bluuebunny/crossref_metadata_2025 huggingface dataset:
Magnetospheric and auroral plasmas: A short survey of progress
Authors: Frank L. A.
Published: February 2008

Important milestones in our researches of auroral and magnetospheric plasmas for the past quadrennium 1971–1975 are reviewed. Many exciting findings, including those of the polar cusp, the polar wind, the explosive disruptions of the magnetotail, the interactions of hot plasmas with the plasmapause, the auroral field‐aligned currents, and the striking inverted V electron precipitation events, were reported during this period. Solutions to major questions concerning the origins and acceleration of these plasmas appear possible in the near future. A comprehensive bibliography of current research is appended to this brief survey of auroral and magnetospheric plasmas.
Magnetic fields of the magnetosheath
Authors: Fairfield D. H.
Published: February 2008

The magnetic field of the magnetosheath is most naturally discussed in terms of its steady state and its fluctuating components. The theory of the steady state field is quite well developed, and its essential features have been confirmed by observations. The interplanetary field is converted through the bow shock where its magnitude is increased and its direction changed by the minimal amount necessary to preserve the normal component across the shock. Convection within the magnetosheath usually increases the magnitude still further near the subsolar point and further distorts the direction until the field is aligned approximately tangent to the magnetopause. Fluctuations of the magnetosheath field are very complex, variable, and not well understood. Power spectra of the field typically vary as 1/f or 1/f² below and 1/f³ above the proton gyrofrequency. Spectral peaks are common features which occur at different frequencies at various times. Transverse waves are often dominant at frequencies ≲0.002 Hz, and compressional waves are often dominant at somewhat higher frequencies. Perturbation vectors of hydromagnetic waves tend to be aligned with the shock and magnetopause surfaces. Magnetosheath waves may be generated upstream, within the magnetosheath, at the bow shock, or at the magnetopause, but the relative importance of these sources is not known.
Depositional and postdepositional processes in the magnetization of sediments
Authors: Verosub Kenneth L.
Published: February 2008

This paper surveys 40 years of research on the processes by which a sediment acquires a detrital remanent magnetization (DRM). These processes can be divided into two types: depositional processes, which arise from interactions between the magnetic carriers and the substrate at the sediment/water interface, and postdepositional processes, which arise from the mobility of magnetic carriers within fluid‐filled voids in the sediment. Depositional DRM is well understood theoretically and experimentally, but its applicability to natural sediments may be quite limited. Postdepositional DRM, which has not been studied in sufficient detail, may well be the dominant process by which sediments acquire a magnetization. The nature and composition of both the magnetic carriers and the matrix as well as the pore water content of the sediment influence the balance between depositional and postdepositional DRM. The identification of the method of magnetization in a given sedimentary environment, such as glacial lakes, the deep sea, or lakes and marginal seas, can be a difficult problem. Since postdepositional DRM accurately records the ambient geomagnetic field, whereas depositional DRM does not, such an identification is necessary in order to use the detrital remanent magnetism of sediments in studies of the fine scale behavior of the geomagnetic field, the paleomagnetic correlation between sedimentary environments, and the possible relation between paleomagnetic parameters and paleoclimatic indicators.
Geomagnetic excursions and their paleomagnetic record
Authors: Verosub Kenneth L. , Banerjee Subir K.
Published: February 2008

The paleomagnetic record of recent lake and marine sediments contains anomalous magnetic directions which have been interpreted as large‐scale fluctuations of the geomagnetic field (excursions). In view of the many ways in which isolated distortions of the paleomagnetic recording process can arise, proof of the existence of an excursion must depend on consistent results from within a given lake or marine environment as well as from adjacent sedimentary environments. A critical review of the proposed excursions reveals that although some excursions probably did occur, there is not yet sufficient evidence to confirm the existence of many of the claimed excursions. When the existence of regional or global excursions is established, additional information will become available on the nature of the geomagnetic field, on the use of excursions as time‐stratigraphic horizons, and on possible correlations between geomagnetic activity and climatic change.
Stratospheric Aitken particles
Authors: Cadle R. D. , Kiang C. S.
Published: February 2008

The nature and sources of stratospheric Aitken particles have remained highly uncertain in spite of considerable research by various groups. Most of the field studies of these particles have been performed by using condensation nucleus counters and by impactors. Numerous theoretical studies have been made of their formation, transport, and fate. This article reviews and analyzes the results. This analysis strongly indicates that the Aitken particles in the stratosphere below 20 km in altitude are usually of tropospheric origin and like the larger particles consist to a major extent of impure sulfuric acid. Above 20 km they may contain a considerable fraction of Aitken particles of meteoric origin.
Theoretical aspects of tidal and planetary wave propagation at thermospheric heights
Authors: Volland H. , Mayr H. G.
Published: February 2008

A simple semiquantitative model is presented which allows analytic solutions of tidal and planetary wave propagation at thermospheric heights. This model is based on perturbation approximation and mode separation. The effects of viscosity and heat conduction are parameterized by Rayleigh friction and Newtonian cooling. Because of this simplicity, one gains a clear physical insight into basic features of atmospheric wave propagation. In particular, we discuss the meridional structures of pressure and horizontal wind (the solutions of Laplace's equation) and their modification due to dissipative effects at thermospheric heights. Furthermore, we solve the equations governing the height structure of the wave modes and arrive at a very simple asymptotic solution valid in the upper part of the thermosphere. That ‘system transfer function’ of the thermosphere allows one to estimate immediately the reaction of the thermospheric wave mode parameters such as pressure, temperature, and winds to an external heat source of arbitrary temporal and spatial distribution. Finally, the diffusion effects of the minor constituents due to the global wind circulation are discussed, and some results of numerical calculations are presented.
The O I (6300 Å) airglow
Authors: Hays P. B. , Rusch D. W. , Roble R. G. , Walker J. C. G.
Published: February 2008

The measurement capability of the Atmosphere Explorer (AE) satellite series has been used to investigate the detailed chemistry of O(¹D) atoms in the earth's thermosphere. Measurements of the O I (³P‐¹D) transition at 6300 Å on AE have been used to infer the strength of the O2+ dissociative recombination source of O(¹D), (β¹D) the quenching rate of O(¹D) by molecular nitrogen (KN2), and the value of the photodissociation rate of O2 (Jo2). Values inferred from the measurements for β¹D, KN2, and Jo2 are 1.33, 3 × 10−11 cm³ s−1, and 3 × 10−6 s−1 respectively. The photoelectron impact source of O(¹D) has also been investigated. A unimolecular rate constant for this process derived from the airglow data agrees well with current theoretical calculations. Morning and evening twilight 6300‐Å data compare favorably with those calculated by a time‐dependent model of the mid‐latitude ionosphere.
Review of rate coefficients of ionic reactions determined from measurements made by the Atmosphere Explorer satellites
Authors: Torr D. G. , Torr M. R.
Published: February 2008

The large data base of aeronomic parameters measured by the Atmosphere Explorer C, D, and E satellites since December 1973 has been used to determine a number of reaction rate coefficients highly relevant to our understanding of thermospheric chemistry. In this paper we review the results for ionic rate coefficients for recombination of NO+, O2+, and N2+, for reactions of O+ + N2, N2+ + O, and O++ + O, and for various reactions involving O+(²D) and O+(²P) ions with O and N2.
The rotation of the Sun
Authors: Howard Robert
Published: February 2008

Observations of solar rotation are reviewed. There are two basic methods of determining the rotation of the sun. One is to measure the daily or monthly positions of tracers on the surface or in the corona, and the other is to measure line‐of‐sight velocities with the Doppler effect in spectrum lines. The results of a number of investigations involving both methods are compared. The experimental and interpretational problems associated with observational determinations of solar rotation are reviewed and compared. The theoretical situation in this field is reviewed, including the significance of different rotation rates for surface magnetic features and the solar plasma. The rotation of the solar interior is discussed in terms of both model calculations and recent p mode oscillation rotation rates, which reflect the interior rotation.
Heating of the solar corona: A new outlook
Authors: Wentzel Donat G.
Published: February 2008

Observations of the last few years show the corona to be highly inhomogeneous. The corona consists of loops of gas aligned with magnetic fields. The most viable theories for heating the corona are those that explicitly incorporate the structure of the magnetic loops. Coronal heating may be due to dissipation of electrical currents running along the loops and/or dissipation of hydromagnetic surface waves. The two theories have different implications for the heating of coronal holes.
The surfaces and interiors of Saturn's satellites
Authors: Cruikshank Dale P.
Published: February 2008

The photometric and bulk parameters of the known and suspected satellites of Saturn are presented in updated tables and are compared. The surface compositions of all the satellites are discussed in terms of modern photometry and spectroscopy; most, if not all, of the inner bodies have water frost surfaces, but the outer three satellites have surfaces of unknown composition. The few reliable mass values of some inner satellites, together with the best current values for the satellite radii, suggest mean densities representative of bulk compositions dominated by frozen volatiles, though Titan may have a substantial volume fraction of silicates. The special case of Iapetus is considered in the light of new studies of its two distinct faces and polar cap.
Recent advances in rock magnetism
Authors: Day Ron
Published: February 2008

It is my aim in this review article to present a personal view of the highlights in rock magnetism research in North America over the past four years. In a previous review (Banerjee, 1975), rock magnetism was presented in terms of “its applications to paleomagnetic, and hence geological and geophysical problems.” This is an extremely important aspect of rock magnetism research and in the past four years rock magnetism has made several important contributions to complex paleomagnetic problems. However, we must not lose sight of the fact that rock magnetism is a legitimate science in its own right.
Main field and secular variation
Authors: Cain Joseph C.
Published: February 2008

Research on the main geomagnetic feld and its secular variation advanced slowly over the period 1975–1978, owing mainly to a significant drop in national support. While some achievements can be reported, we must also acknowledge the impact of this decline on the progress in new scientific results and its effect in degrading the quality of the main field models used in other geophysical disciplines.

The World Magnetic Survey (WMS) (Zmuda, 1971) and work reported in the last Quadrennial Review (Cain, 1975) gave us some new insights into the main field not previously available. We obtained a rough outline of that part of the field describable by spherical harmonic wave numbers from n‐8 to about 20 and for the first time had a picture of the global anomaly structure covering the range from about 2000 Km (n = 20 = 40,000/2000) down to perhaps 400 km. However, the WMS momentum was largely lost during the last quadrennium, and these new features were not investigated in detail. As will be seen subsequently, plans for the next few years may brighten the picture considerably.
Theoretical seismic wave propagation
Authors: Richards Paul G.
Published: February 2008

During the last four years of U.S. research into theoretical seismology, effective techniques of computing synthetic seismograms have come into quite general use. Good agreement between a synthetic record and an instrumental record of ground motion (the raw data of seismology) implies a good understanding of the seismic source; of Earth structure; and of the theory of wave propagation relevant to the frequency content of the data. At periods T greater than about twenty seconds, there is now in general terms a fairly complete understanding of all the details in a seismogram, provided one ignores the (usually) minor effects of lateral variation of Earth structure. For 2 < T < 20 seconds, only limited portions of a seismogram (e.g., 15 seconds following a P‐arrival) may be fully understood, the limitations coming from noises in the data due to lateral scattering, and also from our ignorance of the source, of fine‐scale vertical Earth structure, and attenuation. At periods less than about two seconds, the understanding of seismograms is usually limited only to time windows within which identifiable pulses arrive. At these short periods, our knowledge of Earth structure is inadequate; scattering effects are stronger, but are poorly understood except for some progress in the context of seismic reflection prospecting within crustal layers.
The heterogeneity of the continental crust: Results from deep crustal seismic reflection profiling using the Vibroseis technique
Authors: Schilt S. , Oliver J. , Brown L. , Kaufman S. , Albaugh D. , Brewer J. , Cook F. , Jensen L. , Krumhansl P. , Long G. , Steiner D.
Published: February 2008

Deep reflection surveys carried out by the Consortium for Continental Reflection Profiling (COCORP) are revealing major structures within the continental crust in a variety of tectonic settings across the U.S. In many cases, these structures bear directly upon such geologic problems as the state of stress during large scale crustal deformations, the migration of magma, and the nature of the crust‐mantle transition zone. COCORP, formed during the U.S. Geodynamics Project and funded by the National Science Foundation, has surveyed eight different localities along lines totalling over 800 km in length. The VIBROSEIS technique has been used in all cases and has proven to be a flexible and effective tool for deep crustal exploration. Among the more significant observations made thus far are: (1) the details of the extensional structure of the Rio Grande Rift; (2) evidence for at least 21 km horizontal and 13 km vertical displacement along the Wind River Thrust, which dips uniformly at about 30 degrees and extends to a depth of at least 25 km; (3) evidence for at least 225 km displacement along a major subhorizontal thrust system beneath the southern Appalachians, in which the Brevard Zone appears to be rooted; and (4) the apparently discontinuous nature of the Moho or crust‐mantle transition zone, which has been observed to some degree at most of the sites studied. Taken together, the results of all surveys analyzed thus far demonstrate a much larger degree of heterogeneity in crustal structure than is indicated by more conventional geophysical techniques for exploration of the basement.
On solar cosmic rays
Authors: Van Hollebeke M. A. I.
Published: February 2008

This report summarizes those major results obtained over the last four years, which have contributed to a better understanding of flare accelerated particle phenomena. A detailed review covering the extensive literature on solar cosmic rays in recent years is beyond the scope of this report. Instead, the major developments in this area are high‐lighted and an attempt is made to place them in perspective with some fundamental questions in astrophysics.

The primary goal in studying solar cosmic rays is to understand the processes of particle acceleration in the solar flare and the physics of particle propagation in the solar corona including the storage and release of the accelerated particles. Related to the problem of energetic solar particles is a wide variety of different solar phenomena such as a number of different type of radio emission, X‐ray emission from bremsStrahlung of energetic electrons, γ ray line and continuum emission.
Experimental igneous petrology
Authors: Eggler David H.
Published: February 2008

The 1975–1978 quadrennium was a period in which research in igneous petrology continued in many of the areas of interest of the previous quadrennium (Boettcher, 1975, sect. A)—that is, processes of melting and phase transformations in the Earth and planetary mantles and igneous processes that are peculiar to specific tectonic regimes. The object of these studies is understanding the contribution of igneous events to the evolution of crust‐mantle systems.

The references in the bibliography cover the period from the latter months of 1974 to the end of 1978. References listed are believed to reflect both the contributions of geoscientists of the United States and the interactions between U.S. scientists and their colleagues in foreign countries, in particular other countries of the Western world.
Geothermal systems and their energy resources
Authors: White Donald E. , Guffanti Marianne
Published: February 2008

Geothermal systems have not been reviewed comprehensively in previous IUGG Quadrennial Reports, although thermal aspects of the shallow crust were considered by Diment (1975). Nearly all types of geothermal systems are reviewed in this report, with emphasis on U. S. systems that are most likely to be utilized as energy sources. Active volcanism and the generation and evolution of magma are not considered in detail.

Outstanding advances in geothermal resource utilization include: (1) Rapid growth in electrical generation from hydrothermal convection systems. All installed capacity in the U. S. to date (610 MWe in February, 1979) is from the huge vapor‐dominated system at The Geysers, California. Rapid expansion of capacity to ∼1200 MWe is expected by 1982; this includes at least 200 MW from several hot‐water systems, now that the most serious technological, environmental, and Federal leasing problems seem to have been solved; (2) Increasing interest in low‐temperature geothermal waters for non‐electrical (direct) uses; (3) Recognition of the resource potential of the geopressured environment of the Gulf Coast for geothermal and methane energy.
Meteorite research
Authors: Wood John A. , Motylewski Karen
Published: February 2008

Meteorites contain a record of events and processes in the three earliest stages of solar system history: (1) formation of the raw material that was to become the solar system; (2) processing of the condensable component of this material in a nebular disk that circled the protosun; and (3) processing of condensed material after it had accumulated into planetesimals of asteroidal dimension. To test our acumen, the record has been written in cryptic rather than plain language. Progress toward breaking the cipher, made in the U.S. during the period 1975–1978, is summarized below.

Much of the record in meteorites is contained in patterns of isotope abundances. This particular field of research is admirably reviewed by Podosek [1978].
Review of marine geochemistry
Authors: Schink D. R.
Published: February 2008

The past four years have seen exciting progress in several areas in marine geochemistry and significant advances in many others. The U.S. program continues to benefit from a diversity of research‐sponsoring agencies and has drawn particular strength from the blend of large‐scale programs and small‐scale research efforts. Several of the large‐scale programs under the International Decade of Ocean Exploration are now bearing rich fruit. The data derived from the GEOSECS program have been particularly valuable; Coastal Upwelling (CUEA) and Manganese Nodule (MANOPS) programs are producing significant gains in our studies of the chemistry of the ocean.
New isotopic clues to solar system formation
Authors: Lee Typhoon
Published: February 2008

The presence of two new extinct nuclides 26Al and 107Pd with half‐lives ∼106 years in the early solar system implies that there were nucleosynthetic activities involving a great many elements almost at the instant of solar system formation. Rare gas and oxygen isotopic abundance variations [“anomalies”] relative to the “cosmic” composition were observed in a variety of planetary objects indicating that isotopic heterogeneities caused by the incomplete mixing of distinct nucleosynthetic components permeate the entire solar system. The correlated nuclear [“FUN”] anomalies in O, Mg, Si, Ca, Sr, Ba, Nd, and Sm were found in three rare inclusions in the Allende meteorite, which show large mass‐dependent isotopic fractionation effects. The signature of the nuclear component required to explain these anomalies suggests a source which has received a catastrophic neutron burst [e.g., an r‐process event]. These extinct nuclides and nucleosynthetic anomalies provide new clues to solar system formation. In particular, these results have led to the speculation that a nearby supernova had injected freshly synthesized material into the early solar nebula and possibly triggered the collapse of the proto‐solar interstellar cloud. Furthermore, these new results have major implications on cosmochronology, nucleosynthesis theory, star formation, planetary heating, and the genetic relationship between different planetary bodies.
Planetary geodesy
Authors: Ferrari Alfred J. , Bills Bruce G.
Published: February 2008

This report will attempt to review progress in planetary geodesy during the past four years. We basically restrict the discussion to the traditional subjects of geometrical and physical geodesy, with primary emphasis on gravity, topography, rotation and their physical significance. The format has been kept flexible to accommodate the varied amount of information available for the different planets. The bibliography provided is representative but not exhaustive.
Solar wind plasma processes and transport
Authors: Feldman William C.
Published: February 2008

The solar wind is one of the few examples of an astrophysical plasma accessible to in situ measurement. This accessibility allows a determination of the distribution of internal energy in sufficient detail to evaluate and understand the various kinetic mechanisms which cooperate to determine plasma transport. Because the transport properties of a gas affect its dynamical evolution as well as its internal state, studies of solar wind transport are important toward an eventual understanding of 1 ) acceleration mechanisms responsible for the coronal expansion, 2) the interaction between the solar wind and solar system bodies such as the planets, comets, and asteroids, 3) the propagation and evolution of disturbances through interplanetary space and, 4) interplanetary acceleration mechanisms which contribute to, and affect the distribution of, the local energetic particle population.

The purpose of this report is to outline what I feel were the most significant advances made in solar wind transport since 1974 and to provide a complete listing of relevant literature for this interval. A guide to previous literature can be traced through the individual research papers as well as through the several comprehensive review articles published during this interval. The references are listed at the end of the present report.
Chlorofluoromethanes: Threats to the ozone layer
Authors: Crutzen Paul J.
Published: February 2008

In his contribution to the report of the U. S. National Committee to the International Union of Geodesy and Geophysics for the period 1971–1974, Ralph Cicerone (1975) concluded with the following remark: “Hopefully, it is clear that the period 1971–1974 was a very active one, if mostly because of threats to our climate and well being.” The intensity of the activities in the research of the ozone layer during the past four years have certainly equalled those during the period 1971–1974. Great advances have been made, especially in our understanding of the fundamental photochemical processes which govern the ozone distribution of the atmosphere. Altogether this decade has seen so many unforeseen developments that it will be difficult to find another field in atmospheric science which has provided a comparable amount of excitement.
Advancements in remote sensing of the atmosphere
Authors: Lhermitte Roger
Published: February 2008

The infrared methods developed in the last two decades for the remote sensing of atmospheric parameters by infrared sensors installed aboard orbiting (research and operational) and geostationary (operational) satellites have resulted in numerous meteorological interpretations allowed by the continuous monitoring of cloud and earth surface emission. Also, the inversion methods, in which atmospheric radiances simultaneously observed at several wavelengths in the same general absorption band are used to estimate the vertical profile of temperature or concentration of atmospheric gases, have been further applied to the observation of the vertical profiles of atmospheric temperature and water vapor content.

The results have shown that, in a cloud‐free atmosphere, tropospheric temperature measurements done by satellite are acceptable but have a limited ability to show low level temperature inversions. Except for the case of thin cirrus, clouds are always considered as emitting black body radiation so that their infrared emission observed in the 10 microns atmospheric window is easily converted into temperature at their top.
Dayside cleft aurora and its ionospheric effects
Authors: Shepherd Gordon G.
Published: February 2008

The existence of an opening on the dayside of the earth's magnetic field through which solar plasma could penetrate was noted by Chapman and Ferraro in 1931, and although observational evidence of its auroral and ionospheric effects accumulated steadily over the years, the dayside cleft (or cusp) was not accepted as a real magnetospheric feature until 1971. The history of this development is described, and some reasons for the long delay in recognizing this profound ionospheric influence are given. The entry of magnetosheath plasma to ionospheric levels provides an essentially permanent dayside energy source for the F region that generates a rather constant 1–2 kR of 6300‐Å atomic oxygen emission, a weak hydrogen emission, and some other emissions. It also produces ionospheric irregularities and enhanced electron temperatures that can be detected by a variety of methods, all of this in a region normally centered at noon and 78° in invariant coordinates, with a latitude extent of a few degrees and a longitude extent of a few hours. The cleft ionization is an important source for the polar cap ionosphere, and the detailed nature of its effect depends upon the interplanetary field and on magnetospheric influences on the polar cap convection pattern. Some questions for further study are given in conclusion.
A Lagrangian mean theory of wave, mean‐Flow interaction with applications to nonacceleration and its breakdown
Authors: Dunkerton Timothy
Published: February 2008

A review is given of a new Lagrangian mean theory of wave transport. Attention is focused on the so‐called ‘nonacceleration’ theorem, and it is shown that such a theorem arises naturally in the Lagrangian mean framework. Also discussed is a simple example of the Stokes drift, a concept which is central to nonacceleration. The Lagrangian mean theory substantially simplifies and unifies our understanding of wave driving in cases where nonacceleration is violated because of wave transience and dissipation. Moreover, the theory has given new insights in one particular case, that of Rossby gravity wave, meanflow interaction. These insights have successfully explained some hitherto unresolved paradoxes in the theory of the quasi‐biennial oscillation of zonal wind in the equatorial stratosphere. Some brief remarks are also made concerning some of the outstanding difficulties of the theory in need of future investigation.
Paleomagnetism in orogenic belts
Authors: Van Der Voo Rob , Channell James E. T.
Published: February 2008

Paleomagnetism is a quantitative tool for determining relative displacements and rotations of rock bodies in the geological past. During the last 20 years, paleomagnetic work in continental cratons has contributed greatly to our understanding of continental drift, but more recently, paleomagnetism has begun to be used on a more local scale, to elucidate tectonic problems in mountain belts. We have selected several geographical areas which illustrate an approach to paleomagnetism in mountain belts.
Review of oceanic and global heat flow estimates
Authors: Davies Geoffrey F.
Published: February 2008

Direct comparisons of recent estimates of oceanic and global heat flow from the earth's interior are not simple because of the diversity of assumptions and methods which have been used. Some of these estimates have been based on conceptually inappropriate or quantitatively unreasonable models of the cooling oceanic lithosphere. The cooling uniform half‐space model is the most appropriate first approximation and is presently adequate to describe the preferred selection of oceanic heat flow data. Hydrothermal transport in young oceanic crust may account for 25% of the total global heat flow. After appropriate allowances are made for this, there is general consistency between recent estimates of total heat flow. Total global heat flow is probably 4.1 ± 0.4 × 1013 W, which corresponds to an average flux of 80 ± 8 mW/m². The average oceanic heat flux is roughly 70% greater than the average continental flux: they are about 95 ± 10 mW/m² and 55 ± 5 mW/m², respectively. There may be significant fluctuations in total heat flow on time scales of 107–108 years.
Halogens in the atmosphere
Authors: Cicerone Ralph J.
Published: February 2008

Extant data from measurements of halogens in the atmosphere are reviewed in the following categories: gaseous chlorine compounds (inorganic and organic), particulate chloride and chloride in precipitation, gaseous bromine compounds (inorganic and organic), particulate bromide and bromide in precipitation, gaseous iodine compounds (inorganic and organic), iodine in particles and in precipitation, gaseous fluorine compounds (inorganic and organic), and fluoride in particles and precipitation. The roles that these data and other unavailable data play in defining global cycles of the halogens are discussed. Speciation of the halogen gases in the troposphere is very uncertain: the only inorganic species detected by species‐specific methods are HCl and SF6. More specific data are available on organic forms that contain halogens. Key species of gaseous halogens, either established or suspected to be important, are listed along with key processes that need investigation. Heterogeneous reactions, both gas‐to‐particle and particle‐to‐gas processes, precipitation removal, and sea‐salt aerosol generation and fractionation processes need quantitative investigation to allow progress in estimating halogen sources and sinks. Where practical, as with stratospheric inorganic chlorine gases, quantitative comparisons are made between measured and predicted concentrations.
Alternative formulations of magnetospheric plasma electrodynamics
Authors: Cragin B. L. , Heikkila W. J.
Published: February 2008

The fundamental equations of magnetospheric plasma electrodynamics are considered from a theoretical standpoint that stresses the basic equivalence of various seemingly different formal representations. The mathematical properties of vector fields are reviewed, and their implications in electrodynamics are studied. The irrotational and solenoidal parts of the electric field are associated with two physically distinct types of sources. Relativistic covariance and gauge invariance in electromagnetic theory are reviewed and discussed in the context of an approach in which the mathematical properties of vector fields are taken as primary concepts. Special attention is given to the use and interpretation of the Coulomb gauge potential functions. This choice of gauge is sometimes regarded with undue suspicion, possibly because of a certain paradox concerning causality. The paradox is discussed and resolved. Useful properties of the Coulomb gauge are identified. These need not be limited to the case of slow time variations and can extend beyond the limits of validity of ideal MHD theory.
Optical properties of snow
Authors: Warren Stephen G.
Published: February 2008

Measurements of the dependence of snow albedo on wavelength, zenith angle, grain size, impurity content, and cloud cover can be interpreted in terms of single‐scattering and multiple‐scattering radiative transfer theory. Ice is very weakly absorptive in the visible (minimum absorption at λ = 0.46 µm) but has strong absorption bands in the near infrared (near IR). Snow albedo is therefore much lower in the near IR. The near‐IR solar irradiance thus plays an important role in snowmelt and in the energy balance at a snow surface. The near‐IR albedo is very sensitive to snow grain size and moderately sensitive to solar zenith angle. The visible albedo (for pure snow) is not sensitive to these parameters but is instead affected by snowpack thickness and parts‐per‐million amounts (or less) of impurities. Grain size normally increases as the snow ages, causing a reduction in albedo. If the grain size increases as a function of depth, the albedo may suffer more reduction in the visible or in the near IR, depending on the rate of grain size increase. The presence of liquid water has little effect per se on snow optical properties in the solar spectrum, in contrast to its enormous effect on microwave emissivity. Snow albedo is increased at all wavelengths as the solar zenith angle increases but is most sensitive around λ =1 µm. Many apparently conflicting measurements of the zenith angle dependence of albedo are difficult to interpret because of modeling error, instrument error, and inadequate documentation of grain size, surface roughness, and incident radiation spectrum. Cloud cover affects snow albedo both by converting direct radiation into diffuse radiation and also by altering the spectral distribution of the radiation. Cloud cover normally causes an increase in spectrally integrated snow albedo. Some measurements of spectral flux extinction in snow are difficult to reconcile with the spectral albedo measurements. The bidirectional reflectance distribution function which apportions the reflected solar radiation among the various reflection angles must be known in order to interpret individual satellite measurements. It has been measured at the snow surface and at the top of the atmosphere, but its dependence on wavelength, snow grain size, and surface roughness is still unknown. Thermal infrared emissivity of snow is close to 100% but is a few percent lower at large viewing angles than for overhead viewing. It is very insensitive to grain size, impurities, snow depth, liquid water content, or density. Solar reflectance and microwave emissivity are both sensitive to various of these snowpack parameters. However, none of these parameters can be uniquely determined by satellite measurements at a single wavelength; a multichannel method is thus necessary if they are to be determined by remote sensing.
Nonlinear force‐free magnetic fields
Authors: Low B. C.
Published: February 2008

Astrophysical magnetic fields in a low beta plasma can evolve in a quasi‐steady state for extended periods of time which are much longer than the characteristic dynamical time scale. The evolution proceeds with the electric current flowing largely parallel to the magnetic field, so that as a first approximation the Lorentz force may be set to zero everywhere. This paper reviews in a unified picture the results of various theoretical investigations of this process. These investigations seek to uncover those circumstances under which extreme conditions develop to make the assumption of a quasi‐steady state untenable, and the field must pass into a fast dynamical phase at this point. The astrophysical interest is in explaining how a solar magnetic field would occasionally break into a flare or other eruptions. Two types of mechanisms have been treated. In the first the force‐free field is in a medium of infinite electrical conductivity. The field evolves in response to slowly changing boundary conditions brought about by photospheric motions in the solar active region. In the second mechanism the medium has a small finite electrical conductivity, and the field evolves in response to the slow Ohmic dissipation of the electric current. The field evolution in both cases is nonlinear, posing difficult mathematical problems. This review emphasizes exact mathematical treatment, outlining the progress the theory has made from isolated discoveries of particular solutions to general theorems upon which broad physical conclusions can be based.
Minor constituents in the stratosphere and mesosphere
Authors: Solomon Susan
Published: February 2008

This paper is intended to be a brief survey of research in the field of middle atmosphere chemistry from 1979 to 1982. The possibility of anthropogenic perturbation to the stratospheric ozone layer, particularly as a result of chlorocarbons, remains a subject of interest, and has been studied with increasingly detailed models during this period. A great deal of data on the distributions of many important species have been obtained, leading to substantial progress in our understanding of the processes controlling the photochemistry of minor species in the middle atmosphere.
The composition, propagation and acceleration of energetic solar particles: A review of United States research 1979–1982
Authors: McGuire R. E.
Published: February 2008

We study solar energetic particles in an effort to better understand physical processes which occur at the Sun and in the heliosphere, but improvements in our understanding of the physics of these processes should have broader implications in more general astrophysical problems. Among the questions of greatest interest are: (l) what is the basic elemental and isotopic composition of the solar atmosphere, to what extent is this composition reflected in observed energetic solar particles and how do these abundances relate to or influence our understanding of universal and galactic cosmic ray abundances; (2) by what mechanisms, under what conditions and where does the acceleration of solar energetic particles take place; (3) what are the mechanisms by which energetic particles are transported and/or stored in the vicinity of the Sun; (4) how can we describe the escape from the Sun and subsequent transport of charged solar particles through interplanetary space and how can we relate that description to measurable properties of the medium through which they travel?

Each of the above points raises numerous and difficult subsidiary questions. But probably the primary obstacle to direct study of these problems is that the various processes and mechanisms are almost inextricably interwoven observationally (Wibberenz, 1979). All measurements that we make of particles in space (e.g., composition, time evolution of intensities and anisotropies, energy spectra) are influenced both by the nature of the original particle acceleration and by the propagation of these particles from the acceleration site to the observing instruments.
Heliospheric magnetic fields and plasmas
Authors: Burlaga L. F.
Published: February 2008

Twenty years ago, Mariner 2 was launched and provided the first extensive and definitive measurements in the interplanetary medium. Parker completed his book “Interplanetary Dynamical Processes” [Parker, 1963] at that time, giving a sound theoretical basis for the interplanetary studies which followed. Ten years ago, Pioneer 10 was launched and initiated the exploration of “deep space”. Hundhausen's book “Coronal Expansion and Solar Wind” [Hundhausen, 1972] was published then, and it organized the first decade of interplanetary observations in the framework of supersonic gas‐dynamics.
Magnetic polarity stratigraphy
Authors: Chan Lung S. , Alvarez Walter
Published: February 2008

A series of previous review articles on paleomagnetic polarity stratigraphy has documented the growth of this field and its passage through various stages of development, in which work was concentrated on young lavas, young deep‐sea sediments from piston cores, and red beds [Cox, 1969; Larson and Helsley, 1975; Opdyke, 1972; Harrison, 1974; Irving and Pulliah, 1976; Butler and Opdyke, 1979]. The closely related development of the geomagnetic reversal time scale has been reviewed by Ness et al. [1980]. At the time of the last quadrennial U.S. National Report, Butler and Opdyke [1979] noted that the recent development of digital spinner and cryogenic magnetometers was making it possible to measure large numbers of very weakly magnetized samples. In the last four years cryogenic magnetometers have been acquired by many laboratories and studies of magnetic stratigraphy involving stepwise demagnetization of hundreds of samples have become fairly common. In view of the time and effort that go into a careful study of paleomagnetic stratigraphy, it seems unlikely that this technique will ever become as routine a correlation tool as biostratigraphy.
Advances in remote sensing of the atmosphere
Authors: Gage K. S. , Balsley B. B.
Published: February 2008

The past four years have witnessed a growing awareness of the need for adequate global data to extend the useful range of numerical weather forecasts. This arises, at least in part, from the experience of the Global Weather Experiment: that the tropics greatly influence mid‐latitude weather and climate. Furthermore, in terms of climate analysis and forecasting, it is essential that the vast oceans of the tropics and Southern Hemisphere be well observed. These requirements make the use of satellite‐based remote sensing essential.
Metallogenesis
Authors: Barton Paul B.
Published: February 2008

Like most of the topics covered in this review series, metallogenesis (the genesis of non‐fuel mineral deposits) constitutes a meeting ground for many internationally active disciplines, in this instance, ranging from physical chemistry and metallurgy, through descriptive and interpretive studies of ore deposits, to regional and global syntheses. The reviewer has attempted, with less than complete success, to avoid citations to the “gray” literature (meetings abstracts, reports of contractors, conference reports, annual reports of research institutions, theses, and U. S. Geological Survey (USGS) open‐file reports), concentrating as much as possible on peer‐reviewed journals and books. State geological reports have not received enough attention. Coverage is spotty for late 1982, and only half the 500+ references checked could be noted in the space alloted.
Models of the oceanic internal wave field
Authors: Olbers Dirk J.
Published: February 2008

In recent years, considerable progress has been made in internal wave research by a fruitful combination of experiment and theory. Kinematical models of the wave field appear to be well established, and dynamical models are evolving toward a stage of understanding the energetics and the interrelations of the waves within the oceanic field of motion. This review presents kinematical models of the wave field in terms of vertically progressive waves (WKB waves) as well as standing modes. Some emphasis is attributed to critical layer effects. Spectral models have been successfully developed for the wave field in the main thermocline. This appears to be in a stationary universal state with respect to spectral shape and level, whereas the upper ocean wave field shows considerable temporal and regional variability. Several approaches for separating the internal wave contribution from turbulence and other contaminations in observations have been proposed. This problem is of particular relevance in the transition region between waves and small‐scale turbulence at small vertical wavelengths. An accurate identification of reversible (wave induced) fine structure and irreversible fine structure is needed to determine the dissipation rate of the wave field and the mixing rates of the ocean. The search for dynamical relations of the wave field to environmental conditions has been extensive. The lack of dynamical correspondences between the wave spectrum and possible forcing fields in observations suggests that forcing is weak. Theoretical models of wave generation show that many mechanisms may contribute with equal efficiency. In concert with the observed low dissipation rates in the deep ocean, these results point toward the conclusion that there is no dominant source of energy but weak forcing by many different sources and weak dissipation. Under such conditions the interrelation between forcing and dissipation as well as the spectral form is controlled by internal transfer by wave‐wave interactions which are very efficient in relaxing spectral distortions to the observed universal form.
Paleolatitudes determined from paleomagnetic data from vertical cores
Authors: Cox Allan , Gordon Richard G.
Published: February 2008

Most of the paleomagnetic data available from oceanic plates consist of measurements of inclination but not declination from azimuthally unoriented vertical cores. Similarly, the basic paleomagnetic data to be analyzed from crustal blocks that have rotated by varying amounts about vertical axes are a set of paleoinclinations. A new method is proposed for determining the paleocolatitude of a sampling site and the associated confidence limits. Paleomagnetic inclinations are first converted to paleocolatitudes and averaged to produce a mean colatitude. After showing that this mean is biased, we derive a paleocolatitude correction to remove the bias, using a model for geomagnetic secular variation based on the latitude dependence of secular variation during the past 5 million years. After testing the validity of the model by applying it to paleomagnetic data from Quaternary lavas for which both inclination and declination are known, we apply the method to inclination‐only paleomagnetic data from Suiko Seamount, the most complete data set from a drilling site. The method is then applied to paleomagnetic data from all Deep Sea Drilling Project sites for the Pacific plate to obtain for each site an unbiased mean paleocolatitude and its confidence limits. These paleocolatitudes and confidence limits are then used as input for a least squares analysis to obtain Early and Late Cretaceous poles for the Pacific plate and 95% confidence limits for these poles. It is shown that the scatter of individual site paleocolatitudes about the best fit pole is consistent with the confidence limits at each site as determined by the new method of analysis.