bluuebunny/crossref_metadata_2025 huggingface dataset:
Isotopic composition of methane released from wetlands: Implications for the increase in atmospheric methane
Authors: Quay Paul D. , King Stagg L. , Lansdown John M. , Wilbur David O.
Published: February 2008

Measurements of the δ13C of methane released from tropical, temperate, and arctic wetland sites are reported. The mean δ13C values (relative to PDB) for methane emitted from the Amazon floodplain, Minnesota peat bogs and Alaskan tundra are −53 ± 8, −66 ± 5 and −64 ± 5‰, respectively. These measurements combined with methane flux estimates yield a flux‐weighted global average δ13C value of −59 ± 6‰ for methane released from wetlands, a major natural methane source. The agreement between the measured δ13C for methane emitted from wetlands and the calculated steady state value of approximately −60‰ for the δ13C of preindustrial methane sources suggests that methane was predominantly produced biogenically in the preindustrial era. The industrial era time rate of change of the δ13C of the global methane flux is calculated from estimates of the growth rate of the major anthropogenically derived methane sources and the 13C composition of these sources, and compared to the measured change in the δ13C of methane during the last 300 years. Based on these results, we estimate that 13 ± 8% of the current global methane flux is derived abiogenically from natural gas and biomass burning, whereas the remainder is derived biogenically primarily from wetlands, rice paddies, and livestock.
On suspended barite and the oxygen minimum in the Southern Ocean
Authors: Dehairs F. , Goeyens L. , Stroobants N. , Bernard P. , Goyet C. , Poisson A. , Chesselet R.
Published: February 2008

Particulate Ba profiles were measured in the Indian sector of the southern ocean. The largest fraction (>80%) of this barium is present as barite microcrystals. The profiles of total barium are characterized by a subsurface maximum between 200 and 500 m depth in the vicinity of the oxygen minimum. Highest barium values are found just south of the Polar Front, while lowest values occur close to the Antarctic Divergence. Between the divergence and the Polar Front a tight inverse relationship is observed between oxygen in the oxygen minimum and barium in the barium maximum. This relationship disappears north of the Polar Front. Since suspended barite is known to be of biological origin, the correlation of barite with oxygen suggests that the observed decrease of oxygen in the oxygen minimum, between the divergence and the Polar Front is due to local consumption of oxygen. It is proposed that deep low oxygen water is advected towards the Divergence where upwelling occurs and where this water subsequently partly spreads out to the north, north‐east, as entrained by the Antarctic Circumpolar Current. Oxidation of locally produced organic matter, with which barite crystals are associated, consumes oxygen and sets free individual discrete barites. As a result, oxygen decreases and barite increases away from the divergence, with barite integrating former biological processes.
Ozone and carbon monoxide over the North Atlantic during a boreal summer
Authors: Piotrowicz Stephen R. , Fischer Charles J. , Artz Richard S.
Published: February 2008

Ozone mixing ratios observed on a cruise from the east coast of North America to Bermuda, to Iceland, to the Azores and terminating in Barbados in a boreal summer exhibit wide variability. Increases above a North Atlantic background of 10–20 ppbv appear to be associated with transport from terrestrial systems. In the central gyre of the North Atlantic and in the tropical North Atlantic, ozone mixing ratios below 10 ppbv are commonly observed when the air being sampled does not have a recent (10 days) history of terrestrial input. Carbon monoxide mixing ratios within the boundary layer vary latitudinally from an average of 124 ppbv in the westerlies to 88 ppbv in the tropical North Atlantic. Variability in the distribution of CO appears to be dominated by transport from terrestrial source regions.
Size distributions and statistical analysis of nitrate, excess sulfate, and chloride deficit in the marine boundary layer during GCE/CASE/WATOX
Authors: Sievering H. , Ennis G. , Gorman E. , Nagamoto C.
Published: February 2008

A high‐volume sampler and a two‐stage cascade impactor were used aboard the NOAA ship Mt. Mitchell to obtain a fine‐particle‐fraction and two coarse‐particle‐fraction size cuts of atmospheric marine boundary layer aerosol samples. Ion chromatography analysis yielded NO3−, S04=, Na+, and Cl− concentrations and, by calculation, excess sulfate (XSO4) and chloride deficit (Cld) concentrations. Statistical analysis of the July 1988 sample sets from the Bermuda and U.S. east coast areas showed that most of the observed coarse‐particle Cld in the Bermuda‐area samples may be associated with the equivalence sum of NO3− and XSO4. However, the coarse‐particle Cld observed in the U.S. east coast samples is substantially greater than the equivalence sum of NO3− and XSO4 observed at this location. It is concluded that for the east coast sampling, about 13% of the observed 16.9 nmol XSO4 m−3 displaced Cl− in sea salt aerosol particles. For the Bermuda area, 15‐20% of the observed 11.1 nmol XSO4 m−3 displaced Cl− in sea salt aerosol particles (nearly 30% of the observed Cld) despite a relatively low sea salt mass concentration under light wind speed conditions. Under more typical sea state and wind speed conditions for the western North Atlantic Ocean, substantially more XSO4 may displace chloride ions in sea salt aerosol particles.
Lunar dayside plasma sheet depletion: Inference from magnetic observations
Authors: Schubert G. , Lichtenstein B. R. , Russell C. T. , Coleman P. J. , Smith B. F. , Colburn D. S. , Sonett C. P.
Published: February 2008

Apollo surface and orbital magnetic field observations in the plasma sheet of the geomagnetic tail have identified a region on the day side of the Moon with magnetic characteristics indicative of plasma depletion.
Electrical properties of the surface layers of Mars
Authors: Olhoeft G. R. , Strangway D. W.
Published: February 2008

The electrical properties of returned lunar samples when measured in high vacuum conditions have confirmed that the lunar regolith is an excellent electrical insulator, and that it is relatively transparent to radio waves. It is shown in this paper that the observed Martian surface pressures, temperatures, and water contents are consistent with a model of the planetary surface which is electrically similar to that of the moon. The amounts of moisture present are low enough, that they could be adsorbed as a monolayer on the surface of soil grains in the upper few centimeters. The electrical properties of material which has an adsorbed monolayer of water are virtually indistinguishable from completely dry material.
The Compton‐Getting Effect for low energy particles
Authors: Ipavich F. M.
Published: February 2008

The traditional first‐order Compton‐Getting effect, which relates particle distributions as observed in two frames of reference moving with constant relative velocity, is inadequate for the description of low energy particles (less than a few hundred keV/nucleon) in the solar system. An exact procedure is given for recovering both isotropic and anisotropic distributions in the solar wind frame from observations made in a spacecraft frame. The method is illustrated by analyzing a particle event observed by the Univ. of Maryland experiment on IMP‐7 on 31 October 1972.
NO+ and O+ in the high latitude F‐region
Authors: Banks P. M. , Schunk R. W. , Raitt W. J.
Published: February 2008

From an analysis of ionic reactions, we deduce that NO+ should be an important constituent of the high latitude F‐region. Owing to the rapid increase of the reaction O+ + N2 → NO+ + N with ion velocity and temperature, high latitude electric fields and consequent
drifts act to deplete O+ in favor of NO+. As a consequence of this and the reduced rate of NO+ dissociative recombination arising from high electron temperatures, it seems that NO+ can, at times, replace O+ as the major F2‐region ion in the vicinity of the auroral ovals. The same processes should also be effective in creating nighttime electron density troughs composed primarily of NO+ in regions equatorward of the auroral ovals where large electric fields are often present.
Depth/diameter relations of fresh lunar craters: Revision from spacecraft data
Authors: Pike Richard J.
Published: February 2008

The first systematic data from Apollo photogrammetry provide a high standard of accuracy for the depth/diameter (Ri/Dr) relation of fresh lunar craters. Apollo Ri/Dr results resemble results obtained by measuring shadows on Lunar Orbiter imagery. The Ri/Dr distribution inflects at a crater diameter of 10 km ‐ 15 km. Lunar craters less than 15 km across are at least 50% deeper than older, telescopic data indicated (now, Ri is ∼0.2 Dr), but larger craters are not much deeper. There is no marked Ri/Dr difference between fresh upland and postmare craters. The new Ri/Dr relation for small lunar craters resembles those of experimental and impact craters on Earth.
Cross correlation between cosmic‐ray fluctuations and interplanetary magnetic‐field fluctuations
Authors: Jokipii J. R. , Owens A. J.
Published: February 2008

We present a study of the cross correlation between cosmic‐ray intensity fluctuations and the interplanetary magnetic field, using the low‐frequency limit of the theory of the interplanetary scintillations of cosmic rays. Cross‐spectral analysis of the flux of the Alert neutron monitor and simultaneous values of the interplanetary magnetic field components are presented which support the theory. A model of cosmic‐ray fluctuations is described, with effects of gradients and interplanetary sector structure dominating for very low frequencies (f ≲ 5×10−6Hz) and magnetic‐field induced interplanetary scintillations of cosmic rays dominating for higher frequencies.
The gravity field of Mars
Authors: Reasenberg R. D. , Shapiro I. I. , White R. D.
Published: February 2008

A complete sixth‐degree spherical‐harmonic model of the gravitational potential of Mars has been produced from an analysis of Doppler data obtained from the radio tracking of the Mariner‐9 spacecraft for over 200 orbital revolutions. The equipotential surface defined by this model is estimated to be accurate to within 100 m below 60° North Latitude and to within 300 m above. The dominant feature of this surface is a Tharsis‐related bulge which rises nearly two kilometers above the surrounding areas. Gravitational “lows” are found to correspond to the Hellas depression and the Valles Marineris.
Ferromagnetic phase‐mass equivalence and lunar sample magnetic remanence
Authors: Wasilewski Peter J.
Published: February 2008

Man‐made alloy spheres (∼300 µm) simulating the compositions of particles found in the lunar soil and weighing approximately 10 mg. are shown to be equivalent, insofar as remanence intensity and demagnetization stability are concerned, to ≳ 1010 submicrometer spherical iron particles. The large particles (≳100 µm) not only contain large stable magnetic remanence, but when the polished surfaces of these particles are etched and carefully studied, they provide useful petrogenetic information, imply the mechanism of magnetization, the time‐temperature history, and outline the format for possible paleointensity analysis. The intensity and stability of the remanence in these large spheres is related to the microstructure developed during rapid cooling.
Satellite observation of cloud patterns over East Australian Current anticyclonic eddies
Authors: Scully–Power P. , Twitchell P.
Published: February 2008

A series of circular cumulus cloud patterns of approximately 150 km diameter were observed at night by the Defense Meteorological Satellite's infrared sensors on 20 October 1974 off the east coast of Australia. The observed cloud patterns are thought to be caused by the anticyclonic eddies known to be associated with the East Australian Current. A possible mechanism for this phenomenon is proposed.
Effect of the Jovian oblateness on Pioneer 10/11 radio occultations
Authors: Hubbard W. B. , Hunten D. M. , Kliore A.
Published: February 2008

The oblateness of Jupiter, which was neglected in the standard inversion technique for radio occultation data, has a substantial effect on the refractivity profiles of the neutral Jovian atmosphere derived from the Pioneer 10/11 occultations. The geometry of the Pioneer 10 entry and exit occultations has the effect that oblateness should account for much of the discrepancy of the results with plausible atmospheric models. The effect of the oblateness on Pioneer 11 entry is smaller, where much of the discrepancy could be due to other effects, such as cycle‐slip in the spacecraft transponder. Theory indicates that the Pioneer 11 exit occultation should be affected by the oblateness in the opposite sense from the first three occultations; and, indeed, the data which had not been invertible under the spherical assumption produced reasonable results when an oblateness correction was applied.
A determination of the lunar moment of inertia
Authors: Gapcynski J. P. , Blackshear W. T. , Tolson R. H. , Compton H. R.
Published: February 2008

An estimate of the second zonal coefficient of the spherical harmonic representation of the lunar gravitational field has been obtained from an analysis of particular orbital element variations of the Explorer 35 and Explorer 49 spacecraft. Data from these spacecraft were used because the orbital configurations resulted in variations of the longitude of periapse and node which were, to first order, dependent only on the even zonal harmonics. In addition, the data time span for each satellite was extremely long; 2138 days for Explorer 35, and 230 days for Explorer 49. The value determined for the harmonic coefficient is C20 = (−2.0272±.0148) × 10−4. Use of this value of C20, and values of β = (631.1±.4) × 10−6 and γ = (226.8±1.0) × 10−6 yields a value of the lunar moment of inertia of C/Ma² = .392±.003.
Rotational bursting of interplanetary dust particles
Authors: Paddack Stephen J. , Rhee John W.
Published: February 2008

Solar radiation pressure can cause rotational bursting and eventual elimination from the solar system of asymmetric dust particles by a windmill effect. The life span against this process for metallic particles with radii of 10−5 to 10−2 cm ranges from 10 to 10,000 years. The effects of magnetic spin damping have been considered in this estimate. This depletion mechanism works faster than the traditional Poynting‐Robertson effect by approximately one order of magnitude for metallic particles and about two orders of magnitude for nonmetallic particles.
Paleomagnetic evidence for rotation of northern Calabria
Authors: Manzoni M.
Published: February 2008

A mean paleomagnetic direction of D = 286,6 and I = 44,5 (α95= 17°, pole position at 297 E, 16 N) was obtained from Upper Cretaceous limburgites at M. Cerviero, Northern Calabria. The amount of counterclockwise rotation of the area since the Upper Cretaceous is of about 73°, larger than any known rotation of the surrounding areas: Sicily, Apulia and Campania. According to this data Northern Calabria, which is considered to be wholly allochtonous on geologic grounds, was subject to further differential displacement in respect with Sicily which was relatively fixed to the African plate, as well as in respect with the rotations between the Apennines, the Sardinian‐Corsican microplate and Africa.
Fluctuations and the radial variation of the interplanetary magnetic field
Authors: Jokipii J. R.
Published: February 2008

Correlations between fluctuations in the solar wind velocity and interplanetary magnetic field can influence the observed average interplanetary magnetic field and its variation with heliocentric radius. The average radial magnetic field still varies as 1/r², but, depending on the radial variation of the correlations, the average azimuthal field could depart from the 1/r dependence expected for an Archimedian spiral. This effect could account in part for those observations which indicate a steeper than 1/r dependence for the average azimuthal interplanetary magnetic field.
On‐site measurement of atmospheric tracer gases
Authors: Elias L. , McCooeye M. , Gardner G.
Published: February 2008

In‐situ GC analysis of SF6 and halofluorocarbons in the atmosphere was achieved by sampling a measured volume of ambient air through a short adsorption tube, or precolumn, from which the collected vapours were released by heating and then transferred directly by the carrier stream to the analytical column. The collection, transfer and analysis operations were performed in the one instrument with the aid of gas sampling valves, thereby minimizing the risk of loss or contamination associated with other sample storage and removal procedures. Field trials using CBr2F2 and SF6 as tracers have demonstrated the efficacy of the technique for the quantitative measurement of such gases in the atmosphere. The detection limit attained in this work is estimated to be about 5 × 10−14 v/v.
Evidence for fluid bodies beneath the Sulphur Springs Geothermal Region, St. Lucia, West Indies
Authors: Aspinall W. P. , Michael M. O. , Tomblin J. F.
Published: February 2008

During a 39‐day microearthquake survey in the Sulphur Springs geothermal region, St. Lucia, seven local hypocenters were determined. Emergent P onsets and missing S‐waves were observed for five of these, and attenuated S‐waves recorded for two regional events. These imply the presence of at least two significant fluid bodies beneath the area. Ground noise measurements near natural steam vents suggest a deep source for the steam.
Temperature inversions near 75 km
Authors: Schmidlin F. J.
Published: February 2008

Measurements of temperature in the mesosphere have indicated the occurrence of a temperature inversion near 75 km. Acoustic grenades, falling spheres, thermistors, and pitot probes indicate that this feature also occurs at a number of widely scattered locations, and on occasion has been observed synoptically. No attempt is made in this note to explain the presence of the inversion, only to point out its existence.
Greenhouse effect due to atmospheric nitrous oxide
Authors: Yung Y. L. , Wang W. C. , Lacis A. A.
Published: February 2008

The greenhouse effect due to nitrous oxide in the present atmosphere is about 0.8°K. Increase in atmospheric N 2 O due to perturbation of the nitrogen cycle by man may lead to an increase in surface temperature as large as 0.5°K by 2025, or 1.0°K by 2100. Other climatic effects of N 2 O are briefly discussed.
Correlated measurements of scintillations and in‐situ F‐region irregularities from OGO‐6
Authors: Basu Sunanda , Basu S.
Published: February 2008

Scintillation estimates obtained from in‐situ irregularity measurements by OGO‐6 are compared with simultaneous 137 MHz and 6 GHz scintillations recorded at equatorial stations in the American and African sectors. In this first such correlated study, it is found that the equatorial irregularity amplitudes in these sectors are so large that for a moderately thick irregularity layer the commonly observed monotonic power law spectrum with outer scale dimensions much larger than the Fresnel dimension at VHF can explain the observed GHz scintillations and can locate the VHF band in the saturated scintillation regime. This finding is in contrast to other numerical modelling attempts which usually call for artificial tailoring of irregularity spectra to account for the observed GHz scintillations.
A comparison of measured and inferred temperatures from Aeros‐B
Authors: Chandra S. , Spencer N. W. , Krankowsky D. , Lämmerzahl P.
Published: February 2008

The neutral composition and the temperature data obtained from the AEROS‐B Neutral Atmosphere Temperature Experiment (NATE) and the Neutral and Ion Mass Spectrometer (NIMS) are compared, and the general validity of inferring gas temperatures from N2 and Ar density profiles is examined by comparing them with the in situ measured values of the neutral kinetic temperature (NATE). At times serious discrepancies are noted between the inferred and the measured temperature. This is particularly evident during periods of increased magnetic activity when the normally observed latitudinal variations are apparently modulated by waves propagating from the polar region to low latitudes. Under these conditions the N2 and Ar densities and temperature oscillations are usually out of phase, and the temperatures inferred from N2 and Ar at a given point become meaningless.
Precision leveling with a two‐fluid tiltmeter
Authors: Huggett G. R. , Slater L. E. , Pavlis G.
Published: February 2008

Thermally induced errors, dominant in a water‐tube tiltmeter, are eliminated by using two adjacent tubes containing fluids with densities having different temperature coefficients. Simultaneous measurements of the apparent difference in height between two stations indicated by the two fluids are used to provide the required correction for the density changes. The application of this method could allow precise measurements over long baselines (a resolution of about 10−8 to 10−9 radians in a 1‐kilometer instrument) without a level interconnecting tube or deep burial.
The importance of electrostatic ion‐cyclotron instability for quiet‐time proton auroral precipitation
Authors: Ashour‐Abdalla M. , Thorne Richard Mansergh
Published: February 2008

Even during geomagnetically quiet periods the loss cone distribution of energetic outer zone ions can provide sufficient free energy to excite quasi‐electrostatic instability over a broad frequency range confined to bands centered between multiples of the ion gyrofrequency. Preliminary calculations of the wave growth near the lower cyclotron harmonics indicates that auroral zone (L∼10) wave amplitudes should readily approach the nonlinear range. The expected frequency range together with nonlinear saturation arguments suggest that this instability may be related to the more or less continual presence of the recently reported 1‐10 mV/m broad band electrostatic wave turbulence on auroral field lines. Such turbulence should cause strong diffusion scattering of the ambient ion population (1‐100 keV), thus accounting for the persistent nocturnal proton auroral precipitation from field lines just within the outer boundary of trapping. The instability, however, may be severely suppressed by thermal electron (1‐10 eV) Landau damping. It should therefore be less effective on the dayside (especially at lower L) and it is expected to be quenched entirely within the plasmasphere or detached plasma regions.
Thermomagnetic analysis of natural and synthetic hematite
Authors: Shive Peter N. , Diehl Jimmy F.
Published: February 2008

Thermomagnetic analysis of natural and synthetic samples containing hematite have confirmed Schwarz's (1969) observations that 1.) extensive reduction of hematite to magnetite occurs when the experiment is performed in vacuum but not when it is performed in air 2.) the reduction is arrested when the sample is heated in air before the vacuum run. In addition, we have found that the reduction is controlled by back‐streaming vacuum pump oils, which buffer the atmosphere in the furnace region, but is not dependent upon reducing agents within the samples. Heating of the sample creates a surface layer which is not permeable to the reducing atmosphere and which thus prevents reduction during subsequent heatings. Unusually high Curie temperatures (610°C) of the reduced phase from synthetic hematite samples may be caused by internal stress in the magnetite which coats the hematite grains.
correlated O And Mg isotopic anomalies in Allende Inclusions: II. Magnesium
Authors: Wasserburg G. J. , Lee Typhoon , Papanastassiou D. A.
Published: February 2008

Mg in two Allende Ca‐Al rich inclusions shows large isotopic, mass‐dependent fractionation which enriched the heavier isotopes. After normalization, Mg in these inclusions shows negative δ26Mg which appears to require the presence of nuclear effects in Mg distinct from 26Al decay. The Mg mass fractionation is correlated with distinct but smaller fractionation effects for O reported by Clayton and Mayeda for the same inclusions (see companion paper). The observation of distinctive but uniform Mg isotopic composition in different phases within single Allende inclusions indicates that nuclear effects in O and Mg are not due to the entrapment of interstellar carrier grains as discrete entities, which are preserved as remnants, but are instead due to a homogenized mixture of components of extraordinary isotopic composition mixed with a component of ordinary solar system material and subjected to isotopic fractionation. The distinct O isotopic composition of different phases within a single inclusion is believed to be due to incomplete back‐reaction of the higher temperature condensates with a cooler solar nebula of “normal” composition. The processes responsible for the O and Mg nuclear effects and the astrophysical site of their occurrence remain undefined.
Influence of plants on the atmospheric carbon monoxide
Authors: Seiler W. , Giehl H.
Published: February 2008

A method has been developed for studies of the influence of plants on atmospheric carbon monoxide. The method has been used for extensive laboratory experiments with two plants, Vicia faba and Platanus acerifolia. The experiments show a light dependent CO‐production by plants corresponding to an average production rate per cm² of leaf area of 3 × 10−13 g/sec for a radiation intensity of 5 × 104 erg/cm² sec. Assuming this production rate to be representative of global conditions the world wide annual CO‐production by plants is estimated to be 0.5 × 1014g.
Electromagnetic emission accompanying fracture of quartz‐bearing rocks
Authors: Nitsan Uzi
Published: February 2008

Fracture of quartz‐bearing rocks and other hard piezoelectric materials is associated with radio frequency (RF) electromagnetic emission that can be readily detected in the laboratory. Using a standard RF coil and a transient recorder it was found that small cracks in quartz and tourmaline single crystals produce exponentially‐decaying RF transients with a time constant of about 10−5 s. Failure of quartz‐bearing rocks generates longer and more complex transients, presumably due to interference of radiation emitted by numerous piezoelectric crystals as a result of the sudden drop in piezoelectric field accompanying the release of stress. The spectral content of these transients depends on grain size, shifting to higher frequencies as grain size decreases. This fracture‐related emission has a variety of potential geophysical applications ranging from monitoring cracks in rock deformation experiments to studies of electromagnetic effects associated with earthquakes, hydraulic fracture and mine failure.
Observations of ions of ionospheric origin in the storm‐time ring current
Authors: Johnson R. G. , Sharp R. D. , Shelley E. G.
Published: February 2008

O+, He+, and H+ ions in the energy range 0.5 to 16 keV have been observed in the storm‐time ring current with an energetic ion mass spectrometer aboard the polar‐orbiting S3‐3 satellite. During the main phases of the 29 December 1976, 6 April 1977, and 19 April 1977 magnetic storms, the O+ number density within the instrument energy range in the inner ring current (L = 2.8‐4.0) was larger than the H+ density in the altitude range from about 5000‐7000 km. At two days after the main phase of the 29 December 1976 storm, O+ was still the dominant ion at MLT = 14.5 hours in the L = 2.6‐3.4 range at altitudes near 6000 km.
Characteristics of dayside 5577Å and 3914Å aurora
Authors: Cogger L. L. , Murphree J. S. , Ismail S. , Anger C. D.
Published: February 2008

Aurora on the dayside of the earth observed under especially favorable viewing conditions by the scanning auroral photometer on the ISIS‐2 satellite show several distinctive features. (1) Usually, but not always, a gap or discontinuity in the 5577Å aurora is present through the 10.5 ‐ 12.5 MLT sector, in the same region where the 6300Å aurora typically reaches a maximum. Weak 3914Å emission smoothly fills this gap in most of the passes. (2) A persistent auroral intensity enhancement occurs between 14 and 16 MLT, which is probably related to a statistically deduced maximum in particle fluxes observed in this sector. (3) Aurora in the morning sector at these wavelengths is wider and the poleward boundary is more irregular than in the afternoon.
The latitudinal, diurnal, and altitudinal distributions of upward flowing energetic ions of ionospheric origin
Authors: Ghielmetti A. G. , Johnson R. G. , Sharp R. D. , Shelley E. G.
Published: February 2008

Upward flowing fluxes of energetic (0.5‐16 keV) H+ and O+ ions are frequently observed by the ion mass spectrometer on the polar‐orbiting S3‐3 satellite. Data obtained on the first ∼370 orbits have been used to derive the occurrence frequency of these fluxes. The upward acceleration of ionospheric ions to keV energies is a persistent phenomenon generally occurring in a zone closely associated with the statistical auroral oval. Upward flowing ion events with flux above ∼2 × 106 keV/(cm² sec ster keV) are observed in more than 60% of the orbits. A strong dawn‐dusk asymmetry is found in the frequency of occurrence with the maximum in the dusk sector. The probability of observation increases with altitude up to apogee (8000 km) indicating that the main energization takes place preferentially at altitudes above ∼1 R E.
Electron beam injection experiments: The beam‐plasma discharge at low pressures and magnetic field strengths
Authors: Bernstein W. , Leinbach H. , Kellogg P. , Monson S. , Hallinan T. , Garriott O. K. , Konradi A. , McCoy J. , Daly P. , Baker B. , Anderson H. R.
Published: February 2008

A column of enhanced density plasma, exceeding the density expected from ionization by primary beam electrons, has been observed in a large vacuum system at low magnetic fields (1 to 1.5 G) and low ambient pressures (10−6 to 10−5 torr). The peak luminosity of the discharge is about 10 times that of the beam alone, with a radius increase by a factor of 3. In the absence of the discharge, RF emission is observed at 1.1 to 1.2 fc. A strong band of RF noise with upper frequency cutoff at about fc is observed in the discharge mode, along with higher frequency noise at or near the plasma frequency. The onset of the plasma discharge is critically dependent on beam current. The present results agree with observations made at much higher densities and magnetic fields in fusion research studies.
Electrostatic shocks as the source of discrete auroral arcs
Authors: Torbert R. B. , Mozer F. S.
Published: February 2008

Properties of typical electrostatic shocks, as determined from 207 observations on high latitude magnetic field lines, are summarized. Seven arguments are presented in support of the view that discrete auroral arcs are produced by electron acceleration inside electrostatic shocks.
Magnetic field‐aligned potential drops due to electrostatic ion cyclotron turbulence
Authors: Hudson M. K. , Lysak R. L. , Mozer F. S.
Published: February 2008

Measurements of DC and AC electric fields and plasma densities on the S3‐3 satellite have shown that electrostatic ion cyclotron (EIC) turbulence is associated with significant DC electric fields parallel to auroral field lines. The EIC mode has been identified in regions of strong DC electric fields and magnetic field aligned currents by AC electric field and density fluctuations with frequency components between the local hydrogen gyrofrequency and its harmonics, and by wave vector polarization primarily perpendicular to the magnetic field at wavelengths of an ion gyroradius. The anomalous resistivity has been computed for measured AC electric fields of 50 mV/m in the EIC mode, yielding ∼1 mV/m DC parallel electric fields for measured currents of ∼10 µA/m². This theoretical result implies that several kV potential drops will occur if the anomalous resistivity region extends over several thousand kilometers along auroral field lines. This is adequate to accelerate auroral particles to observed energies and consistent with the scale height over which parallel electric fields and EIC turbulence are statistically observed on S3‐3.
Sulfur and trace element concentration relationships in aerosols from the South American continent
Authors: Lawson Douglas R. , Winchester John W.
Published: February 2008

Sulfur concentrations in fine aerosol particles, aerodynamic diameter <1 µm, from nonurban coastal and inland locations in South America are generally lower than from locations in North America and the Western North Atlantic. In interior Brazil, sulfur is found exclusively in <1 µm particles, but a prominent fine particle mode of K, similar in size distribution to S, suggests a special source for both. Large scale combustion of forest materials may have enhanced fine mode S over levels characteristic of the undisturbed continental atmosphere. In the southeast trade winds submicrometer sulfur, which is less abundant than sulfur in >1 µm particles, does not comprise a distinct fine particle mode and may be accounted for by contributions from sea spray and an admixture of air from the interior. In the polar westerlies a similar particle size distribution of sulfur was found. If an upper limit is to be estimated for the concentration of a fine particle mode of sulfur in the “natural” atmosphere, it is less than indicated merely by total sulfur in the <1 µm diameter range.
Equatorial F‐region neutral winds from nightglow OI 630.0 nm Doppler shifts
Authors: Sipler Dwight P. , Biondi Manfred A.
Published: February 2008

A Fabry‐Perot interferometer has been used to determine equatorial thermospheric wind velocities from measurements of the doppler shifts in the twilight and nightglow 630.0 nm emission line observed from Kwajelein Atoll (9° 24′ N., 167° 29′ E.) during August and September 1977. Shortly after sunset, the F‐region neutral winds typically are directed roughly eastward at velocities ranging from 50 to 120 m/sec. The velocity grows moderately in magnitude for several hours and then turns somewhat southward, sometimes decreasing in the late night (∼03 h local time) to small values (<50 m/sec). These measurements are compatible with recent inferences from measurements of satellite orbit changes but disagree in some respects with pressure‐gradient model predictions and with the winds inferred from OGO‐4 135.6 nm and 630.0 nm airglow intensity measurements.
On volcanism and thermal tectonics on one‐plate planets
Authors: Solomon Sean C.
Published: February 2008

For planets with a single global lithospheric shell or ‘plate’, the thermal evolution of the interior affects the surface geologic history through volumetric expansion and the resultant thermal stress. Interior warming of such planets gives rise to extensional tectonics and a lithospheric stress system conducive to widespread volcanism. Interior cooling leads to compressional tectonics and lithospheric stresses that act to shut off surface volcanism. On the basis of observed surface tectonics, it is concluded that the age of peak planetary volume, the degree of early heating, and the age of youngest major volcanism on the one‐plate terrestrial planets likely decrease in the order Mercury, Moon, Mars.
Clinopyroxenes from deep sea basalts: A statistical analysis
Authors: Schweitzer E. L. , Papike J. J. , Bence A. E.
Published: February 2008

Pyroxene analyses of superior quality, from DSDP Legs 11, 15, 17, 34 and 37 have been studied statistically using cluster and factor analysis. These techniques are used to identify the various basalt groups using pyroxene chemistry, and to gain information about pyroxene crystal chemistry. The tholeiitic and alkalic pyroxene groups differ primarily in Cr2O3, TiO2, and Na2O contents. Relative to an average deep sea pyroxene, the tholeiitic pyroxenes are enriched in Cr2O3 and depleted in TiO2 and Na2O, while the alkalic pyroxenes are depleted in Cr2O3and enriched in TiO2 and Na2O. The primary substitutional couples for the two groups are: VITi‐IVAl2 and VIFe3+‐IVAl.
Polar‐equatorial coupling during magnetically active periods
Authors: Nopper R. W. , Carovillano R. L.
Published: February 2008

Observational evidence indicates that high‐latitude magnetic activity can be causally related to fluctuations and reversals of the equatorial electric field. Using Birkeland currents as the driving forces, we have made numerical calculations of the ionospheric electric fields and currents that distribute globally. Our calculations utilize a fairly realistic empirical ionospheric conductivity model and the field‐aligned current distribution inferred from TRIAD measurements. The results presented here demonstrate that the field‐aligned currents observed during disturbed periods can account for the equatorial fluctuations and reversals in electric field and associated magnetic disturbances noted during such times. In this way, magnetospheric dynamics has a direct and significant influence on the equatorial ionosphere through the ionospheric conductivity.
A numerical evaluation of chamber methods for determining gas fluxes
Authors: Matthias Allan D. , Yarger Douglas N. , Weinbeck Robert S.
Published: February 2008

Mathematical simulations of nitrous oxide (N2O) flux from homogeneous soil into above‐surface chambers have been done for both a closed type of chamber in which soil air is statically collected and an open type of chamber in which ambient air is dynamically drawn across the soil surface. Results indicate that chamber‐measured fluxes over land surfaces may be subject to considerable uncertainty, due in part to concentration gradient changes within the soil profile that are a function of the type and the size of the chamber. Assessment of the uncertainties in chamber flux determinations are reported. For reasonable parameters closed‐chamber flux values may be underestimated by as much as 55%. Data‐analysis procedures are described that can improve the flux estimates. Use of open chambers may yield better flux estimates than closed chambers because of less disturbance to the natural gas concentration profile within the soil. An application to N2O flux measurements over water also is included.
Direct measurements by Voyagers 1 and 2 of the polarization of terrestrial kilometric radiation
Authors: Kaiser M. L. , Alexander J. K. , Riddle A. C. , Pearce J. B. , Warwick J. W.
Published: February 2008

Measurements of the polarization of intense terrestrial kilometric radiation obtained with planetary radio astronomy experiments on Voyager‐1 and 2 during the early portions of each flight show the signals to be predominantly left‐hand circularly polarized. Since these emissions were most probably generated above the Northern hemisphere auroral zone, we conclude that the radiation is emitted primarily in the extraordinary mode.
Direct observation of the oceanic CO2 increase
Authors: Brewer Peter G.
Published: February 2008

The increase in atmospheric CO2 of approximately 50 ppm from the mid‐nineteenth century to 1972 has led to a corresponding increase in the pCO2 of sea water. The record of this increase is present in the oceanic water masses, though the signal is obscured. By observing the alkalinity and total CO2 concentration within a water mass, and stripping off the perturbations of the CO2 system due to respiration, carbonate dissolution and nitrate addition, the original atmospheric equilibration signal may be recovered. The application of these calculations to GEOSECS (1972) data from the core of the Antarctic Intermediate water reveals propagation of the atmospheric CO2 signal northwards.
Polar cap electric field structures with a northward interplanetary magnetic field
Authors: Burke W. J. , Kelley M. C. , Sagalyn R. C. , Smiddy M. , Lai S. T.
Published: February 2008

Polar cap electric fields patterns are presented from times when the S3‐2 Satellite was near the dawn‐dusk meridian and IMF data were available. With Bz ≥ 0.7 γ, two characteristic types of electric field patterns were measured in the polar cap. In the sunlit polar cap the convection pattern usually consisted of four cells. Two of the cells were confined to the polar cap with sunward convection in the central portion of the cap. The other pair of cells were marked by anti‐sunward flow along the flanks of the polar cap and by sunward flow in the auroral oval. These observations are interpreted in terms of a model for magnetic merging at the poleward wall of the dayside polar cusp. The sunward flow in the auroral zone is not predicted by the magnetic model and may be due to a viscous interaction between the solar wind and magnetosphere. The second type, which was observed in some of the summer hemisphere passes and all of the winter ones, was characterized by an electric field pattern which was very turbulent, and may be related to inhomogeneous merging.
On the phase relationship between the energetic particle flux modulation and current disc penetrations in the Jovian magnetosphere: Pioneer 10 inbound
Authors: Jones Douglas E.
Published: February 2008

The surface defined by the locus of field minima along field lines for an unterminated Jovian model magnetosphere is found to coincide with the surface of the model current disc which provides a good fit to the data. However, when the model is terminated by means of magnetopause currents, preservation of the fit by modifying the current distribution near the outer edge of the disc causes the minimum
surface to bifurcate. Energetic electron flux time profiles that are based upon such a minimum
configuration are found to be qualitatively consistent with the inbound Pioneer 10 data.
On the internal structure of the major satellites of the outer planets
Authors: Reynolds Ray T. , Cassen Patrick M.
Published: February 2008

The structures and thermal evolutions of the large icy satellites of the outer solar system are considered. It is shown (for bodies comparable in size and mass to the Galilean satellites, having sizeable mass fraction of H2O, and with meteoritic abundances of radioactive materials contained within their silicate fractions) that the crust of solid ice over a liquid mantle predicted by conductive heat‐transfer calculations is unstable to large‐scale solid‐state convection. For appropriate material parameters, convective heat‐transfer rates are sufficient to freeze a large liquid mantle on a time scale that is short compared to the lifetime of the body. It is also concluded that the ice layer is convecting at the present time. A reevaluation of previous work, using improved values for material parameters and boundary conditions, reverses earlier conclusions and implies a rigid outer crust with resulting long‐term stability of surface features to creep deformation. The combination of a rigid crust with active internal convection presents the additional possibility of surface features that are produced and maintained by dynamic internal processes.
Rotation of principal stress axes caused by faulting
Authors: Rudnicki J. W.
Published: February 2008

This note describes a simple procedure for determining the local rotation of principal stress axes caused by slip on a fault. The procedure employs Eshelby's solution for the elastic field of an ellipsoidal inclusion. An example is used to illustrate that this procedure may be useful in interpreting observations, such as the rotation of compression axes recently inferred from focal mechanisms of earthquakes near the San Andreas fault.
Reduced sulfur emission from the open oceans
Authors: Graedel T. E.
Published: February 2008

The reduced sulfur compounds H2S and CH3SCH3 have been included in a diurnal kinetic photochemical model of the natural marine atmosphere. The self‐consistent solution provides the oceanic emission fluxes necessary to balance atmospheric chemical removal. These fluxes imply global values of 30 Tg S yr−1, near the lower limit prescribed by current global sulfur cycle assessments. The conversion of reduced sulfur gases to SO2 does not result in SO2 concentrations as high as are measured; either a natural or transport source of SO2 is present or additional reduced sulfur compounds are involved in oceanic SO2 production. The calculated upper limit for sulfate formation as a result of oxidation chemistry from the H2S and CH3SCH3 precursors is of order 25 Tg S yr−1, with an additional 29 Tg S yr−1 resulting from oxidation of SO2 generated from sources other than H2S and CH3SCH3.
Venus: eddy coefficients in the thermosphere and the inferred helium content of the lower atmosphere
Authors: von Zahn U. , Fricke K. H. , Hoffmann H.‐J. , Pelka K.
Published: February 2008

The Pioneer Venus bus neutral mass spectrometer (BNMS) has measured number densities of CO2, N2, and He in the dayside Venus thermosphere. Valid data were received down to 128 km, which is below the Venus homopause. From the BNMS data, and other measurements of the N2/CO2 ratio in the lower atmosphere, we derive eddy coefficients K by using one‐dimensional models. A good description of the data is obtained with K = 2 × 1013n− 1/2[cm²s−1], where n is the total number density [cm−3]. The homopause falls close to 132 km altitude for He and 139 km for N2 in our preferred model. Extrapolation of the measured thermospheric He/CO2 ratio to the low atmosphere yields He/CO2 ≃ 2 × 10−5. This He abundance can have accumulated in less than the lifetime of the planet by outgassing from the planetary body as well as by accretion from the solar wind.
A correlation of thermospheric gravity waves with tropospheric lightning
Authors: Chiu Y. T. , Edgar B. C. , Rice C. J. , Sharp L. R.
Published: February 2008

It is demonstrated that a geographic correlation exists between occurrence frequencies of wave‐like structures in the thermosphere and tropospheric lightning at dawn, the latter of which is an indicator of deep convective activity.
Spacecraft charging due to positive ion emission: An experimental study
Authors: Cohen H. A. , Sherman C. , Mullen E. G.
Published: February 2008

Results have been obtained from the flight of a sounding rocket payload instrumented to determine the cause and extent of charging of vehicles in the ionosphere during the ejection of energetic charged particles. Vehicle potential was measured using several independent probes while beams of positive ions or electrons were ejected. Positive and negative potentials were created by the ejection of electrons and positive ions respectively. For constant ion currents of 8 microamperes and energies of 1 keV, vehicle potentials ranged from volts to hundreds of volts, depending on ambient plasma density but independent of neutral density and vehicle pitch angle. A maximum vehicle potential greater than 1 kV was obtained during the emission of 400 microamperes of 2 keV positive xenon ions.
Sulfur dioxide in the Venus atmosphere: Distribution and implications
Authors: Esposito Larry W. , Winick Jeremy R. , Stewart A. Ian
Published: February 2008

The Pioneer Venus Orbiter Ultraviolet Spectrometer sees variable disk brightness features similar to the well‐known "UV markings" seen at longer wavelengths. The bright features are consistent with a homogeneous cloud of H2SO4 aerosols. The darker features show the presence of a broad‐band absorber, which is at some depth in the cloud layer. Additional contrast arises from SO2 absorption. The observed strength of the SO2 absorption as a function of wavelength rules out a uniform mixing ratio for the SO2. The data are well fitted by an inhomogeneous light scattering model in which the SO2 scale height is one‐fifth of the CO2 scale height and the mixing ratio of SO2 at 40 mb is 1 × 10−7. A model of the oxidation of sulfur dioxide in the upper cloud reproduces the observed vertical distribution of SO2 and indicates that SO2 alone is sufficient to produce the observed amount of H2SO4 in this region.