bluuebunny/crossref_metadata_2025 huggingface dataset:
The effects of fire on biogenic soil emissions of nitric oxide and nitrous oxide
Authors: Levine Joel S. , Cofer Wesley R. , Sebacher Daniel I. , Winstead Edward L. , Sebacher Shirley , Boston Penelope J.
Published: February 2008

Measurements of biogenic soil emissions of nitric oxide (NO) and nitrous oxide (N2O) before and after a controlled burn conducted in a chaparral ecosystem on June 22, 1987, showed significantly enhanced emissions of both gases after the burn. Mean NO emissions from heavily burned and wetted (to simulate rainfall) sites exceeded 40 ng N m−2 s−1, an increase of 2 to 3 compared to preburn wetted site measurements. N2O emissions from burned and wetted sites ranged from 9 to 22 ng N m−2 s−1. Preburn N2O emissions from these wetted sites were all below the detection level of the instrumentation, indicating a flux below 2 ng N m−2 s−1. The flux of NO exceeded the N2O flux from burned wetted sites by factors ranging from 2.7 to 3.4. These measurements coupled with preburn and postburn measurements of ammonium and nitrate in the soil of this chaparral ecosystem and measurements of NO and N2O emissions obtained under controlled laboratory conditions suggest that the postfire enhancement of NO and N2O emissions is due to production of these gases by nitrifying bacteria.
Effect of the equatorial Pacific upwelling on atmospheric CO2 during the 1982‐1983 El Niño
Authors: Volk Tyler
Published: February 2008

The 1982‐1983 El Niño event perturbed the otherwise steady growth in atmospheric CO2 due to fossil fuel combustion. Compared to the recent average growth rate in atmospheric CO2 of about 1.5 ppm per year, the growth rate in late 1982 fell to about zero. During this strong El Niño event, additional sinks for atmospheric CO2 operated. By late 1983, the growth rate rebounded to above average, indicating the presence of new sources. To a large extent, the relative roles of the possible actors have eluded us. In this study, box models of the ocean‐atmosphere carbon cycle are used to isolate and estimate the effects of the collapse and return of the upwelling in the equatorial Pacific during an El Niño. The models capture the major trends during the El Niño for sea surface temperature, nutrients, and ΔpCO2. The drop in ΔpCO2 in the normally strong source of the equatorial Pacific can account for a partial amount (probably less than 30%) of the decrease in the growth rate in atmospheric CO2 centered around late 1982. The recovery to normal equatorial conditions plays an even smaller and nearly negligible role in any growth rate overshoot later in El Niño. Changes in the higher‐latitude oceans and disequilibrium in the terrestrial cycle of photosynthesis and respiration continue as major potential agents behind the perturbation.
Carbon oxidation in the deep Mediterranean Sea: Evidence for dissolved organic carbon source
Authors: Christensen J. P. , Packard T. T. , Dortch F. Q. , Minas H. J. , Gascard J. C. , Richez C. , Garfield P. C.
Published: February 2008

The supply and utilization of organic carbon in the deep western Mediterranean Sea was investigated based on measured electron transport system (ETS) activities of the nanoplankton and microplankton. The total carbon oxidation rate between 200 and 3000 m, as calculated from ETS activity, was 15.0 g C m−2 yr−1. This represents 21% of the primary production and is similar to published estimates of the annual new production. A vertical advection ‐ diffusion ‐ reaction model based on profiles of salinity, oxygen, and the carbon oxidation rate converted to oxygen consumption yielded a deepwater residence time of about 7 years, in close agreement with a published estimate based on bomb‐produced tritium profiles. This suggested that the ETS‐based rates in the deep waters were reasonably accurate. These deep rates were much greater than ETS‐based rates from the same depths in the Atlantic and equatorial Pacific Oceans. In the western Mediterranean, ETS‐based rates also greatly exceeded the rate predicted from the primary production rate and sediment trap relationships. The rapid rates observed in the deep western Mediterranean are not consistent with the supply of organic matter via rapidly sinking particulate material. Instead, rates may be supported by dissolved organic carbon (DOC) transported to depth by wintertime deepwater convection. In order to account for the portion of the ETS‐based rate which was not explained by the sediment trap flux, DOC concentrations in the surface waters entrained during deepwater formation would need to be only 11 μmol C L−1 greater than those in the deep waters exiting the basin. ETS activities from the equatorial Pacific (Packard et al., 1988) may also implicate DOC in supporting deep‐sea metabolism. There, ETS‐based carbon oxidation rates between 200 and 5000 m greatly exceeded rates calculated from sediment trap data in the same region. The source of the organic matter being respired may ultimately be the high rates of new production in the equatorial Pacific region, but the mechanism by which this material is transported to depth cannot be determined from these data. The ETS data from both the Mediterranean and the Pacific indicate much greater rates of carbon oxidation in the deep sea than expected from existing sediment trap results. Globally, transport of DOC into the deep sea possibly could rival the sinking particulate flux in importance for deep‐sea metabolism.
Arctic carbon sinks: Present and future
Authors: Walsh John J.
Published: February 2008

Surface air temperatures of the Arctic rose 1.2° −1.5°C from 1880 to 1980, in contrast to a global warming of only 0.4° −0.5°C; since 1980, six of the warmest years in the past century have been observed. Polar enhancement of a temperature rise, induced possibly by anthropogenic release of “greenhouse” gases, CO2, N2O, CH4, and freons, to the atmosphere, is attributed to altered ice/snow albedo at sea level, i.e., melting of sea ice. A 5% decline of sea ice extent in the Arctic and Antarctic from 1979 to 1987 may have resulted in increased light availability within previously ice‐covered polar regions. If such a short‐term trend were to continue, it might lead to a negative biogeochemical feedback, i.e., enhanced extraction of atmospheric CO2 during marine photosynthesis. As a consequence of deep vertical mixing in the Antarctic Ocean, however, primary production during the austral summer may have actually declined in response to a reduction in extent of meltwater regions, where stratified water columns allow carbon fixation tenfold that of open water. In contrast, within shallow adjacent seas of the Arctic Ocean, where shelf regions are tenfold larger than those of the Antarctic, the positive global consequences of greenhouse warming at polar latitudes will probably be felt first. Specifically, the Pacific‐influenced regions of the Chukchi and East Siberian Seas, where sufficient nutrients and shallow depths prevail, now have annual primary productions of >200 g C m−2 yr−1, tenfold that of other high Arctic shelves, and may supply 50% of the carbon respiration demands within the halocline of the deep Canadian and Eurasian basins via brine‐mediated runoff. Continued melting of ice in the Arctic could increase by an order of magnitude the present CO2 sink of ∼0.1 × 109 t C yr−1.
The geochemical cycling of reactive chlorine through the marine troposphere
Authors: Keene William C. , Pszenny Alexander A. P. , Jacob Daniel J. , Duce Robert A. , Galloway James N. , Schultz‐Tokos Joseph J. , Sievering Herman , Boatman Joe F.
Published: February 2008

Heterogeneous reactions involving sea‐salt aerosol in the marine troposphere are the major global source for volatile inorganic chlorine. We measured reactant and product species hypothesized to be associated with these chemical transformations as a function of phase, particle size, and altitude over the North Atlantic Ocean during the summer of 1988. Concentrations of HCl were typically less than 1.0 ppbv near the sea surface and decreased with altitude and with distance from the U.S. east coast. Concentrations of Cl volatilized from aerosols were generally equivalent to the corresponding concentrations of HCl and ranged from less than detection limits to 125 nmol m−3 STP. Highest absolute and percentage losses of particulate Cl were typically associated with elevated concentrations of anthropogenic combustion products. Concentrations of product nss SO42− and N03− in coarse aerosol fractions indicate that on average only 38% of measured Cl− deficits could be accounted for by the combined effects of acid‐base desorption and reactions involving nonacidic N gases. We hypothesize a mechanism for the Cl loss initiated by reaction of O3 at sea‐salt aerosol surfaces, generating Cl2 followed by rapid photochemical conversion of Cl2 to HCl via Cl atoms (Cl˙) and eventual recapture of HCl by the aerosol. Simulations with a zero‐dimension (0‐D) photochemical model suggest that oxidation by Cl˙ may be an important tropospheric sink for dimethyl sulfide and hydrocarbons. Under low‐NOx conditions, the rapid cycling of reactive Cl would provide a catalytic loss mechanism for O3, which would possibly explain the low O3 concentrations often observed above the world's oceans.
Configuration of the Jovian magnetosphere
Authors: Hill T. W. , Dessler A. J. , Michel F. C.
Published: February 2008

We present a model in which the Jovian magnetosphere is severely inflated by the centrifugal stress of partially‐corotating plasma streaming out along field lines from the ionosphere. The model is consistent with observations reported from the Pioneer 10 encounter, including the disc‐like field configuration, the diurnal modulation of trapped‐particle fluxes, and the inferred departure from rigid corotation in the outer magnetosphere. The field configuration is closed on the dayside, but on the night side the plasma can force the magnetic field open to form a planetary wind flowing in the antisolar direction.
Energetic electron scattering from the lunar remanent magnetic field
Authors: Howe Herbert C. , Lin R. P. , McGuire R. E. , Anderson K. A.
Published: February 2008

We present a new technique for the detection of surface remanent magnetic fields from lunar orbiting spacecraft. Energetic (∼14 keV) electrons in the particle population surrounding the moon are observed by the Apollo 15 and 16 Subsatellite particle experiments to be scattered back up from the lunar surface by remanent magnetic fields. The regions of intense lunar remanent magnetization discovered by the Apollo 15 and 16 Subsatellite magnetometers are observed to strongly scatter the 14 keV electrons. In addition, several previously unreported regions of surface remanent magnetization on the lunar near‐side are evident from the electron observation. These appear to be located at the edges of mare. The measured pitch angle distributions and flux levels of these electrons are in agreement with computer simulations of electron scattering from a sub‐surface dipole. Since the scattered electron fluxes are essentially altitude independent and the spatial resolution is only limited by the particle gyro‐radius, this technique is capable of mapping surface remanent magnetization from a lunar orbiting satellite with high sensitivity and spatial resolution.
An observation of O+ 834 Å nightglow emission
Authors: Kumar Shailendra , Bowyer Stuart , Paresce Francesco
Published: February 2008

A 40 Å resolution spectrometer was employed to measure the extreme ultraviolet nightglow emissions. The spectrometer was flown on a Black Brant V‐C rocket, which was launched at 21:08 MST on February 9, 1973, from White Sands Missile Range, New Mexico. The O+ 834 Å emission can be identified in the spectrum and has a brightness of 15±5 R. This emission is probably excited by the conjugate electrons. The data also indicate the presence of some nightglow emission in 950 to 1050 Å region that is still unidentified.
Ground‐based photometric observations of the magnetospheric dayside cleft
Authors: Peterson R. N. , Shepherd G. G.
Published: February 2008

A ground‐based meridian‐scanning photometer was operated at Cape Parry, N.W.T., Canada (70°N, 125°W geographic) in November and December, 1973, to observe the atomic oxygen emissions at 6300 Å and 5577 Å, and the H‐beta emission at 4861 Å. A 6300 Å behaviour pattern that could be identified with the dayside cleft was observed during a quiet afternoon and during a magnetically disturbed period. During quiet times a 1 kR 6300 Å feature was observed at 78° invariant latitude while during a modest disturbance the intensity increased to 4 kR and the feature moved to 73° invariant. This confirmed that the 6300 Å signature is readily identifiable from the ground, and that Cape Parry is one of the few relatively accessible Northern hemisphere sites where the optical cleft emissions can be observed from the ground.
Disproportionation of MgAl2O4 spinel at high pressures and temperatures
Authors: Liu Lin‐gun
Published: February 2008

Synthetic spinel (MgAl2O4) has been found to disproportionate into a mixture of its component oxides, periclase and corundum, at a loading pressure of about 180 kbar and between 1000 and 1400°C. The polycrystalline powder sample was compressed in a diamond‐anvil cell and heated by a continuous YAG laser. The exact transition pressure is not known due to transient increases in pressure during the local and rapid heating process. The phase boundary, however, has been calculated to be P(kbar) = (137±8) + 0.009T(°C) on the basis of the available thermochemical data and compression curves for MgAl2O4, MgO, and Al2O3.
Age of the apatite at Cerro de Mercado, Mexico: A problem for fission‐track annealing corrections
Authors: Naeser C. W. , Fleischer R. L.
Published: February 2008

Fission‐track dating and K‐Ar dating indicate that the age of apatite from Cerro de Mercado, Mexico, is 30 m.y., in contradiction to previous corrected fission track ages of 40 and 57 m.y. by other works. Annealing data for the “plateau method” correction of fission‐track ages for the Cerro de Mercado apatite lead to corrections by a factor of sixty or more, which give geologically unreasonable ages. In addition, published data concerning the length of fission tracks and the annealing of minerals imply that the basic assumptions used in an alternative procedure, the length‐reduction‐correction method, are also invalid for many crystal types and must be approached with caution unless individually justified for a particular mineral.
Variations of VP and VS in granite premonitory to shear rupture and stick‐slip sliding: Application to earthquake prediction
Authors: Wang Chi‐yuen , Goodman Richard E. , Sundaram P. N.
Published: February 2008

We report laboratory results on sound velocities of granite, either sheared to rupture or undergoing stick‐slip sliding. We found that the variations in velocity premonitory to these two types of instability are dramatically different. Velocities of both compressional and shear waves decreased significantly prior to the occurrence of rupture, while no change was found during the stick‐slip motion. We suggest that for shallow earthquakes appreciable variation in the faulting processes is likely: Some faulting may be associated with pervasive dilation and fracturing of surrounding rocks, while others may involve little such processes. These variations may be the cause for the conflicting findings in the variations of seismic velocities premonitory to earthquakes.
Can the Earth's magnetic field be sustained by core oscillations?
Authors: Gubbins David
Published: February 2008

Some recent suggestions for generating the earth's magnetic field via short period oscillations of the liquid core are critically examined. Seismic energy seems inadequate for the purpose. Limits on the minimum amplitude of such oscillations are derived and these are shown to be so large that they would be accompanied by observable gravity anomalies. It is concluded that waves with periods much less than years are unimportant for the dynamo problem.
Shear dilatancy in rock and precursory changes in seismic velocities
Authors: Freudenthal Alfred M.
Published: February 2008

The observed decrease and subsequent increase of the travel time ratio of shear and compressional waves prior to the occurrence of earthquakes in the U.S.S.R. and in the U.S.A. is related to shear dilatancy of rocks around the focal area. Shear‐dilatancy is identified as an integral part of elastic and post‐elastic deformation of solid isotropic media; it is not, as is widely believed, the result of cracking, but the cause of crack initiation.
Discussion of paper by S. S. Prasad and A. Tan “The Jovian ionosphere”
Authors: Strobel Darrell F.
Published: February 2008

The electron density of the Jovian hydrocarbon ion layer due to CH3 photoionization has been overestimated by approximately a factor of 7 and is insignificant when compared with the Pioneer 10 results.
Evidence that pitch angle scattering is an important loss mechanism for energetic electrons in the inner radiation belt of Jupiter
Authors: Fillius Walker , McIlwain Carl , Mogro‐Campero Antonio , Steinberg Gerald
Published: February 2008

Analysis of data from the Pioneer 10 flyby discloses that pitch angle scattering plays an important part in determining the distribution of energetic electrons in the inner magnetosphere of Jupiter. Angular distributions measured by the UCSD Cerenkov detector reveal that redistribution takes place in pitch angle. Additionally, the radial profile of phase space density along the equator demands simultaneous particle losses. The loss rates are too high to be accounted for by synchrotron radiation loss, but are reasonably attributed to pitch angle scattering into the planetary loss cone.
Persistent pressure anisotropy in the subsonic magnetosheath region
Authors: Crooker N. U. , Siscoe G. L. , Geller R. B.
Published: February 2008

Observations of proton flux in the subsonic flow region of the magnetosheath show double peaks as a function of angle in the equatorial plane of the spacecraft. The peaks are separated by a wide angle, usually more than 90°. Suggestions of double flux peaks are present in 95 percent of the data. They are interpreted as the effect of a persistent pressure anisotropy. The clearest cases were analyzed to determine the orientation of the flux peaks relative to the magnetic field and direction of model hydrodynamic flow. They are shown to be consistent with a greater pressure perpendicular to the field. Possible sources of pressure anisotropy in the magnetosheath are discussed.
Preliminary results of coincident current meter and sediment transport observations for wintertime conditions on the Long Island Inner Shelf
Authors: Lavelle J. W. , Gadd P. E. , Han G. C. , Mayer D. A. , Stubblefield W. L. , Swift D. J. P. , Charnell R. L. , Brashear H. R. , Case F. N. , Haff K. W. , Kunselman C. W.
Published: February 2008

We have observed late fall and winter bedload sediment transport and the overlying current field in ridge and swale topography on the inner continental shelf south of Long Island, and can report movement of bed material at a water depth of 20 m to a distance of approximately 1500 m after several storm events. Movement over an 11‐week observation period was longshore and oblique to the ridge crest at the experimental site. Currents were also predominately longshore, but long term averages demonstrate that a vertical shear existed in the fluid motion. Although the number of sediment transport "events" suggested by the current meter data is nearly balanced in eastward and westward directions, both estimates of transport from current speeds and sand tracer dispersion patterns show that several westward flowing events dominated the transport during a two and one‐half month period. A quantitative upper bound of 31 cm/sec on the threshold velocity for sediment movement in this size range is also set by the data.
A first‐motion alternative to Geometrical Ray Theory
Authors: Chapman C. H.
Published: February 2008

An alternative to geometrical ray theory is obtained. This first‐motion approximation is more generally valid than geometrical ray theory. The approximation had previously been obtained using the generalized and quantized ray theories, but can also be derived from the more usual wavenumber‐frequency integral method. The first‐motion approximation is useful not only when geometrical ray theory is valid, but also at caustics and shadows.
Sulfur dioxide, sulfate aerosol, and urban ozone
Authors: Graedel T. E.
Published: February 2008

The interactive kinetic chemistry of oxidized sulfur and other trace gases has been examined in computations for the suburban New Jersey troposphere. The results of several calculations studying alternate chemical pathways for sulfoxy compounds suggest that ozone concentrations are not greatly sensitive to the chemistry of SO2 and its products. The latter are, however, shown to be slight inhibitors to ozone production, under both normal and reduced levels of reactive hydrocarbons. The computed minimum generation rate of sulfate aerosol is ∼1 µg/m³ day, largely through sulfuric acid deposition on aerosols.
Incoherent scatter measurements of ion counterstreaming
Authors: Vickrey James F. , Swartz Wesley E. , Farley Donald T.
Published: February 2008

The large mass differences between the ions present in the transition region between the F layer and protonosphere can cause individual ion species to drift at different velocities during periods of rapid temperature change. Calculations show that these velocity differences can be detected using incoherent scatter. Preliminary observations indicate that velocity differences between H+ and O+ can be as large as 80 m/s after sunset. Such simultaneous measurements of the fluxes of individual ion species are essential for detailed studies of the charge exchange reactions between H+ and O+ and of the morphology of ionospheric‐protonospheric coupling.
Modulation of trapped energetic electrons at 6.6 Re by the direction of the interplanetary magnetic field
Authors: Paulikas G. A. , Blake J. B.
Published: February 2008

Energetic (E > 1.6 MeV, > 3.9 MeV) trapped electron fluxes observed at the synchronous altitude during 1974 and 1975 by an experiment aboard ATS‐6 exhibit a modulation in intensity which is correlated with the passage of sector structure boundaries of the interplanetary magnetic field past the earth. The electron fluxes reach equilibrium intensities during the time the magnetosphere is in a given IMF sector which are highest in the fall for (+) sectors and highest in the spring for (−) sectors.
Mars: Wind friction speeds for particle movement
Authors: Greeley R. , White B. , Leach R. , Iversen J. , Pollack J.
Published: February 2008

Wind friction threshold speeds (V*t) for particle movement were determined in a low pressure boundary layer wind tunnel at an atmospheric pressure of 5.3 mb. The results imply that for comparable pressures on Mars, the minimum V*t is about 2.5 m/sec, which would require free‐stream winds of 50 to 135 m/sec, depending on the character of the surface and the atmospheric conditions. The corresponding wind speeds at the height of the Viking lander meteorology instrument would be about a factor of two less than the free stream wind speed. The particle size most easily moved by winds on Mars is about 160 µm; particles both larger and smaller than this (at least down to about 5 µm) require stronger winds to initiate movement. The results presented here are in general agreement with previously reported values of V*t for particles 12 µm to 300 µm derived from one atmosphere tests, but are inconsistent with values for particles larger than about 300 µm.
Stratospheric areal distribution of water vapor burden and the jet stream
Authors: Kuhn P. M. , Magaziner E. , Stearns L. P.
Published: February 2008

Radiometrically inferred areal observations of the atmospheric water vapor burden have been made in the 270 to 520 cm−1 spectral band over western U. S. and the extreme eastern Pacific from the NASA C‐141 Kuiper Airborne Observatory. Before this very few observations from the upper troposphere and lower stratosphere over such a broad area have been made. 30600 individual observations from eight separate synoptic situations involving eight jet maxima were computer‐averaged over 2° latitude × 2° longitude boxes and related to the polar continental jet. Mean water vapor burdens ranged from 4.6×10−4 g cm−2 to 14.3×10−4 g cm−2 at 13.4 km with a striking peak just north of the jet wind maximum over a region of strong upward vertical motion.
Energetic electron anisotropies in the magnetotail: Identification of open and closed field lines
Authors: Baker D. N. , Stone E. C.
Published: February 2008

Unidirectional anisotropies in the energetic electron fluxes (E ≳ 200 keV) have been observed in the earth's magnetotail with the Caltech Electron/Isotope Spectrometer on IMP‐8. The anisotropies occur during periods of enhanced fluxes and provide essential information on the topology (open or closed) of the magnetotail field lines which are associated with recently identified acceleration regions.
Aftershocks of the Guatemalan Earthquake of February 4, 1976
Authors: Matumoto Tosimatu , Latham Gary V.
Published: February 2008

Several thousand earthquakes were recorded by portable seismic stations operated in Guatemala within the first week following the destructive earthquake of February 4, 1976. The seismically active zone followed the Motagua fault through eastern and central Guatemala, and then branched sharply southward about 35 km west of Guatemala City. These data support the conclusion from field evidence that the main earthquake was caused by movement within the Motagua fault zone. A total rupture length of at least 250 km, defining a segment of the active boundary between the North American and Caribbean plates, is inferred. The southward trending zone of aftershock activity may be a newly defined section of the boundary, or a secondary fault.
Compressional wave anisotropy in the crust and upper mantle
Authors: Bibee L. D. , Shor G. G.
Published: February 2008

We have examined a large number of standard marine refraction stations to determine the general relation of crustal and mantle velocity to spreading direction and age in the Pacific. Crustal anisotropy is insignificant, as is variation of lower crustal velocity with age. Mantle velocities exhibit a high correlation with both age and azimuth indicating an increase of velocity with age and about 5% anisotropy with highest velocity in the direction perpendicular to the local magnetic anomalies.
The temporal structure of HF and VHF radiations during Florida lightning return strokes
Authors: Le Vine David M. , Krider E. Philip
Published: February 2008

Measurements have been made of the HF and VHF radiation at 3, 30, 139, and 295 MHz produced during lightning return strokes, in correlation with wideband electric field measurements covering from about 300 Hz to 2 MHz. Intense pulses of RF are observed during the first return stroke in a discharge to ground, but with a 10‐30 µsec time delay between the beginning of the stroke and the occurrence of significant RF radiation. The delay occurs at all frequencies and is short enough to suggest that the main channel and/or branches are the main initial sources of RF during the first stroke. During a subsequent return stroke, the RF starts an average of 265 µsec prior to the onset of the stroke. At 139 and 295 MHz, the subsequent stroke RF lasts only about 115 µsec; however, at 3 MHz, the radiation frequently persists up to and during the stroke.
Heavy ion circulation in the Earth's magnetosphere
Authors: Freeman J. W. , Hills H. K. , Hill T. W. , Reiff P. H. , Hardy D. A.
Published: February 2008

We propose a mechanism whereby singly charged heavy ions from the plasmasphere are convected intermittently to the dayside magnetopause, accelerated there, swept into the distant tail lobes and boundary layer and convected earthward in the plasma sheet to re‐enter the inner magnetosphere. The outer region of the plasmasphere is known to be stripped off during periods of enhancement of the convection electric field. These cold plasmaspheric ions
drift toward the dayside magnetopause where they may become accelerated and co‐mingled with magnetosheath plasma either through magnetic merging or some viscous process operating at the magnetopause. If the ion motion at the magnetopause is poleward, the ions may become part of the entry layer, entering the cusp and exiting as part of the plasma mantle. The cross‐tail electric field will cause them to drift into the lobes toward the center of the tail, ultimately reaching the plasma sheet in the distant tail. If the ion motion at the dayside magnetopause is equatorial, the plasmaspheric ions become part of the boundary layer, again ultimately reaching the plasma sheet in the distant tail. Once in the plasma sheet some of the heavy ions may flow back toward the earth and re‐enter the magnetosphere as energetic ions.
The distribution of methylamine in the Jovian atmosphere
Authors: Kuhn W. R. , Atreya S. K. , Chang S.
Published: February 2008

An estimate of the methylamine concentration on Jupiter has been made. The maximum production rate of 6 × 104cm−3 (Jovian day)−1 occurs in the vicinity of 60 km above the ammonia cloud layer. If the downward transport of methylamine equals the production rate, then the volumetric mixing ratio is 3 × 10−11.
Possible origins of time variability in Jupiter's outer magnetosphere, 2. Variations in solar wind magnetic field
Authors: Kennel C. F. , Coroniti F. V.
Published: February 2008

We attempt to merge conceptually planetary wind models of Jupiter's outer magnetosphere with reconnection models of Jupiter's outer magnetosphere. Solar wind reconnection scaling arguments predict 2‐4 AU for the length of the Jovian tail, consistent with that inferred from Jovian cosmic ray propagation arguments. Two conceivable limits of solar wind reconnection driven internal magnetospheric convection emerge, depending upon whether or not the centrifugally driven planetary wind transports magnetic flux radially outward.
Mercurian bright patches: Evidence for physio‐chemical alteration of surface material?
Authors: Dzurisin Daniel
Published: February 2008

Morphologically and photometrically anomalous patches of highly‐reflective material exist inside several large mercurian craters. Calculations assuming that the patches exhibit an average lunar photometric function yield normal albedos of .39‐.45, roughly 60% higher than Aristarchus, the brightest feature on the Moon. Color‐ratio images derived from Mariner 10 imaging data indicate that bright patches are bluer than typical mercurian surface material, and are surrounded by material redder than typical surface material. Local physio‐chemical alteration along impact‐induced fractures may have been involved in production of these uniquely mercurian features.
Nitrous oxide ultraviolet absorption spectrum at stratospheric temperatures
Authors: Selwyn Gary , Podolske James , Johnston Harold S.
Published: February 2008

The absorption spectrum of nitrous oxide (N2O) has been determined at five temperatures from 194 to 302 K and over the wavelength range 173‐240 nm. The absorption cross sections as a function of wavelength and temperature are expressed by a nine‐term polynomial in a form useful for atmospheric models. The high resolution structure between 173 and 190 nm has been observed more clearly than by previous studies.
Metallic phases in the Luna 24 soil samples
Authors: Friel John J. , Goldstein Joseph I.
Published: February 2008

The metal and sulfide phases in the Luna 24 soil samples were studied with the optical microscope and the electron microprobe. The compositions of the metal particles fall into three groups based on their Ni and Co contents : (1) Samples of meteoritic composition which have undergone metamorphism on the lunar surface. (2) Samples of submeteoritic, low Ni and low Co contents, including most of the metal particles observed. These particles are contained in glass and agglutinate particles and were probably formed by the mixing of meteoritic metal with lunar metal produced by the reduction of silicates during shock‐impact. (3) Samples of high‐Co content probably formed by mixing of meteoritic material with high‐Co metal from the mare basalt or by fractional crystallization from a metal silicate melt. The sulfide minerals were also studied. These are almost pure FeS, and crystallized from a late stage liquid in the mare basalt. Three high‐Ni sulfides were also found in the glass phase of agglutinates.
Lower stratosphere measurements of variation with latitude of CF 2 Cl 2 , CFCl 3 , CCl 4 , and N 2 O profiles in the northern hemisphere
Authors: Vedder J. F. , Tyson B. J. , Brewer R. B. , Boitnott C. A. , Inn E. C. Y.
Published: February 2008

Profiles of CF 2 Cl 2 , CFCl 3 , CCl 4 , and N 2 O in the lower stratosphere are reported from measurements made during a meridional survey in the Northern Hemisphere in the fall of 1976. The latitude distributions obtained show a marked decrease in mixing ratio with increasing latitude from about lat. 7°N in the region of the Intertropical Convergence Zone to about lat. 79°N along the 159°W meridian. The results suggest the importance of meridional transport and mixing in the stratosphere in accounting, at least in part, for the observed profile variation with latitude.
The magnetic field of Mars: Mars 5 evidence re‐examined
Authors: Russell C. T.
Published: February 2008

The putative magnetotail encounters of the Mars 5 spacecraft cannot be scaled to the terrestrial magnetopause. Furthermore, the magnetic field during these claimed magnetotail encounters tends to be wrapped around the planet rather than rooted in it. There is no conclusive evidence that the Mars 5 spacecraft ever entered a Martian magnetosphere. The upper limit to the Martian magnetic moment is estimated to be 2×1021 Gauss‐cm³, or 2.5×10−5 of the terrestrial magnetic moment.
Midlatitude convection electric fields and their relation to ring current development
Authors: Blanc Michel
Published: February 2008

The extension of magnetospheric convection toward low latitudes is investigated with the help of incoherent scatter measurements of E×B plasma drift velocities in the midlatitude F region above Saint‐Santin (France). The observed relations of these drifts with auroral magnetic activity, the north‐south component Bz of the interplanetary magnetic field, and the time derivative of Dst suggest that this low‐latitude extension is not systematically associated with all polar magnetic substorms, but occurs in conjunction with large (5 gammas or more) southward Bz and is closely related in intensity with the negative excursions of d(Dst)/dt. We propose that plasma injection and the resulting development of an asymmetric ring current are closely linked with the low‐latitude extension of magnetospheric convection.
Dynamic support of the outer rise
Authors: Melosh H. J.
Published: February 2008

A model for the origin of the outer rise is proposed which does not require multi‐kilobar deviatoric stresses in the lithosphere. The model includes stresses developed by viscous flow of the lower part of the lithosphere as it is subducted. Besides the outer rise, features similar to an oceanic trench and island arc develop in the model. The elastic upper part of the lithosphere, treated approximately, is subject to extensional stresses on the seaward side of the trench axis. The observed topography of an oceanic trench and outer rise can be produced by a 90 km thick lithosphere subducting at 60 mm/yr if the average viscosity of the lower lithosphere is about 1023 poise.
Stratospheric measurements of CF2Cl2 and N2O
Authors: Tyson Bennett J. , Vedder James F. , Arvesen John C. , Brewer Robert B.
Published: February 2008

Concentrated samples of stratospheric air were obtained at pressure altitudes of 18.3 km and 21.3 km aboard U‐2 aircraft, and at 28.3 km and 35.9 km aboard a balloon platform. The mixing ratios of CF2Cℓ2 and N2O are reported for locations in California, Oregon, Texas, and Quebec, Canada. The observed mixing ratios compare within a factor of 2 to those reported by other investigators and show a more rapid decrease with altitude than predicted by a two‐dimensional (2‐D) model.
Possibility of a geophysical determination of the Newtonian gravitational constant
Authors: Stacey F. D.
Published: February 2008

The Newtonian gravitational constant G may be determined from a comparison of gravity at the ocean surface and at depth, where the attracting mass is smaller by an amount that can be determined from the measured density of sea water. Uncertainties arising from instrumental limitations and localized gravity anomalies may be reducible to the point of obtaining an improved value for G, but it is in any case of interest to verify that the result coincides with laboratory measurements on a scale 107 times smaller.
Midlatitude oxygen ultraviolet nightglow
Authors: Brune W. H. , Feldman P. D. , Anderson R. C. , Fastie W. G. , Henry R. C.
Published: February 2008

Oxygen 1304 and 1356 Å emissions, the principal features in the 1240 to 1670 Å nightglow spectrum, were measured at 60 Å resolution by a spectrometer carried on an Aries rocket to 347 km above White Sands Missile Range, 26 January 1977. The spectrum and altitude variations of the signal were measured from 180 to 340 km at a zenith angle of approximately 40°. Peak observed intensities near 260 km of 0.61 and 0.45 R for 1304 and 1356 Å emissions respectively are attributed primarily to O+ −e radiative recombination, with an allowable 25% contribution from O+‐O− mutual neutralization. The partial radiative recombination coefficients derived from the data are α1356 = 7.8 × 10−13cm³s−1 and α1304 = 4.9 × 10−13cm³s−1 for a 700°K exospheric temperature.
The lunar highland melt‐rock suite
Authors: Vaniman D. T. , Papike J. J.
Published: February 2008

Size can be used as a criterion to select 18 large (> 1 cm) samples from among 148 melt‐rock fragments of all sizes. This selection provides a suite of large samples which represent the important chemical variants among highland melt rocks; each large sample has enough material for a number of sample‐destructive studies, as well as for future reference. Cluster analysis of the total data base of 148 highland melt rocks shows six distinct groups: anorthosite, gabbroic anorthosite, anorthositic gabbro (“highland basalt”), low‐K Fra Mauro, intermediate‐K Fra Mauro, and high‐K. Large samples are available for four of the melt‐rock groups (gabbroic anorthosite, anorthositic gabbro, low‐K Fra Mauro, and intermediate‐K Fra Mauro). This sample selection reveals two sub‐groups of anorthositic gabbro (one anorthite‐poor with negative Eu anomaly and one anorthite‐rich without Eu anomaly). There is a sharp distinction between those Apollo 16 melt rocks and glasses which have both been classified as “gabbroic anorthosite”.
Volcanism in the cratered terrain hemisphere of Mars
Authors: Greeley Ronald , Spudis Paul D.
Published: February 2008

Viking Orbiter photography has revealed the importance of volcanism in the geologic evolution of the cratered terrain hemisphere (generally in the southern hemisphere) of Mars. Volcanic units in this region are classified morphologically into four major units: 1) Patera, comprising 2.37 × 105 km² (0.3% of the cratered terrain hemisphere), are large, low profile volcanic structures; some appear to be older shield volcanoes, others apparently represent a unique style of volcanism; 2) “Plains” volcanics occupy 2.3 × 106 km² (2.9% of hemisphere) and represent low volume eruptions that formed cones, low shields and other small scale structures; 3) flood volcanics (3.7 × 106 km²; 4.7% of hemisphere) are produced by high volume eruptions, post‐date the older and more degraded plateau plains, and occur mostly as basin‐fill materials; and 4) Plateau plains (28.5 × 106 km²; 36% of hemisphere), the martian intercrater plains, contain many wrinkle ridges and floor‐fractured craters. The results of this study suggest volcanic processes, as well as erosional processes have been important in the obliteration of small (less than 10km) craters on Mars and that volcanic products may constitute a significant fraction (up to 44%) of the surface rocks in the cratered terrain.
Martian intrusions: Possible sites and implications
Authors: Schultz Peter H.
Published: February 2008

Both the Moon and Mars exhibit volcanic modification of impact craters characterized by subfloor intrusions that either lift the old crater floor or result in extrusions of lava. Endogenic modification of martian craters, however, probably has involved interactions between such intrusive bodies and permafrost, as suggested by differences between lunar and martian floor‐fractured craters. Such interactions raise the interesting possibility for hydrothermally concentrating ores in a manner analogous to the Sudbury structure on the Earth that may be consistent with interpretations of Viking lander results.
Field‐line merging and slippage
Authors: Atkinson G.
Published: February 2008

Magnetic‐field‐line merging occurs at a tangential discontinuity in a plasma if regions of finite conductivity occur which are elongated along the direction of current flow. If however they are elongated in a direction perpendicular to the current flow, field‐line slippage occurs. In field‐line slippage, magnetic field‐aligned electric fields occur which allow the frozen‐field regions on each side of the finite‐conductivity region to undergo different flows. These flows are in a direction so as to decrease magnetic energy and transform it to plasma energy. This is believed to be occurring in auroral arcs. It is suggested herein that since finite conductivity occurs when the local plasma cannot carry the required sheet current, the shape, size and orientation of regions of finite conductivity are determined by local plasma and field properties. Hence, if elongated, these regions may be at an arbitrary angle to the current‐flow direction, although still within the plane of the tangential discontinuity. Under these conditions, and also in what is likely to be the commonest situation, that is patches of finite conductivity which are not greatly elongated in any direction, merging and slippage should occur simultaneously.
On large poleward‐directed electric fields at sub‐auroral latitudes
Authors: Maynard N. C.
Published: February 2008

Intense poleward‐directed electric fields were observed by OGO‐6 in the pre‐magnetic midnight F‐region, close to the Harang discontinuity and at latitudes of less than 60° invariant. These results support the recent measurements of Smiddy et al. (1977). Both sets of data are consistent with a compression of equipotentials on the low latitude edge of the pre‐midnight convection cell, caused by an impediment of the sub‐storm‐related southwestward expansion of the convection pattern.
The uncertainty in ozone calculations by a stratospheric photochemistry model
Authors: Butler Dixon M.
Published: February 2008

At present, there is an apparent conflict between one‐dimensional stratospheric photochemistry models used in predicting ozone depletion and average data for stratospheric ozone. This conflict is in three particulars—column density of O3 and ozone density in the regions around 30 km and 50 km altitude. A study of the sensitivity of one such model to the values of reaction rates, boundary conditions, solar intensities, photolysis cross sections, and O(¹D) yield parameters reveals that even at the 2σ uncertainty limit due to these input parameters, the model does not overlap the data for O3 density at 30 km and 50 km. The data is outside the 1σ model uncertainty limit for O3 column density. The study also shows the relative contribution of the various parameters studied to the imprecision in these model results. Temperatures and eddy‐mixing coefficient could substantially affect these results but are not considered in this study.
A 200 year record of carbon‐13 and carbon‐14 variations in a Bermuda coral
Authors: Nozaki Y. , Rye D. M. , Turekian K. K. , Dodge R. E.
Published: February 2008

A 200 year old brain coral, captured in Bermuda in 1976 was slabbed and x‐rayed. Using the annual growth bands sequential, dated samples were taken over the entire growth period of the coral and analyzed for Δ14C, δ13C and δ18O. During the past 80 years atmospheric variations in Δ14C and δ13C due to human effects, such as release of bomb C‐14 and dilution of both C‐14 and C‐13 by fossil fuel burning, are closely tracked by the coral. Prior to 1900 divergences between the coral and tree Δ14C and δ13C can be related to world‐wide changes in plant production and possibly oceanic upwelling rates.
Spacecraft charging at geosynchronous orbit‐generalized solution for eclipse passage
Authors: Garrett Henry B. , Rubin Allen G.
Published: February 2008

Rapid variations in spacecraft potential are observed on entry and exit from the earth's shadow. Generalized equations, based on elementary plasma probe theory, are developed which make quantitative estimates of the spacecraft potential as a function of satellite position in the earth's penumbra and are compared with data from the ATS‐5 and ATS‐6 geosynchronous satellites. The agreement between the observations and the predictions results from the approximate constancy of the ratio of the ambient ion to electron current during injection events. Due to the significant size and shape differences of the ATS‐5 and ATS‐6 satellites, the results are applicable in many space physics situations such as estimating the effects of electron beams on satellite potential and of spacecraft charging on very large space structures.
Discrimination of geologic units in Death Valley using dual frequency and polarization imaging radar data
Authors: Daily M. , Elachi C. , Farr T. , Schaber G.
Published: February 2008

Simultaneous analysis of dual frequency and dual polarization radar imagery of a portion of Death Valley, California has yielded a nearly complete discrimination of surficial geologic units. Radar imagery in like polarized L‐band (i.e., 25 cm wavelength), crosspolarized L‐band and like polarized X‐band (i.e., 3 cm wave‐length) were digitally combined and ratioed to enhance the variation in the backscatter cross‐section (i.e., albedo) of the different geologic units. In the case of Death Valley, the variation between the different geologic units is clearly reflected in the surface roughness or particle size. These, in turn, have a strong effect on the radar backscatter cross‐section.
The effect of negative ions on Thomson scattering in the presence of electron heating
Authors: Mathews J. D. , Bekeny F. S.
Published: February 2008

The total Thomson scatter cross‐section is considered in the presence of electron heating and as a function of the ratio of negative ion to electron number densities. For electron densities typical of the lower D region it is shown that the opposing factors of heating and negative ions lead to a local minimum of the cross‐section in the experimentally accessible range of 1.5 ≤ Te/Ti ≤ 5. Electron heating is thus considered as a method for detecting negative ions and one early experiment may already have done so.
The radial diffusion coefficient of 1.3‐ 23 MeV protons in recurrent proton streams
Authors: Mewaldt R. A. , Stone E. C. , Vogt R. E.
Published: February 2008

Direct estimates of the radial diffusion coefficient κrr for 1.3‐2.3 MeV protons in interplanetary space are made by comparing simultaneous observations of the diffusive anisotropy and radial gradient of these particles within recurrent streams. The 1.3‐2.3 MeV proton anisotropy has been measured at 1 AU by the Caltech Electron/Isotope Spectrometers on IMP‐7 and 8 during recurrent proton events for which measurements of the radial intensity gradient have been reported. The resulting values for κrr near 1 AU range from (3 to 9) × 1020 cm²/sec, corresponding to scattering mean free paths between 0.03 and 0.1 AU.