bluuebunny/crossref_metadata_2025 huggingface dataset:
Scaling properties of potential fields due to scaling sources
Authors: Maus S. , Dimri V. P.
Published: February 2004

The theoretical power spectrum of the 3‐dimensional potential field caused by an arbitrary 3‐dimensional source distribution is derived for gravity and magnetic data. A function with scale‐invariant features has a power spectrum, which is proportional to the frequency raised to minus the scaling exponent. For scaling source distributions, the power spectrum of the gravity and magnetic field is anisotropic and a specific scaling exponent exists only for lower‐dimensional cross sections of the field. We suggest an approach which allows, under certain conditions, to derive the power spectrum of a lower‐dimensional subset from the power spectrum of a 3‐dimensional function. For the special case where the 3‐dimensional function has an isotropic scaling exponent β3D, we confirm a known property, namely that a (3‐k)‐dimensional subset of the function has a scaling exponent of approximately k less than β3D. This property is not applicable to the anisotropic 3‐dimensional fields, but it can be applied to source distributions with isotropic scaling exponent. Summarizing our results, the scaling exponents of the density distribution and the gravity field are related by whereas the relationship between the scaling exponents of the susceptibility distribution and the magnetic field reduced to the pole can be stated as follows:
Thermal expansion of MgSiO3 perovskite at 20.5 GPa
Authors: Morishima Hideaki , Ohtani Eiji , Kato Takumi , Shimomura Osamu , Kikegawa Takumi
Published: February 2004

A high pressure and high temperature in‐situ X‐ray diffraction experiment of MgSiO3 perovskite was conducted using a sintered diamond multianvil apparatus (SDMA8) combined with the synchrotron radiation. The unit cell parameters of the perovskite were measured up to 1095°C at about 20.5 GPa. The thermal expansion coefficient is 0.8(±0.8)×10−5 K−1 at 20.5 GPa and room temperature.
cosmic ray produced 32P and 33P in Cl, S and K at mountain altitude and calculation of oceanic production rates
Authors: Waser N. A. D. , Bacon M. P.
Published: February 2004

The activities of 32P and 33P induced in Cl, S and K targets during exposure to cosmic rays were measured at Mt. Washington (55.7°N, 1917 m) allowing the in situ production rates of the nuclides to be determined in all the major ocean targets. Furthermore, the production rates of 32P and 33P in Cl, the major ocean target, were determined at three different altitudes in the atmosphere at Woods Hole (53°N, 10 m), Mt. Washington and l'Aiguille du Midi (47.4°N, 3820 m). The exponential attenuation length of the production rates of 32P was found to be consistent with the attenuation length of neutrons in the lower atmosphere at mid‐latitudes. The data allow the in situ oceanic production rates of the nuclides to be estimated at all latitudes.
Freja observations of multiple injection events in cusp
Authors: Norberg O. , Yamauchi M. , Eliasson L. , Lundin R.
Published: February 2004

The TICS (Three‐dimensional Ion Composition Spectrometer) instrument on board the Freja satellite provides particle data with high spatial, temporal, spectral, and mass resolution. The Freja orbit (inclination 63°) is suitable for studies of the cusp since the satellite traverses this region longitudinally when the cusp is located lower than 75° geomagnetic latitude, i.e. when the interplanetary magnetic field (IMF) points southward. The satellite traverses the dayside polar region during two weeks every 100 days due to orbit precession, and nearly 50 cusp traversals were recorded during the first year of operation. Both multiple injections and single injections are clearly identified and distinguished, the former being more frequently observed than the latter. Freja has also resolved overlapping injections (special cases of multiple injections), for the first time at low altitudes.
Growth of nitric acid hydrates on thin sulfuric acid films
Authors: Iraci Laura T. , Middlebrook Ann M. , Wilson Margaret A. , Tolbert Margaret A.
Published: February 2004

Type I polar stratospheric clouds (PSCs) are thought to nucleate and grow on stratospheric sulfate aerosols (SSAs). To model this system, thin sulfuric acid films were exposed to water and nitric acid vapors (1 ‐ 3 × 10−4 Torr H2O and 1 ‐ 2.5 × 10−6 Torr HNO3) and subjected to cooling and heating cycles. FTIR spectroscopy was used to probe the phase of the sulfuric acid and to identify the HNO3/H2O films that condensed. Nitric acid trihydrate (NAT) was observed to grow on crystalline sulfuric acid tetrahydrate (SAT) films. NAT also condensed in/on supercooled H2SO4 films without causing crystallization of the sulfuric acid. This growth is consistent with NAT nucleation from ternary solutions as the first step in PSC formation.
Investigating the origins and significance of low‐frequency modes of climate variability
Authors: Allen Myles R. , Smith Leonard A.
Published: February 2004

An analysis of the 130‐year record of the Earth's global mean temperature reveals a significant warming trend and a residual consistent with an auto‐correlated (“red”) noise process whose predictability decays with a timescale of two years. Thus global temperatures, in isolation, do not indicate oscillations at 95% confidence against a red noise null hypothesis. Weak signals identified in the global series can, however, be traced to significant sea surface temperature oscillations in the equatorial Atlantic (period ∼10 years) and the El Niño region of the Pacific (3–5 years). No robust evidence is found in this data for interdecadal oscillations, The 10‐year Atlantic oscillation corresponds to a pattern of temperature anomalies which has been associated with interannual variations in West African rainfall and in U.S. hurricane landfall frequency.
Changes in stratospheric aerosols and solar insolation due to Mt. Pinatubo eruption as observed over the western Pacific
Authors: Hayasaka Tadahiro , Iwasaka Naoto , Hashida Gen , Takizawa Iwao , Tanaka Masayuki
Published: February 2004

Effects of the Mt. Pinatubo eruption on the stratospheric aerosols and the solar insolation over the Western Pacific were estimated by sunphotometer and pyranometer on board ships. The sunphotometer measurements showed that the columnar aerosol optical thickness increased by 0.3 at 500 nm over the latitude from 30°N to 30°S, while that without the influence of volcanic eruptions is less than 0.1. The aerosol optical thickness became minimum in the summer of 1992, and increased again after the summer. The shipboard pyranometer measurements showed that solar insolation decreased after the eruption by 1.4∼4.1% compared with that before the eruption. This value is larger than that calculated with radiative transfer code, based on the aerosol model estimated from the sunphotometry.
The effect of comet Shoemaker‐Levy 9 on Jupiter's synchrotron radiation
Authors: de Pater Imke
Published: February 2004

Solid material from comet Shoemaker‐Levy 9 is expected to modify Jupiter's decimetric radio emission. Electrons passing through dust grains suffer a degradation in their energy, while larger sized material absorbs all electrons impinging on it. If there is enough dust and/or larger sized material in the magnetosphere, the effect on the energetic electrons can be observed via their synchrotron radiation, emitted at microwave frequencies. The planet's radio emission is expected to decrease, and the presence of dust induces a hardening in the radio spectrum. We expect the intensity to decrease immediately after cometary material enters the radiation belts; the radio emission continues to drop for many months as electrons diffuse inwards through a dusty magnetosphere. Radio observations of the planet during and after the cometary impact thus yield information on the amount of cometary material (optical depth of the dust and macroscopic material), impacts between cometary material and Jupiter's ring, and the diffusion process of energetic electrons through the magnetosphere.
The flaring of the Martian magnetotail observed by the Phobos 2 spacecraft
Authors: Zhang T.‐L. , Schwingenschuh K. , Russell C. T. , Luhmann J. G. , Rosenbauer H. , Verigin M. I. , Kotova G.
Published: February 2004

Spacecraft observations from the Earth's magnetotail show that the flaring angle depends on the downtail distance, the upstream solar wind dynamic pressure and the Bz component of the interplanetary magnetic field [Petrinec and Russell, 1993]. Measurements from the Phobos 2 spacecraft along a circular orbit at 2.8 Mars radii allow a similar study of the Mars magnetotail. Under the assumption that the magnetic pressure in the Martian tail lobes is much greater than the plasma pressure in the lobe, we use the pressure balance condition between the tail lobe magnetic pressure and the normal component of the solar wind pressure to infer the angle at which the tail magnetopause flares. As in the case of the terrestrial magnetotail, the flaring angle of Mars tail depends on the solar wind dynamic pressure, but this angle (at 2.5 RM) is about one half the terrestrial value (at 17 RE). The median inferred flaring angle is about 13°.
Persistent features of polarity transition records from western North America
Authors: Glen Jonathan M. , Coe Robert S. , Liddicoat Joseph C.
Published: February 2004

We report on a high resolution transition record from Searles Valley, California that appears not to be hampered by problems of smoothing or recording breakdown, and, unlike many other sedimentary records, defines a path unconfined in longitude. A prominent feature of the record is the steady oscillation of the pole along a swath stretching from west Africa across north Eurasia to the northwest Pacific. The endpoints of the swath are associated with a change between steady and rapid field variation, consistent with results for an older transition from a nearby volcanic record. The transition culminates with poles migrating from west Africa to South America, midway between the two earlier‐proposed longitudinal bands. This path indicates the reversing field has either a wider spectrum of behavior than recently suggested or is described by a more complicated field geometry than one dominated by an equatorial dipole or strong low‐order nondipole component. From a comparison with existing records from the same general geographic area, we address the significance of the swath, the lack of longitudinal confinement, patterns of steady and rapid field changes, and the temporal persistence of these features in relation to the geometry of the reversing field.
Long‐term geometry of the geomagnetic field for the last five million years: An updated secular variation database
Authors: Quidelleur Xavier , Valet Jean‐Pierre , Courtillot Vincent , Hulot Gauthier
Published: February 2004

Lee [1983] assembled more than two thousand paleomagnetic directional data from lava flows in 65 sampling sites with ages spanning the last 5 million years. Constable [1992] recently suggested that the virtual geomagnetic poles (VGP) derived from this data base have been preferentially located within two antipodal bands of longitude. We have reanalyzed and updated the Lee data base, yielding a total of 3179 data from 86 distinct sites. Neither the total data set, nor various subsets of the data unambiguously show any large and clear maxima in the longitude distribution of VGPs. The shape of the common site longitude distribution is far more striking with a pronounced (and robust) minimum close to the common site longitude and secondary maxima about 120° away from it. The former (first order) feature is equivalent to the far‐sided effect discovered by Wilson [1970] and corresponds to a persistent axial quadrupole amounting to about 5% of the axial dipole, as previously found by several authors. The latter (second order) feature could correspond to the VGP biasing effect described by Egbert [1992] although its observed amplitude appears larger than predicted. Part of this effect (an asymmetry in the maxima) may also correspond to Wilson's [1971] right‐handed effect. Given only a small axial quadrupolar component and the very uneven actual site distribution, the expected longitude distribution of VGPs can be calculated: this is found to be in good agreement with the paleomagnetic observations (i.e. rather flat with a moderate maximum near 120°E). This study emphasizes problems related to the unsatisfactory distribution of sites. The amplitude and significance of other terms, beyond the dominant axial dipole and significant axial quadrupole contribution, remain to be assessed.
Ozone heating and the destabilization of traveling waves during summer
Authors: Nathan Terrence R. , Cordero Eugene C. , Li Long
Published: February 2004

The effects of ozone heating on the linear stability of lower stratospheric traveling waves of the summertime, extratropical circulation are examined. Based on coupled equations for the quasigeostrophic potential vorticity and ozone volume mixing ratio, it is shown that the diabatic heating arising from ozone advection can offset the damping due to Newtonian cooling, leading to wave amplification and significant changes in the structure and zonally rectified fluxes of the wave fields in both the lower stratosphere and troposphere. The vertical profile of the zonal mean wind plays a crucial role in determining whether the ozone heating destabilizes eastward and/or westward traveling disturbances.
Formation of formic acid and organic peroxides in the ozonolysis of ethene with added water vapour
Authors: Horie Osamu , Neeb Peter , Limbach Stefan , Moortgat Geert K.
Published: February 2004

Ozonolysis of C2H4 was carried out in a 580 l glass reaction vessel at 1–5 ppm reactant concentrations, with added water vapour. Under dry conditions ([H2O]0 = 0.5 ppm), HCHO, CO, CO2, (CHO)2O (formic acid anhydride), H2O2, and CH3OOH were identified as the reaction products. Under wet conditions ([H2O]0 = 2 × 104 ppm), HCOOH yields approaching ca. 20% of the converted C2H4, were observed, while no (CHO)2O was formed. Hydroxymethyl hydroperoxide, HOCH2OOH, was observed as the major peroxide, and found to be formed only in the presence of water vapour. Direct reactions of H2O vapour with the excited CH2OO* radicals and with stabilized CH2OO radicals are postulated to explain the formation of HCOOH and HOCH2OOH in the presence of water vapour, respectively.
A preliminary assessment of energetic ion species in flux ropes/plasmoids in the distant tail
Authors: Lui A. T. Y. , Williams D. J. , Christon S. P. , McEntire R. W. , Angelopoulos V. , Jacquey C. , Yamamoto T. , Kokubun S.
Published: February 2004

Measurements of the Energetic Particles and Ion Composition (EPIC) instrument on the Geotail satellite are used to investigate at high‐time resolution the relative intensity enhancements of different ion species at energies ∼10 keV‐3 MeV during encounters of magnetic field structures attributed to flux ropes or plasmoids in the distant tail. An examination of six events reveals the new result that the composition varies considerably within the interval of the encounter of each structure as well as among different encounters. There is no consistent trend for enhancement nor reduction of energetic ions from the ionospheric source relative to that from the solar wind source during intervals of flux ropes or plasmoids. A possible interpretation is that these plasma structures are connected to a particle source or sources actively modifying their compositional content while they are being ejected downstream beyond ∼100 REE.
How will dust from Shoemaker‐Levy 9 alter Jupiter's stratospheric aerosol populations?
Authors: Pryor Wayne R. , Na C. Y. , Gladstone G. R.
Published: February 2004

Jupiter's stratospheric haze is most abundant in the polar regions. This polar stratospheric haze has a distinctive signature: bright polar caps are visible in methane absorption band images at 0.89 µm. The upcoming Shoemaker‐Levy 9 impacts should significantly add to the stratospheric haze population, as a result of direct dust impact and perhaps as a result of a splash component of dust explosively ejected from the impact sites. The extra material will predominantly land in the southern hemisphere. Comet dust has a low albedo, and will generally lower Jupiter's brightness in continuum images, particularly near the limb. However, in the 0.89 µm methane absorption band images we expect Jupiter to brighten in dust impact regions, since the dust scatters light above most of the methane absorbers. Stratospheric sedimentation times are generally on the order of years, so this new haze component will be persistent.
Chemical change in the Arctic Vortex during AASE II
Authors: Traub Wesley A. , Jucks Kenneth W. , Johnson David G. , Chance Kelly V.
Published: February 2004

We measured column abundances of HF, HCl, O3, HNO3, and H2O on the NASA DC‐8 during the AASE II campaign, using thermal emission spectroscopy. We made multiple traversals of the Arctic vortex and surroundings. Using HF as a tracer, we remove the effects of subsidence from the measured column abundances; perturbations in the resulting column abundances are attributed to chemical processing. We find that by January 1992 the stratospheric column in the vortex had been chemically depleted by about (55±10)% in HCl and (35±10)% in O3, and enhanced by about (15±10)% in HNO3 and (0±10)% in H2O.
Alfvénon, driven reconnection and the direct generation of the field‐aligned current
Authors: Song Yan , Lysak Robert L.
Published: February 2004

The patchy and intermittent nature of the solar wind‐magnetosphere interaction suggests that MHD mesoscale processes are important in the description of transport at the magnetopause. In order to deal with the nonlinear electromagnetic interaction of localized fluctuations in a highly inhomogeneous region such as the magnetopause, a quasi‐particle description involving compressional and shear Alfvénons is introduced to give the particle‐like behavior of the corresponding MHD waves. The driven nature of the solar wind‐magnetosphere interaction, and in particular driven reconnection, is discussed in terms of the interactions between these Alfvénons, and between Alfvénons and the ambient magnetic field. The dependence of the threshold conditions for the onset of the driven reconnection on the IMF and the dynamic pressure of the solar wind is calculated by analyzing the generation and interaction of the Alfvénons. The conversion of compressional Alfvénons into shear Alfvénons gives a mechanism for the direct generation of field‐aligned current filaments.
Ozone variations related to volcanic activity and disappearance of SO2
Authors: Roldugin V. C. , Henriksen K.
Published: February 2004

The long‐term trend analysis of the total ozone data for the period 1973–1989 was made for three regions of the USSR. A common negative trend is explained by the eruptions of Fuego and El Chichon as one of two considered reasons, and comparison of the ozone and sulphur dioxide data for Murmansk gives further evidence to the study of De Muer and De Backer, finding that an ozone decrease vanishes when correction for tropospheric SO2 decrease is carried out. The well‐known hypothesis about anthropogenic induced depletion of the ozone layer is not confirmed by these data.
Estimating the bow shock normal speed from single spacecraft observations of magnetic wave activity
Authors: Lottermoser R.‐F. , Lühr H.
Published: February 2004

We introduce a reliable method for estimating the speed of the quasi‐perpendicular bow shock from single spacecraft data. It is based on timing the passage of the foot and uses magnetic wave activity to detect the upstream boundary of the foot. The frequency range employed is between 20 and 60 Hz as recorded by the AMPTE‐IRM fluxgate magnetometer. This new technique has been applied to 33 bow shock crossings. The resulting velocities are checked against results from the dual‐spacecraft method and others employed in the past.
Ozone depletion in the Arctic stratosphere in early 1993
Authors: Larsen Niels , Knudsen Bjørn , Mikkelsen Ib Steen , Jørgensen Torben S. , Eriksen Paul
Published: February 2004

During the first three months of 1993 measurements of the vertical ozone profile, with balloon‐borne sensors, were performed in Greenland. A substantial ozone depletion took place from the end of January to the end of March in the altitude range between approximately 14 and 20 km. An ozone decrease of about 1% per day is ascribed to chemical destruction inside the polar vortex based on air parcel trajectory analysis, using measurements of lower stratospheric aerosols as dynamical tracers to correct for diabatic subsidence. The column‐integrated total ozone loss was found to be about 48 Dobson units or 12%. These measurements are in good agreement with satellite observations, and further document the 1993 springtime stratospheric ozone depletion as the most severe and long lasting yet reported for the Arctic.
Simultaneous three‐frequency Na lidar measurements of radial wind and temperature in the mesopause region
Authors: She C. Y. , Yu J. R.
Published: February 2004

Using a uniquely constructed acoustooptic frequency shifter to provide three different excitation frequencies, νa=−652 MHz and νc=188 MHz along with νs=−172 MHz at the spectral slope, the Colorado State Na temperature lidar has been up‐graded to permit simultaneous measurements of radial wind and temperature in the mesopause region. Initial observations were made at Ft. Collins, CO (40.6°N, 105°W) for three nights in September, 1993 (a total of 20.2 h and 1,204 profiles). With a power‐aperture product of 0.06 W‐m², the lidar measured RMS uncertainties with spatial and temporal resolutions of 1.5 km and 6 min are assessed to be 1.6 K and 3.1 m/s at the peak of the Na layer. Observational results for the nights of Sep 3, 4 and 21 (UT) that contain new thermal and dynamical information of the mesopause are presented to show the potential of simultaneous wind/temperature measurements.
Initial GEOTAIL survey of magnetic substorm signatures in the magnetotail
Authors: Nagai T. , Takahashi K. , Kawano H. , Yamamoto T. , Kokubun S. , Nishida A.
Published: February 2004

Substorm signatures in the magnetotail at radial distances from −30 to −210 Re are studied using magnetic field data acquired with the GEOTAIL spacecraft. The current data set consists of GEOTAIL magnetic field data transmitted in real time to Japan from October 1992 to September 1993, and the corresponding GMS‐4 (140°E geographic, geostationary) energetic particle data and 1‐s Kakioka (L=1.2, 140°E) magnetic field record. We first identify substorms from major increases in the particle flux at the geostationary satellite, then determine accurate onset times from Pi 2 pulsations at the Kakioka ground station, and finally examine the corresponding magnetic field signatures at GEOTAIL. Eighty‐nine substorm events occurred when GEOTAIL was either in the plasma sheet or in the tail lobe, and these events were analyzed with a special emphasis on the temporal development of the north‐south magnetic field component Bz. A clear bipolar signature (northward perturbation followed by southward) is observed in Bz for 53 events. The bipolar events have characteristics consistent with the plasmoid or the traveling compression region reported in earlier studies. In the middle and distant tail (X<−60 Re), most of events seem to indicate the passage of a plasmoid. The present results provide evidence for near‐Earth reconnection and the formation and release of plasmoids in association with substorm onsets. A simple model yields the following plasmoid parameters: near‐Earth reconnection around X=−30 Re, the center of the newly‐created plasmoid around X=−60 Re, and the expansion of the tailward‐moving plasmoid to a dimension of 100 Re in the X direction and almost fully across the distant tail (X=−200 Re).
Near‐Earth substorm onset: A coordinated study
Authors: Persson M. A. L. , Opgenoorth H. J. , Pulkkinen T. I. , Eriksson A. I. , Dovner P. O. , Reeves G. D. , Belian R. D. , André M. , Blomberg L. G. , Erlandson R. E. , Boehm M. H. , Aikio A. T. , Häggström I.
Published: February 2004

We present simultaneous satellite and ground‐based measurements of a substorm. Throughout the initial substorm expansion, southward drifting arcs are observed poleward of the expanding substorm aurora, indicating two independent systems of particle precipitation. Freja passes the brightening onset arc in the topside ionosphere near the moment of the substorm onset, observing an Alfvén wave, field aligned current and oxygen ion outflow. The substorm onset occurs at low magnetospheric L‐shells, near the poleward edge of the region of trapped particles. The location and time for the substorm injection are confirmed by geostationary spacecraft together with magnetometers, all‐sky cameras and radar on the ground. We believe that the substorm onset may be triggered by modification of the oxygen content of the inner magnetosphere during the growth‐phase caused by ionospheric ion outflow.
Banded structures in stratospheric aerosol distributions
Authors: Trepte Charles R. , Thomason Larry W. , Kent Geoffrey S.
Published: February 2004

Zonal bands of stratospheric aerosol optical depth are observed by various sensors under both volcanic and non‐volcanic conditions. Maximum optical depths occur within the tropics and at high latitudes, while minima are found between latitudes of approximately 15° and 45°. This structure is shown to result from a reservoir of aerosol over the tropics, poleward transport, and the departure of the tropopause from isentropic surfaces.
The initial rise of a hydrothermal plume from a line segment source—Results from a three‐dimensional numerical model
Authors: Lavelle J. W.
Published: February 2004

Recent measurements of large water column plumes in association with seismic activity and evidence of a fissure release of magma on the sea floor at the CoAxial Segment, northern Juan de Fuca Ridge, initiates questions about the response of the benthic ocean to large and sudden line discharges of heat. Here these issues are investigated using a three‐dimensional non‐hydrostatic hydrodynamical model. The model treats the case of a starting plume from a finite‐length, narrow line source of heat ascending into a rotating environment stratified in temperature and salinity. The developing water column plume is studied over an initial time period of approximately f−1, where f is the Coriolis frequency. Midway into this interval the plume attains its maximum rise height of ∼900 m, for given buoyancy flux and stratification conditions. Thereafter, the plume spreads laterally and the effects of the earth's rotation come into evidence. Outward flow at 400–900 m above bottom is primarily transverse to the line source, quickly making the plume at those heights more circular than line‐like.
Saturated gravity wave spectra measured with balloons in Mendoza (Argentina)
Authors: de la Torre A. , Giraldez A. , Alexander P.
Published: February 2004

Spectral results from a sounding of temperature and wind velocity between 11.9 and 23.1 km performed with an open type stratospheric balloon near the Andes Mountains, are reported. The use of this kind of balloons and high performance instruments, allowed to attain better spatial resolution (around 2.5 meters during the descent) than previous results and other sounding techniques. This high resolution permitted to study the complete interval of altitude data in three consecutive subintervals (below, around and above the tropopause). Each of these subintervals shows different saturation characteristics. Some differences have been found with the general pattern of power spectral densities reported by different theories. A large amplitude wave of around 1.8 km and possibly originated in the mountain relief, is clearly observed in the temperature, vertical and shear wind velocity components.
Static compression of chondrodite: Implications for water in the upper mantle
Authors: Faust Jessica , Knittle Elise
Published: February 2004

We have determined the equation of state of chondrodite (2Mg2SiO4·Mg(OH,F)2), a possible water‐bearing phase in the upper mantle, to 42.3 GPa at room temperature using x‐ray diffraction through the diamond cell. The isothermal bulk modulus of chondrodite, determined using the Birch‐Murnaghan equation of state, is 136.2 GPa with a pressure derivative of 3.7. Using our results, we have constructed density models for hydrous upper mantle compositions. These models indicate that up to 2 weight percent water could be present in a pyrolitic mantle, and be undetectable using seismically‐determined density constraints. We have also investigated the stability of chondrodite under lower mantle pressure and temperature conditions using the laser‐heated diamond cell. From in‐situ x‐ray diffraction at high pressure, and x‐ray diffraction and infrared reflectance and absorption spectra of quenched run products, we conclude that chondrodite breaks down to MgSiO3 perovskite, MgO and a hydrated melt at lower mantle pressures and temperatures.
A double‐planed seismic zone in Kamchatka from local and teleseismic data
Authors: Gorbatov A. , Suárez G. , Kostoglodov V. , Gordeev E.
Published: February 2004

The fine structure of a double‐planed deep seismic zone is studied over a wide area of the Kamchatka peninsula. This prominent feature of deep seismic zone configuration is ascertained through the analysis of microearthquake hypocenters from the local seismic network of the Institute of Volcanology of Kamchatka and 22 focal mechanism solutions from the formal inversion of long‐period P and SH waves for events with mb≥5.5. Additionally, 11 focal mechanism solutions estimated from the first motion of P‐waves and 12 centroid moment tensor solutions of Harvard University are used. The maximum depth of the double seismic zone is 170–180 km. The two planes of seismicity are separated by 40 km at a depth of 50 km, and by 10–15 km at 180 km depth. The focal mechanism solutions of shallow earthquakes show an abrupt change from the thrust events to down‐dip compressional events at approximately 60 km depth at the upper boundary of the descending slab. Within the descending slab, the earthquakes with down‐dip tensional axis form the lower plane of the double‐planed deep seismic zone. Several earthquakes with down‐dip tensional axis are discovered in a narrow area of the upper seismic zone at the depth of about 50 km. The double seismic zone is revealed clearly in the area between ∼52°N to ∼54°N and probably extends up to ∼56°N.
A seismic experiment in the Ulleung Basin (Tsushima Basin), southwestern Japan Sea (East Sea of Korea)
Authors: Kim Han Joon , Park Chan Hong , Hong Jong Kuk , Jou Hyeong Tae , Chung Tae Woong , Zhigulef V. , Anosov G. I.
Published: February 2004

Understanding the crustal structure of the Ulleung basin (Tsushima basin) in the southwestern Japan sea (East sea of Korea) is important for reconstructing the opening tectonics of the Japan sea. A Korea and Russia collaborative seismic experiment was carried out in 1991 to investigate the crustal structure of this basin using ocean bottom seismometers (OBSs) and large capacity air guns. The results of the experiment reveal that the Ulleung basin is floored by distinctive upper and lower crustal layers with velocities typical of layers 2 and 3. The lower crust, however, is unusually thick (7–8 km) and the Moho lies flat at 15–16 km depths. Though similar to the Yamato basin in crustal thickness, the Ulleung basin has a much thicker sedimentary sequence and a slightly thinner lower crust in the center. Geophysical evidence, thus, shows that the crust under the Ulleung basin has velocity range and crustal layering falling closer to those of normal oceanic crust than the Yamato basin. The formation mechanism of the thicker than normal lower crust should be clarified to better understand the complex opening process in the southern Japan sea.
Piezometric levels as possible geodynamic indicators: Analysis of the data from a regional deep waters monitoring network in northern Italy
Authors: Albarello D. , Martinelli G.
Published: February 2004

An extensive piezometric survey has been carried out in the southern part of the Po sedimentary basin (in Northern Italy) since 1976. Periodic measurements on a network of 400 deep wells drilled in confined or semiconfined aquifers have been utilized. The 17‐year data set has been statistically processed and a band pass algorithm has been applied in order both to detect possible multiyear periodicities and to remove long term linear trends and relatively rapid fluctuations induced by meteorological and tidal effects or anthropogenic exploitation. Regional piezometric fluctuations, characterized by multiannual fluctuations with maximum excursions of 50 to 100 cm, have been identified. A slow‐moving crustal deformation front propagating inside a rheologically stratified lithosphere could explain these fluctuations.
Properties of the mantle‐like magnetotail boundary layer: GEOTAIL data compared with a mantle model
Authors: Siscoe G. L. , Frank L. A. , Ackerson K. L. , Paterson W. R.
Published: February 2004

Near the tail boundary beyond about 100 Re, GEOTAIL often encounters a plasma mantle‐like boundary layer in which the plasma flowing tailward transitions smoothly from magnetosheath values of speed and density to much smaller values, more characteristic of the tail lobe. This boundary layer had earlier been recognized on the basis of ISEE 3 measurements. GEOTAIL confirms the existence of this layer and extends the documentation on its behavior. Boundary oscillations sweep the boundary layer over the spacecraft enabling GEOTAIL to “sound” the layer's profile of plasma parameters. The density‐versus‐speed correlogram of the mantle‐like part—a useful diagnostic for comparisons—is reasonably well simulated by a 1‐D, MHD slow‐mode expansion fan model of the plasma mantle. Flow directions are consistent with an open plasma mantle on the northern, duskside flank of the tail, as expected for the standard magnetic merging model of mantle formation.
Survey of electron and ion bulk flows in the distant magnetotail with the Geotail spacecraft
Authors: Frank L. A. , Paterson W. R.
Published: February 2004

A histogramic survey is reported for the electron and ion bulk flows in Earth's magnetotail at geocentric radial distances in the range of about 10 to 210 RE from the Comprehensive Plasma Instrumentation on board the Geotail spacecraft. Specifically the X‐components of the bulk flows are examined for high ion temperatures, > 5 × 106 K, and for the lower ion temperatures. This separation of plasmas provides a reasonably effective criterion for identifying the hot plasmas associated with the plasma sheet and its boundary layers and the colder plasmas found in the magnetotail lobes and magnetopause boundary layer. The survey shows that the distributions of earthward bulk flows of ions and electrons are similar for each of the two temperature regimes, respectively. However, average speeds for the ions and electrons as a function of radial distance are dissimilar in that the electron bulk speeds are greater than those for the ions. All average electron and ion bulk flows are directed tailward at geocentric radial distances >30 RE. The most striking dissimilarity in the occurrence frequencies of the bulk flows is the large number with high tailward speeds for the electrons, >500 km/s, relative to those for the ions. One such example which also exhibits a plasmoid‐like magnetic signature is presented in detail. It is found that the disparity in bulk flows is due to the presence of two ion velocity distributions, one with high temperatures and a bulk speed similar to that of the electrons and the second, colder distribution with higher number density and considerably lesser bulk flow speed. Thus a current is associated with the high‐speed electron flow. An assumption of co‐moving ions and electrons is not valid for this event.
Direct entry of dense flowing plasmas into the distant tail lobes
Authors: Mozer F. S. , Hayakawa H. , Kokubun S. , Nakamura M. , Okada T. , Yamamoto T. , Tsuruda K.
Published: February 2004

Electric field, magnetic field, and spacecraft potential measurements on the Geotail satellite have confirmed earlier observations of relatively dense flowing plasmas in the magnetotail lobes. Within these flowing plasmas, density discontinuities of factors of 2 to 4 were observed. At least 15 of the 18 magnetopause crossings that occurred during a 24‐hour interval when the spacecraft was at GSM coordinates near X=−140 Re, Y=0, and Z=15 Re, were rotational discontinuities across which the magnetosheath plasma had direct entry into the tail lobes. Within the lobes near the rotational discontinuities, the spacecraft typically crossed a second boundary at which the plasma density decreased from its magnetosheath value by a typical factor of 1.5 to 3 while the magnetic field strength and flow speed increased. Equatorward of this density discontinuity, the plasma density and flow remained appreciable. At least 2 of the 18 magnetopause crossings may have been tangential discontinuities across which the density and magnetic field strength both changed. Within the lobes near these tangential discontinuities, significant densities of flowing plasma were observed. Since 11 of the 18 discontinuities were crossed within a time interval of less than 7 seconds, the boundary current layer was well‐defined and very thin.
Gravity study of the Pitcairn‐Easter Hotline
Authors: Maia M. , Dehghani G. A. , Diament M. , Francheteau J. , Stoffers P.
Published: February 2004

Shipboard free air gravity and bathymetric anomalies with an extension of 400 km were identified across the Pitcairn‐Easter hotline in the South Pacific. The anomalies are associated with one of the positive geoid undulations observed in the area from satellite data. Several smaller topographic features, volcano‐tectonic ridges oriented N65°E, are superimposed on the topographic high. Admittance computations and direct modeling show that the swell topography is compensated by a low density zone within the lithosphere, 4 to 8 km below the crust The volcano tectonic ridges are locally compensated in a classical Airy sense. The swell and the associated ridges were probably created by the action of a thermal anomaly resulting from the interaction of the Easter Island hotspot and of the Easter Microplate accretion centers.
Inverted‐V events simultaneously observed with the Freja satellite and from the ground
Authors: Haerendel G. , Frey H. U. , Bauer O. H. , Rieger E. , Clemmons J. , Boehm M. H. , Wallis D. D. , Lühr H.
Published: February 2004

The paper reports data received from the Freja satellite during two passes over broad auroral arc systems or inverted‐V events above Gillam/Manitoba when special wide‐angle CCD cameras were operated at this location in addition to the CANOPUS network. Detailed comparisons of the visible structures with modulations of the primary electron fluxes are performed. Motions of this fine structures are interpreted in terms of high‐altitude electric fields shielded from the lower ionosphere. Simultaneous readings of current density, accelerating voltage and energy flux, the latter determined both from particle and auroral brightness measurements, are found to be internally consistent. We calculate from these data the effective resistance encountered by the electric currents and find agreement with the kinetic theory of the mirror impedance, if we allow for substantial variations in density and energy of the source electrons in the magnetosphere.
An analysis of aircraft exhaust plumes from accidental encounters
Authors: Zheng J. , Weinheimer A. J. , Ridley B. A. , Liu S. C. , Sachse G. W. , Anderson B. E. , Collins J. E.
Published: February 2004

An analysis of data obtained during the second Airborne Arctic Stratospheric Expedition (AASE‐II) was made with emphasis on aircraft exhaust plumes accidentally encountered during the mission. Twenty spikes were found with peak NOy increments ≥1 ppbv. The examination of CO and CO2 indicates that there was only one NOy spike having clearly corresponding spikes of both CO and CO2, and another four with unambiguous CO2 spikes. No significant increases were found for CH4 and N2O for these 5 spikes. The ratio of the excess CO2 and NOy compares well with the ratio of published subsonic aircraft emission indices. The study of the selected spikes from the DC‐8 and another two spikes observed during other missions shows that the odd nitrogen other than NOx accounts for a very small percentage of the NOy increase associated with the observed spikes.
Nitrous oxide and methane emissions from aero engines
Authors: Wiesen P. , Kleffmann J. , Kurtenbach R. , Becker K. H.
Published: February 2004

The emissions of nitrous oxide and methane from a Pratt & Whitney Canada PW 305 and a Rolls Royce RB 211 jet engine were measured under various flight conditions either on a ground level stationary test stand or in altitude test cells by using an off‐line sampling technique. The concentrations of the gases were determined by long path infrared diode laser absorption spectroscopy in the laboratory. The calculated emission indices indicate that, at present, air traffic does not contribute significantly to the global budgets of methane and nitrous oxide.
Rupture process of the 1992 Erzincan Earthquake and its implication for seismotectonics in eastern Turkey
Authors: Pinar A. , Honkura Y. , Kikuchi M.
Published: February 2004

The 13 March 1992 Erzincan earthquake is different from the previous earthquakes which have occured along the North Anatolian fault zone (NAFZ) in that no surface rupture was observed. In order to infer a rupture process of this earthquake, we inverted the teleseismic body waves to the source using the method of Kikuchi and Kanamori [1991]. Three different subevents were then distinguished with total seismic moment of Mo = 1.2 × 1026 dyn·cm. The major energy release was found to be during the first subevent with seismic moment of Mo = 9.4 × 1025 dyn·cm, rupture length of 30 km, slip amount of 0.7 m and stress drop of 25 bars. The second subevent was right‐lateral, as was the case for the first one, with a normal faulting component. It was located 10 km to the southeast from the first one at the intersection of the right‐lateral NAFZ with the left‐lateral Ovacik fault. The third subevent with a right‐lateral mechanism was 10 km to the southeast from the second one. These results are in good harmony with regional seismotectonics in eastern Turkey.
Impact of present aircraft emissions of nitrogen oxides on tropospheric ozone and climate forcing
Authors: Hauglustaine D. A. , Granier C. , Brasseur G. P. , Mégie G.
Published: February 2004

A two‐dimensional (2‐D) model in which dynamics, radiation and chemistry are treated interactively is used to investigate the seasonal changes in tropospheric ozone due to current nitrogen oxide emissions from aircraft and to assess the associated radiative forcing on the climate system. Our results confirm the high efficiency of nitrogen oxide in‐situ emissions in producing ozone in comparison to surface emissions. The ozone increase is characterized by a strong seasonal variation; it reaches more than 7% during summer in the upper troposphere at northen mid‐latitudes. On a global average basis, the radiative forcing associated with this ozone increase appears to be small in comparison to that of other greenhouse gases. However, it may play a significant role in the anthropogenic forcing on northern hemisphere climate.
A new experimental approach for incremental batch melting of peridotite at 1.5 GPa
Authors: Hirose Kei , Kawamura Katsuyuki
Published: February 2004

Melt generation by incremental batch melting of peridotite with a complete melt withdrawal was experimentally investigated. The experiments were made using the “diamond aggregate method” at 1.5 GPa with increasing temperature from 1275° to 1425°C and total degree of partial melting to 22.6 wt.%. The incremental batch melting significantly differs from the batch melting in amount and composition of melt formed. The total degrees of partial melting formed by incremental batch melting are considerably lower than those formed by batch melting at the same temperatures. The compositions of incremental melts change more rapidly than do those of batch melts with increasing temperature. The accumulated compositions of incremental melts are, however, similar to those of batch melts formed by the same total degrees of partial melting. If melts are generated isobarically, both the melting processes can form melts with similar major oxide compositions, but the temperatures needed are significantly different.
Variation of pore fabric across a fold‐thrust structure
Authors: Pfleiderer Sebastian , Kissel Catherine
Published: February 2004

Variations of pore orientation, pore shape, porosity, and hydraulic permeability, within a siltstone unit of a fold‐thrust structure, are determined using magnetic pore fabric analysis, mercury injection porosimetry, and scanning electron microscopy (SEM). While samples in the foreland show evidence for the preservation of depositional pore geometry, the progressively deformed thrust sheet reveals increasingly oblate pore fabric anisotropy with microcrack planes oriented normal to the tectonic transport direction. Porosity, pore throat sizes, and permeability, show corresponding spatial variations across the structure. Independent of the deformation state within the thrust sheet, pore and magnetic grain fabric correlate closely in orientation.
Increase of seismic velocities in upper oceanic crust and hydrothermal circulation in the Juan de Fuca plate
Authors: Rohr Kristin M. M.
Published: February 2004

Two multi‐channel seismic reflection profiles have been analyzed for interval velocities and thicknesses of seismic layer 2A in crust 0–4.5 Ma created at the Endeavour segment of the Juan de Fuca plate. Stacking velocities were interpreted using the Dix assumption for interval velocity and thickness. Stacking velocities were picked from constant velocity stacks as well as normally moved‐out gathers at an interval of .2 to 2 km. Interval velocities are 3000–3500 m/s close to the ridge axis and begin to increase at 0.6 Ma when the crust is covered with a few hundred meters of Pleistocene sediments. Velocities are over 5000 m/s by 1.2 Ma, 20 km from the nearest basement outcrop. This increase is associated with an increase in basement temperature from 2–25°C to 30–50°C as heat flow values approach the predicted conductive cooling curve and the basement hydrothermal regime changes from fully open to mostly closed. Mineralisation in the abundant porosity of the upper crust is probably triggered by these thermal changes and results in increased seismic velocity. This is the first study to correlate an increase in seismic velocity with the hydrothermal regime in upper oceanic crust and demonstrates that such changes can occur in a remarkably short time.
Directional wind wave development
Authors: Long Steven R. , Huang Norden E. , Mollo‐Christensen Erik , Jackson Frederick C. , Geernaert Gerald L.
Published: February 2004

Using aircraft radar instruments designed for sea surface wave measurements, we have obtained fetch‐limited directional wind wave spectra under steady off‐shore wind conditions. The results from these observations in different areas at different times show that, up to a fetch of 150 km, the dominant waves propagate at an angle to the wind. The angle is near to that suggested by the Phillips resonance wind wave generation condition, but with one important difference: The waves are not always symmetric to the left and right of the wind. Most of the cases show the eventual dominance of one side lobe. The asymmetry of the wave direction relative to the wind suggests that the surface wind stress vector may not always be parallel to the mean wind direction.