bluuebunny/crossref_metadata_2025 huggingface dataset:
Transfer zones with en echelon faulting at the northern end of the Suez Rift
Authors: Moustafa Adel R. , Abd‐Allah Ali M.
Published: February 2008

Detailed field mapping of the central part of the area between the northern end of the Suez rift to the Nile Valley (Cairo‐Suez area) shows that the Eocene to Miocene rocks are affected by E‐W elongated belts of left‐stepped en echelon normal faults. These belts act as transfer zones between NW oriented normal faults synchronous with faults of the same trend in the Suez rift. Individual faults within the en echelon fault belts are oriented E‐W to WNW and dip in the same direction as the linked NW faults. Step faulting or horsts and grabens are two possible fault arrangements in the transfer zones depending on the geometry of the linked faults. The linked faults and the transfer zones are joined together in zigzag fault belts that extend northwest‐ward from the northern part of the Suez rift into the Cairo‐Suez area and possibly further northwestward. A substantial amount of the throw of the NW faults of the Suez rift is transferred northwestward by these zigzag fault belts. The throw generally decreases northwestward away from the rift. The en echelon fault belts were probably formed by right‐lateral divergent wrenching on E‐W oriented, deep‐seated, preexisting faults. This right‐lateral divergent wrenching is kinematically related to the dip‐slip movement on the linked, NW oriented, normal faults.
Methane emissions from California rice paddies with varied treatments
Authors: Cicerone R. J. , Delwiche C. C. , Tyler S. C. , Zimmerman P. R.
Published: February 2008

Two field experiments in California rice paddies are reported, one with a single treatment of a research plot and the other with varied treatments in a typical commercial rice field. Small total methane emissions, only 11 g CH4/m2, were measured for the entire growing season in the first experiment. In the second experiment, the addition of exogenous organic matter (rice straw), the presence or absence of vegetation, and the nitrogen fertilizer amounts were examined for their influence on methane emissions. The total methane emission over the growing season varied from 1.2 g CH4/m2 (with no added organic matter) to 58.2 g CH4/m2 (with largest organic matter treatments). Added organic matter was the major factor affecting methane emissions. Vegetation did not greatly affect total methane fluxes, but it did influence the mode and timing of release. Nitrogen fertilizer did not greatly affect the amount of methane emitted, but it influenced slightly the time course of the process. A diurnal effect in methane emission was observed during the early ontogeny of the crop. The variation of methane emission with time during the course of the growing season was very unusual in this experiment; only one peak was observed, and it was early in the season. During the period of largest emissions, δ13C values of the methane were measured to be −55.7 ±1.8‰ in plots with added organic matter.
Factors that control the stable carbon isotopic composition of methane produced in an anoxic marine sediment
Authors: Alperin M. J. , Blair N. E. , Albert D. B. , Hoehler T. M. , Martens C. S.
Published: February 2008

The carbon isotopic composition of methane produced in anoxic marine sediment is controlled by four factors: (1) the pathway of methane formation, (2) the isotopic composition of the methanogenic precursors, (3) the isotope fractionation factors for methane production, and (4) the isotope fractionation associated with methane oxidation. The importance of each factor was evaluated by monitoring stable carbon isotope ratios in methane produced by a sediment microcosm. Methane did not accumulate during the initial 42‐day period when sediment contained sulfate, indicating little methane production from “noncompetitive” substrates. Following sulfate depletion, methane accumulation proceeded in three distinct phases. First, CO2 reduction was the dominant methanogenic pathway and the isotopic composition of the methane produced ranged from −80 to −94‰. The acetate concentration increased during this phase, suggesting that acetoclastic methanogenic bacteria were unable to keep pace with acetate production. Second, acetate fermentation became the dominant methanogenic pathway as bacteria responded to elevated acetate concentrations. The methane produced during this phase was progressively enriched in 13C, reaching a maximum δ13C value of −42‰. Third, the acetate pool experienced a precipitous decline from >5 mM to <20 μM and methane production was again dominated by CO2 reduction. The δ13C of methane produced during this final phase ranged from −46 to −58‰. Methane oxidation concurrent with methane production was detected throughout the period of methane accumulation, at rates equivalent to 1 to 8% of the gross methane production rate. Thus methane oxidation was too slow to have significantly modified the isotopic signature of methane. A comparison of microcosm and field data suggests that similar microbial interactions may control seasonal variability in the isotopic composition of methane emitted from undisturbed Cape Lookout Bight sediment.
Reconstruction of dynamic rupture process of an earthquake with constraints of kinematic parameters
Authors: Miyatake Takashi
Published: February 2008

In this paper, a simple approximate method that converts the distribution of kinematic rupture parameters on a fault into that of physical or dynamic parameters, is proposed. The method in which the static stress drop assumed to be equal to the dynamic stress drop, is applied to investigate rupture dynamics of the 1979 Imperial Valley, California, earthquake (M=6.5). The dynamic rupture process is reconstructed by using a propagating crack, which is a process of expanding area of stress release. If we know the amount of stress drop and rupture time at each point on the fault, dynamic rupture process can be simulated. We use the kinematic parameters previously obtained by using waveform inversion techniques. With constraints of the kinematic parameters, the dynamic rupture process of the event can be reconstructed and several dynamic parameters, stress drop and strength excess (the difference between strength and applied initial stress), can be estimated at each point on the fault. By applying this method to the 1979 Imperial Valley earthquake, we found that the rupture initiated at the low strength excess part first, and then expanded toward the north, and ruptured a large‐size high stress drop region located in the north part of the fault, and finally decelerated and stopped at the north edge where the strength is high and stress drop is low. These features are well explained by barrier model [Das and Aki, 1977] and are quite similar to those obtained by Quin in 1990 who investigated the dynamic rupture process by the Monte Carlo technique with a large number of trials. Since repeated calculation is unnecessary, our method is very effective and practical compared with his method.
Evidence for marine production of isoprene
Authors: Bonsang Bernard , Polle Claude , Lambert Gérard
Published: February 2008

New data obtained in the Mediterranean Sea and Pacific Ocean show that isoprene could be produced in sea water by biological processes, leading to concentrations in the ppb range (10−9 liter of gas per liter of water).

Taking into account Henry's constant for isoprene in water and the very low concentrations measured in the marine atmosphere, the superficial sea water is supersaturated in isoprene by one or two orders of magnitude. From these observations, an oceanic flux of the order of 1.2 Mt per year of isoprene can be estimated.

This is a small value, as compared with the marine fluxes of the other NMHC; it is also practically negligible in the global burden of isoprene. However, because of its short lifetime in air, isoprene in remote marine atmosphere, entirely originates from superficial seawater, it could be therefore an useful tracer of marine emissions of gaseous compounds.
Chaotic structures of nonlinear magnetic fields I: Theory
Authors: Lee Nam C. , Parks George K.
Published: February 2008

Tidman and Krall [1971] have studied extensively the behavior of nonlinear magnetic fields in MHD plasmas. We have closely followed their work but our emphasis is different. We demonstrate here that the nonlinear magnetic field equations can be cast in the form of Duffing's equation. A Duffing system includes chaotic behavior; hence our study provides a different perspective on magnetic field development not previously discussed.
Time and magnitude predictions in shocks due to chaotic fault interactions
Authors: McCloskey John , Bean C. J.
Published: February 2008

The equations of motion for a two block, driven, spring loaded fault model with assymetric frictional forces are iterated in the chaotic regime [4,5]. The seismic moment, M0, of each failure episode whose moment exceeds a threshold, M0t, is recorded together with the time, T, since the last significant event (M0>M0t). Preliminary results from prediction‐regression analysis indicate that the distribution of points in M0‐T space takes the form of a map, Mo(t), T(t) determining the values of M0(t+l), T(t+l). It is suggested that such analysis on real data would be helpful in assessing the applicability of such low‐dimensional systems to earthquake modelling and may prove useful in the prediction of real events.
Field line resonances associated with MHD waveguides in the magnetosphere
Authors: Samson J. C. , Harrold B. G. , Ruohoniemi J. M. , Greenwald R. A. , Walker A. D. M.
Published: February 2008

The Johns Hopkins University/Applied Physics Laboratory HF radar at Goose Bay often sees F‐region drifts or electric fields which are associated with field line resonances in the Earth's magnetosphere. These resonances are seen in the interval from local midnight to morning, and have discrete, latitude‐dependent frequencies at approximately 1.3, 1.9, 2.6–2.7, and 3.2–3.4 mHz. We show that these frequencies are compatible with MHD waveguide modes, with antisunward propagation and reflection at the magnetopause and at turning points on dipolar field lines.
Measurements of unusual aerosol layers in the upper troposphere over Laramie, Wyoming in the spring of 1991: Evidence for long range transport from the oil fires in Kuwait
Authors: Deshler Terry , Hofmann David J.
Published: February 2008

Unusual aerosol layers in the upper troposphere were observed on seven consecutive balloon soundings between 7 March and 17 June 1991, at Laramie, Wyoming (41°N, 106°W). The layers varied in thickness from 1 to 4 km and the top of the layer was always at or near the tropopause. Aerosol concentrations for the size range 0.15 to 1.0 μm radius were increased by factors of 5 to 10 over what is usual at those altitudes. Compared with the previous four year record, these seven soundings represent the highest sustained concentrations observed between 8 and 11 km, with the sounding on March 25 representing the highest concentrations observed. Although the origin of these unusual aerosol layers is not definite, trajectory calculations and impactor measurements indicate that, in the absence of an alternate explanation, the oil fires in Kuwait are the likely source.
Geothermal state of DSDP Holes 333A, 395A AND 534A: Results from the Dianaut Program
Authors: Gable Robert , Morin Roger H. , Becker Keir
Published: February 2008

Heat‐flow values determined from the DIANAUT program provide insight into the geothermal state of three DSDP holes situated on the western flank of the Mid‐Atlantic Ridge. Very low values (20 mW/m2 max.) observed in 3.5‐m.y.‐old crust at Hole 333A decrease with depth and indicate persistent basement cooling due to cold water circulation in the porous level of the upper oceanic crust. Cold ocean bottomwater continues to invade the upper level of fractured 7.3‐m.y.‐old basement at Hole 395A, but temperature v. time records show large‐scale temperature fluctuations, probably associated with borehole convection, at 500 mbsf and stable temperatures, probably indicating a slow return to thermal equilibrium, at 600 mbsf. The 154‐m.y.‐old crust at Hole 534A exhibits a relatively steady thermal state with a heat flow close to theoretical values for a conductively cooling plate; small variations in the thermal gradient recorded in this well probably represent very slow and subtle movement of borehole fluids. The close comparison of these latest results with those obtained several years previously, demonstrates the presence of relatively stable thermal regimes.
Night uv spectra (1100–2900Å) at mid and low latitude during a magnetic storm
Authors: Ishimoto M. , Romick G. J. , Paxton L. J. , Meng C.‐I. , Huffman R. E.
Published: February 2008

Spectral analyses of night atmospheric emission observations from the S3‐4 satellite revealed enhanced OI 1304‐Å, OI 1356‐ Å, and OI 1640‐ Å, NI 1493‐ Å, NI 1744‐ Å and NI 12143‐Å lines and Lyman‐Birge‐Hopfield (LBH) band emissions at low magnetic latitudes. The satellite, at about 260‐km altitude, was over the region between −41° to −15° geomagnetic latitudes at7:55 UT on August 28, 1978 (Dst = −193) during the main phase of a major geomagnetic storm (Maximum Dst = −242 at 10 UT).

The observed ratios of the LBH bands to the NI 1493‐Å and NI 1744‐Å line emissions are an order of magnitude lower than those produced by electron impact and are similar to laboratory measurements of heavy particle impact (H and H+) on N2. Significant precipitation of neutral O atoms, formed by charge exchange of the ring current O+ with exospheric hydrogen and oxygen, can occur when |Dst| is large. Oxygen is observed to dominate the ring current at corresponding low L‐values during a storm main phase. Consideration of these and other factors leads us to conclude that the most likely cause of the observed emissions is oxygen precipitation from the ring current.
Mapping the dayside ionosphere to the magnetosphere according to particle precipitation characteristics
Authors: Newell Patrick T. , Meng Ching‐I.
Published: February 2008

A long standing and vexing problem in magnetospheric physics is mapping the ionosphere to the magnetosphere. To date almost all information on the topic has come from magnetic field mappings. Herein a complementary approach is tried: regions are identified based on the plasma characteristics as observed by low‐altitude satellites. Using an automated identification scheme applied to approximately 60,000 individual satellite passes through the dayside oval, probability maps are computed for observing various types of plasma precipitating into the ionosphere. The synthesis of the various individual maps allows the construction of an ionospheric map into the magnetosphere based on plasma characteristics. The results suggest a cusp which is about 2.5 hours in total local time extent; an LLBL which typically extends to about 0900 MLT; and a mantle which reaches to about 0800/1600. Consistent with earlier results, the extension of the nightside region of discrete aurora into the dayside is far more substantial at dusk than at dawn.
An ice‐ocean coupled model for the Northern Hemisphere
Authors: Cheng Abe , Preller Ruth
Published: February 2008

The Polar Ice Prediction System version of the Hibler ice model [Preller and Posey, 1989] has been modified into spherical coordinates and extended to include most of the sea ice‐covered areas in the northern hemisphere. The earth‐oriented longitudes and latitudes have been transformed into a spherical geometry in which the new “equator” coincides with the 10°E–170°W great circle and the new “north pole” is located at the intersection of the 100°E meridian and the equator. The coordinate transformation is required to avoid a numerical singularity at the north pole and numerical instabilities in high latitudes. The Cox ocean model [1984] is also transformed into the new coordinate system and coupled with the sea ice model. Monthly atmospheric forcing for 1986 from the Naval Operational Global Atmospheric Prediction System has been used to drive the spherical coordinate version of the ice‐ocean coupled model. The estimated ice thickness distribution shows that the thickest ice is located along the northern coasts of Canada, and the ice gradually becomes thinner across the Arctic ocean toward the Soviet coast. The average ice thickness is about 3.5m for March 1986 in the Arctic basin and can vary from open water up to 6m or thicker, depending on location and seasons. The modeled ice edge location is consistent in general with ice data from the Navy‐NOAA Joint Ice Center. River runoff is not included in this coupled model and may affect the ice growth in the Yellow Sea and the Baltic Sea in winter.
Spurious dimension estimates from time series of geomagnetic indices
Authors: Prichard D. , Price C. P.
Published: February 2008

The tools of nonlinear systems analysis can be used to determine the number of effective degrees of freedom, or dimension, of a system. The algorithms for estimating the dimension appear deceptively simple, but must be applied with extreme care or a spurious dimension estimate is likely to result. We discuss various problems, and methods to overcome them, with estimating the dimension of non‐stationary time series with long autocorrelation times such as AE and AL indices. Our results show that previous estimates of the dimension of AE time series were caused by long autocorrelation times and not by the dynamics of the system. Further, calculation of the largest Lyapunov exponent also gives evidence against the presence of low dimensional chaos.
Chaotic structures of nonlinear magnetic fields II: Numerical results
Authors: Lee Nam C. , Parks George K.
Published: February 2008

We present in this paper numerical solutions of the nonlinear magnetic field equations that have been cast in the form of Duffing's equation. These results show features that resemble the behavior of magnetic fields observed in space. Our work suggests that some of the observed magnetic field structures could be chaotic in origin.
Nearfield interseismic vertical strain on the Central Garlock Fault, southern California, 1984–1991
Authors: Sylvester Arthur Gibbs
Published: February 2008

Repeated precise leveling of fault‐crossing arrays at two sites on the central and western parts of the Garlock fault discloses minor height changes of a few centimeters across the fault in seven years. During that time, the seismicity of the fault has been very low relative to other parts of California. Although other investigators have measured a millimeter or two of horizontal displacement per year near each of the leveling arrays, the vertical changes measured in this study probably result from nontectonic differential subsidence across the fault due to the effects of the 1985–1991 drought in southern California. The vertical displacement at Cameron could turn out to be tectonic, but at the Koehn Lake site the subsidence may be related to nearby pumping of groundwater. The changes and rates of heights reported here should not be extrapolated in time or space, because of the relatively short period of observations, and because these sites measure only minuscule parts of the 250 km‐long fault.
A comparison of Doppler and spaced antenna radar techniques for the measurement of turbulent energy dissipation rates
Authors: Vandepeer B. G. W. , Hocking W. K.
Published: February 2008

There has been concern in the past that spaced antenna radar measurements of energy dissipation rates in the Mesosphere using broad beam arrays may be contaminated by the effects of atmospheric gravity waves. To investigate this possibility, a 1.98 MHz Doppler radar operated by the University of Adelaide was used in two separate configurations; a narrow vertical beam (4.5° half power half width) and 3 smaller spaced antenna systems with broad beams (20° half power half width) were used to simultaneously measure energy dissipation rates in the height region 80 to 100km. The 3 broad beams were also used to determine winds by the spaced antenna method. Although extraction of the energy dissipation rate parameter is a difficult process, temporally and spatially coincident data were obtained enabling some important comparisons to be made. Three years of such data were analysed and the following results noted: (1) the mean energy dissipation rates as measured by the two radars are comparable, (2) the variance of the data as measured by the Doppler radar is larger than that measured by the spaced antenna radar, (3) The spaced antenna radar does not generally over‐estimate energy dissipation rates at moderate and large values, but when turbulence is very weak, it may do so. The degree of over‐estimation is not as serious as has been inferred in the past. However, there is considerable scatter in the short term ratio of measurements using the two methods, which emphasizes the large degree of spatial variability of turbulence strengths in the middle atmosphere.
Ulysses particle observations of the March 1991 solar flare events
Authors: Sanderson T. R. , Marsden R. G. , Heras A. M. , Wenzel K.‐P. , Anglin J. D. , Balogh A. , Forsyth R.
Published: February 2008

We present observations of energetic ions from the COSPIN instrument on the Ulysses spacecraft at 2.5 AU during the March 1991 series of solar flare events. The intensity profiles observed during this sequence of events were affected both by the presence of interplanetary shocks and large‐scale discontinuities in the magnetic field, the low‐energy (∼1 MeV) protons being influenced mainly by the shocks and the discontinuities, and the high‐energy (∼100 MeV) protons by the discontinuities.

The first shock observed at Ulysses was followed by several discontinuities and a Coronal Mass Ejection (CME) which were probably moving with the shock. Particles following this shock were prevented from propagating freely into the heliosphere by the structure moving with the shock, and were carried along with it. A second shock was followed by a region containing bi‐directional particle anisotropies. A subsequent enhancement of low‐energy particles suggests the passage of another shock. This was followed by a slow intensity decay which coincided with a second CME and where bi‐directional particle anisotropies were again observed.
Inadequacy of effective CO2 as a proxy in assessing the regional climate change due to other radiatively active gases
Authors: Wang Wei‐Chyung , Dudek Michael P. , Liang Xin‐Zhong
Published: February 2008

Recent general circulation model (GCM) study suggests that CO2 maintains the present regional climate differently than trace gases CH4, N2O, CFC‐11 and CFC‐12, thus raising the question of the adequacy of using “effective” CO2 to assess future climate changes due to the greenhouse effect of these other radiatively active gases. Our GCM simulations indicate that, although the effective CO2 can provide global mean surface temperature responses in good agreement with that when these other trace gases are explicitly considered, it calculates smaller surface warming in several continental regions, notably in northwestern North America by 20–30% during winter and 10–15% during summer.
Orographically forced stratospheric waves over northern Scandinavia
Authors: Volkert Hans , Intes Didier
Published: February 2008

Simulations were carried out using the two‐dimensional version of a non‐hydrostatic numerical model in order to calculate the mesoscale response to flow across the Scandinavian mountain range. The initial conditions were deduced from an upstream sounding of 27 January 1992 during the EASOE campaign. Over and to the east of the mountain crest regions of mesoscale extent developed which experienced cooling up to 7 K. Air parcel trajectories passed these areas in approximately 10 min.
The effect of solar wind dynamic pressure changes on low and mid‐latitude magnetic records
Authors: Russell C. T. , Ginskey M. , Petrinec S. , Le G.
Published: February 2008

Magnetic records from low and mid latitude stations have been examined to determine their response to solar wind pressure changes. The best correlation between ground level changes and the change in the square root of the solar wind dynamic pressure occurs for stations at latitudes from 15° to 30° such as Tahiti, Honolulu, San Juan and Midway. The horizontal component of the field changes on average 16.5 nT for each change of 1(nPa)½ of the square root of dynamic pressure. This is 50% greater than the vacuum model of Tsyganenko would predict for a non‐conducting Earth and therefore what would be expected for a perfectly conducting interior. Thus, low and mid latitude ground level response to solar wind pressure changes is dominated by the variation of the strength and location of the magnetopause current system and the corresponding induced currents within the Earth rather than ionospheric current sources.
Large‐scale waves in the upper‐mesosphere at Antarctic high‐latitudes
Authors: Hernandez G. , Smith R. W. , Fraser G. J. , Jones W. L.
Published: February 2008

Upper‐mesosphere combined optical measurements of wind and temperature fields at Amundsen‐Scott Station (South Pole) and wind radar measurements at Scott Base (78°S, 167°E) show the presence of large‐scale waves in this region of the atmosphere. At Amundsen‐Scott the largest amplitude wave observed with sub‐diurnal periodicity appears with a frequency near 2.4/day (∼10.1 hour period), with a westward phase progression of wavenumber one. The presence of a wave with this periodicity is confirmed by the observations at Scott Base. The combination of the experimentally‐found period, phase progression, associated small‐temperature oscillations, and theoretical considerations lead to the interpretation of this wave as a Lamb wave. The present combination of spatially‐resolved optical measurements and radar measurements illustrates the value of multiple‐station and multiple‐technique observations in elucidating the upper‐mesosphere dynamical state, as well as the properties of the waves propagating through the medium where the observations are being made.
Ulysses: Interplanetary shocks between 1 and 4 AU
Authors: Burton M. E. , Smith E. J. , Goldstein B. E. , Balogh A. , Forsyth R. J. , Bame S. J.
Published: February 2008

The complex solar events of March 1991 are evident as a large increase in the rate of occurrence of interplanetary shocks. Using Ulysses magnetic field and plasma measurements, 32 forward shocks and 7 reverse shocks have been identified in the 280 day interval from October 26, 1990 to August 1, 1991. The March events alone have produced 9 shocks, several in association with coronal mass ejections. The shocks have been identified and analyzed to find θBN, the speeds in the upstream solar wind, the Mach number and the inertial speeds along the radial and magnetic field directions.
Distribution of Reynolds stress carried by mesoscale variability in the Antarctic Circumpolar Current
Authors: Johnson Thomas J. , Stewart Robert H. , Shum C. K. , Tapley Byron D.
Published: February 2008

Satellite altimeter data collected by the U.S. Navy's Geosat Exact Repeat Mission were used to investigate turbulent stress resulting from the variability of surface geostrophic currents in the Antarctic Circumpolar Current. The altimeter measured sea level along the subsatellite track. The variability of the along‐track slope of sea level is directly proportional to the variability of surface geostrophic currents in the cross‐track direction. We used the two components of the slope at points where the satellite ground tracks cross to calculate orthogonal components of the current's variability. Because the grid of crossover points is dense at high latitudes, the satellite data could be used for mapping the temporal and spatial variability of the current. Two and a half years of data were used to compute the statistical structure of the variability, leading to a better understanding of the role of variability in the dynamics of the current. The statistics included the probability distribution functions for each component of the current, the time‐lagged auto correlation functions of the variability, and the Reynolds stress produced by the variability. The results demonstrate that stress is correlated with bathymetry. In some areas the distribution of negative stress indicate that eddies contribute to an acceleration of the mean flow, strengthening the hypothesis that baroclinic instability makes important contributions to strong oceanic currents.
Two‐mechanism model for frictional sliding of serpentinite
Authors: Reinen Linda A. , Tullis Terry E. , Weeks John D.
Published: February 2008

Room‐temperature experiments on antigorite serpentinite indicate that at least two mechanisms accommodate frictional sliding of the serpentinite: a rate‐weakening, history‐dependent mechanism which dominates at fast slip velocities and a rate‐strengthening mechanism with no apparent history dependence which dominates at slow velocities. We present a two‐mechanism model that successfully describes the two types of behavior observed in the friction experimental data without changing the constitutive parameters over the range of experimental conditions. Multiple mechanisms have been identified in higher‐temperature experiments by previous workers and may be required for proper representation of all rock types at low slip rates and elevated temperatures.
Possible regional climate consequences of the Pinatubo eruption: An empirical approach
Authors: Groisman Pavel Ya.
Published: February 2008

The regional climate consequences of the greatest volcanic eruptions of the last two centuries are discussed. The pattern of changes of seasonal temperature after such eruptions is compared to these changes after the Pinatubo eruption (in June 1991). The unusually warm winter of 1991–92 in Eastern Europe coincides with the pattern following earlier eruptions. According to this pattern cool summers in Eastern Europe and the northeastern USA are probable in the next two or three years.
A possible foreshock of a future large earthquake near Odawara, center Japan
Authors: Ishida Mizuho , Kikuchi Masayuki
Published: February 2008

The 1990 Odawara earthquake (M5.1) occurred within an area where a large earthquake of M7 class is expected to occur in the future. This area (the “Odawara area”) has been seismically quiescent since 1933. Analysis of near‐field broadband seismograms and the extent of fore‐ and after‐shocks suggests that the 1990 event had a high stress drop and that the Odawara area remains in a state of high stress which could potentially cause a large earthquake.
A convected K distribution model for hot ions in the Jovian magnetodisc
Authors: Kane M. , Mauk B. H. , Keath E. P. , Krimigis S. M.
Published: February 2008

Hot ion angular anisotropies measured by the Low Energy Charged Particle (LECP) instrument during the Voyager 2 encounter with the Jovian dayside outer magnetosphere (60–30 RJ) have been fitted to a 2 species convected K distribution function using a non‐linear least squares technique. The resulting parameters are well constrained by the data. The heavy ion species was assumed to be either sulfur or oxygen of unknown charge. The light species was assumed to be protons. The bulk flow speeds deduced from the model were found, contrary to some theories, to increase with increasing radial distance from Jupiter within the radial region addressed, remaining a substantial fraction (∼0.6) of the rigid corotation speed. Agreement with the averaged Voyager Plasma Science (PLS) results was obtained near 30 RJ. The core Maxwellian temperature of the heavy ion distribution functions (∼30–100 keV) increased with increasing radial distance, following the trend anticipated from the corotation pickup of heavy ions. The proton temperature (∼20 keV) remained nearly constant.
Standing ULF modes of the magnetosphere: A theory
Authors: Harrold B. G. , Samson J. C.
Published: February 2008

Field line resonances with frequencies in the range 1 to 4 mHz have recently been observed by the JHU/APL HF Doppler radar during quiescent geomagnetic conditions. These structures are observed to have stable frequencies for durations of several hours, leading us to the conclusion that they may be standing waves (in the radial direction, as opposed to standing waves along a field line) of the magnetosphere driven by the solar wind. Using this premise, the propagation of fast mode ULF waves in the magnetosheath and the near earth magnetosphere are examined in an ideal, linearized MHD context. A model is presented in which fast waves propagate in the equatorial plane between the flanks of the bow shock and a turning point deep within the magnetosphere. Due to the magnetic field gradient near the earth, a field line resonance develops between the turning point and the plasmapause. Using a realistic set of magnetospheric parameters, it is possible to reproduce the set of observed frequencies and the respective positions of their field line resonances within the ionosphere (assuming a dipole mapping). However, because the model cavity frequencies are sensitive to magnetosheath parameters, this model does not explain the extreme stability with respect to geomagnetic conditions of the observed frequencies.
Elastic properties of sodium‐rich majorite garnet
Authors: Pacalo Rosemary E. G. , Weidner Donald J. , Gasparik Tibor
Published: February 2008

The adiabatic elastic moduli of a high‐pressure sodium‐rich majorite garnet have been measured at ambient conditions using Brillouin spectroscopy. This garnet has the composition, Na1.87Mg1.18Si4.94O12, with sodium and magnesium in eight‐fold coordination and silicon in octahedral and tetrahedral coordination. While the adiabatic bulk modulus, Ks = 173.5 GPa, falls within the range of common garnets, the shear modulus, μ = 114.7 GPa, is unusually large; sodium garnet is elastically similar to the low‐pressure garnet grossular. The variation of elastic properties for garnets of differing composition within the cubic garnet structure can be expressed as a linear function of the ratio of average cation radii in the eight‐fold versus the six‐fold site. The cations in the AO8 polyhedra apparently brace the structure by controlling rotational freedom within corner‐linked chains of alternating tetrahedra and octahedra.
Topographic relief and sediment thickness: Their effects on the thermal evolution of the oceanic crust
Authors: Abbott Dallas H. , Stein Carol A. , Diachok Orest
Published: February 2008

We compiled a suite of 490 heat flow measurements from the Pacific Ocean in areas with less than 85 m of sediment. Heat flow patterns at different basement ages vary with topographic relief. Areas with reliefs < 300 meters are conductively blanketed at 40–60 m.y. and may stop convecting at 70–90 m.y. Areas with reliefs > 300 meters are conductively blanketed at 70–90 m.y. and convect out to ≥ 90–110 m.y.
Cosmogenic neon in recent lavas from the western United States
Authors: Poreda Robert J. , Cerling Thure E.
Published: February 2008

The absolute cosmogenic production of 21Ne (21Nec) and 3He (3Hec) in olivine (Fo81) is measured for the well‐dated Tabernacle Hill flow. Values scaled to sea level and high latitude ( > 60°) are 45 atoms/g/yr for 21Nec and 109 atoms/g/yr for 3Hec for the past 17,800 years.Production rates for 21Nec are about 50% higher than the theoretical values given by Lal [1991]. A ratio of 21Nec/3Hec of 0.41 ± 0.05 is measured in olivines that have a range of 25 in cosmogenic exposure; there is no evidence of 3Hec loss in samples older than 100,000 years.

Volcanic plagioclase is shown to be a suitable mineral for cosmogenic 21Nec dating of surfaces. 21Nec in co‐existing plagioclase and olivine phenocrysts have a constant ratio of 0.42 ± .04 in samples with more than 106 atoms of 21Nec. Using all of the 21Nec data and the 3Hec as a cosmic ray flux monitor, production of 21Nec in Ab36 plagioclase is calculated at 16.8 ± 1.7 atoms/g‐yr for the past 17,800 years. The production of 21Nec from 23Na is estimated at 160 ± 50 atoms/g/yr at 60° and sea level or equivalent to that on 24Mg.
Shear strength of the Great Pacific Fracture Zones
Authors: Bonneville Alain , McNutt Marcia
Published: February 2008

Shipboard bathymetry and gravity data from 30 crossings of 6 great Pacific fracture zones (FZs), the Mendocino, Murray, Molokai, Clarion, Clipperton, and Udintsev, are compared with the predictions of a model in which FZs are locked beyond the ridge‐transform intersection, such that no vertical motion occurs on the fault in response to differential thermal subsidence. At least some sections of all of these FZs, except the Molokai, are consistent with this model and sustain shear stresses as high as 20 MPa. However, none of the FZs is locked along its entire length, as inferred from observed shear stresses dropping below 75% of the value necessary to maintain a locked fault. There is some suggestion that the unlocking may be related to excess volcanism.
Long‐term variations in magnetization intensity with crustal age in the northeast Pacific, Atlantic, and southeast Indian oceans
Authors: Sayanagi Keizo , Tamaki Kensaku
Published: February 2008

The magnetization intensity of oceanic crust in the Northeast Pacific, Atlantic, and Southeast Indian oceans was calculated from marine magnetic anomaly data to investigate long‐term variations in magnetization intensity with crustal age. The magnetization intensity was derived by two‐dimensional inversion of the upward‐continued marine magnetic anomalies. The principal magnetization intensity variations versus age are summarized as follows: (1) In all the oceans, a high magnetization intensity exists at the ridge crest, followed by a sharp decrease within 8 My, and a minimum is reached at 8–20 Ma; (2) In the Northeast Pacific and Atlantic oceans, the magnetization intensity gradually increases up to at least 70 Ma. This variation pattern is consistent with the previous results of NRM measurements of drilled rocks and inversion of marine magnetic anomalies in the South Atlantic.
Laboratory evidence of earthward electric field in the magnetotail current sheet
Authors: Minami S. , Podgorny A. I. , Podgorny I. M.
Published: February 2008

In a laboratory simulation experiment of the earth's magnetosphere, an evidence of the existence of an earthward electric field is shown in the equatorial current sheet. The earthward electric field may be generated as a result of Hall electric field generation in the current sheet. A simple theoretical model for the existence of an earthward electric field is presented. The ions in the current sheet are accelerated by this earthward electric field, which then penetrate into the near earth dipole magnetic field. At the end of the current sheet near the earth, these ions are accumulated due to the difference of the inertia between ions and electrons. The polarization of charges reverses the electric field from earthward to tailward at this region. The experimental results have shown two directional electric fields along x‐axis in the current sheet. The earthward direction of the electric field is due to the dawn‐dusk current sheet carried by electrons. These experimental results prove the theoretical prediction. A discussion of the application of this result to the real magnetotail physics is also presented.
Waves in the inner magnetosheath: A case study
Authors: Song P. , Russell C. T. , Thomsen M. F.
Published: February 2008

We study the waves within, and upstream of, the density enhancements in front of the magnetopause using magnetic field and plasma measurements from ISEE 1 and 2. The waves upstream of the density enhancements are most likely to be mirror modes and are convected with the magnetosheath flow. Within the density enhancements there is additional wave power at lower frequencies. These low frequency waves appear to be slow modes propagating sunward and quasi‐standing in the flow. These observations lend support to the contention that the outer edge of the density enhancement is a slow mode wave front which marks the greatest distance that slow modes can propagate upstream into the solar wind.
On the Lehmann discontinuity
Authors: Karato Shun‐ichiro
Published: February 2008

The Lehmann discontinuity (∼200km) in the upper mantle is proposed to result from a change in the preferred orientation of olivine as a result of a change in deformation mechanism: in the shallow upper mantle, deformation is due to dislocation creep and results in an anisotropic structure, whereas in the deeper upper mantle, diffusion creep becomes dominant due to a smaller activation volume, resulting in an isotropic structure. For anisotropy due to dislocation‐glide corresponding to a horizontal flow, the resultant anisotropy will yield VSH>VSV and VPH>vPV. Thus, for waves propagating nearly vertically (e.g., ScS waves), there will be discontinuous jumps in the S‐ and P‐wave velocities at this discontinuity. In this model, the depth of the Lehmann discontinuity depends on the deformation conditions such as stress level, geotherm, water fugacity and grain‐size, giving a natural explanation for its observed variation with tectonic setting.
Large‐scale transport of pollution aerosol over the east coast of Asia
Authors: Uematsu Mitsuo , Sugita Takafumi , Anikiev Vladimir V. , Medvedev Alexander N.
Published: February 2008

Eastern Asia contains many large pollution sources whose emissions can be transported over large areas of North Pacific. In order to characterize this transport, we collected a sixty‐day series of daily aerosol samples concurrently from Sapporo, Japan and Vladivostok, CIS from April to May, 1991. These were analyzed for non‐sea‐salt (nss) sulfate and nitrate. The arithmetic mean concentrations of nss‐sulfate (4.66 ± 2.68 μg m−3) and nitrate (2.58 ± 1.62 μg m−3) in Vladivostok were 70% and 40% higher than the corresponding concentrations of nss‐sulfate (2.69 ± 2.06 μg m−3) and nitrate (1.86 ± 1.42 μg m−3) in Sapporo. Several episodic peaks of nss‐sulfate and nitrate in Vladivostok corresponded to the peaks observed in Sapporo, which is located approximately 700 km east of Vladivostok. About 40% and 25% of the variance in the nss‐sulfate and nitrate concentrations at the two sites could be explained by the large‐scale transport of substances under the strong winds from the west and southwest This suggests that the high concentrations are associated with strong regional sources located to windward of these cities and that the concentrations that we measured are probably representative of a large area of the coastal western North Pacific Ocean.
10Be and magnetic susceptibility in Chinese loess
Authors: Beer Jürg , Shen Chengde , Heller Friedrich , Liu Tungsheng , Bonani George , Beate Dittrich , Suter Martin , Kubik Peter W.
Published: February 2008

10Be and magnetic susceptibility have been measured in the top 12 m of a loess profile from Luochuan, Central China. Comparison of the 10Be concentration record with the SPECMAP δ18O profile of the last 130 ka (Imbrie et al., 1984] results in a new time scale which is in good agreement with that of Kukla et al. [1990]. The calculated loess accumulation rates can be compared with existing records of dust falls in Pacific deep sea sediments and Antarctic ice cores. A simple model for the 10Be dust flux demonstrates that a significant part of the magnetic susceptibility signal in palaeosol horizons is due to in situ pedogenic production. During times of high loess accumulation (cold palaeoclimate) this contribution is negligible.
Aircraft observations of the origin and growth of very large snowflakes
Authors: Lawson R. Paul , Stewart Ronald E. , Strapp J. Walter , Isaac George A.
Published: February 2008

A new high‐volume precipitation probe, capable of optically imaging particles up to about 5 cm, was flown in a winter storm during the second Canadian Atlantic Storms Program (CASP II). Dendritic crystals originating aloft in a region of (weak) convective instability were tracked and observed to aggregate into 4–5 cm snowflakes within an isothermal layer near 0° C. The region containing the very large snowflakes was characterized by high radar reflectivities and rapid accumulation of snow at the surface.
Water soluble organic constituents in Arctic aerosols and snow pack
Authors: Li Shao‐Meng , Winchester John W.
Published: February 2008

Eight water‐soluble organic anions were measured in 70 aerosol samples and 10 snow samples at Barrow, Alaska in March–April, 1989. The ranking of the ions in aerosols according to total (coarse+fine aerosol) median concentrations was acetate (44 ng m−3), oxalate (27), benzoate (23), formate (22), propionate (6), methanesulfonate (5), lactate (4), and pyruvate (4). When added up, the median organic anion mass was 156 ng m−3. The organic anions/nssSO4= mass ratio had a median of 0.18 and 0.07 in the coarse (>1 μm) and fine (<1 μm) size fractions, respectively, but can be very high on occasions. On average, the organic anions made up more than 10% of the water‐soluble aerosol mass. A similar ranking in concentration was also found for the organic ions in the snow pack samples. The organic anion/nssSO4= mass ratio in these samples was >0.5, substantially higher than in aerosols.
The applicability of ray perturbation theory to mantle tomography
Authors: Sambridge Malcolm , Snieder Roel
Published: February 2008

Ray perturbation theory is an efficient means of calculating raypaths and travel times in 3‐D heterogeneous media accurate to first and second order respectively. We present results from using perturbation theory in 3‐D quasi‐random models of the earth's mantle and in a subduction model obtained from ISC tomography. We show that the perturbation theory provides travel time estimates with errors smaller than 0.1 s for a very wide range of heterogeneities. The second order travel time correction also removes the implicit bias, towards late arrivals, present in all first order estimates. The computational efficiency of the theory is discussed and actual cpu times are given. It is concluded that ray perturbation theory is both accurate and efficient enough to provide a basis for non‐linear tomography on data sets with the order of a million rays.
Three‐dimensional mantle dynamics with an endothermic phase transition
Authors: Honda S. , Balachandar S. , Yuen D. A. , Reuteler D.
Published: February 2008

Three‐dimensional convection for the spinel to perovskite phase change has been simulated numerically. Results for Rayleigh (Ra) numbers of 0(106) show intermittent layering with a strong robust plume rising through the phase boundary. Many descending instabilities are deflected but merging cold sheets come together at a junction. A pool of cold material accumulates underneath in the phase‐transition zone. A strong gravitational instability results, which precipitates a rapid and massive discharge of upper‐mantle material.
An ab initio study of dissociative electron attachment to NaHCO3 and NaCO3, and the role of these reactions in the formation of sudden sodium layers
Authors: Rajasekhar B. , Plane John M. C.
Published: February 2008

One of the mechanisms that has been proposed to explain the phenomenon of sudden sodium layers (SSLs) in the upper atmosphere is dissociative attachment of electrons to sodium compounds such as NaHCO3 and NaCO3. In this study, abinitio calculations have been used to estimate the reaction enthalpies (ΔH°0(NaX + e− → Na + X−)) for NaHCO3 and NaCO3, which are found to be 72 ± 20 (0.75) and 21 ± 30 (0.22) kJmol−1 (eV), respectively. NaHCO3 is then shown to be relatively stable above the mesopause. This property, together with its rather small threshold for dissociative electron attachment, makes NaHCO3 a possible source of SSLs under certain conditions.