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Sample records for antarctic polar vortex

  1. Antarctic air over New Zealand following vortex breakdown in 1998

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    J. Ajtic

    2003-11-01

    Full Text Available An ozonesonde profile over the Network for Detection of Stratospheric Change (NDSC site at Lauder (45.0° S, 169.7° E, New Zealand, for 24 December 1998 showed atypically low ozone centered around 24 km altitude (600 K potential temperature. The origin of the anomaly is explained using reverse domain filling (RDF calculations combined with a PV/O3 fitting technique applied to ozone measurements from the Polar Ozone and Aerosol Measurement (POAM III instrument. The RDF calculations for two isentropic surfaces, 550 and 600 K, show that ozone-poor air from the Antarctic polar vortex reached New Zealand on 24–26 December 1998. The vortex air on the 550 K isentrope originated in the ozone hole region, unlike the air on 600 K where low ozone values were caused by dynamical effects. High-resolution ozone maps were generated, and their examination shows that a vortex remnant situated above New Zealand was the cause of the altered ozone profile on 24 December. The maps also illustrate mixing of the vortex filaments into southern midlatitudes, whereby the overall mid-latitude ozone levels were decreased.Key words. Atmospheric composition and structure (middle atmosphere composition and chemistry – Meteorology and atmospheric dynamics (middle atmosphere dynamics

  2. Antarctic air over New Zealand following vortex breakdown in 1998

    Directory of Open Access Journals (Sweden)

    J. Ajtic

    Full Text Available An ozonesonde profile over the Network for Detection of Stratospheric Change (NDSC site at Lauder (45.0° S, 169.7° E, New Zealand, for 24 December 1998 showed atypically low ozone centered around 24 km altitude (600 K potential temperature. The origin of the anomaly is explained using reverse domain filling (RDF calculations combined with a PV/O3 fitting technique applied to ozone measurements from the Polar Ozone and Aerosol Measurement (POAM III instrument. The RDF calculations for two isentropic surfaces, 550 and 600 K, show that ozone-poor air from the Antarctic polar vortex reached New Zealand on 24–26 December 1998. The vortex air on the 550 K isentrope originated in the ozone hole region, unlike the air on 600 K where low ozone values were caused by dynamical effects. High-resolution ozone maps were generated, and their examination shows that a vortex remnant situated above New Zealand was the cause of the altered ozone profile on 24 December. The maps also illustrate mixing of the vortex filaments into southern midlatitudes, whereby the overall mid-latitude ozone levels were decreased.

    Key words. Atmospheric composition and structure (middle atmosphere composition and chemistry – Meteorology and atmospheric dynamics (middle atmosphere dynamics

  3. Insights into the three-dimensional Lagrangian geometry of the Antarctic polar vortex

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    Curbelo, Jezabel; José García-Garrido, Víctor; Mechoso, Carlos Roberto; Mancho, Ana Maria; Wiggins, Stephen; Niang, Coumba

    2017-07-01

    In this paper we study the three-dimensional (3-D) Lagrangian structures in the stratospheric polar vortex (SPV) above Antarctica. We analyse and visualize these structures using Lagrangian descriptor function M. The procedure for calculation with reanalysis data is explained. Benchmarks are computed and analysed that allow us to compare 2-D and 3-D aspects of Lagrangian transport. Dynamical systems concepts appropriate to 3-D, such as normally hyperbolic invariant curves, are discussed and applied. In order to illustrate our approach we select an interval of time in which the SPV is relatively undisturbed (August 1979) and an interval of rapid SPV changes (October 1979). Our results provide new insights into the Lagrangian structure of the vertical extension of the stratospheric polar vortex and its evolution. Our results also show complex Lagrangian patterns indicative of strong mixing processes in the upper troposphere and lower stratosphere. Finally, during the transition to summer in the late spring, we illustrate the vertical structure of two counterrotating vortices, one the polar and the other an emerging one, and the invariant separatrix that divides them.

  4. Ozone and water vapour in the austral polar stratospheric vortex and sub-vortex

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    E. Peet

    2004-12-01

    Full Text Available In-situ measurements of ozone and water vapour, in the Antarctic lower stratosphere, were made as part of the APE-GAIA mission in September and October 1999. The measurements show a distinct difference above and below the 415K isentrope. Above 415K, the chemically perturbed region of low ozone and water vapour is clearly evident. Below 415K, but still above the tropopause, no sharp meridional gradients in ozone and water vapour were observed. The observations are consistent with analyses of potential vorticity from the European Centre for Medium Range Weather Forecasting, which show smaller radial gradients at 380K than at 450K potential temperature. Ozone loss in the chemically perturbed region above 415K averages 5ppbv per day for mid-September to mid-October. Apparent ozone loss rates in the sub-vortex region are greater, at 7ppbv per day. The data support, therefore, the existence of a sub-vortex region in which meridional transport is more efficient than in the vortex above. The low ozone mixing ratios in the sub-vortex region may be due to in-situ chemical destruction of ozone or transport of ozone-poor air out of the bottom of the vortex. The aircraft data we use cannot distinguish between these two processes. Key words. Meteorology and atmospheric dynamics polar meteorology – Atmospheric composition and structure (middle atmosphere–composition and chemistry

  5. Chemical ozone losses in Arctic and Antarctic polar winter/spring season derived from SCIAMACHY limb measurements 2002–2009

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    T. Sonkaew

    2013-02-01

    Full Text Available Stratospheric ozone profiles are retrieved for the period 2002–2009 from SCIAMACHY measurements of limb-scattered solar radiation in the Hartley and Chappuis absorption bands of ozone. This data set is used to determine the chemical ozone losses in both the Arctic and Antarctic polar vortices by averaging the ozone in the vortex at a given potential temperature. The chemical ozone losses at isentropic levels between 450 K and 600 K are derived from the difference between observed ozone abundances and the ozone modelled taking diabatic cooling into account, but no chemical ozone loss. Chemical ozone losses of up to 30–40% between mid-January and the end of March inside the Arctic polar vortex are reported. Strong inter-annual variability of the Arctic ozone loss is observed, with the cold winters 2004/2005 and 2006/2007 showing chemical ozone losses inside the polar vortex at 475 K, where 1.7 ppmv and 1.4 ppmv of ozone were removed, respectively, over the period from 22 January to beginning of April and 0.9 ppmv and 1.2 ppmv, respectively, during February. For the winters of 2007/2008 and 2002/2003, ozone losses of about 0.8 ppmv and 0.4 ppmv, respectively are estimated at the 475 K isentropic level for the period from 22 January to beginning of April. Essentially no ozone losses were diagnosed for the relatively warm winters of 2003/2004 and 2005/2006. The maximum ozone loss in the SCIAMACHY data set was found in 2007 at the 600 K level and amounted to about 2.1 ppmv for the period between 22 January and the end of April. Enhanced losses close to this altitude were found in all investigated Arctic springs, in contrast to Antarctic spring. The inter-annual variability of ozone losses and PSC occurrence rates observed during Arctic spring is consistent with the known QBO effects on the Arctic polar vortex, with exception of the unusual Arctic winter 2008/2009.

    The maximum total ozone mass loss of about 25 million tons was found in the

  6. Plasmonic vortex generator without polarization dependence

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    Wang, Han; Liu, Lixia; Liu, Chunxiang; Li, Xing; Wang, Shuyun; Xu, Qing; Teng, Shuyun

    2018-03-01

    In view of the limitations of vortex generators with polarization dependence at present, we propose a plasmonic vortex generator composed of rectangular holes etched in silver film, in which the optical vortex can be generated under arbitrary linearly polarized light illumination. Two sets of rectangular holes are arranged equidistantly on a circle and rotate in postulate directions. Theoretical analysis provides the design principle for the vortex generator, and numerical simulations give guidance on designating the vortex generator parameters. Experimental measurements verify the performance of the proposed vortex generator. Moreover, two alternative structures for the generation of a plasmonic vortex are also provided in this paper. The resulting perfect vortex, compact structure and flexible illumination conditions will lead to wide applications of this plasmonic vortex generator.

  7. Evolution of the Antarctic polar vortex in spring: Response of a GCM to a prescribed Antarctic ozone hole

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    Boville, B. A.; Kiehl, J. T.; Briegleb, B. P.

    1988-01-01

    The possible effect of the Antartic ozone hole on the evolution of the polar vortex during late winter and spring using a general circulation model (GCM) is examined. The GCM is a version of the NCAR Community Climate Model whose domain extends from the surface to the mesosphere and is similar to that described on Boville and Randel (1986). Ozone is not a predicted variable in the model. A zonally averaged ozone distribution is specified as a function of latitude, pressure and month for the radiation parameterization. Rather that explicitly address reasons for the formation of the ozone hole, researchers postulate its existence and ask what effect it has on the subsequent evolution of the vortex. The evolution of the model when an ozone hole is imposed is then discussed.

  8. Persistence of Antarctic polar stratospheric clouds

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    Mccormick, M. Patrick; Trepte, C. R.

    1988-01-01

    The persistence of Polar Stratospheric Clouds (PSCs) observed by the Stratospheric Aerosol Measurement (SAM) 2 satellite sensor over a 9-year period is compared and contrasted. Histograms of the SAM 2 1.0 micron extinction ratio data (aerosol extinction normalized by the molecular extinction) at an altitude of 18 km in the Antarctic have been generated for three 10-day periods in the month of September. Statistics for eight different years (1979 to 1982 and 1984 to 1987) are shown in separate panels for each figure. Since the SAM 2 system is a solar occultation experiment, observations are limited to the edge of the polar night and no measurements are made deep within the vortex where temperatures could be colder. For this reason, use is made of the NMC global gridded fields and the known temperature-extinction relationship to infer additional information on the occurrence and areal coverage of PSCs. Calculations of the daily areal coverage of the 195 K isotherm will be presented for this same period of data. This contour level lies in the range of the predicted temperature for onset of the Type 1 particle enhancement mode at 50 mb (Poole and McCormick, 1988b) and should indicate approximately when formation of the binary HNO3-H2O particles begins.

  9. Spin-orbit torque induced magnetic vortex polarity reversal utilizing spin-Hall effect

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    Li, Cheng; Cai, Li; Liu, Baojun; Yang, Xiaokuo; Cui, Huanqing; Wang, Sen; Wei, Bo

    2018-05-01

    We propose an effective magnetic vortex polarity reversal scheme that makes use of spin-orbit torque introduced by spin-Hall effect in heavy-metal/ferromagnet multilayers structure, which can result in subnanosecond polarity reversal without endangering the structural stability. Micromagnetic simulations are performed to investigate the spin-Hall effect driven dynamics evolution of magnetic vortex. The mechanism of magnetic vortex polarity reversal is uncovered by a quantitative analysis of exchange energy density, magnetostatic energy density, and their total energy density. The simulation results indicate that the magnetic vortex polarity is reversed through the nucleation-annihilation process of topological vortex-antivortex pair. This scheme is an attractive option for ultra-fast magnetic vortex polarity reversal, which can be used as the guidelines for the choice of polarity reversal scheme in vortex-based random access memory.

  10. Determination of the polarization states of an arbitrary polarized terahertz beam: vectorial vortex analysis.

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    Wakayama, Toshitaka; Higashiguchi, Takeshi; Oikawa, Hiroki; Sakaue, Kazuyuki; Washio, Masakazu; Yonemura, Motoki; Yoshizawa, Toru; Tyo, J Scott; Otani, Yukitoshi

    2015-03-24

    Vectorial vortex analysis is used to determine the polarization states of an arbitrarily polarized terahertz (0.1-1.6 THz) beam using THz achromatic axially symmetric wave (TAS) plates, which have a phase retardance of Δ = 163° and are made of polytetrafluorethylene. Polarized THz beams are converted into THz vectorial vortex beams with no spatial or wavelength dispersion, and the unknown polarization states of the incident THz beams are reconstructed. The polarization determination is also demonstrated at frequencies of 0.16 and 0.36 THz. The results obtained by solving the inverse source problem agree with the values used in the experiments. This vectorial vortex analysis enables a determination of the polarization states of the incident THz beam from the THz image. The polarization states of the beams are estimated after they pass through the TAS plates. The results validate this new approach to polarization detection for intense THz sources. It could find application in such cutting edge areas of physics as nonlinear THz photonics and plasmon excitation, because TAS plates not only instantaneously elucidate the polarization of an enclosed THz beam but can also passively control THz vectorial vortex beams.

  11. Controlling vortex chirality and polarity by geometry in magnetic nanodots

    OpenAIRE

    Agramunt Puig, Sebastià

    2014-01-01

    The independent control of both vortex chirality and polarity is a significant challenge in magnetic devices based on nano-sized magnetic vortex structures. By micromagnetic simulations here, we show that in soft ferromagnetic nanodots with an adequate modulated thickness, the desired combination of chirality and polarity can be achieved just by changing the direction of the in-plane applied magnetic field. Despite the complex behavior, the vortex chirality and polarity control can be summari...

  12. Optically induced rotation of Rayleigh particles by vortex beams with different states of polarization

    International Nuclear Information System (INIS)

    Li, Manman; Yan, Shaohui; Yao, Baoli; Liang, Yansheng; Lei, Ming; Yang, Yanlong

    2016-01-01

    Optical vortex beams carry optical orbital angular momentum (OAM) and can induce an orbital motion of trapped particles in optical trapping. We show that the state of polarization (SOP) of vortex beams will affect the details of this optically induced orbital motion to some extent. Numerical results demonstrate that focusing the vortex beams with circular, radial or azimuthal polarizations can induce a uniform orbital motion on a trapped Rayleigh particle, while in the focal field of the vortex beam with linear polarization the particle experiences a non-uniform orbital motion. Among the formers, the vortex beam with circular polarization induces a maximum optical torque on the particle. Furthermore, by varying the topological charge of the vortex beams, the vortex beam with circular polarization gives rise to an optimum torque superior to those given by the other three vortex beams. These facts suggest that the circularly polarized vortex beam is more suitable for rotating particles. - Highlights: • States of polarization of vortex beams affect the optically induced orbital motion of particles. • The dependences of the force and orbital torque on the topological charge, the size and the absorptivity of particles were calculated. • Focused vortex beams with circular, radial or azimuthal polarizations induce a uniform orbital motion on particles. • Particles experience a non-uniform orbital motion in the focused linearly polarized vortex beam. • The circularly polarized vortex beam is a superior candidate for rotating particles.

  13. On the cryogenic removal of NOy from the Antarctic polar stratosphere

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    S. Smyshlyaev

    2003-06-01

    Full Text Available We review current knowledge about the annual cycle of transport of nitrogen oxides to, and removal from, the polar stratosphere, with particular attention to Antarctica where the annual winter denitrifi cation process is both regular in occurrence and severe in effect. Evidence for a large downward fl ux of NOy from the mesosphere to the stratosphere, fi rst seen briefl y in the Limb Infrared Monitor of the Stratosphere (LIMS data from the Arctic winter of 1978-1979, has been found during the 1990s in both satellite and ground-based observations, though this still seems to be omitted from many atmospheric models. When incorporated in the Stony Brook- St. Petersburg two dimensional (2D transport and chemistry model, more realistic treatment of the NOy fl ux, along with sulfate transport from the mesosphere, sulfate aerosol formation where temperature is favorable, and the inclusion of a simple ion-cluster reaction, leads to good agreement with observed HNO3 formation in the mid-winter middle to upper stratosphere. To further emphasize the importance of large fl uxes of thermospheric and mesospheric NOy into the polar stratosphere, we have used observations, supplemented with model calculations, to defi ne new altitude dependent correlation curves between N2O and NOy. These are more suitable than those previously used in the literature to represent conditions within the Antarctic vortex region prior to and during denitrifi cation by Polar Stratospheric Cloud (PSC particles. Our NOy -N2O curves lead to a 40% increase in the average amount of NOy removed during the Antarctic winter with respect to estimates calculated using NOy-N2O curves from the Atmospheric Trace Molecule Spectroscopy (ATMOS/ATLAS-3 data set.

  14. Control of magnetic vortex polarity by the phase difference between voltage signals

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    Cui, Huanqing; Cai, Li; Yang, Xiaokuo; Wang, Sen; Zhang, Mingliang; Li, Cheng; Feng, Chaowen

    2018-02-01

    Using micromagnetic simulations, we investigate the voltage control of magnetic vortex polarity based on a designed multiferroic heterostructure that contains two separate piezoelectric films beneath a magnetostrictive nanodisk. The results show that controllable switching of vortex polarity can be achieved by proper modulation of the phase difference between two sinusoidal voltage pulses V1 and V2, which are applied to the two separate piezoelectric films, respectively. The frequencies of V1 and V2 are set at the gyrotropic eigenfrequency fG of the nanodisk, and the vortex polarity switching is completed via the nucleation-annihilation process of the vortex-antivortex pair. Our findings provide an additional effective means for ultralow power switching of the magnetic vortex, which lays the foundation for voltage-controlled vortex random access memory.

  15. Air mass exchange across the polar vortex edge during a simulated major stratospheric warming

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    G. Günther

    Full Text Available The dynamics of the polar vortex in winter and spring play an important role in explaining observed low ozone values. A quantification of physical and chemical processes is necessary to obtain information about natural and anthropogenic causes of fluctuations of ozone. This paper aims to contribute to answering the question of how permeable the polar vortex is. The transport into and out of the vortex ("degree of isolation" remains the subject of considerable debate. Based on the results of a three-dimensional mechanistic model of the middle atmosphere, the possibility of exchange of air masses across the polar vortex edge is investigated. Additionally the horizontal and vertical structure of the polar vortex is examined. The model simulation used for this study is related to the major stratospheric warming observed in February 1989. The model results show fair agreement with observed features of the major warming of 1989. Complex structures of the simulated polar vortex are illustrated by horizontal and vertical cross sections of potential vorticity and inert tracer. A three-dimensional view of the polar vortex enables a description of the vortex as a whole. During the simulation two vortices and an anticyclone, grouped together in a very stable tripolar structure, and a weaker, more amorphous anticyclone are formed. This leads to the generation of small-scale features. The results also indicate that the permeability of the vortex edges is low because the interior of the vortices remain isolated during the simulation.

  16. Air mass exchange across the polar vortex edge during a simulated major stratospheric warming

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    G. Günther

    1995-07-01

    Full Text Available The dynamics of the polar vortex in winter and spring play an important role in explaining observed low ozone values. A quantification of physical and chemical processes is necessary to obtain information about natural and anthropogenic causes of fluctuations of ozone. This paper aims to contribute to answering the question of how permeable the polar vortex is. The transport into and out of the vortex ("degree of isolation" remains the subject of considerable debate. Based on the results of a three-dimensional mechanistic model of the middle atmosphere, the possibility of exchange of air masses across the polar vortex edge is investigated. Additionally the horizontal and vertical structure of the polar vortex is examined. The model simulation used for this study is related to the major stratospheric warming observed in February 1989. The model results show fair agreement with observed features of the major warming of 1989. Complex structures of the simulated polar vortex are illustrated by horizontal and vertical cross sections of potential vorticity and inert tracer. A three-dimensional view of the polar vortex enables a description of the vortex as a whole. During the simulation two vortices and an anticyclone, grouped together in a very stable tripolar structure, and a weaker, more amorphous anticyclone are formed. This leads to the generation of small-scale features. The results also indicate that the permeability of the vortex edges is low because the interior of the vortices remain isolated during the simulation.

  17. Independent control of the vortex chirality and polarity in a pair of magnetic nanodots

    Energy Technology Data Exchange (ETDEWEB)

    Li, Junqin; Wang, Yong, E-mail: wangyong@sinap.ac.cn; Cao, Jiefeng; Meng, Xiangyu; Zhu, Fangyuan; Wu, Yanqing; Tai, Renzhong

    2017-08-01

    Independent control of the vortex chirality and polarity is realized by changing the in-plane magnetic field direction in nanodot pair through Object Oriented Micromagnetic Framework (OOMMF) simulation. The two magnetic circles are close to each other and have magnetic interaction. The two circles always have the same polarity and opposite chirality at every remanent state. There are totally four predictable magnetic states in the nanodot pair which can be obtained in the remanent state relaxed from the saturation state along all possible directions. An explanation on the formation of vortex states is given by vortex dynamics. The vortex states are stable in large out-of-plane magnetic field which is in a direction opposite to the vortex polarity. The geometry of the nanodot pair gives a way to easily realize a vortex state with specific polarity and chirality.

  18. Antarctic ozone loss in 1989-2010: evidence for ozone recovery?

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    Kuttippurath, J.; Lefèvre, F.; Pommereau, J.-P.; Roscoe, H. K.; Goutail, F.; Pazmiño, A.; Shanklin, J. D.

    2012-04-01

    We present a detailed estimation of chemical ozone loss in the Antarctic polar vortex from 1989 to 2010. The analyses include ozone loss estimates for 12 Antarctic ground-based (GB) stations. All GB observations show minimum ozone in the late September-early October period. Among the stations, the lowest minimum ozone values are observed at South Pole and the highest at Dumont d'Urville. The ozone loss starts by mid-June at the vortex edge and then progresses towards the vortex core with time. The loss intensifies in August-September, peaks by the end of September-early October, and recovers thereafter. The average ozone loss in the Antarctic is revealed to be about 33-50% in 1989-1992 in agreement with the increase in halogens during this period, and then stayed at around 48% due to saturation of the loss. The ozone loss in the warmer winters (e.g. 2002, and 2004) is lower (37-46%) and in the colder winters (e.g. 2003, and 2006) is higher (52-55%). Because of small inter-annual variability, the correlation between ozone loss and the volume of polar stratospheric clouds yields ~0.51. The GB ozone and ozone loss values are in good agreement with those found from the space-based observations of the Total Ozone Mapping Spectrometer/Ozone Monitoring Instrument (TOMS/OMI), the Global Ozone Monitoring Experiment (GOME), the Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY), and the Aura Microwave Limb Sounder (MLS), where the differences are within ±5% and are mostly within the error bars of the measurements. The piece-wise linear trends computed from the September-November vortex average GB and TOMS/OMI ozone show about -4 to -5.6 DU (Dobson Unit) yr-1 in 1989-1996 and about +1 DU yr-1 in 1997-2010. The trend during the former period is significant at 95% confidence intervals, but the trend in 1997-2010 is significant only at 85% confidence intervals. Our analyses suggest a period of about 9-10 yr to get the first detectable ozone

  19. Climate model diversity in the Northern Hemisphere Polar vortex response to climate change.

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    Simpson, I.; Seager, R.; Hitchcock, P.; Cohen, N.

    2017-12-01

    Global climate models vary widely in their predictions of the future of the Northern Hemisphere stratospheric polar vortex, with some showing a significant strengthening of the vortex, some showing a significant weakening and others displaying a response that is not outside of the range expected from internal variability alone. This inter-model spread in stratospheric predictions may account for some inter-model spread in tropospheric predictions with important implications for the storm tracks and regional climate change, particularly for the North Atlantic sector. Here, our current state of understanding of this model spread and its tropospheric impacts will be reviewed. Previous studies have proposed relationships between a models polar vortex response to climate change and its present day vortex climatology while others have demonstrated links between a models polar vortex response and changing wave activity coming up from the troposphere below under a warming climate. The extent to which these mechanisms can account for the spread in polar vortex changes exhibited by the Coupled Model Intercomparison Project, phase 5 models will be assessed. In addition, preliminary results from a series of idealized experiments with the Community Atmosphere Model will be presented. In these experiments, nudging of the stratospheric zonal mean state has been imposed to mimic the inter-model spread in the polar vortex response to climate change so that the downward influence of the spread in zonal mean stratospheric responses on the tropospheric circulation can be assessed within one model.

  20. Correlations of mesospheric winds with subtle motion of the Arctic polar vortex

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    Y. Bhattacharya

    2010-01-01

    Full Text Available This paper investigates the relationship between high latitude upper mesospheric winds and the state of the stratospheric polar vortex in the absence of major sudden stratospheric warmings. A ground based Michelson Interferometer stationed at Resolute Bay (74°43' N, 94°58' W in the Canadian High Arctic is used to measure mesopause region neutral winds using the hydroxyl (OH Meinel-band airglow emission (central altitude of ~85 km. These observed winds are compared to analysis winds in the upper stratosphere during November and December of 1995 and 1996; years characterized as cold, stable polar vortex periods. Correlation of mesopause wind speeds with those from the upper stratosphere is found to be significant for the 1996 season when the polar vortex is subtly displaced off its initial location by a strong Aleutian High. These mesopause winds are observed to lead stratospheric winds by approximately two days with increasing (decreasing mesospheric winds predictive of decreasing (increasing stratospheric winds. No statistically significant correlations are found for the 1995 season when there is no such displacement of the polar vortex.

  1. Generating, Separating and Polarizing Terahertz Vortex Beams via Liquid Crystals with Gradient-Rotation Directors

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    Shi-Jun Ge

    2017-10-01

    Full Text Available Liquid crystal (LC is a promising candidate for terahertz (THz devices. Recently, LC has been introduced to generate THz vortex beams. However, the efficiency is intensely dependent on the incident wavelength, and the transformed THz vortex beam is usually mixed with the residual component. Thus, a separating process is indispensable. Here, we introduce a gradient blazed phase, and propose a THz LC forked polarization grating that can simultaneously generate and separate pure THz vortices with opposite circular polarization. The specific LC gradient-rotation directors are implemented by a photoalignment technique. The generated THz vortex beams are characterized with a THz imaging system, verifying features of polarization controllability. This work may pave a practical road towards generating, separating and polarizing THz vortex beams, and may prompt applications in THz communications, sensing and imaging.

  2. Vortex phase-induced changes of the statistical properties of a partially coherent radially polarized beam.

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    Guo, Lina; Chen, Yahong; Liu, Xianlong; Liu, Lin; Cai, Yangjian

    2016-06-27

    Partially coherent radially polarized (PCRP) beam was introduced and generated in recent years. In this paper, we investigate the statistical properties of a PCRP beam embedded with a vortex phase (i.e., PCRP vortex beam). We derive the analytical formula for the cross-spectral density matrix of a PCRP vortex beam propagating through a paraxial ABCD optical system and analyze the statistical properties of a PCRP vortex beam focused by a thin lens. It is found that the statistical properties of a PCRP vortex beam on propagation are much different from those of a PCRP beam. The vortex phase induces not only the rotation of the beam spot, but also the changes of the beam shape, the degree of polarization and the state of polarization. We also find that the vortex phase plays a role of resisting the coherence-induced degradation of the intensity distribution and the coherence-induced depolarization. Furthermore, we report experimental generation of a PCRP vortex beam for the first time. Our results will be useful for trapping and rotating particles, free-space optical communications and detection of phase object.

  3. Laser microprocessing of steel with radially and azimuthally polarized femtosecond vortex pulses

    International Nuclear Information System (INIS)

    Allegre, O J; Perrie, W; Edwardson, S P; Dearden, G; Watkins, K G

    2012-01-01

    The use of a liquid-crystal spatial light modulator (SLM) device to convert a linearly polarized femtosecond laser beam into a radially or azimuthally polarized vortex beam is demonstrated. In order to verify the state of polarization at the focal plane, laser induced periodic surface structures (LIPSS) are produced on stainless steel, imprinting the complex vectorial polarization structures and confirming the efficacy of the SLM in producing the desired polarization modes. Stainless steel plates of various thicknesses are micromachined with the radially and azimuthally polarized vortex beams and the resulting cut-outs are analysed. The process efficiency and quality of each mode are compared with those of circular polarization. Radial polarization is confirmed to be the most efficient mode for machining high-aspect-ratio (depth/width > 3) channels thanks to its relatively higher absorptivity. Following our microprocessing tests, liquid-crystal SLMs emerged as a flexible off-the-shelf tool for producing radially and azimuthally polarized beams in existing ultrashort-pulse laser microprocessing systems. (paper)

  4. Nitrous oxide as a dynamical tracer in the 1987 Airborne Antarctic Ozone Experiment

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    Loewenstein, M.; Podolske, J. R.; Chan, K. R.; Strahan, S. E.

    1989-01-01

    In situ N2O measurements were made using an airborne tunable laser absorption spectrometer (ATLAS) on 12 flights into the Antarctic vortex, as well as on five transit flights outside the vortex region in August and September 1987, as part of the Airborne Antartic Ozone Experiment. Vertical profiles of N2O were obtained within the vortex on most of these flights and were obtained outside the vortex on several occasions. Flights into the vortex region show N2O decreasing southward between 53 and 72 S latitude on constant potential temperature surfaces in the lower stratosphere. The data lead to two important conclusions about the vortex region: (1) the lower stratosphere in August/September 1987 was occupied by 'old' air, which had subsided several kilometers during polar winter; (2) the N2O profile in the vortex was in an approximately steady state in August/September 1987, which indicates that the spring upwelling, suggested by several theories, did not occur.

  5. Ross Ice Shelf airstream driven by polar vortex cyclone

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    Schultz, Colin

    2012-07-01

    The powerful air and ocean currents that flow in and above the Southern Ocean, circling in the Southern Hemisphere's high latitudes, form a barrier to mixing between Antarctica and the rest of the planet. Particularly during the austral winter, strong westerly winds isolate the Antarctic continent from heat, energy, and mass exchange, bolstering the scale of the annual polar ozone depletion and driving the continent's record-breaking low temperatures. Pushing through this wall of high winds, the Ross Ice Shelf airstream (RAS) is responsible for a sizable amount of mass and energy exchange from the Antarctic inland areas to lower latitudes. Sitting due south of New Zealand, the roughly 470,000-square-kilometer Ross Ice Shelf is the continent's largest ice shelf and a hub of activity for Antarctic research. A highly variable lower atmospheric air current, RAS draws air from the inland Antarctic Plateau over the Ross Ice Shelf and past the Ross Sea. Drawing on modeled wind patterns for 2001-2005, Seefeldt and Cassano identify the primary drivers of RAS.

  6. Structured caustic vector vortex optical field: manipulating optical angular momentum flux and polarization rotation.

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    Chen, Rui-Pin; Chen, Zhaozhong; Chew, Khian-Hooi; Li, Pei-Gang; Yu, Zhongliang; Ding, Jianping; He, Sailing

    2015-05-29

    A caustic vector vortex optical field is experimentally generated and demonstrated by a caustic-based approach. The desired caustic with arbitrary acceleration trajectories, as well as the structured states of polarization (SoP) and vortex orders located in different positions in the field cross-section, is generated by imposing the corresponding spatial phase function in a vector vortex optical field. Our study reveals that different spin and orbital angular momentum flux distributions (including opposite directions) in different positions in the cross-section of a caustic vector vortex optical field can be dynamically managed during propagation by intentionally choosing the initial polarization and vortex topological charges, as a result of the modulation of the caustic phase. We find that the SoP in the field cross-section rotates during propagation due to the existence of the vortex. The unique structured feature of the caustic vector vortex optical field opens the possibility of multi-manipulation of optical angular momentum fluxes and SoP, leading to more complex manipulation of the optical field scenarios. Thus this approach further expands the functionality of an optical system.

  7. A consistent definition of the Arctic polar vortex breakup in both the lower and upper stratosphere

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    Choi, W.; Seo, J.

    2014-12-01

    Breakup of the polar vortex is a dominant feature of the seasonal transition from winter to summer in the stratosphere, which significantly affects stratospheric O3 concentration and tropospheric weather. Previously several criteria for the vortex breakup have been suggested based on the potential vorticity (PV) and wind speed, however, those mainly have focused on the lower stratospheric vortex of which spatiotemporal evolution and decay are more continuous than those of the upper stratospheric vortex. To find a consistent criterion for the vortex breakup in both the lower and upper stratosphere, the present study defined a polar vortex breakup day as when PV gradient at the polar vortex edge becomes lower than that at the subtropical edge on the area equivalent latitude based on PV. With applying the new definition to the UK Met Office reanalysis data, the breakup days of the Arctic polar vortices on 18 isentropic levels from 450 K to 1300 K were calculated for the period of 1993-2005. In comparison with CH4, N2O and O3 measured by the ILAS and POAM II/III satellite instruments, the breakup days are well consistent with changes in the distribution of such tracers as well as their zonal standard deviations associated with the vortex structure breaking and irreversible mixing. The vortex breakup in the upper stratosphere occurs more or less a month prior to that in the middle and lower stratosphere while the stratospheric final warming events occurs simultaneously in the upper and lower stratosphere.

  8. Middle atmospheric water vapour and dynamics in the vicinity of the polar vortex during the Hygrosonde-2 campaign

    Directory of Open Access Journals (Sweden)

    S. Lossow

    2009-07-01

    Full Text Available The Hygrosonde-2 campaign took place on 16 December 2001 at Esrange/Sweden (68° N, 21° E with the aim to investigate the small scale distribution of water vapour in the middle atmosphere in the vicinity of the Arctic polar vortex. In situ balloon and rocket-borne measurements of water vapour were performed by means of OH fluorescence hygrometry. The combined measurements yielded a high resolution water vapour profile up to an altitude of 75 km. Using the characteristic of water vapour being a dynamical tracer it was possible to directly relate the water vapour data to the location of the polar vortex edge, which separates air masses of different character inside and outside the polar vortex. The measurements probed extra-vortex air in the altitude range between 45 km and 60 km and vortex air elsewhere. Transitions between vortex and extra-vortex usually coincided with wind shears caused by gravity waves which advect air masses with different water vapour volume mixing ratios.

    From the combination of the results from the Hygrosonde-2 campaign and the first flight of the optical hygrometer in 1994 (Hygrosonde-1 a clear picture of the characteristic water vapour distribution inside and outside the polar vortex can be drawn. Systematic differences in the water vapour concentration between the inside and outside of the polar vortex can be observed all the way up into the mesosphere. It is also evident that in situ measurements with high spatial resolution are needed to fully account for the small-scale exchange processes in the polar winter middle atmosphere.

  9. Three-dimensional thermal structure of the South Polar Vortex of Venus

    Science.gov (United States)

    Hueso, Ricardo; Garate-Lopez, Itziar; Garcia-Muñoz, Antonio; Sánchez-Lavega, Agustín

    2014-11-01

    We have analyzed thermal infrared images provided by the VIRTIS-M instrument aboard Venus Express (VEX) to obtain high resolution thermal maps of the Venus south polar region between 55 and 85 km altitudes. The maps investigate three different dynamical configurations of the polar vortex including its classical dipolar shape, a regularly oval shape and a transition shape between the different configurations of the vortex. We apply the atmospheric model described by García Muñoz et al. (2013) and a variant of the retrieval algorithm detailed in Grassi et al. (2008) to obtain maps of temperature over the Venus south polar region in the quoted altitude range. These maps are discussed in terms of cloud motions and relative vorticity distribution obtained previously (Garate-Lopez et al. 2013). Temperature maps retrieved at 55 - 63 km show the same structures that are observed in the ~5 µm radiance images. This altitude range coincides with the optimal expected values of the cloud top altitude at polar latitudes and magnitudes derived from the analysis of ~5 µm images are measured at this altitude range. We also study the imprint of the vortex on the thermal field above the cloud level which extends up to 80 km. From the temperature maps, we also study the vertical stability of different atmospheric layers. The cold collar is clearly the most statically stable structure at polar latitudes, while the vortex and subpolar latitudes show lower stability values. Furthermore, the hot filaments present within the vortex at 55-63 km exhibit lower values of static stability than their immediate surroundings.ReferencesGarate-Lopez et al. Nat. Geosci. 6, 254-257 (2013).García Muñoz et al. Planet. Space Sci. 81, 65-73 (2013).Grassi, D. et al. J. Geophys. Res. 113, 1-12 (2008).AcknowledgementsWe thank ESA for supporting Venus Express, ASI, CNES and the other national space agencies supporting VIRTIS on VEX and their principal investigators G. Piccioni and P. Drossart. This work

  10. NSF Antarctic and Arctic Data Consortium; Scientific Research Support & Data Services for the Polar Community

    Science.gov (United States)

    Morin, P. J.; Pundsack, J. W.; Carbotte, S. M.; Tweedie, C. E.; Grunow, A.; Lazzara, M. A.; Carpenter, P.; Sjunneskog, C. M.; Yarmey, L.; Bauer, R.; Adrian, B. M.; Pettit, J.

    2014-12-01

    The U.S. National Science Foundation Antarctic & Arctic Data Consortium (a2dc) is a collaboration of research centers and support organizations that provide polar scientists with data and tools to complete their research objectives. From searching historical weather observations to submitting geologic samples, polar researchers utilize the a2dc to search andcontribute to the wealth of polar scientific and geospatial data.The goals of the Antarctic & Arctic Data Consortium are to increase visibility in the research community of the services provided by resource and support facilities. Closer integration of individual facilities into a "one stop shop" will make it easier for researchers to take advantage of services and products provided by consortium members. The a2dc provides a common web portal where investigators can go to access data and samples needed to build research projects, develop student projects, or to do virtual field reconnaissance without having to utilize expensive logistics to go into the field.Participation by the international community is crucial for the success of a2dc. There are 48 nations that are signatories of the Antarctic Treaty, and 8 sovereign nations in the Arctic. Many of these organizations have unique capabilities and data that would benefit US ­funded polar science and vice versa.We'll present an overview of the Antarctic & Arctic Data Consortium, current participating organizations, challenges & opportunities, and plans to better coordinate data through a geospatial strategy and infrastructure.

  11. Vectorial structures of linear-polarized Butterfly-Gauss vortex beams in the far zone

    Science.gov (United States)

    Cheng, Ke; Zhou, Yan; Lu, Gang; Yao, Na; Zhong, Xianqiong

    2018-05-01

    By introducing the Butterfly catastrophe to optics, the far-zone vectorial structures of Butterfly-Gauss beam with vortex and non-vortex are studied using the angular spectrum representation and stationary phase method. The influence of topological charge, linear-polarized angle, off-axis distance and scaling length on the far-zone vectorial structures, especially in the Poynting vector and angular momentum density of the corresponding beam is emphasized. The results show that the embedded optical vortex at source plane lead to special dark zones in the far zone, where the number of dark zone equals the absolute value of topological charge of optical vortex. Furthermore, the symmetry and direction of the special dark zones can be controlled by off-axis distance and scaling length, respectively. The linear-polarized angle adjusts only the Poynting vectors of TE and TM terms, but it does not affect those of whole beam. Finally, the vectorial expressions also indicate that the total angular momentum density is certainly zero owing to the far-zone stable structures rather than rotation behaviors.

  12. Revisiting Antarctic Ozone Depletion

    Science.gov (United States)

    Grooß, Jens-Uwe; Tritscher, Ines; Müller, Rolf

    2015-04-01

    Antarctic ozone depletion is known for almost three decades and it has been well settled that it is caused by chlorine catalysed ozone depletion inside the polar vortex. However, there are still some details, which need to be clarified. In particular, there is a current debate on the relative importance of liquid aerosol and crystalline NAT and ice particles for chlorine activation. Particles have a threefold impact on polar chlorine chemistry, temporary removal of HNO3 from the gas-phase (uptake), permanent removal of HNO3 from the atmosphere (denitrification), and chlorine activation through heterogeneous reactions. We have performed simulations with the Chemical Lagrangian Model of the Stratosphere (CLaMS) employing a recently developed algorithm for saturation-dependent NAT nucleation for the Antarctic winters 2011 and 2012. The simulation results are compared with different satellite observations. With the help of these simulations, we investigate the role of the different processes responsible for chlorine activation and ozone depletion. Especially the sensitivity with respect to the particle type has been investigated. If temperatures are artificially forced to only allow cold binary liquid aerosol, the simulation still shows significant chlorine activation and ozone depletion. The results of the 3-D Chemical Transport Model CLaMS simulations differ from purely Lagrangian longtime trajectory box model simulations which indicates the importance of mixing processes.

  13. Polar vortex evolution during Northern Hemispheric winter 2004/05

    Directory of Open Access Journals (Sweden)

    T. Chshyolkova

    2007-06-01

    Full Text Available As a part of the project "Atmospheric Wave Influences upon the Winter Polar Vortices (0–100 km" of the CAWSES program, data from meteor and Medium Frequency radars at 12 locations and MetO (UK Meteorological Office global assimilated fields have been analyzed for the first campaign during the Northern Hemispheric winter of 2004/05. The stratospheric state has been described using the conventional zonal mean parameters as well as Q-diagnostic, which allows consideration of the longitudinal variability. The stratosphere was cold during winter of 2004/05, and the polar vortex was relatively strong during most of the winter with relatively weak disturbances occurring at the end of December and the end of January. For this winter the strongest deformation with the splitting of the polar vortex in the lower stratosphere was observed at the end of February. Here the results show strong latitudinal and longitudinal differences that are evident in the stratospheric and mesospheric data sets at different stations. Eastward winds are weaker and oscillations with planetary wave periods have smaller amplitudes at more poleward stations. Accordingly, the occurrence, time and magnitude of the observed reversal of the zonal mesospheric winds associated with stratospheric disturbances depend on the local stratospheric conditions. In general, compared to previous years, the winter of 2004/05 could be characterized by weak planetary wave activity at stratospheric and mesospheric heights.

  14. Maintenance of high HCl/Cly and NOx/NOy in the Antarctic vortex: A chemical signature of confinement during spring

    International Nuclear Information System (INIS)

    Michelsen, H. A.; Webster, C. R.; Manney, G. L.; Scott, D. C.; Margitan, J. J.; May, R. D.; Irion, F. W.; Gunson, M. R.; Russell, J. M. III; Spivakovsky, C. M.

    1999-01-01

    Observations made in the 1994 Antarctic vortex show that Cl y recovered completely into HCl following conversion of Cl y reservoir species to active radicals, and NO x constituted a 4-5 times higher fraction of NO y inside the vortex than outside. Measurements made in October and November from the Airborne Southern Hemisphere Ozone Expedition/Measurements of the Atmospheric Effects of Stratospheric Aircraft (ASHOE/MAESA) ER-2 aircraft mission, the third Atmospheric Laboratory for Applications and Science (ATLAS-3) space shuttle mission, and the Upper Atmosphere Research Satellite (UARS) demonstrate that this unusual partitioning of Cl y and NO y was maintained for at least 4 weeks in the springtime vortex. In response to severe ozone loss, abundances of HCl and NO x remained high despite temperatures low enough to reactivate Cl y and convert NO x to HNO 3 via heterogeneous processes. Thus, under severely ozone depleted conditions, high HCl and NO x abundances in the vortex are maintained until the vortex breaks up or an influx of ozone-rich extravortex air is entrained into the vortex. These observations suggest that the flux of extravortex air entering the core of the lower stratospheric vortex was small or negligible above ∼400 K during late spring, despite weakening of the vortex during this time period. Results of a photochemical model constrained by the measurements suggest that extravortex air entrained into the vortex during October and early November made up less than 5% of the vortex core air at 409 K. The model results also show that heterogeneous chemistry has little effect on the Cl y and NO y partitioning once high abundances of HCl have been attained under ozone depleted conditions, even when aerosol loading is high. (c) 1999 American Geophysical Union

  15. Selective control of vortex polarities by microwave field in two robustly synchronized spin-torque nano-oscillators

    Science.gov (United States)

    Li, Yi; de Milly, Xavier; Klein, Olivier; Cros, Vincent; Grollier, Julie; de Loubens, Grégoire

    2018-01-01

    Manipulating operation states of coupled spin-torque nano-oscillators (STNOs), including their synchronization, is essential for applications such as complex oscillator networks. In this work, we experimentally demonstrate selective control of two coupled vortex STNOs through microwave-assisted switching of their vortex core polarities. First, the two oscillators are shown to synchronize due to the dipolar interaction in a broad frequency range tuned by an external biasing field. Coherent output is demonstrated along with strong linewidth reduction. Then, we show individual vortex polarity control of each oscillator, which leads to synchronization/desynchronization due to accompanied frequency shift. Our methods can be easily extended to multiple-element coupled oscillator networks.

  16. High-Order Dielectric Metasurfaces for High-Efficiency Polarization Beam Splitters and Optical Vortex Generators

    Science.gov (United States)

    Guo, Zhongyi; Zhu, Lie; Guo, Kai; Shen, Fei; Yin, Zhiping

    2017-08-01

    In this paper, a high-order dielectric metasurface based on silicon nanobrick array is proposed and investigated. By controlling the length and width of the nanobricks, the metasurfaces could supply two different incremental transmission phases for the X-linear-polarized (XLP) and Y-linear-polarized (YLP) light with extremely high efficiency over 88%. Based on the designed metasurface, two polarization beam splitters working in high-order diffraction modes have been designed successfully, which demonstrated a high transmitted efficiency. In addition, we have also designed two vortex-beam generators working in high-order diffraction modes to create vortex beams with the topological charges of 2 and 3. The employment of dielectric metasurfaces operating in high-order diffraction modes could pave the way for a variety of new ultra-efficient optical devices.

  17. Tight focusing of radially polarized circular Airy vortex beams

    Science.gov (United States)

    Chen, Musheng; Huang, Sujuan; Shao, Wei

    2017-11-01

    Tight focusing properties of radially polarized circular Airy vortex beams (CAVB) are studied numerically. The light field expressions for the focused fields are derived based on vectorial Debye theory. We also study the relationship between focal profiles, such as light intensity distribution, radius of focal spot and focal length, and the parameters of CAVB. Numerical results demonstrate that we can generate a radially polarized CAVB with super-long focal length, super-strong longitudinal intensity or subwavelength focused spot at the focal plane by properly choosing the parameters of incident light and high numerical aperture (NA) lens. These results have potential applications for optical trapping, optical storage and particle acceleration.

  18. Vulnerability of Polar Oceans to Anthropogenic Acidification: Comparison of Arctic and Antarctic Seasonal Cycles

    OpenAIRE

    E. H. Shadwick; T. W. Trull; H. Thomas; J. A. E. Gibson

    2013-01-01

    Polar oceans are chemically sensitive to anthropogenic acidification due to their relatively low alkalinity and correspondingly weak carbonate buffering capacity. Here, we compare unique CO2 system observations covering complete annual cycles at an Arctic (Amundsen Gulf) and Antarctic site (Prydz Bay). The Arctic site experiences greater seasonal warming (10 vs 3?C), and freshening (3 vs 2), has lower alkalinity (2220 vs 2320??mol/kg), and lower summer pH (8.15 vs 8.5), than the Antarctic sit...

  19. Non-coaxial superposition of vector vortex beams.

    Science.gov (United States)

    Aadhi, A; Vaity, Pravin; Chithrabhanu, P; Reddy, Salla Gangi; Prabakar, Shashi; Singh, R P

    2016-02-10

    Vector vortex beams are classified into four types depending upon spatial variation in their polarization vector. We have generated all four of these types of vector vortex beams by using a modified polarization Sagnac interferometer with a vortex lens. Further, we have studied the non-coaxial superposition of two vector vortex beams. It is observed that the superposition of two vector vortex beams with same polarization singularity leads to a beam with another kind of polarization singularity in their interaction region. The results may be of importance in ultrahigh security of the polarization-encrypted data that utilizes vector vortex beams and multiple optical trapping with non-coaxial superposition of vector vortex beams. We verified our experimental results with theory.

  20. High-efficiency dual-modes vortex beam generator with polarization-dependent transmission and reflection properties.

    Science.gov (United States)

    Tang, Shiwei; Cai, Tong; Wang, Guang-Ming; Liang, Jian-Gang; Li, Xike; Yu, Jiancheng

    2018-04-23

    Vortex beam is believed to be an effective way to extend communication capacity, but available efforts suffer from the issues of complex configurations, fixed operation mode as well as low efficiency. Here, we propose a general strategy to design dual-modes vortex beam generator by using metasurfaces with polarization-dependent transmission and reflection properties. Combining the focusing and vortex functionalities, we design/fabricate a type of compact dual-modes vortex beam generator operating at both reflection/transmission sides of the system. Experimental results demonstrate that the designed metadevice can switch freely and independently between the reflective vortex with topological charge m 1  = 2 and transmissive vortex with m 2  = 1. Moreover, the metadevice exhibits very high efficiencies of 91% and 85% for the reflective and transmissive case respectively. Our findings open a door for multifunctional metadevices with high performances, which indicate wide applications in modern integration-optics and wireless communication systems.

  1. A vortex dynamics perspective on stratospheric sudden warmings

    OpenAIRE

    Matthewman, N. J.

    2009-01-01

    A vortex dynamics approach is used to study the underlying mechanisms leading to polar vortex breakdown during stratospheric sudden warmings (SSWs). Observational data are used in chapter 2 to construct climatologies of the Arctic polar vortex structure during vortex-splitting and vortex-displacement SSWs occurring between 1958 and 2002. During vortex-splitting SSWs, polar vortex breakdown is shown to be typically independent of height (barotropic), whereas breakdown during vor...

  2. Generation of radio vortex beams with designable polarization using anisotropic frequency selective surface

    Science.gov (United States)

    Yang, Jin; Zhang, Cheng; Ma, Hui Feng; Zhao, Jie; Dai, Jun Yan; Yuan, Wei; Yang, Liu Xi; Cheng, Qiang; Cui, Tie Jun

    2018-05-01

    We propose a strategy to convert a linearly polarized wave from a single point source to an orbital angular momentum (OAM) wave by arbitrary polarization via an anisotropic frequency selective surface (FSS) in the microwave frequency. By tailoring the geometries of FSS elements, reflection-phases in x and y polarizations are engineered and encoded independently, which allows us to design the eventual polarization state of the generated OAM vortex beam by elaborately selecting individual coding sequences for each polarization. Two types of FSSs are designed and experimentally characterized to demonstrate the capability of OAM generation with circular and linear polarizations, respectively, showing excellent performance in a wide bandwidth from 14 to 16 GHz. This method provides opportunities for polarization multiplexing in microwave OAM communication systems.

  3. The impact of volcanic aerosol on the Northern Hemisphere stratospheric polar vortex: mechanisms and sensitivity to forcing structure

    Science.gov (United States)

    Toohey, M.; Krüger, K.; Bittner, M.; Timmreck, C.; Schmidt, H.

    2014-12-01

    Observations and simple theoretical arguments suggest that the Northern Hemisphere (NH) stratospheric polar vortex is stronger in winters following major volcanic eruptions. However, recent studies show that climate models forced by prescribed volcanic aerosol fields fail to reproduce this effect. We investigate the impact of volcanic aerosol forcing on stratospheric dynamics, including the strength of the NH polar vortex, in ensemble simulations with the Max Planck Institute Earth System Model. The model is forced by four different prescribed forcing sets representing the radiative properties of stratospheric aerosol following the 1991 eruption of Mt. Pinatubo: two forcing sets are based on observations, and are commonly used in climate model simulations, and two forcing sets are constructed based on coupled aerosol-climate model simulations. For all forcings, we find that simulated temperature and zonal wind anomalies in the NH high latitudes are not directly impacted by anomalous volcanic aerosol heating. Instead, high-latitude effects result from enhancements in stratospheric residual circulation, which in turn result, at least in part, from enhanced stratospheric wave activity. High-latitude effects are therefore much less robust than would be expected if they were the direct result of aerosol heating. Both observation-based forcing sets result in insignificant changes in vortex strength. For the model-based forcing sets, the vortex response is found to be sensitive to the structure of the forcing, with one forcing set leading to significant strengthening of the polar vortex in rough agreement with observation-based expectations. Differences in the dynamical response to the forcing sets imply that reproducing the polar vortex responses to past eruptions, or predicting the response to future eruptions, depends on accurate representation of the space-time structure of the volcanic aerosol forcing.

  4. The Effect of Representing Bromine from VSLS on the Simulation and Evolution of Antarctic Ozone

    Science.gov (United States)

    Oman, Luke D.; Douglass, Anne R.; Salawitch, Ross J.; Canty, Timothy P.; Ziemke, Jerald R.; Manyin, Michael

    2016-01-01

    We use the Goddard Earth Observing System Chemistry Climate Model (GEOSCCM), a contributor to both the 2010 and 2014 WMO Ozone Assessment Reports, to show that inclusion of 5 parts per trillion (ppt) of stratospheric bromine(Br(sub y)) from very short lived substances (VSLS) is responsible for about a decade delay in ozone hole recovery. These results partially explain the significantly later recovery of Antarctic ozone noted in the 2014 report, as bromine from VSLS was not included in the 2010 Assessment. We show multiple lines of evidence that simulations that account for VSLS Br(sub y) are in better agreement with both total column BrO and the seasonal evolution of Antarctic ozone reported by the Ozone Monitoring Instrument (OMI) on NASAs Aura satellite. In addition, the near zero ozone levels observed in the deep Antarctic lower stratospheric polar vortex are only reproduced in a simulation that includes this Br(sub y) source from VSLS.

  5. Polar night vortex breakdown and large-scale stirring in the southern stratosphere

    Energy Technology Data Exchange (ETDEWEB)

    Camara, Alvaro de la [Universidad Complutense de Madrid, Departamento de Geofisica y Meteorologia, Madrid (Spain); University of California, Department of Atmospheric and Oceanic Sciences, Los Angeles, CA (United States); Mechoso, C.R. [University of California, Department of Atmospheric and Oceanic Sciences, Los Angeles, CA (United States); Ide, K. [University of California, Department of Atmospheric and Oceanic Sciences, Los Angeles, CA (United States); University of Maryland, Department of Atmospheric and Oceanic Science, Collage Park, MD (United States); Walterscheid, R. [The Aerospace Corporation, Space Sciences Department, Los Angeles, CA (United States); Schubert, G. [University of California, Department of Earth and Space Sciences, Institute of Geophysics and Planetary Physics, Los Angeles, CA (United States)

    2010-11-15

    The present paper examines the vortex breakdown and large-scale stirring during the final warming of the Southern Hemisphere stratosphere during the spring of 2005. A unique set of in situ observations collected by 27 superpressure balloons (SPBs) is used. The balloons, which were launched from McMurdo, Antarctica, by the Strateole/VORCORE project, drifted for several weeks on two different isopycnic levels in the lower stratosphere. We describe balloon trajectories and compare them with simulations obtained on the basis of the velocity field from the GEOS-5 and NCEP/NCAR reanalyses performed with and without VORCORE data. To gain insight on the mechanisms responsible for the horizontal transport of air inside and outside the well-isolated vortex we examine the balloon trajectories in the framework of the Lagrangian properties of the stratospheric flow. Coherent structures of the flow are visualized by computing finite-time Lyapunov exponents (FTLE). A combination of isentropic analysis and FTLE distributions reveals that air is stripped away from the vortex's interior as stable manifolds eventually cross the vortex's edge. It is shown that two SPBs escaped from the vortex within high potential vorticity tongues that developed in association with wave breaking at locations along the vortex's edge where forward and backward FTLE maxima approximately intersect. The trajectories of three SPBs flying as a group at the same isopycnic level are examined and their behavior is interpreted in reference to the FTLE field. These results support the concept of stable and unstable manifolds governing transport of air masses across the periphery of the stratospheric polar vortex. (orig.)

  6. Polar solar panels: Arctic and Antarctic microbiomes display similar taxonomic profiles.

    Science.gov (United States)

    Tanner, Kristie; Martí, Jose Manuel; Belliure, Josabel; Fernández-Méndez, Mar; Molina-Menor, Esther; Peretó, Juli; Porcar, Manuel

    2018-02-01

    Solar panels located on high (Arctic and Antarctic) latitudes combine the harshness of the climate with that of the solar exposure. We report here that these polar solar panels are inhabited by similar microbial communities in taxonomic terms, dominated by Hymenobacter spp., Sphingomonas spp. and Ascomycota. Our results suggest that solar panels, even on high latitudes, can shape a microbial ecosystem adapted to irradiation and desiccation. © 2017 Society for Applied Microbiology and John Wiley & Sons Ltd.

  7. Dynamics of Venus' Southern hemisphere and South Polar Vortex from VIRTIS data obtained during the Venus Expres Mission

    Science.gov (United States)

    Hueso, R.; Garate-Lopez, I.; Sanchez-Lavega, A.

    2011-12-01

    The VIRTIS instrument onboard Venus Express observes Venus in two channels (visible and infrared) obtaining spectra and multi-wavelength images of the planet. The images have been used to trace the motions of the atmosphere at different layers of clouds [1-3]. We review the VIRTIS cloud image data and wind results obtained by different groups [1-3] and we present new results concerning the morphology and evolution of the South Polar Vortex at the upper and lower cloud levels with data covering the first 900 days of the mission. We present wind measurements of the South hemisphere obtained by cloud tracking individual cloud features and higher-resolution wind results of the polar region covering the evolution of the South polar vortex. The later were obtained by an image correlation algorithm run under human supervision to validate the data. We present day-side data of the upper clouds obtained at 380 and 980 nm sensitive to altitudes of 66-70 km, night-side data in the near infrared at 1.74 microns of the lower cloud (45-50 km) and day and night-side data obtained in the thermal infrared (wavelengths of 3.8 and 5.1 microns) which covers the dynamical evolution of Venus South Polar vortex at the cloud tops (66-70 km). We explore the different dynamics associated to the varying morphology of the vortex, its dynamical structure at different altitudes, the variability of the global wind data of the southern hemisphere and the interrelation of the polar vortex dynamics with the wind dynamics at subpolar and mid-latitudes. Acknowledgements: Work funded by Spanish MICIIN AYA2009-10701 with FEDER support and Grupos Gobierno Vasco IT-464-07. References [1] A. Sánchez-Lavega et al., Geophys. Res. Lett. 35, L13204, (2008). [2] D. Luz et al., Science, 332, 577-580 (2011). [3] R. Hueso, et al., Icarus doi:10.1016/j.icarus.2011.04.020 (2011)

  8. The Antarctic ozone minimum - Relationship to odd nitrogen, odd chlorine, the final warming, and the 11-year solar cycle

    Science.gov (United States)

    Callis, L. B.; Natarajan, M.

    1986-01-01

    Photochemical calculations along 'diabatic trajectories' in the meridional phase are used to search for the cause of the dramatic springtime minimum in Antarctic column ozone. The results indicate that the minimum is principally due to catalytic destruction of ozone by high levels of total odd nitrogen. Calculations suggest that these levels of odd nitrogen are transported within the polar vortex and during the polar night from the middle to upper stratosphere and lower mesosphere to the lower stratosphere. The possibility that these levels are related to the 11-year solar cycle and are increased by enhanced formation in the thermosphere and mesosphere during solar maximum conditions is discussed.

  9. Depletion of stratospheric ozone over the Antarctic and Arctic: Responses of plants of polar terrestrial ecosystems to enhanced UV-B, an overview

    International Nuclear Information System (INIS)

    Rozema, Jelte; Boelen, Peter; Blokker, Peter

    2005-01-01

    Depletion of stratospheric ozone over the Antarctic has been re-occurring yearly since 1974, leading to enhanced UV-B radiation. Arctic ozone depletion has been observed since 1990. Ozone recovery has been predicted by 2050, but no signs of recovery occur. Here we review responses of polar plants to experimentally varied UV-B through supplementation or exclusion. In supplementation studies comparing ambient and above ambient UV-B, no effect on growth occurred. UV-B-induced DNA damage, as measured in polar bryophytes, is repaired overnight by photoreactivation. With UV exclusion, growth at near ambient may be less than at below ambient UV-B levels, which relates to the UV response curve of polar plants. UV-B screening foils also alter PAR, humidity, and temperature and interactions of UV with environmental factors may occur. Plant phenolics induced by solar UV-B, as in pollen, spores and lignin, may serve as a climate proxy for past UV. Since the Antarctic and Arctic terrestrial ecosystems differ essentially (e.g. higher species diversity and more trophic interactions in the Arctic), generalization of polar plant responses to UV-B needs caution. - Polar plant responses to UV-B may be different in the Arctic than Antarctic regions

  10. A-train CALIOP and MLS observations of early winter Antarctic polar stratospheric clouds and nitric acid in 2008

    Directory of Open Access Journals (Sweden)

    A. Lambert

    2012-03-01

    of large-size NAT particles with effective radii >5–7 μm and low NAT number densities <1 × 10−3 cm−3. This denitrification event is observed close to the pole in the Antarctic vortex before synoptic temperatures first fall below the ice frost point and before the widespread occurrence of large-scale NAT PSCs. An episode of mountain wave activity detected by AIRS on 28 May 2008 led to wave-ice formation in the rapid cooling phases over the Antarctic Peninsula and Ellsworth Mountains, seeding an outbreak of NAT PSCs that were detected by CALIOP and MIPAS. The NAT clouds formed at altitudes of 18–26 km in a polar freezing belt and appear to be composed of relatively small particles with estimated effective radii of around 1 μm and high NAT number densities >0.2 cm−3. This NAT outbreak is similar to an event previously reported from MIPAS observations in mid-June 2003.

  11. When will the Antarctic Ozone Hole Recover?

    Science.gov (United States)

    Newman, Paul A.; Nash, Eric R.; Kawa, S. Randolph; Montzka, Steve

    2006-01-01

    The Antarctic ozone hole develops each year and culminates by early Spring. Antarctic ozone values have been monitored since 1979 using satellite observations from the .TOMS instrument. The severity of the hole has been assessed from TOMS using the minimum total ozone value from the October monthly mean (depth of the hole) and by calculating the average size during the September-October period. Ozone is mainly destroyed by halogen catalytic cycles, and these losses are modulated by temperature variations in the collar of the polar lower stratospheric vortex. In this presentation, we show the relationships of halogens and temperature to, both the size and depth of the hole. Because atmospheric halogen levels are responding to international agreements that limit or phase out production, the amount of halogens in the stratosphere should decrease over the next few decades. Using projections of halogen levels combined with age-of-air estimates, we find that the ozone hole is recovering at an extremely slow rate and that large ozone holes will regularly recur over the next 2 decades. The ozone hole will begin to show first signs of recovery in about 2023, and the hole will fully recover to pre-1980 levels in approximately 2070. This 2070 recovery is 20 years later than recent projections.

  12. Marine foraging and annual fish consumption of a south polar Skua population in the maritime Antarctic

    NARCIS (Netherlands)

    Hahn, S.M.; Ritz, M.S.; Reinhardt, K.

    2008-01-01

    Pelagic fish are an important component of Antarctic food webs but few quantitative data exist on energy transfer from fish to seabirds for the Seasonal Pack-ice Zone. We studied a local population of south polar, skuas Catharacta maccormicki during a whole breeding cycle and estimated its entire

  13. Responses of seabirds, in particular prions (Pachyptila sp.), to small-scale processes in the Antarctic Polar Front

    NARCIS (Netherlands)

    Franeker, van J.A.; Brink, van den N.W.; Bathmann, U.V.; Pollard, R.T.; Baar, de H.J.W.; Wolff, W.J.

    2002-01-01

    Small-scale distribution patterns of seabirds in the Antarctic Polar Front (APF) were investigated in relation to other biological, physical, and chemical features during the ANT-XIII/2 research cruise of R.V. Polarstern from December 1995 to January 1996. The APF is characterized by steep gradients

  14. Detecting the Recovery of the Antarctic Ozone Hole

    Science.gov (United States)

    Newman, Paul A.; Nash, Eric R.; Kawa, S. Randolph; Montzka, Steve

    2004-01-01

    The Antarctic ozone hole develops each year and culminates by early Spring. Antarctic ozone values have been monitored since 1979 using satellite observations from the TOMS instrument. The severity of the hole has been assessed from TOMS using the minimum total ozone value from the October monthly mean (depth of the hole) and by calculating the average size during the September-October period. Ozone is mainly destroyed by halogen catalytic cycles, and these losses are modulated by temperature variations in the collar of the polar lower stratospheric vortex. In this presentation, we show the relationships of halogens and temperature to both the size and depth of the hole. Because atmospheric halogen levels are responding to international agreements that limit or phase out production, the amount of halogens in the stratosphere should decrease over the next few decades. Using projections of halogen levels combined with age-of-air estimates, we find that the ozone hole is recovering at an extremely slow rate and that large ozone holes will regularly recur over the next 2 decades. We will show estimates of both when the ozone hole will begin to show first signs of recovery, and when the hole will fully recover to pre-1980 levels.

  15. Oxygen hypothesis of polar gigantism not supported by performance of Antarctic pycnogonids in hypoxia

    Science.gov (United States)

    Woods, H. Arthur; Moran, Amy L.; Arango, Claudia P.; Mullen, Lindy; Shields, Chris

    2008-01-01

    Compared to temperate and tropical relatives, some high-latitude marine species are large-bodied, a phenomenon known as polar gigantism. A leading hypothesis on the physiological basis of gigantism posits that, in polar water, high oxygen availability coupled to low metabolic rates relieves constraints on oxygen transport and allows the evolution of large body size. Here, we test the oxygen hypothesis using Antarctic pycnogonids, which have been evolving in very cold conditions (−1.8–0°C) for several million years and contain spectacular examples of gigantism. Pycnogonids from 12 species, spanning three orders of magnitude in body mass, were collected from McMurdo Sound, Antarctica. Individual sea spiders were forced into activity and their performance was measured at different experimental levels of dissolved oxygen (DO). The oxygen hypothesis predicts that, all else being equal, large pycnogonids should perform disproportionately poorly in hypoxia, an outcome that would appear as a statistically significant interaction between body size and oxygen level. In fact, although we found large effects of DO on performance, and substantial interspecific variability in oxygen sensitivity, there was no evidence for size×DO interactions. These data do not support the oxygen hypothesis of Antarctic pycnogonid gigantism and suggest that explanations must be sought in other ecological or evolutionary processes. PMID:19129117

  16. A simple kinematic model for the Lagrangian description of relevant nonlinear processes in the stratospheric polar vortex

    Directory of Open Access Journals (Sweden)

    V. J. García-Garrido

    2017-06-01

    Full Text Available In this work, we study the Lagrangian footprint of the planetary waves present in the Southern Hemisphere stratosphere during the exceptional sudden Stratospheric warming event that took place during September 2002. Our focus is on constructing a simple kinematic model that retains the fundamental mechanisms responsible for complex fluid parcel evolution, during the polar vortex breakdown and its previous stages. The construction of the kinematic model is guided by the Fourier decomposition of the geopotential field. The study of Lagrangian transport phenomena in the ERA-Interim reanalysis data highlights hyperbolic trajectories, and these trajectories are Lagrangian objects that are the kinematic mechanism for the observed filamentation phenomena. Our analysis shows that the breaking and splitting of the polar vortex is justified in our model by the sudden growth of a planetary wave and the decay of the axisymmetric flow.

  17. Diagnostic Comparison of Meteorological Analyses during the 2002 Antarctic Winter

    Science.gov (United States)

    Manney, Gloria L.; Allen, Douglas R.; Kruger, Kirstin; Naujokat, Barbara; Santee, Michelle L.; Sabutis, Joseph L.; Pawson, Steven; Swinbank, Richard; Randall, Cora E.; Simmons, Adrian J.; hide

    2005-01-01

    Several meteorological datasets, including U.K. Met Office (MetO), European Centre for Medium-Range Weather Forecasts (ECMWF), National Centers for Environmental Prediction (NCEP), and NASA's Goddard Earth Observation System (GEOS-4) analyses, are being used in studies of the 2002 Southern Hemisphere (SH) stratospheric winter and Antarctic major warming. Diagnostics are compared to assess how these studies may be affected by the meteorological data used. While the overall structure and evolution of temperatures, winds, and wave diagnostics in the different analyses provide a consistent picture of the large-scale dynamics of the SH 2002 winter, several significant differences may affect detailed studies. The NCEP-NCAR reanalysis (REAN) and NCEP-Department of Energy (DOE) reanalysis-2 (REAN-2) datasets are not recommended for detailed studies, especially those related to polar processing, because of lower-stratospheric temperature biases that result in underestimates of polar processing potential, and because their winds and wave diagnostics show increasing differences from other analyses between similar to 30 and 10 hPa (their top level). Southern Hemisphere polar stratospheric temperatures in the ECMWF 40-Yr Re-analysis (ERA-40) show unrealistic vertical structure, so this long-term reanalysis is also unsuited for quantitative studies. The NCEP/Climate Prediction Center (CPC) objective analyses give an inferior representation of the upper-stratospheric vortex. Polar vortex transport barriers are similar in all analyses, but there is large variation in the amount, patterns, and timing of mixing, even among the operational assimilated datasets (ECMWF, MetO, and GEOS-4). The higher-resolution GEOS-4 and ECMWF assimilations provide significantly better representation of filamentation and small-scale structure than the other analyses, even when fields gridded at reduced resolution are studied. The choice of which analysis to use is most critical for detailed transport

  18. Antarctic biology in the 21st century - Advances in, and beyond the international polar year 2007-2008’

    Science.gov (United States)

    Stoddart, Michael

    2010-08-01

    The International Polar Year 2007-2008 (IPY) has provided an opportunity for biology to show itself as an important part of Antarctic science in a manner in which it was not seen during earlier Polar Years. Of the 15 endorsed biological projects in Antarctica, 7 included more than 20 scientists and could be deemed truly international. Four were conducted in the marine environment, and one each in the fields of biological invasions, microbial ecology, and terrestrial ecology, and one was SCAR’s over-arching ‘Evolution and Biodiversity in the Antarctic’. The marine projects have left a robust legacy of data for future research into the consequences of environmental change, and into future decisions about marine protected areas. Studies on introductions of exotic organisms reveal an ever-present threat to the warmer parts of the high-latitude Southern Ocean, or parts which might become warmer with climate change. Studies on microbial ecology reveal great complexity of ecosystems with high numbers of unknown species. Terrestrial research has shown how vulnerable the Antarctic is to accidental introductions, and how productive the soils can be under changed climate conditions. Antarctic biology has come-of-age during IPY 2007-2008 and the campaign has set the scene for future research.

  19. Bringing Antarctic Weddell seals to the classroom through PolarTREC

    Science.gov (United States)

    Eilers, A. A.

    2017-12-01

    PolarTREC (Teachers and Researchers Exploring and Collaborating) is an NSF funded professional development opportunity in which K-12 teachers and informal educators participated in hands-on field research experiences in the Polar Regions. The program goal is to invigorate polar science education and understanding by bringing together educators and polar researchers. This unique opportunity for educators has two main components: a 4-6 week field experience and a classroom/community connection piece. In preparation for these experiences, museum educator Alex Eilers and science team lead Dr. Jennifer Burns planned, developed and executed extensive outreach efforts for both students and the community to highlight the Weddell seal research project during the 2012, 2014 and 2016 seasons. The following outreach activities summarize the team's most successful attempts at engaging schoolchildren, teachers and the public, creating a broader impact of the Weddell seal scientific project. On-line Daily journal entries were uploaded to the PolarTREC website encouraging an active interaction between the science team and participants. A Polar Connect event offered participants a real-time, interactive internet presentation with the team. Schools A multitude of on-site presentations were made in classrooms, at teacher workshops and faculty meetings. Two 45 minute labs were developed for students visiting the museum, Animals of the Antarctic and Journey to the Poles, the latter is now included in our ongoing program repertoire. Two travelling kits, Extreme Cold Weather Gear and The Weddell Seal, were developed by museum staff and continue to circulate through schools. A multi-lesson educational module was developed by museum staff to bridge the gap between the scientific research conducted in the field and students in grades 3-8. It contains curriculum-based lessons, field data and strategic methods to assist students in analyzing the data. Community Community-wide interest

  20. Magnetic Vortex Based Transistor Operations

    Science.gov (United States)

    Kumar, D.; Barman, S.; Barman, A.

    2014-01-01

    Transistors constitute the backbone of modern day electronics. Since their advent, researchers have been seeking ways to make smaller and more efficient transistors. Here, we demonstrate a sustained amplification of magnetic vortex core gyration in coupled two and three vortices by controlling their relative core polarities. This amplification is mediated by a cascade of antivortex solitons travelling through the dynamic stray field. We further demonstrated that the amplification can be controlled by switching the polarity of the middle vortex in a three vortex sequence and the gain can be controlled by the input signal amplitude. An attempt to show fan–out operation yielded gain for one of the symmetrically placed branches which can be reversed by switching the core polarity of all the vortices in the network. The above observations promote the magnetic vortices as suitable candidates to work as stable bipolar junction transistors (BJT). PMID:24531235

  1. Invited review: climate change impacts in polar regions: lessons from Antarctic moss bank archives.

    Science.gov (United States)

    Royles, Jessica; Griffiths, Howard

    2015-03-01

    Mosses are the dominant plants in polar and boreal regions, areas which are experiencing rapid impacts of regional warming. Long-term monitoring programmes provide some records of the rate of recent climate change, but moss peat banks contain an unrivalled temporal record of past climate change on terrestrial plant Antarctic systems. We summarise the current understanding of climatic proxies and determinants of moss growth for contrasting continental and maritime Antarctic regions, as informed by 13C and 18O signals in organic material. Rates of moss accumulation are more than three times higher in the maritime Antarctic than continental Antarctica with growing season length being a critical determinant of growth rate, and high carbon isotope discrimination values reflecting optimal hydration conditions. Correlation plots of 13C and 18O values show that species (Chorisodontium aciphyllum / Polytrichum strictum) and growth form (hummock / bank) are the major determinants of measured isotope ratios. The interplay between moss growth form, photosynthetic physiology, water status and isotope composition are compared with developments of secondary proxies, such as chlorophyll fluorescence. These approaches provide a framework to consider the potential impact of climate change on terrestrial Antarctic habitats as well as having implications for future studies of temperate, boreal and Arctic peatlands. There are many urgent ecological and environmental problems in the Arctic related to mosses in a changing climate, but the geographical ranges of species and life-forms are difficult to track individually. Our goal was to translate what we have learned from the more simple systems in Antarctica, for application to Arctic habitats. © 2014 John Wiley & Sons Ltd.

  2. Detection of vortex-core dynamics using current-induced self-bistable rectifying effect

    International Nuclear Information System (INIS)

    Goto, M; Hata, H; Yamaguchi, A; Miyajima, H; Nozaki, Y; Nakatani, Y; Yamaoka, T

    2011-01-01

    A magnetic vortex core confined in a micron-scale magnetic disk is resonantly excited by spin-polarized radio-frequency (rf) current and rf field. We show that rectifying voltage spectra caused by the vortex core resonance is dependent on the core polarity. Rectifying voltage spectra are given by the superposition of the polarity-dependent term and the polarity-independent term. The sign of the polarity-dependent rectifying voltage reverses when the sign of polarity P or external field H is reversed. This experimental result can be explained by the anisotropic magnetoresistance effect caused by the vortex core motion.

  3. Vortex Airy beams directly generated via liquid crystal q-Airy-plates

    Science.gov (United States)

    Wei, Bing-Yan; Liu, Sheng; Chen, Peng; Qi, Shu-Xia; Zhang, Yi; Hu, Wei; Lu, Yan-Qing; Zhao, Jian-Lin

    2018-03-01

    Liquid crystal q-Airy-plates with director distributions integrated by q-plates and polarization Airy masks are proposed and demonstrated via the photoalignment technique. Single/dual vortex Airy beams of opposite topological charges and orthogonal circular polarizations are directly generated with polarization-controllable characteristic. The singular phase of the vortex part is verified by both astigmatic transformation and digital holography. The trajectory of vortex Airy beams is investigated, manifesting separate propagation dynamics of optical vortices and Airy beams. Meanwhile, Airy beams still keep their intrinsic transverse acceleration, self-healing, and nondiffraction features. This work provides a versatile candidate for generating high-quality vortex Airy beams.

  4. Collapse dynamics of a vector vortex optical field with inhomogeneous states of polarization

    International Nuclear Information System (INIS)

    Chen, Rui-Pin; Zhao, Ting-Yu; Zhang, Xiaobo; Zhong, Li-Xin; Chew, Khian-Hooi

    2015-01-01

    Based on a pair of coupled 2D nonlinear Schrödinger equations, the collapse dynamics of a vector field with hybrid states of polarization (SoP) in a Kerr medium is demonstrated. The critical power for an optical field to collapse is present, and the full vectorial numerical simulations provide detailed information about the evolution and partial collapse of the vector field in a Kerr medium. Our results reveal that the optical field prefers to collapse in linearly-polarization, as a result of the self-focusing effect difference in linearly, elliptically and circularly polarized components. The SoP in the field cross-section changes and propagates with a spiral trajectory when the vector beams are imposed with a vortex. The vectorial effect on the collapse of a vector optical field can prevail over the noise even though it reaches 10% amplitude of the optical field. The unique feature of these structured collapses of a vector optical field may lead to new phenomena in the interaction of light with matter. (paper)

  5. The Antarctic Master Directory - a fundamental data management element for the International Polar Year 2007-2008

    Science.gov (United States)

    Scharfen, G.; Bauer, R.

    2004-12-01

    A successful International Polar Year (IPY) in 2007-2008 will extend the scientific spirit of international collaboration and exploration first undertaken in earlier IPYs and the 1957/58 International Geophysical Year (IGY) to the current era of advanced collection and analysis technology. The IGY not only led to a number of important scientific achievements; it also established an enduring data system - the World Data Centers - which continues today. Effective utilization of the vast arrays of data which will result from the coming IPY will challenge data managers and scientists alike. Coordinating the collection, assembly, archival and international exchange of disparate and voluminous data sets requires advance planning and the involvement of the relevant science agencies and data managers to utilize and extend existing capabilities. The IPY Planning Group has identified key objectives indicating that data management is an essential part of the IPY planning process including: - Ensure data collected under the IPY are made available in an open and timely manner - Intensify the recovery of relevant historical data and ensure that these also are made openly available - Develop and embrace new technological and logistical capabilities The Scientific Committee on Antarctic Research (SCAR) and Committee of Managers of National Antarctic Programmes (COMNAP) have established the Joint Committee on Antarctic Data Management (JCADM) to develop the Antarctic Master Directory (AMD) to enable scientists to find and access the data sets collected more than 22 countries in the Antarctic. Incorporating concepts developed as part of the AMD and extending them to cover the scope of the IPY is an important part of a successful IPY data management program. This paper identifies major aspects of the AMD and how it can serve the IPY.

  6. Mechanically Reconfigurable Single-Arm Spiral Antenna Array for Generation of Broadband Circularly Polarized Orbital Angular Momentum Vortex Waves.

    Science.gov (United States)

    Li, Long; Zhou, Xiaoxiao

    2018-03-23

    In this paper, a mechanically reconfigurable circular array with single-arm spiral antennas (SASAs) is designed, fabricated, and experimentally demonstrated to generate broadband circularly polarized orbital angular momentum (OAM) vortex waves in radio frequency domain. With the symmetrical and broadband properties of single-arm spiral antennas, the vortex waves with different OAM modes can be mechanically reconfigurable generated in a wide band from 3.4 GHz to 4.7 GHz. The prototype of the circular array is proposed, conducted, and fabricated to validate the theoretical analysis. The simulated and experimental results verify that different OAM modes can be effectively generated by rotating the spiral arms of single-arm spiral antennas with corresponding degrees, which greatly simplify the feeding network. The proposed method paves a reconfigurable way to generate multiple OAM vortex waves with spin angular momentum (SAM) in radio and microwave satellite communication applications.

  7. Update of the Polar SWIFT model for polar stratospheric ozone loss (Polar SWIFT version 2)

    Science.gov (United States)

    Wohltmann, Ingo; Lehmann, Ralph; Rex, Markus

    2017-07-01

    The Polar SWIFT model is a fast scheme for calculating the chemistry of stratospheric ozone depletion in polar winter. It is intended for use in global climate models (GCMs) and Earth system models (ESMs) to enable the simulation of mutual interactions between the ozone layer and climate. To date, climate models often use prescribed ozone fields, since a full stratospheric chemistry scheme is computationally very expensive. Polar SWIFT is based on a set of coupled differential equations, which simulate the polar vortex-averaged mixing ratios of the key species involved in polar ozone depletion on a given vertical level. These species are O3, chemically active chlorine (ClOx), HCl, ClONO2 and HNO3. The only external input parameters that drive the model are the fraction of the polar vortex in sunlight and the fraction of the polar vortex below the temperatures necessary for the formation of polar stratospheric clouds. Here, we present an update of the Polar SWIFT model introducing several improvements over the original model formulation. In particular, the model is now trained on vortex-averaged reaction rates of the ATLAS Chemistry and Transport Model, which enables a detailed look at individual processes and an independent validation of the different parameterizations contained in the differential equations. The training of the original Polar SWIFT model was based on fitting complete model runs to satellite observations and did not allow for this. A revised formulation of the system of differential equations is developed, which closely fits vortex-averaged reaction rates from ATLAS that represent the main chemical processes influencing ozone. In addition, a parameterization for the HNO3 change by denitrification is included. The rates of change of the concentrations of the chemical species of the Polar SWIFT model are purely chemical rates of change in the new version, whereas in the original Polar SWIFT model, they included a transport effect caused by the

  8. Excitation of high density surface plasmon polariton vortex array

    Science.gov (United States)

    Kuo, Chun-Fu; Chu, Shu-Chun

    2018-06-01

    This study proposes a method to excite surface plasmon polariton (SPP) vortex array of high spatial density on metal/air interface. A doughnut vector beam was incident at four rectangularly arranged slits to excite SPP vortex array. The doughnut vector beam used in this study has the same field intensity distribution as the regular doughnut laser mode, TEM01* mode, but a different polarization distribution. The SPP vortex array is achieved through the matching of both polarization state and phase state of the incident doughnut vector beam with the four slits. The SPP field distribution excited in this study contains stable array-distributed time-varying optical vortices. Theoretical derivation, analytical calculation and numerical simulation were used to discuss the characteristics of the induced SPP vortex array. The period of the SPP vortex array induced by the proposed method had only half SPPs wavelength. In addition, the vortex number in an excited SPP vortex array can be increased by enlarging the structure.

  9. Effect of different temperature regimes on the chlorophyll a concentration in four species of Antarctic macroalgae

    Digital Repository Service at National Institute of Oceanography (India)

    Dhargalkar, V.K.

    th Symp. on Polar Biology, Nat. Inst. Pf Polar Research. Tokyo. Mem. natn. lnst. polar Res. Tokyo(Spec.Issue).32: l12-116. Papenfuss, G. F. 1964. Catalogue and bibliography of Antarctic and sub- antarctic benthic marine algae. Am. Geophys. Union...

  10. Update of the Polar SWIFT model for polar stratospheric ozone loss (Polar SWIFT version 2

    Directory of Open Access Journals (Sweden)

    I. Wohltmann

    2017-07-01

    Full Text Available The Polar SWIFT model is a fast scheme for calculating the chemistry of stratospheric ozone depletion in polar winter. It is intended for use in global climate models (GCMs and Earth system models (ESMs to enable the simulation of mutual interactions between the ozone layer and climate. To date, climate models often use prescribed ozone fields, since a full stratospheric chemistry scheme is computationally very expensive. Polar SWIFT is based on a set of coupled differential equations, which simulate the polar vortex-averaged mixing ratios of the key species involved in polar ozone depletion on a given vertical level. These species are O3, chemically active chlorine (ClOx, HCl, ClONO2 and HNO3. The only external input parameters that drive the model are the fraction of the polar vortex in sunlight and the fraction of the polar vortex below the temperatures necessary for the formation of polar stratospheric clouds. Here, we present an update of the Polar SWIFT model introducing several improvements over the original model formulation. In particular, the model is now trained on vortex-averaged reaction rates of the ATLAS Chemistry and Transport Model, which enables a detailed look at individual processes and an independent validation of the different parameterizations contained in the differential equations. The training of the original Polar SWIFT model was based on fitting complete model runs to satellite observations and did not allow for this. A revised formulation of the system of differential equations is developed, which closely fits vortex-averaged reaction rates from ATLAS that represent the main chemical processes influencing ozone. In addition, a parameterization for the HNO3 change by denitrification is included. The rates of change of the concentrations of the chemical species of the Polar SWIFT model are purely chemical rates of change in the new version, whereas in the original Polar SWIFT model, they included a transport effect

  11. Climate Change Impacts in the sub-Antarctic Islands Technical Report N.2 of ONERC

    International Nuclear Information System (INIS)

    2009-01-01

    Difficult to apprehend as a whole, the polar regions constitute the Arctic to the North, an ocean surrounded by emerged lands, and the Antarctic to the South, a continent bordered by the Austral Ocean where a belt of sub Antarctic islands lies. Climate change impacts on sub Antarctic islands are varied, direct and indirect: glacier retreat, more favourable conditions for introduced species, marine biodiversity modification, etc. This report discusses the French, British, Australian, South African and New Zealand sub Antarctic islands, the climatic evolutions and the resulting impacts, focused especially on biodiversity. The Observatoire National sur les Effets du Rechauffement Climatique and the International Polar Foundation have been joined in this endeavour by the French polar institute Paul-Emile Victor, the administration of the French Southern and Antarctic Lands (TAAF in French) and the International Union for the Conservation of Nature. (authors)

  12. Polar Frontal Migration in the Warm Late Pliocene: Diatom Evidence from The Wilkes Land Margin, East Antarctic

    Science.gov (United States)

    Riesselman, C. R.; Taylor-Silva, B.; Patterson, M. O.

    2017-12-01

    The Late Pliocene is the most recent interval in Earth's history to sustain global temperatures within the range of warming predicted for the 21st century. Published global reconstructions and climate models find an average +2° C summer SST anomaly relative to modern during the 3.3-3.0 Ma PRISM interval, when atmospheric CO2 concentrations last reached 400 ppm. Here, we present a new diatom-based reconstruction of Pliocene interglacial sea surface conditions from IODP Site U1361, on the East Antarctic continental rise. U1361 biogenic silica concentrations document the alternation of diatom-rich and diatom-poor lithologies; we interpret 8 diatom-rich mudstones within this sequence to record interglacial periods between 3.8 and 2.8 Ma. We find that open-ocean conditions in the mid-Pliocene became increasingly influenced by sea ice from 3.6-3.2 Ma, prior to the onset of Northern Hemisphere glaciation. This cooling trend was interrupted by a temporary southward migration of the Antarctic Polar Front, bathing U1361 in warmer subantarctic waters during a single interglacial, marine isotope stage KM3 (3.17-3.15 Ma), that corresponds to a maximum in summer insolation at 65°S. Following this interval of transient warmth, interglacial periods became progressively cooler starting at 3 Ma, coinciding with a transition from obliquity to precession as the dominant orbital driver of Antarctic ice sheet fluctuations. Building on the identification of a single outlier interglacial within the PRISM interval, we have revisited older reconstructions to explore the response of the Southern Ocean/cryosphere system to peak late Pliocene warmth. By applying a modern chronostratigraphic framework to those low-resolution "mean interglacial" records, we identify the same frontal migration in 4 other cores in the Pacific sector of the Southern Ocean, documenting a major migration of the polar front during a key interval of warm climate. These new results suggest that increased summer

  13. Vectorial diffraction properties of THz vortex Bessel beams.

    Science.gov (United States)

    Wu, Zhen; Wang, Xinke; Sun, Wenfeng; Feng, Shengfei; Han, Peng; Ye, Jiasheng; Yu, Yue; Zhang, Yan

    2018-01-22

    A vortex Bessel beam combines the merits of an optical vortex and a Bessel beam, including a spiral wave front and a non-diffractive feature, which has immense application potentials in optical trapping, optical fabrication, optical communications, and so on. Here, linearly and circularly polarized vortex Bessel beams in the terahertz (THz) frequency range are generated by utilizing a THz quarter wave plate, a spiral phase plate, and Teflon axicons with different opening angles. Taking advantage of a THz focal-plane imaging system, vectorial diffraction properties of the THz vortex Bessel beams are comprehensively characterized and discussed, including the transverse (Ex, Ey) and longitudinal (Ez) polarization components. The experimental phenomena are accurately simulated by adopting the vectorial Rayleigh diffraction integral. By varying the opening angle of the axicon, the characteristic parameters of these THz vortex Bessel beams are exhibited and compared, including the light spot size, the diffraction-free range, and the phase evolution process. This work provides the precise experimental and theoretical bases for the comprehension and application of a THz vortex Bessel beam.

  14. Mapping of Polar Areas Based on High-Resolution Satellite Images: The Example of the Henryk Arctowski Polish Antarctic Station

    Science.gov (United States)

    Kurczyński, Zdzisław; Różycki, Sebastian; Bylina, Paweł

    2017-12-01

    To produce orthophotomaps or digital elevation models, the most commonly used method is photogrammetric measurement. However, the use of aerial images is not easy in polar regions for logistical reasons. In these areas, remote sensing data acquired from satellite systems is much more useful. This paper presents the basic technical requirements of different products which can be obtain (in particular orthoimages and digital elevation model (DEM)) using Very-High-Resolution Satellite (VHRS) images. The study area was situated in the vicinity of the Henryk Arctowski Polish Antarctic Station on the Western Shore of Admiralty Bay, King George Island, Western Antarctic. Image processing was applied on two triplets of images acquired by the Pléiades 1A and 1B in March 2013. The results of the generation of orthoimages from the Pléiades systems without control points showed that the proposed method can achieve Root Mean Squared Error (RMSE) of 3-9 m. The presented Pléiades images are useful for thematic remote sensing analysis and processing of measurements. Using satellite images to produce remote sensing products for polar regions is highly beneficial and reliable and compares well with more expensive airborne photographs or field surveys.

  15. Spontaneous Formation of Anti-ferromagnetic Vortex Lattice in a Fast Rotating BEC with Dipole Interactions

    International Nuclear Information System (INIS)

    Yang Shijie; Feng Shiping; Wen Yuchuan; Yu Yue

    2007-01-01

    When a Bose-Einstein condensate is set to rotate, superfluid vortices will be formed, which finally condense into a vortex lattice as the rotation frequency further increases. We show that the dipole-dipole interactions renormalize the short-range interaction strength and result in a distinction between interactions of parallel-polarized atoms and interactions of antiparallel-polarized atoms. This effect may lead to a spontaneous breakdown of the rapidly rotating Bose condensate into a novel anti-ferromagnetic-like vortex lattice. The upward-polarized Bose condensate forms a vortex lattice, which is staggered against a downward-polarized vortex lattice. A phase diagram related to the coupling strength is obtained.

  16. Feasibility of Using Alternate Fuels in the U.S. Antarctic Program: Initial Assessment

    Science.gov (United States)

    2017-09-01

    Polar Programs. Morris, A. 2015a. Email communication. 21 April. Centennial , CO: Antarctic Support Contractor. ———. 2015b. Personal...communication. 19 May. Centennial , CO: Antarctic Support Contractor. ———. 2014. Email communication. 24 November. Centennial , CO: Antarctic Support

  17. An Organic Vortex Laser.

    Science.gov (United States)

    Stellinga, Daan; Pietrzyk, Monika E; Glackin, James M E; Wang, Yue; Bansal, Ashu K; Turnbull, Graham A; Dholakia, Kishan; Samuel, Ifor D W; Krauss, Thomas F

    2018-03-27

    Optical vortex beams are at the heart of a number of novel research directions, both as carriers of information and for the investigation of optical activity and chiral molecules. Optical vortex beams are beams of light with a helical wavefront and associated orbital angular momentum. They are typically generated using bulk optics methods or by a passive element such as a forked grating or a metasurface to imprint the required phase distribution onto an incident beam. Since many applications benefit from further miniaturization, a more integrated yet scalable method is highly desirable. Here, we demonstrate the generation of an azimuthally polarized vortex beam directly by an organic semiconductor laser that meets these requirements. The organic vortex laser uses a spiral grating as a feedback element that gives control over phase, handedness, and degree of helicity of the emitted beam. We demonstrate vortex beams up to an azimuthal index l = 3 that can be readily multiplexed into an array configuration.

  18. Resonant-spin-ordering of vortex cores in interacting mesomagnets

    Science.gov (United States)

    Jain, Shikha

    2013-03-01

    The magnetic system of interacting vortex-state elements have a dynamically reconfigurable ground state characterized by different relative polarities and chiralities of the individual disks; and have a corresponding dynamically controlled spectrum of collective excitation modes that determine the microwave absorption of the crystal. The development of effective methods for dynamic control of the ground state in this vortex-type magnonic crystal is of interest both from fundamental and technological viewpoints. Control of vortex chirality has been demonstrated previously using various techniques; however, control and manipulation of vortex polarities remain challenging. In this work, we present a robust and efficient way of selecting the ground state configuration of interacting magnetic elements using resonant-spin-ordering approach. This is achieved by driving the system from the linear regime of constant vortex gyrations to the non-linear regime of vortex-core reversals at a fixed excitation frequency of one of the coupled modes. Subsequently reducing the excitation field to the linear regime stabilizes the system to a polarity combination whose resonant frequency is decoupled from the initialization frequency. We have utilized the resonant approach to transition between the two polarity combinations (parallel or antiparallel) in a model system of connected dot-pairs which may form the building blocks of vortex-based magnonic crystals. Taking a step further, we have extended the technique by studying many-particle system for its potential as spin-torque oscillators or logic devices. Work at Argonne was supported by the U. S. DOE, Office of BES, under Contract No. DE-AC02-06CH11357. This work was in part supported by grant DMR-1015175 from the U. S. National Science Foundation, by a Contract from the U.S. Army TARDEC and RDECOM.

  19. Different Stratospheric Polar Vortex States linked to Cold-Spells in North America and Northern Eurasia

    Science.gov (United States)

    Kretschmer, M.; Cohen, J. L.; Runge, J.; Coumou, D.

    2017-12-01

    The stratospheric polar vortex in boreal winter can influence the tropospheric circulation and thereby surface weather in the mid-latitudes. Weak states of the vortex, e.g. associated with Sudden Stratospheric Warmings (SSWs), often precede a negative phase of the North Atlantic Oscillation (NAO), and thus increase the risk of mid-latitude cold-spells especially over Eurasia. Here we show using cluster analysis that next to the well-documented relationship between a zonally symmetric disturbed vortex and a negative NAO, there exists a zonally asymmetric pattern linked to a negative Western Pacific Oscillation (WPO) and cold-spells in the northeastern US, like for example observed in February 2014. The latter is more synoptic in time-scale but occurs more frequently than SSWs. A causal effect network (CEN) approach gives insights into the underlying physical pathways and time-lags showing that high-pressure around Greenland leads to vertical wave activity over eastern Siberia leading to downward propagating waves over Alaska and high pressure over the North Pacific. Moreover, composites propose that a rather strong mid-stratospheric vortex seems to be favorable for this zonally asymmetric and reflective mechanism. Overall, the mutual relationship between stratospheric circulation and high-latitude blocking in both the Pacific and Atlantic Oceans is complex and involves mechanisms operating at different time-scales. Our results suggest that the stratospheric influence on winter circulation should not exclusively be analyzed in terms of a downward propagating Northern Annular Mode (NAM) signal and SSWs. In particular when studying the stratospheric impacts on North American temperature it is crucial to also consider the more transient and zonally asymmetric events which might help to improve seasonal winter predictions for this region.

  20. Magnetic vortex racetrack memory

    Science.gov (United States)

    Geng, Liwei D.; Jin, Yongmei M.

    2017-02-01

    We report a new type of racetrack memory based on current-controlled movement of magnetic vortices in magnetic nanowires with rectangular cross-section and weak perpendicular anisotropy. Data are stored through the core polarity of vortices and each vortex carries a data bit. Besides high density, non-volatility, fast data access, and low power as offered by domain wall racetrack memory, magnetic vortex racetrack memory has additional advantages of no need for constrictions to define data bits, changeable information density, adjustable current magnitude for data propagation, and versatile means of ultrafast vortex core switching. By using micromagnetic simulations, current-controlled motion of magnetic vortices in cobalt nanowire is demonstrated for racetrack memory applications.

  1. Antarctic Super Heroes: Using a Graphic Novel to Teach Students About Polar Science. (Invited)

    Science.gov (United States)

    Lougheed, V.; Palsole, S.; Rojas, C.; Tweedie, C. E.

    2009-12-01

    The University of Texas at El Paso received an IPY grant from the US National Science Foundation to take undergraduate and graduate students, as well as teachers, to Antarctica over winter break 2007. The program, called IPY-ROAM (International Polar Year - Research and Educational Experiences in Antarctica for Minorities) aimed to increase the number of underrepresented minorities in the sciences, and increase public awareness about the polar regions. Education and outreach activities have been designed to teach people of all ages about polar science. For example, an interactive museum exhibit was designed to describe how the polar regions are being affected by climate change, and how individuals can make a difference. Our latest outreach strategy involves taking the large amount of educational materials collected for the museum display and making it available to a broader audience. We have created a graphic novel where the story of the ROAM Antarctic trip and existing educational materials are communicated using a combination of comic strips, fact sheets, and classroom activities. Photographic images from the ROAM trip were digitized and converted to a comic strip format. These images were combined with text from film footage collected by a documentary film, as well as personal anecdotes, to convey the successes of the program and the primary messages participants wanted to share with the public. The graphic novel will be made available to local school groups and online, at our website: www.ipyroam.org.

  2. The International Polar Year in Portugal: A New National Polar Programme and a Major Education and Outreach project

    Science.gov (United States)

    Mendes-Victor, L.; Vieira, G.; Xavier, J.; Canario, A.

    2008-12-01

    Before the International Polar Year, in Portugal polar research was conducted by a very small group of scientists integrated in foreign projects or research institutions. Portugal was not member of the Scientific Committee for Antarctic Research (SCAR), the European Polar Board (EPB), neither a subscriber of the Antarctic Treaty. In 2004 Portuguese Polar researchers considered the IPY as an opportunity to change this situation and organized the national Committee for the IPY. The objectives were ambitious: to answer the aforementioned issues in defining and proposing a National Polar Programme. In late 2008, close to the end of the IPY, the objectives were attained, except the Antarctic Treaty signature that is, however, in an advanced stage, having been approved by consensus at the National Parliament in early 2007. Portugal joined SCAR in July 2006, the EPB in 2007 and a set of 5 Antarctic research projects forming the roots of the National Polar Programme (ProPolar) have been approved by the Foundation for Science and Technology (FCT-MCTES). Scientifically, the IPY can already be considered a major success in Portugal with an improvement in polar scientific research, in the number of scientists performing field work in the Antarctic, organizing polar science meetings and producing an expected increase in the number of polar science peer- reviewed papers. The Portuguese IPY scientific activities were accompanied by a major education and outreach project funded by the Agencia Ciência Viva (MCTES): LATITUDE60! Education for the Planet in the IPY. This project lead by the universities of Algarve, Lisbon and by the Portuguese Association of Geography Teachers is heavily interdisciplinary, programmed for all ages, from kindergarten to adults, and hoped to bring together scientists and society. LATITUDE60! was a major success and focussed on showing the importance of the polar regions for Earth's environment, emphasising on the implications of polar change for

  3. The Antarctic Master Directory -- the Electronic Card Catalog of Antarctic Data

    Science.gov (United States)

    Scharfen, G.; Bauer, R.

    2003-12-01

    The Antarctic Master Directory (AMD) is a Web-based, searchable record of thousands of Antarctic data descriptions. These data descriptions contain information about what data were collected, where they were collected, when they were collected, who the scientists are, who the point of contact is, how to get the data, and information about the format of the data and what documentation and bibliographic information exists. With this basic descriptive information about content and access for thousands of Antarctic scientific data sets, the AMD is a resource for scientists to advertise the data they have collected and to search for data they need. The AMD has been created by more than twenty nations which conduct research in the Antarctic under the auspices of the Antarctic Treaty. It is a part of the International Directory Network/Global Change Master Directory (IDN/GCMD). Using the AMD is easy. Users can search on subject matter key words, data types, geographic place-names, temporal or spatial ranges, or conduct free-text searches. To search the AMD go to: http://gcmd.nasa.gov/Data/portals/amd/. Contributing your own data descriptions for Antarctic data that you have collected is also easy. Scientists can start by submitting a short data description first (as a placeholder in the AMD, and to satisfy National Science Foundation (NSF) reporting requirements), and then add to, modify or update their record whenever it is appropriate. An easy to use on-line tool and a simple tutorial are available at: http://nsidc.org/usadcc. With NSF Office of Polar Programs (OPP) funding, the National Snow and Ice Data Center (NSIDC) operates the U.S. Antarctic Data Coordination Center (USADCC), partly to assist scientists in using and contributing to the AMD. The USADCC website is at http://nsidc.org/usadcc.

  4. Magnetic vortex racetrack memory

    Energy Technology Data Exchange (ETDEWEB)

    Geng, Liwei D.; Jin, Yongmei M., E-mail: ymjin@mtu.edu

    2017-02-01

    We report a new type of racetrack memory based on current-controlled movement of magnetic vortices in magnetic nanowires with rectangular cross-section and weak perpendicular anisotropy. Data are stored through the core polarity of vortices and each vortex carries a data bit. Besides high density, non-volatility, fast data access, and low power as offered by domain wall racetrack memory, magnetic vortex racetrack memory has additional advantages of no need for constrictions to define data bits, changeable information density, adjustable current magnitude for data propagation, and versatile means of ultrafast vortex core switching. By using micromagnetic simulations, current-controlled motion of magnetic vortices in cobalt nanowire is demonstrated for racetrack memory applications. - Highlights: • Advance fundamental knowledge of current-driven magnetic vortex phenomena. • Report appealing new magnetic racetrack memory based on current-controlled magnetic vortices in nanowires. • Provide a novel approach to adjust current magnitude for data propagation. • Overcome the limitations of domain wall racetrack memory.

  5. Propagation of stochastic electromagnetic vortex beams through the turbulent biological tissues

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Meilan; Chen, Qi; Hua, Limin; Zhao, Daomu, E-mail: zhaodaomu@yahoo.com

    2014-01-10

    The general analytical expression of the stochastic electromagnetic vortex beams through turbulent biological tissues is derived based on the fractal model. The statistical properties, including the spectral density, the spectral degree of coherence and the spectral degree of polarization are investigated in detail. It can be found that the normalized spectral density of the stochastic electromagnetic vortex beams with higher topological charge is less influenced by turbulence than that with lower topological charge. In addition, the change of the degree of polarization versus propagation distance of the anisotropic vortex beams in biological tissues differs from that of the isotropic vortex beams. The findings might be useful in the investigation of the structures of biological tissues and operation of communication and sensing systems involving biological tissues turbulence channels.

  6. The maintenance of elevated active chlorine levels in the Antarctic lower stratosphere through HCl null cycles

    Science.gov (United States)

    Müller, Rolf; Grooß, Jens-Uwe; Mannan Zafar, Abdul; Robrecht, Sabine; Lehmann, Ralph

    2018-03-01

    The Antarctic ozone hole arises from ozone destruction driven by elevated levels of ozone destroying (active) chlorine in Antarctic spring. These elevated levels of active chlorine have to be formed first and then maintained throughout the period of ozone destruction. It is a matter of debate how this maintenance of active chlorine is brought about in Antarctic spring, when the rate of formation of HCl (considered to be the main chlorine deactivation mechanism in Antarctica) is extremely high. Here we show that in the heart of the ozone hole (16-18 km or 85-55 hPa, in the core of the vortex), high levels of active chlorine are maintained by effective chemical cycles (referred to as HCl null cycles hereafter). In these cycles, the formation of HCl is balanced by immediate reactivation, i.e. by immediate reformation of active chlorine. Under these conditions, polar stratospheric clouds sequester HNO3 and thereby cause NO2 concentrations to be low. These HCl null cycles allow active chlorine levels to be maintained in the Antarctic lower stratosphere and thus rapid ozone destruction to occur. For the observed almost complete activation of stratospheric chlorine in the lower stratosphere, the heterogeneous reaction HCl + HOCl is essential; the production of HOCl occurs via HO2 + ClO, with the HO2 resulting from CH2O photolysis. These results are important for assessing the impact of changes of the future stratospheric composition on the recovery of the ozone hole. Our simulations indicate that, in the lower stratosphere, future increased methane concentrations will not lead to enhanced chlorine deactivation (through the reaction CH4 + Cl → HCl + CH3) and that extreme ozone destruction to levels below ≈ 0.1 ppm will occur until mid-century.

  7. Rewritable ferroelectric vortex pairs in BiFeO3

    Science.gov (United States)

    Li, Yang; Jin, Yaming; Lu, Xiaomei; Yang, Jan-Chi; Chu, Ying-Hao; Huang, Fengzhen; Zhu, Jinsong; Cheong, Sang-Wook

    2017-08-01

    Ferroelectric vortex in multiferroic materials has been considered as a promising alternative to current memory cells for the merit of high storage density. However, the formation of regular natural ferroelectric vortex is difficult, restricting the achievement of vortex memory device. Here, we demonstrated the creation of ferroelectric vortex-antivortex pairs in BiFeO3 thin films by using local electric field. The evolution of the polar vortex structure is studied by piezoresponse force microscopy at nanoscale. The results reveal that the patterns and stability of vortex structures are sensitive to the poling position. Consecutive writing and erasing processes cause no influence on the original domain configuration. The Z4 proper coloring vortex-antivortex network is then analyzed by graph theory, which verifies the rationality of artificial vortex-antivortex pairs. This study paves a foundation for artificial regulation of vortex, which provides a possible pathway for the design and realization of non-volatile vortex memory devices and logical devices.

  8. Phase locking of vortex cores in two coupled magnetic nanopillars

    Directory of Open Access Journals (Sweden)

    Qiyuan Zhu

    2014-11-01

    Full Text Available Phase locking dynamics of the coupled vortex cores in two identical magnetic spin valves induced by spin-polarized current are studied by means of micromagnetic simulations. Our results show that the available current range of phase locking can be expanded significantly by the use of constrained polarizer, and the vortices undergo large orbit motions outside the polarization areas. The effects of polarization areas and dipolar interaction on the phase locking dynamics are studied systematically. Phase locking parameters extracted from simulations are discussed by theoreticians. The dynamics of vortices influenced by spin valve geometry and vortex chirality are discussed at last. This work provides deeper insights into the dynamics of phase locking and the results are important for the design of spin-torque nano-oscillators.

  9. Ferroelectric nanostructure having switchable multi-stable vortex states

    Science.gov (United States)

    Naumov, Ivan I [Fayetteville, AR; Bellaiche, Laurent M [Fayetteville, AR; Prosandeev, Sergey A [Fayetteville, AR; Ponomareva, Inna V [Fayetteville, AR; Kornev, Igor A [Fayetteville, AR

    2009-09-22

    A ferroelectric nanostructure formed as a low dimensional nano-scale ferroelectric material having at least one vortex ring of polarization generating an ordered toroid moment switchable between multi-stable states. A stress-free ferroelectric nanodot under open-circuit-like electrical boundary conditions maintains such a vortex structure for their local dipoles when subject to a transverse inhomogeneous static electric field controlling the direction of the macroscopic toroidal moment. Stress is also capable of controlling the vortex's chirality, because of the electromechanical coupling that exists in ferroelectric nanodots.

  10. Vortex formation and instability in the left ventricle

    Science.gov (United States)

    Le, Trung Bao; Sotiropoulos, Fotis; Coffey, Dane; Keefe, Daniel

    2012-09-01

    We study the formation of the mitral vortex ring during early diastolic filling in a patient-specific left ventricle (LV) using direct numerical simulation. The geometry of the left ventricle is reconstructed from Magnetic Resonance Imaging (MRI) data of a healthy human subject. The left ventricular kinematics is modeled via a cell-based activation methodology, which is inspired by cardiac electro-physiology and yields physiologic LV wall motion. In the fluid dynamics videos, we describe in detail the three-dimensional structure of the mitral vortex ring, which is formed during early diastolic filling. The ring starts to deform as it propagates toward the apex of the heart and becomes inclined. The trailing secondary vortex tubes are formed as the result of interaction between the vortex ring and the LV wall. These vortex tubes wrap around the circumference and begin to interact with and destabilize the mitral vortex ring. At the end of diastole, the vortex ring impinges on the LV wall and the large-scale intraventricular flow rotates in clockwise direction. We show for the first time that the mitral vortex ring evolution is dominated by a number of vortex-vortex and vortex-wall interactions, including lateral straining and deformation of vortex ring, the interaction of two vortex tubes with unequal strengths, helicity polarization of vortex tubes and twisting instabilities of the vortex cores.

  11. Commensurate vortex configurations in thin superconducting films nanostructured by square lattice of magnetic dots

    Energy Technology Data Exchange (ETDEWEB)

    Milosevic, M.V.; Peeters, F.M

    2004-05-01

    Within the phenomenological Ginzburg-Landau (GL) theory, we investigate the vortex structure of a thin superconducting film (SC) with a regular matrix of ferromagnetic dots (FD) deposited on top of it. The vortex pinning properties of such a magnetic lattice are studied, and the field polarity dependent votex pinning is observed. The exact vortex configuration depends on the size of the magnetic dots, their polarity, periodicity of the FD-rooster and the properties of the SC expressed through the effective Ginzburg-Landau parameter {kappa}*.

  12. Commensurate vortex configurations in thin superconducting films nanostructured by square lattice of magnetic dots

    International Nuclear Information System (INIS)

    Milosevic, M.V.; Peeters, F.M.

    2004-01-01

    Within the phenomenological Ginzburg-Landau (GL) theory, we investigate the vortex structure of a thin superconducting film (SC) with a regular matrix of ferromagnetic dots (FD) deposited on top of it. The vortex pinning properties of such a magnetic lattice are studied, and the field polarity dependent votex pinning is observed. The exact vortex configuration depends on the size of the magnetic dots, their polarity, periodicity of the FD-rooster and the properties of the SC expressed through the effective Ginzburg-Landau parameter κ*

  13. The Interaction Between Dynamics and Chemistry of Ozone in the Set-up Phase of the Northern Hemisphere Polar Vortex

    Science.gov (United States)

    Kawa, S. R.; Bevilacqua, R.; Margitan, J. J.; Douglass, A. R.; Schoeberl, M. R.; Hoppel, K.; Sen, B.; Bhartia, P. K. (Technical Monitor)

    2001-01-01

    The morphology and evolution of the stratospheric ozone (O3) distribution at high latitudes in the Northern Hemisphere (NH) are examined for the late summer and fall seasons of 1999. This time period sets the O3 initial condition for the SOLVE/THESEO field mission performed during winter 1999-2000. In situ and satellite data are used along with a three-dimensional model of chemistry and transport (CTM) to determine the key processes that control the distribution of O3 in the lower-to-middle stratosphere. O3 in the vortex at the beginning of the winter season is found to be nearly constant from 500 to above 800 K with a value at 3 ppmv +/- approx. 10%. Values outside the vortex are up to a factor of 2 higher and increase significantly with potential temperature. The seasonal time series of data from POAM shows that relatively low O3 mixing ratios, which characterize the vortex in late fall, are already present at high latitudes at the end of summer before the vortex circulation sets up. Analysis of the CTM output shows that the minimum O3 and increase in variance in late summer are the result of: 1) stirring of polar concentric O3 gradients by nascent wave-driven transport, and 2) an acceleration of net photochemical loss with decreasing solar illumination. The segregation of low O3 mixing ratios into the vortex as the circulation strengthens through the fall suggests a possible feedback role between O3 chemistry and the vortex formation dynamics. Trajectory calculations from O3 sample points early in the fall, however, show only a weak correlation between initial O3 mixing ratio and potential vorticity later in the season consistent with order-of-magnitude calculations for the relative importance of O3 in the fall radiative balance at high latitudes. The possible connection between O3 chemistry and the dynamics of vortex formation does suggest that these feedbacks and sensitivities need to be better understood in order to make confident predictions of the recovery

  14. Investigation of propagation dynamics of truncated vector vortex beams.

    Science.gov (United States)

    Srinivas, P; Perumangatt, C; Lal, Nijil; Singh, R P; Srinivasan, B

    2018-06-01

    In this Letter, we experimentally investigate the propagation dynamics of truncated vector vortex beams generated using a Sagnac interferometer. Upon focusing, the truncated vector vortex beam is found to regain its original intensity structure within the Rayleigh range. In order to explain such behavior, the propagation dynamics of a truncated vector vortex beam is simulated by decomposing it into the sum of integral charge beams with associated complex weights. We also show that the polarization of the truncated composite vector vortex beam is preserved all along the propagation axis. The experimental observations are consistent with theoretical predictions based on previous literature and are in good agreement with our simulation results. The results hold importance as vector vortex modes are eigenmodes of the optical fiber.

  15. Changes in Arctic and Antarctic Sea Ice as a Microcosm of Global Climate Change

    Science.gov (United States)

    Parkinson, Claire L.

    2014-01-01

    Polar sea ice is a key element of the climate system and has now been monitored through satellite observations for over three and a half decades. The satellite observations reveal considerable information about polar ice and its changes since the late 1970s, including a prominent downward trend in Arctic sea ice coverage and a much lesser upward trend in Antarctic sea ice coverage, illustrative of the important fact that climate change entails spatial contrasts. The decreasing ice coverage in the Arctic corresponds well with contemporaneous Arctic warming and exhibits particularly large decreases in the summers of 2007 and 2012, influenced by both preconditioning and atmospheric conditions. The increasing ice coverage in the Antarctic is not as readily explained, but spatial differences in the Antarctic trends suggest a possible connection with atmospheric circulation changes that have perhaps been influenced by the Antarctic ozone hole. The changes in the polar ice covers and the issues surrounding those changes have many commonalities with broader climate changes and their surrounding issues, allowing the sea ice changes to be viewed in some important ways as a microcosm of global climate change.

  16. Environmental contamination in Antarctic ecosystems.

    Science.gov (United States)

    Bargagli, R

    2008-08-01

    Although the remote continent of Antarctica is perceived as the symbol of the last great wilderness, the human presence in the Southern Ocean and the continent began in the early 1900s for hunting, fishing and exploration, and many invasive plant and animal species have been deliberately introduced in several sub-Antarctic islands. Over the last 50 years, the development of research and tourism have locally affected terrestrial and marine coastal ecosystems through fuel combustion (for transportation and energy production), accidental oil spills, waste incineration and sewage. Although natural "barriers" such as oceanic and atmospheric circulation protect Antarctica from lower latitude water and air masses, available data on concentrations of metals, pesticides and other persistent pollutants in air, snow, mosses, lichens and marine organisms show that most persistent contaminants in the Antarctic environment are transported from other continents in the Southern Hemisphere. At present, levels of most contaminants in Antarctic organisms are lower than those in related species from other remote regions, except for the natural accumulation of Cd and Hg in several marine organisms and especially in albatrosses and petrels. The concentrations of organic pollutants in the eggs of an opportunistic top predator such as the south polar skua are close to those that may cause adverse health effects. Population growth and industrial development in several countries of the Southern Hemisphere are changing the global pattern of persistent anthropogenic contaminants and new classes of chemicals have already been detected in the Antarctic environment. Although the Protocol on Environmental Protection to the Antarctic Treaty provides strict guidelines for the protection of the Antarctic environment and establishes obligations for all human activity in the continent and the Southern Ocean, global warming, population growth and industrial development in countries of the Southern

  17. Tracer-tracer relations as a tool for research on polar ozone loss

    Energy Technology Data Exchange (ETDEWEB)

    Mueller, Rolf

    2010-07-01

    The report includes the following chapters: (1) Introduction: ozone in the atmosphere, anthropogenic influence on the ozone layer, polar stratospheric ozone loss; (2) Tracer-tracer relations in the stratosphere: tracer-tracer relations as a tool in atmospheric research; impact of cosmic-ray-induced heterogeneous chemistry on polar ozone; (3) quantifying polar ozone loss from ozone-tracer relations: principles of tracer-tracer correlation techniques; reference ozone-tracer relations in the early polar vortex; impact of mixing on ozone-tracer relations in the polar vortex; impact of mesospheric intrusions on ozone-tracer relations in the stratospheric polar vortex calculation of chemical ozone loss in the arctic in March 2003 based on ILAS-II measurements; (4) epilogue.

  18. Antarctic sea ice losses drive gains in benthic carbon drawdown.

    Science.gov (United States)

    Barnes, D K A

    2015-09-21

    Climate forcing of sea-ice losses from the Arctic and West Antarctic are blueing the poles. These losses are accelerating, reducing Earth's albedo and increasing heat absorption. Subarctic forest (area expansion and increased growth) and ice-shelf losses (resulting in new phytoplankton blooms which are eaten by benthos) are the only significant described negative feedbacks acting to counteract the effects of increasing CO2 on a warming planet, together accounting for uptake of ∼10(7) tonnes of carbon per year. Most sea-ice loss to date has occurred over polar continental shelves, which are richly, but patchily, colonised by benthic animals. Most polar benthos feeds on microscopic algae (phytoplankton), which has shown increased blooms coincident with sea-ice losses. Here, growth responses of Antarctic shelf benthos to sea-ice losses and phytoplankton increases were investigated. Analysis of two decades of benthic collections showed strong increases in annual production of shelf seabed carbon in West Antarctic bryozoans. These were calculated to have nearly doubled to >2x10(5) tonnes of carbon per year since the 1980s. Annual production of bryozoans is median within wider Antarctic benthos, so upscaling to include other benthos (combined study species typically constitute ∼3% benthic biomass) suggests an increased drawdown of ∼2.9x10(6) tonnes of carbon per year. This drawdown could become sequestration because polar continental shelves are typically deeper than most modern iceberg scouring, bacterial breakdown rates are slow, and benthos is easily buried. To date, most sea-ice losses have been Arctic, so, if hyperboreal benthos shows a similar increase in drawdown, polar continental shelves would represent Earth's largest negative feedback to climate change. Copyright © 2015 Elsevier Ltd. All rights reserved.

  19. Burst-mode manipulation of magnonic vortex crystals

    Science.gov (United States)

    Hänze, Max; Adolff, Christian F.; Weigand, Markus; Meier, Guido

    2015-03-01

    The manipulation of polarization states in 4 ×4 vortex crystals using sinusoidal magnetic field bursts is investigated by means of a broadband ferromagnetic-resonance setup. Magnetic field excitation with the proper amplitude and frequency allows tuning different polarization states, which are observed in the measured absorption spectra. The variation of the sinusoidal burst width consecutively identifies the time scale of the underlying process. A memorylike polarization state writing process is demonstrated on the submicrosecond time scale.

  20. Wind profile radar for study of Antarctic air circulation

    International Nuclear Information System (INIS)

    Ragaini, E.; Sarango, M.F.; Vasquez, E.H.

    1992-01-01

    After a brief discussion of meteorological methods used in the Antarctic, the paper gives an outline of a coordinated international research project whose objective is to set up a wind profiler radar station that would give meteorologists information regarding Antarctic atmospheric dynamics useful in their investigation of the causes and effects of the hole in the ozone layer. The radar instrumentation is to provide continuous readings of wind velocity at varying altitudes above the polar continent

  1. Vortex flow in acoustically levitated drops

    Energy Technology Data Exchange (ETDEWEB)

    Yan, Z.L.; Xie, W.J. [Department of Applied Physics, Northwestern Polytechnical University, Xi' an 710072 (China); Wei, B., E-mail: bbwei@nwpu.edu.cn [Department of Applied Physics, Northwestern Polytechnical University, Xi' an 710072 (China)

    2011-08-29

    The internal flow of acoustically levitated water drops is investigated experimentally. This study reveals a kind of vortex flow which rotates in the meridional plane of the levitated drop. The magnitude of fluid velocity is nearly vanishing at the drop center, whereas it increases toward the free surface of a levitated drop until the maximum value of about 80 mm/s. A transition of streamline shapes from concentric circles to ellipses takes place at the distance of about 1.2 mm from the drop center. The fluid velocity distribution is plotted as a function of polar angle for seven characteristic streamlines. -- Highlights: → We experimentally observe the internal flow of acoustically levitated water drops. → We present a fascinating structure of vortex flow inside the levitated water drop. → This vortex flow rotates around the drop center in the meridional plane. → Velocity distribution information of this vortex flow is quantitatively analyzed.

  2. Vortex flow in acoustically levitated drops

    International Nuclear Information System (INIS)

    Yan, Z.L.; Xie, W.J.; Wei, B.

    2011-01-01

    The internal flow of acoustically levitated water drops is investigated experimentally. This study reveals a kind of vortex flow which rotates in the meridional plane of the levitated drop. The magnitude of fluid velocity is nearly vanishing at the drop center, whereas it increases toward the free surface of a levitated drop until the maximum value of about 80 mm/s. A transition of streamline shapes from concentric circles to ellipses takes place at the distance of about 1.2 mm from the drop center. The fluid velocity distribution is plotted as a function of polar angle for seven characteristic streamlines. -- Highlights: → We experimentally observe the internal flow of acoustically levitated water drops. → We present a fascinating structure of vortex flow inside the levitated water drop. → This vortex flow rotates around the drop center in the meridional plane. → Velocity distribution information of this vortex flow is quantitatively analyzed.

  3. 78 FR 51213 - Notice of Permits Issued Under the Antarctic Conservation Act of 1978

    Science.gov (United States)

    2013-08-20

    ... 2401 et seq.), and Article 7 of the Protocol on Environmental Protection to the Antarctic Treaty done... September 4, 2013. Nadene G. Kennedy, Polar Coordination Specialist, Division of Polar Programs. [FR Doc...

  4. Evidence for long-lived polar vortex air in the mid-latitude summer stratosphere from in situ laser diode CH4 and H2O measurements

    Directory of Open Access Journals (Sweden)

    G. Durry

    2005-01-01

    Full Text Available A balloon borne diode laser spectrometer was launched in southern France in June 2000 to yield in situ stratospheric CH4 and H2O measurements. In the altitude region ranging from 20km to 25km, striking large spatial structures were observed in the vertical concentration profiles of both species. We suggest these patterns are due to the presence of long-lived remnants of the wintertime polar vortex in the mid-latitude summer stratosphere. To support this interpretation, a high resolution advection model for potential vorticity is used to investigate the evolution of the Arctic vortex after its breakdown phase in spring 2000.

  5. Regional stratospheric warmings in the Pacific-Western Canada (PWC sector during winter 2004/2005: implications for temperatures, winds, chemical constituents and the characterization of the Polar vortex

    Directory of Open Access Journals (Sweden)

    A. H. Manson

    2008-11-01

    Full Text Available The vortex during winter 2004/2005 was interesting for several reasons. It has been described as "cold" stratospherically, with relatively strong westerly winds. Losses of ozone until the final warming in March were considerable, and comparable to the cold 1999–2000 winter. There were also modest warming events, indicated by peaks in 10 hPa zonal mean temperatures at high latitudes, near 1 January and 1 February. Events associated with a significant regional stratospheric warming in the Pacific-Western Canada (PWC sector then began and peaked toward the end of February, providing strong longitudinal variations in dynamical characteristics (Chshyolkova et al., 2007; hereafter C07. The associated disturbed vortex of 25 February was displaced from the pole and either elongated (upper or split into two cyclonic centres (lower. Observations from Microwave Limb Sounder (MLS on Aura are used here to study the thermal characteristics of the stratosphere in the Canadian-US (253° E and Scandinavian-Europe (16° E sectors. Undisturbed high latitude stratopause (55 km zonal mean temperatures during the mid-winter (December–February reached 270 K, warmer than empirical-models such as CIRA-86, suggesting that seasonal polar warming due to dynamical influences affects the high altitude stratosphere as well as the mesosphere. There were also significant stratopause differences between Scandinavia and Canada during the warming events of 1 January and 1 February, with higher temperatures near 275 K at 16° E. During the 25 February "PWC" event a warming occurred at low and middle stratospheric heights (10–30 km: 220 K at 253° E and the stratopause cooled; while over Scandinavia-Europe the stratosphere below ~30 km was relatively cold at 195 K and the stratopause became even warmer (>295 K and lower (~45 km. The zonal winds followed the associated temperature gradients so that the vertical and latitudinal gradients of the winds differed strongly between

  6. Vortex dynamics during blade-vortex interactions

    Science.gov (United States)

    Peng, Di; Gregory, James W.

    2015-05-01

    Vortex dynamics during parallel blade-vortex interactions (BVIs) were investigated in a subsonic wind tunnel using particle image velocimetry (PIV). Vortices were generated by applying a rapid pitch-up motion to an airfoil through a pneumatic system, and the subsequent interactions with a downstream, unloaded target airfoil were studied. The blade-vortex interactions may be classified into three categories in terms of vortex behavior: close interaction, very close interaction, and collision. For each type of interaction, the vortex trajectory and strength variation were obtained from phase-averaged PIV data. The PIV results revealed the mechanisms of vortex decay and the effects of several key parameters on vortex dynamics, including separation distance (h/c), Reynolds number, and vortex sense. Generally, BVI has two main stages: interaction between vortex and leading edge (vortex-LE interaction) and interaction between vortex and boundary layer (vortex-BL interaction). Vortex-LE interaction, with its small separation distance, is dominated by inviscid decay of vortex strength due to pressure gradients near the leading edge. Therefore, the decay rate is determined by separation distance and vortex strength, but it is relatively insensitive to Reynolds number. Vortex-LE interaction will become a viscous-type interaction if there is enough separation distance. Vortex-BL interaction is inherently dominated by viscous effects, so the decay rate is dependent on Reynolds number. Vortex sense also has great impact on vortex-BL interaction because it changes the velocity field and shear stress near the surface.

  7. CELSS Antarctic Analog Project (CAAP): A New Paradigm for Polar Life Support and CELSS Research

    Science.gov (United States)

    Bubenheim, David L.; Straight, Christian; Flynn, Michael; Bates, Maynard; Harper, Lynn D. (Technical Monitor)

    1994-01-01

    The CELSS Antarctic Analog Project (CAAP) is a joint National Science Foundation (NSF) and National Aeronautics and Space Administration (NASA) project for the development, deployment and operation of CELSS technologies at the Amundsen-Scott South Pole Station. CAAP is implemented through the joint NSF/NASA Antarctic Space Analog Program (ASAP), initiated to support the pursuit of future NASA missions and to promote the transfer of space technologies to the NSF. Under a Memorandum of Agreement, the CAAP represents an example of a working dual agency cooperative project. NASA goals are operational testing of CELSS technologies and the conduct of scientific study to facilitate . technology selection, system design and methods development, including human dynamics as required for the operation of a CELSS. Although not fully closed, food production, water purification, and waste recycle and reduction provided by CAAP will improve the quality of life for the South Pole inhabitants, reduce logistics dependence, and minimize environmental impacts associated with human presence on the polar plateau. The CAAP facility will be highly integrated with the new South Pole Station infrastructure and will be composed of a deployed hardware facility and a research activity. This paper will include a description of CAAP and its functionality, conceptual designs, component selection and sizing for the crop growth chamber, crop production expectations, and a brief report on an initial on-site visit. This paper will also provide a discussion of issues associated with power and energy use and the applicability of CAAP to direct technology transfer to society in general and remote communities in particular.

  8. A differentiated plane wave as an electromagnetic vortex

    International Nuclear Information System (INIS)

    Hannay, J H; Nye, J F

    2015-01-01

    Differentiating a complex scalar plane wave with respect to its direction produces an isolated straight vortex line and has a natural extension, described in earlier papers, to the vector waves of electromagnetism—a differentiated plane wave (DPW). It epitomizes destructive interference and will be shown to have the local structure of an electromagnetic vortex. In this paper its polarization structure and Poynting vector field are compared and contrasted with that of the family of linear polynomial waves, of which it is a special member. By definition this wider family has a general linear complex vector function of position multiplying a plane wave, but the function must be such that the combination satisfies Maxwell’s equations. This forces translational invariance of the function along the wavevector direction—in other words the wave is ‘non-diffracting’. In a natural sense all possible polarizations are exhibited once only. But the DPW has a distinctive polarization structure only partly explored previously. Both classes of waves share similar Poynting vector fields, which can be ‘elliptic’ (helix-like flow lines) or ‘hyperbolic’, of a repulsive nature, unexpected for a vortex. Both classes can be considered as a limit in the superposition of three closely parallel ordinary plane waves in destructive interference, and this derivation is supplied in full here. (paper)

  9. Protecting polar wilderness : Just a western philosophical idea or a useful concept for regulating human activities in the polar regions?

    NARCIS (Netherlands)

    Bastmeijer, Kees; Leary, D.; Koivurova, T.; Alfredsson, G.

    2009-01-01

    Governments involved in Arctic and Antarctic governance have been well aware of the increasing human pressure on the Polar Regions and particularly the last two decades many initiatives have been taken to protect the Arctic and Antarctic environment. But what values are to be protected? This paper

  10. Cases of Lightweight Structures for Polar Areas

    DEFF Research Database (Denmark)

    Pedreros, Jessica Fernandoy; Christ, Julian; Shepherd, Paul

    2017-01-01

    The paper focuses on what the authors call ‘Polar Lightweight Structures’. The first part presents a collection of lightweight structures (LWS) designed and built for Antarctic conditions, with the aim of demonstrating the diversity of approaches attempted by designers. The second part of the paper...... presents two studies where different computational methods were applied for the design of generic LWS based on the local conditions of two particular Polar locations; namely, the Arctic region and Glacier Union in the Antarctic plateau. Both studies were conducted independently with the aim...

  11. Unexpectedly high ultrafine aerosol concentrations above East Antarctic sea ice

    Directory of Open Access Journals (Sweden)

    R. S. Humphries

    2016-02-01

    Full Text Available Better characterisation of aerosol processes in pristine, natural environments, such as Antarctica, have recently been shown to lead to the largest reduction in uncertainties in our understanding of radiative forcing. Our understanding of aerosols in the Antarctic region is currently based on measurements that are often limited to boundary layer air masses at spatially sparse coastal and continental research stations, with only a handful of studies in the vast sea-ice region. In this paper, the first observational study of sub-micron aerosols in the East Antarctic sea ice region is presented. Measurements were conducted aboard the icebreaker Aurora Australis in spring 2012 and found that boundary layer condensation nuclei (CN3 concentrations exhibited a five-fold increase moving across the polar front, with mean polar cell concentrations of 1130 cm−3 – higher than any observed elsewhere in the Antarctic and Southern Ocean region. The absence of evidence for aerosol growth suggested that nucleation was unlikely to be local. Air parcel trajectories indicated significant influence from the free troposphere above the Antarctic continent, implicating this as the likely nucleation region for surface aerosol, a similar conclusion to previous Antarctic aerosol studies. The highest aerosol concentrations were found to correlate with low-pressure systems, suggesting that the passage of cyclones provided an accelerated pathway, delivering air masses quickly from the free troposphere to the surface. After descent from the Antarctic free troposphere, trajectories suggest that sea-ice boundary layer air masses travelled equatorward into the low-albedo Southern Ocean region, transporting with them emissions and these aerosol nuclei which, after growth, may potentially impact on the region's radiative balance. The high aerosol concentrations and their transport pathways described here, could help reduce the discrepancy currently present between

  12. Unexpectedly high ultrafine aerosol concentrations above East Antarctic sea ice

    Science.gov (United States)

    Humphries, R. S.; Klekociuk, A. R.; Schofield, R.; Keywood, M.; Ward, J.; Wilson, S. R.

    2016-02-01

    Better characterisation of aerosol processes in pristine, natural environments, such as Antarctica, have recently been shown to lead to the largest reduction in uncertainties in our understanding of radiative forcing. Our understanding of aerosols in the Antarctic region is currently based on measurements that are often limited to boundary layer air masses at spatially sparse coastal and continental research stations, with only a handful of studies in the vast sea-ice region. In this paper, the first observational study of sub-micron aerosols in the East Antarctic sea ice region is presented. Measurements were conducted aboard the icebreaker Aurora Australis in spring 2012 and found that boundary layer condensation nuclei (CN3) concentrations exhibited a five-fold increase moving across the polar front, with mean polar cell concentrations of 1130 cm-3 - higher than any observed elsewhere in the Antarctic and Southern Ocean region. The absence of evidence for aerosol growth suggested that nucleation was unlikely to be local. Air parcel trajectories indicated significant influence from the free troposphere above the Antarctic continent, implicating this as the likely nucleation region for surface aerosol, a similar conclusion to previous Antarctic aerosol studies. The highest aerosol concentrations were found to correlate with low-pressure systems, suggesting that the passage of cyclones provided an accelerated pathway, delivering air masses quickly from the free troposphere to the surface. After descent from the Antarctic free troposphere, trajectories suggest that sea-ice boundary layer air masses travelled equatorward into the low-albedo Southern Ocean region, transporting with them emissions and these aerosol nuclei which, after growth, may potentially impact on the region's radiative balance. The high aerosol concentrations and their transport pathways described here, could help reduce the discrepancy currently present between simulations and observations of

  13. Are Antarctic ozone variations a manifestation of dynamics or chemistry?

    Science.gov (United States)

    Tung, K.-K.; Ko, M. K. W.; Rodriguez, J. M.; Sze, N. D.

    1986-01-01

    The existence of a reverse circulation cell with rising motion in the polar lower stratosphere is suggested as an explanation for the temporal behavior of the ozone column density in the Antarctic region. The upwelling brings ozone-poor air from below 100 mbar to the stratosphere, possibly contributing to the observed ozone decline in early spring. At the same time, the Antarctic stratosphere might contain a very low concentration of NO(x), a condition that could favor a greatly enhanced catalytic removal of O3 by halogen species. It is argued that heterogeneous processes and formation of OClO by the reaction BrO+ClO - OClO+Br before and after the polar night might help to suppress the NO(x) levels during the early spring period.

  14. Three-dimensional imaging of vortex structure in a ferroelectric nanoparticle driven by an electric field.

    Science.gov (United States)

    Karpov, D; Liu, Z; Rolo, T Dos Santos; Harder, R; Balachandran, P V; Xue, D; Lookman, T; Fohtung, E

    2017-08-17

    Topological defects of spontaneous polarization are extensively studied as templates for unique physical phenomena and in the design of reconfigurable electronic devices. Experimental investigations of the complex topologies of polarization have been limited to surface phenomena, which has restricted the probing of the dynamic volumetric domain morphology in operando. Here, we utilize Bragg coherent diffractive imaging of a single BaTiO 3 nanoparticle in a composite polymer/ferroelectric capacitor to study the behavior of a three-dimensional vortex formed due to competing interactions involving ferroelectric domains. Our investigation of the structural phase transitions under the influence of an external electric field shows a mobile vortex core exhibiting a reversible hysteretic transformation path. We also study the toroidal moment of the vortex under the action of the field. Our results open avenues for the study of the structure and evolution of polar vortices and other topological structures in operando in functional materials under cross field configurations.Imaging of topological states of matter such as vortex configurations has generally been limited to 2D surface effects. Here Karpov et al. study the volumetric structure and dynamics of a vortex core mediated by electric-field induced structural phase transition in a ferroelectric BaTiO 3 nanoparticle.

  15. Experimental observation of a tripolar vortex in a plasma

    International Nuclear Information System (INIS)

    Okamoto, A.; Hara, K.; Nagaoka, K.; Yoshimura, S.; Vranjes, J.; Kono, M.; Tanaka, M. Y.

    2003-01-01

    A tripolar vortex, three aligned vortices with alternate signs of polarity of rotation, has been observed in a plasma for the first time. The tripolar vortex always appears with a deep density depression in the neutral particles, and the rotation direction of each vortex is opposite to that of the ExB rotation due to the ambipolar electric field. It is shown that a net momentum transfer during the charge-exchange interaction produces an effective force acting on the ions. The present experiment shows that this effective force may dominate the ambipolar-electric field and drive the anti-ExB vortical motion of ions

  16. Generation of intense high-order vortex harmonics.

    Science.gov (United States)

    Zhang, Xiaomei; Shen, Baifei; Shi, Yin; Wang, Xiaofeng; Zhang, Lingang; Wang, Wenpeng; Xu, Jiancai; Yi, Longqiong; Xu, Zhizhan

    2015-05-01

    This Letter presents for the first time a scheme to generate intense high-order optical vortices that carry orbital angular momentum in the extreme ultraviolet region based on relativistic harmonics from the surface of a solid target. In the three-dimensional particle-in-cell simulation, the high-order harmonics of the high-order vortex mode is generated in both reflected and transmitted light beams when a linearly polarized Laguerre-Gaussian laser pulse impinges on a solid foil. The azimuthal mode of the harmonics scales with its order. The intensity of the high-order vortex harmonics is close to the relativistic region, with the pulse duration down to attosecond scale. The obtained intense vortex beam possesses the combined properties of fine transversal structure due to the high-order mode and the fine longitudinal structure due to the short wavelength of the high-order harmonics. In addition to the application in high-resolution detection in both spatial and temporal scales, it also presents new opportunities in the intense vortex required fields, such as the inner shell ionization process and high energy twisted photons generation by Thomson scattering of such an intense vortex beam off relativistic electrons.

  17. Stability of barotropic vortex strip on a rotating sphere.

    Science.gov (United States)

    Sohn, Sung-Ik; Sakajo, Takashi; Kim, Sun-Chul

    2018-02-01

    We study the stability of a barotropic vortex strip on a rotating sphere, as a simple model of jet streams. The flow is approximated by a piecewise-continuous vorticity distribution by zonal bands of uniform vorticity. The linear stability analysis shows that the vortex strip becomes stable as the strip widens or the rotation speed increases. When the vorticity constants in the upper and the lower regions of the vortex strip have the same positive value, the inner flow region of the vortex strip becomes the most unstable. However, when the upper and the lower vorticity constants in the polar regions have different signs, a complex pattern of instability is found, depending on the wavenumber of perturbations, and interestingly, a boundary far away from the vortex strip can be unstable. We also compute the nonlinear evolution of the vortex strip on the rotating sphere and compare with the linear stability analysis. When the width of the vortex strip is small, we observe a good agreement in the growth rate of perturbation at an early time, and the eigenvector corresponding to the unstable eigenvalue coincides with the most unstable part of the flow. We demonstrate that a large structure of rolling-up vortex cores appears in the vortex strip after a long-time evolution. Furthermore, the geophysical relevance of the model to jet streams of Jupiter, Saturn and Earth is examined.

  18. Stability of barotropic vortex strip on a rotating sphere

    Science.gov (United States)

    Sohn, Sung-Ik; Sakajo, Takashi; Kim, Sun-Chul

    2018-02-01

    We study the stability of a barotropic vortex strip on a rotating sphere, as a simple model of jet streams. The flow is approximated by a piecewise-continuous vorticity distribution by zonal bands of uniform vorticity. The linear stability analysis shows that the vortex strip becomes stable as the strip widens or the rotation speed increases. When the vorticity constants in the upper and the lower regions of the vortex strip have the same positive value, the inner flow region of the vortex strip becomes the most unstable. However, when the upper and the lower vorticity constants in the polar regions have different signs, a complex pattern of instability is found, depending on the wavenumber of perturbations, and interestingly, a boundary far away from the vortex strip can be unstable. We also compute the nonlinear evolution of the vortex strip on the rotating sphere and compare with the linear stability analysis. When the width of the vortex strip is small, we observe a good agreement in the growth rate of perturbation at an early time, and the eigenvector corresponding to the unstable eigenvalue coincides with the most unstable part of the flow. We demonstrate that a large structure of rolling-up vortex cores appears in the vortex strip after a long-time evolution. Furthermore, the geophysical relevance of the model to jet streams of Jupiter, Saturn and Earth is examined.

  19. Regional stratospheric warmings in the Pacific-Western Canada (PWC sector during winter 2004/2005: implications for temperatures, winds, chemical constituents and the characterization of the Polar vortex

    Directory of Open Access Journals (Sweden)

    A. H. Manson

    2008-11-01

    Full Text Available The vortex during winter 2004/2005 was interesting for several reasons. It has been described as "cold" stratospherically, with relatively strong westerly winds. Losses of ozone until the final warming in March were considerable, and comparable to the cold 1999–2000 winter. There were also modest warming events, indicated by peaks in 10 hPa zonal mean temperatures at high latitudes, near 1 January and 1 February. Events associated with a significant regional stratospheric warming in the Pacific-Western Canada (PWC sector then began and peaked toward the end of February, providing strong longitudinal variations in dynamical characteristics (Chshyolkova et al., 2007; hereafter C07. The associated disturbed vortex of 25 February was displaced from the pole and either elongated (upper or split into two cyclonic centres (lower.

    Observations from Microwave Limb Sounder (MLS on Aura are used here to study the thermal characteristics of the stratosphere in the Canadian-US (253° E and Scandinavian-Europe (16° E sectors. Undisturbed high latitude stratopause (55 km zonal mean temperatures during the mid-winter (December–February reached 270 K, warmer than empirical-models such as CIRA-86, suggesting that seasonal polar warming due to dynamical influences affects the high altitude stratosphere as well as the mesosphere. There were also significant stratopause differences between Scandinavia and Canada during the warming events of 1 January and 1 February, with higher temperatures near 275 K at 16° E. During the 25 February "PWC" event a warming occurred at low and middle stratospheric heights (10–30 km: 220 K at 253° E and the stratopause cooled; while over Scandinavia-Europe the stratosphere below ~30 km was relatively cold at 195 K and the stratopause became even warmer (>295 K and lower (~45 km. The zonal winds followed the associated temperature gradients so that the vertical and latitudinal gradients of the winds differed strongly

  20. Effect of a spiral phase on a vector optical field with hybrid polarization states

    International Nuclear Information System (INIS)

    Chen, Rui-Pin; Zhao, Tingyu; Zhong, Li-Xin; Chew, Khian-Hooi; Gu, Bing; Zhou, Guoquan

    2015-01-01

    The propagation dynamics of a vector field with inhomogeneous states of polarization (SoP) imposed a vortex is studied using the angular spectrum method. The evolution of SoP in the cross section of the field during propagation is analyzed numerically by the Stokes polarization parameters. The results indicate that SoP in the field cross section rotate along the propagation axis during propagation due to the existence of a vortex. In addition, the interaction between the phase singularity and the polarization singularity leads to the creation or annihilation of the optical field in the central region. In particular, the distributions of the transverse energy flow and both spin and orbital optical angular momentum fluxes in the cross section of the vortex vector optical field depend sensitively on both the vortex and polarization topology charges. (paper)

  1. Reversible rectification of vortex motion in magnetic and non-magnetic asymmetric pinning potentials

    International Nuclear Information System (INIS)

    Gonzalez, E.M.; Gonzalez, M.P.; Nunez, N.O.; Villegas, J.E.; Anguita, J.V.; Jaafa, M.; Asenjo, A.; Vicent, J.L.

    2006-01-01

    Nb films have been grown on arrays of asymmetric pinning centers. The lattice vortex dynamics could be modified, almost at will, by periodic pinning potentials. In the case of asymmetric pinning potentials a vortex ratchet effect occurs: the vortex lattice motion is rectified. That is, an injected ac current yields an output dc voltage, which polarity could be tuned. The output signal polarity could be switched with the applied magnetic field and the ac current strength. Ratchet effect occurs when asymmetric potentials induce outward particles flow under external fluctuations in the lack of driven direct outward forces. The output signal is similar using magnetic or non-magnetic submicrometric array of pinning centers. This device works as an adiabatic rocking ratchet. This superconducting ratchet could be a model to study biological motors

  2. Antarctic snow and global climate

    International Nuclear Information System (INIS)

    Granberg, H.B.

    2001-01-01

    Global circulation models (GCM) indicate that global warming will be most pronounced at polar regions and high latitudes, causing concern about the stability of the Antarctic ice cap. A project entitled the Seasonal Snow in Antarctica examined the properties of the near surface snow to determine the current conditions that influence snow cover development. The goal was to assess the response of the snow cover in Queen Maud Land (QML) to an increased atmospheric carbon dioxide content. The Antarctic snow cover in QML was examined as part of the FINNARP expeditions in 1999 and 2000 which examined the processes that influence the snow cover. Its energy and mass balance were also assessed by examining the near surface snow strata in shallow (1-2 m) pits and by taking measurements of environmental variables. This made it possible to determine if the glacier is in danger of melting at this northerly location in the Antarctic. The study also made it possible to determine which variables need to change and by how much, for significant melting to occur. It was shown that the Antarctic anticyclone creates particular conditions that protect the snow cover from melting. The anticyclone brings dry air from the stratosphere during most of the year and is exempt from the water vapour feedback. It was concluded that even a doubling of atmospheric carbon dioxide will not produce major snow melt runoff. 8 refs

  3. Understanding and protecting the world's biodiversity: the role and legacy of the SCAR programme "Evolution and Biodiversity in the Antarctic".

    Science.gov (United States)

    di Prisco, Guido; Convey, Peter; Gutt, Julian; Cowan, Don; Conlan, Kathleen; Verde, Cinzia

    2012-12-01

    Current global changes are prompting scientists and governments to consider the risk of extinction of species inhabiting environments influenced by ice. Concerted, multidisciplinary, international programmes aimed at understanding life processes, evolution and adaptations in the Polar Regions will help to counteract such an event by protecting polar life and ecosystems. There is a long tradition of international scientific cooperation in Antarctica that provides a strong foundation for such approaches. While basic understanding is emerging, we still largely lack predictive biological models, and need to achieve further integration amongst biological and non-biological disciplines. The ongoing SCAR Science Research Programme, "Evolution and Biodiversity in the Antarctic (EBA)" has successfully carried out its crucial role of providing an overarching umbrella for SCAR research in Life Sciences. Now is the time for aiming to progress beyond this important role, and the Antarctic biology community is proposing two programmes, focussed on distinct but complementary aspects of polar biology and working across marine, freshwater and terrestrial environments: "State of the Antarctic Ecosystem (AntEco)", and "Antarctic Thresholds--Ecosystem Resilience and Adaptation (AnT-ERA)". These programmes are the legacy of EBA, and they are key to understanding and protect Antarctic biodiversity. Copyright © 2012 Elsevier B.V. All rights reserved.

  4. Ozone zonal asymmetry and planetary wave characterization during Antarctic spring

    Directory of Open Access Journals (Sweden)

    I. Ialongo

    2012-03-01

    Full Text Available A large zonal asymmetry of ozone has been observed over Antarctica during winter-spring, when the ozone hole develops. It is caused by a planetary wave-driven displacement of the polar vortex. The total ozone data by OMI (Ozone Monitoring Instrument and the ozone profiles by MLS (Microwave Limb Sounder and GOMOS (Global Ozone Monitoring by Occultation of Stars were analysed to characterize the ozone zonal asymmetry and the wave activity during Antarctic spring. Both total ozone and profile data have shown a persistent zonal asymmetry over the last years, which is usually observed from September to mid-December. The largest amplitudes of planetary waves at 65° S (the perturbations can achieve up to 50% of zonal mean values is observed in October. The wave activity is dominated by the quasi-stationary wave 1 component, while the wave 2 is mainly an eastward travelling wave. Wave numbers 1 and 2 generally explain more than the 90% of the ozone longitudinal variations. Both GOMOS and MLS ozone profile data show that ozone zonal asymmetry covers the whole stratosphere and extends up to the altitudes of 60–65 km. The wave amplitudes in ozone mixing ratio decay with altitude, with maxima (up to 50% below 30 km.

    The characterization of the ozone zonal asymmetry has become important in the climate research. The inclusion of the polar zonal asymmetry in the climate models is essential for an accurate estimation of the future temperature trends. This information might also be important for retrieval algorithms that rely on ozone a priori information.

  5. Model of the polar ionosphere with account for the interplanetary medium

    International Nuclear Information System (INIS)

    Uvarov, V.M.; Barashkov, P.D.; Zakharova, A.P.

    1992-01-01

    The effect of IMR B y -component on F-region structure is simulated numerically. An additional convective vortex is reflected in the structure of F2 electronic density isolines in the form of vortex-live depression on the day half of the polar cap when B y y >0), the ionization is more profound on the night (daytime) side of the polar cap; plasma cavity is centered for after (before) midnight hours; F2 electron density increases (decreases) in the auroral peak and vortex-like depression is localized at p.m (a.m) hours

  6. Vector vortex beam generation with dolphin-shaped cell meta-surface.

    Science.gov (United States)

    Yang, Zhuo; Kuang, Deng-Feng; Cheng, Fang

    2017-09-18

    We present a dolphin-shaped cell meta-surface, which is a combination of dolphin-shaped metallic cells and dielectric substrate, for vector vortex beam generation with the illumination of linearly polarized light. Surface plasmon polaritons are excited at the boundary of the metallic cells, then guided by the metallic structures, and finally squeezed to the tips to form highly localized strong electromagnetic fields, which generate the intensity of vector vortex beams at z component. Synchronously, the abrupt phase change produced by the meta-surface is utilized to explain the vortex phase generated by elements. The new kind of structure can be utilized for communication, bioscience, and materiality.

  7. Spatial Patterns of Variability in Antarctic Surface Temperature: Connections to the Southern Hemisphere Annular Mode and the Southern Oscillation

    Science.gov (United States)

    Kwok, Ron; Comiso, Josefino C.; Koblinsky, Chester J. (Technical Monitor)

    2002-01-01

    The 17-year (1982-1998) trend in surface temperature shows a general cooling over the Antarctic continent, warming of the sea ice zone, with moderate changes over the oceans. Warming of the peripheral seas is associated with negative trends in the regional sea ice extent. Effects of the Southern Hemisphere Annular Mode (SAM) and the extrapolar Southern Oscillation (SO) on surface temperature are quantified through regression analysis. Positive polarities of the SAM are associated with cold anomalies over most of Antarctica, with the most notable exception of the Antarctic Peninsula. Positive temperature anomalies and ice edge retreat in the Pacific sector are associated with El Nino episodes. Over the past two decades, the drift towards high polarity in the SAM and negative polarity in the SO indices couple to produce a spatial pattern with warmer temperatures in the Antarctic Peninsula and peripheral seas, and cooler temperatures over much of East Antarctica.

  8. Propagation effects in the generation process of high-order vortex harmonics.

    Science.gov (United States)

    Zhang, Chaojin; Wu, Erheng; Gu, Mingliang; Liu, Chengpu

    2017-09-04

    We numerically study the propagation of a Laguerre-Gaussian beam through polar molecular media via the exact solution of full-wave Maxwell-Bloch equations where the rotating-wave and slowly-varying-envelope approximations are not included. It is found that beyond the coexistence of odd-order and even-order vortex harmonics due to inversion asymmetry of the system, the light propagation effect results in the intensity enhancement of a high-order vortex harmonics. Moreover, the orbital momentum successfully transfers from the fundamental laser driver to the vortex harmonics which topological charger number is directly proportional to its order.

  9. The influence of shape anisotropy on vortex nucleation in Pacman-like nanomagnets

    International Nuclear Information System (INIS)

    Cambel, V.; Tóbik, J.; Šoltýs, J.; Fedor, J.; Precner, M.; Gaži, Š.; Karapetrov, G.

    2013-01-01

    In this paper we explore magnetic properties of Permalloy Pacman-like (PL) nanomagnets in external in-plain magnetic field. PL nanomagnets represent unique magnetic systems with broken symmetry, which are perspective as non-volatile memory elements. In these nanomagnets both bits, chirality and polarity of a single vortex state, can be easily read and written by in-plane magnetic field only. In the experimental part of this work we show that namely chirality of the∼1-μm large PL nanomagnet can be red easily by magnetic force microscopy method. The easy bit reading is enabled due to coupling of the polarity magnetization vector to the magnetic charges located at the surface of the PL missing sector. Using micromagnetic simulations we show the influence of spatial anisotropy on vortex nucleation and annihilation fields in the PL nanomagnets. Angular dependence of the vortex nucleation field is analysed in detail for PL nanomagnets of different diameter, thickness, and missing-sector dimensions. Best control of the ground state can be achieved for diameters not exceeding 100 nm, thicknesses from 40 to 45 nm, and for the missing sector angles from 30 to 60°. - Highlights: ► We explore magnetization dynamics in mesoscopic magnets with broken symmetry. ► We explain how to read and write chirality and polarity into such systems. ► Angular dependence of the vortex nucleation field in the systems is analysed

  10. Bringing Society to a Changing Polar Ocean: Polar Interdisciplinary Coordinated Education (ICE)

    Science.gov (United States)

    Schofield, O.

    2015-12-01

    Environmental changes in the Arctic and Antarctic appear to be accelerating and scientists are trying to understand both the patterns and the impacts of change. These changes will have profound impact on humanity and create a need for public education about these critical habitats. We have focused on a two-pronged strategy to increase public awareness as well as enable educators to discuss comfortably the implications of climate change. Our first focus is on entraining public support through the development of science documentaries about the science and people who conduct it. Antarctic Edge is a feature length award-winning documentary about climate change that has been released in May 2015 and has garnered interest in movie theatres and on social media stores (NetFlix, ITunes). This broad outreach is coupled with our group's interest assisting educators formally. The majority of current polar education is focused on direct educator engagement through personal research experiences that have impact on the participating educators' classrooms. Polar Interdisciplinary Coordinated Education (ICE) proposes to improve educator and student engagement in polar sciences through exposure to scientists and polar data. Through professional development and the creation of data tools, Polar ICE will reduce the logistical costs of bringing polar science to students in grades 6-16. We will provide opportunities to: 1) build capacity of polar scientists in communicating and engaging with diverse audiences; 2) create scalable, in-person and virtual opportunities for educators and students to engage with polar scientists and their research through data visualizations, data activities, educator workshops, webinars, and student research symposia; and 3) evaluate the outcomes of Polar ICE and contribute to our understanding of science education practices. We will use a blended learning approach to promote partnerships and cross-disciplinary sharing. This combined multi-pronged approach

  11. ADMAP-2: The second generation Antarctic crustal magnetic anomaly map.

    Science.gov (United States)

    Ferraccioli, F.; Golynsky, A.; Golynsky, D.; Young, D. A.; Eagles, G.; Damaske, D.; Finn, C.; Aitken, A.; von Frese, R. R. B.; Ghidella, M. E.; Kim, H. R.; Hong, J.

    2017-12-01

    ADMAP-2 is the second generation crustal magnetic anomaly compilation for the Antarctic region south of 60°S. It was produced from more than 3.5 million line-km of near-surface terrestrial, airborne and marine magnetic observations collected since the International Geophysical Year 1957/58 through 2013. The data were edited, IGRF corrected, profile levelled and gridded at a 1.5-km interval on a polar stereographic projection using the minimum curvature technique. Given the ubiquitous polar cover of snow, ice and sea water, the magnetic anomaly compilation offers important constraints on the global tectonic processes and crustal properties of the Antarctic. It also links widely separated areas of outcrop to help unify disparate geologic studies, and provides insights on the lithospheric transition between Antarctica and adjacent oceans, as well as the geodynamic evolution of the Antarctic lithosphere in the assembly and break-up of the Gondwana, Rodinia, and Columbia supercontinents and key piercing points for reconstructing linkages between the protocontinents. The magnetic data together with ice-probing radar and gravity information greatly facilitate understanding the evolution of fundamental large-scale geological processes such as continental rifting, intraplate mountain building, subduction and terrane accretion processes, and intraplate basin formation.

  12. Arctic and Antarctic Sea Ice Changes and Impacts (Invited)

    Science.gov (United States)

    Nghiem, S. V.

    2013-12-01

    The extent of springtime Arctic perennial sea ice, important to preconditioning summer melt and to polar sunrise photochemistry, continues its precipitous reduction in the last decade marked by a record low in 2012, as the Bromine, Ozone, and Mercury Experiment (BROMEX) was conducted around Barrow, Alaska, to investigate impacts of sea ice reduction on photochemical processes, transport, and distribution in the polar environment. In spring 2013, there was further loss of perennial sea ice, as it was not observed in the ocean region adjacent to the Alaskan north coast, where there was a stretch of perennial sea ice in 2012 in the Beaufort Sea and Chukchi Sea. In contrast to the rapid and extensive loss of sea ice in the Arctic, Antarctic sea ice has a trend of a slight increase in the past three decades. Given the significant variability in time and in space together with uncertainties in satellite observations, the increasing trend of Antarctic sea ice may arguably be considered as having a low confidence level; however, there was no overall reduction of Antarctic sea ice extent anywhere close to the decreasing rate of Arctic sea ice. There exist publications presenting various factors driving changes in Arctic and Antarctic sea ice. After a short review of these published factors, new observations and atmospheric, oceanic, hydrological, and geological mechanisms contributed to different behaviors of sea ice changes in the Arctic and Antarctic are presented. The contribution from of hydrologic factors may provide a linkage to and enhance thermal impacts from lower latitudes. While geological factors may affect the sensitivity of sea ice response to climate change, these factors can serve as the long-term memory in the system that should be exploited to improve future projections or predictions of sea ice changes. Furthermore, similarities and differences in chemical impacts of Arctic and Antarctic sea ice changes are discussed. Understanding sea ice changes and

  13. Anthropogenic Radionuglides in Marine Polar Regions

    Science.gov (United States)

    Holm, Elis

    The polar regions are important for the understanding of long range water and atmospheric transport of anthropogenic substances. Investigations show that atmospheric transport of anthropogenic radionuclides is the most important route of transport to the Antarctic while water transport plays a greater role for the Arctic. Fallout from nuclear detonation tests is the major source in the Antarctic while in the Arctic other sources, especially European reprocessing facilities, dominate for conservatively behaving rdionuclides such as 137Cs . The flux of 137Cs and 239+240Pu in the Antarctic is about 1/10 of that for the Arctic and the resulting concentrations in surface sea-water show the same ratio for the two areas. In the Antarctic concentration factors for 137Cs are higher than in the Arctic for similar species

  14. Paraxial propagation of the first-order chirped Airy vortex beams in a chiral medium.

    Science.gov (United States)

    Xie, Jintao; Zhang, Jianbin; Ye, Junran; Liu, Haowei; Liang, Zhuoying; Long, Shangjie; Zhou, Kangzhu; Deng, Dongmei

    2018-03-05

    We introduce the propagation of the first-order chirped Airy vortex beams (FCAiV) in a chiral medium analytically. Results show that the FCAiV beams split into the left circularly polarized vortex (LCPV) beams and the right circularly polarized vortex (RCPV) beams, which have totally different propagation trajectories in the chiral medium. In this paper, we investigate the effects of the first-order chirped parameter β, the chiral parameter γ and the optical vortex on the propagation process of the FCAiV beams. It is shown that the propagation trajectory of the FCAiV beams declines with the chirped parameter increasing. Besides, the increase of the chiral parameter acting on the LCPV beams makes the relative position between the main lobe and the optical vortex further while the effect on the RCPV beams is the opposite. Furthermore, the relative position between the main lobe and the optical vortex contributes to the position of the intensity focusing. Meanwhile, with the chiral parameter increasing, the maximum gradient and scattering forces of the LCPV beams decrease but those of the RCPV beams will increase during the propagation. It is significant that we can control the propagation trajectory, the intensity focusing position and the radiation forces of the FCAiV beams by varying the chirped parameter and the chiral parameter.

  15. Research Activity and Infrastructure of Korea Polar Research Institute: Current and Future Perspectives

    Science.gov (United States)

    Jin, D.; Kim, S.; Lee, H.

    2011-12-01

    The Korea Polar Research Institute (KOPRI) opened the Antarctic King Sejong research station in 1988 at the King George Island off the Antarctic Peninsula and started the polar research mainly in the fields of biology and geology with some atmosphere observations. To extend the view of polar research, the KOPRI opened the Arctic Dasan research station at Ny-Alesund, Spitsbergen Island in 2002 and has studied the rapid climate change diagnostics and some microbiological observation. The KOPRI is now expanding the Arctic research into Alaska and Canada under the international collaboration, and planning to outreach to Russia to monitor the change in permafrost and to understand its impact on global warming. To deepen the views of polar research including the ice covered oceans in both poles, the ice-breaking vessel, the ARAON of about 7000 ton, was launched recently and successfully finished the Arctic and Antarctic cruises for research activity on all perspectives of ocean sciences and support for the King Sejong station. The KOPRI is now building another Antarctic research station, called Jangbogo, at the Terra Nova Bay off the Ross Sea and plan to open the station at the March of 2014. By building the second Antarctic station together with the ARAON, the KOPRI will focus its research on understanding the rapid climate change in west Antarctica such as to monitor the calving of the Larsen Ice shelf, rapid melting of Pine Island Glacier, and upper atmosphere, to study the sea ice and ecosystem change in the Amundsen Sea and the role of the southern annular mode in the west Antarctic warming, upper atmosphere and climate change, to reconstruct paleoclimate records from ice and sediment cores.

  16. Vortex line topology during vortex tube reconnection

    Science.gov (United States)

    McGavin, P.; Pontin, D. I.

    2018-05-01

    This paper addresses reconnection of vortex tubes, with particular focus on the topology of the vortex lines (field lines of the vorticity). This analysis of vortex line topology reveals key features of the reconnection process, such as the generation of many small flux rings, formed when reconnection occurs in multiple locations in the vortex sheet between the tubes. Consideration of three-dimensional reconnection principles leads to a robust measurement of the reconnection rate, even once instabilities break the symmetry. It also allows us to identify internal reconnection of vortex lines within the individual vortex tubes. Finally, the introduction of a third vortex tube is shown to render the vortex reconnection process fully three-dimensional, leading to a fundamental change in the topological structure of the process. An additional interesting feature is the generation of vorticity null points.

  17. Observation of an unusual mid-stratospheric aerosol layer in the Arctic: possible sources and implications for polar vortex dynamics

    Directory of Open Access Journals (Sweden)

    M. Gerding

    Full Text Available By the beginning of winter 2000/2001, a mysterious stratospheric aerosol layer had been detected by four different Arctic lidar stations. The aerosol layer was observed first on 16 November 2000, at an altitude of about 38 km near Søndre Strømfjord, Greenland (67° N, 51° W and on 19 November 2000, near Andenes, Norway (69°  N, 16°  E. Subsequently, in early December 2000, the aerosol layer was observed near Kiruna, Sweden (68°  N, 21°  E and Ny-Ålesund, Spitsbergen (79°  N, 12°  E. No mid-latitude lidar station observed the presence of aerosols in this altitude region. The layer persisted throughout the winter 2000/2001, at least up to 12 February 2001. In November 2000, the backscatter ratio at a wavelength of 532 nm was up to 1.1, with a FWHM of about 2.5 km. By early February 2001, the layer had sedimented from an altitude of 38 km to about 26 km. Measurements at several wavelengths by the ALOMAR and Koldewey lidars indicate the particle size was between 30 and 50 nm. Depolarisation measurements reveal that the particles in the layer are aspherical, hence solid. In the mid-stratosphere, the ambient atmospheric temperature was too high to support in situ formation or existence of cloud particles consisting of ice or an acid-water solution. Furthermore, in the year 2000 there was no volcanic eruption, which could have injected aerosols into the upper stratosphere. Therefore, other origins of the aerosol, such as meteoroid debris, condensed rocket fuel, or aerosols produced under the influence of charged solar particles, will be discussed in the paper. Trajectory calculations illustrate the path of the aerosol cloud within the polar vortex and are used to link the observations at the different lidar sites. From the descent rate of  the layer and particle sedimentation rates, the mean down-ward motion of air within the polar vortex was estimated to be about 124 m/d between 35 and 30 km, with higher values at the edge of the

  18. Observation of an unusual mid-stratospheric aerosol layer in the Arctic: possible sources and implications for polar vortex dynamics

    Directory of Open Access Journals (Sweden)

    M. Gerding

    2003-04-01

    Full Text Available By the beginning of winter 2000/2001, a mysterious stratospheric aerosol layer had been detected by four different Arctic lidar stations. The aerosol layer was observed first on 16 November 2000, at an altitude of about 38 km near Søndre Strømfjord, Greenland (67° N, 51° W and on 19 November 2000, near Andenes, Norway (69°  N, 16°  E. Subsequently, in early December 2000, the aerosol layer was observed near Kiruna, Sweden (68°  N, 21°  E and Ny-Ålesund, Spitsbergen (79°  N, 12°  E. No mid-latitude lidar station observed the presence of aerosols in this altitude region. The layer persisted throughout the winter 2000/2001, at least up to 12 February 2001. In November 2000, the backscatter ratio at a wavelength of 532 nm was up to 1.1, with a FWHM of about 2.5 km. By early February 2001, the layer had sedimented from an altitude of 38 km to about 26 km. Measurements at several wavelengths by the ALOMAR and Koldewey lidars indicate the particle size was between 30 and 50 nm. Depolarisation measurements reveal that the particles in the layer are aspherical, hence solid. In the mid-stratosphere, the ambient atmospheric temperature was too high to support in situ formation or existence of cloud particles consisting of ice or an acid-water solution. Furthermore, in the year 2000 there was no volcanic eruption, which could have injected aerosols into the upper stratosphere. Therefore, other origins of the aerosol, such as meteoroid debris, condensed rocket fuel, or aerosols produced under the influence of charged solar particles, will be discussed in the paper. Trajectory calculations illustrate the path of the aerosol cloud within the polar vortex and are used to link the observations at the different lidar sites. From the descent rate of  the layer and particle sedimentation rates, the mean down-ward motion of air within the polar vortex was estimated to be about 124 m/d between 35 and 30 km, with higher values at the edge of the

  19. Broadband and high-efficiency vortex beam generator based on a hybrid helix array.

    Science.gov (United States)

    Fang, Chaoqun; Wu, Chao; Gong, Zhijie; Zhao, Song; Sun, Anqi; Wei, Zeyong; Li, Hongqiang

    2018-04-01

    The vortex beam which carries the orbital angular momentum has versatile applications, such as high-resolution imaging, optical communications, and particle manipulation. Generating vortex beams with the Pancharatnam-Berry (PB) phase has drawn considerable attention for its unique spin-to-orbital conversion features. Despite the PB phase being frequency independent, an optical element with broadband high-efficiency circular polarization conversion feature is still needed for the broadband high-efficiency vortex beam generation. In this work, a broadband and high-efficiency vortex beam generator based on the PB phase is built with a hybrid helix array. Such devices can generate vortex beams with arbitrary topological charge. Moreover, vortex beams with opposite topological charge can be generated with an opposite handedness incident beam that propagates backward. The measured efficiency of our device is above 65% for a wide frequency range, with the relative bandwidth of 46.5%.

  20. Measurement of the topological charge and index of vortex vector optical fields with a space-variant half-wave plate.

    Science.gov (United States)

    Liu, Gui-Geng; Wang, Ke; Lee, Yun-Han; Wang, Dan; Li, Ping-Ping; Gou, Fangwang; Li, Yongnan; Tu, Chenghou; Wu, Shin-Tson; Wang, Hui-Tian

    2018-02-15

    Vortex vector optical fields (VVOFs) refer to a kind of vector optical field with an azimuth-variant polarization and a helical phase, simultaneously. Such a VVOF is defined by the topological index of the polarization singularity and the topological charge of the phase vortex. We present a simple method to measure the topological charge and index of VVOFs by using a space-variant half-wave plate (SV-HWP). The geometric phase grating of the SV-HWP diffracts a VVOF into ±1 orders with orthogonally left- and right-handed circular polarizations. By inserting a polarizer behind the SV-HWP, the two circular polarization states project into the linear polarization and then interfere with each other to form the interference pattern, which enables the direct measurement of the topological charge and index of VVOFs.

  1. Levels and pattern of polybrominated diphenyl ethers in eggs of Antarctic seabirds: Endemic versus migratory species

    Energy Technology Data Exchange (ETDEWEB)

    Yogui, G.T. [Geochemical and Environmental Research Group, College of Geosciences, Texas A and M University, 833 Graham Road, College Station, TX 77845 (United States)], E-mail: gtyogui@ocean.tamu.edu; Sericano, J.L. [Geochemical and Environmental Research Group, College of Geosciences, Texas A and M University, 833 Graham Road, College Station, TX 77845 (United States)], E-mail: jsericano@gerg.tamu.edu

    2009-03-15

    Chinstrap and gentoo penguins are endemic species that live year round south of the Antarctic Convergence. South polar skua is a migratory seabird that can be observed in Antarctica during the breeding season (i.e., austral summer). This study compares concentration and pattern of polybrominated diphenyl ethers (PBDEs) in eggs of seabirds breeding at King George Island, Antarctic Peninsula. PBDEs in south polar skua eggs are approximately 20 times higher than in penguin eggs suggesting that skuas are more exposed to contaminants during the non-breeding season when they migrate to waters of the northern hemisphere. The pattern of PBDE congeners also differs between south polar skua and penguin eggs. The latter exhibited a pattern similar to that found in the local biota. In contrast, the congener pattern in south polar skua eggs suggests that birds breeding at King George Island may winter in the northwestern Pacific Ocean. - Skua and penguin eggs collected at King George Island have different concentration and pattern of PBDEs.

  2. Levels and pattern of polybrominated diphenyl ethers in eggs of Antarctic seabirds: Endemic versus migratory species

    International Nuclear Information System (INIS)

    Yogui, G.T.; Sericano, J.L.

    2009-01-01

    Chinstrap and gentoo penguins are endemic species that live year round south of the Antarctic Convergence. South polar skua is a migratory seabird that can be observed in Antarctica during the breeding season (i.e., austral summer). This study compares concentration and pattern of polybrominated diphenyl ethers (PBDEs) in eggs of seabirds breeding at King George Island, Antarctic Peninsula. PBDEs in south polar skua eggs are approximately 20 times higher than in penguin eggs suggesting that skuas are more exposed to contaminants during the non-breeding season when they migrate to waters of the northern hemisphere. The pattern of PBDE congeners also differs between south polar skua and penguin eggs. The latter exhibited a pattern similar to that found in the local biota. In contrast, the congener pattern in south polar skua eggs suggests that birds breeding at King George Island may winter in the northwestern Pacific Ocean. - Skua and penguin eggs collected at King George Island have different concentration and pattern of PBDEs

  3. MJO-Related Tropical Convection Anomalies Lead to More Accurate Stratospheric Vortex Variability in Subseasonal Forecast Models.

    Science.gov (United States)

    Garfinkel, C I; Schwartz, C

    2017-10-16

    The effect of the Madden-Julian Oscillation (MJO) on the Northern Hemisphere wintertime stratospheric polar vortex in the period preceding stratospheric sudden warmings is evaluated in operational subseasonal forecasting models. Reforecasts which simulate stronger MJO-related convection in the Tropical West Pacific also simulate enhanced heat flux in the lowermost stratosphere and a more realistic vortex evolution. The time scale on which vortex predictability is enhanced lies between 2 and 4 weeks for nearly all cases. Those stratospheric sudden warmings that were preceded by a strong MJO event are more predictable at ∼20 day leads than stratospheric sudden warmings not preceded by a MJO event. Hence, knowledge of the MJO can contribute to enhanced predictability, at least in a probabilistic sense, of the Northern Hemisphere polar stratosphere.

  4. Structuring Stokes correlation functions using vector-vortex beam

    Science.gov (United States)

    Kumar, Vijay; Anwar, Ali; Singh, R. P.

    2018-01-01

    Higher order statistical correlations of the optical vector speckle field, formed due to scattering of a vector-vortex beam, are explored. Here, we report on the experimental construction of the Stokes parameters covariance matrix, consisting of all possible spatial Stokes parameters correlation functions. We also propose and experimentally realize a new Stokes correlation functions called Stokes field auto correlation functions. It is observed that the Stokes correlation functions of the vector-vortex beam will be reflected in the respective Stokes correlation functions of the corresponding vector speckle field. The major advantage of proposing Stokes correlation functions is that the Stokes correlation function can be easily tuned by manipulating the polarization of vector-vortex beam used to generate vector speckle field and to get the phase information directly from the intensity measurements. Moreover, this approach leads to a complete experimental Stokes characterization of a broad range of random fields.

  5. Vortex profiles and vortex interactions at the electroweak crossover

    OpenAIRE

    Chernodub, M. N.; Ilgenfritz, E. -M.; Schiller, A.

    1999-01-01

    Local correlations of Z-vortex operators with gauge and Higgs fields (lattice quantum vortex profiles) as well as vortex two-point functions are studied in the crossover region near a Higgs mass of 100 GeV within the 3D SU(2) Higgs model. The vortex profiles resemble certain features of the classical vortex solutions in the continuum. The vortex-vortex interactions are analogous to the interactions of Abrikosov vortices in a type-I superconductor.

  6. Unexpectedly high ultrafine aerosol concentrations above East Antarctic sea-ice

    Science.gov (United States)

    Humphries, R. S.; Klekociuk, A. R.; Schofield, R.; Keywood, M.; Ward, J.; Wilson, S. R.

    2015-10-01

    The effect of aerosols on clouds and their radiative properties is one of the largest uncertainties in our understanding of radiative forcing. A recent study has concluded that better characterisation of pristine, natural aerosol processes leads to the largest reduction in these uncertainties. Antarctica, being far from anthropogenic activities, is an ideal location for the study of natural aerosol processes. Aerosol measurements in Antarctica are often limited to boundary layer air-masses at spatially sparse coastal and continental research stations, with only a handful of studies in the sea ice region. In this paper, the first observational study of sub-micron aerosols in the East Antarctic sea ice region is presented. Measurements were conducted aboard the ice-breaker Aurora Australis in spring 2012 and found that boundary layer condensation nuclei (CN3) concentrations exhibited a five-fold increase moving across the Polar Front, with mean Polar Cell concentrations of 1130 cm-3 - higher than any observed elsewhere in the Antarctic and Southern Ocean region. The absence of evidence for aerosol growth suggested that nucleation was unlikely to be local. Air parcel trajectories indicated significant influence from the free troposphere above the Antarctic continent, implicating this as the likely nucleation region for surface aerosol, a similar conclusion to previous Antarctic aerosol studies. The highest aerosol concentrations were found to correlate with low pressure systems, suggesting that the passage of cyclones provided an accelerated pathway, delivering air-masses quickly from the free-troposphere to the surface. After descent from the Antarctic free troposphere, trajectories suggest that sea ice boundary layer air-masses travelled equator-ward into the low albedo Southern Ocean region, transporting with them emissions and these aerosol nuclei where, after growth, may potentially impact on the region's radiative balance. The high aerosol concentrations and

  7. Optical vortex beams: Generation, propagation and applications

    Science.gov (United States)

    Cheng, Wen

    An optical vortex (also known as a screw dislocation or phase singularity) is one type of optical singularity that has a spiral phase wave front around a singularity point where the phase is undefined. Optical vortex beams have a lot of applications in areas such as optical communications, LADAR (laser detection and ranging) system, optical tweezers, optical trapping and laser beam shaping. The concepts of optical vortex beams and methods of generation are briefly discussed. The properties of optical vortex beams propagating through atmospheric turbulence have been studied. A numerical modeling is developed and validated which has been applied to study the high order properties of optical vortex beams propagating though a turbulent atmosphere. The simulation results demonstrate the advantage that vectorial vortex beams may be more stable and maintain beam integrity better when they propagate through turbulent atmosphere. As one important application of optical vortex beams, the laser beam shaping is introduced and studied. We propose and demonstrate a method to generate a 2D flat-top beam profile using the second order full Poincare beams. Its applications in two-dimensional flat-top beam shaping with spatially variant polarization under low numerical aperture focusing have been studied both theoretically and experimentally. A novel compact flat-top beam shaper based on the proposed method has been designed, fabricated and tested. Experimental results show that high quality flat-top profile can be obtained with steep edge roll-off. The tolerance to different input beam sizes of the beam shaper is also verified in the experimental demonstration. The proposed and experimentally verified LC beam shaper has the potential to become a promising candidate for compact and low-cost flat-top beam shaping in areas such as laser processing/machining, lithography and medical treatment.

  8. [History of Polish botanical and mycological researches on sheets of land of Antarctic and Sub-Antarctic in the years 1977-2009].

    Science.gov (United States)

    Köhler, Piotr; Olech, Maria

    2011-01-01

    The work includes a description of the period from the moment of setting up Polish Polar Station on King George Island (1977) to the end of International Polar Year IV in 2009. Researches on flower plants focused, among others, on plants' morphology, morphological composition of the pollen and anatomical ultra-structure of the leaves. There were also carried out biochemical and other searches for the internal mutability. Within physiological studies one concentrated on the problem of reaction to temperature stress. Biological researches focused mainly on solving taxonomic and bio-geographic problems. Finally, were published several monographs and, among others, the first in history complete description of moss' flora of the whole of Antarctic (2008). Research works over algae included also such issues as floristics, bio-geography, taxonomy and ecology (for instance, the rookery's impact on distribution of algae, or the influence of inanimate factors on dynamics of condensing the Diatoma in different water and soil-bound tanks). Up till now, within mycological investigations has been identified a variety of lichen fungi that for the most part of Antarctic are a novelty. There were scientifically described new for science genera and species of Western Antarctic. Lichenological studies were made in the field of taxonomy, geography, lichenometry, biochemistry of lichens, lichenoindication, ecophysiology and from the point of analysis of base metals' content. There were also described new for science species. Since 1991, were published the results of searches for the base metals' content and vestigial chemical elements in lichens' thallus. Ecophysiological researches concerned both micro-climatic conditions' impact on primary production and lichens' adaptation to a very cold climate. One discovered a mechanism of two-phase hydratization/dehydratization of lichens' thallus. On the ground of palaeobotanical analyzes was reconstructed a development of flora in Western

  9. Promoting Diversity Through Polar Interdisciplinary Coordinated Education (Polar ICE)

    Science.gov (United States)

    McDonnell, J. D.; Hotaling, L. A.; Garza, C.; Van Dyk, P. B.; Hunter-thomson, K. I.; Middendorf, J.; Daniel, A.; Matsumoto, G. I.; Schofield, O.

    2017-12-01

    Polar Interdisciplinary Coordinated Education (ICE) is an education and outreach program designed to provide public access to the Antarctic and Arctic regions through polar data and interactions with the scientists. The program provides multi-faceted science communication training for early career scientists that consist of a face-to face workshop and opportunities to apply these skills. The key components of the scientist training workshop include cultural competency training, deconstructing/decoding science for non-expert audiences, the art of telling science stories, and networking with members of the education and outreach community and reflecting on communication skills. Scientists partner with educators to provide professional development for K-12 educators and support for student research symposia. Polar ICE has initiated a Polar Literacy initiative that provides both a grounding in big ideas in polar science and science communication training designed to underscore the importance of the Polar Regions to the public while promoting interdisciplinary collaborations between scientists and educators. Our ultimate objective is to promote STEM identity through professional development of scientists and educators while developing career awareness of STEM pathways in Polar science.

  10. Polarization dependent switching of asymmetric nanorings with a circular field

    Directory of Open Access Journals (Sweden)

    Nihar R. Pradhan

    2016-01-01

    Full Text Available We experimentally investigated the switching from onion to vortex states in asymmetric cobalt nanorings by an applied circular field. An in-plane field is applied along the symmetric or asymmetric axis of the ring to establish domain walls (DWs with symmetric or asymmetric polarization. A circular field is then applied to switch from the onion state to the vortex state, moving the DWs in the process. The asymmetry of the ring leads to different switching fields depending on the location of the DWs and direction of applied field. For polarization along the asymmetric axis, the field required to move the DWs to the narrow side of the ring is smaller than the field required to move the DWs to the larger side of the ring. For polarization along the symmetric axis, establishing one DW in the narrow side and one on the wide side, the field required to switch to the vortex state is an intermediate value.

  11. The Arctic Vortex in March 2011: A Dynamical Perspective

    Science.gov (United States)

    Hurwitz, Margaret M.; Newman, Paul A.; Garfinkel,Chaim I.

    2011-01-01

    Despite the record ozone loss observed in March 2011, dynamical conditions in the Arctic stratosphere were unusual but not unprecedented. Weak planetary wave driving in February preceded cold anomalies in t he polar lower stratosphere in March and a relatively late breakup of the Arctic vortex in April. La Nina conditions and the westerly phas e of the quasi-biennial oscillation (QBO) were observed in March 201 1. Though these conditions are generally associated with a stronger vortex in mid-winter, the respective cold anomalies do not persist t hrough March. Therefore, the La Nina and QBO-westerly conditions cannot explain the observed cold anomalies in March 2011. In contrast, po sitive sea surface temperature anomalies in the North Pacific may ha ve contributed to the unusually weak tropospheric wave driving and s trong Arctic vortex in late winter 2011.

  12. The Temperature of the Arctic and Antarctic Lower Stratosphere

    Science.gov (United States)

    Newman, Paul A.; Nash, Eric R.; Bhartia, P. K. (Technical Monitor)

    2002-01-01

    The temperature of the polar lower stratosphere during spring is the key factor in changing the magnitude of ozone loss in the polar vortices. In this talk, we will review the results of Newman et al. [2000] that quantitatively demonstrate that the polar lower stratospheric temperature is primarily controlled by planetary-scale waves. In particular, the tropospheric eddy heat flux in middle to late winter (January--February) is highly correlated with the mean polar stratospheric temperature during March. Strong midwinter planetary wave forcing leads to a warmer spring Arctic lower stratosphere in early spring, while weak midwinter forcing leads to cooler spring Arctic temperatures. In addition, this planetary wave driving also has a strong impact on the strength of the polar vortex. These results from the Northern Hemisphere will be contrasted with the Southern Hemisphere.

  13. Vortex cores and vortex motion in superconductors with anisotropic Fermi surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Galvis, J.A. [Laboratorio de Bajas Temperaturas, Departamento de Física de la Materia Condensada, Instituto de Ciencia de Materiales Nicolás Cabrera, Condensed Matter Physics Center (IFIMAC), Facultad de Ciencias, Universidad Autónoma de Madrid, E-28049 Madrid (Spain); Departamento de Ciencias Naturales, Facultad de ingeniería y Ciencias Básicas, Universidad Central, Bogotá (Colombia); National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310 (United States); Herrera, E.; Guillamón, I.; Vieira, S. [Laboratorio de Bajas Temperaturas, Departamento de Física de la Materia Condensada, Instituto de Ciencia de Materiales Nicolás Cabrera, Condensed Matter Physics Center (IFIMAC), Facultad de Ciencias, Universidad Autónoma de Madrid, E-28049 Madrid (Spain); Unidad Asociada de Altos Campos Magnéticos y Bajas Temperaturas, UAM, CSIC, Madrid (Spain); Suderow, H., E-mail: hermann.suderow@uam.es [Laboratorio de Bajas Temperaturas, Departamento de Física de la Materia Condensada, Instituto de Ciencia de Materiales Nicolás Cabrera, Condensed Matter Physics Center (IFIMAC), Facultad de Ciencias, Universidad Autónoma de Madrid, E-28049 Madrid (Spain); Unidad Asociada de Altos Campos Magnéticos y Bajas Temperaturas, UAM, CSIC, Madrid (Spain)

    2017-02-15

    Highlights: • The observation of vortex cores is reviewed, with emphasis in new experiments. • Vortex cores are follow superconducting gap and Fermi surface shapes. • The vortex core shape influences vortex dynamics. - Abstract: Explaning static and dynamic properties of the vortex lattice in anisotropic superconductors requires a careful characterization of vortex cores. The vortex core contains Andreev bound states whose spatial extension depends on the anisotropy of the electronic band-structure and superconducting gap. This might have an impact on the anisotropy of the superconducting properties and on vortex dynamics. Here we briefly summarize basic concepts to understand anisotropic vortex cores and review vortex core imaging experiments. We further discuss moving vortex lattices and the influence of vortex core shape in vortex motion. We find vortex motion in highly tilted magnetic fields. We associate vortex motion to the vortex entry barrier and the screening currents at the surface. We find preferential vortex motion along the main axis of the vortex lattice. After travelling integers of the intervortex distance, we find that vortices move more slowly due to the washboard potential of the vortex lattice.

  14. Vortex cores and vortex motion in superconductors with anisotropic Fermi surfaces

    International Nuclear Information System (INIS)

    Galvis, J.A.; Herrera, E.; Guillamón, I.; Vieira, S.; Suderow, H.

    2017-01-01

    Highlights: • The observation of vortex cores is reviewed, with emphasis in new experiments. • Vortex cores are follow superconducting gap and Fermi surface shapes. • The vortex core shape influences vortex dynamics. - Abstract: Explaning static and dynamic properties of the vortex lattice in anisotropic superconductors requires a careful characterization of vortex cores. The vortex core contains Andreev bound states whose spatial extension depends on the anisotropy of the electronic band-structure and superconducting gap. This might have an impact on the anisotropy of the superconducting properties and on vortex dynamics. Here we briefly summarize basic concepts to understand anisotropic vortex cores and review vortex core imaging experiments. We further discuss moving vortex lattices and the influence of vortex core shape in vortex motion. We find vortex motion in highly tilted magnetic fields. We associate vortex motion to the vortex entry barrier and the screening currents at the surface. We find preferential vortex motion along the main axis of the vortex lattice. After travelling integers of the intervortex distance, we find that vortices move more slowly due to the washboard potential of the vortex lattice.

  15. Vortex methods and vortex statistics

    International Nuclear Information System (INIS)

    Chorin, A.J.

    1993-05-01

    Vortex methods originated from the observation that in incompressible, inviscid, isentropic flow vorticity (or, more accurately, circulation) is a conserved quantity, as can be readily deduced from the absence of tangential stresses. Thus if the vorticity is known at time t = 0, one can deduce the flow at a later time by simply following it around. In this narrow context, a vortex method is a numerical method that makes use of this observation. Even more generally, the analysis of vortex methods leads, to problems that are closely related to problems in quantum physics and field theory, as well as in harmonic analysis. A broad enough definition of vortex methods ends up by encompassing much of science. Even the purely computational aspects of vortex methods encompass a range of ideas for which vorticity may not be the best unifying theme. The author restricts himself in these lectures to a special class of numerical vortex methods, those that are based on a Lagrangian transport of vorticity in hydrodynamics by smoothed particles (''blobs'') and those whose understanding contributes to the understanding of blob methods. Vortex methods for inviscid flow lead to systems of ordinary differential equations that can be readily clothed in Hamiltonian form, both in three and two space dimensions, and they can preserve exactly a number of invariants of the Euler equations, including topological invariants. Their viscous versions resemble Langevin equations. As a result, they provide a very useful cartoon of statistical hydrodynamics, i.e., of turbulence, one that can to some extent be analyzed analytically and more importantly, explored numerically, with important implications also for superfluids, superconductors, and even polymers. In the authors view, vortex ''blob'' methods provide the most promising path to the understanding of these phenomena

  16. Sexual Polarities: Shelley’s Frankenstein and Polar Exploration as a Search for Origins Beyond ‘woman’

    Directory of Open Access Journals (Sweden)

    Polly Gould

    2008-02-01

    Full Text Available This paper is about our parents and our predecessors in life and in literature. It specifically interrogates the choice of Polar landscapes for the playing out of narratives of gender difference in stories of Arctic and Antarctic exploration. I have chosen to pay attention to three narratives: Shackleton's South, Mary Shelley's Frankenstein and Ursula Le Guin's short story Sur. They all take place in the icy expanse of the Arctic and Antarctic. I will read them in the light of the question of origins: ‘where do I come from?'

  17. Treatment and prevention of infection following bites of the Antarctic fur seal (Arctocephalus gazella

    Directory of Open Access Journals (Sweden)

    Kouliev T

    2015-04-01

    Full Text Available Timur Kouliev,1 Victoria Cui2 1Beijing United Family Hospital, Beijing, People's Republic of China; 2Department of Biological Sciences, Columbia University, New York, NY, USA Abstract: In recent decades, an increasing number of people have traveled to sub-Antarctic and Antarctic regions each year for research, tourism, and resource exploitation. Hunting of Antarctic fur seals (Arctocephalus gazella almost pushed the species to extinction in the early 1900s, but populations have since shown rapid and substantial recovery. The species' range has re-expanded to include several islands south of the Antarctic Convergence, most notably South Georgia, and now overlaps with many popular Antarctic travel destinations. Both male and female fur seals can become extremely aggressive when provoked, and their bites, if not properly treated, pose a significant risk of infection by microorganisms not usually encountered in cases of animal bites. In this report, we present the case of a patient treated for a fur seal bite during an Antarctic expedition cruise, review the literature concerning seal bites, and suggest the use of antibiotic prophylaxis to prevent complications. Keywords: zoonotic, polar tourism, prophylaxis, seal finger, expedition medicine

  18. 78 FR 66074 - Notice of Permit Applications Received Under the Antarctic Conservation Act of 1978 (Pub. L. 95-541)

    Science.gov (United States)

    2013-11-04

    ... photographs for (Science, Technology, Engineering, and Mathematics) STEM educational purposes. The gathered..., engineering or mathematics aspects of the historic Antarctic expeditions. The lesson plans would be... 30, 2013 to January 31, 2014. Nadene G. Kennedy, Polar Coordination Specialist, Division of Polar...

  19. Precipitation Modeling over the Greenland and Antarctic Ice Sheets and the Relationship to the Surface Mass Balance and Climate

    Science.gov (United States)

    Bromwich, David H.; Chen, Qui-Shi

    2005-01-01

    Atmospheric numerical simulation and dynamic retrieval method with atmospheric numerical analyses are used to assess the spatial and temporal variability of Antarctic precipitation for the last two decades. First, the Polar MM5 has been run over Antarctica to study the Antarctic precipitation. With a horizontal resolution of 60km, the Polar MM5 has been run for the period of July 1996 through June 1999 in a series of short-term forecasts from initial and boundary conditions provided by the ECMWF operational analyses. In comparison with climatological maps, the major features of the spatial distribution of Antarctic precipitation are well captured by the Polar MM5. Drift snow effects on redistribution of surface accumulation over Antarctica are also assessed with surface wind fields from Polar MM5 in this study. There are complex divergence and convergence patterns of drift snow transport over Antarctica, especially along the coast. It is found that areas with large drift snow transport convergence and divergence are located around escarpment areas where there is large katabatic wind acceleration. In addition, areas with large snow transport divergence are generally accompanied by areas with large snow transport convergence nearby, indicating that drift snow transport is of local importance for the redistribution of the snowfall

  20. Vortex Flipping in Superconductor-Ferromagnet Spin Valve Structures

    Science.gov (United States)

    Patino, Edgar J.; Aprili, Marco; Blamire, Mark; Maeno, Yoshiteru

    2014-03-01

    We report in plane magnetization measurements on Ni/Nb/Ni/CoO and Co/Nb/Co/CoO spin valve structures with one of the ferromagnetic layers pinned by an antiferromagnetic layer. In samples with Ni, below the superconducting transition Tc, our results show strong evidence of vortex flipping driven by the ferromagnets magnetization. This is a direct consequence of proximity effect that leads to vortex supercurrents leakage into the ferromagnets. Here the polarized electron spins are subject to vortices magnetic field occasioning vortex flipping. Such novel mechanism has been made possible for the first time by fabrication of the F/S/F/AF multilayered spin valves with a thin-enough S layer to barely confine vortices inside as well as thin-enough F layers to align and control the magnetization within the plane. When Co is used there is no observation of vortex flipping effect. This is attributed to Co shorter coherence length. Interestingly instead a reduction in pinning field of about 400 Oe is observed when the Nb layer is in superconducting state. This effect cannot be explained in terms of vortex fields. In view of these facts any explanation must be directly related to proximity effect and thus a remarkable phenomenon that deserves further investigation. Programa Nacional de Ciencias Basicas COLCIENCIAS (No. 120452128168).

  1. The major stratospheric final warming in 2016: dispersal of vortex air and termination of Arctic chemical ozone loss

    Directory of Open Access Journals (Sweden)

    G. L. Manney

    2016-12-01

    Full Text Available The 2015/16 Northern Hemisphere winter stratosphere appeared to have the greatest potential yet seen for record Arctic ozone loss. Temperatures in the Arctic lower stratosphere were at record lows from December 2015 through early February 2016, with an unprecedented period of temperatures below ice polar stratospheric cloud thresholds. Trace gas measurements from the Aura Microwave Limb Sounder (MLS show that exceptional denitrification and dehydration, as well as extensive chlorine activation, occurred throughout the polar vortex. Ozone decreases in 2015/16 began earlier and proceeded more rapidly than those in 2010/11, a winter that saw unprecedented Arctic ozone loss. However, on 5–6 March 2016 a major final sudden stratospheric warming ("major final warming", MFW began. By mid-March, the mid-stratospheric vortex split after being displaced far off the pole. The resulting offspring vortices decayed rapidly preceding the full breakdown of the vortex by early April. In the lower stratosphere, the period of temperatures low enough for chlorine activation ended nearly a month earlier than that in 2011 because of the MFW. Ozone loss rates were thus kept in check because there was less sunlight during the cold period. Although the winter mean volume of air in which chemical ozone loss could occur was as large as that in 2010/11, observed ozone values did not drop to the persistently low values reached in 2011.We use MLS trace gas measurements, as well as mixing and polar vortex diagnostics based on meteorological fields, to show how the timing and intensity of the MFW and its impact on transport and mixing halted chemical ozone loss. Our detailed characterization of the polar vortex breakdown includes investigations of individual offspring vortices and the origins and fate of air within them. Comparisons of mixing diagnostics with lower-stratospheric N2O and middle-stratospheric CO from MLS (long-lived tracers show rapid vortex erosion and

  2. Vortex-vortex interactions in toroidally trapped Bose-Einstein condensates

    OpenAIRE

    Schulte, T.; Santos, L.; Sanpera, A.; Lewenstein, M.

    2002-01-01

    We analyze the vortex dynamics and vortex-vortex interactions in Bose-Einstein condensates confined in toroidal traps. We show that this particular geometry strongly distorts the vortex dynamics. The numerically calculated vortex trajectories are well explained by an analytical calculation based on image method and conformal mapping. Finally, the dissipation effects are discussed.

  3. Vortex coupling in trailing vortex-wing interactions

    Science.gov (United States)

    Chen, C.; Wang, Z.; Gursul, I.

    2018-03-01

    The interaction of trailing vortices of an upstream wing with rigid and flexible downstream wings has been investigated experimentally in a wind tunnel, using particle image velocimetry, hot-wire, force, and deformation measurements. Counter-rotating upstream vortices exhibit increased meandering when they are close to the tip of the downstream wing. The upstream vortex forms a pair with the vortex shed from the downstream wing and then exhibits large displacements around the wing tip. This coupled motion of the pair has been found to cause large lift fluctuations on the downstream wing. The meandering of the vortex pair occurs at the natural meandering frequency of the isolated vortex, with a low Strouhal number, and is not affected by the frequency of the large-amplitude wing oscillations if the downstream wing is flexible. The displacement of the leading vortex is larger than that of the trailing vortex; however, it causes highly correlated variations of the core radius, core vorticity, and circulation of the trailing vortex with the coupled meandering motion. In contrast, co-rotating vortices do not exhibit any increased meandering.

  4. Polar vortices on Earth and Mars: A comparative study of the climatology and variability from reanalyses.

    Science.gov (United States)

    Mitchell, D M; Montabone, L; Thomson, S; Read, P L

    2015-01-01

    Polar vortices on Mars provide case-studies to aid understanding of geophysical vortex dynamics and may help to resolve long-standing issues regarding polar vortices on Earth. Due to the recent development of the first publicly available Martian reanalysis dataset (MACDA), for the first time we are able to characterise thoroughly the structure and evolution of the Martian polar vortices, and hence perform a systematic comparison with the polar vortices on Earth. The winter atmospheric circulations of the two planets are compared, with a specific focus on the structure and evolution of the polar vortices. The Martian residual meridional overturning circulation is found to be very similar to the stratospheric residual circulation on Earth during winter. While on Earth this residual circulation is very different from the Eulerian circulation, on Mars it is found to be very similar. Unlike on Earth, it is found that the Martian polar vortices are annular, and that the Northern Hemisphere vortex is far stronger than its southern counterpart. While winter hemisphere differences in vortex strength are also reported on Earth, the contrast is not as large. Distinctions between the two planets are also apparent in terms of the climatological vertical structure of the vortices, in that the Martian polar vortices are observed to decrease in size at higher altitudes, whereas on Earth the opposite is observed. Finally, it is found that the Martian vortices are less variable through the winter than on Earth, especially in terms of the vortex geometry. During one particular major regional dust storm on Mars (Martian year 26), an equatorward displacement of the vortex is observed, sharing some qualitative characteristics of sudden stratospheric warmings on Earth.

  5. Water masses, ocean fronts, and the structure of Antarctic seabird communities: putting the eastern Bellingshausen Sea in perspective

    Science.gov (United States)

    Ribic, Christine A.; Ainley, David G.; Ford, R. Glenn; Fraser, William R.; Tynan, Cynthia T.; Woehler, Eric J.

    2015-01-01

    Waters off the western Antarctic Peninsula (i.e., the eastern Bellingshausen Sea) are unusually complex owing to the convergence of several major fronts. Determining the relative influence of fronts on occurrence patterns of top-trophic species in that area, therefore, has been challenging. In one of the few ocean-wide seabird data syntheses, in this case for the Southern Ocean, we analyzed ample, previously collected cruise data, Antarctic-wide, to determine seabird species assemblages and quantitative relationships to fronts as a way to provide context to the long-term Palmer LTER and the winter Southern Ocean GLOBEC studies in the eastern Bellingshausen Sea. Fronts investigated during both winter (April–September) and summer (October–March) were the southern boundary of the Antarctic Circumpolar Current (ACC), which separates the High Antarctic from the Low Antarctic water mass, and within which are embedded the marginal ice zone and Antarctic Shelf Break Front; and the Antarctic Polar Front, which separates the Low Antarctic and the Subantarctic water masses. We used clustering to determine species' groupings with water masses, and generalized additive models to relate species' densities, biomass and diversity to distance to respective fronts. Antarctic-wide, in both periods, highest seabird densities and lowest species diversity were found in the High Antarctic water mass. In the eastern Bellingshausen, seabird density in the High Antarctic water mass was lower (as low as half that of winter) than found in other Antarctic regions. During winter, Antarctic-wide, two significant species groups were evident: one dominated by Adélie penguins (Pygoscelis adeliae) (High Antarctic water mass) and the other by petrels and prions (no differentiation among water masses); in eastern Bellingshausen waters during winter, the one significant species group was composed of species from both Antarctic-wide groups. In summer, Antarctic-wide, a High Antarctic group

  6. NOAA JPSS Visible Infrared Imaging Radiometer Suite (VIIRS) Polar Winds from NDE

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This dataset contains the Level 3 Polar Winds Northern and Southern Hemisphere datasets. The Level 3 Polar Winds data from VIIRS for the Arctic and Antarctic from 65...

  7. Electric polarization of magnetic textures: New horizons of micromagnetism

    International Nuclear Information System (INIS)

    Pyatakov, A.P.; Meshkov, G.A.; Zvezdin, A.K.

    2012-01-01

    A common scenario of magnetoelectric coupling in multiferroics is the electric polarization induced by spatially modulated spin structures. It is shown in this paper that the same mechanism works in magnetic dielectrics with inhomogeneous magnetization distribution: the domain walls and magnetic vortexes can be the sources of electric polarization. The electric field driven magnetic domain wall motion is observed in iron garnet films. The electric field induced nucleation of vortex state of magnetic nanodots is theoretically predicted and numerically simulated. From the practical point of view the electric field control of micromagnetic structures suggests a low-power approach for spintronics and magnonics.

  8. The use of drilling by the U.S. Antarctic program

    Energy Technology Data Exchange (ETDEWEB)

    Wade, M.C.; Webb, J.W.; Hedberg, W.H.

    1994-08-01

    This report on drilling in the Antarctic has been prepared by the U.S. National Science Foundation (NSF) to assist principal investigators and others in complying with the National Environmental Policy Act (NEPA) and the Antarctic Treaty of 1961. Implementing regulations for NEPA are spelled out in 40 CFR 1500-1508. Environmental protection under the Antarctic Treaty is addressed in the Protocol on Environmental Protection to the Antarctic Treaty (hereafter referred to as the Protocol), which was adopted by 26 countries in 1991. In the United States, responsibility for compliance with these requirements rests with the NSF Office of Polar Programs (OPP), which manages the U.S. Antarctic Program (USAP). The USAP recognizes the potentially profound impacts that its presence and activities can have on the antarctic environment. In its extensive support of operations and research in Antarctica, the USAP uses all practical means to foster and maintain natural conditions while supporting scientific endeavors in a safe and healthful manner. Reducing human impacts on the antarctic environment is a major goal of the USAP. The USAP`s operating philosophy is based on broad yet reasonable and practical assumptions concerning environmental protection. The USAP maintains three year-round stations on the continent to support scientific research. Research and associated support operations at these stations and camps sometimes involve drilling into ice, soil, or ocean sediments. In order to comply with NEPA and the Protocol, it is necessary for principal investigators and others to assess the environmental effects of drilling. This report has been prepared to assist in this process by describing various drilling technologies currently available for use in Antarctica, generally characterizing the potential environmental impacts associated with these drilling techniques, and identifying possible mitigation measures to reduce impacts.

  9. Millennial-scale instability of the Antarctic Ice Sheet during the last glaciation.

    NARCIS (Netherlands)

    Kanfoush, S.L.; Hodell, D.A.; Charles, C.D.; Guilderson, T.P.; Mortyn, P.G.

    2000-01-01

    Records of ice-rafted detritus (IRD) concentration in deep-sea cores from the southeast Atlantic Ocean reveal millennial-scale pulses of IRD delivery between 20,000 and 74,000 years ago. Prominent IRD layers correlate across the Polar Frontal Zone, suggesting episodes of Antarctic Ice Sheet

  10. 75 FR 45675 - Notice of Permit Applications Received Under the Antarctic Conservation Act of 1978 (Pub. L. 95-541)

    Science.gov (United States)

    2010-08-03

    .... Applicant: Sam Feola, Director, Raytheon Polar Services Company, 7400 South Tucson Way, Centennial, CO 80112..., Raytheon Polar Services Company, 7400 South Tucson Way, Centennial, CO 80112. Activity for Which Permit is... Way, Centennial, CO 80112. Activity for Which Permit is Requested: Enter Antarctic Specially Protected...

  11. The polar mesosphere

    International Nuclear Information System (INIS)

    Morris, Ray; Murphy, Damian

    2008-01-01

    The mesosphere region, which lies at the edge of space, contains the coldest layer of the Earth's atmosphere, with summer temperatures as low as minus 130 °C. In this extreme environment ice aerosol layers have appeared since the dawn of industrialization—whose existence may arguably be linked to human influence—on yet another layer of the Earth's fragile atmosphere. Ground-based and space-based experiments conducted in the Arctic and Antarctic during the International Polar Year (IPY) aim to address limitations in our knowledge and to advance our understanding of thermal and dynamical processes at play in the polar mesosphere

  12. Biogeography of photoautotrophs in the high polar biome

    Directory of Open Access Journals (Sweden)

    Stephen Brian Pointing

    2015-09-01

    Full Text Available The global latitudinal gradient in biodiversity weakens in the high polar biome and so an alternative explanation for distribution of Arctic and Antarctic photoautotrophs is required. Here we identify how temporal, microclimate and evolutionary drivers of biogeography are important, rather than the macroclimate features that drive plant diversity patterns elsewhere. High polar ecosystems are biologically unique, with a more central role for bryophytes, lichens and microbial photoautotrophs over that of vascular plants. Constraints on vascular plants arise mainly due to stature and ontogenetic barriers. Conversely non-vascular plant and microbial photoautotroph distribution is correlated with favourable microclimates and the capacity for poikilohydric dormancy. Contemporary distribution also depends on evolutionary history, with adaptive and dispersal traits as well as legacy influencing biogeography. We highlight the relevance of these findings to predicting future impacts on polar plant diversity and to the current status of plants in Arctic and Antarctic conservation policy frameworks.

  13. Extremophiles in an Antarctic Marine Ecosystem

    Directory of Open Access Journals (Sweden)

    Iain Dickinson

    2016-01-01

    Full Text Available Recent attempts to explore marine microbial diversity and the global marine microbiome have indicated a large proportion of previously unknown diversity. However, sequencing alone does not tell the whole story, as it relies heavily upon information that is already contained within sequence databases. In addition, microorganisms have been shown to present small-to-large scale biogeographical patterns worldwide, potentially making regional combinations of selection pressures unique. Here, we focus on the extremophile community in the boundary region located between the Polar Front and the Southern Antarctic Circumpolar Current in the Southern Ocean, to explore the potential of metagenomic approaches as a tool for bioprospecting in the search for novel functional activity based on targeted sampling efforts. We assessed the microbial composition and diversity from a region north of the current limit for winter sea ice, north of the Southern Antarctic Circumpolar Front (SACCF but south of the Polar Front. Although, most of the more frequently encountered sequences  were derived from common marine microorganisms, within these dominant groups, we found a proportion of genes related to secondary metabolism of potential interest in bioprospecting. Extremophiles were rare by comparison but belonged to a range of genera. Hence, they represented interesting targets from which to identify rare or novel functions. Ultimately, future shifts in environmental conditions favoring more cosmopolitan groups could have an unpredictable effect on microbial diversity and function in the Southern Ocean, perhaps excluding the rarer extremophiles.

  14. Lagrangian Transport Calculations Using UARS Data. Part 2; Ozone

    Science.gov (United States)

    Manney, Gloria L.; Zurek, R. W.; Froidevaux, L.; Waters, J. W.; ONeill, A.; Swinbank, R.

    1995-01-01

    Trajectory calculations are used to examine ozone transport in the polar winter stratosphere during periods of the Upper Atmosphere Research Satellite (UARS) observations. The value of these calculations for determining mass transport was demonstrated previously using UARS observations of long-lived tracers, In the middle stratosphere, the overall ozone behavior observed by the Microwave Limb Sounder in the polar vortex is reproduced by this purely dynamical model. Calculations show the evolution of ozone in the lower stratosphere during early winter to be dominated by dynamics in December 1992 in the Arctic. Calculations for June 1992 in the Antarctic show evidence of chemical ozone destruction and indicate that approx. 50% of the chemical destruction may be masked by dynamical effects, mainly diabatic descent, which bring higher ozone into the lower-stratospheric vortex. Estimating differences between calculated and observed fields suggests that dynamical changes masked approx. 20% - 35% of chemical ozone loss during late February and early March 1993 in the Arctic. In the Antarctic late winter, in late August and early September 1992, below approx. 520 K, the evolution of vortex-averaged ozone is entirely dominated by chemical effects; above this level, however, chemical ozone depletion can be partially or completely masked by dynamical effects. Our calculations for 1992 showed that chemical loss was nearly completely compensated by increases due to diabatic descent at 655 K.

  15. The widespread influence of Great Lakes microseisms across the United States revealed by the 2014 polar vortex

    Science.gov (United States)

    Anthony, Robert; Ringler, Adam; Wilson, David

    2018-01-01

    During the winter of 2014, a weak polar vortex brought record cold temperatures to the north‐central (“Midwest”) United States, and the Great Lakes reached the highest extent of ice coverage (92.5%) since 1979. This event shut down the generation of seismic signals caused by wind‐driven wave action within the lakes (termed “lake microseisms”), giving an unprecedented opportunity to isolate and characterize these novel signals through comparison with nonfrozen time periods. Using seismic records at 72 broadband stations, we observe Great Lakes microseism signals at distances >300 km from the lakes. In contrast to conventional oceanic microseisms, there is no clear relationship between the frequency content of the seismic signals (observed from ~0.5–5‐s period) and the dominant swell period or resonance periods of the lakes based on their bathymetric profiles. Thus, the exact generation mechanism is not readily explained by conventional microseism theory and warrants further investigation.

  16. Dating Antarctic ice sheet collapse: Proposing a molecular genetic approach

    Science.gov (United States)

    Strugnell, Jan M.; Pedro, Joel B.; Wilson, Nerida G.

    2018-01-01

    Sea levels at the end of this century are projected to be 0.26-0.98 m higher than today. The upper end of this range, and even higher estimates, cannot be ruled out because of major uncertainties in the dynamic response of polar ice sheets to a warming climate. Here, we propose an ecological genetics approach that can provide insight into the past stability and configuration of the West Antarctic Ice Sheet (WAIS). We propose independent testing of the hypothesis that a trans-Antarctic seaway occurred at the last interglacial. Examination of the genomic signatures of bottom-dwelling marine species using the latest methods can provide an independent window into the integrity of the WAIS more than 100,000 years ago. Periods of connectivity facilitated by trans-Antarctic seaways could be revealed by dating coalescent events recorded in DNA. These methods allow alternative scenarios to be tested against a fit to genomic data. Ideal candidate taxa for this work would need to possess a circumpolar distribution, a benthic habitat, and some level of genetic structure indicated by phylogeographical investigation. The purpose of this perspective piece is to set out an ecological genetics method to help resolve when the West Antarctic Ice Shelf last collapsed.

  17. Reaction of chlorine nitrate with hydrogen chloride and water at Antarctic stratospheric temperatures

    Science.gov (United States)

    Tolbert, Margaret A.; Rossi, Michel J.; Malhotra, Ripudaman; Golden, David M.

    1987-01-01

    Laboratory studies of heterogeneous reactions important for ozone depletion over Antarctica are reported. The reaction of chlorine nitrate (ClONO2) with H2O and HCl on surfacers that simulate polar stratospheric clouds are studied at temperatures relevant to the Antarctic stratosphere. The gaseous products of the resulting reactions, HOCl, Cl2O, and Cl2, could readily photolyze in the Antarctic spring to produce active chlorine for ozone depletion. Furthermore, the additional formation of condensed-phase HNO3 could serve as a sink for odd nitrogen species that would otherwise scavenge the active chlorine.

  18. A new variable transformation technique for the nonlinear drift vortex

    International Nuclear Information System (INIS)

    Orito, Kohtaro

    1996-02-01

    The dipole vortex solution of the Hasegawa-Mima equation describing the nonlinear drift wave is a stable solitary wave which is called the modon. The profile of the modon depends on the nonlinearity of the ExB drift. In order to investigate the nonlinear drift wave more accurately, the effect of the polarization drift needs to be considered. In case of containing the effect of the polarization drift the profile of the electrostatic potential is distorted in the direction perpendicular to the ExB drift. (author)

  19. Functional microarray analysis of nitrogen and carbon cycling genes across an Antarctic latitudinal transect.

    NARCIS (Netherlands)

    Yergeau, E.; Kang, S.; He, Z.; Zhou, J.; Kowalchuk, G.A.

    2007-01-01

    Soil-borne microbial communities were examined via a functional gene microarray approach across a southern polar latitudinal gradient to gain insight into the environmental factors steering soil N- and C-cycling in terrestrial Antarctic ecosystems. The abundance and diversity of functional gene

  20. Research of the Electron Cyclotron Emission with Vortex Property excited by high power high frequency Gyrotron

    Science.gov (United States)

    Goto, Yuki; Kubo, Shin; Tsujimura, Tohru; Takubo, Hidenori

    2017-10-01

    Recently, it has been shown that the radiation from a single electron in cyclotron motion has vortex property. Although the cyclotron emission exists universally in nature, the vortex property has not been featured because this property is normally cancelled out due to the randomness in gyro-phase of electrons and the development of detection of the vortex property has not been well motivated. In this research, we are developing a method to generate the vortex radiation from electrons in cyclotron motion with controlled gyro-phase. Electron that rotates around the uniform static magnetic field is accelerated by right-hand circular polarized (RHCP) radiation resonantly when the cyclotron frequency coincides with the applied RHCP radiation frequency. A large number of electrons can be coherently accelerated in gyro-phase by a RHCP high power radiation so that these electrons can radiate coherent emission with vortex feature. We will show that vortex radiation created by purely rotating electrons for the first time.

  1. Poles apart: the "bipolar" pteropod species Limacina helicina is genetically distinct between the Arctic and Antarctic oceans.

    Science.gov (United States)

    Hunt, Brian; Strugnell, Jan; Bednarsek, Nina; Linse, Katrin; Nelson, R John; Pakhomov, Evgeny; Seibel, Brad; Steinke, Dirk; Würzberg, Laura

    2010-03-23

    The shelled pteropod (sea butterfly) Limacina helicina is currently recognised as a species complex comprising two sub-species and at least five "forma". However, at the species level it is considered to be bipolar, occurring in both the Arctic and Antarctic oceans. Due to its aragonite shell and polar distribution L. helicina is particularly vulnerable to ocean acidification. As a key indicator of the acidification process, and a major component of polar ecosystems, L. helicina has become a focus for acidification research. New observations that taxonomic groups may respond quite differently to acidification prompted us to reassess the taxonomic status of this important species. We found a 33.56% (+/-0.09) difference in cytochrome c oxidase subunit I (COI) gene sequences between L. helicina collected from the Arctic and Antarctic oceans. This degree of separation is sufficient for ordinal level taxonomic separation in other organisms and provides strong evidence for the Arctic and Antarctic populations of L. helicina differing at least at the species level. Recent research has highlighted substantial physiological differences between the poles for another supposedly bipolar pteropod species, Clione limacina. Given the large genetic divergence between Arctic and Antarctic L. helicina populations shown here, similarly large physiological differences may exist between the poles for the L. helicina species group. Therefore, in addition to indicating that L. helicina is in fact not bipolar, our study demonstrates the need for acidification research to take into account the possibility that the L. helicina species group may not respond in the same way to ocean acidification in Arctic and Antarctic ecosystems.

  2. Antarctic research today

    International Nuclear Information System (INIS)

    Hempel, G.

    1982-01-01

    With the appetite for living and dead natural resources, the political and economical interest concerning the Antarctic increases throughout the world. There are three interrelated main subjects accounting for the international interest: The shelf tectonic puzzle of the original continent of Gondwana, where the Antarctic is situated in the centre, between Australia, South Africa and South America, and the hopes concerning the existence of mineral resources under the ice of the Antarctic are based thereon. The Antarctic forms the biggest unified living space of the world. (orig.)

  3. The interaction of counter-rotating strained vortex pairs with a third vortex

    International Nuclear Information System (INIS)

    Higgins, Keith; Ooi, Andrew; Chong, M S; Ruetten, Markus

    2009-01-01

    The vortex dynamics caused by the interaction of counter-rotating Burgers vortex pairs with a third Burgers vortex in a straining flow is investigated numerically. These interactions blend vortex merging and cancellation effects, and the aim is to investigate how the third vortex might influence the evolution of the vortex pair. Many different choices of initial conditions for the pair and third vortex exist, so attention is restricted to a class of initial conditions in which the vortex pair initially moves in the general direction of vortex 3, and the distance from vortex 3 to the line of free propagation of the vortex pair is the 'offset' parameter δ. A series of calculations with 0≤δ≤4 reveals three types of intermediate-time vortex dynamics that are called merging, swapping and switching. The evolution of the vortex core separation and core vorticity level diagnostics are used to determine the points of transition from merging to swapping and switching. In the longer term, vortex merging, cancellation and straining reduces the three vortices to a single vortex. Other diagnostics of interest are also monitored, including the spatial distributions of the rate of viscous dissipation and terms contributing to the vorticity transport equation. During the merging phase for the case with δ=0, double-peak and double-trough structures are observed in the dissipation-rate contours. In addition, the diffusion of vorticity dominates the vortex-stretching effect near vortex 1 during its absorbtion by vortex 3. Finally, the dynamics of the three vortices are also examined by computing a co-rotating angular velocity and stream function. A series of peaks in the co-rotating angular velocity is found to be associated with the conservation of angular momentum and interactions with a 'ghost' vortex in the co-rotating stream function.

  4. Discrimination of orbital angular momentum modes of the terahertz vortex beam using a diffractive mode transformer.

    Science.gov (United States)

    Liu, Changming; Wei, Xuli; Niu, Liting; Wang, Kejia; Yang, Zhengang; Liu, Jinsong

    2016-06-13

    We present an efficient method to discriminate orbital angular momentum (OAM) of the terahertz (THz) vortex beam using a diffractive mode transformer. The mode transformer performs a log-polar coordinate transformation of the input THz vortex beam, which consists of two 3D-printed diffractive elements. A following lens separates each transformed OAM mode to a different lateral position in its focal plane. This method enables a simultaneous measurement over multiple OAM modes of the THz vortex beam. We experimentally demonstrate the measurement of seven individual OAM modes and two multiplexed OAM modes, which is in good agreement with simulations.

  5. Two new species of calcareous sponges (Porifera: Calcarea) from the deep Antarctic Eckström Shelf and a revised list of species found in Antarctic waters

    DEFF Research Database (Denmark)

    Rapp, Hans Tore; Göcke, Christian; Tendal, Ole Secher

    2013-01-01

    The paper reports on two new species of calcareous sponges (Porifera, Calcarea) from the Antarctic Weddell Sea, Clathrina brandtae sp. nov. and Leucetta delicata sp. nov., collected at 600 m depth during the ANT XXIV/2-SYSTCO expedition in January 2008. The new species are described based...... on a combination of morphological and molecular data. With these new additions the number of species of calcareous sponges reported from south of 50 degrees S (similar to south of the Polar Front) reaches 50 species. We report an exceptionally high degree of endemism within the group, and as many as 44 out...... of the 50 species of calcareous sponges are solely confined to Antarctic waters. An updated list of species of calcareous sponges from the area is provided....

  6. Quantarctica: A Unique, Open, Standalone GIS Package for Antarctic Research and Education

    Science.gov (United States)

    Roth, George; Matsuoka, Kenichi; Skoglund, Anders; Melvær, Yngve; Tronstad, Stein

    2017-04-01

    The Norwegian Polar Institute has developed Quantarctica (http://quantarctica.npolar.no), an open GIS package for use by the international Antarctic community. Quantarctica includes a wide range of cartographic basemap layers, geophysical and glaciological datasets, and satellite imagery in standardized open file formats with a consistent Antarctic map projection and customized layer and labeling styles for quick, effective cartography. Quantarctica's strengths as an open science platform lie in 1) The complete, ready-to-use data package which includes full-resolution, original-quality vector and raster data, 2) A policy for freely-redistributable and modifiable data including all metadata and citations, and 3) QGIS, a free, full-featured, modular, offline-capable open-source GIS suite with a rapid and active development and support community. The Quantarctica team is actively incorporating more up-to-date, peer-reviewed, freely distributable pan-Antarctic geospatial datasets for the next version release in 2017. As part of this ongoing development, we are investigating the best approaches for quickly and seamlessly distributing new and updated data to users, storing datasets in efficient, open file formats while maintaining full data integrity, and coexisting with numerous online data portals in a way that most actively benefits the Antarctic community. A recent survey of Quantarctica users showed broad geographical adoption among Antarctic Treaty countries, including those outside the large US and UK Antarctic programs. Maps and figures produced by Quantarctica have also appeared in open-access journals and outside of the formal scientific community on popular science and GIS blogs. Our experience with the Quantarctica project has shown the tremendous value of education and outreach, not only in promoting open software, data formats, and practices, but in empowering Antarctic science groups to more effectively use GIS and geospatial data. Open practices are

  7. Ground-based Observations and Atmospheric Modelling of Energetic Electron Precipitation Effects on Antarctic Mesospheric Chemistry

    Science.gov (United States)

    Newnham, D.; Clilverd, M. A.; Horne, R. B.; Rodger, C. J.; Seppälä, A.; Verronen, P. T.; Andersson, M. E.; Marsh, D. R.; Hendrickx, K.; Megner, L. S.; Kovacs, T.; Feng, W.; Plane, J. M. C.

    2016-12-01

    The effect of energetic electron precipitation (EEP) on the seasonal and diurnal abundances of nitric oxide (NO) and ozone in the Antarctic middle atmosphere during March 2013 to July 2014 is investigated. Geomagnetic storm activity during this period, close to solar maximum, was driven primarily by impulsive coronal mass ejections. Near-continuous ground-based atmospheric measurements have been made by a passive millimetre-wave radiometer deployed at Halley station (75°37'S, 26°14'W, L = 4.6), Antarctica. This location is directly under the region of radiation-belt EEP, at the extremity of magnetospheric substorm-driven EEP, and deep within the polar vortex during Austral winter. Superposed epoch analyses of the ground based data, together with NO observations made by the Solar Occultation For Ice Experiment (SOFIE) onboard the Aeronomy of Ice in the Mesosphere (AIM) satellite, show enhanced mesospheric NO following moderate geomagnetic storms (Dst ≤ -50 nT). Measurements by co-located 30 MHz riometers indicate simultaneous increases in ionisation at 75-90 km directly above Halley when Kp index ≥ 4. Direct NO production by EEP in the upper mesosphere, versus downward transport of NO from the lower thermosphere, is evaluated using a new version of the Whole Atmosphere Community Climate Model incorporating the full Sodankylä Ion Neutral Chemistry Model (WACCM SIC). Model ionization rates are derived from the Polar orbiting Operational Environmental Satellites (POES) second generation Space Environment Monitor (SEM 2) Medium Energy Proton and Electron Detector instrument (MEPED). The model data are compared with observations to quantify the impact of EEP on stratospheric and mesospheric odd nitrogen (NOx), odd hydrogen (HOx), and ozone.

  8. Compressible Vortex Ring

    Science.gov (United States)

    Elavarasan, Ramasamy; Arakeri, Jayawant; Krothapalli, Anjaneyulu

    1999-11-01

    The interaction of a high-speed vortex ring with a shock wave is one of the fundamental issues as it is a source of sound in supersonic jets. The complex flow field induced by the vortex alters the propagation of the shock wave greatly. In order to understand the process, a compressible vortex ring is studied in detail using Particle Image Velocimetry (PIV) and shadowgraphic techniques. The high-speed vortex ring is generated from a shock tube and the shock wave, which precedes the vortex, is reflected back by a plate and made to interact with the vortex. The shadowgraph images indicate that the reflected shock front is influenced by the non-uniform flow induced by the vortex and is decelerated while passing through the vortex. It appears that after the interaction the shock is "split" into two. The PIV measurements provided clear picture about the evolution of the vortex at different time interval. The centerline velocity traces show the maximum velocity to be around 350 m/s. The velocity field, unlike in incompressible rings, contains contributions from both the shock and the vortex ring. The velocity distribution across the vortex core, core diameter and circulation are also calculated from the PIV data.

  9. A lunar polar expedition

    Science.gov (United States)

    Dowling, Richard; Staehle, Robert L.; Svitek, Tomas

    1992-09-01

    Advanced exploration and development in harsh environments require mastery of basic human survival skill. Expeditions into the lethal climates of Earth's polar regions offer useful lessons for tommorrow's lunar pioneers. In Arctic and Antarctic exploration, 'wintering over' was a crucial milestone. The ability to establish a supply base and survive months of polar cold and darkness made extensive travel and exploration possible. Because of the possibility of near-constant solar illumination, the lunar polar regions, unlike Earth's may offer the most hospitable site for habitation. The World Space Foundation is examining a scenario for establishing a five-person expeditionary team on the lunar north pole for one year. This paper is a status report on a point design addressing site selection, transportation, power, and life support requirements.

  10. PolarTREC—A Model Program for Taking Polar Literacy into the Future

    Science.gov (United States)

    Warburton, J.; Timm, K.; Larson, A. M.

    2009-12-01

    Polar TREC—Teachers and Researchers Exploring and Collaborating, is a three-year (2007-2009) NSF-funded International Polar Year (IPY) teacher professional development program that advances Science, Technology, Engineering, and Mathematics (STEM) education by improving teacher content knowledge and instructional practices through Teacher Research Experiences (TRE) in the Arctic and Antarctic. Leveraging profound changes and fascinating science taking place in the polar regions, PolarTREC broadly disseminates activities and products to students, educators, researchers, and the public, connecting them with the Arctic and Antarctica and sustaining the widespread interest in the polar regions and building on the enthusiasm that was generated through IPY. Central to the PolarTREC Teacher Research Experience Model, over 40 teachers have spent two to eight weeks participating in hands-on research in the polar regions and sharing their experiences with diverse audiences via live events, online multimedia journals, and interactive bulletin boards. The Connecting Arctic/Antarctic Researchers and Educators (CARE) Network unifies learning community members participants, alumni, and others, developing a sustainable association of education professionals networking to share and apply polar STEM content and pedagogical skills. Educator and student feedback from preliminary results of the program evaluation has shown that PolarTREC’s comprehensive program activities have many positive impacts on educators and their ability to teach science concepts and improve their teaching methods. Additionally, K-12 students polled in interest surveys showed significant changes in key areas including amount of time spent in school exploring research activities, importance of understanding science for future work, importance of understanding the polar regions as a person in today’s world, as well as increased self-reported knowledge and interest in numerous science content areas. Building

  11. Impacts of Atmosphere-Ocean Coupling on Southern Hemisphere Climate Change

    Science.gov (United States)

    Li, Feng; Newman, Paul; Pawson, Steven

    2013-01-01

    Climate in the Southern Hemisphere (SH) has undergone significant changes in recent decades. These changes are closely linked to the shift of the Southern Annular Mode (SAM) towards its positive polarity, which is driven primarily by Antarctic ozone depletion. There is growing evidence that Antarctic ozone depletion has significant impacts on Southern Ocean circulation change. However, it is poorly understood whether and how ocean feedback might impact the SAM and climate change in the SH atmosphere. This outstanding science question is investigated using the Goddard Earth Observing System Coupled Atmosphere-Ocean-Chemistry Climate Model(GEOS-AOCCM).We perform ensemble simulations of the recent past (1960-2010) with and without the interactive ocean. For simulations without the interactive ocean, we use sea surface temperatures and sea ice concentrations produced by the interactive ocean simulations. The differences between these two ensemble simulations quantify the effects of atmosphere-ocean coupling. We will investigate the impacts of atmosphere-ocean coupling on stratospheric processes such as Antarctic ozone depletion and Antarctic polar vortex breakup. We will address whether ocean feedback affects Rossby wave generation in the troposphere and wave propagation into the stratosphere. Another focuson this study is to assess how ocean feedback might affect the tropospheric SAM response to Antarctic ozone depletion

  12. Tailoring optical complex field with spiral blade plasmonic vortex lens

    Science.gov (United States)

    Rui, Guanghao; Zhan, Qiwen; Cui, Yiping

    2015-01-01

    Optical complex fields have attracted increasing interests because of the novel effects and phenomena arising from the spatially inhomogeneous state of polarizations and optical singularities of the light beam. In this work, we propose a spiral blade plasmonic vortex lens (SBPVL) that offers unique opportunities to manipulate these novel fields. The strong interaction between the SBPVL and the optical complex fields enable the synthesis of highly tunable plasmonic vortex. Through theoretical derivations and numerical simulations we demonstrated that the characteristics of the plasmonic vortex are determined by the angular momentum (AM) of the light, and the geometrical topological charge of the SBPVL, which is govern by the nonlinear superposition of the pitch and the number of blade element. In addition, it is also shown that by adjusting the geometric parameters, SBPVL can be utilized to focus and manipulate optical complex field with fractional AM. This miniature plasmonic device may find potential applications in optical trapping, optical data storage and many other related fields. PMID:26335894

  13. Freeing data through The Polar Information Commons

    Science.gov (United States)

    de Bruin, T.; Chen, R. S.; Parsons, M. A.; Carlson, D. J.; Cass, K.; Finney, K.; Wilbanks, J.; Jochum, K.

    2010-12-01

    The polar regions are changing rapidly with dramatic global effect. Wise management of resources, improved decision support, and effective international cooperation on resource and geopolitical issues require deeper understanding and better prediction of these changes. Unfortunately, polar data and information remain scattered, scarce, and sporadic. Inspired by the Antarctic Treaty of 1959 that established the Antarctic as a global commons to be used only for peaceful purposes and scientific research, we assert that data and information about the polar regions are themselves “public goods” that should be shared ethically and with minimal constraint. ICSU’s Committee on Data (CODATA) therefore started the Polar Information Commons (PIC) as an open, virtual repository for vital scientific data and information. The PIC provides a shared, community-based cyber-infrastructure fostering innovation, improving scientific efficiency, and encouraging participation in polar research, education, planning, and management. The PIC builds on the legacy of the International Polar Year (IPY), providing a long-term framework for access to and preservation of both existing and future data and information about the polar regions. Rapid change demands rapid data access. The PIC system enables scientists to quickly expose their data to the world and share them through open protocols on the Internet. A PIC digital label will alert users and data centers to new polar data and ensure that usage rights are clear. The PIC utilizes the Science Commons Protocol for Implementing Open Access Data, which promotes open data access through the public domain coupled with community norms of practice to ensure use of data in a fair and equitable manner. A set of PIC norms has been developed in consultation with key polar data organizations and other stakeholders. We welcome inputs from the broad science community as we further develop and refine the PIC approach and move ahead with

  14. The United States Antarctic Program Data Center (USAP-DC): Recent Developments

    Science.gov (United States)

    Nitsche, F. O.; Bauer, R.; Arko, R. A.; Shane, N.; Carbotte, S. M.; Scambos, T.

    2017-12-01

    Antarctic earth and environmental science data are highly valuable, often unique research assets. They are acquired with substantial and expensive logistical effort, frequently in areas that will not be re-visited for many years. The data acquired in support of Antarctic research span a wide range of disciplines. Historically, data management for the US Antarctic Program (USAP) has made use of existing disciplinary data centers, and the international Antarctic Master Directory (AMD) has served as a central metadata catalog linking to data files hosted in these external repositories. However, disciplinary repositories do not exist for all USAP-generated data types and often it is unclear what repositories are appropriate, leading to many datasets being served locally from scientist's websites or not available at all. The USAP Data Center (USAP-DC; www.usap-dc.org), operated as part of the Interdisciplinary Earth Data Alliance (IEDA), contributes to the broader preservation of research data acquired with funding from NSF's Office of Polar Programs by providing a repository for diverse data from the Antarctic region. USAP-DC hosts data that spans the range of Antarctic research from snow radar to volcano observatory imagery to penguin counts to meteorological model outputs. Data services include data documentation, long-term preservation, and web publication, as well as scientist support for registration of data descriptions into the AMD in fulfillment of US obligations under the International Antarctic Treaty. In Spring 2016, USAP-DC and the NSIDC began a new collaboration to consolidate data services for Antarctic investigators and to integrate the NSF-funded glaciology collection at NSIDC with the collection hosted by USAP-DC. Investigator submissions for NSF's Glaciology program now make use of USAP-DC's web submission tools, providing a uniform interface for Antarctic investigators. The tools have been redesigned to collect a broader range of metadata. Each data

  15. Antarctic Glaciological Data at NSIDC: field data, temperature, and ice velocity

    Science.gov (United States)

    Bauer, R.; Bohlander, J.; Scambos, T.; Berthier, E.; Raup, B.; Scharfen, G.

    2003-12-01

    An extensive collection of many Antarctic glaciological parameters is available for the polar science community upon request. The National Science Foundation's Office of Polar Programs funds the Antarctic Glaciological Data Center (AGDC) at the National Snow and Ice Data Center (NSIDC) to archive and distribute Antarctic glaciological and cryospheric system data collected by the U.S. Antarctic Program. AGDC facilitates data exchange among Principal Investigators, preserves recently collected data useful to future research, gathers data sets from past research, and compiles continent-wide information useful for modeling and field work planning. Data sets are available via our web site, http://nsidc.org/agdc/. From here, users can access extensive documentation, citation information, locator maps, derived images and references, and the numerical data. More than 50 Antarctic scientists have contributed data to the archive. Among the compiled products distributed by AGDC are VELMAP and THERMAP. THERMAP is a compilation of over 600 shallow firn temperature measurements ('10-meter temperatures') collected since 1950. These data provide a record of mean annual temperature, and potentially hold a record of climate change on the continent. The data are represented with maps showing the traverse route, and include data sources, measurement technique, and additional measurements made at each site, i.e., snow density and accumulation. VELMAP is an archive of surface ice velocity measurements for the Antarctic Ice Sheet. The primary objective of VELMAP is to assemble a historic record of outlet glaciers and ice shelf ice motion over the Antarctic. The collection includes both PI-contributed measurements and data generated at NSIDC using Landsat and SPOT satellite imagery. Tabular data contain position, speed, bearing, and data quality information, and related references. Two new VELMAP data sets are highlighted: the Mertz Glacier and the Institute Ice Stream. Mertz Glacier ice

  16. Generating broadband vortex modes in ring-core fiber by using a plasmonic q-plate.

    Science.gov (United States)

    Ye, Jingfu; Li, Yan; Han, Yanhua; Deng, Duo; Su, Xiaoya; Song, He; Gao, Jianmin; Qu, Shiliang

    2017-08-15

    A mode convertor was proposed and investigated for generating vortex modes in a ring-core fiber based on a plasmonic q-plate (PQP), which is composed of specially organized L-shaped resonator (LSR) arrays. A multicore fiber was used to transmit fundamental modes, and the LSR arrays were used to modulate phases of these fundamental modes. Behind the PQP, the transmitted fundamental modes with gradient phase distribution can be considered as the incident lights for generating broadband vortex modes in the ring-core fiber filter. The topological charges of generated vortex modes can be various by using an optical PQP with different q, and the chirality of the generated vortex mode can be controlled by the sign of q and handedness of the incident circularly polarized light. The operation bandwidth is 800 nm in the range of 1200-2000 nm, which covers six communication bands from the O band to the U band. The separation of vortex modes also was addressed by using a dual ring-core fiber. The mode convertor is of potential interest for connecting a traditional network and vortex communication network.

  17. Numerical investigations of two-degree-of-freedom vortex-induced vibration in shear flow

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Hui; Liu, Mengke; Han, Yang; Li, Jian; Gui, Mingyue; Chen, Zhihua, E-mail: zhanghui1902@hotmail.com [Science and Technology on Transient Physics Laboratory, Nanjing University of Science and Technology, Nanjing 210094 (China)

    2017-06-15

    Exponential-polar coordinates attached to a moving cylinder are used to deduce the stream function-vorticity equations for two-degree-of-freedom vortex-induced vibration, the initial and boundary conditions, and the distribution of the hydrodynamic force, which consists of the vortex-induced force, inertial force, and viscous damping force. The fluid-structure interactions occurring from the motionless cylinder to the steady vibration are investigated numerically, and the variations of the flow field, pressure, lift/drag, and cylinder displacement are discussed. Both the dominant vortex and the cylinder shift, whose effects are opposite, affect the shear layer along the transverse direction and the secondary vortex along the streamwise direction. However, the effect of the cylinder shift is larger than that of the dominant vortices. Therefore, the former dominates the total effects of the flow field. Moreover, the symmetry of the flow field is broken with the increasing shear rate. With the effect of the background vortex, the upper vortices are strengthened, and the lower vortices are weakened; thus, the shear layer and the secondary vortices induced by the upper shedding vortices are strengthened, while the shear layer and the secondary vortices induced by the lower shedding vortices are weakened. Therefore, the amplitudes of the displacement and drag/lift dominated by the upper vortex are larger than those of the displacement and drag/lift dominated by the lower vortex. (paper)

  18. Anti-inflammatory activity in selected Antarctic benthic organisms

    Directory of Open Access Journals (Sweden)

    Juan eMoles

    2014-07-01

    Full Text Available Antarctic benthos was prospected in search for anti-inflammatory activity in polar benthic invertebrates, in two different geographical areas: deep-bottoms of the Eastern Weddell Sea and shallow-waters of the South Shetland Islands. A total of 36 benthic algae and invertebrate species were selected to perform solubility tests in order to test them for anti-inflammatory activity. From these, ethanol extracts of ten species from five different phyla resulted suitable to be studied in cell macrophage cultures (RAW 264.7. Cytotoxicity (MTT method and production of inflammatory mediators (prostaglandin E2, leukotriene B4, interleukin-1 were determined at three extract concentrations (50, 125, 250 g/mL. Bioassays resulted in four different species showing anti-inflammatory activity corresponding to three sponges: Mycale (Oxymycale acerata, Isodictya erinacea, and I. toxophila; and one hemichordate: Cephalodiscus sp. These results show that Antarctic sessile invertebrates may have great value as a source of lead compounds with potential pharmaceutical applications.

  19. Vortex configuration and vortex-vortex interaction in nano-structured superconductors

    International Nuclear Information System (INIS)

    Kato, Masaru; Niwa, Yuhei; Suematsu, Hisataka; Ishida, Takekazu

    2012-01-01

    We study the vortex structures and quasi-particle structures in nano-structured superconductors. We used the Bogoliubov-de Gennes equation and the finite element method and obtained stable magnetic flux structures and the quasi-particle states. We found the vortex configurations are affected by the interference of the quasi-particle bound states around the vortices. In order to clarify the interference between the quasi-particle wave-functions around two vortices we have developed a numerical method using the elliptic coordinates and the Mathieu functions. We apply this method to two singly quantized vortex state in a conventional s-wave superconductor and a pair of half-quantum vortices in a chiral p-wave superconductor.

  20. PREFACE: Special section on vortex rings Special section on vortex rings

    Science.gov (United States)

    Fukumoto, Yasuhide

    2009-10-01

    This special section of Fluid Dynamics Research includes five articles on vortex rings in both classical and quantum fluids. The leading scientists of the field describe the trends in and the state-of-the-art development of experiments, theories and numerical simulations of vortex rings. The year 2008 was the 150th anniversary of 'vortex motion' since Hermann von Helmholtz opened up this field. In 1858, Helmholtz published a paper in Crelle's Journal which put forward the concept of 'vorticity' and made the first analysis of vortex motion. Fluid mechanics before that was limited to irrotational motion. In the absence of vorticity, the motion of an incompressible homogeneous fluid is virtually equivalent to a rigid-body motion in the sense that the fluid motion is determined once the boundary configuration is specified. Helmholtz proved, among other things, that, without viscosity, a vortex line is frozen into the fluid. This Helmholtz's law immediately implies the preservation of knots and links of vortex lines and its implication is enormous. One of the major trends of fluid mechanics since the latter half of the 20th century is to clarify the topological meaning of Helmholtz's law and to exploit it to develop theoretical and numerical methods to find the solutions of the Euler equations and to develop experimental techniques to gain an insight into fluid motion. Vortex rings are prominent coherent structures in a variety of fluid motions from the microscopic scale, through human and mesoscale to astrophysical scales, and have attracted people's interest. The late professor Philip G Saffman (1981) emphasized the significance of studies on vortex rings. One particular motion exemplifies the whole range of problems of vortex motion and is also a commonly known phenomenon, namely the vortex ring or smoke ring. Vortex rings are easily produced by dropping drops of one liquid into another, or by puffing fluid out of a hole, or by exhaling smoke if one has the skill

  1. Polish polar research (outline

    Directory of Open Access Journals (Sweden)

    Krzysztof Ludwik Birkenmajer

    2017-12-01

    Full Text Available The article describes Polish research and discoveries in the Arctic and the Antarctic since the 19th century. The author is a geologist and since 1956 has been engaged in scientific field research on Spitsbergen, Greenland and Antarctica (23 expeditions. For many years chairman of the Committee on Polar Research of the Polish Academy of Sciences, he is now its Honorary Chairman.

  2. Antarctic Circumpolar Current Dynamics and Their Relation to Antarctic Ice Sheet and Perennial Sea-Ice Variability in the Central Drake Passage During the Last Climate Cycle

    Science.gov (United States)

    Kuhn, G.; Wu, S.; Hass, H. C.; Klages, J. P.; Zheng, X.; Arz, H. W.; Esper, O.; Hillenbrand, C. D.; Lange, C.; Lamy, F.; Lohmann, G.; Müller, J.; McCave, I. N. N.; Nürnberg, D.; Roberts, J.; Tiedemann, R.; Timmermann, A.; Titschack, J.; Zhang, X.

    2017-12-01

    The evolution of the Antarctic Ice Sheet during the last climate cycle and the interrelation to global atmospheric and ocean circulation remains controversial and plays an important role for our understanding of ice sheet response to modern global warming. The timing and sequence of deglacial warming is relevant for understanding the variability and sensitivity of the Antarctic Ice Sheet to climatic changes, and the continuing rise of atmospheric greenhouse gas concentrations. The Antarctic Ice Sheet is a pivotal component of the global water budget. Freshwater fluxes from the ice sheet may affect the Antarctic Circumpolar Current (ACC), which is strongly impacted by the westerly wind belt in the Southern Hemisphere (SHWW) and constricted to its narrowest extent in the Drake Passage. The flow of ACC water masses through Drake Passage is, therefore, crucial for advancing our understanding of the Southern Ocean's role in global meridional overturning circulation and global climate change. In order to address orbital and millennial-scale variability of the Antarctic ice sheet and the ACC, we applied a multi-proxy approach on a sediment core from the central Drake Passage including grain size, iceberg-rafted debris, mineral dust, bulk chemical and mineralogical composition, and physical properties. In combination with already published and new sediment records from the Drake Passage and Scotia Sea, as well as high-resolution data from Antarctic ice cores (WDC, EDML), we now have evidence that during glacial times a more northerly extent of the perennial sea-ice zone decreased ACC current velocities in the central Drake Passage. During deglaciation the SHWW shifted southwards due to a decreasing temperature gradient between subtropical and polar latitudes caused by sea ice and ice sheet decline. This in turn caused Southern Hemisphere warming, a more vigorous ACC, stronger Southern Ocean ventilation, and warm Circumpolar Deep Water (CDW) upwelling on Antarctic shelves

  3. EVA: Evryscopes for the Arctic and Antarctic

    Science.gov (United States)

    Richichi, A.; Law, N.; Tasuya, O.; Fors, O.; Dennihy, E.; Carlberg, R.; Tuthill, P.; Ashley, M.; Soonthornthum, B.

    2017-06-01

    We are planning to build Evryscopes for the Arctic and Antarctic (EVA), which will enable the first ultra-wide-field, high-cadence sky survey to be conducted from both Poles. The system is based on the successful Evryscope concept, already installed and operating since 2015 at Cerro Tololo in Chile with the following characteristics: robotic operation, 8,000 square degrees simultaneous sky coverage, 2-minute cadence, milli-mag level photometric accuracy, pipelined data processing for real-time analysis and full data storage for off-line analysis. The initial location proposed for EVA is the PEARL station on Ellesmere island; later also an antarctic location shall be selected. The science goals enabled by this unique combination of almost full-sky coverage and high temporal cadence are numerous, and include among others ground-breaking forays in the fields of exoplanets, stellar variability, asteroseismology, supernovae and other transient events. The EVA polar locations will enable uninterrupted observations lasting in principle over weeks and months. EVA will be fully robotic. We discuss the EVA science drivers and expected results, and present the logistics and the outline of the project which is expected to have first light in the winter of 2018. The cost envelope can be kept very competitive thanks to R&D already employed for the CTIO Evryscope, to our experience with both Arctic and Antarctic locations, and to the use of off-the-shelf components.

  4. Direct observation of current-induced motion of a 3D vortex domain wall in cylindrical nanowires

    KAUST Repository

    Ivanov, Yurii P.

    2017-05-08

    The current-induced dynamics of 3D magnetic vortex domain walls in cylindrical Co/Ni nanowires are revealed experimentally using Lorentz microscopy and theoretically using micromagnetic simulations. We demonstrate that a spin-polarized electric current can control the reversible motion of 3D vortex domain walls, which travel with a velocity of a few hundred meters per second. This finding is a key step in establishing fast, high-density memory devices based on vertical arrays of cylindrical magnetic nanowires.

  5. Direct observation of current-induced motion of a 3D vortex domain wall in cylindrical nanowires

    KAUST Repository

    Ivanov, Yurii P.; Chuvilin, Andrey; Lopatin, Sergei; Mohammed, Hanan; Kosel, Jü rgen

    2017-01-01

    The current-induced dynamics of 3D magnetic vortex domain walls in cylindrical Co/Ni nanowires are revealed experimentally using Lorentz microscopy and theoretically using micromagnetic simulations. We demonstrate that a spin-polarized electric current can control the reversible motion of 3D vortex domain walls, which travel with a velocity of a few hundred meters per second. This finding is a key step in establishing fast, high-density memory devices based on vertical arrays of cylindrical magnetic nanowires.

  6. ProFile Vortex and Vortex Blue Nickel-Titanium Rotary Instruments after Clinical Use.

    Science.gov (United States)

    Shen, Ya; Zhou, Huimin; Coil, Jeffrey M; Aljazaeri, Bassim; Buttar, Rene; Wang, Zhejun; Zheng, Yu-feng; Haapasalo, Markus

    2015-06-01

    The aim of this study was to analyze the incidence and mode of ProFile Vortex and Vortex Blue instrument defects after clinical use in a graduate endodontic program and to examine the impact of clinical use on the instruments' metallurgical properties. A total of 330 ProFile Vortex and 1136 Vortex Blue instruments from the graduate program were collected after each had been used in 3 teeth. The incidence and type of instrument defects were analyzed. The lateral surfaces and fracture surfaces of the fractured files were examined by using scanning electron microscopy. Unused and used instruments were examined by full and partial differential scanning calorimetry. No fractures were observed in the 330 ProFile Vortex instruments, whereas 20 (6.1%) revealed bent or blunt defects. Only 2 of the 1136 Vortex Blue files fractured during clinical use. The cause of fracture was shear stress. The fractures occurred at the tip end of the spirals. Only 1.8% (21 of 1136) of the Vortex Blue files had blunt tips. Austenite-finish temperatures were very similar for unused and used ProFile Vortex files and were all greater than 50°C. The austenite-finish temperatures of used and unused Vortex Blue files (38.5°C) were lower than those in ProFile Vortex instruments (P Vortex Blue files had an obvious 2-stage transformation, martensite-to-R phase and R-to-austenite phase. The trends of differential scanning calorimetry plots of unused Vortex Blue instruments and clinically used instruments were very similar. The risk of ProFile Vortex and Vortex Blue instrument fracture is very low when instruments are discarded after clinical use in the graduate endodontic program. The Vortex Blue files have metallurgical behavior different from ProFile Vortex instruments. Copyright © 2015 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

  7. Poles Apart: The “Bipolar” Pteropod Species Limacina helicina Is Genetically Distinct Between the Arctic and Antarctic Oceans

    Science.gov (United States)

    Bednarsek, Nina; Linse, Katrin; Nelson, R. John; Pakhomov, Evgeny; Seibel, Brad; Steinke, Dirk; Würzberg, Laura

    2010-01-01

    The shelled pteropod (sea butterfly) Limacina helicina is currently recognised as a species complex comprising two sub-species and at least five “forma”. However, at the species level it is considered to be bipolar, occurring in both the Arctic and Antarctic oceans. Due to its aragonite shell and polar distribution L. helicina is particularly vulnerable to ocean acidification. As a key indicator of the acidification process, and a major component of polar ecosystems, L. helicina has become a focus for acidification research. New observations that taxonomic groups may respond quite differently to acidification prompted us to reassess the taxonomic status of this important species. We found a 33.56% (±0.09) difference in cytochrome c oxidase subunit I (COI) gene sequences between L. helicina collected from the Arctic and Antarctic oceans. This degree of separation is sufficient for ordinal level taxonomic separation in other organisms and provides strong evidence for the Arctic and Antarctic populations of L. helicina differing at least at the species level. Recent research has highlighted substantial physiological differences between the poles for another supposedly bipolar pteropod species, Clione limacina. Given the large genetic divergence between Arctic and Antarctic L. helicina populations shown here, similarly large physiological differences may exist between the poles for the L. helicina species group. Therefore, in addition to indicating that L. helicina is in fact not bipolar, our study demonstrates the need for acidification research to take into account the possibility that the L. helicina species group may not respond in the same way to ocean acidification in Arctic and Antarctic ecosystems. PMID:20360985

  8. A Polar Rover for Large-Scale Scientific Surveys: Design, Implementation and Field Test Results

    Directory of Open Access Journals (Sweden)

    Yuqing He

    2015-10-01

    Full Text Available Exploration of polar regions is of great importance to scientific research. Unfortunately, due to the harsh environment, most of the regions on the Antarctic continent are still unreachable for humankind. Therefore, in 2011, the Chinese National Antarctic Research Expedition (CHINARE launched a project to design a rover to conduct large-scale scientific surveys on the Antarctic. The main challenges for the rover are twofold: one is the mobility, i.e., how to make a rover that could survive the harsh environment and safely move on the uneven, icy and snowy terrain; the other is the autonomy, in that the robot should be able to move at a relatively high speed with little or no human intervention so that it can explore a large region in a limit time interval under the communication constraints. In this paper, the corresponding techniques, especially the polar rover's design and autonomous navigation algorithms, are introduced in detail. Subsequently, an experimental report of the fields tests on the Antarctic is given to show some preliminary evaluation of the rover. Finally, experiences and existing challenging problems are summarized.

  9. Seasonal variation and sources of atmospheric gravity waves in the Antarctic

    Directory of Open Access Journals (Sweden)

    Kaoru Sato

    2010-12-01

    Full Text Available In the last recent ten years, our knowledge of gravity waves in the Antarctic has been significantly improved through numerous studies using balloon and satellite observations and high-resolution model simulations. In this report, we introduce results from two studies which were performed as a part of the NIPR project "Integrated analysis of the material circulation in the Antarctic atmosphere-cryosphere-ocean" (2004-2009, i.e., Yoshiki et al. (2004 and Sato and Yoshiki (2008. These two studies focused on the seasonal variation and sources of the gravity waves in the Antarctic, because horizontal wavelengths and phase velocities depend largely on the wave sources. The former study used original high-resolution data from operational radiosonde observations at Syowa Station. In the lowermost stratosphere, gravity waves do not exhibit characteristic seasonal variation; instead, the wave energy is intensified when lower latitude air intrudes into the area near Syowa Station in the upper troposphere. This intrusion is associated with blocking events or developed synoptic-scale waves. In the lower and middle stratosphere, the gravity wave energy is maximized in spring and particularly intensified when the axis of the polar night jet approaches Syowa Station. The latter study is based on intensive radiosonde observation campaigns that were performed in 2002 at Syowa Station as an activity of JARE-43. Gravity wave propagation was statistically examined using two dimensional (i.e., vertical wavenumber versus frequency spectra in each season. It was shown that the gravity waves are radiated upward and downward from an unbalanced region of the polar night jet. This feature is consistent with the gravity-wave resolving GCM simulation.

  10. Point vortex modelling of the wake dynamics behind asymmetric vortex generator arrays

    NARCIS (Netherlands)

    Baldacchino, D.; Simao Ferreira, C.; Ragni, D.; van Bussel, G.J.W.

    2016-01-01

    In this work, we present a simple inviscid point vortex model to study the dynamics of asymmetric vortex rows, as might appear behind misaligned vortex generator vanes. Starting from the existing solution of the in_nite vortex cascade, a numerical model of four base-vortices is chosen to represent

  11. Abundance and breeding distribution of seabirds in the northern part of the Danco Coast, Antarctic Peninsula

    Directory of Open Access Journals (Sweden)

    Mariana A. Juáres

    2013-02-01

    Full Text Available Seabird abundances and breeding distribution have the potential to serve as ecological indicators. The western Antarctic Peninsula is one of the three sites in the world with the greatest increases in local temperature during the last 50 years. The aim of this study was to monitor the distribution and abundance of breeding populations of seabirds in the northern sector of the Danco Coast, north-west of the Antarctic Peninsula, during the breeding season 2010/11. The birds were the Wilson′s storm petrel (Oceanites oceanicus, South Polar skua (Stercorarius maccormicki, kelp gull (Larus dominicanus, Antarctic tern (Sterna vittata, snowy sheathbill (Chionis alba, chinstrap penguin (Pygoscelis antarctica, southern giant petrel (Macronectes giganteus, gentoo penguin (Pygoscelis papua, Cape petrel (Daption capense and Antarctic shag (Phalacrocorax bransfieldensis. Annual breeding population growth increased in pygoscelids, southern giant petrel and sheathbill, and for the remaining species, breeding population trends were stable. Given that seabird populations can provide valuable information on the conditions of their feeding and nesting environments, this study highlights the need to maintain basics monitoring studies.

  12. Cassini ISS Observations Of The Early Stages Of The Formation Of Titan's South Polar Hood And Vortex In 2012

    Science.gov (United States)

    West, Robert A.; Del Genio, A.; Perry, J.; Ingersoll, A. P.; Turtle, E. P.; Porco, C.; Ovanessian, A.

    2012-10-01

    Northern spring equinox on Titan occurred on August 11, 2009. In March of 2012 the Imaging Science Subsystem (ISS) on the Cassini spacecraft saw the first evidence for the formation of a polar hood in the atmosphere above Titan’s south pole. Views of the limb showed an optical thickening primarily at about 360 km altitude across a few degrees of latitude centered on the pole. Images of Titan in front of Saturn provide a nearly direct measure of the line-of-sight optical depth as a function of latitude and altitude from about 250 km and higher. Two or more distinct layers are seen, both near the pole and at other latitudes. The highest of these, near 360 km altitude, hosts the embryonic polar hood. On June 27, 2012 ISS observed the pole from high latitude. These images show a distinct and unusual cloudy patch, elongated and not centered on the pole and with an elevated perimeter. The morphology and color indicate an unfamiliar (for Titan) composition and dynamical regime. The interior of the feature consists of concentrations of cloud/haze organized on spatial scales of tens of kilometers. Its morphology is reminiscent of the open cellular convection sometimes seen in the atmospheric boundary layer over Earth’s oceans under conditions of large-scale subsidence. Unlike Earth, where such convection is forced by large surface heat fluxes or the onset of drizzle, convection at 360 km on Titan is more likely to be driven from above by radiative cooling. During the 9 hours we observed Titan, this feature completed a little over one rotation around the pole, providing direct evidence for a polar vortex rotating at a rate roughly consistent with angular-momentum-conserving flow for air displaced from the equator. Part of this work was performed by the Jet Propulsion Laboratory, California Institute of Technology.

  13. The delta18O composition of Antarctic coastal current waters

    International Nuclear Information System (INIS)

    Frew, R.; Heywood, K.; Dennis, P.

    1997-01-01

    The varying proportions of 18 O to 16 O in sea water provide an oceanographic trace like salinity, but with an extra degree of freedom: salt is a tracer for the oceanic fluid, whereas the isotopic composition is a tracer specifically for the water component of that fluid. Hydrogen and oxygen isotopes are the variables most intimately related to the water component in the sea, therefore thay furnish a direct link to the water in the atmosphere and on continents and to the precipitation cycle which caused the salinity changes. The ratio of 18 O to 16 O (delta 18 O) ot waters is a powerful tracer in polar regions where sea and glacial ice processes decouple delta 18 O from salinity. Here we present observations from a significant but relatively unexplored component of the Southern Ocean current system, the Antarctic Coastal Current, and its associated Antarctic Slope Front. (author)

  14. Generation of spirally polarized propagation-invariant beam using fiber microaxicon.

    Science.gov (United States)

    Philip, Geo M; Viswanathan, Nirmal K

    2011-10-01

    We present here a fiber microaxicon (MA)based method to generate spirally polarized propagation-invariant optical beam. MA chemically etched in the tip of a two-mode fiber efficiently converts the generic cylindrically polarized vortex fiber mode into a spirally polarized propagation-invariant (Bessel-type) beam via radial dependence of polarization rotation angle. The combined roles of helico-conical phase and nonparaxial propagation in the generation and characteristics of the output beam from the fiber MA are discussed. © 2011 Optical Society of America

  15. Gravitating monopole-antimonopole chains and vortex rings

    International Nuclear Information System (INIS)

    Kleihaus, Burkhard; Kunz, Jutta; Shnir, Yasha

    2005-01-01

    We construct monopole-antimonopole chain and vortex solutions in Yang-Mills-Higgs theory coupled to Einstein gravity. The solutions are static, axially symmetric, and asymptotically flat. They are characterized by two integers (m,n) where m is related to the polar angle and n to the azimuthal angle. Solutions with n=1 and n=2 correspond to chains of m monopoles and antimonopoles. Here the Higgs field vanishes at m isolated points along the symmetry axis. Larger values of n give rise to vortex solutions, where the Higgs field vanishes on one or more rings, centered around the symmetry axis. When gravity is coupled to the flat space solutions, a branch of gravitating monopole-antimonopole chain or vortex solutions arises and merges at a maximal value of the coupling constant with a second branch of solutions. This upper branch has no flat space limit. Instead in the limit of vanishing coupling constant it either connects to a Bartnik-McKinnon or generalized Bartnik-McKinnon solution, or, for m>4, n>4, it connects to a new Einstein-Yang-Mills solution. In this latter case further branches of solutions appear. For small values of the coupling constant on the upper branches, the solutions correspond to composite systems, consisting of a scaled inner Einstein-Yang-Mills solution and an outer Yang-Mills-Higgs solution

  16. A Coaxial Vortex Ring Model for Vortex Breakdown

    OpenAIRE

    Blackmore, Denis; Brons, Morten; Goullet, Arnaud

    2008-01-01

    A simple - yet plausible - model for B-type vortex breakdown flows is postulated; one that is based on the immersion of a pair of slender coaxial vortex rings in a swirling flow of an ideal fluid rotating around the axis of symmetry of the rings. It is shown that this model exhibits in the advection of passive fluid particles (kinematics) just about all of the characteristics that have been observed in what is now a substantial body of published research on the phenomenon of vortex breakdown....

  17. Preserving Geological Samples and Metadata from Polar Regions

    Science.gov (United States)

    Grunow, A.; Sjunneskog, C. M.

    2011-12-01

    The Office of Polar Programs at the National Science Foundation (NSF-OPP) has long recognized the value of preserving earth science collections due to the inherent logistical challenges and financial costs of collecting geological samples from Polar Regions. NSF-OPP established two national facilities to make Antarctic geological samples and drill cores openly and freely available for research. The Antarctic Marine Geology Research Facility (AMGRF) at Florida State University was established in 1963 and archives Antarctic marine sediment cores, dredge samples and smear slides along with ship logs. The United States Polar Rock Repository (USPRR) at Ohio State University was established in 2003 and archives polar rock samples, marine dredges, unconsolidated materials and terrestrial cores, along with associated materials such as field notes, maps, raw analytical data, paleomagnetic cores, thin sections, microfossil mounts, microslides and residues. The existence of the AMGRF and USPRR helps to minimize redundant sample collecting, lessen the environmental impact of doing polar field work, facilitates field logistics planning and complies with the data sharing requirement of the Antarctic Treaty. USPRR acquires collections through donations from institutions and scientists and then makes these samples available as no-cost loans for research, education and museum exhibits. The AMGRF acquires sediment cores from US based and international collaboration drilling projects in Antarctica. Destructive research techniques are allowed on the loaned samples and loan requests are accepted from any accredited scientific institution in the world. Currently, the USPRR has more than 22,000 cataloged rock samples available to scientists from around the world. All cataloged samples are relabeled with a USPRR number, weighed, photographed and measured for magnetic susceptibility. Many aspects of the sample metadata are included in the database, e.g. geographical location, sample

  18. Vortex cutting in superconductors

    Science.gov (United States)

    Vlasko-Vlasov, Vitalii K.; Koshelev, Alexei E.; Glatz, Andreas; Welp, Ulrich; Kwok, Wai-K.

    2015-03-01

    Unlike illusive magnetic field lines in vacuum, magnetic vortices in superconductors are real physical strings, which interact with the sample surface, crystal structure defects, and with each other. We address the complex and poorly understood process of vortex cutting via a comprehensive set of magneto-optic experiments which allow us to visualize vortex patterns at magnetization of a nearly twin-free YBCO crystal by crossing magnetic fields of different orientations. We observe a pronounced anisotropy in the flux dynamics under crossing fields and the filamentation of induced supercurrents associated with the staircase vortex structure expected in layered cuprates, flux cutting effects, and angular vortex instabilities predicted for anisotropic superconductors. At some field angles, we find formation of the vortex domains following a type-I phase transition in the vortex state accompanied by an abrupt change in the vortex orientation. To clarify the vortex cutting scenario we performed time-dependent Ginzburg-Landau simulations, which confirmed formation of sharp vortex fronts observed in the experiment and revealed a left-handed helical instability responsible for the rotation of vortices. This work was supported by the U.S. Department of Energy, Office of Science, Materials Sciences and Engineering Division.

  19. Spiral Transformation for High-Resolution and Efficient Sorting of Optical Vortex Modes

    Science.gov (United States)

    Wen, Yuanhui; Chremmos, Ioannis; Chen, Yujie; Zhu, Jiangbo; Zhang, Yanfeng; Yu, Siyuan

    2018-05-01

    Mode sorting is an essential function for optical multiplexing systems that exploit the orthogonality of the orbital angular momentum mode space. The familiar log-polar optical transformation provides a simple yet efficient approach whose resolution is, however, restricted by a considerable overlap between adjacent modes resulting from the limited excursion of the phase along a complete circle around the optical vortex axis. We propose and experimentally verify a new optical transformation that maps spirals (instead of concentric circles) to parallel lines. As the phase excursion along a spiral in the wave front of an optical vortex is theoretically unlimited, this new optical transformation can separate orbital angular momentum modes with superior resolution while maintaining unity efficiency.

  20. Satellite magnetic anomalies of the Antarctic crust

    Directory of Open Access Journals (Sweden)

    D. E. Alsdorf

    2000-06-01

    Full Text Available Spatially and temporally static crustal magnetic anomalies are contaminated by static core field effects above spherical harmonic degree 12 and dynamic, large-amplitude external fields. To extract crustal magnetic anomalies from the measurements of NASA's Magsat mission, we separate crustal signals from both core and external field effects. In particular, we define Magsat anomalies relative to the degree 11 field and use spectral correlation theory to reduce them for external field effects. We obtain a model of Antarctic crustal thickness by comparing the region's terrain gravity effects to free-air gravity anomalies derived from the Earth Gravity Model 1996 (EGM96. To separate core and crustal magnetic effects, we obtain the pseudo-magnetic effect of the crustal thickness variations from their gravity effect via Poisson's theorem for correlative potentials. We compare the pseudo-magnetic effect of the crustal thickness variations to field differences between degrees 11 and 13 by spectral correlation analysis. We thus identify and remove possible residual core field effects in the Magsat anomalies relative to the degree 11 core field. The resultant anomalies reflect possible Antarctic contrasts due both to crustal thickness and intracrustal variations of magnetization. In addition, they provide important constraints on the geologic interpretation of aeromagnetic survey data, such as are available for the Weddell Province. These crustal anomalies also may be used to correct for long wavelength errors in regional compilations of near-surface magnetic survey data. However, the validity of these applications is limited by the poor quality of the Antarctic Magsat data that were obtained during austral Summer and Fall when south polar external field activity was maximum. Hence an important test and supplement for the Antarctic crustal Magsat anomaly map will be provided by the data from the recently launched Ørsted mission, which will yield coverage

  1. Understanding and forecasting polar stratospheric variability with statistical models

    Directory of Open Access Journals (Sweden)

    C. Blume

    2012-07-01

    Full Text Available The variability of the north-polar stratospheric vortex is a prominent aspect of the middle atmosphere. This work investigates a wide class of statistical models with respect to their ability to model geopotential and temperature anomalies, representing variability in the polar stratosphere. Four partly nonstationary, nonlinear models are assessed: linear discriminant analysis (LDA; a cluster method based on finite elements (FEM-VARX; a neural network, namely the multi-layer perceptron (MLP; and support vector regression (SVR. These methods model time series by incorporating all significant external factors simultaneously, including ENSO, QBO, the solar cycle, volcanoes, to then quantify their statistical importance. We show that variability in reanalysis data from 1980 to 2005 is successfully modeled. The period from 2005 to 2011 can be hindcasted to a certain extent, where MLP performs significantly better than the remaining models. However, variability remains that cannot be statistically hindcasted within the current framework, such as the unexpected major warming in January 2009. Finally, the statistical model with the best generalization performance is used to predict a winter 2011/12 with warm and weak vortex conditions. A vortex breakdown is predicted for late January, early February 2012.

  2. Structures of single vortex and vortex lattice in a d-wave superconductor

    International Nuclear Information System (INIS)

    Xu, J.; Ren, Y.; Ting, C.

    1996-01-01

    The structures of a single vortex and vortex lattice in a superconductor with d x 2 -y 2 symmetry are studied self-consistently employing a recently developed Ginzburg-Landau theory. Near a single vortex, we found that an s-wave component of the order parameter is always induced, and it causes the local magnetic-field distribution and the d-wave order parameter to have a fourfold anisotropy. It is shown that there is a strong correlation between the structure of a single vortex and the shape of the vortex lattice. Our numerical calculation indicates that the structure of the vortex lattice is always oblique except for temperatures very close to T c where it becomes triangular. The possible connection of the result with experiment is also discussed. copyright 1996 The American Physical Society

  3. Effects of Greenhouse Gas Increase and Stratospheric Ozone Depletion on Stratospheric Mean Age of Air in 1960-2010

    Science.gov (United States)

    Li, F.; Newman, P. A.; Pawson, S.; Perlwitz, J.

    2017-12-01

    The strength of the stratospheric Brewer-Dobson circulation (BDC) in a changing climate has been extensively studied, but the relative importance of greenhouse gas (GHG) increases and stratospheric ozone depletion in driving the BDC changes remains uncertain. This study separates the impacts of GHG and stratospheric ozone forcings on stratospheric mean age of air in the 1960-2010 period using the Goddard Earth Observing System Model (GEOS) Chemistry-Climate Model (CCM). The experiment compares a set of controlled simulations using a coupled atmosphere-ocean version of the GEOS CCM, in which either GHGs, or stratospheric ozone, or both factors evolve over time. The model results show that GHGs and stratospheric ozone have about equal contributions to the simulated mean age decrease. It is also found that GHG increases account for about two thirds of the enhanced strength of the lower stratospheric residual circulation. The results show that ozone depletion causes an increase in the mean age of air in the Antarctic summer lower stratosphere through two processes: 1) a seasonal delay in the Antarctic polar vortex breakup, that inhibits young mid-latitude air from mixing with the older air inside the vortex; and 2) enhanced Antarctic downwelling, that brings older air from middle and upper stratosphere into the lower stratosphere.

  4. Effects of Greenhouse Gas Increase and Stratospheric Ozone Depletion on Stratospheric Mean Age of Air in 1960-2010

    Science.gov (United States)

    Li, Feng; Newman, Paul; Pawson, Steven; Perlwitz, Judith

    2018-01-01

    The relative impacts of greenhouse gas (GHG) increase and stratospheric ozone depletion on stratospheric mean age of air in the 1960-2010 period are quantified using the Goddard Earth Observing System Chemistry-�Climate Model. The experiment compares controlled simulations using a coupled atmosphere-�ocean version of the Goddard Earth Observing System Chemistry-�Climate Model, in which either GHGs or ozone depleting substances, or both factors evolve over time. The model results show that GHGs and ozone-depleting substances have about equal contributions to the simulated mean age decrease, but GHG increases account for about two thirds of the enhanced strength of the lower stratospheric residual circulation. It is also found that both the acceleration of the diabatic circulation and the decrease of the mean age difference between downwelling and upwelling regions are mainly caused by GHG forcing. The results show that ozone depletion causes an increase in the mean age of air in the Antarctic summer lower stratosphere through two processes: (1) a seasonal delay in the Antarctic polar vortex breakup that inhibits young midlatitude air from mixing with the older air inside the vortex, and (2) enhanced Antarctic downwelling that brings older air from middle and upper stratosphere into the lower stratosphere.

  5. Vortex rings

    CERN Document Server

    Akhmetov, D G

    2009-01-01

    This text on vortex rings covers their theoretical foundation, systematic investigations, and practical applications such as the extinction of fires at gushing oil wells. It pays special attention to the formation and motion of turbulent vortex rings.

  6. Antarctic station life: The first 15 years of mixed expeditions to the Antarctic

    Science.gov (United States)

    Sarris, Aspa

    2017-02-01

    This study examined the experiences of women who lived and worked on remote and isolated Antarctic stations for up to 15 months at a time. The study employed purposeful sampling and a longitudinal - processual approach to study women's experiences over the first 15 years of mixed gender Antarctic expeditions. The retrospective analysis was based on a semi-structured interview administered to 14 women upon their return to Australia. The results showed that women referred to the natural physical Antarctic environment as one of the best aspects of their experience and the reason they would recommend the Antarctic to their friends as a good place to work. In describing the worst aspect of their experience, women referred to aspects of Antarctic station life, including: (i) the male dominated nature of station culture; (ii) the impact of interpersonal conflict, including gender based conflict and friction between scientists and trades workers; and (iii) the lack of anonymity associated with living and working with the same group of individuals, mainly men, for up to 12 months or more. The results are discussed within the context of the evolution of Antarctic station culture and recommendations are made in terms of the demography of expeditions, expeditioner selection and recruitment and the ongoing monitoring of Antarctic station culture. The study presents a framework that can be applied to groups and teams living and working in analogous isolated, confined and extreme work environments, including outer space missions.

  7. Comparative Activity and Functional Ecology of Permafrost Soils and Lithic Niches in a Hyper-Arid Polar Desert

    Science.gov (United States)

    Goordial, J.; Davila, A.; Greer, C. W.; Cannam, R.; DiRuggiero, J.; McKay, C. P.; Whyte, L. G.

    2016-01-01

    This study represents the first metagenomic interrogation of Antarctic permafrost and polar cryptoendolithic microbial communities. The results underlie two different habitability conditions in the same location under extreme cold and dryness: the permafrost habitat where viable microbial life and activity is questionable, and the cryptoendolithic habitat which contains organisms capable of growth under the extreme conditions of the Antarctic Dry Valleys.

  8. On the Antarctic Slope Front and Current crossing of the South Scotia Ridge

    Science.gov (United States)

    Orsi, A. H.; Palmer, M.; Gomis, D.; Flexas, M. M.; Kim, Y.-S.; Jordà, G.; Wiederwohl, C.; Álvarez, M.

    2012-04-01

    To unveil the contorted path followed by the Antarctic Slope Current connecting the Weddell and Scotia Seas, hydrographic stations with unprecedented spatial resolution were occupied on a series of sections across the slope and multiple channels in the double-pronged western portion of the South Scotia Ridge. Fieldwork consisted of two cruises from the ESASSI (January 2008) and ACROSS (February 2009) programs, the Spanish and USA/Argentina components of the International Polar Year core project SASSI (Synoptic Antarctic Shelf-Slope Interaction study). In this region the Antarctic Slope Current can be located by the pronounced in-shore deepening of isopycnals over the continental slope, rendering the strong subsurface temperature and salinity gradients characteristic of the Antarctic Slope Front. Before reaching the gaps in the southern Ridge near 51°W and 50°W, the ASC carries about 3 Sv of upper layer waters, but it splits into shallow and deep branches upon turning north through these two gaps. The shallower branch enters the Hesperides Trough at 51°W, then shows a tight cyclonic loop back to that longitude roughly following the slope's 700-m isobath, and turns again westward through a similar gap in the northern Ridge. In the Scotia Sea the westward-flowing Antarctic Slope Current is found as far west as the Elephant Island along slightly deeper levels of slope (1100 m) before it is blocked by the Antarctic Circumpolar Current south of the Shackleton Fracture Zone (56°W). The deeper branch of the ASC in the Powell Basin crosses the southern Ridge near 50°W and roughly follows the 1600-m isobath before entering the Scotia Sea through the Hesperides Gap farther to the east (49°W). Thereafter the deeper waters carried westward by this branch become undistinguishable from those circulating farther offshore. Repeat cross-slope sections at both southern and northern flanks of the South Scotia Ridge showed significant temporal variability in the characteristics

  9. Tolerance of polar phytoplankton communities to metals

    International Nuclear Information System (INIS)

    Echeveste, P.; Tovar-Sánchez, A.; Agustí, S.

    2014-01-01

    Large amounts of pollutants reach polar regions, particularly the Arctic, impacting their communities. In this study we analyzed the toxic levels of Hg, Cd and Pb to natural phytoplankton communities of the Arctic and Southern Oceans, and compared their sensitivities with those observed on phytoplankton natural communities from temperate areas. Mercury was the most toxic metal for both Arctic and Antarctic communities, while both Cd and Pb were toxic only for the Antarctic phytoplankton. Total cell abundance of the populations forming the Arctic community increased under high Cd and Pb concentrations, probably due to a decrease of the grazing pressure or the increase of the most resistant species, although analysis of individual cells indicated that cell death was already induced at the highest levels. These results suggest that phytoplankton may have acquired adapting mechanisms to face high levels of Pb and Cd in the Arctic Ocean. Highlights: • First study analyzing the toxicity of Hg, Cd or Pb to natural polar phytoplankton. • Arctic Ocean communities highly resistant to Cd and Pb, but not to Hg. • Southern Ocean communities sensitive to Cd, Pb and Hg. • Both communities incorporated Pb at a similar level. • Arctic phytoplankton may have acquired adapting mechanisms against Cd and Pb. -- Polar phytoplankton communities are tolerant to Cd and Pb, specially the Arctic ones, suggesting the acquisition of adapting mechanisms to face metals' toxicity

  10. New Data Services for Polar Investigators from Integrated Earth Data Applications (IEDA)

    Science.gov (United States)

    Nitsche, F. O.; Ferrini, V.; Morton, J. J.; Arko, R. A.; McLain, K.; O'hara, S. H.; Carbotte, S. M.; Lehnert, K. A.; IEDA Team, I.

    2013-12-01

    Accessibility and preservation of data is needed to support multi-disciplinary research in the key environmentally sensitive Polar Regions. IEDA (Integrated Earth Data Applications) is a community-based data facility funded by the US National Science Foundation (NSF) to support, sustain, and advance the geosciences by providing data services for observational solid earth data from the Ocean, Earth, and Polar Sciences. IEDA tools and services relevant to the Polar Research Community include the Antarctic and Southern Ocean Data System (ASODS), the U.S. Antarctic Program Data Coordination Center (USAP-DCC), GeoMapApp, as well as a number of services for sample-based data (SESAR and EarthChem). In addition to existing tools, which assist Polar investigators in archiving their data, and creating DIF records for global searches in AMD, IEDA recently added several new tools and services that will provide further support for investigators with the data life cycle process. These include a data management plan (http://www.iedadata.org/compliance/plan) and data compliance reporting tool (http://www.iedadata.org/compliance/report) that will help investigators comply with the requirements of funding agencies such as the National Science Foundation (NSF). Data, especially from challenging Polar Regions, are likely to be used by other scientists for future studies. Therefore, data acknowledgment is an important concern of many investigators. To encourage data acknowledgments by data users, we link references of publications (when known) to datasets and cruises registered within the ASODS system as part of our data curation services (http://www.marine-geo.org/portals/antarctic/references.php). In addition, IEDA offers a data publication service to register scientific data with DOI's, making data sets citable as publications with attribution to investigators as authors. IEDA is a publication agent of the DataCite consortium. Offering such services provides additional incentives

  11. Environmental impact on the polar regions

    International Nuclear Information System (INIS)

    Jaffe, D.A.; Leighton, E.; Tumeo, M.A.

    1994-01-01

    The remote and frigid polar regions are no longer isolated from the activities, pollutants, and controversies that bedevil their more temperate neighbors, say three researchers at the University of Alaska in Fairbanks. For example, Daniel A. Jaffe, Elizabeth Leighton, and Mark A. Tumeo point to traces of DDT, PCBs, and heavy metals that routinely turn up in arctic marine mammals and to the ozone hole over the Antarctic. While similar in environmental makeup, the arctic and Antarctic are poles apart in their political structure and, thus, in their environmental exposure, the researchers note. The Antarctic is managed under a long-standing international treaty, while the arctic is sovereign territory to eight separate nations. The international treaty sets aside the Antarctic for peaceful scientific research within strict environmental boundaries. It bans both military activity and minerals extraction-the two activities that have caused the most damage in the arctic. The main threats to Antarctica's environment come from the intrusion of major scientific research operations and the growing tourism industry. On the other hand, the arctic suffered from the massive Cold War military buildup by both the United States and the former Soviet Union. The environmental residue from that buildup is only now being revealed, the authors say. Major oil and gas drilling and coal and metal-ore mining also have taken a huge environmental toll, they add

  12. Analysis of 16 plasma vortex events in the geomagnetic tail

    International Nuclear Information System (INIS)

    Birn, J.; Hones, E.W. Jr.; Bame, S.J.; Russel, C.T.

    1985-01-01

    The analysis of 16 plasma vortex occurrences in the magnetotail plasma sheet of Hones et al. (1983) is extended. We used two- and three-dimensional plasma measurements and three-dimensional magnetic field measurements to study phase relations, energy propagation, and polarization properties. The results point toward an interpretation as a slow strongly damped MHD eigenmode which is generated by tailward traveling perturbations at the low-latitude interface between plasma sheet and magnetosheath

  13. Vortex mass in a superfluid

    Science.gov (United States)

    Simula, Tapio

    2018-02-01

    We consider the inertial mass of a vortex in a superfluid. We obtain a vortex mass that is well defined and is determined microscopically and self-consistently by the elementary excitation energy of the kelvon quasiparticle localized within the vortex core. The obtained result for the vortex mass is found to be consistent with experimental observations on superfluid quantum gases and vortex rings in water. We propose a method to measure the inertial rest mass and Berry phase of a vortex in superfluid Bose and Fermi gases.

  14. NOAA Climate Data Record (CDR) of AVHRR Polar Pathfinder Extended (APP-X) Cryosphere

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA Climate Data Record (CDR) of the extended AVHRR Polar Pathfinder (APP-x) cryosphere contains 19 geophysical variables over the Arctic and Antarctic for the...

  15. SMM mesospheric ozone measurements

    Science.gov (United States)

    Aikin, A. C.

    1990-01-01

    The main objective was to understand the secular and seasonal behavior of ozone in the lower mesosphere, 50 to 70 km. This altitude region is important in understanding the factors which determine ozone behavior. A secondary objective is the study of stratospheric ozone in the polar regions. Use is made of results from the SBUV satellite borne instrument. In the Arctic the interaction between chlorine compounds and low molecular weight hydrocarbons is studied. More than 30,000 profiles were obtained using the UVSP instrument on the SMM spacecraft. Several orbits of ozone data per day were obtained allowing study of the current rise in solar activity from the minimum until the present. Analysis of Nimbus 7 SBUV data in Antarctic spring indicates that ozone is depleted within the polar vortex relative to ozone outside the vortex. This depletion confirms the picture of ozone loss at altitudes where polar stratospheric clouds exist. In addition, there is ozone loss above the cloud level indicating that there is another mechanism in addition to ozone loss initiated by heterogeneous chlorine reactions on cloud particles.

  16. Dynamics and chemistry of vortex remnants in late Arctic spring 1997 and 2000: Simulations with the Chemical Lagrangian Model of the Stratosphere (CLaMS

    Directory of Open Access Journals (Sweden)

    P. Konopka

    2003-01-01

    Full Text Available High-resolution simulations of the chemical composition of the Arctic stratosphere during late spring 1997 and 2000 were performed with the Chemical Lagrangian Model of the Stratosphere (CLaMS. The simulations were performed for the entire northern hemisphere on two isentropic levels 450 K (~18 km and 585 K (~24 km. The spatial distribution and the lifetime of the vortex remnants formed after the vortex breakup in May 1997 display different behavior above and below 20 km. Above 20 km, vortex remnants propagate southward (up to 40°N and are "frozen in'' in the summer circulation without significant mixing. Below 20 km the southward propagation of the remnants is bounded by the subtropical jet. Their lifetime is shorter by a factor of 2 than that above 20 km, owing to significant stirring below this altitude. The behavior of vortex remnants formed in March 2000 is similar but, due to an earlier vortex breakup, dominated during the first 6 weeks after the vortex breakup by westerly winds, even above 20 km. Vortex remnants formed in May 1997 are characterized by large mixing ratios of HCl indicating negligible, halogen-induced ozone loss. In contrast, mid-latitude ozone loss in late boreal spring 2000 is dominated, until mid-April, by halogen-induced ozone destruction within the vortex remnants, and subsequent transport of the ozone-depleted polar air masses (dilution into the mid-latitudes. By varying the intensity of mixing in CLaMS, the impact of mixing on the formation of ClONO2 and ozone depletion is investigated. We find that the photochemical decomposition of HNO3 and not mixing with NOx-rich mid-latitude air is the main source of NOx within the vortex remnants in March and April 2000. Ozone depletion in the remnants is driven by ClOx photolytically formed from ClONO2. At the end of May 1997, the halogen-induced ozone deficit at 450 K poleward of 30°N amounts to ~12% with ~10% in the polar vortex and ~2% in well-isolated vortex remnants

  17. Front propagation in a regular vortex lattice: Dependence on the vortex structure.

    Science.gov (United States)

    Beauvier, E; Bodea, S; Pocheau, A

    2017-11-01

    We investigate the dependence on the vortex structure of the propagation of fronts in stirred flows. For this, we consider a regular set of vortices whose structure is changed by varying both their boundary conditions and their aspect ratios. These configurations are investigated experimentally in autocatalytic solutions stirred by electroconvective flows and numerically from kinematic simulations based on the determination of the dominant Fourier mode of the vortex stream function in each of them. For free lateral boundary conditions, i.e., in an extended vortex lattice, it is found that both the flow structure and the front propagation negligibly depend on vortex aspect ratios. For rigid lateral boundary conditions, i.e., in a vortex chain, vortices involve a slight dependence on their aspect ratios which surprisingly yields a noticeable decrease of the enhancement of front velocity by flow advection. These different behaviors reveal a sensitivity of the mean front velocity on the flow subscales. It emphasizes the intrinsic multiscale nature of front propagation in stirred flows and the need to take into account not only the intensity of vortex flows but also their inner structure to determine front propagation at a large scale. Differences between experiments and simulations suggest the occurrence of secondary flows in vortex chains at large velocity and large aspect ratios.

  18. Wind profile radar for study of Antarctic air circulation. Progetto di un radar 'wind-profiler' per lo studio della circolazione atmosferica antartica

    Energy Technology Data Exchange (ETDEWEB)

    Ragaini, E.; Sarango, M.F.; Vasquez, E.H.

    1992-10-01

    After a brief discussion of meteorological methods used in the Antarctic, the paper gives an outline of a coordinated international research project whose objective is to set up a wind profiler radar station that would give meteorologists information regarding Antarctic atmospheric dynamics useful in their investigation of the causes and effects of the hole in the ozone layer. The radar instrumentation is to provide continuous readings of wind velocity at varying altitudes above the polar continent.

  19. Formation of quasistationary vortex and transient hole patterns through vortex merger

    International Nuclear Information System (INIS)

    Ganesh, R.; Lee, J.K.

    2002-01-01

    Collection of point-like intense vortices arranged symmetrically outside of a uniform circular vortex patch, both enclosed in a free-slip circular boundary, are numerically time evolved for up to 10-15 patch turnover times. These patterns are found to merge with the patch by successively inducing nonlinear dispersive modes (V-states) on the surface of the patch, draw off fingers of vorticity (filamentation), trap the irrotational regions as the fingers symmetrize under the shear flow of the patch and point-like vortices (wave breaking) followed by the vortex-hole capture. While the hole patterns are observed to break up over several turnover periods the vortex patterns appear to evolve into quasistationary patterns for some cases of an initial number of point-like vortices N pv . The bounded V-states, filamentation, and vortex (hole) pattern formation are discussed in some detail and their possible connection to recently observed vortex 'crystals' is pointed out

  20. Australian and Canadian perspectives and regulations for protecting the polar marine environment

    Energy Technology Data Exchange (ETDEWEB)

    Rothwell, Donald R.

    1997-12-31

    The report compares Australian and Canadian responses for protecting polar marine environments. Vast areas of the polar seas fall within their potential combined EEZ/continental shelf jurisdiction. The Antarctic Treaty provisions, doubts on the status of the Northwest Passage waters and the capacity to enforce legislative initiatives against foreign vessels have been constraints. Australia`s enactment of legislation prohibiting mining within the AAT continental shelf and whaling within the AAT EEZ has tested the Antarctic Treaty. Canada`s reaction to the Manhattan and the enactment of the Arctic Waters Pollution Prevention Act is an example of unilateral action. While the countries have made noteworthy initiatives to enhance the protection of their polar marine environments, doubts remain in some instances on their capacity to give effect to the initiatives. However, sovereignty remains at the heart of their response. Failure to address Antarctic marine environmental issues will rebound on the environment and reflect poorly upon Australia`s sovereignty claim to the AAT. For Canada it is a sovereignty issue and has directly impact upon its citizens inhabiting the islands and coastal areas of the Canadian Arctic. The Madrid Protocol provides the strongest legal basis for the Antarctic Treaty parties to enact laws and regulations in Antarctica. Conservation measures adopted under the Convention for the Conservation of Antarctic Marine Living Resources focuses increasingly on environmental concerns. The most significant regional initiative adopted by Arctic states is the AEPS which does not have a legal foundation. It`s co-operative programs provide basis for co-operation in dealing with environmental problems. It clearly recognises that only co-operative responses will achieve significant outcomes. The 1990s have posed new challenges for marine environmental protection such as ship-based tourism in Antarctica and the growing pressure to use the Northwest Passage on a

  1. 9+ Years of CALIOP PSC Data: An Evolving Climatology

    Science.gov (United States)

    Pitts, Michael C.; Poole, Lamont R.

    2015-01-01

    Polar stratospheric clouds (PSCs) play key roles in the springtime chemical depletion of ozone at high latitudes. PSC particles provide sites for heterogeneous chemical reactions that transform stable chlorine and bromine reservoir species into highly reactive ozone-destructive forms. Furthermore, large nitric acid trihydrate (NAT) PSC particles can irreversibly redistribute odd nitrogen through gravitational sedimentation, which prolongs the ozone depletion process by slowing the reformation of the stable chlorine reservoirs. However, there are still significant gaps in our understanding of PSC processes, particularly concerning the details of NAT particle formation. Spaceborne observations from the CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) lidar on the CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) satellite are providing a rich new dataset for studying PSCs on unprecedented vortex-wide scales. In this paper, we examine the vertical and spatial distribution of PSCs in the Antarctic and Arctic on vortex-wide scales for entire PSC seasons over the more than nine-year data record.

  2. The singing vortex

    Science.gov (United States)

    Arndt, R.; Pennings, P.; Bosschers, J.; van Terwisga, T.

    2015-01-01

    Marine propellers display several forms of cavitation. Of these, propeller-tip vortex cavitation is one of the important factors in propeller design. The dynamic behaviour of the tip vortex is responsible for hull vibration and noise. Thus, cavitation in the vortices trailing from tips of propeller blades has been studied extensively. Under certain circumstances cavitating vortices have been observed to have wave-like disturbances on the surfaces of vapour cores. Intense sound at discrete frequencies can result from a coupling between tip vortex disturbances and oscillating sheet cavitation on the surfaces of the propeller blades. This research article focuses on the dynamics of vortex cavitation and more in particular on the energy and frequency content of the radiated pressures. PMID:26442147

  3. DNS of droplet-vortex interaction with a Karman vortex street

    International Nuclear Information System (INIS)

    Burger, M.; Schmehl, R.; Koch, R.; Wittig, S.; Bauer, H.-J.

    2006-01-01

    Predicting fuel spray interaction with large scale vortex structures still is a major challenge for state-of-the-art CFD codes. In order to elucidate the mechanisms involved, a fundamental study has been carried out in which the interaction of water droplets with a Karman vortex street is investigated. The disperse two-phase flow around a cylinder has been computed taking into account the mass, momentum and heat transfer between both phases. Flow conditions are chosen such that large scale vortices are generated by periodic flow separations of the well known Karman vortex street. A homogeneous distribution of water droplets is injected into the hot air up-stream of the computational domain. The mixing process as well as the impact of the droplets on the gas phase instabilities is analyzed in the downstream region where large scale vortex structures are present

  4. The Impact of Warm Pool El Nino Events on Antarctic Ozone

    Science.gov (United States)

    Hurwitz, Margaret M.; Newman, P. A.; Song, In-Sun; Frith, Stacey M.

    2011-01-01

    Warm pool El Nino (WPEN) events are characterized by positive sea surface temperature (SST) anomalies in the central equatorial Pacific in austral spring and summer. Previous work found an enhancement in planetary wave activity in the South Pacific in austral spring, and a warming of 3-5 K in the Antarctic lower stratosphere during austral summer, in WPEN events as compared with ENSO neutral. In this presentation, we show that weakening of the Antarctic vortex during WPEN affects the structure and magnitude of high-latitude total ozone. We use total ozone data from TOMS and OMI, as well as station data from Argentina and Antarctica, to identify shifts in the longitudinal location of the springtime ozone minimum from its climatological position. In addition, we examine the sensitivity of the WPEN-related ozone response to the phase of the quasi-biennial oscillation (QBO). We then compare the observed response to WPEN events with Goddard Earth Observing System chemistry-climate model, version 2 (GEOS V2 CCM) simulations. Two, 50-year time-slice simulations are forced by annually repeating SST and sea ice climatologies, one set representing observed WPEN events and the second set representing neutral ENSO events, in a present-day climate. By comparing the two simulations, we isolate the impact of WPEN events on lower stratospheric ozone, and furthermore, examine the sensitivity of the WPEN ozone response to the phase of the QBO.

  5. Pakistan and Antarctic research - an overview

    International Nuclear Information System (INIS)

    Rizvi, S.H.

    1993-01-01

    The paper describes the significance of Antarctica and the necessity of conducting scientific research for the understanding of the global environment and through various environmental processes operative in Antarctica. The paper presents a review of the Pakistan's activities and research interests in Antarctica focussing on the salient features of the Pakistan's Antarctic Research Programme and objectives. It summarises the significance of Antarctica, Antarctic Research and the interests of the world in Antarctica and international co-operation for Antarctic Research. The paper also highlights the philosophy of Antarctic Science and provides some guidelines for the development of Antarctic Research programmes for Pakistan and for the newcomers in Antarctica particularly for the developing countries. (author)

  6. Antarctic crabs: invasion or endurance?

    Directory of Open Access Journals (Sweden)

    Huw J Griffiths

    Full Text Available Recent scientific interest following the "discovery" of lithodid crabs around Antarctica has centred on a hypothesis that these crabs might be poised to invade the Antarctic shelf if the recent warming trend continues, potentially decimating its native fauna. This "invasion hypothesis" suggests that decapod crabs were driven out of Antarctica 40-15 million years ago and are only now returning as "warm" enough habitats become available. The hypothesis is based on a geographically and spatially poor fossil record of a different group of crabs (Brachyura, and examination of relatively few Recent lithodid samples from the Antarctic slope. In this paper, we examine the existing lithodid fossil record and present the distribution and biogeographic patterns derived from over 16,000 records of Recent Southern Hemisphere crabs and lobsters. Globally, the lithodid fossil record consists of only two known specimens, neither of which comes from the Antarctic. Recent records show that 22 species of crabs and lobsters have been reported from the Southern Ocean, with 12 species found south of 60 °S. All are restricted to waters warmer than 0 °C, with their Antarctic distribution limited to the areas of seafloor dominated by Circumpolar Deep Water (CDW. Currently, CDW extends further and shallower onto the West Antarctic shelf than the known distribution ranges of most lithodid species examined. Geological evidence suggests that West Antarctic shelf could have been available for colonisation during the last 9,000 years. Distribution patterns, species richness, and levels of endemism all suggest that, rather than becoming extinct and recently re-invading from outside Antarctica, the lithodid crabs have likely persisted, and even radiated, on or near to Antarctic slope. We conclude there is no evidence for a modern-day "crab invasion". We recommend a repeated targeted lithodid sampling program along the West Antarctic shelf to fully test the validity of the

  7. Cylindrical vortex wake model: right cylinder

    DEFF Research Database (Denmark)

    Branlard, Emmanuel; Gaunaa, Mac

    2015-01-01

    The vortex system consisting of a bound vortex disk, a root vortex and a vortex cylinder as introduced by Joukowski in 1912 is further studied in this paper. This system can be used for simple modeling of rotors (e.g. wind turbines) with infinite number of blades and finite tip-speed ratios....... For each vortex element, the velocity components in all directions and in the entire domain are computed analytically in a novel approach. In particular, the velocity field from the vortex actuator disk is derived for the first time. The induction from the entire vortex system is studied and is seen...

  8. A vortex ring interacting with a vortex filament and its deformation near the two-dimensional stagnation point

    International Nuclear Information System (INIS)

    Kiya, M.; Sato, T.

    1986-01-01

    In this paper the interaction between vortex filaments and vortex rings and the deformation of vortex rings near the two-dimensional stagnation point are simulated by a three-dimensional vortex method. The two problems are respectively concerned with the effect of free-stream turbulence on turbulent plane mixing layers and the production of turbulence by the vortex stretching near saddles associated with large-scale coherent structures. The authors assume that the first step to understand the free-stream turbulence effect is to study the interaction between a vortex ring and a vortex filament and that the process of deformation of a vortex ring gives us a clue to understand physical processes occurring near the saddles

  9. Imaging of artificially induced vortex structures

    International Nuclear Information System (INIS)

    Fasano, Yanina; Menghini, M.; Cruz, F. de la

    2004-01-01

    The combination of engineered pinning potentials in superconducting crystals, the detection of the liquid-solid vortex transition and the observation of the vortex structure with single vortex sensitivity allow the microscopic analysis of the response of 3D elastic systems to the presence of these potentials. In this work we review recent results obtained by a combination of those techniques studying different vortex structure induced transformations. On the one hand, we have visualized the transformation, along the vortex direction, of a bulk vortex single crystal with hexagonal symmetry into another crystal with square symmetry induced by an engineered Fe-dot lattice deposited on a surface of the vortex single crystal. On the other hand, we found an infrequent first-order phase transition where a vortex liquid under the presence of a random correlated potential (columnar defects) transforms into a vortex solid with no change of topological order

  10. Persistence of metastable vortex lattice domains in MgB2 in the presence of vortex motion.

    Science.gov (United States)

    Rastovski, C; Schlesinger, K J; Gannon, W J; Dewhurst, C D; DeBeer-Schmitt, L; Zhigadlo, N D; Karpinski, J; Eskildsen, M R

    2013-09-06

    Recently, extensive vortex lattice metastability was reported in MgB2 in connection with a second-order rotational phase transition. However, the mechanism responsible for these well-ordered metastable vortex lattice phases is not well understood. Using small-angle neutron scattering, we studied the vortex lattice in MgB2 as it was driven from a metastable to the ground state through a series of small changes in the applied magnetic field. Our results show that metastable vortex lattice domains persist in the presence of substantial vortex motion and directly demonstrate that the metastability is not due to vortex pinning. Instead, we propose that it is due to the jamming of counterrotated vortex lattice domains which prevents a rotation to the ground state orientation.

  11. Reflectance of Antarctic surfaces from multispectral radiometers: The correction of atmospheric effects

    International Nuclear Information System (INIS)

    Zibordi, G.; Maracci, G.

    1993-01-01

    Monitoring reflectance of polar icecaps has relevance in climate studies. In fact, climate changes produce variations in the morphology of ice and snow covers, which are detectable as surface reflectance change. Surface reflectance can be retrieved from remotely sensed data. However, absolute values independent of atmospheric turbidity and surface altitude can only be obtained after removing masking effects of the atmosphere. An atmospheric correction model, accounting for surface and sensor altitudes above sea level, is described and validated through data detected over Antarctic surfaces with a Barnes Modular Multispectral Radiometer having bands overlapping those of the Landsat Thematic Mapper. The model is also applied in a sensitivity analysis to investigate error induced in reflectance obtained from satellite data by indeterminacy in optical parameters of atmospheric constituents. Results show that indeterminacy in the atmospheric water vapor optical thickness is the main source of nonaccuracy in the retrieval of surface reflectance from data remotely sensed over Antarctic regions

  12. Negative optical spin torque wrench of a non-diffracting non-paraxial fractional Bessel vortex beam

    Science.gov (United States)

    Mitri, F. G.

    2016-10-01

    An absorptive Rayleigh dielectric sphere in a non-diffracting non-paraxial fractional Bessel vortex beam experiences a spin torque. The axial and transverse radiation spin torque components are evaluated in the dipole approximation using the radiative correction of the electric field. Particular emphasis is given on the polarization as well as changing the topological charge α and the half-cone angle of the beam. When α is zero, the axial spin torque component vanishes. However, when α becomes a real positive number, the vortex beam induces left-handed (negative) axial spin torque as the sphere shifts off-axially from the center of the beam. The results show that a non-diffracting non-paraxial fractional Bessel vortex beam is capable of inducing a spin reversal of an absorptive Rayleigh sphere placed arbitrarily in its path. Potential applications are yet to be explored in particle manipulation, rotation in optical tweezers, optical tractor beams, and the design of optically-engineered metamaterials to name a few areas.

  13. Propagation of optical vortex beams and nucleation of vortex-antivortex pairs in disordered nonlinear photonic lattices

    International Nuclear Information System (INIS)

    Cho, Yeong-Kwon; Kim, Ki-Hong

    2014-01-01

    The propagation of optical vortex beams through disordered nonlinear photonic lattices is numerically studied. The vortex beams are generated by using a superposition of several Gaussian laser beams arranged in a radially-symmetric manner. The paraxial nonlinear Schroedinger equation describing the longitudinal propagation of the beam array through nonlinear triangular photonic lattices with two-dimensional disorder is solved numerically by using the split-step Fourier method. We find that due to the spatial disorder, the vortex beam is destabilized after propagating a finite distance and new vortex-antivortex pairs are nucleated at the positions of perfect destructive interference. We also find that in the presence of a self-focusing nonlinearity, the vortex-antivortex pair nucleation is suppressed and the vortex beam becomes more stable, while a self-defocusing nonlinearity enhances the vortex-antivortex pair nucleation.

  14. Constraining the Antarctic contribution to interglacial sea-level rise

    Science.gov (United States)

    Naish, T.; Mckay, R. M.; Barrett, P. J.; Levy, R. H.; Golledge, N. R.; Deconto, R. M.; Horgan, H. J.; Dunbar, G. B.

    2015-12-01

    Observations, models and paleoclimate reconstructions suggest that Antarctica's marine-based ice sheets behave in an unstable manner with episodes of rapid retreat in response to warming climate. Understanding the processes involved in this "marine ice sheet instability" is key for improving estimates of Antarctic ice sheet contribution to future sea-level rise. Another motivating factor is that far-field sea-level reconstructions and ice sheet models imply global mean sea level (GMSL) was up to 20m and 10m higher, respectively, compared with present day, during the interglacials of the warm Pliocene (~4-3Ma) and Late Pleistocene (at ~400ka and 125ka). This was when atmospheric CO2 was between 280 and 400ppm and global average surface temperatures were 1- 3°C warmer, suggesting polar ice sheets are highly sensitive to relatively modest increases in climate forcing. Such magnitudes of GMSL rise not only require near complete melt of the Greenland Ice Sheet and the West Antarctic Ice Sheet, but a substantial retreat of marine-based sectors of East Antarctic Ice Sheet. Recent geological drilling initiatives on the continental margin of Antarctica from both ship- (e.g. IODP; International Ocean Discovery Program) and ice-based (e.g. ANDRILL/Antarctic Geological Drilling) platforms have provided evidence supporting retreat of marine-based ice. However, without direct access through the ice sheet to archives preserved within sub-glacial sedimentary basins, the volume and extent of ice sheet retreat during past interglacials cannot be directly constrained. Sediment cores have been successfully recovered from beneath ice shelves by the ANDRILL Program and ice streams by the WISSARD (Whillans Ice Stream Sub-glacial Access Research Drilling) Project. Together with the potential of the new RAID (Rapid Access Ice Drill) initiative, these demonstrate the technological feasibility of accessing the subglacial bed and deeper sedimentary archives. In this talk I will outline the

  15. Vortex and half-vortex dynamics in a nonlinear spinor quantum fluid.

    Science.gov (United States)

    Dominici, Lorenzo; Dagvadorj, Galbadrakh; Fellows, Jonathan M; Ballarini, Dario; De Giorgi, Milena; Marchetti, Francesca M; Piccirillo, Bruno; Marrucci, Lorenzo; Bramati, Alberto; Gigli, Giuseppe; Szymańska, Marzena H; Sanvitto, Daniele

    2015-12-01

    Vortices are archetypal objects that recur in the universe across the scale of complexity, from subatomic particles to galaxies and black holes. Their appearance is connected with spontaneous symmetry breaking and phase transitions. In Bose-Einstein condensates and superfluids, vortices are both point-like and quantized quasiparticles. We use a two-dimensional (2D) fluid of polaritons, bosonic particles constituted by hybrid photonic and electronic oscillations, to study quantum vortex dynamics. Polaritons benefit from easiness of wave function phase detection, a spinor nature sustaining half-integer vorticity, strong nonlinearity, and tuning of the background disorder. We can directly generate by resonant pulsed excitations a polariton condensate carrying either a full or half-integer vortex as initial condition and follow their coherent evolution using ultrafast imaging on the picosecond scale. The observations highlight a rich phenomenology, such as the spiraling of the half-vortex and the joint path of the twin charges of a full vortex, until the moment of their splitting. Furthermore, we observe the ordered branching into newly generated secondary couples, associated with the breaking of radial and azimuthal symmetries. This allows us to devise the interplay of nonlinearity and sample disorder in shaping the fluid and driving the vortex dynamics. In addition, our observations suggest that phase singularities may be seen as fundamental particles whose quantized events span from pair creation and recombination to 2D+t topological vortex strings.

  16. Vortex generation and wave-vortex interaction over a concave plate with roughness and suction

    Science.gov (United States)

    Bertolotti, Fabio

    1993-01-01

    The generation and amplification of vortices by surface homogeneities, both in the form of surface waviness and of wall-normal velocity, is investigated using the nonlinear parabolic stability equations. Transients and issues of algebraic growth are avoided through the use of a similarity solution as initial condition for the vortex. In the absence of curvature, the vortex decays as the square root of 1/x when flowing over streamwise aligned riblets of constant height, and grows as the square root of x when flowing over a corresponding streamwise aligned variation of blowing/suction transpiration velocity. However, in the presence of wall inhomogeneities having both streamwise and spanwise periodicity, the growth of the vortex can be much larger. In the presence of curvature, the vortex develops into a Gortler vortex. The 'direct' and 'indirect' interaction mechanisms possible in wave-vortex interaction are presented. The 'direct' interaction does not lead to strong resonance with the flow conditions investigated. The 'indirect' interaction leads to K-type transition.

  17. A recent case of Antarctic bioprospecting from Japan

    Directory of Open Access Journals (Sweden)

    Akiho Shibata

    2010-03-01

    Full Text Available Antarctic bioprospecting, namely the search for valuable genetic or chemical compounds in Antarctic nature, has been the subject of intense discussion within Antarctic Treaty Consultative Meetings. In this discussion, based on the so-called "end-users view point," utilizing the patent database to see how much Antarctic biological material has been used in patents, Antarctic bioprospecting has been depicted as a lucrative commercial activity operated by big multinational companies. This paper, instead, proposes an "access view point" for Antarctic bioprospecting, by examining a recent Japanese case in which scientists participating in the Japanese Antarctic Research Expedition in 2007 collected some sediment from Antarctic lakes near Syowa Station, isolated and cultured a particular fungus, and found the first evidence of the presence of antifreezing activity in oomycetes. In 2009, the scientists' affiliate institutions, including the National Institute of Advanced Industrial Science and Technology, applied for a patent on Antarctomyces psychrotrophicus Syw-1 and the antifreeze protein obtained from it. A detailed examination of this case demonstrates that the dichotomy of Antarctic bioprospecting into "commercial" and "scientific" does not reflect the reality of bioprospecting activities and, therefore, does not provide an appropriate ground for legal and policy discussion on Antarctic bioprospecting.

  18. Euphausiid population structure and grazing in the Antarctic Polar ...

    African Journals Online (AJOL)

    The daily ration estimates of autotrophic carbon for the euphausiids suggest that phytoplankton represent a minor component in their diets, with only the sub-adult E. vallentini consuming sufficient phytoplankton to meet their daily carbon requirements. Keywords: euphausiid; ingestion; Polar Frontal Zone; population ...

  19. Manipulation of vortex rings for flow control

    International Nuclear Information System (INIS)

    Toyoda, Kuniaki; Hiramoto, Riho

    2009-01-01

    This paper reviews the dynamics of vortex rings and the control of flow by the manipulation of vortex rings. Vortex rings play key roles in many flows; hence, the understanding of the dynamics of vortex rings is crucial for scientists and engineers dealing with flow phenomena. We describe the structures and motions of vortex rings in circular and noncircular jets, which are typical examples of flows evolving into vortex rings. For circular jets the mechanism of evolving, merging and breakdown of vortex rings is described, and for noncircular jets the dynamics of three-dimensional deformation and interaction of noncircular vortex rings under the effect of self- and mutual induction is discussed. The application of vortex-ring manipulation to the control of various flows is reviewed with successful examples, based on the relationship between the vortex ring dynamics and the flow properties. (invited paper)

  20. Observation of Polarization Vortices in Momentum Space

    Science.gov (United States)

    Zhang, Yiwen; Chen, Ang; Liu, Wenzhe; Hsu, Chia Wei; Wang, Bo; Guan, Fang; Liu, Xiaohan; Shi, Lei; Lu, Ling; Zi, Jian

    2018-05-01

    The vortex, a fundamental topological excitation featuring the in-plane winding of a vector field, is important in various areas such as fluid dynamics, liquid crystals, and superconductors. Although commonly existing in nature, vortices were observed exclusively in real space. Here, we experimentally observed momentum-space vortices as the winding of far-field polarization vectors in the first Brillouin zone of periodic plasmonic structures. Using homemade polarization-resolved momentum-space imaging spectroscopy, we mapped out the dispersion, lifetime, and polarization of all radiative states at the visible wavelengths. The momentum-space vortices were experimentally identified by their winding patterns in the polarization-resolved isofrequency contours and their diverging radiative quality factors. Such polarization vortices can exist robustly on any periodic systems of vectorial fields, while they are not captured by the existing topological band theory developed for scalar fields. Our work provides a new way for designing high-Q plasmonic resonances, generating vector beams, and studying topological photonics in the momentum space.

  1. The Unusual Southern Hemisphere Stratosphere Winter of 2002

    Science.gov (United States)

    Newman, Paul A.; Nash, Eric R.

    2003-01-01

    The southern hemisphere stratospheric winter of 2002 was the most unusual winter yet observed in the southern hemisphere climate record. Temperatures near the edge of the Antarctic polar vortex were considerably warmer than normal over the entire course of the winter. The polar night jet was considerably weaker than normal, and was displaced more poleward than has been observed in previous winters. These record high temperatures and weak jet resulted from a series of wave events that took place over the course of the winter. The first large event occurred on 15 May, and the final warming occurred on 25 October. The propagation of these wave events from the troposphere is diagnosed from time series of Eliassen-Palm flux vectors. The wave events tended to occur irregularly over the course of the winter, and pre-conditioned the polar night jet for the extremely large wave event of 22 September. This large wave event resulted in the first ever observed major stratospheric warming in the southern hemisphere. This wave event split the Antarctic ozone hole. The combined effect of the wave events of the 2002 winter resulted in the smallest ozone hole observed since 1988.

  2. Optical vortex scanning inside the Gaussian beam

    International Nuclear Information System (INIS)

    Masajada, J; Leniec, M; Augustyniak, I

    2011-01-01

    We discussed a new scanning method for optical vortex-based scanning microscopy. The optical vortex is introduced into the incident Gaussian beam by a vortex lens. Then the beam with the optical vortex is focused by an objective and illuminates the sample. By changing the position of the vortex lens we can shift the optical vortex position at the sample plane. By adjusting system parameters we can get 30 times smaller shift at the sample plane compared to the vortex lens shift. Moreover, if the range of vortex shifts is smaller than 3% of the beam radius in the sample plane the amplitude and phase distribution around the phase dislocation remains practically unchanged. Thus we can scan the sample topography precisely with an optical vortex

  3. Multiple helical modes of vortex breakdown

    DEFF Research Database (Denmark)

    Sørensen, Jens Nørkær; Naumov, I. V.; Okulov, Valery

    2011-01-01

    Experimental observations of vortex breakdown in a rotating lid-driven cavity are presented. The results show that vortex breakdown for cavities with high aspect ratios is associated with the appearance of stable helical vortex multiplets. By using results from stability theory generalizing Kelvi......’s problem on vortex polygon stability, and systematically exploring the cavity flow, we succeeded in identifying two new stable vortex breakdown states consisting of triple and quadruple helical multiplets....

  4. Cryptanalysis of Vortex

    DEFF Research Database (Denmark)

    Aumasson, Jean-Philippe; Dunkelman, Orr; Mendel, Florian

    2009-01-01

    Vortex is a hash function that was first presented at ISC'2008, then submitted to the NIST SHA-3 competition after some modifications. This paper describes several attacks on both versions of Vortex, including collisions, second preimages, preimages, and distinguishers. Our attacks exploit flaws...

  5. Halogen species record Antarctic sea ice extent over glacial–interglacial periods

    Directory of Open Access Journals (Sweden)

    A. Spolaor

    2013-07-01

    Full Text Available Sea ice is an integral part of the earth's climate system because it affects planetary albedo, sea-surface salinity, and the atmosphere–ocean exchange of reactive gases and aerosols. Bromine and iodine chemistry is active at polar sea ice margins with the occurrence of bromine explosions and the biological production of organoiodine from sea ice algae. Satellite measurements demonstrate that concentrations of bromine oxide (BrO and iodine oxide (IO decrease over sea ice toward the Antarctic interior. Here we present speciation measurements of bromine and iodine in the TALDICE (TALos Dome Ice CorE ice core (159°11' E, 72°49' S; 2315 m a.s.l. spanning the last 215 ky. The Talos Dome ice core is located 250 km inland and is sensitive to marine air masses intruding onto the Antarctic Plateau. Talos Dome bromide (Br− is positively correlated with temperature and negatively correlated with sodium (Na. Based on the Br−/Na seawater ratio, bromide is depleted in the ice during glacial periods and enriched during interglacial periods. Total iodine, consisting of iodide (I− and iodate (IO3−, peaks during glacials with lower values during interglacial periods. Although IO3− is considered the most stable iodine species in the atmosphere it was only observed in the TALDICE record during glacial maxima. Sea ice dynamics are arguably the primary driver of halogen fluxes over glacial–interglacial timescales, by altering the distance between the sea ice edge and the Antarctic plateau and by altering the surface area of sea ice available to algal colonization. Based on our results we propose the use of both halogens for examining Antarctic variability of past sea ice extent.

  6. Recruitment, growth and mortality of an Antarctic hexactinellid sponge, Anoxycalyx joubini.

    Directory of Open Access Journals (Sweden)

    Paul K Dayton

    Full Text Available Polar ecosystems are sensitive to climate forcing, and we often lack baselines to evaluate changes. Here we report a nearly 50-year study in which a sudden shift in the population dynamics of an ecologically important, structure-forming hexactinellid sponge, Anoxycalyx joubini was observed. This is the largest Antarctic sponge, with individuals growing over two meters tall. In order to investigate life history characteristics of Antarctic marine invertebrates, artificial substrata were deployed at a number of sites in the southern portion of the Ross Sea between 1967 and 1975. Over a 22-year period, no growth or settlement was recorded for A. joubini on these substrata; however, in 2004 and 2010, A. joubini was observed to have settled and grown to large sizes on some but not all artificial substrata. This single settlement and growth event correlates with a region-wide shift in phytoplankton productivity driven by the calving of a massive iceberg. We also report almost complete mortality of large sponges followed over 40 years. Given our warming global climate, similar system-wide changes are expected in the future.

  7. Dynamic signatures of driven vortex motion.

    Energy Technology Data Exchange (ETDEWEB)

    Crabtree, G. W.; Kwok, W. K.; Lopez, D.; Olsson, R. J.; Paulius, L. M.; Petrean, A. M.; Safar, H.

    1999-09-16

    We probe the dynamic nature of driven vortex motion in superconductors with a new type of transport experiment. An inhomogeneous Lorentz driving force is applied to the sample, inducing vortex velocity gradients that distinguish the hydrodynamic motion of the vortex liquid from the elastic and-plastic motion of the vortex solid. We observe elastic depinning of the vortex lattice at the critical current, and shear induced plastic slip of the lattice at high Lorentz force gradients.

  8. Numerical simulations of the internal flow pattern of a vortex pump compared to the Hamel-Oseen vortex

    International Nuclear Information System (INIS)

    Gerlach, Angela; Preuss, Enrico; Thamsen, Paul Uwe; Lykholt-Ustrup, Flemming

    2017-01-01

    We did a numerical study of the internal flow field of a vortex pump. Five operating points were considered and validated through a measured characteristic curve. The internal flow pattern of a vortex pump was analyzed and compared to the Hamel-Oseen vortex model. The calculated flow field was assessed with respect to the circumferential velocity, the vorticity and the axial velocity. Whereas the trajectories of the circumferential velocity were largely in line with the Hamel-Oseen vortex model, the opposite was true for vorticity. Only the vorticity at strong part load was in line with the predictions of the Hamel-Oseen vortex model. We therefore compared the circumferential velocity and vorticity for strong part load operation to the analytical predictions of the Hamel-Oseen vortex model. The simulated values were below the analytical values. The study therefore suggests that a vortex similar to the Hamel-Oseen vortex is only present at the strong part load operation

  9. Numerical simulations of the internal flow pattern of a vortex pump compared to the Hamel-Oseen vortex

    Energy Technology Data Exchange (ETDEWEB)

    Gerlach, Angela; Preuss, Enrico; Thamsen, Paul Uwe [Institute of Fluid System Dynamics, Technische Universitaet, Berlin (Germany); Lykholt-Ustrup, Flemming [Grundfos Holding A/S, Bjerringbro (Denmark)

    2017-04-15

    We did a numerical study of the internal flow field of a vortex pump. Five operating points were considered and validated through a measured characteristic curve. The internal flow pattern of a vortex pump was analyzed and compared to the Hamel-Oseen vortex model. The calculated flow field was assessed with respect to the circumferential velocity, the vorticity and the axial velocity. Whereas the trajectories of the circumferential velocity were largely in line with the Hamel-Oseen vortex model, the opposite was true for vorticity. Only the vorticity at strong part load was in line with the predictions of the Hamel-Oseen vortex model. We therefore compared the circumferential velocity and vorticity for strong part load operation to the analytical predictions of the Hamel-Oseen vortex model. The simulated values were below the analytical values. The study therefore suggests that a vortex similar to the Hamel-Oseen vortex is only present at the strong part load operation.

  10. Growth dynamics of Australia's polar dinosaurs.

    Science.gov (United States)

    Woodward, Holly N; Rich, Thomas H; Chinsamy, Anusuya; Vickers-Rich, Patricia

    2011-01-01

    Analysis of bone microstructure in ornithopod and theropod dinosaurs from Victoria, Australia, documents ontogenetic changes, providing insight into the dinosaurs' successful habitation of Cretaceous Antarctic environments. Woven-fibered bone tissue in the smallest specimens indicates rapid growth rates during early ontogeny. Later ontogeny is marked by parallel-fibered tissue, suggesting reduced growth rates approaching skeletal maturity. Bone microstructure similarities between the ornithopods and theropods, including the presence of LAGs in each group, suggest there is no osteohistologic evidence supporting the hypothesis that polar theropods hibernated seasonally. Results instead suggest high-latitude dinosaurs had growth trajectories similar to their lower-latitude relatives and thus, rapid early ontogenetic growth and the cyclical suspensions of growth inherent in the theropod and ornithopod lineages enabled them to successfully exploit polar regions.

  11. ARM West Antarctic Radiation Experiment (AWARE) Science Plan

    Energy Technology Data Exchange (ETDEWEB)

    Lubin, D [National Science Foundation; Bromwich, DH [Ohio State University; Russell, LM [Scripps Institution of Oceanography; Verlinde, J [The Pennsylvania State University; Vogelmann, AM [Brookhaven National Laboratory

    2015-10-01

    West Antarctica is one of the most rapidly warming regions on Earth, and this warming is closely connected with global sea level rise. The discovery of rapid climate change on the West Antarctic Ice Sheet (WAIS) has challenged previous explanations of Antarctic climate change that focused on strengthening of circumpolar westerlies in response to the positive polarity trend in the Southern Annular Mode. West Antarctic warming does not yet have a comprehensive explanation: dynamical mechanisms may vary from one season to the next, and these mechanisms very likely involve complex teleconnections with subtropical and tropical latitudes. The prime motivation for this proposal is that there has been no substantial atmospheric science or climatological field work on West Antarctica since the 1957 International Geophysical Year and that research continued for only a few years. Direct meteorological information on the WAIS has been limited to a few automatic weather stations for several decades, yet satellite imagery and meteorological reanalyses indicate that West Antarctica is highly susceptible to advection of warm and moist maritime air with related cloud cover, depending on the location and strength of low pressure cells in the Amundsen, Ross, and Bellingshausen Seas. There is a need to quantify the role of these changing air masses on the surface energy balance, including all surface energy components and cloud-radiative forcing. More generally, global climate model simulations are known to perform poorly over the Antarctic and Southern Oceans, and the marked scarcity of cloud information at southern high latitudes has so far inhibited significant progress. Fortunately, McMurdo Station, where the Atmospheric Radiation Measurement Facility’s (ARM’s) most advanced cloud and aerosol instrumentation is situated, has a meteorological relationship with the WAIS via circulation patterns in the Ross and Amundsen Seas. We can therefore gather sophisticated data with cloud

  12. The Future of the United States Antarctic Program

    Science.gov (United States)

    Thom, J. E.; Weidner, G. A.; Lazzara, M. A.; Knuth, S. L.; Cassano, J. J.

    2009-04-01

    The last three decades have seen Antarctic surface meteorological observations augmented by an increasing number of automated weather stations (AWS). Since 1980, the University of Wisconsin-Madison has managed an expanding array of AWS in Antarctica that are funded through the United States' National Science Foundation. The AWS network began with six stations and has grown to approximately 60 stations. The majority of the AWS use a custom electronics package designed in the 1970s and modified over approximately 20 years. However, dramatic changes in the electronics industry have led the UW-Madison to transition its AWS to commercial-off-the-shelf (COTS) components capable of integrating on-station storage, varied sensors, multiple data telemetry options, and a flexible operating system. Among the important technical issues arising from adopting a COTS-based AWS system are limited temperature certification for Antarctic conditions; non-standard integration of the varied telecommunications equipment; potentially inflexible data acquisition schemes; and frequent product upgrades, changes, and obsolescence. The UW-Madison presents the current status of its AWS system; its recent experience with new data loggers, sensors, and communication options; and its attempts to obtain a standardized AWS. The intent is to encourage the development of a forum where groups can document their experiences with varied AWS systems in the extreme polar climate. Recent events have added another challenge within the United States Antarctic Program, as it has become clear that budgetary and logistic limitations will drastically impact the AWS program. With logistical costs playing a bigger factor in funding AWS operations, international coordination and cooperation will be important in deploying and maintaining the AWS networks (such as GCOS) that are critical to monitoring the world's climate.

  13. A New Limit on CMB Circular Polarization from SPIDER

    Science.gov (United States)

    Nagy, J. M.; Ade, P. A. R.; Amiri, M.; Benton, S. J.; Bergman, A. S.; Bihary, R.; Bock, J. J.; Bond, J. R.; Bryan, S. A.; Chiang, H. C.; Contaldi, C. R.; Doré, O.; Duivenvoorden, A. J.; Eriksen, H. K.; Farhang, M.; Filippini, J. P.; Fissel, L. M.; Fraisse, A. A.; Freese, K.; Galloway, M.; Gambrel, A. E.; Gandilo, N. N.; Ganga, K.; Gudmundsson, J. E.; Halpern, M.; Hartley, J.; Hasselfield, M.; Hilton, G.; Holmes, W.; Hristov, V. V.; Huang, Z.; Irwin, K. D.; Jones, W. C.; Kuo, C. L.; Kermish, Z. D.; Li, S.; Mason, P. V.; Megerian, K.; Moncelsi, L.; Morford, T. A.; Netterfield, C. B.; Nolta, M.; Padilla, I. L.; Racine, B.; Rahlin, A. S.; Reintsema, C.; Ruhl, J. E.; Runyan, M. C.; Ruud, T. M.; Shariff, J. A.; Soler, J. D.; Song, X.; Trangsrud, A.; Tucker, C.; Tucker, R. S.; Turner, A. D.; Van Der List, J. F.; Weber, A. C.; Wehus, I. K.; Wiebe, D. V.; Young, E. Y.

    2017-08-01

    We present a new upper limit on cosmic microwave background (CMB) circular polarization from the 2015 flight of Spider, a balloon-borne telescope designed to search for B-mode linear polarization from cosmic inflation. Although the level of circular polarization in the CMB is predicted to be very small, experimental limits provide a valuable test of the underlying models. By exploiting the nonzero circular-to-linear polarization coupling of the half-wave plate polarization modulators, data from Spider's 2015 Antarctic flight provide a constraint on Stokes V at 95 and 150 GHz in the range 33< {\\ell }< 307. No other limits exist over this full range of angular scales, and Spider improves on the previous limit by several orders of magnitude, providing 95% C.L. constraints on {\\ell }({\\ell }+1){C}{\\ell }{VV}/(2π ) ranging from 141 to 255 μK2 at 150 GHz for a thermal CMB spectrum. As linear CMB polarization experiments become increasingly sensitive, the techniques described in this paper can be applied to obtain even stronger constraints on circular polarization.

  14. A New Limit on CMB Circular Polarization from SPIDER

    Energy Technology Data Exchange (ETDEWEB)

    Nagy, J. M.; Ade, P. A. R.; Amiri, M.; Benton, S. J.; Bergman, A. S.; Bihary, R.; Bock, J. J.; Bond, J. R.; Bryan, S. A.; Chiang, H. C.; Contaldi, C. R.; Doré, O.; Duivenvoorden, A. J.; Eriksen, H. K.; Farhang, M.; Filippini, J. P.; Fissel, L. M.; Fraisse, A. A.; Freese, K.; Galloway, M.; Gambrel, A. E.; Gandilo, N. N.; Ganga, K.; Gudmundsson, J. E.; Halpern, M.; Hartley, J.; Hasselfield, M.; Hilton, G.; Holmes, W.; Hristov, V. V.; Huang, Z.; Irwin, K. D.; Jones, W. C.; Kuo, C. L.; Kermish, Z. D.; Li, S.; Mason, P. V.; Megerian, K.; Moncelsi, L.; Morford, T. A.; Netterfield, C. B.; Nolta, M.; Padilla, I. L.; Racine, B.; Rahlin, A. S.; Reintsema, C.; Ruhl, J. E.; Runyan, M. C.; Ruud, T. M.; Shariff, J. A.; Soler, J. D.; Song, X.; Trangsrud, A.; Tucker, C.; Tucker, R. S.; Turner, A. D.; List, J. F. Van Der; Weber, A. C.; Wehus, I. K.; Wiebe, D. V.; Young, E. Y.

    2017-08-01

    We present a new upper limit on CMB circular polarization from the 2015 flight of SPIDER, a balloon-borne telescope designed to search for $B$-mode linear polarization from cosmic inflation. Although the level of circular polarization in the CMB is predicted to be very small, experimental limits provide a valuable test of the underlying models. By exploiting the non-zero circular-to-linear polarization coupling of the HWP polarization modulators, data from SPIDER's 2015 Antarctic flight provides a constraint on Stokes $V$ at 95 and 150 GHz from $33<\\ell<307$. No other limits exist over this full range of angular scales, and SPIDER improves upon the previous limit by several orders of magnitude, providing 95% C.L. constraints on $\\ell (\\ell+1)C_{\\ell}^{VV}/(2\\pi)$ ranging from 141 $\\mu K ^2$ to 203 $\\mu K ^2$ at 150 GHz for a thermal CMB spectrum. As linear CMB polarization experiments become increasingly sensitive, the techniques described in this paper can be applied to obtain stronger constraints on circular polarization.

  15. Distribution and abundance of Antarctic krill (Euphausia superba) along the Antarctic Peninsula

    Science.gov (United States)

    Siegel, Volker; Reiss, Christian S.; Dietrich, Kimberly S.; Haraldsson, Matilda; Rohardt, Gerhard

    2013-07-01

    Net-based data on the abundance, distribution, and demographic patterns of Antarctic krill are quantified from a contemporaneous two ship survey of the Antarctic Peninsula during austral summer 2011. Two survey areas were sampled focussed on Marguerite Bay in the south, and the tip of the Antarctic Peninsula in the north. Data from 177 stations showed that the highest concentrations of krill were found in the southern sampling area. Differences between areas were associated with a few large catches of one year old krill found in anomalously warm and productive waters in Marguerite Bay, and small krill catches in the less-productive, offshore waters in the north. Estimated krill density across the survey area was 3.4 krill m-2, and was low compared to the long-term average of 45 krill m-2 for the Elephant Island area. Overall recruitment between the two survey regions was similar, but per capita recruitment was about 60% lower than historical mean recruitment levels measured at Elephant Island since the late 1970s. Demographic patterns showed small krill concentrated near the coast, and large krill concentrated offshore on the shelf and slope all along the survey area. The offshore distribution of adult krill was delineated by the warm (˜1 °C), low salinity (33.8) water at 30 m, suggesting that most krill were present shoreward of the southern boundary of Antarctic Circumpolar Current Front. Distributions of larvae indicated that three hotspot areas were important for the production of krill: slope areas outside Marguerite Bay and north of the South Shetland Islands, and near the coast around Antarctic Sound. Successful spawning, as inferred from larval abundance, was roughly coincident with the shelf break and not with inshore waters. Given the rapid changes in climate along the Antarctic Peninsula and the lower per capita recruitment observed in recent years, studies comparing and contrasting production, growth, and recruitment across the Peninsula will be

  16. Development of a Regional Glycerol Dialkyl Glycerol Tetraether (GDGT) - Temperature Calibration for Antarctic and sub-Antarctic Lakes

    Science.gov (United States)

    Roberts, S. J.; Foster, L. C.; Pearson, E. J.; Steve, J.; Hodgson, D.; Saunders, K. M.; Verleyen, E.

    2016-12-01

    Temperature calibration models based on the relative abundances of sedimentary glycerol dialkyl glycerol tetraethers (GDGTs) have been used to reconstruct past temperatures in both marine and terrestrial environments, but have not been widely applied in high latitude environments. This is mainly because the performance of GDGT-temperature calibrations at lower temperatures and GDGT provenance in many lacustrine settings remains uncertain. To address these issues, we examined surface sediments from 32 Antarctic, sub-Antarctic and Southern Chilean lakes. First, we quantified GDGT compositions present and then investigated modern-day environmental controls on GDGT composition. GDGTs were found in all 32 lakes studied. Branched GDGTs (brGDGTs) were dominant in 31 lakes and statistical analyses showed that their composition was strongly correlated with mean summer air temperature (MSAT) rather than pH, conductivity or water depth. Second, we developed the first regional brGDGT-temperature calibration for Antarctic and sub-Antarctic lakes based on four brGDGT compounds (GDGT-Ib, GDGT-II, GDGT-III and GDGT-IIIb). Of these, GDGT-IIIb proved particularly important in cold lacustrine environments. Our brGDGT-Antarctic temperature calibration dataset has an improved statistical performance at low temperatures compared to previous global calibrations (r2=0.83, RMSE=1.45°C, RMSEP-LOO=1.68°C, n=36 samples), highlighting the importance of basing palaeotemperature reconstructions on regional GDGT-temperature calibrations, especially if specific compounds lead to improved model performance. Finally, we applied the new Antarctic brGDGT-temperature calibration to two key lake records from the Antarctic Peninsula and South Georgia. In both, downcore temperature reconstructions show similarities to known Holocene warm periods, providing proof of concept for the new Antarctic calibration model.

  17. Aircraft Wake Vortex Deformation in Turbulent Atmosphere

    OpenAIRE

    Hennemann, Ingo; Holzaepfel, Frank

    2007-01-01

    Large-scale distortion of aircraft wake vortices appears to play a crucial role for aircraft safety during approach and landing. Vortex distortion is investigated based on large eddy simulations of wake vortex evolution in a turbulent atmosphere. A vortex identification method is developed that can be adapted to the vortex scales of interest. Based on the identified vortex center tracks, a statistics of vortex curvature radii is established. This statistics constitutes the basis for understan...

  18. High-charge and multiple-star vortex coronagraphy from stacked vector vortex phase masks.

    Science.gov (United States)

    Aleksanyan, Artur; Brasselet, Etienne

    2018-02-01

    Optical vortex phase masks are now installed at many ground-based large telescopes for high-contrast astronomical imaging. To date, such instrumental advances have been restricted to the use of helical phase masks of the lowest even order, while future giant telescopes will require high-order masks. Here we propose a single-stage on-axis scheme to create high-order vortex coronagraphs based on second-order vortex phase masks. By extending our approach to an off-axis design, we also explore the implementation of multiple-star vortex coronagraphy. An experimental laboratory demonstration is reported and supported by numerical simulations. These results offer a practical roadmap to the development of future coronagraphic tools with enhanced performances.

  19. Defect-Induced Hedgehog Polarization States in Multiferroics

    Science.gov (United States)

    Li, Linze; Cheng, Xiaoxing; Jokisaari, Jacob R.; Gao, Peng; Britson, Jason; Adamo, Carolina; Heikes, Colin; Schlom, Darrell G.; Chen, Long-Qing; Pan, Xiaoqing

    2018-03-01

    Continuous developments in nanotechnology require new approaches to materials synthesis that can produce novel functional structures. Here, we show that nanoscale defects, such as nonstoichiometric nanoregions (NSNRs), can act as nano-building blocks for creating complex electrical polarization structures in the prototypical multiferroic BiFeO3 . An array of charged NSNRs are produced in BiFeO3 thin films by tuning the substrate temperature during film growth. Atomic-scale scanning transmission electron microscopy imaging reveals exotic polarization rotation patterns around these NSNRs. These polarization patterns resemble hedgehog or vortex topologies and can cause local changes in lattice symmetries leading to mixed-phase structures resembling the morphotropic phase boundary with high piezoelectricity. Phase-field simulations indicate that the observed polarization configurations are mainly induced by charged states at the NSNRs. Engineering defects thus may provide a new route for developing ferroelectric- or multiferroic-based nanodevices.

  20. Regulating Antarctic Tourism and the Precautionary Principle

    NARCIS (Netherlands)

    Bastmeijer, C.J.; Roura, R.

    2004-01-01

    On the basis of an overview of the developments in Antarctic tourism since 1956, this current development note examines the issue of international regulation of Antarctic tourism. After discussing one of the main management issues in respect of Antarctic tourism ¿ the assessment and prevention of

  1. Vortex rings in classical and quantum systems

    International Nuclear Information System (INIS)

    Barenghi, C F; Donnelly, R J

    2009-01-01

    The study of vortex rings has been pursued for decades and is a particularly difficult subject. However, the discovery of quantized vortex rings in superfluid helium has greatly increased interest in vortex rings with very thin cores. While rapid progress has been made in the simulation of quantized vortex rings, there has not been comparable progress in laboratory studies of vortex rings in a viscous fluid such as water. This article overviews the history and current frontiers of classical and quantum vortex rings. After introducing the classical results, this review discusses thin-cored vortex rings in superfluid helium in section 2, and recent progress in understanding vortex rings of very thin cores propagating in water in section 3. (invited paper)

  2. Negative optical spin torque wrench of a non-diffracting non-paraxial fractional Bessel vortex beam

    International Nuclear Information System (INIS)

    Mitri, F.G.

    2016-01-01

    An absorptive Rayleigh dielectric sphere in a non-diffracting non-paraxial fractional Bessel vortex beam experiences a spin torque. The axial and transverse radiation spin torque components are evaluated in the dipole approximation using the radiative correction of the electric field. Particular emphasis is given on the polarization as well as changing the topological charge α and the half-cone angle of the beam. When α is zero, the axial spin torque component vanishes. However, when α becomes a real positive number, the vortex beam induces left-handed (negative) axial spin torque as the sphere shifts off-axially from the center of the beam. The results show that a non-diffracting non-paraxial fractional Bessel vortex beam is capable of inducing a spin reversal of an absorptive Rayleigh sphere placed arbitrarily in its path. Potential applications are yet to be explored in particle manipulation, rotation in optical tweezers, optical tractor beams, and the design of optically-engineered metamaterials to name a few areas. - Highlights: • Optical nondiffracting nonparaxial fractional Bessel vortex beam is considered. • Negative spin torque on an absorptive dielectric Rayleigh sphere is predicted numerically. • Negative spin torque occurs as the sphere departs from the center of the beam.

  3. Snow surface microbiome on the High Antarctic Plateau (DOME C).

    Science.gov (United States)

    Michaud, Luigi; Lo Giudice, Angelina; Mysara, Mohamed; Monsieurs, Pieter; Raffa, Carmela; Leys, Natalie; Amalfitano, Stefano; Van Houdt, Rob

    2014-01-01

    The cryosphere is an integral part of the global climate system and one of the major habitable ecosystems of Earth's biosphere. These permanently frozen environments harbor diverse, viable and metabolically active microbial populations that represent almost all the major phylogenetic groups. In this study, we investigated the microbial diversity in the surface snow surrounding the Concordia Research Station on the High Antarctic Plateau through a polyphasic approach, including direct prokaryotic quantification by flow cytometry and catalyzed reporter deposition fluorescence in situ hybridization (CARD-FISH), and phylogenetic identification by 16S RNA gene clone library sequencing and 454 16S amplicon pyrosequencing. Although the microbial abundance was low (<10(3) cells/ml of snowmelt), concordant results were obtained with the different techniques. The microbial community was mainly composed of members of the Alpha-proteobacteria class (e.g. Kiloniellaceae and Rhodobacteraceae), which is one of the most well-represented bacterial groups in marine habitats, Bacteroidetes (e.g. Cryomorphaceae and Flavobacteriaceae) and Cyanobacteria. Based on our results, polar microorganisms could not only be considered as deposited airborne particles, but as an active component of the snowpack ecology of the High Antarctic Plateau.

  4. Snow surface microbiome on the High Antarctic Plateau (DOME C.

    Directory of Open Access Journals (Sweden)

    Luigi Michaud

    Full Text Available The cryosphere is an integral part of the global climate system and one of the major habitable ecosystems of Earth's biosphere. These permanently frozen environments harbor diverse, viable and metabolically active microbial populations that represent almost all the major phylogenetic groups. In this study, we investigated the microbial diversity in the surface snow surrounding the Concordia Research Station on the High Antarctic Plateau through a polyphasic approach, including direct prokaryotic quantification by flow cytometry and catalyzed reporter deposition fluorescence in situ hybridization (CARD-FISH, and phylogenetic identification by 16S RNA gene clone library sequencing and 454 16S amplicon pyrosequencing. Although the microbial abundance was low (<10(3 cells/ml of snowmelt, concordant results were obtained with the different techniques. The microbial community was mainly composed of members of the Alpha-proteobacteria class (e.g. Kiloniellaceae and Rhodobacteraceae, which is one of the most well-represented bacterial groups in marine habitats, Bacteroidetes (e.g. Cryomorphaceae and Flavobacteriaceae and Cyanobacteria. Based on our results, polar microorganisms could not only be considered as deposited airborne particles, but as an active component of the snowpack ecology of the High Antarctic Plateau.

  5. On vortex shedding and prediction of vortex-induced vibrations of circular cylinders

    Energy Technology Data Exchange (ETDEWEB)

    Halse, Karl Henning

    1998-12-31

    In offshore installations, many crucial components can be classified as slender marine structures: risers, mooring lines, umbilicals and cables, pipelines. This thesis studies the vortex shedding phenomenon and the problem of predicting vortex-induced vibrations of such structures. As the development of hydrocarbons move to deeper waters, the importance of accurately predicting the vortex-induced response has increased and so the need for proper response prediction methods is large. This work presents an extensive review of existing research publications about vortex shedding from circular cylinders and the vortex-induced vibrations of cylinders and the different numerical approaches to modelling the fluid flow. The response predictions from different methods are found to disagree, both in response shapes and in vibration amplitudes. This work presents a prediction method that uses a fully three-dimensional structural finite element model integrated with a laminar two-dimensional Navier-Stokes solution modelling the fluid flow. This solution is used to study the flow both around a fixed cylinder and in a flexibly mounted one-degree-of-freedom system. It is found that the vortex-shedding process (in the low Reynolds number regime) is well described by the computer program, and that the vortex-induced vibration of the flexibly mounted section do reflect the typical dynamic characteristics of lock-in oscillations. However, the exact behaviour of the experimental results found in the literature was not reproduced. The response of the three-dimensional structural model is larger than the expected difference between a mode shape and a flexibly mounted section. This is due to the use of independent hydrodynamic sections along the cylinder. The predicted response is not unrealistic, and the method is considered a powerful tool. 221 refs., 138 figs., 36 tabs.

  6. On vortex shedding and prediction of vortex-induced vibrations of circular cylinders

    Energy Technology Data Exchange (ETDEWEB)

    Halse, Karl Henning

    1997-12-31

    In offshore installations, many crucial components can be classified as slender marine structures: risers, mooring lines, umbilicals and cables, pipelines. This thesis studies the vortex shedding phenomenon and the problem of predicting vortex-induced vibrations of such structures. As the development of hydrocarbons move to deeper waters, the importance of accurately predicting the vortex-induced response has increased and so the need for proper response prediction methods is large. This work presents an extensive review of existing research publications about vortex shedding from circular cylinders and the vortex-induced vibrations of cylinders and the different numerical approaches to modelling the fluid flow. The response predictions from different methods are found to disagree, both in response shapes and in vibration amplitudes. This work presents a prediction method that uses a fully three-dimensional structural finite element model integrated with a laminar two-dimensional Navier-Stokes solution modelling the fluid flow. This solution is used to study the flow both around a fixed cylinder and in a flexibly mounted one-degree-of-freedom system. It is found that the vortex-shedding process (in the low Reynolds number regime) is well described by the computer program, and that the vortex-induced vibration of the flexibly mounted section do reflect the typical dynamic characteristics of lock-in oscillations. However, the exact behaviour of the experimental results found in the literature was not reproduced. The response of the three-dimensional structural model is larger than the expected difference between a mode shape and a flexibly mounted section. This is due to the use of independent hydrodynamic sections along the cylinder. The predicted response is not unrealistic, and the method is considered a powerful tool. 221 refs., 138 figs., 36 tabs.

  7. Antarctic news clips, 1991

    Science.gov (United States)

    1991-08-01

    Published stories are presented that sample a year's news coverage of Antarctica. The intent is to provide the U.S. Antarctic Program participants with a digest of current issues as presented by a variety of writers and popular publications. The subject areas covered include the following: earth science; ice studies; stratospheric ozone; astrophysics; life science; operations; education; antarctic treaty issues; and tourism

  8. Antarctic 20th Century Accumulation Changes Based on Regional Climate Model Simulations

    Directory of Open Access Journals (Sweden)

    Klaus Dethloff

    2010-01-01

    investigated on the basis of ERA-40 data and HIRHAM simulations. It is shown that the regional accumulation changes are largely driven by changes in the transient activity around the Antarctic coasts due to the varying AAO phases. During positive AAO, more transient pressure systems travelling towards the continent, and Western Antarctica and parts of South-Eastern Antarctica gain more precipitation and mass. Over central Antarctica the prevailing anticyclone causes a strengthening of polar desertification connected with a reduced surface mass balance in the northern part of East Antarctica.

  9. Regional genetic diversity patterns in Antarctic hairgrass (Deschampsia antartica Desv.)

    NARCIS (Netherlands)

    van de Wouw, M.J.; Van Dijk, P.J.; Huiskes, A.H.L.

    2008-01-01

    Aim To determine patterns in diversity of a major Antarctic plant species, including relationships of Antarctic populations with those outside the Antarctic zone. Location Antarctic Peninsula, Maritime Antarctica, sub-Antarctic islands, Falkland Islands and South America. Methods Amplified fragment

  10. To the Extremes! A Teacher Research Experience Program in the Polar Regions

    Science.gov (United States)

    Warburton, J.; Bartholow, S.

    2014-12-01

    PolarTREC-Teachers and Researchers Exploring and Collaborating, a teacher professional development program, began with the International Polar Year in 2004 and continues today in the United States. In 2007, the National Science Foundation designated PolarTREC as potentially transformative, meaning that the "research results often do not fit within established models or theories and may initially be unexpected or difficult to interpret; their transformative nature and utility might not be recognized until years later." PolarTREC brings U.S. K-12 educators and polar researchers together through an innovative teacher research experience model. Teachers spend three to six weeks in remote arctic and Antarctic field camps. Since 2007, over 100 teachers have been placed in field experiences throughout the Arctic and Antarctic and with half of them participating in field experiences in Antarctica. During their experience, teachers become research team members filling a variety of roles on the team. They also fulfil a unique role of public outreach officer, conducting live presentations about their field site and research as well as journaling, answering questions, and posting photos. Evaluation data collected over the past eight years on program participants shows that PolarTREC has clearly achieved it goals and strongly suggests programs that link teachers and researchers can have the potential to transform the nature of science education. By giving teachers the content knowledge, pedagogical tools, confidence, understanding of science in the broader society, and experiences with scientific inquiry, participating teachers are using authentic scientific research in their classrooms. Not surprisingly this has also led to increases in student interest and knowledge about the Polar Regions. In this presentation, we will highlight the best practices of teacher research experiences as well as discuss why it is vital to have teachers and researchers work together to communicate

  11. Lift enhancement by trapped vortex

    Science.gov (United States)

    Rossow, Vernon J.

    1992-01-01

    The viewgraphs and discussion of lift enhancement by trapped vortex are provided. Efforts are continuously being made to find simple ways to convert wings of aircraft from an efficient cruise configuration to one that develops the high lift needed during landing and takeoff. The high-lift configurations studied here consist of conventional airfoils with a trapped vortex over the upper surface. The vortex is trapped by one or two vertical fences that serve as barriers to the oncoming stream and as reflection planes for the vortex and the sink that form a separation bubble on top of the airfoil. Since the full three-dimensional unsteady flow problem over the wing of an aircraft is so complicated that it is hard to get an understanding of the principles that govern the vortex trapping process, the analysis is restricted here to the flow field illustrated in the first slide. It is assumed that the flow field between the two end plates approximates a streamwise strip of the flow over a wing. The flow between the endplates and about the airfoil consists of a spanwise vortex located between the suction orifices in the endplates. The spanwise fence or spoiler located near the nose of the airfoil serves to form a separated flow region and a shear layer. The vorticity in the shear layer is concentrated into the vortex by withdrawal of fluid at the suction orifices. As the strength of the vortex increases with time, it eventually dominates the flow in the separated region so that a shear or vertical layer is no longer shed from the tip of the fence. At that point, the vortex strength is fixed and its location is such that all of the velocity contributions at its center sum to zero thereby making it an equilibrium point for the vortex. The results of a theoretical analysis of such an idealized flow field are described.

  12. Vortex Ring Dynamics in Radially Confined Domains

    Science.gov (United States)

    Stewart, Kelley; Niebel, Casandra; Jung, Sunghwan; Vlachos, Pavlos

    2010-11-01

    Vortex ring dynamics have been studied extensively in semi-infinite quiescent volumes. However, very little is known about vortex-ring formation in wall-bounded domains where vortex wall interaction will affect both the vortex ring pinch-off and propagation velocity. This study addresses this limitation and studies vortex formation in radially confined domains to analyze the affect of vortex-ring wall interaction on the formation and propagation of the vortex ring. Vortex rings were produced using a pneumatically driven piston cylinder arrangement and were ejected into a long cylindrical tube which defined the confined downstream domain. A range of confinement domains were studied with varying confinement diameters Velocity field measurements were performed using planar Time Resolved Digital Particle Image Velocimetry (TRDPIV) and were processed using an in-house developed cross-correlation PIV algorithm. The experimental analysis was used to facilitate the development of a theoretical model to predict the variations in vortex ring circulation over time within confined domains.

  13. Evaluation of soil bioremediation techniques in an aged diesel spill at the Antarctic Peninsula.

    Science.gov (United States)

    de Jesus, Hugo E; Peixoto, Raquel S; Cury, Juliano C; van Elsas, Jan D; Rosado, Alexandre S

    2015-12-01

    Many areas on the Antarctic continent already suffer from the direct and indirect influences of human activities. The main cause of contamination is petroleum hydrocarbons because this compound is used as a source of energy at the many research stations around the continent. Thus, the current study aims to evaluate treatments for bioremediation (biostimulation, bioaugmentation, and bioaugmentation + biostimulation) using soils from around the Brazilian Antarctic Station "Comandante Ferraz" (EACF), King George Island, Antarctic Peninsula. The experiment lasted for 45 days, and at the end of this period, chemical and molecular analyses were performed. Those analyses included the quantification of carbon and nitrogen, denaturing gradient gel electrophoresis (DGGE) analysis (with gradient denaturation), real-time PCR, and quantification of total hydrocarbons and polyaromatics. Molecular tests evaluated changes in the profile and quantity of the rrs genes of archaea and bacteria and also the alkB gene. The influence of the treatments tested was directly related to the type of soil used. The work confirmed that despite the extreme conditions found in Antarctic soils, the bacterial strains degraded hydrocarbons and bioremediation treatments directly influenced the microbial communities present in these soils even in short periods. Although the majority of the previous studies demonstrate that the addition of fertilizer seems to be most effective at promoting bioremediation, our results show that for some conditions, autochthonous bioaugmentation (ABA) treatment is indicated. This work highlights the importance of understanding the processes of recovery of contaminated environments in polar regions because time is crucial to the soil recovery and to choosing the appropriate treatment.

  14. Acoustic scattering of a Bessel vortex beam by a rigid fixed spheroid

    Science.gov (United States)

    Mitri, F. G.

    2015-12-01

    Partial-wave series representation of the acoustic scattering field of high-order Bessel vortex beams by rigid oblate and prolate spheroids using the modal matching method is developed. The method, which is applicable to slightly elongated objects at low-to-moderate frequencies, requires solving a system of linear equations which depends on the partial-wave index n and the order of the Bessel vortex beam m using truncated partial-wave series expansions (PWSEs), and satisfying the Neumann boundary condition for a rigid immovable surface in the least-squares sense. This original semi-analytical approach developed for Bessel vortex beams is demonstrated for finite oblate and prolate spheroids, where the mathematical functions describing the spheroidal geometry are written in a form involving single angular (polar) integrals that are numerically computed. The transverse (θ = π / 2) and 3D scattering directivity patterns are evaluated in the far-field for both prolate and oblate spheroids, with particular emphasis on the aspect ratio (i.e., the ratio of the major axis over the minor axis of the spheroid) not exceeding 3:1, the half-cone angle β and order m of the Bessel vortex beam, as well as the dimensionless size parameter kr0. Periodic oscillations in the magnitude plots of the far-field scattering form function are observed, which result from the interference of the reflected waves with the circumferential (Franz') waves circumnavigating the surface of the spheroid in the surrounding fluid. Moreover, the 3D directivity patterns illustrate the far-field scattering from the spheroid, that vanishes in the forward (θ = 0) and backward (θ = π) directions. Particular applications in underwater acoustics and scattering, acoustic levitation and the detection of submerged elongated objects using Bessel vortex waves to name a few, would benefit from the results of the present investigation.

  15. Controlling vortex motion and vortex kinetic friction

    International Nuclear Information System (INIS)

    Nori, Franco; Savel'ev, Sergey

    2006-01-01

    We summarize some recent results of vortex motion control and vortex kinetic friction. (1) We describe a device [J.E. Villegas, S. Savel'ev, F. Nori, E.M. Gonzalez, J.V. Anguita, R. Garcia, J.L. Vicent, Science 302 (2003) 1188] that can easily control the motion of flux quanta in a Niobium superconducting film on an array of nanoscale triangular magnets. Even though the input ac current has zero average, the resulting net motion of the vortices can be directed along either one direction, the opposite direction, or producing zero net motion. We also consider layered strongly anisotropic superconductors, with no fixed spatial asymmetry, and show [S. Savel'ev, F. Nori, Nature Materials 1 (2002) 179] how, with asymmetric drives, the ac motion of Josephson and/or pancake vortices can provide a net dc vortex current. (2) In analogy with the standard macroscopic friction, we present [A. Maeda, Y. Inoue, H. Kitano, S. Savel'ev, S. Okayasu, I. Tsukada, F. Nori , Phys. Rev. Lett. 94 (2005) 077001] a comparative study of the friction force felt by vortices in superconductors and charge density waves

  16. Controlling vortex motion and vortex kinetic friction

    Science.gov (United States)

    Nori, Franco; Savel'ev, Sergey

    2006-05-01

    We summarize some recent results of vortex motion control and vortex kinetic friction. (1) We describe a device [J.E. Villegas, S. Savel'ev, F. Nori, E.M. Gonzalez, J.V. Anguita, R. Garcìa, J.L. Vicent, Science 302 (2003) 1188] that can easily control the motion of flux quanta in a Niobium superconducting film on an array of nanoscale triangular magnets. Even though the input ac current has zero average, the resulting net motion of the vortices can be directed along either one direction, the opposite direction, or producing zero net motion. We also consider layered strongly anisotropic superconductors, with no fixed spatial asymmetry, and show [S. Savel'ev, F. Nori, Nature Materials 1 (2002) 179] how, with asymmetric drives, the ac motion of Josephson and/or pancake vortices can provide a net dc vortex current. (2) In analogy with the standard macroscopic friction, we present [A. Maeda, Y. Inoue, H. Kitano, S. Savel'ev, S. Okayasu, I. Tsukada, F. Nori , Phys. Rev. Lett. 94 (2005) 077001] a comparative study of the friction force felt by vortices in superconductors and charge density waves.

  17. Draft genome of the Antarctic dragonfish, Parachaenichthys charcoti.

    Science.gov (United States)

    Ahn, Do-Hwan; Shin, Seung Chul; Kim, Bo-Mi; Kang, Seunghyun; Kim, Jin-Hyoung; Ahn, Inhye; Park, Joonho; Park, Hyun

    2017-08-01

    The Antarctic bathydraconid dragonfish, Parachaenichthys charcoti, is an Antarctic notothenioid teleost endemic to the Southern Ocean. The Southern Ocean has cooled to -1.8ºC over the past 30 million years, and the seawater had retained this cold temperature and isolated oceanic environment because of the Antarctic Circumpolar Current. Notothenioids dominate Antarctic fish, making up 90% of the biomass, and all notothenioids have undergone molecular and ecological diversification to survive in this cold environment. Therefore, they are considered an attractive Antarctic fish model for evolutionary and ancestral genomic studies. Bathydraconidae is a speciose family of the Notothenioidei, the dominant taxonomic component of Antarctic teleosts. To understand the process of evolution of Antarctic fish, we select a typical Antarctic bathydraconid dragonfish, P. charcoti. Here, we have sequenced, de novo assembled, and annotated a comprehensive genome from P. charcoti. The draft genome of P. charcoti is 709 Mb in size. The N50 contig length is 6145 bp, and its N50 scaffold length 178 362 kb. The genome of P. charcoti is predicted to contain 32 712 genes, 18 455 of which have been assigned preliminary functions. A total of 8951 orthologous groups common to 7 species of fish were identified, while 333 genes were identified in P. charcoti only; 2519 orthologous groups were also identified in both P. charcoti and N. coriiceps, another Antarctic fish. Four gene ontology terms were statistically overrepresented among the 333 genes unique to P. charcoti, according to gene ontology enrichment analysis. The draft P. charcoti genome will broaden our understanding of the evolution of Antarctic fish in their extreme environment. It will provide a basis for further investigating the unusual characteristics of Antarctic fishes. © The Author 2017. Published by Oxford University Press.

  18. What Controls the Size of the Antarctic Ozone Hole?

    Science.gov (United States)

    Bhartia, P. K. (Technical Monitor); Newman, Paul A.; Kawa, S. Randolph; Nash, Eric R.

    2002-01-01

    The Antarctic ozone hole is a region of extremely large ozone depletion that is roughly centered over the South Pole. Since 1979, the area coverage of the ozone hole has grown from near zero size to over 24 Million square kilometers. In the 8-year period from 1981 to 1989, the area expanded by 18 Million square kilometers. During the last 5 years, the hole has been observed to exceed 25 Million square kilometers over brief periods. We will review these size observations, the size trends, and the interannual variability of the size. The area is derived from the area enclosed by the 220 DU total ozone contour. We will discuss the rationale for the choice of 220 DU: 1) it is located near the steep gradient between southern mid-latitudes and the polar region, and 2) 220 DU is a value that is lower than the pre- 1979 ozone observations over Antarctica during the spring period. The phenomenal growth of the ozone hole was directly caused by the increases of chlorine and bromine compounds in the stratosphere. In this talk, we will show the relationship of the ozone hole's size to the interannual variability of Antarctic spring temperatures. In addition, we will show the relationship of these same temperatures to planetary-scale wave forcings.

  19. Interaction of Vortex Ring with Cutting Plate

    Science.gov (United States)

    Musta, Mustafa

    2015-11-01

    The interaction of a vortex ring impinging on a thin cutting plate was made experimentally using Volumetric 3-component Velocitmetry (v3v) technique. The vortex rings were generated with piston-cylinder vortex ring generator using piston stroke-to-diameter ratios and Re at 2-3 and 1500 - 3000, respectively. The cutting of vortex rings below center line leads to the formation of secondary vortices on each side of the plate which is look like two vortex rings, and a third vortex ring propagates further downstream in the direction of the initial vortex ring, which is previously showed by flow visualization study of Weigand (1993) and called ``trifurcation''. Trifurcation is very sensitive to the initial Reynolds number and the position of the plate with respect to the vortex ring generator pipe. The present work seeks more detailed investigation on the trifurcation using V3V technique. Conditions for the formation of trifurcation is analyzed and compared with Weigand (1993). The formed secondary vortex rings and the propagation of initial vortex ring in the downstream of the plate are analyzed by calculating their circulation, energy and trajectories.

  20. The Polar Rock Repository: Rescuing Polar Collections for New Research

    Science.gov (United States)

    Grunow, A.

    2016-12-01

    Geological field expeditions in polar regions are logistically difficult, financially expensive and can have a significant environmental impact on pristine regions. The scarcity of outcrop in Antarctica (98% ice-covered) makes previously collected rock samples very valuable to the science community. NSF recognized the need for preserving rock, dredge, and terrestrial core samples from polar areas and created the Polar Rock Repository (PRR). The PRR collection allows for full and open access to both samples and metadata via the PRR website. In addition to the physical samples and their basic metadata, the PRR archives supporting materials from the collector, field notebooks, images of the samples, field maps, air photos, thin sections and any associated bibliography/DOI's. Many of these supporting materials are unique. More than 40,000 samples are available from the PRR for scientific analysis to researchers around the globe. Most of the samples cataloged at the PRR were collected more than 30 years ago, some more than 100 years ago. The rock samples and metadata are made available online through an advanced search engine for the PRR website. This allows scientists to "drill down" into search results using categories and look-up object fields similar to websites like Amazon. Results can be viewed in a table, downloaded as a spreadsheet, or plotted on an interactive map that supports display of satellite imagery and bathymetry layers. Samples can be requested by placing them in the `shopping cart'. These old sample collections have been repeatedly used by scientists from around the world. One data request involved locating coal deposits in Antarctica for a global compilation and another for looking at the redox state of batholithic rocks from the Antarctic Peninsula using magnetic susceptibilities of PRR rocks. Sample usage has also included non-traditional geologic studies, such as a search for monopoles in Cenozoic volcanic samples, and remote sensing

  1. Electric vortex in MHD flow

    International Nuclear Information System (INIS)

    Garcia, M.

    1995-01-01

    An electric vortex is the circulation of electron space charge about a magnetic field line that is transported by ion momentum. In cold, or low β flow the vortex diameter is the minimum length scale of charge neutrality. The distinctive feature of the vortex is its radial electric field which manifests the interplay of electrostatics, magnetism, and motion

  2. Some observations of tip-vortex cavitation

    Science.gov (United States)

    Arndt, R. E. A.; Arakeri, V. H.; Higuchi, H.

    1991-08-01

    Cavitation has been observed in the trailing vortex system of an elliptic platform hydrofoil. A complex dependence on Reynolds number and gas content is noted at inception. Some of the observations can be related to tension effects associated with the lack of sufficiently large-sized nuclei. Inception measurements are compared with estimates of pressure in the vortex obtained from LDV measurements of velocity within the vortex. It is concluded that a complete correlation is not possible without knowledge of the fluctuating levels of pressure in tip-vortex flows. When cavitation is fully developed, the observed tip-vortex trajectory flows. When cavitation is fully developed, the observed tip-vortex trajectory shows a surprising lack of dependence on any of the physical parameters varied, such as angle of attack, Reynolds number, cavitation number, and dissolved gas content.

  3. Personal care products and steroid hormones in the Antarctic coastal environment associated with two Antarctic research stations, McMurdo Station and Scott Base.

    Science.gov (United States)

    Emnet, Philipp; Gaw, Sally; Northcott, Grant; Storey, Bryan; Graham, Lisa

    2015-01-01

    Pharmaceutical and personal care products (PPCPs) are a major source of micropollutants to the aquatic environment. Despite intense research on the fate and effects of PPCPs in temperate climates, there is a paucity of data on their presence in polar environments. This study reports the presence of selected PPCPs in sewage effluents from two Antarctic research stations, the adjacent coastal seawater, sea ice, and biota. Sewage effluents contained bisphenol-A, ethinylestradiol, estrone, methyl triclosan, octylphenol, triclosan, and three UV-filters. The maximum sewage effluent concentrations of 4-methyl-benzylidene camphor, benzophenone-1, estrone, ethinylestradiol, and octylphenol exceeded concentrations previously reported. Coastal seawaters contained bisphenol-A, octylphenol, triclosan, three paraben preservatives, and four UV-filters. The sea ice contained a similar range and concentration of PPCPs as the seawater. Benzophenone-3 (preferential accumulation in clams), estradiol, ethinylestradiol, methyl paraben (preferential accumulation in fish, with concentrations correlating negatively with fillet size), octylphenol, and propyl paraben were detected in biota samples. PPCPs were detected in seawater and biota at distances up to 25 km from the research stations WWTP discharges. Sewage effluent discharges and disposal of raw human waste through sea ice cracks have been identified as sources of PPCPs to Antarctic coastal environments. Copyright © 2014 Elsevier Inc. All rights reserved.

  4. Can gravity waves significantly impact PSC occurrence in the Antarctic?

    Directory of Open Access Journals (Sweden)

    R. M. Woollands

    2009-11-01

    Full Text Available A combination of POAM III aerosol extinction and CHAMP RO temperature measurements are used to examine the role of atmospheric gravity waves in the formation of Antarctic Polar Stratospheric Clouds (PSCs. POAM III aerosol extinction observations and quality flag information are used to identify Polar Stratospheric Clouds using an unsupervised clustering algorithm.

    A PSC proxy, derived by thresholding Met Office temperature analyses with the PSC Type Ia formation temperature (TNAT, shows general agreement with the results of the POAM III analysis. However, in June the POAM III observations of PSC are more abundant than expected from temperature threshold crossings in five out of the eight years examined. In addition, September and October PSC identified using temperature thresholding is often significantly higher than that derived from POAM III; this observation probably being due to dehydration and denitrification. Comparison of the Met Office temperature analyses with corresponding CHAMP observations also suggests a small warm bias in the Met Office data in June. However, this bias cannot fully explain the differences observed.

    Analysis of CHAMP data indicates that temperature perturbations associated with gravity waves may partially explain the enhanced PSC incidence observed in June (relative to the Met Office analyses. For this month, approximately 40% of the temperature threshold crossings observed using CHAMP RO data are associated with small-scale perturbations. Examination of the distribution of temperatures relative to TNAT shows a large proportion of June data to be close to this threshold, potentially enhancing the importance of gravity wave induced temperature perturbations. Inspection of the longitudinal structure of PSC occurrence in June 2005 also shows that regions of enhancement are geographically associated with the Antarctic Peninsula; a known mountain wave "hotspot". The

  5. Growth dynamics of Australia's polar dinosaurs.

    Directory of Open Access Journals (Sweden)

    Holly N Woodward

    Full Text Available Analysis of bone microstructure in ornithopod and theropod dinosaurs from Victoria, Australia, documents ontogenetic changes, providing insight into the dinosaurs' successful habitation of Cretaceous Antarctic environments. Woven-fibered bone tissue in the smallest specimens indicates rapid growth rates during early ontogeny. Later ontogeny is marked by parallel-fibered tissue, suggesting reduced growth rates approaching skeletal maturity. Bone microstructure similarities between the ornithopods and theropods, including the presence of LAGs in each group, suggest there is no osteohistologic evidence supporting the hypothesis that polar theropods hibernated seasonally. Results instead suggest high-latitude dinosaurs had growth trajectories similar to their lower-latitude relatives and thus, rapid early ontogenetic growth and the cyclical suspensions of growth inherent in the theropod and ornithopod lineages enabled them to successfully exploit polar regions.

  6. Computing the flow past Vortex Generators: Comparison between RANS Simulations and Experiments

    DEFF Research Database (Denmark)

    Manolesos, M.; Sørensen, Niels N.; Troldborg, Niels

    2016-01-01

    The flow around a wind turbine airfoil equipped with Vortex Generators (VGs) is examined. Predictions from three different Reynolds Averaged Navier Stokes (RANS) solvers with two different turbulence models and two different VG modelling approaches are compared between them and with experimental ...... data. The best results are obtained with the more expensive fully resolved VG approach. The cost efficient BAY model can also provide acceptable results, if grid related numerical diffusion is minimized and only force coefficient polars are considered....

  7. Air-sea interaction regimes in the sub-Antarctic Southern Ocean and Antarctic marginal ice zone revealed by icebreaker measurements

    Science.gov (United States)

    Yu, Lisan; Jin, Xiangze; Schulz, Eric W.; Josey, Simon A.

    2017-08-01

    This study analyzed shipboard air-sea measurements acquired by the icebreaker Aurora Australis during its off-winter operation in December 2010 to May 2012. Mean conditions over 7 months (October-April) were compiled from a total of 22 ship tracks. The icebreaker traversed the water between Hobart, Tasmania, and the Antarctic continent, providing valuable in situ insight into two dynamically important, yet poorly sampled, regimes: the sub-Antarctic Southern Ocean and the Antarctic marginal ice zone (MIZ) in the Indian Ocean sector. The transition from the open water to the ice-covered surface creates sharp changes in albedo, surface roughness, and air temperature, leading to consequential effects on air-sea variables and fluxes. Major effort was made to estimate the air-sea fluxes in the MIZ using the bulk flux algorithms that are tuned specifically for the sea-ice effects, while computing the fluxes over the sub-Antarctic section using the COARE3.0 algorithm. The study evidenced strong sea-ice modulations on winds, with the southerly airflow showing deceleration (convergence) in the MIZ and acceleration (divergence) when moving away from the MIZ. Marked seasonal variations in heat exchanges between the atmosphere and the ice margin were noted. The monotonic increase in turbulent latent and sensible heat fluxes after summer turned the MIZ quickly into a heat loss regime, while at the same time the sub-Antarctic surface water continued to receive heat from the atmosphere. The drastic increase in turbulent heat loss in the MIZ contrasted sharply to the nonsignificant and seasonally invariant turbulent heat loss over the sub-Antarctic open water.Plain Language SummaryThe icebreaker Aurora Australis is a research and supply vessel that is regularly chartered by the Australian Antarctic Division during the southern summer to operate in waters between Hobart, Tasmania, and Antarctica. The vessel serves as the main lifeline to three permanent research stations on the

  8. Regimes of flow past a vortex generator

    DEFF Research Database (Denmark)

    Velte, Clara Marika; Okulov, V.L.; Naumov, I.V.

    2012-01-01

    A complete parametric investigation of the development of multi-vortex regimes in a wake past simple vortex generator has been carried out. It is established that the vortex structure in the wake is much more complicated than a simple monopole tip vortex. The vortices were studied by stereoscopic...... particle image velocimetry (SPIV). Based on the obtained SPIV data, a map of the regimes of flow past the vortex generator has been constructed. One region with a developed stable multivortex system on this map reaches the vicinity of the optimum angle of attack of the vortex generator....

  9. Lichen flora around the Korean Antarctic Scientific Station, King George Island, Antarctic.

    Science.gov (United States)

    Kim, Ji Hee; Ahn, In-Young; Hong, Soon Gyu; Andreev, Mikhail; Lim, Kwang-Mi; Oh, Mi Jin; Koh, Young Jin; Hur, Jae-Seoun

    2006-10-01

    As part of the long-term monitoring projects on Antarctic terrestrial vegetation in relation to global climate change, a lichen floristical survey was conducted around the Korean Antarctic Station (King Sejong Station), which is located on Barton Peninsula, King George Island, in January and February of 2006. Two hundred and twenty-five lichen specimens were collected and sixty-two lichen species in 38 genera were identified by morphological characteristics, chemical constituents, TLC analysis and ITS nucleotide sequence analysis.

  10. Laboratory demonstration of an optical vortex mask coronagraph using photonic crystal

    Science.gov (United States)

    Murakami, N.; Baba, N.; Ise, A.; Sakamoto, M.; Oka, K.

    2010-10-01

    Photonic crystal, artificial periodic nanostructure, is an attractive device for constructing focal-plane phase-mask coronagraphs such as segmented phase masks (four-quadrant, eight-octant, and 4N-segmented ones) and an optical vortex mask (OVM), because of its extremely small manufacturing defect. Recently, speckle-noise limited contrast has been demonstrated for two monochromatic lasers by using the eight-octant phase-mask made of the photonic crystal (Murakami et al. 2010, ApJ, 714, 772). We applied the photonic-crystal device to the OVM coronagraph. The OVM is more advantageous over the segmented phase masks because it does not have discontinuities other than a central singular point and provides a full on-sky field of view. For generating an achromatic optical vortex, we manufactured an axially-symmetric half-wave plate (ASHWP). It is expected that a size of the manufacturing defect due to the central singularity is an order of several hundreds nanometers. The ASHWP is placed between two circular polarizers for modulating a Pancharatnam phase. A continuous spiral phase modulation is then implemented achromatically. We carried out preliminary laboratory demonstration of the OVM coronagraph using two monochromatic lasers as a model star (wavelengths of 532 nm and 633 nm). We report a principle of the achromatic optical-vortex generation, and results of the laboratory demonstration of the OVM coronagraph.

  11. Focusing properties of cylindrical vector vortex beams

    Science.gov (United States)

    Xiaoqiang, Zhang; Ruishan, Chen; Anting, Wang

    2018-05-01

    In this paper, following Richards and Wolf vectorial diffraction theory, the focusing properties of cylindrical vector vortex beams (CVVB) are investigated, and a diffractive optical element (DOE) is designed to spatially modulate the amplitude of the CVVB. Simulated results show that the CVVB focused by an objective also carry orbital angular momentum (OAM), and the optical fields near the focal region can be modulated by changing the topological charge of the CVVB. We numerically simulate the focus properties of radially and azimuthally polarized beams with topological charge equal to 0, 1, 2 and 10 respectively. As a result, a dark channel with a length about 20 λ can be obtained. These new properties have the potential applications such as particle acceleration, optical trapping and material processing.

  12. RADARSAT: The Antarctic Mapping Project

    Science.gov (United States)

    Jezek, Kenneth C.; Lindstrom, E. (Technical Monitor)

    2002-01-01

    The first Antarctic Imaging Campaign (AIC) occurred during the period September 9, 1997 through October 20, 1997. The AIC utilized the unique attributes of the Canadian RADARSAT-1 to acquire the first, high-resolution, synthetic aperture imagery covering the entire Antarctic Continent. Although the primary goal of the mission was the acquisition of image data, the nearly flawless execution of the mission enabled additional collections of exact repeat orbit data. These data, covering an extensive portion of the interior Antarctic, potentially are suitable for interferometric analysis of topography and surface velocity. This document summarizes the Project through completion with delivery of products to the NASA DAACs.

  13. Imported anthropogenic bacteria may survive the Antarctic winter and introduce new genes into local bacterial communities

    Directory of Open Access Journals (Sweden)

    Brat Kristian

    2016-03-01

    Full Text Available We studied dynamic changes in anthropogenic bacterial communities at a summer-operated Czech research base (the Mendel Research Station in the Antarctic during 2012 and 2013. We observed an increase in total numbers of detected bacteria between the beginning and the end of each stay in the Antarctic. In the first series of samples, bacteria of Bacillus sp. predominated. Surprisingly, high numbers of Gram-positive cocci and coliforms were found (including opportunistic human pathogens, although the conditions for bacterial life were unfavourable (Antarctic winter. In the second series of samples, coliforms and Gram-positive cocci predominated. Dangerous human pathogens were also detected. Yersinia enterocolitica was identified as serotype O:9. Antibiotic susceptibility testing showed medium-to-high resistance rates to ampicillin, cefalotin, cefuroxime, amoxicillin-clavulanate and gentamicin in Enterobacteriaceae. 16S rRNA sequencing showed high rates of accordance between nucleotide sequences among the tested strains. Three conclusions were drawn: (1 Number of anthropogenic bacteria were able to survive the harsh conditions of the Antarctic winter (inside and outside the polar station. Under certain circumstances (e.g. impaired immunity, the surviving bacteria might pose a health risk to the participants of future expeditions or to other visitors to the base. (2 The bacteria released into the outer environment might have impacts on local ecosystems. (3 New characteristics (e.g. resistance to antibiotics may be introduced into local bacterial communities.

  14. Spectral analysis of point-vortex dynamics: first application to vortex polygons in a circular domain

    International Nuclear Information System (INIS)

    Speetjens, M F M; Meleshko, V V; Van Heijst, G J F

    2014-01-01

    The present study addresses the classical problem of the dynamics and stability of a cluster of N-point vortices of equal strength arranged in a polygonal configuration (‘N-vortex polygons’). In unbounded domains, such N-vortex polygons are unconditionally stable for N⩽7. Confinement in a circular domain tightens the stability conditions to N⩽6 and a maximum polygon size relative to the domain radius. This work expands on existing studies on stability and integrability by a first giving an exploratory spectral analysis of the dynamics of N vortex polygons in circular domains. Key to this is that the spectral signature of the time evolution of vortex positions reflects their qualitative behaviour. Expressing vortex motion by a generic evolution operator (the so-called Koopman operator) provides a rigorous framework for such spectral analyses. This paves the way to further differentiation and classification of point-vortex behaviour beyond stability and integrability. The concept of Koopman-based spectral analysis is demonstrated for N-vortex polygons. This reveals that conditional stability can be seen as a local form of integrability and confirms an important generic link between spectrum and dynamics: discrete spectra imply regular (quasi-periodic) motion; continuous (sub-)spectra imply chaotic motion. Moreover, this exposes rich nonlinear dynamics as intermittency between regular and chaotic motion and quasi-coherent structures formed by chaotic vortices. (ss 1)

  15. Vortex diode jet

    Science.gov (United States)

    Houck, Edward D.

    1994-01-01

    A fluid transfer system that combines a vortex diode with a jet ejector to transfer liquid from one tank to a second tank by a gas pressurization method having no moving mechanical parts in the fluid system. The vortex diode is a device that has a high resistance to flow in one direction and a low resistance to flow in the other.

  16. Polarization Properties of Laser Solitons

    Directory of Open Access Journals (Sweden)

    Pedro Rodriguez

    2017-04-01

    Full Text Available The objective of this paper is to summarize the results obtained for the state of polarization in the emission of a vertical-cavity surface-emitting laser with frequency-selective feedback added. We start our research with the single soliton; this situation presents two perpendicular main orientations, connected by a hysteresis loop. In addition, we also find the formation of a ring-shaped intensity distribution, the vortex state, that shows two homogeneous states of polarization with very close values to those found in the soliton. For both cases above, the study shows the spatially resolved value of the orientation angle. It is important to also remark the appearance of a non-negligible amount of circular light that gives vectorial character to all the different emissions investigated.

  17. Decreasing vortex flux in channels

    International Nuclear Information System (INIS)

    Migaj, V.K.; Nosova, I.S.

    1979-01-01

    A new method for reducing vortex flow losses in power plant channels is suggested. The method is based on vortex splitting in vortex flow areas with transverse barriers placed on the channel walls. The upper barrier ends are at the level of the upper boundary of the vortex area and don't protrude to the active flow beyond this boundary. The effectiveness of the method suggested is illustrated taking as an example the investigation of square and flat channels with abrupt widening in one plane, diffusers with widening in one plane, or a rectangualr bend. It is shown that splitting the vortex areas with transverse barriers in the channels results in reduction of hydraulic losses by 10-25%. The above method is characteristic of an extreme simplicity, its application doesn't require changes in the channel shape nor installation of any devices in the flow

  18. Mesoscale distribution of dominant diatom species relative to the hydrographical field along the Antarctic Polar Front

    Science.gov (United States)

    Smetacek, Victor; Klaas, Christine; Menden-Deuer, Susanne; Rynearson, Tatiana A.

    The quantitative distribution of dominant phytoplankton species was mapped at high spatial resolution (15 km spacing) during a quasi-synoptic, mesoscale survey of hydrographical, chemical, pigment, and zooplankton fields carried out along the Antarctic Polar Front within a grid 140×130 km 2 during austral summer. A rapid assessment method for quantifying phytoplankton species by microscopy in concentrated samples on board enabled estimation of total biomass and that of dominant species at hourly sampling intervals. The biomass distribution pattern derived from this method was remarkably coherent and correlated very well with chlorophyll concentrations and the location of different water masses covered by the grid. A "background" chlorophyll concentration of 0.5 mg m -3 in the grid could be assigned to the uniformly distributed pico- and nanophytoplankton; all higher values (up to 2.0 mg m -3) were contributed by large diatoms. Three species complexes ( Chaetoceros atlanticus/dichaeta, Pseudo-nitzschia cf. Lineola, and Thalassiothrix antarctica) contributed about one-third each to the biomass. Although all species were found throughout the study area, distinct patterns in abundance emerged: The Thalassiothrix maximum was located north of the frontal jet, Chaetoceros biomass was highest along the jet, and Pseudo-nitzschia was the most uniformly distributed of the three taxa. Since the meridional pattern of biomass and species composition persisted for about 5 weeks, despite heavy grazing pressure of small copepods, we hypothesize that the dominant species reflect the highest degree of grazer protection in the assemblage. This is accomplished by large size, needle-shaped cells, and long spines armed with barbs. We suggest that these persistent species sequester the limiting nutrient—iron—from the assemblage of smaller, less-defended species that must hence have higher turn-over rates.

  19. Trans-Atlantic variability in ecology of the pelagic tunicate Salpa thompsoni near the Antarctic Polar Front

    Science.gov (United States)

    Pakhomov, Evgeny A.; Hunt, Brian P. V.

    2017-04-01

    The distribution, density, demography and feeding dynamics of the pelagic tunicate Salpa thompsoni were investigated during the trans-Atlantic ANTARKTIS XXVIII/3 expedition to the Southern Ocean, on board RV Polarstern, between January and March 2012. Net samples were collected using an RMT-8 at four major sampling regions in the proximity of the Antarctic Polar Front (APF): along a 10°E transect, Salpastan, 12°W eulerian study, and the South Georgia Basin. Salps, mostly S. thompsoni, were found at all but one station and with few exceptions contributed Salp abundance and biomass was lowest (6.2 ind.1000 m-3 and 0.8 mgDW m-3) north of the APF along the 10°E transect and highest (3150 ind.1000 m-3 and 20.5 mgDW m-3) at the Salpastan station south of the APF. Size distributions of S. thompsoni aggregates and solitaries, and their developmental dynamics, were similar in all locations except the Salpastan region. In aggregates, the overall salp size distributions were strongly right-tailed with the mass of the distribution always concentrated in the left where small aggregates (6-10 mm) dominated. During the eulerian study at 12°W, several cohorts of aggregates and solitaries were traceable allowing assessment of the daily growth rates of S. thompsoni. Estimated in situ growth rates of aggregates and solitaries were 0.53±0.18 and 2.83±0.42 mm day-1, respectively, and the complete S. thompsoni life cycle duration (sexual+asexual) during austral summer at the APF region may have been as short as 2-3 months. The rapid growth rates of S. thompsoni found in this study urgently require further research to re-evaluate salp life cycle in the Southern Ocean.

  20. Vertical and interhemispheric links in the stratosphere-mesosphere as revealed by the day-to-day variability of Aura-MLS temperature data

    Directory of Open Access Journals (Sweden)

    X. Xu

    2009-09-01

    that the temporal variability of zonal mean temperature at the Antarctic summer mesopause is also positively (negatively correlated with the polar winter stratosphere (mesosphere during three (2004/2005, 2005/2006, and 2007/2008 out of the four winters. The highest value of the correlation coefficient is over 0.7 in the winter-stratosphere for the three winters. The remaining winter (2006/2007 has more complex correlations structures; correspondingly the polar vortex was distinguished this winter. The time-lags obtained for 2004/2005 and 2006/2007 are distinct from 2005/2006 and 2007/2008 where a 6-day lag dominates for the coupling between the winter stratosphere and the summer mesopause. The correlations are also provided using temperatures in northern longitudinal sectors in a comparison with the Antarctic-mesopause zonal mean temperature. For northern mid-high latitudes (~50–70° N, temperatures in Scandinavia-Eastern Europe and in the Pacific-Western Canada longitudinal sectors often have opposite signs of correlations with zonal mean temperatures near the Antarctic summer mesopause during northern mid-winters. The statistical results are shown to be associated with the Northern Hemisphere's polar vortex characteristics.

  1. Vertical and interhemispheric links in the stratosphere-mesosphere as revealed by the day-to-day variability of Aura-MLS temperature data

    Directory of Open Access Journals (Sweden)

    X. Xu

    2009-09-01

    variability of zonal mean temperature at the Antarctic summer mesopause is also positively (negatively correlated with the polar winter stratosphere (mesosphere during three (2004/2005, 2005/2006, and 2007/2008 out of the four winters. The highest value of the correlation coefficient is over 0.7 in the winter-stratosphere for the three winters. The remaining winter (2006/2007 has more complex correlations structures; correspondingly the polar vortex was distinguished this winter. The time-lags obtained for 2004/2005 and 2006/2007 are distinct from 2005/2006 and 2007/2008 where a 6-day lag dominates for the coupling between the winter stratosphere and the summer mesopause. The correlations are also provided using temperatures in northern longitudinal sectors in a comparison with the Antarctic-mesopause zonal mean temperature. For northern mid-high latitudes (~50–70° N, temperatures in Scandinavia-Eastern Europe and in the Pacific-Western Canada longitudinal sectors often have opposite signs of correlations with zonal mean temperatures near the Antarctic summer mesopause during northern mid-winters. The statistical results are shown to be associated with the Northern Hemisphere's polar vortex characteristics.

  2. PolarTREC-Teachers and Researchers Exploring and Collaborating: Science Education from the Poles to the World

    Science.gov (United States)

    Warnick, W. K.; Breen, K.; Warburton, J.; Fischer, K.; Wiggins, H.; Owens, R.; Polly, B.; Wade, B.; Buxbaum, T.

    2007-12-01

    PolarTREC-Teachers and Researchers Exploring and Collaborating is a three-year (2007-2009) teacher professional development program celebrating the International Polar Year (IPY) that advances polar science education by bringing K-12 educators and polar researchers together in hands-on field experiences in the Arctic and Antarctic. Currently in its second year, the program fosters the integration of research and education to produce a legacy of long-term teacher-researcher collaborations, improved teacher content knowledge through experiences in scientific inquiry, and broad public interest and engagement in polar science. Through PolarTREC, over 40 U.S. teachers will spend two to six weeks in the Arctic or Antarctic, working closely with researchers in the field as an integral part of the science team. Research projects focus on a wide range of IPY science themed topics such as sea-ice dynamics, terrestrial ecology, marine biology, atmospheric chemistry, and long-term climate change. While in the field, teachers and researchers will communicate extensively with their colleagues, communities, and hundreds of students of all ages across the globe, using a variety of tools including satellite phones, online journals, podcasts and interactive "Live from IPY" calls and web-based seminars. The online outreach elements of the project convey these experiences to a broad audience far beyond the classrooms of the PolarTREC teachers. In addition to field research experiences, PolarTREC will support teacher professional development and a sustained community of teachers, scientists, and the public through workshops, Internet seminars, an e-mail listserve, and teacher peer groups. To learn more about PolarTREC visit the website at: http://www.polartrec.com or contact info@polartrec.com or 907-474-1600. PolarTREC is funded by NSF and managed by the Arctic Research Consortium of the US (ARCUS).

  3. Environmental constraints on West Antarctic ice-sheet formation

    Energy Technology Data Exchange (ETDEWEB)

    Lindstrom, D R; MacAyeal, D R

    1987-01-01

    Small perturbations in Antarctic environmental conditions can culminate in the demise of the Antarctic ice sheet's western sector. This may have happened during the last interglacial period, and could recur within the next millennium due to atmospheric warming from trace gas and CO/sub 2/ increases. In this study, we investigate the importance of sea-level, accumulation rate, and ice influx from the East Antarctic ice sheet in the re-establishment of the West Antarctic ice sheet from a thin cover using a time-dependent numerical ice-shelf model. Our results show that a precursor to the West Antarctic ice sheet can form within 3000 years. Sea-level lowering caused by ice-sheet development in the Northern Hemisphere has the greatest environmental influence. Under favorable conditions, ice grounding occurs over all parts of the West Antarctic ice sheet except up-stream of Thwaites Glacier and in the Ross Sea region.

  4. Backreaction of excitations on a vortex

    OpenAIRE

    Arodz, Henryk; Hadasz, Leszek

    1996-01-01

    Excitations of a vortex are usually considered in a linear approximation neglecting their backreaction on the vortex. In the present paper we investigate backreaction of Proca type excitations on a straightlinear vortex in the Abelian Higgs model. We propose exact Ansatz for fields of the excited vortex. From initial set of six nonlinear field equations we obtain (in a limit of weak excitations) two linear wave equations for the backreaction corrections. Their approximate solutions are found ...

  5. Educational and Community Outreach Efforts by the United States Polar Rock Repository during the International Polar Year

    Science.gov (United States)

    Grunow, A.; Codispoti, J. E.

    2010-12-01

    The US Polar Rock Repository (USPRR) houses more than 19,000 rock samples from polar regions and these samples are made available to the scientific, educational and museum community. The USPRR has been active in promoting polar earth science to educational and community groups. During the past year, outreach efforts reached over 12,000 people. The USPRR outreach involve tours of the facility, school presentations, online laboratory exercises, working with the Columbus Metro Parks, teaching at summer camps, teaching special geology field assignments at the middle school level, as well as offering an ‘Antarctic Rock Box’ that contains representative samples of the three types of rocks, minerals, fossils, and books and activities about geology and Antarctica. The rock box activities have been designed and reviewed by educators and scientists to use as an educational supplement to the Earth Science course of study. The activities have been designed around the Academic Content Standards: k-12 Science manual published by the Ohio Department of Education to ensure that the activities and topics are focused on those mandated by the state of Ohio. The USPRR website has a Virtual Web Antarctic Expedition with many activities for Middle to High School age students. The students learn about how to plan a field season, safety techniques, how to make a remote field camp, identify what equipment is needed, learn about the different transportation choices, weather issues, understanding GPS, etc. Educational and community networks have been built in part, by directly contacting individuals at an institution and partnering with them on educational outreach. The institutions have been very interested in doing this because it brings scientists to the classroom and to the public. This type of outreach has also served as an opening for children to consider possible career choices in science that they may not have considered before. In many of the presentations, a female geologist

  6. Airspace: Antarctic Sound Transmission

    OpenAIRE

    Polli, Andrea

    2009-01-01

    This paper investigates how sound transmission can contribute to the public understanding of climate change within the context of the Poles. How have such transmission-based projects developed specifically in the Arctic and Antarctic, and how do these works create alternative pathways in order to help audiences better understand climate change? The author has created the media project Sonic Antarctica from a personal experience of the Antarctic. The work combines soundscape recordings and son...

  7. Exploring the effect of East Antarctic ice mass loss on GIA-induced horizontal bedrock motions

    Science.gov (United States)

    Konfal, S. A.; Whitehouse, P. L.; Hermans, T.; van der Wal, W.; Wilson, T. J.; Bevis, M. G.; Kendrick, E. C.; Dalziel, I.; Smalley, R., Jr.

    2017-12-01

    Ice history inputs used in Antarctic models of GIA include major centers of ice mass loss in West Antarctica. In the Transantarctic Mountains (TAM) region spanning the boundary between East and West Antarctica, horizontal crustal motions derived from GPS observations from the Antarctic Network (ANET) component of the Polar Earth Observing Network (POLENET) are towards these West Antarctic ice mass centers, opposite to the pattern of radial crustal motion expected in an unloading scenario. We investigate alternative ice history and earth structure inputs to GIA models in an attempt to reproduce observed crustal motions in the region. The W12 ice history model is altered to create scenarios including ice unloading in the Wilkes Subglacial Basin based on available glaciological records. These altered ice history models, along with the unmodified W12 ice history model, are coupled with 60 radially varying (1D) earth model combinations, including approximations of optimal earth profiles identified in published GIA models. The resulting model-predicted motions utilizing both the modified and unmodified ice history models fit ANET GPS-derived crustal motions in the northern TAM region for a suite of earth model combinations. Further south, where the influence of simulated Wilkes unloading is weakest and West Antarctic unloading is strongest, observed and predicted motions do not agree. The influence of simulated Wilkes ice unloading coupled with laterally heterogeneous earth models is also investigated. The resulting model-predicted motions do not differ significantly between the original W12 and W12 with simulated Wilkes unloading ice histories.

  8. Hydrodynamical model of anisotropic, polarized turbulent superfluids. I: constraints for the fluxes

    Science.gov (United States)

    Mongiovì, Maria Stella; Restuccia, Liliana

    2018-02-01

    This work is the first of a series of papers devoted to the study of the influence of the anisotropy and polarization of the tangle of quantized vortex lines in superfluid turbulence. A thermodynamical model of inhomogeneous superfluid turbulence previously formulated is here extended, to take into consideration also these effects. The model chooses as thermodynamic state vector the density, the velocity, the energy density, the heat flux, and a complete vorticity tensor field, including its symmetric traceless part and its antisymmetric part. The relations which constrain the constitutive quantities are deduced from the second principle of thermodynamics using the Liu procedure. The results show that the presence of anisotropy and polarization in the vortex tangle affects in a substantial way the dynamics of the heat flux, and allow us to give a physical interpretation of the vorticity tensor here introduced, and to better describe the internal structure of a turbulent superfluid.

  9. An investigation of the vortex method

    Energy Technology Data Exchange (ETDEWEB)

    Pryor, Jr., Duaine Wright [Univ. of California, Berkeley, CA (United States)

    1994-05-01

    The vortex method is a numerical scheme for solving the vorticity transport equation. Chorin introduced modern vortex methods. The vortex method is a Lagrangian, grid free method which has less intrinsic diffusion than many grid schemes. It is adaptive in the sense that elements are needed only where the vorticity is non-zero. Our description of vortex methods begins with the point vortex method of Rosenhead for two dimensional inviscid flow, and builds upon it to eventually cover the case of three dimensional slightly viscous flow with boundaries. This section gives an introduction to the fundamentals of the vortex method. This is done in order to give a basic impression of the previous work and its line of development, as well as develop some notation and concepts which will be used later. The purpose here is not to give a full review of vortex methods or the contributions made by all the researchers in the field. Please refer to the excellent review papers in Sethian and Gustafson, chapters 1 Sethian, 2 Hald, 3 Sethian, 8 Chorin provide a solid introduction to vortex methods, including convergence theory, application in two dimensions and connection to statistical mechanics and polymers. Much of the information in this review is taken from those chapters, Chorin and Marsden and Batchelor, the chapters are also useful for their extensive bibliographies.

  10. PolarTREC-Teachers and Researchers Exploring and Collaborating: Innovative Science Education from the Poles to the World

    Science.gov (United States)

    Warnick, W. K.; Warburton, J.; Breen, K.; Wiggins, H. V.; Larson, A.; Behr, S.

    2006-12-01

    PolarTREC-Teachers and Researchers Exploring and Collaborating is a three-year (2007-2009) teacher professional development program celebrating the International Polar Year (IPY) that will advance polar science education by bringing K-12 educators and polar researchers together in hands-on field experiences in the Arctic and Antarctic. PolarTREC builds on the strengths of the existing TREC program in the Arctic, an NSF supported program managed by the Arctic Research Consortium of the US (ARCUS), to embrace a wide range of activities occurring at both poles during and after IPY. PolarTREC will foster the integration of research and education to produce a legacy of long-term teacher-researcher collaborations, improved teacher content knowledge through experiences in scientific inquiry, and broad public interest and engagement in polar science and IPY. PolarTREC will enable thirty-six teachers to spend two to six weeks in the Arctic or Antarctic, working closely with researchers investigating a wide range of IPY science themed topics such as sea-ice dynamics, terrestrial ecology, marine biology, atmospheric chemistry, and long-term climate change. While in the field, teachers and researchers will communicate extensively with their colleagues, communities, and hundreds of students of all ages across the globe, using a variety of tools including satellite phones, online journals, podcasts and interactive "Live from IPY" calls and web-based seminars. The online outreach elements of the project convey these experiences to a broad audience far beyond the classrooms of the PolarTREC teachers. In addition to field research experiences, PolarTREC will support teacher professional development and a sustained community of teachers, scientists, and the public through workshops, Internet seminars, an e-mail listserve, and teacher peer groups. For further information on PolarTREC, contact Wendy Warnick, ARCUS Executive Director at warnick@arcus.org or 907-474-1600 or visit www.arcus.org/trec/

  11. Instability of vortex pair leapfrogging

    DEFF Research Database (Denmark)

    Tophøj, Laust; Aref, Hassan

    2013-01-01

    Leapfrogging is a periodic solution of the four-vortex problem with two positive and two negative point vortices all of the same absolute circulation arranged as co-axial vortex pairs. The set of co-axial motions can be parameterized by the ratio 0 vortex pair sizes at the time when one...... pair passes through the other. Leapfrogging occurs for α > σ2, where is the silver ratio. The motion is known in full analytical detail since the 1877 thesis of Gröbli and a well known 1894 paper by Love. Acheson ["Instability of vortex leapfrogging," Eur. J. Phys.21, 269-273 (2000...... pairs fly off to infinity, and a "walkabout" mode, where the vortices depart from leapfrogging but still remain within a finite distance of one another. We show numerically that this transition is more gradual, a result that we relate to earlier investigations of chaotic scattering of vortex pairs [L...

  12. Soliton on thin vortex filament

    International Nuclear Information System (INIS)

    Konno, Kimiaki; Mituhashi, Masahiko; Ichikawa, Y.H.

    1990-12-01

    Showing that one of the equations found by Wadati, Konno and Ichikawa is equivalent to the equation of motion of a thin vortex filament, we investigate solitons on the vortex filament. N vortex soliton solution is given in terms of the inverse scattering method. We examine two soliton collision processes on the filament. Our analysis provides the theoretical foundation of two soliton collision processes observed numerically by Aref and Flinchem. (author)

  13. ASRS Reports on Wake Vortex Encounters

    Science.gov (United States)

    Connell, Linda J.; Taube, Elisa Ann; Drew, Charles Robert; Barclay, Tommy Earl

    2010-01-01

    ASRS is conducting a structured callback research project of wake vortex incidents reported to the ASRS at all US airports, as well as wake encounters in the enroute environment. This study has three objectives: (1) Utilize the established ASRS supplemental data collection methodology and provide ongoing analysis of wake vortex encounter reports; (2) Document event dynamics and contributing factors underlying wake vortex encounter events; and (3) Support ongoing FAA efforts to address pre-emptive wake vortex risk reduction by utilizing ASRS reporting contributions.

  14. New scanning technique for the optical vortex microscope.

    Science.gov (United States)

    Augustyniak, Ireneusz; Popiołek-Masajada, Agnieszka; Masajada, Jan; Drobczyński, Sławomir

    2012-04-01

    In the optical vortex microscopy the focused Gaussian beam with optical vortex scans a sample. An optical vortex can be introduced into a laser beam with the use of a special optical element--a vortex lens. When moving the vortex lens, the optical vortex changes its position inside the spot formed by a focused laser beam. This effect can be used as a new precise scanning technique. In this paper, we study the optical vortex behavior at the sample plane. We also estimate if the new scanning technique results in observable effects that could be used for a phase object detection.

  15. Initiation and long-term instability of the East Antarctic Ice Sheet.

    Science.gov (United States)

    Gulick, Sean P S; Shevenell, Amelia E; Montelli, Aleksandr; Fernandez, Rodrigo; Smith, Catherine; Warny, Sophie; Bohaty, Steven M; Sjunneskog, Charlotte; Leventer, Amy; Frederick, Bruce; Blankenship, Donald D

    2017-12-13

    Antarctica's continental-scale ice sheets have evolved over the past 50 million years. However, the dearth of ice-proximal geological records limits our understanding of past East Antarctic Ice Sheet (EAIS) behaviour and thus our ability to evaluate its response to ongoing environmental change. The EAIS is marine-terminating and grounded below sea level within the Aurora subglacial basin, indicating that this catchment, which drains ice to the Sabrina Coast, may be sensitive to climate perturbations. Here we show, using marine geological and geophysical data from the continental shelf seaward of the Aurora subglacial basin, that marine-terminating glaciers existed at the Sabrina Coast by the early to middle Eocene epoch. This finding implies the existence of substantial ice volume in the Aurora subglacial basin before continental-scale ice sheets were established about 34 million years ago. Subsequently, ice advanced across and retreated from the Sabrina Coast continental shelf at least 11 times during the Oligocene and Miocene epochs. Tunnel valleys associated with half of these glaciations indicate that a surface-meltwater-rich sub-polar glacial system existed under climate conditions similar to those anticipated with continued anthropogenic warming. Cooling since the late Miocene resulted in an expanded polar EAIS and a limited glacial response to Pliocene warmth in the Aurora subglacial basin catchment. Geological records from the Sabrina Coast shelf indicate that, in addition to ocean temperature, atmospheric temperature and surface-derived meltwater influenced East Antarctic ice mass balance under warmer-than-present climate conditions. Our results imply a dynamic EAIS response with continued anthropogenic warming and suggest that the EAIS contribution to future global sea-level projections may be under-estimated.

  16. The 2002 Antarctic Ozone Hole

    Science.gov (United States)

    Newman, P. A.; Nash, E. R.; Douglass, A. R.; Kawa, S. R.

    2003-01-01

    Since 1979, the ozone hole has grown from near zero size to over 24 Million km2. This area is most strongly controlled by levels of inorganic chlorine and bromine oncentrations. In addition, dynamical variations modulate the size of the ozone hole by either cooling or warming the polar vortex collar region. We will review the size observations, the size trends, and the interannual variability of the size. Using a simple trajectory model, we will demonstrate the sensitivity of the ozone hole to dynamical forcing, and we will use these observations to discuss the size of the ozone hole during the 2002 Austral spring. We will further show how the Cly decreases in the stratosphere will cause the ozone hole to decrease by 1-1.5% per year. We will also show results from a 3-D chemical transport model (CTM) that has been continuously run since 1999. These CTM results directly show how strong dynamics acts to reduce the size of the ozone hole.

  17. Moving vortex matter with coexisting vortices and anti-vortices

    International Nuclear Information System (INIS)

    Carneiro, Gilson

    2009-01-01

    Moving vortex matter, driven by transport currents independent of time, in which vortices and anti-vortices coexist is investigated theoretically in thin superconducting films with nanostructured defects. A simple London model is proposed for the vortex dynamics in films with periodic arrays of nanomagnets or cylindrical holes (antidots). Common to these films is that vortex anti-vortex pairs may be created in the vicinity of the defects by relatively small transport currents, because it adds to the current generated by the defects - the nanomagnets screening current, or the antidots backflow current - and may exceed locally the critical value for vortex anti-vortex pair creation. The model assumes that vortex matter dynamics is governed by Langevin equations, modified to account for creation and annihilation of vortex anti-vortex pairs. For pair creation, it is assumed that whenever the total current at some location exceeds a critical value, equal to that needed to separate a vortex from an anti-vortex by a vortex core diameter, a pair is created instantaneously around this location. Pair annihilation occurs by vortex anti-vortex collisions. The model is applied to films at zero external magnetic field and low temperatures. It is found that several moving vortex matter steady-states with equal numbers of vortices and anti-vortices are possible.

  18. Review of Idealized Aircraft Wake Vortex Models

    Science.gov (United States)

    Ahmad, Nashat N.; Proctor, Fred H.; Duparcmeur, Fanny M. Limon; Jacob, Don

    2014-01-01

    Properties of three aircraft wake vortex models, Lamb-Oseen, Burnham-Hallock, and Proctor are reviewed. These idealized models are often used to initialize the aircraft wake vortex pair in large eddy simulations and in wake encounter hazard models, as well as to define matched filters for processing lidar observations of aircraft wake vortices. Basic parameters for each vortex model, such as peak tangential velocity and circulation strength as a function of vortex core radius size, are examined. The models are also compared using different vortex characterizations, such as the vorticity magnitude. Results of Euler and large eddy simulations are presented. The application of vortex models in the postprocessing of lidar observations is discussed.

  19. Antarctic climate change and the environment

    Science.gov (United States)

    2009-11-01

    This volume provides a comprehensive, up-to-date account of how the physical and biological : environment of the Antarctic continent and Southern Ocean has changed from Deep Time until : the present day. It also considers how the Antarctic environmen...

  20. Ultrafast magnetic vortex core switching driven by the topological inverse Faraday effect.

    Science.gov (United States)

    Taguchi, Katsuhisa; Ohe, Jun-ichiro; Tatara, Gen

    2012-09-21

    We present a theoretical discovery of an unconventional mechanism of inverse Faraday effect which acts selectively on topological magnetic structures. The effect, topological inverse Faraday effect, is induced by the spin Berry's phase of the magnetic structure when a circularly polarized light is applied. Thus a spin-orbit interaction is not necessary unlike that in the conventional inverse Faraday effect. We demonstrate by numerical simulation that topological inverse Faraday effect realizes ultrafast switching of a magnetic vortex within a switching time of 150 ps without magnetic field.

  1. Studying the Representation Accuracy of the Earth's Gravity Field in the Polar Regions Based on the Global Geopotential Models

    Science.gov (United States)

    Koneshov, V. N.; Nepoklonov, V. B.

    2018-05-01

    The development of studies on estimating the accuracy of the Earth's modern global gravity models in terms of the spherical harmonics of the geopotential in the problematic regions of the world is discussed. The comparative analysis of the results of reconstructing quasi-geoid heights and gravity anomalies from the different models is carried out for two polar regions selected within a radius of 1000 km from the North and South poles. The analysis covers nine recently developed models, including six high-resolution models and three lower order models, including the Russian GAOP2012 model. It is shown that the modern models determine the quasi-geoid heights and gravity anomalies in the polar regions with errors of 5 to 10 to a few dozen cm and from 3 to 5 to a few dozen mGal, respectively, depending on the resolution. The accuracy of the models in the Arctic is several times higher than in the Antarctic. This is associated with the peculiarities of gravity anomalies in every particular region and with the fact that the polar part of the Antarctic has been comparatively less explored by the gravity methods than the polar Arctic.

  2. Meissner effects, vortex core states, and the vortex glass phase transition

    International Nuclear Information System (INIS)

    Huang, Ming.

    1991-01-01

    This thesis covers three topics involving Meissner effects and the resulting defect structures. The first is a study of Meissner effects in superconductivity and in systems with broken translational symmetry. The Meissner effect in the superconductors is a rigidity against external magnetic field caused by the breaking of the gauge symmetry. Other condensed matter systems also exhibit rigidities like this: The breaking of the translational symmetry in a cubic-liquid-crystal causes the system to expel twist deformations and the breaking of the translational symmetry in a nematic liquid crystal gives it a tendency to expel twist and bend deformations. In this thesis, the author studies these generalized Meissner effects in detail. The second is a study of the quasiparticle states bound to the vortex defect in superconductors. Scanning-tunneling-microscope measurements by Harald Hess et al. of the local density of states in a vortex core show a pronounced peak at small bias. These measurements contradict with previous theoretical calculations. Here, he solves the Bogoliubov equations to obtain the local density of states in the core and satisfactorily explain the experimental observations. He also predicted additional structure in the local density of states which were later observed in experiments. The third is a study of vortex dynamics in the presence of disorder. A mean field theory is developed for the recently proposed normal to superconducting vortex glass transition. Using techniques developed to study the critical dynamics of spin glasses, he calculates the mean field vortex glass phase boundary and the critical exponents

  3. Leapfrogging of multiple coaxial viscous vortex rings

    International Nuclear Information System (INIS)

    Cheng, M.; Lou, J.; Lim, T. T.

    2015-01-01

    A recent theoretical study [Borisov, Kilin, and Mamaev, “The dynamics of vortex rings: Leapfrogging, choreographies and the stability problem,” Regular Chaotic Dyn. 18, 33 (2013); Borisov et al., “The dynamics of vortex rings: Leapfrogging in an ideal and viscous fluid,” Fluid Dyn. Res. 46, 031415 (2014)] shows that when three coaxial vortex rings travel in the same direction in an incompressible ideal fluid, each of the vortex rings alternately slips through (or leapfrogs) the other two ahead. Here, we use a lattice Boltzmann method to simulate viscous vortex rings with an identical initial circulation, radius, and separation distance with the aim of studying how viscous effect influences the outcomes of the leapfrogging process. For the case of two identical vortex rings, our computation shows that leapfrogging can be achieved only under certain favorable conditions, which depend on Reynolds number, vortex core size, and initial separation distance between the two rings. For the case of three coaxial vortex rings, the result differs from the inviscid model and shows that the second vortex ring always slips through the leading ring first, followed by the third ring slipping through the other two ahead. A simple physical model is proposed to explain the observed behavior

  4. Aerodynamically shaped vortex generators

    DEFF Research Database (Denmark)

    Hansen, Martin Otto Laver; Velte, Clara Marika; Øye, Stig

    2016-01-01

    An aerodynamically shaped vortex generator has been proposed, manufactured and tested in a wind tunnel. The effect on the overall performance when applied on a thick airfoil is an increased lift to drag ratio compared with standard vortex generators. Copyright © 2015 John Wiley & Sons, Ltd....

  5. Parasites of the Antarctic toothfish (Dissostichus mawsoni Norman, 1937 (Perciformes, Nototheniidae in the Pacific sector of the Antarctic

    Directory of Open Access Journals (Sweden)

    Ilya I. Gordeev

    2016-06-01

    Full Text Available The Antarctic toothfish (Dissostichus mawsoni Norman, 1937 is one of the main target species of commercial fisheries in the Antarctic. It is an endemic and is found along the shelf of Antarctica, as well as on the slopes of seamounts, underwater elevations and islands in the sub-Antarctic. It feeds on a variety of fish and cephalopods and can be an intermediate/paratenic host of some helminthes, whose final hosts are whales, seals, large rays and sharks. This article presents new data on toothfish infection in the Pacific sector of the Antarctic. Specimens were examined during commercial longline fishing in the Ross Sea and the Amundsen Sea in January–February 2013. Fourteen species of parasites were found using standard parasitological methods and genetic analysis.

  6. Experiments concerning the theories of vortex breakdown

    Science.gov (United States)

    Panton, Ronald L.; Stifle, Kirk E.

    1991-01-01

    An experimental project was undertaken to investigate the character of vortex breakdown with particular regard to the stagnation and wave guide theories of vortex breakdown. Three different wings were used to produce a trailing vortex which convected downstream without undergoing breakdown. Disturbances were then introduced onto the vortex using a moving wire to 'cut' the vortex. The development of upstream and downstream propagating disturbance waves was observed and the propagation velocities measured. A downstream traveling wave was observed to produce a structure similar in appearance to a vortex breakdown. An upstream traveling wave produced a moving turbulent region. The upstream disturbance moved into an axial velocity profile that had a wake-like defect while the downstream moving vortex breakdown moved against a jet-like overshoot. The longitudinal and swirl velocity profiles were documented by LDV measurement. Wave velocities, swirl angles, and swirl parameters are reported.

  7. South African antarctic biological research programme

    CSIR Research Space (South Africa)

    SASCAR

    1981-07-01

    Full Text Available This document provides a description of the past, current and planned South African biological research activities in the sub-Antarctic and Antarctic regions. Future activities will fall under one of the five components of the research programme...

  8. Propeller and inflow vortex interaction : vortex response and impact on the propeller performance

    NARCIS (Netherlands)

    Yang, Y.; Zhou, T; Sciacchitano, A.; Veldhuis, L.L.M.; Eitelberg, G.

    2016-01-01

    The aerodynamic operating conditions of a propeller can include complex situations where vorticity from sources upstream can enter the propeller plane. In general, when the vorticity enters in a concentrated form of a vortex, the interaction between the vortex and blade is referred to as

  9. What is happening in the International Polar Year? Latest news about the climate changes

    International Nuclear Information System (INIS)

    Orheim, Olav

    2008-01-01

    The International Polar (IPY) Year 2007-2008 is a large scientific programme focused on the Arctic and the Antarctic. Scientists from over 60 nations participates. The IPY have two primary objectives: to improve weather forecasts especially regarding extreme weather and to improve climatic models for better understanding of possible instabilities, especially regarding ocean currents. The presentation includes data on natural climate change, temperature anomaly, the ice in the Arctic Ocean and Northern and Southern Hemisphere sea ice area, current in Southern and Northern hemisphere sea ice area and variations of the surface temperature ice arctic regions antarctic regions. The presentation was held at the MNT-Forum, 29. January 2008

  10. Polar Voices: Relaying the Science and Story of Polar Climate Change through Podcast

    Science.gov (United States)

    Moloney, M.; Quinney, A.; Murray, M. S.

    2016-12-01

    The resurgence of audio programming with the advent of podcasting in the early 2000's spawned a new medium for communicating advances in science, research, and technology. To capitalize on this informal educational outlet, the Arctic Institute of North America (AINA) partnered with the International Arctic Research Center, the University of Alaska Fairbanks, and the UA Museum of the North to develop a podcast series called PoLAR Voices for the Polar Learning and Responding (PoLAR) Climate Change Education Partnership. Now entering its third season of production, PoLAR Voices has facilitated the communication of scientific knowledge regarding the impact of climate change on the Arctic and Antarctic from the perspectives of both scientific researchers and Arctic indigenous peoples. We present a holistic program detailing both data and research related to climate change in addition to personal stories from those people and communities most affected. An evaluation of the program has been conducted by the Goodman Research Group to assess the effectiveness of the program for relaying the whole story of climate change to the public. The results of this assessment will be used to further develop the program to effectively reach larger and more diverse audiences. The series is currently available on thepolarhub.org and iTunes, and we are exploring opportunities to air the program on radio to reach as many people as possible.

  11. Observation Impact over the Antarctic During the Concordiasi Field Campaign

    Science.gov (United States)

    Boullot, Nathalie; Rabier, Florence; Langland, Rolf; Gelaro, Ron; Cardinali, Carla; Guidard, Vincent; Bauer, Peter; Doerenbecher, Alexis

    2014-01-01

    The impact of observations on analysis uncertainty and forecast performance was investigated for Austral Spring 2010 over the Southern polar area for four different systems (NRL, GMAO, ECMWF and Meteo-France), at the time of the Concordiasi field experiment. The largest multi model variance in 500 hPa height analyses is found in the southern sub-Antarctic oceanic region, where there are strong atmospheric dynamics, rapid forecast error growth, and fewer upper air wind observation data to constrain the analyses. In terms of data impact the most important observation components are shown to be AMSU, IASI, AIRS, GPS-RO, radiosonde, surface and atmospheric motion vector observations. For sounding data, radiosondes and dropsondes, one can note a large impact of temperature at low levels and a large impact of wind at high levels. Observing system experiments using the Concordiasi dropsondes show a large impact of the observations over the Antarctic plateau extending to lower latitudes with the forecast range, with a large impact around 50 to 70deg South. These experiments indicate there is a potential benefit of better using radiance data over land and sea-ice and innovative atmospheric motion vectors obtained from a combination of various satellites to fill the current data gaps and improve NWP in this region.

  12. Validation of a limited area model over Dome C, Antarctic Plateau, during winter

    Energy Technology Data Exchange (ETDEWEB)

    Gallee, Hubert; Gorodetskaya, Irina V. [Laboratoire de Glaciologie et de Geophysique de l' Environnement, CNRS, 54, rue Moliere, BP. 96, St Martin d' Heres Cedex (France)

    2010-01-15

    The limited area model MAR (Modele Atmospherique Regional) is validated over the Antarctic Plateau for the period 2004-2006, focussing on Dome C during the cold season. MAR simulations are made by initializing the model once and by forcing it through its lateral and top boundaries by the ECMWF operational analyses. Model outputs compare favourably with observations from automatic weather station (AWS), radiometers and atmospheric soundings. MAR is able to simulate the succession of cold and warm events which occur at Dome C during winter. Larger longwave downwelling fluxes (LWD) are responsible for higher surface air temperatures and weaker surface inversions during winter. Warm events are better simulated when the small Antarctic precipitating snow particles are taken into account in radiative transfer computations. MAR stratosphere cools during the cold season, with the coldest temperatures occurring in conjunction with warm events at the surface. The decrease of saturation specific humidity associated with these coldest temperatures is responsible for the formation of polar stratospheric clouds (PSCs) especially in August-September. PSCs then contribute to the surface warming by increasing the surface downwelling longwave flux. (orig.)

  13. Vortex Thermometry for Turbulent Two-Dimensional Fluids.

    Science.gov (United States)

    Groszek, Andrew J; Davis, Matthew J; Paganin, David M; Helmerson, Kristian; Simula, Tapio P

    2018-01-19

    We introduce a new method of statistical analysis to characterize the dynamics of turbulent fluids in two dimensions. We establish that, in equilibrium, the vortex distributions can be uniquely connected to the temperature of the vortex gas, and we apply this vortex thermometry to characterize simulations of decaying superfluid turbulence. We confirm the hypothesis of vortex evaporative heating leading to Onsager vortices proposed in Phys. Rev. Lett. 113, 165302 (2014)PRLTAO0031-900710.1103/PhysRevLett.113.165302, and we find previously unidentified vortex power-law distributions that emerge from the dynamics.

  14. Manipulation of dielectric Rayleigh particles using highly focused elliptically polarized vector fields.

    Science.gov (United States)

    Gu, Bing; Xu, Danfeng; Rui, Guanghao; Lian, Meng; Cui, Yiping; Zhan, Qiwen

    2015-09-20

    Generation of vectorial optical fields with arbitrary polarization distribution is of great interest in areas where exotic optical fields are desired. In this work, we experimentally demonstrate the versatile generation of linearly polarized vector fields, elliptically polarized vector fields, and circularly polarized vortex beams through introducing attenuators in a common-path interferometer. By means of Richards-Wolf vectorial diffraction method, the characteristics of the highly focused elliptically polarized vector fields are studied. The optical force and torque on a dielectric Rayleigh particle produced by these tightly focused vector fields are calculated and exploited for the stable trapping of dielectric Rayleigh particles. It is shown that the additional degree of freedom provided by the elliptically polarized vector field allows one to control the spatial structure of polarization, to engineer the focusing field, and to tailor the optical force and torque on a dielectric Rayleigh particle.

  15. Criterion for vortex breakdown on shock wave and streamwise vortex interactions.

    Science.gov (United States)

    Hiejima, Toshihiko

    2014-05-01

    The interactions between supersonic streamwise vortices and oblique shock waves are theoretically and numerically investigated by three-dimensional (3D) Navier-Stokes equations. Based on the two inequalities, a criterion for shock-induced breakdown of the streamwise vortex is proposed. The simple breakdown condition depends on the Mach number, the swirl number, the velocity deficit, and the shock angle. According to the proposed criterion, the breakdown region expands as the Mach number increases. In numerical simulations, vortex breakdown appeared under conditions of multiple pressure increases and the helicity disappeared behind the oblique shock wave along the line of the vortex center. The numerical results are consistent with the predicted breakdown condition at Mach numbers 2.0 and 3.0. This study also found that the axial velocity deficit is important for classifying the breakdown configuration.

  16. Experimental Study of Shock Generated Compressible Vortex Ring

    Science.gov (United States)

    Das, Debopam; Arakeri, Jaywant H.; Krothapalli, Anjaneyulu

    2000-11-01

    Formation of a compressible vortex ring and generation of sound associated with it is studied experimentally. Impulse of a shock wave is used to generate a vortex ring from the open end of a shock-tube. Vortex ring formation process has been studied in details using particle image Velocimetry (PIV). As the shock wave exits the tube it diffracts and expands. A circular vortex sheet forms at the edge and rolls up into a vortex ring. Far field microphone measurement shows that the acoustic pressure consists of a spike due to shock wave followed by a low frequency pressure wave of decaying nature, superimposed with high frequency pressure wave. Acoustic waves consist of waves due to expansion, waves formed in the tube during diaphragm breakage and waves associated with the vortex ring and shear-layer vortices. Unsteady evolution of the vortex ring and shear-layer vortices in the jet behind the ring is studied by measuring the velocity field using PIV. Corresponding vorticity field, circulation around the vortex core and growth rate of the vortex core is calculated from the measured velocity field. The velocity field in a compressible vortex ring differs from that of an incompressible ring due to the contribution from both shock and vortex ring.

  17. Assessing fuel spill risks in polar waters: Temporal dynamics and behaviour of hydrocarbons from Antarctic diesel, marine gas oil and residual fuel oil.

    Science.gov (United States)

    Brown, Kathryn E; King, Catherine K; Kotzakoulakis, Konstantinos; George, Simon C; Harrison, Peter L

    2016-09-15

    As part of risk assessment of fuel oil spills in Antarctic and subantarctic waters, this study describes partitioning of hydrocarbons from three fuels (Special Antarctic Blend diesel, SAB; marine gas oil, MGO; and intermediate grade fuel oil, IFO 180) into seawater at 0 and 5°C and subsequent depletion over 7days. Initial total hydrocarbon content (THC) of water accommodated fraction (WAF) in seawater was highest for SAB. Rates of THC loss and proportions in equivalent carbon number fractions differed between fuels and over time. THC was most persistent in IFO 180 WAFs and most rapidly depleted in MGO WAF, with depletion for SAB WAF strongly affected by temperature. Concentration and composition remained proportionate in dilution series over time. This study significantly enhances our understanding of fuel behaviour in Antarctic and subantarctic waters, enabling improved predictions for estimates of sensitivities of marine organisms to toxic contaminants from fuels in the region. Copyright © 2016 Elsevier Ltd. All rights reserved.

  18. Metabolic cold adaptation of polar fish based on measurements of aerobic oxygen consumption: fact or artefact? Artefact!

    DEFF Research Database (Denmark)

    Steffensen, John Fleng

    2002-01-01

    Whether metabolic cold adaptation in polar fish, based on measurements of aerobic standard metabolic rate, is a fact or an artefact has been a dispute since Holeton asked the question in 1974. So far polar fish had been considered to be metabolically cold adapted because they were reported to have...... a considerably elevated resting oxygen consumption, or standard metabolic rate, compared with oxygen consumption values of tropical or temperate fish extrapolated to similar low polar temperatures. Recent experiments on arctic and Antarctic fish, however, do not show elevated resting aerobic oxygen consumption...

  19. Analytical model of the optical vortex microscope.

    Science.gov (United States)

    Płocinniczak, Łukasz; Popiołek-Masajada, Agnieszka; Masajada, Jan; Szatkowski, Mateusz

    2016-04-20

    This paper presents an analytical model of the optical vortex scanning microscope. In this microscope the Gaussian beam with an embedded optical vortex is focused into the sample plane. Additionally, the optical vortex can be moved inside the beam, which allows fine scanning of the sample. We provide an analytical solution of the whole path of the beam in the system (within paraxial approximation)-from the vortex lens to the observation plane situated on the CCD camera. The calculations are performed step by step from one optical element to the next. We show that at each step, the expression for light complex amplitude has the same form with only four coefficients modified. We also derive a simple expression for the vortex trajectory of small vortex displacements.

  20. Microscale vortex laser with controlled topological charge

    Science.gov (United States)

    Wang, Xing-Yuan; Chen, Hua-Zhou; Li, Ying; Li, Bo; Ma, Ren-Min

    2016-12-01

    A microscale vortex laser is a new type of coherent light source with small footprint that can directly generate vector vortex beams. However, a microscale laser with controlled topological charge, which is crucial for virtually any of its application, is still unrevealed. Here we present a microscale vortex laser with controlled topological charge. The vortex laser eigenmode was synthesized in a metamaterial engineered non-Hermitian micro-ring cavity system at exceptional point. We also show that the vortex laser cavity can operate at exceptional point stably to lase under optical pumping. The microscale vortex laser with controlled topological charge can serve as a unique and general building block for next-generation photonic integrated circuits and coherent vortex beam sources. The method we used here can be employed to generate lasing eigenmode with other complex functionalities. Project supported by the “Youth 1000 Talent Plan” Fund, Ministry of Education of China (Grant No. 201421) and the National Natural Science Foundation of China (Grant Nos. 11574012 and 61521004).

  1. A note on integral vortex strength

    Czech Academy of Sciences Publication Activity Database

    Kolář, Václav

    2010-01-01

    Roč. 58, č. 1 (2010), s. 23-28 ISSN 0042-790X R&D Projects: GA AV ČR IAA200600801 Institutional research plan: CEZ:AV0Z20600510 Keywords : circulation * unsteady Taylor vortex * vortex intensity * vortex strength * vorticity * vorticity decomposition Subject RIV: BK - Fluid Dynamics Impact factor: 0.553, year: 2010

  2. Obstacle-induced spiral vortex breakdown

    OpenAIRE

    Pasche, Simon; Gallaire, François; Dreyer, Matthieu; Farhat, Mohamed

    2014-01-01

    An experimental investigation on vortex breakdown dynamics is performed. An adverse pressure gradient is created along the axis of a wing-tip vortex by introducing a sphere downstream of an elliptical hydrofoil. The instrumentation involves high-speed visualizations with air bubbles used as tracers and 2D Laser Doppler Velocimeter (LDV). Two key parameters are identified and varied to control the onset of vortex breakdown: the swirl number, defined as the maximum azimuthal velocity divided by...

  3. Vortex and source rings

    DEFF Research Database (Denmark)

    Branlard, Emmanuel Simon Pierre

    2017-01-01

    The velocity field, vector potential and velocity gradient of a vortex ring is derived in this chapter. The Biot-Savart law for the vector potential and velocity is expressed in a first section. Then, the flow is derived at specific locations: on the axis, near the axis and in the far field where...... the analogy to a doublet field is made. The following section derive the value of the vector potential and velocity field in the full domain. The expression for the velocity gradient is also provided since it may be relevant in a simulation with vortex particles and vortex rings. Most of this chapter...

  4. The effects of greenhouse gases on the Antarctic ozone hole in the past, present, and future

    Science.gov (United States)

    Newman, P. A.; Li, F.; Lait, L. R.; Oman, L.

    2017-12-01

    The Antarctic ozone hole is primarily caused by human-produced ozone depleting substances such as chlorine-containing chlorofluorocarbons (CFCs) and bromine-containing halons. The large ozone spring-time depletion relies on the very-cold conditions of the Antarctic lower stratosphere, and the general containment of air by the polar night jet over Antarctica. Here we show the Goddard Earth Observing System Chemistry Climate Model (GEOSCCM) coupled ocean-atmosphere-chemistry model for exploring the impact of increasing greenhouse gases (GHGs). Model simulations covering the 1960-2010 period are shown for: 1) a control ensemble with observed levels of ODSs and GHGs, 2) an ensemble with fixed 1960 GHG concentrations, and 3) an ensemble with fixed 1960 ODS levels. We look at a similar set of simulations (control, 2005 fixed GHG levels, and 2005 fixed ODS levels) with a new version of GEOSCCM over the period 2005-2100. These future simulations show that the decrease of ODSs leads to similar ozone recovery for both the control run and the fixed GHG scenarios, in spite of GHG forced changes to stratospheric ozone levels. These simulations demonstrate that GHG levels will have major impacts on the stratosphere by 2100, but have only small impacts on the Antarctic ozone hole.

  5. Development of vortex model with realistic axial velocity distribution

    International Nuclear Information System (INIS)

    Ito, Kei; Ezure, Toshiki; Ohshima, Hiroyuki

    2014-01-01

    A vortex is considered as one of significant phenomena which may cause gas entrainment (GE) and/or vortex cavitation in sodium-cooled fast reactors. In our past studies, the vortex is assumed to be approximated by the well-known Burgers vortex model. However, the Burgers vortex model has a simple but unreal assumption that the axial velocity component is horizontally constant, while in real the free surface vortex has the axial velocity distribution which shows large gradient in radial direction near the vortex center. In this study, a new vortex model with realistic axial velocity distribution is proposed. This model is derived from the steady axisymmetric Navier-Stokes equation as well as the Burgers vortex model, but the realistic axial velocity distribution in radial direction is considered, which is defined to be zero at the vortex center and to approach asymptotically to zero at infinity. As the verification, the new vortex model is applied to the evaluation of a simple vortex experiment, and shows good agreements with the experimental data in terms of the circumferential velocity distribution and the free surface shape. In addition, it is confirmed that the Burgers vortex model fails to calculate accurate velocity distribution with the assumption of uniform axial velocity. However, the calculation accuracy of the Burgers vortex model can be enhanced close to that of the new vortex model in consideration of the effective axial velocity which is calculated as the average value only in the vicinity of the vortex center. (author)

  6. Persistent organohalogen contaminant burdens in Antarctic krill (Euphausia superba) from the eastern Antarctic sector: A baseline study

    International Nuclear Information System (INIS)

    Bengtson Nash, S.M.; Poulsen, A.H.; Kawaguchi, S.; Vetter, W.; Schlabach, M.

    2008-01-01

    A baseline for persistent organohalogen compound (POC) accumulation in the Antarctic keystone species, Antarctic krill (Euphausia superba) has been established for a 50 deg. longitudinal range of the eastern Antarctic sector. Samples of adult krill, caught from 12 sites distributed between 30 deg. and 80 deg. E (60-70 deg. S), were analysed for > 100 organohalogen compounds including chlorinated pesticides, polychlorinated biphenyls (PCBs), polybrominated organic compounds and polychlorinated dibenzo-p-dioxins/furans (PCDD/Fs). Organochlorine pesticides dominated measured krill contaminant burdens with hexachlorobenzene (HCB) as the single most abundant compound quantified. Krill HCB concentrations were comparable to those detected at this trophic level in both the Arctic and temperate northwest Atlantic, lending support for the hypothesis that HCB will approach global equilibrium at a faster rate than other POCs. Para, para'-dichlorodiphenylethene (p,p'-DDE) was detected at notable concentrations. Measurements of DDT and its degradation products provide an important baseline for monitoring the temporal and geographical influence of renewed, DDT usage for malaria-control in affected southern hemisphere countries. In contrast to the Arctic, PCBs did not feature prominently in contaminant burdens of Antarctic krill. The major commercial polybrominated diphenyl ether (PBDE) congeners -99 and -47 were quantified at low background levels with clear concentration spikes observed at around 70 deg. E , in the vicinity of modern, active research stations. The likelihood that local anthropogenic activities are supplementing low PBDE levels, delivered otherwise primarily via long range environmental transport, is discussed. The suspected naturally occurring brominated organic compound, 2,4,6-tribromoanisole (TBA), was a ubiquitous contaminant in all samples whereas the only PCDD/Fs quantifiable were trace levels of octachlorodibenzo-p-dioxin (OCDD) and 1

  7. The changing form of Antarctic biodiversity.

    Science.gov (United States)

    Chown, Steven L; Clarke, Andrew; Fraser, Ceridwen I; Cary, S Craig; Moon, Katherine L; McGeoch, Melodie A

    2015-06-25

    Antarctic biodiversity is much more extensive, ecologically diverse and biogeographically structured than previously thought. Understanding of how this diversity is distributed in marine and terrestrial systems, the mechanisms underlying its spatial variation, and the significance of the microbiota is growing rapidly. Broadly recognizable drivers of diversity variation include energy availability and historical refugia. The impacts of local human activities and global environmental change nonetheless pose challenges to the current and future understanding of Antarctic biodiversity. Life in the Antarctic and the Southern Ocean is surprisingly rich, and as much at risk from environmental change as it is elsewhere.

  8. On the Size of the Antarctic Ozone Hole

    Science.gov (United States)

    Newman, Paul A.; Nash, Eric R.; Kawa, S. Randolph

    2002-01-01

    The Antarctic ozone hole is a region of extremely large ozone depletion that is roughly centered over the South Pole. Since 1979, the area coverage of the ozone hole has grown from near zero size to over 24 Million sq km. In the 8-year period from 1981 to 1989, the area expanded by 18 Million sq km. During the last 5 years, the hole has been observed to exceed 25 Million sq km over brief periods. In the spring of 2002, the size of the ozone hole barely reached 20 Million sq km for only a couple of days. We will review these size observations, the size trends, and the interannual variability of the size. The area is derived from the area enclosed by the 220 DU total ozone contour. We will discuss the rationale for the choice of 220 DU: 1) it is located near the steep gradient between southern mid-latitudes and the polar region, and 2) 220 DU is a value that is lower than the pre-1979 ozone observations over Antarctica during the spring period. The phenomenal growth of the ozone hole was directly caused by the increases of chlorine and bromine compounds in the stratosphere. In this talk, we will show the relationship of the ozone hole's size to the interannual variability of Antarctic spring temperatures. In addition, we will show the relationship of these same temperatures to planetary-scale wave forcings.

  9. Libre: Freeing Polar Data in an Information Commons

    Science.gov (United States)

    Duerr, R. E.; Parsons, M. A.

    2010-12-01

    As noted in the session description “The polar regions are at the forefront of modern environmental change, currently experiencing the largest and fastest changes in climate and environment”. Wise use of resources, astute management of our environment, improved decision support, and effective international cooperation on natural resource and geopolitical issues require a deeper understanding of, and an ability to predict change and its impact. Understanding and knowledge are built on data and information, yet polar information is scattered, scarce, and sporadic. Rapid change demands rapid data access. We envision a system where investigators quickly expose their data to the world and share them, without restriction, through open protocols on the Internet. A single giant, central archive is not practical for all polar data held around the world. Instead, we seek a collaborative, virtual space, where scientific data and information could be shared ethically and with minimal constraints. Inspired by the Antarctic Treaty of 1959 that established the Antarctic as a global commons to generate greater scientific understanding, the International Council of Science leads the Polar Information Commons (PIC). The PIC, engendered by the International Polar Year (IPY) and work on the IPY data policy, serves as an open, virtual repository for vital scientific data and information. An international network of scientific and data management organizations concerned with the scientific quality, integrity, and stewardship of data is developing the PIC. The PIC utilizes the Science Commons Protocol for Implementing Open Access Data, including establishment of community norms to encourage appropriate contributions to and use of PIC content. Data descriptions (metadata) are not necessarily registered in formal repositories or catalogues. They may simply be exposed to search engines or broadcast through syndication services such as RSS or Atom. The data are labeled or branded as part

  10. Secondary metabolites of Antarctic fungi antagonistic to aquatic pathogenic bacteria

    Directory of Open Access Journals (Sweden)

    Zhao Huibin

    2018-03-01

    Full Text Available Polar microbial derived antibiotics have potential as alternatives to traditional antibiotics in treating fish against pathogenic bacteria. In this paper, 23 strains of polar fungi were fermented to detect bacteriostatic products on three aquatic pathogenic bacteria, subsequently the active fungus was identified. It was indicated that secondary metabolites of 23 strains weredistinct; of these, the extract of strain B-7 (belonging to Bjerkandera according to molecular identification demonstrated a strong antibacterial activity to Streptococcus agalactiae, Vibrio anguillarum and Aeromonas hydrophila ATCC7966 by Kirby-Bauerpaper strip method. During one fermentation cycle, the pH curve of the fermentation liquor became lowest (4.0 on the 4th day and rose back to 7.6 finally after 5 days, The residual sugar curve was decreased before stablising on the 6th day. It is presumed that a large amount of alkaline secondary metabolites might have been produced during fermentation. This study focuses on antagonism between aquatic pathogenic bacteria and fermentation metabolites from Antarctic fungi for the first time, which may provide data on research of antibiotics against aquatic pathogenic bacteria.

  11. Advancing Environmental Prediction Capabilities for the Polar Regions and Beyond during The Year of Polar Prediction

    Science.gov (United States)

    Werner, Kirstin; Goessling, Helge; Hoke, Winfried; Kirchhoff, Katharina; Jung, Thomas

    2017-04-01

    Environmental changes in polar regions open up new opportunities for economic and societal operations such as vessel traffic related to scientific, fishery and tourism activities, and in the case of the Arctic also enhanced resource development. The availability of current and accurate weather and environmental information and forecasts will therefore play an increasingly important role in aiding risk reduction and safety management around the poles. The Year of Polar Prediction (YOPP) has been established by the World Meteorological Organization's World Weather Research Programme as the key activity of the ten-year Polar Prediction Project (PPP; see more on www.polarprediction.net). YOPP is an internationally coordinated initiative to significantly advance our environmental prediction capabilities for the polar regions and beyond, supporting improved weather and climate services. Scheduled to take place from mid-2017 to mid-2019, the YOPP core phase covers an extended period of intensive observing, modelling, prediction, verification, user-engagement and education activities in the Arctic and Antarctic, on a wide range of time scales from hours to seasons. The Year of Polar Prediction will entail periods of enhanced observational and modelling campaigns in both polar regions. With the purpose to close the gaps in the conventional polar observing systems in regions where the observation network is sparse, routine observations will be enhanced during Special Observing Periods for an extended period of time (several weeks) during YOPP. This will allow carrying out subsequent forecasting system experiments aimed at optimizing observing systems in the polar regions and providing insight into the impact of better polar observations on forecast skills in lower latitudes. With various activities and the involvement of a wide range of stakeholders, YOPP will contribute to the knowledge base needed to managing the opportunities and risks that come with polar climate change.

  12. Measurement of vortex velocities over a wide range of vortex age, downstream distance and free stream velocity

    Science.gov (United States)

    Rorke, J. B.; Moffett, R. C.

    1977-01-01

    A wind tunnel test was conducted to obtain vortex velocity signatures over a wide parameter range encompassing the data conditions of several previous researchers while maintaining a common instrumentation and test facility. The generating wing panel was configured with both a revolved airfoil tip shape and a square tip shape and had a semispan aspect of 4.05/1.0 with a 121.9 cm span. Free stream velocity was varied from 6.1 m/sec to 76.2 m/sec and the vortex core velocities were measured at locations 3, 6, 12, 24 and 48 chordlengths downstream of the wing trailing edge, yielding vortex ages up to 2.0 seconds. Wing pitch angles of 6, 8, 9 and 12 deg were investigated. Detailed surface pressure distributions and wing force measurements were obtained for each wing tip configuration. Correlation with vortex velocity data taken in previous experiments is good. During the rollup process, vortex core parameters appear to be dependent primarily on vortex age. Trending in the plateau and decay regions is more complex and the machanisms appear to be more unstable.

  13. Shock/vortex interaction and vortex-breakdown modes

    Science.gov (United States)

    Kandil, Osama A.; Kandil, H. A.; Liu, C. H.

    1992-01-01

    Computational simulation and study of shock/vortex interaction and vortex-breakdown modes are considered for bound (internal) and unbound (external) flow domains. The problem is formulated using the unsteady, compressible, full Navier-Stokes (NS) equations which are solved using an implicit, flux-difference splitting, finite-volume scheme. For the bound flow domain, a supersonic swirling flow is considered in a configured circular duct and the problem is solved for quasi-axisymmetric and three-dimensional flows. For the unbound domain, a supersonic swirling flow issued from a nozzle into a uniform supersonic flow of lower Mach number is considered for quasi-axisymmetric and three-dimensional flows. The results show several modes of breakdown; e.g., no-breakdown, transient single-bubble breakdown, transient multi-bubble breakdown, periodic multi-bubble multi-frequency breakdown and helical breakdown.

  14. Three-vortex configurations in trapped Bose-Einstein condensates

    International Nuclear Information System (INIS)

    Seman, J. A.; Henn, E. A. L.; Shiozaki, R. F.; Ramos, E. R. F.; Caracanhas, M.; Castilho, P.; Castelo Branco, C.; Tavares, P. E. S.; Poveda-Cuevas, F. J.; Magalhaes, K. M. F.; Bagnato, V. S.; Haque, M.; Roati, G.

    2010-01-01

    We report on the creation of three-vortex clusters in a 87 Rb Bose-Einstein condensate by oscillatory excitation of the condensate. This procedure can create vortices of both circulations, so that we are able to create several types of vortex clusters using the same mechanism. The three-vortex configurations are dominated by two types, namely, an equilateral-triangle arrangement and a linear arrangement. We interpret these most stable configurations respectively as three vortices with the same circulation and as a vortex-antivortex-vortex cluster. The linear configurations are very likely experimental signatures of predicted stationary vortex clusters.

  15. Large-scale vortex structures and local heat release in lean turbulent swirling jet-flames under vortex breakdown conditions

    Science.gov (United States)

    Chikishev, Leonid; Lobasov, Aleksei; Sharaborin, Dmitriy; Markovich, Dmitriy; Dulin, Vladimir; Hanjalic, Kemal

    2017-11-01

    We investigate flame-flow interactions in an atmospheric turbulent high-swirl methane/air lean jet-flame at Re from 5,000 to 10,000 and equivalence ratio below 0.75 at the conditions of vortex breakdown. The focus is on the spatial correlation between the propagation of large-scale vortex structures, including precessing vortex core, and the variations of the local heat release. The measurements are performed by planar laser-induced fluorescence of hydroxyl and formaldehyde, applied simultaneously with the stereoscopic particle image velocimetry technique. The data are processed by the proper orthogonal decomposition. The swirl rate exceeded critical value for the vortex breakdown resulting in the formation of a processing vortex core and secondary helical vortex filaments that dominate the unsteady flow dynamics both of the non-reacting and reacting jet flows. The flame front is located in the inner mixing layer between the recirculation zone and the annular swirling jet. A pair of helical vortex structures, surrounding the flame, stretch it and cause local flame extinction before the flame is blown away. This work is supported by Russian Science Foundation (Grant No 16-19-10566).

  16. Propagation of partially coherent vector anomalous vortex beam in turbulent atmosphere

    Science.gov (United States)

    Zhang, Xu; Wang, Haiyan; Tang, Lei

    2018-01-01

    A theoretical model is proposed to describe a partially coherent vector anomalous vortex(AV) beam. Based on the extended Huygens-Fresnel principle, analytical propagation formula for the proposed beams in turbulent atmosphere is derived. The spectral properties of the partially coherent vector AV beam are explored by using the unified theory of coherence and polarization in detail. It is interesting to find that the turbulence of atmosphere and the source parameter of the partially coherent vector AV beam( order, topological charge, coherence length, beam waist size etc) have significantly impacted the propagation properties of the partially coherent vector AV beam in turbulent atmosphere.

  17. Interaction of vortex lattice with ultrasound and the acoustic Faraday effect

    International Nuclear Information System (INIS)

    Dominguez, D.; Bulaevskii, L.; Ivlev, B.; Maley, M.; Bishop, A.R.

    1995-01-01

    The interaction of sound with the vortex lattice is considered for high-T c superconductors, taking into account pinning and electrodynamic forces between vortices and crystal displacements. At low temperatures the Magnus force results in the acoustic Faraday effect; the velocity of sound propagating along the magnetic field depends on the polarization. This effect is linear in the Magnus force and magnetic field in crystals with equivalent a and b axes for a field parallel to the c axis. In the thermally activated flux flow regime, the Faraday effect is caused by electric and magnetic fields induced by vortices and acting on ions

  18. On the evolution of vortex rings with swirl

    International Nuclear Information System (INIS)

    Naitoh, Takashi; Okura, Nobuyuki; Gotoh, Toshiyuki; Kato, Yusuke

    2014-01-01

    A laminar vortex ring with swirl, which has the meridional velocity component inside the vortex core, was experimentally generated by the brief fluid ejection from a rotating outlet. The evolution of the vortex ring was investigated with flow visualizations and particle image velocimetry measurements in order to find the influence of swirling flow in particular upon the transition to turbulence. Immediately after the formation of a vortex ring with swirl, a columnar strong vortex along the symmetric axis is observed in all cases of the present experiment. Then the characteristic fluid discharging from a vortex ring with swirl referred to as “peeling off” appears. The amount of discharging fluid due to the “peeling off” increases with the angular velocity of the rotating outlet. We conjectured that the mechanism generating the “peeling off” is related to the columnar strong vortex by close observations of the spatio-temporal development of the vorticity distribution and the cutting 3D images constructed from the successive cross sections of a vortex ring. While a laminar vortex ring without swirl may develop azimuthal waves around its circumference at some later time and the ring structure subsequently breaks, the swirling flow in a vortex ring core reduces the amplification rate of the azimuthal wavy deformation and preserved its ring structure. Then the traveling distance of a vortex ring can be extended using the swirl flow under certain conditions

  19. On the evolution of vortex rings with swirl

    Energy Technology Data Exchange (ETDEWEB)

    Naitoh, Takashi, E-mail: naitoh.takashi@nitech.ac.jp [Department of Engineering Physics, Electronics and Mechanics, Graduate School of Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan); Okura, Nobuyuki, E-mail: ohkura@meijo-u.ac.jp [Department of Vehicle and Mechanical Engineering, Meijo University, 1-501 Shiogamaguchi Tempaku-ku, Nagoya 468-8502 (Japan); Gotoh, Toshiyuki, E-mail: gotoh.toshiyuki@nitech.ac.jp [Department of Scientific and Engineering Simulation, Graduate School of Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan); Kato, Yusuke [Controller Business Unit Engineering Division 1, Engineering Department 3, Denso Wave Incorporated, 1 Yoshiike Kusagi Agui-cho, Chita-gun Aichi 470-2297 (Japan)

    2014-06-15

    A laminar vortex ring with swirl, which has the meridional velocity component inside the vortex core, was experimentally generated by the brief fluid ejection from a rotating outlet. The evolution of the vortex ring was investigated with flow visualizations and particle image velocimetry measurements in order to find the influence of swirling flow in particular upon the transition to turbulence. Immediately after the formation of a vortex ring with swirl, a columnar strong vortex along the symmetric axis is observed in all cases of the present experiment. Then the characteristic fluid discharging from a vortex ring with swirl referred to as “peeling off” appears. The amount of discharging fluid due to the “peeling off” increases with the angular velocity of the rotating outlet. We conjectured that the mechanism generating the “peeling off” is related to the columnar strong vortex by close observations of the spatio-temporal development of the vorticity distribution and the cutting 3D images constructed from the successive cross sections of a vortex ring. While a laminar vortex ring without swirl may develop azimuthal waves around its circumference at some later time and the ring structure subsequently breaks, the swirling flow in a vortex ring core reduces the amplification rate of the azimuthal wavy deformation and preserved its ring structure. Then the traveling distance of a vortex ring can be extended using the swirl flow under certain conditions.

  20. Phase diagram of a lattice of pancake vortex molecules

    International Nuclear Information System (INIS)

    Tanaka, Y.; Crisan, A.; Shivagan, D.D.; Iyo, A.; Shirage, P.M.; Tokiwa, K.; Watanabe, T.; Terada, N.

    2009-01-01

    On a superconducting bi-layer with thickness much smaller than the penetration depth, λ, a vortex molecule might form. A vortex molecule is composed of two fractional vortices and a soliton wall. The soliton wall can be regarded as a Josephson vortex missing magnetic flux (degenerate Josephson vortex) due to an incomplete shielding. The magnetic energy carried by fractional vortices is less than in the conventional vortex. This energy gain can pay a cost to form a degenerate Josephson vortex. The phase diagram of the vortex molecule is rich because of its rotational freedom.

  1. Phenomenological Model of Vortex Generators

    DEFF Research Database (Denmark)

    Hansen, Martin Otto Laver; Westergaard, C.

    1995-01-01

    For some time attempts have been made to improve the power curve of stall regulated wind turbines by using devices like vortex generators VG and Gurney flaps. The vortex produces an additional mixing of the boundary layer and the free stream and thereby increasing the momentum close to the wall......, which again delays separation in adverse pressure gradient regions. A model is needed to include the effect of vortex generators in numerical computations of the viscous flow past rotors. In this paper a simple model is proposed....

  2. Three-dimensional parallel vortex rings in Bose-Einstein condensates

    International Nuclear Information System (INIS)

    Crasovan, Lucian-Cornel; Perez-Garcia, Victor M.; Danaila, Ionut; Mihalache, Dumitru; Torner, Lluis

    2004-01-01

    We construct three-dimensional structures of topological defects hosted in trapped wave fields, in the form of vortex stars, vortex cages, parallel vortex lines, perpendicular vortex rings, and parallel vortex rings, and we show that the latter exist as robust stationary, collective states of nonrotating Bose-Einstein condensates. We discuss the stability properties of excited states containing several parallel vortex rings hosted by the condensate, including their dynamical and structural stability

  3. Experimental and numerical studies in a vortex tube

    International Nuclear Information System (INIS)

    Sohn, Chang Hyun; Kim, Chang Soo; Gowda, B. H. L Lakshmana; Jung, Ui Hyun

    2006-01-01

    The present investigation deals with the study of the internal flow phenomena of the counter-flow type vortex tube using experimental testing and numerical simulation. Visualization was carried out using the surface tracing method, injecting dye on the vortex tube wall using a needle. Vortex tube is made of acrylic to visualize the surface particle tracing and the input air pressure was varied from 0.1 MPa to 0.3 MPa. The experimentally visualized results on the tube show that there is an apparent sudden changing of the trajectory on the vortex tube wall which was observed in every experimental test case. This may indicate the stagnation position of the vortex flow. The visualized stagnation position moves towards the vortex generator with increase in cold flow ratio and input pressure. Three-dimensional computational study is also conducted to obtain more detailed flow information in the vortex tube. Calculated total pressure, static pressure and total temperature distributions in the vortex tube were in good agreement with the experimental data. The computational particle trace on the vortex tube wall is very similar to that observed in experiments

  4. Vortex phase diagram and vortex dynamics at low temperature in a thick a-MgxB1-x film

    International Nuclear Information System (INIS)

    Okuma, S.; Kohara, M.

    2007-01-01

    We report on the equilibrium vortex phase diagram and vortex dynamics at low temperature T in a thick amorphous (a-)Mg x B 1-x film based on the measurements of the dc resistivity ρ and time (t)-dependent component of the flux-flow voltage, δV(t), respectively. Both ρ(T) in perpendicular fields and the vortex phase diagram are qualitatively similar to those for the a-Mo x Si 1-x films, in which evidence for the quantum-vortex-liquid (QVL) phase has been obtained. In either material system we observe anomalous vortex flow with the asymmetric distribution of δV(t) in the QVL phase, suggesting that the anomalous flow is a universal phenomenon commonly observed for disordered amorphous films, independent of material

  5. Report on workshop "Study of the Antarctic ice sheet and glacier using ERS-1/JERS-1 SAR data"

    Directory of Open Access Journals (Sweden)

    Naohiko Hirasawa

    1996-07-01

    Full Text Available The main purpose of the workshop is to discuss recent results of Antarctic research using SAR data. It was held on February 6,1996 at the National Institute of Polar Research (NIPR, the number of participants being about 30. The contents of the workshop are demonstration of various SAR images, comparison with pictures from an airplane and visible images, comparison with observational data on ice conditions and demonstration of problems in interferometry.

  6. Green functions of vortex operators

    International Nuclear Information System (INIS)

    Polchinski, J.; California Univ., Berkeley

    1981-01-01

    We study the euclidean Green functions of the 't Hooft vortex operator, primarly for abelian gauge theories. The operator is written in terms of elementary fields, with emphasis on a form in which it appears as the exponential of a surface integral. We explore the requirement that the Green functions depend only on the boundary of this surface. The Dirac veto problem appears in a new guise. We present a two-dimensional solvable model of a Dirac string, which suggests a new solution of the veto problem. The renormalization of the Green functions of the abelian Wilson loop and abelian vortex operator is studied with the aid of the operator product expansion. In each case, an overall multiplication of the operator makes all Green functions finite; a surprising cancellation of divergences occurs with the vortex operator. We present a brief discussion of the relation between the nature of the vacuum and the cluster properties of the Green functions of the Wilson and vortex operators, for a general gauge theory. The surface-like cluster property of the vortex operator in an abelian Higgs theory is explored in more detail. (orig.)

  7. Carbon dioxide emissions of Antarctic tourism

    NARCIS (Netherlands)

    Farreny, R.; Oliver-Solà, J.; Lamers, M.A.J.; Amelung, B.; Gabarrell, X.; Rieradevall, J.; Boada, M.; Benayas, J.

    2011-01-01

    The increase of tourism to the Antarctic continent may entail not only local but also global environmental impacts. These latter impacts, which are mainly caused by transport, have been generally ignored. As a result, there is a lack of data on the global impacts of Antarctic tourism in terms of

  8. Constraining the Antarctic contribution to global sea-level change: ANDRILL and beyond

    Science.gov (United States)

    Naish, Timothy

    2016-04-01

    Observations, models and paleoclimate reconstructions suggest that Antarctica's marine-based ice sheets behave in an unstable manner with episodes of rapid retreat in response to warming climate. Understanding the processes involved in this "marine ice sheet instability" is key for improving estimates of Antarctic ice sheet contribution to future sea-level rise. Another motivating factor is that far-field sea-level reconstructions and ice sheet models imply global mean sea level (GMSL) was up to 20m and 10m higher, respectively, compared with present day, during the interglacials of the warm Pliocene (~4-3Ma) and Late Pleistocene (at ~400ka and 125ka). This was when atmospheric CO2 was between 280 and 400ppm and global average surface temperatures were 1 to 3°C warmer, suggesting polar ice sheets are highly sensitive to relatively modest increases in climate forcing. Such magnitudes of GMSL rise not only require near complete melt of the Greenland Ice Sheet and the West Antarctic Ice Sheet, but a substantial retreat of marine-based sectors of East Antarctic Ice Sheet. Recent geological drilling initiatives on the continental margin of Antarctica from both ship- (e.g. IODP; International Ocean Discovery Program) and ice-based (e.g. ANDRILL/Antarctic Geological Drilling) platforms have provided evidence supporting retreat of marine-based ice. However, without direct access through the ice sheet to archives preserved within sub-glacial sedimentary basins, the volume and extent of ice sheet retreat during past interglacials cannot be directly constrained. Sediment cores have been successfully recovered from beneath ice shelves by the ANDRILL Program and ice streams by the WISSARD (Whillans Ice Stream Sub-glacial Access Research Drilling) Project. Together with the potential of the new RAID (Rapid Access Ice Drill) initiative, these demonstrate the technological feasibility of accessing the subglacial bed and deeper sedimentary archives. In this talk I will outline the

  9. Single vortex states in a confined Bose-Einstein condensate

    International Nuclear Information System (INIS)

    Komineas, S.; Cooper, N. R.; Papanicolaou, N.

    2005-01-01

    It has been demonstrated experimentally that non-axisymmetric vortices precess around the center of a Bose-Einstein condensate. Two types of single vortex states have been observed, usually referred to as the S vortex and the U vortex. We study theoretically the single vortex excitations in spherical and elongated condensates as a function of the interaction strength. We solve numerically the Gross-Pitaevskii equation and calculate the angular momentum as a function of precession frequency. The existence of two types of vortices means that we have two different precession frequencies for each angular momentum value. As the interaction strength increases the vortex lines bend and the precession frequencies shift to lower values. We establish that for given angular momentum the S vortex has higher energy than the U vortex in a rotating elongated condensate. We show that the S vortex is related to the solitonic vortex, which is a nonlinear excitation in the nonrotating system. For small interaction strengths the S vortex is related to the dark soliton. In the dilute limit a lowest Landau level calculation provides an analytic description of these vortex modes in terms of the harmonic oscillator states

  10. Vortex dynamics in the wake of a pivoted cylinder undergoing vortex-induced vibrations with elliptic trajectories

    Science.gov (United States)

    Marble, Erik; Morton, Christopher; Yarusevych, Serhiy

    2018-05-01

    Vortex-induced vibrations of a pivoted cylinder are investigated experimentally at a fixed Reynolds number of 3100, a mass ratio of 10.8, and a range of reduced velocities, 4.42 ≤ U^* ≤ 9.05. For these conditions, the cylinder traces elliptic trajectories, with the experimental conditions producing three out of four possible combinations of orbiting direction and primary axis alignment relative to the incoming flow. The study focuses on the quantitative analysis of wake topology and its relation to this type of structural response. Velocity fields were measured using time-resolved, two-component particle image velocimetry (TR-PIV). These results show that phase-averaged wake topology generally agrees with the Morse and Williamson (J Fluids Struct 25(4):697-712, 2009) shedding map for one-degree-of-freedom vortex-induced vibrations, with 2S, 2{P}o, and 2P shedding patterns observed within the range of reduced velocities studied here. Vortex tracking and vortex strength quantification are used to analyze the vortex shedding process and how it relates to cylinder response. In the case of 2S vortex shedding, vortices are shed when the cylinder is approaching the maximum transverse displacement and reaches the streamwise equilibrium. 2P vortices are shed approximately half a period earlier in the cylinder's elliptic trajectory. Leading vortices shed immediately after the peak in transverse oscillation and trailing vortices shed near the equilibrium of transverse oscillation. The orientation and direction of the cylinder's elliptic trajectory are shown to influence the timing of vortex shedding, inducing changes in the 2P wake topology.

  11. Revision of Eocene Antarctic carpet sharks (Elasmobranchii, Orectolobiformes) from Seymour Island, Antarctic Peninsula.

    Science.gov (United States)

    Engelbrecht, Andrea; Mörs, Thomas; Reguero, Marcelo A; Kriwet, Jürgen

    2017-01-01

    Seymour Island, Antarctic Peninsula, was once called the 'Rosetta Stone' of Southern Hemisphere palaeobiology, because this small island provides the most complete and richly fossiliferous Palaeogene sequence in Antarctica. Among fossil marine vertebrate remains, chondrichthyans seemingly were dominant elements in the Eocene Antarctic fish fauna. The fossiliferous sediments on Seymour Island are from the La Meseta Formation, which was originally divided into seven stratigraphical levels, TELMs 1-7 (acronym for Tertiary Eocene La Meseta) ranging from the upper Ypresian (early Eocene) to the late Priabonian (late Eocene). Bulk sampling of unconsolidated sediments from TELMs 5 and 6, which are Ypresian (early Eocene) and Lutetian (middle Eocene) in age, respectively, yielded very rich and diverse chondrichthyan assemblages including over 40 teeth of carpet sharks representing two new taxa, Notoramphoscyllium woodwardi gen. et sp. nov. and Ceolometlaouia pannucae gen. et sp. nov. Two additional teeth from TELM 5 represent two different taxa that cannot be assigned to any specific taxon and thus are left in open nomenclature. The new material not only increases the diversity of Eocene Antarctic selachian faunas but also allows two previous orectolobiform records to be re-evaluated. Accordingly, Stegostoma cf. faciatum is synonymized with Notoramphoscyllium woodwardi gen. et sp. nov., whereas Pseudoginglymostoma cf. brevicaudatum represents a nomen dubium . The two new taxa, and probably the additional two unidentified taxa, are interpreted as permanent residents, which most likely were endemic to Antarctic waters during the Eocene and adapted to shallow and estuarine environments.

  12. Increased West Antarctic and unchanged East Antarctic ice discharge over the last 7 years

    Science.gov (United States)

    Gardner, Alex S.; Moholdt, Geir; Scambos, Ted; Fahnstock, Mark; Ligtenberg, Stefan; van den Broeke, Michiel; Nilsson, Johan

    2018-02-01

    Ice discharge from large ice sheets plays a direct role in determining rates of sea-level rise. We map present-day Antarctic-wide surface velocities using Landsat 7 and 8 imagery spanning 2013-2015 and compare to earlier estimates derived from synthetic aperture radar, revealing heterogeneous changes in ice flow since ˜ 2008. The new mapping provides complete coastal and inland coverage of ice velocity north of 82.4° S with a mean error of image pairs acquired during the daylight period. Using an optimized flux gate, ice discharge from Antarctica is 1929 ± 40 Gigatons per year (Gt yr-1) in 2015, an increase of 36 ± 15 Gt yr-1 from the time of the radar mapping. Flow accelerations across the grounding lines of West Antarctica's Amundsen Sea Embayment, Getz Ice Shelf and Marguerite Bay on the western Antarctic Peninsula, account for 88 % of this increase. In contrast, glaciers draining the East Antarctic Ice Sheet have been remarkably constant over the period of observation. Including modeled rates of snow accumulation and basal melt, the Antarctic ice sheet lost ice at an average rate of 183 ± 94 Gt yr-1 between 2008 and 2015. The modest increase in ice discharge over the past 7 years is contrasted by high rates of ice sheet mass loss and distinct spatial patters of elevation lowering. The West Antarctic Ice Sheet is experiencing high rates of mass loss and displays distinct patterns of elevation lowering that point to a dynamic imbalance. We find modest increase in ice discharge over the past 7 years, which suggests that the recent pattern of mass loss in Antarctica is part of a longer-term phase of enhanced glacier flow initiated in the decades leading up to the first continent-wide radar mapping of ice flow.

  13. Chilean Antarctic Stations on King George Island

    OpenAIRE

    Katsutada Kaminuma

    2000-01-01

    The purpose of my visit to Chilean Antarctic Stations was to assess the present status of geophysical observations and research, as the South Shetland Island, West Antarctica, where the stations are located, are one of the most active tectonic regions on the Antarctic plate. The Instituto Antartico Chileno (INACH) kindly gave me a chance to stay in Frei/Escudero Bases as an exchange scientist under the Antarctic Treaty for two weeks in January 2000. I stayed in Frei Base as a member of a geol...

  14. A pivotal role for ocean eddies in the distribution of microbial communities across the Antarctic Circumpolar Current.

    Directory of Open Access Journals (Sweden)

    Siddarthan Venkatachalam

    Full Text Available Mesoscale variability and associated eddy fluxes play crucial roles in ocean circulation dynamics and the ecology of the upper ocean. In doing so, these features are biologically important, providing a mechanism for the mixing and exchange of nutrients and biota within the ocean. Transient mesoscale eddies in the Southern Ocean are known to relocate zooplankton communities across the Antarctic Circumpolar Current (ACC and are important foraging grounds for marine top predators. In this study we investigated the role of cyclonic and anti-cyclonic eddies formed at the South-West Indian Ridge on the spatial variability and diversity of microbial communities. We focused on two contrasting adjacent eddies within the Antarctic Polar Frontal Zone to determine how these features may influence the microbial communities within this region. The water masses and microbiota of the two eddies, representative of a cyclonic cold core from the Antarctic zone and an anti-cyclonic warm-core from the Subantarctic zone, were compared. The data reveal that the two eddies entrain distinct microbial communities from their points of origin that are maintained for up to ten months. Our findings highlight the ecological impact that changes, brought by the translocation of eddies across the ACC, have on microbial diversity.

  15. Vortex matter stabilized by many-body interactions

    Science.gov (United States)

    Wolf, S.; Vagov, A.; Shanenko, A. A.; Axt, V. M.; Aguiar, J. Albino

    2017-10-01

    This work investigates interactions of vortices in superconducting materials between standard types I and II, in the domain of the so-called intertype (IT) superconductivity. Contrary to common expectations, the many-body (many-vortex) contribution is not a correction to the pair-vortex interaction here but plays a crucial role in the formation of the IT vortex matter. In particular, the many-body interactions stabilize vortex clusters that otherwise could not exist. Furthermore, clusters with large numbers of vortices become more stable when approaching the boundary between the intertype domain and type I. This indicates that IT superconductors develop a peculiar unconventional type of the vortex matter governed by the many-body interactions of vortices.

  16. Back reaction of excitations on a vortex

    Science.gov (United States)

    Arodź, Henryk; Hadasz, Leszek

    1997-01-01

    Excitations of a vortex are usually considered in a linear approximation neglecting their back reaction on the vortex. In the present paper we investigate back reaction of Proca-type excitations on a straight linear vortex in the Abelian Higgs model. We propose an exact ansatz for fields of the excited vortex. From an initial set of six nonlinear field equations we obtain (in a limit of weak excitations) two linear wave equations for the back reaction corrections. Their approximate solutions are found in the cases of plane wave and wave-packet-type excitations. We find that the excited vortex radiates the vector field and that the Higgs field has a very broad oscillating component.

  17. Generalized Kutta–Joukowski theorem for multi-vortex and multi-airfoil flow (a lumped vortex model

    Directory of Open Access Journals (Sweden)

    Bai Chenyuan

    2014-02-01

    Full Text Available For purpose of easy identification of the role of free vortices on the lift and drag and for purpose of fast or engineering evaluation of forces for each individual body, we will extend in this paper the Kutta–Joukowski (KJ theorem to the case of inviscid flow with multiple free vortices and multiple airfoils. The major simplification used in this paper is that each airfoil is represented by a lumped vortex, which may hold true when the distances between vortices and bodies are large enough. It is found that the Kutta–Joukowski theorem still holds provided that the local freestream velocity and the circulation of the bound vortex are modified by the induced velocity due to the outside vortices and airfoils. We will demonstrate how to use the present result to identify the role of vortices on the forces according to their position, strength and rotation direction. Moreover, we will apply the present results to a two-cylinder example of Crowdy and the Wagner example to demonstrate how to perform fast force approximation for multi-body and multi-vortex problems. The lumped vortex assumption has the advantage of giving such kinds of approximate results which are very easy to use. The lack of accuracy for such a fast evaluation will be compensated by a rigorous extension, with the lumped vortex assumption removed and with vortex production included, in a forthcoming paper.

  18. Numerical study of the vortex tube reconnection using vortex particle method on many graphics cards

    Science.gov (United States)

    Kudela, Henryk; Kosior, Andrzej

    2014-08-01

    Vortex Particle Methods are one of the most convenient ways of tracking the vorticity evolution. In the article we presented numerical recreation of the real life experiment concerning head-on collision of two vortex rings. In the experiment the evolution and reconnection of the vortex structures is tracked with passive markers (paint particles) which in viscous fluid does not follow the evolution of vorticity field. In numerical computations we showed the difference between vorticity evolution and movement of passive markers. The agreement with the experiment was very good. Due to problems with very long time of computations on a single processor the Vortex-in-Cell method was implemented on the multicore architecture of the graphics cards (GPUs). Vortex Particle Methods are very well suited for parallel computations. As there are myriads of particles in the flow and for each of them the same equations of motion have to be solved the SIMD architecture used in GPUs seems to be perfect. The main disadvantage in this case is the small amount of the RAM memory. To overcome this problem we created a multiGPU implementation of the VIC method. Some remarks on parallel computing are given in the article.

  19. Numerical study of the vortex tube reconnection using vortex particle method on many graphics cards

    International Nuclear Information System (INIS)

    Kudela, Henryk; Kosior, Andrzej

    2014-01-01

    Vortex Particle Methods are one of the most convenient ways of tracking the vorticity evolution. In the article we presented numerical recreation of the real life experiment concerning head-on collision of two vortex rings. In the experiment the evolution and reconnection of the vortex structures is tracked with passive markers (paint particles) which in viscous fluid does not follow the evolution of vorticity field. In numerical computations we showed the difference between vorticity evolution and movement of passive markers. The agreement with the experiment was very good. Due to problems with very long time of computations on a single processor the Vortex-in-Cell method was implemented on the multicore architecture of the graphics cards (GPUs). Vortex Particle Methods are very well suited for parallel computations. As there are myriads of particles in the flow and for each of them the same equations of motion have to be solved the SIMD architecture used in GPUs seems to be perfect. The main disadvantage in this case is the small amount of the RAM memory. To overcome this problem we created a multiGPU implementation of the VIC method. Some remarks on parallel computing are given in the article.

  20. Airborne Arctic Stratospheric Expedition II: An overview

    Science.gov (United States)

    Anderson, James G.; Toon, Owen B.

    1993-11-01

    The sudden onset of ozone depletion in the antarctic vortex set a precedent for both the time scale and the severity of global change. The Airborne Antarctic Ozone Experiment (AAOE), staged from Punta Arenas, Chile, in 1987, established that CFCs, halons, and methyl bromide, the dominant sources of chlorine and bromine radicals in the stratosphere, control the rate of ozone destruction over the Antarctic; that the vortex is depleted in reactive nitrogen and water vapor; and that diabatic cooling during the Antarctic winter leads to subsidence within the vortex core, importing air from higher altitudes and lower latitudes. This last conclusion is based on observed dramatic distortion in the tracer fields, most notably N2O.In 1989, the first Airborne Arctic Stratospheric Expedition (AASE-I), staged from Stavanger, Norway, and using the same aircraft employed for AAOE (the NASA ER-2 and the NASA DC-8), discovered that while NOx and to some degree NOy were perturbed within the arctic vortex, there was little evidence for desiccation. Under these (in contrast to the antarctic) marginally perturbed conditions, however, ClO was found to be dramatically enhanced such that a large fraction of the available (inorganic) chlorine resided in the form of ClO and its dimer ClOOCl.This leaves two abiding issues for the northern hemisphere and the mission of the second Airborne Arctic Stratospheric Expedition (AASE-II): (1) Will significant ozone erosion occur within the arctic vortex in the next ten years as chlorine loading in the stratosphere exceeds four parts per billion by volume? (2) Which mechanisms are responsible for the observed ozone erosion poleward of 30°N in the winter/spring northern hemisphere reported in satellite observations?

  1. Convection in the polar ionosphere and the state of the interplanetary medium

    Science.gov (United States)

    Uvarov, V. M.; Barashkov, P. D.

    A model of the continuous distribution of electric fields (E) controlled by parameters of the interplanetary medium has been developed which reproduces all the empirically known types of E distributions. This model is used to calculate the corresponding types of plasma convection in the polar ionosphere, represented by two-, three-, and four-vortex structures.

  2. ADMAP-2: The next-generation Antarctic magnetic anomaly map

    Science.gov (United States)

    Golynsky, Alexander; Golynsky, Dmitry; Ferraccioli, Fausto; Jordan, Tom; Damaske, Detlef; Blankenship, Don; Holt, Jack; Young, Duncan; Ivanov, Sergey; Kiselev, Alexander; Jokat, Wilfried; Gohl, Karsten; Eagles, Graeme; Bell, Robin; Armadillo, Egidio; Bozzo, Emanuelle; Caneva, Giorgio; Finn, Carol; Forsberg, Rene; Aitken, Alan

    2017-04-01

    and diurnal effects, edited for high-frequency errors, and levelled to minimize line-correlated noise. The magnetic anomaly data collected mainly in the 21-st century clearly cannot be simply stitched together with the previous surveys. Thus, mutual levelling adjustments were required to accommodate overlaps in these surveys. The final compilation merged all the available aeromagnetic and marine grids to create the new composite grid of the Antarctic with minimal mismatch along the boundaries between the datasets. Regional coverage gaps in the composite grid will be filled with anomaly estimates constrained by both the near-surface data and satellite magnetic observations taken mainly from the CHAMP and Swarm missions. Magnetic data compilations are providing tantalizing new views into regional-scale subglacial geology and crustal architecture in interior of East and West Antarctica. The ADMAP-2 map provides a new geophysical foundation to better understand the geological structure and tectonic history of Antarctica and surrounding marine areas. In particular, it will provide improved constraints on the lithospheric transition of Antarctica to its oceanic basins, and thus enable improved interpretation of the geodynamic evolution of the Antarctic lithosphere that was a key component in the assembly and break-up of the Rodinia and Gondwana supercontinents. This work was supported by the Korea Polar Research Institute.

  3. Climate-dependent evolution of Antarctic ectotherms: An integrative analysis

    Science.gov (United States)

    Pörtner, Hans O.

    2006-04-01

    , and the use of lipid body stores for neutral buoyancy. Important trade-offs result from obligatory energy savings in the permanent cold: low metabolic rates support cold-compensated growth but imply narrow windows of thermal tolerance and reduced scopes for activity. The degree of thermal specialization is not uniformly defined by cold temperature but varies with life style characteristics and activity levels and associated aerobic scope. Trade-offs for the sake of cold compensated growth parallel reduced capacities for exercise performance, exacerbated by the effect of high haemolymph magnesium levels in crustaceans and, possibly, other invertebrates. High magnesium levels likely exclude the group of reptant decapod crustaceans from Antarctic waters below 0 °C. The hypothesis is developed that energy savings imposed by the permanent cold bear specific life history consequences. Due to effects of allometry, energy savings are exacerbated at small body size, favouring passive lecithotrophic larvae. At all stages of life history, reduced energy turnover for the sake of growth causes delays and low rates in other higher functions, with the result of late maturity, fecundity and offspring release, as well as extended development. As a consequence, extended life spans evolved due to life history requirements. At the same time, polar gigantism is enabled by a combination of elevated oxygen levels in cold waters, of reduced metabolism and of extended periods of growth at slow developmental rates.

  4. Vortex Ring Interaction with a Heated Screen

    Science.gov (United States)

    Smith, Jason; Krueger, Paul S.

    2008-11-01

    Previous examinations of vortex rings impinging on porous screens has shown the reformation of the vortex ring with a lower velocity after passing through the screen, the creation of secondary vortices, and mixing. A heated screen could, in principle, alter the vortex-screen interaction by changing the local liquid viscosity and density. In the present investigation, a mechanical piston-cylinder vortex ring generator was used to create vortex rings in an aqueous sucrose solution. The rings impinged on a screen of horizontal wires that were heated using electrical current. The flow was visualized with food color and video imaging. Tests with and without heat were conducted at a piston stroke-to-jet diameter ratio of 4 and a jet Reynolds number (Re) of 1000. The vortex rings slowed after passing through the screen, but in tests with heat, they maintained a higher fraction of their before-screen velocity due to reduction in fluid viscosity near the wires. In addition, small ``fingers'' that developed on the front of the vortex rings as they passed through the screen exhibited positive buoyancy effects in the heated case.

  5. Reconsidering connectivity in the sub-Antarctic.

    Science.gov (United States)

    Moon, Katherine L; Chown, Steven L; Fraser, Ceridwen I

    2017-11-01

    Extreme and remote environments provide useful settings to test ideas about the ecological and evolutionary drivers of biological diversity. In the sub-Antarctic, isolation by geographic, geological and glaciological processes has long been thought to underpin patterns in the region's terrestrial and marine diversity. Molecular studies using increasingly high-resolution data are, however, challenging this perspective, demonstrating that many taxa disperse among distant sub-Antarctic landmasses. Here, we reconsider connectivity in the sub-Antarctic region, identifying which taxa are relatively isolated, which are well connected, and the scales across which this connectivity occurs in both terrestrial and marine systems. Although many organisms show evidence of occasional long-distance, trans-oceanic dispersal, these events are often insufficient to maintain gene flow across the region. Species that do show evidence of connectivity across large distances include both active dispersers and more sedentary species. Overall, connectivity patterns in the sub-Antarctic at intra- and inter-island scales are highly complex, influenced by life-history traits and local dynamics such as relative dispersal capacity and propagule pressure, natal philopatry, feeding associations, the extent of human exploitation, past climate cycles, contemporary climate, and physical barriers to movement. An increasing use of molecular data - particularly genomic data sets that can reveal fine-scale patterns - and more effective international collaboration and communication that facilitates integration of data from across the sub-Antarctic, are providing fresh insights into the processes driving patterns of diversity in the region. These insights offer a platform for assessing the ways in which changing dispersal mechanisms, such as through increasing human activity and changes to wind and ocean circulation, may alter sub-Antarctic biodiversity patterns in the future. © 2017 Cambridge

  6. Vortex dynamics in superconducting Corbino disk at zero field

    International Nuclear Information System (INIS)

    Enomoto, Y.; Ohta, M.

    2007-01-01

    We study the radial current driven vortex dynamics in the Corbino disk sample at zero field, by using a logarithmically interacting point vortex model involving effect of temperature, random pinning centers, and disk wall confinement force. We also take into account both the current induced vortex pair nucleation and the vortex pair annihilation processes in the model. Simulation results demonstrate that the vortex motion induced voltage exhibits almost periodic pulse behavior in time, observed experimentally, for a certain range of the model parameters. Such an anomalous behavior is thought to originate from large fluctuations of the vortex number due to the collective dynamics of this vortex system

  7. Square vortex lattice in p-wave superconductors

    International Nuclear Information System (INIS)

    Shiraishi, J.

    1999-01-01

    Making use of the Ginzburg Landau equation for isotropic p-wave superconductors, we construct the single vortex solution in part analytically. The fourfold symmetry breaking term arising from the tetragonal symmetry distortion of the Fermi surface is crucial, since this term indicates a fourfold distortion of the vortex core somewhat similar to the one found in d-wave superconductors. This fourfold distortion of the vortex core in turn favors the square vortex lattice as observed recently by small angle neutron scattering (SANS) experiment from Sr 2 RuO 4 . We find that the hexagonal vortex lattice at H = H c1 transforms into the square one for H = H cr = 0.26 H c2 . On the other hand the SANS data does not reveal such transition. The square vortex covers everywhere studied by the SANS implying H cr is very close to H c1 . Therefore some improvement in the present model is certainly desirable. (orig.)

  8. Environmental radioactivity in the antarctic station

    International Nuclear Information System (INIS)

    Gonzalez, S.; Osores, J.; Martinez, J.; Lopez, E.; Jara, R.

    1998-01-01

    Study about environmental radioactivity in the Peruvian antarctic station Machu Pichu they were carried out during the last three periods to the southern summer. The objective of the project it is to evaluate environmental component in order to elaborate a study it base on the levels background radioactivity and artificial in the antarctic region

  9. Guiding-center dynamics of vortex dipoles in Bose-Einstein condensates

    International Nuclear Information System (INIS)

    Middelkamp, S.; Schmelcher, P.; Torres, P. J.; Kevrekidis, P. G.; Frantzeskakis, D. J.; Carretero-Gonzalez, R.; Freilich, D. V.; Hall, D. S.

    2011-01-01

    A quantized vortex dipole is the simplest vortex molecule, comprising two countercirculating vortex lines in a superfluid. Although vortex dipoles are endemic in two-dimensional superfluids, the precise details of their dynamics have remained largely unexplored. We present here several striking observations of vortex dipoles in dilute-gas Bose-Einstein condensates, and develop a vortex-particle model that generates vortex line trajectories that are in good agreement with the experimental data. Interestingly, these diverse trajectories exhibit essentially identical quasiperiodic behavior, in which the vortex lines undergo stable epicyclic orbits.

  10. Vortex sorter for Bose-Einstein condensates

    International Nuclear Information System (INIS)

    Whyte, Graeme; Veitch, John; Courtial, Johannes; Oehberg, Patrik

    2004-01-01

    We have designed interferometers that sort Bose-Einstein condensates into their vortex components. The Bose-Einstein condensates in the two arms of the interferometer are rotated with respect to each other through fixed angles; different vortex components then exit the interferometer in different directions. The method we use to rotate the Bose-Einstein condensates involves asymmetric phase imprinting and is itself new. We have modeled rotation through fixed angles and sorting into vortex components with even and odd values of the topological charge of two-dimensional Bose-Einstein condensates in a number of states (pure or superposition vortex states for different values of the scattering length). Our scheme may have applications for quantum information processing

  11. Vortex 'puddles' and magic vortex numbers in mesoscopic superconducting disks

    Energy Technology Data Exchange (ETDEWEB)

    Connolly, M R; Milosevic, M V; Bending, S J [Department of Physics, University of Bath - Claverton Down, Bath, BA2 7AY (United Kingdom); Clem, J R [Ames Laboratory Department of Physics and Astronomy - Iowa State University, Ames, IA 50011-3160 (United States); Tamegai, T, E-mail: mrc61@cam.ac.u [Department of Applied Physics, University of Tokyo - Hongo, Bunkyo-ku, Tokyo 113-8627 (Japan)

    2009-03-01

    The magnetic properties of a superconducting disk change dramatically when its dimensions become mesoscopic. Unlike large disks, where the screening currents induced by an applied magnetic field are strong enough to force vortices to accumulate in a 'puddle' at the centre, in a mesoscopic disk the interaction between one of these vortices and the edge currents can be comparable to the intervortex repulsion, resulting in a destruction of the ordered triangular vortex lattice structure at the centre. Vortices instead form clusters which adopt polygonal and shell-like structures which exhibit magic number states similar to those of charged particles in a confining potential, and electrons in artificial atoms. We have fabricated mesoscopic high temperature superconducting Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+delta} disks and investigated their magnetic properties using magneto-optical imaging (MOI) and high resolution scanning Hall probe microscopy (SHPM). The temperature dependence of the vortex penetration field measured using MOI is in excellent agreement with models of the thermal excitation of pancake vortices over edge barriers. The growth of the central vortex puddle has been directly imaged using SHPM and magic vortex numbers showing higher stability have been correlated with abrupt jumps in the measured local magnetisation curves.

  12. Interaction of a strong vortex with decaying turbulence

    International Nuclear Information System (INIS)

    Terry, P.W.

    1988-01-01

    The evolution of a localized, axially symmetric vortex under the action of shear stresses associated with decaying two-dimensional turbulent vorticity which is inhomogeneous in the presence of the vortex is studied analytically. For a vortex which is sufficiently strong relative to the coefficient of turbulent eddy viscosity, it is shown that turbulent fluctuations in the vortex interior and diffusion of coherent vorticity by the turbulence localize to the vortex periphery. It is also found that the coefficient of diffusion is small compared to the coefficient of eddy viscosity. 8 refs

  13. Ring vortex solitons in nonlocal nonlinear media

    DEFF Research Database (Denmark)

    Briedis, D.; Petersen, D.E.; Edmundson, D.

    2005-01-01

    We study the formation and propagation of two-dimensional vortex solitons, i.e. solitons with a phase singularity, in optical materials with a nonlocal focusing nonlinearity. We show that nonlocality stabilizes the dynamics of an otherwise unstable vortex beam. This occurs for either single...... or higher charge fundamental vortices as well as higher order (multiple ring) vortex solitons. Our results pave the way for experimental observation of stable vortex rings in other nonlocal nonlinear systems including Bose-Einstein condensates with pronounced long-range interparticle interaction....

  14. Back reaction of excitations on a vortex

    International Nuclear Information System (INIS)

    Arodz, H.; Hadasz, L.

    1997-01-01

    Excitations of a vortex are usually considered in a linear approximation neglecting their back reaction on the vortex. In the present paper we investigate back reaction of Proca-type excitations on a straight linear vortex in the Abelian Higgs model. We propose an exact ansatz for fields of the excited vortex. From an initial set of six nonlinear field equations we obtain (in a limit of weak excitations) two linear wave equations for the back reaction corrections. Their approximate solutions are found in the cases of plane wave and wave-packet-type excitations. We find that the excited vortex radiates the vector field and that the Higgs field has a very broad oscillating component. copyright 1997 The American Physical Society

  15. Spectral analysis of point-vortex dynamics : first application to vortex polygons in a circular domain

    NARCIS (Netherlands)

    Speetjens, M.F.M.; Meleshko, V.V.; Heijst, van G.J.F.

    2014-01-01

    The present study addresses the classical problem of the dynamics and stability of a cluster of N point vortices of equal strength arranged in a polygonal configuration ("N-vortex polygons"). In unbounded domains, such N-vortex polygons are unconditionally stable for N

  16. Mutual-friction induced instability of normal-fluid vortex tubes in superfluid helium-4

    Science.gov (United States)

    Kivotides, Demosthenes

    2018-06-01

    It is shown that, as a result of its interactions with superfluid vorticity, a normal-fluid vortex tube in helium-4 becomes unstable and disintegrates. The superfluid vorticity acquires only a small (few percents of normal-fluid tube strength) polarization, whilst expanding in a front-like manner in the intervortex space of the normal-fluid, forming a dense, unstructured tangle in the process. The accompanied energy spectra scalings offer a structural explanation of analogous scalings in fully developed finite-temperature superfluid turbulence. A macroscopic mutual-friction model incorporating these findings is proposed.

  17. Effect of Recent Sea Surface Temperature Trends on the Arctic Stratospheric Vortex

    Science.gov (United States)

    Garfinkel, Chaim I.; Oman, Luke; Hurwitz, Margaret

    2015-01-01

    The springtime Arctic polar vortex has cooled significantly over the satellite era, with consequences for ozone concentrations in the springtime transition season. The causes of this cooling trend are deduced by using comprehensive chemistry-climate model experiments. Approximately half of the satellite era early springtime cooling trend in the Arctic lower stratosphere was caused by changing sea surface temperatures (SSTs). An ensemble of experiments forced only by changing SSTs is compared to an ensemble of experiments in which both the observed SSTs and chemically- and radiatively-active trace species are changing. By comparing the two ensembles, it is shown that warming of Indian Ocean, North Pacific, and North Atlantic SSTs, and cooling of the tropical Pacific, have strongly contributed to recent polar stratospheric cooling in late winter and early spring, and to a weak polar stratospheric warming in early winter. When concentrations of ozone-depleting substances and greenhouse gases are fixed, polar ozone concentrations show a small but robust decline due to changing SSTs. Ozone changes are magnified in the presence of changing gas concentrations. The stratospheric changes can be understood by examining the tropospheric height and heat flux anomalies generated by the anomalous SSTs. Finally, recent SST changes have contributed to a decrease in the frequency of late winter stratospheric sudden warmings.

  18. Dynamically controlled energy dissipation for fast magnetic vortex switching

    Science.gov (United States)

    Badea, R.; Berezovsky, J.

    2017-09-01

    Manipulation of vortex states in magnetic media provides new routes towards information storage and processing technology. The typical slow relaxation times (˜100 ns) of magnetic vortex dynamics may present an obstacle to the realization of these applications. Here, we investigate how a vortex state in a ferromagnetic microdisk can be manipulated in a way that translates the vortex core while enhancing energy dissipation to rapidly damp the vortex dynamics. We use time-resolved differential magneto-optical Kerr effect microscopy to measure the motion of the vortex core in response to applied magnetic fields. We first map out how the vortex core becomes sequentially trapped by pinning sites as it translates across the disk. After applying a fast magnetic field step to translate the vortex from one pinning site to another, we observe long-lived dynamics of the vortex as it settles to the new equilibrium. We then demonstrate how the addition of a short (<10 ns) magnetic field pulse can induce additional energy dissipation, strongly damping the long-lived dynamics. A model of the vortex dynamics using the Thiele equation of motion explains the mechanism behind this effect.

  19. Vortex Filaments in Grids for Scalable, Fine Smoke Simulation.

    Science.gov (United States)

    Meng, Zhang; Weixin, Si; Yinling, Qian; Hanqiu, Sun; Jing, Qin; Heng, Pheng-Ann

    2015-01-01

    Vortex modeling can produce attractive visual effects of dynamic fluids, which are widely applicable for dynamic media, computer games, special effects, and virtual reality systems. However, it is challenging to effectively simulate intensive and fine detailed fluids such as smoke with fast increasing vortex filaments and smoke particles. The authors propose a novel vortex filaments in grids scheme in which the uniform grids dynamically bridge the vortex filaments and smoke particles for scalable, fine smoke simulation with macroscopic vortex structures. Using the vortex model, their approach supports the trade-off between simulation speed and scale of details. After computing the whole velocity, external control can be easily exerted on the embedded grid to guide the vortex-based smoke motion. The experimental results demonstrate the efficiency of using the proposed scheme for a visually plausible smoke simulation with macroscopic vortex structures.

  20. Giant moving vortex mass in thick magnetic nanodots.

    Science.gov (United States)

    Guslienko, K Y; Kakazei, G N; Ding, J; Liu, X M; Adeyeye, A O

    2015-09-10

    Magnetic vortex is one of the simplest topologically non-trivial textures in condensed matter physics. It is the ground state of submicron magnetic elements (dots) of different shapes: cylindrical, square etc. So far, the vast majority of the vortex dynamics studies were focused on thin dots with thickness 5-50 nm and only uniform across the thickness vortex excitation modes were observed. Here we explore the fundamental vortex mode in relatively thick (50-100 nm) dots using broadband ferromagnetic resonance and show that dimensionality increase leads to qualitatively new excitation spectra. We demonstrate that the fundamental mode frequency cannot be explained without introducing a giant vortex mass, which is a result of the vortex distortion due to interaction with spin waves. The vortex mass depends on the system geometry and is non-local because of important role of the dipolar interaction. The mass is rather small for thin dots. However, its importance increases drastically with the dot thickness increasing.

  1. Modeling Vortex Generators in a Navier-Stokes Code

    Science.gov (United States)

    Dudek, Julianne C.

    2011-01-01

    A source-term model that simulates the effects of vortex generators was implemented into the Wind-US Navier-Stokes code. The source term added to the Navier-Stokes equations simulates the lift force that would result from a vane-type vortex generator in the flowfield. The implementation is user-friendly, requiring the user to specify only three quantities for each desired vortex generator: the range of grid points over which the force is to be applied and the planform area and angle of incidence of the physical vane. The model behavior was evaluated for subsonic flow in a rectangular duct with a single vane vortex generator, subsonic flow in an S-duct with 22 corotating vortex generators, and supersonic flow in a rectangular duct with a counter-rotating vortex-generator pair. The model was also used to successfully simulate microramps in supersonic flow by treating each microramp as a pair of vanes with opposite angles of incidence. The validation results indicate that the source-term vortex-generator model provides a useful tool for screening vortex-generator configurations and gives comparable results to solutions computed using gridded vanes.

  2. Non-Abelian vortex lattices

    Science.gov (United States)

    Tallarita, Gianni; Peterson, Adam

    2018-04-01

    We perform a numerical study of the phase diagram of the model proposed in [M. Shifman, Phys. Rev. D 87, 025025 (2013)., 10.1103/PhysRevD.87.025025], which is a simple model containing non-Abelian vortices. As per the case of Abrikosov vortices, we map out a region of parameter space in which the system prefers the formation of vortices in ordered lattice structures. These are generalizations of Abrikosov vortex lattices with extra orientational moduli in the vortex cores. At sufficiently large lattice spacing the low energy theory is described by a sum of C P (1 ) theories, each located on a vortex site. As the lattice spacing becomes smaller, when the self-interaction of the orientational field becomes relevant, only an overall rotation in internal space survives.

  3. Vorticity and vortex dynamics

    CERN Document Server

    Wu, Jie-Zhi; Zhou, M-D

    2006-01-01

    The importance of vorticity and vortex dynamics has now been well rec- nized at both fundamental and applied levels of ?uid dynamics, as already anticipatedbyTruesdellhalfcenturyagowhenhewrotethe?rstmonograph onthesubject, The Kinematics of Vorticity(1954);andasalsoevidencedby the appearance of several books on this ?eld in 1990s. The present book is characterizedbythefollowingfeatures: 1. A basic physical guide throughout the book. The material is directed by a basic observation on the splitting and coupling of two fundamental processes in ?uid motion, i.e., shearing (unique to ?uid) and compre- ing/expanding.Thevorticityplaysakeyroleintheformer,andavortex isnothingbuta?uidbodywithhighconcentrationofvorticitycompared to its surrounding ?uid. Thus, the vorticity and vortex dynamics is - cordinglyde?nedasthetheoryofshearingprocessanditscouplingwith compressing/expandingprocess. 2. A description of the vortex evolution following its entire life.Thisbegins from the generation of vorticity to the formation of thi...

  4. Three-dimensional supersonic vortex breakdown

    Science.gov (United States)

    Kandil, Osama A.; Kandil, Hamdy A.; Liu, C. H.

    1993-01-01

    Three-dimensional supersonic vortex-breakdown problems in bound and unbound domains are solved. The solutions are obtained using the time-accurate integration of the unsteady, compressible, full Navier-Stokes (NS) equations. The computational scheme is an implicit, upwind, flux-difference splitting, finite-volume scheme. Two vortex-breakdown applications are considered in the present paper. The first is for a supersonic swirling jet which is issued from a nozzle into a supersonic uniform flow at a lower Mach number than that of the swirling jet. The second is for a supersonic swirling flow in a configured circular duct. In the first application, an extensive study of the effects of grid fineness, shape and grid-point distribution on the vortex breakdown is presented. Four grids are used in this study and they show a substantial dependence of the breakdown bubble and shock wave on the grid used. In the second application, the bubble-type and helix-type vortex breakdown have been captured.

  5. Future Marine Polar Research Capacities - Science Planning and Research Services for a Multi-National Research Icebreaker

    Science.gov (United States)

    Biebow, N.; Lembke-Jene, L.; Wolff-Boenisch, B.; Bergamasco, A.; De Santis, L.; Eldholm, O.; Mevel, C.; Willmott, V.; Thiede, J.

    2011-12-01

    Despite significant advances in Arctic and Antarctic marine science over the past years, the polar Southern Ocean remains a formidable frontier due to challenging technical and operational requirements. Thus, key data and observations from this important region are still missing or lack adequate lateral and temporal coverage, especially from time slots outside optimal weather seasons and ice conditions. These barriers combined with the obligation to efficiently use financial resources and funding for expeditions call for new approaches to create optimally equipped, but cost-effective infrastructures. These must serve the international science community in a dedicated long-term mode and enable participation in multi-disciplinary expeditions, with secured access to optimally equipped marine platforms for world-class research in a wide range of Antarctic science topics. The high operational and technical performance capacity of a future joint European Research Icebreaker and Deep-sea Drilling Vessel (the AURORA BOREALIS concept) aims at integrating still separately operating national science programmes with different strategic priorities into joint development of long-term research missions with international cooperation both in Arctic and Antarctica. The icebreaker is planned to enable, as a worldwide first, autonomous year-round operations in the central Arctic and polar Southern Ocean, including severest ice conditions in winter, and serving all polar marine disciplines. It will facilitate the implementation of atmospheric, oceanographic, cryospheric or geophysical observatories for long-term monitoring of the polar environment. Access to the biosphere and hydrosphere e.g. beneath ice shelves or in remote regions is made possible by acting as advanced deployment platform for instruments, robotic and autonomous vehicles and ship-based air operations. In addition to a report on the long-term strategic science and operational planning objectives, we describe foreseen

  6. High Magnetic Field Vortex Microscopy by NMR

    Science.gov (United States)

    Mitrović, V. F.; Sigmund, E. E.; Bachman, H. N.; Halperin, W. P.; Reyes, A. P.; Kuhns, P.; Moulton, W. G.

    2001-03-01

    At low temperatures the ^17O NMR spectrum of HTS exhibits a characteristic vortex lattice line shape. Measurements of spin-lattice relaxation rate, T_1-1, across the vortex spectrum represent a probe of low-energy quasiparticle excitations as a function of distance from the vortex core. We report ^17O(2,3) T_1-1 measurements of YBa_2Cu_3O7 at low temperatures in magnetic fields up to 37 T. We find that the rate increases on approaching the vortex core. In the vortex core region at 37 T we observe an additional increase in the relaxation rate. The temperature dependence of the rate will also be discussed. Work at Northwestern University is supported by the NSF (DMR 91-20000) through the Science and Technology Center for Superconductivity.

  7. Vortex molecule in a nanoscopic square superconducting plate

    International Nuclear Information System (INIS)

    Suematsu, Hisataka; Kato, Masaru; Ishida, Takekazu; Koyama, Tomio; Machida, Masahiko

    2010-01-01

    Using the finite element method and solving the Bogoliubov-de Gennes equation, we have investigated magnetic field dependence of the stable vortex structures in a mesoscopic superconducting plate at low temperature (T = 0.1T c ). Because of the compactness of vortex configuration, there is interference between bound states around vortices and such quasi-particle structure affects the vortex configuration. Especially in two-vortices state, vortices form a molecule-like state, where bound states of each vortex form molecular orbital like bonding and anti-bonding states. The vortex configuration is different from that, which is expected from the repulsive interaction between vortices. (author)

  8. Tunable magnetic vortex resonance in a potential well

    Science.gov (United States)

    Warnicke, P.; Wohlhüter, P.; Suszka, A. K.; Stevenson, S. E.; Heyderman, L. J.; Raabe, J.

    2017-11-01

    We use frequency-resolved x-ray microscopy to fully characterize the potential well of a magnetic vortex in a soft ferromagnetic permalloy square. The vortex core is excited with magnetic broadband pulses and simultaneously displaced with a static magnetic field. We observe a frequency increase (blueshift) in the gyrotropic mode of the vortex core with increasing bias field. Supported by micromagnetic simulations, we show that this frequency increase is accompanied by internal deformation of the vortex core. The ability to modify the inner structure of the vortex core provides a mechanism to control the dynamics of magnetic vortices.

  9. Dynamic Control of Collapse in a Vortex Airy Beam

    Science.gov (United States)

    Chen, Rui-Pin; Chew, Khian-Hooi; He, Sailing

    2013-01-01

    Here we study systematically the self-focusing dynamics and collapse of vortex Airy optical beams in a Kerr medium. The collapse is suppressed compared to a non-vortex Airy beam in a Kerr medium due to the existence of vortex fields. The locations of collapse depend sensitively on the initial power, vortex order, and modulation parameters. The collapse may occur in a position where the initial field is nearly zero, while no collapse appears in the region where the initial field is mainly distributed. Compared with a non-vortex Airy beam, the collapse of a vortex Airy beam can occur at a position away from the area of the initial field distribution. Our study shows the possibility of controlling and manipulating the collapse, especially the precise position of collapse, by purposely choosing appropriate initial power, vortex order or modulation parameters of a vortex Airy beam. PMID:23518858

  10. Vortex-line fluctuations in model high-temperature superconductors

    International Nuclear Information System (INIS)

    Li, Y.; Teitel, S.

    1993-01-01

    We carry out Monte Carlo simulations of the uniformly frustrated three-dimensional XY model, as a model for vortex-line fluctuations in a high-T c superconductor in an external magnetic field. A density of vortex lines of f=1/25 is considered. We find two sharp phase transitions. The low-T superconducting phase is an ordered vortex-line lattice. The high-T normal phase is a vortex-line liquid, with much entangling, cutting, and loop excitations. An intermediate phase is found, which is characterized as a vortex-line liquid of disentangled, approximately straight, lines. In this phase, the system displays superconducting properties in the direction parallel to the magnetic field, but normal behavior in planes perpendicular to the field. A detailed analysis of the vortex structure function is carried out

  11. Aperiodicity Correction for Rotor Tip Vortex Measurements

    Science.gov (United States)

    Ramasamy, Manikandan; Paetzel, Ryan; Bhagwat, Mahendra J.

    2011-01-01

    The initial roll-up of a tip vortex trailing from a model-scale, hovering rotor was measured using particle image velocimetry. The unique feature of the measurements was that a microscope was attached to the camera to allow much higher spatial resolution than hitherto possible. This also posed some unique challenges. In particular, the existing methodologies to correct for aperiodicity in the tip vortex locations could not be easily extended to the present measurements. The difficulty stemmed from the inability to accurately determine the vortex center, which is a prerequisite for the correction procedure. A new method is proposed for determining the vortex center, as well as the vortex core properties, using a least-squares fit approach. This approach has the obvious advantage that the properties are derived from not just a few points near the vortex core, but from a much larger area of flow measurements. Results clearly demonstrate the advantage in the form of reduced variation in the estimated core properties, and also the self-consistent results obtained using three different aperiodicity correction methods.

  12. Superconductivity and vortex properties in various multilayers

    International Nuclear Information System (INIS)

    Koorevaar, P.

    1994-01-01

    In this thesis three qualitatively different type of superconducting multilayers are studied. We discuss the vortex lattice structure in Nb/NbZr multilayers, a system where both type of constituting layers are superconducting. At certain temperatures and for parallel fields close to H c2parallel , the Nb/NbZr system has a strongly modulated order parameter, and in this aspect resembles the high-Tc materials. By lowering the field the modulation decreases, having important consequences for the vortex lattice structure. By studying the transport critical currents we show that in the case of strong modulation the vortex lattice has a kinked structure, but at weaker modulations the vortices are straight, and the change in modulation actually results in a vortex lattice transition. Our study confirms the picture of the existence of kinked vortex lattices, but it is rather surprising that these kinked structures can exist in a system which in itself is not at all that anisotropic. It indicates the relevance of other parameters governing the vortex lattice structure. (orig.)

  13. Computational investigation of the temperature separation in vortex chamber

    International Nuclear Information System (INIS)

    Anish, S.; Setoguchi, T.; Kim, H. D.

    2014-01-01

    The vortex chamber is a mechanical device, without any moving parts that separates compressed gas into a high temperature region and a low temperature region. Functionally vortex chamber is similar to a Ranque-Hilsch vortex tube (RVHT), but it is a simpler and compact structure. The objective of the present study is to investigate computationally the physical reasoning behind the energy separation mechanism inside a vortex chamber. A computational analysis has been performed using three-dimensional compressible Navier Stokes equations. A fully implicit finite volume scheme was used to solve the governing equations. A commercial software ANSYS CFX is used for this purpose. The computational predictions were validated with existing experimental data. The results obtained show that the vortex chamber contains a large free vortex zone and a comparatively smaller forced vortex region. The physical mechanism that causes the heating towards periphery of the vortex chamber is identified as the work done by the viscous force. The cooling at the center may be due to expansion of the flow. The extent of temperature separation greatly depends on the outer diameter of the vortex chamber. A small amount of compression is observed towards the periphery of the vortex chamber when the outer diameter is reduced.

  14. Topological Vortex and Knotted Dissipative Optical 3D Solitons Generated by 2D Vortex Solitons.

    Science.gov (United States)

    Veretenov, N A; Fedorov, S V; Rosanov, N N

    2017-12-29

    We predict a new class of three-dimensional (3D) topological dissipative optical one-component solitons in homogeneous laser media with fast saturable absorption. Their skeletons formed by vortex lines where the field vanishes are tangles, i.e., N_{c} knotted or unknotted, linked or unlinked closed lines and M unclosed lines that thread all the closed lines and end at the infinitely far soliton periphery. They are generated by embedding two-dimensional laser solitons or their complexes in 3D space after their rotation around an unclosed, infinite vortex line with topological charge M_{0} (N_{c}, M, and M_{0} are integers). With such structure propagation, the "hula-hoop" solitons form; their stability is confirmed numerically. For the solitons found, all vortex lines have unit topological charge: the number of closed lines N_{c}=1 and 2 (unknots, trefoils, and Solomon knots links); unclosed vortex lines are unknotted and unlinked, their number M=1, 2, and 3.

  15. Investigation of the weathering effect on Rb-Sr systematics and trace element abundances in Antarctic and non-Antarctic meteorites

    International Nuclear Information System (INIS)

    Nishikawa, Yoshiyuki; Nakamura, Noboru; Misawa, Keiji; Okano, Osamu; Yamamoto, Koshi; Kagami, Hiroo.

    1990-01-01

    In order to examine weathering effects on chondritic meteorites in Antarctic and non-Antarctic environments, the Rb-Sr isotopic ratios and abundances of REE, Ba, Sr, Rb, and K were determined for 8H-group chondrites (Yamato-790986 [H3], Yamato-74492 [H3], Grady [H3], Brownfield [H3], Clovis (No.1) [H3], Yamato-74155 [H4], Allegan [H5] [one whole-rock and two chondrules], and Yamato-74371 [H5]), and partly for the Etter (L5) chondrite. The Allegan whole-rock shows a flat REE pattern with a large negative Eu anomaly and Sr depletion. Analyses of Rb-Sr systematics of one whole-rock and two chondrules show somewhat younger age 4.38±0.12 b.y. It is suggested that REE and Rb-Sr were redistributed during the early thermal metamorphism. Except for Allegan, most other H-chondrites (finds) show the perturbation of the Rb-Sr systematics, indicating recent loss of Rb. It was found that the weathering degree is related with the Rb-Sr disturbance in Antarctic H-chondrite. In spite of different degrees of weathering, all the Antarctic H-chondrites studied (including heavily weathered ones) show flat REE patterns normal as H-chondrite with occasional occurrence of minor Eu anomalies, indicating the tough resistance of REE in H-chondrites to the Antarctic weathering. On the other hand, non-Antarctic finds (particularly the weathered chondrites) indicate light-REE enriched patterns with a large negative Ce anomaly and extreme enrichment of Ba, suggestive of terrestrial contaminations. (author)

  16. Investigation of the late summer Si-budget in the Sub-Antarctic and Polar Front Zones south of Tasmania (SAZ-SENSE)

    Science.gov (United States)

    Fripiat, F.; Leblanc, K.; Elskens, M.; Quéguiner, B.; Armand, L.; Cornet-Barthaux, V.; André, L.; Cardinal, D.

    2009-04-01

    In the surface ocean, the Si-biogeochemical budget can be estimated by the ratio between the integrated biogenic silica dissolution and production rates. However such data are scarce in the ocean mostly because of methodology limitation. This is especially true in the Sub-Antarctic Zone (SAZ) where only two profiles were measured so far, exhibiting large variation (dissolution: production ratio of 0.3 and 3.1 for spring and summer, respectively). Though, the SAZ plays a crucial role in the efficiency of the silicate pump and the fertility of the Sub-Antarctic Mode Waters which then replenish in nutrients the majority of the surface waters of the world ocean. Therefore, better constraining the dissolution: production ratios in this region will certainly improve our understanding of these processes. During the SAZ-SENSE cruise (Jan.-Feb. 2007), the Si-budget of three stations (two in the SAZ and one in the Polar Frontal Zone, PFZ, for a total of nine profiles) covering different biogeochemical properties (e.g., Fe enriched vs. depleted conditions, dominance of diatoms vs. other phytoplankton,…) was investigated. This was implemented in the framework of an exhaustive characterization of the Si-biogeochemical cycle using different parameters: PDMPO labelling, 32Si and 30Si spiked incubations, and, taxonomy. We have developed a new method for the determination of the production and dissolution rates from the 30Si isotopic dilution technique. We now measure the changes of the 30Si-abundances in particulate and liquid phases by High Resolution Sector Field Inductively Coupled Plasma Mass Spectrometer (HR-SF-ICP-MS). This method, which is faster, more sensitive and more precise than the traditional ones using an Isotope Ratio Mass Spectrometer (IRMS) or Thermal Ionization Mass Spectrometer (TIMS), will significantly aid in expanding the biogenic silica production-dissolution dataset in the ocean. The results obtained on Si budget indicate that the Si

  17. The bathtub vortex in a rotating container

    DEFF Research Database (Denmark)

    Andersen, Anders Peter; Bohr, Tomas; Stenum, B.

    2006-01-01

    We study the time-independent free-surface flow which forms when a fluid drains out of a container, a so-called bathtub vortex. We focus on the bathtub vortex in a rotating container and describe the free-surface shape and the complex flow structure using photographs of the free surface, flow...... expansion approximation of the central vortex core and reduce the model to a single first-order equation. We solve the equation numerically and find that the axial velocity depends linearly on height whereas the azimuthal velocity is almost independent of height. We discuss the model of the bathtub vortex...

  18. A counter-rotating vortex pair in inviscid fluid

    Science.gov (United States)

    Habibah, Ummu; Fukumoto, Yasuhide

    2017-12-01

    We study the motion of a counter-rotating vortex pair with the circulations ±Γ move in incompressible fluid. The assumption is made that the core is very thin, that is the core radius σ is much smaller than the vortex radius d such that ɛ = σ/d ≪ 1. With this condition, the method of matched asymptotic expansion is employed. The solutions of the Navier-Stokes equations and the Biot-Savart law, regarding the inner and outer solutions respectively, are constructed in the form of a small parameter. An asymptotic expansion of the Biot-Savart law near the vortex core provides with the matching condition for an asymptotic expansion for limiting the Navier-Stokes equations for large radius r. The general formula of an anti-parallel vortex pair is established. At leading order O(ɛ0), we apply the special case in inviscid fluid, the Rankine vortex, a circular vortex of uniform vorticity. Furthermore at leading order O(ɛ5) we show the traveling speed of a vortex pair.

  19. Quantum Kinematics of Bosonic Vortex Loops

    International Nuclear Information System (INIS)

    Goldin, G.A.; Owczarek, R.; Sharp, D.H.

    1999-01-01

    Poisson structure for vortex filaments (loops and arcs) in 2D ideal incompressible fluid is analyzed in detail. Canonical coordinates and momenta on coadjoint orbits of the area-preserving diffeomorphism group, associated with such vortices, are found. The quantum space of states in the simplest case of ''bosonic'' vortex loops is built within a geometric quantization approach to the description of a quantum fluid. Fock-like structure and non-local creation and annihilation operators of quantum vortex filaments are introduced

  20. Bifurcation and instability problems in vortex wakes

    DEFF Research Database (Denmark)

    Aref, Hassan; Brøns, Morten; Stremler, Mark A.

    2007-01-01

    A number of instability and bifurcation problems related to the dynamics of vortex wake flows are addressed using various analytical tools and approaches. We discuss the bifurcations of the streamline pattern behind a bluff body as a vortex wake is produced, a theory of the universal Strouhal......-Reynolds number relation for vortex wakes, the bifurcation diagram for "exotic" wake patterns behind an oscillating cylinder first determined experimentally by Williamson & Roshko, and the bifurcations in topology of the streamlines pattern in point vortex streets. The Hamiltonian dynamics of point vortices...... in a periodic strip is considered. The classical results of von Kármán concerning the structure of the vortex street follow from the two-vortices-in-a-strip problem, while the stability results follow largely from a four-vortices-in-a-strip analysis. The three-vortices-in-a-strip problem is argued...

  1. Increased West Antarctic and unchanged East Antarctic ice discharge over the last 7 years

    Directory of Open Access Journals (Sweden)

    A. S. Gardner

    2018-02-01

    Full Text Available Ice discharge from large ice sheets plays a direct role in determining rates of sea-level rise. We map present-day Antarctic-wide surface velocities using Landsat 7 and 8 imagery spanning 2013–2015 and compare to earlier estimates derived from synthetic aperture radar, revealing heterogeneous changes in ice flow since ∼ 2008. The new mapping provides complete coastal and inland coverage of ice velocity north of 82.4° S with a mean error of < 10 m yr−1, resulting from multiple overlapping image pairs acquired during the daylight period. Using an optimized flux gate, ice discharge from Antarctica is 1929 ± 40 Gigatons per year (Gt yr−1 in 2015, an increase of 36 ± 15 Gt yr−1 from the time of the radar mapping. Flow accelerations across the grounding lines of West Antarctica's Amundsen Sea Embayment, Getz Ice Shelf and Marguerite Bay on the western Antarctic Peninsula, account for 88 % of this increase. In contrast, glaciers draining the East Antarctic Ice Sheet have been remarkably constant over the period of observation. Including modeled rates of snow accumulation and basal melt, the Antarctic ice sheet lost ice at an average rate of 183 ± 94 Gt yr−1 between 2008 and 2015. The modest increase in ice discharge over the past 7 years is contrasted by high rates of ice sheet mass loss and distinct spatial patters of elevation lowering. The West Antarctic Ice Sheet is experiencing high rates of mass loss and displays distinct patterns of elevation lowering that point to a dynamic imbalance. We find modest increase in ice discharge over the past 7 years, which suggests that the recent pattern of mass loss in Antarctica is part of a longer-term phase of enhanced glacier flow initiated in the decades leading up to the first continent-wide radar mapping of ice flow.

  2. Trace-element analysis of Antarctic H chondrites: Chemical weathering and comparisons with their non-Antarctic counterparts

    International Nuclear Information System (INIS)

    Kwok, J.E.

    1986-01-01

    Large numbers of meteorites have been discovered in Antarctica over the last decade (7000 fragments probably representing over 1200 separate events). They are important for their numbers and for their complement of unique or rare specimens; they also have long terrestrial ages (up to 1,000,000 years) compared to non-Antarctic falls (usually < 200 years). We report compositional data for mobile/volatile trace elements Ag, Au, Bi, Cd, Co, Cs, In, Rb, Sb, Se, Te, Ti, U, and Zn in a suite of Antarctic H chondrites. Our data show that heavily oxidized H chondrites are leached of a portion of their trace elements and, therefore, have been chemically compromised by their stay in Antarctica. The less oxidized specimens seem to have retained their chemical integrity. We suggest possibilities for using chemical data to measure the degree of a chondrite's chemical weathering. We compare our data to that obtained previously for non-Antarctic H chondrites (Linger et al., 1986), by petrologic type (H4, H5, H6, H4-6) and shock-loading (moderately shocked facies a-c, heavily shocked facies d-f). Many statistically significant differences are found between non-Antarctic and Victoria Land, Antarctica H chondrites of each petrologic type and of shock facies d-f

  3. On the self-induced motion of a helical vortex

    NARCIS (Netherlands)

    Boersma, J.; Wood, D.H.

    1999-01-01

    The velocity field in the immediate vicinity of a curved vortex comprises a circulation around the vortex, a component due to the vortex curvature, and a ‘remainder’ due to the more distant parts of the vortex. The first two components are relatively well understood but the remainder is known only

  4. Low-frequency (0.7-7.4 mHz geomagnetic field fluctuations at high latitude: frequency dependence of the polarization pattern

    Directory of Open Access Journals (Sweden)

    L. Cafarella

    2001-06-01

    Full Text Available A statistical analysis of the polarization pattern of low-frequency geomagnetic field fluctuations (0.7-7.4 mHz covering the entire 24-h interval was performed at the Antarctic station Terra Nova Bay (80.0°S geomagnetic latitude throughout 1997 and 1998. The results show that the polarization pattern exhibits a frequency dependence, as can be expected from the frequency dependence of the latitude where the coupling between the magnetospheric compressional mode and the field line resonance takes place. The polarization analysis of single pulsation events shows that wave packets with different polarization sense, depending on frequency, can be simultaneously observed.

  5. Melting of heterogeneous vortex matter: The vortex 'nanoliquid'

    Indian Academy of Sciences (India)

    E ZELDOV2, A SOIBEL3, F de la CRUZ4,CJ van der BEEK5,. M KONCZYKOWSKI5, T ... 2Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot. 76100, Israel ..... heterogeneous nature of the vortex nanoliquid.

  6. Motion of a single quantized vortex in an orifice

    International Nuclear Information System (INIS)

    Schwarz, K.W.

    1993-01-01

    Discrete phase-slip events are observed when superfluid 4 He moves through a microscopic orifice. In order to understand such behavior, one must know (a) how a quantized vortex is introduced into the orifice, and (b) how such a vortex evolves fluid dynamically so as to absorb energy from the applied flow field. To begin the study of the latter question, the authors present calculations done with an idealized orifice geometry. It is found that vortex loops larger than a critical size are carried out of the orifice and stretched by the diverging flow. As it stretches, such a vortex will cross the orifice, the energy required to stretch the vortex being absorbed from the flow field. Both a vortex loop introduced directly into the orifice and a remanent vortex extending to infinity will be discussed

  7. Meteorological observatory for Antarctic data collection

    International Nuclear Information System (INIS)

    Grigioni, P.; De Silvestri, L.

    1996-01-01

    In the last years, a great number of automatic weather stations was installed in Antarctica, with the aim to examine closely the weather and climate of this region and to improve the coverage of measuring points on the Antarctic surface. In 1987 the Italian Antarctic Project started to set up a meteorological network, in an area not completely covered by other countries. Some of the activities performed by the meteorological observatory, concerning technical functions such as maintenance of the AWS's and the execution of radio soundings, or relating to scientific purposes such as validation and elaboration of collected data, are exposed. Finally, some climatological considerations on the thermal behaviour of the Antarctic troposphere such as 'coreless winter', and on the wind field, including katabatic flows in North Victoria Land are described

  8. Theory of vortex flows in partially ionized magnetoplasmas

    Energy Technology Data Exchange (ETDEWEB)

    Jovanovic, D.; Shukla, P.K

    2004-06-07

    A complete theory for vortex flows in partially ionized magnetoplasmas is presented. Accurate analytical and numerical results are obtained concerning the structure of a Burger's vortex and a tripolar vortex. A novel type of rotating tripolar vortices with elliptic cores are found in the systems dominated by the convection in incompressible flows, but whose generation is triggered by the diffusive and compressible effects. Our vortex flow models successfully explain recent observations from laboratory magnetoplasmas and geophysical flows.

  9. Vortex Lattices in the Bose-Fermi Superfluid Mixture.

    Science.gov (United States)

    Jiang, Yuzhu; Qi, Ran; Shi, Zhe-Yu; Zhai, Hui

    2017-02-24

    In this Letter we show that the vortex lattice structure in the Bose-Fermi superfluid mixture can undergo a sequence of structure transitions when the Fermi superfluid is tuned from the BCS regime to the BEC regime. This is due to the difference in the vortex core structure of a Fermi superfluid in the BCS regime and in the BEC regime. In the BCS regime the vortex core is nearly filled, while the density at the vortex core gradually decreases until it empties out in the BEC regime. Therefore, with the density-density interaction between the Bose and the Fermi superfluids, interaction between the two sets of vortex lattices gets stronger in the BEC regime, which yields the structure transition of vortex lattices. In view of the recent realization of this superfluid mixture and vortices therein, our theoretical predication can be verified experimentally in the near future.

  10. Unveiling the Antarctic subglacial landscape.

    Science.gov (United States)

    Warner, Roland; Roberts, Jason

    2010-05-01

    Better knowledge of the subglacial landscape of Antarctica is vital to reducing uncertainties regarding prediction of the evolution of the ice sheet. These uncertainties are associated with bedrock geometry for ice sheet dynamics, including possible marine ice sheet instabilities and subglacial hydrological pathways (e.g. Wright et al., 2008). Major collaborative aerogeophysics surveys motivated by the International Polar Year (e.g. ICECAP and AGAP), and continuing large scale radar echo sounding campaigns (ICECAP and NASA Ice Bridge) are significantly improving the coverage. However, the vast size of Antarctica and logistic difficulties mean that data gaps persist, and ice thickness data remains spatially inhomogeneous. The physics governing large scale ice sheet flow enables ice thickness, and hence bedrock topography, to be inferred from knowledge of ice sheet surface topography and considerations of ice sheet mass balance, even in areas with sparse ice thickness measurements (Warner and Budd, 2000). We have developed a robust physically motivated interpolation scheme, based on these methods, and used it to generate a comprehensive map of Antarctic bedrock topography, using along-track ice thickness data assembled for the BEDMAP project (Lythe et al., 2001). This approach reduces ice thickness biases, compared to traditional inverse distance interpolation schemes which ignore the information available from considerations of ice sheet flow. In addition, the use of improved balance fluxes, calculated using a Lagrangian scheme, eliminates the grid orientation biases in ice fluxes associated with finite difference methods (Budd and Warner, 1996, Le Brocq et al., 2006). The present map was generated using a recent surface DEM (Bamber et al., 2009, Griggs and Bamber, 2009) and accumulation distribution (van de Berg et al., 2006). Comparing our results with recent high resolution regional surveys gives confidence that all major subglacial topographic features are

  11. Generalized Kutta–Joukowski theorem for multi-vortex and multi-airfoil flow with vortex production — A general model

    Directory of Open Access Journals (Sweden)

    Bai Chenyuan

    2014-10-01

    Full Text Available By using a special momentum approach and with the help of interchange between singularity velocity and induced flow velocity, we derive in a physical way explicit force formulas for two-dimensional inviscid flow involving multiple bound and free vortices, multiple airfoils, and vortex production. These force formulas hold individually for each airfoil thus allowing for force decomposition, and the contributions to forces from singularities (such as bound and image vortices, sources, and doublets and bodies out of an airfoil are related to their induced velocities at the locations of singularities inside this airfoil. The force contribution due to vortex production is related to the vortex production rate and the distance between each pair of vortices in production, thus frame-independent. The formulas are validated against a number of standard problems. These force formulas, which generalize the classic Kutta–Joukowski theorem (for a single bound vortex and the recent generalized Lagally theorem (for problems without a bound vortex and vortex production to more general cases, can be used to identify or understand the roles of outside vortices and bodies on the forces of the actual body, optimize arrangement of outside vortices and bodies for force enhancement or reduction, and derive analytical force formulas once the flow field is given or known.

  12. Polar gravity fields from GOCE and airborne gravity

    DEFF Research Database (Denmark)

    Forsberg, René; Olesen, Arne Vestergaard; Yidiz, Hasan

    2011-01-01

    Airborne gravity, together with high-quality surface data and ocean satellite altimetric gravity, may supplement GOCE to make consistent, accurate high resolution global gravity field models. In the polar regions, the special challenge of the GOCE polar gap make the error characteristics...... of combination models especially sensitive to the correct merging of satellite and surface data. We outline comparisons of GOCE to recent airborne gravity surveys in both the Arctic and the Antarctic. The comparison is done to new 8-month GOCE solutions, as well as to a collocation prediction from GOCE gradients...... in Antarctica. It is shown how the enhanced gravity field solutions improve the determination of ocean dynamic topography in both the Arctic and in across the Drake Passage. For the interior of Antarctica, major airborne gravity programs are currently being carried out, and there is an urgent need...

  13. Modeling of aerodynamics in vortex furnace

    Energy Technology Data Exchange (ETDEWEB)

    Anufriev, I.; Krasinsky, D. [Russian Academy of Sciences, Novosibirsk (Russian Federation). Inst. of Thermophysics; Salomatov, V.; Anikin, Y.; Sharypov, O. [Russian Academy of Sciences, Novosibirsk (Russian Federation). Inst. of Thermophysics; Novosibirsk State Univ. (Russian Federation); Enkhjargal, Kh. [Mongol Univ. of Science and Technology, Ulan Bator (Mongolia)

    2013-07-01

    At present, the torch burning technology of pulverized-coal fuel in vortex flow is one of the most prospective and environmentally-friendly combustion technologies of low-grade coals. Appropriate organization of aerodynamics may influence stability of temperature and heat flux distributions, increase slag catching, and reduce toxic emissions. Therefore, from scientific point of view it is interesting to investigate aerodynamics in the devices aiming at justification of design and operating parameters for new steam generators with vortex furnace, and upgrade of existing boiler equipment. The present work is devoted to physical and mathematical modeling of interior aerodynamics of vortex furnace of steam generator of thermal power plants. Research was carried out on the air isothermal model which geometry was similar to one section of the experimental- industrial boiler TPE-427 of Novosibirsk TPS-3. Main elements of vortex furnace structure are combustion chamber, diffuser, and cooling chamber. The model is made from organic glass; on the front wall two rectangular nozzles (through which compressed air is injected) are placed symmetrically at 15 to the horizon. The Laser Doppler Velocimeter LAD-05 was used for non-contact measurement of vortex flow characteristics. Two velocity components in the XY-plane (in different cross- sections of the model) were measured in these experiments. Reynolds number was 3.10{sup 5}. Numerical simulation of 3-D turbulent isothermal flow was performed with the use of CFD package FLUENT. Detailed structure of the flow in vortex furnace model has been obtained in predictions. The distributions of main flow characteristics (pressure, velocity and vorticity fields, turbulent kinetic energy) are presented. The obtained results may be used at designing boilers with vortex furnace. Computations were performed using the supercomputer NKS-160.

  14. Vortex operators in gauge field theories

    International Nuclear Information System (INIS)

    Polchinski, J.

    1980-07-01

    Several related aspects of the 't Hooft vortex operator are studied. The current picture of the vacuum of quantum chromodynamics, the idea of dual field theories, and the idea of the vortex operator are reviewed first. The Abelian vortex operator written in terms of elementary fields and the calculation of its Green's functions are considered. A two-dimensional solvable model of a Dirac string is presented. The expression of the Green's functions more neatly in terms of Wu and Yang's geometrical idea of sections is addressed. The renormalization of the Green's functions of two kinds of Abelian looplike operators, the Wilson loop and the vortex operator, is studied; for both operators only an overall multiplicative renormalization is needed. In the case of the vortex this involves a surprising cancellation. Next, the dependence of the Green's functions of the Wilson and 't Hooft operators on the nature of the vacuum is discussed. The cluster properties of the Green's functions are emphasized. It is seen that the vortex operator in a massive Abelian theory always has surface-like clustering. The form of Green's functions in terms of Feynman graphs is the same in Higgs and symmetric phases; the difference appears in the sum over all tadpole trees. Finally, systems having fields in the fundamental representation are considered. When these fields enter only weakly into the dynamics, a vortex-like operator is anticipated. Any such operator can no longer be local looplike, but must have commutators at long range. A U(1) lattice gauge theory with two matter fields, one singly charged (fundamental) and one doubly charged (adjoint), is examined. When the fundamental field is weakly coupled, the expected phase transitions are found. When it is strongly coupled, the operator still appears to be a good order parameter, a discontinuous change in its behavior leads to a new phase transition. 18 figures

  15. Idealized numerical modeling of polar mesocyclones dynamics diagnosed by energy budget

    Science.gov (United States)

    Sergeev, Dennis; Stepanenko, Victor

    2014-05-01

    Polar mesocyclones (MC) refer to a wide class of mesoscale vortices occuring poleward of the main polar front [1]. Their subtype - polar low - is commonly known for its intensity, that can result in windstorm damage of infrastructure in high latitudes. The observational data sparsity and the small size of polar MCs are major limitations for the clear understanding and numerical prediction of the evolution of these objects. The origin of polar MCs is still a matter of uncertainty, though the recent numerical investigations have exposed a strong dependence of the polar mesocyclone development upon the magnitude of baroclinicity and upon the water vapor concentration in the atmosphere. However, most of the previous studies focused on the individual polar low (the so-called case studies), with too many factors affecting it simultaneously and none of them being dominant in polar MC generation. This study focuses on the early stages of polar MC development within an idealized numerical experiments with mesoscale atmospheric model, where it is possible to look deeper into each single physical process. Our aim is to explain the role of such mechanisms as baroclinic instability or diabatic heating by comparing their contribution to the structure and dynamics of the vortex. The baroclinic instability, as reported by many researchers [2], can be a crucial factor in a MC's life cycle, especially in polar regions. Besides the baroclinic instability several diabatic processes can contribute to the energy generation that fuels a polar mesocyclone. One of the key energy sources in polar regions is surface heat fluxes. The other is the moisture content in the atmosphere that can affect the development of the disturbance by altering the latent heat release. To evaluate the relative importance of the diabatic and baroclinic energy sources for the development of the polar mesocyclone we apply energy diagnostics. In other words, we examine the rate of change of the kinetic energy (that

  16. Vorticity budget of a tornado-like vortex

    Energy Technology Data Exchange (ETDEWEB)

    Sassa, Koji; Takemura, Saki, E-mail: sassa@kochi-u.ac.jp [Department of Applied Science, Kochi University (Japan)

    2011-12-22

    We evaluated the vorticity budget of a tornado-like vortex by measuring vertical and horizontal circulations of it. Though spiral horizontal vortices are clearly observed to converge and tilted into the tornado-like vortex, their circulation is quite small. The conversion of the vertical vorticity concentrated at the side of the spiral horizontal vortices was found to mainly contribute to the maintenance of the tornado-like vortex.

  17. Distributed amplifier using Josephson vortex flow transistors

    International Nuclear Information System (INIS)

    McGinnis, D.P.; Beyer, J.B.; Nordman, J.E.

    1986-01-01

    A wide-band traveling wave amplifier using vortex flow transistors is proposed. A vortex flow transistor is a long Josephson junction used as a current controlled voltage source. The dual nature of this device to the field effect transistor is exploited. A circuit model of this device is proposed and a distributed amplifier utilizing 50 vortex flow transistors is predicted to have useful gain to 100 GHz

  18. Nonlinear Binormal Flow of Vortex Filaments

    Science.gov (United States)

    Strong, Scott; Carr, Lincoln

    2015-11-01

    With the current advances in vortex imaging of Bose-Einstein condensates occurring at the Universities of Arizona, São Paulo and Cambridge, interest in vortex filament dynamics is experiencing a resurgence. Recent simulations, Salman (2013), depict dissipative mechanisms resulting from vortex ring emissions and Kelvin wave generation associated with vortex self-intersections. As the local induction approximation fails to capture reconnection events, it lacks a similar dissipative mechanism. On the other hand, Strong&Carr (2012) showed that the exact representation of the velocity field induced by a curved segment of vortex contains higher-order corrections expressed in powers of curvature. This nonlinear binormal flow can be transformed, Hasimoto (1972), into a fully nonlinear equation of Schrödinger type. Continued transformation, Madelung (1926), reveals that the filament's square curvature obeys a quasilinear scalar conservation law with source term. This implies a broader range of filament dynamics than is possible with the integrable linear binormal flow. In this talk we show the affect higher-order corrections have on filament dynamics and discuss physical scales for which they may be witnessed in future experiments. Partially supported by NSF.

  19. The Acoustically Driven Vortex Cannon

    Science.gov (United States)

    Perry, Spencer B.; Gee, Kent L.

    2014-01-01

    Vortex cannons have been used by physics teachers for years, mostly to teach the continuity principle. In its simplest form, a vortex cannon is an empty coffee can with a hole cut in the bottom and the lid replaced. More elaborate models can be purchased through various scientific suppliers under names such as "Air Cannon" and…

  20. Vortex lattices in layered superconductors

    International Nuclear Information System (INIS)

    Prokic, V.; Davidovic, D.; Dobrosavljevic-Grujic, L.

    1995-01-01

    We study vortex lattices in a superconductor--normal-metal superlattice in a parallel magnetic field. Distorted lattices, resulting from the shear deformations along the layers, are found to be unstable. Under field variation, nonequilibrium configurations undergo an infinite sequence of continuous transitions, typical for soft lattices. The equilibrium vortex arrangement is always a lattice of isocell triangles, without shear

  1. Total ozone changes in the 1987 Antarctic ozone hole

    Science.gov (United States)

    Krueger, Arlin J.; Schoeberl, Mark R.; Doiron, Scott D.; Sechrist, Frank; Galimore, Reginald

    1988-01-01

    The development of the Antarctic ozone minimum was observed in 1987 with the Nimbus 7 Total Ozone Mapping Spectrometer (TOMS) instrument. In the first half of August the near-polar (60 and 70 deg S) ozone levels were similar to those of recent years. By September, however, the ozone at 70 and 80 deg S was clearly lower than any previous year including 1985, the prior record low year. The levels continued to decrease throughout September until October 5 when a new record low of 109 DU was established at a point near the South Pole. This value is 29 DU less than the lowest observed in 1985 and 48 DU less than the 1986 low. The zonal mean total ozone at 60 deg S remained constant throughout the time of ozone hole formation. The ozone decline was punctuated by local minima formed away from the polar night boundary at about 75 deg S. The first of these, on August 15 to 17, formed just east of the Palmer Peninsula and appears to be a mountain wave. The second major minimum formed on September 5 to 7 again downwind of the Palmer Peninsula. This event was larger in scale than the August minimum and initiated the decline of ozone across the polar region. The 1987 ozone hole was nearly circular and pole centered for its entire life. In previous years the hole was perturbed by intrusions of the circumpolar maximum into the polar regions, thus causing the hole to be elliptical. The 1987 hole also remained in place until the end of November, a few days longer than in 1985, and this persistence resulted in the latest time for recovery to normal values yet observed.

  2. Reaching for the Horizon: Enabling 21st Century Antarctic Science

    Science.gov (United States)

    Rogan-Finnemore, M.; Kennicutt, M. C., II; Kim, Y.

    2015-12-01

    The Council of Managers of National Antarctic Programs' (COMNAP) Antarctic Roadmap Challenges(ARC) project translated the 80 highest priority Antarctic and Southern Ocean scientific questionsidentified by the community via the SCAR Antarctic Science Horizon Scan into the highest prioritytechnological, access, infrastructure and logistics needs to enable the necessary research to answer thequestions. A workshop assembled expert and experienced Antarctic scientists and National AntarcticProgram operators from around the globe to discern the highest priority technological needs includingthe current status of development and availability, where the technologies will be utilized in the Antarctic area, at what temporal scales and frequencies the technologies will be employed,and how broadly applicable the technologies are for answering the highest priority scientific questions.Secondly the logistics, access, and infrastructure requirements were defined that are necessary todeliver the science in terms of feasibility including cost and benefit as determined by expected scientific return on investment. Finally, based on consideration of the science objectives and the mix oftechnologies implications for configuring National Antarctic Program logistics capabilities andinfrastructure architecture over the next 20 years were determined. In particular those elements thatwere either of a complexity, requiring long term investments to achieve and/or having an associated cost that realistically can only (or best) be achieved by international coordination, planning and partnerships were identified. Major trends (changes) in logistics, access, and infrastructure requirements were identified that allow for long-term strategic alignment of international capabilities, resources and capacity. The outcomes of this project will be reported.

  3. Psychrotrophic metal tolerant bacteria for mobilisation of metals in Antarctic waters

    Digital Repository Service at National Institute of Oceanography (India)

    Gonsalves, M.J.B.D.

    Cold tolerant psychrotrophic bacteria abound in the Antarctic waters. While Antarctic krills are known to concentrate heavy metals at ppm levels, psychrotrophic bacteria from Antarctic fresh and marine waters have been reported to tolerate them...

  4. Vortex particle method in parallel computations on graphical processing units used in study of the evolution of vortex structures

    International Nuclear Information System (INIS)

    Kudela, Henryk; Kosior, Andrzej

    2014-01-01

    Understanding the dynamics and the mutual interaction among various types of vortical motions is a key ingredient in clarifying and controlling fluid motion. In the paper several different cases related to vortex tube interactions are presented. Due to problems with very long computation times on the single processor, the vortex-in-cell (VIC) method is implemented on the multicore architecture of a graphics processing unit (GPU). Numerical results of leapfrogging of two vortex rings for inviscid and viscous fluid are presented as test cases for the new multi-GPU implementation of the VIC method. Influence of the Reynolds number on the reconnection process is shown for two examples: antiparallel vortex tubes and orthogonally offset vortex tubes. Our aim is to show the great potential of the VIC method for solutions of three-dimensional flow problems and that the VIC method is very well suited for parallel computation. (paper)

  5. A Model for the Onset of Vortex Breakdown

    Science.gov (United States)

    Mahesh, K.

    1996-01-01

    A large body of information exists on the breakdown of incompressible streamwise vortices. Less is known about vortex breakdown at high speeds. An interesting example of supersonic vortex breakdown is the breakdown induced by the interaction of vortices with shock waves. The flow in supersonic engine inlets and over high-speed delta wings constitute technologically important examples of this phenomenon, which is termed 'shock-induced vortex breakdown'. In this report, we propose a model to predict the onset of shock-induced vortex breakdown. The proposed model has no adjustable constants, and is compared to both experiment and computation. The model is then extended to consider two other problems: the breakdown of a free compressible vortex, and free incompressible vortex breakdown. The same breakdown criterion is used in all three problems to predict the onset of breakdown. Finally, a new breakdown map is proposed that allows the simultaneous comparison of data from flows ranging from incompressible breakdown to breakdown induced by a shock wave.

  6. Examples of Applications of Vortex Methods to Wind Energy

    DEFF Research Database (Denmark)

    Branlard, Emmanuel Simon Pierre

    2017-01-01

    The current chapter presents wind-energy simulations obtained with the vortex code OmniVor (described in Chap. 44 ) and compared to BEM, CFD and measurements. The chapter begins by comparing rotor loads obtained with vortex methods, BEM and actuator-line simulations of wind turbines under uniform...... and yawed inflows. The second section compares wakes and flow fields obtained by actuator-disk simulations and a free-wake vortex code that uses vortex segments and vortex particles. The third section compares different implementations of viscous diffusion models and investigate their effects...

  7. Controlling abruptly autofocusing vortex beams to mitigate crosstalk and vortex splitting in free-space optical communication.

    Science.gov (United States)

    Yan, Xu; Guo, Lixin; Cheng, Mingjian; Li, Jiangting

    2018-05-14

    Orbital angular momentum (OAM) mode crosstalk induced by atmospheric turbulence is a challenging phenomenon commonly occurring in OAM-based free-space optical (FSO) communication. Recent advances have facilitated new practicable methods using abruptly autofocusing light beams for weakening the turbulence effect on the FSO link. In this work, we show that a circular phase-locked Airy vortex beam array (AVBA) with sufficient elements has the inherent ability to form an abruptly autofocusing light beam carrying OAM, and its focusing properties can be controlled on demand by adjusting the topological charge values and locations of these vortices embedded in the array elements. The performance of a tailored Airy vortex beam array (TAVBA) through atmospheric turbulence is numerically studied. In a comparison with the ring Airy vortex beam (RAVB), the results indicate that TAVBA can be a superior light source for effectively reducing the intermodal crosstalk and vortex splitting, thus leading to improvement in the FSO system performance.

  8. Antarctic Martian Meteorites at Johnson Space Center

    Science.gov (United States)

    Funk, R. C.; Satterwhite, C. E.; Righter, K.; Harrington, R.

    2018-01-01

    This past year marked the 40th anniversary of the first Martian meteorite found in Antarctica by the ANSMET Antarctic Search for Meteorites) program, ALH 77005. Since then, an additional 14 Martian meteorites have been found by the ANSMET program making for a total of 15 Martian meteorites in the U. S. Antarctic meteorite collection at Johnson Space Center (JSC). Of the 15 meteorites, some have been paired so the 15 meteorites actually represent a total of approximately 9 separate samples. The first Martian meteorite found by ANSMET was ALH 77005 (482.500 g), a lherzolitic shergottite. When collected, this meteorite was split as a part of the joint expedition with the National Institute of Polar Research (NIPR) Japan. Originally classified as an "achondrite-unique", it was re-classified as a Martian lherzolitic shergottite in 1982. This meteorite has been allocated to 137 scientists for research and there are 180.934 g remaining at JSC. Two years later, one of the most significant Martian meteorites of the collection at JSC was found at Elephant Moraine, EET 79001 (7942.000 g), a shergottite. This meteorite is the largest in the Martian collection at JSC and was the largest stony meteorite sample collected during the 1979 season. In addition to its size, this meteorite is of particular interest because it contains a linear contact separating two different igneous lithologies, basaltic and olivine-phyric. EET 79001 has glass inclusions that contain noble gas and nitrogen compositions that are proportionally identical to the Martian atmosphere, as measured by the Viking spacecraft. This discovery helped scientists to identify where the "SNC" meteorite suite had originated, and that we actually possessed Martian samples. This meteorite has been allocated to 205 scientists for research and 5,298.435 g of sample is available.

  9. Biological studies in the Antarctic waters: A review

    Digital Repository Service at National Institute of Oceanography (India)

    Dhargalkar, V.K.

    stream_size 12 stream_content_type text/plain stream_name Proc_Workshop_Antarct_Stud_1990_407.pdf.txt stream_source_info Proc_Workshop_Antarct_Stud_1990_407.pdf.txt Content-Encoding ISO-8859-1 Content-Type text/plain; charset...

  10. Correlation of Ice-Rafted Detritus in South Atlantic Sediments with Climate Proxies in Polar Ice over the Last Glacial Period

    Directory of Open Access Journals (Sweden)

    Sharon L. Kanfoush

    2013-03-01

    Full Text Available Previous study identified 6–7 millennial-scale episodes of South Atlantic ice-rafted sediment deposition (SA events during the glaciation. Questions remain, however, regarding their origin, significance for sea-ice and/or Antarctic ice-sheet dynamics, and relationship to climate. Here I correlate sediment core (TTN057–21 SA events to Greenland and Antarctic ice using two independent methods, stable isotopes and geomagnetic paleointensity, placing SA events in the context of polar climate change in both hemispheres. Marine isotopic stage (MIS 3 SA events generally coincided with Greenland interstadials and with cooling following Antarctic warm events (A1-A4. This anti-phase behavior is best illustrated when SA0 coincided with both the Antarctic Cold Reversal and Bolling-Allerod warming in Greenland. Moreover, SA events coincide with sea-level rises during the deglaciation (mwp1A and MIS 3 (30.4, 38.3, 43.7, 51.5 ka, implying unpinning of grounded Weddell Sea region ice masses discharged debris-laden bergs that had a chilling effect on South Atlantic surface temperatures.

  11. Vortex Shedding Inside a Baffled Air Duct

    Science.gov (United States)

    Davis, Philip; Kenny, R. Jeremy

    2010-01-01

    Common in the operation of both segmented and un-segmented large solid rocket motors is the occurrence of vortex shedding within the motor chamber. A portion of the energy within a shed vortex is converted to acoustic energy, potentially driving the longitudinal acoustic modes of the motor in a quasi-discrete fashion. This vortex shedding-acoustic mode excitation event occurs for every Reusable Solid Rocket Motor (RSRM) operation, giving rise to subsequent axial thrust oscillations. In order to better understand this vortex shedding/acoustic mode excitation phenomena, unsteady CFD simulations were run for both a test geometry and the full scale RSRM geometry. This paper covers the results from the subscale geometry runs, which were based on work focusing on the RSRM hydrodynamics. Unsteady CFD simulation parameters, including boundary conditions and post-processing returns, are reviewed. The results were further post-processed to identify active acoustic modes and vortex shedding characteristics. Probable locations for acoustic energy generation, and subsequent acoustic mode excitation, are discussed.

  12. Phenomena, dynamics and instabilities of vortex pairs

    International Nuclear Information System (INIS)

    Williamson, C H K; Asselin, D J; Leweke, T; Harris, D M

    2014-01-01

    Our motivation for studying the dynamics of vortex pairs stems initially from an interest in the trailing wake vortices from aircraft and the dynamics of longitudinal vortices close to a vehicle surface. However, our motivation also comes from the fact that vortex–vortex interactions and vortex–wall interactions are fundamental to many turbulent flows. The intent of the paper is to present an overview of some of our recent work concerning the formation and structure of counter-rotating vortex pairs. We are interested in the long-wave and short-wave three-dimensional instabilities that evolve for an isolated vortex pair, but also we would like to know how vortex pairs interact with a wall, including both two-dimensional interactions, and also the influence of the surface on the three-dimensional instabilities. The emphasis of this presentation is on physical mechanisms by which vortices interact with each other and with surfaces, principally from an experimental approach, but also coupled with analytical studies. (paper)

  13. Optical force and torque on a dielectric Rayleigh particle by a circular Airy vortex beam

    Science.gov (United States)

    Chen, Musheng; Huang, Sujuan; Shao, Wei; Liu, Xianpeng

    2018-03-01

    Optical force and torque exerted on the Rayleigh particles by tightly focused circularly polarized circular Airy vortex beams (CAVB) in the far field are studied in this paper. The relation between parameters of circularly polarized CAVB and the trapping properties is numerically analyzed based on Rayleigh models and the Debye diffraction theory. The results show that both the high refractive index and low refractive index particles can be fully stably trapped in three dimensions by circularly polarized CAVB. The parameters of circularly polarized CAVB greatly affect the optical force. The longitudinal and transverse gradient force increase with the increase of decay factor and scaling factor, and decrease with the increase of the radius of the first primary ring and topological charges. The positions of the longitudinal stable equilibrium move toward the high numerical aperture lens when the scaling factor and the radius of the primary ring increase. The trapping range is broadened with the decrease of scaling factor. The optical orbital torque (OOT) of circularly polarized CAVB has circular symmetry and remains positive or negative. With the increase of topological charges, the peak value of OOT first increases and then decreases after reaches a maximum. These results are useful for optical trapping, optical levitation and particle acceleration.

  14. Chilean Antarctic Stations on King George Island

    Directory of Open Access Journals (Sweden)

    Katsutada Kaminuma

    2000-07-01

    Full Text Available The purpose of my visit to Chilean Antarctic Stations was to assess the present status of geophysical observations and research, as the South Shetland Island, West Antarctica, where the stations are located, are one of the most active tectonic regions on the Antarctic plate. The Instituto Antartico Chileno (INACH kindly gave me a chance to stay in Frei/Escudero Bases as an exchange scientist under the Antarctic Treaty for two weeks in January 2000. I stayed in Frei Base as a member of a geological survey group named "Tectonic Evolution of the Antarctic Peninsula" which was organized by Prof. F. Herve, University of Chile, from January 05 to 19,2000. All my activity in the Antarctic was organized by INACH. During my stay in Frei Base, I also visited Bellingshausen (Russian, Great Wall (China and Artigas (Uruguay stations. All these stations are located within walking distance of Frei Base. King Sejong Station (Korea, located 10km east from Frei Base, and Jubany Base (Argentine, another 6km south-east from King Sejong Station, were also visited with the aid of a zodiac boat that was kindly operated for us by King Sejong Station. All stations except Escudero Base carry out meteorological observations. The seismological observations in Frei Base are operated by Washington State University of the U. S. monitoring of earthquake activity and three-component geomagnetic observations are done at King Sejong and Great Wall stations. Earth tide is monitored at Artigas Base. Continuous monitoring of GPS and gravity change are planned at King Sejong Station in the near future. Scientific research activities of each country in the area in the 1999/2000 Antarctic summer season were studied and the logistic ability of all stations was also assessed for our future international cooperation.

  15. Vortex dynamics in nonrelativistic version of Abelian Higgs model: Effects of the medium on the vortex motion

    Directory of Open Access Journals (Sweden)

    Kozhevnikov Arkadii

    2016-01-01

    Full Text Available The closed vortex dynamics is considered in the nonrelativistic version of the Abelian Higgs Model. The effect of the exchange of excitations propagating in the medium on the vortex string motion is taken into account. The obtained are the effective action and the equation of motion both including the exchange of the propagating excitations between the distant segments of the vortex and the possibility of its interaction with the static fermion asymmetric background. They are applied to the derivation of the time dependence of the basic geometrical contour characteristics.

  16. Formation Number Of Laminar Vortex Rings. Numerical Simulations

    International Nuclear Information System (INIS)

    Rosenfeld, M.; Rambod, E.; Gharib, M.

    1998-01-01

    The formation time scale of axisymmetric vortex rings is studied numerically for relatively long discharge times. Experimental findings on the existence and universality of a formation time scale, referred to as the formation number, are confirmed. The formation number is indicative of the time a vortex ring acquires its maximal circulation. For vortex rings generated by impulsive motion of a piston, the formation number was found experimentally to be approximately 4. Numerical extension of the experimental study to thick shear layers indicates that the scaled circulation of the pinched-off vortex is relatively insensitive of the details of the formation process, such as the velocity program, velocity profile or vortex generator geometry. In contrast, the formation number does depend on the velocity profile

  17. Tolerance of Antarctic soil fungi to hydrocarbons

    Energy Technology Data Exchange (ETDEWEB)

    Hughes, Kevin A.; Bridge, Paul; Clark, Melody S. [British Antarctic Survey, Natural Environment Research Council, High Cross, Madingley Road, Cambridge CB3 0ET (United Kingdom)

    2007-01-01

    Little is known about the effects of hydrocarbons and fuel oil on Antarctic filamentous fungi in the terrestrial Antarctic environment. Growth of fungi and bacteria from soils around Rothera Research Station (Adelaide Island, Antarctic Peninsula) was assessed in the presence of ten separate aromatic and aliphatic hydrocarbons [marine gas oil (MGO), dodecane, hexadecane, benzoic acid, p-hydroxybenzoic acid, toluene, phenol, biphenyl, naphthalene and m- and p-xylenes with ethylbenzene]. Aromatic hydrocarbons inhibited soil microbial growth more than aliphatic hydrocarbons. Soil microorganisms from a moss patch, where little previous impact or hydrocarbon contamination had occurred, were less tolerant of hydrocarbons than those from high impact sites. Fungal growth rates of Mollisia sp., Penicillium commune, Mortierella sp., Trichoderma koningii, Trichoderma sp. and Phoma herbarum were assessed in the presence of hydrocarbons. Generally, aromatic hydrocarbons inhibited or stopped hyphal extension, though growth rates increased with some aliphatic hydrocarbons. Hyphal dry weight measurements suggested that Mortierella sp. may be able to use dodecane as sole carbon and energy source. Hydrocarbon-degrading Antarctic fungi may have use in future hydrocarbon spill bioremediation. (author)

  18. The genome of the Antarctic-endemic copepod, Tigriopus kingsejongensis.

    Science.gov (United States)

    Kang, Seunghyun; Ahn, Do-Hwan; Lee, Jun Hyuck; Lee, Sung Gu; Shin, Seung Chul; Lee, Jungeun; Min, Gi-Sik; Lee, Hyoungseok; Kim, Hyun-Woo; Kim, Sanghee; Park, Hyun

    2017-01-01

    The Antarctic intertidal zone is continuously subjected to extremely fluctuating biotic and abiotic stressors. The West Antarctic Peninsula is the most rapidly warming region on Earth. Organisms living in Antarctic intertidal pools are therefore interesting for research into evolutionary adaptation to extreme environments and the effects of climate change. We report the whole genome sequence of the Antarctic-endemic harpacticoid copepod Tigriopus kingsejongensi . The 37 Gb raw DNA sequence was generated using the Illumina Miseq platform. Libraries were prepared with 65-fold coverage and a total length of 295 Mb. The final assembly consists of 48 368 contigs with an N50 contig length of 17.5 kb, and 27 823 scaffolds with an N50 contig length of 159.2 kb. A total of 12 772 coding genes were inferred using the MAKER annotation pipeline. Comparative genome analysis revealed that T. kingsejongensis -specific genes are enriched in transport and metabolism processes. Furthermore, rapidly evolving genes related to energy metabolism showed positive selection signatures. The T. kingsejongensis genome provides an interesting example of an evolutionary strategy for Antarctic cold adaptation, and offers new genetic insights into Antarctic intertidal biota. © The Author 2017. Published by Oxford University Press.

  19. Report on Workshop "Planning of Future Science in the Polar Ocean Study with Cooperation among Study Groups"

    Directory of Open Access Journals (Sweden)

    Mitsuo Fukuchi

    2001-03-01

    Full Text Available A workshop on "Planning of Future Science in the Polar Ocean Study with Cooperation among Study Groups" was held on November 1,2000,at the National Institute of Polar Research with 21 participants. In this workshop, a plan to charter a research vessel other than "Shirase" was introduced and a science plan using the chartered research vessel by 43rd Japanese Antarctic Research Expedition was discussed. This study is going to be conducted in the sea ice area around 140-150°E in mid-summer (February 2002, when biological production becomes active in the Antarctic Ocean. Oceanographic observations using "Shirase" are difficult to conduct in this season since she supports a wide range of summer operations around Syowa Station. The relationships between biological production and greenhouse effect gas production and the vertical transport of organic materials from the surface to deep ocean will be the focus of this study. At this stage, one deputy leader and three members of JARE, and 25-26 other scientists including graduate students and foreign scientists, will participate in the field observations using the chartered vessel. The members of JARE will conduct a project science program of the VI Phase of JARE, while the other participants will do part of the science program "Antarctic Ocean in Earth System". Since further observations for several years after the summer of 2002 will be required to understand the role of the Antarctic Ocean in global climate change, we have applied for a Grant-in-Aid for Scientific Research for the next project, which will start from 2001,to the Ministry of Education, Science, Sports and Culture of Japan. The proposal was discussed in detail in this workshop.

  20. Vortex Analysis of Intra-Aneurismal Flow in Cerebral Aneurysms.

    Science.gov (United States)

    Sunderland, Kevin; Haferman, Christopher; Chintalapani, Gouthami; Jiang, Jingfeng

    2016-01-01

    This study aims to develop an alternative vortex analysis method by measuring structure ofIntracranial aneurysm (IA) flow vortexes across the cardiac cycle, to quantify temporal stability of aneurismal flow. Hemodynamics were modeled in "patient-specific" geometries, using computational fluid dynamics (CFD) simulations. Modified versions of known λ 2 and Q -criterion methods identified vortex regions; then regions were segmented out using the classical marching cube algorithm. Temporal stability was measured by the degree of vortex overlap (DVO) at each step of a cardiac cycle against a cycle-averaged vortex and by the change in number of cores over the cycle. No statistical differences exist in DVO or number of vortex cores between 5 terminal IAs and 5 sidewall IAs. No strong correlation exists between vortex core characteristics and geometric or hemodynamic characteristics of IAs. Statistical independence suggests this proposed method may provide novel IA information. However, threshold values used to determine the vortex core regions and resolution of velocity data influenced analysis outcomes and have to be addressed in future studies. In conclusions, preliminary results show that the proposed methodology may help give novel insight toward aneurismal flow characteristic and help in future risk assessment given more developments.

  1. Vortex deformation and reduction of the Lorentz force

    International Nuclear Information System (INIS)

    Vuorio, M.

    1977-01-01

    A vortex of an extreme II-type superconductor is considered in the presence of a transport current. The equivalence of Magnus and Lorentz forces in a static vortex is discussed and the effect of vortex deformation is included in calculating corrections to the conventional expression of the Lorentz force. (author)

  2. Fundamental vortices, wall-crossing, and particle-vortex duality

    Energy Technology Data Exchange (ETDEWEB)

    Hwang, Chiung; Yi, Piljin [School of Physics, Korea Institute for Advanced Study,Seoul 02455 (Korea, Republic of); Yoshida, Yutaka [Research Institute for Mathematical Sciences, Kyoto University,Kyoto 606-8502 (Japan)

    2017-05-18

    We explore 1d vortex dynamics of 3d supersymmetric Yang-Mills theories, as inferred from factorization of exact partition functions. Under Seiberg-like dualities, the 3d partition function must remain invariant, yet it is not a priori clear what should happen to the vortex dynamics. We observe that the 1d quivers for the vortices remain the same, and the net effect of the 3d duality map manifests as 1d Wall-Crossing phenomenon; although the vortex number can shift along such duality maps, the ranks of the 1d quiver theory are unaffected, leading to a notion of fundamental vortices as basic building blocks for topological sectors. For Aharony-type duality, in particular, where one must supply extra chiral fields to couple with monopole operators on the dual side, 1d wall-crossings of an infinite number of vortex quiver theories are neatly and collectively encoded by 3d determinant of such extra chiral fields. As such, 1d wall-crossing of the vortex theory encodes the particle-vortex duality embedded in the 3d Seiberg-like duality. For N=4, the D-brane picture is used to motivate this 3d/1d connection, while, for N=2, this 3d/1d connection is used to fine-tune otherwise ambiguous vortex dynamics. We also prove some identities of 3d supersymmetric partition functions for the Aharony duality using this vortex wall-crossing interpretation.

  3. Evaluation of Aircraft Wing-Tip Vortex Using PIV

    Science.gov (United States)

    Alsayed, Omer A.; Asrar, Waqar; Omar, Ashraf A.

    2010-06-01

    The formation and development of a wing-tip vortex in a near and extended near filed were studied experimentally. Particle image velocimetry was used in a wind tunnel to measure the tip vortex velocity field and hence investigate the flow structure in a wake of aircraft half-wing model. The purpose of this investigation is to evaluate the main features of the lift generated vortices in order to find ways to alleviate hazardous wake vortex encounters for follower airplanes during start and approach such that the increase in airport capacity can be achieved. First the wake structure at successive downstream planes crosswise to the axis of the wake vortices was investigated by measuring parameters such as core radius, maximum tangential velocities, vorticities and circulation distributions. The effect of different angles of attack setting on vortex parameters was examined at one downstream location. In very early stages the vortex sheet evolution makes the tip vortex to move inward and to the suction side of the wing. While the core radius and circulation distributions hardly vary with the downstream distance, noticeable differences for the same vortex parameters at different angles of attack settings were observed. The center of the wing tip vortices scatter in a circle of radius nearly equal to 1% of the mean wing chord and wandering amplitudes shows no direct dependence on the vortex strength but linearly increase with the downstream distance.

  4. Stratospheric temperatures and tracer transport in a nudged 4-year middle atmosphere GCM simulation

    Science.gov (United States)

    van Aalst, M. K.; Lelieveld, J.; Steil, B.; Brühl, C.; Jöckel, P.; Giorgetta, M. A.; Roelofs, G.-J.

    2005-02-01

    We have performed a 4-year simulation with the Middle Atmosphere General Circulation Model MAECHAM5/MESSy, while slightly nudging the model's meteorology in the free troposphere (below 113 hPa) towards ECMWF analyses. We show that the nudging 5 technique, which leaves the middle atmosphere almost entirely free, enables comparisons with synoptic observations. The model successfully reproduces many specific features of the interannual variability, including details of the Antarctic vortex structure. In the Arctic, the model captures general features of the interannual variability, but falls short in reproducing the timing of sudden stratospheric warmings. A 10 detailed comparison of the nudged model simulations with ECMWF data shows that the model simulates realistic stratospheric temperature distributions and variabilities, including the temperature minima in the Antarctic vortex. Some small (a few K) model biases were also identified, including a summer cold bias at both poles, and a general cold bias in the lower stratosphere, most pronounced in midlatitudes. A comparison 15 of tracer distributions with HALOE observations shows that the model successfully reproduces specific aspects of the instantaneous circulation. The main tracer transport deficiencies occur in the polar lowermost stratosphere. These are related to the tropopause altitude as well as the tracer advection scheme and model resolution. The additional nudging of equatorial zonal winds, forcing the quasi-biennial oscillation, sig20 nificantly improves stratospheric temperatures and tracer distributions.

  5. Vortex dynamics in Josephson junctions arrays

    International Nuclear Information System (INIS)

    Shalom, Diego Edgar

    2005-01-01

    In this work we study the dynamics of vortices in two-dimensional overdamped Josephson Junctions Arrays (JJA) driven by dc current in a wide range of conditions varying magnetic field and temperature using experiments, numerical simulations and analytic studies.We develop the Fixed Phase method, a variation of numeric relaxation techniques in which we fix and control the phase of some islands, adjacent to the vortex center, while allowing all other phases in the system to relax.In this way we are able to pull and push the vortex uphill, as we are forcing the center of rotation of the vortex currents to be in a defined location, allowing us to calculate the potential energy of a vortex located in any arbitrary position.We use this method to study the potential energy of a vortex in a variety of situations in homogeneous and non-homogeneous JJA, such as arrays with defects, channel arrays and ratchets.We study the finite size effects in JJA by means of analytic and numerical tools.We implement the rings model, in which we replace the two-dimensional square array by a series of square, concentric, uncoupled rings. This is equivalent to disregarding the radial junctions that couple consecutive rings.In spite of its extreme simplicity, this model holds the main ingredients of the magnetic dependence of the energy.We combine this model with other terms that take into account the dependence in the position of the vortex to obtain a general expression for the potential energy of a vortex in a finite JJA with applied magnetic field.We also present an expression for the first critical field, corresponding to the value of the magnetic field in which the entrance of the first vortex becomes energetically favorable.We build and study JJA modulated to form periodic and asymmetrical potentials for the vortices, named ratchet potentials.The experimental results clearly show the existence of a rectification in the motion of vortices in these potentials.Under certain conditions we

  6. Review of Vortex Methods for Simulation of Vortex Breakdown

    National Research Council Canada - National Science Library

    Levinski, Oleg

    2001-01-01

    The aim of this work is to identify current developments in the field of vortex breakdown modelling in order to initiate the development of a numerical model for the simulation of F/A-18 empennage buffet...

  7. Rotation of a single vortex in dusty plasma

    International Nuclear Information System (INIS)

    Yan Jia; Feng Fan; Liu Fu-Cheng; He Ya-Feng

    2017-01-01

    A single vortex is obtained in radio-frequency capacitive discharge in argon gas. The dust subsystem is confined in the horizontal plane with an asymmetrical saw structure placed on the lower electrode. The vortex rotates as a whole along the long side of the saw-teeth. Asymmetry of the saw structure plays an important role in the rotation of the vortex. Nonzero curl of the total force resulting from the local ion flow and the electric field in the plasma sheath could be attributed to the persistent rotation of vortex. (paper)

  8. Proposed thermodynamic method to determine the vortex mass in layered superconductors

    International Nuclear Information System (INIS)

    Moler, K.A.; Fetter, A.L.; Kapitulnik, A.

    1995-01-01

    The authors describe a simple method to study vortex dynamics that can determine or set an upper limit on the vortex mass. The specific heat of the vortex lattice in layered superconductors has a classical limit of 1 k B per pancake vortex if the vortex mass is zero. If the vortex mass m v is finite, a new Einstein branch of normal modes will appear with a crossover temperature Θ E ∝ m v -1 , and the specific heat will saturate at a new classical limit of 2 k B per pancake vortex

  9. Transverse force on a moving vortex with the acoustic geometry

    International Nuclear Information System (INIS)

    Zhang Pengming; Cao Liming; Duan Yishi; Zhong Chengkui

    2004-01-01

    We consider the transverse force on a moving vortex with the acoustic metric using the phi-mapping topological current theory. In the frame of effective space-time geometry the vortex appear naturally by virtue of the vortex tensor in the Lorentz space-time and we show that it is just the vortex derived with the order parameter in the condensed matter. With the usual Lagrangian we obtain the equation of motion for the vortex. At last, we show that the transverse force on the moving vortex in our equation is just the usual Magnus force in a simple model

  10. RANS computations of tip vortex cavitation

    Science.gov (United States)

    Decaix, Jean; Balarac, Guillaume; Dreyer, Matthieu; Farhat, Mohamed; Münch, Cécile

    2015-12-01

    The present study is related to the development of the tip vortex cavitation in Kaplan turbines. The investigation is carried out on a simplified test case consisting of a NACA0009 blade with a gap between the blade tip and the side wall. Computations with and without cavitation are performed using a R ANS modelling and a transport equation for the liquid volume fraction. Compared with experimental data, the R ANS computations turn out to be able to capture accurately the development of the tip vortex. The simulations have also highlighted the influence of cavitation on the tip vortex trajectory.

  11. Vortex breakdown in a supersonic jet

    Science.gov (United States)

    Cutler, Andrew D.; Levey, Brian S.

    1991-01-01

    This paper reports a study of a vortex breakdown in a supersonic jet. A supersonic vortical jets were created by tangential injection and acceleration through a convergent-divergent nozzle. Vortex circulation was varied, and the nature of the flow in vortical jets was investigated using several types of flow visualization, including focusing schlieren and imaging of Rayleigh scattering from a laser light sheet. Results show that the vortical jet mixed much more rapidly with the ambient air than a comparable straight jet. When overexpanded, the vortical jet exhibited considerable unsteadiness and showed signs of vortex breakdown.

  12. Aerosol Effects on Microphysical Processes, Storm Structure, and Cold Pool Strength in Simulated Supercell Thunderstorms from VORTEX-2 and VORTEX-SE

    Science.gov (United States)

    Guo, M.; Dawson, D. T., II; Baldwin, M. E.; Mansell, E. R.

    2017-12-01

    The cloud condensation nuclei (CCN) concentration has been found to strongly affect microphysical, dynamical and thermodynamical processes in supercells and other deep convective storms. Moreover, recent simulation studies have shown aerosols effects differ between higher- and lower-CAPE environments. Owing to the known sensitivity of severe storms to microphysical differences, studying the impact of aerosols supercell storms different environments is of clear societal importance. Tornadic environments in the southwastern U.S. are generally characterized by lower magnitudes CAPE and deeper tropospheric moisture than those in the Great Plains. These two regions were the focus of Verification of the Origins of Rotation in Tornadoes Experiment (VORTEX)-2 and VORTEX-Southeast (SE) field campaigns, respectively. In our study, we simulate several cases from VORTEX-2 and -SE with the Advanced Regional Prediction System (ARPS) Model at 6 different CCN concentrations (100-3000 cm-3). We use NSSL 3-moment microphysics parameterization schemeto explicitly predict precipitation particle size distributions and microphysirocess rates. Overall, storms under the higher-CAPE VORTEX-2 environments are more sensitiveto the change of CCN than those under the lower-CAPE VORTEX-SE environments. Updraft volume decreases as CCN increases for the VORTEX-2 cases, whereas the opposite is true but with a much weaker trend for the VORTEX-SE cases. Moreover, the cold pool strength drops dramatically as CCN surpasses 1000 cm-3n the VORTEX-2 cases but barely changes for the VORTEX-SE cases. Through a microphysics budget analysis, we show the change of the importance of ice processes is key to the differing sensitivities. in the VORTEX-2 cases, deposition to ice nuclei, cloud drop freezing and rain drop freezing in the upper levels (5-11km) contribute more to latent heating since more rain and cloud drops are lifted above the freezing level due to stronger updrafts. For CCN concentration over 1000

  13. Drift wave coherent vortex structures in inhomogeneous plasmas

    International Nuclear Information System (INIS)

    Su, X.N.

    1992-01-01

    Nonlinear drift wave vortex structures in magnetized plasmas are studied theoretically and numerically in the various physical environments. The effects of density and temperature gradients on drift wave vortex dynamics are analyzed using a fully nonlinear model with the Boltzmann density distribution. The equation, based on the full Boltzmann relation, possess no localized monopole solution in the short wavelength (∼ρ s ) region, while in the longer wavelength (∼(ρ s (r) n ) 1/2 ) region the density profile governs the existence of monopole-like solutions. In the longer wavelength regime, however, the monopoles cannot be localized sufficiently to avoid coupling to propagating drift waves due to the inhomogeneity of the plasma. Thus, the monopole vortex is a long lived coherent structure, but it is not precisely a stationary structure since the coupling results in a open-quote flapping close-quote tail. The tail causes energy of the vortex to leak out, but the effect of the temperature gradient is to reduce the leaking of this energy. Nonlinear coherent structures governing by the coupled drift wave-ion acoustic mode equations in sheared magnetic field are studied analytically and numerically. A solitary vortex equation that includes the effects of density and temperature gradients and magnetic shear is derived and analyzed. The results show that for a plasma in a sheared magnetic field, there exist the solitary vortex solutions. The new vortex structures are dipole-like in their symmetry, but not the modon type of dipoles. The numerical simulations are performed in 2-D with the coupled vorticity and parallel mass flow equations. The vortex structures in an unstable drift wave system driven by parallel shear flow are studied. The nonlinear solitary vortex solutions are given and the formation of the vortices from a turbulent state is observed from the numerical simulations

  14. Basin-scale heterogeneity in Antarctic precipitation and its impact on surface mass variability

    Directory of Open Access Journals (Sweden)

    J. Fyke

    2017-11-01

    Full Text Available Annually averaged precipitation in the form of snow, the dominant term of the Antarctic Ice Sheet surface mass balance, displays large spatial and temporal variability. Here we present an analysis of spatial patterns of regional Antarctic precipitation variability and their impact on integrated Antarctic surface mass balance variability simulated as part of a preindustrial 1800-year global, fully coupled Community Earth System Model simulation. Correlation and composite analyses based on this output allow for a robust exploration of Antarctic precipitation variability. We identify statistically significant relationships between precipitation patterns across Antarctica that are corroborated by climate reanalyses, regional modeling and ice core records. These patterns are driven by variability in large-scale atmospheric moisture transport, which itself is characterized by decadal- to centennial-scale oscillations around the long-term mean. We suggest that this heterogeneity in Antarctic precipitation variability has a dampening effect on overall Antarctic surface mass balance variability, with implications for regulation of Antarctic-sourced sea level variability, detection of an emergent anthropogenic signal in Antarctic mass trends and identification of Antarctic mass loss accelerations.

  15. Theory of pairing symmetry in the vortex states

    NARCIS (Netherlands)

    Yokoyama, Takehito; Ichioka, Yukio; Yanaka, Yukio; Golubov, Alexandre Avraamovitch

    2010-01-01

    We investigate pairing symmetry in an Abrikosov vortex and vortex lattice. It is shown that the Cooper pair wave function at the center of an Abrikosov vortex with vorticity m has a different parity with respect to frequency from that in the bulk if m is an odd number, while it has the same parity

  16. Emerging spatial patterns in Antarctic prokaryotes.

    Science.gov (United States)

    Chong, Chun-Wie; Pearce, David A; Convey, Peter

    2015-01-01

    Recent advances in knowledge of patterns of biogeography in terrestrial eukaryotic organisms have led to a fundamental paradigm shift in understanding of the controls and history of life on land in Antarctica, and its interactions over the long term with the glaciological and geological processes that have shaped the continent. However, while it has long been recognized that the terrestrial ecosystems of Antarctica are dominated by microbes and their processes, knowledge of microbial diversity and distributions has lagged far behind that of the macroscopic eukaryote organisms. Increasing human contact with and activity in the continent is leading to risks of biological contamination and change in a region whose isolation has protected it for millions of years at least; these risks may be particularly acute for microbial communities which have, as yet, received scant recognition and attention. Even a matter apparently as straightforward as Protected Area designation in Antarctica requires robust biodiversity data which, in most parts of the continent, remain almost completely unavailable. A range of important contributing factors mean that it is now timely to reconsider the state of knowledge of Antarctic terrestrial prokaryotes. Rapid advances in molecular biological approaches are increasingly demonstrating that bacterial diversity in Antarctica may be far greater than previously thought, and that there is overlap in the environmental controls affecting both Antarctic prokaryotic and eukaryotic communities. Bacterial dispersal mechanisms and colonization patterns remain largely unaddressed, although evidence for regional evolutionary differentiation is rapidly accruing and, with this, there is increasing appreciation of patterns in regional bacterial biogeography in this large part of the globe. In this review, we set out to describe the state of knowledge of Antarctic prokaryote diversity patterns, drawing analogy with those of eukaryote groups where appropriate

  17. Seasonal Evolution of the North and South Polar Vortex on Titan From 2004 to 2017 as Seen by Cassini/VIMS

    Science.gov (United States)

    Le Mouelic, S.; Robidel, R.; Rousseau, B.; Rodriguez, S.; Cornet, T.; Sotin, C.; Barnes, J. W.; Brown, R. H.; Buratti, B. J.; Baines, K. H.; Clark, R. N.; Nicholson, P. D.

    2017-12-01

    Cassini entered in Saturn's orbit in July 2004. In thirteen years, 127 targeted flybys of Titan have been performed. We focus our study on the analysis of the complete Visual and Infrared Mapping Spectrometer data set, with a particular emphasis on the evolving features on both poles. We have computed individual global maps of the north and south poles for each of the 127 targeted flybys, using VIMS wavelengths sensitive both to clouds and surface features. First evidences for a vast ethane cloud covering the North Pole is seen as soon as the first and second targeted flyby in October 2004 and December 2005 [1]. The first detailed imaging of this north polar feature with VIMS was obtained in December 2006, thanks to a change in inclination of the spacecraft orbit [2]. At this time, the northern lakes and seas of Titan were totally masked to the optical instruments by the haze and clouds, whereas the southern pole was well illuminated and mostly clear of haze and vast clouds. The vast north polar feature progressively vanished around the equinox in 2009 [2,3,4], in agreement with the predictions of Global Circulation Models [5]. It revealed progressively the underlying lakes to the ISS and VIMS instruments, which show up very nicely in VIMS in a series of flybys between T90 and T100. First evidences of an atmospheric vortex growing over the south pole occurred in May 2012 (T82), with a high altitude feature being detected consistently at each flyby up to the last T126 targeted flyby, and also appearing in more distant observations up to the end of the Cassini mission. Cassini has covered almost half a titanian year, corresponding to two seasons. The situation observed at the South Pole in the last images may correspond to what was observed in the north as Cassini just arrived. [1] Griffith et al., Science, 2006. [2] Le Mouélic et al., PSS, 2012. [3] Rodriguez et al., Nature, 2009. [4] Rodriguez et al., Icarus 2011. [4] Hirtzig et al., Icarus, 2013. [5] Rannou et al

  18. The Vortex and the Line: Performative Gestures in Allen Ginsberg's ‘Wichita Vortex Sutra’

    DEFF Research Database (Denmark)

    Sørensen, Bent

    and their identity politics… Queering the straight lines of Modernism, Allen Ginsberg suggests in his long poem about America and the Vietnam War, ‘Wichita Vortex Sutra’, that lying media discourses and corrupt political and military statements about the necessity of participation in the war may be cancelled out...... by a poet performing the simple, yet impossible speech act of declaring the end of the war, and in doing so queering the original declaratory speech act of the executive power. The poet must enter intrepidly the vortex of lies told by the voices disseminated by the media on behalf of politicians, authority...... to provide the reader of the Sutra with the possibility of Enlightenment. While the poet may be forced to travel along straight lines to penetrate the vortex, he should at any given opportunity queer these lines as much as possible....

  19. Possible connections of the opposite trends in Arctic and Antarctic sea-ice cover.

    Science.gov (United States)

    Yu, Lejiang; Zhong, Shiyuan; Winkler, Julie A; Zhou, Mingyu; Lenschow, Donald H; Li, Bingrui; Wang, Xianqiao; Yang, Qinghua

    2017-04-05

    Sea ice is an important component of the global climate system and a key indicator of climate change. A decreasing trend in Arctic sea-ice concentration is evident in recent years, whereas Antarctic sea-ice concentration exhibits a generally increasing trend. Various studies have investigated the underlying causes of the observed trends for each region, but possible linkages between the regional trends have not been studied. Here, we hypothesize that the opposite trends in Arctic and Antarctic sea-ice concentration may be linked, at least partially, through interdecadal variability of the Pacific Decadal Oscillation (PDO) and the Atlantic Multidecadal Oscillation (AMO). Although evaluation of this hypothesis is constrained by the limitations of the sea-ice cover record, preliminary statistical analyses of one short-term and two long-term time series of observed and reanalysis sea-ice concentrations data suggest the possibility of the hypothesized linkages. For all three data sets, the leading mode of variability of global sea-ice concentration is positively correlated with the AMO and negatively correlated with the PDO. Two wave trains related to the PDO and the AMO appear to produce anomalous surface-air temperature and low-level wind fields in the two polar regions that contribute to the opposite changes in sea-ice concentration.

  20. Direct visualization of the vortex distributions in a superconducting film with a Penrose array of magnetic pinning centers: Symmetry induced giant vortex state

    International Nuclear Information System (INIS)

    Kramer, R.B.G.; Silhanek, A.V.; Van de Vondel, J.; Raes, B.; Moshchalkov, V.V.

    2010-01-01

    Using scanning Hall probe microscopy a direct visualization of the flux distribution in a Pb film covering a fivefold Penrose array of Co dots is obtained. We demonstrate that stable vortex configurations can be found for fields H ∼ 0.8H 1 , H 1 and 1.6H 1 , where H 1 corresponds to one flux quantum per pinning site. The vortex pattern at 0.8H 1 corresponds to one vacancy in one of the vertices of the thin tiles whereas at 1.6H 1 the vortex structure can be associated with one interstitial vortex inside each thick tile. Strikingly, for H = 1.6H 1 interstitial and pinned vortices arrange themselves in ring-like structures ('vortex corrals') which favor the formation of a giant vortex state at their center.