bluuebunny/crossref_metadata_2025 huggingface dataset:
Tropical Atlantic wind field variations during sequal: Preliminary results
Authors: Harrison D. E. , Cardone Vincent J.
Published: February 2008

An evaluation of the U.S. Navy NOGAPS surface wind product is made to establish its utility as an initial descriptor of the surface wind field in the tropical Atlantic during SEQUAL. In this preliminary study, NOGAPS synoptic fields are compared to synoptic ship reports, and to winds measured at three separate stations along the equator during SEQUAL I. At least within 20° of the equator the comparisons suggest that the mean monthly surface winds from NOGAPS almost always differ by less than 2 m/s from averages of surface wind observations, and can be less than 1 m/s. Similar comparisons are also found from daily mean winds derived from NOGAPS, along the equator near 30°W. A comparison of NOGAPS monthly mean winds with 100‐year climatology of merchant ship reports suggests that the major surface wind anomaly during SEQUAL I in the tropical Atlantic occurred in March and April 1983 along the equator west of 30°W.
Tropical Atlantic thermal structures along the Europe‐Brazil ship line
Authors: Rual P. , Jarrige F.
Published: February 2008

Beginning in 1981 expendable bathythermograph (XBT) temperature sections, down to 460 meters, have been made two to three times per month between 20°N and 20°S along the ship of opportunity line from Europe to Brazil. Three thermal zones are described: the Guinea dome at 10°N‐15°N, the equatorial region, and the Brazilian warm waters between 2°S and 18°S. The Guinea dome is characterized by a shallow thermocline with little seasonal cycle and a doming or surfacing of the isotherms. In the equatorial region the thermocline is almost flat but moves up and down with the season and the changes in the trade winds. In the Brazilian warm waters the mixed layer is always thick with some seasonal cycle and the thermocline spreads from 100 meters down to the maximum depth of the measurements. The presence of absence of the major currents is infered from the slopes of the thermocline. The most striking event of the period is the development of a warm anomaly, in conjunction with light trade winds, during the southern hemisphere warm seasons of 1982, 1983 and 1984, reaching +1.5°C over a large area in April 1984.
Preliminary paleomagnetic data from the Jurassic Humboldt Lopolith, west‐central Nevada: Evidence for thrust belt rotation in the Fencemaker Allochthon
Authors: Hudson Mark R. , Geissman John Wm.
Published: February 2008

Layered and massive gabbros of the Humboldt Lopolith and extrusive equivalents in west‐central Nevada yield well‐grouped paleomagnetic data on a site basis. With corrections for attitudes of compositional layering in gabbros and flow contacts in lavas (kcorr/kin situ = 5.5), the mean of 15 site means is: D = 307°, I = 21°, α95 = 9°, k = 17. While K‐Ar data imply a Late Jurassic age, we prefer an older, probably Early Jurassic, age for the lopolith and its magnetization based upon magnetization data and relations of these rocks with host strata. Compared with Early Jurassic expected directions, the data reveal a discordancy in declination of −37° (+/− 14‐22°) which implies a significant counterclockwise rotation of the lopolith. Local rotation of Fence‐maker allochthon units most likely occurred when southeasterly‐directed thrust sheets obliquely contacted a generally north‐south trending shelf margin. Mesozoic deformation will be more accurately estimated with better age control and measurement of possible Cenozoic crustal rotation.
F‐region ionospheric structure associated with antisunward flow near the dayside polar cusp
Authors: Kelly John D. , Vickrey James F.
Published: February 2008

After one year of measurements using the Sondrestrom incoherent‐scatter radar (74° Λ), a number of repeatable features have been identified that interrelate the F‐region ionization and plasma convection patterns. One of these is an extended (poleward) ridge of ionization frequently present overhead near magnetic local noon. This ionization enhancement is associated with large ion drift velocities with a significant poleward component. Similar ionization features have been reported and thought to be produced by convection of F layer plasma through an ionization source—soft particle precipitation associated with the polar cusp. In this study, however, we are able to measure the electron temperature as well as number density and drift velocity. These measurements indicate that the electron temperature is not elevated within the density enhancement suggesting that the enhancement is not caused by local soft particle precipitation. Rather, it may simply be F‐region plasma convected from lower latitudes with correspondingly lower solar zenith angles.
Initial Millstone Hill, Sondrestrom, and HILAT observations of thermospheric temperatures and frictional heating
Authors: Oliver W. L. , Foster J. C. , Holt J. M. , Loriot G. B. , Wickwar V. B. , Kelly J. D. , de la Beaujardière O. , Bythrow P. F. , Meng C. I. , Rich F. J. , Huffman R. E.
Published: February 2008

Elevation scan observations made by the Millstone Hill and Sondrestrom incoherent scatter radars are combined to provide extended latitudinal coverage of thermospheric measurements. Maps of the latitudinal and temporal structure of the exospheric temperature are presented for two 24‐hour periods over the latitude range 45 to 72 degrees north. On the magnetically quiet June day the Millstone and Sondrestrom data formed a consistent picture of thermospheric structure. On the disturbed July day the two radars observed very different behavior, with Millstone Hill observing strong, long‐lived ion frictional heating events but Sondrestrom observing more quiescent behavior. Comparison with HILAT satellite data recorded on the July day suggest that the two radars were observing different ionospheric regions separated by a bright auroral arc with a very turbulent ionosphere to the south of the arc but smooth flow to the north.
Nighttime thermospheric winds over Sondre Stromfjord, Greenland
Authors: Meriwether J. W. , Shih P. , Killeen T. L. , Wickwar V. B. , Roble R. G.
Published: February 2008

Observations of nighttime thermospheric neutral winds made at Sondre Stromfjord, Greenland, with optical and radar instrumentation, showed an occasional abatement in the equatorward meridional wind at a magnetic local time corresponding to the nighttime division between the evening and morning convection cells. This abatement appeared primarily in the poleward observations. In contrast, however, the characteristic midnight “surge” was usually seen in the equatorward set of observations. The apparent acceleration of about 250 m/s or greater within 4.6° latitude we attribute, in part, to a merging of neutral jet streams generated by polar cap ion drag adjacent to the auroral zone boundary, and, in part, to the higher electron densities and plasma convection speeds adjacent to the auroral zone. Comparison of these results with those from NCAR/TGCM computations that assumed an analytical plasma convection model showed reasonable agreement, except for the abatement feature.
Chromium isotopic anomalies in Allende Refractory Inclusions
Authors: Birck Jean‐Louis , Allègre Claude J.
Published: February 2008

Measurements of both 53Cr/52Cr and 54Cr/52Cr ratios with a precision of 10−4 in Allende inclusions display widespread chromium isotopic anomalies which are in the range of 5• 10−4. Instrumental mass fractionation precludes specific identification of the affected isotopes, but there are strong arguments favoring excesses in 54Cr and a hint of a very small deficit in 53Cr (≃ 10−4). These samples also display excesses in 50Ti and no significant effect in nickel isotopes.
A magnetohydrodynamic simulation of the bifurcation of tail lobes during intervals with a northward interplanetary magnetic field
Authors: Ogino Tatsuki , Walker Raymond J.
Published: February 2008

The interaction of the solar wind with the Earth’s magnetosphere during a northward interplanetary magnetic field was studied by using a three‐dimensional magneto‐hydrodynamic model. For a northward interplanetary magnetic field of 5 nT, the plasma sheet thickens near the noon‐midnight meridian plane. When projected onto the polar cap this appears as a narrow channel extending from midnight towards noon. This plasma pattern is associated with three pairs of convection cells. The high latitude sunward convection and northern Bz Birkeland current are caused by magnetic merging in the polar region.
Correlation between proton anisotropy and magnetic field direction in the distant Geotail
Authors: Klecker B. , Scholer M. , Hovestadt D. , Gloeckler G. , Ipavich F. M. , Smith E. J. , Tsurutani B. T.
Published: February 2008

We report the results of a statistical analysis of the anisotropy of suprathermal protons and of the polarity of the magnetic field during the time period April 10‐16, 1983, when the ISEE‐3 spacecraft was at lunar distances (˜61‐78 radii) in the geomagnetic tail of the earth, well within the nominal magnetopause. Using 128 sec time averages of the angular distributions of 33 keV protons, we correlate the first order anisotropy with the latitude angle, θ, and the z‐component, Bz, of the magnetic field. We find that the frequency distribution of the anisotropy direction, in particular for large anisotropies, is strongly peaked in the earthward and tailward direction, indicative of fast earthward and tailward flows. For large anisotropies and within 5 RE (earth radii) of the nominal neutral sheet position we find a strong correlation of earthward streaming suprathermal protons with northward polarity of the magnetic field whereas large tailward anisotropies are generally correlated with southward magnetic field polarity. The simplest interpretation of this correlation is in terms of a neutral line (or reconnection) model, with the neutral line being tailward or earthward of the spacecraft, respectively.
Absorption of cosmic noise in the E‐region during electron heating events. A new class of riometer absorption events
Authors: Stauning Peter
Published: February 2008

The incoherent scatter radar facility (ISR) recently installed at Søndre Strømfjord, Greenland (inv. lat. = 74°) has been used to investigate events of substantially elevated E‐region temperatures related to the occurrence of strong horizontal electric fields. It has been found that a peculiar type of weak, slowly fluctuating cosmic noise absorption commonly observed in the daytime on riometers in the polar region could be caused by non‐deviative collisional absorption resulting from the strongly enhanced electron‐neutral collision frequencies in the heated E‐region.
New in‐situ measurements of the absorption cross‐sections of O2 in the Herzberg Continuum
Authors: Pirre Michel , Rigaud Pierre , Huguenin Daniel
Published: February 2008

The absorption cross‐sections of both O2, from 200 to 220 nm, and O3 from 220 to 235 nm have been deduced from measurements of the atmospheric absorption performed at night aboard a stratospheric balloon launched from Aire sur 1'Adour (France)

The ozone column content was previously determined using the absorption measured from 278 to 289 nm, assuming that the ozone absorption cross sections are well known in this wavelength interval. The O2 and O3 cross sections have been found to meet most of the laboratory measurements. From 200 to 210 nm the results concerning the O2 cross‐sections do not confirm the low values measured recently in the stratosphere and in the laboratory.
Clinker deposits, Powder River Basin, Wyoming and Montana: A new source of high‐fidelity paleomagnetic data for the Quaternary
Authors: Jones Alison H. , Geissman John W. , Coates Donald A.
Published: February 2008

Clinker, rock baked and fused by in situ burning of underlying coal, posesses a thermoremanent and/or thermochemical magnetization that resides in magnetite, hematite, and goethite. Data from individual sites imply that clinker may provide a high resolution recording of the geomagnetic field (e.g., within‐site virtual geomagnetic pole angular standard deviations are usually less than 10°) , but this is dependent on its thermal history and the time over which magnetic phases formed. Data from 17 sites in the Powder River Basin (13 normal polarity, 4 reverse) yield a mean of Decl. = 348°, Incl. = 62°, α95 = 5°, k = 42 and a corresponding pole position of 81° lat., 158° long. with a virtual geomagnetic pole angular standard deviation of 17.3°. The mechanism of clinker formation, the wide geographic distribution, and the range of available fission‐track ages suggest that clinker may contain a nearly complete geomagnetic field record for much of the Quaternary.
Satellite magnetic anomalies over subduction zones: The Aleutian Arc anomaly
Authors: Clark Sherren C. , Frey Herbert , Thomas Herman H.
Published: February 2008

Positive magnetic anomalies seen in MAGSAT average scalar anomaly data overlying some subduction zones can be explained in terms of the magnetization contrast between the cold subducted oceanic slab and the surrounding hotter, nonmagnetic mantle. Three‐dimensional modeling studies show that peak anomaly amplitude and location depend on slab length and dip. A model for the Aleutian Arc anomaly matches the general trend of the observed MAGSAT anomaly if a slab thickness of 7 km and a relatively high (induced plus viscous) magnetization contrast of 4 A/m are used. A second source body along the present day continental margin is required to match the observed anomaly in detail, and may be modeled as a relic slab from subduction prior to 60 m.y. ago.
Computer simulation of particle acceleration and wave excitation by electron beam injection from space shuttle
Authors: Matsumoto Hiroshi , Fukuchi Koichi
Published: February 2008

An interesting phenomenon of particle acceleration was discovered by the recent SEPAC electron beam experiment onboard the Space Shuttle/Spacelab 1. We present here our results of particle simulation study on the particle acceleration and related wave excitation caused by the injection of an electron beam from the Space Shuttle. We found that a strong acceleration of electrons is caused by a pulsive LHR wave packet locally excited by the injection of the electron beam. The simulation shows that the acceleration takes place in the perpendicular direction to the Earth's magnetic field. This agrees well with the experimental results and gives its reasonable interpretation.
Hydrocarbons and carbon monoxide in African savannah air
Authors: Greenberg J. P. , Zimmerman P. R. , Chatfield R. B.
Published: February 2008

Recent measurements of tropospheric mixing ratios of methane, non‐methane hydrocarbons (NMHC), and carbon monoxide (CO) from the Kenyan savannah are reported. NMHC mixing ratios are among the lowest reported for the continental boundary layer. CO mixing ratios are higher than marine measurements at these latitudes. Biomass burning may contribute significantly to mixing ratios of CO and NMHC's. Calculations based on the reactivity of the OH radical with NMHC's and CO indicate that NMHC's often initially consume more OH than CO.
Surface topography due to convection in a variable viscosity fluid: Application to short wavelength gravity anomalies in the central Pacific Ocean
Authors: Jian Lin , Parmentier E. M.
Published: February 2008

To examine the topography and gravity anomalies due to mantle convection, we have carried out finite difference calculations of thermal convection in a fluid layer with a viscosity exponentially decreasing with temperature. Both surface topography and gravity anomalies are shown to be positive over regions of ascending flow and negative over regions of descending flow. These results differ significantly from those of McKenzie (1977) which for similar conditions predict negative topography and gravity anomalies above rising plumes. At large Rayleigh number, the amplitude of surface topography is found to depend on Rayleigh number to the seven‐ninths power as predicted by boundary layer theory. These results are applied to test the hypothesis that the linear small‐scale gravity undulations in the Central Pacific Ocean (Haxby and Weissel, 1983) are caused by convective rolls in a layer at the base of the lithosphere. For a convecting layer thickness one‐half the observed gravity wavelength and with plausible values of flexural rigidity and heat flux, we show that convection can produce gravity anomalies of the observed magnitude with a layer viscosity comparable to that determined by post‐glacial rebound. However, a large increase of viscosity with depth is required to confine convection to a thin layer. If these anomalies are actively maintained by convective stresses, one possibility is that layered convection may result from compositional stratification of the mantle.
Quasi‐neutrality in the polar cusp
Authors: Burch J. L.
Published: February 2008

Data from the High Altitude Plasma Instrument on Dynamics Explorer have shown a remarkably close correspondence between the densities of suprathermal electrons and positive ions at altitudes between 16,000 and 23,000 km in the polar cusp. It is argued that this quasi‐neutrality results from an ambipolar electric field at the magnetopause, which allows the entry of magnetosheath electrons only to the extent required to balance the charge carried by the positive ions.
P‐wave fault‐plane solutions and the generation of surface waves by earthquakes in the western United States
Authors: Patton Howard J.
Published: February 2008

Surface waves recorded at regional distances are used to study the source mechanisms of seven earthquakes in the western United States with magnitudes between 4.3 and 5.5. The source mechanisms of events in or on the margins of the Basin and Range show T‐axis with an azimuth of N85°W +/− 16° and a plunge of 12° +/− 16°. Of the seven events, four have P‐wave solutions that are inconsistent with surface‐wave observations. Azimuths of the T‐axis obtained from the surface‐wave mechanisms and from the P‐wave solutions differ by up to 45°. These events have dip‐slip or oblique‐slip mechanisms, and the source depths for three of the events are 5 km or less. Their source mechanisms and small magnitudes make identification of the P‐wave first motion difficult due to poor signal‐to‐noise ratio of the initial P‐wave and close arrivals of pP or sP with significant amplitude. We suggest that mis‐identification of the P‐wave first motion and distortion of the body‐wave ray paths due to non‐planar structure were sources of error in determining the nodal planes for these events.
First principles equations of state of MgO and CaO
Authors: Bukowinski M. S. T.
Published: February 2008

The ability of local density functional theory to predict properties of oxide minerals at high pressures is tested by computing some thermodynamic properties of MgO and CaO in the B1 (NaCl) and B2 (CsCl) structures. Both static and dynamic contributions to the equations of state are computed ab initio, thus yielding predictions that are completely independent of data. Except for a possible overestimate of the density of B2 phases, the theoretical room temperature isotherms, shock‐wave Hugoniots and zero pressure density and elastic parameters are in excellent agreement with data. The predicted B1‐B2 transformation pressure for CaO is 32 GPa, compared to the experimental value of 61 GPa. The corresponding pressure for MgO is 205 GPa and is believed to be a lower bound on the actual transformation pressure.
Observations of field‐aligned currents at the plasma sheet boundary: An ISEE‐1 and 2 survey
Authors: Elphic R. C. , Mutch P. A. , Russell C. T.
Published: February 2008

Using ISEE‐1 and 2 magnetometer data we have performed a survey of field‐aligned currents at the boundary of the plasmasheet between 10 and 22 Earth radii down the magnetotail. Most cases are observed as the plasma sheet expands across the spacecraft. We find that the currents are most often observed flowing earthward throughout this region of the tail; however, a fraction of the cases correspond to tailward flowing currents and these tend to be found dawnward of midnight. Toward dusk no tailward currents are found. The currents at the plasma sheet boundary should map to the high latitude boundary of the auroral zone, and consequently one might expect them to have a Region 1 polarity; just the opposite is observed. Typical sheet current densities for these cases are roughly 5 mA/m.
Titan's latitudinal temperature distribution and seasonal cycle
Authors: Stevenson David J. , Potter Brian E.
Published: February 2008

Voyager IRIS brightness temperature measurements of Titan at a wavelength of 530 cm−1 are crudely indicative of ground or lower tropospheric temperatures and indicate 93 K for the equator and 91 K for both northern and southern high latitudes. The symmetry between north and south is unexpected for the time of Voyager encounter (Northern Titan spring). We show that this near‐symmetry can arise naturally in a model where the poles are "pinned" year‐round at the dew point of CH4‐N2 lakes or, more probably, a CH4‐N2 rich surface layer on a deep ethane‐rich ocean. For a polar temperature of 91 K, the model implies that the atmosphere contains somewhat less than 8% mole fraction of CH4.
Suprathermal electrons in small‐scale field‐aligned currents
Authors: Bankov L. , Bankov N. , Bochev A. , Kutiev I. , Todorieva L. , Dubinin E. M. , Podgorny I. M. , Potanin Yu. N.
Published: February 2008

The data obtained from the Intercosmos‐Bulgaria‐1300 Satellite have shown that during strong magnetic storms a halo of suprathermal electrons with number density equal to 0, 1% of the ionospheric plasma density with effective transverse temperature of the order of several eV appeared in the region of the intense small‐scale (1 km) field‐aligned currents. These electrons are believed to be the main carriers of narrow field‐aligned currents. The observed approach to isotropy of the electron flux is interpreted in terms of Coulomb scattering, although it is hard to explain the electric fields necessary for the electron acceleration without the presence of anomalous resistance.
Models and time constants for permeability evolution
Authors: Gueguen Yves , David Christian , Darot Michel
Published: February 2008

Permeability of crystalline rocks results mainly of cracks. Using percolation theory and a statistical approach, Dienes has recently derived a model which appears to be very adequate to describe and calculate permeability in such rocks at a scale which is larger than the scale of the cracks. Using this model, we show that three microstructural parameters are of primary importance : the crack shape factor A, the mean crack length
and the average crack spacing
Although the third one,
is frequently presented as the most important parameter, we suggest that A and
are indeed as much important. Percolation transition depends on
and
but high permeabilities are obtained if either A or
are large. Using these results we discuss time constants for permeability evolution by taking into account slow crack growth processes. We suggest that slow crack growth could result in large increases of permeability with or without developing a macroscopic fracture. Such effects are of interest for seismogenesis, underground repositories and other problems concerned with fluid flow in the crust.
Superrotation in the pre‐dawn Jovian magnetosphere: Evidence for corotating convection
Authors: Hairston M. R. , Hill T. W.
Published: February 2008

We report evidence for superrotation of plasma in the pre‐dawn magnetosphere of Jupiter during the outbound segments of the Voyager 1 and 2 encounters. The evidence consists of a forward spiral of magnetic field lines crossing the equatorial plasma sheet, as distinct from the more typical backward spiral associated with subcorotational flow. (The Voyager plasma instruments were not pointed favorably for measurement of the azimuthal flow component during the outbound trajectories.) The limited available statistics indicate that superrotational flow is restricted in local time to the night side, and also restricted in system III longitude to the hemisphere opposite the active sector of the magnetic‐anomaly model. The results are thus compatible with the planetary‐wind concept in general and with the corotating convection model in particular.
Measurement of the ozone absorption cross‐section at the 253.7 nm mercury line
Authors: Mauersberger K. , Barnes J. , Hanson D. , Morton J.
Published: February 2008

The absorption cross‐section of ozone at 253.7 nm is frequently used as a standard for the entire UV wavelength range. The presently accepted value is 1.147 × 10−17 cm², known with an uncertainty of about 2%. The cross‐section has been recently measured by simultaneously monitoring the ozone pressure, the impurities in the ozone gas, the gas temperature and the UV beam intensity. The cross‐section at room temperature was found to be 1.137 × 10−17 cm², having an uncertainty of ±.7%. The improved accuracy will aid a number of ozone experiments including the in situ photometers and Solar Backscatter Ultraviolet instruments.
Detection of carbonyl fluoride in the stratosphere
Authors: Rinsland C. P. , Zander R. , Brown L. R. , Farmer C. B. , Park J. H. , Norton R. H. , Russell J. M. , Raper O. F.
Published: February 2008

Infrared solar absorption spectra of the stratosphere recorded at a resolution of 0.01 cm−1 by the ATMOS (Atmospheric Trace Molecule Spectroscopy) instrument from onboard Spacelab 3 (04/30 to 05/6/85) have revealed the existence of many previously unobserved absorption features in the 1925 to 1960 cm−1 and 1249 to 1255 cm−1regions and one at 774 cm−1. On the basis of comparisons with laboratory spectra, these features have been identified as belonging to the ν1, ν4; and ν6 bands of carbonyl fluoride, respectively. Volume mixing ratios of COF2 between 17 and 40 km have been deduced from analysis of the ν1 and ν6 bands.
Specialized image processing technique applied to Halley multicolour camera images of the Earth
Authors: Wilhelm Klaus , Schmidt Wolfgang K. H. , Hartmann Gerd K.
Published: February 2008

A special image processing technique has been applied to earth images taken by the Halley Multicolour Camera (HMC) on‐board ESA's space probe Giotto on its way to a close encounter with comet Halley on March 14, 1986. The method depends on the knowledge of the point spread function of the optical system. Deconvolution has been achieved by a direct inversion of the convolution process subject to boundary conditions that would correspond to non‐linear filter processes. Experimental evidence is presented that under the prevailing conditions the technique can provide pixel resolution. Comparison with weather satellite images allow verification of the results for the earth observations.
Electron emission by gas and dust impacts during the flybys of comet Halley
Authors: Grard R. , Gringauz K.
Published: February 2008

The space probes which flew through the environment of Comet Halley have been bombarded by a flow of molecules and dust particles which impacted their surface with a relative velocity of the order of 70‐80 km s−1. The emission of secondary electrons and sputtered ions caused by these impacts was a potential source of interference for the experiments which analyzed the gas and plasma environment of the comet. The impact plasma detector is a simple device which measured the saturation current of the secondary electrons emitted from a gold target mounted on Vega‐1 and Vega‐2. The effects of the gas and dust impacts can be easily separated; the total gas production rate of the nucleus is estimated to be of the order of 1030 molecules/s at 0.8 AU.
Uniaxial and triaxial mechanical experiments on rock salt samples from three Gulf Coast Domes
Authors: Price R. H.
Published: February 2008

Seventeen quasi‐static experiments on rock salt from three gulf coast domes are presented. The experiments were run at a constant loading rate in compression and extension, over pressures ranging from 0.1 to 13.8 MPa and temperatures ranging from 22 to 100°C. Minor variations in sample grain sizes and composition did not appear to have a distinct effect on strength and behavior trends. Specimen strength was directly related to the least principal stress and inversely related to temperature; furthermore, pressure and temperature increases resulted in larger axial strains to failure (ductility). While strengths in extension and compression were similar, ultimate strains were substantially higher in compression than in extension.
Petrologic evidence for a terrane boundary in south‐central Circle Quadrangle, Alaska
Authors: Laird Jo , Foster Helen L. , Biggs Donald L.
Published: February 2008

Greenschist to amphibolite facies pelitic, mafic, and aluminous calc‐silicate schists from the south‐central Circle quadrangle, east‐central Alaska, are in contact with carbonaceous quartzite and calcareous phyllite recording diagenetic temperatures. Their mutual contact is best explained as a post‐metamorphic fault, indicating that the Yukon crystalline terrane was, at least in part, assembled after the peak of regional metamorphism. Mineral equilibria within the schists indicate metamorphism at minimum conditions of about 440° to 380°C at 0.3 GPa (3Kbar, biotite grade), 500°C at 0.5 GPa and XCO2 = 0.3 (garnet grade), and 550°C at 0.5 GPa and XCO2 = 0.2 (staurolite‐kyanite grade). Reflectance measurements on vitrinite and inertinite from the carbonaceous unit give temperatures of 170° to 230° ± 50°C.
Ion heating by waves with frequencies below the ion gyrofrequency
Authors: Temerin M. , Roth I.
Published: February 2008

Waves with frequencies satisfying ω1 + ω2 = Ω can heat ions. In this nonlinear interaction mechanism, coupling of a wave with frequency ω1 and an ion trajectory, distorted by a wave with frequency ω2, results in a force varying at the gyrofrequency Ω at the ion position. The heating rate, verified by test particle calculations, is found for both broadband and coherent waves in the small gyroradius limit and is applied to ion conics above the auroral zone. This heating mechanism may be significant in other geophysical and astrophysical environments.
Potassium and the Earth's core
Authors: Liu Lin‐gun
Published: February 2008

The hypothesis that the Earth's "missing" K may be chemically fractionated into the iron core is examined, in terms of atomic size and electronic structure between K and Fe metals at high pressures. The very compressible nature and possible 4s → 3d electronic transitions of K at high pressures would permit K to be chemically fractionated into the Earth's iron core. Models which exclude K from the core on the basis of size and electronic structure are thus inadequate. However, evidence that the terrestrial depletion of K is not due to segregation of K into the core can be inferred from the similar depletion of K on Venus and Mars. The central pressure in Mars (400 kbar) is too low for K to enter a metallic core. However, the K/U ratios for SNC meteorites (assumed to be derived from Mars) overlap terrestrial and Venusian values, implying that the planetary depletion in K relative to CI abundances, is characteristic of the inner solar system.
A burst of energetic O+ ions during an upstream particle event
Authors: Möbius E. , Hovestadt D. , Klecker B. , Scholer M. , Ipavich F. M. , Carlson C. W. , Lin R. P.
Published: February 2008

During an extended energetic particle event upstream of the earth's bow shock on September 5, 1984, a brief burst of energetic O+ ions has been observed using the time‐of‐flight spectrometer SULEICA on the AMPTE/IRM spacecraft. The event occurred during very active geomagnetic conditions. The onset of the O+ event coincides with a brief electron burst. O+ is predominantly streaming into the sunward direction, while the H+ and He2+ ions exhibit a net flow toward the bow shock with a second order anisotropy perpendicular to the interplanetary magnetic field (which was almost radial throughout the whole event). The energy spectrum of O+ is significantly harder than those of H+, He2+ and CNO (Q>2). The observations of two particle populations, different in temporal evolution, anisotropies and energy spectra, are discussed in terms of bow shock accelerated ions over the entire time period accompanied by a brief injection of magnetospheric particles.
The intercomparison of ozone measured from the SME and Nimbus‐7 satellites on short and long time scales
Authors: Chandra S. , McPeters R. D. , Srivastava D. N.
Published: February 2008

The spatial and temporal characteristics of ozone density measured from the SBUV (Solar Backscatter Ultraviolet) spectrometer on Nimbus‐7 and the UV and the IR spectrometers on SME (Solar Mesosphere Explorer) are compared in the altitude region near 50 km where the three data sets overlap. Their temporal characteristics, when averaged over the same longitude range, are remarkably similar with respect to seasonal variations and short term fluctuations induced by transient planetary waves. The long term trends in the three data sets, however, differ significantly with each other. Over the three year period after 1982 ozone mixing ratio at 1 mb decreased by about 10 percent based on SBUV measurements but increased by 12 and 30 percent respectively based on SME‐IR and SME‐UV measurements. None of these estimates are consistent with the predicted decrease of about 2 percent based on solar UV flux and temperature changes during this period.
The kinetics of NaO + O2 + M and NaO + CO2 + M and their role in atmospheric sodium chemistry
Authors: Ager Joel W. , Howard Carleton J.
Published: February 2008

We have discovered a new type of reaction for atmospheric Na species and propose that this type of reaction will dominate its chemistry. The third order rate constants for NaO + O2 + M and NaO + CO2 + M were measured at 297 K in a flow tube study. The rate constants for NaO + O2 with He, N2, and N2O as third bodies are (1.3±0.8), (3.5±0.7), and (11±4)×10−30 cm6 molecule−2 s−1. The rate constants for NaO + CO2 with N2 and N2O as third bodies are (8.7±2.6) and (12±5)×10−28 cm6 molecule−2 s−1. We show that these association reactions, and others like them, will produce Na compounds that are likely to render Na species inactive in stratospheric ozone chemistry. The reactivities of NaO, NaO2, NaO3, and NaCO3 with O atoms were also tested.
Correlation between roof and floor cumulates of the Kiglapait Intrusion, Labrador
Authors: Morse S. A. , Allison John P.
Published: February 2008

A successful correlation between floor and roof rocks is needed to study the effects of cooling rates on the nucleation, solidification, and trace element content of cumulate igneous rocks. In felsic intrusions, the most obvious assumption to test is that the core compositions of plagioclase feldspar correlate, because the mineral is abundant and resistant to subsolidus exchange. A test of that assumption is provided by the modal abundance of apatite, which peaks near a plagioclase composition of An 38 in both floor and roof rocks of the Kiglapait Intrusion. The test is made adequately sensitive by dividing the measured mode of apatite by an independently estimated residual porosity, a procedure which helps correct for large amounts of trapped liquid that produced apatite in the roof rocks. The procedure is applicable to other intrusions and its success here suggests that failures of correlation found elsewhere deserve another look.
Topography at the core‐mantle boundary
Authors: Bowin Carl
Published: February 2008

Analysis of the Earth's gravity field using ratio of gravity to geoid (g/N) and cumulative degree contribution curve techniques improves resolution of the mass, depth, and dimensions of anomalous mass sources within the planet. The source for four of the ten major geoid anomalies of the Earth has large contributions from harmonic degrees 2 and 3, lie at the core‐mantle boundary, and the greatest has a mass anomaly of 4.2·1022 grams. That boundary has a density contrast (4.4 gm/cm³) which is greater than at any other location, including the contrast at the Earth's surface with space. Thus, relatively small vertical undulations of that boundary produce very large mass anomalies. Topographic relief of less than 3 km at the core‐mantle boundary occurs, and accounts for the existence of the largest geoid anomalies occurring on the Earth.
Conjugacies of pulsating auroras by all‐sky TV observations
Authors: Fujii R. , Sato N. , Ono T. , Fukunishi H. , Hirasawa T. , Kokubun S. , Araki T. , Saemundsson Th.
Published: February 2008

Simultaneous observations of pulsating auroras were carried out in September, 1984, using all‐sky TV cameras at a geomagnetically conjugate pair of stations: Syowa Station in Antarctica and Husafell in Iceland. From the data obtained at the two places on 26 September, the following characteristics are found: Spatial configuration of pulsating auroras is very similar in the conjugate regions. In this particular event each pulsating aurora has its counterpart with topologically the same shape in the other hemisphere. However, the timing of the appearance or fade‐out of the pulsating auroras depends on the type of aurora. That is, the patchy type of aurora appears nearly simultaneously in both hemispheres, but the expansion type of pulsating aurora, extending from an aurora with much slower variations, is not synchronously observed and often appears almost out of phase between the conjugate regions.
Crustal heterogeneities and the thermal structure of the continental crust
Authors: Furlong Kevin P. , Chapman David S.
Published: February 2008

The observed linear relationship between surface heat flow (q0) and the radiogenic heat production of near surface rocks (A0) discovered almost two decades ago has been a primary tool used to infer the distribution of heat production in the continental crust. Recent evidence on the nature of compositional heterogeneities in the continental crust has led us to reexamine the q0‐A0 relationship and the likely implications for the thermal structure of the lower continental crust. Numerical simulations of crustal thermal models indicate that some interpretations derived from this relation may be flawed. In particular, the length scale determined from the q0‐A0 function, normally thought to describe the depth distribution of crustal heat sources, is significantly affected by the horizontal scale of crustal heterogeneity. As a consequence, most estimates of lower crustal heat flow and lower crustal temperatures obtained using heat flow data with the q0‐A0 relationship are overestimates. This overestimation is (proportionally) largest in areas of low mantle heat flux such as cratons, where basal heat flux may be overestimated by more than a factor of two.
Electric field measurements on Viking: First results
Authors: Block L. P. , Fälthammar C.‐G. , Lindqvist P.‐A. , Marklund G. , Mozer F. S. , Pedersen A. , Potemra T. A. , Zanetti L. J.
Published: February 2008

After a brief description of the electric field instrument some features of the measured electric field are illustrated by specific examples. Overviews are given of two satellite passes over the northern auroral oval and polar cap, one noon‐midnight and one evening‐morning pass. An example of a Pi2 pulsation event is given and interpreted in terms of a damped resonant oscillation, probably caused by a sudden impulse. A ULF wave is shown, which due to the high Alfvén velocity can be seen only in the electric field. An auroral arc crossing is presented, where the electric and magnetic field data are consistent with an upward directed magnetic‐field aligned electric field associated with an upward Birkeland current.
Observations of intense electrostatic hiss bands in the source regions of auroral kilometric radiation
Authors: Pottelette R. , Malingre M. , Bahnsen A. , Jespersen M.
Published: February 2008

The source regions of Auroral Kilometric Radiation (AKR), as observed by the VIKING satellite, are usually characterized by steep gradients of the thermal electron density. On the polar and equatorial edges of these thermal density depletions, very intense bursts of broadband electrostatic noise are detected in a frequency range extending from the low frequency cutoff of the high frequency wave receiver (10 kHz) up to the neighborhood of the local electron gyrofrequency. The intensity of these bursts is at least of the same order of magnitude as the maximum intensity of AKR, which takes place in the center of the cavity. A possible link between the presence of the electrostatic bursts and the AKR generation mechanisms is investigated.
The influence of strong hydromagnetic turbulence on newborn cometary ions
Authors: Price C. P. , Wu C. S.
Published: February 2008

By means of a test particle model we have studied the time evolution of the velocity distribution function of newborn cometary ions in the presence of strong hydromagnetic turbulence. The test particle model employs a realistic spectrum of hydromagnetic turbulence corresponding to the observations of the International Cometary Explorer spacecraft at comet Giacobini‐Zinner. It is found that pitch‐angle scattering processes can rapidly result in the formation of a shell distribution which has been observed near comets Giacobini‐Zinner and Halley. The model also indicates that radial diffusion in velocity space develops on a much longer time scale.
Macroscale particle simulation of jinetic Alfven waves
Authors: Tanaka Motohiko , Sato Tetsuya , Hasegawa Akira
Published: February 2008

Simulation of the kinetic Alfven wave, which has many applications in solar terrestrial physics, astrophysics and fusion plasma physics, has been performed using macroscale (magnetohydrodynamic scale) particle simulation code. Dispersion properties and wave‐particle interactions of the kinetic Alfven wave (Landau damping and electron acceleration) are successfully obtained.
S‐wave scattering by 3‐D heterogeneities at the base of the mantle
Authors: Haddon R. A. W. , Buchbinder G. G. R.
Published: February 2008

The hypothesis of S‐wave scattering by three‐dimensional heterogeneity in the lowermost mantle is shown to provide a plausible alternative to the spherically stratified models recently proposed by Lay and Helmberger to explain certain observed complexities in long period S‐wave data. A result of central importance is that, contrary to the conclusions of Lay and Helmberger and, most recently, Young and Lay, sharp increases of S velocity with depth are not required to explain their data.
Equatorial plasma bubble zonal velocity height gradient from spaced VHF polarimeter and scanning 630 nm measurements
Authors: Abdu M. A. , Sobral J. H. A. , Nakamura Y. , Zamlutti C. J.
Published: February 2008

Simultaneous measurements of equatorial ionosphere plasma bubble zonal velocities by two different techniques, namely, an east‐west spaced vhf electronic polarimeter system and an east‐west scan 630nm airglow photometer, carried out over Brazilian low latitude sites, yielded different velocities, but similar local time variation pattern; the polarimeters always measuring higher velocities than the photometer. Based on the difference in the height regions sensitive to the two techniques the results are interpreted as evidence of the presence of a vertical shear in the zonal plasma motion over our low latitude observing site. The results are compared with existing evidences on the velocity shears over the equator as measured by vhf radars and other different techniques. The implications of these results are briefly discussed.
A laboratory study of the electron temperature in the near wake of a conducting body
Authors: Morgan M. A. , Chan Chung , Allen Ryne C.
Published: February 2008

The temporal evolution of the electron energy distribution in the near wake of a conducting object has been studied experimentally, using a pulsed plasma stream. We have found that depending on the electron energy distribution of the incident plasma stream and on the extent to which the ion flow energy is greater or lower than the potential energy of the object, the electron temperature may be hotter or colder than the ambient value in the region.
The effects of adiabatic and viscous heatings on plumes
Authors: Zhao Wuling , Yuen David A.
Published: February 2008

We have assessed the influences of viscous and adiabatic heatings on the transient development of plumes by employing the time‐dependent convection equations in the extended‐Boussinesq limit. Both temperature‐dependent and temperature‐ and pressure‐dependent viscosities are employed. For constant thermal expansion of coefficient we find the vigor of plume flows is diminished with larger magnitudes of the thermal expansivity. This effect is caused by the local domination of adiabatic decompression over viscous heating inside the developing plume for both the cartesian and axisymmetric domains. For deep mantle flows a thermal expansivity decreasing with depth is required for thin plume structures to exist. Values of the thermal expansivity contrast, which can promote plume growth, are in accord with estimates from recent studies in seismic equation of state.
Bipole patterns revealed by lightning locations in mesoscale storm systems
Authors: Orville Richard E. , Henderson Ronald W. , Bosart Lance F.
Published: February 2008

A bipole pattern has been observed in the locations of lightning flashes that lower positive and negative charge to earth in mesoscale storm systems. The pattern has a characteristic size of about 100 km and may last for many hours. The pattern is aligned with the upper level winds and has been observed in all seasons, but is more apparent in the fall and winter. The ratio of the positive flash density to the negative flash density is approximately 0.1, but varies from 0.05 to 0.2. This ratio occurs because there are fewer positive flashes and they are more spatially dispersed than negative flashes in storm systems.
Is there a twenty year wave in the dirunal anisotropy of cosmic rays?
Authors: Ahluwalia H. S.
Published: February 2008

We have analyzed data obtained with the Deep River neutron monitor and the underground vertical muon telescope at Embudo for the period 1965–79. Our data in conjunction with other published data show that for 1957–70 the diurnal anisotropy is unidirectional; with direction along 18 hour LT (east‐west). During 1971–79, the diurnal anisotropy consists of two components. One is in east‐west direction and the other is the radial component, with direction along 12 hour LT. The latter attains a maximum amplitude in 1976. We find no evidence for the existence of the twenty year wave in the diurnal anisotropy of cosmic rays.
Evidence of stratospheric fallout of caesium isotopes from the Chernobyl accident
Authors: Aoyama Michio
Published: February 2008

The Cs‐137 and Cs‐134 monthly deposition at Tsukuba through August 1987 are reported and the origins of caesium isotopes in spring 1987 are discussed. The monthly Cs‐137 deposition increased to 131 Bq m−2 in May 1986 just after the reactor accident at Chernobyl, and thereafter it reached a minimum at the end of 1986. Cs‐134, which is difficult to identify in the fallout from atmospheric nuclear weapon tests, has been detected in all fallout samples since May 1986, and it shows a trend similar to the Cs‐137 deposition. The caesium isotopes fallout shows a maximum in spring 1987 due to the stratospheric fallout. In 1987, about 80 percent of the Cs‐137 fallout came from Chernobyl radioactivity transported into the stratosphere, and 20 percent came from previous atmospheric nuclear tests. It is estimated that several times 10−3 of released caesium isotopes from the Chernobyl reactor have been transported into the stratosphere.