bluuebunny/crossref_metadata_2025 huggingface dataset:
The electrical conductivity of materials containing partial melt: A simple model from Archie's law
Authors: Hermance John F.
Published: February 2008

The presence of partial melt can profoundly affect the bulk electrical properties of composite materials. A class of melt distributions is considered where melt forms is one place and accumulates elsewhere; a case modelled by a simple modification of Archie's Law for porous media. This relation provides values for the bulk conductivity intermediate to those for a thoroughly connected melt distribution and those for isolated melt pockets. Thus, if melt is tortuously distributed, larger amounts are required to produce a given increase of the bulk conductivity, than if it is thoroughly interconnected along grain boundaries.
The distribution of beryllium‐7 within high‐pressure systems in the eastern United States
Authors: Wolff George T. , Ferman Martin A. , Monson Paul R.
Published: February 2008

During a 1976 rural ozone field study conducted in McKee, Kentucky, and Busick, North Carolina, simultaneous measurements of ozone and beryllium‐7, a tracer of stratospheric air, were obtained. The purpose of this study was to assess the importance of naturally produced stratospheric ozone on ground‐level ozone concentrations observed in rural areas in the Eastern United States. It is currently accepted that the stratospheric contribution to the surface ozone is about 30‐50 ppb, and that the occurrence of this is confined to the front part of high‐pressure systems immediately behind a cold front. Furthermore, it is thought that the stratospheric contribution is negligible on the back side of the high‐pressure system where higher levels of ozone occur. This study seriously questions both of these hypotheses because the highest levels of beryllium‐7 were observed on the back side and not on the front side of high‐pressure systems.
Theoretical estimate of compressional changes of decay constant of 40K
Authors: Bukowinski M. S. T.
Published: February 2008

A theoretical calculation of the charge density in metallic K is used to estimate pressure induced changes in the electron‐capture decay constant λeof 40K. It is predicted that λe goes through a maximum at approximately 3.5‐fold compression and approaches its one atmosphere value at pressures corresponding to those in the outer‐core of the earth. The maximum predicted change of about 4 × 104 years in the half‐life is negligible when compared to the current experimental uncertaintieswhich are of the order of 107 years.
Is there liquid water on Europa?
Authors: Cassen P. , Reynolds R. T. , Peale S. J.
Published: February 2008

It is possible that tidal dissipation in an ice crust on Europa preserved a liquid water layer beneath it, provided that the three‐body orbital resonance for Io, Europa, and Ganymede is ancient. The liquid water layer could be a continuing source of the observed surface frost. If Europa's water mantle were ever completely frozen, heating by tidal dissipation would not exceed that produced by radioactive elements, and the mantle would remain frozen.
Stratospheric distribution of ClONO2
Authors: Murcray D. G. , Goldman A. , Murcray F. H. , Murcray F. J. , Williams W. J.
Published: February 2008

Balloon‐borne infrared solar spectra in the 1292 cm−1 regionat 0.02 cm−1 resolutionobtained during sunsetare used to derive a mixing ratio altitude profile of ClONO2.
On the production of nitric oxide by lightning
Authors: Hill R. D.
Published: February 2008

Basic differences in the shock heating and channel heating methods of evaluating the yield of NO produced in air by lightning are investigated. It is estimated that the NO yields evaluated by the two models could be an order of magnitude different, with the channel heating model being higher.
Tectonics and composition of Venus
Authors: Anderson Don L.
Published: February 2008

The uncompressed density of Venus is a few percent less than the Earth. The high upper mantle temperature of Venus deepens the eclogite stability field and inserts a partial melt field. A thick basaltic crust is therefore likely. The anomalous density of Venus relative to the progression from Mercury to Mars may therefore have a tectonic rather than a cosmo‐chemical explanation. There may be no need to invoke differences in composition or oxidization state.
Correlated whistler and electron plasma oscillation bursts detected on ISEE‐3
Authors: Kennel C. F. , Scarf F. L. , Coroniti F. V. , Fredricks R. W. , Gurnett D. A. , Smith E. J.
Published: February 2008

The ISEE‐3 plasma wave instrument detects associated bursts of electron plasma oscillations and whistler mode waves at an average rate of event one every two days. The plasma wave measurements give the electron number density, and simultaneously measured E and B amplitudes are used to deduce an index of refraction consistent with whistler mode propagation for the measured number density and magnetic field. Burst durations are a few minutes, with some trains of bursts lasting up to an hour. Individual spectral scans (two per second) reveal that the whistler and plasma wave amplitude‐time profiles differ within a burst. Peak plasma wave amplitudes are near one mV/m, and the peak whistler mode energy density exceeds that of the plasma oscillations by about a factor 100. The frequency of the whistler mode wave observed in one well diagnosed event agrees with the predictions of the heat flux whistler instability theory. The associated plasma wave instability probably requires a bump‐on‐tail feature in the heat flux electron component, possibly due to impulsive heating elsewhere on the field‐line connecting to ISEE 3.
Criteria for impulsive rock fracture
Authors: Grady D. E. , Lipkin J.
Published: February 2008

Explosive or percussive breakage of rock relies on impulsive rock fracture and both the fracture stress and fracture energy under such conditions are observed to be significantly greater than measured quasi‐statically. The implication of rate dependence has been verified in recent tensile fracture studies and in the present report this data has been compiled, significant trends noted, and comparisons made with earlier impulsive fracture criteria.
A search for isotopic anomalies in uranium
Authors: Chen J. H. , Wasserburg G. J.
Published: February 2008

The 238U/235U ratios for nine bulk chondritic meteorites and a terrestrial basalt were measured. The total range in 238U/235U determined for both total meteorites and for acid leaches was from 137.2 to 138.3 and to within the error limits indistinguishable from normal terrestrial U. The typical errors in a single determination are ±6‰ (2σM) for a 2 ng U sample from a chondrite. Taking the extreme values of δ235U for each measurement the maximum amount of excess 235U that can be allowed to be present ranges from 2 × 108 to 2 × 109 atoms per gram of bulk meteorite. These results do not support the claims of variations in 238U/235U at the percentage levels or number of excess 235U atoms in some of the same meteorites as reported by several other previous workers.
Microearthquakes and crustal structure off the Makran Coast of Iran
Authors: Niazi M. , Shimamura H. , Matsu’ura M.
Published: February 2008

On the basis of bathymetric and seismic data collected recently off the coast of Makran in the Gulf of Oman, it has been suggested that the folding of the sediments at the northern edge of the abyssal plain is taking place at the present time. The folding is thought to be the consequence of ongoing subduction of the Arabian plate beneath the Eurasian lithosphere along the Makran coast. The model assigns a far more significant role to the Makran coast in shaping the tectonics of the region than has thus far been assumed.

In order to examine whether, despite the lack of teleseismically observable seismicity, the suggested deformation is associated with any microearthquake activity or not, a network of high gain seismographs, including three OBS’s, was installed near the western end of the Makran coast in May 1977 and operated for about two weeks. During the observation period no noticeable microearthquake activity associated with the suggested boundary was observed. Nearly 40 of the earthquakes located by the network data are aftershocks of the destructive earthquake which occurred on March 21, 1977, north of Bandar‐Abbas, more than 400 km from the OBS’s. From the observed travel times of the three 180 kilogram explosions set off for regional calibration, a 20 km thick two layered oceanic crust was obtained.
Remote infrared heterodyne radiometer measurements of atmospheric ammonia profiles
Authors: Hoell James M. , Harward Charles N. , Williams Burnie S.
Published: February 2008

An Infrared Heterodyne Radiometer (IHR) located at Langley Research Center, Hampton, Va., has been used to study the seasonal variation of the vertical distribution of atmospheric ammonia. The ammonia profiles are inferred from high resolution atmospheric solar transmittance measurements around the ammonia absorption feature at 927.32323 cm−1. The transmittance data are obtained from six IF channels with spectral resolutions ranging from .0067 cm−1 to .033 cm−1. Results from this study show a marked decrease in the tropospheric ammonia level with a decrease at ground level from ∼ 10 ppb in March 1979 to ∼ 1.3 ppb in August 1979.
Preearthquake animal behavior: A closer look for alternative causes
Authors: McClellan Patrick H.
Published: February 2008

Recently published results of post‐earthquake interviews with animal owners in two epicentral areas seem to indicate that animals behave unusually before some earthquakes. A review of the environmental circumstances surrounding one event that yielded positive results (the 22 November 1977 M=4.7 Willits, Calif., earthquake) shows that, in addition to possible geophysical earthquake precursors, three factors not known to be related to the ensuing earthquake may have caused the observed behavioral anomalies: (1) unusually heavy rainfall and local flooding, (2) a relatively large change in barometric pressure, and (3) a very large enhancement in solar‐flare cosmic radiation at ground surface. A modified approach in future studies of behavioral anomalies is recommended that would include an evaluation of all important behavioral stimuli in the local environment before the associated earthquake.
Preliminary tests of an airborne meteorological pulse Doppler radar
Authors: Trotter B. L. , Strauch R. G. , Frush C. L.
Published: February 2008

An X‐band Doppler radar in the tail of a WP‐3D research aircraft has been used to conduct tests which demonstrate that technology developed for ground‐based Doppler radar can be applied to an airborne system. The Doppler spectra of meteorological targets and chaff have been measured with the airborne radar, and these measurements compared favorably with data obtained by wind sensors on the aircraft and with measurements made with a ground‐based Doppler radar. This letter describes the airborne Doppler radar and the preliminary test results.
The solar ultraviolet heating efficiency of the midlatitude thermosphere
Authors: Torr M. R. , Torr D. G. , Richards P. G.
Published: February 2008

In this paper we quantify the major channels by which solar UV energy is transferred to the atmosphere, and determine the UV heating efficiency for the thermosphere. Current knowledge of the solar ultraviolet fluxes, thermospheric chemistry and neutral atmosphere is used in a steady state, interhemispheric solution of the ionospheric continuity, momentum and energy equations. The heating efficiency is found to be a strong function of altitude, and peaks near the altitude of maximum EUV deposition at a value of approximately 50%.
On the vapor pressure of sulfuric acid
Authors: Ayers G. P. , Gillett R. W. , Gras J. L.
Published: February 2008

The vapor pressure of H2SO4 over 98.01 mass‐% sulfuric acid solution has been determined experimentally over the temperature interval 338 to 445 K. Values of the enthalpy and entropy changes upon vaporization deduced from the data accord well with other estimates available in the literature. Extrapolation to 99.0 mass‐% and 296.15 K allows us to confirm another recent vapor pressure determination, thereby supporting the conclusion that the vapor pressures most often used in nucleation calculations in the past are as much as an order of magnitude high.
Further evidence of localized geomagnetic field changes before the 1974 Thanksgiving Day Earthquake, Hollister, California
Authors: Davis Paul M. , Jackson David D. , Johnston Malcolm J. S.
Published: February 2008

Seven weeks prior to the M=5.1 Hollister, Calif., Thanksgiving Day earthquake of 28 November, 1974, an anomalous magnetic variation was observed at one of the magnetometers of the USGS array. The anomaly lasted for about three weeks. Recently developed methods of reducing noise on magnetic records reveal that anomalous magnetic changes occurred at about the same time at three, of the six stations analysed. Such changes have not been seen either previously or subsequently. The largest variation occurred at the two stations closest to the earthquake, but a change also occurred at a station 44 km to the south.
Simultaneous measurements of ionospheric and magnetospheric electric fields in the outer plasmasphere
Authors: Gonzales C. A. , Kelley M. C. , Carpenter D. L. , Miller T. R. , Wand R. H.
Published: February 2008

The eastward component of the electric field was measured simultaneously at ionospheric heights and in the equatorial plane of the magnetosphere by using the incoherent scatter radar at Millstone Hill and whistler data from Siple, Antarctica, respectively. The locations of the two data sets correspond to approximately magnetically conjugate areas within the outer plasmaphere, and thus a unique opportunity arises for testing the electric field mapping hypothesis and for intercomparing the measurement techniques. The whistler results are averaged for L = 3.5‐4.7, while the radar data correspond to L = 4.4. The measurements represent time averages over about 20 minutes. There is excellent correlation during most of the 12 hour period of simultaneous data on 10 July 1978. The period was one of moderate disturbance (Kp = 2‐3). A 500 gamma substorm developed around 0830 UT (0330 LT). During this substorm, both of the electric field measurements showed a large westward perturbation, in agreement with previous observations. The meridional component of the electric field was also measured at Millstone Hill. Taken together, these data indicate an enhanced flow with components inward and towards dawn during the substorm. Except for a time near magnetic midnight the magnitude of the zonal field scales from the ionosphere to the equator in direct ratio with the spreading of magnetic field lines in the IGRF 1975 model. The whistler data clearly show that the measurements were obtained inside the plasmasphere. The middle latitude substorm perturbations appeared to be related to a reconfiguration of the magnetospheric current system.
A random stress model for seismicity statistics and earthquake prediction
Authors: von Seggern David
Published: February 2008

Seismicity related to a given fault area is governed by the distribution of the difference between shear stress and frictional stress over the fault surface. Extent of rupture in any given earthquake depends on the size of the area around the nucleation point for which a dynamic rupture criterion is satisfied. The distribution of this “size” follows a negative power law with an exponent which implies a certain falloff in the wavenumber spectrum of the stress difference over the fault. This exponent decreases as the time of a main shock approaches, with an associated reddening of the wavenumber power spectrum from k−1 to k−2 decay. The cause of such changes is the intervening seismicity between main shocks, including aftershocks. The observation of stresses at only sparse points along a fault or at points removed from the fault will be of little value in the prediction of the time or magnitude of a future earthquake.
Sulfide precipitates at 21°N on the East Pacific Rise: 226Ra, 210Pb and 210Po
Authors: Finkel R. C. , Macdougall J. D. , Chung Y. C.
Published: February 2008

Sulfide samples collected by the deep submersible ALVIN from hydrothermal vents at 21°N on the East Pacific Rise have extremely variable contents of uranium series nuclides. In samples we have analyzed, 210Pb and 210Po activities vary by more than an order of magnitude within the same vent. In two out of three samples measured 210Po activities are higher than the parent 210Pb activities. Consideration of 210Pb/Pb in particulate sulfide filtered from hot vent water indicates that the lead in these deposits has a basalt as opposed to a seawater origin. Comparison of 210Po and 210Pb contents of active and inactive vent particulates suggests that the cycle of buildup, cessation and decay by oxidation of these sulfide chimneys is measured in tens to a few hundreds of years.
Reactivity of stratospheric aerosols to small amounts of ammonia in the laboratory environment
Authors: Hayes Dennis , Snetsinger Kenneth , Ferry Guy , Oberbeck Verne , Farlow Neil
Published: February 2008

Trace ammonia in laboratory air reacts easily with sulfuric acid aerosol samples to form crystalline ammonium sulfate. Using argon atmospheres, however, we have succeeded in protecting sampling surfaces from ammonia contamination. We find that atmospheric aerosols treated in this way contain only sulfuric acid. After an hour exposed to laboratory air, these same samples convert to ammonium sulfate. We are continuing to collect aerosol particles, using argon control, to determine if the absence of crystalline sulfate is common. But so far there is no evidence that aerosols are being neutralized by ammonia in the stratosphere.
Seasonal variability in the 14C/12C ratio for surface ocean water
Authors: Broecker Wallace S. , Peng Tsung‐Hung
Published: February 2008

Evidence is provided for seasonality in the bomb 14C content of surface ocean water in temperate and polar regions. The GEOSECS results show that the surface waters in the north temperate Atlantic had 14C/12C ratio 35‰ higher just before late fall deepening of the mixed layer than just before the reestablishment of the summer mixed layer six months later. This is the difference expected from the summer exchange of CO2 between the atmosphere and the surface mixed layer.
The UV dayglow 3, OI emissions at 989, 1027, 1152, 1304, and 1356A
Authors: Anderson D. E. , Meier R. R. , Feldman P. D. , Gentieu E. P.
Published: February 2008

Rocket observations of the dayglow spectrum between 530 and 1500A were obtained on 9 January 1978 at a solar zenith angle of 56°. Data were obtained from 80 to 260km with viewing angles of 40°, 90°, and 180° to the local zenith. OI emissions were observed at 989, 1027, 1152, 1304, and 1356A. Analysis of these data with a radiative transfer model using the energy dependences of currently accepted excitation cross sections, branching ratios, and photoelectron fluxes shows that electron impact excitation is the primary source of these emissions. The infrared emission rates at 7990 and 11287A are also calculated in this analysis for comparison with previous observations and estimates.
A new method for slant stacking refraction data
Authors: Henry Marilee , Orcutt John A. , Parker Robert L.
Published: February 2008

We describe a method for slant stacking seismic records at a number of ranges to synthesize the τ—ρ curve. The seismograms do not have to be evenly spaced in range and the correct three‐dimensional point‐source geometry is retained throughout. The problem is posed as a linear inverse problem in a form that permits the construction of a special solution in a very efficient manner.
A study of stratospheric aerosol maturity
Authors: Oberbeck Verne R. , Farlow Neil H. , Ferry Guy V. , Lem Homer Y. , Hayes Dennis M.
Published: February 2008

In this paper we describe a sampling and analysis technique that uses the binomial distribution to characterize stratospheric aerosol populations at the 95% level of confidence. Particle samples obtained over Alaska during July 15‐19, 1979, are used; the results show the presence of more small particles at lower altitude than at high altitudes. We also give calculations of the surface area and volume distributions for all aerosol samples collected. Evidence from these data suggests either that Aitken nuclei are injected or diffused across the tropopause and rise into the stratosphere, where they mature into larger particles, or nuclei form in the lower stratosphere and become mature aerosols at high altitude. Samples obtained at another site give the same results, supporting the view that the process of injection or nucleation and maturing of aerosols with altitude may be global and need not occur only in locations exhibiting unique meteorologic features.
Experimental high temperature and high pressure faults
Authors: Shelton Glenmore L. , Tullis Jan , Tullis Terry
Published: February 2008

Deformation experiments on Hale albite rock have produced faults at 5 to 15 kb confining pressure and 700° to 1125°C, when hydrolytic weakening is suppressed by either the absence of water or by low pressure. The faults are characterized by: 1) an angle of about 45° to σ1, 2) very little gouge, and 3) several percent permanent strain before failure. Temperature dependent friction is believed to allow frictional sliding and faulting at stresses below those predicted by the Coulomb failure criterion, but above those of hydrolytically weakened crystal plastic flow. High confining pressure, low friction and reduced tensile stress concentrations may allow the fault to propagate as a shear rather than a tensile crack.
Radiocarbon in annual coral rings from the eastern Tropical Pacific Ocean
Authors: Druffel Ellen M.
Published: February 2008

Sixty radiocarbon measurements were performed on aragonite from annually banded corals collected from three sites in the Galápagos Islands. Preanthropogenic Δ14C values of coral that grew around A.D. 1930 averaged −70‰. This is substantially lower than average values previously reported (−51‰) for corals from Florida and Belize in the western North Atlantic Ocean. A decrease of 6‰ was noticed in coral that grew from 1930 to 1954. This decrease could be interpreted as a Suess effect in surface ocean water. The 100‰ increase in Δ14C for coral that grew from 1954 to 1973 is the result of bomb‐produced 14C that was introduced to the surface ocean waters. The 14C levels in corals that grew during El Niño years were considerably higher than those for normal years. These higher values are attributed to the absence of up welling at the equator during El Niño events.
The response of open channel aqueduct water levels to local and regional tilt fields
Authors: Leary P. C.
Published: February 2008

Simple hydraulics of open channel water flow is used to find the water level response to earth tilt along the 200 km long Los Angeles Aqueduct. The water level changes are shown to depend on the length scale of the tilt field. Tilts over lengths greater than 10 km permit the water to assume an essentially equilibrium level throughout the tilt field; change in water depth is therefore directly proportional to the degree of slope change. Tilts occurring on length scales shorter than 10 km require the use of an integral relation between tilt and water depth. The relation is used to model a tilt field corresponding to an anomalous water level event observed on the Los Angeles Aqueduct.
Simultaneous measurements of NOx, NO, and O3 production in a laboratory discharge: Atmospheric implications
Authors: Levine Joel S. , Rogowski Robert S. , Gregory Gerald L. , Howell William E. , Fishman Jack
Published: February 2008

Simultaneous measurements of NOx (NO + NO2), NO, and O3 production in a laboratory discharge show that within the uncertainties of the experiment, all of the NOx produced was NO, and no detectable enhancement of O3 after the discharge was observed. The laboratory experiments described gave an NO production rate of 5 ± 2 × 1016 molecules joule−1 for a 105 ‐ 106 joules m−1 spark. Assuming that the global dissipation of lightning energy is about 10−8 joules cm−2 s−1 (Dawson, 1980; and Hill et al., 1980), our NO production rate results in a global source of NO due to lightning of about 1.8 Mt(N)/yr, which is considerably lower than earlier estimates. This lower value for NOx production by lightning suggests that NOx emissions from anthropogenic sources, estimated to be at least 20 Mt(N)/yr, may be the dominant source of NOx to the global troposphere. Furthermore, since most of the anthropogenic sources of NOx are located in the Northern Hemisphere, this new interpretation of the relative source strengths of this species favors a highly skewed asymmetric distribution of NOx.
Ionospheric origin of magnetospheric O+ ions
Authors: Lockwood M. , Titheridge J. E.
Published: February 2008

Flows of thermal atomic oxygen (O+) ions are deduced from topside ionospheric plasma density profiles. The mean flux within most of the polar cap is of the order of 1012 m−2 s−1, a figure which is consistent with both theoretical and experimental estimates of the light ion polar wind at greater altitudes. Larger flows (up to 6 × 1012 m−2 s−1) are observed near the poleward edge of the night‐side statistical auroral oval, a feature not reproduced in the light ion flux. The implication is one of a low altitude acceleration mechanism, acting upon the O+ ions at these latitudes and at heights above that at which the fluxes are observed. Such a process would enable ions to escape from the ionosphere because they do not exchange charge with neutral hydrogen. The observations are in general agreement with energetic O+ ions as previously observed in various parts of the magnetosphere.
An intense wave/particle event in the auroral ionosphere
Authors: Johnstone A. D. , Sojka J. J. , Gibbons W. , Madahar B. K. , Woolliscroft L. J. C.
Published: February 2008

An intense burst of VLF waves, at frequencies just above the local proton gyrofrequency, was observed shortly after each of two intense bursts of field‐aligned suprathermal electrons (E < 250eV) by instruments carried on a sounding rocket flown in diffuse aurora. If the two phenomena are associated with each other, the implication is that the electron acceleration occurred nearby, in a relatively small volume.
Detection of the Io plasma torus by Pioneer 10
Authors: Intriligator D. S. , Miller W. D.
Published: February 2008

Evidence of corotating ions which appear to be primarily S++ and O++ has been discovered in data from the Pioneer 10 plasma analyzer, recorded as the spacecraft moved inward from 6.9 to 5.4 RJ during its encounter with Jupiter in 1973. H+ or He++ ions or other light ions are also observed during this time. The Pioneer 10 plasma profile shows a relative variation with radial distance remarkably similar to the Voyager density profile. Both show a well‐defined peak falling off steeply toward Jupiter and gradually decreasing away from Jupiter. The Pioneer 10 plasma data are also consistent with a constant temperature plasma for at least 0.5 RJ outside Io’s orbit. A radially inward deflection from strict corotation is also evident in our data. Our detailed analysis of the Pioneer 10 plasma instrument’s behavior and data in the inner Jovian magnetosphere indicates that the above results are not seriously distorted by radiation background. The previous study of Pioneer 10 data of the inner Jovian magnetosphere (Frank et al., 1976) did not include the particular telemetered values from which our detection of these ions has been inferred.
A search for Co‐variance among seismicity, groundwater chemistry, and groundwater radon in southern California
Authors: Hammond D. E. , Teng T. L. , Miller L. , Haraguchi G.
Published: February 2008

Several wells and springs near active faults in southern California have been monitored for the concentration of Rn, Na+, K+, Mg+2, and Cl− for periods of up to 24 months in an effort to see if any of these constituents show variations which may be related to seismic activity or environmental phenomena. A few of these sites have shown significant fluctuations.

One site in the San Gabriel Mountains has shown relatively high radon in the summer and low radon in the winter, apparently following the annual precipitation cycle. However, this site showed no corresponding change in its chemistry. A second site near Wrightwood, California has shown an annual cycle in its chemical composition, but shows no change in radon. Ten days prior to the Big Bear earthquake (M ∼ 4.9), 70 km to the east, one sample from this site showed a 50% increase in radon, but no change in chemistry. A third site, 20 km north of the Malibu earthquake (M ∼ 5.0) showed radon variation ranging from 0.4 to 4 times the normal concentration for two months preceding and two months following the event. The chemistry at this site did not change.

Within this study area, radon appears to exhibit anomalous variations within several tens of kilometers of impending earthquakes. The mechanism creating these signals has not been elucidated, but does not influence the composition of important ionic constituents. Groundwater radon concentrations may also reflect variations in precipitation but do not appear to reflect variations in atmospheric pressure. Data from cold springs are consistent with a model in which ionic constituents are controlled by reactions in the soil zone and radon concentrations are controlled by flow rates in the aquifer.
Experimental studies of the mechanisms of seismo‐geochemical precursors
Authors: Fong‐liang Jiang , Gui‐ru Li
Published: February 2008

The following aspects of modeling experiments on seismo‐geochemical precursors are described: (1) gas emission during laboratory stress loading and rupture of rocks, (2) field measurements with explosion sources, (3) aquifer mixing tests in the field, (4) experimental studies of physico‐chemical processes caused by stress events. From these studies, three conclusions have been drawn:

(1) Long‐term seismo‐geochemical anomalies appear to be related to the stage of elastic deformation of rocks under stress loading prior to a seismic event. Short‐term anomalies appear to be related to the plastic deformation of rock, and spike‐like anomalies appear to be related to shear displacement before an earthquake.

(2) Anomalous changes in chemical composition of groundwater and the escape of gases from the ground appear to result from rock fracturing which opens up pathways for the upward migration of water from deep, confined aquifers, and for the upward migration of gases from the deeper crust.

(3) Chemical reactions induced by increasing stress in the epicentral region may result in the anomalous changes in chemical composition of groundwater observed before some large earthquakes.
An S3‐3 search for confined regions of large parallel electric fields
Authors: Boehm M. H. , Mozer F. S.
Published: February 2008

Electrostatic shocks observed previously on the S3‐3 satellite all have electric fields primarily perpendicular to the magnetic field, while the double layers observed in the laboratory and in computer simulations generally involve a mode whose electric field would be parallel to the magnetic field in the magnetized case. Since parallel potentials are known to exist in association with the perpendicular shocks, electric field data from the S3‐3 satellite were searched for mostly parallel fields of hundreds of millivolts per meter. The data set consisted of auroral zone passes containing 207 perpendicular shocks, which were used in previous statistical studies, plus 40 additional orbits. At most a few events were found. Hence upper limits are placed on the number and size of double layer structures associated with perpendicular shocks. For most reasonable sets of parameters, the double layer structures cannot be greater than roughly 3 km in latitudinal extent when mapped to the ionosphere.
The dependence of upstream wave periods on the interplanetary magnetic field strength
Authors: Russell C. T. , Hoppe M. M.
Published: February 2008

It has long been known that the periods of Pc 3, 4 pulsations on the ground correlate with the magnitude of the interplanetary magnetic field. This fact has been used to argue for an exogenic source for these pulsations. Particularly attractive candidates for the source of pulsations in this frequency range are the upstream waves of similar frequencies which are associated with populations of ions reflected from the bow shock. However, the dependence of the period of these waves on the strength of the interplanetary magnetic field has never been checked. This paper performs such a check and confirms that the upstream waves have the proper functional relationship.
Cosmic ray gradients in the heliosphere and particle drifts
Authors: Newkirk Gordon , Lockwood John A.
Published: February 2008

K ‐ coronameter, solar wind, and neutron monitor data are used to estimate the latitudinal gradient of ∼5GeV protons in the heliosphere at 1 AU during 1965 and 1975. The reversal of sign of the gradient between 1965 and 1975 and the strong positive latitudinal gradient in 1975 predicted by models in which drifts are dominant are not observed.
IO: Could SO2 condensation/sublimation cause the sometimes reported post‐eclipse brightening?
Authors: Fanale F. P. , Banerdt W. B. , Cruikshank D. P.
Published: February 2008

Io’s sometimes‐reported post eclipse brightening may be caused by SO2 frost formation during eclipse and sublimation on emergence. The known properties of SO2 can be used to explain quantitatively the amplitude of brightening and its duration, and (qualitatively) its variability.
Paleomagnetism of the Late Ordovician Neda iron ore from Wisconsin, Iowa and Illinois
Authors: Kean William F.
Published: February 2008

The Neda Iron Formation (latest Ordovician) is a hematite and goethite rich oolitic ore which occurs in lens shaped deposits on top of the Maquoketa shale (Late Ordovician), at only a few locations in Wisconsin, Iowa and Illinois. Thermal demagnetization of samples from these three states, indicates the remanence is carried by hematite. Chemical demagnetization suggests the remanence is produced by the interstitial material rather than the oolites.

The paleopole averaged for all sites from 25 samples of the Neda ore is at S45.4°, W48° (α95 = 16°). This pole position is similar to late Mississippian to early Permian of North America rather than latest Ordovician. The difference between the known age of the Neda and the time of magnetization suggests that the hematite in the ore was produced from dehydration of goethite probably as a result of tectonic uplift in Wisconsin during late Mississippian time. In addition, these results add evidence to the theory that the Neda ore was formed in two stages. The oolites were produced in a near shore environment during the shoaling of the Ordovician seas. The oolites were then incorporated in iron rich muds. Burial and later uplift dehydrated the iron hydroxide to hematite.
Methane flux in forested freshwater swamps of the southeastern United States
Authors: Harriss Robert C. , Sebacher Daniel I.
Published: February 2008

Methane emissions to the atmosphere from cypress swamp habitat in four wetland ecosystems of the southeastern United States range from 0.0046 to 0.068 gCH4m−2day−1. The possible causes for this range include differences in nutrient input and organic accumulation. These results indicate that existing data are inadequate to estimate the role of wetlands as a source of methane to the global troposphere.
Information theoretic processing of seismic data
Authors: Inguva Ramarao , Schick Lee H.
Published: February 2008

The principle of maximum entropy with a χ² constraint is developed as a stacking technique for seismic data. The formalism is applied to the stacking of single correlated Vibroseis traces. The computational results can differ significantly from those of a mean stack. They also illustrate the effectiveness of the method in the reduction of noisy amplitudes compared to those that are less noisy.
Observation of non‐lithophile behavior for U
Authors: Furst Marian J. , Stapanian Maritza I. , Burnett D. S.
Published: February 2008

In the Hvittis enstatite chondrite fission track radiography shows that U is highly concentrated in CaS (oldhamite), with a concentration of 400±50 ppb. The oldhamite U concentrations are equilibrated, although intergrain concentration variations of less than 15% would not be detected. Various approaches to a U material balance do not agree, but at least 50% and, more likely, nearly 100% of the U is concentrated in CaS. It is likely that CaS is the major reservoir for other actinide and lanthanide elements as well. Consequently, enstatite chondrites may provide reliable Pu/U abundance ratios. The highly reducing formation conditions for enstatite chondrites have caused U to deviate from lithophile behaviour, but K is observed to remain lithophile. Although this observation may not be generalizable, we propose that discussions of radioactive heating of planetary cores should include U and Th and not focus exclusively on K.
Seismic strain release along the Middle America Trench, Mexico
Authors: Wang Shi‐Chen , McNally Karen C. , Geller Robert J.
Published: February 2008

We measure the seismic moment of five great (Ms ≥ 7.8) earthquakes from 1928 to 1942 along the Mexican portion of the Middle American Trench directly from recorded seismograms, and obtain considerably lower moment values than had previously been estimated from Ms. Such direct moment determinations are inherently more reliable.

As the average seismic slip rate along this portion of the arc appears to be essentially constant, these measurements of the past seismic moment are used to estimate that the current (end of 1980) moment deficiency, is 46 × 1027 dyne‐cm, or an average slip of 97 cm along the arc. Although this is much lower than past estimates, at the current rate of increase, 1.6 × 1027 dyne‐cm/yr (3.4 cm/yr of seismic displacement), the moment deficiency by 1985 will be the equivalent of five magnitude 8 earthquakes; and by 1990, six such events. The slip along this portion of the Middle America Trench arc appears to fit Shimazaki and Nakata's "slip predictable" model, in which the size, but not the time of occurrence, of future large events may be estimated.
On the nature of particles in Saturn's spokes
Authors: Thomsen M. F. , Goertz C. K. , Northrop T. G. , Hill J. R.
Published: February 2008

An observed deviation of the angular velocity of spoke features from the Keplerian value can yield the charge to mass ratio of spoke particles. Published observations of spoke motion are consistent with q/m in the neighborhood of −10 coul/kg. Since a lower limit on q is one electronic charge, this value yields a lower limit to the size of spoke particles of about 10−2 µm. The criteria for electrostatically ejecting small particles from larger parent bodies indicate an upper limit of about 10³ m for the parent bodies. Stability of the grains against electrostatic disruption or field emission yields an upper limit of ∼3 µm for the spoke particle size and leads to the conclusion that the spoke particles must consist of material which is stronger than loose dust balls.
The relationship between interplanetary quantities and Birkeland current densities
Authors: Iijima T. , Potemra T. A.
Published: February 2008

We have examined the relationship between hourly values of solar wind density, speed and the interplanetary magnetic field and the densities of Region 1 Birkeland currents. Magnetic field observations acquired by the TRIAD satellite were used to determine the Birkeland current densities. Data acquired from 51 passes in the morning sector (0800 to 1300 MLT) during IMF By > 0 and 74 passes in the afternoon sector (1100 to 1600 MLT) during IMF By < 0 were used in this study. This separation of data by polarity of IMF By was done to avoid the complicated Birkeland current patterns related to the cusp region. To avoid further complications involving the seasonal dependence of Birkeland currents (c.f. Fujii et al., 1981), north polar data were selected during the period from May to August in 1973, 1974, 1976, and 1977. Correlation coefficients were computed for the morning and afternoon Region 1 densities (Jm and Ja, respectively) related to a variety of combinations of solar wind density (N), speed (V), and IMF By and Bz. The current densities show good correlation with negative values of Bz (R = 0.39 for Jm and R = 0.56 for Ja), but relatively poor correlation with positive values of Bz (R = 0.07 for Jm and R = 0.1 for Ja). Relating Jm and Ja with BT = (By² + Bz²)½ provides correlation coefficients of 0.50 and 0.48; with BT sin (θ/2), where θ is measured from the positive z axis, provides coefficients of 0.56 and 0.68; with the Akasofu “ϵ” parameter provides coefficients of 0.39 and 0.67; with VBT sin (θ/2) gives 0.52 and 0.74; with [N½ VBT sin (θ/2)]½ = (NVVA)½ gives 0.66 and 0.75. The dominant factor in these correlations appears to involve the magnitude of the IMF in the y‐z plane (BT) and its orientation with respect to the geomagnetic field, sin (θ/2). This suggests that magnetic reconnection may play an important role in determining the strength of Region 1 Birkeland currents. Substantial current densities (1 to 2 µA/m²) exist at the origin of these plots (i.e. for θ = 0). These persistent Birkeland currents may be related to the convective flow (and associated electric fields) which prevail during periods of northward IMF.
The magnetotail boundary and energy transfer processes
Authors: Swift Daniel W. , Lee Lou C.
Published: February 2008

A particle code is used to simulate the magnetopause region in the high latitude geomagnetic tail in which the magnetic field undergoes a significant increase in going from the magnetosheath to the magnetotail lobe. The simulation indicates that plasma can flow from the magnetosheath to the lobe, which is accompanied by a drop in pressure and density. In the earth's inertial frame, the particles do work against the convection electric field. Hence the magnetopause region serves as a dynamo. The simulation also shows that the width of the transition region increases with time. In the earth's inertial frame this is seen as an expansion of the magnetopause thickness in the antisunward direction.
Seasonal changes in thermospheric molecular oxygen: A solar activity control
Authors: Fontanari J. , Alcayde D. , Bauer P.
Published: February 2008

Incoherent scatter data from high solar activity conditions revealed that a large seasonal variation of molecular oxygen at constant pressure was needed to explain the seasonal ionospheric behaviour around 200 km altitude. This suggestion however was not supported by in situ measurements of molecular oxygen abundances onboard Atmosphere Explorer C and D satellites, but during much lower solar activity conditions. It is shown that incoherent scatter data gathered during the same periods of low solar flux are in agreement with the in situ data: the results suggest therefore that the seasonal variation of molecular oxygen is controlled by the solar activity. Part of this control can be linked to the general circulation in the upper atmosphere.
A dehydration mechanism for the stratosphere
Authors: Danielsen Edwin F.
Published: February 2008

Although mean circulations are generally credited with dehydration of the earth's stratosphere, convective instability in the tropics converts mean circulations to small residuals of local convective circulations. The effects of large cumulonimbus which penetrate the stratosphere and form huge anvils in the lower stratosphere are discussed with respect to hydration and dehydration of the stratosphere. Radiative heating at anvil base combined with cooling at anvil top drives a dehydration engine considered essential to explain the dry stratosphere. Seasonal and longitudinal variations in dehydration potentials are examined with maximum potential attributed to Micronesian area during winter and early spring.
Transport of water through the tropical tropopause
Authors: Kley D. , Schmeltekopf A. L. , Kelly K. , Winkler R. H. , Thompson T. L. , McFarland M.
Published: February 2008

Total water was measured in the high troposphere and low stratosphere over Panama during ten aircraft flights. The results show that convective storms provide the means of transporting water into the stratosphere. From a consideration of the anvil heights over different areas of the tropical zone, it follows that a negative gradient of water vapor mixing ratio with altitude must exist over most of the lower stratosphere.
Sea foam reflectance and influence on optimum wavelength for remote sensing of ocean aerosols
Authors: Whitlock Charles H. , Bartlett David S. , Gurganus Ernest A.
Published: February 2008

According to previous investigations, sea foam is a major variable in the accurate determination of aerosol turbidity over the oceans with remote‐sensing systems. As a result, tests have been conducted to measure sea foam reflectance at wavelengths from 0.55 µm to 2.8 µm. Data from the tests offer an improved knowledge of the effects of sea foam on radiation upwelled from the ocean surface at near‐infrared wavelengths. Application of the new data suggests potential for a 40 percent improvement in signal to noise characteristics of aerosol measurements over the oceans if a 1.56 µm waveband is used instead of 0.75 µm.
A comparison of tiltmeters at tidal frequencies
Authors: Wyatt F. , Cabaniss G. , Agnew D. C.
Published: February 2008

Different techniques for measuring crustal deformation are now being tested at Piñon Flat Geophysical Observatory in southern California. As a part of this comparison, we have analyzed five months of data from four different tiltmeters: three borehole instruments, two 4.5 m and one 26 m deep; and a long‐base (535 m) instrument at the surface. For periods from 1 hour to 10 days, the signals from the deep borehole and long‐base instruments show comparable noise levels; the shallow instruments are much noisier. Tidal analyses give results for the different sensors which agree to within the errors, which are several percent.
Induction anomalies in geomagnetic Sq in peninsular India
Authors: Srivastava B. J. , Prasad S. N. , Singh B. P. , Arora B. R. , Thakur N. K. , Mahashabde M. V.
Published: February 2008

Anomalies in geomagnetic Sq(H), Sq(Z) and Sq(D), as recorded at an array of 21 magnetometers and 5 permanent observatories in peninsular India during 1979‐1980, are analyzed and discussed in relation to geology. Signatures of the Kodaikanal batholith, the Dharwar series of rocks and a graben structure in the Palk Strait on the geomagnetic records of nearby stations are unmistakably identified and associated with internal induction effect. The extent and influence of the ionospheric equatorial electrojet and oceanic induced currents observed on the ground in this complex region are also mapped.
Particle size distribution of nitrate and sulfate in the marine atmosphere
Authors: Savoie D. L. , Prospero J. M.
Published: February 2008

Cascade impactor samples were collected at coastal sites on Sal Island, Barbados, and Virginia Key, Miami during 1974 and at two Miami coastal sites on Virginia Key and Key Biscayne during 1981. In all of the samples, the majority of the nitrate mass was found on intermediate size particles and exhibited a mass median diameter (MMD) of about 4 µm. The ratio of the MMD of nitrate to that of sea‐salt (about 7 µm) varied from 0.54 to 0.60 which indicates that the nitrate mass distribution is well defined by the surface area distribution of the sea‐salt aerosols. This sharply contrasts with the distribution of non‐sea‐salt sulfate (also produced from gas‐to‐particle conversion reactions) which is present primarily on submicron aerosols. The lower levels of nitrate in the small particles are probably a consequence of the higher volatility and photochemical reactivity of the nitrate compounds expected to exist in the acidic aerosols.