bluuebunny/crossref_metadata_2025 huggingface dataset:
The gabbro‐eclogite phase transition and the elevation of mountain belts on Venus
Authors: Namiki Noriyuki , Solomon Sean C.
Published: February 2008

Maxwell Montes, standing up to 7 km above the adjacent highland plateaus, constitute the highest mountain belt on Venus. Because the thickness of the crust is likely to be limited by the gabbro‐garnet granulite‐eclogite phase transitions, this relief is difficult to reconcile with the assumption of thermodynamic equilibrium and a standard Airy isostatic model. We explore the hypothesis that the crust‐mantle boundary is not in phase equilibrium, but rather is rate limited by the temperature‐dependent volume diffusion of the slowest ionic species. Under the simplifying assumption that the mountains formed by uniform horizontal shortening of the crust and lithospheric mantle at a constant rate, we solve the one‐dimensional thermal evolution problem. The time‐dependent density structure and surface elevation are calculated by assuming a temperature‐dependent reaction rate and local Airy isostatic compensation. For a rate of horizontal strain of 10−15 s−1 or greater, the rise in temperature at the base of the crust during mountain formation is modest to negligible, the deepening lower crust is metastable, and surface elevation increases as the crust is thickened. For strain rates less than 10−16 s−1, in contrast, crustal temperature increases with time because of internal heat production, and the lower crust is more readily transformed to the dense eclogite assemblage. For such models a maximum elevation is reached during crustal shortening. While this maximum relief is 7 km or more for some models, a smaller density contrast between crust and mantle than assumed here (500 kg m−3) and incorporation of horizontal heat transport would lessen this value. We therefore favor formation of the mountain belt at a strain rate at least of order 10−15 s−1. By this reasoning, Maxwell Montes must be comparatively young, of order 50 Ma.
Paleoclimate Record for Northwind Ridge, Western Arctic Ocean
Authors: Poore R. Z. , Phillips R. L. , Rieck H. J.
Published: February 2008

Core NWR 5 from Northwind Ridge in the western Arctic Ocean contains a climatic record that extends back for over 1 million years. Dark brown beds with abundant planktonic foraminifers represent interglacial conditions, whereas glacial and transitional conditions are represented by lithologies barren or nearly barren of planktonic foraminifers. We conclude that seven, and possibly all nine, interglacials of the Brunhes magnetic chronozone (the last 780,000 years) are represented in NWR 5. For about the last 800,000 years, the western Arctic Ocean apparently had a permanent, thick ice cover and was unable to support significant populations of planktonic foraminifers except during major interglacials when seasonally open and high‐productivity surface waters occurred at least along the basin margins. Our results support previous interpretations that climate variations in the Arctic are in phase with glacial/interglacial cycles observed in other proxy records of the Brunhes.
Effect of wind changes during the Last Glacial Maximum on the circulation in the Southern Ocean
Authors: Klinck John M. , Smith David A.
Published: February 2008

Present‐day surface wind stress climatology is manipulated to simulate wind conditions during the last glacial maximum. These estimated wind fields force a one‐layer, wind‐driven numerical model of the southern ocean to determine if a change in the strength of the surface wind stress can shift the location of the Antarctic Polar Front, which is part of the Antarctic Circumpolar Current. A change in the forcing by a factor of 0.5–2.0 results in a change in the speed of the flow by an identical factor with no change in position. However, if the present‐day wind climatology is shifted meridionally, there is a change in both strength of the circulation and spatial pattern. A shift of the wind stress of more than 5° of latitude is required to produce a shift in the location of the polar front.
The δ13C in benthic foraminiferal tests of Fontbotia wuellerstorfi (Schwager) Relative to the δ13C of dissolved inorganic carbon in Southern Ocean Deep Water: Implications for glacial ocean circulation models
Authors: Mackensen A. , Hubberten H. ‐W. , Bickert T. , Fischer G. , Fütterer D. K.
Published: February 2008

On a transect between 20° and 70°S in the eastern Atlantic Ocean and Weddell Sea, water samples from 19 hydrographic stations and bottom water from 55 surface sediment samples taken with a multiple corer were investigated for the stable carbon isotopic composition of the total dissolved inorganic carbon (δ13CΣCO2). These measurements were compared to δ13C values determined on live specimens of the benthic foraminifer Fontbotia wuellerstorfi and closely related genera from the same stations. In addition, at 16 stations the stable carbon isotope composition of sedimentary organic carbon was measured. General deepwater and bottom‐water mass circulation patterns as inferred from the δ13CΣCO2 are in close agreement with those known from other nonconservative tracers. Very low δ13C values of upper Circumpolar Deep Water (<0.3‰ Pee Dee belemnite (PDB)) in the Polar Front region and the eastern limb of the Weddell gyre coincide with nutrient maxima. However, a significant decoupling of the dissolved phosphate signal from the δ13CΣCO2 signal is indicated in the abyssal Weddell Sea. We attribute this to temperature‐dependent fractionation processes during gas exchange of surface waters with the atmosphere at sites of bottom‐water formation. Multiple corer water from the sediment/water interface is slightly δ13C depleted relative to deepwater and bottom‐water δ13ΣCO2. The surface sediment organic carbon δ13C is 3 to 4‰ lower south of the Polar Front than north of it, and the δ13Corg in freshly accumulated phytodetritus is 3 to 4‰ lower than surface sediment organic carbon δ13C. Comparison of live F. wuellerstorfi δ13C and related genera with bottom‐water δ13CΣCO2 exhibits at most stations between the Subtropical Front (≈41°S) and the southern boundary of the Antarctic Circumpolar Current (≈55°S) a significant lowering of foraminiferal δ13C values. Compilation of a mean last glacial/interglacial δ13C amplitude (Δδ13C) from six published southern ocean cores results in a shift of −0.99± 0.13‰ PDB; this shift is greater than that in all other regions. However, all of these cores are from positions close to Recent oceanic fronts. Thus, for these peripheral areas of the southern ocean, we suggest about half of the glacial/interglacial shift can be explained by varying frontal zone positions and widths accompanied by a change in mode and height of export production.
On the structure and origin of major glaciation cycles 2. The 100,000‐year cycle
Authors: Imbrie J. , Berger A. , Boyle E. A. , Clemens S. C. , Duffy A. , Howard W. R. , Kukla G. , Kutzbach J. , Martinson D. G. , McIntyre A. , Mix A. C. , Molfino B. , Morley J. J. , Peterson L. C. , Pisias N. G. , Prell W. L. , Raymo M. E. , Shackleton N. J. , Toggweiler J. R.
Published: February 2008

Climate over the past million years has been dominated by glaciation cycles with periods near 23,000, 41,000, and 100,000 years. In a linear version of the Milankovitch theory, the two shorter cycles can be explained as responses to insolation cycles driven by precession and obliquity. But the 100,000‐year radiation cycle (arising from eccentricity variation) is much too small in amplitude and too late in phase to produce the corresponding climate cycle by direct forcing. We present phase observations showing that the geographic progression of local responses over the 100,000‐year cycle is similar to the progression in the other two cycles, implying that a similar set of internal climatic mechanisms operates in all three. But the phase sequence in the 100,000‐year cycle requires a source of climatic inertia having a time constant (∼15,000 years) much larger than the other cycles (∼5,000 years). Our conceptual model identifies massive northern hemisphere ice sheets as this larger inertial source. When these ice sheets, forced by precession and obliquity, exceed a critical size, they cease responding as linear Milankovitch slaves and drive atmospheric and oceanic responses that mimic the externally forced responses. In our model, the coupled system acts as a nonlinear amplifier that is particularly sensitive to eccentricity‐driven modulations in the 23,000‐year sea level cycle. During an interval when sea level is forced upward from a major low stand by a Milankovitch response acting either alone or in combination with an internally driven, higher‐frequency process, ice sheets grounded on continental shelves become unstable, mass wasting accelerates, and the resulting deglaciation sets the phase of one wave in the train of 100,000‐year oscillations.

Whether a glacier or ice sheet influences the climate depends very much on the scale…. The interesting aspect is that an effect on the local climate can still make an ice mass grow larger and larger, thereby gradually increasing its radius of influence.

Johannes Oerlemans [1991, p. 155]
Efficient and accurate computation of the incomplete Airy functions
Authors: Constantinides E. D. , Marhefka R. J.
Published: February 2008

The incomplete Airy integrals serve as canonical functions for the uniform ray optical solutions to several high‐frequency scattering and diffraction problems that involve a class of integrals characterized by two stationary points that are arbitrarily close to one another or to an integration endpoint. Integrals with such analytical properties describe transition region phenomena associated with composite shadow boundaries. An efficient and accurate method for computing the incomplete Airy functions would make the solutions to such problems useful for engineering purposes. In this paper a convergent series solution for the incomplete Airy functions is derived. Asymptotic expansions involving several terms are also developed and serve as large argument approximations. The combination of the series solution with the asymptotic formulae provides for an efficient and accurate computation of the incomplete Airy functions. Validation of accuracy is accomplished using direct numerical integration data.
Modeling the effect of meteor radiant distributions on the detection rate of meteor signals over forward‐scatter links
Authors: Mawrey R. S. , Broadhurst A. D.
Published: February 2008

This paper investigates currently accepted methods of modeling the effect of meteor radiant distributions of meteors on the detection rate of meteor signals over forward‐scatter links. A currently accepted radiant distribution is investigated, and an alternative radiant model is presented. The derivation of the currently accepted radiant distribution of meteors is also critically examined. Furthermore, an alternative, simpler method of including the effect of nonuniform geocentric radiant distributions of meteors on the detection rate of meteor signals over forward‐scatter links is given. Other nonuniform distributions of meteors are also presented.
A revised model for the prediction of differential rain attenuation on adjacent Earth‐space propagation paths
Authors: Kanellopoulos J. D. , Ventouras S. , Vazouras C. N.
Published: February 2008

The main propagation effect on interference between adjacent Earth‐space paths is differential rain attenuation. In the present paper, a revised method to predict the rain differential attenuation statistics is proposed which is based on a model convective rain cell structure of the rainfall medium and the assumption that the point rainfall statistics follows a lognormal form. Moreover, the revised model analyzes the general problem of differential attenuation taking into account the difference of elevation angles of the slant paths under consideration. The numerical results are referred to the interference problem from an adjacent satellite located in symmetrical geostationary positions in relation to the intended satellite and examine the significance of the difference of elevation angles for various parameters of the problem.
Effects of temperature gradient and radial range decay on the spectrum analysis of the radio acoustic sounding system using FM CW radar
Authors: Pang Shixuan
Published: February 2008

To develop the theory of FM CW radio acoustic sounding system (RASS), in this paper an analysis of influences from temperature gradient and radial range decay is presented. A nonconstant temperature gradient will significantly modify the spectrum of scattered signals and also cause a deviation of the maximum position of amplitude spectrum from the Bragg resonance, which should involve using any retrieval algorithm that will correct for this temperature bias. Without considering this effect, the error of 0.5–1 K will probably be introduced in the RASS temperature profile. An approximate retrieval algorithm is provided in text. Moreover, for the application of RASS using FM CW radar in lowest 100‐ to 200‐m atmosphere, the far‐field aspect sometimes will not be the case, and radial range decay will play a certain role, which is investigated also in this paper.
Simulated annealing searches for long binary phase codes with application to radar remote sensing
Authors: Sahr John D. , Grannan Eric R.
Published: February 2008

We apply the technique of simulated annealing to search for long discrete codes with special autocorrelation and ambiguity function properties, suitable for radar applications. This technique provides access to codes which are far too long for exhaustive search, and to codes whose correlation properties do not lend themselves to algebraic investigation. We illustrate the process with two new kinds of binary phase codes.
Chronology of tectonic events in the crystalline core of the Himalaya, langtang National Park, central Nepal
Authors: Macfarlane A. M.
Published: February 2008

The Main Central Thrust (MCT) is an important intracontinental subduction zone that accommodated a significant proportion of shortening between India and Asia during Tertiary Himalayan orogenesis. Argon 40/argon 39 geochronology indicates at least two distinct periods of thrust movement on the MCT in the Langtang National Park region of central Nepal. Ductile deformation and associated mylonitization characterizing the earlier event are constrained by 40Ar/39Ar dating of muscovites to have occurred sometime before 5.8 Ma. A later period of brittle deformation, resulting in the juxtaposition of rocks of different lithology within the MCT zone, occurred at approximately 2.3 Ma, based on 40Ar/39Ar dating of neoblastic muscovites from the brittle fault zones. The hanging wall of the MCT contains amphibolite to upper amphibolite grade gneisses and small leucogranite bodies assigned to the Greater Himalayan sequence. Argon 40/argon 39 cooling ages of muscovite and biotite from the gneisses range from 4.6 to 9.7 Ma. These dates contrast with previously obtained 16–21 Ma U‐Pb monazite and zircon ages for metasedimentary rocks from the same structural levels [Parrish et al., 1992], indicating relatively slow cooling over the early to middle Miocene interval for much of the MCT hanging wall. However, one 19.3 Ma biotite 40Ar/39Ar cooling age for a sample from the uppermost portion of the hanging wall is only slightly younger than U‐Pb monazite ages for nearby anatexites, possibly suggesting rapid cooling of the uppermost Greater Himalayan sequence by tectonic denudation associated with the structurally higher South Tibetan detachment system. The general consistency of 40Ar/39Ar ages throughout the 11‐km‐thick Greater Himalayan sequence suggests rapid cooling in late Miocene time, probably due to an increase in erosion rate related to ramping on the structurally lower Main Boundary Thrust. An alternative possibility would be massive hydrothermal resetting in late Miocene time of the entire sequence.
Kinematic evolution of the Miller Range Shear Zone, Central Transantarctic Mountains, Antarctica, and implications for Neoproterozoic to Early Paleozoic tectonics of the East Antarctic Margin of Gondwana
Authors: Goodge John W. , Hansen Vicki L. , Peacock Simon M. , Smith Brad K. , Walker Nicholas W.
Published: February 2008

High‐grade ductile tectonites of the Precambrian Nimrod Group in the central Transantarctic Mountains form the Miller Range shear zone (MRSZ). With no exposed boundaries, this zone has a minimum structural thickness of 12–15 km. Shear‐sense indicators record consistent top‐to‐the‐SE, or left‐lateral, shear within the NW striking, moderately SW dipping zone. Cylindrical folds with axes normal to elongation lineation (Le) are kinematically consistent with other shear indicators. They may represent early stages in the development of subordinate noncylindrical sheath folds, which indicate locally high bulk ductile strain and a moderate strain gradient. Pervasive, open to tight cylindrical folds with axes parallel to Le formed during shear and may reflect a component of constrictional strain. Quartz c axis fabrics from micaceous quartzites show asymmetric single girdles evident of dominantly rhombohedral slip, with limited basal‐plane slip, affirming both the consistency of shear sense and high‐grade syn‐kinematic conditions. Deformation did not persist during subamphibolite facies cooling, as shown by (1) a lack of basal‐plane slip in ductilely deformed quartz, (2) a lack of quartz subgrains and grain shape‐preferred orientation, and (3) the presence of oriented muscovite “fish” included within polygonal quartz grains, which show that quartz grain boundaries migrated and annealed under static conditions following ductile shear. From the uniform Le orientation and consistent shear sense, we interpret that ductile deformation resulted from a single, kinematically simple, left‐lateral (top‐to‐the‐SE) shear event. Together, the scale, high total strains (γ ≥ 5), fabric uniformity, and the widespread presence of asymmetric microstructures formed at high temperatures, all indicate that strain rates within the MRSZ were high and that it represents a major crustal structure. Orogen‐parallel displacements within this zone during the latest Neoproterozoic to Early Cambrian were at a high angle to penecontemporaneous orogen‐normal contraction in outboard supracrustal rocks, suggesting that the Neoproterozoic to early Paleozoic plate margin of Antarctica was characterized by left‐oblique convergence in which strain within the orogen was partitioned into deep‐level strike slip and shallow‐level contraction.
Steady and non‐steady state magma chambers below the East Pacific Rise
Authors: Batiza Rodey , Niu Y. , Karsten J. L. , Boger W. , Potts E. , Norby L. , Butler R.
Published: February 2008

Volcanic rocks collected on flowline traverses on the flanks of the East Pacific Rise (EPR) document changes in axial magma chemistry with time, providing a record of the thermal history of axial magma chambers (AMC). We present data for a sample set of closely spaced (1–2 km) samples along EPR flowlines at three localities out to ∼800 ka showing both steady (constant average temperature) and non‐steady state behavior of magma chambers on time scales of 200–500 ka. Though based on only three symmetrical traverses so far, it appears that magmatically robust ridge locations (11°20′N and 9°30′N) have steady state chambers, whereas a magmatically starved axis (10°30′N) shows large temperature changes with time. These observations provide a new petrologic perspective to the ongoing debate regarding the significance and causes of morphologic variations along the axis of the East Pacific Rise.
Considerations for Robust Compositional Simulations of Subsurface Nonaqueous Phase Liquid Contamination and Remediation
Authors: Pandy Sorab , Forsyth Peter A. , Falta Ronald W. , Wu Yu‐Shu , Huyakorn Peter S.
Published: February 2008

A nonisothermal compositional model has been developed for examining nonaqueous phase liquid contamination and remediation scenarios. The governing mass balance equations and constraints have been presented, and various type of compositional formulations available have been examined. An efficient and robust formulation has been developed that addressed certain issues related to groundwater situations and overcomes numerical difficulties encountered with previous formulations. The proposed formulation collapses to that corresponding to the multiphase flow equation set when interface mass transfer is neglected. Numerical implementation of the formulation has been discussed, and example problems have been presented for benchmark and verification. The present formulation outperforms other currently used formulations for the isothermal case studied and performs at least as well as its counterparts for the nonisothermal case. Characteristics of the simulator that hinder convergence for difficult problems have been identified, and directions for even further improvements have been noted.
Hydroclimatic trends and possible climatic warming in the Canadian Prairies
Authors: Gan Thian Yew
Published: February 2008

Results from applying Kendall's test to temperature and precipitation data from 37 weather stations, along with 50 sets of natural streamflow data and 13 sets of evapotranspiration, data show that the Canadian Prairies have become warmer and somewhat drier in the last 4–5 decades. Warming trends are detected in more weather stations than are drying trends. Temperature data are more highly correlated across sites than precipitation. No link was found between precipitation and maximum temperature. Kendall's test on the drought duration, severity, and magnitude for two Saskatchewan sites did not detect any significant trend.
Carbon cycle instability as a cause of the Late Pleistocene Ice Age Oscillations: Modeling the asymmetric response
Authors: Saltzman Barry , Maasch Kirk A.
Published: February 2008

A dynamical model of the Pleistocene ice ages, incorporating many of the qualitative ideas advanced recently regarding the possible role of ocean circulation, chemistry, temperature, and productivity in regulating long‐term atmospheric carbon dioxide variations, has been constructed. This model involves one additional term (and free parameter) beyond that included in a previous model (B. Saltzman and A. Sutera, 1987), providing the capacity for an asymmetic (for example, “saw‐toothed”) response. It is shown that many of the main features exhibited by the δ18O‐derived ice record and the Vostok core/δ13C‐derived carbon dioxide record in the late Pleistocene can be deduced as a free oscillatory solution of the model, including a rapid déglaciation during which a spike of high CO2 and a rapid surge in North Atlantic deep water production occurs. It is expected that the addition of reasonable levels of external (for example, Earth orbital) forcing will enable the model to account for a significant amount of the remaining observed variance and covariance of the slow response climatic variables over the full Pleistocene including the mid‐Pleistocene transition.
Transport and carbon exchanges in Red Sea Inverse Methodology
Authors: Metzl Nicolas , Moore Berrien , Papaud Anne , Poisson Alain
Published: February 2008

In this paper, we use an inverse methodology to parameterize a box model of the Red Sea to study carbon exchanges and transport. In this application, we use simultaneously the information contained in physical and biogeochemical tracer profiles such as temperature, salinity, dissolved inorganic carbon, alkalinity, oxygen, and phosphate. Since the Red Sea is subject to a seasonal monsoon regime and because we are interested in resolving exchanges from the surface to the bottom, we have decoupled the temporal regime into two seasons : winter (November to May) and summer (June to October). We present the two solutions which include advective and mixing (eddy diffusion) exchanges as well as new primary production, decomposition, carbonate formation, and dissolution. The circulation is reversed from one season to the next. The net biological exchanges (new production) of carbon, compatible with the dynamical solutions, are almost null for the organic processes (negative in summer, positive in winter); the budgets for the mineral processes are negative for both seasons. This result is consistent with the view that carbonates play an important role in the budget of carbon in Red Sea. Finally, taking advantage of richer data sets for the summer season, we present two box designs for this period. It appears that transport solutions are sensitive to the choice of box topology, whereas biochemical exchanges are roughly the same for both designs.
Volume and surface area size distribution, water mass and model fitting of GCE/CASE/WATOX marine aerosols
Authors: Kim Y. , Sievering H. , Boatman J.
Published: February 2008

As a part of the Global Change Expedition/Coordinated Air‐Sea Experiment/Western Atlantic Ocean Experiment (GCE/CASE/WATOX), size distributions of marine aerosols were measured at two altitudes of about 2750 and 150 m above sea level (asl) over the size range 0.1 ∼ 32 μm. Lognormal fitting was applied to the corrected aerosol size spectra to determine the volume and surface area size distributions of the CASE‐WATOX marine aerosols. Each aerosol size distribution was fitted with three lognormal distributions representing fine‐, large‐, and giant‐particle modes. Water volume fraction and dry particle size of each aerosol size distribution were also calculated using empirical formulas for particle size as a function of relative humidity and particle type. Because of the increased influence from anthropogenic sources in the continental United States, higher aerosol volume concentrations were observed in the fine‐particle mode near‐shore off the east coast; 2.11 and 3.63 μm3 cm−3 for free troposphere (FT) and marine boundary layer (MBL), compared with the open‐sea Bermuda area values; 0.13 and 0.74 μm3 cm−3 for FT and MBL. The large‐particle mode exhibits the least variations in volume distributions between the east coast and open‐sea Bermuda area, having a volume geometric median diameter (VGMD) between 1.4 and 1.6 μm and a geometric standard deviation between 1.57 and 1.68. For the giant‐particle mode, larger VGMD and volume concentrations were observed for marine aerosols nearshore off the east coast than in the open‐sea Bermuda area because of higher relative humidity and higher surface wind speed conditions. Wet VGMD and aerosol water volume concentrations at 15 m asl ship level were determined by extrapolating from those obtained by analysis of the CASE‐WATOX aircraft aerosol data. Abundance of aerosol water in the MBL serves as an important pathway for heterogeneous conversion of SO2 in sea salt aerosol particles.
Aerosol black carbon and radon as tracers for air mass origin over the North Atlantic Ocean
Authors: Hansen A. D. A. , Artz R. S. , Pszenny A. A. P. , Larson R. E.
Published: February 2008

We present results from the Global Change Expedition/ Coordinated Air‐Sea Experiment/Western Atlantic Ocean Experiment (GCE/CASE/WATOX) research cruise conducted from July to September 1988 in the North Atlantic Ocean aboard the NOAA shipMt. Mitchell. We examine the correlations between measurements of aerosol black carbon (BC, a tracer for combustion emissions), radon 222 (Rn, a tracer for natural emissions from land masses), and calculated isentropic back trajectories from the ship's position during two portions of the cruise that circled the North Atlantic Ocean. The results suggest four distinct categories of origin of the sampled air mass, with trajectories connecting back to different geographical areas: case A, trajectories from inhabited land, with the air mass containing strongly correlated BC and Rn; case B, trajectories from uninhabited (far northern) land, with Rn but little BC; case C, contaminated marine air, with little Rn but moderate BC, correlated with observations of combustion sources (other ships, etc.) in the vicinity; and case D, air masses of remote marine origin, with low BC and low Rn content. The requirements of the trajectory analyses lead to an improved understanding of the transport pathways across the ocean. We conclude that real‐time measurements of aerosol black carbon and radon, coupled with timely meteorological analyses, can be a powerful indicator of air mass origin both retrospectively and during the course of an experiment to assist in the scheduling of other measurements.
Altitude profiles of infrared radiance of O3(9.6 µm) and CO2(15 µm)
Authors: Stair A. T. , Ulwick James C. , Baker Doran J. , Wyatt Clair L. , Baker Kay D.
Published: February 2008

The infrared spectrum of the upper atmospheric emissions between 7 and 23 µm has been measured with two spectrometers carried to high altitude by sounding rockets. Radiance profiles of O3(9.6 µm) and CO2(15 µm) radiations have been obtained to nearly 100 and 150 km, respectively.
Preliminary results of a cosmic dust experiment on the Moon
Authors: Berg O. E. , Richardson F. F. , Rhee J. W. , Auer S.
Published: February 2008

A 3‐axes cosmic dust experiment placed on the lunar surface by the APOLLO 17 crew is registering impact parameters of cosmic dust and lunar ejecta. 1,117 events have been recorded in 8 months of data. Preliminary conclusions on the nature of the data include possible evidence of lunar soil transport associated with the terminators. Particle fluxes derived for two of the three sensor systems and for specified conditions of exposure are:

urn:x-wiley:00948276:media:grl78:grl78-math-0001

urn:x-wiley:00948276:media:grl78:grl78-math-0002
Secular‐invariant relationships among internal geomagnetic field coefficients
Authors: Roederer Juan G.
Published: February 2008

Some features of the secular variation of the geomagnetic field are examined. Contours encircling constant magnetic flux (third adiabatic invariant), corresponding to a “shell” of field lines in secular motion, reveal a general westward drift that is longitude and latitude dependent (with minima in the north Pacific and south Atlantic areas). Some invariant relationships appear among the field coefficients in the tilted, centered dipole (geomagnetic) coordinate system. The quadrupole phases ϕ2¹ and ϕ2², with a westward drift of 0.38 degrees per year, seem to bear a constant phase difference of 45° physically this corresponds to a n=2, m=1 current system that is tilted with respect to the geomagnetic equator. The octupole phases, particularly ϕ3², appear to be locked to the earth's rotation vector (no drift at all in the tilted dipole system). In our present epoch, the energy contained in the quadrupole and octupole field outside the core is increasing at a rate roughly equal to that of decrease of main dipole field energy. The hexadecapole terms show a mixture of westward and eastward drifts. On the average, the total hexadecapole current system does not reveal any notable drift in the original (geographic) frame of reference.
Residence times of aerosols and gases in the stratosphere
Authors: Hunten D. M.
Published: February 2008

Vertical distributions of particles (0.1 µm radius) and gases are derived for a simplified model of the stratosphere. A constant source acts at a specific range of heights, and the troposphere is a sink. Gravitational settling is shown to have a large effect on the distribution and residence time of the particles. This effect cannot be ignored in derivation of vertical eddy coefficients from tracer data, and is of the right magnitude to reconcile the results obtained from particulate and gaseous radioactivity.
Near‐simultaneous observations of intermittent internal waves on the continental shelf from ship and spacecraft
Authors: Apel John R. , Proni John R. , Byrne H. Michael , Sellers Ronald L.
Published: February 2008

Internal waves on the continental shelf off New York have been observed from ship and the ERTS‐1 spacecraft, and positive correlations made between surface and subsurface measurements of temperature, acoustic volume reflectivity, and surface slicks. The spacecraft imagery senses the quasi‐periodic variations in surface optical reflectivity induced by the internal waves. The waves appear to be tidally generated at the shelf edge and occur intermittently in packets, which propagate shoreward and disappear in water near 50‐m depth.
Variations in the solar wind stand‐off distance at Mercury
Authors: Siscoe G. , Christopher L.
Published: February 2008

The intrinsic dipole model of the magnetosphere of Mercury is combined with statistics on the solar wind dynamic pressure from Explorers 33 and 35 to obtain histograms of the solar wind stand‐off distance for aphelion, perihelion and median distance of Mercury from the sun. The results show that even at perihelion the stand‐off distance lies above the surface the great majority of the time. On rare occasions, direct impact of the solar wind onto the surface will occur.
Hα emission in charge exchange collisions of protons in nitrogen and argon
Authors: Suchannek Rudolf G. , Sheridan J. Roger
Published: February 2008

Under non‐equilibrium conditions, apparent cross sections for the emission of the Hα line in charge changing collisions of protons in nitrogen and argon were measured in the energy range from 0.64 to 29 kev. Since emission cross sections above 10 kev are known, only our measurements below 10 kev are of importance for applications because they represent lower bounds for the unknown emission cross sections. The reduction factors for the Hα emission from 3S and 3D levels due to non‐equilibrium conditions in the observation region of the beam were computed for our experimental conditions as a function of impact energy.
Atmospheric halocarbons: A discussion with emphasis on chloroform
Authors: Yung Yuk Ling , McElroy Michael B. , Wofsy Steven C.
Published: February 2008

Bleaching of paper pulp represents a major industrial use of chlorine and could provide an environmentally significant source of atmospheric halocarbons. The related global production of chloroform is estimated at 3 × 105 ton yr−1 and there could be additional production associated with atmospheric decomposition of perchloroethylene. Estimates are given for the production of methyl chloride, methyl bromide and methyl iodide, 5.2 × 106, 7.7 × 104, and 7.4 × 105 ton yr−1 respectively. The relative yields of CH3Cl, CH3Br and CH3I are consistent with the hypothesis of a marine biological source for these compounds. Concentrations of other halocarbons observed in the atmosphere appear to indicate industrial sources.
The partitioning of rare earth elements between garnet and liquid at high pressures: Preliminary experiments
Authors: Shimizu N. , Kushiro I.
Published: February 2008

Preliminary experiments were made to determine the partition coefficients of rare earth elements between garnet and liquid at 30 kb and 1275°C in the system diopside(30 wt%)‐pyrope(70%)‐water. REE were added to the system by titration at concentration levels in the range of natural basalts. The phases were separated by differential dissolution technique(DDT) and analized for REE by isotope dilution. The partition coefficients(solid/liquid) are: 0.021 for Ce, 0.087 for Nd, 0.217 for Sm, 0.320 for Eu, 0.498 for Gd, 1.06 for Er and 4.03 for Yb. They are in excellent agreement with those estimated from cpx‐liq and cpx‐gar relationships currently used in the literature.
Effects of plate structure and dilatancy on relative teleseismic P‐wave residuals
Authors: Engdahl E. R.
Published: February 2008

A study intended to detect time‐dependent velocity decreases beneath the Aleutians and/or Alaska has resulted in the discovery of some remarkable plate effects on relative teleseismic P‐wave residuals. The data are relative residuals between an Aleutian station (ADK) and two Alaskan stations (PMR, GIL) from deep focus (> 300 km) earthquakes in the Fiji‐Tonga source region. These stations have maximum differences of only 17° in distance and 12° in azimuth from this source. Differences of up to 2 sec in the relative residuals correlate very well with the geographic location of events at the source. The persistence of these differences in the residuals at 600–700 km depth indicates most likely the presence of velocity anomalies of large magnitude below 700 km beneath the slab. Observed changes in relative residuals with depth of focus appear bounded by 10% velocity differences at the source between station ray paths. A subset of these data shows no well defined velocity change near ADK before the magnitude 6.8 Adak Canyon earthquake of May 2, 1971.
The Brawley, California Earthquake Sequence of January, 1975, and triggering by Earth tides
Authors: Sauck William A.
Published: February 2008

Occurrence times of many individual events in the 1975 Brawley swarm correlate with times of theoretical gravity tide maxima and minima. Most events occur near the extrema or during declining gravity, with relatively few occurring during increases in gravity. The swarm itself began at a time when daily peak‐to‐peak gravity tide variations were increasing. Review of previous correlations and correlation attempts shows negative results for global or regional distributions of earthquakes, but successful correlations for small areas and individual swarms or aftershock sequences. The explanation proposed for this dichotomy is that the oceanic tides cause large and variable phase differences between the theoretical gravity tide (based on the positions of the sun and moon) and the actual deformational solid earth tide for locations in and near ocean basins. If it is indeed the deformational earth tide (strain) which triggers some earthquakes, then the correlation of earthquake times with theoretical gravity tides is always unsuccessful for large geographic areas because of the variable phase of oceanic tides, and is often successful for small areas because the oceanic effect is constant.
Pulsating aurora in high‐latitude satillite photographs
Authors: Siren Jan C.
Published: February 2008

Pulsating aurora has been identified in DMSP photographs. Its unique zebra‐stripe appearance is due to the interaction of the aurora pulsation period with the imaging device's raster scan period. It most commonly, but not exclusively, occurs on the equatorward edge of the auroral oval after midnight and is positively correlated with global magnetic activity. Pulsating aurora also occurs on the poleward leading edge of midnight sector surges.
Nitric oxide gamma band emission in an aurora
Authors: Feldman Paul D.
Published: February 2008

Emission of the NO γ(1,0) band at 2150 A has been observed by a rocket‐borne spectrophotometer in an IBC II+ aurora. The v'=0 progression of the γ‐system does not appear in the spectrum. The observed emission rate of the 2150 A feature increases relative to N2+ first negative band emission with increasing altitude. We suggest radiative recombination of NO+ ions with electrons as a possible excitation mechanism compatible with the data.
Estimating soil moisture in the root zone of crops: A technique adaptable to remote sensing
Authors: Idso Sherwood B. , Ehrler William L.
Published: February 2008

A technique for estimating water contents within the root zones of crops from measurements of midday leaf‐air temperature differentials is developed. Pertinent data used in the analysis were obtained from a cotton crop and two sorghum crops grown on an Avondale loam at Phoenix, Arizona. Since air temperature is the most commonly measured meteorological parameter on earth, and since crop canopy temperatures can be obtained by radiometric means, the technique appears to point the way toward the eventual development of a procedure for the estimation of crop yields via remote sensing.
Thermal inertia imaging: A new geologic mapping tool
Authors: Kahle Anne B. , Gillespie Alan R. , Goetz Alexander F. H.
Published: February 2008

A thermal model of the Earth's surface has been developed and used to determine the thermal inertia of a test site in the Mojave Desert, California. The model, which includes meteorological heating terms as well as radiation and conduction heating terms, is used with remotely sensed surface temperature and reflectance data to determine the thermal inertia of the surface materials at the test site. The thermal inertia is displayed in image form, and can aid in the differentiation of the various lithologic materials in the test site. Since this thermal property is representative of the upper several cm of the surface, it complements visible and reflected near‐IR image data.
Petrology, structure and origin of the Manicouagan Melt Sheet, Quebec, Canada: A preliminary report Floran ET AL.
Authors: Floran R. J. , Simonds C. H. , Grieve R. A. F. , Phinney W. C. , Warner J. L. , Rhodes M. J. , Jahn B. M. , Dence M. R.
Published: February 2008

Chemical, petrographic, isotopic and field studies of igneous‐textured rocks within the Manicouagan structure indicate that they are the product of impact melting. Features of the melt sheet include a high degree of textural variation combined with chemical homogeneity. The textures record a complex thermal history and are due primarily to the interaction of clasts with melt. An inverse correlation between clast abundance and matrix grain size allows the melt sheet to be divided into three vertically gradational units of variable thickness. Chemical homogeneity indicates that the impact melting process has the first order effect of homogenizing heterogeneous target material. The process, however, is not totally effective, because significant (although small) deviations from a calculated average composition exist, particularly in the basal clast‐laden unit. These differences depend on clast composition and abundance. The results presented here are consistent with proposed models for the generation of terrestrial and lunar impact melts.
Magnetic permeability measurements and a lunar core
Authors: Goldstein B. E. , Phillips R. J. , Russell C. T.
Published: February 2008

Measurements of the magnetic field induced in the moon while it is in the geomagnetic tail lobes have been interpreted in terms of lunar magnetic permeability due to free iron content; such studies ignored the possibility that a highly conducting lunar core (Fe or FeS) would exclude magnetic fields with an apparent diamagnetic effect. Using lunar chemical and thermal models to determine plausible limits of magnetic permeability, we interpret measurements of the induced moment. The maximum likely radius of a lunar core is 580 km. Subsatellite and ALSEP measurements of the induced field are in disagreement. Resolving the differences is critical to determining whether a core could or does exist.
Local vertical motions and kinetic temperature from AE‐C as evidence for aurora‐induced gravity waves
Authors: Spencer N. W. , Theis R. F. , Wharton L. E. , Carignan G. R.
Published: February 2008

In situ measurements of local vertical neutral particle motions have been made using the Neutral Atmosphere Temperature Instrument (NATE) on Atmosphere Explorer‐C from observations of the direction of flow of neutral particles into the antechamber of the sensor (mass spectrometer). Values ranging from a few to more than 80 meters per second have been observed. The data show vertical motions greater than a few meters per second to be present most of the time, the magnitude being a function of many factors including magnetic activity, location, and magnetic storm history. In a specific case, it is concluded that the observed vertical motions and kinetic temperature are evidence of a travelling disturbance originating as a gravity wave in the auroral zone.
Evidence for a Rayleigh‐Taylor type instability and upwelling of depleted density regions during equatorial spread F
Authors: Kelley M. C. , Haerendel G. , Kappler H. , Valenzuela A. , Balsley B. B. , Carter David A. , Ecklund Warner L. , Carlson C. W. , Häusler B. , Torbert R.
Published: February 2008

Recent rocket probe, barium cloud and radar measurements conducted during equatorial spread F conditions are interpreted in terms of a Rayleigh‐Taylor gravitational instability operating on the bottomside of the F peak. The persistent theoretical problems associated with strong radar echoes typically observed in patch‐like structures at high altitudes are explained in terms of regions of depleted plasma density which bouyantly rise against the gravitational field.
Determination of the O+(²P) ionization frequency using satellite airglow and neutral composition data and its implications on the EUV solar flux
Authors: Rusch D. W. , Torr D. G. , Hays P. B. , Torr M. R.
Published: February 2008

Simultaneous measurements of the O+(²D ‐ ²P) emission at 7319‐30Å and the atomic oxygen density in the optically thin region of the atmosphere offer a straightforward means of determining the photoionization frequency, I∞, for the production of O+(²P) ions. The ionization frequency is found to be 4.7 × 10−8sec−1 ±30% on June 8, 1974 and 3.4 × 10−8sec−1 ±30% on December 17, 1975. The wavelength dependent solar flux intensity in the relevant spectral region was also measured June 8, 1974 on the same spacecraft (Atmosphere Explorer‐C). A calculation of I∞ using this solar flux and currently accepted values of the photoionization excitation cross sections gives a value of 4.9 × 10−8sec−1, thus confirming the measured solar EUV flux.
The spiral structure of the interplanetary magnetic field
Authors: Parker G. D. , Jokipii J. R.
Published: February 2008

We examine the Pioneer 10 data concerning the heliocentric radial variation of the interplanetary magnetic field. Incorporating the systematic increase in solar wind velocity observed during the mission leads to much improved agreement between the usual Parker Archimedean spiral and the data. The effects of correlations between short‐period fluctuations of speed and azimuthal field are discussed and it is concluded that during the period under study they did not substantially affect the average magnetic field.
Oxidation of the Martian surface: Constraints due to chemical processes in the atmosphere
Authors: McElroy M. B. , Kong T. Y.
Published: February 2008

Dissociation of water in the Martian atmosphere may supply oxygen to the surface and may result in the formation of minerals such as goethite, as proposed by Huguenin. The supply rate is limited by chemical processes in the atmosphere which regulate the abundance of O2. The net surface sink for atmospheric oxygen can be as large as 3.3 × 107 atoms cm−2 sec−1 which compares to the escape rate of 6 × 107 atoms cm−2 sec−1.
Observations of intercrater plains on Mercury
Authors: Malin Michael C.
Published: February 2008

Analysis of Mariner 10 stereoscopic images of the surface of Mercury suggest that ancient, intercrater plains consist in part of visually indistinct but topographically defined circular depressions inferred to be highly degraded craters and basins. Embayment of some craters within the heavily cratered terrain and transection of basins and craters by intercrater plains suggest that formation of at least some intercrater plains postdates the later portions of the bombardment of Mercury by large objects. On the other hand, superposition of crater ejecta onto portions of intercrater plains in other areas indicates that some large craters formed into a pre‐existing, intercrater plains unit. A single episode of obliteration (to form intercrater plains) or bombardment (to produce the large craters) cannot be reconciled with available observations. A more complex history of contemporaneous crater and plains formation is suggested.
The magnetosphere of Venus: Evidence for a boundary layer and a magnetotail
Authors: Russell C. T.
Published: February 2008

A detailed examination of Mariner 5 magnetic field data reveals evidence for a boundary layer beginning in the dayside ionosphere, and a magnetotail much like the terrestrial magnetotail in accord with Venera measurements.