bluuebunny/crossref_metadata_2025 huggingface dataset:
Extreme ultraviolet dayglow observations with a helium gas absorption cell
Authors: Freeman Jay , Paresce Francesco , Bowyer Stuart , Lampton Michael
Published: February 2008

During the Apollo‐Soyuz Test Project, an extreme‐ultraviolet photometer with a cyclically operated helium gas absorption cell observed the daytime sky from an orbital altitude of 225 km. When the line of sight pointed more than 60° from the Sun, the instrument detected 2 to 70 rayleighs of flux scattered from neutral geocoronal helium at wavelengths from 504 to 584 Å. The instrument also detected other radiation in the band 500‐700 Å of similar spatial distribution to the helium flux, which was definitely not due to the He I 584 Å spectral line, and which has not been detected by previous experimenters in data from 400 km altitude. Possible sources of this radiation are discussed.
Preliminary investigation of volume changes in crushed granite preceding stick‐slip failure
Authors: Weeks John , Byerlee James
Published: February 2008

A large granite sample containing a saw‐cut filled with crushed granite, modeling a natural fault with gouge, was loaded triaxially at confining pressure of 400 MPa. Changes in pore volume of the simulated gouge layer were measured during application of confining pressure and during axial loading to failure by sudden stick‐slip. Pore volume strain in this configuration, with a thin layer of gouge between rock surfaces, was significantly less with increasing confining pressure than in similar experiments in which the entire sample was of crushed granite. Our sample continued to decrease in volume upon application of axial load up to the point at which sliding on the saw‐cut started. At this point, the decrease in volume slowed down, and the volume increased just before failure. Failure occurred at a stress below that required to cause dilatancy in intact rock, suggesting that gouge might show premonitory changes before earthquakes that would not appear in intact rock surrounding a fault zone.
Acoustic microscope images of rock samples
Authors: Danburg J. S. , Yuhas D. E.
Published: February 2008

We have used an acoustic microscope to examine polished sections of sedimentary rock samples, producing elastic‐wave images with a resolution of about 25 μ. We have observed variations of rock elastic properties on a granular scale and compared them with optical features in the same field of view.
Helium isotope ratios in Yellowstone and Lassen Park volcanic gases
Authors: Craig H. , Lupton J. E. , Welhan J. A. , Poreda R.
Published: February 2008

Helium isotope ratios (³He/4He) in Lassen Park and Yellowstone Park volcanic gases show large ³He enrichments relative to atmospheric and crustal helium indicating the presence of a dominant mantle‐helium component. The ratios in Lassen helium are 8 times atmospheric in acid hot spring gases, and about 3 times atmospheric in the gas phase in near‐neutral high‐temperature waters; the acid‐spring helium is thus isotopically similar to helium in island‐arc and other continental‐margin orogenic areas. At Yellowstone, however, the isotopic ratio in helium from the Mud Volcano area, in the eastern part of Yellowstone caldera, is 15.6 times atmospheric, similar to the ratio in helium from Kilauea and Iceland. These high ratios, 15 times atmospheric or greater, are probably distinctively associated with deep‐mantle plumes under hot‐spots, while ratios about 10 times atmospheric characterize mantle helium in basalt glasses at the crests of mid‐ocean rises. The presence of “Kilauea‐type” helium at Yellowstone indicates that at least in certain areas the continental crust is essentially transparent to mantle volatiles.
Velocity of sound as a function of bubble distribution in gas‐bearing sediments
Authors: Kepkay P. E. , Cooke R. C.
Published: February 2008

The velocity of sound in a water‐saturated sediment is controlled by the distribution of interstitial microbubbles (no greater than 60 µm in diameter) rather than simply by total gas volume. A continuously increasing gas volume fraction in the sediment is accompanied by a discontinuous decrease of compressional wave velocity, and the overall velocity reduction is only 11% at a gas volume fraction of 0.18. Neither of these observations agrees with the predictions of either emulsion theory or theory for a fluid‐saturated porous solid when modified to describe gas‐bearing sediments.
A single‐station fault‐Plane solution method
Authors: Langston Charles A.
Published: February 2008

Body wave forms contain a wealth of information on the nature of the seismic source which generated them. In the case of a shallow earthquake, the interference of direct waves and surface reflections can be advantageously used in finding standard orientation parameters by modeling the shape and amplitude of the wave form. This paper examines the assertion that a single, three‐component, long‐period station can be used to find fault‐plane solutions by using both P and S wave amplitudes and interpreting the shape of the waveform. This assertion is tested using the Santa Barbara earthquake (mb = 5.3, SCP) of August 13, 1978, for which there is a fault‐plane solution from local data. Using a simple method of calculating amplitudes from the shape of observed P and SH pulses recorded at SCP (State College, PA), it is shown that the type of mechanism can easily be found (e.g. thrust vs strike‐slip) and, surprisingly, that there is general agreement with the local solution.
Oxidation of SO2 on the surface of fly ash particles under low relative humidity conditions
Authors: Mamane Yaacov , Pueschel Rudolf F.
Published: February 2008

Submicron fly ash particles can accumulate sulfate by surface oxidation of SO2 in amounts between 9% and 45% of their mass at residence times between 0.3 and 12.5 hours at low humidities in the plume of a coal‐fired power plant. The accumulation is size dependent and rapid decrease in the amount of fly ash due to fallout and dispersion prevents efficient removal of sulfur from the atmosphere by this mechanism.
Earth resistivity, self potential variations, and earthquakes: A negative result for M = 4.0
Authors: Morrison H. F. , Fernandez Ricardo , Corwin R. F.
Published: February 2008

No precursory variations of either resistivity or self‐potential were seen to precede an earthquake of magnitude 4.0 which occurred in December 1977 on the San Andreas Fault in central California. This result is in contrast with an earlier result, in which a variation of about 10 to 15% was seen to precede an earthquake of similar magnitude and location which occurred in June 1973. As the present accuracy of the resistivity measurement is about ± 2%, this result suggests either that the relationship between earth strain and resistivity was different for the two events, or that the earlier result was erroneous and that the amplitude of any resistivity variation preceding an earthquake of magnitude 4 in this area is less than 2%. This result implies that much better measurement accuracy will be required to detect any variations preceding earthquakes of magnitude 4 or less in this area.
Measurements of carbon monoxide, condensation nuclei, and ozone on a B 747SP aircraft flight around the world
Authors: Gauntner Daniel J. , Nyland Ted , Tiefermann Marv , Dudzinski Thomas
Published: February 2008

Measurements of carbon monoxide, condensation nuclei, and ozone concentrations were obtained during a 54 hour polar flight around the world by an automated instrument package carried by a B‐747SP commercial aircraft. These and other data were obtained as part of the NASA Global Atmospheric Sampling Program. All data exhibited longitudinal and hemispheric differences. Analysis of the data indicate increased concentrations of carbon monoxide and condensation nuclei at flight levels in the troposphere over tropical land masses. A background concentration for condensation nuclei was found to be 200 cm−3 for tropical tropospheric maritime air.
Investigation of the chevron structure of some Pcl pulsations
Authors: Gendrin Roger , Laurent Georges
Published: February 2008

A new variety of fine frequency structure of some Pcl geomagnetic pulsations has been recently reported. For these pulsations, each periodic element consists of a chevron‐shaped combination of rising and falling tones. A careful spectral analysis of one of these events, based upon a new numerical technique known as the Modified Moving Window Method (MMWM) allows us to establish the reality of this structure. This is tentatively interpreted in terms of propagation in a magnetospheric plasma containing a non negligible fraction of helium ions, the presence of helium ions resulting in a minimum in the ULF group velocity between the ion hybrid and ion crossover frequencies.
Convection in the ice crusts of satellites and its effect on surface relief
Authors: Golitsyn G. S.
Published: February 2008

Using our knowledge about convective processes and the heat flow estimated by Reynolds and Cassen (1979), we find for the outer Gailiean satellites that the mean temperature within the convecting ice crust is about 180°K. The time scale of convection, thought to be a measure of a period of tectonic activity, is of order 5 million years and the velocities of order of 1‐20 cm per year depending on the thickness of the convecting layers (50‐1000 km). The thickness of the conducting upper layer is estimated to be of order 30 km. Due to low temperatures T at the surface and strong dependence of the viscosity on T, the time scale of smaller topographic features is estimated after Johnson and McGetchin (1973) to be of order from several hundred million years to several billion years. It is proposed that comparatively short tectonic processes, repeating every few million years, may serve as an erosion factor in shaping the form of the surfaces.
Characteristics of the spectra of protons and alpha particles in recurrent events at 1 Au
Authors: Mewaldt R. A. , Stone E. C. , Vogt R. E.
Published: February 2008

The spectra of both protons and alpha particles (1 ≲ E ≲ 7 MeV/nucleon) during 31 recurrent particle streams are fit well by an exponential in particle rigidity. Although the spectra show considerable temporal variation, the proton and alpha particle spectra are correlated such that the e‐folding rigidities Po(α) and Po(p) of the two spectra are in the ratio Po(α)/Po(p) = 1.5 ± 0.1. The consistency of this ratio may be a characteristic of the interplanetary acceleration process.
Microplume model of spatial‐yield spectra
Authors: Green A. E. S. , Singhal R. P.
Published: February 2008

We develop an analytic representation for the spatial (radial and longitudinal) yield spectra in terms of a model containing three simple "microplumes." We apply the model to electron energy degradation in molecular nitrogen gas for 0.1 to 5 KeV incident electrons. From the nature of the cross section input to this model it is expected that the scaled spatial yield spectra for other gases will be quite similar. The model indicates that each excitation, ionization, etc. plume should have its individual spatial and energy dependence. Extensions of the model and aeronomical and radiological applications of our model are discussed.
The Tabas Earthquake of September 161978 in east‐central IranA preliminary field report
Authors: Mohajer‐Ashjai A. , Nowroozi A. A.
Published: February 2008

The largest historic magnitude earthquake of inland Iran occurred at 15H35M and 53.05 (GMT) on Sept. 16th1978. This event measured 7.7 in Richter scale and left behind over 15,000 casualties in township of Tabasa traditional oasis at the edge of east Iranian desert. The area of total destruction extended for 1,000 km2 along the western foot of the Shotori Range. Other earthquake effects such as fresh thrust faultingextensive landslidingstone up‐throw and collapse of underground irrigation channels were observed within the mezoseismal area. A principal contraction to the east could be taken as the causative agentwhich is in accord with the general tectonic regime of the area.
An isostatic model for the Tharsis ProvinceMars
Authors: Sleep Norman H. , Phillips Roger J.
Published: February 2008

A crust‐upper mantle configuration is proposed for the Tharsis province of Mars which is isostatic and satisfies the observed gravity data. The model is that of a low density upper mantle compensating loads at both the surface and crust‐mantle boundary. Solutions are found for lithospheric thickness greater than about 300 kmfor which the stress differences are less than 750 bars. This model for Tharsis is similar to the compensation mechanism under the Basin and Range province of the western United States. These provinces also compare favorably in the sense that they are both elevated regions of extensional tectonics and extensive volcanism.
Paleomagnetic results from northern Maine and the western limit of "Avalon" in the mid Paleozoic
Authors: Brown Laurie
Published: February 2008

Lower Devonian volcanic rocks from Chapman syncline near Presque IsleMaine yield paleomagnetic directions unlike those determined for stable North America. Sites in four different igneous units of the Dockendorff Group give a pole position of 24° N latitude and 132° E longitude. These rocks are unmetamorphosedand appear to be unaffected by the mid‐Devonian Acadian orogeny. The pole agrees with other published data for upper Devonian rocks of eastern New England and the Canadian Maritimes. This indicates that the Avalon microcontinent may have extended further west than supposed on the basis of faunal and geologic data.
The Poker Flat Mst Radar: First results
Authors: Balsley B. B. , Ecklund W. L. , Carter D. A. , Johnston P. E.
Published: February 2008

We describe initial results obtained during the first 60 days of continuous operation of the MST radar under construction at Poker Flat, Alaska. Tropospheric‐stratospheric wind profiles obtained by the radar are compared with concurrent windsonde profiles. Mesospheric echoes between 57‐72 km are observed during daytime periods of ionospheric absorption. Mesospheric winds obtained following a stratospheric warming show a more easterly component than winds measured somewhat later. The present system, which is three orders of magnitude less sensitive than the final system, is also capable of measuring ten day average winds between 83‐95 km via meteor trail echoes.
Counterstreaming of O+ and H+ ions in the plasmasphere
Authors: Young E. R. , Torr D. G. , Richards P. G.
Published: February 2008

Although the ion flux along plasmaspheric flux tubes has been both measured and numerically modeled for many years, it is only recently that H+‐O+ counterstreaming, with O+ upwards, has been encountered experimentally and studied theoretically. The theoretical studies indicate that counterstreaming occurs under special conditions which occur primarily near twilight. In this paper we show that such counterstreaming arises not only from a combination of several particular conditions but is a more fundamental characteristic of the flow of plasma in the closed field‐line magnetosphere. We analyze the causes of counterstreaming and show that the phenomenon must occur under steady state conditions. We then examine how diurnal variations modify the steady state pattern.
Disturbances observed near Ganymede by Voyager 2
Authors: Burlaga L. F. , Belcher J. W. , Ness N. F.
Published: February 2008

We investigated disturbances in the field and particle environment observed by Voyager 2 as it passed near the Jovian moon Ganymede in Jupiter's magnetosphere. The plasma analyzer observed at least a dozen sharply bounded depressions in density (cavities). We estimated that they probably extended at least 20 RG along the ambient magnetic field lines (RG = 2635 km is the radius of Ganymede) and between 2‐50 RG in the directions transverse to
. Depressions in the magnetic field strength of the order of 5% of the ambient field strength (60nT to 135nT) were observed at the boundaries of the cavities in more than half of the cases; they were probably produced by currents flowing transverse to
on the boundaries. In some cases, the magnetic field strength inside the cavities was a few percent higher than the ambient value. This gives an upper limit on β = nkT/(B²/8π) outside the cavities, viz. β < 0.2; in most cases β was appreciably smaller than this. The flux of ≥ 2.5 MeV protons was strongly anti‐correlated with the plasma density, the flux being higher inside the cavities than outside. One possible mechanism for the production of these flux enhancements and the cavities themselves is a local, magnetic field‐aligned electric field,
. It is possible that Ganymede is responsible for the energetic protons in the cavities, in which case
. Such a localized source implies radial motions of the magnetospheric plasma with speeds of the order of a few hundred km/s. Such motions could be produced by long‐wavelength, small‐amplitude Alfvén waves in Jupiter's magnetosphere.
Lack of evidence of southerly propagating continental shelf waves in Onslow Bay, N. C.
Authors: Pietrafesa Leonard J. , Janowitz Gerald S.
Published: February 2008

Within the past decade several studies have postulated the existence of southerly propagating Continental Shelf Waves in Onslow Bay, N.C. from comparisons of sea level data collected at various stations located at or upstream of the Cape Fear River, N.C. and from a coastal tide gage located at Beaufort, N.C., to the north. Inter‐comparison of sea level data collected at Beaufort, an open ocean station, to that collected at Wilmington, a site to the south and 45.6 km upstream of the mouth, led to the conclusion that the phase lag displayed by the Wilmington versus Beaufort cross spectrum was indicative of the southerly propagation of the first three modes of zero group speed shelf waves. However, as we show in this paper, while Wilmington sea level may lag that of Beaufort, the spectrum of sea level data collected at the mouth of the Cape Fear leads that of Beaufort, as well as that of Wilmington. What is suggested herein is that the phase lag observed at Wilmington is actually due to an estuarine, river caused delay and not due to the explicit detection of southerly propagating Continental Shelf Waves.
Dependence of CO2, aerosol, and ozone concentrations on wind direction at Barrow, Alaska during winter
Authors: Peterson James T. , Hanson Kirby J. , Bodhaine Barry A. , Oltmans Samuel J.
Published: February 2008

Measurements of CO2, aerosol scattering, condensation nuclei, and ozone made continuously at the NOAA baseline observatory at Barrow, Alaska, have been analyzed in conjunction with low‐level trajectories of airflow arriving at Barrow during periods from January to March of 1977 and 1978. Ozone concentrations had no dependence on wind direction whereas CO2 and aerosol values did show directional dependence; higher values occurred with airflow from the Arctic Basin than with that from the south. The aerosol analyses support the hypothesis that Arctic haze results from advection of aerosols to the Arctic from European or North American anthropogenic sources. CO2 results suggest two possible sources for the higher concentrations: transfer from the ocean through annual sea ice to the Arctic atmosphere or advection from mid‐latitude anthropogenic sources similar to that for the Arctic haze.
Comparison of ISEE‐1 and ‐3 interplanetary magnetic field observations
Authors: Russell C. T. , Siscoe G. L. , Smith E. J.
Published: February 2008

Three hourly correlation coefficients and the lag at maximum correlation are computed using one minute averages of ISEE‐1 and ‐3 magnetometer data during the period in which ISEE‐3 moved from the earth to its halo orbit around the libration point. The maximum correlation coefficients are highly variable ranging from close to zero to almost unity. The lags, while on the average approximating the expected corotation delay, have very large departures from this value. These results suggest that the normals to the planes separating fields of differing orientation often make large angles to the ecliptic plane and/or that the interplanetary magnetic field has a significant amount of bending on a scale length the order of 200 earth radii. Furthermore, there often appears to be a significant amount of propagating structure in the IMF. Thus, ISEE‐3 magnetic field measurements should be used with caution if precise timing of arrival at the earth or precise directions of the field upon arrival are important.
High time resolution observations of the solar wind and backstreaming ions in the Earth’s foreshock region
Authors: Formisano V. , Orsini S. , Bonifazi C. , Egidi A. , Moreno G.
Published: February 2008

The interaction of the solar wind with ions backstreaming from the earth’s bow shock is studied at high time resolution. It turns out that the bulk velocity of the solar wind oscillates, both in magnitude and direction, with typical periods of ∼1 minute in presence of the ‘diffuse’ ion population. Oscillations of comparable periods are also observed in the angular distribution and energy spectrum of the diffuse ions.
Identification of Ice VI on the Hugoniot of Ice Ih
Authors: Gaffney Edward S. , Ahrens Thomas J.
Published: February 2008

Ice VI has been produced by shock compression of ice Ih to about 2 GPa. This is the second high‐pressure polymorph of water observed in shock loading. These experiments point out the ease with which high‐pressure phases can form when ice Ih is impacted. The new shock data, combined with previous static measurements, provide preliminary equation of state parameters for ice VI of
Hydrophone recordings of underground nuclear explosions
Authors: Walker Daniel A.
Published: February 2008

Hydrophone recordings from 1962 through 1974 have been examined for evidence of high‐frequency, mantle‐refracted P phases from underground nuclear explosions and from major earthquakes at comparable distances. While observable P phases are found for all Russian underground explosions with yields in excess of 270 kilotons, no such phases are found for earthquakes at comparable distances.
Stratospheric NO2 and H2O mixing ratio profiles from high resolution infrared solar spectra using nonlinear least squares
Authors: Niple E. , Mankin W. G. , Goldman A. , Murcray D. G. , Murcray F. J.
Published: February 2008

Nonlinear least squares spectral curve fitting has been used to derive vertical mixing ratio profiles for NO2 and H2O above 16 km from high resolution (∼.02 cm−1) solar spectra collected during sunset with a balloon borne interferometer. The NO2 profile shows a sharp peak of ˜8 ppbv at 32 km falling rapidly to <0.5 ppbv at 17 km. The H2O profile shows a broad peak of ˜6.5 ppmv at 30 km falling to <4 ppmv at 17 km.
Identification of isolated NO lines in balloon‐borne infrared solar spectra
Authors: Murcray F. J. , Goldman A. , Murcray D. G. , Cook G. R. , Van Allen J. W. , Blatherwick R. D.
Published: February 2008

Balloon‐borne infrared solar spectra at ∼0.02 cm−1 resolution show a number of atmospheric NO lines isolated from other atmospheric and solar lines in the 1830‐1930 cm−1 region. Typical spectra are presented and NO total column values are derived.
Midlatitude thermospheric winds and temperatures and their relation to the auroral electrojet activity index
Authors: Hernandez G. , Roble R. G. , Allen J. H.
Published: February 2008

Nighttime thermospheric winds and temperatures over Fritz Peak Observatory (39.9°N, 105.5°W) have been determined from measurements of the Doppler shifts and line profiles of the OI 15867‐K (6300 Å) line emission. Measurements have been made during various geomagnetic storm periods from 1973 to 1979. The peak equatorward meridional wind and westward zonal wind during these storms are linearly correlated with the square of the auroral electrojet index,
, with correlation coefficients of 0.815 and 0.754, respectively. The measured neutral gas temperature increase is related to the time integral of the
index with a correlation coefficient of 0.938.
The Dehoop‐Knopoff representation theorem as a linear inverse problem
Authors: Spudich P. K. P.
Published: February 2008

The deHoop‐Knopoff representation theorem, which relates observed seismic waves to a displacement discontinuity s defined on a surface S, is posed so that seismograms may be directly inverted for estimates of s and of the spatial and temporal resolution of s. Solutions s can be constructed either by parametrizing the fault surface as a number of point double couples or by representing s as an expansion of orthogonal functions. Of the infinite number of possible solutions satisfying a single seismic‐data set, methods for constructing particular solutions (e.g., best fitting, or closest to a desired solution) are given. Application of inverse theory to the deHoop‐Knopoff representation theorem leads to a convenient way to include various types of seismic data—e.g., long‐ and short‐period teleseismic, near field accelerogram, and geodetic—into a single inversion.
A search for correlation between geomagnetic activity and stratospheric ozone
Authors: Chandra S. , Maeda K.
Published: February 2008

The total ozone column content (TOZ) measured from the Nimbus 4 BUV experiment is analyzed in geomagnetic coordinates to study a possible link between the solar corpuscular radiation and the lower stratosphere. Using planetary magnetic index Ap as a measure of the solar corpuscular radiation, it is shown that the correlation between TOZ and Ap, if any, occurs predominantly at high latitudes during winter seasons. This is typical of most of the claimed correlations between sun and weather and may be the result of the winter increase of planetary wave activity which by coincidence have periods comparable to magnetic activity. The fact that even major magnetic storms have no detectable effect on the stratospheric ozone during summer does not support a direct cause and effect relation between solar and stratospheric perturbations.
Method of estimating on‐shore propagation of storm waves
Authors: Dawdy David , Maloney M. David
Published: February 2008

The National Academy of Sciences has published a suggested procedure for determining wave heights to be added to hurricane surge elevations. The equation suggested for regeneration of waves over open stretches is shown to be incorrect, and a more physically correct approach is developed.
Backscatter measurements of 11‐cm equatorial spread‐F irregularities
Authors: Tsunoda Roland T.
Published: February 2008

In the equatorial F‐region ionosphere, a turbulent cascade process has been found to exist that extends from irregularity spatial wavelengths longer than tens of kilometers down to wavelengths as short as 36 cm. To investigate the small‐scale regime of wavelengths less than 36 cm, an equatorial radar experiment was conducted using a frequency of 1320 MHz that corresponds to an irregularity wavelength of 11 cm. The first observations of radar backscatter from 11‐cm field‐aligned irregularities (FAI) are described. These measurements extend the spatial wavelength regime of F‐region FAI to lengths that approach both electron gyroradius and the Debye length. Agreement of these results with the theory of high‐frequency drift waves suggests that these observations may be unique to the equatorial ionosphere. That is, the requirement for low electron densities for which the theory calls may preclude the existence of 11‐cm FAI elsewhere in the F‐region ionosphere, except in equatorial plasma bubbles.
Rate of reaction of OH with COS
Authors: Ravishankara A. R. , Kreutter N. M. , Shah R. C. , Wine P. H.
Published: February 2008

The laser/flash photolysis‐resonance fluorescence technique was employed to study the kinetics of the reaction OH + COS →k1 products. Complicating secondary reactions involving COS photofragments were eliminated by using 193 nm laser photolysis of HNO3 as a source of OH. The rate constant was found to be much slower than previous measurements indicated. Based on our experiments, the upper limit for k1 at 298K is 8.8 × 10−15 cm³molecule−1s−1. Our results suggest that the title reaction is only a minor COS degradation pathway in the troposphere.
Absorption of light in the atmosphere by collision pairs of oxygen (O2)2
Authors: Perner D. , Platt U.
Published: February 2008

Atmospheric absorption bands by collision complexes of oxygen have been measured in long path optical experiments. About 1.5×10−3 of the incoming solar energy is absorbed by the O4 bands in the near uv, visible and near infrared spectral regions. A larger fraction of this energy goes into the 2 km layer above the surface. The possible consequences of excited metastable (O2)2 molecules for atmospheric chemistry are discussed.
Structure of the lunar crust at Highland Site Apollo Station 16
Authors: Goins Neal R. , Dainty Anton M. , Toksöz M. Nafi
Published: February 2008

The seismic crustal structure of the moon is known in the region of Oceanus Procellarum from the analysis of artificial impact data. To extend this knowledge we have used data from natural lunar seismic events to search for secondary seismic wave arrivals in the form of peg‐leg multiples caused by reflections at crustal interfaces and converted arrivals caused by refractions at crustal interfaces. A polarization filter has been applied to the data to enhance the rectilinear particle motion expected for the onset of these body wave arrivals in the scattered coda of lunar seismograms. The results of this work tentatively indicate that the highland site at station 16 has a 75 km thick crust with an intermediate 20 km interface, compared to the 60 km crust and 20 km interface in Oceanus Procellarum, a mare region. Since the 20 km upper crust appears to exist at both highland and mare sites, it probably does not represent a mare basalt layer but rather a more general feature of the crust. Crustal thickness may partially control elevation by isostasy.
Crustal genesis in Iceland: Geophysical constraints on crustal thickening with age
Authors: Hermance John F.
Published: February 2008

Geophysical experiments on Iceland and adjacent areas suggest that crustal thickening due to underplating provides a significant contribution to mechanisms of crustal genesis in this region. According to this model, mantle derived melt accumulates in a thin layer (T<4km) at the base of the crust beneath the neovolcanic zone. With time, this melt cools, solidifies, and accretes to the base of the crust leading to crustal thickening. The crust increases in thickness from 8‐10 km directly beneath the neovolcanic zone to an average value of 20 km for the generally older (∼10 my) Iceland plateau. The much older Iceland‐Faeroe Ridge has a crustal thickness of 30 km. Therefore, segregation of material from a significant volume of the mantle and continued crustal underplating may persist well beyond the boundaries of surface manifestations of volcanic activity. Hence, crustal genesis may continue beneath regions as old as 10 my at the surface.
Detecting the movement of oceanic fronts using registered Tiros‐N imagery
Authors: Clark J. R. , LaViolette P. E.
Published: February 2008

An examination of TIROS‐N AVHRR data distributed by NOAA Environmental Data Information Service (EDIS) shows that with these data one has greatly improved positioning capability in comparison with data gathered by earlier NOAA satellites. In four of five distinct TIROS‐N data sets, involving earth scenes approximately 500 km square, we obtained a mean positioning error of 3.7 km with a standard deviation of 1.7 km based on 32 landmark points. The fifth data set shows discrepancies apparently resulting from erroneous EDIS data coordinates, and accurate positioning of this specific scene could not be made. In general, TIROS‐N data can be reliably registered into geographic grids of various map projections by using two‐dimensional, third‐order polynomials. The resulting image projections can be used to monitor and to measure the movements of oceanic fronts accurately. Examples of such measurements are presented using data from the May 1979 phase of the Grand Banks Experiments. These examples include four consecutive days of registered TIROS‐N imagery that show detailed southeasterly movement of horizontal frontal waves traveling at an average speed of 70 cm/sec. The accurate registration also allows precise compositing of several days' imagery. A four‐day composite based on the highest daily temperature per pixel position shows that an oceanic front can often be monitored despite cloud conditions.
Ground‐based observations of the Io torus during Voyager 1 encounter: Indications of enhanced plasma injection and transport
Authors: Eviatar Aharon , Mekler Yuri , Brosch Noah , Mazah Tsvi
Published: February 2008

Ground‐based spectroscopic observations of the cold Io torus made before, during and after the Voyager 1 encounter are compared to the published spacecraft data. During the encounter itself neither sodium nor sulfur emissions were detected. The implications of this finding for the injection and transport of plasma are assessed.
Tidal analysis of intermittent acoustic observations
Authors: Zetler Bernard D.
Published: February 2008

Intermittent data from acoustic transmissions (hourly or bi‐hourly every third day) to be obtained in an acoustic tomography experiment in 1981 will be analyzed for tides so that the tidal effect can be removed. Two methods of analyzing the tides (1) tidal interpolation across 75 hours to patch the series, followed by response analysis, and (2) harmonic analysis with corrections for interference by nearby constituents, have been tested with a real set of acoustic extended phase data. The results by the two methods are found to be consistent and adequate.
Plasma waves excited in the upstream region by density gradient of energetic‐particle streams associated with the Earth's bow shock
Authors: Wu C. S. , Lin C. S. , Wong H. K.
Published: February 2008

The present study is concerned with the excitation of plasma waves at the boundaries of the streams of energetic particles which are associated with the earth's bow shock. The analysis was motivated by observational results acquired with the ISEE spacecraft (Parks et al. 1981). It is shown theoretically that the density gradient of energetic ions can only excite ion waves, whereas that of energetic electrons can excite both ion waves and Langmuir waves. This conclusion appears to be consistent with observations.
A special collection of reports on earthquake prediction: Hydrologic and geochemical studies
Authors: King Chi‐Yu
Published: February 2008

This issue of the Geophysical Research Letters contains a collection of 15 reports derived mainly from papers presented at a special session on the same theme at the 1980 Fall Meeting of the American Geophysical Union held in San Francisco during December 8‐12 (EOS Trans. AGU, 61(46), 1032‐1035, 1980). The purpose of the session was to gather together all U.S. scientists known to be working in this study area to review research progress since 1978, when a similar session was convened (EOS Trans. AGU, 59(12), 1195‐1197, 1978). Some of the papers presented in 1978 have since been published in a special issue of the Journal of Geophysical Research (85(B6), 3051‐3121, 1980).
Variations in Mercury and radon emission at an aseismic site
Authors: Klusman Ronald W.
Published: February 2008

Considerable variation occurs at one aseismic location in the emission rate of mercury and emanation rate of radon from the earth. Improvements are made in the use of seasonal parameters to explain variance in mercury emission. The rate of emission of mercury and radon have contrasting seasonal fluctuations. This may be the result of radon emanation being dominated by diffusion and possible convection processes, whereas mercury emission is strongly influenced by sorption of mercury by soil particles. An understanding of the non‐seismic induced variation in gas emission processes may allow reliable application of these techniques to earthquake prediction. The data presented suggest radon offers more promise than mercury in this application.
The application of geochemical methods in earthquake prediction in China
Authors: Fong‐liang Jiang , Gui‐ru Li
Published: February 2008

Several geochemical anomalies were observed before the Haichen, Longling, Tangshan, and Songpan earthquakes and their strong aftershocks. They included changes in groundwater radon levels; chemical composition of the groundwater (concentration of Ca++, Mg++, Cl−, SO4= and HCO3− ions); conductivity; and dissolved gases such as H2, CO2, etc. In addition, anomalous changes in water color and quality were observed before these large earthquakes. Before some events gases escaped from the surface, and there were reports of "ground odors" being smelled by local residents. The large amount of radon data can be grouped into long‐term and short‐term anomalies. The long‐term anomalies have a radon emission build up time of from a few months to more than a year. The short‐term anomalies have durations from a few hours or less to a few months.
Permeability and frictional properties of San Andreas Fault Gouges
Authors: Chu C. L. , Wang C. Y. , Lin W.
Published: February 2008

The permeability of a San Andreas fault gouge is determined under confining pressures up to 220 bars; it decreases with pressure from 10 nanodarcy at 15 bars to 0.3 nanodarcy at 220 bars. These values are lower than the values determined by Morrow et al. (1981). Five different samples of fault gouge with significantly different grain‐size distributions were sheared between rock joints under confining pressures to determine the effects of grain size and constitution on the strength of the fault gouge. The strength of fault gouge clearly depends on its constitution and grain size distribution, with the coarser sandy fault gouge being stronger than the finer clayey gouge. Furthermore, the coarser gouge tends to strain harden after yielding, leading to greater strength. Thus, on the San Andreas fault, inhomogeneities in gouge materials may cause spatial variations in strength. Using the permeability determined above, we estimate that the excess pore pressure generated in the fault gouge samples during the experimental shear loading may be negligible.
The F‐ring of Saturn
Authors: Smoluchowski R.
Published: February 2008

One of the startling discoveries made by the Voyager Saturn flyby is the existence of a split and twisted F‐ring located outside of the well known A‐ring of this planet. It is proposed that the twist is the result of the action of Saturn's magnetic field on charged particles in the F‐ring. A quantitative argument shows that small particles will be deflected away from a circular orbit maintained by the larger particles. The two "shepherding" satellites prevent the small particles from being lost entirely from the ring.
Acoustic velocities in heated block of granite subjected to uniaxial stress
Authors: King M. S. , Paulsson B. N. P.
Published: February 2008

Acoustic velocities have been measured within a 38 cm cubic block of granite isolated from the surrounding rock. The block was subjected to uniaxial stresses in the range 0‐24 Mpa and to heating in the range 14° to 98°C. An increase in temperature from 14° to 72°C in the unstressed block resulted in an increase in velocities in directions parallel and perpendicular to the applied stress. A further increase in temperature to 98°C in the unstressed block resulted in a decrease in velocities. Application of uniaxial stress with the block at a temperature of 98°C resulted first in uniform increases in velocity to an applied stress of MPa and then sharp decreases from 10 to 14 MPa, followed by uniform increases in velocity to a maximum stress of 24 MPa. A reduction in temperature to 16°C resulted in a sharp reduction in velocity, 25 percent less than originally measured at ambient temperature. It is concluded that, at temperatures rising to 72°C, anisotropic thermal expansion of the crystals comprising the granite causes the closure of microcracks present in the unheated rock. Between 72° and 98°C, particularly when stress was applied, irreversible mechanical changes occurred in the block.
Multiaxial loading of large‐diameter, thin‐walled tube rock specimens
Authors: Hecker S. S. , Petrovic J. J.
Published: February 2008

A large‐scale mechanical testing facility permits previously impossible thin‐walled tube multiaxial loading experiments on rock materials. Constraints are removed regarding tube wall thickness in relation to rock microstructural features and tube diameter as well as test machine load capacity. Thin‐walled tube studies clarify the influence of intermediate principal stress σ2 on rock fracture and help define a realistic rock fracture criterion for all multiaxial stressing situations. By comparing results of thin‐walled and thick‐walled tube fracture investigations, effects of stress gradients can be established. Finally, influences of stress path on rock fracture, an area largely ignored in current rock failure criteria, can be examined in detail using controlled loading changes as well as specimen prestrains.
On pressure demagnetization
Authors: Pearce G. W. , Karson J. A.
Published: February 2008

The effects of pressure on the ramanent magnetization of rocks may well be important in regions of low geothermal gradients, for example subduction zones, or at localities where a magnetization is associated with a meteorite impact. In a series of experiments undertaken to determine the effects of hydrostatic pressure on the saturation magnetic remanent moment in a variety of materials, a ‘pressure demagnetization’ has been observed. From these experiments we conclude that there is a relationship between coercivity and the extent of this pressure demagnetization for rocks bearing magnetite and titanomagnetites.
Measured infrared radiances near sea horizon and their interpretation ‐ Preliminary results
Authors: Ben‐Shalom Ami , Otterman Joseph , Schechner Pinhas
Published: February 2008

The spectral radiances at wavelengths 7.8 ‐ 11.5 µm of the sea surface at small angles below the horizon show a well defined minimum. The location of the minimum, its sharpness and its magnitude depend on wavelength, sea state, atmospheric turbidity, sea and air temperatures. Remote sensing of sea state appears possible by interpreting spectral radiances measured in a vertical scan of the sea near the horizon. A close proximity of the minimum to the horizon indicates a high sea state.
On the warming of the polar troposphere during the stratospheric warming of January 1977
Authors: Hansen Anthony R. , Chen Tsing‐Chang
Published: February 2008

In January 1977, a warming of the polar troposphere occurred following a major stratospheric warming. The temperature increase in the polar troposphere is found to be larger below 400 mb than in the upper troposphere. Analysis of the heat budget of the polar troposphere shows that the eddy heat flux convergence is the major factor responsible for the tropospheric warming.
Plumex II: A second set of coincident radar and rocket observations of equatorial spread‐F
Authors: Szuszczewicz E. P. , Tsunoda R. T. , Narcisi R. , Holmes J. C.
Published: February 2008

PLUMEX II, the second rocket in a two‐rocket operation that successfully executed coincident rocket and radar measurements of backscatter plumes and plasma depletions, was launched into the mid‐phase of well‐developed equatorial spread‐F. In contrast with the first operation, the PLUMEX II results show large scale F‐region irregularities only on the bottomside gradient with smaller scale irregularities (i.e., small scale structure imbedded in larger scale features) less intense than corresponding observations in PLUMEX I. The latter result could support current interpretations of east‐west plume asymmetry which suggests that during initial upwelling the western wall of a plume (the PLUMEX I case) is more unstable than its eastern counterpart (the PLUMEX II case). In addition, ion mass spectrometer results are found to provide further support for an ion transport model which "captures" bottomside ions in an upwelling bubble and transports them to high altitudes.
Longitudinal variations of plasmapause radius and the propagation of VLF noise within small (ΔL ∼ 0.5) extensions of the plasmasphere
Authors: Smith A. J. , Carpenter D. L. , Lester M.
Published: February 2008

Simultaneous broadband whistler recordings made during the International Magnetospheric Study (IMS) at the two Antarctic stations Halley and Siple have been used to study longitudinal variations in the radius of the plasmapause observed during local afternoon. In both of the two periods studied thus far, whistler‐derived equatorial electron density profiles imply an increase in plasmapause radius between the longitudes of Siple and Halley (Δϕ ∼ 30°) of ΔL ∼ 0.5. Intense VLF noise (∼2.5 kHz) was observed at Halley but not at Siple, and by echo analysis its propagation path was identified with that of a whistler component travelling close to the plasmapause within the region of larger radius. This leads to the conclusion that the noise was generated by a gyroresonance instability when energetic electrons (typically 10 keV), drifting eastwards in the plasmatrough, encountered enhanced plasma density in the small extension of the plasmasphere.
Revised age estimates of Brunhes palaeomagnetic events: Support for a link between geomagnetism and eccentricity
Authors: Rampino Michael R.
Published: February 2008

Revisions in the dates of reported geomagnetic excursions during the Brunhes Epoch are proposed in light of possible correlations between a section at Gioia Tauro, Italy, deep‐sea cores, a core from Lake Biwa, Japan, and some lava flows. The anomalously long, double Blake Event reported at Gioia Tauro is here correlated with the Blake Event (∼110 kyr) and the Biwa 1 event (180 ± 5 kyr); an hiatus may be present in the section between these two events. The α event at Gioia Tauro is correlated with the Biwa 2 event at about 295 kyr; the β event with the "Biwa 3" event at about 400 kyr; the γ event with the Snake River event at 480 ± 50; and the δ event, not recorded elsewhere, is estimated to have occurred at ∼620 kyr. These proposed refinements in the age estimates of the excursions suggest an approximately 100 kyr cyclicity. If the events are real and the revised dating is correct, the timing of the geomagnetic events seems to coincide with times of peak eccentricity of the earth's orbit, suggesting a causal connection.
X‐ray enhancements detected during thunderstorm and lightning activities
Authors: Parks G. K. , Mauk B. H. , Spiger R. , Chin J.
Published: February 2008

An X‐ray detector has been flown on‐board a NASA F‐106 jet into thunderstorms. We have concluded that significant quantities of 3 to >12 keV X‐rays are produced within thunderstorm clouds which support lightning discharge activity. It is inferred that the X‐rays are the bremsstrahlung radiation emitted from energetic electrons which have been accelerated through run‐away processes. It is suggested and supported that the structures responsible for the acceleration are strong double‐layers which are supported by the very high current densities attributed to lightning discharges.
Attenuation of short period seismic waves due to scattering
Authors: Ru‐Shan Wu
Published: February 2008

We point out first the inadequacy of the two widely used approaches in calculating the amplitude attenuation of seismic waves in a random medium, the formulation of mean field attenuation and that of the scattering coefficient under the single‐scattering approximation. Then we calculate the average amplitude attenuation due to scattering in an infinite random slab. We slice the random slab into layers of thickness a correlation length and use the Born approximation for each slice to calculate the scattered field. To include the effect of multiple scattering, we take the back‐halfspace integration of the scattered energy as the energy loss and do energy correction for each successive slice. Taking scalar wave approximation for seismic waves, we get a formula for average amplitude attenuation essentially valid for high frequency range (ka»1). The attenuation depends strongly on the form of correlation function of the random inhomogeneities. We derive the formulas for Gaussian, exponential and Von Kárman correlation functions. The frequency dependence of attenuation by our formulation agrees well with experiments.