bluuebunny/crossref_metadata_2025 huggingface dataset:
Topographical attributes to predict soil hydraulic properties along a hillslope transect
Authors: Leij Feike J. , Romano Nunzio , Palladino Mario , Schaap Marcel G. , Coppola Antonio
Published: February 2004

Basic soil properties have long been used to predict unsaturated soil hydraulic properties with pedotransfer function (PTFs). Implementation of such PTFs is usually not feasible for catchment‐scale studies because of the experimental effort that would be required. On the other hand, topographical attributes are often readily available. This study therefore examines how well PTFs perform that use both basic soil properties and topographical attributes for a hillslope in Basilicata, Italy. Basic soil properties and hydraulic data were determined on soil samples taken at 50‐m intervals along a 5‐km hillslope transect. Topographical attributes were determined from a digital elevation model. Spearman coefficients showed that elevation (z) was positively correlated with organic carbon (OC) and silt contents (0.62 and 0.59, respectively) and negatively with bulk density (ρb) and sand fraction (−0.34 and −0.37). Retention parameters were somewhat correlated with topographical attributes z, slope (β), aspect (cosϕ), and potential solar radiation. Water contents were correlated most strongly with elevation (coefficient between 0.38 and 0.48) and aspect during “wet” conditions. Artificial neural networks (ANNs) were developed for 21 different sets of predictors to estimate retention parameters, saturated hydraulic conductivity (Ks), and water contents at capillary heads h = 50 cm and 12 bar (103 cm). The prediction of retention parameters could be improved with 10% by including topography (RMSE = 0.0327 cm3 cm−3) using textural fractions, ρb, OC, z, and β as predictors. Furthermore, OC became a better predictor when the PTF also used z as predictor. The water content at h = 50 cm could be predicted 26% more accurately (RMSE = 0.0231 cm3cm−3) using texture, ρb, OC, z, β, and potential solar radiation as input. Predictions of ANNs with and without topographical attributes were most accurate in the wet range (0 < h < 250 cm). Semivariograms of the hydraulic parameters and their residuals showed that the ANNs could explain part of the (spatial) variability. The results of this study confirm the utility of topographical attributes such as z, β, cosϕ, and potential solar radiation as predictors for PTFs when basic soil properties are available. A next step would be the use of topographical attributes when no or limited other predictors are available.
Light reflected by an atmosphere containing irregular mineral dust aerosol
Authors: Veihelmann B. , Volten H. , van der Zande W. J.
Published: February 2004

We simulate polarimetric satellite observations of sunlight reflected by a turbid atmosphere over the ocean. We determine the sensitivity of these observations with respect to the optical thickness and the single‐scattering albedo of irregular mineral aerosol. Simulated results indicate that both quantities can be retrieved from simultaneous polarization and intensity measurements. Aerosol scattering is modelled using a true measured scattering matrix of irregularly‐shaped mineral dust aerosol. We study the suitability of various approximations of the particle shape used for the numerical calculation of scattering matrices. Approximations with spheres or spheroids with a distribution of moderate axis ratios can lead to large errors of the simulated light intensities. A spheroidal approximation including extreme axis ratios is found to be the most appropriate one for simulations of light scattering by irregular mineral aerosol particles, if measured scattering matrices are not available.
On the solar wind control of cusp aurora during northward IMF
Authors: Bobra M. G. , Petrinec S. M. , Fuselier S. A. , Claflin E. S. , Spence H. E.
Published: February 2004

The location of cusp aurora during northward interplanetary magnetic field (IMF) conditions and the solar wind control of that location are explored. The cusp aurora is imaged by the Imager for Magnetopause‐to‐Aurora Global Exploration's (IMAGE) Far Ultraviolet Instrument (FUV). Predicted locations of the cusp aurora were computed by assuming anti‐parallel reconnection between the observed IMF orientation and the 1996 Tsyganenko model magnetopause magnetic field. While the majority of anti‐parallel reconnection sites tailward of the cusp, when mapped to the ionosphere, coincide with the observed cusp aurora, the anti‐parallel merging hypothesis cannot explain certain aspects of the observations, including its location dependence with IMF + By.
Conditions governing localized high‐latitude dayside aurora
Authors: Korth H. , Anderson B. J. , Frey H. U. , Immel T. J. , Mende S. B.
Published: February 2004

In a recent study of IMAGE FUV data, Frey et al. [2003] examined cases of high‐latitude dayside aurora (HiLDA) caused by precipitating electrons predominantly during northward IMF with a strongly positive IMF By component. To determine the conditions that control these auroral emissions, we examine field‐aligned currents observed by the Iridium constellation for 25 events of prolonged steady IMF orientation with both Bz and By positive. We find that localized FACs are sustained under all observed solar wind conditions, but that the occurrence of HiLDA is generally restricted to solar wind proton densities below 4 cm−3 and peak current densities higher than 0.7 μA/m2. That the solar wind density orders the occurrence of the auroral emissions indicates that magnetosheath plasma has ready access to the field lines carrying the upward current. Assuming that the magnetosheath plasma density and temperature govern the high‐altitude conditions on these field lines, we find that the intensity of the HiLDA emissions correlates with an estimate for the particle precipitation energy density based on the Knight relation, using the measured current density and the magnetosheath temperature and density.
Assessment of MISR and MODIS cloud top heights through inter‐comparison with a back‐scattering lidar at SIRTA
Authors: Naud Catherine , Muller Jan‐Peter , Haeffelin Martial , Morille Yohann , Delaval Arnaud
Published: February 2004

One year of back‐scattering lidar cloud boundaries and optical depth were analysed for coincident inter‐comparison with the latest processed versions of the NASA‐TERRA MISR stereo and MODIS CO2‐slicing operational cloud top heights. Optically thin clouds were found to be accurately characterised by the MISR cloud top height product as long as no other cloud was present at lower altitude. MODIS cloud top heights were generally found within the cloud extent retrieved by lidar; agreement improved as cloud optical depth increased and when CO2‐slicing was the only technique used for the retrieval. The difference between Lidar and MISR cloud top heights was found to lie between −0.1 and 0.4 km for low clouds and between 0.1 and 3.1 km for high clouds. The difference between Lidar and MODIS cloud top heights was found to lie between −1.2 and 1.5 km for low clouds and between −1.4 and 2.7 km for high clouds.
Roles of the EMP and QE field in the generation of columniform sprites
Authors: Adachi T. , Fukunishi H. , Takahashi Y. , Sato M.
Published: February 2004

In order to elucidate the electrodynamic coupling process between sprites and their causative cloud‐to‐ground lightning discharges, we investigated 38 columniform sprite events observed in the wintertime sprite campaigns in Japan. By analyzing the data of sprite images, transient Schumann resonance waveforms and the JLDN/LPATS lightning detection network systems, we found that the number of columns in each sprite event was proportional to the peak current intensity of positive cloud‐to‐ground lightning discharges (+CGs) while the average vertical length of columns was proportional to the charge moment of the causative +CGs. Based on these results, we suggest that electromagnetic pulses (EMPs) radiated from +CGs contribute to the formation of seeds for sprite streamers while the QE field contribute to the development of the streamers from the seeds.
Novel iodine chemistry in the marine boundary layer
Authors: Saiz‐Lopez Alfonso , Plane John M. C.
Published: February 2004

The atmospheric chemistry of iodine is important for several reasons, including the influence of iodine oxides on the oxidising capacity of the troposphere, the formation of new particles, and the enrichment of iodine in marine aerosols and the transport of this essential dietary element to the continents. It is shown here that a substantial iodine source is I2, most likely emitted from macro‐algae at low tide. This source accounts for the daytime production of new particles in the coastal marine boundary layer, and also explains the discovery of significant night‐time levels of iodine oxides.
The dependence of traction evolution on the earthquake source time function adopted in kinematic rupture models
Authors: Piatanesi Alessio , Tinti Elisa , Cocco Massimo , Fukuyama Eiichi
Published: February 2004

We compute the temporal evolution of traction by solving the elasto‐dynamic equation and by using the slip velocity history as a boundary condition on the fault plane. We use different source time functions to derive a suite of kinematic source models to image the spatial distribution of dynamic and breakdown stress drop, strength excess and critical slip weakening distance (Dc). Our results show that the source time functions, adopted in kinematic source models, affect the inferred dynamic parameters. The critical slip weakening distance, characterizing the constitutive relation, ranges between 30% and 80% of the total slip. The ratio between Dcand total slip depends on the adopted source time functions and, in these applications, is nearly constant over the fault. We propose that source time functions compatible with earthquake dynamics should be used to infer the traction time history.
Reconnection and scale‐free avalanching in a driven current‐sheet model
Authors: Klimas Alex J. , Uritsky Vadim M. , Vassiliadis Dimitris , Baker Daniel N.
Published: February 2004

Uritsky et al. [2002], through a study of Polar UVI auroral image sequences, have produced a set of scale‐free probability distributions for several characteristic properties of the evolving bright emission regions in the nightside auroral oval. These distributions almost certainly reflect the dynamics of the plasma sheet. A scale‐free avalanching process involving reconnection and/or current diversion over an exceptionally broad range of spatiotemporal scales is implied. The most straightforward, and at present sole, explanation for this behavior is that the plasma sheet dynamics is in the neighborhood of self‐organized criticality (SOC). However, the auroral images provide only an indirect measure of the plasma sheet dynamics. Confirmation of this state in the plasma sheet would require multispatiotemporal‐scale in situ plasma sheet studies that, with the advent of multispacecraft missions, are now possible. To suggest specific tests for such studies, a numerical current‐sheet model has been constructed and analyzed to develop the properties and requirements of SOC in a plasma physical setting. The model incorporates the anomalous resistivity of a current‐driven kinetic instability into a two‐dimensional resistive MHD system. The disparate scales of these two systems enable multiscale behavior in the intervening range. Several novel features in the model's behavior are enabled through the assumption of hysteresis in the kinetic instability threshold. Under steady loading of plasma containing a reversed magnetic field topology, an irregular loading‐unloading cycle is established in which unloading is due primarily to annihilation at the field reversal. Following a loading interval during which the current‐sheet supporting the field reversal thins and intensifies, an unloading event originates at a localized reconnection site that then becomes the source of waves of unstable current sheets. These current sheets propagate away from the reconnection site, each leaving a trail of anomalous resistivity behind. An expanding cascade of field line merging results. Some statistical properties of this cascade are examined. It is shown that the diffusive contribution to the Poynting flux in these cascades occurs in bursts, whose duration, integrated size, and total energy content exhibit scale‐free power law probability distributions over large ranges of scales. Although not conclusive, these distributions do provide strong evidence that the model has evolved into SOC.
Exospheric distributions of minor ions in the solar wind
Authors: Pierrard V. , Lamy H. , Lemaire J.
Published: February 2004

We investigate the acceleration of heavy solar wind ions on the basis of an exospheric Lorentzian model and show that the heavy ions can flow faster than the protons when their temperatures in the corona are more than proportional to their mass. The Lorentzian kinetic exospheric model [Pierrard and Lemaire, 1996], initially developed only for electrons and protons of the solar wind in a monotonic potential energy, is here generalized for the case of a nonmonotonic potential energy and applied to the heavy solar wind ions. We study how the mass, the charge, and the coronal temperature of the heavy ions influence their motion. The present work indicates that the temperature of the ions in the corona characterizing the dispersion of their velocities is a crucial factor determining their bulk velocity at large radial distances. Pierrard and Lamy [2003] showed that the velocity filtration effect can produce very high values of ion temperatures in the solar corona, considering that ion velocity distribution functions are enhanced with suprathermal tails in the low corona. We show that for sufficiently high ion temperatures at the exobase, our exospheric model can account for large bulk speeds of the heavy solar wind ions and for their relative abundances at 1 AU.
Current sheet structure around the near‐Earth neutral line observed by Geotail
Authors: Asano Y. , Mukai T. , Hoshino M. , Saito Y. , Hayakawa H. , Nagai T.
Published: February 2004

The current sheet structure around the near‐Earth neutral line during substorms is investigated using ion and electron velocity moments directly obtained by the Geotail satellite. The intense cross‐tail current sheet is found to be thinner closer to the X line and becomes as thin as 500 km. This is less than the ion inertial length (720 km), where ions are decoupled from electrons. The current sheet is found to be bifurcated from the ion diffusion region to the off‐neutral sheet and forms a double‐peaked current sheet away from the X line. Fast dawnward moving electrons with the strong ambipolar electric field toward the neutral sheet (Ens) carry the intense electron‐dominated current, and such Ens is larger than Ey in the bursty bulk flows. So‐called Hall current system into/out of the X line caused by the large separation between ion and electron motions is fully identified. The Hall current system is observed around the neutral sheet in the vicinity of the X line and bifurcates to the north/south boundary regions as the distance from the X line increases. There, the inward and outward currents form antiparallel current layers, whose boundaries are identified as 0.8 ∼ 0.85 of lobe magnetic field intensity.
Transient hydrogeologic models for submarine flow in volcanic seamounts: 2. Comparison of the Hawaiian, Canary, and Marquesas Islands
Authors: Christiansen L. B. , Garven G.
Published: February 2004

Large bathymetric gradients associated with volcanic seamounts can drive convective flow, while thick sedimentary aprons that typically surround volcanic edifices host compaction‐driven flow. In these submarine environments the interactions of compaction‐driven and buoyancy‐driven fluid flow lead to complex hydrogeologic regimes. We apply transient numerical models of coupled fluid flow and heat transport to the Hawaiian, Canary, and Marquesas Islands to examine the role of volcanic architecture on the evolution of fluid flow and pore pressure during volcanic building, lithospheric flexure, sedimentation, and compaction. The islands differ in edifice size, sedimentary apron structure, amount of lithospheric flexure, and sedimentation and volcanic growth rates. By comparing these variations, we examine how geometry and geologic history affect fluid flow and pore pressure patterns. Buoyancy‐driven flow is most influenced by edifice height and amount of lithospheric flexure. Compaction‐driven flow is altered primarily by thickness of prevolcanic sediment, the sedimentation rate, and the size of the volcanic edifice. In Hawaii, the area with the highest edifice and most flexure, flow velocities and excess pore pressures are greatest, with Darcy velocities of >30 mm/yr and excess pressures of >7 MPa during the beginning of volcanic building. High sedimentation rates in the Marquesas sedimentary apron increase fluid velocities in the later portion of volcanic building, with Darcy velocities >12 mm/yr. In the Canary Islands, compaction‐driven flow occurs for an extended time period because of long, slower volcanic building, resulting in Darcy velocities >10 mm/yr that endure over 5 Myr.
Fault mechanisms of induced seismicity at the superdeep German Continental Deep Drilling Program (KTB) borehole and their relation to fault structure and stress field
Authors: Bohnhoff Marco , Baisch Stefan , Harjes Hans‐Peter
Published: February 2004

One hundred twenty‐five fault plane solutions for microearthquakes induced during a long‐term fluid injection experiment at the German Continental Deep Drilling Program (KTB) boreholes (Germany) in 2000 are investigated. A predominant strike‐slip mechanism is observed, partly with components of normal but also with reverse faulting. Adding 54 fault plane solutions of an earlier injection experiment at the KTB, we determine the local stress field and find a subhorizontal north‐south orientation for the maximum principal stress and a near‐vertical orientation for the intermediate principal stress. The stress field exhibits no temporal or spatial variations within the resolved accuracy of ±15°. However, the results of the stress tensor inversion point to heterogeneities of second order. On the basis of the hypocentral distribution of the induced microearthquakes and the similarity of fault mechanisms, we relate our data to the fault structure at the KTB. We find that the larger faults act as pathways for the injected fluid, whereas the brittle failure occurs on fault asperities of the larger mapped faults and nearby smaller faults, both in agreement with the local stress field. Applying a thorough error analysis of the individual fault plane solutions, we correlate the diversity of mechanisms with their strength and find that the strongest events tend to a representative mechanism that is in good correspondence with the stress field. In contrast, the diversity of fault mechanisms is larger for the smaller events, indicating local stress perturbations.
A new nonlinear finite fault inversion with three‐dimensional Green's functions: Application to the 1989 Loma Prieta, California, earthquake
Authors: Liu Pengcheng , Archuleta Ralph J.
Published: February 2004

We present a new procedure to invert for kinematic source parameters on a finite fault. On the basis of the reciprocity relation of the Green's functions, we use a newly developed fourth‐order viscoelastic finite‐difference algorithm to calculate three‐dimensional (3‐D) Green's functions (actually the tractions) on the fault. We invert the data for the unknown source parameters at the nodes (or corners) of the subfaults. The source parameters within a subfault area are allowed to vary; this variation is calculated through bilinear interpolation of the four nodal quantities. We have developed a global nonlinear inversion algorithm that is based on simulated annealing methods to solve efficiently for the nodal parameters. We apply this method to the 1989 Loma Prieta, California,M6.9 earthquake for both a 1‐D and 3‐D velocity structure. We show (1) the bilinear interpolation technique reduces the dependence of inversion results on the subfault size by naturally including the effects of nearby subfaults. (2) While the number of synthetic seismograms that must be computed is greatly increased by the bilinear interpolation, the structure of the inversion method minimizes the actual numbers of computations. (3) As expected, complexity in the velocity structure is mapped into the source parameters that describe the rupture process; there are significant differences between faulting models derived from 1‐D and 3‐D structural models.
Heat and freshwater budgets of the Texas‐Louisiana shelf
Authors: Etter Paul C. , Howard Matthew K. , Cochrane John D.
Published: February 2004

A self‐consistent climatology comprising monthly mean heat budgets and seasonal mean freshwater budgets was constructed for the Texas‐Louisiana shelf. The heat‐budget phase amplitude was dominated by net heat gain and heat storage. The freshwater‐budget phase amplitude was dominated by river discharge and freshwater storage. Flux divergences of heat and freshwater were computed as residuals. Heat flux diverged in June and July but converged the rest of the year. Freshwater flux showed a persistent divergence throughout the year. This new climatology provided a baseline against which to evaluate synoptic fields computed over the period May 1992 to November 1994 using hydrographic data supplemented by meteorological data derived from a novel mixture of measurements and model products. Analysis of the synoptic fields advanced understanding of the freshwater filling and flushing times (the times required, respectively, to accumulate and remove the freshwater content present on the shelf at any instant). Filling times were calculated by performing a reverse time integration of the net amount of fresh water added to the shelf through the effects of precipitation, river discharge and evaporation. Flushing times were calculated apparently for the first time for this region by performing a forward time integration of the amount of fresh water advected off the shelf through divergence. Filling and flushing times were balanced by adjusting the fraction of Mississippi River discharge assumed to flow westward onto the shelf. The results, which are within the estimated uncertainty, provide new insights into the freshwater balance on the Texas‐Louisiana shelf.
Nonlinear spectral mixing: Quantitative analysis of laboratory mineral mixtures
Authors: Poulet F. , Erard S.
Published: February 2004

Applications of nonlinear unmixing models based on the Shkuratov theory to fit laboratory spectra of intimate mixtures and to derive imaginary refraction indices of minerals are presented. The tests are performed using mafic minerals (pyroxenes, olivine, plagioclase). Abundance estimates of end‐members are accurate to within 5–10% for the analyzed mixtures, while the estimate particle sizes are within the intervals of actual sizes, given the reflectance spectra of the end‐members only. The type of mixture (areal versus intimate) can be tested. A quantitative modeling of basalt, a dark rock mainly composed of bright minerals, is also presented. The limitations of our modeling method are discussed.
Millennial‐scale variability in western subtropical North Atlantic surface and deep water circulation during marine isotope stages 11 and 12
Authors: Healey Stephanie , Thunell Robert
Published: February 2004

Marine isotope stages (MISs) 11 and 12 (∼460–380 ka) contain what may be the most extreme climate conditions of the last 500,000 years and occurred at a time when Earth received a similar amount of solar insolation as the most recent glacial‐interglacial cycle. Two high‐deposition rate sediment cores, Ocean Drilling Program Sites 1059 (31.6°N, 75.4°W, 2985 m) and 1055 (32.6°N, 76.2°W, 1799 m) from the western North Atlantic were studied in order to examine the nature of millennial‐scale variability in North Atlantic surface and thermohaline circulation during this time interval. Detailed records of δ18O and δ13C in the benthic foraminifera species Cibicidoides wuellerstorfi and the planktonic species Globigerinoides ruber (white) as well as detailed records of carbonate content were generated for both sites. These records suggest rapid variability in the strength of North Atlantic Deep Water production throughout MISs 11 and 12. Most of the observed changes in deep‐water circulation appear to be associated with or coupled to changes in sea‐surface hydrography. The duration of interglacial conditions during MIS 11 (20,000–30,000 years) is much longer than subsequent interglacial stages. Combined δ18O measurements and Mg/Ca based temperature estimates from G. ruber suggest sea‐surface temperatures increased 2–3°C across the MIS 12–MIS 11 transition.
Automated diagnostics for resonance signature recognition on IMAGE/RPI plasmagrams
Authors: Galkin Ivan A. , Reinisch Bodo W. , Huang Xueqin , Benson Robert F. , Fung Shing F.
Published: February 2004

The Radio Plasma Imager (RPI) aboard the IMAGE spacecraft probes plasma at both far and near ranges by means of radio sounding. The RPI plasmagrams, similar in their concept to the ground‐based and topside ionograms, contain not only a variety of signatures pertaining to the remote plasma structures and boundaries, but also a suite of the local plasma resonances stimulated by the RPI radio transmissions. Detection and interpretation of the resonance signatures is a valuable diagnostic tool providing the actual electron density and magnetic field strength at the spacecraft location, which are needed for the accurate processing of the remote sensing information on the plasmagrams. The high volume of the RPI sounding data demanded the development of automated techniques for routine interpretation of the plasmagrams. This paper discusses a new method for the detection and interpretation of the resonance signatures in the RPI plasmagrams that employs pattern recognition techniques to localize the signatures and identifies them in relation to model‐based resonances.
Development of a dual‐beam intersection technique for microwave breakdown plasma spectroscopy and detection of air compositions
Authors: Suto Hiroshi , Iinuma Koichi , Uchida Shunsuke , Takayama Ken
Published: February 2004

A dual‐beam intersection apparatus for microwave breakdown plasma spectroscopy (MBS) has been developed and tested for real‐time, simultaneous, and in situ monitoring of the trace gases in the air. The dual microwave beams, which are supplied by a 9.4G Hz pulse magnetron (feed power: 0–80 kW, pulse width: 5 μs, pulse repetition frequency: 10 Hz) using a power divider, are focused and superposed on a center of a reaction chamber through two dielectric lenses. The superposed electric field brings about the gaseous breakdown phenomena on the focusing point, where the photons emitted from the proper gas components can be detected and assigned using two‐dimensional wavelength/time‐resolved photoemission spectroscopy. The preliminary experiment has demonstrated that the emission intensities of breakdown plasma strongly depended on the phase difference between two microwave beams. Also, almost all the plasma spectra of the dual‐beam system were more intensified than that of the single‐beam system developed previously by us, and the relative continuum background decreased remarkably as well. For the 81 ppm of CCl2F2 gas mixed with the model atmosphere, the Cl atomic line of 837.6 nm (4p4D − 4s4P5/2) could clearly be detected at room temperature in total pressure of 10Torr. Present experiments have proved that the beam controllability of the dual‐beam system is superior to that of the single‐beam system to realize the appropriate breakdown conditions.
Visualization of High-Dimensional Data with Relational Perspective Map
Authors: Li James Xinzhi
Published: February 2004

This paper introduces a method called relational perspective map (RPM) to visualize distance information in high-dimensional spaces. Like conventional multidimensional scaling, the RPM algorithm aims to produce proximity preserving 2-dimensional (2-D) maps. The main idea of the RPM algorithm is to simulate a multiparticle system on a closed surface: whereas the repulsive forces between the particles reflect the distance information, the closed surface holds the whole system in balance and prevents the resulting map from degeneracy. A special feature of RPM algorithm is its ability to partition a complex dataset into pieces and map them onto a 2-D space without overlapping. Compared to other multidimensional scaling methods, RPM is able to reveal more local details of complex datasets. This paper demonstrates the properties of RPM maps with four examples and provides extensive comparison to other multidimensional scaling methods, such as Sammon Mapping and Curvilinear Principle Analysis.
Multiple Foci Visualisation of Large Hierarchies with FlexTree
Authors: Song Hongzhi , Curran Edwin P. , Sterritt Roy
Published: February 2004

One of the main tasks in information visualisation research is creating visual tools to facilitate human understanding of large and complex information spaces. Hierarchies, being a good mechanism for organising such information, are ubiquitous. Although much research effort has been spent on finding useful representations for hierarchies, visualising large hierarchies is still a difficult topic. One of the difficulties is how to handle the ever increasing scale of hierarchies. Another is how to enable the user to focus on multiple selections of interest while maintaining context. This paper describes a hierarchy visualisation technique called FlexTree to address these problems. It contains some important features that have not been exploited so far. A profile or contour unique to the hierarchy being visualised can be viewed in a bar chart layout. A normalised view of a common attribute of all nodes can be selected by the user. Multiple foci are consistently accessible within a global context through interaction. Furthermore it can handle a large hierarchy that contains 10,000 nodes in a PC environment. This technique has been applied to visualise computer file system structures and decision trees from data mining results. The results from informal user evaluations against these two applications are also presented. User feedback suggests that FlexTree is suitable for visualising large decision trees.
Electron Bernstein wave electron temperature profile diagnostic (invited)
Authors: Taylor G. , Efthimion P. , Jones B. , Munsat T. , Spaleta J. , Hosea J. , Kaita R. , Majeski R. , Menard J.
Published: February 2004

Electron cyclotron emission (ECE) has been employed as a standard electron temperature profile diagnostic on many tokamaks and stellarators, but most magnetically confined plasma devices cannot take advantage of standard ECE diagnostics to measure temperature. They are either “overdense,” operating at high density relative to the magnetic field (e.g., ωpe≫Ωce in a spherical torus) or they have insufficient density and temperature to reach the blackbody condition (τ>2). Electron Bernstein waves (EBWs) are electrostatic waves that can propagate in overdense plasmas and have a high optical thickness at the electron cyclotron resonance layers as a result of their large kperp. In this article we report on measurements of EBW emission on the CDX-U spherical torus, where B0∼2 kG, 〈ne〉∼1013 cm−3 and Te≈10–200 eV. Results are presented for electromagnetic measurements of EBW emission, mode converted near the plasma edge. The EBW emission was absolutely calibrated and compared to the electron temperature profile measured by a multipoint Thomson scattering diagnostic. Depending on the plasma conditions, the mode-converted EBW radiation temperature was found to be ⩽Te and the emission source was determined to be radially localized at the electron cyclotron resonance layer. A Langmuir triple probe and a 140 GHz interferometer were employed to measure changes in the edge density profile in the vicinity of the upper hybrid resonance where the mode conversion of the EBWs is expected to occur. Initial results suggest EBW emission and EBW heating are viable concepts for plasmas where ωpe≫Ωce.
Performance of the microwave reflectometry diagnostic for density profile measurements on ASDEX Upgrade
Authors: Silva A. , Manso M. , Vergamota S. , Cupido L. , Meneses L. , Nunes I. ,   ASDEX Upgrade Team
Published: February 2004

The broadband reflectometry system on ASDEX Upgrade is now routinely providing electron density profiles with a minimum temporal spacing of 30 μs. The plasma is probed from zero density to ne=6.64×1019 m−3 at the low field side with combined O and X modes, and from ne=0.318×1019 to ne=6.64×1019 m−3 at the high field side using O mode. Here we analyze the performance of the diagnostic for profile measurements taking into account its design options and the experimental results obtained in a wide range of plasma regimes. We address several questions, in particular the measuring range of the antennas and the range of density gradients. It is shown that it is possible to obtain a detailed evolution of the density profile and density gradient even in the presence of turbulence, providing that sufficient data can be extracted from the plasma. The radial movements of the plasma can be measured with great accuracy, which is especially important for the use of reflectometry for plasma position control, as is proposed for the International Thermonuclear Experimental Reactor. The experimental results demonstrate that the frequency modulation of a continuous wave reflectometry system on ASDEX Upgrade can provide reliable and accurate density profile measurements at both sides of the plasma with automatic analysis.
Ultrashort pulse reflectometry for electron density profile measurements on SSPX
Authors: Roh Y. , Domier C. W. , Luhmann N. C.
Published: February 2004

A broadband ultrashort pulse reflectometry (USPR) diagnostic has been developed for measuring electron density profiles of the sustained spheromak physics experiment (SSPX) device. In USPR, an extremely short pulse or chirped wave form is propagated which contains a broad range of frequency components spanning the desired plasma density profile (or a significant fraction thereof). Upon reflection, each frequency component in the incident waveform reflects from a different spatial location (density layer) in the plasma, thus spreading out the reflected wave packet in time. By simultaneously collecting double-pass time delay data at many distinct frequencies, the time delay data may then be inverted to generate plasma density profiles using a single source and a single set of measurements. On SSPX, wideband mixers are utilized to up- and downconvert 6–18 GHz chirp signals to millimeter-wave frequencies (33–158 GHz) to form a 48 channel O-mode reflectometer system. In this article we describe details of the new USPR system installed on the SSPX device and provide preliminary time-of-flight results.
Millimeter-wave imaging array development for microwave reflectometry and ECE imaging
Authors: Hsu P. L. , Deng B. H. , Wang J. , Domier C. W. , Luhmann N. C.
Published: February 2004

Millimeter-wave imaging arrays employing slot bow-tie (SBT) antenna elements and GaAs Schottky diodes have previously been previously successfully developed and utilized in electron cyclotron emission imaging systems, which have proven to be an important new plasma diagnostic technique for measuring plasma electron temperature profiles and fluctuations. More recently, there has been interest in applying similar arrays for reflectrometric imaging. Here, the design of SBT antennas for proof-of-principle millimeter-wave imaging reflectometry receiver arrays for use on Torus Experiment for Technology Oriented Research is presented. These low-cost, 14-channel Schottky mixer diode arrays, designed at 85 GHz, have been developed for measuring plasma electron density fluctuation profiles, which are expected to solve the long standing issue of ambiguity in the interpretation of reflectometric data. The final layout of the array is shown, together with details and experimental results of single SBT antennas.
Advances in quasioptical grid array technology for millimeter-wave plasma imaging diagnostics
Authors: Rosenau S. A. , Liang C. , Chang C.-C. , Hsu P. L. , Luhmann N. C. , Zhang W.-K. , Li W.-Y. , Domier C. W. , Hsia R. P.
Published: February 2004

Quasioptical grid array technologies can provide low cost, wide bandwidth sources supplying 100–500 mW power levels needed for reflectometric and electron cyclotron imaging of fusion plasmas. Broadband quasioptical overmoded waveguide frequency multiplier grid array systems have been designed, simulated, fabricated, and are under test with a goal of providing Watt level output powers from 50 to 200 GHz. Both 1×8, one-dimensional and 4×4, two-dimensional phased antenna arrays utilizing Schottky varactor loaded transmission lines have been designed, simulated, fabricated, and are being tested. Microelectromechanical systems have been designed and fabricated on silicon wafers with traditional integrated circuit processing techniques, resulting in devices with physical dimensions on the order of a few tens of microns.
Performance test of sample coils in the Korea superconducting tokamak advanced research magnetic diagnostics test chamber
Authors: Bak J. G. , Lee S. G.
Published: February 2004

Most of the Korea Superconducting Tokamak Advanced Research (KSTAR) magnetic diagnostics (MDs) are proposed to be installed inside of the vacuum vessel which is baked out up to 250 °C, and whose base pressure will be ∼5×10−9 Torr. Therefore, MDs must be compatible with the KSTAR vacuum vessel conditions. Sample coils are fabricated in order to prepare the preliminary data for the engineering design of the KSTAR MDs, and they are calibrated under the known magnetic field. A magnetic diagnostics test chamber (MDTC) is fabricated to test sample coils under similar conditions with the KSTAR vacuum vessel. Several experiments are carried out in the MDTC for investigating the reliability of the flux measurement with sample coils: the temperature effect on the measurement, the time delay of the measurement due to the conducting wall of the MDTC, and the frequency response of sample coil for detecting high frequency fluctuation. The results from these performance tests of sample coils are presented.
Application of the continuous wavelet transform to the fluctuations and electric field analysis in the H-1 heliac
Authors: Shi X. , Boman J. , Shats M. G.
Published: February 2004

We apply the continuous wavelet transform (CWT) and a CWT spectral technique to the analysis of the time-resolved fluctuation-driven particle flux in the H-1 heliac. The results confirm that in some cases the outward radial flux reverses its direction. In addition, time-resolved frequency spectra of fluctuation signals obtained by CWT show that the dominant frequency component as a function of time closely follows changes in the radial electric field. This suggests that the VE×B drift velocity dominates the poloidal phase velocity of the fluctuations in the laboratory frame, in which case the time-resolved frequency can be used to characterize the radial electric field.
Effect of film development on uniformity and modulation transfer function of the gated/fast x-ray imagers data
Authors: Kyrala George A. , Schappert Gottfried T. , Evans Scott C.
Published: February 2004

We have been investigating the different phenomena that affect the modulation transfer function response of the gated x-ray imagers and fast x-ray imagers that we use to record subnanosecond x-ray images at different laser facilities. As part of that investigation, we noticed that there is definite nonuniformity to the recorded images, even when the incident radiation was uniform. After a significant effort to track down that effect we found that the automatic developing processors, which process the film along the length of the roll, cause the effect. Manual development, which depends primarily on transverse agitation in the developer, and automatic processors that do not use a feed mechanism but emulate this agitation, do not introduce such artifacts. We recommend that for absolutely critical missions, such as target symmetry measurements, certain automatic machines should not be used.
Precision metrology of NSTX surfaces using coherent laser radar ranging
Authors: Kugel H. W. , Loesser D. , Roquemore A. L. , Menon M. M. , Barry R. E.
Published: February 2004

A frequency modulated Coherent Laser Radar ranging diagnostic is being used on the National Spherical Torus Experiment (NSTX) for precision metrology. The distance (range) between the 1.5 μm laser source and the target is measured by the shift in frequency of the linearly modulated beam reflected off the target. The range can be measured to a precision of <100 μm at distances of up to 22 m. A description is given of the geometry and procedure for measuring NSTX interior and exterior surfaces during open vessel conditions, and the results of measurements are elaborated.
Debris characterization diagnostic for the NIF
Authors: Miller M. C. , Celeste J. R. , Stoyer M. A. , Suter L. J. , Tobin M. T. , Grun J. , Davis J. F. , Barnes C. W. , Wilson D. C.
Published: February 2004

Generation of debris from targets and by x-ray ablation of surrounding materials will be a matter of concern for experimenters and National Ignition Facility (NIF) operations. Target chamber and final optics protection, for example debris shield damage, drive the interest for NIF operations. Experimenters are primarily concerned with diagnostic survivability, separation of mechanical versus radiation induced test object response in the case of effects tests, and radiation transport through the debris field when the net radiation output is used to benchmark computer codes. In addition, radiochemical analysis of activated capsule debris during ignition shots can provide a measure of the ablator 〈ρr〉. Conceptual design of the Debris Monitor and Rad-Chem Station, one of the NIF core diagnostics, is presented. Methods of debris collection, particle size and mass analysis, impulse measurement, and radiochemical analysis are given. A description of recent experiments involving debris collection and impulse measurement on the OMEGA and Pharos lasers is also provided.
Plasma diagnostics for INTER-FEAT
Authors: Ebisawa K. , Costley A. E. , Donne A. J. H. , Janeschitz G. , Kasai S. , Malaquias A. , Vayakis G. , Walker C. I. , Yamamoto S. , Zaveriaev V.
Published: February 2004

A comprehensive set of diagnostics is planned for ITER-FEAT. The design of the systems is a substantial technical challenge because of the combination of the harsh environment with the demanding measurement requirements. Through a combination of careful choice of technique, materials, and design, supported by dedicated research and development, an extensive diagnostic set has been developed. The designs are based on existing techniques as much as possible but in some cases novel approaches have to be adopted. In the article the requirements for measurements are outlined and representative diagnostic designs are presented. Key issues in the design are identified and areas requiring further development are highlighted.
Diagnostics for a magnetized target fusion experiment
Authors: Wurden G. A. , Intrator T. P. , Clark D. A. , Maqueda R. J. , Taccetti J. M. , Wysocki F. J. , Coffey S. K. , Degnan J. H. , Ruden E. L.
Published: February 2004

We are planning experiments using a field reversed configuration plasma injected into a metal cylinder, which is subsequently electrically imploded to achieve a fusing plasma. Diagnosing this plasma is quite challenging due to the short timescales, high energy densities, high magnetic fields, and difficult access. We outline our diagnostic sets in both a phase I study (where the plasma will be formed and translated), and phase II study (where the plasma will be imploded). The precompression plasma (diameter of only 8–10 cm, length of 30–40 cm) is expected to have n∼1017 cm−3, T∼100–300 eV, B∼5 T, and a lifetime of 10–20 μs. We will use visible laser interferometry across the plasma, along with a series of fiber-optically coupled visible light monitors to determine the plasma density and position. Excluded flux loops will be placed outside the quartz tube of the formation region, but inside of the diameter of the θ-pinch formation coils. Impurity emission in the visible and extreme ultraviolet range will be monitored spectroscopically, and fast bolometers will measure the total radiated power. A 20 J Thomson scattering laser beam will be introduced in the axial direction, and scattered light (from multiple spatial points) will be collected from the sides. Neutron diagnostics (activation and time-resolved scintillation detectors) will be fielded during both phases of the DD experiments.
Measurements of the plasma potential by HIBP using a TOF method
Authors: Nedzelskiy I. S. , Malaquias A. , Cabral J. A. C. , Varandas C. A. F.
Published: February 2004

A heavy ion beam diagnostic is being developed for the tokamak ISTTOK (R=0.46 m, a=0.085 m, Bt≅0.5 T, Ip=6–9 kA), based on multiple cell array detectors, aimed at the study of the time variation of the plasma density, electron temperature, poloidal magnetic field, and plasma potential radial profiles. In this article we describe an alternative method to the traditional electrostatic energy analyzers for measurements of the plasma potential based on the time-of-flight technique. The initial results of the measurements of the changes on the average plasma potential during tokamak discharges with minor disruptions are also presented. These results have been obtained measuring the time-of-flight of the ions of a pulsed primary beam from the electrostatic plates of the ion gun to the primary detector.
Collective microwave scattering diagnostic on the H-1 heliac
Authors: Solomon W. M. , Shats M. G. , Korneev D. , Nagasaki K.
Published: February 2004

A multichannel microwave scattering diagnostic has been developed and installed on the H-1 heliac. The purpose of the new diagnostic is to study small-scale plasma fluctuations in H-1, which are believed to be responsible for the loss of particles and energy from the plasma. The diagnostic is a 132 GHz, four-channel superheterodyne system. The transmitter and receiver antennas (consisting of horns and focusing bispherical mirrors) are located inside the vacuum vessel of H-1. A radial resolution of Δr/a∼0.2 is achieved. The scattering volume is positioned in the density gradient region at r/a∼0.6. At present, the system is aligned to measure fluctuations in the poloidal wave number range from approximately 10 to 25 cm−1. The use of the heterodyne detection system allows the fluctuation propagation direction to be determined. The low frequency bandwidth of the system is 1 MHz. The instrument sensitivity is about Ps/Pi∼10−6.
Probe wave system for studying excitation of Alfvén eigenmodes in the ion cyclotron range of frequency
Authors: Ichimura M. , Ohta Y. , Motegi S. , Nakamura M. , Tanaka S. , Kanazawa S. , Saosaki S. , Nakagawa C. , Sakata K. , Kadoya K. , Kawabata T. , Oikawa M. , Kano H. , Sasaki M. , Hojo H. , Yatsu K.
Published: February 2004

A probe wave system was constructed for studying the excitation of the Alfvén ion cyclotron (AIC) modes in the anchor cell of the GAMMA 10 tandem mirror. In the central cell, the AIC modes are spontaneously excited as axial eigenmodes due to the strong temperature anisotropy. In the anchor cell, the AIC modes were not observed though the anisotropy is the same as in the central cell. The axial profiles of the magnetic field strength and plasma parameters in the anchor cell are different from those in the central cell. Eigenmodes are excited externally in the AIC frequency range by injecting probe waves. This suggests the AIC modes are unstable in the anchor cell and grow to the detectable level when boundary conditions are realized.