bluuebunny/crossref_metadata_2025 huggingface dataset:
The effect of irrigation and sowing date on crop yield and yield components of Kabuli chickpea (Cicer arietinum L.) in a cool-temperate subhumid climate
Authors: ANWAR M. RAJIN , McKENZIE B. A. , HILL G. D.
Published: March 2004

The canopy development, radiation absorption and its utilization for biomass production in response to irrigation at different growth stages of three Kabuli chickpea (Cicer arietinum L.) cultivars was studied on a Wakanui silt loam soil in Canterbury, New Zealand (43°38S, 172°30E). The study also aimed at quantifying the yield potential of the crop under varying irrigation regimes and sowing dates. Green area duration (GAD), intercepted radiation (Fi), radiation use efficiency (U) and total intercepted PAR were significantly (P<0·001) increased by irrigation. Total dry matter (TDM) yield was more strongly correlated (R2=0·69–0·83) with GAD than seed yield (R2=0·60–0·69). Accumulation of TDM was highly related to intercepted PAR. Fully irrigated November-sown crops had a final U of 1·46 g DM/MJ PAR. The unirrigated crop had a U of only 0·92 g DM/MJ PAR. The U tended to decrease with delayed sowing.

Averaged over the 2 years, irrigation increased seed yield by 74–124% and trends were similar for TDM yield. Seed yield was doubled in November-sown chickpeas (4·6 t/ha) and cv. Sanford produced 14 and 16% more seed than cvs Dwelley and B-90 respectively. Full irrigation from emergence to physiological maturity always gave the highest seed yield (>4·7 t/ha), and there was no indication of a critical period of sensitivity to water stress. Based on results collected in the first growing season a simple model relating seed yield to radiation interception, U and HI was made. Results from the second growing season were then used as a simple verification to test the accuracy of predictions. The results suggest that these varieties have the potential to yield more than 4·5 t/ha of seed in Canterbury.
The Origins of State Pure Food Regulation
Authors: LAW MARC T.
Published: March 2004

Why did state governments begin to regulate the food industry in the late nineteenth century? One possible explanation is that pure food regulation was the result of rent seeking on the part of traditional food producers who wanted to limit the availability of new substitutes. Another potential hypothesis is that regulation was desired because it helped solve an asymmetric information problem in the market for food products. I find the evidence to be more consistent with the latter hypothesis.
Bulk turbulent transport and structure in Rayleigh–Taylor, Richtmyer–Meshkov, and variable acceleration instabilities
Authors: LLOR ANTOINE
Published: March 2004

Directed energy and turbulence structure are shown to be crucial in understanding the growth of self-similar Rayleigh–Taylor and incompressible Richtmyer–Meshkov turbulent mixing zones. Averaging over the mixing zone is used to analyze the response of a modifiedk–ε model and a turbulent two-fluid model. Three different transport regimes are then identified by considering self-similar variable acceleration RT flows (SSVARTs), which appear as promising reference flows for model testing.
Nonlinear analytic growth rate of a single-mode
Richtmyer–Meshkov instability
Authors: VANDENBOOMGAERDE M.
Published: March 2004

A perturbation method in which only the most secular terms are
retained gives simple results for the weakly nonlinear growth of a
single-mode shock-accelerated interface (Vandenboomgaerde et al., 2002). This
result can be written as a series in integer powers of time. It can be
considered as the Taylor expansion of an analytic function. We believe
that an approximation of such a function has been identified; it
described the evolution of the instability from linear to intermediate
nonlinear regime. Furthermore, this function has no singularity. The
relevance of this analytic formula is checked against two-dimensional
simulations and experimental data.
Modeling turbulent mixing in inertial confinement fusion implosions
Authors: SREBRO YAIR , KUSHNIR DORON , ELBAZ YONI , SHVARTS DOV
Published: March 2004

Recent direct drive implosion experiments, performed on the OMEGA
laser, have been analyzed by comparing full two-dimensional (2D) and
one-dimensional (1D) numerical simulations. The 2D simulations result
in a fusion yield higher than experimental results. A simple
full-mixing model, leaving only the clean region, overestimates yield
degradation. Fully turbulent mixing is expected to develop in most of
the mixing region; however regions slightly beyond the radius of the
most penetrating spike are expected to remain clean and to contribute
to fusion yield. One can correct the mixing model by redefining the
clean region. Accounting for this unmixed region results in improved
agreement with experimental results. Differences in central pressure,
density, temperature, and fusion rate in implosions dominated by low
mode number perturbations imply that mix effects might not be limited
to the mix region, and that 2D simulations are necessary to describe
the large scale flow affecting the central region. The same analysis
has been undertaken for implosions with different convergence ratios,
but with similar initial perturbation spectra. These implosions should
be compared to implosions dominated by high mode number perturbations,
which might be described by models based on 1D simulations.
Experimental study of the influence of the stabilizing properties
of transitional layers on the turbulent mixing evolution
Authors: KUCHERENKO Yu.A. , BALABIN S.I. , ARDASHOVA R.I. , KOZELKOV O.E. , DULOV A.V. , ROMANOV I.A.
Published: March 2004

Experiments conducted on the EKAP facility at the Russian Federal
Nuclear Center–VNIITF concerning the stabilization of
Rayleigh–Taylor instability-induced mixing in miscible liquids by
the formation of a molecular diffusion (or transitional) layer between
the liquids initially were described. The experiments had an Atwood
number of 1/3. The acceleration was 3500 times that of Earth's
gravity, and several values of diffusion layer thickness were
considered. The experiments showed that the growth of the turbulent
mixing zone could be delayed by adjusting the amplitude of the initial
perturbations and the characteristic thickness of the diffusion layer.
This has been observed in experiments conducted with water and mercury.
The mixing layer evolution was imaged using X-ray radiography.
Experimental investigation into the self-similar mode of mixing of
different density gases in the Earth's gravitational field
Authors: KUCHERENKO Yu.A. , SHESTACHENKO O.E. , PISKUNOV Yu.A. , SVIRIDOV E.V. , MEDVEDEV V.M. , BAISHEV A.I.
Published: March 2004

Experiments on self-similar Rayleigh–Taylor instability-induced
mixing in gases in the Earth's gravity conducted on the OSA
facility at the Russian Federal Nuclear Center–VNIITF are
described. These experiments are distinguished from other experiments,
usually performed with immiscible liquids in a tank or with miscible
liquids initially separated by a solid barrier that is retracted, in
that a membrane (of ∼1 μm thickness) with liquid soap film
embedded in a thin wire array (with microconductors of diameter 20
μm and with a spacing of 4 mm) initially separates the fluids. An
electric current to initiate the fluid interpenetration and mixing
destroys the membrane. Experiments performed for three different Atwood
numbers are described: in SF6-Ar with A = 0.54, in SF6-He with
A = 0.94, and in Kr-Ar with A = 0.35. Various
parameters of the mixing were measured from Schlieren photographs. In
particular, the dimensionless rate of mixing front growth is α =
0.078.
Experimental investigation into the evolution of turbulent mixing
of gases by using the OSA facility
Authors: KUCHERENKO Yu.A. , SHESTACHENKO O.E. , PISKUNOV Yu.A. , SVIRIDOV E.V. , MEDVEDEV V.M. , BAISHEV A.I.
Published: March 2004

Experiments conducted at the OSA shock tube facility at the Russian
Federal Nuclear Center–VNIITF to investigate the compressible
turbulent mixing of argon and krypton gases induced by the
Rayleigh–Taylor instability are described. A liquid soap film
membrane of thickness ∼1 micrometer embedded in an array of
microconductors is used, on which specified initial perturbations can
be applied. The shock is piston driven by compressed gas. The gas
interface was accelerated with an acceleration g′4 3104
m0s2. The membrane is disintegrated at the beginning of the experiment
by a strong electric explosion. Imaging is performed using Schlieren
photography. The dimensionless growth rate of the mixing zone was
determined to be 0.04.
Evolution of the Rayleigh–Taylor instability in the mixing
zone between gases of different densities in a field of variable
acceleration
Authors: ZAYTSEV S.G. , KRIVETS V.V. , MAZILIN I.M. , TITOV S.N. , CHEBOTAREVA E.I. , NIKISHIN V.V. , TISHKIN V.F. , BOUQUET S. , HAAS J.-F.
Published: March 2004

The interaction of the mixing zone between two gases of different
densities with compression waves and shock waves has been investigated.
The characteristics of the mixing zone in which the
Rayleigh–Taylor instability is developing have been analyzed. The
evolution of the mixing zone volume and mass during the accelerated
motion has been defined. A qualitative distinction in the evolution of
the mixing zone under the influence of a continuous deceleration
resulting from the interaction with the reflected compression
wave—shockless deceleration—is revealed as compared to
deceleration that is accompanied by appearance of a shock wave moving
through the mixing zone—shock-induced deceleration.
Shock-tube experiments on Richtmyer–Meshkov instability growth using an enlarged double-bump perturbation
Authors: HOLDER D.A. , SMITH A.V. , BARTON C. J. , YOUNGS D.L.
Published: March 2004

This article reports on the latest experiments in the series of Richtmyer–Meshkov instability (RMI) shock-tube experiments. Previous work described a double-bump experiment that evidenced some degree of unrepeatability. The present work features an enlarged perturbation introduced to improve repeatability. In common with the previous work, the experiments were conducted at shock Mach number 1.26 (70 kPa overpressure), using the Atomic Weapons Establishment 200 × 100 mm shock tube with a three-zone test cell arrangement of air/sulphur hexafluoride/air. The sulphur hexafluoride gas (SF6) was chosen for its high density (5.1 relative to air) providing an Atwood number of 0.67. Gas separation was by means of microfilm membranes, supported by fine wire meshes. A double-bump perturbation of two-dimensional geometry was superimposed on the downstream membrane representing a 0.6% addition to the dense gas volume. Visualization of the turbulent gas mixing was by laser sheet illumination of the seeded SF6gas using a copper vapor laser pulsing at 12.5 kHz. Mie scattered light was recorded using a 35-mm rotating drum camera to capture a sequence of 50 images per experiment. Sample experimental results shown alongside corresponding three-dimensional hydrocode calculations highlight the problems in both analysis and comparison caused by multiple scattering arising from the necessary use of a high seeding concentration. Included is a demonstration of the effectiveness of introducing into the hydrocode a Monte Carlo-based simulation of the multiple scattering process. The results so derived yield greatly improved qualitative agreement with the experimental images. Quantitative analysis took the form of deriving relative intensity data from line-outs through experimental images and their code equivalents. A comparison revealed substantial agreement on major features.
The verbal fluency task in the Greek population: Normative data, and clustering and switching strategies
Authors: KOSMIDIS MARY H. , VLAHOU CHRISTINA H. , PANAGIOTAKI PANAGIOTA , KIOSSEOGLOU GRIGORIOS
Published: March 2004

We assessed 300 healthy adults in Greece on measures of semantic and phonemic verbal fluency in order to develop norms for the Greek population. We also evaluated the strategies that the participants used spontaneously in order to maximize word production, namely clustering and switching techniques. Our tasks comprised three semantic and three phonemic categories. Consistent with previous investigations of English-speaking samples, we found a contribution of demographic variables to word fluency. Specifically, level of education contributed to total word production, number of switches, and number of repetitive responses on both semantic and phonemic tasks, and the average cluster size only on the phonemic task. Age contributed to total word production and cluster size on the semantic task, and to number of switches on both semantic and phonemic tasks. Sex contributed only to total word production on the semantic task. In our sample, clustering and switching strategies were related to total word production on both tasks, suggesting that these strategies were used effectively. We present tables of normative data stratified by age and level of education. We have also included detailed guidelines for scoring clusters relevant to the Greek population. (JINS, 2004,10, 164–172.)
Awareness of activity limitations and prediction of performance in patients with brain injuries and orthopedic disorders
Authors: FISCHER SONJA , TREXLER LANCE E. , GAUGGEL SIEGFRIED
Published: March 2004

The aim of this study was to compare the accuracy of performance predictions in experimental tasks with patients' awareness of activity limitations. Participants were 24 patients with brain injuries (i.e., traumatic brain injury and cerebrovascular disorders) and 22 patients with orthopedic disorders. Prediction of performance was examined in a memory task (word list learning) and a motor task (finger tapping). Awareness of activity limitations was measured by comparing patients' self-ratings and staff ratings in the Patient Competency Rating Scale (PCRS). Results for the PCRS showed that patients with orthopedic disorders underestimated and patients with brain injuries (i.e., patients with TBI) overestimated their level of functioning in the total scale and thesocial/emotionalsubscale in comparison to staff ratings. Both patient groups agreed with staff ratings inphysical/basic self-careitems. In the predicted performance tasks a similar pattern could be observed: None of the groups showed an overestimation of performance in the motor task, whereas patients with brain injuries overestimated their competency in the memory task. However, the agreement between both awareness measures (PCRS, predicted performance) was only low, which indicates that they might measure different aspects or levels of self-awareness. (JINS, 2004,10, 190–199.)
Reduced autonomic responsiveness to gambling task losses in
Huntington's disease
Authors: CAMPBELL MEGHAN C. , STOUT JULIE C. , FINN PETER R.
Published: March 2004

We examined the possible role of autonomic activity in
Huntington's disease (HD) during a risky decision making task.
Skin conductance responses (SCRs) of 15 HD participants and 16 healthy
controls were measured while they performed a computerized version of
the Simulated Gambling Task (SGT). The results replicated our previous
finding of a performance decrement in HD, and showed that HD was
associated with an altered pattern of SCRs during the risky decision
task. Specifically, the healthy controls produced increased SCRs
following selections from the disadvantageous decks and following
losing selections. In contrast, the SCRs of the HD group did not
differentiate between wins and losses. These findings indicate a
reduced impact of loss on decision-making processes under risky
conditions in HD. (JINS, 2004, 10,
239–245.)
Classifying children with heavy prenatal alcohol exposure using measures of attention
Authors: LEE KARA T. , MATTSON SARAH N. , RILEY EDWARD P.
Published: March 2004

Deficits in attention are a hallmark of the effects of heavy prenatal alcohol exposure but although such deficits have been described in the literature, no attempt to use measures of attention to classify children with such exposure has been described. Thus, the current study attempted to classify children with heavy prenatal alcohol exposure (ALC) and non-exposed controls (CON), using four measures of attentional functioning: the Freedom from Distractibility index from the Wechsler Intelligence Scale for Children–Third Edition (WISC–III), the Attention Problems scale from the Child Behavior Checklist (CBCL), and omission and commission error scores from the Test of Variables of Attention (TOVA). Data from two groups of children were analyzed: children with heavy prenatal alcohol exposure and non-exposed controls. Children in the alcohol-exposed group included both children with or without fetal alcohol syndrome. Groups were matched on age, sex, ethnicity, and social class. Data were analyzed using backward logistic regression. The final model included the Freedom from Distractibility index from the WISC–III and the Attention Problems scale from the CBCL. The TOVA variables were not retained in the final model. Classification accuracy was 91.7% overall. Specifically, 93.3% of the alcohol-exposed children and 90% of the control children were accurately classified. These data indicate that children with heavy prenatal alcohol exposure can be distinguished from non-exposed controls with a high degree of accuracy using 2 commonly used measures of attention. (JINS, 2004,10, 271–277.)
Stroop performance in drug users classified by HIV and hepatitis C
virus serostatus
Authors: MARTIN EILEEN M. , NOVAK RICHARD M. , FENDRICH MICHAEL , VASSILEVA JASMIN , GONZALEZ RAUL , GRBESIC SILVANA , NUNNALLY GERALD , SWOROWSKI LISA
Published: March 2004

Hepatitis C virus (HCV) can be detected in the brain (Radkowski et al., 2002) and investigators speculate
that HCV has neuroinvasive properties (Forton et al.,
2003) with direct effects on cerebral function. MRS
studies show that the basal ganglia and white matter of individuals with HCV
have abnormal choline/creatine ratios, indicating CNS inflammation or
infection (Forton et al., 2003). Patients with HCV
show defects in working memory and information processing speed (Forton et al., 2003; Hilsabeck et
al., 2002), similar to patients with basal ganglia disorders and HIV
(e.g., Heaton et al., 1995).
Insights into the biogenic contribution to total sulphate in aerosol and precipitation in the Fraser Valley afforded by isotopes of sulphur and oxygen
Authors: Norman A.‐L. , Belzer W. , Barrie L.
Published: March 2004

Contributions to atmospheric sulphate aerosol and precipitation in the Fraser Valley and at Saturna Island, Canada, from oxidation of biogenic dimethyl sulphide were determined using an isotopic mass balance approach. The S‐isotope composition of aerosol sulphate, and sulphur dioxide from a variety of industrial sources in the region were investigated and were found to have δ34S values ranging between −1.6 and +9‰. Isotopic analysis suggests a U.S. oil refinery and/or H2S from tidal flats on the coast contributes to the aerosol sulphate load in both summer and winter. On average, well‐mixed air in the region had δ34S values for SO2 near +1‰. Assuming this represents the average isotope composition of multiple sulphate sources from urban pollution, refinery emissions, and H2S, the DMS contributions to sulphate aerosol were calculated. On average, biogenic DMS‐sulphate made up 30% of the non‐sea salt sulphate in precipitation at Saturna Island in the Strait of Georgia. In contrast, it comprised only 13% of the aerosol sulphate load in the Fraser Valley. Proportionately more DMS aerosol sulphate is observed at Powell River and on Vancouver Island than in the vicinity of the city of Vancouver. Estimated concentrations are highest in the north, reaching 1.4 μgS/m3. These results are consistent with the isotope composition of oxygen in sulphate which show that at least half the aerosol sulphate in the Fraser Valley is formed from oxidation of SO2 at ambient temperatures.
Syncollisional delamination and tectonic wedge development in convergent orogens
Authors: Moore Vernon M. , Wiltschko David V.
Published: March 2004

Delamination of the lower crust and lithospheric mantle has occurred in several convergent orogens, most notably the Alps and Pyrenees. Some workers suggest that the process is mechanically similar to tectonic wedging and triangle‐zone development, and dependent on the pattern of mechanical layering. A search of over 35 orogens that have been explored by geophysical techniques showed that no correlation exists between crustal composition and delamination. Delamination of passive subducting plate margins is more common than that of tectonically and/or volcanically active overriding margins. Estimates show that the lithospheric mantle of cool passive margins may contain greater net negatively buoyant mass than warmer active margins. The top of the lower lithospheric layer containing the greatest net negatively buoyant mass is aligned with a weak zone near the Moho. Passive margin lithosphere thus has a greater tendency to delaminate during a collisional event than active margin lithosphere. For delamination to initiate above the Moho, the lower crust must be subducted or depressed to allow for exposure to eclogite grade conditions. Transformation of the mafic lower crust to mafic eclogite also creates a likely delamination horizon above a lower lithospheric layer containing net negatively buoyant mass aligned with a weak zone in the lithosphere. In contrast to the stratigraphic delamination that is key to the development of small‐scale wedge structures, syncollisional delamination is likely to occur in response to an increase in the lateral tectonic stress on a weak horizon already stressed by net negatively buoyant mass in the lower lithosphere.
Normal faulting at convergent plate boundaries: Mylonitic extensional fabrics in the Franciscan subduction complex in Del Puerto Canyon, California, revisited
Authors: Ring Uwe , Richter Peter P.
Published: March 2004

Using a strain and rotation analysis we tested the hypotheses that top‐east mylonitic extensional structures in the uppermost Franciscan subduction complex in Del Puerto Canyon, California, accomplished exhumation of the Franciscan blueschists. We found no evidence of strongly noncoaxial deformation, instead our data indicate overall coaxial deformation in the proposed zone of mylonitic extensional deformation. There are no extensional strains, moderate vertical shortening occurred without horizontal extension and was compensated by modest deformation‐related volume loss. There is also no strain gradient toward and within the proposed shear zone. Therefore the results of our work indicate that mylonitic extensional structures in Del Puerto Canyon do not exist. Overall, we conclude that there is no currently identifiable structure adjacent to or within the Franciscan in California that could have accommodated large‐scale horizontal extension. Exhumation of the Franciscan blueschists was mainly achieved by erosion of an emergent forearc high. Our strain results and published data are also inconsistent with the development of a supercritically tapered Franciscan wedge that ultimately should have triggered normal faulting. Strain magnitudes are low despite the relatively long residence time of the rocks in the accretionary wedge. From this we infer that strain rates were low and that the wedge material flowed with a relatively high viscosity. Therefore ductile flow probably was not fast enough to form a supercritically tapered Franciscan wedge.
Strong directivity of ocean‐generated seismic noise
Authors: Schulte‐Pelkum Vera , Earle Paul S. , Vernon Frank L.
Published: March 2004

We measure direction and amplitude of ocean‐generated continuous seismic noise in the western United States. Slowness direction of the noise is determined using array beamforming, and particle motion direction from individual three‐component stations. We find two surprising results. First, the noise is highly monodirectional at all sites, regardless of coastal distance. A single narrow generation area dominates for most of the time period, interrupted by a second well defined direction during ocean swell events. Second, we find that a storm off the Labrador coast with not unusual wave heights generates coherent noise across the entire continent. We show the causal relationship between swells arriving at different North American coastal areas and the triggered microseisms in time‐lapse movies (Animations 1 and 2) of ocean swells and concurrent microseisms. Our results have a number of implications for different fields of research. A useful by‐product of our finding that microseisms are a strongly directional noise source is the possibility of using automated processing of the continuous noise as a near real‐time check on station polarity and calibration problems, which would be a simply implemented indicator for the state of health of a seismic network. Consistent monodirectional noise may have an influence on seismic azimuthal measurements such as shear wave splitting. Most importantly, our findings should be taken into account in proposed studies which will use seismic noise as a proxy for ocean wave height in investigations of interdecadal climate change.
Atmospheric CO2 balance: The role of Arctic sea ice
Authors: Semiletov Igor , Makshtas Alexander , Akasofu Syun‐Ichi , L Andreas Edgar
Published: March 2004

Climatic changes in the Northern Hemisphere have led to remarkable environmental changes in the Arctic Ocean, including significant shrinking of sea‐ice cover in summer, increased time between sea‐ice break‐up and freeze‐up, and Arctic surface water freshening and warming associated with melting sea‐ice, thawing permafrost, and increased runoff [Carmack, 2000; Morison et al., 2000; Semiletov et al., 2000; Serreze et al., 2000]. These changes are commonly attributed to the greenhouse effect resulting from increased carbon dioxide (CO2) concentration. The greenhouse effect should be most pronounced in the Arctic where the largest air CO2 concentrations and winter‐summer variations in the world for a clean background environment were detected [Conway et al., 1994; Climate Monitoring and Diagnostics Laboratory Data Archive, http://www.cmdl.noaa.gov/info/ftpdata.html]. Some increased seasonal variation may be a consequence of increasing summer CO2 assimilation by plants in response to higher temperature and longer growing season [Keeling et al., 1996]. Here we show that sea‐ice melt ponds and open brine channels form an important spring/summer air CO2 sink that also must be included in any Arctic regional CO2 budget; both the direction and amount of CO2 transfer between air and sea during the open water season may be different from transfer during freezing and thawing, or during winter when CO2 accumulates beneath Arctic sea‐ice.
The relationship of Pacific deep tropical convection to the winter and springtime extratropical atmospheric circulation of the South Pacific in El Niño events
Authors: Harangozo S. A.
Published: March 2004

During some El Niño events Rossby wave trains (RWT) are observed to strongly modulate the seasonal atmospheric circulation of the South Pacific extratropics in the austral winter and spring. Here it is shown that seasonally intensified deep tropical convection is confined to the Pacific Intertropical Convergence Zone (ITCZ) close to the dateline in those events with strong RWT modulation but not in other cases. In other cases deep convection either withdraws from the ITCZ or the ITCZ strongly interacts with the South Pacific Convergence Zone (SPCZ) lying at 5–10°S. In both cases this points to a weakening of the local tropical Hadley circulation that may be crucial for Rossby wave generation. It is also found that the expected RWT response in the high latitudes can fail to occur even when SST in the central tropical Pacific are very high.
Measurements of x‐ray emission from rocket‐triggered lightning
Authors: Dwyer J. R. , Rassoul H. K. , Al‐Dayeh M. , Caraway L. , Wright B. , Chrest A. , Uman M. A. , Rakov V. A. , Rambo K. J. , Jordan D. M. , Jerauld J. , Smyth C.
Published: March 2004

We report measurements of the x‐ray emission from rocket‐triggered lightning, made during the summer of 2003, using four instruments placed between 15 and 40 m from the lightning channels. X‐rays were measured 0–80 μs just prior to and at the beginning of 73% of the 26 return strokes observed. The emission was composed of multiple, very brief bursts of x‐rays in the 30–250 keV range, with each burst typically lasting less than 1 μs. The x‐rays were primarily observed to be spatially and temporally associated with the dart leaders with a possible contribution from the beginning of the return strokes, with the most intense x‐ray bursts coming from the part of the lightning channel within ∼50 m of the ground. Because triggered lightning strokes are similar to subsequent strokes in natural lightning, it is likely that x‐ray emission is a common property of natural lightning.
A ground level gamma‐ray burst observed in association with rocket‐triggered lightning
Authors: Dwyer J. R. , Rassoul H. K. , Al‐Dayeh M. , Caraway L. , Wright B. , Chrest A. , Uman M. A. , Rakov V. A. , Rambo K. J. , Jordan D. M. , Jerauld J. , Smyth C.
Published: March 2004

We report the observation of an intense gamma‐ray burst observed on the ground at sea level, produced in association with the initial‐stage of rocket‐triggered lightning at the International Center for Lightning Research and Testing at Camp Blanding, FL. The burst was observed simultaneously on three NaI(Tl)/photomultiplier tube detectors that were located 650 m from the triggered lightning channel with gamma‐ray energies extending up to more than 10 MeV. The burst consisted of 227 individual gamma‐rays that arrived over a 300 μs time period in coincidence with an 11 kA current pulse. The burst of gamma‐rays had very different characteristics from the x‐ray emission frequently seen in association with the dart leader/return stroke sequences of triggered lightning and may represent a new kind of event, likely originating from cloud processes thousands of meters overhead.
The 2003 M8.0 Tokachi‐Oki earthquake – How much has the great event paid back slip debts?
Authors: Miura Satoshi , Suwa Yoko , Hasegawa Akira , Nishimura Takuya
Published: March 2004

A great earthquake with M8.0 (the 2003 Tokachi‐Oki earthquake) occurred on September 26, 2003, on the plate boundary south of Hokkaido, at about the same epicenter as that of the 1952 M8.2 Tokachi‐Oki earthquake. We estimated the coseismic slip‐distribution using GPS data to obtain consistent results with that inferred from waveform inversions; a maximum slip larger than 5m exists around 30km NNE from the epicenter. Though the slip‐deficit estimated there (80 mm/yr) by our recent study is based on a rather short period of observation (5 years) to discuss the whole seismic cycle, the maximum coseismic slip roughly accounts for the slip‐deficit accumulated in the past 51 years, assuming that the back‐slip rate has been nearly constant since 1952. Besides the area of the largest slip, however, an accumulated slip‐deficit still remains and should be released by seismic or aseismic slip, which is now actually observed in part as postseismic slip.
Raman lidar observations of aerosol emitted during the 2002 Etna eruption
Authors: Pappalardo Gelsomina , Amodeo Aldo , Mona Lucia , Pandolfi Marco , Pergola Nicola , Cuomo Vincenzo
Published: March 2004

Results of a lidar measurement campaign performed at IMAA‐CNR (Potenza, Italy) during the 2002 Etna volcano eruption, are reported. With combined Raman elastic‐backscatter lidar, independent measurements of aerosol extinction and backscatter coefficients at 355 nm are retrieved, whereas aerosol backscatter coefficient at 532 nm is retrieved from elastic lidar signal. A volcanic aerosol layer has been observed in the free troposphere on 1–2 November. AVHRR images show direct plume transport from Etna to Potenza. Optical depth of 0.1 and lidar ratio of 55 sr at 355 nm have been observed at the moment of direct transport. For the first time, a measurement of the lidar ratio for tropospheric volcanic aerosol has been performed. This lidar ratio value and the estimation of the wavelength dependence of the aerosol backscatter coefficient of 2.4 indicate the presence of young sub‐micron sulfate particles, a low soot content, and the absence of large ash particles.
Land boundary conditions from MODIS data and consequences for the albedo of a climate model
Authors: Tian Y. , Dickinson R. E. , Zhou L. , Myneni R. B. , Friedl M. , Schaaf C. B. , Carroll M. , Gao F.
Published: March 2004

This paper compares seasonal and spatial variations of MODIS albedos with those from the Community Land Model (CLM2). MODIS surface albedo data from September 2000 to August 2002 were used to investigate the model biases. To assess how inaccuracies in the land surface data used in CLM2 contribute to the model albedo biases, we created a new land surface dataset using the highest quality reprocessed MODIS products of leaf area index (LAI), plant functional type (PFT), and fraction of bare soil. A sensitivity experiment using this new data set quantifies the role of each variable and its contribution to the albedo biases. Our results indicate that most of the positive albedo biases result from an underestimation of LAI or an overestimation of the grass/crop fraction. Such biases can be largely reduced when the new data set is used. These results provide information on improving albedo in the model. This new land surface data set is available for use in CLM2.
Multi‐objective inversion of surface waves and receiver functions by competent genetic algorithm applied to the crustal structure of the Paraná Basin, SE Brazil
Authors: An Meijian , Assumpção Marcelo S.
Published: March 2004

Surface wave dispersion and receiver functions are sensitive to different, but dependent, seismic properties. Their joint inversion is multi‐objective and can provide tight constraints on layer‐interfaces and S‐velocities. We used one of the competent genetic algorithms, Bayesian optimization algorithm, as the multi‐objective inversion technique. Multi‐objective criterion of receiver functions and surface wave dispersion can better constrain solutions than each separate objective. We applied this new method to data from three stations in the Paraná Basin, Brazil, and found S‐velocity structure well‐constrained down to 150 km depth. The inverted S‐velocities in the lower crust are less than 3.8 km/s and are lower than in the surrounding foldbelts. Some indication of high velocities (Vs > 4 km/s) in the 5–7 km lowermost crust is given by a Moho transition zone. This may suggest that possible underplating was not widespread in the Paraná basin.
Remote forcing annihilates barrier layer in southeastern Arabian Sea
Authors: Shenoi S. S. C. , Shankar D. , Shetye S. R.
Published: March 2004

Time‐series measurements of temperature and salinity profiles were made every two hours at 74°30′E, 9°13′N in the southeastern Arabian Sea (SEAS) during 22‐March–7‐April and 23‐May–7‐June 2003 as part of the Arabian Sea Monsoon Experiment (ARMEX). The observations show that a 20 m thick barrier layer (BL) exists during March–April owing to a surface layer of low‐salinity waters advected earlier during December–January from the Bay of Bengal. The BL is almost annihilated by 7 April owing to upwelling. The relic BL that survives is annihilated later in May by upwelling, and by the inflow of high‐salinity waters from the north and by mixing due to stronger winds, which deepen the mixed layer. We present evidence from satellite data and arguments based on existing theories to show that both the upwelling and the advection of high‐salinity waters are remotely forced.
Auroral substorm timescales: IMF and seasonal variations
Authors: Chua D. , Parks G. , Brittnacher M. , Germany G. , Spann J.
Published: March 2004

The timescales and phases of auroral substorm activity are quantified in this study using the hemispheric power computed from Polar Ultraviolet Imager (UVI) observations. With this approach we are able to determine substorm phase self consistently from the UVI optical measurements without needing any ancillary metrics for auroral activity. This technique also allows us to combine a quantitative measurement of substorm timescales with the qualitative description of auroral morphology during each event. We show how the characteristics of substorms vary with IMF BZ orientation and season for several hundred substorm events. Substorm intensity, as measured by the rate of energy deposition by electron precipitation, exhibits greater variation with IMF BZ orientation than with season. The timescale of substorm expansion shows comparable variation with both IMF BZ orientation and season. On the other hand, substorm recovery times vary more strongly with season than with IMF BZ direction. The recovery time for substorm activity is well ordered by whether or not the nightside auroral region is sunlit: substorms occurring in the winter and equinox periods have similar recovery timescales which are both roughly a factor of two longer than that for summer when the auroral oval is sunlit. However, IMF BZ orientation is shown to have a strong modulating effect on both substorm expansion and recovery timescales during the summer. The winter‐summer asymmetries in the aurora described by previous studies are more completely explained by the seasonal variations of substorm recovery timescales characterized in this work. Our results support the hypothesis that the ionosphere plays an active role in governing the dynamics of the aurora.
Solar wind control of auroral substorm onset locations observed with the IMAGE‐FUV imagers
Authors: Gérard J.‐C. , Hubert B. , Grard A. , Meurant M. , Mende S. B.
Published: March 2004

The FUV imagers on board the IMAGE satellite provide multispectral snapshots of the polar region every 2 min. The combination of the Wide‐Angle Imaging Camera (WIC) with SI12 (Doppler shifted Lyman‐α) and SI13 (135.6 nm) spectral imagers is used to discriminate between the electron and the proton aurora. We describe a statistical study of the location of 78 substorms observed close to the 2000–2001 winter solstice. The latitudinal distribution of the onsets observed with WIC is asymmetric with a median at 65.6° MLAT and a full width at half maximum (FWHM) of 3.5°. Their local time distribution is concentrated between 2000 and 0200 MLT with a median at 23.4 ± 0.3 hours MLT and a FWHM of 1.8 hours. No statistically significant difference is found in the spatial distribution of the proton and electron onsets. All onsets take place within a region of preexisting proton precipitation, indicating that substorm initiation occurs in regions of stretched but dipole‐like field lines that cross the equatorial plane close to the Earth. Latitudes of substorm onsets are located at a variable distance from the poleward FUV auroral boundary but remain at a nearly constant distance from the equatorward limit of both proton and electron auroral ovals. The magnetic latitudes of the onsets are correlated with some of the solar wind plasma properties measured by the ACE satellite prior to the substorm breakup. In particular, a clear anticorrelation is found between the onset MLAT and the 1‐hour averaged solar wind dynamic pressure. A decrease of the onset latitude is also observed for larger B intensity values. No dependence of the onset MLT on the solar wind speed is observed, in contrast to the relationship expected from the thermal catastrophe model for substorm initiation. Our results are in agreement with models locating the initial instability in the near magnetosphere such as the near‐Earth current disruption models.
Dissociative recombination of N2+, O2+, and NO+: Rate coefficients for ground state and vibrationally excited ions
Authors: Sheehan Clint H. , St.‐Maurice J.‐P.
Published: March 2004

We review recent advances in the study of the dissociative recombination of molecular ions with electrons with a primary emphasis on experimental studies. In particular, we focus on previous experimental measurements of recombination rates for N2+, O2+, and NO+ ions. In the context of this review, we present temperature dependent rate coefficients from recent merged beam studies of the dissociative recombination of N2+, O2+, and NO+ ions with electrons. Identifying underlying physical differences between the various experimental techniques enables a discussion of the effects of vibrational excitation on the dissociative recombination of these major ionospheric species of ions. For T < 1200 K, we conclude that the recombination rates for N2+, O2+, and NO+ ions in the ground electronic and vibrational states respectively are 2.2 × 10−7 (Te/300)−0.39 cm3 s−1, 1.95 × 10−7(Te/300)−0.70 cm3 s−1, and (3.5 ± 0.5) × 10−7(Te/300)−0.69 cm3 s−1. Vibrational excitation is shown to play a significant role in laboratory measurements of these recombination rates. For each of these species, vibrationally excited ions yielded a lower recombination rate than the ground state. We also discuss the recombination of these species of ions for T > 1200 K.
Solar variability of the daytime atomic oxygen O(1S) emission in the middle and lower thermosphere
Authors: Maharaj‐Sharma Rawatee , Shepherd Gordon G.
Published: March 2004

The Wind Imaging Interferometer (WINDII) on board the Upper Atmosphere Research Satellite (UARS) measures winds from the Doppler shifts of airglow emissions, and as a by‐product the volume emission rates (photon cm−3 s−1) of those emissions. This includes the atomic oxygen O(1S) emission at 557.7 nm, which during the daytime is emitted over a large altitude range from about 85 km to over 250 km. Two distinct peaks in altitude are formed, one near 100 km (herein denoted the E region) and one near 150 km (herein the F region). The daytime E region emission was virtually unknown prior to WINDII – it resembles its nighttime counterpart, but the emission rate is much higher and it is broader in vertical extent. Both regions are produced by direct and indirect processes, but the WINDII data show that both behave as Chapman layers, corresponding to production of emission by absorption of solar radiation. The F region processes are fairly well understood, but the direct E region process has not previously been identified. The data are consistent with excitation by photodissociation of O2 dominantly by Lyman‐β. The solar influence is investigated through correlations of daily values of emission rate with six solar indices; the E region yields higher coefficients than the F region, with the highest value for solar Ly‐α at 0.82, which is consistent with the Ly‐β process. For one of the six indices, the GOES xl x‐rays (0.1–0.8 nm), no correlation is evident, in part because the radiances are too low to produce the observed emission, but also because the radiances are seemingly random, not following the solar cycle variation. Variations of atmospheric origin with latitude and longitude are briefly reported upon, and an F region emission rate scale height correlation with temperature is also found.
Comparison of a thermospheric photochemical model with Student Nitric Oxide Explorer (SNOE) observations of nitric oxide
Authors: Barth C. A. , Bailey S. M.
Published: March 2004

A time‐dependent thermospheric model has been used to calculate the nitric oxide density in the lower thermosphere for a 935‐day period, 11 March 1998 to 30 September 2000. This model uses daily values of the observed solar soft X‐ray irradiance (2–7 nm) as an energy input parameter. The model does not include an energy input from auroral electron precipitation. The results of the model calculation of nitric oxide density at 110 km were compared with observations of nitric oxide density made with the Student Nitric Oxide Explorer (SNOE) for the 935‐day period. At the equator the model calculations and the observations agree very well with a linear correlation coefficient of 0.876. The correlation coefficient remains high for the altitude region 107–117 km, the region where solar soft X‐rays (2–7 nm) are the major source of nitric oxide production. The comparison of the model calculations with the observations as a function of latitude show that there is excess nitric oxide poleward of 30°N and S latitude particularly during the fall‐winter season. We believe that the source of this excess nitric oxide is the nitric oxide that is produced in the auroral region (65°–75°N and S geomagnetic latitude) by precipitating auroral electrons. We believe that aurorally produced nitric oxide is transported equatorward by horizontal winds. At midlatitudes the excess nitric oxide decays to about half of its initial value in one day. At times of large geomagnetic storms we believe that aurorally produced nitric oxide is transported all the way to the equator by horizontal winds. The excellent correlation of the model calculations and the SNOE observations of nitric oxide at 110 km between 30°S and 30°N support the hypothesis that solar soft X‐rays are the source of the variability of nitric oxide in the thermosphere at low latitudes.
Numerical modeling of lava flow cooling applied to the 1997 Okmok eruption: Approach and analysis
Authors: Patrick M. R. , Dehn J. , Dean K.
Published: March 2004

Throughout February and March of 1997 Okmok Volcano, in the eastern Aleutian Islands of Alaska, erupted a 6 km long lava flow of basaltic 'a'a within its caldera. A numerical model for lava flow cooling was developed and applied to the flow to better understand the nature of its cooling. Radiation and convection from the surface, as well as conduction to the ground, were used to transport the flow's heat to its surroundings in the model. Internally, a conduction‐only approach moved heat from the interior outward. Vesiculation, latent heat generation, and thermal conductivity changes with temperature are among the other factors that were dynamically accounted for. Results indicate that ambient temperature fluctuations, on the scale of days to weeks, must be taken into account to create an accurate short‐term prediction of lava surface temperature. Daily data of rainfall and ambient temperature, as opposed to yearly averages, greatly increased the accuracy of the model. Furthermore, convective cooling of the lava surface was observed to be a dominant heat loss process during the first 200 days, indicating the convective heat transfer coefficient is a prime determinant of the accuracy of the model for predicting surface temperatures. Over a longer cooling period (2 years), thermal conductivity and porosity proved to be among the dominating factors for heat loss because of the limiting role of conductive heat flow in the interior. The model's flexibility allows application to flows other than the 1997 Okmok eruption.