bluuebunny/crossref_metadata_2025 huggingface dataset:
Multiple‐Rate Mass Transfer for Modeling Diffusion and Surface Reactions in Media with Pore‐Scale Heterogeneity
Authors: Haggerty Roy , Gorelick Steven M.
Published: February 2008

Mass transfer between immobile and mobile zones is a consequence of simultaneous processes. We develop a “multirate” model that allows modeling of small‐scale variation in rates and types of mass transfer by using a series of first‐order equations to represent each of the mass transfer processes. The multirate model is incorporated into the advective‐dispersive equation. First, we compare the multirate model to the standard first‐order and diffusion models of mass transfer. The spherical, cylindrical, and layered diffusion models are all shown to be specific cases of the multirate model. Mixtures of diffusion from different geometries and first‐order rate‐limited mass transfer can be combined and represented exactly with the multirate model. Second, we develop solutions to the multirate equations under conditions of no flow, fast flow, and radial flow to a pumping well. Third, using the multirate model, it is possible to accurately predict rates of mass transfer in a bulk sample of the Borden sand containing a mixture of different grain sizes and diffusion rates. Fourth, we investigate the effects on aquifer remediation of having a heterogeneous mixture of types and rates of mass transfer. Under some circumstances, even in a relatively homogeneous aquifer such as at Borden, the mass transfer process is best modeled by a mixture of diffusion rates.
The travel times of solutes at the Cape Cod Tracer Experiment: Data analysis, modeling, and structural parameters inference
Authors: Rubin Yoram , Ezzedine Souheil
Published: February 2008

A method for analyzing and interpreting travel times of solutes in heterogeneous aquifers is presented based on the peak concentration arrival times as measured at various samplers in the aquifer. The method allows separation of the effects of pore‐scale dispersion from the effects of the large‐scale aquifer heterogeneity. An analysis of data from the Cape Cod field experiment is presented, and we found that the values of the hydrogeological parameters inferred from the travel times match very well the values obtained from direct interpretation of cores. Analysis of the spatial correlations of the travel times also allows inference of spatial covariances of the log conductivity and the anisotropy ratio of the correlation lengths. Separate analyses of the travel times carried over planes at different travel distances show that the variance of the log conductivity increases with travel distance.
Seasonal variation in surface‐subsurface water exchange and lateral hyporheic area of two stream‐aquifer systems
Authors: Wroblicky Gregory J. , Campana Michael E. , Valett H. Maurice , Dahm Clifford N.
Published: February 2008

We used two‐dimensional unconfined transient groundwater flow models to investigate the interface between stream and groundwater flow systems, or hyporheic zone, of two first‐order streams that drain catchments with distinctly different alluvial sediments and bedrock lithology. Particle tracking showed that lateral hyporheic area (planimetric area of flow paths lateral to the stream that are recharged by and return to the stream with travel times of 10 days or less) differed between the two study streams and varied with discharge within each system. At the Rio Calaveras (welded tuff), lateral hyporheic area ranged from 1.7 to 4 m2 over the annual cycle. In the Aspen Creek system (sandstone), lateral hyporheic area (1–1.5 m2) was restricted to roughly half of that observed at Rio Calaveras. The size of the hyporheic zone lateral to the streams at both sites decreased by approximately 50% during high flows. Sensitivity analyses indicated that changes in the hydraulic conductivity of alluvial and streambed sediments and variation in recharge rates have greatest impact on the magnitude, direction, and spatial distribution of stream‐groundwater exchange.
Trace gases over the western Atlantic Ocean: Fluxes From the eastern United States and distributions in and above the planetary boundary layer
Authors: Khalil M. A. K. , Rasmussen R. A.
Published: February 2008

During January 1986 we took about 80 air samples on four aircraft flights over a horizontal surface parallel to the east coast of the United States spanning latitudes from 30°N to 46°N and altitudes from near the Earth's surface to about 6 km above. These measurements were part of the Western Atlantic Ocean Experiment (WATOX). The prevailing winds carry man‐made pollutants from the densely populated and industrialized eastern United States to regions over the western Atlantic. The measurements taken over the vertical surface intercept the pollutants. By calculating the fluxes of gases through this surface we obtained estimates of emissions from the eastern United States during winter. We estimate that every day about 165 tons of man‐made chlorine‐containing gases passed through the region of measurements. Some 3,200 tons/day of light hydrocarbons (C2 and C3) , 25,300 tons of methane, and nearly 40,000 tons of carbon monoxide were also transported every day from the east coast to the western Atlantic. These estimates can probably be extended to the entire winter; however, the fluxes can change dramatically during other seasons.
Methane efflux from the pelagic regions of four lakes
Authors: Miller Laurence G. , Oremland Ronald S.
Published: February 2008

Methane emission to the atmosphere was studied in the deepest, central (“pelagic”) regions of one freshwater and three meromictic, alkaline saline lakes. The range of methane emissions was 0.0004 to 2.916 mmol m−2 h−1 (n = 41). Outward flux was dominated by bubble ebullition only in the freshwater lake. Diffusive gas exchange was the sole mechanism of transfer in the meromictic lakes, and flux from these lakes was equivalent to or lower than that from the freshwater lake during its periods of ebullition. A comparison of measured flux with flux calculated using a model of gas exchange in Mono Lake suggested that floating chambers provide reasonable estimates of the magnitude of methane emissions from diffusion‐dominated systems.
Biogeochemical aspects of atmospheric methane
Authors: Cicerone R. J. , Oremland R. S.
Published: February 2008

Methane is the most abundant organic chemical in Earth's atmosphere, and its concentration is increasing with time, as a variety of independent measurements have shown. Photochemical reactions oxidize methane in the atmosphere; through these reactions, methane exerts strong influence over the chemistry of the troposphere and the stratosphere and many species including ozone, hydroxyl radicals, and carbon monoxide. Also, through its infrared absorption spectrum, methane is an important greenhouse gas in the climate system. We describe and enumerate key roles and reactions. Then we focus on two kinds of methane production: microbial and thermogenic. Microbial methanogenesis is described, and key organisms and substrates are identified along with their properties and habitats. Microbial methane oxidation limits the release of methane from certain methanogenic areas. Both aerobic and anaerobic oxidation are described here along with methods to measure rates of methane production and oxidation experimentally. Indicators of the origin of methane, including C and H isotopes, are reviewed. We identify and evaluate several constraints on the budget of atmospheric methane, its sources, sinks and residence time. From these constraints and other data on sources and sinks we construct a list of sources and sinks, identities, and sizes. The quasi‐steady state (defined in the text) annual source (or sink) totals about 310(±60) × 1012 mol (500(±95) × 1012 g), but there are many remaining uncertainties in source and sink sizes and several types of data that could lead to stronger constraints and revised estimates in the future. It is particularly difficult to identify enough sources of radiocarbon‐free methane.
Particulate organic sulfur in the waters of the Southern California Bight
Authors: Matrai Patricia A. , Eppley Richard W.
Published: February 2008

The organic sulfur content of suspended and sinking particulate matter was examined in the upper 1000 m of the water column in the Southern California Bight. Depth distributions of suspended particulate organic sulfur (POS) showed a subsurface maximum in most stations that deepened offshore. POS concentrations in suspended matter averaged 1.26 ± 0.50 μg S L−1 within the euphotic zone during the two cruises analyzed (August and October, 1987). The downward fluxes of mass, carbon, nitrogen and sulfur of sinking particulate matter increased with increasing sample depth to 350 m in the water column. Fluxes were similar during the three deployments. POS was correlated with and directly proportional to POC, PON, and chlorophyll a in the suspended material. Similar correlations were obtained in the trap material although a positive POC intercept value suggested the presence of more refractory material, with sulfur being selectively removed relative to carbon. The average molar ratios were C : N : S = 224 : 27: 1 in suspended and 119 : 17 : 1 in sinking particulate organic matter. Particulate organic sulfur appeared to have a biological origin, most likely planktonic.
Ocean to atmosphere carbon monoxide flux: Global inventory and climate implications
Authors: Erickson David J.
Published: February 2008

The global ocean to atmosphere flux of carbon monoxide (CO) is simulated with 4.5° × 7.5° latitude‐longitude spatial resolution using global data fields derived from an atmospheric general circulation model. The cloud and radiation package in the National Center for Atmospheric Research Community Climate Model is used to estimate the solar energy at the Earth's surface. This quantity is empirically related to photochemical interaction with dissolved organic matter, and the global concentration field of CO in surface seawater is estimated. Areas associated with the Intertropical Convergence Zone and mid‐ to high‐latitude winter hemisphere regions have relatively low climatological CO surface ocean concentrations on a local scale. The global surface wind and temperature fields are simultaneously used to calculate the global transfer velocity field of CO. Coupling these two computed fields, a global ocean to atmosphere CO flux of 165± 80 Tg yr−1 is proposed. The CO flux rates vary globally from 0.1 to 12 ug cm−2 month−1. The fluxes are largest in the mid‐latitude summer hemispheres, with a maximum at 40° S during the austral summer that is 40% larger on a zonal average than at any northern hemisphere latitude. Relatively small continental sources of CO to the southern hemisphere atmosphere and the short atmospheric residence time of this trace gas indicate that ocean‐derived CO may influence the local photochemical dynamics in the remote marine boundary layer of this region. A possible climate feedback scenario involving UV radiation, ozone, OH, and the air‐sea exchange of CO is proposed. The global ocean to atmosphere CO flux proposed here is at the high end of those used in previous atmospheric CO budgets. This estimate however must be considered a lower limit because no explicit simulation of global oceanic primary productivity is presently in the model.
Methane emissions from the Florida Everglades: Patterns of variability in a regional wetland ecosystem
Authors: Bartlett David S. , Bartlett Karen B. , Hartman Jean M. , Harriss Robert C. , Sebacher Daniel I. , Pelletier‐Travis Ramona , Dow David D. , Brannon David P.
Published: February 2008

Natural wetlands are presumed to be major sources of atmospheric methane, but current estimates of the global wetland emission vary by almost a factor of 20. Estimates of global source strengths are based on extrapolation of in situ flux measurements to large areas occupied by broad classes of wetland environments, and recent efforts at refinement of these estimates have concentrated on improving inventories of the global distribution of major wetland types. An additional potential source of uncertainty which has not been quantified is regional scale variability in emission rates within the major wetland types. We conducted an experiment which examined the spatial variability of methane flux within a large regional wetland system, the Florida Everglades. We also investigated the association of flux variability with relevant surface characteristics such as soil thickness, water depth, soil temperature, and vegetative community distribution. Unit area methane flux to the atmosphere from water‐saturated Everglades environments, measured in situ, varied over more than an order of magnitude (4.2 to 81.9 mg CH4/m2/d), depending on which habitat component of the ecosystem was sampled. Observed physical characteristics of the surface (water and soil depth, soil temperature) were not quantitatively associated with the variability in flux rates. However, the distribution of vegetative community types provided an empirical indicator of flux, permitting an inventory of emissions to be based on mapping of regional vegetation patterns. Use of high‐resolution, orbital remote sensing data helped reduce uncertainty in the emission inventory of the Everglades by directing in situ sampling efforts to important habitat types and by providing a means for calculating area‐weighted mean flux for the system as a whole. The results indicated that spatial variability in flux within a major wetland ecosystem can introduce significant uncertainty in extrapolations to larger areas, even if the extent of the major ecosystem itself is well known. The results also suggested that the response of total ecosystem flux to changing water level is not a linear function of flooded area, but is damped, with regional flux at lowered water levels decreasing proportionally less than flooded area. Both sources of variability can be addressed by the combination of remote sensing and in situ techniques we have employed in the Everglades.
The distribution of radiocarbon in the glacial ocean
Authors: Broecker Wallace S. , Peng Tsung‐Hung , Trumbore Sue , Bonani Georges , Wolfli Willy
Published: February 2008

Accelerator mass spectrometric radiocarbon measurements on benthic foraminifera shells, picked from samples on which concordant ages were obtained on the shells of two species of planktonic foraminifera, reveal that the age of deep water in the equatorial Atlantic during glacial time was 675±80 years (compared to today's age of 350 years) and that the age of deep water in the South China Sea was 1670±105 years (compared to today's value of 1600 years). These results demonstrate that the 1.3 to 1.5 times higher radiocarbon content of carbon in glacial surface waters of the Caribbean Sea reconstructed by Bard et al. [1990] was primarily the result of a higher global inventory of radiocarbon rather than a decrease in rate of mixing between surface and deep waters of the ocean. The results are also consistent with the conclusion by Boyle and Keigwin [1987] that the flow of North Atlantic Deep Water was considerably weakened during glacial time, allowing deep waters of Antarctic origin to push much further north into the Atlantic than they do today.
Amine nitrogen in the atmospheric environment over the North Atlantic Ocean
Authors: Gorzelska Krystyna , Galloway James N.
Published: February 2008

During the course of the Global Change Expedition/Coordinated Air‐Sea Experiment/Western Atlantic Ocean Experiment, we collected 77 aerosol and 20 precipitation samples over the North Atlantic Ocean; we speciated and quantified the organic nitrogen in these samples in the form of 18 different water‐soluble primary amine compounds. We calculated the nitrogen contribution from these 18 amine species as the total amine nitrogen (TAN). Concentrations of TAN in aerosol samples ranged from 0.3 to 1630 pmol N m−3. Serine, glycine, arginine, alanine, ethanolamine, and methylamine contributed approximately 90% of TAN. Highest concentrations were in the samples collected near North America, Bermuda, the Azores, and in the Arctic Circle; low concentrations were in the samples collected in the Gulf Stream and in the equatorial North Atlantic. Radon concentrations, trajectory analyses, and correlations between different amine species provided clues to the origin and atmospheric history of these compounds. The long‐range transport of terrestrial materials and oceanic inputs contributed to TAN. At low background concentrations, there was a statistically significant linear correlation between TAN and ammonium (NH4+) that persisted over the entire ocean area. Although their deposition flux may approach 10% of ammonium flux, relative to NH4+ the aerosol concentrations of the water‐soluble primary amines were small (average=2%). The TAN in rain samples ranged from <5 to727 nM (average=164 nM). Generally, the amine species in precipitation paralleled those in aerosol. The scavenging ratio for individual species ranged from 200 to 3000.

Supplemental table is available with entire article on microfiche. Order from American Geophysical Union, 2000 Florida Avenue, N.W., Washington, D.C. 20009. Document G90‐001; $2.50. Payment must accompany order.
A search for teleseismic travel‐time anomalies along the San Andreas Fault Zone
Authors: Cramer Chris H. , Kovach Robert L.
Published: February 2008

Teleseismic arrivals for earth‐quakes occurring in the Tonga Island source region were examined at four stations of the University of California, Berkeley seismographic network to search for local P‐wave velocity variations from 1971 through 1972. The method of two station residuals was used so that only variations in residuals of one station are examined. The difference in two station residuals indicate a generally stable P‐wave velocity and no velocity variation at station LLA associated with the Bear Valley earthquake 23 kilometers from the station. There is also no large variation in P‐wave velocity at station SAO prior to the magnitude 4.9 San Juan Bautista earthquake located 11 km from that station. If P‐wave velocity variations do occur along the San Andreas Fault in central California, our results suggest that an anomalous P‐wave velocity zone would not exceed a radius of 10 kilometers for a magnitude 5 event.
The planetary primordial component of rare gases in the deep Earth
Authors: Fisher David E.
Published: February 2008

Ar, Kr, and Xe were measured in basalts dredged from several deep sea locations, one of which may indicate entrapment of planetary primordial gases. The data support earlier suggestion that Xe was depleted in the earth's atmosphere by selective adsorbtion.
Intensity variation of ELF hiss and chorus during isolated substorms
Authors: Thorne R. M. , Smith E. J. , Fiske K. J. , Church S. R.
Published: February 2008

Electromagnetic ELF emissions (100‐1000 Hz) observed on the polar‐orbiting OGO‐6 satellite within three hours of the dawn‐dusk meridian consistently exhibit a predictable response to isolated substorm activity. Near dawn the emissions intensify during the substorm and then subside following the magnetic activity; the waves are most intense at L \>4, exhibit considerable structure and have been primarily identified as chorus. At dusk the response is entirely different; the wave intensity falls to background levels during substorm activity but subsequently intensifies usually reaching levels well in excess of that before the disturbance. The emissions near dusk extend to low L, are relatively featureless, and have been identified as plasmaspheric hiss. These features are interpreted in terms of changes in the drift orbits of outerzone electrons which cyclotron resonate with ELF waves.
Estimates of possible future ozone reductions from continued use of fluoro‐chloro‐methanes (CF2Cl2, CFCl3)
Authors: Crutzen P. J.
Published: February 2008

In agreement with arguments put forward by Molina and Rowland (1974) it is concluded that very large reductions in ozone concentrations above about 30 km may result from the continued use of fluoro‐chloro‐methanes (CF2Cl2 and CFCl3), which are dissociated by ultraviolet radiation in the stratosphere and mesosphere, thereby giving rise to ozone‐attacking Cl and ClO. Below about 30 km the reductions in ozone are much smaller and even a slight increase in ozone concentrations may result. The total column abundance of ozone in the atmosphere is, however, reduced by about 10%, assuming that the present rate of production of CF2Cl2 and CFCl3 remains unaltered.
Premonitory vertical migration of microearthquakes in central California—Evidence of dilatancy biasing?
Authors: Bufe Charles G. , Pfluke John H. , Wesson Robert L.
Published: February 2008

Mean apparent focal depths of microearthquakes occurring along a 20‐km stretch of the San Andreas fault southeast of Hollister, California, increased by 25 percent some 60 days before the magnitude 4.6 Stone Canyon earthquake of September 4, 1972. The shape of the time‐depth anomaly is virtually identical to the time plots of Vp/Vs preceding moderate earthquakes at Garm, U.S.S.R. A less well‐defined depth anomaly occurred in October‐December 1971, preceding the Limekiln Road swarm in December 1971 and the magnitude 5.0 Melendy Ranch earthquake in February 1972. The observed depth anomalies can be attributed to dilatancy biasing of hypocenters, although true vertical migration of seismicity cannot be ruled out.
A magnetotelluric traverse across the Yellowstone Region
Authors: Leary P. , Phinney R. A.
Published: February 2008

Five magnetotelluric stations were taken in the Yellowstone region. Sufficient coherent signal was obtained in the frequency band 10−4 to 10−1 hz to yield useful apparent resistivity (ρa) spectrums. At stations near Yellowstone the resistivity was linearly proportional to ω at long periods; this is due to the existence of a high conductivity substrate at some depth. The effective thickness of the low conductivity surface zone as inferred from the intercept of the response curve is consonant with the geological setting; it is thin (<5 km) in the Yellowstone thermal area, and thicker on the Snake River Plain (≈ 15 km). Stations well away from Yellowstone show ρa ∼ ω0.7, suggesting a lower, gradient of conductivity in the substrate. Precise inversion of the data is not practical: however, the comparison of ρa at neighboring stations shows distinct differences in electrical response of the crust which may be discussed in a geological context.
Heliographic‐latitude dependence of the cosmic‐ray intensity
Authors: Antonucci Ester , Marocchi Daniela
Published: February 2008

Evidence for a semi‐annual variation in the galactic cosmic‐ray intensity is presented. This effect can be associated with the heliographic latitude excursion of the earth during its orbital motion. Therefore the phase evaluation of the semi‐annual variation can be used to infer the direction of the cosmic‐ray gradient perpendicular to the solar equatorial plane through the solar cycle.
Predicted present stratospheric abundances of chlorine species from photodissociation of carbon tetrachloride
Authors: Molina Mario J. , Rowland F. S.
Published: February 2008

We have calculated that stratospheric photodissociation in the 1950–2250 Å range removes CCl4 at a rate corresponding to an atmospheric lifetime of 30‐50 years. Whether CCl4 is of natural or anthropogenic (in use since early 1900's) origin, the ratios between it and its photodissociation products should be approximately those characteristic of a steady state. The present level of 7 × 10−11 v/v for CCl4 in tropospheric air can thus be used to estimate the present minimum levels of HCl, ClO, and Cl which should be present in the stratosphere from the photodissociation of CCl4. The current average HCl concentration is predicted to be about 10−10 v/v above 30 kms from this source, while ClO is predicted to approach 10−10 v/v near 35 kms.
Comment on “On wind profiles over sea ice” by M. P. Langleben
Authors: Paulson C. A. , Untersteiner N.
Published: February 2008

In anticipation of the caution offered by Dr. Langleben, the Arctic Ice Dynamics Joint Experiment plan to determine air stress from wind speed observations at two levels has been modified. It is suggested that observations by Langleben of wind profiles exhibiting extrema cannot be satisfactorily attributed to non‐stationary flow.
Bottom homogeneous layers in the Florida Current
Authors: Weatherly Georges L. , Niiler Pearn P.
Published: February 2008

A total of 495 STD traces obtained from surface to bottom casts made in transects of the Florida Current east of Miami is examined for bottom homogeneous layers. Bottom layers are seen at all stations; however, at none of the examined stations was a bottom layer a permanent feature. The variation of frequency of occurrence and the variation of the depth of these layers across the Florida Current are examined and a possible explanation for their distribution is presented. The observations show that generally thicker layers are associated with cooler water and thinner layers with warmer water. We suggest that horizontal advection across topographic slopes is an essential ingredient of homogeneous layer formation.
The Jovian ionosphere
Authors: Prasad S. S. , Tan Arjun
Published: February 2008

Models for the Jovian ionosphere which incorporate the role of hydrocarbons in the production and loss of ionization, are presented. A new feature is the possible existence of a second peak in the electron density distribution. On comparing our model with the results of the Pioneer‐10 measurements of the Jovian ionospheric electron density‐distribution, we find several important differences. Plausible explanations for these differences are also discussed.
Evidence consistent with a multiple‐event mechanism for large earthquakes
Authors: Sweetser Erton I. , Cohen Theodore J.
Published: February 2008

We analyzed the short‐period codas of 418 small events (NOS mb ≤ 5.8) and 148 large‐events (NOS mb, NOS Ms, or mb from Pasadena or Berkeley ≥7.0). The normalized large‐event codas are found to be significantly larger at any given time after the first‐arrival onset than corresponding values for small‐event codas. This suggests that large events are multiple events, and that the occurrence of later events in a given sequence retards coda decay and elevates the relative amplitudes of the codas above those expected for a small (single) event. Large events are also found to be emergent, displaying a 0.2 to 0.3 mb increase in amplitude between 5 and 30 seconds after the P wave arrival over that observed in the first 5 seconds after the arrival. Coda decay characteristics for large events may be used to estimate the length of the fault zone. We suggest that multiple events are a more common phenomenon than has been generally suspected, and that most if not all events of high or intermediate Ms are probably multiple events.
Chemical analysis of Aitken particles (< 0.2 µm radius) over the Atlantic Ocean
Authors: Winkler P.
Published: February 2008

During cruise No. 32 of RV “Meteor”, 6.Nov.–6.Dec. 1973 across the Atlantic at 15°N, samples of Aitken nuclei were taken and the chemical compsition determined by an X‐ray fluorescence technique. The samples consisted mainly of sulfur with concentration of 0.2 µg/m³ in pure Atlantic air and about double this value in air influenced by the Sahara. The concentrations of the elements chlorine, calcium and potassium were about one order of magnitude lower and suggest the absence of sea salt in the Aitken particle range. The elements vanadium, selenium and bromine were just below the positive detection limits but seemed to be present, since all values were higher than the blank values but within the error limits. The results show that in clean air conditions the dynamics of the Aitken particles are closely related to the sulfur cycle.
A microearthquake survey of the San Miguel Fault Zone, Baja California, Mexico
Authors: Reyes Alfonso , Brune James , Barker Terrance , Canales Luis , Madrid Juan , Rebollar Javier , Munguia Luis
Published: February 2008

High gain portable seismographs have been operated at 22 sites along the San Miguel fault zone, Baja California, Mexico. We report results in terms of normalized rates of microearthquakes per day. Very high rates, exceeding 100 events/day, were observed near the southeast end of the San Miguel fault. Sixteen of the 22 sites recorded rates exceeding 20 events/day. The overall micro‐seismicity is higher than along most of the San Andreas fault in Southern California. At two sites, arrays were operated to obtain accurate locations. Locations near the southeast end of the San Miguel fault were very near the fault trace and at depths of 8 to 14 km. Relatively high microearthquake rates were observed at a site 70 km from Tijuana, suggesting that the northwestern San Miguel fault zone is active and might pose a significant seismic hazard to the cities of Tijuana and San Diego.
Higher Rayleigh modes in western Europe
Authors: Nolet Guust
Published: February 2008

An array of standard long period stations is applied to measure phase velocities of seismic surface waves by way of frequency‐wavenumber analysis. The number of interfering modes is reduced by windowing the signal for successive group velocity intervals. The method is powerful, even with relatively small arrays: up to 6 higher Rayleigh modes at periods between 20 and 100 sec. have been resolved.
Modulation of Jovian interplanetary electrons and the longitude variation of decametric emissions
Authors: Vasyliunas Vytenis M.
Published: February 2008

Interplanetary electrons of Jovian origin show minimum intensity and softest energy spectrum when the subsolar point on Jupiter is near the longitude of most frequent non‐Io‐related decametric emissions.
Paleomagnetospheric radial diffusion
Authors: Schulz Michael
Published: February 2008

Temporal variations of the geomagnetic dipole moment (Me) are found to modulate the radial‐diffusion coefficient (DΦΦ) of geomagnetically trapped particles (Φ = third adiabatic invariant). Acceptable models of this effect suggest that DΦΦ ⧜ Mep, with 5<p<6, for radial diffusion caused either by magnetic impulses or by electrostatic impulses of magnetospheric extent. Since Me is known to fluctuate by ±50% about its present (and mean) value, with a quasi‐period ∼8000 yr, the resulting modulation of DΦΦ spans about 2.5 orders of magnitude. Particles that have probably resided in the magnetosphere for the past 1500 yr (viz., sufficiently energetic inner‐zone protons) have thus sampled a systematic order‐of‐magnitude decrease in DΦΦ. Such a large variation of DΦΦ must influence the interpretation of their presently observed intensities (directional fluxes).
Elasticity of microcrystals
Authors: Weidner Donald J. , Swyler Karl , Carleton Herbert R.
Published: February 2008

Acoustic velocities for a very small crystal are presented. The longitudinal velocities in the .3 mm single crystal of quartz are accurate to about 1–2%. The technique involves only optical measurements and is based on analysis of Brillouin scattering. The minimal sample size for acoustic velocity measurements using this technique is estimated to be about 0.01–0.03 mm.
Seasonal and latitudinal variation of the stratospheric concentration of HNO3
Authors: Murcray D. G. , Barker D. B. , Brooks J. N. , Goldman A. , Williams W. J.
Published: February 2008

A sensitive spectral radiometer system capable of measuring the atmospheric emission in the 6.5µm to 13.0µm region has been constructed for use on the WB57F aircraft used on the Department of Transportation Climatic Impact Assessment Program. The data obtained with this instrument on a number of flights have been analyzed to determine the total HNO3 column density above the aircraft at various latitudes and seasons. Examination of these data indicate a definite variation of HNO3 column density with latitude and possible seasonal variations.
A study of lateral inhomogeneities in the upper mantle by multiple Scs travel‐time residuals
Authors: Okal Emile A. , Anderson Don L.
Published: February 2008

An analysis of records of multiply reflected ScS phases from ten deep‐focus earthquakes yields near‐vertical one‐way travel‐time residuals varying from +5.0 to −3.5 s. Continental and oceanic residuals overlap and both indicate large lateral variations. Similar values are found for the older oceanic basins and for continental shields. Most, if not all, of the variations can be attributed to differences in the lithosphere and asthenosphere. The mantle under Hawaii, Iceland and Trindade (South Atlantic) Islands is anomalously slow, all being postulated hotspots. In the case of Trindade, petrological data is consistent with a pronounced low‐velocity zone and large S delays. Some recent studies assumed that stations on oceanic islands were representative of the ocean as a whole and it has been suggested that continent‐ocean differences extend deeper than 400 km. The present results indicate that oceanic islands are anomalous, and that differences between oceans and continents need not extend below 200 km. This does not rule out the existence of deep lateral inhomogeneities, but only the proposal that continents, in general, are faster than oceans to depths greater than 400 km.
On the thermal evolution of the oceanic lithosphere
Authors: Williams David L. , Poehls Kenneth A.
Published: February 2008

The synthesis of extensive seafloor heat‐flow and subsidence data for the North Atlantic and North Pacific Oceans reveals that these quantities approach equilibrium values before the oceanic lithosphere is 80 million years old. These are fundamental constraints on any model describing the thermal evolution of the oceanic lithosphere, but previously they have not been well established and have been ignored in recent thermal models. To satisfy these constraints, either the lithosphere must establish a nearly constant thickness by interacting with the asthenosphere, or a tenuous set of conditions interrelating plate thickness, density changes, basal heat flow, and asthenosphere temperature gradients must prevail. Failure to recognize this has led to the acceptance of thermal models that are inconsistent with a vast amount of oceanographic data.
Field measurements of submicron aerosol washout by snow
Authors: Graedel T. E. , Franey J. P.
Published: February 2008

Direct field measurements of the washout of submicron aerosols by snow have been accomplished by high‐speed sampling of the atmospheric aerosol spectrum and of the rate of snowfall. For the aerosol size range 0.29 µm ≤ D ≤ 1.48 µm, the values of the measured washout coefficients are 4.82×10−4 ≤ λS ≤ 6.35×10−3 sec−1, and show no systematic dependence on aerosol diameter. Comparison of the results with those previously derived for rain washout indicate that snow scavenging is ∼28–50 times more efficient per equivalent water content. Average aerosol lifetimes due to washout by snowfall are of the order of 0.7 hours, thus establishing snow scavenging as the dominant aerosol sink in regions having significant snowfall during the winter season.
Depletion of the F2 region ionosphere and the protonosphere by the release of molecular hydrogen
Authors: Bernhardt P. A. , Park C. G. , Banks P. M.
Published: February 2008

Theoretical models have been used to investigate the effects of artificially injected H2 gas on plasma densities in the ionospheric F region and the overlying protonosphere. Owing to large reaction rates between H2 and ionospheric O+ ions, plasma densities in both daytime and nighttime ionospheres can be greatly reduced by modest amounts of H2 gas released. 100 kg of H2 released at 300 km altitude reduces local O+ densities by more than three orders of magnitude and produces ∼5% depression in H+ densities in the overlying protonosphere. These results suggest that it should be possible to conduct controlled chemical modification experiments for investigation of many outstanding ionospheric and magnetospheric problems.
Rocket‐borne particle, field, and plasma observations in the cleft region
Authors: Ungstrup E. , Bahnsen A. , Olesen J. K. , Primdahl F. , Spangslev F. , Heikkila W. J. , Klumpar D. M. , Winningham J. D. , Fahleson U. , Falthammar C.‐G. , Pedersen A.
Published: February 2008

First results of comprehensive observations of magnetic and electric fields, and ambient and suprathermal plasmas above the dayside auroral oval with rocket‐borne instrumentation which penetrated the cleft region are reported. Measurements were also obtained equatorward and poleward of the cleft. Convection velocities as inferred from electric field measurements were generally toward noon equatorward of the cleft and were antisunward over the polar cap. Our observations of electron temperatures, electric fields and low‐frequency electrostatic noise provide strong evidence of a plasma instability (Farley‐Buneman) in the E‐layer, which is associated with the appearance of the ‘slant E condition’ identified in ground‐acquired ionograms. The positions of these measurements relative to that of the cleft were firmly established via the determination of the plasma environment with an electrostatic analyzer.
Post‐oxide phases of forsterite and enstatite
Authors: Liu Lin‐gun
Published: February 2008

Both forsterite (Mg2SiO4) and enstatite (MgSiO3) enter a post‐oxide phase characterized by the orthorhombic perovskite structure when subjected to high pressure and temperature in the diamond‐anvil press coupled with laser heating. The lattice parameters for the perovskite phase of MgSiO3 are ao = 4.790 ± 0.002, bo = 4.943 ± 0.002, and co = 6.897 ± 0.003 Å with Z = 4. The calculated density of MgSiO3 (perovskite) is thus 4.083 g/cm³, or 2.8% denser than its isochemical mixed oxides with rocksalt and rutile structures. The density of a mixture of MgSiO3 (perovskite) plus MgO (periclase) is 1.9% greater than that of the mixed oxides with the forsterite stoichiometry.
Radial variation of solar‐wind parameters
Authors: Jokipii J. R.
Published: February 2008

It is demonstrated that since fluctuations in the solar wind are not small, they can have important effects on the observed average values of parameters in the solar wind and their radial variation. The effect is distinct from the dynamical effect of waves and turbulence and results from the averaging process. It is concluded that, for example, the average density of the solar wind need not vary as 1/r², even if the average velocity is constant and radial. The effect on thermal anisotropies might also be important. The magnitudes of the effects depend on presently unknown correlations between fluctuations in the solar wind.
Observational evidence for time‐dependent zonal winds in the exosphere
Authors: Blum Peter W. , Schuchardt Klaus G. H.
Published: February 2008

One of the few methods that allows the determination of zonal thermospheric winds is the analysis of the variation of the inclination of satellite orbits. Until now mainly the diurnally averaged zonal wind velocity was determined by this method. From the analysis of the orbit of the balloon satellite Explorer 24 (1964‐76A) both the diurnal average and the diurnal variation of the zonal wind have been determined in the height region between 540‐610 km. Within the limits of the accuracy of the method there results a diurnally averaged zonal wind velocity that is nearly zero. This is contrary to the results of previous investigations by a similar method where an average rotational velocity of the exosphere appreciably less than the rotational velocity of the earth has been found. The diurnal component of the zonal wind is shown to have an amplitude of 90 ± 65 m/sec, and the zonal wind has its maximum from West to East at 23.96 ± 2.33 hr local time. Both the amplitude and the phase of the diurnal component of the zonal exospheric wind velocity agree approximately with the theoretical results of Blum and Harris.
Matched filtering for the seismic moment tensor
Authors: Buland Ray , Gilbert Freeman
Published: February 2008

By a process of matched filtering it is possible to deconvolve a small number of acceleration or strain records for the moment rate tensor of a seismic source. Theoretically, one horizontal accelerometer (or strain meter) or two vertical accelerometers is sufficient. Practically, five to ten records can be shown to suffice. Specifically, the mechanism of the Colombian event of July 31, 1970 can be retrieved from a sparse network of ten WWSSN vertical instruments.
Jupiter's magnetotail as the source of interplanetary Jovian MeV electrons observed at Earth
Authors: Pesses M. E. , Goertz C. K.
Published: February 2008

The source of interplanetary Jovian MeV electron enhancements observed at Earth is found to be Jupiter's magnetotail. If an average solar wind speed of 400 km sec−1 is assumed, the main region of emission extends from ∼ 1.0 AU downstream from Jupiter to ∼ 2.0 AU beyond the planet. (If a value of 350 km sec−1 is assumed, it extends from ∼ 0.4 AU to ∼ 1.2 AU.) Individual "active" zones are ∼ 0.2 AU in length. It is proposed that interplanetary magnetic field line connection with the tail is the mechanism providing the Jovian Electrons observed at Earth.
Direct measurements of natural tropospheric levels of OH via an aircraft borne tunable dye laser
Authors: Davis D. D. , Heaps W. , McGee T.
Published: February 2008

Using an airborne mounted UV tunable laser system, natural tropospheric OH radical concentrations at 7 and 11.5 km are here reported for the first time. The technique employed was that of Laser Induced Fluorescence where the OH radicals were excited at 2820.6Å with the fluorescence being monitored at ∼3095Å. Sampling of the OH was carried out continuously using a laminar flow intake manifold in which the UV laser beam (7mm diameter) was passed through the center core of the gas stream. Measurements at 32° north latitude and 21° north latitude at 7 and 11.5 km revealed significant latitude and altitude variations of the OH radical during the month of October 1975. Details on the importance of these measurements to tropospheric chemistry are discussed.
Shear wave anisotropy in the upper mantle of the Pacific Basin
Authors: Schlue J. W. , Knopoff L.
Published: February 2008

Phase travel‐times for Love and Rayleigh waves across the Pacific Basin were inverted to obtain models of the upper mantle of the Pacific Basin. Inversion of the Rayleigh wave data yielded a model with S‐velocities in the lid and channel of 4.597 ± .018 and 4.103 ± .016 km/sec, respectively, while inversion of the Love wave data resulted in lid and channel S‐velocities of 4.634 ± .050 and 4,244 ± .031 km/sec respectively (95% confidence level). To within the indicated uncertainties, these results suggest a model with a lid which is isotropic and a channel which is anisotropic with respect to S‐wave velocity. No significant evidence of azimuthal anisotropy was found. Anisotropy in the LVC and its absence in the lid is presumed to be associated with preferred orientation of partially molten material in the LVC. One model of partial melting adequate to explain the results is a configuration of small penny‐shaped cracks of zero volume and radius a. The number density of spheres of radius a, N4πa³/3V, each containing one randomly oriented crack is 71%; the number density of such spheres containing one horizontal crack is 12%. The preferred orientation of cracks may be related to a shear flow gradient in the channel.
Observation of a new abyssal current at the western foot of the Bermuda Rise
Authors: Schmitz William J.
Published: February 2008

A new abyssal current of magnitude 2.0 ± .3 cm s−1 has been found near 4000 m depth at the western foot of the Bermuda Rise. This estimate is based on about two years of moored current meter data. Preliminary indications are that the current penetrates downward to the ocean bottom, and upward to 1500 m depth with diminished intensity.
Measurement of the stratospheric mixing ratio of HCl using infrared absorption technique
Authors: Williams W. J. , Kosters J. J. , Goldman A. , Murcray D. G.
Published: February 2008

Approximate mixing ratios of HCl in the stratosphere have been derived from solar spectra obtained during sunset with a balloon‐borne grating spectrometer. The HCl mixing ratio increases from 0.15 × 10−9 to 1.2 × 10−9 vol HCl/vol Air in the 13.4‐27 km altitude range with a possible decrease above 27 km.
On the minimum variance direction of magnetic field fluctuations in the azimuthal velocity structure of the solar wind
Authors: Solodyna Craig V. , Belcher John W.
Published: February 2008

Studies of waves in the interplanetary medium often assume that the direction of minimum variance is parallel (or anti‐parallel) to the direction of the wave normal vector
. In an azimuthally structured solar wind, geometrical optics predicts that the
vectors of magneto‐hydrodynamic (MHD) waves should be refracted in a characteristic manner. The present study considers the properties of microscale magnetic field fluctuations for divers classes of large‐scale azimuthal velocity structures in the solar wind. Using 168.75 sec and 22.5 min variance matrices obtained by Mariner 5, we find that the direction of minimum variance does not exhibit any characteristic refraction pattern with respect to large scale velocity structures in the solar wind. The distribution of minimum variance directions is always strongly peaked at and symmetric about the average field direction, and shows no tendency to refract towards a more radial configuration. These observational results suggest that either the predictions of geometrical optics are incorrect, or that the direction of minimum variance is not indicative of the
vector direction. We favor the latter interpretation.
Euv indices for solar‐terrestrial relations
Authors: Schmidtke G.
Published: February 2008

Modern studies of solar‐terrestrial relations require a new type of solar activity indices suitable for numerical computations. Since in this context solar extreme ultraviolet radiation is the most important variable influence, EUV indices are proposed representing the EUV energy flux from the whole solar disc at Earth' distance. Examples derived from AEROS measurements are presented.
Aerosol formation during coal combustion: Condensation of sulfates and chlorides on flyash
Authors: Pueschel R. F.
Published: February 2008

Submicron flyash particles show a preferential surface concentration of sulfur and chlorine in comparison to their matrix elements, e.g., aluminum and silicon. The relationship between concentration of surface deposited matter and inverse particle diameter suggests that S and Cl are adsorbed and oxidized on flyash particles after volatilization in the high‐temperature zone of the boiler. This leads to the formation of cloud nuclei even before a sulfur gas‐to‐particle conversion takes place.
Formation of secondary sulfuric acid aerosols in urban atmosphere
Authors: Kiang C. S. , Middleton P.
Published: February 2008

A numerical kinetic aerosol model is utilized to study conditions under which secondary sulfuric acid aerosol can be formed in an urban atmosphere. This model incorporates the mechanisms of photochemical reactions, heteromolecular nucleation, heteromolecular condensation and thermal coagulation. Various atmospheric conditions are used to study the effects of production rate of sulfuric acid gaseous molecules, relative humidity, temperature, initial particle size distribution and kinetic coefficient for nucleation and condensation growth on the formation of new secondary sulfuric acid aerosol. Our model calculations show that the rate‐limiting factor for the formation of these secondary aerosols is the amount of the sulfuric acid gaseous molecules available in the atmosphere.