bluuebunny/crossref_metadata_2025 huggingface dataset:
THE ROLE OF NEGATIVE BELIEFS IN POSTTRAUMATIC STRESS DISORDER: A COMPARISON OF ASSAULT VICTIMS AND NON VICTIMS
Authors: Ali Tarick , Dunmore Emma , Clark David , Ehlers Anke
Published: September 2002

The aim of this study was to compare the trauma sensitive beliefs of individuals who had never experienced an assault with the preassault and postassault beliefs of assault victims. Seventy-two individuals who had never experienced an assault completed a questionnaire designed to assess trauma sensitive beliefs (including beliefs about self-worth, safety and the trustworthiness of others). The beliefs of this group were then compared with the preassault and postassault beliefs of assault victims with persistent PTSD and assault victims who had never experienced PTSD, recruited for previous studies (Dunmore, Clark, & Ehlers, 1999, 2001). Results showed that victims who did not develop PTSD following assault reported significantly more positive preassault beliefs in comparison with those who had never been assaulted. The postassault beliefs of the persistent PTSD group were significantly more negative than the beliefs of the never assaulted group and the no PTSD assault group. Findings support evidence that suggests a relationship between negative beliefs after assault and the development of PTSD. In addition, positive preassault beliefs might play a “buffering” role, minimizing the impact of assault for those assault victims who do not subsequently develop PTSD.
Overview of the Issue
Authors: BROWN JEFFREY , HABERMAN STEVEN , MILEVSKY MOSHE , ORSZAG MIKE
Published: September 2002

As we noted in our introduction to the first issue of the Journal, the mission of the
journal is to serve as a forum for the international debate on pension provision. We
are therefore keen as the Editors that the articles and ideas discussed in each issue are
made accessible to as broad an audience as possible. This ‘Overview’ will introduce
each issue, reviewing what the editors view as the main results and context for each
article.
Cooperative and Competitive Binding in Synergistic Mixtures of Thermobifida fuscaCellulases Cel5A, Cel6B, and Cel9A
Authors: Jeoh Tina , Wilson David B. , Walker Larry P.
Published: September 2002

Synergism between cellulases facilitates efficient hydrolysis of microcrystalline cellulose. We hypothesize that the effects of synergism, observed as enhanced extents of hydrolysis, are related to cellulase binding to the substrate in mixtures. In this study, direct measurements of bound concentrations of fluorescence‐labeled T. fuscaCel5A, Cel6B, and Cel9A on bacterial microcrystalline cellulose were used to study binding behaviors of cellulases in binary component reactions. The accuracy of the determination of fluorescence‐labeled cellulase concentrations in binary component mixtures was in the range of 7–9%. Data at 5 °C show that binding levels of cellulases in mixture reactions are only 22–70% of the binding levels in single component reactions. At 50 °C, however, most of the cellulase components in the same mixtures bound to extents of 40–126% higher than in the corresponding single component reactions. The degrees of synergistic effect (DSE) observed for the reactions at 50 °C were greater than 1, indicating that the components in the mixture acted synergistically, whereas DSE < 1 was generally observed for the reactions at 5 °C indicating anti‐synergistic behavior. Degrees of synergistic binding (DSB) were also calculated, where anti‐synergistic mixtures had DSB < 1 and synergistic mixtures had DSB>1. We conclude that the lower extents of binding at 5 °C are due to competition for binding sites by the cellulase components in the mixtures and the enhanced binding extents at 50 °C are due to increased availability of binding sites on the substrates brought about by the higher extents of hydrolysis.
Synthesis of New Polymer‐Bound Adenine Nucleotides Using Starburst PAMAM Dendrimers
Authors: Abdelmoez Wael , Yasuda Masahiro , Ogino Hiroyasu , Ishimi Kosaku , Ishikawa Haruo
Published: September 2002

Two types of new polymer‐bound adenine nucleotides were synthesized by coupling adenine nucleotides (ATP and ADP) with starburst polyamidoamine (PAMAM) dendrimers. The first type was obtained by coupling native adenine nucleotides directly with a carboxy‐terminated PAMAM dendrimer. In the second type, the nucleotides were modified by introducing a spacer arm containing a carboxylic end group ( N6‐R‐ATP and N6‐R‐ADP) and coupled with an amine‐terminated PAMAM dendrimer. Both types of the dendrimers were coupled with native or the modified nucleotides using the well‐known carbodiimide activation technique. The optimum coupling pH and temperature were 4 and 30 °C, respectively, for preparing the carboxy‐terminated PAMAM‐bound ATP or ADP, and were 9 and 50 °C, respectively, for preparing the amine‐terminated PAMAM‐bound N6‐R‐ATP or N6‐R‐ADP. The ATP or ADP contents in the synthesized polymers were found to be 4 mol of ATP or of ADP/mol of carboxy‐terminated PAMAM‐bound ATP or ADP and 25 mol of ATP or of ADP/mol of amine‐terminated PAMAM‐bound N6‐R‐ATP or N6‐R‐ADP. The coenzymatic activities relative to the native ATP of the carboxy‐terminated PAMAM‐bound ATP against glucokinase and hexokinase were 16 and 7%, respectively, and those of the amine‐terminated PAMAM‐bound N6‐R‐ATP 2 and 1%, respectively. The coenzymatic activities relative to the native ADP of the carboxy‐terminated PAMAM‐bound ADP and the amine‐terminated PAMAM‐bound N6‐R‐ADP against acetate kinase were 24 and 3.5%, respectively.
Optimal Approach for Classification of Acute Leukemia Subtypes Based on Gene Expression Data
Authors: Cho Ji‐Hoon , Lee Dongkwon , Park Jin Hyun , Kim Kunwoo , Lee In‐Beum
Published: September 2002

The classification of cancer subtypes, which is critical for successful treatment, has been studied extensively with the use of gene expression profiles from oligonucleotide chips or cDNA microarrays. Various pattern recognition methods have been successfully applied to gene expression data. However, these methods are not optimal, rather they are high‐performance classifiers that emphasize only classification accuracy. In this paper, we propose an approach for the construction of the optimal linear classifier using gene expression data. Two linear classification methods, linear discriminant analysis (LDA) and discriminant partial least‐squares (DPLS), are applied to distinguish acute leukemia subtypes. These methods are shown to give satisfactory accuracy. Moreover, we determined optimally the number of genes participating in the classification (a remarkably small number compared to previous results) on the basis of the statistical significance test. Thus, the proposed method constructs the optimal classifier that is composed of a small size predictor and provides high accuracy.
Siberian shelf sediments contain clues to paleoclimate forcing
Authors: Bauch Henning A. , Cremer Holger , Kunz‐Pirrung Martina
Published: September 2002

The Earth's heat budget is the result of a complex interaction that depends on the atmosphere, the oceans, and how this heat is exchanged geographically. Most people today are somewhat aware of a number of problems that may arise from global warming. However, to what extent these changes will occur remains a major issue in climate prediction. Obviously, one of the imminent features of the global climate system is the natural, steep temperature gradient that exists between the cold polar regions—where the Earth is most easily able to release heat—and the much warmer, lower latitudes. If one follows the more recent literature, there seems to be little doubt that future temperature increase will first be detected in the Arctic [Dickson, 1999], due to the various temperature‐related processes that occur there [Johannessen et al., 1995; Grotefendt et al., 1998].
Gilbert's De Magnete: An early study of magnetism and electricity
Authors: Malin Stuart , Barraclough David
Published: September 2002

Four hundred years might seem an excessively long time to wait for a book review, but there are reasons why a prompt review would have been difficult. Not only is De Magnete written in Latin, but it is also in the form of a scientific textbook. The language problem was overcome by Paul Fleury Mottelay and Silvanus P. Thompson, who translated the book into English in 1893 and 1900, respectively. The latter was published in connection with a beautiful tercentenary limited edition by the Chiswick Press that retains much of the flavor and appearance of the original. But the notion of a scientific textbook was unfamiliar when De Magnete first appeared in 1600. Certainly, scientific subjects and even geomagnetism had been written about (for example, by Petrus Peregrinus in his Epistola De Magnete, 1269), but as reports of equipment and phenomena rather than as in‐depth investigations of a subject with experimental evidence and interpretation.
Space geodesy monitors mass transports in global geophysical fluids
Authors: Chao Ben F. , Dehant V. , Gross R. S. , Ray R. D. , Salstein D. A. , Watkins M. M. , Wilson C. R.
Published: September 2002

Large‐scale mass transports in the Earth system produce variations in Earth's rotation, gravity field, and geocenter. Although relatively small, these global geodynamic effects have been measured by space geodetic techniques to increasing, unprecedented accuracy, opening up important new avenues of research that will lead to a better understanding of global mass transport processes and the Earth's dynamic responses.

To take full advantage of these advances, the International Earth Rotation Service (IERS), the organization that monitors the rotational motions of the Earth and related properties, saw the need in 1998 to create an infrastructure to facilitate the link between the space geodetic measurement and the geodynamic “global change” research communities [Dehant et al., 1997]. Hence was born the IERS Global Geophysical Fluids Center (GGFC).
Isoprene emission from tropical forest canopy leaves
Authors: Keller Michael , Lerdau Manuel
Published: September 2002

We screened 51 species of trees and vines for isoprene emission by using a tower crane to gain access to the top of the canopy in a semideciduous forest in the Republic of Panama. Of the species screened, 15 emitted isoprene at rates greater than 0.8 nmol m−2 s−1. We measured the influence of light and temperature on emissions. The species‐dependent emission rates at 303 K and 1000 μmol m−2 s−1 of incident photosynthetically active radiation ranged from 9 to 43 nmol m−2 s−1 with coefficients of variation of about 20%. Isoprene emission showed a hyperbolic response to light intensity and an exponential response to temperature. We modified an existing algorithm developed for temperate plants to fit the temperature response of these tropical species. We suggest a new algorithm to fit the light response of isoprene emission. The new and modified algorithms are compared to the algorithms developed for temperate plants that are used in global models of isoprene emission. Both sets of algorithms also are compared to additional validation data collected in Panama and to published data on isoprene emission from a tropical dry forest in Puerto Rico. Our comparisons suggest that algorithms developed for temperate plants can significantly underestimate isoprene emissions from tropical forests at high‐light and high‐temperature levels.
Carbon accumulation in the mineral subsoil of boreal mires
Authors: Turunen Jukka , Tolonen Kimmo , Tolvanen Satu , Remes Markku , Ronkainen Jaana , Jungner Högne
Published: September 2002

The carbon density and the long‐term (apparent) rate of carbon accumulation (LORCA) in the mineral subsoil of boreal mires in Finland formed by paludification were studied by comparison to adjacent forest soil sites with similar podzolic texture and topography. On the basis of 273 soil profiles from six areas, the mean carbon density in the mineral subsoil of mire sites was 1.5‐fold higher than in adjacent forest profiles. The average carbon input was 13.6 ± 1.8 (SE) g m−2 yr−1 which differed according to length of time since the onset of paludification. LORCA estimates were highest on the youngest mire sites (< 500 years) and agree with estimates obtained for peat deposits elsewhere in the boreal region. Bogs and topographically flat areas were found to have higher LORCA values than the fens and the topographically steeper areas. The carbon stored in podzols in boreal forest reach equilibrium with soil age after 1500–2000 years, while in the mineral subsoil of mires the equilibrium is reached after 4500–5000 years after initial paludification. A direct comparison of carbon below mires to the equivalent depths of peat above indicates that peats are much more efficient in C sequestration. In this study, the average total C density in the mineral subsoil of mire areas to a depth of 70 cm from the bottom of the A horizon would correspond to a peat depth of about 18 cm. Still, the mineral subsoil under mires is a significant carbon sink, hitherto overlooked, and could account for some 5% of the unaccounted for carbon in the global carbon budget.
O‐Mode Emission at the Io Torus: A Real or Virtual Source?
Authors: Farrell W. M. , Hess R. A. , MacDowall R. J.
Published: September 2002

We examine the nature of an ordinary (o‐mode) emission observed near the Io plasma torus during the 1992 Ulysses encounter with Jupiter. The emission appears to intensify by factors of 10–100 in local torus density depletions. We examine whether these intensifications are due to local generation within the density depletion or reflection of a remotely generated emission. Based on the observed emission spectra, we find that a virtual source is most consistent with the character of the local enhancements. This virtual source observation near the dense torus may be relevant to the understanding of a newly discovered torus‐related hectometric emission by the Galileo orbiter.
A clue regarding the origin of rock varnish
Authors: Fleisher Martin , Liu Tanzhuo , Broecker Wallace S. , Moore Willard
Published: September 2002

137Cs and excess 210Pb have been found in rock varnish samples from several localities in the desert regions of the western United States. As 137Cs was absent in the environment prior to the atmospheric testing of nuclear weapons, and as 210Pb has a half life of only 22 years, these isotopes must have been added to this slow growing patina during the last half of the present century, demonstrating that, at least in part, the elements constituting varnish are supplied from the atmosphere. The discovery opens a window into the mechanism by which this mysterious substance forms. Not only radioisotopes but also anthropogenic metals can be harnessed to assess the ratio of rate of accumulation of a given element on varnish to its delivery rate from the atmosphere. Based on measurements reported here, for 210Pb this ratio is about 0.1 and for 137Cs about 0.01.
Evidence of non‐LTE effects in mesospheric water vapor from spectrally‐resolved emissions observed by CIRRIS‐1A
Authors: Zhou D. K. , Mlynczak M. G. , López‐Puertas M. , Zaragoza G.
Published: September 2002

Evidence of non‐LTE effects in mesospheric water vapor as determined by infrared spectral emission measurements taken from the space shuttle is reported. A cryogenic Michelson interferometer in the CIRRIS‐1A shuttle payload yielded high quality atmospheric infrared spectra. These measurements demonstrate the enhanced daytime emissions of H2O (020→010) which are the result of non‐LTE processes and in agreement with non‐LTE models. The radiance ratios of H2O (010→000) and (020→010) Q(1) transitions during daytime are compared with non‐LTE model calculations to assess the vibration‐to‐vibration exchange rate between H2O and O2 in the mesosphere. An exchange rate of 1.2×10−12 cm³ s−1 is derived.
Detecting sub‐wavelength layers and interfaces in synthetic sediments using seismic wave transmission
Authors: Pyrak‐Nolte Laura J. , Mullenbach Beth L. , Li Xun , Nolte David D. , Grader Abraham S.
Published: September 2002

The interface between two different homogeneous sediment layers, each composed of uniform grain sizes, is a region of heterogeneity comprising a thin layer with a thickness typically much smaller than a seismic wavelength. Seismic waves propagating parallel to the interface experience a reduction in both their amplitude and frequency content but the effect on group velocity is unresolvable. In the case of a single homogeneous layer bounded on both sides by homogeneous halfspaces, the ability to spatially resolve the layer thickness from amplitude or frequency information is limited by diffraction when the layer thickness is smaller than a seismic wavelength. However, the presence of a subwavelength interface or layer is always marked by a decrease in amplitude and in some cases by a decrease in frequency.
Energetic particle abundances at CIR shocks
Authors: Fränz M. , Keppler E. , Lauth U. , Reuss M. K. , Mason G. M. , Mazur J. E.
Published: September 2002

The forward and reverse shocks that bound corotating interaction regions (CIRs) travel into different solar wind regimes. In order to test whether the energetic ions associated with the CIR shocks reflect the ambient solar wind, we investigate the elemental composition of 0.1–4.0 MeV/N ions in CIRs observed from 1 to 5 AU with instrumentation on board the Wind and Ulysses spacecraft. This is the first comparison of the abundances of energetic minor ions in CIR forward and reverse shocks. We find that apart from Helium (and Neon at 1 AU) the energetic particle abundances are roughly in agreement with the respective solar wind thermal abundances. He is overabundant by a factor of 2.5 at the CIR reverse shock at distances of 4 to 5 AU, while the forward shock abundance shows no He enhancement. There is no energy cutoff for the He acceleration observed below 2.0 MeV/N at 2 to 5 AU. This result is in qualitative agreement with models for pickup abundances in the inner heliosphere and suggests that only pickup He dominates the suprathermal solar wind He spectrum in coronal high speed streams.
Impact of future subsonic aircraft NOx emissions on the atmospheric composition
Authors: Grewe Volker , Dameris Martin , Hein Ralf , Köhler Ines , Sausen Robert
Published: September 2002

The effect of future subsonic aircraft emissions on the chemical composition of the atmosphere is investigated by means of the coupled dynamic‐chemical circulation model ECHAM3/CHEM. Present (1992) and future (2015 and 2050) atmospheric compositions are simulated with three sets of time slice experiments. Expected changes of the sea surface temperatures (SST), surface emissions of CFCs, greenhouse gases (GHG), and NOx (=NO+NO2) are prescribed. Model results show future increases in NOx and O3 due to aircraft NOx emissions, which scale almost linearily with the magnitude of the emission. The calculated climate change reduces the NOx concentration as well as its increase due to aircraft emissions by more than 10% at flight altitude in 2015. However, the aircraft induced ozone perturbation decreases only slightly when climate change is regarded.
Observations of heliospheric planar and offset‐planar magnetic structures
Authors: Jones G. H. , Balogh A. , Horbury T. S.
Published: September 2002

Planar magnetic structures are regions of solar wind plasma where the magnetic field orientation is constrained within a fixed plane for durations of several hours. Within these structures, magnetic field discontinuities are seen, with the discontinuity surfaces being almost co‐planar. The results of a survey of planar magnetic strutures detected by the Ulysses spacecraft are presented. When searching for these events using minimum variance analysis, a large population was detected of magnetic field structures whose directions described small circles in the spacecraft's field of view (as opposed to great circles described by “classic” planar magnetic structures). It is likely that these “small‐circle” events represents Alfvénic structures. Variations in the nature of the structures at various heliographic latitudes and differing solar wind conditions are described. Implications of the results of the survey are discussed.
The interannual change of atmospheric CO2: Contribution of subtropical ecosystems?
Authors: Gérard J. C. , Nemry B. , François L. M. , Warnant P.
Published: September 2002

The global terrestrial carbon cycle model CARAIB (CARbon Assimilation In the Biosphere) is used to study the response of the terrestrial ecosystems to the large scale climate variations over the period 1980–1993. The global net carbon exchange flux with the atmosphere is calculated and compared with the terrestrial contribution derived from the deconvolution of the atmospheric CO2 and δ13C measurements. A fairly large CO2 biospheric source is predicted during the strong El Niño events of 1982–83 and 1986–87 as a consequence of the induced global warming. The direct and indirect temperature controls of the primary production and respiration dominate the CO2 anomaly. An analysis of the relative contribution by latitudinal bands and ecosystems shows that low‐latitude vegetation dominates the variability at the El Niño time scale. In savannas, the model indicates that the interannual changes result, to a large extent, from the control of soil water content on gross primary production (GPP). In the tropical rain forests, both respiration and GPP contribute to the response of the net biospheric flux.
Sensitivity of equilibrium surface temperature of CCM3 to systematic changes in atmospheric CO2
Authors: Kothavala Zavareh , Oglesby Robert J. , Saltzman Barry
Published: September 2002

We have redone our computations of the equilibrium response of surface temperature to atmospheric CO2 concentrations using the latest version of the NCAR Community Climate Model (version 3 rather than version 1). Eight GCM simulations with CO2 concentrations varying from 180 to 3000 ppmv were conducted with CCM3 compared to six CO2 concentrations with CCM1. A preliminary examination of the CCM3 simulations showed the same basic non‐linear behaviour of temperature to CO2 concentrations obtained previously with CCM1. The magnitude of the sensitivities, however, were much lower in the new CCM3 runs than in the older CCM1 runs. Four possible reasons for the reduced sensitivity in CCM3 are discussed.
Simultaneous observations of energetic (∼150 keV) protons upstream of the Earth's bow shock at ACE and WIND
Authors: Haggerty D. K. , Desai M. I. , Mason G. M. , Dwyer J. R. , Gold R. E. , Krimigis S. M. , Mazur J. E. , von Rosenvinge T. T.
Published: September 2002

We report measurements of ∼150 keV proton intensity enhancements obtained at ACE and WIND when both spacecraft were upstream of the Earth's bow shock. We investigate differences in the onset times, the duration's, and the local magnetic field orientations for 4 events observed simultaneously at the two spacecraft. A simple statistical analysis shows only 2% of the simultaneous events could be random coincidences, which indicates that out of the 20 events observed at each spacecraft, the 4 simultaneous measurements are probably observations of the same events. Since these measurements were obtained when the two spacecraft were separated by distances >25 RE, these particles probably originate from a source region that possibly covers the scale size of the Earth's bow shock (∼10 RE), and this is substantially larger than the smaller source regions proposed by existing models.
Streamflow trends in the United States
Authors: Lins Harry F. , Slack James R.
Published: September 2002

Secular trends in streamflow are evaluated for 395 climate‐sensitive streamgaging stations in the conterminous United States using the non‐parametric Mann‐Kendall test. Trends are calculated for selected quantiles of discharge, from the 0th to the 100th percentile, to evaluate differences between low‐, medium‐, and high‐flow regimes during the twentieth century. Two general patterns emerge; trends are most prevalent in the annual minimum (Q0) to median (Q50) flow categories and least prevalent in the annual maximum (Q100) category; and, at all but the highest quantiles, streamflow has increased across broad sections of the United States. Decreases appear only in parts of the Pacific Northwest and the Southeast. Systematic patterns are less apparent in the Q100 flow. Hydrologically, these results indicate that the conterminous U.S. is getting wetter, but less extreme.
An Experiment Using NSCAT Winds in the Numerical Prediction of Tropical Mesoscale Rainfall Systems under the influence of terrain
Authors: Chang C. ‐P. , Lin S. ‐C. , Liou C. ‐S. , Liu W. Timothy
Published: September 2002

The rich mesoscale information in NSCAT winds over tropical coastal regions is used in numerical simulations of two June 1997 monsoonal cases occurring over Taiwan. It is shown that transient NSCAT mesoscale information over a localized area as small as 120 km × 240 km can result in significant improvement in the 24 h heavy rainfall forecast due to its effect on monsoonal convection and terrain effects.
Tropical E region field aligned irregularities: Simultaneous observations of continuous and quasiperiodic echoes
Authors: Choudhary R. K. , Mahajan K. K.
Published: September 2002

The antenna beam at 13°N off zenith direction of the Indian mesosphere‐stratosphere‐troposphere (MST) radar at Gadanki (13.5°N, 79.2°E) is orthogonal to geomagnetic field lines at 110 km altitude. This beam was used to observe E region field‐aligned irregularities during July–August 1994, February and June 1996, and July–September 1997 with a range resolution of 600 m. On a few occasions the radar was operated at 150 m range resolution also. Observations showed continuous and multiple echo regions during nighttime. However, out of the 15 nights of observations, quasiperiodic (QP) echoes were also detected on the nights of July 20–21, 1994, and September 3–4, 1997. In this paper, major features of these quasiperiodic echoes in the form of height‐time maps of echo intensity are presented. On July 20–21, 1994, quasiperiodic echoes with a periodicity of about 2–4 min from the altitude between 102 and 116 km appeared as tilted striations in the height‐time‐intensity maps. The rate of descent of altitude associated with these tilted striations was in the range of 40–60 m s−1. The fluctuations in the Doppler velocity along the length of striations resembled a wave structure with vertical wavelength of the order of 18–20 km. Observations on September 3–4, 1997, suggest that these high‐frequency waves initially modulate the Es layer up to an altitude as high as 120 km and produce the quasiperiodic variation in the echoes. As time progresses, the period of QP echoes as well as the echo expanse decreases, and finally the normal continuous layer emerges.
Studies of the auroral E region neutral wind through a solar cycle: Quiet days
Authors: Nozawa S. , Brekke A.
Published: September 2002

On the basis of the data obtained by the European Incoherent Scatter radar located in northern Scandinavia, we have studied E region neutral wind characteristics between 95 and 119 km under geomagnetic quiet conditions (Ap < 16) over a solar cycle between November 1986 and October 1996. Data of 56 days were analyzed and grouped in order to investigate variations of the wind in different seasons and solar cycle conditions. Seasonal and solar cycle dependences of mean winds as well as diurnal and semidiurnal amplitudes are found. Phase differences of the diurnal and semidiurnal components are less than 2 hours between different season and solar activity conditions. No prominent seasonal nor solar cycle dependence is found for the vertical component. Comparisons are made with model predictions and radar observations as well as UARS observations in terms of seasonal and solar cycle dependences of the wind. Possible roles of gravity waves are discussed in terms of the seasonal variation of zonal mean wind.
Widely spaced wave‐particle observations during GEOTAIL and Wind magnetic conjunctions in the Earth's ion foreshock with near‐radial interplanetary magnetic field
Authors: Berdichevsky D. , Thejappa G. , Fitzenreiter R. J. , Lepping R. L. , Yamamoto T. , Kokubun S. , McEntire R. W. , Williams D. J. , Lin R. P.
Published: September 2002

Several events have been identified of an ion foreshock extending up to 250 RE upstream of the Earth. These events occur mostly during periods of slowly drifting radial interplanetary magnetic field (IMF) when the 1‐min average values of the strengths of the IMF and the solar wind (SW) speeds are mostly steady. For their analysis an analytical solution to the problem of the closest approach of an IMF line to two spacecraft is given. We used this method to find intervals of magnetic conjunction between the bow shock and the upstream regions at GEOTAIL and Wind. This solution is obtained by determining the minimum angle θ (as a function of time) between the mean direction of the IMF (measured at Wind) and the vector‐difference (rWI‐r) of the locations of Wind and the point (attached on the field line) which went earlier by GEOTAIL. Here we take into account the mean drift of the flux lines with the SW, by assuming that the spacecraft were located in the same heliospheric magnetic domain. We have tested this method against a set of selected cases which show a steady presence of the ion foreshock close to the bow shock (GEOTAIL) and its sporadic presence far upstream (Wind). We have found our method to be accurate within a few Earth radii (RE). We have identified an outstanding candidate for the bow shock, GEOTAIL, and Wind sequential magnetic conjunction, which occurred on June 11, 1995. Additionally, this diagnostic technique has been applied to nine more intervals of simultaneous occurrences of intensity enhancements of broadband ultralow‐frequency (ULF) waves, and fluctuating fluxes of scattered energetic ions (40–140 keV). Very broad ion foreshock regions (> 40 RE) are commonly observed during the subset of events characterized by a high‐speed SW. The observed frequencies of the ULF waves are basically enhanced transversal modes in the range from ∼ 1/10 to 2/3 of proton cyclotron frequency, fcp. Fluctuations in the energetic ion fluxes were also observed in this frequency range for all the cases. Therefore we argue that the nature of the coupling between ULF waves and energetic ions is similar both in the near as well as far upstream regions of the Earth's bow shock.
Excitation of magnetospheric waveguide modes by magnetosheath flows
Authors: Mann Ian R. , Wright Andrew N. , Mills Katharine J. , Nakariakov Valery M.
Published: September 2002

Standard models of the Earth's outer magnetospheric waveguide assume that a perfectly reflecting magnetopause can trap energy inside the waveguide. In contrast, we show that the near‐noon magnetopause often acts as a leaky boundary, wave trapping only being possible for large magnetosheath flow speeds. Moreover, for sufficiently fast flow speeds, we show how waveguide modes may be energized by magnetosheath flows via the overreflection mechanism. Unbounded simulations of the growth of surface waves via the development of a Kelvin‐Helmholtz instability (KHI) vortex sheet show growth rates which increase without limit proportional to wavenumber (ky), until the assumption of a thin boundary is no longer valid. For a bounded magnetosphere, however, overreflected body type waveguide modes can introduce wavenumber selection, that is, generate modes with maximum linear growth rates at finite ky. A necessary condition is that the wave is propagating in the magnetosphere, that is, the wave's turning point lies inside the magnetosphere. By developing a new description of both KHI and waveguide mode growth in terms of overreflection and the propagation of negative energy waves, we show how the maximum growth rate can be understood in terms of the reflection coefficient of waves incident upon the magnetopause. Our model can also explain the observed local time dependence of Pc5 field line resonance wave power, and can explain the observed correlation between high solar wind speeds and Pc5 wave power. Finally, we show how a waveguide with a free magnetopause boundary supports quarter‐wavelength modes. These modes have lower frequencies than the standard (magnetopause velocity node) half‐wavelength modes, perhaps generating the millihertz waveguide mode eigenfrequencies which appear to drive field line resonances in HF radar data.
Parameterization of the Defense Meteorological Satellite Program ionospheric electrostatic potentials by the interplanetary magnetic field strength and direction
Authors: Papitashvili V. O. , Rich F. J. , Heinemann M. A. , Hairston M. R.
Published: September 2002

In this study we applied a linear regression analysis technique to the interplanetary magnetic field (IMF) data and the ionospheric electrostatic potentials obtained from thermal ion drift measurements made by the Defense Meteorological Satellite Program (DMSP) satellites F8 and F10–F13 in 1993–1996. The ionospheric potentials are binned by every 1° of the corrected geomagnetic latitude and 0.5 hour of magnetic local time over both the northern and southern polar regions. The regression analyses are applied to the DMSP data in each bin in a similar way to what was done with the ground magnetometer data in the IZMIRAN Electrodynamic Model (IZMEM). This allowed us to parameterize the DMSP ionospheric potentials by the IMF strength and direction, as well as to recalibrate the IZMEM model against experimental satellite data. From the analysis it is calculated that the “background” cross‐polar potential drop estimated from DMSP data equals ∼33 kV if IMF ≈ 0. The calculated ionospheric potential responses to changes in the southward and northward IMF components are 11.5 kV/nT and −5.0 kV/nT, respectively.
Measurements of early and late time plasmasphere refilling as observed from geosynchronous orbit
Authors: Lawrence D. J. , Thomsen M. F. , Borovsky J. E. , McComas D. J.
Published: September 2002

Measurements of the cold ion density at geosynchronous orbit obtained by Los Alamos magnetospheric plasma analyzers over the course of 7 years are used to estimate the rate of plasmaspheric refilling at early times in the refilling process (≤24 hours) and at late times (up to several days during intervals of prolonged geomagnetic quiet). While the measured refilling rates are highly variable, we find that plasmasphere refilling at geosynchronous orbit occurs as a two‐step process: for early times the refilling rate is ∼0.6–12 cm−3 d−1, while for later times the refilling rate rises up to 10–50 cm−3 d−1. These results are consistent with a model of plasmasphere refilling which uses Coulomb collisions as a dominant trapping mechanism [see Wilson et al. 1992].
Polar cap area and boundary motion during substorms
Authors: Brittnacher M. , Fillingim M. , Parks G. , Germany G. , Spann J.
Published: September 2002

The area of the polar cap as a function of local time and substorm phase was measured using images from the Polar Ultraviolet Imager (UVI) for different interplanetary magnetic field (IMF) orientations during three substorms in January 1997. We measured changes in the polar cap area and motion of the poleward and equatorward boundary of the auroral oval. It was found that the polar cap boundary is strongly influenced by thinning of the oval, decrease in polar cap structures, the poleward expansion of the substorm at midnight, and the fading of luminosity below the instrument sensitivity threshold. Generally, these effects dominate over the latitudinal motion of the auroral oval at its equatorward edge. A new feature is that the polar cap region clears of precipitation during the substorm growth phase, which expands the size of the polar cap but is not necessarily related to an expansion of the open flux region. Another finding is that the increase in polar cap area prior to onset can be independent of the strength of the southward IMF component. For one case the polar cap area increased while the southward component of the IMF was 0 ± 0.5 nT. These observations have strong implications for models that use the polar cap area to estimate the magnitude of energy storage in the lobe magnetic field and loss during substorms.
An equilibrium model of the Earth's magnetotail: Thin current sheet and a near‐Earth neutral line
Authors: Wang Xiaogang , Bhattacharjee A.
Published: September 2002

An asymptotic two‐dimensional equilibrium model of the Earth's magnetotail, containing a thin current sheet and a near‐Earth neutral line, is derived. The effect of the dipole field is included. The model may be useful for investigations of particle orbits and magnetotail stability.
Basic physical mechanism of reconnection development and magnetic loop dynamics
Authors: Ugai M.
Published: September 2002

The basic features of nonlinear reconnection and magnetic loop development are studied by computer simulations in a wide variety of physical situations. Initiated by a small disturbance in a long current sheet system, magnetic reconnection builds up, and a magnetic loop is formed near the (left) wall boundary. For the spontaneous fast reconnection model, if the reconnection site is far from the wall, the quasi‐steady and symmetric fast reconnection mechanism is set up without any significant dependence on plasma parameters. The supersonic reconnection jet between a pair of standing slow shocks collides with the loop and gives rise to a strong fast shock ahead of the loop top. When the reconnection site is very close to the wall, the fast shock is much weaker and soon decays, and the fast reconnection process becomes asymmetric since the waves, reflected from the loop top, notably influence the X point. For the uniform resistivity model, magnetic reconnection proceeds much more slowly with no definite fast shock formation at the loop top. The X neutral point is not stable but collapses into a long diffusion region, and the elongation of the diffusion region becomes more rapid for the smaller resistivity. In this case, the magnetic energy conversion is performed by the Ohmic heating, whereas it is by the large‐scale motor (slow shock) effect for the spontaneous fast reconnection model.
Scaling of the shear rupture process from nucleation to dynamic propagation: Implications of geometric irregularity of the rupturing surfaces
Authors: Ohnaka Mitiyasu , Shen Lin‐feng
Published: September 2002

A series of systematic, high‐resolution laboratory experiments have been performed on the nucleation of propagating slip failure on preexisting faults having different surface roughnesses to demonstrate how the size scale and duration of shear rupture nucleation are affected by geometric irregularity of the rupturing surfaces. On the basis of the experimental results it has been discussed theoretically how consistently scale‐dependent physical quantities inherent in shear rupture are scaled. The experiments led to conclusive results that the nucleation process consists of two phases (phase I, an initial, quasi‐static phase, and phase II, a subsequent accelerating phase) and that the nucleation process is greatly affected by geometric irregularities on the rupturing surfaces. In phase I the rupture grows at a slow, steady speed which is independent of the rupture growth length L. In contrast, during phase II the rupture develops at accelerating speeds V, which increase with an increase in L, obeying a power law V/VS = α(L/λc)n, where VS is the shear wave velocity, λc is the characteristic length representing the geometric irregularity of the fault surfaces, and α and n are constants (α = 8.87 × 10−29 and n = 7.31). Scale dependency of scale‐dependent physical quantities, including the nucleation zone size and its duration, is commonly ascribed to scale dependency of the slip‐dependent constitutive law parameter Dc, which is in turn governed by λc. It has been discussed that a unified comprehension can be provided for shear rupture of any size scale if the constitutive law for shear rupture is formulated as a slip‐dependent law.
Geophysical interpretation of observed geocenter variations
Authors: Chen J. L. , Wilson C. R. , Eanes R. J. , Nerem R. S.
Published: September 2002

Geocenter variations are caused by mass redistribution within the Earth system, especially the atmosphere, oceans, and continental water. Using surface pressure fields, and soil moisture and snow depth fields of the NCEP‐NCAR Climate Data Assimilation System I (CDAS‐I)1, we estimate contributions from variations in atmospheric surface pressure and continental water storage to the Earth's geocenter (center of mass) variation. In addition, sea surface anomalies determined by the TOPEX/POSEIDON altimeter are used to investigate geocenter variations resulting from ocean mass redistribution. These sea surface height data were corrected using a simplified steric model. A comparison with observed geocenter variations derived from Lageos 1 and 2 satellite laser ranging data indicates that the atmosphere, oceans, and continental hydrological cycle all provide significant contributions at different frequencies. Geocenter variations estimated in this paper are in reasonably good agreement with results given by Dong et al. [1997] for atmospheric and ocean contributions, but not for the estimates of continental hydrological contributions.
Multifractal properties of visible reflectance fields from basaltic volcanoes
Authors: Laferrière A. , Gaonac'h H.
Published: September 2002

We investigate the multifractal characteristics of the visible reflected radiance field of active basaltic volcanoes acquired from satellite (SPOT) and aircraft sensors. Using various statistical methods, we first have demonstrated the scaling behavior of volcanic reflectance fields from Mount Etna (Italy) and Mauna Loa (Hawaii). For example, using box counting, we show that areas darker than a given threshold are fractal sets but with dimension depending critically on the threshold. Hence on the one hand, the optimum threshold for defining lava flows from the images is simply the one that gives the same dimension as that for flows measured on geological maps (even if maps and images are at quite different resolutions). On the other hand, the areas of the lava flows will themselves be strong power law functions of the resolution. For more quantitative statistical analysis we studied how statistical moments change with scale over a range of scales from 3 m to more than 40 km. Once again we found that the observed scaling involved a nonlinear exponent function instead of unique fractal dimension; i.e., we find multiscaling rather than monoscaling. This multiscaling is then shown to be well described by a universal multifractal process whose three parameters we estimate. We find quantitative similar multiscaling for the three fields with an index of multifractality (α = 1.8), which is near the theoretical maximum (α = 2) and which implies that monofractal frameworks (α = 0) are too simplistic. We compare and contrast these multifractal parameters with those of related geophysical fields, finding in particular that (unsurprisingly) the radiance field is statistically very close to the gradient of the topography. Finally, we argue that this scaling framework provides a promising avenue for understanding and modeling the heterogeneity, integrating remotely sensed data and other geological data into Geographical Information System (GIS) algorithms, and studying volcanological phenomena existing on Earth and other planets.
A degree 8 mantle shear velocity model from normal mode observations below 3 mHz
Authors: Resovsky Joseph S. , Ritzwoller Michael H.
Published: September 2002

We present inversions for a new three‐dimensional mantle υs model, MM2_L12D8, using a recently compiled catalogue of ∼2300 normal mode structure coefficients for 90 multiplets below 3 mHz. These inversions demonstrate the capabilities and limitations of existing normal mode data and reveal new images of structures in the midmantle (900–1800 km depth), which is poorly resolved by surface wave and body wave data. Our inversions are distinguished both by efforts to maintain consistency with a variety of seismic models, and hence data sets, and by attempts to characterize the sensitivity of our model to the choice of damping, to unspecified structures, and to data errors. We find that sensitivity to damping is the dominant source of model uncertainty, but MM2_L12D8 proves to be a robust model of υs with amplitude uncertainties less than 35% for most depths and degrees. Other characteristics of MM2_L12D8 include χ2 misfit to normal mode structure coefficients which is 58% smaller than that of the best existing models, greater similarity to existing models than they have to each other, perturbations relative to existing υs models that are largest in the midmantle, and amplitudes that are most consistent with existing models that employ global, rather than local, basis functions. MM2_L12D8 also displays definite images of “slabs” and “plumes” in the midmantle and a spectrum of heterogeneity that is more continuous with depth than in most other models. These characteristics suggest that the midmantle participates in a very long wavelength pattern of circulation that involves at least the whole lower mantle. Inversions for υp and ρ heterogeneities decorrelated from υs structure demonstrate that there is a significant signal from such structures in the normal mode data, but υp and ρ models are much more sensitive to damping than are υs models. The normal mode catalogue must be expanded before normal mode models of υp and ρ approach the reliability of the υs structures in MM2_L12D8. (This model, together with our catalogue of structure coefficients, is available at web site phys‐geophys.colorado.edu/geophysics/nm.dir.).
Relationship between seismicity and subsurface fluids, central Coast Ranges, California
Authors: Melchiorre E. B. , Criss R. E. , Davisson M. L.
Published: September 2002

Seismicity is irregularly distributed in the central Coast Ranges of California, with several large areas having virtually no seismic activity since 1968. Aseismic areas correlate with zones of abnormally high pore fluid pressures (AHPs) >130% of hydrostatic. Level line surveys suggest that aseismic areas have experienced significant historical uplift. Moreover, these aseismic areas show a remarkable correlation with perennial saline springs that represent technically expelled formation fluid, as indicated by their perennial flow, δ18O and δD enrichment to +6.3‰ and −13‰ respectively, elevated [B] to 331 ppm, and chemistry dominated by Na and Cl. Aseismic areas are dominantly located at the center of structural blocks that are under compression and are bounded by major faults and seismicity belts. Volumetric strain within these blocks creates pockets of overpressured formation fluid that greatly reduce seismic activity while promoting aseismic uplift. Seismic cross sections reveal three‐dimensional pockets of aseismicity that are floored and surrounded by scattered hypocenters. We suggest that overpressured formation fluids originate at depths of 1 to 7 km within these pockets, on the basis of Na‐K‐Ca geothermometry estimates that are consistent with stratigraphic information and available drill hole data. These overpressured fluid pockets may also influence seismicity on major faults, such as the upper 3 km of the active Greenville fault, which is relatively aseismic where it separates two overpressured pockets. Decreasing flow rates observed at some saline springs may represent a local transition to a period of increased seismic activity. While many studies have linked generation of earthquakes to man‐made fluid overpressures, our data show that the dominant, long‐term effect of AHPs is to reduce seismicity and promote uplift.