bluuebunny/crossref_metadata_2025 huggingface dataset:
Methane flux from Minnesota Peatlands
Authors: Crill P. M. , Bartlett K. B. , Harriss R. C. , Gorham E. , Verry E. S. , Sebacher D. I. , Madzar L. , Sanner W.
Published: February 2008

Northern (>40°N) wetlands have been suggested as the largest natural source of methane (CH4) to the troposphere. To refine our estimates of source strengths from this region and to investigate climatic controls on the process, fluxes were measured from a variety of Minnesota peatlands during May, June, and August 1986. Sites included forested and unforested ombrotrophic bogs and minerotrophic fens in and near the U.S. Department of Agriculture Marcell Experimental Forest and the Red Lake peatlands. Late spring and summer fluxes ranged from 11 to 866 mg CH4 m−2 d−1, averaging 207 mg CH4 m−2 d−1 overall. At Marcell Forest, forested bogs and fen sites had lower fluxes (averages of 77 ± 21 mg CH4 m−2 d−1 and 142 ± 19 mg CH4 m−2 d−1) than open bogs (average of 294 ± 30 mg CH4 m−2 d−1). In the Red Lake peatland, circumneutral fens, with standing water above the peat surface, produced more methane than acid bog sites in which the water table was beneath the moss surface (325 ± 31 and 102 ± 13 mg CH4 m−2 d−1, respectively). Peat temperature was an important control. Methane flux increased in response to increasing soil temperature. For example, the open bog in the Marcell Forest with the highest CH4 flux exhibited a 74‐fold increase in flux over a three‐fold increase in temperature. We estimate that the methane flux from all peatlands north of 40° may be on the order of 70 to 90 Tg/yr though estimates of this sort are plagued by uncertainties in the areal extent of peatlands, length of the CH4 producing season, and the spatial and temporal variability of the flux.
Pollutant concentrations upwind and downwind of Bermuda
Authors: Whelpdale Douglas M. , Knap Anthony H. , Toom Desiree L.
Published: February 2008

This paper describes atmospheric concentration measurements of a number of inorganic and organic species which are of interest as tracers of continental emissions in the marine atmosphere, upwind and downwind of the island of Bermuda. Measurements made downwind during 4 days of GCE/CASE/WATOX in July 1988 showed that concentrations of inorganic species (non‐sea‐salt sulfate, total nitrate, non‐sea‐salt potassium, and sulfur dioxide) and some organic species (total PCBs and n‐alkanes) were greater, on average, by factors of 3 to 15 than the upwind values. Other organics (HCB, alpha, gamma and total HCH, dieldrin, and chlordane) showed smaller increases downwind. Downwind concentrations were less than those found along the east coast of North America. Upwind values were similar to other “remote” North Atlantic data; taken together, they show that the North Atlantic atmosphere, while clean, is not pristine.
Measurements of dimethyl sulfide oxidation products in the summertime North Atlantic marine boundary layer
Authors: Pszenny A. A. P. , Harvey G. R. , Brown C. J. , Lang R. F. , Keene W. C. , Galloway J. N. , Merrill J. T.
Published: February 2008

Chemical data derived from air and precipitation samples collected during the Global Change Expedition/Coordinated Air‐Sea Experiment/ Western Atlantic Ocean Experiment (GCE/CASE/WATOX) over the North Atlantic Ocean (NAO) are interpreted using simple box models. Estimated total sulfur (S) deposition fluxes from air masses with tropical oceanic, African, clean North American, and polluted North American origins are 4.4, 16, 33, and 70 μmol m−2 day−1, respectively, with associated uncertainties of at least factors of 2 to 3. Crude estimates of the fractions of deposition attributable to marine biogenic versus anthropogenic S sources suggest that the latter may be enhancing the natural NAO atmospheric S cycle by a factor of 0.5 to 0.8. Combination with similar estimates for the North Pacific region [Savoie and Prospero, 1989] yields an overall, area‐weighted enhancement factor of approximately 0.3 for northern hemisphere ocean areas, consistent with estimates by Wigley [1989] based on climate modeling studies.
Effects of air pollutants on cloud nucleation
Authors: Pueschel Rudolf F. , Van Valin Charles C. , Parungo Farn P.
Published: February 2008

The nucleation efficiency of an urban aerosol is closely related to its chemical composition, which is strongly affected by human activities. Sulfates and leadbromochloride have been found to temporarily increase the surface solubility and capillarity of naturally produced insoluble clay particles. This phenomenon alters the atmospheric nuclei budget and affects the natural mechanisms that remove pollutants from the atmosphere.
A method for oxygen isotope analyses of organic material
Authors: Hardcastle K. G. , Friedman I.
Published: February 2008

A technique has been developed to measure 18O/16O ratios in milligram amounts of organic material. The organic material is pyrolyzed at 1250°C in the presence of diamonds (easily outgassed carbon source) as the reducing agent. The carbon monoxide formed is converted to carbon dioxide by a high voltage discharge, and the CO2 is analyzed on a mass spectrometer. The precision of the method is ±0.35 permil (1 sigma).
Silicate perovskite from phase transformations of pyrope‐garnet at high pressure and temperature
Authors: Liu Lin‐gun
Published: February 2008

Both natural and synthetic pyrope have been compressed to pressures above 300 kbar in a diamond‐anvil press and heated to temperatures above 800°C by a continuous YAG laser. After quenching and release of pressure, X‐ray diffraction shows that the natural pyrope transforms to a single phase with perovskite‐like structure whereas the synthetic pyrope disproportinates into a mixture of MgSiO3 (perovskite) plus Al2O3 (corundum). The orthorhombic perovskite lattice parameters for the natural pyrope are ao = 4.816 ± 0.004 Å, bo = 4.973 ± 0.004 Å, and co = 6.997 ± 0.006 Å with Z = 4. The orthorhombic cell dimensions for MgSiO3 (perovskite) are ao = 4.818 ± 0.005 Å, bo = 4.869 ± 0.005 Å, and co = 6.906 ± 0.007 Å with Z=4. The calculated density of MgSiO3 perovskite is thus 4.12 g/cm³, or 3.7% denser than the isochemical mixed oxides. These experiments are the first demonstration of static high pressure phase transformations in silicate garnets and the first examples of a pure silicate existing in the perovskite structure.
Initial observations of plasma electrons from the Pioneer 10 flyby of Jupiter
Authors: Intriligator Devrie S. , Wolfe John H.
Published: February 2008

Initial results are presented from the electron measurements made by the Ames Research Center Plasma Analyzer during the inbound passage of Pioneer 10 in the vicinity of Jupiter. The observations indicate that as in the case of the earth's magnetosheath, there is an increase in electron temperature across the Jovian bow shock. During the second extended magnetosheath traversal (∼ 54 RJ to 46.5 RJ) the electron temperatures were generally higher than those observed during the first magnetosheath traversal (109 RJ to 96 RJ). These higher electron temperatures are in agreement with the measured higher magnitude of the magnetic field and ion density during this traversal. These observations are consistent with the contraction of the Jovian magnetosphere due to an increase in the solar wind dynamic pressure. In the outer Jovian magnetosphere the electron component of the thermal plasma was measured. These plasma electrons were associated with a peak in the electron counts at ∼ 4 eV and do not seem to be associated with the periodic behavior observed for the energetic electrons. The dayside magnetosphere is inflated with a high beta (β ∼ 1) plasma which in some respects is similar to that observed in the earth's magnetotail. The plasma electron measurements are consistent with a thick Jovian magnetosphere.
Cyclonic disturbances and their consequences in the thermosphere
Authors: Banks P. M. , Nagy A. F.
Published: February 2008

We draw attention to the possible existence of cyclonic type of disturbances in the thermosphere which are created by localized energy sources in the vicinity of the nightside (and possibly the dayside) auroral oval. Due to the Coriolis force and the character of F‐region ion motions, cyclonic disturbance cells of limited extent (3000 to 5000 km) may appear in conjunction with auroral substorms or more prolonged geomagnetic activity. Owing to prevailing thermospheric winds, these disturbances can be expected to drift equatorwards to mid‐latitude regions. The disturbance zone can be characterized in terms of a cyclonic wind pattern and significant changes in thermospheric neutral gas composition. This latter effect results in decreased plasma densities in the F‐region for the lifetime of the disturbance.
A regional approach to urban storm water detention
Authors: McCuen Richard H.
Published: February 2008

To control the increase in storm water runoff due to urban development many states require some form of storm water detention. However, existing laws use an “individual‐site” approach to storm water management rather than the more efficient regional approach. An individual site approach to storm water detention may actually increase the potential for localized flooding.
Asteroid size distribution: Implications for the origin of stony‐iron and iron meteorites
Authors: Chapman Clark R.
Published: February 2008

The diameter‐frequency distribution of large asteroids is analyzed, based on polarimetric and radiometric albedo data. The population of carbonaceous objects shows a high degree of fragmentation. But a class of apparently stony‐iron asteroids shows a relative excess frequency between diameters of 100 to 200 km. It is proposed that the latter objects are predominantly metallic cores of a group of chemically differentiated planetesimals all of which (except Vesta) have suffered catastrophic collisions. Collision frequencies in the asteroid belt may have been much greater than previously supposed.
Ozone measurements between 90 and 110 km altitude by mass spectrometer
Authors: Trinks H.
Published: February 2008

On June 29, 1974 at 15:14 LST a rocket‐borne cryogenic neutral gas mass spectrometer was flown above Wallops Island as part of the NASA/AFCRL ALADDIN 74 program. The altitude profiles of the signals obtained from argon between 90 and 200 km and ozone between 90 and 110 km are presented. From a comparison of Ar and O3 signals, the mixing ratio for O3 in the atmosphere is shown to be 10−6 or slightly less in the 90–100 km range. At 110 km the mixing ratio drops to around 10−7.
Initial observations of the artificial stimulation of ULF pulsations by pulsed VLF transmissions
Authors: Fraser‐Smith A. C. , Cole C. A.
Published: February 2008

Initial results are presented from an experiment to generate artificial ultra‐low‐frequency (ULF) hydromagnetic waves in the magnetosphere and ionosphere by means of specially modulated very‐low‐frequency (VLF) transmissions into the magnetosphere. The data were obtained predominantly during the interval September 1–7, 1973, when frequency‐shift‐keyed (FSK) VLF transmissions were made from Siple Station, Antarctica, and simultaneous VLF and ULF recordings were made at the conjugate point (Roberval, Quebec). The same 8‐hour transmission schedule was followed each day; it consisted primarily of intervals of FSK transmission (pulse lengths in the range 200 msec to 3.2 sec) interspersed with intervals of no transmission. All ULF pulsations with frequencies in the Pc 1 range (0.2 to 5 Hz) that occurred during the experiment started in an interval of FSK transmission and the average rate of occurrence of the ULF activity was about twice the rate observed on days with no transmissions.
Volume dependence of the vibrational free energy
Authors: Palciauskas V. V.
Published: February 2008

The explicit volume dependence of the vibrational part of the free energy is derived in terms of the first two moments of the mode gamma distribution and general characteristics of the lattice potential. Contrary to what is generally assumed, the approximation 〈γ²〉 = 〈γ〉² is inadequate for compounds in the NaCl structure and the distribution in mode gamma values has a significant contribution to the volume dependence of the Grüneisen parameter.
Further observational evidence regarding the origin of plasmaspheric hiss
Authors: Thorne Richard Mansergh , Barfield Joseph N.
Published: February 2008

Explorer 45 satellite observations of medium energy electrons and ELF waves (100‐1000 hz) have been analysed during a modest isolated substorm which occurred at about 0430 UT on Feb. 13, 1972. Approximately 50 minutes before the sharp rise in AE the electron flux (E ∼ 30 ‐ 240 KeV) measured within the plasmapause near dusk at L = 5 dropped below the normal quiet time level. Simultaneously the intensity of plasmaspheric hiss emissions fell to background levels. Following the substorm activity the electron flux recovered and plasmaspheric emissions first reappeared when the electron flux (E >30 KeV) attained a value comparable to the Kennel‐Petschek stably trapped level required for cyclotron resonant instability. The substorm associated electron flux reduction is explained as a modification in the drift orbits of geomagnetically trapped electrons caused by the onset of a large scale convection electric field. The simultaneous wave and particle observations are consistent with electron cyclotron resonant generation for plasmaspheric hiss emissions. During this relatively quiet period the source location appears to be restricted to the outer plasmasphere (L ≳ 5).
Electronic structure of iron and models of the Earth's core
Authors: Bukowinski M. S. T. , Knopoff L.
Published: February 2008

The possibility that iron might undergo a transition to the 3d8 state at core pressures is investigated. A detailed calculation of the electronic band structure of iron indicates that the transition occurs at approximately fourfold compression. At core pressures, the band structure is essentially similar to that at STP conditions. Thus, it appears that the only proposed alternative to freezing as the mechanism for the formation of the inner core from the outer core has been disqualified. In addition, a quantum mechanical calculation of the density and bulk‐modulus of iron gives values which are in excellent agreement with the latest inner core models. On the other hand, the density of the outer core is significantly lower than that of pure iron. This lends strong support to those theories which postulate an essentially pure iron solid inner core, and significant amounts of impurities in the outer core.
The possible importance of CSO for the sulfate layer of the stratosphere
Authors: Crutzen Paul J.
Published: February 2008

Photodissociation of CSO (and possibly CS2) may provide an interesting stratospheric source of SO2 and further conversion of this SO2 to H2SO4 may contribute significantly to the non‐volcanic background sulfate layer in the stratosphere. Assuming a tropospheric background volume mixing ratio of 2‐3 × 10−10, as indicated by some tropospheric measurements, the input of SO2 in the stratosphere coming from the decay of CSO is estimated to be 6 × 106 ‐ 107 molecules cm−2s−1. Little is known about the sources and sinks of CSO. It is, therefore, clear that, as a matter of caution, a possible growth of industrial releases of CSO (and CS2) into the atmosphere, e.g., from coal combustion, should be watched carefully with regard to their influence on the stratospheric aerosol layer and the earth's radiation balance.
Effect of odd hydrogen on ozone depletion by chlorine reactions
Authors: Donahue T. M. , Cicerone R. J. , Liu S. C. , Chameides W. L.
Published: February 2008

The odd hydrogen species, especially OH and HO2 are important in the chemistry of the natural stratosphere because of their direct reactions with O and O3 and their role in nitrogen oxide (NOx) cycles. When chlorine is added to the stratosphere the interaction of NOx, HOx and ClX species yields several potential feedback effects for O3 perturbations, some stabilizing and some destabilizing. Here we focus on the effects of HOx on O3 changes due to ClX injections. As ClX selectively attacks the ozone layer above 28 km the layer below tends to be thickened by the increased incidence of solarUV. If HOx densities are high they dampen this radiative feedback and prevent the healing at low altitudes. We demonstrate how the ozone‐layer shape changes under the influence of injected ClX for several choices of key HOx reaction rates. These same reaction rates exert partial control over the apportioning of Cl atoms among HCl, ClO and Cl, over the total amount of HOx, the ratios of OH to HO2 and H2O2 and the ratio of [NO + NO2] to [HNO3]. The uncertainty in these rates leads to at least a factor of three uncertainty in predicted ozone reductions due to ClX injections.
Electron pitch‐angle distributions in an inverted ‘v’ structure
Authors: Mizera Paul F. , Croley Donald R. , Fennell Joseph F.
Published: February 2008

The pitch‐angle distributions of 0.36 to 28.5 keV electrons in an inverted ‘V’ structure show characteristics that are consistent with an acceleration due to an electric field above an altitude of 750 km. The peak of the energy flux increases from Ep ≈ 0.5 keV to Ep ≈ 10 keV and then decreases back to low energies over a 2° −3° latitude interval and thus gives an inverted ‘V’ appearance on an energy‐time spectrogram. As the energy (Ep) at the maximum energy flux increases, the reflected flux becomes essentially the same as the precipitated flux for E < Ep; while field‐aligned enhancements are found only at E ≃ Ep. The magnitude of these enhancements are consistent with a simple electric field model. The pitch‐angle distributions of 28.5 keV electrons show a double loss cone at latitudes poleward of the inverted ‘V’ structure. These observations argue strongly for the existence of an electric field in a region of closed magnetic field lines.
Mt. Saint Helens seismic events: Volcanic earthquakes or glacial noises?
Authors: Weaver Craig S. , Malone Stephen D.
Published: February 2008

Low frequency seismic events have been recorded on Mt. Saint Helens, an historically active stratovolcano in the Cascade Range of Washington State. While the character of the events is similar to volcanic seismic events recorded on active volcanoes in many parts of the world, the seismic evidence gathered during an experiment on Saint Helens indicates the glaciers on the mountain as the source of the low frequency activity. The experimental results illustrate the current problem of predicting volcanic behavior from seismic data in such geophysically complex areas as glacier‐clad volcanoes.
Seismic structure of the oceanic crust from deep drilling on the Mid‐Atlantic Ridge
Authors: Hyndman R. D. , Aumento F. , Melson W. G. , Hall J. M. , Bougault H. , Dmitriev L. , Fisher J. F. , Flower M. , Howe R. C. , Miles G. A. , Robinson P. T. , Wright T. L.
Published: February 2008

Five deep crustal holes were drilled into the Mid‐Atlantic Ridge near 37°N by Glomar Challenger on Leg 37 of the Deep Sea Drilling Project. The drilling results and laboratory measurements of seismic velocity on samples from one hole of over 500 m into basement have shown that the low velocity upper crustal layer 2a consists of interlayered solid basalt and shattered and fractured volcanic material with extensive large scale porosity and voids and some intercalated sediments. Gabbros and serpentinites with velocity appropriate for the lower crust were recovered from another hole.
Determination of exospheric neutral gas temperatures
Authors: Mauersberger K. , Nier A. O. , Kayser D. C. , Potter W. E. , Engebretson M. J.
Published: February 2008

The Atmosphere Explorer satellites (AE‐C, ‐D, and ‐E) were initially placed into highly elliptical orbits with perigees around 140 km and apogees of 4000 km. As a result of such an orbital geometry, measurements of neutral constituents at high altitudes represent mainly vertical changes in densities. The influence of horizontal density gradients on measurements above 400 km is small. Under geomagnetically quiet conditions, the density profiles can be used to derive scale height temperatures of the exosphere. The Open Source Neutral Mass Spectrometer (OSS) flown on all three AE‐satellites measured neutral constituents such as N2, O and N well above 400 km. The temperatures derived from scale heights show a good agreement among the constituents and the expected close correlation with the F10.7 cm solar flux. Satellites with highly elliptical orbits provide the opportunity to measure simultaneously both densities and temperatures.
The interplanetary magnetic field and energetic electrons from Jupiter
Authors: Jokipii J. R.
Published: February 2008

The reported ∼4‐month "season" for observation of Jovian electron events at 1 a.u. is shown to be a plausible consequence of field‐line random walk in the solar wind. Values of the field‐line random‐walk coefficient deduced earlier in connection with observations of solar protons, photospheric supergranulation and the interplanetary magnetic‐field power spectrum, lead to an approximate value for the spread of Jovian electrons at 1 a.u. which corresponds to a ∼4‐month duration of events. This model is consistent with a point source at Jupiter.
The magnetic field of Mercury and models of thermal evolution
Authors: Sharp H. N. , Strangeway D. W.
Published: February 2008

Recent planetary probes have performed in situ measurements of the magnetic fields of all the terrestrial planets. Consideration is given to the origin of these fields, with attention to the equilibrium — condensation hypothesis for the formation of the solar system. In particular, it is shown that Mercury's present day magnetic field could have been acquired during or shortly after a cold accretion or that it could be due to a presently operating dynamo, resulting from a ‘hot evolution’. Two parameters which would help to distinguish between these possibilities are the present‐day surface heat flow and the moment of inertia.
Io's atmosphere and ionosphere: New limits on surface pressure from plasma models
Authors: Johnson T. V. , Matson D. L. , Carlson R. W.
Published: February 2008

We have studied charge particle impact as a mechanism for the production of Io's ionosphere. Pioneer 10 thermal plasma measurements and magnetospheric plasma models which explain the observed spatial distribution of neutral hydrogen and sodium atoms in the vicinity of Jupiter’s satellite Io imply electron fluxes of ∼1010 cm−2 sec−1. The fluxes and the temperature (∼100 eV) of this plasma suggest that electron impact ionizaion is the dominant process in forming the ionosphere of Io. It is found that the surface number density of the neutral species required to match the observed electron density profiles is ∼109 cm−3 or less. This value is two orders of magnitude lower than previous estimates.
Venera‐9 magnetic field measurements in the Venus wake: Evidence for an Earth‐like interaction
Authors: Russell C. T.
Published: February 2008

Venera‐9 magnetic field measurements in the Venus wake provide additional support for the hypothesis that Venus has an intrinsic planetary field. The observed field is in the direction expected for a northward moment, and is similar to that observed in equivalent locations in the terrestrial magnetosphere, both in its temporal and spatial behavior. In particular, Venera‐9 appears to have observed a plasma sheet expansion, field‐aligned currents, and tail‐field dipolarization.
Recovery of atmospheric parameters from the Apollo/Soyuz‐ATS‐F radio occultation data
Authors: Rangaswamy S.
Published: February 2008

As part of the Apollo‐Soyuz Test Project (ASTP), Apollo was tracked in the satellite‐to‐satellite tracking mode by the NASA synchronous satellite ATS‐F. The tracking data obtained at occultation of Apollo by the earth has been used in this study to compute atmospheric parameters like pressure and temperature. The results of the numerical inversion have been compared with data from a radiosonde station near the occultation site. Although this comparison lacks exact space‐time coincidence because of the paucity of the data, it is of interest to report that near the surface of the earth, the refractivity computed from occultation data agreed with the radiosonde‐derived values to within 3 percent. A pressure profile deduced from the refractivity profile by using a simplified model of the atmosphere showed good agreement with radiosonde measurements. Although the present results are based on one occultation pass and lack statistical validity, they demonstrate the feasibility of determining absolute pressure levels in the atmosphere from occultation measurements.
Submarine canyons: Internal wave traps?
Authors: Gordon R. L. , Marshall N. F.
Published: February 2008

Kinetic energy of water currents near the axis of La Jolla submarine canyon is enhanced in a broad frequency band above tidal frequencies and below the Väisälä frequency when compared with water motions nearby but not within the canyon. This energy appears to be derived from first mode internal waves over the adjacent continental shelf.
Satellite observations of an ionospheric acceleration mechanism
Authors: Shelley E. G. , Sharp R. D. , Johnson R. G.
Published: February 2008

A satellite‐borne energetic ion mass spectrometer experiment has detected fluxes of O+ and H+ ions flowing up out of the ionosphere in the auroral and polar regions. The observed ions have energies in the keV range, narrow pitch‐angle distributions aligned along the magnetic field direction and peak flux intensities of the order of 108 (cm²‐sec‐sterad‐keV)−1. The observations were made at altitudes between 5000 and 8000 km on both the day and nightsides of the earth.
An alternative interpretation of Jupiter's “plasmapause”
Authors: Neugebauer M. , Eviatar A.
Published: February 2008

It has recently been suggested that Io is an important source of ions for the plasma detected by Pioneer 10 in the inner magnetosphere of Jupiter. Assuming this to be true, we show that near the orbit of Io the central collector of the Pioneer‐10 plasma instrument could detect only inwardly diffusing ions created at a radial distance greater than that of the spacecraft. The rapid decrease in ion density observed beyond Io's orbit is attributed, at least partially, to this effect and thus may not represent a real plasma boundary such as a "plasmapause." Instead, the drop in observed ion density could correspond to a decrease in the density of Io‐associated neutral particles orbiting Jupiter.
More evidence for an exospheric hydrogen sub‐solar bulge
Authors: Emerich C. , Cazes S. , Vidal‐Madjar A.
Published: February 2008

Measurements of the geocoronal absorption at the center of the solar Lyman‐α line, performed by the University of Paris instrument on board OSO‐5 are compared to aspherical models. The deduced values of the minimum hydrogen density were analysed over periods of one year, between 1969 and 1972. They indicate a systematic departure up to 40% from exospheric models. This feature corresponds to a dayside sub‐solar hydrogen bulge characterized by a 25% decrease of the hydrogen density at 50° away (northward or southward) from the solar direction. This bulge could be due to solar direction related anisotropies of the hydrogen production, diffusion, transport and loss mechanisms which are neglected in the exospheric theories.
Vibrationally‐excited hydroxyl molecules in the lower atmosphere
Authors: Nagy A. F. , Liu S. C. , Baker D. J.
Published: February 2008

The vibrational energy distributions of hydroxyl molecules in the lower atmosphere were calculated; as expected, the distributions are found to be highly nonequilibrated. Attention is drawn to the role that vibrationally‐excited molecules may play in modifying the chemistry of the lower atmosphere. The most likely role for OH‡ in the stratosphere is via reactions that may not otherwise be energetically viable.
Large‐scale vertical motion calculations in the AVE IV Experiment
Authors: Wilson Gregory S.
Published: February 2008

Using 3‐ and 6‐h consecutive rawinsonde and surface data from NASA's AVE IV Experiment, synoptic‐scale vertical motion calculations are made using an adiabatic technique and three variations of the kinematic technique. Both subjective and objective comparisons in space and time between the sign and magnitude of the computed vertical velocities and precipitation intensities (from Manually Digitized Radar data [Foster and Reap, 1973]) are made. These comparisons are conducted to determine which method would consistently produce realistic magnitudes, patterns, and vertical profiles of vertical velocity essential to the diagnostic study of the relationship between severe convective storms and their environment in AVE IV. The kinematic method, adjusted to the adiabatic value at 100 mb, proved to produce the best overall vertical velocities.
Jovian and terrestrial “harmonic” radiations
Authors: Jones Dyfrig
Published: February 2008

Some theories of Jovian decametric and Terrestrial kilometric radiations require that the emissions escape at the plasma frequency in the magnetospheres of these planets. This requirement creates difficulties in explaining a number of characteristics of these radiations. It seems that the problems may be overcome by invoking wave‐wave interaction between Z‐mode waves, and it is suggested that an estimate of Saturn's magnetic field on the basis of the observed hectometric radiation could be erroneous.
The magnetopause electron layer along the distant magnetotail
Authors: Baker D. N. , Stone E. C.
Published: February 2008

An energetic electron layer is found immediately adjacent to, and outside of, the magnetopause surface along the distant magnetotail (−40 ≲ XSM ≲ −15 RE). The layer has been detected using Caltech instrumentation aboard the earth‐orbiting spacecraft IMP‐8 and is observed for electrons with energies E ≳ 200 keV. The present study shows that such electrons form a layer ∼ 3 RE thick and are strongly streaming in a well‐ordered pattern, especially along the dusk magnetopause. The energy dissipation implied by the persistent flow may be a direct indication of nearly continuous magnetic merging at or near the magnetopause.
Upper limits of the rate constants for the reactions of CFCl3(F‐11), CF2Cl2(F‐12), and N2O with OH. Estimates of corresponding lower limits to their tropospheric lifetimes
Authors: Chang Jenq Sian , Kaufman Frederick
Published: February 2008

The reactions of CFCl3, CF2Cl2, and N2O with OH are studied at temperatures up to 480 K in a discharge‐flow system with resonance fluorescence detection of OH. Little, if any reaction is found, upper limits of 5, 6, and 4 × 10−16 cm³ s−1 are reported at 480 K for the three rate constants. The results are compared with other investigations and with reaction rate theory. On the basis of a very simple model, removal times greater than 104 years are calculated for reaction with tropospheric OH, i.e. they are negligibly slow removal processes.
Short arc reductions of Geos‐3 altimetric data
Authors: Hadgigeorge George , Trotter Jerry E.
Published: February 2008

The Air Force Geophysics Laboratory (AFGL) computer program SARRA (Short Arc Reduction of Radar Altimetry) has been used for geoid determination with altimetric observations from the GEOS‐3 satellite. A unique feature of SARRA is the simultaneous recovery of the orbit parameters and the surface coefficients as defined by the kernel function analysis. Orbits good to approximately 20 meters are adequate for precise geoid determinations by virtue of the orbital adjustment in the reductions. Altimetric data over adjacent areas of the Indian and South Pacific Oceans and a portion of the North Atlantic have been processed with the SARRA program. Preliminary results indicate that highly accurate reference orbits are not a stringent requirement for the AFGL SARRA reductions. The recovered geoid in the GEOS‐3 calibration area shows good agreement with gravimetric geoids in that area.
Observations of a Nuée Ardente from the St. Augustine Volcano
Authors: Stith Jeffrey L. , Hobbs Peter V. , Radke Lawrence F.
Published: February 2008

A series of aerial photographs were obtained of a nuée ardente produced by the February 8, 1976 eruption of the St. Augustine volcano, Alaska. The nuée ardente reached a maximum velocity of 50 m s−1 while descending the steeper (∼1∶3) slope of the volcano. It later slowed to a velocity of 6 m s−1 as it traversed the gentler slope (∼1∶25) at the base of the volcano, where it formed a deposit. The nuée ardente appeared to originate with the collapse or penetration of a newly formed dome, rather than the collapse of a vertical eruption column. Fluidization by fine particles in the nuée ardente probably contributed to its mobility.
On the relative locations of the bow shocks of the terrestrial planets
Authors: Russell C. T.
Published: February 2008

The observed bow shock encounters at Mercury, Venus and Mars are least square fit using the same technique so that their sizes and shapes can be intercompared. The shock front of Mercury most resembles the terrestrial shock in shape, and the shock stand off distance is consistent with the observed moment. The shapes of the Venus and Mars shock fronts more resemble each other than the earth's and the stand off distances are consistent with direct interaction of the solar wind with the ionosphere on the dayside. The Venus shock is closer to the planet than the Mars shock suggesting more absorption of the solar wind at Venus.
Local perturbations of the atomic hydrogen density distribution near the exobase, inferred from D2A Lyman α airglow measurements
Authors: Emerich Claude , Cazes Serge
Published: February 2008

The atomic hydrogen density variation near the exobase has been inferred from measurements of both polarization and resonance‐cell absorption of the hydrogen Lyman‐alpha geocoronal emission, performed onboard the D2A satellite. Comparison of simultaneous measurements made in three different lines‐of‐sight, on April 27, 1971, have shown firstly, a steep North pole depletion at 0600 L.T., with a density ratio of a factor of 2.4 between midlatitude and North pole densities, and secondly, a non‐sinusoidal diurnal variation with two steep, local density depletions occuring around 0400 L.T. (+ 40° latitude), and around 1600 L.T. (− 20°). These observations, compared to earlier measurements of hydrogen density and correlated parameters, suggest that the non‐thermal loss processes are dominant in determining the density distribution, and subject to large and local perturbations.
The mass of Phobos
Authors: Tolson R. H. , Blackshear W. T. , Mason M. L. , Kelly G. M.
Published: February 2008

Radio tracking data associated with the February 1977 encounters between the Martian satellite Phobos and the Viking Orbiter I spacecraft have been analyzed to determine the gravitational constant (GM) of Phobos. A linear error analysis was conducted to determine the selection of data and the parameter solution set which would yield the best estimate of GM. This error analysis indicated that the optimal data set was a data arc beginning just prior to the closest encounter and spanning three consecutive spacecraft orbits; data near periapsis were deleted. The most feasible parameter solution set consisted of the Phobos GM and the spacecraft initial conditions. The result of the data analysis was an estimate of (7.3 ± 0.7) × 10−4 km³/sec² for GM of Phobos.
Meteoritic evidence for the Maunder minimum in solar activity
Authors: Forman M. A. , Schaeffer O. A. , Schaeffer G. A.
Published: February 2008

Concentrations of argon‐39 (t1/2 = 269 years, production threshold about 400 MeV) produced by cosmic rays in the metal in 30 meteorites are remarkably similar, but they are slightly higher than expected for the present solar‐cycle averaged flux of cosmic rays. This supports the idea suggested by Eddy (1976a) that there were prolonged minima in solar activity before 1715 which caused the deVries maximum in carbon‐14 in the earth's atmosphere by reducing the amount of cosmic ray modulation in interplanetary space. Our observations are easily consistent with 180 years of "sunspot minimum" modulation during the Maunder and Spörer minima, and possibly with virtually no solar modulation at all, during that time. This would indicate the solar wind then contained very little magnetic turbulence, or whatever it is in the solar wind that causes the modulation of galactic cosmic rays.
An experiment to verify the permeability of Hele‐Shaw cells
Authors: Hartline Beverly K. , Lister C. R. B.
Published: February 2008

A fluid layer sandwiched between two flat plates (Hele‐Shaw cell) has been assumed to model a saturated porous medium with permeability, d²/12, dependent only on the gap width, d. For situations where the properties of the porous matrix are important, such as thermal convection, the total cross‐section (y) of the sandwich should enter into the computation of permeability. To decide which of these approaches is valid, we observed the onset of convection in a Hele‐Shaw cell with constant gap width but spatially varying wall thickness. Convection begins in the thin‐walled section at a lower temperature difference than it does where the walls are thick. Our data confirm that d³3/12y is the permeability of Hele‐Shaw cells used to model thermal convection in porous layers.
Ophiolites found in oceanic crust?
Authors: Spudich Paul K. P. , Salisbury Matthew H. , Orcutt John A.
Published: February 2008

We have demonstrated that a seismic solution to a set of ocean crustal P and S wave data from the Guadalupe Island area is consistent with measured P and S velocity samples from the Bay of Islands Ophiolite Suite and the observed stratigraphy. The seismic model (SOD‐1), derived separately for the P and S wave propagation, contains no major interfaces in velocity between the sea floor and the upper mantle. Although the observations do not prove the Bay of Islands Ophiolite Suite is obducted oceanic crust they do lend considerable support to this hypothesis. These observations also demonstrate that a layered sequence of rock types is not incompatible with velocity models in which the velocity changes smoothly rather than abruptly with depth. A new method for determining lithology as a function of depth, which is based on Vp and Vs, is presented.
High pressure phase transformation in FeF⊂2 (Rutile)
Authors: Ming Li‐chung , Manghnani Murli H.
Published: February 2008

The structural relationships in FeF2 have been studied under pressure up to 320 kbar and 25°C by use of the diamond anvil pressure cell. In situ X‐ray diffraction analysis shows that at about 50 kbar, FeF2(I) with rutile structure transforms into FeF2(II) of distorted fluorite structure and at about 250 kbar FeF2(II) further transforms into FeF2(III) with a hexagonal unit‐cell structure. The zero‐pressure density increase for the transition FeF2(I) → FeF2(II) is ∼ 8%, and the density increase for FeF2(II) → FeF2(III) at 320 kbar is ∼ 5%, if the number of formula units per unit cell is assigned at 2 for the hexagonal unit cell.
Photochemical‐radiative damping and instability in the stratosphere, II. Numerical results
Authors: Strobel Darrell F.
Published: February 2008

Numerical results of the photochemical relaxation of large vertical scale height ozone density perturbations are presented to illustrate the importance of opacity effects. Instabilities generated by opacity changes are shown to occur only for ungeophysically large disturbances. They have a short growth phase before eventually decaying to the unperturbed state. For disturbances with a vertical scale height comparable to the ozone scale height analytic results from the linear perturbation theory in Paper I accurately describe the joint photochemical‐radiative relaxation above 35 km.
Identification of the ν2 vibration‐rotation band of ammonia in ground level solar spectra
Authors: Murcray D. G. , Goldman A. , Bradford C. M. , Cook G. R. , Van Allen J. W. , Bonomo F. S. , Murcray F. H.
Published: February 2008

Ground‐based infrared solar spectra in the 750 to 950 cm−1 region at 0.06 cm−1 resolution were obtained from the University of Denver. Comparisons of spectra obtained during sunrise and sunset show that a number of features due to ν2 NH3 band are present on the sunset spectra but show only a trace on the sunrise spectra. The sunset path shows approximately 0.007 atm‐cm NH3.
Evidence of lateral variations from free oscillations and surface waves
Authors: Jobert N. , Lévêque J. J. , Roult G.
Published: February 2008

From measurements of the apparent periods of free oscillations in the spectra of long period records a procedure defines the extraction of systematic residuals with respect to the values for a global model. These shifts are different for different great circle paths and can be attributed to lateral variations of phase velocity. On two examples a comparison is made, showing a quantitative agreement of the result of the procedure with measurements on progressive mantle waves. Thus, residuals obtained from free oscillation data can be used for regionalization as well as those from progressive wave data.
CO2 fugacity at high temperatures and pressures from experimental decarbonation reactions
Authors: Haselton H. T. , Sharp W. E. , Newton R. C.
Published: February 2008

The presence of CO2 in the upper mantle has been inferred from several sources of evidence. To aid the understanding of the behavior of CO2 at high pressures and temperatures, CO2 fugacities have been deduced from the following decarbonation reactions: MgCO3 + SiO2 = MgSiO3 + CO2, MgCO3 + MgSiO3 = Mg2SiO4 + CO2, MgCO3 + TiO2 = MgTiO3 + CO2, and CaCO3 + SiO2 = CaSiO3 + CO2. The deduced fugacities indicate that CO2 is more compressible at high pressures than previously predicted. This discrepancy could cause serious errors in the calculation of stabilities of mineral assemblages under upper mantle conditions.
Relativistic solar cosmic rays during the current sunspot cycle
Authors: Pomerantz M. A. , Duggal S. P.
Published: February 2008

Four ground level enhancements (GLE) have occurred during the ascending phase of solar cycle 21. The first two, on September 19 and 24, 1977, emanated from the same active region belonging to the old cycle more than a year after sunspot minimum. Evaluation of data recorded during the November 22, 1977, GLE reveals that the attenuation length for particles detected by an atmospheric neutron detector is 88 gm/cm² compared with 100 gm/cm² for the standard lead‐polyethylene pile. The increased response to relativistic solar cosmic rays is displayed in all four events. The May 7, 1978, GLE was highly anisotropic over an extended period. Observations to date show that small GLEs (<25%) are equally likely to occur during Forbush decreases or quiet periods, whereas larger GLEs are concurrent with a preexisting cosmic ray storm. As in the case of other manifestations of solar activity, there is a marked north‐south asymmetry in the heliolatitude of GLE‐producing flares.
Radiocarbon in annual coral rings of Florida
Authors: Druffel Ellen M. , Linick Timothy W.
Published: February 2008

Radiocarbon measurements on a 175‐year (A.D. 1800 to 1974) growth of the coral Montastrea annularis from The Rocks reef off the Florida Keys reveal the rate of local uptake of fossil fuel CO2 and bomb 14C by surface ocean waters of the Gulf Stream. In the nineteenth century, the pre‐bomb, pre‐industrial Δ14C value of surface ocean waters as seen in these corals of the Gulf Stream in the Florida Straits was −51 ± 2‰. By 1955, uptake of industrial CO2 by these waters had lowered the Δ14C values to about −61‰. The results can be used to make predictions regarding anthropogenic CO2 that can be expected to enter the oceans in future decades. Bomb‐produced 14C is found to be present in the corals in comparable concentrations to that found in the dissolved inorganic carbon (DIOC) of the North Pacific and North Atlantic Oceans.
Venus: Chemistry of the lower atmosphere prior to the Pioneer Venus mission
Authors: Prinn Ronald G.
Published: February 2008

Using laboratory studies of the high temperature kinetics of a number of sulfur gases together with a simple chemical‐dynamical model of the lower atmosphere of Venus, we conclude that the relative concentrations of photochemically‐produced oxidized sulfur gases (SO2, SO3) and thermochemically‐produced reduced sulfur gases (COS, S2, H2S) are strongly dependent on the rate of vertical mixing. For values of the vertical eddy diffusion coefficient in excess of 104 cm² sec−1 we predict that the reduced gases will dominate over the oxidized gases in the lower atmosphere. Measurements of the important sulfur gases by Pioneer Venus will thus provide valuable knowledge of lower atmospheric mixing in addition to furthering our understanding of the chemistry which maintains the visible sulfuric acid cloud layer.
Oceanic crust: Age of hydrothermal alteration
Authors: Hart S. R. , Staudigel H.
Published: February 2008

Times of vein mineral deposition in the ocean crust have been determined both by Rb‐Sr isochron ages of vein smectites and by comparison of 87Sr/86Sr ratios of vein calcites with the known variations of seawater 87Sr/86Sr ratio with time. Results from drill sites 105, 332B and 418A, Atlantic Ocean, which have basement formation ages of 155 m.y., 3.5 m.y., and 110 m.y., respectively, show that vein deposition is essentially complete within 5‐10 m.y. after formation of the basaltic crust. This provides direct evidence that hydrothermal circulation of seawater through the oceanic crust is an important process for only 5‐10 m.y. after crust formation.
Large lunar secondary craters: Size‐range relationships
Authors: Allen Carlton C.
Published: February 2008

The relationship between primary crater diameter and mean maximum secondary crater diameter for lunar craters is essentially linear for primary diameters from 0.5 to 260 km. The mean range from the primary to the largest secondary craters is also nearly linearly related to primary diameter. Extrapolation of these results to lunar basin scale supports the contention that basin secondaries of large diameter are to be found across much of the Moon.
Influence of physical processes on the concentration of heavy metals and organic carbon in the surface microlayer
Authors: Owen Robert M. , Meyers Philip A. , Mackin James E.
Published: February 2008

Particulate and dissolved phase concentrations of heavy metals (Fe, Mn, Cu, and Ni) and organic carbon were determined in surface microlayer and subsurface (1m) samples collected in the vicinity of a river plume. Observed variations in dissolved Ni and Mn concentrations are attributed to mixing between river and lake waters. Heavy metal concentrations in the particulate organic carbon show a progressive decrease between the river mouth, a down‐plume station, and the open lake area outside the river plume. These trends are due to segregation between mineralized and organic particulates as well as differential transport of different mineralogical groups. The pronounced influence that these physical processes have on the composition of the surface microlayer raised a serious doubt concerning our ability to identify compositional variations due to strictly chemical processes within the microlayer.
Late Pleistocene magnetic stratigraphy recorded in some New England tills
Authors: Soloyanis Susan C. , Brown Laurie L.
Published: February 2008

Magnetic remanence data from six till sites in New England indicate that the predominant late Pleistocene till types found in southern and central New England can be differentiated on the basis of statistically distinct virtual geomagnetic poles (VGPs). The lower till records an excursion (VGP = lat. 27.7° N, long. 165.2° E) tentatively correlated with the Lake Mungo excursion dated at approximately 32,000 years BP. The use of characteristic remanence is suggested for dating of tills in New England where other conventional methods cannot be applied.