existence of a high‐Q, high‐velocity zone about 100 km thick that dips from the vicinity of the trench beneath the arc to a depth of several hundred kilometers, and two low‐Q, low‐velocity zones in the upper mantle on the inner (continental) and outer (oceanic) sides of this dipping zone. Most of the seismic activity is confined to this dipping zone and to the crust near and on the inner side of the volcanic belt. In other island‐arc regions, such as Kurile‐Kamchatka, Indonesia, Tonga‐Kermadec, and New Zealand, a number of seismological studies have indicated the existence of similar anomalous structure. At present, more detailed, more accurate determination of the configuration and physical parameters of these anomalous zones by seismological techniques is in progress, providing important information for understanding the global tectonic process and the origins of regional geophysical and geological features found in island‐arc regions.
Energy‐momentum tensor for linearized waves in material media
Authors: Jones Walter L.
Published: February 2008

Within the WKB (Wentzel‐Kremers‐Brillouin) or geometrical optics approximation, a wave packet can be taken to be made up of phonons transporting energy, momentum, and angular momentum. The energy‐momentum tensor formalism provides single generalized expressions for the conservation of these quantities and for the exchange of energy and momentum between the wave packet and the background medium. The formalism also leads to a clearer interpretation of wave energy and wave momentum; in many problems of geophysical interest, it is necessary to introduce modified concepts of the momentum density of a packet.
Hydromagnetic oscillations of the Earth's core
Authors: Hide R. , Stewartson K.
Published: February 2008

The dispersion relationship for hydromagnetic waves in a rotating system indicates that, under plausible assumptions concerning the strength of the toroidal magnetic field in the earth's liquid core, the periods associated with slow planetary‐scale waves in the core would be comparable with the characteristic time scales found in the geomagnetic secular variation, decades to centuries, and it now seems likely that such waves could also play a key role in the production of the geomagnetic field by the ‘dynamo’ process. Attempts to interpret specific features of the field in terms of hydromagnetic oscillations of the core (or of any other type of fluid motion, for that matter) have not yet proved entirely successful, for they encounter serious and in some cases fundamental mathematical difficulties. The present paper reviews theoretical work on free hydromagnetic oscillations of a bounded rotating fluid in the context of the geomagnetic problem.
Formation of ordinary chondrites
Authors: Wasson John T.
Published: February 2008

Most of the chemical and mineralogical properties of the ordinary chondrites were established by processes that occurred in the solar nebula during a short time span near the time of formation of the solar system. Four separate and distinct fractionation events appear to have been involved in their formation from more primitive material of mean solar‐system composition. In order of occurrence these were (1) a refractory‐element fractionation, which resulted in the lower Mg/Si, Ca/Si, Ai/Si and other refractory‐element/Si ratios relative to Cl chondrites; (2) a siderophilic‐element fractionation, which produced the monotonic reduction of siderophilic‐element/Si ratios as one proceeds from the H group toward the LL group and the variation in ratios of one siderophilic element to another through this sequence; (3) a fractionation of slightly volatile elements (such as Cu, Ga, and Ge), probably during chondrule formation; and (4) a fractionation of highly volatile elements, probably by thermal metamorphism while the chondritic material was stored in planetesimals of the meter‐to‐100‐meter size range. In each of the four cases the most plausible fractionation mechanism involves a separation of gases from solids. The ambient temperature in the planetary portion of the solar nebula during the formation of these chondrites appears to have been characterized by two maximums.
Geomagnetic indices
Authors: Rostoker Gordon
Published: February 2008

The purpose of this review is to outline the definition and method of derivation of the indices of geomagnetic activity that are most commonly used at present. The first part of the review presents the methods of derivation of Kp, ap, AE, and Dst; the second part involves a discussion of the strengths and weaknesses of each index. It is shown that the distribution of magnetic observatories whose data are used in the production of the indices strongly influences the quantitative reliability of the indices in varying degrees. Furthermore, it is found that, in general, indices are only capable of defining the lower limit of geomagnetic activity at any given time. It is concluded that indices should only be used in statistical studies of solar‐terrestrial interactions; their use in the study of individual events is generally not advisable.
High‐energy proton radiation belt
Authors: White R. Stephen
Published: February 2008

The experiments and theories to explain the high‐energy protons trapped in the earth's radiation belt are reviewed. The theory of cosmic ray albedo neutron decay injection of protons into the radiation belt is discussed. Radial diffusion and change in the earth's dipole moment are considered along with losses of protons by ionization and nuclear collision. It is found that the measured albedo neutron escape current is sufficient to supply trapped protons above 30 Mev. The theoretical calculations of the trapped protons are in agreement with the measurements for L ≤ 1.7 both on and off the equator. Although it appears that diffusion of solar wind protons is responsible for most of the protons less than 30 Mev, additional measurements of the angular distributions and fluxes of low‐energy neutrons are required to determine the contribution of the cosmic ray albedo neutron decay source. For L ≥ 1.7, additional trapped proton differential energy measurements should be made before the theory can be adequately tested. It appears that an additional loss mechanism such as pitch angle scattering may be required.
Partial ring current models for worldwide geomagnetic disturbances
Authors: Fukushima Naoshi , Kamide Yohsuke
Published: February 2008

In recent years the longitudinal asymmetry of the ring current in the magnetosphere encircling the earth has been advocated to explain the geomagnetic field variation in middle and low latitudes. Direct observations of particles and magnetic field by means of satellites in the magnetosphere have given some supporting evidence for the existence of partial ring current in the magnetosphere. In this article a review is made of the analysis of low‐latitude geomagnetic variation during magnetic storms or substorms, and the contribution of the partial ring current system to low‐latitude geomagnetic variations is discussed. After examining the magnetic effect of each part of the partial ring current system, i.e., (1) the equatorial ring current in a limited longitude range, (2) the Birkeland (field aligned) current in the magnetosphere connecting the equatorial plane and the ionosphere, and (3) the current in the ionosphere, including an electrojet along the auroral zone or oval, we conclude that the main contribution to the longitudinal ΔH asymmetry in middle and low latitudes (H is the horizontal component of the geomagnetic field) comes primarily from the Birkeland current and neither from the partial ring current in the equatorial plane nor from the auroral electrojet. Therefore the models of partial ring current need to be modified so as not to overemphasize the ring‐form current closure in the equatorial plane. This article explains the reason for the above conclusions and gives some necessary considerations for interpreting the geomagnetic variations in low latitudes during magnetic storms and substorms and on quiet days.
Tracing of high‐latitude magnetic field lines by solar particles
Authors: Paulikas G. A.
Published: February 2008

Recent measurements of solar particles in the energy interval between hundreds of keV and a few MeV have shown that a direct connection exists between a portion of the high‐latitude geomagnetic field and the interplanetary magnetic field. The access window for 300‐keV solar protons that reach the center of the polar cap may be as near as 150 RE in the downstream magnetotail. Solar protons that precipitate into the atmosphere at latitudes near the geomagnetic cutoff enter through the flanks of the magnetosphere and the nearby neutral sheet, possibly within 30 RE of the earth. Comparison of the patterns of auroral particle precipitation with the zones of access of energetic solar electrons and protons indicates that a substantial fraction of the aurora originates on field lines connected to the interplanetary field.
Lunar basin formation and highland stratigraphy
Authors: Howard K. A. , Wilhelms D. E. , Scott D. H.
Published: February 2008

Multiring impact basins, formed after solidification of the lunar crust, account for most or all premare regional deposits and structures expressed in the lunar landscape and for major topographic and gravity variations. A fresh basin has two or more concentric mountain rings, a lineated ejecta blanket, and secondary impact craters. Crackled material on the floor may be impact melt. The ejecta blanket was emplaced at least partly as a ground‐hugging flow and was probably hot. A suggested model of basin formation is that the center lifts up and the rings form by inward collapse during evisceration. The resulting basin is shallow and has a central uplift of the mantle. This results in a central gravity high and a ring low. Later flooding by mare basalt has since modified most near side basins. Highland deposits of plains, furrowed and pitted terrain, and various hills, domes, and craters that were interpreted before the Apollo missions as being volcanic can now be interpreted as being basin related. A province map of the whole moon shows that the relatively young Orientale and Imbrium basins imprinted and rejuvenated much of the moon's surface; older basins must have also. The most primitive cratered surface remaining is mostly on the far side, distant from Imbrium and Orientale and other large relatively young basins. All five lunar landings in the highlands sampled stratigraphic units probably related to basins. Several nearly obliterated basins have been discovered recently, including a deep one on the far side that is as wide as the moon's radius. The presence of these ancient basins suggests that the surface is effectively saturated by basins and that many others were completely destroyed by later impacts. Basin impacts may have churned the lunar crust to large depths.
Modes of magnetohydrodynamic waves in the magnetosphere
Authors: Lanzerotti L. J. , Fukunishi H.
Published: February 2008

Magnetohydrodynamic plasma waves (waves with frequencies less than the local ion gyrofrequency) constitute an important part of the wave frequency spectrum in the earth's magnetosphere and in the solar wind. Such plasma waves also probably play an important role in astrophysical plasmas. The nature and modes of the plasma waves excited in the earth’s magnetosphere are of interest because they are generated and propagate in a plasma environment imbedded in a dipole magnetic field configuration. As such, analyses of the nature of these waves may prove useful in studies of some planetary and stellar plasma environments. Measurements made at conjugate points on the earth's surface and in the magnetosphere between spacecraft altitudes and the ground provide information on the nature of the modes of the magnetohydrodynamic waves excited in the magnetosphere. This paper reviews the available data on wave modes and concludes that near L=4 (corresponding to geomagnetic latitudes ∼60°) the mode for waves in the period range ∼20 to ∼200 s is predominantly odd mode. This may be a fundamental aspect of the physical process that couples the driving source to the resonant field line. For other geomagnetic and frequency ranges there is presently a disappointing dearth of experimental observations.
Observations and theory of the formation of stable auroral red arcs
Authors: Rees M. H. , Roble R. G.
Published: February 2008

A population of protons with energy of some tens of keV, called the ring current, is found near the equatorial region of the magnetosphere at several earth radii. During the main phase of geomagnetic storms the ring current shifts toward lower L values into the region of the plasmapause, which is characterized by steep gradients in the plasma density. This interaction together with an anisotropic pitch angle distribution leads to ring current instability and the growth of ion cyclotron wave turbulence. As wave energy is dissipated in the ambient electron gas by Landau damping, the plasmapause electron temperature is raised to a few electron volts, and a substantial temperature gradient is created with respect to the ionosphere. The energy transferred to the ionosphere by pitch angle scattering in the low collision frequency region and by heat conduction in the collision‐dominated regime raises the ionospheric electron temperature to several thousand degrees. Therefore an appreciable number of electrons in the high‐energy tail of the Maxwellian distribution, i.e., electrons with energy greater than 2 eV, exist in the F region of the ionosphere at about 400 km, where atomic oxygen is the dominant neutral gas constituent. Two eV is the threshold for excitation of oxygen atoms to the metastable ¹D level, and these O(¹D) atoms emit 6300‐Å radiation, the signature of stable auroral red (SAR) arcs. Although the energy input rate required to produce electron temperatures sufficient to cause average SAR arcs is less than 0.1 erg cm−2 s−1, the energy radiated in the red line is only about 0.003 erg cm−2 s−1. Thus an SAR arc is an optical manifestation of a slow release of energy from the magnetosphere during a geomagnetic storm. Energetically it is small in comparison with high‐latitude auroral processes.
Magnetic anomalies over the continents and their analyses
Authors: Zietz Isidore , Bhattacharyya B. K.
Published: February 2008

It is significant that many countries of the world have undertaken aeromagnetic mapping programs to survey their nations in a reasonable period of time. The U.S.S.R., for example [Solov'yeva, 1968, 1971], had finished complete coverage by 1967 using a flight spacing of 2 km. The Canadian Geological Survey had initiated a program to map the entire Canadian Shield at a flight separation of 1/2 mi (804 m). Almost three fourths of the shield has now been flown, and the maps have been made available to the public [Hood, 1974]. Yet at this writing there is no national program to map the United States aeromagnetically. To date, published aeromagnetic maps are available for only 10% of the United States. Although at least half of the country has been adequately surveyed by private industry, the results have not been made available to the public. Most of the coverage in the United States has been provided by the U.S. Geological Survey, the funds often coming from other organizations, such as state geological surveys. For the past few years the U.S. Geological Survey has adopted a policy of promptly releasing aero‐magnetic data to the public via the open file route. These recent publications, mostly at a scale of 1:250,000, are cited in the bibliography at the end of this report.
High‐temperature flow of rocks
Authors: Carter Neville L.
Published: February 2008

A lot of activity has taken place in this area of tectonophysics during the last quadrennium, all of which has led to a much more fundamental understanding of the mechanical behavior and deformational processes of rocks undergoing flow in the crust and upper mantle. The most important advancements have come in the following areas: (1) direct observations of dislocation configurations and substructure in several important rock‐forming minerals deformed both experimentally and in natural environments, (2) determinations of preferred crystal orientations resulting from plastic deformation and from syntectonic and annealing recrystallization, (3) determinations of flow laws for several important types of aggregates undergoing steady state flow in laboratory experiments, and (4) detailed investigations of the internal structure of certain alpine‐type peridotites and of textures and deformational processes in peridotite xenoliths from the upper mantle. This information has provided the basis for preliminary interpretations of the creep state of the upper mantle as well as a better understanding of the origin of certain crustal structures.
Marine gravity
Authors: Watts A. B.
Published: February 2008

The technique of measuring gravity at sea has been greatly enhanced by the development of spring‐type surface ship gravimeters which can be operated under a wide variety of sea conditions. Since about 1961 surface ship measurements have been obtained on a continuous basis over each of the world's ocean basins. By combining measurements obtained on surface ships with measurements obtained earlier on submarines it is now possible to construct gravity anomaly maps of large parts of the world's oceans. These maps form an important basis for geological, geophysical, and geodetic studies.
Tropical meteorology
Authors: Yanai Michio
Published: February 2008

In the past few years we have witnessed a tremendous expansion of the scope of tropical meteorology. Advances in satellite technology and numerical simulation of the global general circulation have made it impossible to maintain the isolation of this classical branch of meteorology from the rest of the atmospheric sciences.

During the years 1971–1974 the data obtained by many pre‐Garp experiments became available for scientific analysis. The experiments include the Line Islands Experiment (Lie) in 1967, the Florida State University Barbados Experiment in 1968, the Atlantic Trade Wind Experiment (Atex) and the Barbados Oceanographic and Meteorological Experiment (Bomex) in 1969, and the Venezuelan International Meteorological and Hydrological Experiment (Vimhex) in 1969 and 1972. The data from these experiments prompted especially studies of the structure of trade wind subcloud layer.
Progress in atmospheric electricity
Authors: Uman Martin A. , Dawson George A. , Hoppel William A.
Published: February 2008

This report will concentrate on highlights of the work done in atmospheric electricity during the period 1971–1975, although an extensive bibliography is included for reference purposes. For convenience, the report has been (arbitrarily) divided into sections on fair‐weather and global electricity, cloud electricity, and lightning.

It is useful to divide fair‐weather and global electricity into the following areas: (1) ions, aerosols, and radioactivity, (2) boundary layer effects, (3) global circuit and free atmosphere electricity, and (4) applications of atmospheric electricity.
Atmospheric chemistry and air quality
Authors: Covert D. S. , Charlson R. J. , Rasmussen R. , Harrison H.
Published: February 2008

Before proceeding to a discussion of recent developments and advances in the research areas of atmospheric chemistry and air quality it will be useful to describe briefly the subjects with which we are dealing. Atmospheric chemistry is a mixture of traditional subjects from chemistry and from meteorology. Its practitioners range from chemists with an interest in the atmosphere to meteorologists working on atmospheric composition. At the core is a small group trained or experienced in both fields who are often members of both the American Meteorological Society and the American Chemical Society and feel comfortable in both communities. As a subject, atmospheric chemistry has theoreticians, experimentalists, bureaucrats, and politicians like any other branch of science.
Large‐scale inhomogeneities in the solar wind of solar origin
Authors: Gosling J. T.
Published: February 2008

The most notable contributions to our understanding of large‐scale inhomogeneities in the solar wind have come from the following developments: the creation of realistic nonlinear models of solar wind stream interactions and evolution with increasing heliocentric distance; the careful observational study of solar wind stream structure, particularly that work that delineated the role of stream interactions and evolution in producing solar wind variability; the coming of age of radio scintillation measurements which have allowed the routine observation of stream flow far from the ecliptic; the discovery of coronal holes and their identification as the probable source of many recurrent solar wind streams; the development of nonspherically symmetric models of the coronal expansion which included effects of the coronal magnetic field; the recognition that alpha particle enhancements often identify material ejected from the sun at the time of large solar flares; the application of the Culgoora spectroheliograph to the study of type 2 and 4 radio bursts; the advent of low‐frequency observations of radio bursts from the sun; and the observation and analysis of numerous mass ejections from the sun with both ground‐based and satellite coronagraphs. The present report concentrates on the author's interpretation of the most outstanding developments in these and other areas. A comprehensive bibliography of all U.S. work and some foreign work in the field published or in press from January 1971 through November 1974 is attempted at the end of the article.
Classification and properties of iron meteorites
Authors: Scott Edward R. D. , Wasson John T.
Published: February 2008

Most (86%) iron meteorites can be assigned to one of 12 genetic groups on the basis of systematic variations in their chemical, mineralogical, and structural properties; the remaining 14% are termed anomalous. The groups are best resolved on Ga‐Ni or Ge‐Ni plots, but they may also be defined using other elements, the distribution and morphology of characteristic minerals, and very often kamacite bandwidths. The power of this classification to reveal correlations of numerous and diverse properties within these groups and systematic variations between groups emphasizes its validity. Its use is essential for understanding the formation of iron meteorites. A comparison of the 12 groups suggests that there are two types with very different histories: (1) the major groups IIAB, IIIAB, and IVA (11, 32, and 8% of all irons, respectively), probably IIC, IID, and IVB, and possibly also IC, IIIE, and IIIF; within these groups, most properties are correlated and chemical and mineralogical trends closely similar and (2) the large group IAB (19% of all irons), IIICD, and probably IIE, in which correlations between properties are generally much weaker and the observed trends distinctly different from those in groups of the former type. Each group very probably formed in its own parent body. Groups of the second type seem to have diverse formational histories, but we believe that, unlike the first type, they were not once part of molten cores. This study is based on results from nearly 500 different iron meteorites, which are listed with their classification together with 70 other paired irons. We present a comparative study of the properties of the 12 groups without attempting to fit these data to detailed models for their formation.
Stratospheric ozone: An introduction to its study
Authors: Nicolet Marcel
Published: February 2008

An analysis is made of the various reactions in which ozone and atomic oxygen are involved in the stratosphere. At the present time, hydrogen, nitrogen, and chlorine compounds in the ranges parts per million, parts per billion, and parts per trillion may have significant chemical effects. In the upper stratosphere, above the ozone peak, where there is no strong departure from photochemical equilibrium conditions, the action of hydroxyl and hydroperoxyl radicals of nitrogen dioxide and chlorine monoxide on atomic oxygen and of atomic chlorine on ozone can be introduced. A precise determination of their exact effects requires knowledge of (1) the vertical distribution of the H2O, CH4, and H2dissociation by reaction of these molecules with electronically excited oxygen atom O(¹D); (2) the ratio of the OH and HO2concentrations and their absolute values, which depend on insufficiently known rate coefficients; (3) the various origins of nitric oxide production, with their vertical distributions related to latitude and season; and (4) the various sources giving different chlorine compounds that may be dissociated in the stratosphere. In the lower stratosphere, below the ozone peak, there is no important photochemical production of O3, but there exist various possibilities of transport. The predictability of the action of chemical reactions depends strongly on important interactions between OH and HO2radicals with CO and NO, respectively, which affect the ration(OH)/n(HO2) at the tropopause level; between OH and NO2, which lead to the formation of nitric acid with its downward transport toward the troposphere; between NO and HO2, which lead to NO2and its subsequent photodissociation; between ClO and NO, which also lead to NO2and become more important than the reaction of ClO with O; and between Cl and various molecules, such as CH4and H2, which lead to HCl with its downward transport toward the troposphere. All these chemical processes are subject to many changes since they occur in the lower stratosphere where seasonal, latitudinal, and even day‐to‐day variations of the ozone concentrations are observed in association with advective and dynamic transports, which depend on meteorological conditions as indicated by variations of tropopause heights.
A comparison of one‐dimensional theoretical models of stratospheric minor constituents
Authors: Shimazaki T. , Whitten R. C.
Published: February 2008

The density profiles of stratospheric minor constituents are compiled from several one‐dimensional theoretical models that have appeared in the literature. The models are compared with each other and also with observations if data are available. The similarity and disparity of the models are clarified and discussed. If a large difference exists among the models, attempts are made to interpret it as much as possible in terms of the physical and chemical data employed in each model. The inadequacy of one‐dimensional models in calculating the realistic ozone density distributions and the problems related to it are briefly discussed.
Vertical crustal movements from leveling data and their relation to geologic structure in the eastern United States
Authors: Brown Larry D. , Oliver Jack E.
Published: February 2008

Through analysis of leveling data, rates of relative vertical motion have been determined for points of a grid of profiles over much of the eastern United States. The rates are commonly too large to be attributed to leveling errors and therefore must reflect true earth movements. With some exceptions, modern movements appear to be related to earlier Phanerozoic trends, but the rates of modern movements are much larger than average rates over the past 130 m.y. Thus movements are either episodic or oscillatory about a long‐term trend. If oscillatory, the periods must be less than about 106 yr and may be much smaller. The spatial patterns of the rates of relative motion, or tilts, can be correlated with certain geological features. The Atlantic and Gulf coastal plains are tilting downward away from the continental interior. Along a profile from Savannah, Georgia, to Philadelphia, Pennsylvania, the Atlantic Coastal Plain is also tilting downward to the north, with a perturbation at the Cape Fear arch. The Appalachian Highlands are rising relative to the Atlantic Coast at rates of up to 6 mm/yr. The pattern of maxima and minima in relative velocities along the profiles crossing the Appalachian Highlands province suggests elongated zones of relative uplift and subsidence paralleling either the Appalachian drainage divide or the trend of Appalachian structure. The maxima correlate strongly with topographic highs. There is a suggestion of correlation of modern seismicity with extremes of relative velocities in the Appalachian Highlands province. The Interior Plains are tilting downward to the east at a rate of 2 × 10−8 rad/yr, the implication being that glacial rebound is not an important factor south of the Great Lakes at the present time. The wavelength between successive zones of relative uplift in the Appalachian Highlands is about 300 km, suggesting that at least the entire thickness of the lithosphere is involved, and probably the asthenosphere as well. Possible explanations for these phenomena include the effects of hydrologic variations, phase transitions in the lower crust and/or the upper mantle, asthenospheric currents driven by ocean and ice loads or plate motions, and stresses derived from nonequilibrium crustal loads or crustal unloading by erosion.
Plasma waves and instabilities in the polar cusp: A review
Authors: D'Angelo N.
Published: February 2008

A review is presented of the experimental and theoretical work performed in recent years on plasma waves and instabilities in the polar cusp (cleft).
Satellite beacon contributions to studies of the structure of the ionosphere
Authors: Evans J. V.
Published: February 2008

The signals transmitted by radio beacons on board artificial earth satellites have been widely used for studies of the earth's ionosphere. Following the launch of Sputnik 1, two lines of investigation quickly emerged, the study of the total columnar content of the ionosphere (up to the height of the satellite) and the study of the fine‐scale irregularities within the layer responsible for causing rapid fading of the received signals. Early studies of total content employed either the Faraday rotation or the differential Doppler method and suffered because of an ambiguity in the results. This was overcome when satellites were launched that carried beacons transmitting on closely spaced frequencies. The measurements then provided information on the diurnal, seasonal, and sunspot cycle variations of the total content. In addition, by comparing the measurements with true height analyses of ionosonde records, useful results were obtained concerning the ratio of the number of electrons lying above the peak of the F layer to the number below and the layer thickness. Presently, the most useful product of the low‐altitude satellite measurements of ionospheric total content is in revealing latitudinal irregularities produced, for example, by traveling ionospheric disturbances or by auroral zone processes. The advent of geostationary satellites has made possible long continuous records of total content for many fixed locations on the earth, and by using multiple frequencies it has also been possible to study the exchange of plasma between the ionosphere and the magnetosphere. An extension of these observations to higher latitudes could resolve the question of whether the shrinkage of the plasmasphere during magnetically disturbed periods is accomplished by ‘peeling away’ the outer shells or by an inward compression of the plasma into the ionosphere. The morphology of ionospheric scintillation has been studied extensively by using beacon signals. In addition, these studies have shown that the spectrum of irregularities is power law (rather than Gaussian) and at the equator can extend to very small spatial scales. It is generally agreed that the irregularities responsibile for scintillation are created by some form of plasma instability; there seems to be a good candidate in the case of the equatorial irregularities but not in the case of irregularities at mid‐and auroral latitudes. It may be that different instability mechanisms operate in the auroral zone and at mid‐latitudes and/or at different times.
The homogeneous chemistry of atmospheric sulfur
Authors: Graedel T. E.
Published: February 2008

Sulfur is present in the atmosphere as a constituent of more than 15 compounds and in valence states ranging from −2 to +6. Nearly all of the compounds have both natural and anthropogenic sources. This paper reviews the present information on the reactions of these compounds and their products with typical atmospheric species. It is shown that atmospheric sulfur chemistry proceeds monotonically in the direction of increasing sulfur oxidation and that the gas phase transformation of reduced sulfur compounds to sulfate aerosol in all ambient atmospheres can be described by a common chain consisting of five chemical steps followed by a heterogeneous loss process.