bluuebunny/crossref_metadata_2025 huggingface dataset:
Musik, Hemisphärenaktivation und das Gefallen von Portraits
Authors: Leichner Reinhard
Published: July 2003

Zusammenfassung. Die zentrale Hypothese besagt, dass Urteile über Portraits von Frauen und Männern positiv ausfallen, wenn beide Hemisphären annähernd ausgeglichen belastet bzw. aktiviert sind. Fließende oder rhythmusbetonte Musik wurde während des Betrachtens der Portraits monaural am rechten oder linken Ohr oder biaural eingespielt mit dem Ziel, bei monauraler Einspielung hauptsächlich die contralaterale Hemisphäre zu belasten. Da Portraits vorrangig rechtshemisphärisch verarbeitet werden, ist folglich die Belastung beider Hemisphären ausgeglichen, wenn die Musik der linken Hemisphäre dargeboten wird. Die zentrale Hypothese wurde bestätigt. Der Effekt war bei weiblichen Portraits ausgeprägter als bei männlichen. Im Sinne einer Passung von Geschlecht der Portraits und Musikart wurde der Effekt bei weiblichen durch fließende und bei männlichen Portraits durch rhythmische Musik unterstützt. Weiterhin ergab sich, dass weibliche Versuchspersonen die Musik als intensiver erlebten. Am Versuch nahmen 112 weibliche und männliche studentische Versuchspersonen teil.
Ein Instrument zur Messung der Wirkung emotionaler Valenzen auf die Wortverarbeitung
Authors: Huckauf Anke , Heller Dieter , Gouzoulis-Mayfrank Euphrosyne
Published: July 2003

Zusammenfassung. Um der Frage nach der Wirkung emotionaler Valenz auf die Wortverarbeitung nachzugehen wurde ein Instrument konstruiert, in dem auf positiv und negativ valente Wörter sowie auf neutrale Kontrollwörter reagiert werden muss. Die Konstruktion umfasste zunächst eine Selektion möglicher Items anhand von Bestimmungen ihrer emotionalen Valenz sowie ihrer Häufigkeit, Wortart, Buchstabenanzahl, Silbenanzahl und Konkretheit. In einer Durchführung mit einer lexikalischen Entscheidungsaufgabe zeigten 30 gesunde Probanden kürzere Reaktionszeiten für valente als für neutrale Wörter. Im Anschluss wurden zwei Parallelformen entwickelt, die auch vorher-nachher-Messungen erlauben. In beiden Parallelversionen wurden die Befunde mit 10 Versuchspersonen repliziert. Das Instrument bietet eine Grundlage für weitere Untersuchungen der Wechselwirkungen von Emotionen und Kognitionen.
Persönlichkeitstests in der Personalauswahl:
Authors: Marcus Bernd
Published: July 2003

Zusammenfassung. Die - vielfach belegte - Tatsache, dass Testpersonen in der Lage sind, ihre Ergebnisse in nicht leistungsbezogenen Testverfahren in Richtung sozialer Erwünschtheit zu erhöhen, wenn sie entsprechend instruiert werden, wird häufig als Begründung für die Empfehlung angeführt, auf den Einsatz von Persönlichkeitstests in der Personalauswahl generell zu verzichten. In dem Beitrag wird aufgezeigt, dass (a) dieser Schluss logisch falsch ist, (b) die empirische Befundlage nicht für eine Beeinträchtigung der Validität von Persönlichkeitstests durch “soziale Erwünschtheit“ spricht, (c) bei der Interpretation der Folgen von “faking“ oder “impression management“ eine sehr viel differenziertere Betrachtung der Implikationen theoretischer Überlegungen und empirischer Befunde notwendig ist sowie (d) die besonderen Anregungsbedingungen einer Bewerbungssituation sogar genutzt werden können, um die kriterienbezogene Validität von Persönlichkeitstests zu verbessern. Eine alternative Sichtweise der Selbstdarstellung in Persönlichkeitstests in Auswahlsituationen wird vorgestellt und es wird diskutiert, welche möglichen Folgen sich aus den Komponenten der Fähigkeit und Motivation zur Selbstdarstellung ergeben, die zusammen die Ergebnisse in Persönlichkeitstests determinieren.
Kontextabhängige Kreativität
Authors: Förster Jens , Friedmann Ron
Published: July 2003

Zusammenfassung. Menschliche Kreativität ist nicht nur ein Persönlichkeitsmerkmal, sie wird vielmehr stark durch den sozialen Kontext beeinflusst. Unsere motivationale Theorie der Kreativität basiert auf der regulatorischen Fokustheorie und dem Stimmung als Informations-Ansatz. Wir nehmen darin an, dass Menschen durch Reize in der Umgebung in einen Promotion Fokus der Annäherung oder einen Prevention Fokus der Vermeidung versetzt werden können. Ein Promotion Fokus begünstigt kreatives Denken, während ein Prevention Fokus dieses eher behindert. In zahlreichen Experimenten fanden sich hypothesenkonforme Ergebnisse, die in einem Überblick zusammengefasst werden sollen. Weiterhin werden neuere Ergebnisse präsentiert, die zeigen, dass vor allem die starke Perseveranz auf konventionellen Lösungen zu einer Minderung der Kreativität in einem Prevention Fokus führt. Abschließend sollen erste Experimente präsentiert werden, die zeigen, dass Annäherungsmotive die rechte Gehirnhälfte aktivieren, was wiederum kreatives Denken fördert, während Vermeidungsmotive die linke Gehirnhälfte aktivieren, was analytisches Denken fördert. Die Befunde werden auf der Grundlage bestehender Theorien diskutiert und Konsequenzen für den Alltag werden aufgezeigt.
Suicide Risk in Outpatients with Specific Mood and Anxiety Disorders
Authors: Chioqueta Andrea P. , Stiles Tore C.
Published: July 2003

Summary: The present study examined the relationships between specific anxiety, mood disorders, levels of hopelessness, and suicide ideation. The sample consisted of 606 outpatients recruited from several psychiatric settings. It was found that dysthymia was significantly associated with hopelessness. Patients presenting major depressive episode with higher anxiety symptoms had significantly increased scores on the hopelessness scale. Major depressive episode and bipolar disorder, but not dysthymia, were significantly associated with higher levels of suicide ideation. Increased levels of anxiety symptoms in patients with dysthymia were associated with increased levels of suicide ideation, while increased depressive symptoms in patients with specific phobia and generalized anxiety disorder were associated with significantly lower levels of suicide ideation. The findings suggest that depressive disorders, but not anxiety disorders, constitute risk for suicide. Moreover, the differentiation between a depressive and an anxiety disorder as the principal diagnosis, as well as the assessment of anxiety-level symptoms in patients with major depressive episode and dysthymia, seems of special relevance when assessing suicide risk.
Suicide Outside the Care of Mental Health Services
Authors: Owens Christabel , Booth Nicholas , Briscoe Martin , Lawrence Clive , Lloyd Keith
Published: July 2003

Summary: Background: Three-quarters of people who commit suicide are not in contact with mental health services at the time of death. No previous UK study has focused specifically on this group of suicides. Aims: To identify the characteristics of people who commit suicide while outside the care of mental health services. Method: A case-control study was conducted in SW England involving 100 individuals who committed suicide while not in contact with mental health services and 100 age-sex matched controls drawn from the living population. Data were collected by means of semistructured interviews with key informants and from medical records. Results: Key predictors of suicide were previous attempted suicide, social and interpersonal problems, current mental illness, past mental illness, and previous contact with specialist services. However, nearly a third of cases (32%) appeared to have no current mental disorder. Conclusion: This group is distinguished by a markedly lower rate of mental illness than has previously been recorded. The findings highlight the difficulty of identifying individuals outside specialist mental health care who are at risk of suicide and therefore support the continued development of broad population-based measures rather than the targeting of high-risk groups.
Injury and Poisoning Mortality among Young Men—Are There any Common Factors Amenable to Prevention?
Authors: Stanistreet D. , Jeffrey V.
Published: July 2003

Summary: Background: Deaths from injury and poisoning (suicide, accidents, undetermined deaths, and homicide) are the major cause of death among young men aged 15-39 years in England and Wales and have been increasing in recent years. Aim: To describe common characteristics among young men who die from injury and poisoning. Design: We employed a retrospective survey methodology to investigate factors associated with deaths by injury and poisoning among young men aged 15-39 years (n = 268) in Merseyside and Cheshire during 1995. Data were collected from Coroner's inquest notes and General Practitioner records. Main results: The most common cause of death was poisoning by alcohol and drugs (29.1%, n = 78). A high proportion of cases were unemployed (39.4%, n = 106). Cases were also more likely to be single compared to the general population (74.2% vs 55.5%). Self-destructive behaviour was evident in 77% of deaths (n = 206). Conclusions: Alcohol and drug use are important contributory factors to injury and poisoning deaths. More research is needed into the effects of unemployment and being single on the health of young men, and to investigate the motivations behind risk taking and self-destructive behaviour.
Seasonality in Suicide: A Study of Farming Suicides in England and Wales
Authors: Simkin Sue , Hawton Keith , Yip Paul S.F. , Yam Carrie H.K.
Published: July 2003

Summary: Seasonality in suicide rates has long been reported. Spring peaks in suicide deaths have been positively correlated with the proportion of the workforce engaged in agriculture. Some studies have indicated that suicides using violent methods are more likely to show seasonality. Recent research has suggested that seasonal patterns have diminished. This study examined deaths in male farmers, an occupational group which might be expected to be more vulnerable to seasonal influences because of the nature of their work and the relatively high proportion of farmers using violent methods for suicide. Data on suicides between 1982 and 1999 by males in England and Wales aged 15 years and over were provided by the Office for National Statistics. Seasonal patterns of suicide in farmers and nonfarmers were examined by nonparametric tests and harmonic analysis. No significant seasonal variation was found for farmers. For nonfarmers, although a chi-square test showed significant variation in monthly distribution, this was not found when a harmonic analysis was applied. There was no significant difference in the variation of violent suicides throughout the year. This study reinforces recent findings that seasonal variation in suicide appears to be diminishing, even in an occupational group where this might be expected.
Suicidal Behavior in a Young Offender Population
Authors: Howard J. , Lennings C.J. , Copeland J.
Published: July 2003

Summary: Young offenders have numerous problems, including increased psychopathology, housing, and psycho-social stresses and increased rates of substance abuse. The current study investigated the contribution that substance use might make to a particularly vulnerable group of young people. Of the 300 young people approached for the study, 23.7% reported a prior suicide attempt. For this group, the most significant predictors of a prior suicide attempt were negative affect, prior exposure to violence, and housing stress. Life-time substance-use variables were most predictive of the number of suicide attempts a young person might make. Self-reported lethality (the expectation that on the last attempt the young person expected to die) was not strongly predicted by any variable. The research identifies the important role that dynamic risk factors (such as mood, substance use, and psychosocial stressors) play in increasing the risk of self-harm for young offenders, and raises the need to provide for more comprehensive discharge planning and support in order to manage these needs.
Hydroplaning of subaqueous debris flows and glide blocks: Analytical solutions and discussion
Authors: Harbitz Carl B. , Parker Gary , Elverhøi Anders , Marr Jeffrey G. , Mohrig David , Harff Peter A.
Published: July 2003

Subaqueous debris flows often attain significantly higher velocities and longer run‐out distances than their subaerial counterparts in spite of increased viscous drag and reduced effective gravity due to buoyancy. Recent experimental research suggests that a basal lubricating layer of water associated with hydroplaning decouples the sediments from the bed, resulting in a dramatic reduction of the basal shear stress. Hydroplaning thus provides an explanation for these observations. The conditions for onset of hydroplaning are discussed in terms of critical densimetric Froude number. The stress reduction due to a lubricating layer of water or mud slurry is studied via equilibrium solutions for a two‐layer Couette flow. The calculations reveal that the stresses in both the low‐viscosity lubricating layer and the high‐viscosity deforming deposits below it are substantially reduced. The principles of laminar boundary layers are used to develop an equilibrium solution for the steady motion of a hydroplaning debris glide block. This adjusted version of lubrication theory properly accounts for hydroplaning associated with a dynamic pressure generated at the head of the block. Example calculations at both laboratory and field scale support the experimental results of reduced bed friction, limited erosion, sediment rheology independence, and high velocities. The results also reveal the possibility for a net up‐slope discharge in the lubricating layer.
Properties of flow and pressure over Georges Bank as observed with near‐surface drifters
Authors: Brink K. H. , Limeburner R. , Beardsley R. C.
Published: July 2003

During the 1995–1999 Northwest Atlantic GLOBEC project, 203 drifters drogued at nominally 10 m were deployed on or near Georges Bank. The objectives of the deployments were to characterize flow patterns and residence time properties. During all seasons, there was a tendency for clockwise flow around the bank, and this flow, along with the residence time, increased during the summer. Residence times ranged from typically 40 days during the winter to 90 days during the summer. The seasonal change in mean flow implies a role for processes beyond simple barotropic tidal rectification to be important in the dynamics. Regional subtidal frequency pressure patterns (estimated using the drifter data) dominate the sea level variability, but they play less of a role in the subtidal current variability. Instead, current variations seem to be more dominated by shorter‐scale patterns and (during winter) by flow associated with the surface Ekman layer. At 10 m depth, net current variability does not change much on a seasonal basis. A few events with particularly good drifter coverage are used to illustrate the effects of a Warm Core Ring south of the bank, and of strong winter and spring storms.
Deflation/erosion rates for the Parva Member, Dorsa Argentea Formation and implications for the south polar region of Mars
Authors: Bleacher Jacob E. , Sakimoto Susan E. H. , Garvin James B. , Wong Martin
Published: July 2003

The origins of the surficial materials in the geologic units surrounding the Martian southern polar region have been poorly constrained on the basis of pre‐Mars Global Surveyor (MGS) data and studies. MGS studies suggest that these units are the remnant of volatile loss from an originally massive volatile‐rich debris blanket or the result of fluidized slurries resulting from magma/volatile interactions or impact shaking. We use Mars Orbiter Laser Altimeter data to examine a region adjacent to the south polar layered terrain at 72°–79°S and 230°–275°E, generally equivalent to the mapped Parva member of the Dorsa Argentea Formation (DAF). The pedestal and “ghost” impact crater morphologies in this area suggest that extensive deposits of loosely consolidated materials have been removed from this region. The Parva member is thus likely to be the remaining debris blanket from the deflated remnant of an unprotected deposit that was originally similar to the buried DAF deposits in the adjacent Cavi member. Crater counts indicate that the Parva member is of Hesperian age and overlies an older Noachian surface, likely the highland cratered terrain (Npl1). If regional deflation began in the Hesperian and continues through today, the region has been exposed to erosion rates of 1.3–1.6 × 10−7 m/yr. However, if deflation started later than the assumed times or ceased in the Amazonian, when deposition of the polar layered deposits began, erosion rates as high as 2.–5.2 × 10−7 m/yr might have existed. These erosion rates are within the range of published Martian nonbedrock erosion rates of 10−8–10−5 m/yr.
Structure‐function‐based approach to analyzing received signals for spaced antenna radars
Authors: Praskovsky Alexander A. , Praskovskaya Eleanor A.
Published: July 2003

This paper describes an alternative approach to analyzing multiple received signals for spaced antenna radars. The approach is based on computation and analysis of the different order auto and cross structure functions (SF) for the received signal's power. SF of order p ≥ 2 is the p‐th order statistical moment of the difference between signals. Equations for cross and auto SF at p = 2 and 4 are derived for a spaced antenna radar with a vertically directed transmitted beam. SF parameters in these equations are related to the mean horizontal velocity components and turbulence characteristics of a scattering medium. Theoretical limitations on applying the derived equations to a specific radar are presented. Advantages and shortcomings of the proposed approach with respect to the correlation function and spectra‐based approaches are discussed as well. The major advantage of the proposed approach is that SF of any order p ≥ 2 can be derived and applied to practical measurements; the higher‐order SF provide additional information about the scattering medium.
Reconstructing the total shortening history of the NW Himalaya
Authors: Guillot Stéphane , Garzanti Eduardo , Baratoux David , Marquer Didier , Mahéo Gweltaz , de Sigoyer Julia
Published: July 2003

The onset of India‐Asia contact can be dated with both biostratigraphic analysis of syn‐collisional sedimentary successions deposited on each side of the Indus Suture zone, and by radiometric dating of Indian crustal rocks which have undergone subduction to great depths in the earliest subduction‐collision stages. These data, together with paleomagnetic data, show that the initial contact of the Indian and Asian continental margins occurred at the Paleocene/Eocene boundary, corresponding to 55 ± 2 Ma. Such dating, which is consistent with all available geological evidence, including the record of magnetic anomalies in the Indian ocean and decrease of magmatic activity related to oceanic subduction can thus be considered as accurate and robust. The sedimentary record of the Tethys Himalaya rules out obduction of oceanic allochtons directly onto the Indian continental margin during the Late Cretaceous. The commonly inferred Late Cretaceous ophiolite obduction events may have thus occurred in intraoceanic setting close to the Asian margin before its final emplacement onto the India margin during the Eocene. Granitoid and sedimentary rocks of the Indian crust, deformed during Permo‐Carboniferous rifting, reached a depth of some 100 km about 1 Myr after the final closure of the Neo‐Tethys, and began to be exhumed between 50 and 45 Ma. At this stage, the foreland basin sediments from Pakistan to India show significant supply from volcanic arcs and ophiolites of the Indus Suture Zone, indicating the absence of significant relief along the proto‐Himalayan belt. Inversion of motion may have occurred within only 5 to 10 Myr after the collision onset, as soon as thicker and buoyant Indian crust chocked the subduction zone. The arrival of thick Indian crust within the convergent zone 50–45 Myr ago led to progressive stabilization of the India/Asia convergent rate and rapid stabilization of the Himalayan shortening rate of about 2 cm yr−1. This first period also corresponds to the onset of terrestrial detrital sedimentation within the Indus Suture zone and to the Barrovian metamorphism on the Indian side of the collision zone. Equilibrium of the Himalayan thrust belt in terms of amount of shortening versus amount of erosion and thermal stabilization less than 10 Myr after the initial India/Asia contact is defined as the collisional regime. In contrast, the first 5 to 10 Myr corresponds to the transition from oceanic subduction to continental collision, characterized by a marked decrease of the shortening rate, onset of aerial topography, and progressive heating of the convergent zone. This period is defined as the continental subduction phase, accommodating more than 30% of the total Himalayan shortening.
Stratospheric ozone profiles retrieved from limb scattered sunlight radiance spectra measured by the OSIRIS instrument on the Odin satellite
Authors: von Savigny C. , Haley C. S. , Sioris C. E. , McDade I. C. , Llewellyn E. J. , Degenstein D. , Evans W. F. J. , Gattinger R. L. , Griffioen E. , Kyrölä E. , Lloyd N. D. , McConnell J. C. , McLinden C. A. , Mégie G. , Murtagh D. P. , Solheim B. , Strong K.
Published: July 2003

Stratospheric ozone density profiles between 15 and 40 km altitude are derived from scattered sunlight limb radiance spectra measured with the Optical Spectrograph and InfraRed Imager System (OSIRIS) on the Odin satellite. The method is based on the analysis of limb radiance profiles in the centre and the wings of the Chappuis‐Wulf absorption bands of ozone. It employs a non‐linear Newtonian iteration version of Optimal Estimation (OE) coupled with the radiative transfer model LIMBTRAN. The derived zonally averaged ozone field for August 2001 is in excellent agreement with the main characteristics of the global morphology of stratospheric ozone, indicating that the limb scatter technique is capable of providing ozone profiles with high accuracy and high vertical resolution on a global scale and a daily basis.
Comment on “Origins of energetic ions in the cusp” by K. J. Trattner et al.
Authors: Sheldon Robert , Chen Jiasheng , Fritz T. A.
Published: July 2003

The paper by Trattner et al. [2001, hereinafter referred to as TETAL] reanalyzes the data of Chen et al. [1998, hereinafter referred to as CFS] and attempts to prove two statements: first, that the energetic ions observed in the cusp by CFS were actually accelerated at the bow shock and then transported to the cusp, and second, that the detected ions are not accelerated locally. Quoting TETAL's abstract, “An alternative explanation for the energetic particle events is that they are accelerated at the quasi‐parallel bowshock, then transported downstream and enter the cusp along newly reconnected field lines or some other solar wind entry mechanism… No local acceleration is required to explain the observed CEP events up to 150 keV/e.” We object that neither assertion of TETAL is defensible on theoretical or experimental grounds. Indeed we find the conclusions of the paper are flawed by both statistical and logical errors. In section 1 we outline the logical flaws, in section 2 we outline the misuse of the scientific method, in section 3 we outline the improper use of statistics, and in section 4 we outline the mishandling of spacecraft data. Finally, in section 5 we apply the scientific method of hypothesis testing to the two theories, arguing that given complete ignorance of the data, the hypotheses of CFS are preferable to TETAL.
Solar wind coupling to and predictability of ground magnetic fields and their time derivatives
Authors: Weigel R. S. , Klimas A. J. , Vassiliadis D.
Published: July 2003

A spatial and dynamic study of solar wind driving of high‐latitude ground magnetic fields and their time derivatives is given. Nonlinear, data‐derived basis functions are used to determine the optimal solar wind driven dynamic coupling function at high‐latitude locations. The method does not assume a solar wind driving function a priori so that an unbiased determination of the relative influence of different driving processes can be made. Using this method, the locations where high‐latitude models capture signatures of different driving processes, such as reconnection and the Kelvin‐Helmholtz instability, are revealed for both the amplitude of the field and its time derivative. The time rate of change of the field is a disturbance measure related to geomagnetically induced currents. For the amplitude of the ground magnetic field the primary driver is reconnection; the time rate of change of the field has signatures of both reconnection driving in the nightside sector and Kelvin‐Helmholtz driving in the prenoon sector. The independent influence of the solar wind ion density and azimuthal component of the magnetic field in driving magnetic field fluctuations is found to be small at auroral‐zone latitudes. The data‐derived coupling functions are also used to estimate the expected prediction error of a general class of models that specify the ground magnetic field or its time derivative given solar wind plasma measurements. Prediction efficiencies as small as zero and as large as 0.7 for both the amplitude of the field and its time derivative are possible. The prediction efficiency is highly dependent on spatial location and the direction of field being predicted.
Spin‐up circulation of high‐latitude ion drag‐driven gyres
Authors: Walterscheid R. L. , Brinkman D. G.
Published: July 2003

We have used a model of thermospheric gyres with simplified geometry (azimuthally symmetric cylindrical coordinate) to study dynamical adjustment for high‐latitude gyres spun‐up into rapid motion by ion drag. In our simulations, winds are spun‐up for an hour subject only to circumgyre ion drag forcing from strong radial electric fields with peak values of ±75 mV m−1 centered at a radial distance of 1500 km. The winds in the core of the jets approach 500 m s−1. The major finding is that the imbalance between the inertial forces (centrifugal and Coriolis) and the pressure gradient force during the spin‐up of high‐latitude gyres drives a strong radial circulation, and this circulation is a significant contributor to the radial circulation forced by all sources. This agradient circulation attempts to establish a gradient‐wind balance between the inertial and pressure gradient forces. A feature of general circulation model simulations of the high‐latitude lower thermosphere is that, subtracting the warming of the whole polar cap due to Joule heating, the counterrotating gyres driven into motion by ion convection have opposite thermal polarities, with the cyclonic gyre developing a cold core (low density) and the anticyclonic gyre a warm core (high density). We suggest that this is accomplished by the radial circulation forced by the aforementioned imbalance between the inertial and pressure gradient forces. While diabatic heating over the polar cap acts to elevate the temperature (raise the density) over the polar cap as a whole, the changes induced by the dynamically induced circulation account for the fact that cyclonic gyres in the lower thermosphere are relatively colder and denser and the anticyclonic gyres are relatively warmer and less dense. We also examine the radial circulation forced by the initial stages of spin‐down and show that the spin‐down circulation is significant.
Birkeland currents in the plasma sheet
Authors: Kaufmann Richard L. , Paterson W. R. , Frank L. A.
Published: July 2003

Geotail particle and magnetic field measurements were combined to generate long‐term‐averaged 3‐D models of the plasma sheet. Ampere's law was used to calculate the Birkeland current j∥ in the −30 < x < −16RE, ∣z∣ > 1RE region. Current diversion, or the growth of current in a unit flux tube j∥/B, took place throughout the region studied. This suggests that electron scattering is broadly distributed. No substantial change in j∥/B could be detected between the plasma sheet boundary layer and the ionosphere. Birkeland currents were strongest and exhibited a dawn‐dusk asymmetry when the interplanetary magnetic field (IMF) was southward. This asymmetry may be associated with the formation of thin current sheets on the dusk side during disturbed periods. Symmetries were apparent above and below the neutral sheet when the IMF was northward or southward, but these symmetries were not present when the IMF pointed dawnward or duskward. For these latter cases, separate surfaces were found on which Bx = 0, By = 0, and j∥ = 0. This apparently complex structure could be understood as a consequence of the tendency for By in the neutral sheet to have the same sign as the IMF By. The observed Birkeland currents were in the region 1 sense when leaving the plasma sheet for all IMF orientations. Current diversion was analyzed in an MHD framework. The analysis suggested that the reduction of gradient and curvature guiding center drifts, and the presence of polarization currents in the diversion region can provide sources of electrons to sustain a steady j∥. It also was noted that the formation of an E∥ region in the topside ionosphere can make it appear to the conducting ionosphere as if it is being driven by a current source rather than by the plasma sheet electric field.
The 27‐day variations of plasma densities and temperatures in the topside ionosphere
Authors: Rich Frederick J. , Sultan Peter J. , Burke William J.
Published: July 2003

Defense Meteorological Satellite Program (DMSP) spacecraft at 840 km observe a 27‐day variation in plasma density and temperature at all subauroral latitudes. At the peak of the solar cycle, evening‐sector variations are ∼40–50% in plasma density and ∼5–10% in electron temperature. The percent of variation decreases with decreasing solar activity to or below the threshold of detectability for the DMSP sensors. We compare in situ densities with simultaneous observations of total electron content but find that similar variations are not present in a consistent manner. Thus we conclude that the variations exist mostly as topside phenomena. However, comparisons with variations in the radio flux at 10.7 cm (F10.7), a standard proxy for solar EUV, indicate that the topside variations are driven by the solar EUV flux. When compared with the variations of several alternative proxies for the solar EUV flux, we find that only one of them correlates better than F10.7. Because the topside ionosphere couples with the plasmasphere, we suggest that similar 27‐day variations should appear in plasmaspheric parameters.
Neutral hydrogen density profiles derived from geocoronal imaging
Authors: Østgaard N. , Mende S. B. , Frey H. U. , Gladstone G. R. , Lauche H.
Published: July 2003

Measurements of the Lyman α column brightness by the Geocoronal Imager (GEO), part of the FUV imaging system on board the IMAGE satellite, have been used to derive an empirical model of the neutral hydrogen density distribution at high altitudes (>3.5 RE geocentric distance) on the night‐side of the Earth. The model presented is an effort to provide the density profiles needed to analyze the energetic neutral atom imaging data at ring current altitudes and above. The variable solar Lyman α flux is obtained from the UARS/SOLSTICE measurements and the scattered solar Lyman α emissions from interplanetary hydrogen are obtained from a model. Assuming that the exosphere at high altitudes (>3.5 RE geocentric distance) can be considered as an optical thin medium and that the hydrogen density profile can be expressed as a double exponential we show that the Lyman α column brightness can be converted to hydrogen density profiles. The hydrogen density above 5 RE is found to be slightly higher for large solar zenith angles than for 90° solar zenith angle. The hydrogen density shows temporal variations which are not controlled by any solar quantity or geomagnetic parameter alone. Our Lyman α profiles and derived hydrogen density profiles are close to what was observed by Dynamics Explorer 1 [Rairden et al., 1986]. Above 8 RE we find higher densities than they did for all solar zenith angles >90°. We do not find any evidence of depletion due to charge exchange with solar wind protons outside the magnetopause. Our results are only valid above 3.5 RE.
Permeability evolution during progressive development of deformation bands in porous sandstones
Authors: Ngwenya B. T. , Kwon O. , Elphick S. C. , Main I. G.
Published: July 2003

Triaxial deformation experiments were carried out on large (0.1 m) diameter cores of a porous sandstone in order to investigate the evolution of bulk sample permeability as a function of axial strain and effective confining pressure. The log permeability of each sample evolved via three stages: (1) a linear decrease prior to sample failure associated with poroelastic compaction, (2) a transient increase associated with dynamic stress drop, and (3) a systematic quasi‐static decrease associated with progressive formation of new deformation bands with increasing inelastic axial strain. A quantitative model for permeability evolution with increasing inelastic axial strain is used to analyze the permeability data in the postfailure stage. The model explicitly accounts for the observed fault zone geometry, allowing the permeability of individual deformation bands to be estimated from measured bulk parameters. In a test of the model for Clashach sandstone, the parameters vary systematically with confining pressure and define a simple constitutive rule for bulk permeability of the sample as a function of inelastic axial strain and effective confining pressure. The parameters may thus be useful in predicting fault permeability and sealing potential as a function of burial depth and fault displacement.
Formation of internally drained contractional basins by aridity‐limited bedrock incision
Authors: Sobel Edward R. , Hilley George E. , Strecker Manfred R.
Published: July 2003

Low internal relief, aridity, and internal drainage characterize the Puna‐Altiplano Plateau and the Tibetan Plateau and the Tarim basin. Structurally, these areas are reverse fault bounded terrains with intervening wedge‐top basins that store thick accumulations of sediment for millions of years. Orographic barriers along the margins of these basins are oriented normal to moisture bearing winds, resulting in regional aridity. The combination of this aridity, rapid shortening and uplift rates, and resistant exposed lithologies coincides with the location of these internally drained basins. We hypothesize that these large, internally drained areas persist indefinitely when uplift overwhelms the fluvial systems and defeats the channel network. To test this hypothesis, we developed models of channel defeat to examine the threshold conditions required to fragment the channel network. The results of these models suggest that low‐erodibility rocks, moderate to high uplift rates, and low precipitation favor defeat of orogen‐traversing channels. Most coupled tectonic‐landscape development models prevent the development of internal drainage and so may overestimate the voracity of erosion in regimes that favor internal drainage, profoundly influencing predicted orogenic growth patterns.
Interplay between tectonics, climate, and fluvial transport during the Cenozoic evolution of the Ebro Basin (NE Iberia)
Authors: Garcia‐Castellanos Daniel , Vergés Jaume , Gaspar‐Escribano Jorge , Cloetingh Sierd
Published: July 2003

Three‐dimensional modeling that integrates fluvial sediment transport, crustal‐scale tectonic deformation, and lithospheric flexural subsidence is carried out to simulate the landscape and drainage evolution of the Ebro sedimentary basin (NE Iberia). The Ebro Basin underwent a long period of closed intramountain drainage as a result of tectonic topography generation at the Pyrenees, the Iberian Range, and the Catalan Coastal Range. In the late Oligocene, the Catalan Coastal Range underwent extension leading to the formation of the Valencia Trough (NW Mediterranean), but the Ebro Basin remained closed for nearly 15 Myr more before the Ebro River cut through the remnants of the topographic barrier. This drainage opening caused widespread basin incision that shaped spectacular outcrops of the syntectonic and posttectonic infill. Here we investigate the processes controlling these major drainage changes. The modeling results, constrained by a large data set on the tectonic and transport evolution of the area, predict a closed phase characterized by a large lake in the central eastern Ebro Basin. Dry climatic conditions probably lowered the lake level and contributed, together with rift flank uplift, to prolong this endorheic basin stage. The age and amount of reworked sediment after the opening are consistent with an onset of basin incision between 13 and 8.5 Ma as a result of lake capture by escarpment erosion and lake level rise associated with sediment accumulation and wetter climatic conditions. Sea level changes in the Mediterranean had no major impact in the large‐scale drainage evolution of the Ebro Basin.
Reconstruction of the Altyn Tagh fault based on U‐Pb geochronology: Role of back thrusts, mantle sutures, and heterogeneous crustal strength in forming the Tibetan Plateau
Authors: Cowgill Eric , Yin An , Harrison T. Mark , Xiao‐Feng Wang
Published: July 2003

Reconstructing deformation along the northwestern margin of the Tibetan Plateau is critical for evaluating the relative importance of microplate versus continuum models of the Indo‐Asian collision. Questions regarding this margin's evolution are as follows: (1) What is the total offset along the sinistral Altyn Tagh strike‐slip system? (2) How has that offset been absorbed in the western Kunlun Shan? (3) Why does the N‐S width of the plateau vary along strike? Ion microprobe U‐Pb zircon apparent ages of 17 plutons from NW Tibet, together with regional geologic observations, define a discrete, E‐W trending boundary between two tectonic belts that has been offset along the Altyn Tagh system by 475 ± 70 km. Kinematic arguments indicate that this offset cannot be the result of north directed thrusting in the western Kunlun Shan. Therefore we propose that south directed faulting in the Tianshuihai thrust belt both offset the tectonic boundary and produced the asymmetry in the plateau. Shortening appears to have been absorbed in the upper crust by thin‐skinned thrusting, in the middle/lower crust by east directed ductile flow and/or subduction, and in the mantle by north dipping subduction. Factors controlling the formation of the south directed thrust system appear to be the contrast between the rigid Tarim and the weaker Songpan‐Ganzi flysch belt and a mantle suture inherited from late Paleozoic subduction. The evolution of western Tibet leads to a view of continental deformation that integrates elements of the microplate model (e.g., plate‐like mantle and crust‐mantle decoupling) with aspects of the continuum model (weak crustal flow beneath the plateau).
Percolation conditions in binary fractal fracture networks: Applications to rock fractures and active and seismogenic faults
Authors: Nakaya Shinji , Yoshida Tatsuya , Shioiri Naoya
Published: July 2003

The fracture network patterns in crystalline rock are treated using a binary fractal model described by three fractal geometric parameters: the fractal dimension D of the spatial distribution of fractures, the fractal dimension a of the fracture length distribution, and the maximum fracture length (lmax) normalized by the domain length (L), lmax/L. We present a percolation threshold relationship describing the boundary between percolating and nonpercolating conditions in random binary fractal fracture networks (RBFFNs) and apply this to observations of natural fractures. Our results indicate that the three fractal parameters identified indeed control the connectivity of fracture networks, and hence the migration of fluids through rock fractures, and active and seismogenic faults. Moreover, our numerical approach may be applied in the future to investigating fluid migration associated with seismicity based on fractal parameters determined from earthquake catalog data.
Very shallow melting of oceanic crust during spreading ridge subduction: Origin of near‐trench Quaternary volcanism at the Chile Triple Junction
Authors: Guivel Christèle , Lagabrielle Yves , Bourgois Jacques , Martin Hervé , Arnaud Nicolas , Fourcade Serge , Cotten Joseph , Maury René C.
Published: July 2003

Recent dacites and basaltic andesites carrying a subduction‐related geochemical imprint were dredged within the active Chile Trench off the Taitao Peninsula, where the Chile Ridge is being subducted beneath the South America Plate. Their maximal Ar/Ar ages range from 70–127 ka to 2 Ma. The basaltic andesites, which have a predominantly mantle‐derived geochemical signature are thought to result from the mixing of dacitic magmas with MORB‐type liquids derived from the buried spreading ridge. Two groups are distinguished among the dacites: the low‐Si group has the chemical characteristics of adakitic slab melts, with depleted heavy rare earth element (HREE) abundances suggesting the occurrence of residual garnet in their source. The high‐Si group has less depleted HREE contents. The Sr, Nd, and O isotopic signatures of both groups are ∈Sr = −14.9 to +0.8, ∈Nd = +2.9 to +3.8, and δ18O values = +6.4 to +6.9‰ respectively, consistent with mixed magma sources that include a MORB‐type component and sediments. We propose that the high‐Si dacites are derived from the hydrous melting of a mixture of MORB and sediments at high temperatures (800°–900°C) under low pressures (<0.8 GPa). The low‐Si dacites originate from the melting of a similar source under higher pressures consistent with depths of 25–45 km. Two scenarios accounting for the near‐trench position of these latter rocks are envisioned. The first invokes rapid tectonic erosion and changes in sedimentary wedge geometry. The second one postulates that parts of the slab are subducted rapidly to depths of 20–30 km right under the trench.
Numerical simulation of seasonal and interannual Indian Ocean upper layer circulation using Miami Isopycnic Coordinate Ocean Model
Authors: Manghnani Vijay , Subrahmanyam Bulusu , Xie Lian , Morrison John M.
Published: July 2003

The evolution of the upper layer circulation in the Indian Ocean is studied with a varying resolution global Miami Isopycnic Coordinate Ocean Model (MICOM). The model solutions are in general agreement with existing descriptions of the Indian Ocean circulation. The seasonal and interannual variability of model fields is analyzed in detail for four important regions of the Indian Ocean, namely the Somali current region, the monsoon currents south of Sri Lanka, the equatorial region, and the Indonesian Through‐flow (ITF) region. In the Somali current region, subsurface processes (100–300 m) are found to play an important role in determining the upper layer characteristics. The strength of the eastward flowing Southwest Monsoon Current (SMC), which transports about 20 × 106 m3 s−1, is closely tied to the local zonal wind stress anomaly. The interannual variability in the semiannual Wyrtki Jets results from the variability in the eastward equatorial winds along the equator. The zonal wind stress components along the equator and the monsoon current regions vary strongly with the El Niño‐Southern Oscillation (ENSO) phenomenon with weaker (stronger) winds during El Niño (La Niña), thus establishing an indirect link between the ENSO and the transport in these regions. The onset of the Equatorial Undercurrent (EUC) also shows significant interannual variability. The EUC appears from February to March every year but in some years it is also observed during late boreal summer. In the ITF region, the transports are generally stronger (weaker) during La Niña (El Niño) events.
Assimilation of drifter observations in primitive equation models of midlatitude ocean circulation
Authors: Özgökmen Tamay M. , Molcard Anne , Chin Toshio M. , Piterbarg Leonid I. , Griffa Annalisa
Published: July 2003

Motivated by increases in the realism of OGCMs and the number of drifting buoys in the ocean observing system, a new Lagrangian assimilation technique is implemented in an idealized, reduced‐gravity configuration of the layered primitive equation model MICOM. Using an extensive set of twin experiments, the effectiveness of the Lagrangian observation operator and of a dynamical balancing technique for corrected model variables, which is based on geostrophy and mass conservation, are explored in comparison to a conventional Pseudo‐Lagrangian observation operator and an implementation of the Kalman filter method. The results clearly illustrate that the Lagrangian observation operator is superior to the Pseudo‐Lagrangian in the parameter range that is relevant for typical oceanic drifter observations, and that the simple dynamical balancing technique works well for midlatitude ocean circulation.
Evaluation of the Moderate‐Resolution Imaging Spectroradiometer (MODIS) retrievals of dust aerosol over the ocean during PRIDE
Authors: Levy Robert C. , Remer Lorraine A. , Tanré Didier , Kaufman Yoram J. , Ichoku Charles , Holben Brent N. , Livingston John M. , Russell Philip B. , Maring Hal
Published: July 2003

The Puerto Rico Dust Experiment (PRIDE) took place in Roosevelt Roads, Puerto Rico from 26 June to 24 July 2000 to study the radiative and physical properties of African dust aerosol transported into the region. PRIDE had the unique distinction of being the first major field experiment to allow direct comparison of aerosol retrievals from the Moderate Imaging Spectroradiometer (MODIS) with Sun photometer and in situ aerosol measurements. Over the ocean the MODIS algorithm retrieves aerosol optical depth (AOD) as well as information about the aerosols' size distribution. During PRIDE, AODs derived by MODIS in the red wavelengths (0.66 μm) compare closely with Sun photometers. However, MODIS‐derived AODs are too large in the blue and green wavelengths (0.47 and 0.55 μm) and too small in the near infrared (0.87 μm). This error in AOD spectral dependence results in retrieved particle size distributions that are small compared to in situ measurements and smaller still when compared to Sun photometer sky radiance inversions. The differences in size distributions may be, in part, associated with MODIS' simplification of dust as spherical particles. Analysis of this PRIDE data set is a first step toward derivation of realistic models for future MODIS retrievals.
Radiative properties and direct effect of Saharan dust measured by the C‐130 aircraft during Saharan Dust Experiment (SHADE): 2. Terrestrial spectrum
Authors: Highwood Eleanor J. , Haywood James M. , Silverstone Michael D. , Newman Stuart M. , Taylor Jonathan P.
Published: July 2003

In situ measurements of terrestrial radiation from the C‐130 aircraft during the Saharan Dust Experiment (SHADE) are used to quantify the effect of a strong dust outbreak on radiance and brightness temperatures. The dust gives a distinct spectral signature in upwelling and downwelling terrestrial radiation when high spectral resolution data for a dusty day is compared to data from a clear day. A radiative transfer model is used together with a size distribution retrieved from Sun photometers and atmospheric profiles from dropsondes to simulate the radiance data and provide a constraint on the refractive indices of Saharan dust in the terrestrial part of the spectrum. The degree of agreement between observed and simulated brightness temperatures is dominated by the choice of refractive index, the mass loading, and the altitude of the dust layer. The uncertainties in size distribution appear to have less of an effect so long as large particles (radius greater than 1 μm) are included. In the terrestrial spectrum the dust produced a relative warming rate of up to 0.5 K/day below the dust and a relative cooling of up to 0.5 K/day within the dust layer itself. The effect on irradiance due to this dust outbreak was a decrease in upwelling terrestrial radiation at the top of the atmosphere of 6.5 Wm−2 and an increase in downwelling terrestrial radiation at the surface of 11.5 Wm−2. The dust led to decreases in brightness temperature of 2–4 K in the window region, consistent with apparent features in the sea surface temperature retrieved from the advanced very high resolution radiometer.