bluuebunny/crossref_metadata_2025_split huggingface dataset:
Period and damping factor of Pi2 pulsations during oscillatory flow braking in the magnetotail
Authors: Panov E. V. , Baumjohann W. , Nakamura R. , Kubyshkina M. V. , Glassmeier K.‐H. , Angelopoulos V. , Petrukovich A. A. , Sergeev V. A. 
Published: June 2014

AbstractUsing 25 observations of damped oscillatory flow behavior in the near‐Earth plasma sheet by the Time History of Events and Macroscale Interactions during Substorms (THEMIS) probes during the 2008–2009 magnetotail seasons, we compare the oscillation period and the damping factor of the plasma sheet flows with those of the Pi2 magnetic pulsations on the ground at auroral and midlatitudes near the local time of the conjugate ionospheric THEMIS footprints. Whereas the damping of the plasma sheet flows and of the pulsations on the ground occurs on the same time scales, the frequency of the pulsations is on average twice the frequency of the plasma sheet flows. We conclude that larger‐amplitude ground pulsations at auroral latitudes were caused by the oscillatory flow braking in the plasma sheet, presumably through alternating field‐aligned currents as suggested by Panov et al. (2013c).
Seasonal variability of the East Greenland Coastal Current
Authors: Bacon Sheldon , Marshall Abigail , Holliday N. Penny , Aksenov Yevgeny , Dye Stephen R. 
Published: June 2014

AbstractThe East Greenland Coastal Current (EGCC) is characterized as cold, low‐salinity polar waters flowing equatorward on the east Greenland shelf. It is an important conduit of freshwater from the Arctic Ocean, but our present understanding of it is poor, outside of an assortment of measurements which stem mainly from summertime visits by research vessels. This manuscript first describes measurements from moored instruments deployed on the East Greenland shelf (∼63°N) between 2000 and 2004. The measurements are then used to show that a high‐resolution coupled ice‐ocean global general circulation model supports a realistic representation of the EGCC. The results show that the EGCC exists throughout the year and is stronger in winter than in summer. The model EGCC seawater transports are a maximum (minimum) in February (August), at 3.8 (1.9) × 106 m3 s−1. Freshwater transports, including modeled estimates of sea ice transport and referenced to salinity 35.0, are a maximum (minimum) in February (August) at 106 (59) × 103 m3 s−1. The model results show that wind and buoyancy forcing are of similar importance to EGCC transport. An empirical decomposition of the buoyancy‐forced transport into a buoyancy‐only component and a coupled wind and buoyancy component indicates the two to be of similar magnitude in winter. The model annual mean freshwater flux of ∼80–90 × 103 m3 s−1 approaches 50% of the net rate of Arctic freshwater gain, underlining the climatic importance of the EGCC.
Eddies in the Red Sea: A statistical and dynamical study
Authors: Zhan Peng , Subramanian Aneesh C. , Yao Fengchao , Hoteit Ibrahim 
Published: June 2014

AbstractSea level anomaly (SLA) data spanning 1992–2012 were analyzed to study the statistical properties of eddies in the Red Sea. An algorithm that identifies winding angles was employed to detect 4998 eddies propagating along 938 unique eddy tracks. Statistics suggest that eddies are generated across the entire Red Sea but that they are prevalent in certain regions. A high number of eddies is found in the central basin between 18°N and 24°N. More than 87% of the detected eddies have a radius ranging from 50 to 135 km. Both the intensity and relative vorticity scale of these eddies decrease as the eddy radii increase. The averaged eddy lifespan is approximately 6 weeks. AEs and cyclonic eddies (CEs) have different deformation features, and those with stronger intensities are less deformed and more circular. Analysis of long‐lived eddies suggests that they are likely to appear in the central basin with AEs tending to move northward. In addition, their eddy kinetic energy (EKE) increases gradually throughout their lifespans. The annual cycles of CEs and AEs differ, although both exhibit significant seasonal cycles of intensity with the winter and summer peaks appearing in February and August, respectively. The seasonal cycle of EKE is negatively correlated with stratification but positively correlated with vertical shear of horizontal velocity and eddy growth rate, suggesting that the generation of baroclinic instability is responsible for the activities of eddies in the Red Sea.
A catalog of moisture sources for continental climatic regions
Authors: Nieto Raquel , Castillo Rodrigo , Drumond Anita , Gimeno Luis 
Published: June 2014

AbstractThis technical note describes a catalog of moisture sources for two sets of continental climatic regions: one based on regions with similar late 20th century mean climate and similar projected late 21st century precipitation changes, and the other widely used in IPCC assessment reports. By illustrating with one region by classification, the European one was selected and we identify and characterize all the major sources of moisture, and analyze their interannual variability and the role of the three dominant modes of global climate variability, including the El Niño‐Southern Oscillation (ENSO) and the Northern and Southern Annular Modes (NAM, SAM). We also estimate the influence of those oceanic regions that will see the greatest increases in evaporation rate in future years.
Constraining mid to late Holocene relative sea level change in the southern equatorial Pacific Ocean relative to the Society Islands, French Polynesia
Authors: Rashid Rashid , Eisenhauer Anton , Stocchi Paolo , Liebetrau Volker , Fietzke Jan , Rüggeberg Andres , Dullo Wolf‐Christian 
Published: June 2014

AbstractPrecisely quantifying the current climate‐related sea level change requires accurate knowledge of long‐term geological processes known as Glacial Isostatic Adjustments (GIA). Although the major postglacial melting phase is likely to have ended ∼6–4 ka BP (before present), GIA is still significantly affecting the present‐day vertical position of the mean sea surface and the sea bottom. Here we present empirical rsl (relative sea level) data based on U/Th dated fossil corals from reef platforms of the Society Islands, French Polynesia, together with the corresponding GIA‐modeling. Fossil coral data constrain the timing and amplitude of rsl variations after the Holocene sea level maximum (HSLM). Upon correction for isostatic island subsidence, we find that local rsl was at least ∼1.5 ± 0.4 m higher than present at ∼5.4 ka. Later, minor amplitude variations occurred until ∼2 ka, when the rsl started dropping to its present position with a rate of ∼0.4 mm/yr. The data match with predicted rsl curves based on global ice‐sheet chronologies confirming the role of GIA‐induced ocean siphoning effect throughout the mid to late Holocene. A long lasting Late Holocene highstand superimposed with second‐order amplitudinal fluctuations as seen from our data suggest that the theoretical predicted timing of rsl change can still be refined pending future calibration.
Brittle‐viscous deformation, slow slip, and tremor
Authors: Fagereng Åke , Hillary Graeme W. B. , Diener Johann F. A. 
Published: June 2014

AbstractGeophysical observations have illuminated a spectrum of fault slip styles from continuous aseismic sliding to fast earthquake slip. We study exhumed intercalated lenses of oceanic crust and sedimentary rocks, deformed to high shear strains. Deformation was partitioned between fractured, rigid blocks, with lengths of tens to hundreds of meters, and surrounding metapelites characterized by interconnected phyllosilicate networks. Under inferred conditions of low effective stress at temperatures > 500°C, locally and transiently elevated shear strain rate in phyllosilicates deforming by dislocation creep can reach those needed for transient slow slip. Concurrently, increased matrix strain rate likely stimulates brittle failure in rigid lenses. The ubiquitous presence of quartz veins and microfractures within rigid material provides evidence for brittle deformation occurring coincident with viscous shearing flow. We suggest that geophysically observed tremor and slow slip may be a manifestation of strain partitioning, where deformation is accommodated viscously in a matrix enveloping rigid lenses.
Empirical estimates of kinetic energy from some recent U.S. tornadoes
Authors: Fricker T. , Elsner J. B. , Camp P. , Jagger T. H. 
Published: June 2014

AbstractData from some recent tornado damage assessments are used to compute the percentage of damage path area by enhanced Fujita (EF) rating and to estimate kinetic energy. Only a small fraction of the damage area gets the highest damage rating, and this fraction is lower than a model used by the U.S. Nuclear Regulatory Commission. However, estimates of kinetic energy derived from a characteristic wind speed for each EF rating and the fraction of area with that rating match kinetic energy estimates using the model percentages. On average, the higher the EF rating, the larger the kinetic energy, but there is large variability in the relationship. The average total kinetic energy over the EF1 tornadoes examined in the study is 0.61 TJ, which compares with an average of 2.37 TJ, 40.1 TJ, 36.5 TJ, and 50.4 TJ for the EF2, EF3, EF4, and EF5 tornadoes, respectively. The most energetic tornado examined had a maximum damage rating of EF3.
Magnetic fluctuations embedded in dipolarization inside geosynchronous orbit and their associated selective acceleration of O+ ions
Authors: Nosé M. , Takahashi K. , Keika K. , Kistler L. M. , Koga K. , Koshiishi H. , Matsumoto H. , Shoji M. , Miyashita Y. , Nomura R. 
Published: June 2014

AbstractWe study magnetic fluctuations embedded in dipolarizations in the inner magnetosphere (a geocentric distance of ≤6.6 RE) and their associated ion flux changes, using the Engineering Test Satellite VIII and Active Magnetospheric Particle Tracer Explorers/CCE satellites. We select seven events of dipolarization that occur during the main phase of magnetic storms having a minimum value of the Dst index less than −40 nT. It is found that (1) all of the dipolarization events are accompanied by strong magnetic fluctuations with the major frequency close to the local O+ gyrofrequency; (2) the magnetic fluctuations appear with significant amplitude in the component nearly parallel to the local magnetic field; (3) the strong flux enhancement is seen in the energy range of 1–10 keV only for O+ ions. In terms of frequency and dominant components of the magnetic fluctuations, they are considered to be excited by the drift‐driven electromagnetic ion cyclotron (EMIC) instability that is recently identified with the linear theory. We perform particle tracing for H+ and O+ ions in the electromagnetic fields modeled by the linear dispersion relation of the drift‐driven EMIC instability. Results show that the O+ ions are accelerated to the energy range of 0.5–5 keV and undergo a significant modification of the spectral shape, while the H+ ions have no clear change of spectral shape, being consistent with the observations. We therefore suggest that the electromagnetic fluctuations associated with the dipolarizations can accelerate O+ ions locally and nonadiabatically in the inner magnetosphere. This selective acceleration of O+ ions may play a role in enhancing the O+ energy density in the storm time ring current.
The effect of background conditions on the ionospheric response to solar flares
Authors: Zhu Jie , Ridley Aaron J. 
Published: June 2014

AbstractThe ionospheric response to two X5 solar flares that occurred in different seasons was investigated using the global ionosphere‐thermosphere model. Two questions were investigated: (a) how do different solar flares with similar X‐ray peak intensities disturb the ionosphere during the same background and driving conditions? and (b) how do the geomagnetic field and season affect the ionospheric response to solar flares? These questions were investigated by exchanging the two X5 flares for each other so that there were two pairs of flares with (1) the same background conditions but different irradiances and (2) different background conditions but the same irradiance. The simulations showed that the different solar flares into the same background caused ionospheric disturbances of similar profiles but different magnitudes due to differences in the incident energies, while the same flare spectra caused perturbations of similar magnitudes but different profiles in different backgrounds. On the dayside, the response is primarily controlled by the total integrated energy of the flare, independent of the background. For the northern and southern polar regions, the response is strongly controlled by the solar zenith angle and the incident energy, while the background plays a secondary role. On the nightside, the background conditions, including the magnetic field and season, play a primary role, with the neutral winds and electrodynamics driving the ionospheric response.
The kinetic ballooning/interchange instability as a source of dipolarization fronts and auroral streamers
Authors: Pritchett P. L. , Coroniti F. V. , Nishimura Y. 
Published: June 2014

AbstractThe possibility that the dipolarization fronts (DFs) observed in the plasma sheet could be produced by the ballooning/interchange instability is explored using three‐dimensional electromagnetic particle‐in‐cell simulations. The localized interchange heads produced in the nonlinear stage of the instability exhibit the main near‐equatorial properties of a DF: the cross‐tail extent is on the order of 1 RE, the ramp‐ups in Bz and the magnitude of Ey as well as the sharp density decrease all occur on the ion inertial scale, while there is a more gradual increase in the bulk flow. The field‐aligned currents associated with the breakup of the head should produce a structuring of the corresponding auroral streamer in the ionosphere, a result that is confirmed by Time History of Events and Macroscale Interactions during Substorms (THEMIS) all‐sky imager data. The dissipation associated with the head occurs in electron‐scale regions in the center of the plasma sheet. Away from the center, the head is strongly modulated by waves with frequency on the order of the ion gyrofrequency. The strength of the accompanying Ey oscillations is in the range of 30–50 mV/m, and the δE/δB ratio is 3–4 times the local Alfvén speed. The waves appear to be produced by the electromagnetic current‐driven ion cyclotron instability.
Radiation belt electron acceleration by chorus waves during the 17 March 2013 storm
Authors: Li W. , Thorne R. M. , Ma Q. , Ni B. , Bortnik J. , Baker D. N. , Spence H. E. , Reeves G. D. , Kanekal S. G. , Green J. C. , Kletzing C. A. , Kurth W. S. , Hospodarsky G. B. , Blake J. B. , Fennell J. F. , Claudepierre S. G. 
Published: June 2014

AbstractLocal acceleration driven by whistler‐mode chorus waves is fundamentally important for accelerating seed electron populations to highly relativistic energies in the outer radiation belt. In this study, we quantitatively evaluate chorus‐driven electron acceleration during the 17 March 2013 storm, when the Van Allen Probes observed very rapid electron acceleration up to several MeV within ~12 hours. A clear radial peak in electron phase space density (PSD) observed near L* ~4 indicates that an internal local acceleration process was operating. We construct the global distribution of chorus wave intensity from the low‐altitude electron measurements made by multiple Polar Orbiting Environmental Satellites (POES) satellites over a broad region, which is ultimately used to simulate the radiation belt electron dynamics driven by chorus waves. Our simulation results show remarkable agreement in magnitude, timing, energy dependence, and pitch angle distribution with the observed electron PSD near its peak location. However, radial diffusion and other loss processes may be required to explain the differences between the observation and simulation at other locations away from the PSD peak. Our simulation results, together with previous studies, suggest that local acceleration by chorus waves is a robust and ubiquitous process and plays a critical role in accelerating injected seed electrons with convective energies (~100 keV) to highly relativistic energies (several MeV).
Altitudinal dependence of evening equatorial F region vertical plasma drifts
Authors: Fejer B. G. , Hui D. , Chau J. L. , Kudeki E. 
Published: June 2014

AbstractWe use Jicamarca incoherent scatter radar measurements to study for the first time the altitudinal variations of late afternoon and early night equatorial F region vertical plasma drifts. We also present the initial vertical drift measurements over the altitudinal range from about 200 to 2000 km. These data show that the afternoon drifts decrease weakly with altitude. Near their evening prereversal enhancements, the vertical drifts generally increase with altitude below about the F layer peak, decrease with height near the F layer peak and above, and are nearly height independent in the (solar flux dependent) topside ionosphere. The transition altitudes from height‐decreasing to height‐independent evening upward drifts decrease with altitude from solar maximum to solar minimum. After their reversal to downward, the vertical drifts do not change much with height. The altitudinal dependence of the evening vertical drifts has large day‐to‐day variability and is closely related to the time dependence of the zonal drifts, as expected from the curl‐free electric field condition.
Increasing life expectancy of water resources literature
Authors: Heistermann M. , Francke T. , Georgi C. , Bronstert A. 
Published: June 2014

AbstractIn a study from 2008, Larivière and colleagues showed, for the field of natural sciences and engineering, that the median age of cited references is increasing over time. This result was considered counterintuitive: with the advent of electronic search engines, online journal issues and open access publications, one could have expected that cited literature is becoming younger. That study has motivated us to take a closer look at the changes in the age distribution of references that have been cited in water resources journals since 1965. Not only could we confirm the findings of Larivière and colleagues. We were also able to show that the aging is mainly happening in the oldest 10–25% of an average reference list. This is consistent with our analysis of top‐cited papers in the field of water resources. Rankings based on total citations since 1965 consistently show the dominance of old literature, including text books and research papers in equal shares. For most top‐cited old‐timers, citations are still growing exponentially. There is strong evidence that most citations are attracted by publications that introduced methods which meanwhile belong to the standard toolset of researchers and practitioners in the field of water resources. Although we think that this trend should not be overinterpreted as a sign of stagnancy, there might be cause for concern regarding how authors select their references. We question the increasing citation of textbook knowledge as it holds the risk that reference lists become overcrowded, and that the readability of papers deteriorates.
Estimating information entropy for hydrological data: One‐dimensional case
Authors: Gong Wei , Yang Dawen , Gupta Hoshin V. , Nearing Grey 
Published: June 2014

AbstractThere has been a recent resurgence of interest in the application of Information Theory to problems of system identification in the Earth and Environmental Sciences. While the concept of entropy has found increased application, little attention has yet been given to the practical problems of estimating entropy when dealing with the unique characteristics of two commonly used kinds of hydrologic data: rainfall and runoff. In this paper, we discuss four important issues of practical relevance that can bias the computation of entropy if not properly handled. The first (zero effect) arises when precipitation and ephemeral streamflow data must be viewed as arising from a discrete‐continuous hybrid distribution due to the occurrence of many zero values (e.g., days with no rain/no runoff). Second, in the widely used bin‐counting method for estimation of PDF's, significant error can be introduced if the bin width is not carefully selected. The third (measurement effect) arises due to the fact that continuously varying hydrologic variables can typically only be observed discretely to some degree of precision. The Fourth (skewness effect) arises when the distribution of a variable is significantly skewed. Here we present an approach that can deal with all four of these issues, and test them with artificially generated and real hydrological data. The results indicate that the method is accurate and robust.
Using the Type II Cycloisomerization Reaction of 1,6‐Enynes as a Mechanistic Probe to Identify the Real Catalytic Species of GaX3 and InX3
Authors: Zhuo Lian‐Gang , Shi Yao‐Cheng , Yu Zhi‐Xiang 
Published: June 2014

AbstractPreviously, we found that InCl2+ is the real catalytic species in InCl3‐catalyzed type II cycloisomerization of 1,6‐enynes for generating nonconjugated dienes. We further used this cycloisomerization reaction as a mechanistic probe to study whether GaCl3, GaBr3, InBr3, InI3 also have GaCl2+, GaBr2+, InBr2+, and InI2+ as the real catalytic species. Experimental and computational results from the mechanistic probe reaction here support that the real catalytic species are positively charged GaCl2+, GaBr2+, InBr2+, and InI2+.
Bio‐composites for structural applications: Poly‐l‐lactide reinforced with long sisal fiber bundles
Authors: Prajer Marek , Ansell Martin P. 
Published: June 2014

ABSTRACTFully bio‐based and biodegradable composites were compression molded from unidirectionally aligned sisal fiber bundles and a polylactide polymer matrix (PLLA). Caustic soda treatment was employed to modify the strength of sisal fibers and to improve fiber to matrix adhesion. Mechanical properties of PLLA/sisal fiber composites improved with caustic soda treatment: the mean flexural strength and modulus increased from 279 MPa and 19.4 GPa respectively to 286 MPa and 22 GPa at a fiber volume fraction of Vf = 0.6. The glass transition temperature decreased with increasing fiber content in composites reinforced with untreated sisal fibers due to interfacial friction. The damping at the caustic soda‐treated fibers‐PLLA interface was reduced due to the presence of transcrystalline morphology at the fiber to matrix interface. It was demonstrated that high strength, high modulus sisal‐PLLA composites can be produced with effective stress transfer at well‐bonded fiber to matrix interfaces. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40999.
A slow shape‐recovery polymer based on polylactic acid
Authors: Okamoto Hirotaka , Katagiri Yoshihide , Nakano Mitsuru , Usuki Arimitsu 
Published: June 2014

ABSTRACTShape‐recovery materials are expected to have numerous applications as ductile structural compounds which can recover their shape after significant deformations. We report a new type of shape‐recovery polymer consisting of polylactic acid (PLA) derived from glucose compounded with a cinnamic acid ester derived from lignin. Unlike existing shape‐memory polymers, this shape‐recovery polymer exhibits a spontaneous but gradual recovery of its original dimensions, following elongation and release of stress, over a period ranging from several hours to days, without the requirement for external stimulus. In the case of a typical rubber or elastomer, shape‐recovery takes place almost instantaneously after deformation due to the energy stored by the material. Although the slow shape‐recovery polymer reported herein appears to exhibit plastic deformation as if the energy of elongation is lost, it eventually recovers from the deformation in the same manner as an elastic material. This material may have applicability to the energy‐absorbing and shape restoration automotive parts. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 41004.