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Sample records for magnetic fields structure

  1. Structure of magnetic fields in intracluster cavities

    CERN Document Server

    Gourgouliatos, Konstantinos Nektarios; Lyutikov, Maxim

    2010-01-01

    Observations of clusters of galaxies show ubiquitous presence of X-ray cavities, presumably blown by the AGN jets. We consider magnetic field structures of these cavities. Stability requires that they contain both toroidal and poloidal magnetic fields, while realistic configurations should have vanishing magnetic field on the boundary. For axisymmetric configurations embedded in unmagnetized plasma, the continuity of poloidal and toroidal magnetic field components on the surface of the bubble then requires solving the elliptical Grad-Shafranov equation with both Dirichlet and Neumann boundary conditions. This leads to a double eigenvalue problem, relating the pressure gradients and the toroidal magnetic field to the radius of the bubble. We have found fully analytical stable solutions. This result is confirmed by numerical simulation. We present synthetic X-ray images and synchrotron emission profiles and evaluate the rotation measure for radiation traversing the bubble.

  2. Magnetic fields during high redshift structure formation

    CERN Document Server

    Schleicher, Dominik R G; Schober, Jennifer; Schmidt, Wolfram; Bovino, Stefano; Federrath, Christoph; Niemeyer, Jens; Banerjee, Robi; Klessen, Ralf S

    2012-01-01

    We explore the amplification of magnetic fields in the high-redshift Universe. For this purpose, we perform high-resolution cosmological simulations following the formation of primordial halos with \\sim10^7 M_solar, revealing the presence of turbulent structures and complex morphologies at resolutions of at least 32 cells per Jeans length. Employing a turbulence subgrid-scale model, we quantify the amount of unresolved turbulence and show that the resulting turbulent viscosity has a significant impact on the gas morphology, suppressing the formation of low-mass clumps. We further demonstrate that such turbulence implies the efficient amplification of magnetic fields via the small-scale dynamo. We discuss the properties of the dynamo in the kinematic and non-linear regime, and explore the resulting magnetic field amplification during primordial star formation. We show that field strengths of \\sim10^{-5} G can be expected at number densities of \\sim5 cm^{-3}.

  3. Magnetic Field Structure in Relativistic Jets

    Directory of Open Access Journals (Sweden)

    Jermak Helen

    2013-12-01

    Full Text Available Relativistic jets are ubiquitous when considering an accreting black hole. Two of the most extreme examples of these systems are blazars and gamma-ray bursts (GRBs, the jets of which are thought to be threaded with a magnetic field of unknown structure. The systems are made up of a black hole accreting matter and producing, as a result, relativistic jets of plasma from the poles of the black hole. Both systems are viewed as point sources from Earth, making it impossible to spatially resolve the jet. In order to explore the structure of the magnetic field within the jet we take polarisation measurements with the RINGO polarimeters on the world’s largest fully autonomous, robotic optical telescope: The Liverpool Telescope. Using the polarisation degree and angle measured by the RINGO polarimeters it is possible to distinguish between global magnetic fields created in the central engine and random tangled magnetic fields produced locally in shocks. We also monitor blazar sources regularly during quiescence with periods of flaring monitored more intensively. Reported here are the early polarisation results for GRBs 060418 and 090102, along with future prospects for the Liverpool Telescope and the RINGO polarimeters.

  4. Magnetic Field and Force Calculations for ATLAS Asymmetrical Structure

    CERN Document Server

    Nessi, Marzio

    2001-01-01

    Magnetic field distortion in the assymetrical ATLAS structure are calculated. Magnetic forces in the system are estimated. 3D magnetic field simulation by the Opera3D code for symmetrical and asymmetrical systems is used.

  5. Magnetic Field Structure from Synchrotron Polarization

    CERN Document Server

    Beck, R

    2006-01-01

    Total magnetic fields in spiral galaxies, as observed through their total synchrotron emission, are strongest (up to \\simeq 30\\mu G) in the spiral arms. The degree of radio polarization is low; the field in the arms must be mostly turbulent or tangled. Polarized synchrotron emission shows that the resolved regular fields are generally strongest in the interarm regions (up to \\simeq 15\\mu G), sometimes forming 'magnetic arms' parallel to the optical arms. The field structure is spiral in almost every galaxy, even in flocculent and bright irregular types which lack spiral arms. The observed large-scale patterns of Faraday rotation in several massive spiral galaxies reveal coherent regular fields, as predicted by dynamo models. However, in most galaxies observed so far no simple patterns of Faraday rotation could be found. Either many dynamo modes are superimposed and cannot be resolved by present-day telescopes, or most of the apparently regular field is in fact anisotropic random, with frequent reversals, due ...

  6. Molecular structure and motion in zero field magnetic resonance

    Energy Technology Data Exchange (ETDEWEB)

    Jarvie, T.P.

    1989-10-01

    Zero field magnetic resonance is well suited for the determination of molecular structure and the study of motion in disordered materials. Experiments performed in zero applied magnetic field avoid the anisotropic broadening in high field nuclear magnetic resonance (NMR) experiments. As a result, molecular structure and subtle effects of motion are more readily observed.

  7. Manipulation of molecular structures with magnetic fields

    NARCIS (Netherlands)

    Boamfa, M.I.

    2003-01-01

    The present thesis deals with the use of magnetic fields as a handle to manipulate matter at a molecular level and as a tool to probe molecular properties or inter molecular interactions. The work consists of in situ optical studies of (polymer) liquid crystals and molecular aggregates in high magne

  8. Periodical Plasma Structures Controlled by Oblique Magnetic Field

    CERN Document Server

    Schweigert, Irina

    2016-01-01

    The propulsion type plasma in oblique external magnetic field is studied in 2D3V PIC MCC simulations. A periodical structure with maxima of electron and ion densities appears with an increase of an obliqueness of magnetic field. These ridges of electron and ion densities are aligned with the magnetic field vector and shifted relative each other. As a result the two-dimensional double-layers structure forms in cylindrical plasma chamber. The ion and electron currents on the side wall are essential modulated by the oblique magnetic field.

  9. Solar and stellar magnetic fields and atmospheric structures - Theory

    Science.gov (United States)

    Parker, E. N.

    1989-01-01

    Theoretical understanding of the role of magnetic fields in the formation of solar atmospheric structure is reviewed. The origin of the solar magnetic field, the dynamical behavior of the azimuthal field in the convective zone, the fibril state of the field in the photosphere, the formation of sunspots and prominences, and the spontaneous formation of current sheets in the bipolar field above the solar surface are addressed. The relation of the latter to coronal heating and flare formation is considered.

  10. Influence of magnetic fields on structural martensitic transitions

    Energy Technology Data Exchange (ETDEWEB)

    Lashley, J C [Los Alamos National Laboratory; Cooley, J C [Los Alamos National Laboratory; Smith, J L [Los Alamos National Laboratory; Fisher, R A [NON LANL; Modic, K A [Los Alamos National Laboratory; Yang, X- D [TEMPLE UNIV; Riseborough, P S [TEMPLE UNIV.; Opeil, C P [BOSTON COLLEGE; Finlayson, T R [UNIV OF MELBOURNE; Goddard, P A [UNIV OF OXFORD; Silhanek, A V [INPAC

    2009-01-01

    We show evidence that a structural martensitic transition is related to significant changes in the electronic structure, as revealed in thermodynamic measurements made in high-magnetic fields. The magnetic field dependence is considered unusual as many influential investigations of martensitic transitions have emphasized that the structural transitions are primarily lattice dynamical and are driven by the entropy due to the phonons. We provide a theoretical framework which can be used to describe the effect of magnetic field on the lattice dynamics in which the field dependence originates from the dielectric constant.

  11. Magnetic fields and the large-scale structure

    CERN Document Server

    Battaner, E

    1999-01-01

    The large-scale structure of the Universe has been observed to be characterized by long filaments, forming polyhedra, with a remarkable 100-200 Mpc periodicity, suggesting a regular network. The introduction of magnetic fields into the physics of the evolution of structure formation provides some clues to understanding this unexpected lattice structure. A relativistic treatment of the evolution of pre-recombination inhomogeneities, including magnetic fields, is presented to show that equivalent-to-present field strengths of the order of $10^{-8}$ G could have played an important role. Primordial magnetic tubes generated at inflation, at scales larger than the horizon before recombination, could have produced filamentary density structures, with comoving lengths larger than about 10 Mpc. Structures shorter than this would have been destroyed by diffusion due to the small pre-recombination conductivity. If filaments constitute a lattice, the primordial magnetic field structures that produced the post-recombinat...

  12. Electronegative Plasma Sheath Structure in a Magnetic Field

    Institute of Scientific and Technical Information of China (English)

    ZOU Xiu; LIU Jin-Yuan; WANG Zheng-Xiong; GONG Ye; LIU Yue; WANG Xiao-Gang

    2004-01-01

    @@ The structure of an electronegative plasma sheath in an oblique magnetic field is investigated with a fluid model. We assume the system consists of hot electrons and negative ions as well as cold positive ions. Densities of particles and distributions of the spacious potential in various states of magnetic field are studied. The result shows that the existence of magnetic field and negative ions has great effects on the plasma sheath structures. In addition, the effects of negative ion density and temperature on the structure of the electronegative plasma sheath are discussed.

  13. Effect of strong magnetic fields on the pasta phase structure

    CERN Document Server

    de Lima, Rafael Camargo Rodrigues; Providência, Constança

    2013-01-01

    The effect of strong magnetic fields on the properties of the pasta structures is calculated within a Thomas Fermi approach using relativistic mean field models to modulate stellar matter. It is shown how quantities such as the size of the clusters and Wigner-Seitz cells, the surface tension and the transition between configurations are affected. It is expected that these effects may give rise to large stresses in the pasta phase if the local magnetic field suffers fluctuations.

  14. The interplanetary and solar magnetic field sector structures, 1962 - 1968

    Science.gov (United States)

    Jones, D. E.

    1972-01-01

    The interplanetary magnetic field sector structure was observed from late 1962 through 1968. During this time it has been possible to study the manner in which the sector pattern and its relation to the photospheric magnetic field configuration changes from solar minimum to solar maximum. Observations were also made relating sector boundaries to specific regions on the solar disk. These and other observations related to the solar origin of the interplanetary field are briefly reviewed.

  15. Spot--like Structures of Neutron Star Surface Magnetic Fields

    CERN Document Server

    Geppert, U; Gil, J

    2003-01-01

    There is growing evidence, based on both X-ray and radio observations of isolated neutron stars, that besides the large--scale (dipolar) magnetic field, which determines the pulsar spin--down behaviour, small--scale poloidal field components are present, which have surface strengths one to two orders of magnitude larger than the dipolar component. We argue in this paper that the Hall--effect can be an efficient process in producing such small--scale field structures just above the neutron star surface. It is shown that due to a Hall--drift induced instability, poloidal magnetic field structures can be generated from strong subsurface toroidal fields, which are the result of either a dynamo or a thermoelectric instability acting at early times of a neutron star's life. The geometrical structure of these small--scale surface anomalies of the magnetic field resembles that of some types of ``star--spots''. The magnetic field strength and the length--scales are comparable with values that can be derived from vario...

  16. MESSENGER observations of Mercury's magnetic field structure

    Science.gov (United States)

    Johnson, Catherine L.; Purucker, Michael E.; Korth, Haje; Anderson, Brian J.; Winslow, Reka M.; Al Asad, Manar M. H.; Slavin, James A.; Alexeev, Igor. I.; Phillips, Roger J.; Zuber, Maria T.; Solomon, Sean C.

    2012-12-01

    We present a baseline, time-averaged model for Mercury's magnetosphere, derived from MESSENGER Magnetometer data from 24 March to 12 December 2011, comprising the spacecraft's first three Mercury years in orbit around the innermost planet. The model, constructed under the approximation that the magnetospheric shape can be represented as a paraboloid of revolution, includes two external (magnetopause and magnetotail) current systems and an internal (dipole) field and allows for reconnection. We take advantage of the geometry of the orbital Magnetometer data to estimate all but one of the model parameters, and their ranges, directly from the observations. These parameters are then used as a priori constraints in the paraboloid magnetospheric model, and the sole remaining parameter, the dipole moment, is estimated as 190 nT RM3 from a grid search. We verify that the best fit dipole moment is insensitive to changes in the other parameters within their determined ranges. The model provides an excellent first-order fit to the MESSENGER observations, with a root-mean-square misfit of less than 20 nT globally. The results show that the magnetopause field strength ranges from 10% to 50% of the dipole field strength at observation locations on the dayside and at nightside latitudes north of 60°N. Globally, the residual signatures observed to date are dominated by the results of magnetospheric processes, confirming the dynamic nature of Mercury's magnetosphere.

  17. Controllability of brushite structural parameters using an applied magnetic field.

    Science.gov (United States)

    Kuznetsov, V N; Yanovska, A A; Stanislavov, A S; Danilchenko, S N; Kalinkevich, A N; Sukhodub, L F

    2016-03-01

    The paper studies the influence of low intensity static magnetic field on brushite structural and microstructural parameters using the X-ray diffraction and the transmission electron microscopy. This effect was shown to have various influences on DCPD (Dicalcium Phosphate Dihydrate) structure depending on a magnetic field configuration or time of synthesis, which allows achieving controllability of the main properties of an obtained material. The influence of the magnetic field leads mostly to the decrease of crystallite sizes with no impact on the crystal lattice parameters. In (0 2 0) and (1 5 0) planes the growth of crystallite sizes is observed after 2 and 3 days of crystallization, respectively. The analysis of different contributions to peak broadening in [0 b 0] direction showed a similar trend for the crystallite sizes with the lower lattice microstrains after 2 days of synthesis. The effect similar to the preferred orientation was observed and classified with the Harris method.

  18. A Magnetic Field Sensor Based on a Magnetic Fluid-Filled FP-FBG Structure

    Directory of Open Access Journals (Sweden)

    Ji Xia

    2016-04-01

    Full Text Available Based on the characteristic magnetic-controlled refractive index property, in this paper, a magnetic fluid is used as a sensitive medium to detect the magnetic field in the fiber optic Fabry-Perot (FP cavity. The temperature compensation in fiber Fabry-Perot magnetic sensor is demonstrated and achieved. The refractive index of the magnetic fluid varies with the applied magnetic field and external temperature, and a cross-sensitivity effect of the temperature and magnetic field occurs in the Fabry-Perot magnetic sensor and the accuracy of magnetic field measurements is affected by the thermal effect. In order to overcome this problem, we propose a modified sensor structure. With a fiber Bragg grating (FBG written in the insert fiber end of the Fabry-Perot cavity, the FBG acts as a temperature compensation unit for the magnetic field measurement and it provides an effective solution to the cross-sensitivity effect. The experimental results show that the sensitivity of magnetic field detection improves from 0.23 nm/mT to 0.53 nm/mT, and the magnetic field measurement resolution finally reaches 37.7 T. The temperature-compensated FP-FBG magnetic sensor has obvious advantages of small volume and high sensitivity, and it has a good prospect in applications in the power industry and national defense technology areas.

  19. A Magnetic Field Sensor Based on a Magnetic Fluid-Filled FP-FBG Structure.

    Science.gov (United States)

    Xia, Ji; Wang, Fuyin; Luo, Hong; Wang, Qi; Xiong, Shuidong

    2016-04-29

    Based on the characteristic magnetic-controlled refractive index property, in this paper, a magnetic fluid is used as a sensitive medium to detect the magnetic field in the fiber optic Fabry-Perot (FP) cavity. The temperature compensation in fiber Fabry-Perot magnetic sensor is demonstrated and achieved. The refractive index of the magnetic fluid varies with the applied magnetic field and external temperature, and a cross-sensitivity effect of the temperature and magnetic field occurs in the Fabry-Perot magnetic sensor and the accuracy of magnetic field measurements is affected by the thermal effect. In order to overcome this problem, we propose a modified sensor structure. With a fiber Bragg grating (FBG) written in the insert fiber end of the Fabry-Perot cavity, the FBG acts as a temperature compensation unit for the magnetic field measurement and it provides an effective solution to the cross-sensitivity effect. The experimental results show that the sensitivity of magnetic field detection improves from 0.23 nm/mT to 0.53 nm/mT, and the magnetic field measurement resolution finally reaches 37.7 T. The temperature-compensated FP-FBG magnetic sensor has obvious advantages of small volume and high sensitivity, and it has a good prospect in applications in the power industry and national defense technology areas.

  20. Magnetic Field Structure in a High-mass System

    NARCIS (Netherlands)

    Beuther, H.; Vlemmings, W. H. T.; Rao, R.; van der Tak, F. F. S.

    2010-01-01

    To characterize the magnetic field structure of the outflow and core region within a prototypical high-mass star-forming region, we analyzed polarized CO(3-2)-for the first time observed with the Submillimeter Array-as well as 880 mu m submillimeter continuum emission from the high-mass outflow/disk

  1. Assessing the Structure of Isotropic and Anisotropic Turbulent Magnetic Fields

    Science.gov (United States)

    Fatuzzo, Marco; Holden, Lisa; Grayson, Lindsay; Wallace, Kirk

    2016-10-01

    Turbulent magnetic fields permeate our universe, impacting a wide range of astronomical phenomena across all cosmic scales. A clear example is the magnetic field that threads the interstellar medium (ISM), which impacts the motion of cosmic rays through that medium. Understanding the structure of magnetic turbulence within the ISM and how it relates to the physical quantities that characterize it can thus inform our analysis of particle transport within these regions. Toward that end, we probe the structure of magentic turbulence through the use of Lyapunov exponents for a suite of isotropic and nonisotropic Alfvénic turbulence profiles. Our results provide a means of calculating a “turbulence lengthscale” that can then be connected to how cosmic rays propagate through magentically turbulent environments, and we perform such an analysis for molecular cloud environments.

  2. New insights into chromospheric structures from vector magnetic field measurements

    Science.gov (United States)

    Lagg, A.

    During the last decade advances in instrumentation atomic physics and modeling have greatly improved the access to the chromospheric magnetic field vector High sensitivity polarimeters like the Tenerife Infrared Polarimeter TIP2 VTT or the Spectro-Polarimeter for Infrared and Optical Regions SPINOR HAO lead to reliable Zeeman measurements using the He I 10830 nm triplet Theoretical modeling of the Hanle and the Paschen Back effect helped to significantly improve the analysis of polarization measurements in this triplet allowing to directly visualize the magnetic structure of spicules polar prominences and active regions In this presentation I will summarize the results of chromospheric magnetic field measurements using this interesting triplet obtained in the last couple of years and discuss the great potential it has to further uncover the complex structure of the chromosphere

  3. Structure of the photospheric magnetic field during sector crossings of the heliospheric magnetic field

    Science.gov (United States)

    Getachew, Tibebu; Virtanen, Ilpo; Mursula, Kalevi

    2017-04-01

    The photospheric magnetic field is the source of the coronal and heliospheric magnetic fields (HMF), but their mutual correspondence is non-trivial and depends on the phase of the solar cycle. The photospheric field during the HMF sector crossings observed at 1 AU has been found to contain enhanced field intensities and definite polarity ordering, forming regions called Hale boundaries. Here we study the structure of the photospheric field during the HMF sector crossings during solar cycles 21-24, separately for the four phases of each solar cycle. We use a refined version of Svalgaard's list of major HMF sector crossings, mapped to the Sun using the solar wind speed observed at the Earth, and the daily level-3 magnetograms of the photospheric field measured at the Wilcox Solar Observatory in 1976-2014. We find that the structure of the photospheric field corresponding to the HMF sector crossings, and the existence and properties of the corresponding Hale bipolar regions varies significantly with solar cycle and with solar cycle phase. We find evidence for Hale boundaries in many, but not all ascending, maximum and declining phases of solar cycles but no minimum phase. The most clear Hale boundaries are found during the (+,-) HMF crossings in the northern hemisphere of odd cycles 21 and 23, but less systematically during the (+,-) crossings in the southern hemisphere of even cycles 22 and 24. We also find that the Hale structure of cycles 23 and 24 is more systematic than during cycles 21 and 22. This may be due to the weakening activity, which reduces the complexity of the photospheric field and clarifies the Hale pattern. The photospheric field distribution also depicts a larger area for the field of the northern hemisphere during the declining and minimum phases, in a good agreement with the bashful ballerina phenomenon. The HMF sector crossings observed at 1AU have only a partial correspondence to Hale boundaries in the photosphere, indicating that the two HMF

  4. Structure of ferrofluid nanofilms in homogeneous magnetic fields

    Science.gov (United States)

    Jordanovic, Jelena; Klapp, Sabine H. L.

    2009-02-01

    We report molecular dynamics simulations results for model ferrofluid films subject to an external, homogeneous magnetic field directed parallel or perpendicular to the film surfaces. The interactions between the magnetic nanoparticles are modeled via the Stockmayer potential. In a previous study [J. Jordanovic and S. H. L. Klapp, Phys. Rev. Lett. 101, 038302 (2008)] we have shown that an external field can control the number and internal structure of the layers characterizing the fluid films, in qualitative agreement with experiments. Here we explore the dependence of the layering effects on thermodynamic conditions, and we analyze the results from an energetic (microscopic and macroscopic) perspective. As a special case we investigate a monolayer to bilayer transition induced via a perpendicular field.

  5. Variation of magnetic braking by non-axisymmetric magnetic fields depending on the perturbed field structure in the KSTAR tokamak

    Science.gov (United States)

    Kim, Kimin; Jeon, Y. M.; Park, J.-K.; Ko, W. H.; In, Y.; Choe, W.; Kim, J.; Lee, S. G.; Yoon, S. W.; Kwak, J. G.; Oh, Y. K.

    2017-03-01

    The variation of a magnetic braking profile by non-axisymmetric magnetic fields has been experimentally demonstrated and numerically validated in the KSTAR tokamak. Two types of n  =  2 non-resonant magnetic fields were applied by changing the relative phase of non-axisymmetric field coils. One is even parity, of which non-resonant fields deeply penetrate into the plasma core, and the other is odd parity localized at the plasma edge. The even and odd parity produced significantly different perturbed magnetic field structures, and thereby drove global and edge-dominant toroidal rotation damping, respectively. These distinct braking profiles are consistently reproduced by drift-kinetic particle simulations, indicating the possibility of the predictive utilization of non-resonant magnetic fields for rotation profile control.

  6. Benzene at 1 GHz. Magnetic field-induced fine structure

    Science.gov (United States)

    Heist, L. M.; Poon, C.-D.; Samulski, E. T.; Photinos, D. J.; Jokisaari, J.; Vaara, J.; Emsley, J. W.; Mamone, S.; Lelli, M.

    2015-09-01

    The deuterium NMR spectrum of benzene-d6 in a high field spectrometer (1 GHz protons) exhibits a magnetic field-induced deuterium quadrupolar splitting Δν. The magnitude of Δν observed for the central resonance is smaller than that observed for the 13C satellite doublets Δν‧. This difference, Δ(Δν) = Δν‧ - Δν, is due to unresolved fine structure contributions to the respective resonances. We determine the origins of and simulate this difference, and report pulse sequences that exploit the connectivity of the peaks in the 13C and 2H spectra to determine the relative signs of the indirect coupling, JCD, and Δν. The positive sign found for Δν is consonant with the magnetic field biasing of an isolated benzene molecule-the magnetic energy of the aromatic ring is lowest for configurations where the C6 axis is normal to the field. In the neat liquid the magnitude of Δν is decreased by the pair correlations in this prototypical molecular liquid.

  7. Probe measurements of the three-dimensional magnetic field structure in a rotating magnetic field sustained field-reversed configuration

    Science.gov (United States)

    Velas, K. M.; Milroy, R. D.

    2014-01-01

    A translatable three-axis probe was constructed and installed on the translation, confinement, and sustainment upgrade (TCSU) experiment. With ninety windings, the probe can simultaneously measure Br, Bθ, and Bz at 30 radial positions, and can be placed at any desired axial position within the field reversed configuration (FRC) confinement chamber. Positioning the probe at multiple axial positions and taking multiple repeatable shots allows for a full r-z map of the magnetic field. Measurements were made for odd-parity rotating magnetic field (RMF) antennas and even-parity RMF. The steady state data from applying a 10 kHz low pass filter used in conjunction with data at the RMF frequency yields a map of the full 3D rotating field structure. Comparisons will be made to the 3D magnetic structure predicted by NIMROD simulations, with parameters adjusted to match that of the TCSU experiments. The probe provides sufficient data to utilize a Maxwell stress tensor approach to directly measure the torque applied to the FRC's electrons, which combined with a resistive torque model, yields an estimate of the average FRC resistivity.

  8. STRUCTURE OF PROMINENCE LEGS: PLASMA AND MAGNETIC FIELD

    Energy Technology Data Exchange (ETDEWEB)

    Levens, P. J.; Labrosse, N. [SUPA School of Physics and Astronomy, University of Glasgow, Glasgow, G12 8QQ (United Kingdom); Schmieder, B. [Observatoire de Paris, Meudon, F-92195 (France); Ariste, A. López, E-mail: p.levens.1@research.gla.ac.uk [Institut de Recherche en Astrophysique et Planétologie, Toulouse (France)

    2016-02-10

    We investigate the properties of a “solar tornado” observed on 2014 July 15, and aim to link the behavior of the plasma to the internal magnetic field structure of the associated prominence. We made multi-wavelength observations with high spatial resolution and high cadence using SDO/AIA, the Interface Region Imaging Spectrograph (IRIS) spectrograph, and the Hinode/Solar Optical Telescope (SOT) instrument. Along with spectropolarimetry provided by the Télescope Héliographique pour l’Etude du Magnétisme et des Instabilités Solaires telescope we have coverage of both optically thick emission lines and magnetic field information. AIA reveals that the two legs of the prominence are strongly absorbing structures which look like they are rotating, or oscillating in the plane of the sky. The two prominence legs, which are both very bright in Ca ii (SOT), are not visible in the IRIS Mg ii slit-jaw images. This is explained by the large optical thickness of the structures in Mg ii, which leads to reversed profiles, and hence to lower integrated intensities at these locations than in the surroundings. Using lines formed at temperatures lower than 1 MK, we measure relatively low Doppler shifts on the order of ±10 km s{sup −1} in the tornado-like structure. Between the two legs we see loops in Mg ii, with material flowing from one leg to the other, as well as counterstreaming. It is difficult to interpret our data as showing two rotating, vertical structures that are unrelated to the loops. This kind of “tornado” scenario does not fit with our observations. The magnetic field in the two legs of the prominence is found to be preferentially horizontal.

  9. Anomalous plasma transport and induced electric field in a stochastic magnetic field structure

    Energy Technology Data Exchange (ETDEWEB)

    Kubota, Tetsuyuki; Itoh, Sanae-I.; Toda, Shinichiro; Yamaguchi, Hiroki [Kyushu Univ., Fukuoka (Japan); Fukuyama, Atsushi [Okayama Univ. (Japan)

    1995-04-01

    The plasma transport matrix is formulated using the kinetic equation for the particles in the stochastic magnetic field. The radial electric field generation is analyzed using this transport matrix. This thermoelectric field is dictated by the difference between the electron heat flux and the ion heat flux. We calculate the spatial structures of the radial electric field and the temperature in the stochastic field region. 7 refs., 3 figs.

  10. A Study of Neutron Star Structure in Strong Magnetic Fields that includes Anomalous Magnetic Moments

    Institute of Scientific and Technical Information of China (English)

    Guang-Jun Mao; Akira Iwamoto; Zhu-Xia Li

    2003-01-01

    We study the effect of strong magnetic fields on the structure of neutronstar. We find that if the interior field is on the same order as the surface fieldcurrently observed, then the influences of the field on the star's mass and radius arenegligible; if the field is as large as that estimated from the scalar virial theorem,then considerable effects will be induced. The maximum mass of the star will beincreased substantially while the central density is greatly reduced. The radius ofa magnetic star can be larger by about 10% ~ 20% than a nonmagnetic star of thesame mass.

  11. Magnetic field in atypical prominence structures: Bubble, tornado and eruption

    CERN Document Server

    Levens, P J; Ariste, A López; Labrosse, N; Dalmasse, K; Gelly, B

    2016-01-01

    Spectropolarimetric observations of prominences have been obtained with the THEMIS telescope during four years of coordinated campaigns. Our aim is now to understand the conditions of the cool plasma and magnetism in `atypical' prominences, namely when the measured inclination of the magnetic field departs, to some extent, from the predominantly horizontal field found in `typical' prominences. What is the role of the magnetic field in these prominence types? Are plasma dynamics more important in these cases than the magnetic support? We focus our study on three types of `atypical' prominences (tornadoes, bubbles and jet-like prominence eruptions) that have all been observed by THEMIS in the He I D_3 line, from which the Stokes parameters can be derived. The magnetic field strength, inclination and azimuth in each pixel are obtained by using the Principal Component Analysis inversion method on a model of single scattering in the presence of the Hanle effect. The magnetic field in tornadoes is found to be more ...

  12. Improvement of neutral beam injection heating efficiency with magnetic field well structures in a tokamak with a low magnetic field

    Science.gov (United States)

    Kim, S. K.; Na, D. H.; Lee, J. W.; Yoo, M. G.; Kim, H.-S.; Hwang, Y. S.; Hahm, T. S.; Na, Yong-Su

    2016-10-01

    Magnetic well structures are introduced as an effective means to reduce the prompt loss of fast ions, the so-called first orbit loss from neutral beam injection (NBI), which is beneficial to tokamaks with a low magnetic field strength such as small spherical torus devices. It is found by single-particle analysis that this additional field structure can modify the gradient of the magnetic field to reduce the shift of the guiding center trajectory of the fast ion. This result is verified by a numerical calculation of following the fast ion’s trajectory. We apply this concept to the Versatile Experiment Spherical Torus [1], where NBI is under design for the purpose of achieving high-performance plasma, to evaluate the effect of the magnetic well structure on NBI efficiency. A 1D NBI analysis code and the NUBEAM code are employed for detailed NBI calculations. The simulation results show that the orbit loss can be reduced by 70%-80%, thereby improving the beam efficiency twofold compared with the reference case without the well structure. The well-shaped magnetic field structure in the low-field side can significantly decrease orbit loss by broadening the non-orbit loss region and widening the range of the velocity direction, thus improving the heating efficiency. It is found that this magnetic well can also improve orbit loss during the slowing down process.

  13. Filament Shape Versus Coronal Potential Magnetic Field Structure

    CERN Document Server

    Filippov, Boris

    2015-01-01

    Solar filament shape in projection on disc depends on the structure of the coronal magnetic field. We calculate the position of polarity inversion lines (PILs) of coronal potential magnetic field at different heights above the photosphere, which compose the magnetic neutral surface, and compare with them the distribution of the filament material in H$\\alpha$ chromospheric images. We found that the most of the filament material is enclosed between two polarity inversion lines (PILs), one at a lower height close to the chromosphere and one at a higher level, which can be considered as a height of the filament spine. Observations of the same filament on the limb by the {\\it STEREO} spacecraft confirm that the height of the spine is really very close to the value obtained from the PIL and filament border matching. Such matching can be used for filament height estimations in on-disk observations. Filament barbs are housed within protruding sections of the low-level PIL. On the base of simple model, we show that th...

  14. On the Low Surface Magnetic Field Structure of Quark Stars

    CERN Document Server

    Nag, Nandini; Saha, Roni; Chakrabarty, Somenath

    2008-01-01

    Following some of the recent articles on hole super-conductivity and related phenomena by Hirsch \\cite{H1,H2,H3}, a simple model is proposed to explain the observed low surface magnetic field of the expected quark stars. It is argued that the diamagnetic moments of the electrons circulating in the electro-sphere induce a magnetic field, which forces the existing quark star magnetic flux density to become dilute. We have also analysed the instability of normal-superconducting interface due to excess accumulation of magnetic flux lines, assuming an extremely slow growth of superconducting phase through a first order bubble nucleation type transition.

  15. Radio polarization and magnetic field structure in M 101

    CERN Document Server

    Berkhuijsen, E M; Beck, R; Han, J L

    2016-01-01

    We observed total and polarized radio continuum emission from the spiral galaxy M 101 at 6.2 cm and 11.1 cm wavelengths with the Effelsberg telescope. We use these data to study various emission components in M 101 and properties of the magnetic field. Separation of thermal and non-thermal emission shows that the thermal emission is closely correlated with the spiral arms, while the non-thermal emission is more smoothly distributed indicating diffusion of cosmic ray electrons away from their places of origin. The radial distribution of both emissions has a break near R=16 kpc, where it steepens to an exponential scale length of about 5 kpc, which is about 2.5 times smaller than at R<16 kpc. The distribution of the polarized emission has a broad maximum near R=12 kpc and beyond R=16 kpc also decreases with about 5 kpc scalelength. It seems that near R=16 kpc a major change in the structure of M 101 takes place, which also affects the distributions of the strength of the random and ordered magnetic field. Be...

  16. Magnetic Field

    DEFF Research Database (Denmark)

    Olsen, Nils

    2015-01-01

    of the fluid flow at the top of the core. However, what is measured at or near the surface of the Earth is the superposition of the core field and fields caused by magnetized rocks in the Earth’s crust, by electric currents flowing in the ionosphere, magnetosphere, and oceans, and by currents induced......he Earth has a large and complicated magnetic field, the major part of which is produced by a self-sustaining dynamo operating in the fluid outer core. Magnetic field observations provide one of the few tools for remote sensing the Earth’s deep interior, especially regarding the dynamics...... in the Earth by time-varying external fields. These sources have their specific characteristics in terms of spatial and temporal variations, and their proper separation, based on magnetic measurements, is a major challenge. Such a separation is a prerequisite for remote sensing by means of magnetic field...

  17. Subsurface magnetic field and flow structure of simulated sunspots

    CERN Document Server

    Rempel, Matthias

    2011-01-01

    We present a series of numerical sunspot models addressing the subsurface field and flow structure in up to 16 Mm deep domains covering up to 2 days of temporal evolution. Changes in the photospheric appearance of the sunspots are driven by subsurface flows in several Mm depth. Most of magnetic field is pushed into a downflow vertex of the subsurface convection pattern, while some fraction of the flux separates from the main trunk of the spot. Flux separation in deeper layers is accompanied in the photosphere with light bridge formation in the early stages and formation of pores separating from the spot at later stages. Over a time scale of less than a day we see the development of a large scale flow pattern surrounding the sunspots, which is dominated by a radial outflow reaching about 50% of the convective rms velocity in amplitude. Several components of the large scale flow are found to be independent from the presence of a penumbra and the associated Evershed flow. While the simulated sunspots lead to blo...

  18. Structure of magnetic fields on the quiet sun

    Science.gov (United States)

    Wang, Haimin

    1988-01-01

    To obtain quantitative temporal and spatial information on the network magnetic fields, auto- and cross-correlation techniques are applied to the Big Bear videomagnetogram data. The average size of the network magnetic elements derived from the auto-correlation curve is about 5700 km. The distance between the primary and secondary peak in the auto-correlation curve is about 17,000 km, which is half of the size of the supergranule as determined from the velocity map. The canceling features and the emergence of ephemeral regions are the major sources for the loss and replenishment of magnetic flux on the quiet sun.

  19. Surface structure of quark stars with magnetic fields

    Indian Academy of Sciences (India)

    Prashanth Jaikumar

    2006-11-01

    We investigate the impact of magnetic fields on the electron distribution of the electrosphere of quark stars. For moderately strong magnetic fields of ∼ 1013 G, quantization effects are generally weak due to the large number density of electrons at surface, but can nevertheless affect the photon emission properties of quark stars. We outline the main observational characteristics of quark stars as determined by their surface emission, and briefly discuss their formation in explosive events termed as quark-novae, which may be connected to the -process.

  20. Isolated magnetic field structures in Mercury's magnetosheath as possible analogues for terrestrial magnetosheath plasmoids and jets

    Science.gov (United States)

    Karlsson, Tomas; Liljeblad, Elisabet; Kullen, Anita; Raines, Jim M.; Slavin, James A.; Sundberg, Torbjörn

    2016-09-01

    We have investigated MESSENGER magnetic field data from the Mercury magnetosheath and near solar wind, to identify isolated magnetic field structures (defined as clear, isolated changes in the field magnitude). Their properties are studied in order to determine if they may be considered as analogues to plasmoids and jets known to exist in Earth's magnetosheath. Both isolated decreases of the magnetic field absolute value ('negative magnetic field structures') and increases ('positive structures') are found in the magnetosheath, whereas only negative structures are found in the solar wind. The similar properties of the solar wind and magnetosheath negative magnetic field structures suggests that they are analogous to diamagnetic plasmoids found in Earth's magnetosheath and near solar wind. The latter have earlier been identified with solar wind magnetic holes. Positive magnetic field structures are only found in the magnetosheath, concentrated to a region relatively close to the magnetopause. Their proximity to the magnetopause, their scale sizes, and the association of a majority of the structures with bipolar magnetic field signatures identify them as flux transfer events (which generally are associated with a decrease of plasma density in the magnetosheath). The positive magnetic field structures are therefore not likely to be analogous to terrestrial paramagnetic plasmoids but possibly to a sub-population of magnetosheath jets. At Earth, a majority of magnetosheath jets are associated with the quasi-parallel bow shock. We discuss some consequences of the findings of the present investigation pertaining to the different nature of the quasi-parallel bow shock at Mercury and Earth.

  1. Turbulent Amplification and Structure of the Intracluster Magnetic Field

    CERN Document Server

    Beresnyak, Andrey

    2015-01-01

    We compare DNS calculations of homogeneous isotropic turbulence with the statistical properties of intra-cluster turbulence from the Matryoshka Run (Miniati 2014) and find remarkable similarities between their inertial ranges. This allowed us to use the time dependent statistical properties of intra-cluster turbulence to evaluate dynamo action in the intra-cluster medium, based on earlier results from numerically resolved nonlinear magneto-hydrodynamic turbulent dynamo (Beresnyak 2012). We argue that this approach is necessary (a) to properly normalize dynamo action to the available intra-cluster turbulent energy and (b) to overcome the limitations of low Re affecting current numerical models of the intra-cluster medium. We find that while the properties of intra-cluster magnetic field are largely insensitive to the value and origin of the seed field, the resulting values for the Alfven speed and the outer scale of the magnetic field are consistent with current observational estimates, basically confirming th...

  2. Spiral structures and regularities in magnetic field variations and auroras

    Directory of Open Access Journals (Sweden)

    Y. I. Feldstein

    2012-02-01

    Full Text Available The conception of spiral shaped precipitation regions, where solar corpuscles penetrate the upper atmosphere, was introduced into geophysics by C. Störmer and K. Birkeland at the beginning of the last century. Later, in the course of the XX-th century, spiral distributions were disclosed and studied in various geophysical phenomena. Most attention was devoted to spiral shapes in the analysis of regularities pertaining to the geomagnetic activity and auroras.

    We review the historical succession of perceptions about the number and positions of spiral shapes, that characterize the spatial-temporal distribution of magnetic disturbances. We describe the processes in the upper atmosphere, which are responsible for the appearance of spiral patterns. We considered the zones of maximal aurora frequency and of maximal particle precipitation intensity, as offered in the literature, in their connection with the spirals.

    We discuss the current system model, that is closely related to the spirals and that appears to be the source for geomagnetic field variations during magnetospheric substorms and storms. The currents in ionosphere and magnetosphere constitute together with field-aligned (along the geomagnetic field lines currents (FACs a common 3-D current system. At ionospheric heights, the westward and eastward electrojets represent characteristic elements of the current system. The westward electrojet covers the longitudinal range from the morning to the evening hours, while the eastward electrojet ranges from afternoon to near-midnight hours. The polar electrojet is positioned in the dayside sector at cusp latitudes. All these electrojets map along the magnetic field lines to certain plasma structures in the near-Earth space. The first spiral distribution of auroras was found based on observations in Antarctica for the nighttime-evening sector (N-spiral, and later in the nighttime-evening (N-spiral and morning (M-spiral sectors both in

  3. Structural Organization in the System of Magnetized Aggregates in Elliptically Polarized Rotating Magnetic Field

    Directory of Open Access Journals (Sweden)

    Yu.I. Dikansky

    2014-07-01

    Full Text Available Observed data supporting the possibility of magnetic ordering in magnetic colloids are reported. A possibility of aggregate spatial ordering in a system of magnetized aggregates was found under the influence of rotating and crossed constant and alternating magnetic fields.

  4. TURBULENT AMPLIFICATION AND STRUCTURE OF THE INTRACLUSTER MAGNETIC FIELD

    Energy Technology Data Exchange (ETDEWEB)

    Beresnyak, Andrey [Nordita, KTH Royal Institute of Technology and Stockholm University, SE-10691 Stockholm (Sweden); Miniati, Francesco [Physics Dept., ETH Zurich, Wolfgang-Pauli-Strasse 27, CH-8093 (Switzerland)

    2016-02-01

    We compare DNS calculations of homogeneous isotropic turbulence with the statistical properties of intracluster turbulence from the Matryoshka Run and find remarkable similarities between their inertial ranges. This allowed us to use the time-dependent statistical properties of intracluster turbulence to evaluate dynamo action in the intracluster medium, based on earlier results from a numerically resolved nonlinear magneto-hydrodynamic turbulent dynamo. We argue that this approach is necessary (a) to properly normalize dynamo action to the available intracluster turbulent energy and (b) to overcome the limitations of low Re affecting current numerical models of the intracluster medium. We find that while the properties of intracluster magnetic field are largely insensitive to the value and origin of the seed field, the resulting values for the Alfvén speed and the outer scale of the magnetic field are consistent with current observational estimates, basically confirming the idea that the magnetic field in today’s galaxy clusters is a record of its past turbulent activity.

  5. Spin structure factors of Heisenberg spin chain in the presence of anisotropy and magnetic field

    Science.gov (United States)

    Rezania, H.

    2017-02-01

    We have theoretically studied the spin structure factors of spin chain in the presence of longitudinal field and transverse anisotropy. The possible effects of easy axis magnetization are investigated in terms of anisotropy in the Heisenberg interactions. This anisotropy is considered for exchange coupling constants perpendicular to magnetic field direction. The original spin model hamiltonian is mapped to a bosonic model via a hard core bosonic transformation where an infinite hard core repulsion is imposed to constrain one boson occupation per site. Using Green's function approach, the energy spectrum of quasiparticle excitation has been obtained. The spectrum of the bosonic gas has been implemented in order to obtain two particle propagator which corresponds to spin structure factor of original Heisenberg chain model Hamiltonian. The results show the position of peak in the longitudinal structure factor at fixed value for anisotropy moves to higher frequency with magnetic field. Also the intensity of dynamical structure factor decreases with magnetic field. A small dependence of longitudinal dynamical spin structure factor on the anisotropy is observed for fixed value of magnetic field. Our results show longitudinal static structure factor is found to be monotonically increasing with magnetic field due to increase of spins aligning along magnetic field. Furthermore the dispersion behaviors of static longitudinal and transverse structure factors for different magnetic fields and anisotropy parameters are addressed.

  6. Probing of field-induced structures and tunable rheological properties of surfactant capped magnetically polarizable nanofluids.

    Science.gov (United States)

    Felicia, Leona J; Philip, John

    2013-01-08

    Oil-based nanofluid containing surfactant-capped magnetite nanoparticles are synthesized by a simple coprecipitation approach, and their magnetorheological properties are studied for different magnetic field strengths and volume fractions. We observe a distinct "plateau-like region" in the shear thinning viscosity curve, under an external magnetic field, possibly due to a peculiar alignment of the chains with respect to the field direction where the structure is stable against fragmentation. The observed plateau regime is reminiscent to that of kinetically arrested gel networks. Interestingly, such a plateau regime has been observed only above certain critical magnetic field when the dipolar interaction strength is much greater than the thermal energy where the aggregation becomes a nonequilibrium transport-limited process. The good collapse of specific viscosity data against Mason number for different magnetic field strengths onto a single curve suggests the dominance of hydrodynamic and magnetic forces on thermal force above a certain magnetic field strength. The observed increase in both static and dynamic yield stresses under the magnetic field confirms the formation of columnar structures that hinder the flow behavior. The hysteresis observed in the magnetic sweep experiments shows the inability of the chains to relax within the measurement time. The dynamic measurements confirm that the field-induced structures impart elastic behavior to the dispersion, which is found to increase with magnetic field and saturates at higher field strengths.

  7. Magnetic fields in the Large-Scale Structure of the Universe

    CERN Document Server

    Ryu, Dongsu; Treumann, Rudolf A; Tsagas, Christos G; Widrow, Lawrence M

    2011-01-01

    Magnetic fields appear to be ubiquitous in astrophysical environments. Their existence in the intracluster medium is established through observations of synchrotron emission and Faraday rotation. On the other hand, the nature of magnetic fields outside of clusters, where observations are scarce and controversial, remains largely unknown. In this chapter, we review recent developments in our understanding of the nature and origin of intergalactic magnetic fields, and in particular, intercluster fields. A plausible scenario for the origin of galactic and intergalactic magnetic fields is for seed fields, created in the early universe, to be amplified by turbulent flows induced during the formation of the large scale structure. We present several mechanisms for the generation of seed fields both before and after recombination. We then discuss the evolution and role of magnetic fields during the formation of the first starts. We describe the turbulent amplification of seed fields during the formation of large scal...

  8. Radio polarization and magnetic field structure in M 101

    Science.gov (United States)

    Berkhuijsen, E. M.; Urbanik, M.; Beck, R.; Han, J. L.

    2016-04-01

    We observed total and polarized radio continuum emission from the spiral galaxy M 101 at λλ 6.2 cm and 11.1 cm with the Effelsberg telescope. The angular resolutions are 2.´ 5 (=5.4 kpc) and 4.´ 4 (=9.5 kpc), respectively. We use these data to study various emission components in M 101 and properties of the magnetic field. Separation of thermal and non-thermal emission shows that the thermal emission is closely correlated with the spiral arms, while the non-thermal emission is more smoothly distributed indicating diffusion of cosmic ray electrons away from their places of origin. The radial distribution of both emissions has a break near R = 16 kpc (=7.´ 4), where it steepens to an exponential scale length of L ≃ 5 kpc, which is about 2.5 times smaller than at Rlength of both fields is about 20 kpc, which implies that they decrease to about 0.3 μG at R = 70 kpc, which is the largest optical extent. The equipartition strength of the total field ranges from nearly 10 μG at R< 2 kpc to 4 μG at R = 22-24 kpc. As the random field dominates in M 101 (Bran/Bord ≃ 2.4), wavelength-independent polarization is the main polarization mechanism. We show that energetic events causing H i shells of mean diameter < 625 pc could partly be responsible for this. At radii < 24 kpc, the random magnetic field depends on the star formation rate/area, ΣSFR, with a power-law exponent of b = 0.28 ± 0.02. The ordered magnetic field is generally aligned with the spiral arms with pitch angles that are about 8° larger than those of H i filaments. Based on observations with the 100 m telescope of the MPIfR at Effelsberg.FITS files of the images are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/588/A114

  9. Nonaxisymmetric Rossby vortex instability with toroidal magnetic fields in structured disks

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Cong [Los Alamos National Laboratory; Li, Hui [Los Alamos National Laboratory

    2009-01-01

    We investigate the global nonaxisymmetric Rossby vortex instability (RVI) in a differentially rotating, compressible magnetized accretion disk with radial density structures. Equilibrium magnetic fields are assumed to have only the toroidal component. Using linear theory analysis, we show that the density structure can be unstable to nonaxisymmetric modes. We find that, for the magnetic field profiles we have studied, magnetic fields always provide a stabilizing effect to the unstable RVI modes. We discuss the physical mechanism of this stabilizing effect. The threshold and properties of the unstable modes are also discussed in detail. In addition, we present linear stability results for the global magnetorotational instability when the disk is compressible.

  10. Investigation of the field dependent spin structure of exchange coupled magnetic heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Gurieva, Tatiana

    2016-05-15

    This thesis describes the investigation of the field dependent magnetic spin structure of an antiferromagnetically (AF) coupled Fe/Cr heterostructure sandwiched between a hardmagnetic FePt buffer layer and a softmagnetic Fe top layer. The depth-resolved experimental studies of this system were performed via Magneto-optical Kerr effect (MOKE), Vibrating Sample Magnetometry (VSM) and various measuring methods based on nuclear resonant scattering (NRS) technique. Nucleation and evolution of the magnetic spiral structure in the AF coupled Fe/Cr multilayer structure in an azimuthally rotating external magnetic field were observed using NRS. During the experiment a number of time-dependent magnetic side effects (magnetic after-effect, domain-wall creep effect) caused by the non-ideal structure of a real sample were observed and later explained. Creation of the magnetic spiral structure in rotating external magnetic field was simulated using a one-dimensional micromagnetic model.The cross-sectional magnetic X-ray diffraction technique was conceived and is theoretically described in the present work. This method allows to determine the magnetization state of an individual layer in the magnetic heterostructure. It is also applicable in studies of the magnetic structure of tiny samples where conventional x-ray reflectometry fails.

  11. The magnetic phase diagram and zero field structure of holmium-lutetium superlattices

    Energy Technology Data Exchange (ETDEWEB)

    Swaddling, P.P. [Clarendon Laboratory, Oxford University, Oxford (United Kingdom); McMorrow, D.F. [Risoe National Laboratory, Roskilde (Denmark); Cowley, R.A. [Clarendon Laboratory, Oxford University, Oxford (United Kingdom); Simpson, J.A. [Clarendon Laboratory, Oxford University, Oxford (United Kingdom); Wells, M.R. [Clarendon Laboratory, Oxford University, Oxford (United Kingdom); Ward, R.C.C. [Clarendon Laboratory, Oxford University, Oxford (United Kingdom); Clausen, K.N. [Risoe National Laboratory, Roskilde (Denmark); Collins, M.F. [Dept of Physics and Astronomy, McMaster University, Hamilton (Canada); Buyers, W.J.L. [AECL, Chalk River, Ontario (Canada)

    1995-02-09

    Neutron diffraction has been used to study the magnetic structure of a series of Ho/Lu superlattices. In zero field a transition to a ferromagnetic phase of Ho is observed at low temperatures, and the stability of this phase has been investigated by applying a magnetic field in the basal plane. ((orig.)).

  12. Effect of alternate magnetic field on LY12 structure properties after thermal plastic forming

    Institute of Scientific and Technical Information of China (English)

    陈革新; 付宇明; 尹京; 肖宏

    2008-01-01

    The powerful alternate magnetic field treatment is an effective not-heat treatment, which improves the coriaceous performance of the material. In order to reveal the effect rule of the powerful alternate magnetic field on the structure capability after thermal plastic forming, the experimental methods were adopted to compare the microcosmic structure of the LY12 aluminium alloy test pieces before and after the powerful alternate magnetic field treatment. The mechanism of the structure refining was analyzed theoretically. According to the effect rule of the alternate magnetic field on critical grain growth work and the magnetic vibration-constriction mechanism, the structure dynamics factors were analyzed. The results show that, after a certain powerful alternate magnetic field treatment, the mechanical capability of the LY12 aluminium alloy after thermal plastic forming can be reinforced, the structure intertwist deriving from the thermal plastic forming becomes even and the branch crystal is also smashed, consequently refines the structure. The powerful alternate magnetic field treatment can be regarded as an effective method to improve metal structure performance after heat plastic forming.

  13. Tuning the Colloidal Crystal Structure of Magnetic Particles by External Field

    NARCIS (Netherlands)

    Pal, Antara; Malik, Vikash; He, Le; Erne, Ben H.; Yin, Yadong; Kegel, Willem K.; Petukhov, A. V.

    2015-01-01

    Manipulation of the self-assembly of magnetic colloidal particles by an externally applied magnetic field paves a way toward developing novel stimuli responsive photonic structures. Using microradian X-ray scattering technique we have investigated the different crystal structures exhibited by self-a

  14. Kinetic simulations of electric field structure within magnetic island during magnetic reconnection and their applications to the satellite observations

    Science.gov (United States)

    Huang, S. Y.; Zhou, M.; Yuan, Z. G.; Deng, X. H.; Sahraoui, F.; Pang, Y.; Fu, S.

    2014-09-01

    Magnetic islands are considered to play a crucial role in collisionless magnetic reconnection. We use particle-in-cell simulations to investigate electric field Ez structure in the magnetic islands (including primary and secondary islands) with and without a guide field during magnetic reconnection. It is found that the electric field has multilayers in the primary island and a large bipolar structure in the secondary island in the absence of guide field. The electric field is provided by the Hall term (J × B)z (mainly), the divergence of electron pressure tensor, and the convective term (Vi × B)z in the outer and the inner region of primary island, while the electric field is much smaller (~0) in the middle and the core region of primary island due to the cancelation of the three terms. The single bipolar electric field is primarily provided by the Hall term in the secondary island. In the presence of a guide field, the electric field has multiple layers in the primary island (similar to zero guide field case) and the secondary island. However, there still exists one single large sharp bipolar structure of electric field in the central region of the secondary island. The differences of electric field in the primary and secondary islands are essentially due to the variations of the current Jy. These features can be used as the observational criteria to identify different types of magnetic islands in the magnetosphere using the data of future mission, such as the Magnetospheric Multiscale mission.

  15. Quark-hadron phase structure and QCD equations of state in vanishing and finite magnetic field

    CERN Document Server

    Tawfik, Abdel Nasser; Hussein, M T

    2016-01-01

    In characterizing the quark-hadron phase structure, determining various thermodynamic quantities and investigating their temperature dependencies on vanishing and finite magnetic field, SU(3) Polyakov linear-sigma model (PLSM) is utilized. The dependence of the chiral order-parameter on vanishing and finite magnetic field is calculated in mean-field approximation. In a wide range of temperatures and magnetic field strengths, the thermodynamic observables including trace anomaly, speed of sound squared, entropy density, specific heat and magnetization are presented. An excellent agreement is found when these are confronted to recent lattice QCD calculations. The temperature dependence of these quantities confirms our previous result that the transition temperature is reduced with magnetic field. Furthermore, the temperature dependence of magnetization verifies the conclusion that the QCD matter has paramagnetic properties near and far above the critical temperature. The excellent agreement with recent lattice ...

  16. Magnetic fields in galaxies

    CERN Document Server

    Beck, Rainer

    2013-01-01

    Most of the visible matter in the Universe is ionized, so that cosmic magnetic fields are quite easy to generate and due to the lack of magnetic monopoles hard to destroy. Magnetic fields have been measured in or around practically all celestial objects, either by in-situ measurements of spacecrafts or by the electromagnetic radiation of embedded cosmic rays, gas or dust. The Earth, the Sun, solar planets, stars, pulsars, the Milky Way, nearby galaxies, more distant (radio) galaxies, quasars and even intergalactic space in clusters of galaxies have significant magnetic fields, and even larger volumes of the Universe may be permeated by "dark" magnetic fields. Information on cosmic magnetic fields has increased enormously as the result of the rapid development of observational methods, especially in radio astronomy. In the Milky Way, a wealth of magnetic phenomena was discovered, which are only partly related to objects visible in other spectral ranges. The large-scale structure of the Milky Way's magnetic fie...

  17. Octupolar out-of-plane magnetic field structure generation during collisionless magnetic reconnection in a stressed X-point collapse

    Energy Technology Data Exchange (ETDEWEB)

    Graf von der Pahlen, J.; Tsiklauri, D. [School of Physics and Astronomy, Queen Mary University of London, London E1 4NS (United Kingdom)

    2014-06-15

    The out-of-plane magnetic field, generated by fast magnetic reconnection, during collisionless, stressed X-point collapse, was studied with a kinetic, 2.5D, fully electromagnetic, relativistic particle-in-cell numerical code, using both closed (flux conserving) and open boundary conditions on a square grid. It was discovered that the well known quadrupolar structure in the out-of-plane magnetic field gains four additional regions of opposite magnetic polarity, emerging near the corners of the simulation box, moving towards the X-point. The emerging, outer, magnetic field structure has opposite polarity to the inner quadrupolar structure, leading to an overall octupolar structure. Using Ampere's law and integrating electron and ion currents, defined at grid cells, over the simulation domain, contributions to the out-of-plane magnetic field from electron and ion currents were determined. The emerging regions of opposite magnetic polarity were shown to be the result of ion currents. Magnetic octupolar structure is found to be a signature of X-point collapse, rather than tearing mode, and factors relating to potential discoveries in experimental scenarios or space-craft observations are discussed.

  18. On the Relationship Between Sunspot Structure and Magnetic Field Changes Associated with Solar Flares

    Science.gov (United States)

    Song, Y. L.; Zhang, M.

    2016-08-01

    Many previous studies have shown that magnetic fields and sunspot structures present rapid and irreversible changes associated with solar flares. In this paper, we first use five X-class flares observed by Solar Dynamics Observatory/Helioseismic and Magnetic Imager to show that not only do magnetic fields and sunspot structures show rapid, irreversible changes, but also that these changes are closely related both spatially and temporally. The magnitudes of the correlation coefficients between the temporal variations of the horizontal magnetic field and sunspot intensity are all larger than 0.90, with a maximum value of 0.99 and an average value of 0.96. Then, using four active regions during quiescent periods, three observed and one simulated, we show that in sunspot penumbra regions there also exists a close correlation between sunspot intensity and horizontal magnetic field strength in addition to the well-known correlation between sunspot intensity and the normal magnetic field strength. By connecting these two observational phenomena, we show that the sunspot structure change and magnetic field change are two facets of the same phenomena of solar flares; one change might be induced by the change of the other due to a linear correlation between sunspot intensity and magnetic field strength out of a local force balance.

  19. The First Magnetic Fields

    CERN Document Server

    Widrow, Lawrence M; Schleicher, Dominik; Subramanian, Kandaswamy; Tsagas, Christos G; Treumann, Rudolf A

    2011-01-01

    We review current ideas on the origin of galactic and extragalactic magnetic fields. We begin by summarizing observations of magnetic fields at cosmological redshifts and on cosmological scales. These observations translate into constraints on the strength and scale magnetic fields must have during the early stages of galaxy formation in order to seed the galactic dynamo. We examine mechanisms for the generation of magnetic fields that operate prior during inflation and during subsequent phase transitions such as electroweak symmetry breaking and the quark-hadron phase transition. The implications of strong primordial magnetic fields for the reionization epoch as well as the first generation of stars is discussed in detail. The exotic, early-Universe mechanisms are contrasted with astrophysical processes that generate fields after recombination. For example, a Biermann-type battery can operate in a proto-galaxy during the early stages of structure formation. Moreover, magnetic fields in either an early genera...

  20. SEMICONDUCTOR DEVICES MEMS magnetic field sensor based on silicon bridge structure

    Science.gov (United States)

    Guangtao, Du; Xiangdong, Chen; Qibin, Lin; Hui, Li; Huihui, Guo

    2010-10-01

    A MEMS piezoresistive magnetic field sensor based on a silicon bridge structure has been simulated and tested. The sensor consists of a silicon sensitivity diaphragm embedded with a piezoresistive Wheatstone bridge, and a ferromagnetic magnet adhered to the sensitivity diaphragm. When the sensor is subjected to an external magnetic field, the magnetic force bends the silicon sensitivity diaphragm, producing stress and resistors change of the Wheatstone bridge and the output voltage of the sensor. Good agreement is observed between the theory and measurement behavior of the magnetic field sensor. Experimental results demonstrate that the maximum sensitivity and minimum resolution are 48 m V/T and 160 μT, respectively, making this device suitable for strong magnetic field measurement. Research results indicate that the sensor repeatability and dynamic response time are about 0.66% and 150 ms, respectively.

  1. Structure, dynamical impact and origin of magnetic fields in nearby galaxies in the SKA era

    CERN Document Server

    Beck, Rainer; Colafrancesco, Sergio; Dettmar, Ralf-Jürgen; Ferrière, Katia; Fletcher, Andrew; Heald, George; Heesen, Volker; Horellou, Cathy; Krause, Marita; Lou, Yu-Qing; Mao, Sui Ann; Paladino, Rosita; Schinnerer, Eva; Sokoloff, Dmitry; Stil, Jeroen; Tabatabaei, Fatemeh

    2015-01-01

    Magnetic fields are an important ingredient of the interstellar medium (ISM). Besides their importance for star formation, they govern the transport of cosmic rays, relevant to the launch and regulation of galactic outflows and winds, which in turn are pivotal in shaping the structure of halo magnetic fields. Mapping the small-scale structure of interstellar magnetic fields in many nearby galaxies is crucial to understand the interaction between gas and magnetic fields, in particular how gas flows are affected. Elucidation of the magnetic role in, e.g., triggering star formation, forming and stabilising spiral arms, driving outflows, gas heating by reconnection and magnetising the intergalactic medium has the potential to revolutionise our physical picture of the ISM and galaxy evolution in general. Radio polarisation observations in the very nearest galaxies at high frequencies (>= 3 GHz) and with high spatial resolution (<= 5") hold the key here. The galaxy survey with SKA1 that we propose will also be a...

  2. Potential Magnetic Field around a Helical Flux-rope Current Structure in the Solar Corona

    CERN Document Server

    Petrie, G J D

    2007-01-01

    We consider the potential magnetic field associated with a helical electric line current flow, idealizing the near-potential coronal field within which a highly localized twisted current structure is embedded. It is found that this field has a significant axial component off the helical magnetic axis where there is no current flow, such that the flux winds around the axis. The helical line current field, in including the effects of flux rope writhe, is therefore more topologically complex than straight line and ring current fields sometimes used in solar flux rope models. The axial flux in magnetic fields around confined current structures may be affected by the writhe of these current structures such that the field twists preferentially with the same handedness as the writhe. This property of fields around confined current structures with writhe may be relevant to classes of coronal magnetic flux rope, including structures observed to have sigmoidal forms in soft X-rays and prominence magnetic fields. For ex...

  3. Effect of high magnetic field on structure and magnetic properties of evaporated crystalline and amorphous Fe-Sm thin films

    Science.gov (United States)

    Li, Guojian; Li, Mengmeng; Wang, Jianhao; Du, Jiaojiao; Wang, Kai; Wang, Qiang

    2017-02-01

    Crystalline and amorphous Fe-Sm thin films have been fabricated by using molecular beam vapor deposition method. Then, the effects of both variation of Sm content and application of high magnetic field during film growth on the structure and magnetic properties of the Fe-Sm films have been explored. The results show that bcc structure of the Fe-Sm films with 5.8% Sm transforms to amorphization with 33.0% Sm. Meanwhile, nanocrystallite is formed in the amorphous Fe-Sm films. However, no Fe-Sm compound exists with the change of Sm content and with the application of high magnetic field. Nevertheless, high magnetic field decreases interplanar spacing. The structural evolution has a significant effect on magnetic properties. Saturation magnetization decreases 290% from 1456 emu/cm3 to 373 emu/cm3 with the increase of Sm content from 5.8% to 33.0%. The coercivity increases 1225% from 20 Oe to 265 Oe. Meanwhile, both the saturation magnetization and coercivity of the films decrease with the application of high magnetic field. The reason has been discussed.

  4. Ultra-fine-scale filamentary structures in the Outer Corona and the Solar Magnetic Field

    Science.gov (United States)

    Woo, Richard

    2006-01-01

    Filamentary structures following magnetic field lines pervade the Sun's atmosphere and offer us insight into the solar magnetic field. Radio propagation measurements have shown that the smallest filamentary structures in the solar corona are more than 2 orders of magnitude finer than those seen in solar imaging. Here we use radio Doppler measurements to characterize their transverse density gradient and determine their finest scale in the outer corona at 20-30 R(circled dot operator), where open magnetic fields prevail. Filamentary structures overly active regions have the steepest gradient and finest scale, while those overlying coronal holes have the shallowest gradient and least finest scale. Their organization by the underlying corona implies that these subresolution structures extend radially from the entire Sun, confirming that they trace the coronal magnetic field responsible for the radial expansion of the solar wind. That they are rooted all over the Sun elucidates the association between the magnetic field of the photosphere and that of the corona, as revealed by the similarity between the power spectra of the photospheric field and the coronal density fluctuations. This association along with the persistence of filamentary structures far from the Sun demonstrate that subresolution magnetic fields must play an important role not only in magnetic coupling of the photosphere and corona, but also in coronal heating and solar wind acceleration through the process of small-scale magnetic reconnection. They also explain why current widely used theoretical models that extrapolate photospheric magnetic fields into the corona do not predict the correct source of the solar wind.

  5. The magnetic field structure in NGC 253 in presence of a galactic wind

    CERN Document Server

    Heesen, V; Beck, R; Dettmar, R J

    2008-01-01

    We present radio continuum polarimetry observations of the nearby edge-on galaxy NGC 253 which possesses a very bright radio halo. Using the vertical synchrotron emission profiles and the lifetimes of cosmic-ray electrons, we determined the cosmic-ray bulk speed as (300+/-30) km/s, indicating the presence of a galactic wind in this galaxy. The large-scale magnetic field was decomposed into a toroidal axisymmetric component in the disk and a poloidal component in the halo. The poloidal component shows a prominent X-shaped magnetic field structure centered on the nucleus, similar to the magnetic field observed in other edge-on galaxies. Faraday rotation measures indicate that the poloidal field has an odd parity (antisymmetric). NGC 253 offers the possibility to compare the magnetic field structure with models of galactic dynamos and/or galactic wind flows.

  6. Effects of magnetic-fluid flow on structural instability of a carbon nanotube conveying nanoflow under a longitudinal magnetic field

    Science.gov (United States)

    Sadeghi-Goughari, Moslem; Jeon, Soo; Kwon, Hyock-Ju

    2017-09-01

    In drug delivery systems, carbon nanotubes (CNTs) can be used to deliver anticancer drugs into target site to kill metastatic cancer cells under the magnetic field guidance. Deep understanding of dynamic behavior of CNTs in drug delivery systems may enable more efficient use of the drugs while reducing systemic side effects. In this paper, we study the effect of magnetic-fluid flow on the structural instability of a CNT conveying nanoflow under a longitudinal magnetic field. The Navier-Stokes equation of magnetic-fluid flow is coupled with Euler-Bernoulli beam theory for modeling fluid structure interaction (FSI). Size effects of the magnetic fluid and the CNT are addressed through small-scale parameters including the Knudsen number (Kn) and the nonlocal parameter. Results show the positive role of magnetic properties of fluid flow on the structural stability of CNT. Specifically, magnetic force applied to the fluid flow has an effect of decreasing the structural stiffness of system while increasing the critical flow velocity. Furthermore, we discover that the nanoscale effects of CNT and fluid flow tend to amplify the influence of magnetic field on the vibrational behavior of the system.

  7. Hysteresis in the field-induced magnetic structure in TmNi2B2C

    DEFF Research Database (Denmark)

    Eskildsen, M.R.; Harada, K.; Gammel, P.L:

    1999-01-01

    Using small-angle neutron scattering we have studied the flux line lattice and the magnetic structure in TmNi2B2C. With an applied field parallel to the crystalline c-axis several magnetic and flux line lattice symmetry transitions have been reported. The subject of this paper is the held-induced...

  8. Determination of the Structure of the Coronal Magnetic Field Using Microwave Polarization Measurements

    Science.gov (United States)

    Bogod, V. M.; Yasnov, L. V.

    2016-11-01

    An analysis of the oscillatory motions and wave processes in active regions requires knowledge of the structure of the magnetic fields in the chromosphere and corona. We study the magnetic field structure of active regions at coronal heights, as they are determined by means of multiwave observations of polarized radio emission of active regions in the microwave range. Two methods, a stereoscopic method and the analysis of the radio spectrum are used. The method of stereoscopy rotation allows estimating the height of radio sources in a stable active region relative to the photosphere, based on its apparent motion in the image plane recorded over several days of observation. At various times one-dimensional scans at multiple frequencies spanning the 5.98 - 15.95 GHz frequency range from the RATAN-600 instrument are used. The gyroresonance emission mechanism, which is sensitive to the coronal magnetic field strength, is applied to convert the radio source estimated heights at various frequencies, h(f), to information as regards magnetic field vs. height, B(h). Diagrams of longitude - height of some polarized radio sources revealed multiple reversals, suggestive of a spiral magnetic structure. In all cases, the magnetic field strength maintains high values (800 - 1000 G) at the highest altitudes analysed, which reflects a relatively weak divergence in the field of magnetic flux tubes (in the height range 8 - 14 Mm) responsible for the main part of the radio emission of active regions.

  9. Synthesis of highly magnetic iron nanoparticles suitable for field structuring using a β-diketone surfactant

    Science.gov (United States)

    Huber, Dale L.; Venturini, Eugene L.; Martin, James E.; Provencio, Paula P.; Patel, Rina J.

    2004-07-01

    We describe the synthesis of highly magnetic iron nanoparticles using a novel surfactant, a β-diketone. We have produced 6 nm iron nanoparticles with an unusually high saturation magnetization of more than 80% the value of bulk iron. Additionally, we measured a particle susceptibility of 14 (MKS units), which is far above the value possible for micron-scale spherical particles. These properties will allow for formation of composites that can be highly structured by magnetic fields.

  10. Synthesis of highly magnetic iron nanoparticles suitable for field structuring using a {beta}-diketone surfactant

    Energy Technology Data Exchange (ETDEWEB)

    Huber, D.L. E-mail: dlhuber@sandia.gov; Venturini, E.L.; Martin, J.E.; Provencio, P.P.; Patel, R.J

    2004-07-01

    We describe the synthesis of highly magnetic iron nanoparticles using a novel surfactant, a {beta}-diketone. We have produced 6 nm iron nanoparticles with an unusually high saturation magnetization of more than 80% the value of bulk iron. Additionally, we measured a particle susceptibility of 14 (MKS units), which is far above the value possible for micron-scale spherical particles. These properties will allow for formation of composites that can be highly structured by magnetic fields.

  11. On the 3D Structure of the Magnetic Field in Regions of Emerging Flux

    CERN Document Server

    Ramos, A Asensio

    2010-01-01

    We explore the photospheric and chromospheric magnetic field in an emerging flux region. An image of the equivalent width of the He I 10830 A red blended component shows the presence of filamentary structures that might be interpreted as magnetic loops. We point out that the magnetic field strength in the chromosphere resembles a smoothed version of that found in the photosphere and that it is not correlated at all with the above-mentioned equivalent width map. Lacking other diagnostics, this suggests that one cannot discard the possibility that the chromospheric field we infer from the observations is tracing the lower chromosphere of the active region instead of tracing the magnetic field along loops. If the He I line is formed within magnetic loops, we point out a potential problem that appears when interpreting observations using only one component along the line-of-sight.

  12. Modeling the structure of magnetic fields in Neutron Stars: from the interior to the magnetosphere

    CERN Document Server

    Bucciantini, N; Del Zanna, L

    2015-01-01

    The phenomenology of the emission of pulsars and magnetars depends dramatically on the structure and properties of their magnetic field. In particular it is believed that the outbursting and flaring activity observed in AXPs and SRGs is strongly related to their internal magnetic field. Recent observations have moreover shown that charges are present in their magnetospheres supporting the idea that their magnetic field is tightly twisted in the vicinity of the star. In principle these objects offer a unique opportunity to investigate physics in a regime beyond what can be obtained in the laboratory. We will discuss the properties of equilibrium models of magnetized neutron stars, and we will show how internal and external currents can be related. These magnetic field configurations will be discussed considering also their stability, relevant for their origin and possibly connected to events like SNe and GRBs. We will also show what kind of deformations they induce in the star, that could lead to emission of g...

  13. Research on optical fiber magnetic field sensors based on multi-mode fiber and spherical structure

    Science.gov (United States)

    Wang, Yan; Tong, Zheng-rong; Zhang, Wei-hua; Luan, Pan-pan; Zhao, Yue; Xue, Li-fang

    2017-01-01

    A magnetic field sensor with a magnetic fluid (MF)-coated intermodal interferometer is proposed and experimentally demonstrated. The interferometer is formed by sandwiching a segment of single mode fiber (SMF) between a segment of multi-mode fiber (MMF) and a spherical structure. It can be considered as a cascade of the traditional SMF-MMF-SMF structure and MMF-SMF-sphere structure. The transmission spectral characteristics change with the variation of applied magnetic field. The experimental results exhibit that the magnetic field sensitivities for wavelength and transmission loss are 0.047 nm/mT and 0.215 dB/mT for the interference dip around 1 535.36 nm. For the interference dip around 1548.41nm, the sensitivities are 0.077 nm/mT and 0.243 dB/mT. Simultaneous measurement can be realized according to the different spectral responses.

  14. He I vector magnetic field maps of a sunspot and its superpenumbral fine-structure

    CERN Document Server

    Schad, T A; Lin, H; Tritschler, A

    2015-01-01

    Advanced inversions of high-resolution spectropolarimetric observations of the He I triplet at 1083 nm are used to generate unique maps of the chromospheric magnetic field vector across a sunspot and its superpenumbral canopy. The observations were acquired by the Facility Infrared Spectropolarimeter (FIRS) at the Dunn Solar Telescope (DST) on 29 January 2012. Multiple atmospheric models are employed in the inversions, as superpenumbral Stokes profiles are dominated by atomic-level polarization while sunspot profiles are Zeeman-dominated but also exhibit signatures perhaps induced by symmetry breaking effects of the radiation field incident on the chromospheric material. We derive the equilibrium magnetic structure of a sunspot in the chromosphere, and further show that the superpenumbral magnetic field does not appear finely structured, unlike the observed intensity structure. This suggests fibrils are not concentrations of magnetic flux but rather distinguished by individualized thermalization. We also dire...

  15. Evolution of the magnetic field structure outside the magnetopause under radial IMF conditions

    Science.gov (United States)

    Pi, Gilbert; Shue, Jih-Hong; Grygorov, Kostiantyn; Li, Hsien-Ming; Němeček, Zdeněk.; Å afránková, Jana; Yang, Ya-Hui; Wang, Kaiti

    2017-04-01

    We use the Time History of Events and Macroscale Interactions during Substorms data to investigate the magnetic field structure just outside the magnetopause and its time evolution for radial interplanetary magnetic field (IMF) events. When the magnetic field drapes around the magnetopause in the magnetosheath region, an asymmetric magnetic field orientation in different hemispheres is expected. Our two-case study reveals some conflicts with the predicted draped field configuration in the Southern Hemisphere. The magnetosheath Bz component had a different sign depending on the upstream IMF Bx component's polarity at the beginning of the radial IMF intervals. With time, the observed Bz became northward in both cases with increasing positive values through the events. The increasing value of the Bz component may be explained by two possible mechanisms: by a change of the upstream IMF and by a reconnection between magnetosheath and magnetospheric field lines. Our study shows that both mechanisms contributed to the observed changes. Thus, there was a correlation between the change of the upstream IMF conditions and an increase in the magnetosheath northward magnetic field component. The observed formation of the boundary layer near the magnetopause proves that the reconnection process was ongoing at least for a part of the time. We suggest two possible reconnection scenarios: one near subsolar point and another tailward of the one cusp due to lobe reconnection. The asymmetry of reconnection locations causes rearrangement of the magnetic field structure near the magnetopause and turns the observed magnetosheath Bz component even further into positive values.

  16. Seismology of the Sun : Inference of Thermal, Dynamic and Magnetic Field Structures of the Interior

    CERN Document Server

    Hiremath, K M

    2012-01-01

    Recent overwhelming evidences show that the sun strongly influences the Earth's climate and environment. Moreover existence of life on this Earth mainly depends upon the sun's energy. Hence, understanding of physics of the sun, especially the thermal, dynamic and magnetic field structures of its interior, is very important. Recently, from the ground and space based observations, it is discovered that sun oscillates near 5 min periodicity in millions of modes. This discovery heralded a new era in solar physics and a separate branch called helioseismology or seismology of the sun has started. Before the advent of helioseismology, sun's thermal structure of the interior was understood from the evolutionary solution of stellar structure equations that mimicked the present age, mass and radius of the sun. Whereas solution of MHD equations yielded internal dynamics and magnetic field structure of the sun's interior. In this presentation, I review the thermal, dynamic and magnetic field structures of the sun's inter...

  17. Structural control of Fe-based alloys through diffusional solid/solid phase transformations in a high magnetic field.

    Science.gov (United States)

    Ohtsuka, Hideyuki

    2008-01-01

    A magnetic field has a remarkable influence on solid/solid phase transformations and it can be used to control the structure and function of materials during phase transformations. The effects of magnetic fields on diffusional solid/solid phase transformations, mainly from austenite to ferrite, in Fe-based alloys are reviewed. The effects of magnetic fields on the transformation temperature and phase diagram are explained thermodynamically, and the transformation behavior and transformed structures in magnetic fields are discussed.

  18. Resolved Magnetic-Field Structure and Variability Near the Event Horizon of Sagittarius A*

    CERN Document Server

    Johnson, Michael D; Doeleman, Sheperd S; Marrone, Daniel P; Plambeck, Richard L; Wardle, John F C; Akiyama, Kazunori; Asada, Keiichi; Beaudoin, Christopher; Blackburn, Lindy; Blundell, Ray; Bower, Geoffrey C; Brinkerink, Christiaan; Broderick, Avery E; Cappallo, Roger; Chael, Andrew A; Crew, Geoffrey B; Dexter, Jason; Dexter, Matt; Freund, Robert; Friberg, Per; Gold, Roman; Gurwell, Mark A; Ho, Paul T P; Honma, Mareki; Inoue, Makoto; Kosowsky, Michael; Krichbaum, Thomas P; Lamb, James; Loeb, Abraham; Lu, Ru-Sen; MacMahon, David; McKinney, Jonathan C; Moran, James M; Narayan, Ramesh; Primiani, Rurik A; Psaltis, Dimitrios; Rogers, Alan E E; Rosenfeld, Katherine; SooHoo, Jason; Tilanus, Remo P J; Titus, Michael; Vertatschitsch, Laura; Weintroub, Jonathan; Wright, Melvyn; Young, Ken H; Zensus, J Anton; Ziurys, Lucy M

    2015-01-01

    Near a black hole, differential rotation of a magnetized accretion disk is thought to produce an instability that amplifies weak magnetic fields, driving accretion and outflow. These magnetic fields would naturally give rise to the observed synchrotron emission in galaxy cores and to the formation of relativistic jets, but no observations to date have been able to resolve the expected horizon-scale magnetic-field structure. We report interferometric observations at 1.3-millimeter wavelength that spatially resolve the linearly polarized emission from the Galactic Center supermassive black hole, Sagittarius A*. We have found evidence for partially ordered fields near the event horizon, on scales of ~6 Schwarzschild radii, and we have detected and localized the intra-hour variability associated with these fields.

  19. Fine structure in a strong magnetic field: Paschen-Back effect reconsidered in Rydberg atoms

    Science.gov (United States)

    Liu, Wenyu; Gu, Sihong; Li, Baiwen

    1996-05-01

    Using a kind of potential model wave function for alkali metal atoms, we nonperturbatively study the effect of fine structure on the Rydberg spectra of Cs atom in a strong magnetic field. Our numerical results reveal spectral structure dramatically different from the well-established Paschen-Back effect, and we argue that the fine structure of the Rydberg Cs atom cannot be neglected even in a magnetic field as strong as several teslas. We also give an error estimate of our results and a word on possible experimental verification.

  20. Magnetic field structure in a high-mass outflow/disk system

    CERN Document Server

    Beuther, H; Rao, R; van der Tak, F F S

    2010-01-01

    To characterize the magnetic field structure of the outflow and core region within a prototypical high-mass star-forming region, we analyzed polarized CO(3-2) - for the first time observed with the Submillimeter Array -- as well as 880mum submm continuum emission from the high-mass outflow/disk system IRAS18089-1732. Both emission features with polarization degrees at a few percent level indicate that the magnetic field structure is largely aligned with the outflow/jet orientation from the small core scales to the larger outflow scales. Although quantitative estimates are crude, the analysis indicates that turbulent energy dominates over magnetic energy. The data also suggest a magnetic field strength increase from the lower-density envelope to the higher-density core.

  1. An interplanetary magnetic field enhancement observed by five spacecraft: Deducing the magnetic structure, size and mass

    Science.gov (United States)

    Lai, H.; Russell, C. T.; Delzanno, G.; Angelopoulos, V.

    2012-12-01

    Interplanetary Field Enhancements (IFEs) were discovered almost 30 years ago in the PVO magnetic-field records and attributed to the interaction between solar wind and dust particles from comets or asteroids, but the physics of this interaction remained obscure. Our current understanding is that IFEs result from collisions of small interplanetary bodies that produce electrically charged nanometer-scale dust particles possibly enhanced by tribo-electric charging in the collision. These charged dust particles in turn interact with the magnetized solar wind. Momentum is transferred from the solar wind to the dust cloud via the collective effect of the formation of a magnetic barrier. This momentum transfer accelerates the particles to near the solar wind speed and moves the dust outward through the solar gravitational potential well. Multi-spacecraft observations can help us to determine the speed of the IFE and the orientation of the current sheet. They enable us to reconstruct the pressure profile of an IFE in three dimensions and estimate the mass contained in the IFE. We have done these reconstructions with an IFE observed on March 3, 2011 with Wind, ACE, ARTEMIS P1 and P2 and Geotail. We find that the magnetic field near the center of the IFE is highly twisted indicating a complicated magnetic topology as expected in a plasma-charged dust interaction. The magnetic field and plasma properties during this event distinguish it from a typical flux rope. Based on the statistical results obtained at 1 AU and the assumption that all the IFEs are self-similar, we find that this IFE has a radial scale length several times longer than the cross flow radius and contains a mass of about 108 kg. The rates of collisions expected for objects of this size are consistent with the observed rates of these disturbances.

  2. Quiet Sun Magnetic Field Measurements Based on Lines with Hyperfine Structure

    CERN Document Server

    Almeida, J Sanchez; Degl'Innocenti, E Landi; Berrilli, F

    2007-01-01

    The Zeeman pattern of MnI lines is sensitive to hyperfine structure (HFS) and, they respond to hG magnetic field strengths differently from the lines used in solar magnetometry. This peculiarity has been employed to measure magnetic field strengths in quiet Sun regions. However, the methods applied so far assume the magnetic field to be constant in the resolution element. The assumption is clearly insufficient to describe the complex quiet Sun magnetic fields, biasing the results of the measurements. We present the first syntheses of MnI lines in realistic quiet Sun model atmospheres. The syntheses show how the MnI lines weaken with increasing field strength. In particular, kG magnetic concentrations produce NnI 5538 circular polarization signals (Stokes V) which can be up to two orders of magnitude smaller than the weak magnetic field approximation prediction. Consequently, (1) the polarization emerging from an atmosphere having weak and strong fields is biased towards the weak fields, and (2) HFS features c...

  3. Determination of the structure of active region magnetic fields in the singular point problem

    Science.gov (United States)

    Kulikova, G. N.; Molodenskij, M. M.; Filippov, B. P.

    1990-02-01

    The solution to the inverse problem of active region magnetic field structure using fibril orientation is examined, focusing on the case where the field of the direction of the vector tau has singular points. In this case, the integrating factor for the field line equation in the z = 0 plane cannot be solved using the method of Kulikova et al. (1989). However, model representations of the field produce a solution which is accurate up to a factor common to the total distribution of the case. Nodes, foci, and saddle points are observed in the chromosphere. It is suggested that these singular points play an important role in constructing the large-scale structure of the magnetic field. Also, it is shown that the small-scale field is associated with surface currents. Good agreement is found between calculations and measurements of the longitudinal field on the photosphere of the active region HR 16862-16864.

  4. Pulsar rotation measures and the large-scale structure of Galactic magnetic field

    CERN Document Server

    Han, J L; Manchester, R N; Qiao, G J; Van Straten, W

    2006-01-01

    The large-scale magnetic field of our Galaxy can be probed in three dimensions using Faraday rotation of pulsar signals. We report on the determination of 223 rotation measures from polarization observations of relatively distant southern pulsars made using the Parkes radio telescope. Combined with previously published observations these data give clear evidence for large-scale counterclockwise fields (viewed from the north Galactic pole) in the spiral arms interior to the Sun and weaker evidence for a counterclockwise field in the Perseus arm. However, in interarm regions, including the Solar neighbourhood, we present evidence that suggests that large-scale fields are clockwise. We propose that the large-scale Galactic magnetic field has a bisymmetric structure with reversals on the boundaries of the spiral arms. Streaming motions associated with spiral density waves can directly generate such a structure from an initial inwardly directed radial field. Large-scale fields increase toward the Galactic Center, ...

  5. Planck intermediate results XXXIV. The magnetic field structure in the Rosette Nebula

    DEFF Research Database (Denmark)

    Aghanim, N.; Alves, M. I. R.; Arnaud, M.

    2016-01-01

    of ionized gas and the formation of a shell of swept-up ISM. From the RM data we estimate a mean value of the line-of-sight component of the magnetic field of about 3 mu G (towards the observer) in the Rosette Nebula, for a uniform electron density of about 12 cm(-3). The dust shell that surrounds......, the Rosette Nebula in the Monoceros molecular cloud, to study its magnetic field structure and the impact of an expanding H II region on the morphology of the field. We derive an analytical solution for the magnetic field, assumed to evolve from an initially uniform configuration following the expansion...... molecular cloud to be mostly aligned with the large-scale field along the Galactic plane. The Planck data are compared with the analytical model, which predicts the mean polarization properties of a spherical and uniform dust shell for a given orientation of the field. This comparison leads to an upper...

  6. Properties of the "island" structures of the background magnetic field in the 20th solar cycle.

    Science.gov (United States)

    Golub, P. A.

    It is shown that the "island" structure of the background magnetic field and sunspot groups has a common zone of localization and a common law of latitude drift with the phase of the 20th solar cycle. An important role of the "island" structure is noted in the formation of the 11 year solar cycle.

  7. Effect of pulse magnetic field on solidification structure and properties of pure copper

    Institute of Scientific and Technical Information of China (English)

    LIAO Xi-liang; GONG Yong-yong; LI Ren-xing; CHEN Wen-jie; ZHAI Qi-jie

    2007-01-01

    The application of pulse magnetic field to metal solidification is an advanced technique which can remarkably refine solidification structure. In this paper, the effect of pulse magnetic field on solidification structure,mechanical properties and conductivity of pure copper was experimentally investigated. The results showed that the solidification structure transformed from coarse columnar crystal to fine globular crystal with increasing pulse voltage.Increasing pulse voltage also improved the tensile strength. However, with the increase of pulse voltage, the elongation and electrical resistivity firstly decreased, then increased when the pulse voltage beyond a critical value. Moreover,in some conditions, pulse magnetic field can simultaneously improve the conductivity and mechanical property of pure copper.

  8. Effect of long-range structural corrugations on magnetotransport properties of phosphorene in tilted magnetic field

    Science.gov (United States)

    Mogulkoc, A.; Modarresi, M.; Rudenko, A. N.

    2017-08-01

    Rippling is an inherent quality of two-dimensional materials playing an important role in determining their properties. Here, we study the effect of structural corrugations on the electronic and transport properties of monolayer black phosphorus (phosphorene) in the presence of tilted magnetic field. We follow a perturbative approach to obtain analytical corrections to the spectrum of Landau levels induced by a long-wavelength corrugation potential. We show that surface corrugations have a non-negligible effect on the electronic spectrum of phosphorene in tilted magnetic field. Particularly, the Landau levels are shown to exhibit deviations from the linear field dependence. The observed effect become especially pronounced at large tilt angles and corrugation amplitudes. Magnetotransport properties are further examined in the low temperature regime taking into account impurity scattering. We calculate magnetic field dependence of the longitudinal and Hall resistivities and find that the nonlinear effects reflecting the corrugation might be observed even in moderate fields (B <10 T).

  9. Energy of coronal mass ejections and large-scale structure of solar magnetic fields

    Science.gov (United States)

    Ivanov, E. V.

    2016-12-01

    The relationship between variations of the energy and linear velocity of coronal mass ejections (CME) and the typical dimensions of structural elements of the large-scale solar magnetic field structure (LSMFS) is investigated for the period of 1996-2014. It is shown that the maximum linear velocity and maximum energy of CME correspond to the values of the effective solar multipole index n 4.0-4.4. These values determine the maximum size of the complexes of active regions, which, together with the observed maximum values of magnetic field intensity in the complexes, limit the possible maximum CME energy.

  10. Magnetic field enhanced structural instability in EuTiO3

    Science.gov (United States)

    Guguchia, Zurab; Keller, Hugo; Köhler, Jürgen; Bussmann-Holder, Annette

    2013-03-01

    EuTiO3 undergoes a structural phase transition from cubic to tetragonal at TS = 282 K which is not accompanied by any long range magnetic order. However, it is related to the oxygen ocathedra rotation driven by a zone boundary acoustic mode softening. Here we show that this displacive second order structural phase transition can be shifted to higher temperatures by the application of an external magnetic field (ΔTS ~= 4 K for μ0 H = 9 T). This observed field dependence is in agreement with theoretical predictions based on a coupled spin-anharmonic-phonon interaction model.

  11. Magnetic field enhanced structural instability in EuTiO_{3}

    OpenAIRE

    Guguchia, Z.; Keller, H.; Kohler, J; Bussmann-Holder, A.

    2012-01-01

    EuTiO_{3} undergoes a structural phase transition from cubic to tetragonal at T_S = 282 K which is not accompanied by any long range magnetic order. However, it is related to the oxygen ocathedra rotation driven by a zone boundary acoustic mode softening. Here we show that this displacive second order structural phase transition can be shifted to higher temperatures by the application of an external magnetic field (increased by 4 K for mu_{0}H = 9 T). This observed field dependence is in agre...

  12. Multifractal structure of the large-scale heliospheric magnetic field strength fluctuations near 85AU

    Directory of Open Access Journals (Sweden)

    L. F. Burlaga

    2004-01-01

    Full Text Available During 2002, the Voyager 1 spacecraft was in the heliosphere between 83.4 and 85.9AU (1AU is the mean distance from the Sun to Earth at 34° N heliographic latitude. The magnetic field strength profile observed in this region had a multifractal structure in the range of scales from 2 to 16 days. The multifractal spectrum observed near 85AU is similar to that observed near 40AU, indicating relatively little evolution of the multifractal structure of the magnetic field with increasing distance in the distant heliosphere in the epoch near solar maximum.

  13. Magnetization of Steel Building Materials and Structures in the Natural Geomagnetic Field

    Directory of Open Access Journals (Sweden)

    E. Čermáková

    2005-01-01

    Full Text Available This paper presents the physical basis of the magnetic properties of ferromagnetic materials and shows their relationships with external geomagnetic field. It graphically processes the experimental data detected by an HMR magnetometer. Taking into account the natural geomagnetic field under the effects of steel U profiles, variations of the natural geomagnetic field in a steel structure building are indicated and the potential existence of Sick Building Syndrome (SBS in these types of buildings is pointed out. 

  14. On the relationship between sunspot structure and magnetic field changes associated with solar flares

    CERN Document Server

    Song, Yongliang

    2016-01-01

    Many previous studies have shown that magnetic fields as well as sunspot structures present rapid and irreversible changes associated with solar flares. In this paper we first use five X-class flares observed by SDO/HMI to show that not only the magnetic fields and sunspot structures do show rapid, irreversible changes but also these changes are closely related, both spatially and temporally. The magnitudes of the correlation coefficients between the temporal variations of horizontal magnetic field and sunspot intensity are all larger than 0.90, with a maximum value of 0.99 and an average value of 0.96. Then using four active regions in quiescent times, three observed and one simulated, we show that in sunspot penumbra regions there also exists a close correlation between sunspot intensity and horizontal magnetic field strength, in addition to the well-known one between sunspot intensity and normal magnetic field strength. Connecting these two observational phenomena, we show that the sunspot structure change...

  15. IBEX views the global structure of the heliosphere influenced by the Interstellar Magnetic Field

    Science.gov (United States)

    Schwadron, Nathan

    The IBEX ribbon has been separated from the surrounding globally distributed flux (GDF), revealing ENA emission largely from the inner heliosheath. The line-of-sight (LOS) integrated pressure in the GDF is quite large, requiring that the interstellar magnetic field be sufficiently strong (e.g. 3 microG) to balance the pressure of the inner heliosheath. The LOS emissions from the GDF have revealed signatures of the nose of the heliosphere, and the heliotail, which has been examined carefully. The strong interstellar magnetic field has broad implications for the structure of the heliosphere and the existence or lack of a bow shock. These global heliospheric structures also filter primary interstellar neutral atoms and lead to creation of secondary atoms through charge-exchange in the outer heliosheath. IBEX observations of H atoms from the Local Interstellar Medium reveal remarkable signatures of both filtration and the secondary component likely reflecting influences of the interstellar magnetic field on the outer heliosheath. New determinations of the LISM velocity from neutral atom measurments and the LISM magnetic field direction from the IBEX ribbon are shown to be consistent with the interstellar modulation of TeV cosmic rays revealed in global anisotropy maps of Milagro, Asgamma and IceCube. Thus, IBEX observations reveal a new picture of heliospheric structures and interactions that are strongly influenced by the interstellar magnetic field.

  16. Nuclear structure in strong magnetic fields: nuclei in the crust of a magnetar

    CERN Document Server

    Arteaga, Daniel Pena; Khan, Elias; Ring, Peter

    2011-01-01

    Covariant density functional theory is used to study the effect of strong magnetic fields, up to the limit predicted for neutron stars (for magnetars $B \\approx10^{18}$G), on nuclear structure. All new terms in the equation of motion resulting from time reversal symmetry breaking by the magnetic field and the induced currents, as well as axial deformation, are taken into account in a self-consistent fashion. For nuclei in the iron region of the nuclear chart it is found that fields in the order of magnitude of $10^{17}$G significantly affect bulk properties like masses and radii.

  17. Effect of structural steel ion plasma nitriding on material durability in pulsed high magnetic fields

    Science.gov (United States)

    Spirin, A. V.; Krutikov, V. I.; Koleukh, D. S.; Mamaev, A. S.; Paranin, S. N.; Gavrilov, N. V.; Kaigorodov, A. S.

    2017-05-01

    The work was aimed to study the influence of plasma nitriding on electrical and mechanical properties of structural steels and their durability in pulsed high magnetic field. The plates and cylindrical magnetic flux concentrators were made of several steel grades (30KhGS, 40Kh, 50KhGA, 38Kh2MYuA, and U8A), heat-treated, and subjected to the low-temperature (400, 500°C) plasma nitriding. Electrical and mechanical properties of materials, phase composition of steel surface layer, microstructure and microhardness profiles were investigated on the plates before and after plasma treatment. Microstructure and microhardness profiles across the subsurface layer of plasma treated and untreated concentrators applied for high magnetic field generation were also studied. Magnetic field of 50 T under tens of microseconds in duration inside the flux concentrators was generated by long-life outer coil.

  18. Origin and Evolution of Magnetic Field in PMS Stars: Influence of Rotation and Structural Changes

    Science.gov (United States)

    Emeriau-Viard, Constance; Brun, Allan Sacha

    2017-09-01

    During stellar evolution, especially in the pre-main-sequence phase, stellar structure and rotation evolve significantly, causing major changes in the dynamics and global flows of the star. We wish to assess the consequences of these changes on stellar dynamo, internal magnetic field topology, and activity level. To do so, we have performed a series of 3D HD and MHD simulations with the ASH code. We choose five different models characterized by the radius of their radiative zone following an evolutionary track computed by a 1D stellar evolution code. These models characterized stellar evolution from 1 to 50 Myr. By introducing a seed magnetic field in the fully convective model and spreading its evolved state through all four remaining cases, we observe systematic variations in the dynamical properties and magnetic field amplitude and topology of the models. The five MHD simulations develop a strong dynamo field that can reach an equipartition state between the kinetic and magnetic energies and even superequipartition levels in the faster-rotating cases. We find that the magnetic field amplitude increases as it evolves toward the zero-age main sequence. Moreover, the magnetic field topology becomes more complex, with a decreasing axisymmetric component and a nonaxisymmetric one becoming predominant. The dipolar components decrease as the rotation rate and the size of the radiative core increase. The magnetic fields possess a mixed poloidal-toroidal topology with no obvious dominant component. Moreover, the relaxation of the vestige dynamo magnetic field within the radiative core is found to satisfy MHD stability criteria. Hence, it does not experience a global reconfiguration but slowly relaxes by retaining its mixed stable poloidal-toroidal topology.

  19. Magnetic field structure and torque in accretion discs around millisecond pulsars

    CERN Document Server

    Naso, L; Miller, J C

    2013-01-01

    Millisecond pulsars are rather weakly-magnetized neutron stars which are thought to have been spun up by disc accretion, with magnetic linkage between the star and the disc playing a key role. Their spin history depends sensitively on details of the magnetic field structure, but idealized models from the 1980s and 1990s are still commonly used for calculating the magnetic field components. This paper is the third in a series presenting results from a step-by-step analysis which we are making of the problem, starting with very simple models and then progressively including additional features one at a time, with the aim of gaining new insights into the mechanisms involved. In our first two papers, the magnetic field structure in the disc was calculated for a standard Shakura and Sunyaev model, by solving the magnetic induction equation numerically in the stationary limit within the kinematic approximation; here we consider a more general velocity field in the disc, including backflow. We find that the profiles...

  20. Quantum transport through a multilevel magnetic structure with multiple inelastic scattering in a magnetic field taken into account

    Science.gov (United States)

    Val'kov, V. V.; Aksenov, S. V.; Ulanov, E. A.

    2015-02-01

    We present a solution for the problem of quantum electron transport through a magnetic atom adsorbed inside a break junction with paramagnetic metal electrodes. In agreement with experimental data, it was assumed that the conduction electrons experience inelastic scattering by the adsorbate due to s-d(f)-exchange interaction. The Keldysh technique was employed to obtain a general expression describing a current through the multilevel structure at finite temperatures in terms of the nonequilibrium Green's function. The use of the atomic representation allowed to exactly account for the non-equidistant structure of the energy spectrum of a magnetic atom and to simplify substantially the application of the Wick theorem for construction of the nonequilibrium diagrammatic technique for the Hubbard operators. The calculation of the current-voltage characteristics of the magnetic adatom in the tunnel regime at low temperatures revealed the presence of regions with a negative differential conductance in a magnetic field.

  1. Magnetic field effect on nuclear shell structure and implications to physics of neutron stars

    Energy Technology Data Exchange (ETDEWEB)

    Kondratyev, V.N.; Maruyama, Toshiki; Chiba, Satoshi [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    1999-12-01

    The effect of the magnetic field on the shell structure of nuclei is considered by employing the shell-correction method. The shift of a phase in shell-oscillations is shown to represent the main feature of the field effect. Such a phase-change is originating from the Pauli-magnetic response associated with the relative shift of spin-up and spin-down energy levels. The neutron shell-correction energy behaves almost periodically as a function of the field strength with a slightly enhanced amplitude of the shell-oscillations at a large field. The period of the sign change is determined by the energy difference between neighbour levels. The proton shell-correction energy displays an anomalous dependence on the field. The proton orbital magnetism enhances the nuclear shell effect especially when the field influence is comparable to the spin-orbit coupling. The nuclear magic numbers are demonstrated to depend considerably on the magnetic field on the strength scale B {approx} 10{sup 16} - 10{sup 17} G relevant for neutron stars and supernovas. Such a field is found to shift significantly nuclear magics of the iron region towards smaller mass numbers. (author)

  2. Hyperfine structure of the hydroxyl free radical (OH) in electric and magnetic fields

    Science.gov (United States)

    Maeda, Kenji; Wall, Michael L.; Carr, Lincoln D.

    2015-05-01

    We investigate single-particle energy spectra of the hydroxyl free radical (OH) in the lowest electronic and rovibrational level under combined static electric and magnetic fields, as an example of heteronuclear polar diatomic molecules. In addition to the fine-structure interactions, the hyperfine interactions and centrifugal distortion effects are taken into account to yield the zero-field spectrum of the lowest 2Π3 / 2 manifold to an accuracy of less than 2kHz. We also examine level crossings and repulsions in the hyperfine structure induced by applied electric and magnetic fields. Compared to previous work, we found more than 10 percent reduction of the magnetic fields at level repulsions in the Zeeman spectrum subjected to a perpendicular electric field. In addition, we find new level repulsions, which we call Stark-induced hyperfine level repulsions, that require both an electric field and hyperfine structure. It is important to take into account hyperfine structure when we investigate physics of OH molecules at micro-Kelvin temperatures and below. This research was supported in part by AFOSR Grant No.FA9550-11-1-0224 and by the NSF under Grants PHY-1207881 and NSF PHY-1125915. We appreciate the Aspen Center for Physics, supported in part by the NSF Grant No.1066293, for hospitality.

  3. Spatial structure of the modified Coulomb potential in a superstrong magnetic field

    CERN Document Server

    Glazyrin, S I

    2016-01-01

    The modification of the Coulomb potential due to the enhancement of loop corrections in a superstrong magnetic field is studied numerically. We calculate the modified potential with high precision and obtain the pattern of equipotential lines. The results confirm the general features known from previous studies, however we emphasize some differences in potential structure that can be important for problems with spatially distributed charges.

  4. Magnetic structure and electric field effects in multiferroic YMn2O5

    Science.gov (United States)

    de Souza, R. A.; Staub, U.; Scagnoli, V.; Garganourakis, M.; Bodenthin, Y.; Huang, S.-W.; García-Fernández, M.; Ji, S.; Lee, S.-H.; Park, S.; Cheong, S.-W.

    2011-09-01

    The magnetic structure of multiferroic RMn2O5 (R = Y, Er) has been investigated by means of resonant soft x-ray diffraction. Energy, temperature, and azimuthal angle scans were performed in addition to reciprocal space maps on the magnetic reflection in the different magnetic phases of YMn2O5. We also investigated the orbital magnetic moment at the oxygen K-edge for RMn2O5 with both, R = Y and R = Er compositions. These moments reflect the strong hybridization between Mn 3d and oxygen 2p states. Experiments with applied electric fields are additionally presented, showing that the helical component of the magnetic structure in the CM phase of YMn2O5 can be reversed by the application of an electric field. However, the incommensurate magnetic reflection in the high-temperature phase is unaffected. Interestingly, this is observed only in the presence of a small electrical current, indicative of a current-induced/-enhanced switching of magnetic domains.

  5. Structure of Mercury's Global Magnetic Field Determined from MESSENGER Orbital Observations

    Science.gov (United States)

    Anderson, B. J.; Johnson, C. L.; Korth, H.; Purucker, M. E.; Winslow, R. M.; Slavin, J. A.; Solomon, S. C.; McNutt, R. L.; Raines, J. M.; Zurbuchen, T.

    2011-12-01

    tail current systems, and detrending magnetic field data to study higher-order structure in the internal and external field. An overview is also presented of results for signatures of the cusps, plasma sheet, field-aligned currents, and higher-order planetary field signatures.

  6. Competition between magnetic field dependent band structure and coherent backscattering in multiwall carbon nanotubes

    Science.gov (United States)

    Stojetz, B.; Roche, S.; Miko, C.; Triozon, F.; Forró, L.; Strunk, C.

    2007-03-01

    Magnetotransport measurements in large diameter multiwall carbon nanotubes (20 40 nm) demonstrate the competition of a magnetic-field dependent bandstructure and Altshuler Aronov Spivak oscillations. By means of an efficient capacitive coupling to a backgate electrode, the magnetoconductance oscillations are explored as a function of Fermi level shift. Changing the magnetic field orientation with respect to the tube axis and by ensemble averaging, allows the contributions of different Aharonov Bohm phases to be identified. The results are in qualitative agreement with numerical calculations of the band structure and the conductance.

  7. Evolution of the Interplanetary Magnetic Field sector structure during the last 15 solar cycles

    Science.gov (United States)

    Vokhmyanin, Mikhail

    We have inferred for the first time Interplanetary Magnetic Field (IMF) polarities from ground-based geomagnetic observations back to 1844. Reconstructions are reliable enough to study sector structure of the IMF in the past. The inferred daily polarities demonstrate solar-cycle changes during the nineteenth and twentieth centuries. We have analyzed statistics of the sector boundaries and found recurrences that reflect evolution of the solar wind sources. Additionally, seasonal variations of the ratio of positive and negative sectors provide evidence of solar magnetic field reversals during the last 15 solar cycles.

  8. Magnetic field structure in single late-type giants: The effectively single giant V390 Aur

    CERN Document Server

    Konstantinova-Antova, R; Petit, P; Charbonnel, C; Tsvetkova, S; Lebre, A; Bogdanovski, R

    2012-01-01

    We have studied the active giant V390 Aur using spectropolarimetry to obtain direct and simultaneous measurements of the magnetic field and the activity indicators in order to get a precise insight of its activity. We used the spectropolarimeter NARVAL at the Bernard Lyot Telescope (Observatoire du Pic du Midi, France) to obtain a series of Stokes I and Stokes V profiles. The Least Square deconvolution (LSD) technique was applied to detect the Zeeman signature of the magnetic field in each of our 13 observations and to measure its longitudinal component. We could also monitor the CaII K & H and IR triplet, as well as the H_alpha lines which are activity indicators. In order to reconstruct the magnetic field geometry of V390 Aur, we applied the Zeeman Doppler Imaging (ZDI) inversion method and present a map for the magnetic field. Based on the obtained spectra, we also refined the fundamental parameters of the star and the Li abundance. The ZDI revealed a structure in the radial magnetic field consisting o...

  9. Structurization of ferrofluids in the absence of an external magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Zubarev, A. Yu., E-mail: Andrey.Zubarev@usu.ru; Iskakova, L. Yu. [Ural Federal University (Russian Federation)

    2013-02-15

    Structural transformations in a model ferrofluid in the absence of an external magnetic field have been theoretically studied. The results agree with well-known laboratory experiments and computer simulations in showing that, if the concentration of particles and their magnetic interaction energy are below certain critical values, most particles form separate linear chains. If these parameters exceed the critical values, most particles concentrate so as to form branched network structures. The passage from chains to network has a continuous character rather than represents a discontinuous first-order phase transition.

  10. Magnetic Field Calculator

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Magnetic Field Calculator will calculate the total magnetic field, including components (declination, inclination, horizontal intensity, northerly intensity,...

  11. Observational Evidences for Multi-component Magnetic Field Structure in Solar Flares

    Indian Academy of Sciences (India)

    V. G. Lozitsky; J. Staude

    2008-09-01

    Two solar flares of 25 July 1981 and 5 November 2004 of importance 2 and M4.1/1B, respectively, were investigated using observational data obtained with the Echelle spectrograph of the Kyiv University Astronomical Observatory. Stokes and profiles of the FeI lines 5233, 5247.1, 5250.2, 5250.6, 5576.1 and of CrI 5247.6 Å have been analyzed. We found several evidences for the existence of spatially unresolved magnetic field structures with kG strengths. In particular, the values of the measured average longitudinal field ∥ depend on the Lande factors of the lines: in general, ∥ increases with increasing factor . Analogously, the observed line ratio ∥ (5250.2)/∥(5247.1) is increasing with increasing distance from the line center. The observed Stokes profiles show some deviations from that of an assumed homogeneous field, presented by the Stokes gradient, /. A comparison with the non-split line FeI 5576.1 Å shows that some of these deviations are real and indicate the presence of subtelescopic magnetic elements with discrete field strengths of several kG. The lines with large Lande factors have considerable broadenings of the Stokes profiles, indicating a strong background magnetic field of mixed polarity. On the basis of all these data we conclude that a four-component magnetic field structure is a possible explanation. The field strengths are about ±1.05 kG in the background field, and 1.3–1.5, 3.9–4.0, and 7.4–7.8 kG at level of middle photosphere (ℎ ≈ 300 km) in the spatially unresolved, small-scale magnetic elements.

  12. HD 18078: A very slowly rotating Ap star with an unusual magnetic field structure

    Science.gov (United States)

    Mathys, G.; Romanyuk, I. I.; Kudryavtsev, D. O.; Landstreet, J. D.; Pyper, D. M.; Adelman, S. J.

    2016-02-01

    Context. The existence of a significant population of Ap stars with very long rotation periods (up to several hundred years) has progressively emerged over the past two decades. However, only lower limits of the periods are known for most of them because their variations have not yet been observed over a sufficient timebase. Aims: We determine the rotation period of the slowly rotating Ap star HD 18078 and we derive constraints on the geometrical structure of its magnetic field. Methods: We combine measurements of the mean magnetic field modulus obtained from 1990 to 1997 with determinations of the mean longitudinal magnetic field spanning the 1999-2007 time interval to derive an unambiguous value of the rotation period. We show that this value is consistent with photometric variations recorded in the Strömgren uvby photometric system between 1995 and 2004. We fit the variations of the two above-mentioned field moments with a simple model to constrain the magnetic structure. Results: The rotation period of HD 18078 is (1358 ± 12) d. The geometrical structure of its magnetic field is consistent to first order with a colinear multipole model whose axis is offset from the centre of the star. Conclusions: HD 18078 is only the fifth Ap star with a rotation period longer than 1000 d for which the exact value of that period (as opposed to a lower limit) could be determined. The strong anharmonicity of the variations of its mean longitudinal magnetic field and the shift between their extrema and those of the mean magnetic field modulus are exceptional and indicative of a very unusual magnetic structure. Based in part on observations made at Observatoire de Haute Provence (CNRS), France; at Kitt Peak National Observatory, National Optical Astronomy Observatory (NOAO Prop. ID: KP2442; PI: T. Lanz), which is operated by the Association of Universities for Research in Astronomy (AURA) under cooperative agreement with the National Science Foundation; at the Canada

  13. Planck intermediate results. XXXIV. The magnetic field structure in the Rosette Nebula

    CERN Document Server

    Aghanim, N; Arnaud, M; Arzoumanian, D; Aumont, J; Baccigalupi, C; Banday, A J; Barreiro, R B; Bartolo, N; Battaner, E; Benabed, K; Benoit-Lévy, A; Bernard, J -P; Bersanelli, M; Bielewicz, P; Bonaldi, A; Bonavera, L; Bond, J R; Borrill, J; Bouchet, F R; Boulanger, F; Bracco, A; Burigana, C; Calabrese, E; Cardoso, J -F; Catalano, A; Chamballu, A; Chiang, H C; Christensen, P R; Colombi, S; Colombo, L P L; Combet, C; Couchot, F; Crill, B P; Curto, A; Cuttaia, F; Danese, L; Davies, R D; Davis, R J; de Bernardis, P; de Rosa, A; de Zotti, G; Delabrouille, J; Dickinson, C; Diego, J M; Dole, H; Donzelli, S; Doré, O; Douspis, M; Ducout, A; Dupac, X; Efstathiou, G; Elsner, F; Enßlin, T A; Eriksen, H K; Falgarone, E; Ferrière, K; Finelli, F; Forni, O; Frailis, M; Fraisse, A A; Franceschi, E; Frejsel, A; Galeotta, S; Galli, S; Ganga, K; Ghosh, T; Giard, M; Gjerløw, E; González-Nuevo, J; Górski, K M; Gregorio, A; Gruppuso, A; Guillet, V; Hansen, F K; Hanson, D; Harrison, D L; Henrot-Versillé, S; Herranz, D; Hildebrandt, S R; Hivon, E; Hobson, M; Holmes, W A; Hornstrup, A; Hovest, W; Huffenberger, K M; Hurier, G; Jaffe, A H; Jaffe, T R; Jewell, J; Juvela, M; Keskitalo, R; Kisner, T S; Knoche, J; Kunz, M; Kurki-Suonio, H; Lagache, G; Lamarre, J -M; Lasenby, A; Lattanzi, M; Lawrence, C R; Leonardi, R; Levrier, F; Liguori, M; Lilje, P B; Linden-Vørnle, M; López-Caniego, M; Lubin, P M; Macías-Pérez, J F; Maffei, B; Maino, D; Mandolesi, N; Mangilli, A; Maris, M; Martin, P G; Martínez-González, E; Masi, S; Matarrese, S; Melchiorri, A; Mendes, L; Mennella, A; Migliaccio, M; Miville-Deschênes, M -A; Moneti, A; Montier, L; Morgante, G; Mortlock, D; Moss, A; Munshi, D; Murphy, J A; Naselsky, P; Nati, F; Natoli, P; Netterfield, C B; Noviello, F; Novikov, D; Novikov, I; Oppermann, N; Pagano, L; Pajot, F; Paladini, R; Paoletti, D; Pasian, F; Patanchon, G; Perdereau, O; Pettorino, V; Piacentini, F; Piat, M; Pietrobon, D; Plaszczynski, S; Pointecouteau, E; Polenta, G; Ponthieu, N; Pratt, G W; Prézeau, G; Prunet, S; Puget, J -L; Rebolo, R; Reinecke, M; Remazeilles, M; Renault, C; Renzi, A; Ristorcelli, I; Rocha, G; Rosset, C; Rossetti, M; Roudier, G; Rubiño-Martín, J A; Rusholme, B; Sandri, M; Santos, D; Savelainen, M; Savini, G; Scott, D; Soler, J D; Spencer, L D; Stolyarov, V; Sutton, D; Suur-Uski, A -S; Sygnet, J -F; Tauber, J A; Terenzi, L; Toffolatti, L; Tomasi, M; Tristram, M; Tucci, M; Tuovinen, J; Valenziano, L; Valiviita, J; Van Tent, B; Vielva, P; Villa, F; Wade, L A; Wandelt, B D; Wehus, I K; Wiesemeyer, H; Yvon, D; Zacchei, A; Zonca, A

    2015-01-01

    Planck has mapped the polarized dust emission over the whole sky, making it possible to trace the Galactic magnetic field structure that pervades the interstellar medium (ISM). We combine polarization data from Planck with rotation measure (RM) observations towards a massive star-forming region, the Rosette Nebula in the Monoceros molecular cloud, to study its magnetic field structure and the impact of an expanding HII region on the morphology of the field. We derive an analytical solution for the magnetic field, assumed to evolve from an initially uniform configuration following the expansion of ionized gas and the formation of a shell of swept-up ISM. From the RM data we estimate a mean value of the line-of-sight component of the magnetic field of about +3 microG in the Rosette nebula, for a uniform electron density of about 11cm-3. The dust shell that surrounds the Rosette HII region is clearly observed in the Planck intensity map at 353 GHz. The Planck observations constrain the plane-of-the-sky orientati...

  14. 3D Global Coronal Density Structure and Associated Magnetic Field near Solar Maximum

    Directory of Open Access Journals (Sweden)

    Maxim Kramar

    2016-08-01

    Full Text Available Measurement of the coronal magnetic field is a crucial ingredient in understanding the nature of solar coronal dynamic phenomena at all scales. We employ STEREO/COR1 data obtained near maximum of solar activity in December 2012 (Carrington rotation, CR 2131 to retrieve and analyze the three-dimensional (3D coronal electron density in the range of heights from $1.5$ to $4 R_odot$ using a tomography method and qualitatively deduce structures of the coronal magnetic field. The 3D electron density analysis is complemented by the 3D STEREO/EUVI emissivity in 195 AA band obtained by tomography for the same CR period. We find that the magnetic field configuration during CR 2131 has a tendency to become radially open at heliocentric distances below $sim 2.5 R_odot$. We compared the reconstructed 3D coronal structures over the CR near the solar maximum to the one at deep solar minimum. Results of our 3D density reconstruction will help to constrain solar coronal field models and test the accuracy of the magnetic field approximations for coronal modeling.

  15. 3D Global Coronal Density Structure and Associated Magnetic Field near Solar Maximum

    Science.gov (United States)

    Kramar, Maxim; Airapetian, Vladimir; Lin, Haosheng

    2016-08-01

    Measurement of the coronal magnetic field is a crucial ingredient in understanding the nature of solar coronal dynamic phenomena at all scales. We employ STEREO/COR1 data obtained near maximum of solar activity in December 2012 (Carrington rotation, CR 2131) to retrieve and analyze the three-dimensional (3D) coronal electron density in the range of heights from 1.5 to 4 R_⊙ using a tomography method and qualitatively deduce structures of the coronal magnetic field. The 3D electron density analysis is complemented by the 3D STEREO/EUVI emissivity in 195 Å band obtained by tomography for the same CR period. We find that the magnetic field configuration during CR 2131 has a tendency to become radially open at heliocentric distances below ˜ 2.5 R_⊙. We compared the reconstructed 3D coronal structures over the CR near the solar maximum to the one at deep solar minimum. Results of our 3D density reconstruction will help to constrain solar coronal field models and test the accuracy of the magnetic field approximations for coronal modeling.

  16. Structure and properties of Co-doped ZnO films prepared by thermal oxidization under a high magnetic field.

    Science.gov (United States)

    Li, Guojian; Wang, Huimin; Wang, Qiang; Zhao, Yue; Wang, Zhen; Du, Jiaojiao; Ma, Yonghui

    2015-01-01

    The effect of a high magnetic field applied during oxidation on the structure, optical transmittance, resistivity, and magnetism of cobalt (Co)-doped zinc oxide (ZnO) thin films prepared by oxidizing evaporated Zn/Co bilayer thin films in open air was studied. The relationship between the structure and properties of films oxidized with and without an applied magnetic field was analyzed. The results show that the high magnetic field obviously changed the structure and properties of the Co-doped ZnO films. The Lorentz force of the high magnetic field suppressed the oxidation growth on nanowhiskers. As a result, ZnO nanowires were formed without a magnetic field, whereas polyhedral particles formed under a 6 T magnetic field. This morphology variation from dendrite to polyhedron caused the transmittance below 1,200 nm of the film oxidized under a magnetic field of 6 T to be much lower than that of the film oxidized without a magnetic field. X-ray photoemission spectroscopy indicated that the high magnetic field suppressed Co substitution in the ZnO lattice, increased the concentration of oxygen vacancies, and changed the chemical state of Co. The increased concentration of oxygen vacancies affected the temperature dependence of the resistivity of the film oxidized under a magnetic field of 6 T compared with that of the film oxidized without a magnetic field. The changes of oxygen vacancy concentration and Co state caused by the application of the high magnetic field also increase the ferromagnetism of the film at room temperature. All of these results indicate that a high magnetic field is an effective tool to modify the structure and properties of ZnO thin films.

  17. Limits for primordial magnetic fields

    CERN Document Server

    Caprini, Chiara

    2011-01-01

    A possible explanation for the origin of the magnetic fields observed today in matter structures is that they were generated in the primordial universe. After briefly revising the model of a primordial stochastic magnetic field and sketching the main features of its time evolution in the primordial plasma, we illustrate the current upper bounds on the magnetic field amplitude and spectral index from Cosmic Microwave Background observations and gravitational wave production. We conclude that a primordial magnetic field generated by a non-causal process such as inflation with a red spectrum seems to be favoured as a seed for the magnetic fields observed today in structures.

  18. On the structure of guide magnetic field in the inertia-driven magnetic reconnection with the presence of shear flow

    Energy Technology Data Exchange (ETDEWEB)

    Hosseinpour, M.; Mohammadi, M. A. [Department of Plasma Physics, Faculty of Physics, University of Tabriz, Tabriz (Iran, Islamic Republic of)

    2013-11-15

    The effect of equilibrium shear flow on the structure of out-of-plane magnetic field is analytically investigated in the two-fluid magnetohydrodynamic (MHD) regimes of the collisionless tearing instability, where the electron inertia breaks the frozen-in condition. Our scaling analysis reveals that the Alfvénic and sub-Alfvénic shear flows cannot significantly modify the linear regimes of applicability. In addition, we show that the structure of out-of-plane magnetic field can either be quadrupolar or non-quadrupolar in Hall-MHD regimes. In particular, both types of structures can dominate at β < 1 (β is the ratio of plasma kinetic pressure to the pressure in the magnetic field) depending on the value of the normalized ion inertial skin depth. This conclusion, however, is in contradiction to the claim presented by Rogers et al. [J. Geophys. Res. 108, A3 (2003)], which states that the quadrupolar structure cannot appear at β < 1. The reasons of this disagreement are discussed in our study.

  19. Molecules in Magnetic Fields

    Science.gov (United States)

    Berdyugina, Svetlana

    2015-08-01

    Molecules probe cool matter in the Universe and various astrophysical objects. Their ability to sense magnetic fields provides new insights into magnetic properties of these objects. During the past fifteen years we have carried out a theoretical study of molecular magnetic effects such as the Zeeman, Paschen-Back and Hanle effects and their applications for inferring magnetic structures and spatial inhomogeneities on the Sun, cool stars, brown dwarfs, and exoplanets from molecular spectro-polarimetry (e.g., Berdyugina 2011). Here, we present an overview of this study and compare our theoretical predictions with recent laboratory measurements of magnetic properties of some molecules. We present also a new web-based tool to compute molecular magnetic effects and polarized spectra which is supported by the ERC Advanced Grant HotMol.

  20. Neutron diffraction investigations of zero-field and field-induced magnetic structures of DyNiSn single crystal

    Energy Technology Data Exchange (ETDEWEB)

    Murogaki, K. [Graduate School of Science, Kyoto University, Kyoto 606-8502 (Japan)]. E-mail: murogaki@fiberbit.net; Kawano, S. [Research Reactor Institute, Kyoto University, Osaka 590-0494 (Japan); Andoh, Y. [Faculty of Regional Sciences, Tottori University, Tottori 680-8551 (Japan); Takahashi, M. [Institute of Materials Science, University of Tsukuba, Ibaraki 305-8573 (Japan); Kurisu, M. [Japan Advanced Institute of Science and Technology, Ishikawa 923-1292 (Japan); Nakamoto, G. [Japan Advanced Institute of Science and Technology, Ishikawa 923-1292 (Japan); Anh, D.T. Kim [Japan Advanced Institute of Science and Technology, Ishikawa 923-1292 (Japan); Tsutaoka, T. [Graduate School of Education, Hiroshima University, Hiroshima 739-8524 (Japan)

    2006-02-09

    Single crystal neutron diffraction studies have been performed on the rare-earth ternary compound, DyNiSn. This crystal exhibits an incommensurate magnetic structure expressed by the propagation vector, Q = (0.662 0.352 0) with its third harmonics at low temperatures. In an external magnetic field applied along the c-axis DyNiSn shows incommensurate modulation with Q = (1 0.315 0) at 1.6 K, while along the easy magnetization direction of the b-axis a commensurate modulation with Q = (2/3 0 0) develops at 2 K. The results along the b-axis are fully consistent with the magnetization curve.

  1. Recent perspectives in solar physics - Elemental composition, coronal structure and magnetic fields, solar activity

    Science.gov (United States)

    Newkirk, G., Jr.

    1975-01-01

    Elemental abundances in the solar corona are studied. Abundances in the corona, solar wind and solar cosmic rays are compared to those in the photosphere. The variation in silicon and iron abundance in the solar wind as compared to helium is studied. The coronal small and large scale structure is investigated, emphasizing magnetic field activity and examining cosmic ray generation mechanisms. The corona is observed in the X-ray and EUV regions. The nature of coronal transients is discussed with emphasis on solar-wind modulation of galactic cosmic rays. A schematic plan view of the interplanetary magnetic field during sunspot minimum is given showing the presence of magnetic bubbles and their concentration in the region around 4-5 AU by a fast solar wind stream.

  2. Upper Chromospheric Magnetic Field of a Sunspot Penumbra: Observations of Fine Structure

    CERN Document Server

    Joshi, J; Solanki, S K; Feller, A; Collados, M; Suárez, D Orozco; Schlichenmaier, R; Franz, M; Balthasar, H; Denker, C; Berkefeld, T; Hofmann, A; Kiess, C; Nicklas, H; Yabar, A Pastor; Rezaei, R; Schmidt, D; Schmidt, W; Sobotka, M; Soltau, D; Staude, J; Strassmeier, K G; Volkmer, R; von der Lühe, O; Waldmann, T

    2016-01-01

    The fine-structure of magnetic field of a sunspot penumbra in the upper chromosphere is to be explored and compared to that in the photosphere. High spatial resolution spectropolarimetric observations were recorded with the 1.5-meter GREGOR telescope using the GREGOR Infrared Spectrograph (GRIS). The observed spectral domain includes the upper chromospheric He I triplet at 1083.0 nm and the photospheric Si I 1082.7 nm and Ca I 1083.3 nm spectral lines. The upper chromospheric magnetic field is obtained by inverting the He I triplet assuming a Milne-Eddington type model atmosphere. A height dependent inversion was applied to the Si I 1082.7 nm and Ca I 1083.3 nm lines to obtain the photospheric magnetic field. We find that the inclination of the magnetic field shows variations in the azimuthal direction both in the photosphere, but also in the upper chromosphere. The chromospheric variations remarkably well coincide with the variations in the inclination of the photospheric field and resemble the well-known sp...

  3. How does an asymmetric magnetic field change the vertical structure of a hot accretion flow?

    Science.gov (United States)

    Samadi, M.; Abbassi, S.; Lovelace, R. V. E.

    2017-09-01

    This paper explores the effects of large-scale magnetic fields in hot accretion flows for asymmetric configurations with respect to the equatorial plane. The solutions that we have found show that the large-scale asymmetric magnetic field can significantly affect the dynamics of the flow and also cause notable outflows in the outer parts. Previously, we treated a viscous resistive accreting disc in the presence of an odd symmetric B-field about the equatorial plane. Now, we extend our earlier work by taking into account another configuration of large-scale magnetic field that is no longer symmetric. We provide asymmetric field structures with small deviations from even and odd symmetric B-field. Our results show that the disc's dynamics and appearance become different above and below the equatorial plane. The set of solutions also predicts that even a small deviation in a symmetric field causes the disc to compress on one side and expand on the other. In some cases, our solution represents a very strong outflow from just one side of the disc. Therefore, the solution may potentially explain the origin of one-sided jets in radio galaxies.

  4. Effects of seed magnetic fields on magnetohydrodynamic implosion structure and dynamics

    KAUST Repository

    Mostert, W.

    2014-12-01

    The effects of various seed magnetic fields on the dynamics of cylindrical and spherical implosions in ideal magnetohydrodynamics are investigated. Here, we present a fundamental investigation of this problem utilizing cylindrical and spherical Riemann problems under three seed field configurations to initialize the implosions. The resulting flows are simulated numerically, revealing rich flow structures, including multiple families of magnetohydrodynamic shocks and rarefactions that interact non-linearly. We fully characterize these flow structures, examine their axi- and spherisymmetry-breaking behaviour, and provide data on asymmetry evolution for different field strengths and driving pressures for each seed field configuration. We find that out of the configurations investigated, a seed field for which the implosion centre is a saddle point in at least one plane exhibits the least degree of asymmetry during implosion.

  5. Structure and Stability of Magnetic Fields in Solar Active Region12192 Based on Nonlinear Force-Free Field Modeling

    CERN Document Server

    Inoue, S; Kusano, K

    2016-01-01

    We analyze a three-dimensional (3D) magnetic structure and its stability in large solar active region(AR) 12192, using the 3D coronal magnetic field constructed under a nonlinear force-free field (NLFFF) approximation. In particular, we focus on the magnetic structure that produced an X3.1-class flare which is one of the X-class flares observed in AR 12192. According to our analysis, the AR contains multiple-flux-tube system, {\\it e.g.}, a large flux tube, both of whose footpoints are anchored to the large bipole field, under which other tubes exist close to a polarity inversion line (PIL). These various flux tubes of different sizes and shapes coexist there. In particular, the later are embedded along the PIL, which produces a favorable shape for the tether-cutting reconnection and is related to the X-class solar flare. We further found that most of magnetic twists are not released even after the flare, which is consistent with the fact that no observational evidence for major eruptions was found. On the oth...

  6. Periodical structure in a magnetic fluid under the action of an electric field and with a shear flow

    Energy Technology Data Exchange (ETDEWEB)

    Veguera, Janna G. [Stavropol State University, 1 Pushkin st., Stavropol 355009 (Russian Federation)]. E-mail: veguera@yandex.ru; Dikansky, Yury I. [Stavropol State University, 1 Pushkin st., Stavropol 355009 (Russian Federation)

    2005-03-15

    The results of ordering structural formation in a flowing magnetic fluid under the action of an electric field are described. The influence of structural formation process on a viscosity and conductivity of this fluids has been considered.

  7. Effects of high magnetic field on martensitic transformation behavior and structure in Fe-based alloys

    Energy Technology Data Exchange (ETDEWEB)

    Ohtsuka, H.; Wada, H. [Tsukuba Labs., Ibaraki (Japan). Nat. Res. Inst. for Metals; Ghosh, G. [Northwestern Univ., Evanston, IL (United States). Dept. of Materials Science and Engineering

    2000-07-01

    Effects of magnetic field on lath-type martensitic transformation behavior and the reverse transformation behavior from lath math martensite to austenite have been investigated in 18Ni maraging steel. It was found that the reverse transformation temperature during heating is increased by magnetic field. Reverse transformation behavior during isothermal holding was also found to be retarded by magnetic field. (orig.)

  8. New Shell Structures and Their Ground Electronic States in Spherical Quantum Dots (II) under Magnetic Field

    Science.gov (United States)

    Asari, Yusuke; Takeda, Kyozaburo; Tamura, Hiroyuki

    2005-04-01

    We theoretically studied the electronic structure of the three-dimensional spherical parabolic quantum dot (3D-SPQD) under a magnetic field. We obtained the quantum dot orbitals (QDOs) and determined the ground state by using the extended UHF approach where the expectation values of the z component of the total orbital angular momentum are conserved during the scf-procedure. The single-electron treatment predicts that the applied magnetic field (B) creates k-th new shells at the magnetic field of Bk=k(k+2)/(k+1)ω0 with the shell-energy interval of \\hbarω0/(k+1), where ω0(=\\hbar/m*l02) is the characteristic frequency originating from the spherical parabolic confinement potential. These shells are formed by the level crossing among multiple QDOs. The interelectron interaction breaks the simple level crossing but causes complicated dependences among the total energy, the chemical potential and their differences (magic numbers) with the magnetic field or the number of confinement electrons. The ground state having a higher spin multiplicity is theoretically predicted on the basis of the \\textit{quasi}-degeneracies of the QDOs around these shells.

  9. Parsec-scale Magnetic-Field Structures in HEAO-1 BL Lacs

    CERN Document Server

    Kharb, P; Shastri, P

    2007-01-01

    We present very long baseline interferometry polarization images of an X-ray selected sample of BL Lacertae objects belonging to the first High Energy Astronomy Observatory (HEAO-1) and the ROSAT-Green Bank (RGB) surveys. These are primarily high-energy-peaked BL Lacs (HBLs) and exhibit core-jet radio morphologies on pc-scales. They show moderately polarized jet components, similar to those of low-energy-peaked BL Lacs (LBLs). The fractional polarization in the unresolved cores of the HBLs is, on average, lower than in the LBLs, while the fractional polarizations in the pc-scale jets of HBLs and LBLs are comparable. However a difference is observed in the orientation of the inferred jet magnetic fields -- while LBL jets are well-known to preferentially exhibit transverse magnetic fields, the HBL jets tend to display longitudinal magnetic fields. Although a `spine-sheath' jet velocity structure, along with larger viewing angles for HBLs could produce the observed magnetic field configuration, differences in ot...

  10. Matching dust emission structures and magnetic field in high-latitude cloud L1642: comparing Herschel and Planck maps

    CERN Document Server

    Malinen, J; Montillaud, J; Juvela, M; Ristorcelli, I; Clark, S E; Berné, O; Bernard, J -Ph; Pelkonen, V -M; Collins, D C

    2015-01-01

    The nearby cloud L1642 is one of only two known very high latitude (|b| > 30 deg) clouds actively forming stars. It is a rare example of star formation in isolated conditions, and can reveal important details of star formation in general, e.g., of the effect of magnetic fields. We compare Herschel dust emission structures and magnetic field orientation revealed by Planck polarization maps in L1642. The high-resolution (~18-40") Herschel data reveal a complex structure including a dense, compressed central blob with elongated extensions, low density striations, "fishbone" like structures with a spine and perpendicular striations, and a spiraling "tail". The Planck polarization data (at 10' resolution) reveal an ordered magnetic field pervading the cloud and aligned with the surrounding striations. There is a complex interplay between the cloud structure and large scale magnetic field. This suggests that magnetic field is closely linked to the formation and evolution of the cloud. CO rotational emission confirm...

  11. The role of magnetic fields in the structure and interaction of supershells

    Science.gov (United States)

    Ntormousi, Evangelia; Dawson, Joanne R.; Hennebelle, Patrick; Fierlinger, Katharina

    2017-03-01

    Context. Large-scale shocks formed by clustered feedback of young OB stars are considered an important source of mechanical energy for the interstellar medium (ISM) and a trigger of molecular cloud formation. Their interaction sites are locations where kinetic energy and magnetic fields are redistributed between ISM phases. Aims: In this work we address two questions, both involving the role of galactic magnetic fields in the dynamics of supershells and their interactions. On the one hand, we study the effect of the magnetic field on the expansion and fragmentation of supershells and, on the other hand, we look for the signatures of supershell collisions on dense structures and on the kinetic and magnetic energy distribution of the ISM. Methods: We performed a series of high-resolution, three-dimensional simulations of colliding supershells. The shocks are created by time-dependent feedback and evolve in a diffuse turbulent environment that is either unmagnetized or has different initial magnetic field configurations. Results: In the hydrodynamical situation, the expansion law of the superbubbles is consistent with the radius-time relation R ∝ t3/5 that is theoretically predicted for wind-blown bubbles. The supershells fragment over their entire surface into small dense clumps that carry more than half of the total kinetic energy in the volume. However, this is not the case when a magnetic field is introduced, either in the direction of the collision or perpendicular to the collision. In both situations, the shell surfaces are more stable to dynamical instabilities. When the magnetic field opposes the collision, the expansion law of the supershells also becomes significantly flatter than in the hydrodynamical case. Although a two-phase medium arises in all cases, in the magnetohydrodynamical (MHD) simulations the cold phase is limited to lower densities and the cold clumps are located further away from the shocks with respect to the hydrodynamical simulations

  12. First Cluster results of the magnetic field structure of the mid- and high-altitude cusps

    Directory of Open Access Journals (Sweden)

    P. J. Cargill

    Full Text Available Magnetic field measurements from the four Cluster spacecraft from the mid- and high-altitude cusp are presented. Cluster underwent two encounters with the mid-altitude cusp during its commissioning phase (24 August 2000. Evidence for field-aligned currents (FACs was seen in the data from all three operating spacecraft from northern and southern cusps. The extent of the FACs was of the order of 1 RE in the X-direction, and at least 300 km in the Y-direction. However, fine-scale field structures with scales of the order of the spacecraft separation (300 km were observed within the FACs. In the northern crossing, two of the spacecraft appeared to lie along the same magnetic field line, and observed very well matched signals. However, the third spacecraft showed evidence for structuring transverse to the field on scales of a few hundred km. A crossing of the high-altitude cusp from 13 February 2001 is presented. It is revealed to be a highly dynamic structure with the boundaries moving with velocities ranging from a few km/s to tens of km/s, and having structure on timescales ranging from less than one minute up to several minutes. The cusp proper is associated with the presence of a very disordered magnetic field, which is entirely different from the magnetosheath turbulence.

    Key words. Magnetospheric physics (current systems; magnetopause, cusp, and boundary layers – Space plasma physics (discontinuities

  13. Solar Magnetic Fields

    Indian Academy of Sciences (India)

    J. O. Stenflo

    2008-03-01

    Since the structuring and variability of the Sun and other stars are governed by magnetic fields, much of present-day stellar physics centers around the measurement and understanding of the magnetic fields and their interactions. The Sun, being a prototypical star, plays a unique role in astrophysics, since its proximity allows the fundamental processes to be explored in detail. The PRL anniversary gives us an opportunity to look back at past milestones and try to identify the main unsolved issues that will be addressed in the future.

  14. Co thickness dependence of structural and magnetic properties in spin quantum cross devices utilizing stray magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Kaiju, H., E-mail: kaiju@es.hokudai.ac.jp; Kasa, H.; Mori, S.; Misawa, T.; Abe, T.; Nishii, J. [Research Institute for Electronic Science, Hokkaido University, Sapporo, Hokkaido 001-0020 (Japan); Komine, T. [Faculty of Engineering, Ibaraki University, Hitachi, Ibaraki 316-8511 (Japan)

    2015-05-07

    We investigate the Co thickness dependence of the structural and magnetic properties of Co thin-film electrodes sandwiched between borate glasses in spin quantum cross (SQC) devices that utilize stray magnetic fields. We also calculate the Co thickness dependence of the stray field between the two edges of Co thin-film electrodes in SQC devices using micromagnetic simulation. The surface roughness of Co thin films with a thickness of less than 20 nm on borate glasses is shown to be as small as 0.18 nm, at the same scanning scale as the Co film thickness, and the squareness of the hysteresis loop is shown to be as large as 0.96–1.0. As a result of the establishment of polishing techniques for Co thin-film electrodes sandwiched between borate glasses, we successfully demonstrate the formation of smooth Co edges and the generation of stray magnetic fields from Co edges. Theoretical calculation reveals that a strong stray field beyond 6 kOe is generated when the Co thickness is greater than 10 nm at a junction gap distance of 5 nm. From these experimental and calculation results, it can be concluded that SQC devices with a Co thickness of 10–20 nm can be expected to function as spin-filter devices.

  15. 3D Global Coronal Density Structure and Associated Magnetic Field near Solar Maximum

    CERN Document Server

    Kramar, Maxim; Lin, Haosheng

    2016-01-01

    Measurement of the coronal magnetic field is a crucial ingredient in understanding the nature of solar coronal dynamic phenomena at all scales. We employ STEREO/COR1 data obtained near maximum of solar activity in December 2012 (Carrington rotation, CR 2131) to retrieve and analyze the three-dimensional (3D) coronal electron density in the range of heights from $1.5$ to $4\\ \\mathrm{R}_\\odot$ using a tomography method and qualitatively deduce structures of the coronal magnetic field. The 3D electron density analysis is complemented by the 3D STEREO/EUVI emissivity in 195 \\AA \\ band obtained by tomography for the same CR period. We find that the magnetic field configuration during CR 2131 has a tendency to become radially open at heliocentric distances below $\\sim 2.5 \\ \\mathrm{R}_\\odot$. We compared the reconstructed 3D coronal structures over the CR near the solar maximum to the one at deep solar minimum. Results of our 3D density reconstruction will help to constrain solar coronal field models and test the a...

  16. The influence of outflow and global magnetic field on the structure and spectrum of resistive CDAFs

    Science.gov (United States)

    Ghasemnezhad, Maryam; Abbassi, Shahram

    2016-12-01

    We examine the effects of a global magnetic field and outflow on radiatively inefficient accretion flow (RIAF) in the presence of magnetic resistivity. We find self-similar solutions for the height integrated equations that govern the behavior of the flow. We use the mixing length mechanism for studying the convection parameter. We adopt the radius dependent mass accretion rate dot{M}=dot{M}_{out}{(r/r_{out})s}, with s> 0, to investigate the influence of outflow on the structure of inflow where s is a constant and is an indication of the effect of the wind. Also, we have studied the radiation spectrum and temperature of convection dominated accretion flows (CDAFs). The thermal bremsstrahlung emission as a radiation mechanism is taken into account for calculating the spectra emitted by the CDAFs. The energy that powers bremsstrahlung emission at large radii is provided by convective transport from small radii and viscous and resistivity dissipation. Our results indicate that the disc rotates slower and accretes faster, it becomes hotter and thicker for a stronger wind. By increasing all components of the magnetic field, the disc rotates faster and accretes more slowly, while it becomes hotter and thicker. We show that the outflow parameter and all components of the magnetic field have the same effects on the luminosity of the disc. We compare the dynamical structure of the disc in two different solutions (with and without resistivity parameter). We show that only the radial infall velocity and the surface density could be changed by the resistivity parameter obviously. Increasing the effect of the wind increases the disc's temperature and the luminosity of the disc. The effect of the magnetic field is similar to the effect of the wind on the disc's temperature and the luminosity of the disc, but the influence of the resistivity on the observational properties is not evident.

  17. Automated tracing of open-field coronal structures for an optimized large-scale magnetic field reconstruction

    Science.gov (United States)

    Uritsky, V. M.; Davila, J. M.; Jones, S. I.

    2014-12-01

    Solar Probe Plus and Solar Orbiter will provide detailed measurements in the inner heliosphere magnetically connected with the topologically complex and eruptive solar corona. Interpretation of these measurements will require accurate reconstruction of the large-scale coronal magnetic field. In a related presentation by S. Jones et al., we argue that such reconstruction can be performed using photospheric extrapolation methods constrained by white-light coronagraph images. Here, we present the image-processing component of this project dealing with an automated segmentation of fan-like coronal loop structures. In contrast to the existing segmentation codes designed for detecting small-scale closed loops in the vicinity of active regions, we focus on the large-scale geometry of the open-field coronal features observed at significant radial distances from the solar surface. The coronagraph images used for the loop segmentation are transformed into a polar coordinate system and undergo radial detrending and initial noise reduction. The preprocessed images are subject to an adaptive second order differentiation combining radial and azimuthal directions. An adjustable thresholding technique is applied to identify candidate coronagraph features associated with the large-scale coronal field. A blob detection algorithm is used to extract valid features and discard noisy data pixels. The obtained features are interpolated using higher-order polynomials which are used to derive empirical directional constraints for magnetic field extrapolation procedures based on photospheric magnetograms.

  18. Electron states in quantum rings with structural distortions under axial or in-plane magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Planelles, J [Departament de Quimica Fisica i Analitica, Universitat Jaume I, Box 224, E-12080 Castello (Spain); Rajadell, F [Departament de Quimica Fisica i Analitica, Universitat Jaume I, Box 224, E-12080 Castello (Spain); Climente, J I [Departament de Quimica Fisica i Analitica, Universitat Jaume I, Box 224, E-12080 Castello (Spain)

    2007-09-19

    A comprehensive study of anisotropic quantum rings, QRs, subject to axial and in-plane magnetic field, both aligned and transverse to the anisotropy direction, is carried out. Elliptical QRs for a wide range of eccentricity values and also perfectly circular QRs including one or more barriers disturbing the QR current are considered. These models mimic anisotropic geometry deformations and mass diffusion occurring in the QR fabrication process. Symmetry considerations and simplified analytical models supply physical insight into the obtained numerical results. Our study demonstrates that, except for unusual extremely large eccentricities, QR geometry deformations only appreciably influence a few low-lying states, while the effect of barriers disturbing the QR current is stronger and affects all studied states to a similar extent. We also show that the response of the electron states to in-plane magnetic fields provides accurate information on the structural anisotropy.

  19. Cosmological Magnetic Fields

    CERN Document Server

    Kunze, Kerstin E

    2013-01-01

    Magnetic fields are observed on nearly all scales in the universe, from stars and galaxies upto galaxy clusters and even beyond. The origin of cosmic magnetic fields is still an open question, however a large class of models puts its origin in the very early universe. A magnetic dynamo amplifying an initial seed magnetic field could explain the present day strength of the galactic magnetic field. However, it is still an open problem how and when this initial magnetic field was created. Observations of the cosmic microwave background (CMB) provide a window to the early universe and might therefore be able to tell us whether cosmic magnetic fields are of primordial, cosmological origin and at the same time constrain its parameters. We will give an overview of the observational evidence of large scale magnetic fields, describe generation mechanisms of primordial magnetic fields and possible imprints in the CMB.

  20. Tailoring the exciton fine structure of cadmium selenide nanocrystals with shape anisotropy and magnetic field.

    Science.gov (United States)

    Sinito, Chiara; Fernée, Mark J; Goupalov, Serguei V; Mulvaney, Paul; Tamarat, Philippe; Lounis, Brahim

    2014-11-25

    We use nominally spheroidal CdSe nanocrystals with a zinc blende crystal structure to study how shape perturbations lift the energy degeneracies of the band-edge exciton. Nanocrystals with a low degree of symmetry exhibit splitting of both upper and lower bright state degeneracies due to valence band mixing combined with the isotropic exchange interaction, allowing active control of the level splitting with a magnetic field. Asymmetry-induced splitting of the bright states is used to reveal the entire 8-state band-edge fine structure, enabling complete comparison with band-edge exciton models.

  1. Light and electric field control of ferromagnetism in magnetic quantum structures.

    Science.gov (United States)

    Boukari, H; Kossacki, P; Bertolini, M; Ferrand, D; Cibert, J; Tatarenko, S; Wasiela, A; Gaj, J A; Dietl, T

    2002-05-20

    A strong influence of illumination and electric bias on the Curie temperature and saturation value of the magnetization is demonstrated for semiconductor structures containing a modulation-doped p-type Cd(0.96)Mn(0.04)Te quantum well placed in various built-in electric fields. It is shown that both light beam and bias voltage generate an isothermal and reversible crossover between the paramagnetic and ferromagnetic phases, in the way that is predetermined by the structure design. The observed behavior is in quantitative agreement with the expectations for systems, in which ferromagnetic interactions are mediated by the weakly disordered two-dimensional hole liquid.

  2. Could the stellar magnetic field explain the vertical structures in the AU Mic debris disk?

    Science.gov (United States)

    Sezestre, É.; Augereau, J.-C.

    2016-12-01

    Recent observations of the edge-on debris disk of AU Mic have revealed asymmetric, fast-moving wave-like structures above its disk midplane. Although asymmetries are frequent in debris disks, no model can readily explain these features.} {In this paper, we present a model aiming to reproduce such structures, particularly the wave morphology and the high projected speeds. We test the hypothesis of dust emitted by a point source, interacting with the stellar wind and the large-scale magnetic field of the star.} {We perform numerical simulations of test particle trajectories to explore the available parameter space. The impact of the stellar wind and the magnetic field on the dust dynamics is discussed separately, then together.} {The stellar wind and, to a smaller extent, the magnetic topology, can reproduce the arches. The observed structures cannot be explained by a single trajectory common to all dust grains emitted intermittently by a fixed point source in space.} {This excludes a giant collision as the emission process. Therefore, our preferred scenario relies on an orbiting source of dust, possibly a planetary companion, emitting at different epochs.

  3. Structure of the magnetopause for low Mach number and strongly northward interplanetary magnetic field

    Science.gov (United States)

    Le, G.; Russell, C. T.; Gosling, J. T.

    1994-12-01

    We use International Sun-Earth Explorer (ISEE) magnetic field and plasma data to examine dayside magnetopause crossing under conditions of low Mach number and strongly northward interplanetary magnetic field (IMF). When the solar wind Mach number is low, the IMF stregth and magnetoseath field stregth are large, and we expect the effects of magnetic reconection to be the strongest. When the IMF is strongly northward, we find that the location of the magnetopause boundary layer is very stationary in the space, and we observe many features that are common for both typical and low Mach numbers. However, under low Mach number conditions, we have observed some features that would be expected for cusp reconnection. The boundary layer near the subsolar region contains heated magnetosheath plasma with little hot magnetospheric component that has clearly entered the magnetosphere elsewhere. At least some of the structures present in the boundary layer are impulsive. Inside the boundary layer there is also clear evidence of acceleratedflow from the cusp region for strongly northward IMF at low Mach number. Reconnection beyond the cusp can explain the observed field, plasma, and flow signatures. Therefore at low Mach number, reconection is important in the formation of the boundary layer for northward IMF.

  4. Constraints from Faraday rotation on the magnetic field structure in the Galactic halo

    CERN Document Server

    Terral, Philippe

    2016-01-01

    We examine the constraints imposed by Faraday rotation measures of extragalactic point sources on the structure of the magnetic field in the halo of our Galaxy. Guided by radio polarization observations of external spiral galaxies, we look in particular into the possibility that field lines in the Galactic halo have an X shape. We employ the analytical models of spiraling, possibly X-shape magnetic fields derived in a previous paper to generate synthetic all-sky maps of the Galactic Faraday depth, which we fit to an observational reference map with the help of Markov Chain Monte Carlo simulations. We find that the magnetic field in the Galactic halo is slightly more likely to be bisymmetric (azimuthal wavenumber, $m = 1$) than axisymmetric ($m = 0$). If it is indeed bisymmetric, it must appear as X-shaped in radio polarization maps of our Galaxy seen edge-on from outside, but if it is actually axisymmetric, it must instead appear as nearly parallel to the Galactic plane.

  5. STRUCTURE AND STABILITY OF MAGNETIC FIELDS IN SOLAR ACTIVE REGION 12192 BASED ON NONLINEAR FORCE-FREE FIELD MODELING

    Energy Technology Data Exchange (ETDEWEB)

    Inoue, S. [Max-Planck-Institute for Solar System Research, Justus-von-Liebig-Weg 3 D-37077 Göttingen Germany (Germany); Hayashi, K.; Kusano, K., E-mail: inoue@mps.mpg.de [Institute for Space-Earth Environmental Research, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601 (Japan)

    2016-02-20

    We analyze a three-dimensional (3D) magnetic structure and its stability in large solar active region (AR) 12192, using the 3D coronal magnetic field constructed under a nonlinear force-free field (NLFFF) approximation. In particular, we focus on the magnetic structure that produced an X3.1-class flare, which is one of the X-class flares observed in AR 12192. According to our analysis, the AR contains a multiple-flux-tube system, e.g., a large flux tube, with footpoints that are anchored to the large bipole field, under which other tubes exist close to a polarity inversion line (PIL). These various flux tubes of different sizes and shapes coexist there. In particular, the latter are embedded along the PIL, which produces a favorable shape for the tether-cutting reconnection and is related to the X-class solar flare. We further found that most of magnetic twists are not released even after the flare, which is consistent with the fact that no observational evidence for major eruptions was found. On the other hand, the upper part of the flux tube is beyond a critical decay index, essential for the excitation of torus instability before the flare, even though no coronal mass ejections were observed. We discuss the stability of the complicated flux tube system and suggest the reason for the existence of the stable flux tube. In addition, we further point out a possibility for tracing the shape of flare ribbons, on the basis of a detailed structural analysis of the NLFFF before a flare.

  6. Role of rf electric and magnetic fields in heating of micro-protrusions in accelerating structures

    CERN Document Server

    Nusinovich, Gregory S

    2011-01-01

    It is known that high-gradient operation in metallic accelerating structures causes significant deterioration of structure surfaces that, in turn, greatly increases the probability of microwave breakdown. At the same time, the physical reason for this deterioration so far is not well understood. In the present paper, the role of two effects is analyzed, viz. (a) the microwave heating caused by penetration of the rf magnetic field into microprotrusion of a radius on the order of the skin depth and (b) the Joule heating caused by the field emitted current, i.e. the effect of the rf electric field magnified by a sharp protrusion. Corresponding expressions for the power densities of both effects are derived and the criterion for evaluating the dominance of one of these two is formulated. This criterion is analyzed and illustrated by the discussion of an example with parameters typical for recent experiments at the Stanford Linear Accelerator Center (SLAC) National Accelerator Laboratory.

  7. CLUSTER encounters with the high altitude cusp: boundary structure and magnetic field depletions

    Directory of Open Access Journals (Sweden)

    P. J. Cargill

    2004-04-01

    Full Text Available Data from the four spacecraft Cluster mission during a high altitude cusp crossing on 13 February 2001 are presented. The spacecraft configuration has one leading spacecraft, with the three trailing spacecraft lying in a plane that corresponds roughly to the nominal magnetopause surface. The typical spacecraft separation is approximately 600km. The encounter occurs under conditions of strong and steady southward Interplanetary Magnetic Field (IMF. The cusp is identified as a seven-minute long depression in the magnetic field, associated with ion heating and a high abundance of He+. Cusp entry involves passage through a magnetopause boundary that has undergone very significant distortion from its nominal shape, is moving rapidly, and exhibits structure on scales of the order of the spacecraft separation or less. This boundary is associated with a rotation of the magnetic field, a normal field component, and a plasma flow into the cusp of approximately 35 km/s. However, it cannot be identified positively as a rotational discontinuity. Exit from the cusp into the lobe is through a boundary that is initially sharp, but then retreats tailward at a few km/s. As the leading spacecraft passes through this boundary, there is a plasma flow out of the cusp of approximately 30km/s, suggesting that this is not a tangential discontinuity. A few minutes after exit from the cusp, the three trailing the spacecraft see a single cusp-like signature in the magnetic field. There is an associated temperature increase at two of the three trailing spacecraft. Timing measurements indicate that this is due to cusp-like regions detaching from the rear of the cusp boundary, and moving tailward. The magnetic field in the cusp is highly disordered, with no obvious relation between the four spacecraft, indicative of structure on scales <<600km. However, the plasma moments show only a gradual change over many minutes. A similar cusp crossing on 20 February 2001 also

  8. Quantification of local geometric distortion in structural magnetic resonance images: Application to ultra-high fields.

    Science.gov (United States)

    Lau, Jonathan C; Khan, Ali R; Zeng, Tony Y; MacDougall, Keith W; Parrent, Andrew G; Peters, Terry M

    2017-01-06

    Ultra-high field magnetic resonance imaging (MRI) provides superior visualization of brain structures compared to lower fields, but images may be prone to severe geometric inhomogeneity. We propose to quantify local geometric distortion at ultra-high fields in in vivo datasets of human subjects scanned at both ultra-high field and lower fields. By using the displacement field derived from nonlinear image registration between images of the same subject, focal areas of spatial uncertainty are quantified. Through group and subject-specific analysis, we were able to identify regions systematically affected by geometric distortion at air-tissue interfaces prone to magnetic susceptibility, where the gradient coil non-linearity occurs in the occipital and suboccipital regions, as well as with distance from image isocenter. The derived displacement maps, quantified in millimeters, can be used to prospectively evaluate subject-specific local spatial uncertainty that should be taken into account in neuroimaging studies, and also for clinical applications like stereotactic neurosurgery where accuracy is critical. Validation with manual fiducial displacement demonstrated excellent correlation and agreement. Our results point to the need for site-specific calibration of geometric inhomogeneity. Our methodology provides a framework to permit prospective evaluation of the effect of MRI sequences, distortion correction techniques, and scanner hardware/software upgrades on geometric distortion. Copyright © 2017 Elsevier Inc. All rights reserved.

  9. High-temperature annealing effects on multiwalled carbon nanotubes: electronic structure, field emission and magnetic behaviors.

    Science.gov (United States)

    Ray, Sekhar Chandra; Pao, Chih-Wen; Tsai, Huang-Ming; Chen, Huang-Chin; Chen, Yu-Shin; Wu, Shang-Lun; Ling, Dah-Chin; Lin, I-Nan; Pong, Way-Faung; Gupta, Sanju; Giorcelli, Mauro; Bianco, Stefano; Musso, Simone; Tagliaferro, Alberto

    2009-12-01

    This work elucidates the effects of high-temperature annealing on the microscopic and electronic structure of multiwalled carbon nanotubes (MWCNTs) using high-resolution transmission electron microscopy, micro-Raman spectroscopy, X-ray diffraction, X-ray absorption near-edge structure (XANES) and valence-band photoemission spectroscopy (VBPES), respectively. The field emission and magnetization behaviors are also presented. The results of annealing are as follows: (1) MWCNTs tend to align in the form of small fringes along their length, promote graphitization and be stable in air, (2) XANES indicates an enhancement in oxygen content on the sample, implying that it can be adopted for sensing and storing oxygen gas, (3) the electron field emission current density (J) is enhanced and the turn-on electric field (E(TOE)) reduced, suggesting potential use in field emission displays and as electron sources in microwave tube amplifiers and (4) as-grown MWCNTs with embedded iron nanoparticles exhibits significantly higher coercivity approximately 750 Oe than its bulk counterpart (Fe(bulk) approximately 0.9 Oe), suggesting its potential use as low-dimensional high-density magnetic recording media.

  10. Magnetic Field Grid Calculator

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Magnetic Field Properties Calculator will computes the estimated values of Earth's magnetic field(declination, inclination, vertical component, northerly...

  11. Particle in short-range potential in two dimensional structure in magnetic field

    NARCIS (Netherlands)

    Andreev, S. P.; Pavlova, T. V.

    2006-01-01

    An exact solution is given for the problem of determining the ground state of a charge particle in a zero range force field located in a quantum well and in a magnetic field. The dependence of the electron's ground state on the potential depth and the magnetic field is investigated in a semiconducto

  12. Investigation of the Three-Dimensional Structure of a Rotating Magnetic Field Driven Field-Reversed Configuration using Internal Magnetic Field Measurements

    Science.gov (United States)

    Velas, Katherine M.

    The Translation, Confinement, Sustainment Upgrade device (TCSU) used a rotating magnetic field (RMF) to form and sustain plasma in a field-reversed configuration (FRC). The physics of RMF current drive can be modeled in terms of the torque acting on the FRC. A fully translatable three-axis internal magnetic probe was built and used to generate a full r-z map of the magnetic field in the FRC and open field line region. Probe measurements are used to calculate the torques acting on the FRC formed using even-parity and odd-parity RMF antenna configurations. Odd-parity current drive was found to be more efficient and yields a plasma with lower resistivity than in even-parity current drive. An extrapolation method was developed to generate 3D magnetic field line plots which show that unlike in even-parity, field lines in odd-parity sustained FRCs make multiple transits of the FRC. Analysis using the three-axis probe data has greatly expanded our understanding of the physics of RMF driven FRCs.

  13. Primordial Magnetic Field Effects on the CMB and Large-Scale Structure

    Directory of Open Access Journals (Sweden)

    Dai G. Yamazaki

    2010-01-01

    Full Text Available Magnetic fields are everywhere in nature, and they play an important role in every astronomical environment which involves the formation of plasma and currents. It is natural therefore to suppose that magnetic fields could be present in the turbulent high-temperature environment of the big bang. Such a primordial magnetic field (PMF would be expected to manifest itself in the cosmic microwave background (CMB temperature and polarization anisotropies, and also in the formation of large-scale structure. In this paper, we summarize the theoretical framework which we have developed to calculate the PMF power spectrum to high precision. Using this formulation, we summarize calculations of the effects of a PMF which take accurate quantitative account of the time evolution of the cutoff scale. We review the constructed numerical program, which is without approximation, and an improvement over the approach used in a number of previous works for studying the effect of the PMF on the cosmological perturbations. We demonstrate how the PMF is an important cosmological physical process on small scales. We also summarize the current constraints on the PMF amplitude Bλ and the power spectral index nB which have been deduced from the available CMB observational data by using our computational framework.

  14. The Earth's Magnetic Field

    OpenAIRE

    Edda Lína Gunnarsdóttir 1988

    2012-01-01

    The Earth's magnetic field is essential for life on Earth, as we know it, to exist. It forms a magnetic shield around the planet, protecting it from high energy particles and radiation from the Sun, which can cause damage to life, power systems, orbiting satellites, astronauts and spacecrafts. This report contains a general overview of the Earth's magnetic field. The different sources that contribute to the total magnetic field are presented and the diverse variations in the field are describ...

  15. Cluster magnetic field observations in the magnetosheath: four-point measurements of mirror structures

    Directory of Open Access Journals (Sweden)

    E. A. Lucek

    Full Text Available The Cluster spacecraft have returned the first simultaneous four-point measurements of the magnetosheath. We present an analysis of data recorded on 10 November 2000, when the four spacecrafts observed an interval of strong mirrorlike activity. Correlation analysis between spacecraft pairs is used to examine the scale size of the mirror structures in three dimensions. Two examples are presented which suggest that the scale size of mirror structures is ~ 1500–3000 km along the flow direction, and shortest along the magnetopause normal (< 600 km, which, in this case, is approximately perpendicular to both the mean magnetic field and the magnetosheath flow vector. Variations on scales of ~ 750–1000 km are found along the maximum variance direction. The level of correlation in this direction, however, and the time lag observed, are found to be variable. These first results suggest that variations occur on scales of the order of the spacecraft separation ( ~ 1000 km in at least two directions, but analysis of further examples and a statistical survey of structures observed with different magnetic field orientations and tetrahedral configurations will enable us to describe more fully the size and orientation of mirror structures.

    Key words. Magnetosphenic physics (magnetosheath; plasma waves and instabilities

  16. Chaotic structures of nonlinear magnetic fields. I - Theory. II - Numerical results

    Science.gov (United States)

    Lee, Nam C.; Parks, George K.

    1992-01-01

    A study of the evolutionary properties of nonlinear magnetic fields in flowing MHD plasmas is presented to illustrate that nonlinear magnetic fields may involve chaotic dynamics. It is shown how a suitable transformation of the coupled equations leads to Duffing's form, suggesting that the behavior of the general solution can also be chaotic. Numerical solutions of the nonlinear magnetic field equations that have been cast in the form of Duffing's equation are presented.

  17. Effects of Magnetic Field and FUV Radiation on the Structures of Bright-rimmed Clouds

    CERN Document Server

    Motoyama, Kazutaka; Shang, Hsien; Hasegawa, Tatsuhiko

    2013-01-01

    The bright-rimmed cloud SFO 22 was observed with the 45 m telescope of Nobeyama Radio Observatory in the ^{12}CO (J = 1-0), ^{13}CO (J = 1-0), and C^{18}O (J = 1-0) lines, where well-developed head-tail structure and small line widths were found. Such features were predicted by radiation-driven implosion models, suggesting that SFO 22 may be in a quasi-stationary equilibrium state. We compare the observed properties with those from numerical models of a photo-evaporating cloud, which include effects of magnetic pressure and heating due to strong far-ultraviolet (FUV) radiation from an exciting star. The magnetic pressure may play a more important role in the density structures of bright-rimmed clouds, than the thermal pressure that is enhanced by the FUV radiation. The FUV radiation can heat the cloud surface to near 30 K, however, its effect is not enough to reproduce the observed density structure of SFO 22. An initial magnetic field of 5 \\mu G in our numerical models produces the best agreement with the ob...

  18. Probing the surface magnetic field structure in RX J1856.5-3754

    CERN Document Server

    Popov, S B; Turolla, R

    2016-01-01

    The evolution of magnetic field in isolated neutron stars is one of the most important ingredients in the attempt to build a unified description of these objects. A prediction of field evolution models is the existence of an equilibrium configuration, in which the Hall cascade vanishes. Recent calculations have explored the field structure in this stage, called the Hall attractor. We use X-ray data of near-by, cooling neutron stars to probe this prediction, as these sources are surmised to be close to or at Hall attractor phase. We show that the source RX J1856.5-3754 might be closer to the attractor than other sources of its class. Our modelling indicates that the properties of surface thermal emission, assuming that the star is in the Hall attractor, are in contradiction with the spectral data of RX J1856.5-3754.

  19. Aligned Solidification Structure of the MnBi Phase in Semisolidified Bi-Mn Alloy with a Static Magnetic Field

    Institute of Scientific and Technical Information of China (English)

    Zhongming REN; Hui WANG; Kang DENG; Kuangdi XU

    2004-01-01

    The solidification structure of Bi-3 wt pct Mn alloy grown up in the semisolid zone under the influence of a static magnetic field (up to 1.0 T) and the relation of the magnetic property with the solidification structure have been investigated experimentally. It was shown that the primary phase MnBi crystals in the alloy aligned and oriented along the direction of the applied magnetic field. The orientating tendency and the average length of the elongated MnBi crystals increased with the increase of the applied field and the solidification time. Moreover, the remanence of the alloy along the aligned direction of the MnBi phase in the case of solidification with a magnetic field was apparently anisotropic and nearly double of that without the magnetic field. This indicated that the MnBi crystals oriented and aligned along their easy magnetization axis. A model was proposed to explain the alignment and orientation growth of the MnBi crystals in a magnetic field in terms of the magnetic anisotropy of the crystals and the magnetic interaction between them.

  20. Hydrodynamic structures generated by a rotating magnetic field in a cylindrical vessel

    Energy Technology Data Exchange (ETDEWEB)

    Zibold, A F, E-mail: zibold@mail.donbass.com [Artiom str., 127/54, Donetsk, Ukraine, 83001 (Ukraine)

    2015-02-01

    The hydrodynamic structures arising in a cylinder under the influence of a rotating magnetic field were considered, and the stability of a primary stationary flow in an infinitely long cylinder was investigated by linear approximation. The curves of neutral stability were obtained for a wide range of flow parameters and the calculations generated a single-vortex (in the radial direction) structure of Taylor’s vortices. The flow stability in the infinitely long cylinder was evaluated based on energy balance. The problem of three-dimensional stationary flow of a viscous incompressible conducting liquid induced by a rotating magnetic field in a cylindrical vessel of limited length was solved using an iteration method. The values of the parameters were found for which the iterative process still converges. Numerical experiment made it possible to investigate the arising spatial flow patterns and to track their evolution with changes in the flow parameters. Results of modelling showed the appearance of a three-dimensional structure of Taylor-type vortices in the middle portion of a sufficiently long vessel. The appearance of a double laminar boundary layer was demonstrated under certain conditions of azimuthal velocity distribution along the vessel height at the location of the end-wave vortex. (paper)

  1. Near-infrared Imaging Polarimetry of GGD 27: Circular Polarization and Magnetic Field Structures

    Science.gov (United States)

    Kwon, Jungmi; Tamura, Motohide; Hough, James H.; Nagata, Tetsuya; Kusakabe, Nobuhiko; Saito, Hiro

    2016-06-01

    Near-infrared imaging polarimetry in the J, H, and K s bands was carried out for GGD 27 in the dark cloud Lynds 291. Details of an infrared reflection nebula associated with the optical nebulosity GGD 27 and the infrared nebula GGD 27 IRS are presented. Aperture photometry of 1263 point-like sources, detected in all three bands, was used to classify them based on a color-color diagram, and the linear polarization of several hundred sources was determined, with the latter used to map the magnetic field structure around GGD 27. This field, around GGD 27 IRS, appears to be associated with the extended CO outflow of IRAS 18162-2048 however, there are partly distorted or bent components in the field. The Chandrasekhar-Fermi method gives an estimate of the magnetic field strength as ˜90 μG. A region associated with GGD 27 IRS is discovered to have a circular polarization in the range of ˜2%-11% in the K s band. The circular polarization has an asymmetric positive/negative pattern and extends out to ˜ 120″ or 1.0 pc. The circular and linear polarization patterns are explained as resulting from a combination of dense inner and fainter outer lobes, suggesting episodic outflow.

  2. Comparing Herschel dust emission structures, magnetic fields observed by Planck, and dynamics: high-latitude star forming cloud L1642

    Science.gov (United States)

    Malinen, Johanna

    2016-01-01

    The nearby high-latitude cloud L1642 is one of only two known very high latitude (|b| > 30 deg) clouds actively forming stars. This cloud is a rare example of star formation in isolated conditions, and can reveal important details of star formation in general, e.g., of the effect of magnetic fields. We compare Herschel dust emission structures and magnetic field orientation revealed by Planck polarization maps in L1642, and also combine these with dynamic information from molecular line observations. The high-resolution Herschel data reveal a complex structure including a dense, compressed central blob with elongated extensions, low density striations, "fishbone" like structures with a spine and perpendicular striations, and a spiraling "tail". The Planck polarization data reveal an ordered magnetic field that pervades the cloud and is aligned with the surrounding low density striations. We show that there is a complex interplay between the cloud structure and large scale magnetic fields revealed by Planck polarization data at 10' resolution. This suggests that the magnetic field is closely linked to the formation and evolution of the cloud. We see a clear transition from aligned to perpendicular structures approximately at a column density of NH = 2x10^21 cm-2. We conclude that Planck polarization data revealing the large scale magnetic field orientation can be very useful even when comparing to the finest structures in higher resolution data, e.g. Herschel at ~18" resolution.

  3. Magnetic field structure in accretion columns on HMXB and effects on CRSF

    Directory of Open Access Journals (Sweden)

    Mukherjee Dipanjan

    2014-01-01

    Full Text Available In accreting neutron star binaries, matter is channelled by the magnetic fields from the accretion disc to the poles of neutron stars forming an accretion mound. We model such mounds by numerically solving the Grad-Shafranov equation for axisymmetric static MHD equilibria. From our solutions we infer local distortion of field lines due to the weight of accreted matter. Variation in mass loading at the accretion disc will alter the shape of the accretion mound which will also affect the local field distortion. From simulations of cyclotron resonance scattering features from HMXBs, we conclude that local field distortion will greatly affect the shape and nature of the CRSF. From phase resolved spectral analysis one can infer the local field structure and hence the nature of mass loading of field lines at the accretion disc. We also study the stability of such mounds by performing MHD simulations using the PLUTO MHD code. We find that pressure and gravity driven instabilities depend on the total mass accreted and the nature of mass loading of the field lines.

  4. Effect of magnetic field on the crystalline structure of magnetostrictive TbFe2 alloy solidified unidirectionally in microgravity.

    Science.gov (United States)

    Okutani, Takeshi; Nakata, Yoshinori; Nagai, Hideaki

    2004-11-01

    We performed unidirectional solidification experiments on TbFe(2) alloy in a static magnetic field in microgravity of 10(-4) g for 10 sec obtained by a 490 m free fall of the Japan microgravity center (JAMIC). When the magnetic field strength was increased from zero to 4.5 x 10(-2) T during unidirectional solidification in microgravity, a [1 1 1] crystallographic alignment dominated, and the maximum magnetostriction constant increased from 1,000 ppm to 4,000 ppm. For unidirectional solidification in normal gravity, the maximum magnetostriction constant remained at 2,000 ppm with increasing magnetic field. The columnar structure grows and orients along the magnetic field. TbFe(2) crystals grow in microgravity predominantly in the same direction as the magnetic field.

  5. Probing the magnetic field structure in Sgr A* on Black Hole Horizon Scales with Polarized Radiative Transfer Simulations

    CERN Document Server

    Gold, Roman; Johnson, Michael D; Doeleman, Sheperd S

    2016-01-01

    Magnetic fields are believed to drive accretion and relativistic jets in black hole accretion systems, but the magnetic-field structure that controls these phenomena remains uncertain. We perform general relativistic (GR) polarized radiative transfer of time-dependent three-dimensional GR magnetohydrodynamical (MHD) simulations to model thermal synchrotron emission from the Galactic Center source Sagittarius A$^\\ast$ (Sgr A*). We compare our results to new polarimetry measurements by the Event Horizon Telescope (EHT) and show how polarization in the visibility (Fourier) domain distinguishes and constrains accretion flow models with different magnetic field structures. These include models with small-scale fields in disks driven by the magnetorotational instability (MRI) as well as models with large-scale ordered fields in magnetically-arrested disks (MAD). We also consider different electron temperature and jet mass-loading prescriptions that control the brightness of the disk, funnel-wall jet, and Blandford-...

  6. Temperature and Magnetic Field Driven Modifications in the I-V Features of Gold-DNA-Gold Structure

    Directory of Open Access Journals (Sweden)

    Nadia Mahmoudi Khatir

    2014-10-01

    Full Text Available The fabrication of Metal-DNA-Metal (MDM structure-based high sensitivity sensors from DNA micro-and nanoarray strands is a key issue in their development. The tunable semiconducting response of DNA in the presence of external electromagnetic and thermal fields is a gift for molecular electronics. The impact of temperatures (25–55 °C and magnetic fields (0–1200 mT on the current-voltage (I-V features of Au-DNA-Au (GDG structures with an optimum gap of 10 μm is reported. The I-V characteristics acquired in the presence and absence of magnetic fields demonstrated the semiconducting diode nature of DNA in GDG structures with high temperature sensitivity. The saturation current in the absence of magnetic field was found to increase sharply with the increase of temperature up to 45 °C and decrease rapidly thereafter. This increase was attributed to the temperature-assisted conversion of double bonds into single bond in DNA structures. Furthermore, the potential barrier height and Richardson constant for all the structures increased steadily with the increase of external magnetic field irrespective of temperature variations. Our observation on magnetic field and temperature sensitivity of I-V response in GDG sandwiches may contribute towards the development of DNA-based magnetic sensors.

  7. Observations of the field-aligned residual flow inside magnetic cloud structure

    Institute of Scientific and Technical Information of China (English)

    LI HuiJun; FENG XueShang; ZUO PingBing; XIE YanQiong

    2009-01-01

    In this paper, we report two MC events observed by WIND spacecraft with good examples of field-aligned residual flow inside the MC structure. For both events, the co-moving frames are determined through the deHoffman-Teller (HT) analysis and the axial orientations are inferred by the newly devel-oped minimal residue (MR) method. The nature coordinate system for both events are constructed with velocity of the HT frame and the inferred MC axis, the field and flow remaining in the HT frame are analyzed st this coordinate system. As a result, we find that the residual flows in the co-moving HT frame of the two MC events are almost anti-parallel to the helical magnetic field. We speculate that the field-aligned residual flows are large scale coherent hydrodynamic vortices co-moving with the MCs at the supersonic speed near 1 AU. Data analyses show that the event in slow ambient solar wind is ex- panding at 1 AU and another one in fast solar wind does not show apparent expansion. Proton behav-iors for both events are quasi-isothermal. Accelerated HT analysis shows that both events have no suitable HT frame with constant accelerations, which suggests that both events may be moving at the constant speed near 1 AU under the assumptions of the HT analysis. For both events, the ratio of the dynamic pressure to the magnetic pressure is larger than that of the thermal pressure to magnetic pressure, which suggests that the dynamic effects due to the plasma flows remaining in the co-moving HT frame are more important than the thermal effects in the study of MC evolution and propagation.

  8. Dipolar structures in magnetite ferrofluids studied with small-angle neutron scattering with and without applied magnetic field

    NARCIS (Netherlands)

    Klokkenburg, M.; Erne, B.H.; Wiedenmann, A.; Petukhov, A.V.; Philipse, A.P.

    2007-01-01

    Field-induced structure formation in a ferrofluid with well-defined magnetite nanoparticles with a permanent magnetic dipole moment was studied with small-angle neutron scattering (SANS) as a function of the magnetic interactions. The interactions were tuned by adjusting the size of the well-defined

  9. Dipolar structures in magnetite ferrofluids studied with small-angle neutron scattering with and without applied magnetic field

    NARCIS (Netherlands)

    Klokkenburg, M.; Erne, B.H.; Wiedenmann, A.; Petukhov, A.V.; Philipse, A.P.

    2007-01-01

    Field-induced structure formation in a ferrofluid with well-defined magnetite nanoparticles with a permanent magnetic dipole moment was studied with small-angle neutron scattering (SANS) as a function of the magnetic interactions. The interactions were tuned by adjusting the size of the well-defined

  10. Electronic structure and trajectory control of Dirac fermions in graphene ribbons under the competition between electric and magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Mou, E-mail: yangmou1222@gmail.com [Laboratory of Quantum Information Technology, School of Physics and Telecommunication Engineering, South China Normal University, Guangzhou 510006 (China); Cui, Yan; Wang, Rui-Qiang; Zhao, Hong-Bo [Laboratory of Quantum Information Technology, School of Physics and Telecommunication Engineering, South China Normal University, Guangzhou 510006 (China)

    2012-03-05

    We investigate the electronic structure of graphene ribbons under the competition between lateral electric and normal magnetic fields. The squeezing of quantum level spacings caused by either field is studied. Based on the knowledge of the dispersion under both fields, we analyze the electronic trajectories near the junctions of different electric and magnetic fields configurations. The junctions can split and join electron beams, and the conductance is quite robust against disorder near the junction interfaces. These junction devices can be used as bricks for building more complicated interference devices. -- Highlights: ► Unified physical picture of graphene ribbon under electric and magnetic fields is provided. ► Squeezing of level spacings caused by electric and magnetic fields is investigated. ► Graphene devices for electron beam split and joint are proposed.

  11. Synthesis of highly magnetic iron nanoparticles suitable for field-structuring using a b-diketone surfactant.

    Energy Technology Data Exchange (ETDEWEB)

    Martin, James Ellis; Patel, Rina J.; Huber, Dale L.; Provencio, Paula Polyak; Venturini, Eugene Leo

    2003-06-01

    We describe the synthesis of highly magnetic iron nanoparticles using a novel surfactant, a {beta}-diketone. We have produced 6 nm iron nanoparticles with an unusually high saturation magnetization of more than 80% the value of bulk iron. Additionally, we measured a particle susceptibility of 14 (MKS units), which is far above the value possible for micron-scale spherical particles. These properties will allow for formation of composites that can be highly structured by magnetic fields.

  12. The Juno Magnetic Field Investigation

    DEFF Research Database (Denmark)

    Connerney, J. E. P.; Benn, Mathias; Bjarnø, Jonas Bækby

    2017-01-01

    The Juno Magnetic Field investigation (MAG) characterizes Jupiter’s planetary magnetic field and magnetosphere, providing the first globally distributed and proximate measurements of the magnetic field of Jupiter. The magnetic field instrumentation consists of two independent magnetometer sensor ...

  13. Structures and magnetic properties of Fe-Si-O films RF-sputtered in a high magnetic field

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    We have investigated the effects of high magnetic fields on the microstructures and magnetic properties of Fe-Si-O films deposited by RF sputtering. Three typical sample appearances,hole-in-center,phase-separation and hybridization were obtained for the Fe-Si-O films prepared in the oxygen-argon flow ratio VO2/Vtotal<1.0%,magnetic field Bappl≤1.0 T regime,indicating that not only the dis-tribution of plasma but also the angular distribution of sput-tered atoms are influenced by a high magnetic field. In the oxygen-argon flow ratio VO2/Vtotal>2.0%,magnetic field Bappl≥2.0 T regime,strong (110) orientation of Fe3O4 grains and larger remanence and coercivity measured in the direction normal to the film plane appeared in the Fe-Si-O films. This result indicates that the high magnetic fields not only orient the Fe-Si-O film but also induce remarkable perpendicular magnetic anisotropy during the deposition.

  14. Magnetic field structure of IC 63 and IC 59 associated with H II region Sh 185

    Science.gov (United States)

    Soam, A.; Maheswar, G.; Lee, Chang Won; Neha, S.; Andersson, B.-G.

    2017-02-01

    Bright-rimmed clouds (BRCs) are formed at the periphery of H II regions as the radiation from the central star interacts with dense gas. The ionization and resulting compression of the clouds may lead to cloud disruption causing secondary star formation depending on the stellar and gas parameters. Here we use R-band polarimetry to probe the plane-of-the sky magnetic field for two nearby BRCs, IC 59 and IC 63. Both nebulae are illuminated by γ Cas with the direction of the ionizing radiation being orientated parallel or perpendicular to the local magnetic field, allowing us to probe the importance of magnetic field pressure in the evolution of BRCs. Because of the proximity of the system (˜200 pc), we have acquired a substantial sample of over 500 polarization measurements for stars that form the background to the nebulae. On large scales, the magnetic field geometries of both clouds are anchored to the ambient magnetic field. For IC 63, the magnetic field is aligned parallel to the head-tail morphology of the main condensation, with a convex morphology relative to the direction of the ionizing radiation. We estimate the plane-of-the-sky magnetic field strength in IC 63 to be ˜ 90 μG. In IC 59, the projected magnetic field follows the M-shape morphology of the cloud. Here, field lines present a concave shape with respect to the direction of the ionizing radiation from γ Cas. Comparing our observations to published theoretical models, we find good general agreement, supporting the importance of magnetic fields in BRC evolution.

  15. Observations of the field-aligned residual flow inside magnetic cloud structure

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    In this paper,we report two MC events observed by WIND spacecraft with good examples of fieldaligned residual flow inside the MC structure. For both events,the co-moving frames are determined through the deHoffman-Teller (HT) analysis and the axial orientations are inferred by the newly developed minimal residue (MR) method. The nature coordinate system for both events are constructed with velocity of the HT frame and the inferred MC axis,the field and flow remaining in the HT frame are analyzed at this coordinate system. As a result,we find that the residual flows in the co-moving HT frame of the two MC events are almost anti-parallel to the helical magnetic field. We speculate that the field-aligned residual flows are large scale coherent hydrodynamic vortices co-moving with the MCs at the supersonic speed near 1 AU. Data analyses show that the event in slow ambient solar wind is expanding at 1 AU and another one in fast solar wind does not show apparent expansion. Proton behaviors for both events are quasi-isothermal. Accelerated HT analysis shows that both events have no suitable HT frame with constant accelerations,which suggests that both events may be moving at the constant speed near 1 AU under the assumptions of the HT analysis. For both events,the ratio of the dynamic pressure to the magnetic pressure is larger than that of the thermal pressure to magnetic pressure,which suggests that the dynamic effects due to the plasma flows remaining in the co-moving HT frame are more important than the thermal effects in the study of MC evolution and propagation.

  16. Determination of the zero-field magnetic structure of the helimagnet MnSi at low temperature

    Science.gov (United States)

    Dalmas de Réotier, P.; Maisuradze, A.; Yaouanc, A.; Roessli, B.; Amato, A.; Andreica, D.; Lapertot, G.

    2016-04-01

    Below a temperature of approximately 29 K the manganese magnetic moments of the cubic binary compound MnSi order to a long-range incommensurate helical magnetic structure. Here we quantitatively analyze a high-statistic zero-field muon spin rotation spectrum recorded in the magnetically ordered phase of MnSi by exploiting the result of representation theory as applied to the determination of magnetic structures. Instead of a gradual rotation of the magnetic moments when moving along a axis, we find that the angle of rotation between the moments of certain subsequent planes is essentially quenched. It is the magnetization of pairs of planes which rotates when moving along a axis, thus preserving the overall helical structure.

  17. Inoculation of pure aluminium structure with Ti + B addition in impulse magnetic field

    Directory of Open Access Journals (Sweden)

    J. Szajnar

    2005-12-01

    Full Text Available Purpose: The main aim of investigations was the reduction of grain size and unification of structure for clean metal casting by introduction of small amount of inoculant with impulse magnetic field.Design/methodology/approach: Experimental plan was planed on the basis of statistical factor design on two levels for three variables (pouring parameters. The equiaxed crystals zone content was calculated by computer program to processing and image analysis after metallographic research.Findings: The results of study show relationship between area of equiaxial zone and pouring parameters.Research limitations/implications: Towards lack of resolute relations between casting parameters and structure was selected statistical analysis to determine these relations using stepwise regression. Practical implications: The work presents refinement of structure methods which are particularly important in continuous and semi-continuous casting where products are used for plastic forming. Large columnar crystals zone result in forces extrusion rate reduction and during the ingot rolling delamination of external layers can occur.Originality/value: The value of this paper resides in coupling of two refinement of structure methods. The first method is internal factor - inoculation with Ti+B and the second method is external factor - influence of electromagnetic field on crystallization process.

  18. Properties of the prominence magnetic field and plasma distributions as obtained from 3D whole-prominence fine structure modeling

    Science.gov (United States)

    Gunár, S.; Mackay, D. H.

    2016-07-01

    Aims: We analyze distributions of the magnetic field strength and prominence plasma (temperature, pressure, plasma β, and mass) using the 3D whole-prominence fine structure model. Methods: The model combines a 3D magnetic field configuration of an entire prominence, obtained from non-linear force-free field simulations, with a detailed semi-empirically derived description of the prominence plasma. The plasma is located in magnetic dips in hydrostatic equilibrium and is distributed along multiple fine structures within the 3D magnetic model. Results: We show that in the modeled prominence, the variations of the magnetic field strength and its orientation are insignificant on scales comparable to the smallest dimensions of the observed prominence fine structures. We also show the ability of the 3D whole-prominence fine structure model to reveal the distribution of the prominence plasma with respect to its temperature within the prominence volume. This provides new insights into the composition of the prominence-corona transition region. We further demonstrate that the values of the plasma β are small throughout the majority of the modeled prominences when realistic photospheric magnetic flux distributions and prominence plasma parameters are assumed. While this is generally true, we also find that in the region with the deepest magnetic dips, the plasma β may increase towards unity. Finally, we show that the mass of the modeled prominence plasma is in good agreement with the mass of observed non-eruptive prominences.

  19. Organic magnetic field sensor

    Energy Technology Data Exchange (ETDEWEB)

    McCamey, Dane; Boehme, Christoph

    2017-01-24

    An organic, spin-dependent magnetic field sensor (10) includes an active stack (12) having an organic material with a spin-dependence. The sensor (10) also includes a back electrical contact (14) electrically coupled to a back of the active stack (12) and a front electrical contact (16) electrically coupled to a front of the active stack (12). A magnetic field generator (18) is oriented so as to provide an oscillating magnetic field which penetrates the active stack (12).

  20. Interaction of optical phonons with magnons in orthorhombic crystals. Effect of a magnetic field on structural phase transitions

    Science.gov (United States)

    Men'shenin, V. V.

    2007-05-01

    Interaction of polar optical phonons with magnons in manganates RMn2O5 (where R is a rare-earth ion) has been studied in the approximation of collinear antiferromagnetic ordering of manganese sublattices. It is shown that such interaction takes place only in multisublattice antiferromagnets in which exchange magnetic structures exist that are both even and odd with respect to space inversion. Effect of a magnetic field on the structural phase transitions in these oxides is analyzed.

  1. Assembly of alginate microfibers to form a helical structure using micromanipulation with a magnetic field

    Science.gov (United States)

    Sun, Tao; Huang, Qiang; Shi, Qing; Wang, Huaping; Hu, Chengzhi; Li, Pengyun; Nakajima, Masahiro; Fukuda, Toshio

    2016-10-01

    Helical structures assembled using alginate microfibers have a promising spatial architecture mimicking in vivo vessels for culturing vascular cells. However, the helical structure can only be assembled at the macroscale, since a microassembly-based approach has not yet been developed. In this paper, we propose a magnetic-field-based micromanipulation method to fabricate a helical microstructure. By microfluidic spinning, alginate microfibers encapsulating magnetic nanoparticles are synthesized to enable the control of an electromagnetic needle (EMN). We developed a microrobotic system to actuate a micropipette to fix a free end of the microfiber, and then move the EMN to reel the microfiber around a micropillar. The motion of the EMN is guided using an upright microscope and a side-view camera. Because of the limitation of operation space, a spacer sleeve was designed to keep the tip of the EMN attracted to the microfiber, and simultaneously to keep the other part of the EMN isolated from the microfiber. To ensure the availability of the microfiber for continuously coiling, we enable the EMN tip to slide on the surface of the microfiber without changing the tensioning of the microfiber for positioning control. Furthermore, stable and repeatable micromanipulation was achieved to form multi-turn microfiber coils based on the motion planning of the EMN. Finally, we successfully fabricated a helical microstructure that can be applied in vascular tissue engineering in the future.

  2. Formation of structure and crystallographic texture in Fe-50%Ni thin tapes under high magnetic field annealing

    Energy Technology Data Exchange (ETDEWEB)

    Gervasyeva, I.V., E-mail: gervasy@imp.uran.ru [Institute of Metal Physics, Ural Division, Russian Academy of Sciences, 620990 Ekaterinburg (Russian Federation); Beaugnon, E. [National Laboratory of High Magnetic Field, CNRS, B.P. 166 38042, Grenoble cedex 9 (France); Milyutin, V.A.; Volkova, E.G.; Rodionov, D.P.; Khlebnikova, Yu.V. [Institute of Metal Physics, Ural Division, Russian Academy of Sciences, 620990 Ekaterinburg (Russian Federation); Shishkin, D.A. [Institute of Metal Physics, Ural Division, Russian Academy of Sciences, 620990 Ekaterinburg (Russian Federation); Institute of Natural Sciences, Ural Federal University, 620083 Ekaterinburg (Russian Federation)

    2015-07-15

    For the first time the influence of a high direct current (DC) magnetic field on the structure and texture formation in tapes of Ni{sub 48.8}Fe{sub 51.2} alloy was investigated. Cube texture formation was studied in tapes after cold rolling to 98.8% and annealing in a high magnetic field up to 20 T. Samples were subjected to magnetic annealing below and above the Curie point. Structure and texture were studied using electron backscatter diffraction (EBSD) technique, transmission electron microscopy, and magnetic hysteresis loops measurements. The experiments show a significant increase of the {001}±10° volume fraction in the recrystallization texture with the main orientation {100}〈001〉, when the magnetic annealing is carried out at a temperature below the Curie point.

  3. Evolution of views on the structure of the ambipolar electric field in toroidal magnetic confinement systems

    Energy Technology Data Exchange (ETDEWEB)

    Kovrizhnykh, L. M., E-mail: lmkov@fpl.gpi.ru [Russian Academy of Sciences, Prokhorov General Physics Institute (Russian Federation)

    2015-12-15

    Various methods of determining the ambipolar electric field in toroidal magnetic systems (predominantly, in stellarators) and the evolution of views on this problem are discussed. Paradoxes encountered in solving this problem are analyzed, and ways of resolving them are proposed.

  4. Fractal Nature of the Electronic Structure of a Penrose Tiling Lattice in a Magnetic Field

    Science.gov (United States)

    Hatakeyama, Tetsuo; Kamimura, Hiroshi

    1989-01-01

    The one-electron energy spectrum of a Penrose tiling lattice in a magnetic field is studied with a tight-binding Hamiltonian. We show the following remarkable results characteristic of a Penrose lattice. (1) The density of states in a magnetic field has a central peak with zero width at zero energy. It is shown that the zero-energy states correspond to the ring states in which wavefunction has nonvanishing amplitudes only at the sites circling the origin. (2) The magnetic field dependence of the energy spectrum shows a butterfly shape caused by Landau quantization. (3) The magnetic field dependence of the energy spectrum also shows a fractal nature. In particular it is characterized by two periods whose ratio is equal to the golden mean (1+\\sqrt{5})/2, and two periods comprising a Fibonacci sequence. We have clarified the origin of this fractal behavior of the energy spectrum analytically.

  5. Gravity and magnetic field and tectonic structure character in the southern Yellow Sea

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The research of the geophysical survey in the east of the southern Yellow Sea (SYS) (122°-125°E) in 1999 reveals that the SYS has a structure of three-uplifts and two-basins. The structure can be well concordant with the gravity and magnetic anomalies. In the basins, most of the gravity and magnetic anomalies are low and gentle. As well in the uplifts, the gravity anomalies are high positive ones, but the magnetic anomalies are plus and minus variant ones. Seismic data show that the mid-uplift is a Cenozoic one. The Paleozoic is under the Q+N strata, the thickness of which is less than 1 km, with no Palaeogene. The Wunansha uplift area and the Sunan uplift area have good continuity, which indicates that they belong to the same geological unit. The basin in the northern part of SYS, which developed in the late Cretaceous period, is a Cenozoic one mainly made up of Cenozoic sediment. On the contrary, the basin in the southern part is the seaward extension of Subei basin and is a medial Cenozoic sediment basin mainly made up of Cenozoic sediment. Because of the striking left-lateral sense translation of Tanlu fault zone, the east plate of fault zone moved northward on a large scale, which generated a massive north-south pull-apart stress field to make the earth crust pulled apart, revolved and tilted, and the pulling-apart basin came into being in the upper part of the crust.

  6. Gravity and magnetic field and tectonic structure character in the southern Yellow Sea

    Institute of Scientific and Technical Information of China (English)

    LlANGRuicai; PEIYanliang; ZHENGYanpeng; WEIJianwei; LIUYanguang

    2003-01-01

    The research of the geophysical survey in the cast of the southern Yellow Sea (SYS) (122°-125°E) in 1999 reveals that the SYS has a structure of three-uplifts and two-basins. The structure can be well concordant with the gravity and magnetic anomalies. In the basins, most of the gravity and magnetic anomalies are low and gentle. As well in the uplifts, the gravity anomalies are high positive ones,but the magnetic anomalies are plus and minus variant ones.Seismic data show that the mid-uplift is a Cenozoic one. The Paleozoic is under the Q+N strata, the thickness of which is less than 1 km, with no Palaeogene. The Wunansha uplift area and the Sunan uplift area have good continuity, which indicates that they belong to the same geological unit. The basin in the northern part of SYS, which developed in the late Cretaceous period, is a Cenozoic one mainly made up of Cenozoic sediment. On the contrary, the basin in the southern part is the seaward extension of Subei basin and is a medial Cenozoic sediment basin mainly made up of Cenozoic sediment. Because of the striking left-lateral sense translation of Tanlu fault zone, the east plate of fault zone moved northward on a large scale, which generated a massive north-south pull-apart stress field to make the earth crust pulled apart, revolved and tilted, and the pulling-apart basin came into being in the upper part of the crust.

  7. Magneto-Structural Properties of Ni2MnGa Ferromagnetic Shape Memory Alloy in Magnetic Fields

    Directory of Open Access Journals (Sweden)

    Takuo Sakon

    2013-05-01

    Full Text Available The purpose of this review was to investigate the correlation between magnetism and crystallographic structures as it relates to the martensite transformation of Ni2MnGa type alloys, which undergo martensite transformation below the Curie temperature. In particular, this paper focused on the physical properties in magnetic fields. Recent researches show that the martensite starting temperature (martensite transformation temperature TM and the martensite to austenite transformation temperature (reverse martensite temperature TR of Fe, Cu, or Co-doped Ni–Mn–Ga ferromagnetic shape memory alloys increase when compared to Ni2MnGa. These alloys show large field dependence of the martensite transformation temperature. The field dependence of the martensite transformation temperature, dTM/dB, is −4.2 K/T in Ni41Co9Mn32Ga18. The results of linear thermal strain and magnetization indicate that a magneto-structural transition occurred at TM and magnetic field influences the magnetism and also the crystal structures. Magnetocrystalline anisotropy was also determined and compared with other components of Ni2MnGa type shape memory alloys. In the last section, magnetic field-induced strain and magnetostriction was determined with some novel alloys.

  8. Analysis of the electrolyte convection inside the concentration boundary layer during structured electrodeposition of copper in high magnetic gradient fields.

    Science.gov (United States)

    König, Jörg; Tschulik, Kristina; Büttner, Lars; Uhlemann, Margitta; Czarske, Jürgen

    2013-03-19

    To experimentally reveal the correlation between electrodeposited structure and electrolyte convection induced inside the concentration boundary layer, a highly inhomogeneous magnetic field, generated by a magnetized Fe-wire, has been applied to an electrochemical system. The influence of Lorentz and magnetic field gradient force to the local transport phenomena of copper ions has been studied using a novel two-component laser Doppler velocity profile sensor. With this sensor, the electrolyte convection within 500 μm of a horizontally aligned cathode is presented. The electrode-normal two-component velocity profiles below the electrodeposited structure show that electrolyte convection is induced and directed toward the rim of the Fe-wire. The measured deposited structure directly correlates to the observed boundary layer flow. As the local concentration of Cu(2+) ions is enhanced due to the induced convection, maximum deposit thicknesses can be found at the rim of the Fe-wire. Furthermore, a complex boundary layer flow structure was determined, indicating that electrolyte convection of second order is induced. Moreover, the Lorentz force-driven convection rapidly vanishes, while the electrolyte convection induced by the magnetic field gradient force is preserved much longer. The progress for research is the first direct experimental proof of the electrolyte convection inside the concentration boundary layer that correlates to the deposited structure and reveals that the magnetic field gradient force is responsible for the observed structuring effect.

  9. Phonon structures in the electronic density of states of graphene in magnetic field

    Science.gov (United States)

    Pound, Adam; Carbotte, J. P.; Nicol, E. J.

    2011-06-01

    Unlike in ordinary metals, in graphene, phonon structure can be seen in the quasiparticle electronic density of states, because the latter varies on the scale of the phonon energy. In a magnetic field, quantization into Landau levels creates even more significant variations. We calculate the density of states incorporating electron-phonon coupling in this case and find that the coupling has pronounced new effects: shifting and broadening of Landau levels, creation of new peaks, and splitting of any Landau levels falling near one of the new peaks. Comparing our calculations with a recent experiment, we find evidence for a phonon with energy similar to but somewhat greater than the optical E2g mode and a coupling corresponding to a mass enhancement parameter λsime0.07.

  10. Magnetic field structure of IC 63 and IC 59 associated to H II region - Sh 185

    CERN Document Server

    Soam, A; Lee, Chang Won; Neha, S; Andersson, B-G

    2016-01-01

    Bright-rimmed clouds (BRCs) are formed at the periphery of H$~$II regions as the radiation from the central star interacts with dense gas. The ionization and resulting compression of the clouds may lead to cloud disruption causing secondary star formation depending on the stellar and gas parameters. Here we use R-band polarimetry to probe the plane-of-the sky magnetic field in the two near-by BRCs IC\\,59 and IC\\,63. Both nebulae are illuminated by $\\gamma$ Cas with the direction of ionizing radiation being orientated parallel or perpendicular to the local magnetic field, allowing us to probe the importance of magnetic field pressure in the evolution of BRCs. Because of the proximity of the system ($\\sim$200pc) we have acquired a substantial sample of over 500 polarization measurements for stars background to the nebulae. On large scales, the magnetic field geometries of both clouds are anchored to the ambient magnetic field. For IC 63, the magnetic field is aligned parallel to the head-tail morphology of the ...

  11. Effect of magnetic field on an electronic structure and intraband quantum transitions in multishell quantum dots

    Science.gov (United States)

    Holovatsky, V. A.; Voitsekhivska, O. M.; Yakhnevych, M. Ya.

    2017-09-01

    The electron energy spectrum and wave functions in multishell spherical quantum dot, consisting of core and two spherical shells - potential wells separated by thin potential barriers, are obtained in the framework of the effective mass approximation and single band model. The investigations are performed within the matrix method for the nanostructure driven by magnetic field using the complete set of wave functions obtained without the magnetic field. The electron dipole momentum and oscillator strengths of intraband quantum transitions as functions of the magnetic field induction are numerically calculated. In order to increase the sensibility to magnetic field, the geometric parameters of the shells are chosen in such a way that the electron in the ground state is to be located in outer spherical well, but when the magnetic field induction becomes bigger, it moves into the core. It is shown that size of the middle potential well causes the smooth change of the electron location due to the effect of magnetic field, what is displayed on optical properties of nanostructure. The calculations are performed for multishell quantum dot CdSe/ZnS/CdSe/ZnS/CdSe.

  12. On the scales of structures of the large-scale background magnetic field in the 20th solar cycle.

    Science.gov (United States)

    Makarov, V. I.; Tavastsherna, K. S.

    On the basis of Hα maps two scale distributions of longitudinal structures of the large-scale magnetic field are found at 10 - 40° in both solar hemispheres. One of them is a gaussian distribution for the dimensions from 3 to 15°. These are "islands" of the predominant polarity of the magnetic field. They are outlined by filaments and filament channels and are connected with the appearance of a new magnetic flux. The other is a Pearson curve of type I for 15° to 60° with maximum at 25°. At the equator and latitudes φ > 40° there are no predominant dimensions.

  13. Three-dimensional structure of the magnetic field in the disk of the Milky Way

    Science.gov (United States)

    Ordog, A.; Brown, J. C.; Kothes, R.; Landecker, T. L.

    2017-07-01

    Aims: We present rotation measures (RM) of the diffuse Galactic synchrotron emission from the Canadian Galactic Plane Survey (CGPS) and compare them to RMs of extragalactic sources in order to study the large-scale reversal in the Galactic magnetic field (GMF). Methods: Using Stokes Q, U and I measurements of the Galactic disk collected with the Synthesis Telescope at the Dominion Radio Astrophysical Observatory, we calculate RMs over an extended region of the sky, focusing on the low longitude range of the CGPS (ℓ = 52° to ℓ = 72°). Results: We note the similarity in the structures traced by the compact sources and the extended emission and highlight the presence of a gradient in the RM map across an approximately diagonal line, which we identify with the well-known field reversal of the Sagittarius-Carina arm. We suggest that the orientation of this reversal is a geometric effect resulting from our location within a GMF structure arising from current sheets that are not perpendicular to the Galactic plane, as is required for a strictly radial field reversal, but that have at least some component parallel to the disk. Examples of models that fit this description are the three-dimensional dynamo-based model of Gressel et al. (2013, A&A, 560, A93) and a Galactic scale Parker spiral (Akasofu & Hakamada 1982, ApJ, 253, 552), although the latter may be problematic in terms of Galactic dynamics. Conclusions: We emphasize the importance of constructing three-dimensional models of the GMF to account for structures like the diagonal RM gradient observed in this dataset.

  14. Aligned Structures of Fe3O4 Nanoparticles in a Curable Polymer Carrier Induced by a Magnetic Field

    Institute of Scientific and Technical Information of China (English)

    FANG Wen-Xiao; HE Zhen-Hui; XU Xue-Qing; SHEN Hui

    2005-01-01

    @@ To understand the interaction in dipolar systems, it is necessary to investigate the structures formed by the interacting particles. We introduce a polymer acrylic resin carrier to fix the structures in the magnetic fluid(Fe3O4). An aligned structure is investigated, which is formed under a magnetic field, and fixed in the cured acrylic resin film by evaporating the solvent at room temperature. The aligned structure is confirmed with the help of optical microscopy and optical diffraction for the cured film. Furthermore, we find substructures by using a scanning electronic microscope. Based on the curable and observable structures, a platform can be developed for investigating the aligned structures and configurations dominant by dipolar interaction. This is also helpful for the development of magnetic devices with orderly aligned structures.

  15. Structure of magneto-Keplerian discs: an analytical solution for thin accretion discs threatened by stellar magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Kaburaki, O.

    1986-05-15

    The structure of Keplerian discs which are threaded by the magnetic field lines of each central star are considered. Under the assumptions of thin discs, stationarity and of axisymmetry, a fairly simple analytical solution is found. In such a disc, the electromagnetic force does not play any important role in the radial force balance, but it is this force that maintains the disc structure in the latitudinal direction. As suggested by previous authors, the angular momentum transfer is controlled by the global structure of the magnetic field. In contrast to their results, however, the present solution does not predict the switching of the azimuthal component of the magnetic field as a function of the radial distance in the disc.

  16. Full 3-D MHD calculations of accretion flow Structure in magnetic cataclysmic variable stars with strong and complex magnetic fields

    CERN Document Server

    Zhilkin, A G; Mason, P A; 10.1134/S1063772912040087

    2012-01-01

    We performed 3D MHD calculations of stream accretion in cataclysmic variable stars for which the white dwarf primary star possesses a strong and complex magnetic field. These calculations are motivated by observations of polars; cataclysmic variables containing white dwarfs with magnetic fields sufficiently strong to prevent the formation of an accretion disk. So an accretion stream flows from the L1 point and impacts directly onto one or more spots on the surface of the white dwarf. Observations indicate that the white dwarf, in some binaries, possesses a complex (non-dipolar) magnetic field. We perform simulations of 10 polars or equivalently one asynchronous polar at 10 different beat phases. Our models have an aligned dipole plus quadrupole magnetic field centered on the white dwarf primary. We find that for a sufficiently strong quadrupole component an accretion spot occurs near the magnetic equator for slightly less than half of our simulations while a polar accretion zone is active for most of the rest...

  17. Magnetic fields in ring galaxies

    CERN Document Server

    Moss, D; Silchenko, O; Sokoloff, D; Horellou, C; Beck, R

    2016-01-01

    Many galaxies contain magnetic fields supported by galactic dynamo action. However, nothing definitive is known about magnetic fields in ring galaxies. Here we investigate large-scale magnetic fields in a previously unexplored context, namely ring galaxies, and concentrate our efforts on the structures that appear most promising for galactic dynamo action, i.e. outer star-forming rings in visually unbarred galaxies. We use tested methods for modelling $\\alpha-\\Omega$ galactic dynamos, taking into account the available observational information concerning ionized interstellar matter in ring galaxies. Our main result is that dynamo drivers in ring galaxies are strong enough to excite large-scale magnetic fields in the ring galaxies studied. The variety of dynamo driven magnetic configurations in ring galaxies obtained in our modelling is much richer than that found in classical spiral galaxies. In particular, various long-lived transients are possible. An especially interesting case is that of NGC 4513 where th...

  18. CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES: Hofstadter's Butterfly and Phase Transition of Checkerboard Superconducting Network in a Magnetic Field

    Science.gov (United States)

    Hou, Jing-Min; Tian, Li-Jim

    2010-03-01

    We study the magnetic effect of the checkerboard superconducting wire network. Based on the de Gennes-Alexader theory, we obtain difference equations for superconducting order parameter in the wire network. Through solving these difference equations, we obtain the eigenvalues, linked to the coherence length, as a function of magnetic field. The diagram of eigenvalues shows a fractal structure, being so-called Hofstadter's butterfly. We also calculate and discuss the dependence of the transition temperature of the checkerboard superconducting wire network on the applied magnetic field, which is related to up-edge of the Hofstadter's butterfly spectrum.

  19. Motions of CMS Detector structures due to the magnetic field forces as observed by the Link Alignment System during the Test of the 4 Tesla Magnet Solenoid

    CERN Document Server

    Calderón, Alicia; González-Sánchez, F J; Martínez-Rivero, C; Matorras, Francisco; Rodrigo, Teresa; Martínez, P; Scodellaro, Luca; Sobrón, M; Vila, Ivan; Virto, A L; Alberdi, Javier; Arce, Pedro; Barcala, Jose Miguel; Calvo, Enrique; Ferrando, Antonio; Josa-Mutuberria, I; Molinero, Antonio; Navarrete, Jose Javier; Oller, Juan Carlos; Yuste, Ceferino

    2008-01-01

    This document describes results obtained from the Link Alignment System data recorded during the CMS Magnet Test. A brief description of the system is followed by the discussion of the detected relative displacements (from micrometres to centimetres) between detector elements and rotations of detector structures (from microradians to milliradians). Observed displacements are studied as functions of the magnetic field intensity. In addition, the reconstructed positions of active element sensors are compared to their positions as measured by photogrammetry and the reconstructed motions due to the magnetic field strength are described.

  20. Motions of CMS detector structures due to the magnetic field forces as observed by the Link alignment system during the test of the 4 T magnet solenoid

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Moral, L.A.; Gomez, G.; Gonzalez-Sanchez, F.J.; Martinez-Rivero, C.; Matorras, F.; Rodrigo, T.; Martinez, P.; Scodellaro, L.; Vila, I.; Virto, A.L. [Instituto de Fisica de Cantabria (IFCA), CSIC-Universidad de Cantabria, Santander (Spain); Sobron, M. [Instituto de Fisica de Cantabria (IFCA), CSIC-Universidad de Cantabria, Santander (Spain)], E-mail: sobron@ifca.unican.es; Alberdi, J.; Arce, P.; Barcala, J.M.; Calvo, E.; Ferrando, A.; Josa, M.I.; Molinero, A.; Navarrete, J.; Oller, J.C. [Centro de Investigaciones Energeticas Medioambientales y Tecnologicas (CIEMAT), Madrid (Spain)] (and others)

    2009-07-21

    This document describes results obtained from the Link alignment system data recorded during the Compact Muon Solenoid (CMS) Magnet Test. A brief description of the system is followed by a discussion of the detected relative displacements (from micrometres to centimetres) between detector elements and rotations of detector structures (from microradians to milliradians). Observed displacements are studied as functions of the magnetic field intensity. In addition, the reconstructed positions of active element sensors are compared to their positions as measured by photogrammetry and the reconstructed motions due to the magnetic field strength are described.

  1. Evolution of the magnetic structure of TbRu{sub 2}Al{sub 10} in applied field

    Energy Technology Data Exchange (ETDEWEB)

    White, R., E-mail: Reyner.White@student.adfa.edu.au [School of Physical, Environmental and Mathematical Sciences, The University of New South Wales, Canberra, ACT, 2600 (Australia); Hutchison, W.D. [School of Physical, Environmental and Mathematical Sciences, The University of New South Wales, Canberra, ACT, 2600 (Australia); Mizushima, T. [Graduate School of Science and Engineering, University of Toyama, Toyama, 930-8555 (Japan); Studer, A.J. [Bragg Institute, Australian Nuclear Science and Technology Organisation, Kirrawee DC, NSW, 2232 (Australia)

    2016-09-15

    TbRu{sub 2}Al{sub 10} is found to undergo two magnetic phase transitions as a function of temperature and three as a function of applied field at low temperature. The Tb{sup 3+} magnetic moments order antiferromagnetically along the c-axis at 15.0(3) K, with an incommensurate sinusoidally modulated structure with a propagation vector of k = (0, 0.759(1), 0). At 6.5(3) K the structure switches to square wave order. Analysis of single crystal TbRu{sub 2}Al{sub 10} has revealed that this square wave structure is altered to a ‘pulse wave’ on application of a 1.30 T magnetic field along the c-axis, with two in fifty of the magnetic moments across the structure changing direction to be aligned parallel with the direction of the field. At 1.85 T a further three moments flip, leading to a duty cycle of 60% and resulting in a total change of one in ten moments from the starting square wave structure. - Highlights: • The magnetic and physical properties of the intermetallic TbRu{sub 2}Al{sub 10} were examined. • TbRu{sub 2}Al{sub 10} was found to order antiferromagnetically at 15.0(3) K. • Neutron powder diffraction revealed sinusoidal magnetic ordering below 15 K. • Single crystal neutron diffraction revealed square wave magnetic order at 2 K. • An applied magnetic field along the c-axis forces the moments into pulse wave order.

  2. Origin of cosmic magnetic fields

    Science.gov (United States)

    Rees, M. J.

    2006-06-01

    The first significant cosmic fields, and the seed field for galactic dynamos probably developed after the formation of the first non-linear structures. The history of star formation and the intergalactic medium is controlled, at least in part, by how and when galaxies and their precursors acquired their fields. The amplification of fields behind shocks, and the diffusivity of the magnetic flux, are crucial to the interpretation of radio sources, gamma ray burst afterglows, and other energetic cosmic phenomena. The build-up of magnetic fields is an important aspect of the overall cosmogonic process.

  3. Planck intermediate results XXXII. The relative orientation between the magnetic field and structures traced by interstellar dust

    DEFF Research Database (Denmark)

    Adam, R.; Ade, P. A. R.; Aghanim, N.;

    2016-01-01

    The role of the magnetic field in the formation of the filamentary structures observed in the interstellar medium (ISM) is a debated topic owing to the paucity of relevant observations needed to test existing models. The Planck all-sky maps of linearly polarized emission from dust at 353 GHz prov...... in the context of models and MHD simulations, which attempt to describe the respective roles of turbulence, magnetic field, and self-gravity in the formation of structures in the magnetized ISM.......The role of the magnetic field in the formation of the filamentary structures observed in the interstellar medium (ISM) is a debated topic owing to the paucity of relevant observations needed to test existing models. The Planck all-sky maps of linearly polarized emission from dust at 353 GHz...... an algorithm to estimate the orientation of the ridges from the dust intensity map. We use analytical models to account for projection effects. Comparing polarization angles on and off the structures, we estimate the mean ratio between the strengths of the turbulent and mean components of the magnetic field...

  4. Study of the internal structure, instabilities, and magnetic fields in the dense Z-pinch

    Energy Technology Data Exchange (ETDEWEB)

    Ivanov, Vladimir V. [Univ. of Nevada, Reno, NV (United States)

    2016-08-17

    Z-pinches are sources of hot dense plasma which generates powerful x-ray bursts and can been applied to various areas of high-energy-density physics (HEDP). The 26-MA Z machine is at the forefront of many of these applications, but important aspects of HEDP have been studied on generators at the 1 MA current level. Recent development of laser diagnostics and upgrade of the Leopard laser at Nevada Terawatt Facility (NTF) give new opportunities for the dense Z-pinch study. The goal of this project is the investigation of the internal structure of the stagnated Z pinch including sub-mm and micron-scale instabilities, plasma dynamics, magnetic fields, and hot spots formation and initiation. New plasma diagnostics will be developed for this project. A 3D structure and instabilities of the pinch will be compared with 3D MHD and spectroscopic modeling and theoretical analysis. The structure and dynamics of stagnated Z pinches has been studied with x-ray self-radiation diagnostics which derive a temperature map of the pinch with a spatial resolution of 70-150 µm. The regular laser diagnostics at 532 nm does not penetrate in the dense pinch due to strong absorption and refraction in trailing plasma. Recent experiments at NTF showed that shadowgraphy at the UV wavelength of 266 nm unfolds a fine structure of the stagnated Z-pinch with unprecedented detail. We propose to develop laser UV diagnostics for Z pinches with a spatial resolution <5 μm to study the small-scale plasma structures, implement two-frame shadowgraphy/interferometry, and develop methods for investigation of strong magnetic fields. New diagnostics will help to understand better basic physical processes in Z pinches. A 3D internal structure of the pinch and characteristic instabilities will be studied in wire arrays with different configurations and compared with 3D MHD simulations and analytical models. Mechanisms of “enhanced heating” of Z-pinch plasma will be studied. Fast dynamics of stagnated

  5. Study of the internal structure, instabilities, and magnetic fields in the dense Z-pinch

    Energy Technology Data Exchange (ETDEWEB)

    Ivanov, Vladimir V. [Univ. of Nevada, Reno, NV (United States)

    2016-08-17

    Z-pinches are sources of hot dense plasma which generates powerful x-ray bursts and can been applied to various areas of high-energy-density physics (HEDP). The 26-MA Z machine is at the forefront of many of these applications but important aspects of HEDP have been studied on generators at the 1 MA current level. Recent development of laser diagnostics and upgrade of the Leopard laser at Nevada Terawatt Facility (NTF) give new opportunities for the dense Z-pinch study. The goal of this project is the investigation of the internal structure of the stagnated Z pinch including sub-mm and micron-scale instabilities, plasma dynamics, magnetic fields, and hot spots formation and initiation. New plasma diagnostics will be developed for this project. A 3D structure and instabilities of the pinch will be compared with 3D MHD and spectroscopic modeling and theoretical analysis. The structure and dynamics of stagnated Z pinches has been studied with x-ray self-radiation diagnostics which derive a temperature map of the pinch with a spatial resolution of 70-150 µm. The regular laser diagnostics at 532 nm does not penetrate in the dense pinch due to strong absorption and refraction in trailing plasma. Recent experiments at NTF showed that shadowgraphy at the UV wavelength of 266 nm unfolds a fine structure of the stagnated Z-pinch with unprecedented detail. We propose to develop laser UV diagnostics for Z pinches with a spatial resolution <5 μm to study the small-scale plasma structures, implement two-frame shadowgraphy/interferometry, and develop methods for investigation of strong magnetic fields. New diagnostics will help to understand better basic physical processes in Z pinches. A 3D internal structure of the pinch and characteristic instabilities will be studied in wire arrays with different configurations and compared with 3D MHD simulations and analytical models. Mechanisms of “enhanced heating” of Z-pinch plasma will be studied. Fast dynamics of stagnated plasma

  6. Probing the Magnetic Field Structure in {Sgr}\\,{\\rm{A}}* on Black Hole Horizon Scales with Polarized Radiative Transfer Simulations

    Science.gov (United States)

    Gold, Roman; McKinney, Jonathan C.; Johnson, Michael D.; Doeleman, Sheperd S.

    2017-03-01

    Magnetic fields are believed to drive accretion and relativistic jets in black hole accretion systems, but the magnetic field structure that controls these phenomena remains uncertain. We perform general relativistic (GR) polarized radiative transfer of time-dependent three-dimensional GR magnetohydrodynamical simulations to model thermal synchrotron emission from the Galactic Center source Sagittarius A* (Sgr A*). We compare our results to new polarimetry measurements by the Event Horizon Telescope (EHT) and show how polarization in the visibility (Fourier) domain distinguishes and constrains accretion flow models with different magnetic field structures. These include models with small-scale fields in disks driven by the magnetorotational instability as well as models with large-scale ordered fields in magnetically arrested disks. We also consider different electron temperature and jet mass-loading prescriptions that control the brightness of the disk, funnel-wall jet, and Blandford–Znajek-driven funnel jet. Our comparisons between the simulations and observations favor models with ordered magnetic fields near the black hole event horizon in Sgr A*, though both disk- and jet-dominated emission can satisfactorily explain most of the current EHT data. We also discuss how the black hole shadow can be filled-in by jet emission or mimicked by the absence of funnel jet emission. We show that stronger model constraints should be possible with upcoming circular polarization and higher frequency (349 GHz) measurements.

  7. MAGNETIC FIELD STRUCTURE OF THE LARGE MAGELLANIC CLOUD FROM FARADAY ROTATION MEASURES OF DIFFUSE POLARIZED EMISSION

    Energy Technology Data Exchange (ETDEWEB)

    Mao, S. A. [National Radio Astronomy Observatory, P.O. Box O, Socorro, NM 87801 (United States); McClure-Griffiths, N. M.; McConnell, D. [Australia Telescope National Facility, CSIRO Astronomy and Space Science, Epping, NSW 1710 (Australia); Gaensler, B. M. [Sydney Institute for Astronomy, School of Physics, University of Sydney, Sydney, NSW 2006 (Australia); Haverkorn, M. [Department of Astrophysics, Radboud University, P.O. Box 9010, 6500-GL Nijmegen (Netherlands); Beck, R. [Max-Planck-Institut fuer Radioastronomie, D-53121 Bonn (Germany); Wolleben, M. [Square Kilometre Array South Africa, The Park, Pinelands 7405 (South Africa); Stanimirovic, S. [Department of Astronomy, University of Wisconsin, Madison, WI 53706 (United States); Dickey, J. M. [Physics Department, University of Tasmania, Hobart, TAS 7001 (Australia); Staveley-Smith, L., E-mail: mao@astro.wisc.edu [International Centre for Radio Astronomy Research (ICRAR), The University of Western Australia, Crawley, WA 6009 (Australia)

    2012-11-01

    We present a study of the magnetic field of the Large Magellanic Cloud (LMC), carried out using diffuse polarized synchrotron emission data at 1.4 GHz acquired at the Parkes Radio Telescope and the Australia Telescope Compact Array. The observed diffuse polarized emission is likely to originate above the LMC disk on the near side of the galaxy. Consistent negative rotation measures (RMs) derived from the diffuse emission indicate that the line-of-sight magnetic field in the LMC's near-side halo is directed coherently away from us. In combination with RMs of extragalactic sources that lie behind the galaxy, we show that the LMC's large-scale magnetic field is likely to be of quadrupolar geometry, consistent with the prediction of dynamo theory. On smaller scales, we identify two brightly polarized filaments southeast of the LMC, associated with neutral hydrogen arms. The filaments' magnetic field potentially aligns with the direction toward the Small Magellanic Cloud (SMC). We suggest that tidal interactions between the SMC and the LMC in the past 10{sup 9} years are likely to have shaped the magnetic field in these filaments.

  8. A model of basement structure from magnetic anomalies of the Bombay High oil-field west of India

    Digital Repository Service at National Institute of Oceanography (India)

    Rao, D.G.

    -122 111 Elsevier Science Publishers B.V., Amsterdam A model of basement structure from magnetic anomalies of the Bombay High Oil-Field west of India D. Gopala Rao National Institute of Oceanography, Dona Paula, Goa 403 004, India (Revision accepted....5 kin LOWER MIOCENE LIMESTONE REFLECTOR (FROM SEISMIC DATA) ~',r V,,- v • - ~'¥¥YYYVV . ..... \\[~~'vvwvwyvvvvWvvvv " ":" ":'wv ..... I"'T .... L CLAY/CLAYSTONE ~ OBSERVED MAGNETIC ANOMALIES SHALE ~ THEORETICAL MAOHETIC ANOMALIES LIMESTONE...

  9. Static magnetic fields enhance turbulence

    CERN Document Server

    Pothérat, Alban

    2015-01-01

    More often than not, turbulence occurs under the influence of external fields, mostly rotation and magnetic fields generated either by planets, stellar objects or by an industrial environment. Their effect on the anisotropy and the dissipative behaviour of turbulence is recognised but complex, and it is still difficult to even tell whether they enhance or dampen turbulence. For example, externally imposed magnetic fields suppress free turbulence in electrically conducting fluids (Moffatt 1967), and make it two-dimensional (2D) (Sommeria & Moreau 1982); but their effect on the intensity of forced turbulence, as in pipes, convective flows or otherwise, is not clear. We shall prove that since two-dimensionalisation preferentially affects larger scales, these undergo much less dissipation and sustain intense turbulent fluctuations. When higher magnetic fields are imposed, quasi-2D structures retain more kinetic energy, so that rather than suppressing forced turbulence, external magnetic fields indirectly enha...

  10. Deriving global structure of the Galactic Magnetic Field from Faraday Rotation Measures of extragalactic sources

    CERN Document Server

    Pshirkov, M S; Kronberg, P P; Newton-McGee, K J

    2011-01-01

    We made use of the two latest sets of Rotational Measures (RMs) of extra-galactic radio sources, namely the NRAO VLA Sky Survey otation Measures Catalogue, and a compilation by Kronberg&Newton-McGee(2011), to infer the global structure of the Galactic Magnetic Field (GMF). We have checked that these two data sets are consistent with each other. Motivated by clear patterns in the observed distribution of RMs over the sky, we considered GMF models consisting of the two components: disk (spiral or ring) and halo. The parameters of these components were determined by fitting different model field geometries to the observed RMs. We found that the model consisting of a symmetric (with respect to the Galactic plane) spiral disk and anti-symmetric halo fits the data best, and reproduces the observed distribution of RMs over the sky very well. We confirm that ring disk models are disfavored. Our results favor small pitch angles around -5 degrees and an increased vertical scale of electron distribution, in agreemen...

  11. ANALYSIS AND CHARACTERIZATION OF MICROSCOPIC MORPHOLOGY AND ORIENTATION STRUCTURE OF POLYANILINE POLYMERIZED IN A CONSTANT MAGNETIC FIELD

    Institute of Scientific and Technical Information of China (English)

    Li Ma; Wei Lu; Ke-long Huang; Meng-yu Gan; Chao Chen; Jun Yan

    2009-01-01

    Conductive polyaniline (Pan-M and Pan-O) doped with dodecylbenzene sulfonic acid (DBSA) was synthesized by using emulsion polymerization method in the presence of a constant magnetic field (0.4 T) and the absence of magnetic field, respectively. The effects of magnetic field on the microscopic morphology and orientation structure of Pan were generally analyzed and characterized by using transmission electron microscope (TEM), X-ray diffraction (XRD) and through the conductivity anisotropy of unit resistance of the Pan/PVA(polyvinyl alcohol) composite film. The results showed that, compared with Pan-O, Pan-M had higher crystallinity and more obvious microscopic orientation structure: its particles were arranged orderly and piled into many banded aggregates with a certain length/diameter ratio, after magnetization treatment, it demonstrated a high degree of consistent orientation; Pan-M/PVA composite films showed conductivity anisotropy after magnetization in the film-forming process. The results all fully confirmed that Pan prepared in a magnetic field condition had a high degree of orientation.

  12. Solitary structures in a spatially nonuniform degenerate plasma in the presence of quantizing magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Masood, W. [COMSATS, Institute of Information Technology, Park Road, Chak Shahzad, Islamabad 44000 (Pakistan); National Center for Physics (NCP), Islamabad 44000 (Pakistan); Shaukat, Muzzamal I. [University of Engineering and Technology, Lahore (RCET Campus) 54000 (Pakistan); Theoretical Plasma Physics Group, Quaid-i-Azam University, Islamabad 44000 (Pakistan); Shah, H. A. [Department of Physics, Forman Christian College, Lahore 54000 (Pakistan); Mirza, Arshad M. [Theoretical Plasma Physics Group, Quaid-i-Azam University, Islamabad 44000 (Pakistan)

    2015-03-15

    In the present investigation, linear and nonlinear propagation of low frequency (ω≪Ω{sub ci}) electrostatic waves have been studied in a spatially inhomogeneous degenerate plasma with one dimensional electron trapping in the presence of a quantizing magnetic field and finite temperature effects. Using the drift approximation, formation of 1 and 2D drift ion solitary structures have been studied both for fully and partially degenerate plasmas. The theoretical results obtained have been analyzed numerically for the parameters typically found in white dwarfs for illustrative purpose. It is observed that the inclusion of Landau quantization significantly changes the expression of the electron number density of a dense degenerate plasma which affects the linear and nonlinear propagation of drift acoustic solitary waves in such a system. The present work may be beneficial to understand the propagation of drift solitary structures with weak transverse perturbation in a variety of physical situations, such as white dwarfs and laser-induced plasmas, where the quantum effects are expected to dominate.

  13. Magnetotropism of roots and structure of their statocytes exposed to high gradient magnetic field

    Science.gov (United States)

    Belyavskaya, N. A.; Polishchuk, O. V.; Kondrachuk, A. V.

    In most living organisms gravity perception is based on the response of the gravisensing system to displacement of specific mass induced by a gravitational force The amyloplasts in higher plants are known to play the important role as the specific mass in gravisensing cells As was shown by Kuznetsov Hasenstein 1996 the high-gradient magnetic field HGMF exerts a directional ponderomotive force on such diamagnetic structures as amyloplasts This effect of the HGMF results in root curvature similar to that produced by gravity It was suggested that the HGMF could allow to imitate the effects of gravity in microgravity and or to change them in laboratory conditions correspondingly as well as to study statolith-related processes in graviperception Therefore the correlation between the direction of the ponderomotive force resulting in statolith displacements and the direction of the HGMF-induced plant curvature can be the serious argument to support this suggestion and needs the detailed structural analysis We have designed the HGMF facility that allows for generating the HGMF and analyzing its effects on higher plants roots The parameters of kinetics of Lepidium sativum L and Pisum sativum L root curvatures under both the HGMF action and gravistimulation were recorded by video system and measured by means of image analysis software The main results of the study are followings 1 the magnetotropic effect of the HGMF on root growth was found for pea and cress roots 2 the critical value of ponderomotive force that

  14. Are Spine--Sheath Polarization Structures in the Jets of Active Galactic Nuclei Associated with Helical Magnetic Fields?

    CERN Document Server

    Gabuzda, Denise C; O'Neill, Eamonn L

    2014-01-01

    One possible origin for polarization structures across jets of Active Galactic Nuclei (AGNs) with a central "spine" of orthogonal magnetic field and a "sheath" of longitudinal magnetic field along one or both edges of the jet is the presence of a helical jet magnetic field. Simultaneous Very Long Baseline Array (VLBA) polarization observations of AGN displaying partial or full spine--sheath polarization structures were obtained at 4.6, 5.0, 7.9, 8.9, 12.9 and 15.4 GHz, in order to search for additional evidence for helical jet magnetic fields, such as transverse Faraday rotation gradients (due to the systematic change in the line-of-sight magnetic-field component across the jet). Results for eight sources displaying monotonic transverse Faraday rotation gradients with significances $\\geq 3\\sigma$ are presented here. Reversals in the directions of the transverse RM gradients with distance from the core or with time are detected in three of these AGNs. These can be interpreted as evidence for a nested helical m...

  15. DEMETER Observations of Highly Structured Plasma Density and Associated ELF Electric Field and Magnetic Field Irregularities at Middle and Low Latitudes

    Science.gov (United States)

    Pfaff, R.; Liebrecht, C.; Berthelier, J.-J.; Parrot, M.; Lebreton, J.-P.

    2008-01-01

    The DEMETER spacecraft frequently encounters structured plasma and electric field irregularities associated with equatorial spread-F. However, during severe geonagnetic storms, the spacecraft detects broader regions of density structures that extend to higher latitudes, in some instances to the sub-auroral regions. In addition to the electric field irregularities, ELF magnetic field irregularities are sometimes observed. for example, on the walls of the density structures, and appear related to finely-structured spatial currents and/or Alfven waves. The mid-latitude irregularities are compared with those of equatorial spread-F as well as wit11 intense irregularities associated with the trough region observed at sub-auroral latitudes.

  16. The Electronic Structure of Coupled Semiconductor Quantum Dots Arranged as a Graphene Hexagonal Lattice under a Magnetic Field

    Institute of Scientific and Technical Information of China (English)

    PENG Juan; LI Shu-Shen

    2012-01-01

    We study the electronic spectrum of coupled quantum dots (QDs) arranged as a graphene hexagonal lattice in the presence of an external perpendicular magnetic Geld. In our tight-binding model, the effect of the magnetic field is included in both the Peierls phase of the Hamiltonian and the tight-binding basis Wannier function. The energy of the system is analyzed when the magnetic flux through the lattice unit cell is a rational fraction of the quantum flux. The calculated spectrum has recursive properties, similar to those of the classical Hofstadter butterfly. However, unlike the ideal Hofstadter butterfly structure, our result is asymmetric since the impacts of the specific material and the magnetic field on the wavefunctions are included, making the results more realistic.%We study the electronic spectrum of coupled quantum dots (QDs) arranged as a graphene hexagonal lattice in the presence of an external perpendicular magnetic field.In our tight-binding model,the effect of the magnetic field is included in both the Peierls phase of the Hamiltonian and the tight-binding basis Wannier function.The energy of the system is analyzed when the magnetic flux through the lattice unit cell is a rational fraction of the quantum flux.The calculated spectrum has recursive properties,similar to those of the classical Hofstadter butterfly.However,unlike the ideal Hofstadter butterfly structure,our result is asymmetric since the impacts of the specific material and the magnetic field on the wavefunctions are included,making the results more realistic.

  17. The structure of MHD turbulence under an external magnetic field: results from simulations on elongated domains

    Science.gov (United States)

    Zhai, X. M.; Yeung, P. K.

    2016-11-01

    Turbulence in an electrically conducting fluid in the limit of low magnetic Reynolds number is, because of the Lorentz force due to an external magnetic field, very different from classical turbulence at both the large scales and the small scales. The importance of minimizing finite domain-size effects on the large scale development has often tended to limit the Reynolds number reached in the past. In this work we use periodic domains stretched along the magnetic field with aspect ratio up to 8 and beyond. The initial state is obtained from decaying isotropic turbulence with large-eddy length scales of order 1% of the length of the domain. After a transient period the kinetic energy returns to a power law decay while the integral length scales in the direction parallel to the magnetic field show preferential growth. At early times the parallel velocity component becomes stronger than the other two but this anisotropy is subsequently reversed under the combined effects of anisotropic Joule dissipation and viscous dissipation. The small scales show characteristics of quasi two-dimensional behavior in the transverse plane. Results over a range of magnetic interaction parameters and Reynolds numbers are compared with known theoretical predictions. Supported by NSF Grant CBET-1510749 and supercomputer resources at TACC/XSEDE and ALCF.

  18. Magneto-acoustic waves driven by self-generated magnetic field: relevance to helical structures in MagLIF experiments

    Science.gov (United States)

    Davies, Jonathan; Barnak, Daniel; Betti, Riccardo; Carreon, Adam; Chang, Po-Yu; Fiksel, Gennady

    2014-10-01

    The observation of coherent helical structures in liner implosions on Z when an axial magnetic field more than 100 times smaller than the azimuthal field is added has yet to be adequately explained. The results have been reproduced in a 3D MHD code by initializing helices on the outer surface, but this produces helices independently of the axial magnetic field. We present the hypothesis that helices are seeded by self-generated magnetic field, which adds a driving term to the dispersion relation for magneto-acoustic waves when there is a temperature gradient perpendicular to the fluid motion. The key feature of this instability is that it is stable when magnetic pressure exceeds a fraction of the thermal pressure, therefore, instability driven by the helical field resulting from the combination of the initial axial field and the growing azimuthal field will stabilize before the net field has a small pitch angle and before the implosion starts, seeding helices on the surface. This work was supported by the Department of Energy National Nuclear Security Administration, Award Number DE-NA0001944, and the Fusion Science Center supported by the Office of Fusion Energy Sciences, Number DE-FG02-04ER54786.

  19. Influence of the initial parameters of the magnetic field and plasma on the spatial structure of the electric current and electron density in current sheets formed in helium

    Energy Technology Data Exchange (ETDEWEB)

    Ostrovskaya, G. V., E-mail: galya-ostr@mail.ru [Russian Academy of Sciences, Ioffe Physical Technical Institute (Russian Federation); Markov, V. S.; Frank, A. G., E-mail: annfrank@fpl.gpi.ru [Russian Academy of Sciences, Prokhorov General Physics Institute (Russian Federation)

    2016-01-15

    The influence of the initial parameters of the magnetic field and plasma on the spatial structure of the electric current and electron density in current sheets formed in helium plasma in 2D and 3D magnetic configurations with X-type singular lines is studied by the methods of holographic interferometry and magnetic measurements. Significant differences in the structures of plasma and current sheets formed at close parameters of the initial plasma and similar configurations of the initial magnetic fields are revealed.

  20. Magnetic multilayer structure

    Energy Technology Data Exchange (ETDEWEB)

    Herget, Philipp; O' Sullivan, Eugene J.; Romankiw, Lubomyr T.; Wang, Naigang; Webb, Bucknell C.

    2017-03-21

    A mechanism is provided for an integrated laminated magnetic device. A substrate and a multilayer stack structure form the device. The multilayer stack structure includes alternating magnetic layers and diode structures formed on the substrate. Each magnetic layer in the multilayer stack structure is separated from another magnetic layer in the multilayer stack structure by a diode structure.

  1. Magnetic multilayer structure

    Science.gov (United States)

    Herget, Philipp; O'Sullivan, Eugene J.; Romankiw, Lubomyr T.; Wang, Naigang; Webb, Bucknell C.

    2016-07-05

    A mechanism is provided for an integrated laminated magnetic device. A substrate and a multilayer stack structure form the device. The multilayer stack structure includes alternating magnetic layers and diode structures formed on the substrate. Each magnetic layer in the multilayer stack structure is separated from another magnetic layer in the multilayer stack structure by a diode structure.

  2. The Origin and Structure of the Magnetic Fields and Currents of AGN Jets

    Directory of Open Access Journals (Sweden)

    Denise Gabuzda

    2017-02-01

    Full Text Available This paper reviews observational evidence obtained to date about the overall structure of the magnetic fields in the jets of Active Galactic Nuclei (AGN. Because they are sensitive to the line-of-sight magnetic-field component, Faraday rotation observations of AGN jets provide an effective tool for searching for toroidal jet magnetic fields, whose line-of-sight component changes systematically across the jet. Transverse Faraday rotation measure (RM gradients providing direct evidence for helical/toroidal magnetic fields have been reliably detected in nearly 40 AGN on parsec scales. Helical magnetic fields are believed to form due to the combined action of the rotation of the central black hole and accretion disk, and these observations demonstrate that at least some of this helical field survives to distances well beyond the Very Long Baseline Interferometry (VLBI core. Observations of reversals in the direction of the transverse RM gradients in a number of AGN provide evidence for a“return”magnetic field forming a nested helical-field structure with oppositely directed azimuthal components in the inner and outer regions of the helical magnetic field. The collected data now provide firm evidence for a predominance of inward jet currents on parsec scales and outward currents on scales greater than a few tens of parsecs. This suggests a global pattern of magnetic fields and currents with an inward current near the jet axis and an outward current farther from the jet axis, with these currents closing in the accretion disk and far out in the radio lobes, forming a self-consistent set of fields and currents together with the implied nested helical-field structure.

  3. Hyperfine field and magnetic structure in the B phase of CeCoIn5

    Energy Technology Data Exchange (ETDEWEB)

    Graf, Matthias J [Los Alamos National Laboratory; Curro, Nicholas J [UNIV OF CAL; Young, Ben - Li [NATIONAL CHIAO UNIV; Urbano, Ricardo R [FL STATE UNIV

    2009-01-01

    We re-analyze Nuclear Magnetic Resonance (NMR) spectra observed at low temperatures and high magnetic fields in the field-induced B-phase of CeCoIn{sub 5}. The NMR spectra are consistent with incommensurate antiferromagnetic order of the Ce magnetic moments. However, we find that the spectra of the In(2) sites depend critically on the direction of the ordered moments, the ordering wavevector and the symmetry of the hyperfine coupling to the Ce spins. Assuming isotropic hyperfine coupling, the NMR spectra observed for H {parallel} [100] are consistent with magnetic order with wavevector Q = {pi}(1+{delta}/a, 1/a, 1/c) and Ce moments ordered antiferromagnetically along the [100] direction in real space. If the hyperfine coupling has dipolar symmetry, then the NMR spectra require Ce moments along the [001] direction. The dipolar scenario is also consistent with recent neutron scattering measurements that find an ordered moment of 0.15{micro}{sub B} along [001] and Q{sub n} = {pi}(1+{delta}/a, 1+{delta}c, 1/c) with incommensuration {delta} = 0.12 for field H {parallel} [1{bar 1}0]. Using these parameters, we find that the hyperfine field is consistent with both experiments. We speculate that the B phase of CeCoIn{sub 5} represents an intrinsic phase of modulated superconductivity and antiferromagnetism that can only emerge in a highly clean system.

  4. Magnetization reversal in ultrashort magnetic field pulses

    CERN Document Server

    Bauer, M; Fassbender, J; Hillebrands, B

    2000-01-01

    We report the switching properties of a thin magnetic film subject to an ultrashort, laterally localized magnetic field pulse, obtained by numerical investigations. The magnetization distribution in the film is calculated on a grid assuming Stoner-like coherent rotation within the grid square size. Perpendicularly and in-plane magnetized films exhibit a magnetization reversal due to a 4 ps magnetic field pulse. Outside the central region the pulse duration is short compared to the precession period. In this area the evolution of the magnetization during the field pulse does not depend strongly on magnetic damping and/or pulse shape. However, the final magnetization distribution is affected by the magnetic damping. Although the pulse duration is short compared to the precession period, the time needed for the relaxation of the magnetization to the equilibrium state is rather large. The influence of the different magnetic anisotropy contributions and the magnetic damping parameter enters into the magnetization ...

  5. Structural and morphological modifications of the Co-thin films caused by magnetic field and pH variation

    Energy Technology Data Exchange (ETDEWEB)

    Franczak, Agnieszka [LISM EA 4695, Universite de Reims Champagne-Ardenne, UFR Sciences et Naturelles, Bat. 6, Moulin de la Housse, BP 1039, 51687 Reims Cedex 2 (France); Levesque, Alexandra, E-mail: alexandra.levesque@univ-reims.fr [LISM EA 4695, Universite de Reims Champagne-Ardenne, UFR Sciences et Naturelles, Bat. 6, Moulin de la Housse, BP 1039, 51687 Reims Cedex 2 (France); Bohr, Frederic; Douglade, Jacques; Chopart, Jean-Paul [LISM EA 4695, Universite de Reims Champagne-Ardenne, UFR Sciences et Naturelles, Bat. 6, Moulin de la Housse, BP 1039, 51687 Reims Cedex 2 (France)

    2012-09-01

    Highlights: Black-Right-Pointing-Pointer Co electrodeposits were obtained at high electrolyte temperature under applied magnetic field. Black-Right-Pointing-Pointer The temperature is commonly used in the industrial process. Black-Right-Pointing-Pointer The effects of magnetic field up to 1 T and pH on structure and morphology were investigated. Black-Right-Pointing-Pointer The high process temperature enhances HER which is diminishing by the magnetic field application. - Abstract: Cobalt films were deposited by use of the electrochemical process from a cobalt (II) sulfate solution on a titanium electrode and characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray diffraction (XRD). The experiments at electrolyte temperature of 50 Degree-Sign C were performed which is commonly used in the industrial process. The effects of pH and low uniform magnetic field up to 1 T on structure and morphology changes were investigated. The detected phase composition indicates the presence of both phases: hexagonal centered packed and face centered cubic independent on the pH value and the applied magnetic field amplitude. Calculation of the orientation index of Co phase shows the preferential orientation in the films obtained at higher pH. SEM micro-imagines have shown the nucleus shape transition from coarse-grained to needle-shaped dependent on the application of B-field as well as on the pH variation in the case of higher pH level. Co-films obtained from the electrolyte of low pH were characterized by the fine-grained morphology which was not modified by the influence of magnetic field. AFM images proved the effect on roughness of the Co-films which is closely related with the obtained morphology.

  6. Investigation of the stability of polysilicon layers in SOI-structures under irradiation by electrons and hard magnetic field influence

    Directory of Open Access Journals (Sweden)

    Khoverko Yu. N.

    2010-10-01

    Full Text Available The properties of recrystallized polysilicon on insulator layers of p-type conductive SOI-structures with different carrier concentration irradiated with high-energy electrons flow about 1017 сm–2 in temperature range 4,2—300 К and high magnetic fields were investigated. It was found that heavily doped laser recrystallized polysilicon on insulator layers show its radiation resistance under irradiation with high-energy electrons and magnetoresistance of such material remains quite low in magnetic field about 14 T does not exceed 1—2%. Such qulity can be applied in designing of microelectronic sensors of mechanical values operable in hard conditions of exploitation.

  7. Effect of magnetic field on property and structure of polyaniline doped with multiple sulfonic acids

    Institute of Scientific and Technical Information of China (English)

    MA Li; HUANG Ke-long; CHEN Chao; GAN Meng-yu; LU Wei; CHEN Feng-qiang

    2008-01-01

    Polyaniline(PAn) doped with multiple sulfonic acid system of dodecylbenzenesulfonic acid(DBSA) and sulfosalicylic acid(SSA) was synthesized by emulsion polymerization using ammonium persulfate(APS) as an oxidizing agent in the presence and the absence of a constant magnetic field(MF)of 0.8 T. The structure and properties of the PAn were characterized by X-ray diffractometer(XRD), thermogravimetric apparatus(TGA), FT-IR spectroscope(FT-IR) and four probe digital multimeter. The results indicate that, when the molar ratio of DBSA to SSA is 1/3, that of dopant to An is 3/2, that of APS to An is 4/5 in the synthesizing media, and the doping time is 3 h, the conductivity of the PAn synthesized in the presence of the MF of 0.8 T reaches 5.88 S/cm,which is higher than that of the PAn synthesized in the absence of the MF. The thermal stability, the crystallinity and the doping degree of the PAn synthesized in the presence of the MF are also improved. MF not only enhances the conductivity, but also reduces the doping time, the dosage of the dopant and the oxidizing agent when the conductivity reaches the maximum.

  8. Planck intermediate results XXXII. The relative orientation between the magnetic field and structures traced by interstellar dust

    DEFF Research Database (Denmark)

    Adam, R.; Ade, P. A. R.; Aghanim, N.

    2016-01-01

    counterparts in the Stokes Q and/or U maps. We focus our study on structures at intermediate and high Galactic latitudes, which cover two orders of magnitude in column density, from 1020 to 1022 cm2. We measure the magnetic field orientation on the plane of the sky from the polarization data, and present...... to be between 0.6 and 1.0, with a preferred value of 0.8. We find that the ridges are usually aligned with the magnetic field measured on the structures. This statistical trend becomes more striking for increasing polarization fraction and decreasing column density. There is no alignment for the highest column...... density ridges. We interpret the increase in alignment with polarization fraction as a consequence of projection effects. We present maps to show that the decrease in alignment for high column density is not due to a loss of correlation between the distribution of matter and the geometry of the magnetic...

  9. Planck intermediate results. XXXV. Probing the role of the magnetic field in the formation of structure in molecular clouds

    CERN Document Server

    Ade, P A R; Alves, M I R; Arnaud, M; Arzoumanian, D; Ashdown, M; Aumont, J; Baccigalupi, C; Banday, A J; Barreiro, R B; Bartolo, N; Battaner, E; Benabed, K; Benoît, A; Benoit-Lévy, A; Bernard, J -P; Bersanelli, M; Bielewicz, P; Bock, J J; Bonavera, L; Bond, J R; Borrill, J; Bouchet, F R; Boulanger, F; Bracco, A; Burigana, C; Calabrese, E; Cardoso, J -F; Catalano, A; Chiang, H C; Christensen, P R; Colombo, L P L; Combet, C; Couchot, F; Crill, B P; Curto, A; Cuttaia, F; Danese, L; Davies, R D; Davis, R J; de Bernardis, P; de Rosa, A; de Zotti, G; Delabrouille, J; Dickinson, C; Diego, J M; Dole, H; Donzelli, S; Doré, O; Douspis, M; Ducout, A; Dupac, X; Efstathiou, G; Elsner, F; Enßlin, T A; Eriksen, H K; Falgarone, E; Ferrière, K; Finelli, F; Forni, O; Frailis, M; Fraisse, A A; Franceschi, E; Frejsel, A; Galeotta, S; Galli, S; Ganga, K; Ghosh, T; Giard, M; Gjerløw, E; González-Nuevo, J; Górski, K M; Gregorio, A; Gruppuso, A; Gudmundsson, J E; Guillet, V; Harrison, D L; Helou, G; Henrot-Versillé, S; Hernández-Monteagudo, C; Herranz, D; Hildebrandt, S R; Hivon, E; Holmes, W A; Hornstrup, A; Huffenberger, K M; Hurier, G; Jaffe, A H; Jaffe, T R; Jones, W C; Juvela, M; Keihänen, E; Keskitalo, R; Kisner, T S; Knoche, J; Kunz, M; Kurki-Suonio, H; Lagache, G; Lamarre, J -M; Lasenby, A; Lattanzi, M; Lawrence, C R; Leonardi, R; Levrier, F; Liguori, M; Lilje, P B; Linden-Vørnle, M; López-Caniego, M; Lubin, P M; Macías-Pérez, J F; Maino, D; Mandolesi, N; Mangilli, A; Maris, M; Martin, P G; Martínez-González, E; Masi, S; Matarrese, S; Melchiorri, A; Mendes, L; Mennella, A; Migliaccio, M; Miville-Deschênes, M -A; Moneti, A; Montier, L; Morgante, G; Mortlock, D; Munshi, D; Murphy, J A; Naselsky, P; Nati, F; Netterfield, C B; Noviello, F; Novikov, D; Novikov, I; Oppermann, N; Oxborrow, C A; Pagano, L; Pajot, F; Paladini, R; Paoletti, D; Pasian, F; Perotto, L; Pettorino, V; Piacentini, F; Piat, M; Pierpaoli, E; Pietrobon, D; Plaszczynski, S; Pointecouteau, E; Polenta, G; Ponthieu, N; Pratt, G W; Prunet, S; Puget, J -L; Rachen, J P; Reinecke, M; Remazeilles, M; Renault, C; Renzi, A; Ristorcelli, I; Rocha, G; Rossetti, M; Roudier, G; Rubiño-Martín, J A; Rusholme, B; Sandri, M; Santos, D; Savelainen, M; Savini, G; Scott, D; Soler, J D; Stolyarov, V; Sudiwala, R; Sutton, D; Suur-Uski, A -S; Sygnet, J -F; Tauber, J A; Terenzi, L; Toffolatti, L; Tomasi, M; Tristram, M; Tucci, M; Umana, G; Valenziano, L; Valiviita, J; Van Tent, B; Vielva, P; Villa, F; Wade, L A; Wandelt, B D; Wehus, I K; Ysard, N; Yvon, D; Zonca, A

    2015-01-01

    Within ten nearby (d < 450 pc) Gould Belt molecular clouds we evaluate statistically the relative orientation between the magnetic field projected on the plane of sky, inferred from the polarized thermal emission of Galactic dust observed by Planck at 353 GHz, and the gas column density structures, quantified by the gradient of the column density, $N_H$. The relative orientation is evaluated pixel by pixel and analyzed in bins of column density using the novel statistical tool Histogram of Relative Orientations. Within most clouds we find that the relative orientation changes progressively with increasing $N_H$ from preferentially parallel or no preferred orientation to preferentially perpendicular. In simulations of magnetohydrodynamic turbulence in molecular clouds this trend in relative orientation is a signature of Alfv\\'enic or sub-Alfv\\'enic turbulence, implying that the magnetic field is significant for the gas dynamics at the scales probed by Planck. We compare the deduced magnetic field strength w...

  10. Activity and Magnetic Field Structure of the Sun-Like Planet Hosting Star HD 1237

    CERN Document Server

    Alvarado-Gómez, J D; Grunhut, J; Fares, R; Donati, J -F; Alecian, E; Kochukhov, O; Oksala, M; Morin, J; Redfield, S; Cohen, O; Drake, J J; Jardine, M; Matt, S; Petit, P; Walter, F M

    2015-01-01

    We analyse the magnetic activity characteristics of the planet hosting Sun-like star, HD 1237, using HARPS spectro-polarimetric time-series data. We find evidence of rotational modulation of the magnetic longitudinal field measurements consistent with our ZDI analysis, with a period of 7 days. We investigate the effect of customising the LSD mask to the line depths of the observed spectrum and find that it has a minimal effect on shape of the extracted Stokes V profile but does result in a small increase in the S/N ($\\sim$ 7%). We find that using a Milne-Eddington solution to describe the local line profile provides a better fit to the LSD profiles in this slowly rotating star, which also impacts the recovered ZDI field distribution. We also introduce a fit-stopping criterion based on the information content (entropy) of the ZDI maps solution set. The recovered magnetic field maps show a strong (+90 G) ring-like azimuthal field distribution and a complex radial field dominating at mid latitudes ($\\sim$45 degr...

  11. Magnetic field of a combined plasma trap

    Science.gov (United States)

    Kotenko, V. G.; Moiseenko, V. E.; Ågren, O.

    2012-06-01

    This paper presents numerical simulations performed on the structure of a magnetic field created by the magnetic system of a combined plasma trap. The magnetic system includes the stellarator-type magnetic system and one of the mirror-type. For the stellarator type magnetic system the numeric model contains a magnetic system of an l=2 torsatron with the coils of an additional toroidal magnetic field. The mirror-type magnetic system element is considered as being single current-carrying turn enveloping the region of existence of closed magnetic surfaces of the torsatron. The calculations indicate the existence of a vast area of the values of the additional magnetic field magnitude and magnetic field of the single turn where, in principle, the implementation of the closed magnetic surface configuration is quite feasible.

  12. Cluster magnetic field observations of the bowshock: Orientation, motion and structure

    Directory of Open Access Journals (Sweden)

    T. S. Horbury

    Full Text Available Four spacecraft Cluster magnetic field observations of the low quasi-perpendicular terrestrial bowshock are presented for the first time. Multiple quasi-perpendicular crossings on 25 December 2000 are analysed. By combining data from the four spacecraft, bowshock orientations and velocities can be calculated. It is shown that, even while in rapid motion, the bowshock normal direction remains remarkably constant, and that coplanarity estimates are accurate to, typically, around 20°. Magnetic field magnitude profiles are shown to be very well correlated between spacecraft although downstream waves with fluctuations perpendicular to the local field, while statistically similar at all four spacecraft, are poorly correlated on separation scales of several hundred km. Examples are shown of a number of bowshock phenomena, including non-standing fluctuations in the shock foot and the shock interacting with changing solar wind conditions.

    Key words. Interplanetary physics (planetary bow shocks Space plasma physics (shock waves; waves and instabilities

  13. Spatial Structures of Polar Magnetic Field During the Last Solar Cycle

    Science.gov (United States)

    Sun, Xudong; Hoeksema, T.

    2009-05-01

    The Sun's polar field is closely related to the large scale coronal structure. It is important for coronal modeling and greatly affects the result. However, the polar field is not well observed because the ecliptic lies near the Sun's equator. In this study, we make use of the data from various observatories (MDI/WSO/MWO/Hinode) to study its spatial structures during the last solar cycle. The result is useful to improve the polar field extrapolation schemes.

  14. Ultrasonic study of structural instabilities in nickel induced by magnetic fields

    Directory of Open Access Journals (Sweden)

    Ariel Moreno-Gobbi

    2008-03-01

    Full Text Available The ultrasonic phase velocity was measured on a high purity nickel single crystal with a bias magnetic field in cooling and heating runs over the interval of temperatures from approximately 100 to 325 K. An evident anomaly of the phase velocity was observed in both branches of the temperature cycle. The temperature of the anomaly in the heating run was always greater than that in the cooling run, indicating the presence of a hysteretic mechanism. The observed changes are attributed to dimensional alignment of the nickel single crystal twins which are able to distort the crystalline network. The temperature of the anomalies and its hysteretic behavior depend on the synergy between the direction and strength of the magnetic field, the direction of the ultrasonic wave propagation, the internal friction between the domains and the crystallographic orientation. The frictions between magnetic domains that do not contribute to the velocity anomaly produce a hysteretic loop. The process can be easily inhibited by disorientation of the magnetic field.

  15. Structural transformation of NANOPERM-type metallic glasses followed in situ by synchrotron radiation during thermal annealing in external magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Procházka, V., E-mail: v.prochazka@upol.cz [Department of Experimental Physics, Faculty of Science, Palacký University, 17. listopadu 12, 771 46 Olomouc (Czech Republic); Vrba, V.; Smrčka, D. [Department of Experimental Physics, Faculty of Science, Palacký University, 17. listopadu 12, 771 46 Olomouc (Czech Republic); Rüffer, R. [ESRF-The European Synchrotron, CS40220, 38043 Grenoble Cedex 9 (France); Matúš, P. [Institute of Laboratory Research on Geomaterials, Faculty of Natural Sciences, Comenius University, Mlynská dolina, 842 15 Bratislava (Slovakia); Mašláň, M. [Department of Experimental Physics, Faculty of Science, Palacký University, 17. listopadu 12, 771 46 Olomouc (Czech Republic); Miglierini, M.B. [Institute of Nuclear and Physical Engineering, Slovak University of Technology, 812 19 Bratislava (Slovakia); Regional Centre of Advanced Technologies and Materials, Palacký University, 17. listopadu 12, 771 46 Olomouc (Czech Republic)

    2015-07-25

    Highlights: • On-fly inspection of structural transformations during magnetic annealing. • Crystallization starts by ∼100 K earlier during magnetic annealing. • Potential for modification of the material properties using magnetic field. • The whole crystallization process was followed with high time resolution. - Abstract: Kinetics of the crystallization process of Fe–Mo–Cu–B-type metallic glass is studied to fine details during heat treatment under weak external magnetic field (0.652 T). Structural arrangement as well as magnetic microstructure is followed on-fly using sophisticated method of in situ nuclear forward scattering (NFS) of synchrotron radiation. The latter provides both quantitative (relative fractions) and qualitative (hyperfine magnetic fields) temperature dependencies of all structurally different samples’ components. They belong to the amorphous residual matrix, the newly formed nanocrystalline grains, and to their surfaces, respectively. The onset of crystallization during in-field magnetic annealing starts ∼100 K earlier than that in zero field.

  16. Estimation of Plasma Properties and Magnetic Field in a Prominence-like Structure as Observed by SDO/AIA

    CERN Document Server

    Dwivedi, Bhola N; Mohan, Anita

    2013-01-01

    We analyze a prominence-like cool plasma structure as observed by Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO). We perform the Differential Emission Measure (DEM) analysis using various filters of AIA, and also deduce the temperature and density structure in and around the observed flux-tube. In addition to deducing plasma parameters, we also find an evidence of multiple harmonics of fast magnetoacoustic kink waves in the observed prominence-like magnetic structure. Making use of estimated plasma parameters and observed wave parameters, under the baseline of MHD seismology, we deduce magnetic field in the flux-tube. The wave period ratio P1/P2 = 2.18 is also observed in the flux-tube, which carries the signature of magnetic field divergence where we estimate the tube expansion factor as 1.27. We discuss constraints in the estimation of plasma and magnetic field properties in such a structure in the current observational perspective, which may shed new light on the localized ...

  17. SMARTer for magnetic structure studies

    Indian Academy of Sciences (India)

    E G R Putra; A Ikram; J Kohlbrecher

    2008-11-01

    SMARTer, a 36-meter small angle neutron scattering (SANS) spectrometer was installed at the Neutron Scattering Laboratory (NSL), National Nuclear Energy Agency of Indonesia – BATAN in Serpong, Indonesia and has performed the experiment for studying the magnetic structures of Cu(NiFe), CuCo and FeSiBNbCu metal alloys. The experiments were conducted at room temperature and up to 1 T (10 kOe) of external magnetic field. At zero fields, isotropic scattering identified as nuclear scattering is dominant. When a magnetic field is applied in a horizontal direction perpendicular to the neutron beam, the response of the magnetic scattering permits extraction of the field-induced re-arrangement of the magnetic moment. With increasing field the distortion is more pronounced and the magnetic scattering dominates the intensity and affects the peak position. Radial and angular averaging from experimental data are given to show the details of magnetic structures.

  18. CME Magnetic Structure and Magnetic Cloud Signature

    Science.gov (United States)

    Li, Yan; Luhmann, J.

    2006-06-01

    An interplanetary coronal mass ejection (ICME) is the counterpart of a coronal mass ejection by definition. However, the relationship between the magnetic structures of the CMEs and that of the situ observations of ICMEs is still quite far from clear, due to observational gaps and the state of our understanding of CMEs. Some studies suggested that the magnetic cloud (MC, a group of ICMEs with fluxrope signatures) magnetic polarity follows the solar large scale magnetic field, and others suggested it follows the local magnetic field of the CME source region. Recent studies found that the relationship is more complex. While solar cycle dependence of the magnetic signature of MCs is clearly evident, the polarity of the MCs does not reverse at the same time when the solar large scale field reverses around solar maximum, but begins to have mixed polarities, and the new polarity may only prevail at the midst of the declining phase. Interestingly, in an independent study of the magnetic topology at the CME source regions, we found a similar solar cycle dependence of the bipolar and quadrupolar topologie. In this work, the link between CMEs and ICMEs is made and the results will shed light on our understanding about the relationship between CME and ICME magnetic structures and how these structures are related to solar local and large scale magnetic fields.Acknowledgement: ATM/NSF-0451438, SRT/NASA-NNG06GE51G and CISM/NSF.

  19. ISR Radial Field Magnet

    CERN Multimedia

    1983-01-01

    There were 37 (normal) + 3 (special) Radial Field magnets in the ISR to adjust vertically the closed orbit. Gap heights and strengths were 200 mm and .12 Tm in the normal magnets, 220 mm and .18 Tm in the special ones. The core length was 430 mm in both types. Due to their small length as compared to the gap heights the end fringe field errors were very important and had to be compensated by suitably shaping the poles. In order to save on cables, as these magnets were located very far from their power supplies, the coils of the normal type magnets were formed by many turns of solid cpper conductor with some interleaved layers of hollow conductor directly cooled by circulating water

  20. Magnetization Response of the Bulk and Supplementary Magnetic Domain Structure in High-Permeability Steel Laminations Visualized In Situ by Neutron Dark-Field Imaging

    Science.gov (United States)

    Betz, B.; Rauscher, P.; Harti, R. P.; Schäfer, R.; Irastorza-Landa, A.; Van Swygenhoven, H.; Kaestner, A.; Hovind, J.; Pomjakushina, E.; Lehmann, E.; Grünzweig, C.

    2016-08-01

    Industrial transformer cores are composed of stacked high-permeability steel laminations (HPSLs). The performance and degree of efficiency of transformers are directly determined by the magnetic properties of each HPSL. In this article, we show how the neutron dark-field image (DFI) allows for the in situ visualization of the locally resolved response of the bulk and supplementary magnetic domain structures in HPSLs under the influence of externally applied magnetic fields. In particular, we investigate the domain formation and growth along the initial magnetization curve up to the saturated state. For decreasing field, we visualize the recurrence of the hysteretic domain structure down to the remanent state. Additionally, the DFI allows us to derive a correlation between the grain orientation and the corresponding volume and supplementary domain structure. Furthermore, we visualize the influence of the insulation coating, introducing desired tensile stresses on the domain structures. To compare our DFI findings to traditional methods, we perform complementary surface-sensitive magneto-optical Kerr-microscopy investigations.

  1. Real-space phase field investigation of evolving magnetic domains and twin structures in a ferromagnetic shape memory alloy

    Science.gov (United States)

    Wu, H. H.; Pramanick, A.; Ke, Y. B.; Wang, X.-L.

    2016-11-01

    A real-space phase field model combining Landau-Lifshitz-Gilbert equation and time-dependent Ginzburg-Landau equation is developed to investigate the evolution of ferromagnetic domains and martensitic twin structures in a ferromagnetic shape memory alloy at different lengthscales. Both domain and twin structures are obtained by simultaneously solving for minimization of magnetic, elastic, and magnetoelastic coupling energy terms via a nonlinear finite element method. The model is applied to simulate magneto-structural evolution within a nanoparticle and a bulk single-crystal of the alloy Ni2MnGa, which are subjected to mechanical strains. It is shown that a nanoparticle contains magnetic vortex structures within a single twin variant, whereas for a bulk crystal both 90° and 180° domain structures are present within multiple twin variants.

  2. The new magnetic white dwarf PG 1031 + 234 - Polarization and field structure at more than 500 milion Gauss

    Science.gov (United States)

    Schmidt, Gary D.; West, Steven C.; Liebert, James; Green, Richard F.; Stockman, H. S.

    1986-01-01

    The discovery and study of a PG white dwarf which shows strong linear and circular polarization modulated with a rotation period of 3 hr 24 min is reported. The new star, PG 1031 + 234, is more highly magnetic than even Grw +70 deg 8247, with absorption components of hydrogen in its optical and UV spectra corresponding to fields from 200 to more than 500 MG. An asymmetric dependence of polarization on rotational phase shows that the surface field structure on the star is more complex than a simple centered dipole. The basic observational features can be well reproduced by a rotating star containing an oblique centered dipole punctuated near its magnetic equator by a high-field spot containing primarily radial field lines.

  3. Planck intermediate results. XXXII. The relative orientation between the magnetic field and structures traced by interstellar dust

    CERN Document Server

    Adam, R; Aghanim, N; Alves, M I R; Arnaud, M; Arzoumanian, D; Ashdown, M; Aumont, J; Baccigalupi, C; Banday, A J; Barreiro, R B; Bartolo, N; Battaner, E; Benabed, K; Benoit-Lévy, A; Bernard, J -P; Bersanelli, M; Bielewicz, P; Bonaldi, A; Bonavera, L; Bond, J R; Borrill, J; Bouchet, F R; Boulanger, F; Bracco, A; Burigana, C; Butler, R C; Calabrese, E; Cardoso, J -F; Catalano, A; Chamballu, A; Chiang, H C; Christensen, P R; Colombi, S; Colombo, L P L; Combet, C; Couchot, F; Crill, B P; Curto, A; Cuttaia, F; Danese, L; Davies, R D; Davis, R J; de Bernardis, P; de Rosa, A; de Zotti, G; Delabrouille, J; Dickinson, C; Diego, J M; Dole, H; Donzelli, S; Doré, O; Douspis, M; Ducout, A; Dupac, X; Efstathiou, G; Elsner, F; Enßlin, T A; Eriksen, H K; Falgarone, E; Ferrière, K; Finelli, F; Forni, O; Frailis, M; Fraisse, A A; Franceschi, E; Frejsel, A; Galeotta, S; Galli, S; Ganga, K; Ghosh, T; Giard, M; Gjerløw, E; González-Nuevo, J; Górski, K M; Gregorio, A; Gruppuso, A; Guillet, V; Hansen, F K; Hanson, D; Harrison, D L; Henrot-Versillé, S; Hernández-Monteagudo, C; Herranz, D; Hildebrandt, S R; Hivon, E; Holmes, W A; Hovest, W; Huffenberger, K M; Hurier, G; Jaffe, A H; Jaffe, T R; Jones, W C; Keihänen, E; Keskitalo, R; Kisner, T S; Kneissl, R; Knoche, J; Kunz, M; Kurki-Suonio, H; Lagache, G; Lamarre, J -M; Lasenby, A; Lattanzi, M; Lawrence, C R; Leonardi, R; Levrier, F; Liguori, M; Lilje, P B; Linden-Vørnle, M; López-Caniego, M; Lubin, P M; Macías-Pérez, J F; Maffei, B; Maino, D; Mandolesi, N; Maris, M; Marshall, D J; Martin, P G; Martínez-González, E; Masi, S; Matarrese, S; Mazzotta, P; Melchiorri, A; Mendes, L; Mennella, A; Migliaccio, M; Miville-Deschênes, M -A; Moneti, A; Montier, L; Morgante, G; Mortlock, D; Munshi, D; Murphy, J A; Naselsky, P; Natoli, P; Nørgaard-Nielsen, H U; Noviello, F; Novikov, D; Novikov, I; Oppermann, N; Oxborrow, C A; Pagano, L; Pajot, F; Paoletti, D; Pasian, F; Perdereau, O; Perotto, L; Perrotta, F; Pettorino, V; Piacentini, F; Piat, M; Plaszczynski, S; Pointecouteau, E; Polenta, G; Ponthieu, N; Popa, L; Pratt, G W; Prunet, S; Puget, J -L; Rachen, J P; Reach, W T; Reinecke, M; Remazeilles, M; Renault, C; Ristorcelli, I; Rocha, G; Roudier, G; Rubiño-Martín, J A; Rusholme, B; Sandri, M; Santos, D; Savini, G; Scott, D; Soler, J D; Spencer, L D; Stolyarov, V; Sudiwala, R; Sunyaev, R; Sutton, D; Suur-Uski, A -S; Sygnet, J -F; Tauber, J A; Terenzi, L; Toffolatti, L; Tomasi, M; Tristram, M; Tucci, M; Umana, G; Valenziano, L; Valiviita, J; Van Tent, B; Vielva, P; Villa, F; Wade, L A; Wandelt, B D; Wehus, I K; Wiesemeyer, H; Yvon, D; Zacchei, A; Zonca, A

    2014-01-01

    The role of the magnetic field in the formation of the filamentary structures observed in the interstellar medium (ISM) is a debated topic. The Planck all-sky maps of linearly polarized emission from dust at 353GHz provide the required combination of imaging and statistics to study the correlation between the structures of the Galactic magnetic field and of interstellar matter, both in the diffuse ISM and in molecular clouds. The data reveal structures, or ridges, in the intensity map with counterparts in the Stokes Q and/or U maps. We focus on structures at intermediate and high Galactic latitudes with column density from $10^{20}$ to $10^{22}$ cm$^{-2}$. We measure the magnetic field orientation on the plane of the sky from the polarization data, and present an algorithm to estimate the orientation of the ridges from the dust intensity map. We use analytical models to account for projection effects. Comparing polarization angles on and off the structures, we estimate the mean ratio between the strengths of ...

  4. The magnetic field structure of the central region in M31

    CERN Document Server

    Gießübel, René

    2014-01-01

    The Andromeda Galaxy (M31) is the nearest grand-design spiral galaxy. Thus far most studies in the radio regime concentrated on the 10 kpc ring. The central region of M31 has significantly different properties than the outer parts: The star formation rate is low, and inclination and position angle are largely different from the outer disk. The existing model of the magnetic field in the radial range 6<=r<=14 kpc is extended to the innermost part r<=0.5 kpc to ultimately achieve a picture of the entire magnetic field in M31. We combined observations taken with the VLA at 3.6 cm and 6.2 cm with data from the Effelsberg 100-m telescope to fill the missing spacings of the synthesis data. The resulting polarization maps were averaged in sectors to analyse the azimuthal behaviour of the polarized intensity (PI), rotation measure (RM), and apparent pitch angle (\\phi_obs). We developed a simplified 3-D model for the magnetic field in the central region to explain the azimuthal behaviour of the three observab...

  5. Jovian Plasmas Torus Interaction with Europa. Plasma Wake Structure and Effect of Inductive Magnetic Field: 3D Hybrid Kinetic Simulation

    Science.gov (United States)

    Lipatov, A. S.; Cooper, J F.; Paterson, W. R.; Sittler, E. C., Jr.; Hartle, R. E.; Simpson, David G.

    2013-01-01

    The hybrid kinetic model supports comprehensive simulation of the interaction between different spatial and energetic elements of the Europa moon-magnetosphere system with respect to a variable upstream magnetic field and flux or density distributions of plasma and energetic ions, electrons, and neutral atoms. This capability is critical for improving the interpretation of the existing Europa flyby measurements from the Galileo Orbiter mission, and for planning flyby and orbital measurements (including the surface and atmospheric compositions) for future missions. The simulations are based on recent models of the atmosphere of Europa (Cassidy et al., 2007; Shematovich et al., 2005). In contrast to previous approaches with MHD simulations, the hybrid model allows us to fully take into account the finite gyroradius effect and electron pressure, and to correctly estimate the ion velocity distribution and the fluxes along the magnetic field (assuming an initial Maxwellian velocity distribution for upstream background ions). Photoionization, electron-impact ionization, charge exchange and collisions between the ions and neutrals are also included in our model. We consider the models with Oþ þ and Sþ þ background plasma, and various betas for background ions and electrons, and pickup electrons. The majority of O2 atmosphere is thermal with an extended non-thermal population (Cassidy et al., 2007). In this paper, we discuss two tasks: (1) the plasma wake structure dependence on the parameters of the upstream plasma and Europa's atmosphere (model I, cases (a) and (b) with a homogeneous Jovian magnetosphere field, an inductive magnetic dipole and high oceanic shell conductivity); and (2) estimation of the possible effect of an induced magnetic field arising from oceanic shell conductivity. This effect was estimated based on the difference between the observed and modeled magnetic fields (model II, case (c) with an inhomogeneous Jovian magnetosphere field, an inductive

  6. Cosmic magnetic fields

    CERN Document Server

    Kronberg, Philipp P

    2016-01-01

    Magnetic fields are important in the Universe and their effects contain the key to many astrophysical phenomena that are otherwise impossible to understand. This book presents an up-to-date overview of this fast-growing topic and its interconnections to plasma processes, astroparticle physics, high energy astrophysics, and cosmic evolution. The phenomenology and impact of magnetic fields are described in diverse astrophysical contexts within the Universe, from galaxies to the filaments and voids of the intergalactic medium, and out to the largest redshifts. The presentation of mathematical formulae is accessible and is designed to add insight into the broad range of topics discussed. Written for graduate students and researchers in astrophysics and related disciplines, this volume will inspire readers to devise new ways of thinking about magnetic fields in space on galaxy scales and beyond.

  7. Magnetic fields in spiral galaxies

    Science.gov (United States)

    Beck, Rainer

    2015-12-01

    Radio synchrotron emission, its polarization and Faraday rotation of the polarization angle are powerful tools to study the strength and structure of magnetic fields in galaxies. Unpolarized synchrotron emission traces isotropic turbulent fields which are strongest in spiral arms and bars (20-30 \\upmu G) and in central starburst regions (50-100 \\upmu G). Such fields are dynamically important; they affect gas flows and drive gas inflows in central regions. Polarized emission traces ordered fields, which can be regular or anisotropic turbulent, where the latter originates from isotropic turbulent fields by the action of compression or shear. The strongest ordered fields (10-15 \\upmu G) are generally found in interarm regions. In galaxies with strong density waves, ordered fields are also observed at the inner edges of spiral arms. Ordered fields with spiral patterns exist in grand-design, barred and flocculent galaxies and in central regions. Ordered fields in interacting galaxies have asymmetric distributions and are a tracer of past interactions between galaxies or with the intergalactic medium.—Faraday rotation measures of the diffuse polarized radio emission from galaxy disks reveal large-scale spiral patterns that can be described by the superposition of azimuthal modes; these are signatures of regular fields generated by mean-field dynamos. "Magnetic arms" between gaseous spiral arms may also be products of dynamo action, but need a stable spiral pattern to develop. Helically twisted field loops winding around spiral arms were found in two galaxies so far. Large-scale field reversals, like the one found in the Milky Way, could not yet be detected in external galaxies. In radio halos around edge-on galaxies, ordered magnetic fields with X-shaped patterns are observed. The origin and evolution of cosmic magnetic fields, in particular their first occurrence in young galaxies and their dynamical importance during galaxy evolution, will be studied with

  8. Carrier relaxation in (In,Ga)As quantum dots with magnetic field-induced anharmonic level structure

    Energy Technology Data Exchange (ETDEWEB)

    Kurtze, H.; Bayer, M. [Experimentelle Physik 2, TU Dortmund, D-44221 Dortmund (Germany)

    2016-07-04

    Sophisticated models have been worked out to explain the fast relaxation of carriers into quantum dot ground states after non-resonant excitation, overcoming the originally proposed phonon bottleneck. We apply a magnetic field along the quantum dot heterostructure growth direction to transform the confined level structure, which can be approximated by a Fock–Darwin spectrum, from a nearly equidistant level spacing at zero field to strong anharmonicity in finite fields. This changeover leaves the ground state carrier population rise time unchanged suggesting that fast relaxation is maintained upon considerable changes of the level spacing. This corroborates recent models explaining the relaxation by polaron formation in combination with quantum kinetic effects.

  9. Magnetic Nano-structures

    Institute of Scientific and Technical Information of China (English)

    姚永德

    2004-01-01

    Fabrication of magnetic nano-structures with dots array and wires has been paid attention recently due to the application of high-density magnetic recording. In this study, we fabricated the magnetic dots array and wires through several ways that ensure the arrangement of magnetic dots and wires to be the structures we designed. Their magnetic properties are studied experimentally.

  10. Solar Magnetic Fields

    CERN Document Server

    Hood, Alan W

    2011-01-01

    This review provides an introduction to the generation and evolution of the Sun's magnetic field, summarising both observational evidence and theoretical models. The eleven year solar cycle, which is well known from a variety of observed quantities, strongly supports the idea of a large-scale solar dynamo. Current theoretical ideas on the location and mechanism of this dynamo are presented. The solar cycle influences the behaviour of the global coronal magnetic field and it is the eruptions of this field that can impact on the Earth's environment. These global coronal variations can be modelled to a surprising degree of accuracy. Recent high resolution observations of the Sun's magnetic field in quiet regions, away from sunspots, show that there is a continual evolution of a small-scale magnetic field, presumably produced by small-scale dynamo action in the solar interior. Sunspots, a natural consequence of the large-scale dynamo, emerge, evolve and disperse over a period of several days. Numerical simulation...

  11. Relationship of magnetic field strength and brightness of fine-structure elements in the solar temperature minimum region

    Science.gov (United States)

    Cook, J. W.; Ewing, J. A.

    1990-01-01

    A quantitative relationship was determined between magnetic field strength (or magnetic flux) from photospheric magnetograph observations and the brightness temperature of solar fine-structure elements observed at 1600 A, where the predominant flux source is continuum emission from the solar temperature minimum region. A Kitt Peak magnetogram and spectroheliograph observations at 1600 A taken during a sounding rocket flight of the High Resolution Telescope and Spectrograph from December 11, 1987 were used. The statistical distributions of brightness temperature in the quiet sun at 1600 A, and absolute value of magnetic field strength in the same area were determined from these observations. Using a technique which obtains the best-fit relationship of a given functional form between these two histogram distributions, a quantitative relationship was determined between absolute value of magnetic field strength B and brightness temperature which is essentially linear from 10 to 150 G. An interpretation is suggested, in which a basal heating occurs generally, while brighter elements are produced in magnetic regions with temperature enhancements proportional to B.

  12. A Noninvasive Magnetic Stimulator Utilizing Secondary Ferrite Cores and Resonant Structures for Field Enhancement

    CERN Document Server

    Pradhan, Raunaq

    2016-01-01

    In this paper, secondary ferrite cores and resonant structures have been used for field enhancement. The tissue was placed between the double square source coil and the secondary ferrite core. Resonant coils were added which aided in modulating the electric field in the tissue. The field distribution in the tissue was measured using electromagnetic simulations and ex-vivo measurements with tissue. Calculations involve the use of finite element analysis (Ansoft HFSS) to represent the electrical properties of the physical structure. The setup was compared to a conventional design in which the secondary ferrite cores were absent. It was found that the induced electric field could be increased by 122%, when ferrite cores were placed below the tissue at 450 kHz source frequency. The induced electric field was found to be localized in the tissue, verified using ex-vivo experiments. This preliminary study maybe further extended to establish the verified proposed concept with different complicated body parts modelled...

  13. Magnetic Fields in Spiral Galaxies

    CERN Document Server

    Beck, Rainer

    2015-01-01

    Radio synchrotron emission is a powerful tool to study the strength and structure of magnetic fields in galaxies. Unpolarized synchrotron emission traces isotropic turbulent fields which are strongest in spiral arms and bars (20-30\\mu G) and in central starburst regions (50-100\\mu G). Such fields are dynamically important; they affect gas flows and drive gas inflows in central regions. Polarized emission traces ordered fields, which can be regular or anisotropic turbulent, where the latter originates from isotropic turbulent fields by the action of compression or shear. The strongest ordered fields (10-15\\mu G) are generally found in interarm regions. In galaxies with strong density waves, ordered fields are also observed at the inner edges of spiral arms. Ordered fields with spiral patterns exist in grand-design, barred and flocculent galaxies, and in central regions. Ordered fields in interacting galaxies have asymmetric distributions and are a tracer of past interactions between galaxies or with the interg...

  14. High field superconducting magnets

    Science.gov (United States)

    Hait, Thomas P. (Inventor); Shirron, Peter J. (Inventor)

    2011-01-01

    A superconducting magnet includes an insulating layer disposed about the surface of a mandrel; a superconducting wire wound in adjacent turns about the mandrel to form the superconducting magnet, wherein the superconducting wire is in thermal communication with the mandrel, and the superconducting magnet has a field-to-current ratio equal to or greater than 1.1 Tesla per Ampere; a thermally conductive potting material configured to fill interstices between the adjacent turns, wherein the thermally conductive potting material and the superconducting wire provide a path for dissipation of heat; and a voltage limiting device disposed across each end of the superconducting wire, wherein the voltage limiting device is configured to prevent a voltage excursion across the superconducting wire during quench of the superconducting magnet.

  15. Magnetic Structure of the Heavy-fermion Compound CeAuSb2 in Zero-field

    Science.gov (United States)

    Marcus, Guy G.; Kim, Dae-Jeong; Lee, Hannoh; Fisk, Zachary; Rodriguez-Rivera, Jose A.; Broholm, Collin L.

    2015-03-01

    We have used neutron diffraction to determine the zero-field magnetic structure of the heavy-fermion compound CeAuSb2. Below TN ~ 6 . 2 K, we observe the development of antiferromagnetic Bragg diffraction consistent with previous transport and magnetization measurements. The intensities observed at 7 magnetic satellite locations indicate the staggered magnetization is predominantly along the c-axis. The maximum moment size is 1 . 15 +/- 0 . 08μB which is large compared with the 0 . 4μB moment in the iso-structural heavy fermion ferromagnet CeAgSb2. This suggests that the antiferromagnetic CeAuSb2 is deeper into a magnetic phase. The spin structure, due mainly to the Ce-4f sites, is described as a transverse polarized spin density wave with an incommensurate component of the wave vector in the basal plane. We will discuss these results and bulk measurements in terms of an ANNNI model and effective near neighbor exchange interactions. The work at IQM was supported by the US Department of Energy, Office of Basic Energy Sciences, Division of Material Sciences and Engineering under Grant No. DE-FG02-08ER46544. GGM also acknowledges support from the NSF-GRFP Grant No. DGE-1232825.

  16. Roles of hydrogenation, annealing and field in the structure and magnetic entropy change of Tb-based bulk metallic glasses

    Directory of Open Access Journals (Sweden)

    Qiang Luo

    2013-03-01

    Full Text Available The reduction of open-volume regions in Tb-based metallic glass (MG by annealing and hydrogen charging was found to rearrange the atomic structure and tune the magnetic behaviors. After crystallization, the magnetic structure and magnetic entropy change (MEC alters due to the structural transformation, and a plateau-like-MEC behavior can be obtained. The hydrogen concentration after charging at 1mA/cm2 for 576 h reaches as high as 3290 w-ppm. The magnetization behavior and the MEC change due to the modification of the exchange interaction and the random magnetic anisotropy (RMA upon hydrogenation. At low temperatures, irreversible positive MEC was obtained, which is related to the internal entropy production. The RMA-to-exchange ratio acts as a switch to control the irreversible entropy production channel and the reversible entropy transfer channel. The field dependence of the MEC is discussed in term of the competition among Zeeman energy, exchange interaction and RMA.

  17. Anisotropically structured magnetic aerogel monoliths

    Science.gov (United States)

    Heiligtag, Florian J.; Airaghi Leccardi, Marta J. I.; Erdem, Derya; Süess, Martin J.; Niederberger, Markus

    2014-10-01

    Texturing of magnetic ceramics and composites by aligning and fixing of colloidal particles in a magnetic field is a powerful strategy to induce anisotropic chemical, physical and especially mechanical properties into bulk materials. If porosity could be introduced, anisotropically structured magnetic materials would be the perfect supports for magnetic separations in biotechnology or for magnetic field-assisted chemical reactions. Aerogels, combining high porosity with nanoscale structural features, offer an exceptionally large surface area, but they are difficult to magnetically texture. Here we present the preparation of anatase-magnetite aerogel monoliths via the assembly of preformed nanocrystallites. Different approaches are proposed to produce macroscopic bodies with gradient-like magnetic segmentation or with strongly anisotropic magnetic texture.Texturing of magnetic ceramics and composites by aligning and fixing of colloidal particles in a magnetic field is a powerful strategy to induce anisotropic chemical, physical and especially mechanical properties into bulk materials. If porosity could be introduced, anisotropically structured magnetic materials would be the perfect supports for magnetic separations in biotechnology or for magnetic field-assisted chemical reactions. Aerogels, combining high porosity with nanoscale structural features, offer an exceptionally large surface area, but they are difficult to magnetically texture. Here we present the preparation of anatase-magnetite aerogel monoliths via the assembly of preformed nanocrystallites. Different approaches are proposed to produce macroscopic bodies with gradient-like magnetic segmentation or with strongly anisotropic magnetic texture. Electronic supplementary information (ESI) available: Digital photographs of dispersions and gels with different water-to-ethanol ratios; magnetic measurements of an anatase aerogel containing 0.25 mol% Fe3O4 nanoparticles; XRD patterns of the iron oxide and

  18. Magnetic Field Structures in Star Forming Regions: Mid-Infrared Imaging Polarimetry of K3-50

    CERN Document Server

    Barnes, Peter; Telesco, Charles; Tanakul, Nahathai; Mariñas, Naibí; Wright, Chris; Packham, Chris; Pantin, Eric; Roche, Patrick; Hough, James

    2015-01-01

    We report new imaging polarimetry observations of the Galactic compact HII region K3-50 using CanariCam at the Gran Telescopio Canarias. We use a standard polarimetric analysis technique, first outlined by Aitken, to decompose the observed polarisation images centred at 8.7, 10.3, and 12.5 $\\mu$m into the emissive and absorptive components from silicate grains that are aligned with the local magnetic field. These components reveal the spatially-resolved magnetic field structures across the mid-infrared emission area of K3-50. We examine these structures and show that they are consistent with previously observed features and physical models of K3-50, such as the molecular torus and the ionised outflow. We propose a 3D geometry for all the structures seen at different wavelengths. We also compute relevant physical quantities in order to estimate the associated magnetic field strengths that would be implied under various physical assumptions. We compare these results with MHD simulations of protostar formation t...

  19. Magnetic Helicity and Large Scale Magnetic Fields: A Primer

    CERN Document Server

    Blackman, Eric G

    2014-01-01

    Magnetic fields of laboratory, planetary, stellar, and galactic plasmas commonly exhibit significant order on large temporal or spatial scales compared to the otherwise random motions within the hosting system. Such ordered fields can be measured in the case of planets, stars, and galaxies, or inferred indirectly by the action of their dynamical influence, such as jets. Whether large scale fields are amplified in situ or a remnant from previous stages of an object's history is often debated for objects without a definitive magnetic activity cycle. Magnetic helicity, a measure of twist and linkage of magnetic field lines, is a unifying tool for understanding large scale field evolution for both mechanisms of origin. Its importance stems from its two basic properties: (1) magnetic helicity is typically better conserved than magnetic energy; and (2) the magnetic energy associated with a fixed amount of magnetic helicity is minimized when the system relaxes this helical structure to the largest scale available. H...

  20. The structure and dynamics of self-assembling colloidal monolayers in oscillating magnetic fields

    CERN Document Server

    Koser, Alison E; Arratia, Paulo E

    2013-01-01

    Many fascinating phenomena such as large-scale collective flows, enhanced fluid mixing and pattern formation have been observed in so-called active fluids, which are composed of particles that can absorb energy and dissipate it into the fluid medium. For active particles immersed in liquids, fluid-mediated viscous stresses can play an important role on the emergence of collective behavior. Here, we experimentally investigate their role in the dynamics of self-assembling magnetically-driven colloidal particles which can rapidly form organized hexagonal structures. We find that viscous stresses reduce hexagonal ordering, generate smaller clusters, and significantly decrease the rate of cluster formation, all while holding the system at constant number density. Furthermore, we show that time and length scales of cluster formation depend on the Mason number (Mn), or ratio of viscous to magnetic forces, scaling as t / Mn and L / Mn^(1/2). Our results suggest that viscous stresses hinder collective behavior in a se...

  1. The relation between the column density structures and the magnetic field orientation in the Vela C molecular complex

    Science.gov (United States)

    Soler, J. D.; Ade, P. A. R.; Angilè, F. E.; Ashton, P.; Benton, S. J.; Devlin, M. J.; Dober, B.; Fissel, L. M.; Fukui, Y.; Galitzki, N.; Gandilo, N. N.; Hennebelle, P.; Klein, J.; Li, Z.-Y.; Korotkov, A. L.; Martin, P. G.; Matthews, T. G.; Moncelsi, L.; Netterfield, C. B.; Novak, G.; Pascale, E.; Poidevin, F.; Santos, F. P.; Savini, G.; Scott, D.; Shariff, J. A.; Thomas, N. E.; Tucker, C. E.; Tucker, G. S.; Ward-Thompson, D.

    2017-07-01

    We statistically evaluated the relative orientation between gas column density structures, inferred from Herschel submillimetre observations, and the magnetic field projected on the plane of sky, inferred from polarized thermal emission of Galactic dust observed by the Balloon-borne Large-Aperture Submillimetre Telescope for Polarimetry (BLASTPol) at 250, 350, and 500 μm, towards the Vela C molecular complex. First, we find very good agreement between the polarization orientations in the three wavelength-bands, suggesting that, at the considered common angular resolution of 3.´0 that corresponds to a physical scale of approximately 0.61 pc, the inferred magnetic field orientation is not significantly affected by temperature or dust grain alignment effects. Second, we find that the relative orientation between gas column density structures and the magnetic field changes progressively with increasing gas column density, from mostly parallel or having no preferred orientation at low column densities to mostly perpendicular at the highest column densities. This observation is in agreement with previous studies by the Planck collaboration towards more nearby molecular clouds. Finally, we find a correspondencebetween (a) the trends in relative orientation between the column density structures and the projected magnetic field; and (b) the shape of the column density probability distribution functions (PDFs). In the sub-regions of Vela C dominated by one clear filamentary structure, or "ridges", where the high-column density tails of the PDFs are flatter, we find a sharp transition from preferentially parallel or having no preferred relative orientation at low column densities to preferentially perpendicular at highest column densities. In the sub-regions of Vela C dominated by several filamentary structures with multiple orientations, or "nests", where the maximum values of the column density are smaller than in the ridge-like sub-regions and the high-column density

  2. Magnetic field control and wavelength tunability of SPP excitations using Al2O3/SiO2/Fe structures

    Science.gov (United States)

    Kaihara, Terunori; Shimizu, Hiromasa; Cebollada, Alfonso; Armelles, Gaspar

    2016-09-01

    Here, we show the high wavelength tunability and magnetic field modulation of surface plasmon polaritons (SPPs) of a waveguide mode that Double-layer Dielectrics and Ferromagnetic Metal, Al2O3/SiO2/Fe, trilayer structures exhibit when excited in the Otto configuration of attenuated total reflection setup. First by modeling, and then experimentally, we demonstrate that it is possible to tune the wavelength at which the angular dependent reflectance of these structures reaches its absolute minimum by simply adjusting the SiO2 intermediate dielectric layer thickness. This precise wavelength corresponds to the cut-off condition of SPPs' waveguide mode supported by the proposed structure, and it can be then switched between two values upon magnetization reversal of the Fe layer. In this specific situation, a large enhancement of the transverse magneto-optical effect is also obtained.

  3. Domain wall dynamics under electric field in CoFeB-MgO structures with perpendicular magnetic anisotropy (Conference Presentation)

    Science.gov (United States)

    Ravelosona, Dafine

    2016-10-01

    One crucial breakthrough in spin electronics has recently been achieved regarding the possibility to move magnetic domain walls (DWs) in magnetic tracks using the sole action of an electrical current instead of a conventional magnetic field. Here, we will present our recent results of DW dynamics obtained in Ta-CoFeB-MgO nanodevices with perpendicular magnetic anisotropy (PMA), which are widely used in STT-RAM applications, and discuss the critical problems to be addressed for implementation into a memory device. Using NV center microscopy to map DW pinning along a magnetic wire, we will first show1 that Ta/CoFeB(1nm)/MgO structures exhibit a very low density of pinning defects with respect to others materials with PMA. Then, we will focus on the possibility to use Electric Field Effect to control domain wall motion with low power dissipation. We will demonstrate gate voltage modulation of DW dynamics using different approaches based on dielectrics, piezoelectrics and ionic liquid layers.

  4. MEGAGAUSS SPECTRA OF SEMICONDUCTORS: MERCURYSELENIDE LOW-DIMENSIONAL STRUCTURES IN MAGNETIC FIELDS UP TO 1000 T

    Institute of Scientific and Technical Information of China (English)

    Michael von ORTENBERG

    2005-01-01

    Mercuryselenide is a zero-gap semiconductor of Ⅱ- Ⅵ-family. The iron-doped modification HgSe:Fe has a "Fermi-level pinning" beyond the electron concentration of 5 × 1018 cm-3. Due to the short-range correlation of Fe + +/Fe + + +system, a dramatic increase of carrier mobility is observed, so that any quantum effect in 3D, 2D, 1D, and 0D is well detected. Applying molecular-beam epitaxy for the sample preparation, we present magnetospectral data of selected samples of this compound demonstrating various features in magnetic fields up to 1000 T by applying different field generators. The resulting data are explained in connection with suitable theoretical concepts basing on the k * p-method as well as on the tightbinding approximation.

  5. Magnetic field perturbartions in closed-field-line systems with zero toroidal magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Mauel, M; Ryutov, D; Kesner, J

    2003-12-02

    In some plasma confinement systems (e.g., field-reversed configurations and levitated dipoles) the confinement is provided by a closed-field-line poloidal magnetic field. We consider the influence of the magnetic field perturbations on the structure of the magnetic field in such systems and find that the effect of perturbations is quite different from that in the systems with a substantial toroidal field. In particular, even infinitesimal perturbations can, in principle, lead to large radial excursions of the field lines in FRCs and levitated dipoles. Under such circumstances, particle drifts and particle collisions may give rise to significant neoclassical transport. Introduction of a weak regular toroidal magnetic field reduces radial excursions of the field lines and neoclassical transport.

  6. The Magnetic Field Effect on Planetary Nebulae

    Institute of Scientific and Technical Information of China (English)

    A. R. Khesali; K. Kokabi

    2006-01-01

    In our previous work on the 3-dimensional dynamical structure of planetary nebulae the effect of magnetic field was not considered. Recently Jordan et al. have directly detected magnetic fields in the central stars of some planetary nebulae. This discovery supports the hypothesis that the non-spherical shape of most planetary nebulae is caused by magnetic fields in AGB stars. In this study we focus on the role of initially weak toroidal magnetic fields embedded in a stellar wind in altering the shape of the PN. We found that magnetic pressure is probably influential on the observed shape of most PNe.

  7. Influence of magnetic field-aided filler orientation on structure and transport properties of ferrite filled composites

    Energy Technology Data Exchange (ETDEWEB)

    Goc, K., E-mail: Kamil.Goc@fis.agh.edu.pl [Department of Solid State Physics, AGH University of Science and Technology, 30 Mickiewicza Street, 30-059 Krakow (Poland); Gaska, K.; Klimczyk, K.; Wujek, A.; Prendota, W.; Jarosinski, L. [Department of Solid State Physics, AGH University of Science and Technology, 30 Mickiewicza Street, 30-059 Krakow (Poland); Rybak, A.; Kmita, G. [ABB Corporate Research Center, 13A Starowislna Street, 31-038 Krakow (Poland); Kapusta, Cz. [Department of Solid State Physics, AGH University of Science and Technology, 30 Mickiewicza Street, 30-059 Krakow (Poland)

    2016-12-01

    Epoxy resins are materials commonly used for insulations and encapsulations due to their easy processing process and mechanical strength. For their applications in power industry and electronics the effective heat dissipation is essential, thus their thermal conductivity is one of the most important properties. Introduction of appropriate dielectric powders, preferably in an ordered way, can increase the thermal conductivity of the polymer while keeping its good electrical insulation properties. In this work we used strontium ferrite as a filler to study the evolution of the filler particles distribution in the fluid before curing. Magnetic ferrite particles were dispersed in liquid epoxy resin and formation of chain-like or more complex structures under applied external magnetic field was observed and investigated. Computer simulations made show that with increasing magnetic field these structures are characterized by longer chains, higher speed of particles displacement and stronger structural anisotropy. However, for highly-filled systems, stronger inter-particle interactions make the alignment process less effective. The effective thermal conductivity simulated with FEM methods increases with increasing filler content and the percolation threshold in aligned systems is achieved at lower filler concentrations than for reference isotropic samples. The results are compared with the experimental data and a good qualitative agreement is obtained. - Highlights: • Influence of magnetic field on the particle chains in epoxy composites is analysed. • Strontium ferrite fillers with good thermal and low electrical conductivity. • Influence of interparticle interactions for agglomeration efficiency. • The impact of chains formed on the heat transfer by creating conductive paths. • Connection between structural anisotropy and transport properties anisotropy.

  8. Magnetic fields of neutron stars

    CERN Document Server

    Reisenegger, Andreas

    2013-01-01

    Neutron stars contain the strongest magnetic fields known in the Universe. In this paper, I discuss briefly how these magnetic fields are inferred from observations, as well as the evidence for their time-evolution. I show how these extremely strong fields are actually weak in terms of their effects on the stellar structure, as is also the case for magnetic stars on the upper main sequence and magnetic white dwarfs, which have similar total magnetic fluxes. I propose a scenario in which a stable hydromagnetic equilibrium (containing a poloidal and a toroidal field component) is established soon after the birth of the neutron star, aided by the strong compositional stratification of neutron star matter, and this state is slowly eroded by non-ideal magnetohydrodynamic processes such as beta decays and ambipolar diffusion in the core of the star and Hall drift and breaking of the solid in its crust. Over sufficiently long time scales, the fluid in the neutron star core will behave as if it were barotropic, becau...

  9. Magnetic fields in diffuse media

    CERN Document Server

    Pino, Elisabete; Melioli, Claudio

    2015-01-01

    This volume presents the current knowledge of magnetic fields in diffuse astrophysical media. Starting with an overview of 21st century instrumentation to observe astrophysical magnetic fields, the chapters cover observational techniques, origin of magnetic fields, magnetic turbulence, basic processes in magnetized fluids, the role of magnetic fields for cosmic rays, in the interstellar medium and for star formation. Written by a group of leading experts the book represents an excellent overview of the field. Nonspecialists will find sufficient background to enter the field and be able to appreciate the state of the art.

  10. Indoor localization using magnetic fields

    Science.gov (United States)

    Pathapati Subbu, Kalyan Sasidhar

    Indoor localization consists of locating oneself inside new buildings. GPS does not work indoors due to multipath reflection and signal blockage. WiFi based systems assume ubiquitous availability and infrastructure based systems require expensive installations, hence making indoor localization an open problem. This dissertation consists of solving the problem of indoor localization by thoroughly exploiting the indoor ambient magnetic fields comprising mainly of disturbances termed as anomalies in the Earth's magnetic field caused by pillars, doors and elevators in hallways which are ferromagnetic in nature. By observing uniqueness in magnetic signatures collected from different campus buildings, the work presents the identification of landmarks and guideposts from these signatures and further develops magnetic maps of buildings - all of which can be used to locate and navigate people indoors. To understand the reason behind these anomalies, first a comparison between the measured and model generated Earth's magnetic field is made, verifying the presence of a constant field without any disturbances. Then by modeling the magnetic field behavior of different pillars such as steel reinforced concrete, solid steel, and other structures like doors and elevators, the interaction of the Earth's field with the ferromagnetic fields is described thereby explaining the causes of the uniqueness in the signatures that comprise these disturbances. Next, by employing the dynamic time warping algorithm to account for time differences in signatures obtained from users walking at different speeds, an indoor localization application capable of classifying locations using the magnetic signatures is developed solely on the smart phone. The application required users to walk short distances of 3-6 m anywhere in hallway to be located with accuracies of 80-99%. The classification framework was further validated with over 90% accuracies using model generated magnetic signatures representing

  11. Influence of magnetic field-aided filler orientation on structure and transport properties of ferrite filled composites

    Science.gov (United States)

    Goc, K.; Gaska, K.; Klimczyk, K.; Wujek, A.; Prendota, W.; Jarosinski, L.; Rybak, A.; Kmita, G.; Kapusta, Cz.

    2016-12-01

    Epoxy resins are materials commonly used for insulations and encapsulations due to their easy processing process and mechanical strength. For their applications in power industry and electronics the effective heat dissipation is essential, thus their thermal conductivity is one of the most important properties. Introduction of appropriate dielectric powders, preferably in an ordered way, can increase the thermal conductivity of the polymer while keeping its good electrical insulation properties. In this work we used strontium ferrite as a filler to study the evolution of the filler particles distribution in the fluid before curing. Magnetic ferrite particles were dispersed in liquid epoxy resin and formation of chain-like or more complex structures under applied external magnetic field was observed and investigated. Computer simulations made show that with increasing magnetic field these structures are characterized by longer chains, higher speed of particles displacement and stronger structural anisotropy. However, for highly-filled systems, stronger inter-particle interactions make the alignment process less effective. The effective thermal conductivity simulated with FEM methods increases with increasing filler content and the percolation threshold in aligned systems is achieved at lower filler concentrations than for reference isotropic samples. The results are compared with the experimental data and a good qualitative agreement is obtained.

  12. Evolution with applied field of the magnetic structure of TbNiAl{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    White, R., E-mail: Reyner.White@student.adfa.edu.au; Hutchison, W. D. [The University of New South Wales, School of Physical, Environmental and Mathematical Sciences (Australia); Goossens, D. J. [Australian National University, Research School of Chemistry (Australia); Studer, A. J. [Bragg Institute, Australian Nuclear Science and Technology Organisation (Australia); Nishimura, K. [University of Toyama, Graduate School of Science and Engineering (Japan)

    2015-04-15

    Neutron powder diffraction data of TbNiAl{sub 4} has been re-examined using a representational analysis, allowing a new model of the magnetic structure to be deduced. The basis vectors obtained describe an ‘elliptical helix’ type structure in which the moments rotate in the ab-plane as one moves along the c-axis. This new model has been used to simulate the expected result of a Low Temperature Nuclear Orientation (LTNO) experiment involving 299 keV gamma-ray emission from the {sup 160}Dy daughter of aligned {sup 160}Tb nuclei. Results of the simulation along the a-axis appear to partly match currently existing experimental data, with good agreement in the magnitude of lost anisotropy.

  13. Coronal Magnetic Field Models

    Science.gov (United States)

    Wiegelmann, Thomas; Petrie, Gordon J. D.; Riley, Pete

    2017-09-01

    Coronal magnetic field models use photospheric field measurements as boundary condition to model the solar corona. We review in this paper the most common model assumptions, starting from MHD-models, magnetohydrostatics, force-free and finally potential field models. Each model in this list is somewhat less complex than the previous one and makes more restrictive assumptions by neglecting physical effects. The magnetohydrostatic approach neglects time-dependent phenomena and plasma flows, the force-free approach neglects additionally the gradient of the plasma pressure and the gravity force. This leads to the assumption of a vanishing Lorentz force and electric currents are parallel (or anti-parallel) to the magnetic field lines. Finally, the potential field approach neglects also these currents. We outline the main assumptions, benefits and limitations of these models both from a theoretical (how realistic are the models?) and a practical viewpoint (which computer resources to we need?). Finally we address the important problem of noisy and inconsistent photospheric boundary conditions and the possibility of using chromospheric and coronal observations to improve the models.

  14. Electrical characterization of gold-DNA-gold structures in presence of an external magnetic field by means of I-V curve analysis.

    Science.gov (United States)

    Khatir, Nadia Mahmoudi; Banihashemian, Seyedeh Maryam; Periasamy, Vengadesh; Ritikos, Richard; Abd Majid, Wan Haliza; Abdul Rahman, Saadah

    2012-01-01

    This work presents an experimental study of gold-DNA-gold structures in the presence and absence of external magnetic fields with strengths less than 1,200.00 mT. The DNA strands, extracted by standard method were used to fabricate a Metal-DNA-Metal (MDM) structure. Its electric behavior when subjected to a magnetic field was studied through its current-voltage (I-V) curve. Acquisition of the I-V curve demonstrated that DNA as a semiconductor exhibits diode behavior in the MDM structure. The current versus magnetic field strength followed a decreasing trend because of a diminished mobility in the presence of a low magnetic field. This made clear that an externally imposed magnetic field would boost resistance of the MDM structure up to 1,000.00 mT and for higher magnetic field strengths we can observe an increase in potential barrier in MDM junction. The magnetic sensitivity indicates the promise of using MDM structures as potential magnetic sensors.

  15. Temperature and magnetic field effect on oscillations observed in GaInNAs/GaAs multiple quantum wells structures

    Energy Technology Data Exchange (ETDEWEB)

    Khalil, H.M., E-mail: hkhalia@essex.ac.uk [School of Computer Science and Electronic Engineering, University of Essex, CO4 3SQ, Colchester (United Kingdom); Mazzucato, S. [School of Computer Science and Electronic Engineering, University of Essex, CO4 3SQ, Colchester (United Kingdom); Ardali, S.; Celik, O.; Mutlu, S. [Anadolu University, Faculty of Science, Department of Physics, Yunus Emre Campus 26470, Eskisehir (Turkey); Royall, B. [School of Computer Science and Electronic Engineering, University of Essex, CO4 3SQ, Colchester (United Kingdom); Tiras, E. [Anadolu University, Faculty of Science, Department of Physics, Yunus Emre Campus 26470, Eskisehir (Turkey); Balkan, N. [School of Computer Science and Electronic Engineering, University of Essex, CO4 3SQ, Colchester (United Kingdom); Puustinen, J.; Korpijaervi, V.-M.; Guina, M. [Optoelectronics Research Centre, Tampere University of Technology, Korkeakoulunkatu 10, FI-33720 Tampere (Finland)

    2012-06-05

    Highlights: Black-Right-Pointing-Pointer We studied p-i-n GaInNAs MQW devices as function of temperature and magnetic field. Black-Right-Pointing-Pointer Observed oscillations in the sample current-voltage curves at low temperature. Black-Right-Pointing-Pointer Shift in oscillation position with magnetic field described by Landau level split. Black-Right-Pointing-Pointer Resonant tunnelling and thermionic emission used to describe oscillations. - Abstract: The photoconductivity of p-i-n GaInNAs/GaAs multiple quantum well (MQW) mesa structures is investigated. When illuminated with photons at energy greater than the GaAs bandgap, a number of oscillations are observed in the current-voltage I-V characteristics. The amplitude and position of the oscillations is shown to depend upon the temperature, as well as upon the exciting wavelength and intensity. Due to the absence of the oscillations in the dark I-V and at temperatures above T = 200 K, we explain them in terms of photogenerated electrons escaping from quantum wells via tunnelling or thermionic emission. Magnetic fields up to B = 11 T were applied parallel to the planes of the QWs. A small voltage shift in the position of the oscillations was observed, proportional to the magnetic field intensity and dependent upon the temperature. Calculation of the Landau level energy separation (16 meV) agrees with the observed experimental data. Magneto-tunnelling spectroscopy probes in detail the nature of band- or impurity-like states responsible for resonances in first and second subbands, observing the I-V plot in dark condition and under illumination. The field-dependence of the amplitude of the oscillation peaks in I-V has the characteristic form of a quantum mechanical admixing effect. This enhancement is also probably due to the hole recombination with majority electrons tunnelling in the N-related states of the quantum wells.

  16. The core structure and pseudo-magnetic field of the dislocation in graphene

    Science.gov (United States)

    Wang, Shaofeng; Wang, Rui

    2013-10-01

    An analytical theory is presented for the dislocation (pentagon-heptagon pair) in graphene. In order to fully determine the nonlinear interaction which is responsible for the appearance of dislocation, a γ-potential is proposed and calculated from the electron-density functional theory. The improved dislocation equation, which takes into account the change in space between the mismatched chains, is solved by the variational principle. The strain and stress, in particular the change in the bond length and bond angle at the dislocation core, are obtained explicitly and verified by the first-principle calculation. The pseudo-magnetic field felt by electrons at the band edge is investigated including contribution from topology as well as deformation.

  17. The Need For High Resolution In Studies Of The 3-D Magnetic Field Structure Of AGN Jets

    Science.gov (United States)

    O'Sullivan, S. P.; Gabuzda, D. C.

    2009-08-01

    We are using ``broadband" (4.6 to 43 GHz) multi-frequency VLBA polarization observations of compact AGN to investigate the 3-D structure of their jet magnetic (B) fields. Observing at several frequencies, separated by short and long intervals, enables reliable determination of the distribution of Faraday Rotation, and thereby the intrinsic B field structure. Transverse Rotation Measure (RM) gradients were detected in the jets of 0954+658 and 1418+546, providing evidence for the presence of a helical B field surrounding the jet. The RM in the core regions of 2200+420 (BL Lac), 0954+658 and 1418+546 display different signs in different frequency-intervals (on different spatial scales); we suggest an explanation for this in terms of modest bends in a helical B field surrounding their jets. In future, polarization observations with a combination of VSOP-2 at 8, 22 and 43 GHz and ground arrays at frequencies with corresponding resolution will help map out the distributions of Faraday rotation, spectral index and the 3-D B field structure both across the jet and closer to the central engine, providing strong constraints for any jet B field models.

  18. Integrated Analysis on Gravity and Magnetic Fields of the Hailar Basin, NE China: Implications for Basement Structure and Deep Tectonics

    Science.gov (United States)

    Sun, B.; Wang, L.; Dong, P.; Scientific Team Of Applied Geophysics

    2010-12-01

    The Hailar Basin is one of the most representative basins among the Northeast China Basin Group, which is situated in the east of East Asia Orogene between the Siberia Plate and the North China Plate. Based on the detailed analysis of the Bouguer gravity anomaly, aeromagnetic anomaly as well as petrophysical data, we studied the features of gravity-magnetic fields in the basin and its neighboring areas. A combined approach of Wavelet Multi-scale Decomposition and Power Spectrum Analysis was adopted to quantitatively grade the gravity and magnetic anomalies into four levels. Accordingly, the apparent depths of the source fields can be assessed. The results reveal the crustal density and magnetic structures of the Hailar Basin. Low-order wavelet details of gravity-magnetic anomalies were carried out on studying basin basement structure. Seven major basement faults of the basin were identified, and the basement lithology was discussed and predicted. Three major uplifts and 14 depressions were delineated according to basement depth inversion by the Park method. High-order wavelet approximations of gravity-magnetic anomalies were carried out on studying deep tectonics of the basin. The average Moho depth of the study area is about 40 km, with a mantle uplift located in the northeast of the basin. The average depth of the Curie interface is about 19 km, while the uplift of the Curie interface is in the basin center and its east and west sides are depressions. Finally, inversion of Bouguer gravity anomalies was conducted on an across-basin GGT profile using the Wavelet Multi-scale Decomposition. The inversion results are consistent with those of GGT seismic inversion, suggesting that the Wavelet Multi-scale Decomposition can be applied to distinguish major crustal density interfaces.

  19. Numerical Simulation of Level Magnetic Field

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    According to Maxwell electromagnetic field theory and magnetic vector potential integral equation, a mathematical model of LMF (Level Magnetic Field) for EMBR (Electromagnetic brake) was proposed, and the reliable software for LMF calculation was developed. The distribution of magnetic flux density given by numerical simulation shows that the magnetic flux density is greater in the magnet and magnetic leakage is observed in the gap. The magnetic flux density is uniform in horizontal plane and a peak is observed in vertical plane. Furthermore, the effects of electromagnetic and structural parameters on magnetic flux density were discussed. The relationship between magnetic flux, electromagnetic parameters and structural parameters is obtained by dimensional analysis, simulation experiment and least square method.

  20. Magnetic properties and electronic structure of neptunyl(VI) complexes: wavefunctions, orbitals, and crystal-field models

    Energy Technology Data Exchange (ETDEWEB)

    Gendron, Frederic; Pritchard, Ben; Autschbach, Jochen [Department of Chemistry, University at Buffalo, State University of New York, Buffalo, NY (United States); Paez-Hernandez, Dayan; Bolvin, Helene [Laboratoire de Physique et de Chimie Quantiques, Universite Toulouse 3 (France); Notter, Francois-Paul [Laboratoire de Chimie Quantique, Universite de Strasbourg (France)

    2014-06-23

    The electronic structure and magnetic properties of neptunyl(VI), NpO{sub 2}{sup 2+}, and two neptunyl complexes, [NpO{sub 2}(NO{sub 3}){sub 3}]{sup -} and [NpO{sub 2}Cl{sub 4}]{sup 2-}, were studied with a combination of theoretical methods: ab initio relativistic wavefunction methods and density functional theory (DFT), as well as crystal-field (CF) models with parameters extracted from the ab initio calculations. Natural orbitals for electron density and spin magnetization from wavefunctions including spin-orbit coupling were employed to analyze the connection between the electronic structure and magnetic properties, and to link the results from CF models to the ab initio data. Free complex ions and systems embedded in a crystal environment were studied. Of prime interest were the electron paramagnetic resonance g-factors and their relation to the complex geometry, ligand coordination, and nature of the nonbonding 5f orbitals. The g-factors were calculated for the ground and excited states. For [NpO{sub 2}Cl{sub 4}]{sup 2-}, a strong influence of the environment of the complex on its magnetic behavior was demonstrated. Kohn-Sham DFT with standard functionals can produce reasonable g-factors as long as the calculation converges to a solution resembling the electronic state of interest. However, this is not always straightforward. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  1. Magnetic Field Topology in Jets

    Science.gov (United States)

    Gardiner, T. A.; Frank, A.

    2000-01-01

    We present results on the magnetic field topology in a pulsed radiative. jet. For initially helical magnetic fields and periodic velocity variations, we find that the magnetic field alternates along the, length of the jet from toroidally dominated in the knots to possibly poloidally dominated in the intervening regions.

  2. Magnetic field switchable dry adhesives.

    Science.gov (United States)

    Krahn, Jeffrey; Bovero, Enrico; Menon, Carlo

    2015-02-01

    A magnetic field controllable dry adhesive device is manufactured. The normal adhesion force can be increased or decreased depending on the presence of an applied magnetic field. If the magnetic field is present during the entire normal adhesion test cycle which includes both applying a preloading force and measuring the pulloff pressure, a decrease in adhesion is observed when compared to when there is no applied magnetic field. Similarly, if the magnetic field is present only during the preload portion of the normal adhesion test cycle, a decrease in adhesion is observed because of an increased stiffness of the magnetically controlled dry adhesive device. When the applied magnetic field is present during only the pulloff portion of the normal adhesion test cycle, either an increase or a decrease in normal adhesion is observed depending on the direction of the applied magnetic field.

  3. Methodology and design synthesis of source of the magnetic fields with complicated energy-frequency and polarization structure

    Directory of Open Access Journals (Sweden)

    Zhitnik N. E.

    2008-12-01

    Full Text Available The method of synthesis of the rotating magnetic fields, created by combination of three mutually perpendicular solenoidal contours power supplied by an alternating current, is discussed. Possibility of construction of the magnetoforming system with changing direction of the magnetic field rotation, allowing in practical realization to take into account the chiral dissymmetry of molecules of matters, subject to treatment by the magnetic field, is shown.

  4. Magnetic structure and effect of magnetic field on its domain structure in magnetoelectric Ba1.3Sr0.7CoZnFe11AlO22

    Science.gov (United States)

    Ueda, H.; Tanaka, Y.; Nakajima, H.; Mori, S.; Ohta, K.; Haruki, K.; Hirose, S.; Wakabayashi, Y.; Kimura, T.

    2016-10-01

    The magnetic structure and the effect of a magnetic field on its domain structure were investigated in a magnetoelectric Y-type hexaferrite, Ba1.3Sr0.7CoZnFe11AlO22, by means of mapping with a micro-focused and circularly polarized X-ray beam in the resonant X-ray diffraction. It was revealed that this hexaferrite exhibits a magnetic order characterized by two distinct antiferromagnetic components: incommensurate helical and commensurate collinear ones, which can be explained as the development of the so-called alternating longitudinal conical structure. A multi-domain state due to the handedness of the helical component, i.e., spin-chirality, is transformed into nearly a mono-domain one by using only a magnetic field. Furthermore, the sign of the spin-chirality in the mono-domain state is reversed by reversing the sign of a magnetic field. These results demonstrate that the spin-chirality in this hexaferrite can be manipulated by a magnetic field alone at room temperature.

  5. Effect of Structure Parameters on Power and Magnetic Field in Electromagnetic Soft-Contact Continuous Casting System

    Institute of Scientific and Technical Information of China (English)

    DENG An-yuan; WANG En-gang; HE Ji-cheng

    2008-01-01

    To design a power source system and mold for electromagnetic soft-contact continuous casting process and to theoretically estimate the heat losses from the charges and the system power, the effect of structure parameters on system power and magnetic flux density distribution was calculated using finite element method. The results show that as for electromagnetic soft-contact continuous casting system with partial-segment type mold, the power consumption is much more than that with a full-segment type mold; about 62% of electric power is dissipated in the mold, and the effective acting range of magnetic field is relatively narrow. Optimizing mold structure is a crucial measure of remarkably reducing mold power consumption and saving electric energy. Increasing slit number, width, and length can remarkably increase the magnetic flux density in the mold and can reduce the electric energy consumption. Among structure parameters, slit number and slit width are relatively more effective to reduce energy consumption. For a round billet electromagnetic continuous casting system with diameter of 178 mm, the reasonable slit number, width, and length are about 24-32, 0.5-1.0 mm, and 160 mm, respectively.

  6. Study of magnetic, structural and magnetocaloric properties of La0.6Pr0.4Mn2Si2 under high pressures and magnetic field

    Science.gov (United States)

    Kaštil, J.; Arnold, Z.; Isnard, O.; Skourski, Y.; Kamarád, J.; Itié, J. P.

    2017-02-01

    The structural, magnetic and magnetocaloric properties of La0.6Pr0.4Mn2Si2 compound were measured in wide range of temperature, magnetic field and hydrostatic pressure. The structural study up to 10 GPa confirmed the existence of critical Mn-Mn distance 0.2883 nm for the ferromagnetic to antiferromagnetic transition at room temperature. The results demonstrated the crucial role of the volume in the suppression of the ferromagnetic phase above the transition temperature T1=168 K under pressure. The huge pressure shift of the transition temperature T1, dT1/dp=230 K/GPa, was observed. Based on our magnetization measurement the low temperature transition at T2=30 K is connected with reorientation of Mn moment and the rare-earth sublattice is not ordered in this case. The direct magnetocaloric measurement showed moderate values of the adiabatic temperature change connected with the magnetic transition at Tc and T1 and confirmed the first order character of the transition at T1 and second order character of the transition at Tc.

  7. Magnetic domain structures and stray fields of individual elongated magnetite grains revealed by magnetic force microscopy (MFM)

    DEFF Research Database (Denmark)

    Frandsen, Cathrine; Stipp, S. L. S.; McEnroe, S. A.

    2004-01-01

    In order to clarify the relationship between microscopic and macroscopic magnetic features of a rock, we applied magnetic force microscopy (MFM) as a local probe on a sample with an intense natural remanent magnetisation, a norite from Heskestad, Norway. We studied in detail seven magnetite (Fe3O4...

  8. Scanning transmission X-ray microscopy study of the stretched magnetic-domain structure of Co/Pt multilayers under an in-plane field

    Science.gov (United States)

    Handoko, Djati; Quach, Duy-Truong; Lee, Sang-Hyuk; Shim, Je-Ho; Kim, Dong-Hyun; Lee, Kyung-Min; Jeong, Jong-Ryul; Kim, Namdong; Shin, Hyun-Joon

    2015-06-01

    We report our investigation on the magnetic-domain structure of a Co/Pt multilayer with perpendicular magnetic anisotropy under a horizontal in-plane field by using a high-resolution scanning transmission X-ray microscope (STXM) developed at Pohang Accelerator Laboratory. The ruggedshaped striped magnetic-domain structure that was initially formed under a field cycle along the out-of-the plane magnetic easy axis was found to be stretched and elongated along the direction of the horizontal in-plane field. As the in-plane field was strengthened, the striped pattern exhibited an anisotropic domain growth with further stretching and aligning, as well as with a modification of the magnetic-domain's width.

  9. Alfv\\'en wave phase mixing in flows -- why over-dense solar coronal open magnetic field structures are cool?

    CERN Document Server

    Tsiklauri, D

    2015-01-01

    Our magnetohydrodynamic (MHD) simulations and analytical calculations show that, when a background flow is present, mathematical expressions for the Alfv\\'en wave (AW) damping via phase mixing are modified by a following substitution $C_A^\\prime(x) \\to C_A^\\prime(x)+V_0^\\prime(x)$, where $C_A$ and $V_0$ are AW phase and the flow speeds and prime denotes derivative in the direction across the background magnetic field. In uniform magnetic field and over-dense plasma structures, in which $C_A$ is smaller compared to surrounding plasma, the flow, that is confined to the structure, in the same direction as the AW, reduces the effect of phase mixing, because on the edges of the structure $C_A^\\prime$ and $V_0^\\prime$ have opposite sign. Thus, the wave damps via phase mixing {\\it slower} compared to the case without the flow. This is the consequence of the co-directional flow reducing the wave front stretching in the transverse direction. Although, the result is generic and is applicable to different laboratory or ...

  10. Superhorizon magnetic fields

    CERN Document Server

    Campanelli, Leonardo

    2015-01-01

    [Abridged] We analyze the evolution of superhorizon-scale magnetic fields from the end of inflation till today. Whatever is the mechanism responsible for their generation during inflation, we find that a given magnetic mode with wavenumber $k$ evolves, after inflation, according to the values of $k\\eta_e$, $n_{\\mathbf{k}}$, and $\\Omega_k$, where $\\eta_e$ is the conformal time at the end of inflation, $n_{\\mathbf{k}}$ is the number density spectrum of inflation-produced photons, and $\\Omega_k$ is the phase difference between the two Bogolubov coefficients which characterize the state of that mode at the end of inflation. For any realistic inflationary magnetogenesis scenario, we find that $n_{\\mathbf{k}}^{-1} \\ll |k\\eta_e| \\ll 1$, and three evolutionary scenarios are possible: ($i$) $|\\Omega_k \\mp \\pi| = \\mathcal{O}(1)$, in which case the evolution of the magnetic spectrum $B_k(\\eta)$ is adiabatic, $a^2B_k(\\eta) = \\mbox{const}$, with $a$ being the expansion parameter; ($ii$) $|\\Omega_k \\mp \\pi| \\ll |k\\eta_e|$,...

  11. Electronic structure of a spherical quantum dot: Effects of the Kratzer potential, hydrogenic impurity, external electric and magnetic fields

    Science.gov (United States)

    Dehyar, A.; Rezaei, G.; Zamani, A.

    2016-10-01

    In the present work, we have investigated the simultaneous effects of external electric and magnetic fields on the energy spectrum of an electron bound to an impurity confined in a spherical quantum dot with Kratzer potential. To this end, energy eigenvalues are obtained using the asymptotic iteration method. The energy dependencies upon the confinement potential and external fields are reported. Our results indicate that the confinement potential, external electric and magnetic fields have a great influence on the energy eigenvalues of the system. We found that, an increase in the magnetic field increases the energy eigenvalues of the states with positive magnetic quantum number, m ≽ 0 . While, the states with negative m decrease, reaching to their minimum values and increase again, with increasing the magnetic field. Moreover, an increase in electric field strength leads to decrease the confinement effects and energy eigenvalues of the system.

  12. Dynamics and structure of self-generated magnetics fields on solids following high contrast, high intensity laser irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Albertazzi, B. [LULI, École Polytechnique, CNRS, CEA, UPMC, 91128 Palaiseau (France); INRS-EMT, 1650 bd L. Boulet, J3X1S2, Varennes, Québec (Canada); Graduate School of Engineering, University of Osaka, Suita, Osaka 565-087 (Japan); Chen, S. N.; Fuchs, J., E-mail: julien.fuchs@polytechnique.fr [LULI, École Polytechnique, CNRS, CEA, UPMC, 91128 Palaiseau (France); Institute of Applied Physics, 46 Ulyanov Street, 603950 Nizhny Novgorod (Russian Federation); Antici, P. [INRS-EMT, 1650 bd L. Boulet, J3X1S2, Varennes, Québec (Canada); Dept. SBAI, Universita di Roma “La Sapienza,” Via A. Scarpa 14, 00161 Rome (Italy); Böker, J.; Swantusch, M.; Willi, O. [Institut für Laser-und Plasmaphysik, Heinrich-Heine-Universität, Düsseldorf (Germany); Borghesi, M. [School of Mathematics and Physics, The Queen' s University, Belfast (United Kingdom); Breil, J.; Feugeas, J. L.; Nicolaï, Ph.; Tikhonchuk, V. T.; D' Humières, E. [CELIA, University of Bordeaux - CNRS - CEA, 33405 Talence (France); Dervieux, V.; Nakatsutsumi, M.; Romagnagni, L. [LULI, École Polytechnique, CNRS, CEA, UPMC, 91128 Palaiseau (France); Lancia, L. [Dept. SBAI, Universita di Roma “La Sapienza,” Via A. Scarpa 14, 00161 Rome (Italy); Shepherd, R. [LLNL, East Av., Livermore, California 94550 (United States); Sentoku, Y. [Department of Physics, University of Nevada, Reno, Nevada 89557-0058 (United States); Starodubtsev, M. [Institute of Applied Physics, 46 Ulyanov Street, 603950 Nizhny Novgorod (Russian Federation); and others

    2015-12-15

    The dynamics of self-generated magnetic B-fields produced following the interaction of a high contrast, high intensity (I > 10{sup 19 }W cm{sup −2}) laser beam with thin (3 μm thick) solid (Al or Au) targets is investigated experimentally and numerically. Two main sources drive the growth of B-fields on the target surfaces. B-fields are first driven by laser-generated hot electron currents that relax over ∼10–20 ps. Over longer timescales, the hydrodynamic expansion of the bulk of the target into vacuum also generates B-field induced by non-collinear gradients of density and temperature. The laser irradiation of the target front side strongly localizes the energy deposition at the target front, in contrast to the target rear side, which is heated by fast electrons over a much larger area. This induces an asymmetry in the hydrodynamic expansion between the front and rear target surfaces, and consequently the associated B-fields are found strongly asymmetric. The sole long-lasting (>30 ps) B-fields are the ones growing on the target front surface, where they remain of extremely high strength (∼8–10 MG). These B-fields have been recently put by us in practical use for focusing laser-accelerated protons [B. Albertazzi et al., Rev. Sci. Instrum. 86, 043502 (2015)]; here we analyze in detail their dynamics and structure.

  13. External-field-free magnetic biosensor

    Energy Technology Data Exchange (ETDEWEB)

    Li, Yuanpeng; Wang, Yi; Klein, Todd; Wang, Jian-Ping, E-mail: jpwang@umn.edu [Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, Minnesota 55455 (United States)

    2014-03-24

    In this paper, we report a magnetic nanoparticle (MNP) detection scheme without the presence of any external magnetic field. The proposed magnetic sensor uses a patterned groove structure within the sensor so that no external magnetic field is needed to magnetize the MNPs. An example is given based on a giant magnetoresistance (GMR) sensing device with a spin valve structure. For this structure, the detection of MNPs located inside the groove and near the free layer is demonstrated under no external magnetic field. Micromagnetic simulations are performed to calculate the signal to noise level of this detection scheme. A maximum signal to noise ratio (SNR) of 18.6 dB from one iron oxide magnetic nanoparticle with 8 nm radius is achieved. As proof of concept, this external-field-free GMR sensor with groove structure of 200 nm × 200 nm is fabricated using a photo and an electron beam integrated lithography process. Using this sensor, the feasibility demonstration of the detection SNR of 9.3 dB is achieved for 30 μl magnetic nanoparticles suspension (30 nm iron oxide particles, 1 mg/ml). This proposed external-field-free sensor structure is not limited to GMR devices and could be applicable to other magnetic biosensing devices.

  14. Magnetic fields in spiral galaxies

    Science.gov (United States)

    Krause, Marita

    2015-03-01

    The magnetic field structure in edge-on galaxies observed so far shows a plane-parallel magnetic field component in the disk of the galaxy and an X-shaped field in its halo. The plane-parallel field is thought to be the projected axisymmetric (ASS) disk field as observed in face-on galaxies. Some galaxies addionionally exhibit strong vertical magnetic fields in the halo right above and below the central region of the disk. The mean-field dynamo theory in the disk cannot explain these observed fields without the action of a wind, which also probably plays an important role to keep the vertical scale heights constant in galaxies of different Hubble types and star formation activities, as has been observed in the radio continuum: At λ6 cm the vertical scale heights of the thin disk and the thick disk/halo in a sample of five edge-on galaxies are similar with a mean value of 300 +/- 50 pc for the thin disk and 1.8 +/- 0.2 kpc for the thick disk (a table and references are given in Krause 2011) with our sample including the brightest halo observed so far, NGC 253, with strong star formation, as well as one of the weakest halos, NGC 4565, with weak star formation. If synchrotron emission is the dominant loss process of the relativistic electrons the outer shape of the radio emission should be dumbbell-like as has been observed in several edge-on galaxies like e.g. NGC 253 (Heesen et al. 2009) and NGC 4565. As the synchrotron lifetime t syn at a single frequency is proportional to the total magnetic field strength B t -1.5, a cosmic ray bulk speed (velocity of a galactic wind) can be defined as v CR = h CR /t syn = 2 h z /t syn , where h CR and h z are the scale heights of the cosmic rays and the observed radio emission at this freqnency. Similar observed radio scale heights imply a self regulation mechanism between the galactic wind velocity, the total magnetic field strength and the star formation rate SFR in the disk: v CR ~ B t 1.5 ~ SFR ~ 0.5 (Niklas & Beck 1997).

  15. SCUPOL Magnetic Field Analysis

    CERN Document Server

    Poidevin, Frederick; Kowal, Grzegorz; Pino, Elisabete de Gouveia Dal; Magalhaes, Antonio-Mario

    2013-01-01

    We present an extensive analysis of the 850 microns polarization maps of the SCUPOL Catalog produced by Matthews et al. (2009), focusing exclusively on the molecular clouds and star-forming regions. For the sufficiently sampled regions, we characterize the depolarization properties and the turbulent-to-mean magnetic field ratio of each region. Similar sets of parameters are calculated from 2D synthetic maps of dust emission polarization produced with 3D MHD numerical simulations scaled to the S106, OMC-2/3, W49 and DR21 molecular clouds polarization maps. For these specific regions the turbulent MHD regimes retrieved from the simulations, as described by the turbulent Alfv\\`en and sonic Mach numbers, are consistent within a factor 1 to 2 with the values of the same turbulent regimes estimated from the analysis of Zeeman measurements data provided by Crutcher (1999). Constraints on the values of the inclination angle of the mean magnetic field with respect to the LOS are also given. The values obtained from th...

  16. Rotating artificial gauge magnetic and electric fields

    CERN Document Server

    Lembessis, V E; Alshamari, S; Siddig, A; Aldossary, O M

    2016-01-01

    We consider the creation of artificial gauge magnetic and electric fields created when a two-level atom interacts with an optical Ferris wheel light field.These fields have the spatial structure of the optical Ferris wheel field intensity profile. If this optical field pattern is made to rotate in space then we have the creation of artificial electromagnetic fields which propagate in closed paths. The properties of such fields are presented and discussed

  17. Magnetic Fields: Visible and Permanent.

    Science.gov (United States)

    Winkeljohn, Dorothy R.; Earl, Robert D.

    1983-01-01

    Children will be able to see the concept of a magnetic field translated into a visible reality using the simple method outlined. Standard shelf paper, magnets, iron filings, and paint in a spray can are used to prepare a permanent and well-detailed picture of the magnetic field. (Author/JN)

  18. Formation of H i Clouds in Shock-compressed Interstellar Medium: Physical Origin of Angular Correlation between Filamentary Structure and Magnetic Field

    Science.gov (United States)

    Inoue, Tsuyoshi; Inutsuka, Shu-ichiro

    2016-12-01

    Recent observations of the neutral Galactic interstellar medium showed that filamentary structures of H i clouds are aligned with the interstellar magnetic field. Many interesting applications are proposed based on the alignment, such as measurement of magnetic field strength through the Chandrasekhar-Fermi method and removal of foreground dust emissions for the detection of inflationary polarized emission in the cosmic microwave background radiation. However, the physical origin of the alignment remains to be explained. To understand the mechanism, we examine the formation of H i clouds triggered by shock compression of the diffuse warm neutral medium using three-dimensional magnetohydrodynamic simulations. We show that the shock-compressed medium of density n˜ 1 cm-3 evolves into H i clouds with n˜ 50 cm-3 via thermal instability consistent with previous studies. We apply a machine vision transformation developed by Clark et al. to the simulated column density structures to measure angle correlation between filamentary structures of H i clouds and magnetic field. We find that the orientation of H i filaments depends on the environmental turbulent velocity field, particularly on the strength of shear strain in the direction of the magnetic field, which is controlled by the angle between the shock propagation direction and upstream magnetic field. When the strain along the magnetic field is weak, filamentary components of H i clouds lie perpendicular to the magnetic field. However, the filaments have come to align with the magnetic field, if we enhance the turbulent strain along the magnetic field or if we set turbulence in the preshock medium.

  19. Size-dependent structure and magnetic properties of co-evaporated Fe-SiO2 nanoparticle composite film under high magnetic field

    Directory of Open Access Journals (Sweden)

    Yonghui Ma

    2016-05-01

    Full Text Available Composite film of Fe nanoparticles embedded in a SiO2 matrix has been prepared by the co-evaporation of Fe and SiO2. Both source temperature and in-situ high magnetic field (HMF have been used to adjust the Fe particle size and the growth of Fe-SiO2 film. The size of Fe particle decreased with increasing the source temperature without HMF. When HMF was presented during the growth of the film, the size of Fe particle was enlarged and reduced for source temperatures of 1300 °C and 1400 °C, respectively. Meanwhile, the preferred orientation of the film grown at 1400 °C became uniform with the application of HMF. In addition, it is also found that the film was formed in two layers. One layer is formed by the Fe particle, while the other is free of Fe particles due to the existence of more SiO2. The structural variation has a significant effect on the magnetic properties. The coercivity (90 Oe of the 1300 °C film is much higher than that (6 Oe of the 1400 °C film with a small particle size and uniform orientation. The saturation magnetization can be increased by increasing the Fe particle volume fraction. This study develops a new method to tune the soft magnetic properties by the co-evaporation of Fe and SiO2.

  20. Two-axis magnetic field sensor

    Science.gov (United States)

    Jander, Albrecht (Inventor); Nordman, Catherine A. (Inventor); Qian, Zhenghong (Inventor); Smith, Carl H. (Inventor)

    2006-01-01

    A ferromagnetic thin-film based magnetic field sensor with first and second sensitive direction sensing structures each having a nonmagnetic intermediate layer with two major surfaces on opposite sides thereof having a magnetization reference layer on one and an anisotropic ferromagnetic material sensing layer on the other having a length in a selected length direction and a smaller width perpendicular thereto and parallel to the relatively fixed magnetization direction. The relatively fixed magnetization direction of said magnetization reference layer in each is oriented in substantially parallel to the substrate but substantially perpendicular to that of the other. An annealing process is used to form the desired magnetization directions.

  1. Improvement of magnetosphere structure calculations using eccentric dipole to account for the internal magnetic field

    Science.gov (United States)

    Parunakian, David

    2014-05-01

    In this paper we build upon the results previously produced by numerous attempts, including our own, to approximate the geomagnetic field with a an eccentric dipole instead of spherical harmonics expansions. Among other motivations to do so is that dipole-related effects are much more pronounced relative to higher-order harmonics at large distances from the Earth, and that the shift of the order of magnitude about 0.1 Earth radii is significant enough for many magnetospheric structures such as the current sheet. We present the results of multivariate simulated annealing, which includes translational and rotational repositioning of the dipole. We also include similar results produced for Mercury and Saturn, and we extend Earth-related data with Oersted and Cluster measurements in order to further improve our accuracy.

  2. Magnetospheric Multiscale Satellite Observations of Parallel Electron Acceleration in Magnetic Field Reconnection by Fermi Reflection from Time Domain Structures.

    Science.gov (United States)

    Mozer, F S; Agapitov, O A; Artemyev, A; Burch, J L; Ergun, R E; Giles, B L; Mourenas, D; Torbert, R B; Phan, T D; Vasko, I

    2016-04-08

    The same time domain structures (TDS) have been observed on two Magnetospheric Multiscale Satellites near Earth's dayside magnetopause. These TDS, traveling away from the X line along the magnetic field at 4000  km/s, accelerated field-aligned ∼5  eV electrons to ∼200  eV by a single Fermi reflection of the electrons by these overtaking barriers. Additionally, the TDS contained both positive and negative potentials, so they were a mixture of electron holes and double layers. They evolve in ∼10  km of space or 7 ms of time and their spatial scale size is 10-20 km, which is much larger than the electron gyroradius (<1  km) or the electron inertial length (4 km at the observation point, less nearer the X line).

  3. Magnetic fields and rotation of spiral galaxies

    CERN Document Server

    Battaner, E; Florido, E

    1998-01-01

    We present a simplified model in which we suggest that two important galactic problems -the magnetic field configuration at large scales and the flat rotation curve- may be simultaneously explained. A highly convective disc produces a high turbulent magnetic diffusion in the vertical direction, stablishing a merging of extragalactic and galactic magnetic fields. The outer disc may then adquire a magnetic energy gradient very close to the gradient required to explain the rotation curve, without the hypothesis of galactic dark matter. Our model predicts symmetries of the galactic field in noticeable agreement with the large scale structure of our galaxy.

  4. Reconnection of Magnetic Fields

    Science.gov (United States)

    Birn, J.; Priest, E. R.

    2007-01-01

    Preface; Part I. Introduction: 1.1 The Sun E. R. Priest; 1.2 Earth's magnetosphere J. Birn; Part II. Basic Theory of MHD Reconnection: 2.1 Classical theory of two-dimensional reconnection T. G. Forbes; 2.2 Fundamental concepts G. Hornig; 2.3 Three-dimensional reconnection in the absence of magnetic null points G. Hornig; 2.4 Three-dimensional reconnection at magnetic null points D. Pontin; 2.5 Three-dimensional flux tube reconnection M. Linton; Part III. Basic Theory of Collisionless Reconnection: 3.1 Fundamentals of collisionless reconnection J. Drake; 3.2 Diffusion region physics M. Hesse; 3.3 Onset of magnetic reconnection P. Pritchett; 3.4 Hall-MHD reconnection A. Bhattacharjee and J. Dorelli; 3.5 Role of current-aligned instabilities J. Büchner and W. Daughton; 3.6 Nonthermal particle acceleration M. Hoshino; Part IV. Reconnection in the Magnetosphere: 4.1 Reconnection at the magnetopause: concepts and models J. G. Dorelli and A. Bhattacharjee; 4.2 Observations of magnetopause reconnection K.-H. Trattner; 4.3 On the stability of the magnetotail K. Schindler; 4.4 Simulations of reconnection in the magnetotail J. Birn; 4.5 Observations of tail reconnection W. Baumjohann and R. Nakamura; 4.6 Remote sensing of reconnection M. Freeman; Part V. Reconnection in the Sun's Atmosphere: 5.1 Coronal heating E. R. Priest; 5.2 Separator reconnection D. Longcope; 5.3 Pinching of coronal fields V. Titov; 5.4 Numerical experiments on coronal heating K. Galsgaard; 5.5 Solar flares K. Kusano; 5.6 Particle acceleration in flares: theory T. Neukirch; 5.7 Fast particles in flares: observations L. Fletcher; 6. Open problems J. Birn and E. R. Priest; Bibliography; Index.

  5. Catalog of fine-structured electron velocity distribution functions - Part 1: Antiparallel magnetic-field reconnection (Geospace Environmental Modeling case)

    Science.gov (United States)

    Bourdin, Philippe-A.

    2017-09-01

    To understand the essential physics needed to reproduce magnetic reconnection events in 2.5-D particle-in-cell (PIC) simulations, we revisit the Geospace Environmental Modeling (GEM) setup. We set up a 2-D Harris current sheet (that also specifies the initial conditions) to evolve the reconnection of antiparallel magnetic fields. In contrast to the GEM setup, we use a much smaller initial perturbation to trigger the reconnection and evolve it more self-consistently. From PIC simulation data with high-quality particle statistics, we study a symmetric reconnection site, including separatrix layers, as well as the inflow and the outflow regions. The velocity distribution functions (VDFs) of electrons have a fine structure and vary strongly depending on their location within the reconnection setup. The goal is to start cataloging multidimensional fine-structured electron velocity distributions showing different reconnection processes in the Earth's magnetotail under various conditions. This will enable a direct comparison with observations from, e.g., the NASA Magnetospheric MultiScale (MMS) mission, to identify reconnection-related events. We find regions with strong non-gyrotropy also near the separatrix layer and provide a refined criterion to identify an electron diffusion region in the magnetotail. The good statistical significance of this work for relatively small analysis areas reveals the gradual changes within the fine structure of electron VDFs depending on their sampling site.

  6. Effect of temperature and magnetic fields on the structural state of the Fe-Zr-B amorphous alloy below crystallization temperature

    Directory of Open Access Journals (Sweden)

    Fedotova N.L.

    2011-05-01

    Full Text Available Amorphous materials give the possibility to observe the phase and structural transformations in sufficiently narrow temperature intervals with the retention of their unchanged chemical composition. The present report is concerned with the results of the study of structure evolution and its dependence on magnetic field upon heating in the Fe-Zr-B amorphous alloy by the method of the photometric analysis of structural images (PHASI. The PHASI method makes it possible to establish the effect of external temperature and magnetic fields on the brightness spectra of the reflection from the surface of the object under study and the distribution of the zones, in which these changes are localized. The established temperature dependence of the energy characteristics of the reflection brightness spectrum in arbitrary units indicates the complex structural transformations caused by heating of the alloy under study. Also it is shown that the magnetic field produces residual structural changes in the alloy in comparison with its initial state

  7. A structurally-controllable spin filter in a δ-doped magnetically modulated semiconductor nanostructure with zero average magnetic field

    Science.gov (United States)

    Shen, Li-Hua; Ma, Wen-Yue; Zhang, Gui-Lian; Yang, Shi-Peng

    2015-07-01

    We report on a theoretical investigation of spin-polarized transport in a δ-doped magnetically modulated semiconductor nanostructure, which can be experimentally realized by depositing a ferromagnetic stripe on the top of a semiconductor heterostructure and by using the atomic layer doping technique such as molecular beam epitaxy (MBE). It is shown that although such a nanostructure has a zero average magnetic filed, a sizable spin polarization exists due to the Zeeman splitting mechanism. It is also shown that the degree of spin polarization varies sensitively with the weight and/or position of the δ-doping. Therefore, one can conveniently tailor the behaviour of the spin-polarized electron by tuning the δ -doping, and such a device can be employed as a controllable spin filter for spintronics.

  8. Assembly of magnetic spheres in strong homogeneous magnetic field

    Science.gov (United States)

    Messina, René; Stanković, Igor

    2017-01-01

    The assembly in two dimensions of spherical magnets in strong magnetic field is addressed theoretically. It is shown that the attraction and assembly of parallel magnetic chains is the result of a delicate interplay of dipole-dipole interactions and short ranged excluded volume correlations. Minimal energy structures are obtained by numerical optimization procedure as well as analytical considerations. For a small number of constitutive magnets Ntot ≤ 26, a straight chain is found to be the ground state. In the regime of larger Ntot ≥ 27, the magnets form two touching chains with equally long tails at both ends. We succeed to identify the transition from two to three touching chains at Ntot = 129. Overall, this study sheds light on the mechanisms of the recently experimentally observed ribbon formation of superparamagnetic colloids via lateral aggregation of magnetic chains in magnetic field (Darras et al., 2016).

  9. Vestibular stimulation by magnetic fields

    Science.gov (United States)

    Ward, Bryan K.; Roberts, Dale C.; Della Santina, Charles C.; Carey, John P.; Zee, David S.

    2015-01-01

    Individuals working next to strong static magnetic fields occasionally report disorientation and vertigo. With the increasing strength of magnetic fields used for magnetic resonance imaging (MRI) studies, these reports have become more common. It was recently learned that humans, mice and zebrafish all demonstrate behaviors consistent with constant peripheral vestibular stimulation while inside a strong, static magnetic field. The proposed mechanism for this effect involves a Lorentz force resulting from the interaction of a strong static magnetic field with naturally occurring ionic currents flowing through the inner ear endolymph into vestibular hair cells. The resulting force within the endolymph is strong enough to displace the lateral semicircular canal cupula, inducing vertigo and the horizontal nystagmus seen in normal mice and in humans. This review explores the evidence for interactions of magnetic fields with the vestibular system. PMID:25735662

  10. Magnetic response to applied electrostatic field in external magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Adorno, T.C. [Universidade de Sao Paulo, Instituto de Fisica, Caixa Postal 66318, Sao Paulo, SP (Brazil); University of Florida, Department of Physics, Gainesville, FL (United States); Gitman, D.M. [Universidade de Sao Paulo, Instituto de Fisica, Caixa Postal 66318, Sao Paulo, SP (Brazil); Tomsk State University, Department of Physics, Tomsk (Russian Federation); Shabad, A.E. [P. N. Lebedev Physics Institute, Moscow (Russian Federation)

    2014-04-15

    We show, within QED and other possible nonlinear theories, that a static charge localized in a finite domain of space becomes a magnetic dipole, if it is placed in an external (constant and homogeneous) magnetic field in the vacuum. The magnetic moment is quadratic in the charge, depends on its size and is parallel to the external field, provided the charge distribution is at least cylindrically symmetric. This magneto-electric effect is a nonlinear response of the magnetized vacuum to an applied electrostatic field. Referring to the simple example of a spherically symmetric applied field, the nonlinearly induced current and its magnetic field are found explicitly throughout the space; the pattern of the lines of force is depicted, both inside and outside the charge, which resembles that of a standard solenoid of classical magnetostatics. (orig.)

  11. Magnetic response to applied electrostatic field in external magnetic field

    CERN Document Server

    Adorno, T C; Shabad, A E

    2014-01-01

    We show, within QED and other possible nonlinear theories, that a static charge localized in a finite domain of space becomes a magnetic dipole, if it is placed in an external (constant and homogeneous) magnetic field in the vacuum. The magnetic moment is quadratic in the charge, depends on its size and is parallel to the external field, provided the charge distribution is at least cylindrically symmetric. This magneto-electric effect is a nonlinear response of the magnetized vacuum to an applied electrostatic field. Referring to a simple example of a spherically-symmetric applied field, the nonlinearly induced current and its magnetic field are found explicitly throughout the space, the pattern of lines of force is depicted, both inside and outside the charge, which resembles that of a standard solenoid of classical magnetostatics.

  12. Structure of Long-Term Variations of the Plasma Parameters and Magnetic Field in the Near-Earth Heliosphere

    Science.gov (United States)

    Veselovskii, I. S.; Dmitriev, A. V.; Suvorova, A. V.; Minaeva, Yu. S.

    The methods of the fast Fourier transform, spectrumtime analysis, and wavelet analysis are used to study the structure and dynamics of rhythmic and arrythmic variations of the main param- eters of solar wind, as well as the interplanetary and solar magnetic field at time scales from days to tens of years. A large variety of the observed regular and irregular variations in the near-Earth helio- sphere is explained by a number of reasons: (1) the variability of unstable processes and in the region of solar wind formation, (2) the solar rotation of the Sun and the associated inhomogeneities in its corona, (3) and the Earth's orbital motion. Irregular, aperiodic variations are present for all parame- ters and at all time scales. The most prominent regular variations are related to cyclic processes on the Sun and its rotation.

  13. NMR in pulsed magnetic field

    KAUST Repository

    Abou-Hamad, Edy

    2011-09-01

    Nuclear magnetic resonance (NMR) experiments in pulsed magnetic fields up to 30.4 T focused on 1H and 93Nb nuclei are reported. Here we discuss the advantage and limitation of pulsed field NMR and why this technique is able to become a promising research tool. © 2011 Elsevier Inc. All Rights Reserved.

  14. The MAVEN Magnetic Field Investigation

    Science.gov (United States)

    Connerney, J. E. P.; Espley, J.; Lawton, P.; Murphy, S.; Odom, J.; Oliversen, R.; Sheppard, D.

    2014-01-01

    The MAVEN magnetic field investigation is part of a comprehensive particles and fields subsystem that will measure the magnetic and electric fields and plasma environment of Mars and its interaction with the solar wind. The magnetic field instrumentation consists of two independent tri-axial fluxgate magnetometer sensors, remotely mounted at the outer extremity of the two solar arrays on small extensions ("boomlets"). The sensors are controlled by independent and functionally identical electronics assemblies that are integrated within the particles and fields subsystem and draw their power from redundant power supplies within that system. Each magnetometer measures the ambient vector magnetic field over a wide dynamic range (to 65,536 nT per axis) with a quantization uncertainty of 0.008 nT in the most sensitive dynamic range and an accuracy of better than 0.05%. Both magnetometers sample the ambient magnetic field at an intrinsic sample rate of 32 vector samples per second. Telemetry is transferred from each magnetometer to the particles and fields package once per second and subsequently passed to the spacecraft after some reformatting. The magnetic field data volume may be reduced by averaging and decimation, when necessary to meet telemetry allocations, and application of data compression, utilizing a lossless 8-bit differencing scheme. The MAVEN magnetic field experiment may be reconfigured in flight to meet unanticipated needs and is fully hardware redundant. A spacecraft magnetic control program was implemented to provide a magnetically clean environment for the magnetic sensors and the MAVEN mission plan provides for occasional spacecraft maneuvers - multiple rotations about the spacecraft x and z axes - to characterize spacecraft fields and/or instrument offsets in flight.

  15. Magnetic Field Structure and Activity of the He-burning Giant 37 Comae

    CERN Document Server

    Tsvetkova, S; Konstantinova-Antova, R; Aurière, M; Wade, G A; Charbonnel, C; Drake, N A

    2013-01-01

    We present the first magnetic map of the late-type giant 37 Com. The Least Squares Deconvolution (LSD) method and Zeeman Doppler Imaging (ZDI) inversion technique were applied. The chromospheric activity indicators H?_alpha, S-index, Ca ii IRT and the radial velocity were also measured. The evolutionary status of the star has been studied on the basis of state-of-the-art stellar evolutionary models and chemical abundance analysis. 37 Com appears to be in the core Helium-burning phase.

  16. Dispersion of Magnetic Fields in Molecular Clouds

    CERN Document Server

    Hildebrand, Roger H; Dotson, Jessie L; Houde, Martin; Vaillancourt, John E

    2008-01-01

    We describe a method for determining the dispersion of magnetic field vectors about local mean fields in turbulent molecular clouds. The method is designed to avoid inaccurate estimates of MHD or turbulent dispersion - and hence to avoid inaccurate estimates of field strengths - due to large-scale, non-turbulent field structure when using the well-known method of Chandrasekhar and Fermi. Our method also provides accurate, independent estimates of the turbulent to mean magnetic field strength ratio. We discuss applications to the molecular clouds Orion, M17, and DR21.

  17. Synthesis and characterization of CoFe{sub 2}O{sub 4} magnetic nanotubes, nanorods and nanowires. Formation of magnetic structured elastomers by magnetic field-induced alignment of CoFe{sub 2}O{sub 4} nanorods

    Energy Technology Data Exchange (ETDEWEB)

    Antonel, P. Soledad [Universidad de Buenos Aires, Departamento de Química Inorgánica, Analítica y Química Física, Facultad de Ciencias Exactas y Naturales, Instituto de Química Física de Materiales, Ambiente y Energía (INQUIMAE) (Argentina); Oliveira, Cristiano L. P. [Universidade de São Paulo, Grupo de Fluidos Complexos, Instituto de Física (Brazil); Jorge, Guillermo A. [Universidad Nacional de General Sarmiento, Instituto de Ciencias (Argentina); Perez, Oscar E. [Universidad de Buenos Aires, Departamento de Industrias, Facultad de Ciencias Exactas y Naturales (Argentina); Leyva, A. Gabriela, E-mail: leyva@tandar.cnea.gov.ar [Universidad Nacional de San Martín, Grupo de Materia Condensada, Centro Atómico Constituyentes, Comisión Nacional de Energía Atómica (Argentina); Escuela de Ciencia y Tecnología (Argentina); Negri, R. Martín, E-mail: rmn@qi.fcen.uba.ar [Universidad de Buenos Aires, Departamento de Química Inorgánica, Analítica y Química Física, Facultad de Ciencias Exactas y Naturales, Instituto de Química Física de Materiales, Ambiente y Energía (INQUIMAE) (Argentina)

    2015-07-15

    Magnetic CoFe{sub 2}O{sub 4} nanotubes, nanorods and nanowires were synthesized by the template method. The materials are highly crystalline and formed by compactly packed ceramic particles whose equivalent size diameter depends on the nanostructure type. Nanotubes and nanorods present the remarkable characteristic of having very large coercive fields (1000–1100 Oe) in comparison with nanoparticles of the same crystallite size (400 Oe) while keeping similar saturation magnetization (53–55 emu/g). Nanorods were used as filler material in polydimethylsiloxane elastomer composites, which were structured by curing in the presence of uniform magnetic field, H{sub curing}. In that way the nanorods agglomerate in the cured elastomer, forming needles-like structures (pseudo-chains) oriented in the direction of H{sub curing}. SEM analysis show that pseudo-chains are formed by bunches of nanorods oriented in that direction. At the considered filler concentration (1 % w/w), the structured elastomers conserve the magnetic properties of the fillers, that is, high coercive fields without observing magnetic anisotropy. The elastomer composites present strong elastic anisotropy, with compression constants about ten times larger in the direction parallel to the pseudo-chains than in the perpendicular direction, as determined by compression stress–strain curves. That anisotropic factor is about three-four times higher than that observed when using spherical CoFe{sub 2}O{sub 4} nanoparticles or elongated Ni nanochains. Hence, the use of morphological anisotropic structures (nanorods) results in composites with enhanced elastic anisotropy. It is also remarkable that the large elastic anisotropy was obtained at lower filler concentration compared with the above-mentioned systems (1 % w/w vs. 5–10 % w/w)

  18. Polarized radiation diagnostics of stellar magnetic fields

    Science.gov (United States)

    Mathys, Gautier

    The main techniques used to diagnose magnetic fields in stars from polarimetric observations are presented. First, a summary of the physics of spectral line formation in the presence of a magnetic field is given. Departures from the simple case of linear Zeeman effect are briefly considered: partial Paschen-Back effect, contribution of hyperfine structure, and combined Stark and Zeeman effects. Important approximate solutions of the equation of transfer of polarized light in spectral lines are introduced. The procedure for disk-integration of emergent Stokes profiles, which is central to stellar magnetic field studies, is described, with special attention to the treatment of stellar rotation. This formalism is used to discuss the determination of the mean longitudinal magnetic field (through the photographic technique and through Balmer line photopolarimetry). This is done within the specific framework of Ap stars, which, with their unique large-scale organized magnetic fields, are an ideal laboratory for studies of stellar magnetism. Special attention is paid to those Ap stars whose magnetically split line components are resolved in high-dispersion Stokes I spectra, and to the determination of their mean magnetic field modulus. Various techniques of exploitation of the information contained in polarized spectral line profiles are reviewed: the moment technique (in particular, the determination of the crossover and of the mean quadratic field), Zeeman-Doppler imaging, and least-squares deconvolution. The prospects that these methods open for linear polarization studies are sketched. The way in which linear polarization diagnostics complement their Stokes I and V counterparts is emphasized by consideration of the results of broad band linear polarization measurements. Illustrations of the use of various diagnostics to derive properties of the magnetic fields of Ap stars are given. This is used to show the interest of deriving more physically realistic models of the

  19. Structural and mechanical properties of 7075 alloy strips fabricated by roll-casting in a static magnetic field

    Science.gov (United States)

    Su, Xin; Xu, Guang-ming; Jiang, Jiu-wen

    2014-07-01

    The influences of a 0.2 T static magnetic field on the microstructure of 7075 aluminum alloys sheets produced with a twin-roll continuous caster at 675°C were investigated in this paper. Under a uniform magnetic field, the primary dendrites were refined and tended to be equiaxed. The microstructure consisted of an intermediate case between dendritic and equiaxed grains. Moreover, the use of an external static field in the twin-roll casting process can reduce heat discharge, resulting in a decrease in undercooling, and may also account for the abatement of segregation bands. In addition, the static magnetic field effectively improved the solute mixing capacity, and the added atoms more easily diffused from precipitates to the α-Al matrix, which resulted in an increase in the mechanical properties of the rolled sheets. Specimens prepared both in the presence of a static magnetic field and in the absence of a static magnetic field exhibited brittle-fracture characteristics.

  20. Structural and mechanical properties of 7075 alloy strips fabricated by roll-casting in a static magnetic field

    Institute of Scientific and Technical Information of China (English)

    Xin Su; Guang-ming Xu; Jiu-wen Jiang

    2014-01-01

    The influences of a 0.2 T static magnetic field on the microstructure of 7075 aluminum alloys sheets produced with a twin-roll continuous caster at 675°C were investigated in this paper. Under a uniform magnetic field, the primary dendrites were refined and tended to be equiaxed. The microstructure consisted of an intermediate case between dendritic and equiaxed grains. Moreover, the use of an external static field in the twin-roll casting process can reduce heat discharge, resulting in a decrease in undercooling, and may also account for the abatement of segregation bands. In addition, the static magnetic field effectively improved the solute mixing capacity, and the added atoms more easily diffused from precipitates to theα-Al matrix, which resulted in an increase in the mechanical properties of the rolled sheets. Specimens prepared both in the presence of a static magnetic field and in the absence of a static magnetic field exhibited brittle-fracture characteristics.

  1. Extremely high magnetic-field sensitivity of charge transport in the Mn/SiO2/p-Si hybrid structure

    Science.gov (United States)

    Volkov, N. V.; Tarasov, A. S.; Smolyakov, D. A.; Gustaitsev, A. O.; Rautskii, M. V.; Lukyanenko, A. V.; Volochaev, M. N.; Varnakov, S. N.; Yakovlev, I. A.; Ovchinnikov, S. G.

    2017-01-01

    We report on abrupt changes in dc resistance and impedance of a diode with the Schottky barrier based on the Mn/SiO2/p-Si structure in a magnetic field. It was observed that at low temperatures the dc and ac resistances of the device change by a factor of more than 106 with an increase in a magnetic field to 200 mT. The strong effect of the magnetic field is observed only above the threshold forward bias across the diode. The ratios between ac and dc magnetoresistances can be tuned from almost zero to 108% by varying the bias. To explain the diversity of magnetotransport phenomena observed in the Mn/SiO2/p-Si structure, it is necessary to attract several mechanisms, which possibly work in different regions of the structure. The anomalously strong magnetotransport effects are attributed to the magnetic-field-dependent impact ionization in the bulk of a Si substrate. At the same time, the conditions for this process are specified by structure composition, which, in turn, affects the current through each structure region. The effect of magnetic field attributed to suppression of impact ionization via two mechanisms leads to an increase in the carrier energy required for initiation of impact ionization. The first mechanism is related to displacement of acceptor levels toward higher energies relative to the top of the valence band and the other mechanism is associated with the Lorentz forces affecting carrier trajectories between scatterings events. The estimated contributions of these two mechanisms are similar. The proposed structure is a good candidate for application in CMOS technology-compatible magnetic- and electric-field sensors and switching devices.

  2. Extremely high magnetic-field sensitivity of charge transport in the Mn/SiO2/p-Si hybrid structure

    Directory of Open Access Journals (Sweden)

    N. V. Volkov

    2017-01-01

    Full Text Available We report on abrupt changes in dc resistance and impedance of a diode with the Schottky barrier based on the Mn/SiO2/p-Si structure in a magnetic field. It was observed that at low temperatures the dc and ac resistances of the device change by a factor of more than 106 with an increase in a magnetic field to 200 mT. The strong effect of the magnetic field is observed only above the threshold forward bias across the diode. The ratios between ac and dc magnetoresistances can be tuned from almost zero to 108% by varying the bias. To explain the diversity of magnetotransport phenomena observed in the Mn/SiO2/p-Si structure, it is necessary to attract several mechanisms, which possibly work in different regions of the structure. The anomalously strong magnetotransport effects are attributed to the magnetic-field-dependent impact ionization in the bulk of a Si substrate. At the same time, the conditions for this process are specified by structure composition, which, in turn, affects the current through each structure region. The effect of magnetic field attributed to suppression of impact ionization via two mechanisms leads to an increase in the carrier energy required for initiation of impact ionization. The first mechanism is related to displacement of acceptor levels toward higher energies relative to the top of the valence band and the other mechanism is associated with the Lorentz forces affecting carrier trajectories between scatterings events. The estimated contributions of these two mechanisms are similar. The proposed structure is a good candidate for application in CMOS technology-compatible magnetic- and electric-field sensors and switching devices.

  3. Solar Force-free Magnetic Fields

    CERN Document Server

    Wiegelmann, Thomas

    2012-01-01

    The structure and dynamics of the solar corona is dominated by the magnetic field. In most areas in the corona magnetic forces are so dominant that all non-magnetic forces like plasma pressure gradient and gravity can be neglected in the lowest order. This model assumption is called the force-free field assumption, as the Lorentz force vanishes. This can be obtained by either vanishing electric currents (leading to potential fields) or the currents are co-aligned with the magnetic field lines. First we discuss a mathematically simpler approach that the magnetic field and currents are proportional with one global constant, the so-called linear force-free field approximation. In the generic case, however, the relation between magnetic fields and electric currents is nonlinear and analytic solutions have been only found for special cases, like 1D or 2D configurations. For constructing realistic nonlinear force-free coronal magnetic field models in 3D, sophisticated numerical computations are required and boundar...

  4. Effect of Compactified Dimensions and Background Magnetic Fields on the Phase Structure of S U (N ) Gauge Theories

    Science.gov (United States)

    D'Elia, Massimo; Mariti, Marco

    2017-04-01

    We discuss the properties of non-Abelian gauge theories formulated on manifolds with compactified dimensions and in the presence of fermionic fields coupled to magnetic backgrounds. We show that different phases may emerge, corresponding to different realizations of center symmetry and translational invariance, depending on the compactification radius and on the magnitude of the magnetic field. Our discussion then focuses on the case of an S U (3 ) gauge theory in four dimensions with fermions fields in the fundamental representation, for which we provide some exploratory numerical lattice results.

  5. Indoor transformer stations and ELF magnetic field exposure: use of transformer structural characteristics to improve exposure assessment.

    Science.gov (United States)

    Okokon, Enembe Oku; Roivainen, Päivi; Kheifets, Leeka; Mezei, Gabor; Juutilainen, Jukka

    2014-01-01

    Previous studies have shown that populations of multiapartment buildings with indoor transformer stations may serve as a basis for improved epidemiological studies on the relationship between childhood leukaemia and extremely-low-frequency (ELF) magnetic fields (MFs). This study investigated whether classification based on structural characteristics of the transformer stations would improve ELF MF exposure assessment. The data included MF measurements in apartments directly above transformer stations ("exposed" apartments) in 30 buildings in Finland, and reference apartments in the same buildings. Transformer structural characteristics (type and location of low-voltage conductors) were used to classify exposed apartments into high-exposure (HE) and intermediate-exposure (IE) categories. An exposure gradient was observed: both the time-average MF and time above a threshold (0.4 μT) were highest in the HE apartments and lowest in the reference apartments, showing a statistically significant trend. The differences between HE and IE apartments, however, were not statistically significant. A simulation exercise showed that the three-category classification did not perform better than a two-category classification (exposed and reference apartments) in detecting the existence of an increased risk. However, data on the structural characteristics of transformers is potentially useful for evaluating exposure-response relationship.

  6. Optimally segmented magnetic structures

    DEFF Research Database (Denmark)

    Insinga, Andrea Roberto; Bahl, Christian; Bjørk, Rasmus;

    ], or are applicable only to analytically solvable geometries[4]. In addition, some questions remained fundamentally unanswered, such as how to segment a given design into N uniformly magnetized pieces.Our method calculates the globally optimal shape and magnetization direction of each segment inside a certain......We present a semi-analytical algorithm for magnet design problems, which calculates the optimal way to subdivide a given design region into uniformly magnetized segments.The availability of powerful rare-earth magnetic materials such as Nd-Fe-B has broadened the range of applications of permanent...... designarea with an optional constraint on the total amount of magnetic material. The method can be applied to any objective functional which is linear respect to the field, and with any combination of linear materials. Being based on an analytical-optimization approach, the algorithm is not computationally...

  7. Rotating superconductor magnet for producing rotating lobed magnetic field lines

    Science.gov (United States)

    Hilal, Sadek K.; Sampson, William B.; Leonard, Edward F.

    1978-01-01

    This invention provides a rotating superconductor magnet for producing a rotating lobed magnetic field, comprising a cryostat; a superconducting magnet in the cryostat having a collar for producing a lobed magnetic field having oppositely directed adjacent field lines; rotatable support means for selectively rotating the superconductor magnet; and means for energizing the superconductor magnet.

  8. Magnetic Structure of Erbium

    DEFF Research Database (Denmark)

    Gibbs, D.; Bohr, Jakob; Axe, J. D.

    1986-01-01

    , and at positions split symmetrically about the fundamental. As the temperature is lowered below 52 K the charge and magnetic scattering display a sequence of lock-in transitions to rational wave vectors. A spin-slip description of the magnetic structure is presented which explains the wave vectors...

  9. Magnetic structure determination using zero-field neutron polarimetry. [Cr-O; Cu-Ce

    Energy Technology Data Exchange (ETDEWEB)

    Nunez, V. (Inst. Laue-Langevin, 38 - Grenoble (France) Dept. of Physics, King' s Coll. London, Strand (United Kingdom)); Brown, P.J.; Tasset, F. (Inst. Laue-Langevin, 38 - Grenoble (France)); Chattopadhyay, T. (Inst. Laue-Langevin, 38 - Grenoble (France) Centre d' Etudes Nucleaires, 38 - Grenoble (France)); Forsyth, J.B. (Rutherford Appleton Lab., Chilton (United Kingdom))

    1992-06-01

    A simple interpretation of the formulae which predict the polarisation of elastically scattered neutrons and a pictorial representation of the polarisation directions before and after the scattering process are presented. Some results from recent zero-field neutron polarimetry experiments are used to demonstrate the theory. (orig.).

  10. Low Cost Magnetic Field Controller

    CERN Document Server

    Malafronte, Alexandre A

    2005-01-01

    The Physics Institute of the University of São Paulo (IFUSP) is building a continuous wave (cw) racetrack microtron. This machine has several dipole magnets, like the first and second stage recirculators, and a number of smaller ones in the transport line. These magnets must produce very stable magnetic fields to allow the beam to recirculate along very precise orbits and paths. Furthermore, the fields must be reproducible with great accuracy to allow an easier setup of the machine, though the effects of hysteresis tend to jeopardize the reproducibility. If the magnetic field is chosen by setting the current in the coils, temperature effects over the magnet and power supply tend to change the field. This work describes an inexpensive magnetic field controller that allows a direct measure of the magnetic field through an Hall probe. It includes a microcontroller running a feedback algorithm to control the power supply, in order to keep the field stable and reproducible. The controller can also execu...

  11. Resonant magnetic fields from inflation

    CERN Document Server

    Byrnes, Christian T; Jain, Rajeev Kumar; Urban, Federico R

    2012-01-01

    We propose a novel scenario to generate primordial magnetic fields during inflation induced by an oscillating coupling of the electromagnetic field to the inflaton. This resonant mechanism has two key advantages over previous proposals. First of all, it generates a narrow band of magnetic fields at any required wavelength, thereby allaying the usual problem of a strongly blue spectrum and its associated backreaction. Secondly, it avoids the need for a strong coupling as the coupling is oscillating rather than growing or decaying exponentially. Despite these major advantages, we find that the backreaction is still far too large during inflation if the generated magnetic fields are required to have a strength of ${\\cal O}(10^{-15}\\, \\Gauss)$ today on observationally interesting scales. We provide a more general no-go argument, proving that this problem will apply to any model in which the magnetic fields are generated on subhorizon scales and freeze after horizon crossing.

  12. Structure and thermoelectric properties of Al-doped ZnO films prepared by thermal oxidization under high magnetic field

    Science.gov (United States)

    Liu, Shiying; Peng, Sunjuan; Ma, Jun; Li, Guojian; Qin, Xuesi; Li, Mengmeng; Wang, Qiang

    2017-04-01

    This paper studies the effects of high magnetic field (HMF) on the structure, optical and thermoelectric properties of the doped ZnO thin films. The results show that both Al dopant and application of HMF can affect the crystal structure, surface morphology, elemental distribution and so on. The particles of the thin films become small and regular by doping Al. The ZnO films oxidized from the Au/Zn bilayer have needle structure. The ZnO films oxidized from the Au/Zn-Al bilayer transform to spherical from hexagonal due to the application of HMF. The transmittance decreases with doping Al because of the opaque of Al element and decreases with the application of HMF due to the dense structure obtained under HMF. Electrical resistivity (ρ) of the ZnO films without Al decreases with increasing measurement temperature (T) and is about 1.5 × 10-3 Ω·m at 210 °C. However, the ρ of the Al-doped ZnO films is less than 10-5 Ω·m. The Seebeck coefficient (S) of the films oxidized from the Au/Zn-Al films reduces with increasing T. The S values oxidized under 0 T and 12 T conditions are 2.439 μV/K and -3.415 μV/K at 210 °C, respectively. Power factor reaches the maximum value (3.198 × 10-4 W/m·K2) at 210 °C for the film oxidized under 12 T condition. These results indicate that the Al dopant and the application of HMF can be used to control structure and thermoelectric properties of doped ZnO films.

  13. On the jet structure and magnetic field configuration of GRB 020813

    NARCIS (Netherlands)

    Lazzati, D.; Covino, S.; Gorosabel, J.; Rossi, E.; Ghisellini, G.; Rol, E.; Castro Cerón, J.M.; Castro-Tirado, A.J.; Della Valle, M.; di Serego Alighieri, S.; Fruchter, A.S.; Fynbo, J.P.U.; Goldoni, P.; Hjorth, J.; Israel, G.L.; Kaper, L.; Kawai, N.; Le Floc'h, E.; Malesani, D.; Mazzali, P.; Mirabel, F.; Møller, P.; Ortolani, S.; Palazzi, E.; Pian, E.; Rhoads, J.; Ricker, G.; Salmonson, J.D.; Stella, L.; Tagliaferri, G.; Tanvir, N.; van den Heuvel, E.; Wijers, R.A.M.J.; Zerbi, F.M.

    2004-01-01

    The polarization curve of GRB 020813 is discussed and compared to different models for the structure, evolution and magnetisation properties of the jet and the interstellar medium onto which the fireball impacts. GRB 020813 is best suited for this kind of analysis for the smoothness of its afterglow

  14. Magnetic structure of Coronal Mass Ejections

    CERN Document Server

    Lyutikov, Maxim

    2012-01-01

    We present several models of the magnetic structure of solar coronal mass ejections (CMEs). First, we model CMEs as expanding force-free magnetic structures. While keeping the internal magnetic field structure of the stationary solutions, expansion leads to complicated internal velocities and rotation, while the field structures remain force-free. Second, expansion of a CME can drive resistive dissipation within the CME changing the ionization states of different ions. We fit in situ measurements of ion charge states to the resistive spheromak solutions. Finally, we consider magnetic field structures of fully confined stable magnetic clouds containing both toroidal and poloidal magnetic fields and having no surface current sheets. Expansion of such clouds may lead to sudden onset of reconnection events.

  15. Structural and low-field magnetic characterization of superconducting MgB{sub 2} wires

    Energy Technology Data Exchange (ETDEWEB)

    Kilic, A. [Faculty of Sciences, Department of Physics, Ankara University, 06100-Tandogan/Ankara (Turkey); Okur, S. [Izmir Institute of Technology, Department of Physics, 35437-Urla/Izmir (Turkey); Gueclue, N. [Faculty of Sciences and Art, Department of Physics, Gaziosmanpasa University, 60100-Taslicftlik/Tokat (Turkey)]. E-mail: guclu06@hotmail.com; Koelemen, U. [Faculty of Sciences and Art, Department of Physics, Gaziosmanpasa University, 60100-Taslicftlik/Tokat (Turkey); Uzun, O. [Faculty of Sciences and Art, Department of Physics, Gaziosmanpasa University, 60100-Taslicftlik/Tokat (Turkey); Oezyuezer, L. [Izmir Institute of Technology, Department of Physics, 35437-Urla/Izmir (Turkey); Gencer, A. [Faculty of Sciences, Department of Physics, Ankara University, 06100-Tandogan/Ankara (Turkey)

    2004-10-01

    Superconducting MgB{sub 2} composite wires were prepared by packing blend of MgB{sub 2} inside of Cu tubes using powder in tube (PIT) method. The produced samples of the wires were then characterised by using SEM, XRD and AC susceptibility measurements. The measured fundamental susceptibility is compared with Bean model. We have obtained an empirical functions for the penetration field H{sub p} = H{sub {alpha}}(1-t){sup {beta}}, where t is the reduced temperature. In addition, ac losses were calculated at the same fixed temperatures to compare theoretical solutions. There is a qualitative agreement between the experimental results and theory.

  16. Singularities of the dynamical structure factors of the spin-1/2 XXX chain at finite magnetic field

    Science.gov (United States)

    Carmelo, J. M. P.; Sacramento, P. D.; Machado, J. D. P.; Campbell, D. K.

    2015-10-01

    We study the longitudinal and transverse spin dynamical structure factors of the spin-1/2 XXX chain at finite magnetic field h, focusing in particular on the singularities at excitation energies in the vicinity of the lower thresholds. While the static properties of the model can be studied within a Fermi-liquid like description in terms of pseudoparticles, our derivation of the dynamical properties relies on the introduction of a form of the ‘pseudofermion dynamical theory’ (PDT) of the 1D Hubbard model suitably modified for the spin-only XXX chain and other models with two pseudoparticle Fermi points. Specifically, we derive the exact momentum and spin-density dependences of the exponents {{\\zeta}τ}(k) controlling the singularities for both the longitudinal ≤ft(τ =l\\right) and transverse ≤ft(τ =t\\right) dynamical structure factors for the whole momentum range k\\in ]0,π[ , in the thermodynamic limit. This requires the numerical solution of the integral equations that define the phase shifts in these exponents expressions. We discuss the relation to neutron scattering and suggest new experiments on spin-chain compounds using a carefully oriented crystal to test our predictions.

  17. Effects of high magnetic field assisted annealing on structure and optical, electric properties of electrodeposited ZnO films

    Science.gov (United States)

    Gao, Yang; Li, Guojian; Wu, Chun; Sui, Xudong; Du, Jiaojiao; Wang, Qiang

    2017-01-01

    Electrodeposited ZnO films have been annealed at 300 °C for 2 h under 12 T high magnetic field (HMF) with the directions of parallel and perpendicular to the films, respectively. The structural, optical and electric properties were characterized by scanning electron microscopy, X-ray diffraction, photoluminescence (PL) spectra, X-ray photoemission spectroscopy (XPS) and Seebeck coefficient/electrical resistance measuring system. The results show that HMF has a significant effect on the growth of ZnO films along c-axis and leads to hexagonal platelets of ZnO growing parallel to the direction of HMF. Furthermore, the hexagonal platelets become bulky platelets with an obvious trendy rotating their c-axis parallel to the substrate. The PL spectra of all the films exhibits the UV and blue emission, moreover, the blue emission plays the main role. The resistivity of ZnO films increases with the increase of measure temperature, which shows a typical degenerate semiconductor characteristic. HMF reduces significantly the intensity of whole emission peaks and the resistivity of ZnO films. These may be attribute to the significant changes of the structure and morphology of ZnO films, leading to various amounts of the defects in the ZnO crystal.

  18. First-principles study of electric field and structural strain impact on perpendicular magnetic anisotropy of Fe/MgO interfaces

    Science.gov (United States)

    Ibrahim, Fatima; Yang, Hongxin; Dieny, Bernard; Chshiev, Mairbek

    2015-03-01

    Electric-field (EF) control of magnetic anisotropy is promising in the context of establishing low-energy consumption memory devices since it allows EF-assisted switching of magnetization in magnetic tunnel junctions with perpendicular magnetic anisotropy (PMA). Using first-principles calculations, we demonstrate that both the EF and structural strain induce changes of the PMA in Fe/MgO interfaces which originally exhibit strong PMA. Namely, we find that the PMA change in response to strain is much larger than that induced by applied EF. This suggests that the EF control of PMA is caused not only by charge accumulation and depletion mechanism but rather mediated by structural modifications occurring at the interface in agreement with recent experimental reports. In addition, using atomic and orbital-resolved analysis of PMA, we elucidate the effect of both the EF and structural strain on PMA showing in particular that it extends beyond the interfacial layer.

  19. Polarized scattering of light for arbitrary magnetic fields with level-crossings from the combination of hyperfine and fine structure splittings

    CERN Document Server

    Sowmya, K; Sampoorna, M; Stenflo, J O

    2015-01-01

    Interference between magnetic substates of the hyperfine structure states belonging to different fine structure states of the same term influences the polarization for some of the diagnostically important lines of the Sun's spectrum, like the sodium and lithium doublets. The polarization signatures of this combined interference contain information on the properties of the solar magnetic fields. Motivated by this, in the present paper, we study the problem of polarized scattering on a two-term atom with hyperfine structure by accounting for the partial redistribution in the photon frequencies arising due to the Doppler motions of the atoms. We consider the scattering atoms to be under the influence of a magnetic field of arbitrary strength and develop a formalism based on the Kramers--Heisenberg approach to calculate the scattering cross section for this process. We explore the rich polarization effects that arise from various level-crossings in the Paschen--Back regime in a single scattering case using the li...

  20. Magnetic field homogeneity perturbations in finite Halbach dipole magnets.

    Science.gov (United States)

    Turek, Krzysztof; Liszkowski, Piotr

    2014-01-01

    Halbach hollow cylinder dipole magnets of a low or relatively low aspect ratio attract considerable attention due to their applications, among others, in compact NMR and MRI systems for investigating small objects. However, a complete mathematical framework for the analysis of magnetic fields in these magnets has been developed only for their infinitely long precursors. In such a case the analysis is reduced to two-dimensions (2D). The paper details the analysis of the 3D magnetic field in the Halbach dipole cylinders of a finite length. The analysis is based on three equations in which the components of the magnetic flux density Bx, By and Bz are expanded to infinite power series of the radial coordinate r. The zeroth term in the series corresponds to a homogeneous magnetic field Bc, which is perturbed by the higher order terms due to a finite magnet length. This set of equations is supplemented with an equation for the field profile B(z) along the magnet axis, presented for the first time. It is demonstrated that the geometrical factors in the coefficients of particular powers of r, defined by intricate integrals are the coefficients of the Taylor expansion of the homogeneity profile (B(z)-Bc)/Bc. As a consequence, the components of B can be easily calculated with an arbitrary accuracy. In order to describe perturbations of the field due to segmentation, two additional equations are borrowed from the 2D theory. It is shown that the 2D approach to the perturbations generated by the segmentation can be applied to the 3D Halbach structures unless r is not too close to the inner radius of the cylinder ri. The mathematical framework presented in the paper was verified with great precision by computations of B by a highly accurate integration of the magnetostatic Coulomb law and utilized to analyze the inhomogeneity of the magnetic field in the magnet with the accuracy better than 1 ppm.

  1. Measuring Earth's Magnetic Field Simply.

    Science.gov (United States)

    Stewart, Gay B.

    2000-01-01

    Describes a method for measuring the earth's magnetic field using an empty toilet paper tube, copper wire, clear tape, a battery, a linear variable resistor, a small compass, cardboard, a protractor, and an ammeter. (WRM)

  2. ISR split-field magnet

    CERN Multimedia

    1975-01-01

    The experimental apparatus used at intersection 4 around the Split-Field Magnet by the CERN-Bologna Collaboration (experiment R406). The plastic scintillator telescopes are used for precise pulse-height and time-of-flight measurements.

  3. What Are Electric and Magnetic Fields? (EMF)

    Science.gov (United States)

    ... take for granted. What are electric and magnetic fields? Electric and magnetic fields (EMF) are invisible lines of ... humans. AC electric power produces electric and magnetic fields that create weak electric currents in humans. Being exposed to some kinds ...

  4. The Juno Magnetic Field Investigation

    Science.gov (United States)

    Connerney, J. E. P.; Benn, M.; Bjarno, J. B.; Denver, T.; Espley, J.; Jorgensen, J. L.; Jorgensen, P. S.; Lawton, P.; Malinnikova, A.; Merayo, J. M.; Murphy, S.; Odom, J.; Oliversen, R.; Schnurr, R.; Sheppard, D.; Smith, E. J.

    2017-02-01

    The Juno Magnetic Field investigation (MAG) characterizes Jupiter's planetary magnetic field and magnetosphere, providing the first globally distributed and proximate measurements of the magnetic field of Jupiter. The magnetic field instrumentation consists of two independent magnetometer sensor suites, each consisting of a tri-axial Fluxgate Magnetometer (FGM) sensor and a pair of co-located imaging sensors mounted on an ultra-stable optical bench. The imaging system sensors are part of a subsystem that provides accurate attitude information (to ˜20 arcsec on a spinning spacecraft) near the point of measurement of the magnetic field. The two sensor suites are accommodated at 10 and 12 m from the body of the spacecraft on a 4 m long magnetometer boom affixed to the outer end of one of 's three solar array assemblies. The magnetometer sensors are controlled by independent and functionally identical electronics boards within the magnetometer electronics package mounted inside Juno's massive radiation shielded vault. The imaging sensors are controlled by a fully hardware redundant electronics package also mounted within the radiation vault. Each magnetometer sensor measures the vector magnetic field with 100 ppm absolute vector accuracy over a wide dynamic range (to 16 Gauss = 1.6 × 106 nT per axis) with a resolution of ˜0.05 nT in the most sensitive dynamic range (±1600 nT per axis). Both magnetometers sample the magnetic field simultaneously at an intrinsic sample rate of 64 vector samples per second. The magnetic field instrumentation may be reconfigured in flight to meet unanticipated needs and is fully hardware redundant. The attitude determination system compares images with an on-board star catalog to provide attitude solutions (quaternions) at a rate of up to 4 solutions per second, and may be configured to acquire images of selected targets for science and engineering analysis. The system tracks and catalogs objects that pass through the imager field of

  5. The Juno Magnetic Field Investigation

    Science.gov (United States)

    Connerney, J. E. P.; Benna, M.; Bjarno, J. B.; Denver, T.; Espley, J.; Jorgensen, J. L.; Jorgensen, P. S.; Lawton, P.; Malinnikova, A.; Merayo, J. M.; hide

    2017-01-01

    The Juno Magnetic Field investigation (MAG) characterizes Jupiter's planetary magnetic field and magnetosphere, providing the first globally distributed and proximate measurements of the magnetic field of Jupiter. The magnetic field instrumentation consists of two independent magnetometer sensor suites, each consisting of a tri-axial Fluxgate Magnetometer (FGM) sensor and a pair of co-located imaging sensors mounted on an ultra-stable optical bench. The imaging system sensors are part of a subsystem that provides accurate attitude information (to approx. 20 arcsec on a spinning spacecraft) near the point of measurement of the magnetic field. The two sensor suites are accommodated at 10 and 12 m from the body of the spacecraft on a 4 m long magnetometer boom affixed to the outer end of one of 's three solar array assemblies. The magnetometer sensors are controlled by independent and functionally identical electronics boards within the magnetometer electronics package mounted inside Juno's massive radiation shielded vault. The imaging sensors are controlled by a fully hardware redundant electronics package also mounted within the radiation vault. Each magnetometer sensor measures the vector magnetic field with 100 ppm absolute vector accuracy over a wide dynamic range (to 16 Gauss = 1.6 x 10(exp. 6) nT per axis) with a resolution of approx. 0.05 nT in the most sensitive dynamic range (+/-1600 nT per axis). Both magnetometers sample the magnetic field simultaneously at an intrinsic sample rate of 64 vector samples per second. The magnetic field instrumentation may be reconfigured in flight to meet unanticipated needs and is fully hardware redundant. The attitude determination system compares images with an on-board star catalog to provide attitude solutions (quaternions) at a rate of up to 4 solutions per second, and may be configured to acquire images of selected targets for science and engineering analysis. The system tracks and catalogs objects that pass through

  6. Magnetic-Field Hazards Bibliography.

    Science.gov (United States)

    1985-09-01

    produced during pulsed- magnetic-field therapy for non-union of the tibia." Med. Biol. Eng. Comput., Vol. 20, pp. 501-511 (1982). 32. Miller, D. A...Phenum Publishing Co. (1983). 40. Topper, R. F., "Electromagnetic shielding feasibility study," ASD -TDR-63-194 (Armour Research Foundation, Chicago...mammalian cells by strong magnetic fields (1976). 93. Malins, D. C., and Collier, T. K., "Xenobiotic interactions in aquatic organisms-effects on

  7. Influence of constant magnetic field (cmf) and gamma radiation on hereditary structures of somatic cells

    Energy Technology Data Exchange (ETDEWEB)

    Mileva, M.; Ivanov, B.; Bulanova, M. (Meditsinska Akademiya, Sofia (Bulgaria). Nauchen Inst. po Rentgenologiya i Radiobiologiya)

    1981-01-01

    White mice, line ''N'' were exposed in CMF with induction of the field 0.3T within: 30, 60, 120, 180, 240, 300 and 360 minutes. 15 minutes before the action the mice were irradiated with 0.0516 K/kg gamma quanta (/sup 137/C) at dosage rate 1 96 A/kg. The preparation with metaphase plates were formed from femoral bone using the modified method of Ford. Metabolic, chromatid, chromosome and isochromatid fragments were established. Already the 30 minute action lowers the radiation effect (Pless0.05). The effect of CMF increases with the increase of radiation time. Peak effect is observed at the 240th minute when the aberrations decrease compared with the control, as follows: aberrant cells 2.3 times and aberrations 3.3 times altogether. After the elapse of 330 minutes the radiomodifying effect begins to fall, keeping the same value after 360 minutes too, reaching the level of the 30 minute action.

  8. Particle Acceleration and Magnetic Field Structure in PKS 2155-304: Optical Polarimetric Observations

    CERN Document Server

    de Almeida, U Barres; Dominici, T P; Abraham, Z; Franco, G A P; Daniel, M K; Chadwick, P M; Boisson, C

    2010-01-01

    In this paper we present multiband optical polarimetric observations of the VHE blazar PKS 2155-304 made simultaneously with a H.E.S.S./Fermi high-energy campaign in 2008, when the source was found to be in a low state. The intense daily coverage of the dataset allowed us to study in detail the temporal evolution of the emission and we found that the particle acceleration timescales are decoupled from the changes in the polarimetric properties of the source. We present a model in which the optical polarimetric emission originates at the polarised mm-wave core and propose an explanation for the lack of correlation between the photometric and polarimetric fluxes. The optical emission is consistent with an inhomogeneous synchrotron source in which the large scale field is locally organised by a shock in which particle acceleration takes place. Finally, we use these optical polarimetric observations of PKS 2155-304 at a low state to propose an origin for the quiescent gamma-ray flux of the object, in an attempt t...

  9. Framework of collagen type I - vasoactive vessels structuring invariant geometric attractor in cancer tissues: insight into biological magnetic field.

    Directory of Open Access Journals (Sweden)

    Jairo A Díaz

    Full Text Available In a previous research, we have described and documented self-assembly of geometric triangular chiral hexagon crystal-like complex organizations (GTCHC in human pathological tissues. This article documents and gathers insights into the magnetic field in cancer tissues and also how it generates an invariant functional geometric attractor constituted for collider partners in their entangled environment. The need to identify this hierarquic attractor was born out of the concern to understand how the vascular net of these complexes are organized, and to determine if the spiral vascular subpatterns observed adjacent to GTCHC complexes and their assembly are interrelational. The study focuses on cancer tissues and all the macroscopic and microscopic material in which GTCHC complexes are identified, which have been overlooked so far, and are rigorously revised. This revision follows the same parameters that were established in the initial phase of the investigation, but with a new item: the visualization and documentation of external dorsal serous vascular bed areas in spatial correlation with the localization of GTCHC complexes inside the tumors. Following the standard of the electro-optical collision model, we were able to reproduce and replicate collider patterns, that is, pairs of left and right hand spin-spiraled subpatterns, associated with the orientation of the spinning process that can be an expansion or contraction disposition of light particles. Agreement between this model and tumor data is surprisingly close; electromagnetic spiral patterns generated were identical at the spiral vascular arrangement in connection with GTCHC complexes in malignant tumors. These findings suggest that the framework of collagen type 1 - vasoactive vessels that structure geometric attractors in cancer tissues with invariant morphology sets generate collider partners in their magnetic domain with opposite biological behavior. If these principles are incorporated

  10. Electric field control of magnetization in Cu2O/porous anodic alumina hybrid structures at room temperature

    Science.gov (United States)

    Qi, L. Q.; Liu, H. Y.; Sun, H. Y.; Liu, L. H.; Han, R. S.

    2016-04-01

    Cu2O nanoporous films are deposited on porous anodic alumina (PAA) substrates by DC-reactive magnetron sputtering. This paper focuses on voltage driven magnetization switching in Cu2O/PAA (CP) composite films prepared by DC-reactive magnetron sputtering. By applying a dc electric field, the magnetization of the CP composite films can be controlled in a reversible and reproducible way and shows an analogous on-off behavior. The magnitude of the change in the magnetization was about 75 emu/cm3 as the electric field was switched on and off. Resistive switching behavior was also observed in as-prepared CP composite films. Further analysis indicated that the formation/rupture of conducting filaments composed of oxygen vacancies is likely responsible for the changes in the magnetization as well as in the resistivity. Such reversible change of magnetization controlled by an electric field at room temperature may have applications in spintronics and power efficient data storage technologies.

  11. A self-consistent two-dimensional resistive fluid theory of field-aligned potential structures including charge separation and magnetic and velocity shear

    Science.gov (United States)

    Hesse, Michael; Birn, Joachim; Schindler, Karl

    1990-01-01

    A self-consistent two-fluid theory that includes the magnetic field and shear patterns is developed to model stationary electrostatic structures with field-aligned potential drops. Shear flow is also included in the theory since this seems to be a prominent feature of the structures of interest. In addition, Ohmic dissipation, a Hall term, and pressure gradients in a generalized Ohm's law, modified for cases without quasi-neutrality, are included. In the analytic theory, the electrostatic force is balanced by field-aligned pressure gradients (i.e., thermal effects in the direction of the magnetic field) and by pressure gradients and magnetic stresses in the perpendicular direction. Within this theory, simple examples of applications are presented to demonstrate the kind of solutions resulting from the model. The results show how the effects of charge separation and shear in the magnetic field and the velocity can be combined to form self-consistent structures such as are found to exist above the aurora, suggested also in association with solar flares.

  12. Constant Electric and Magnetic Fields Effect on the Structuring and Thermomechanical and Thermophysical Properties of Nanocomposites Formed from Pectin-Cu2+-Polyethyleneimine Interpolyelectrolyte-Metal Complexes

    Science.gov (United States)

    Demchenko, V.; Shtompel', V.; Riabov, S.; Lysenkov, E.

    2015-12-01

    Applying wide-angle X-ray scattering method, thermomechanical analysis, and differential scanning calorimetry, the structural organization and properties of nanocomposites formed by chemical reduction of Cu2+ cations in the interpolyelectrolyte-metal complex (pectin-Cu2+-polyethyleneimine) under the influence of a constant magnetic and electric fields have been studied. It has been found that the chemical reduction of Cu2+ cations in the interpolyelectrolyte-metal complex bulk under constant electric and magnetic fields leads to formation of nanocomposite consisting of interpolyelectrolyte complex, including pectin-polyethyleneimine and nanoparticles of the metal Cu phase, whereas nanocomposite with Cu/Cu2O nanoparticles is formed in original state (without any field). It was observed that, under constant field, nanocomposites obtained have higher structural glass-transition temperatures and thermal stability.

  13. Induced superconductivity in Nb/InAs-hybrid structures in parallel and perpendicular magnetic fields; Induzierte Supraleitung in Nb/InAs-Hybridstrukturen in parallelen und senkrechten Magnetfeldern

    Energy Technology Data Exchange (ETDEWEB)

    Rohlfing, Franziska

    2007-07-15

    The thesis in hand investigates experimentally Josephson contacts based on Nb/InAs-hybrid structures. The experiments discussed here were done on samples of different width of the Josephson contacts (between 500 nm and 2000 nm). They were realized by means of different methods of the semiconductor technology. The length of the Josephson contacts was about 600 nm and, as superconducting material, niobium was used. Both critical current and characteristics in the resistive regime (excess-current and multiple Andreev reflection) are studied as a function of temperature and external magnetic fields. Measurements in perpendicular and parallel magnetic fields with respect to the plain of the two-dimensional electron gas, are presented. The Andreev reflection amplitude determining the supercurrent is calculated by means of the Greens functions of the two-dimensional electron gas beneath the superconductors which is modified by the proximity effect. From the fit to the data with this model, the transparency of the boundary between the superconductor and the two-dimensional electron gas can be estimated to be about 0.1. The transparency of the point contacts in the two-dimensional electrons gas can be determined independently from the Josephson junction width dependence of the normal resistance (T=10 K). This transparency amounts to about 0.8 in the examined samples. The measurements of the critical current in a magnetic field perpendicular to the two-dimensional electron gas show a Fraunhofer pattern. In order to study the transition from perpendicular orientation into parallel orientation, measurements of the critical current as a function of the magnetic field were done for different angles. In the resistive regime, the excess current measurements in the magnetic field show a very interesting behaviour: In parallel magnetic fields, the excess current becomes zero at about 2.5 T. In perpendicular magnetic field however, the excess current is strongly suppressed below 30 m

  14. Planck intermediate results XXXV. Probing the role of the magnetic field in the formation of structure in molecular clouds

    DEFF Research Database (Denmark)

    Ade, P. A. R.; Aghanim, N.; Alves, M. I. R.;

    2016-01-01

    Within ten nearby (d <450 pc) Gould belt molecular clouds we evaluate statistically the relative orientation between the magnetic field projected on the plane of sky, inferred from the polarized thermal emission of Galactic dust observed by Planck at 353 GHz, and the gas column density structures...... for the gas dynamics at the scales probed by Planck. We compare the deduced magnetic field strength with estimates we obtain from other methods and discuss the implications of the Planck observations for the general picture of molecular cloud formation and evolution....

  15. Nanometric alternating magnetic field generator.

    Science.gov (United States)

    Espejo, A P; Tejo, F; Vidal-Silva, N; Escrig, J

    2017-07-05

    In this work we introduce an alternating magnetic field generator in a cylindrical nanostructure. This field appears due to the rotation of a magnetic domain wall located at some position, generating a magnetic region that varies its direction of magnetization alternately, thus inducing an alternating magnetic flux in its vicinity. This phenomenon occurs due to the competition between a spin-polarized current and a magnetic field, which allows to control both the angular velocity and the pinning position of the domain wall. As proof of concept, we study the particular case of a diameter-modulated nanowire with a spin-polarized current along its axis and the demagnetizing field produced by its modulation. This inhomogeneous field allows one to control the angular velocity of the domain wall as a function of its position along the nanowire allowing frequencies in the GHz range to be achieved. This generator could be used in telecommunications for devices in the range of radiofrequencies or, following Faraday's induction law, could also induce an electromotive force and be used as a movable alternate voltage source in future nanodevices.

  16. Where is magnetic anisotropy field pointing to?

    CERN Document Server

    Gutowski, Marek W

    2013-01-01

    The desired result of magnetic anisotropy investigations is the determination of value(s) of various anisotropy constant(s). This is sometimes difficult, especially when the precise knowledge of saturation magnetization is required, as it happens in ferromagnetic resonance (FMR) studies. In such cases we usually resort to `trick' and fit our experimental data to the quantity called \\emph{anisotropy field}, which is strictly proportional to the ratio of the searched anisotropy constant and saturation magnetization. Yet, this quantity is scalar, simply a number, and is therefore of little value for modeling or simulations of the magnetostatic or micromagnetic structures. Here we show how to `translate' the values of magnetic anisotropy constants into the complete vector of magnetic anisotropy field. Our derivation is rigorous and covers the most often encountered cases, from uniaxial to cubic anisotropy.

  17. Torsional oscillations of neutron stars with highly tangled magnetic fields

    CERN Document Server

    Sotani, Hajime

    2015-01-01

    To determine the frequencies of magnetic oscillations in the neutron stars with highly tangled magnetic fields, we derive the perturbation equations. We assume that the field strength of the global magnetic structure is so small that such fields are negligible compared with the tangled fields, which may still be far from a realistic configuration. Then, we systematically examine the spectra of the magnetic oscillations, as varying the magnetic field strength and stellar mass. The frequencies without crust elasticity are completely proportional to the strength of magnetic field, whose proportionality constant depends strongly on the stellar mass. On the other hand, the oscillation spectra with crust elasticity become more complicated, where the frequencies even for weak magnetic fields are different from the crustal torsional oscillations without magnetic fields. For discussing the spectra, the critical field strength can play an important role, which is determined in such a way that the shear velocity is equi...

  18. Magnetic field characteristics analysis of a single assembled magnetic medium using ANSYS software

    Institute of Scientific and Technical Information of China (English)

    Ren Liuyi; Zeng Shanglin; Zhang Yimin

    2015-01-01

    The section shape of an assembled magnetic medium is the most important structural parameter of a high gradient magnetic separator, which directly affects the induction distribution and magnetic field gradient of the magnetic separator. In this study, equilateral triangle, square, hexagonal, octagon, dode-cagon, and round shape sections of the assembled magnetic medium are chosen to study their influence on magnetic field distribution characteristics using the ANSYS analysis. This paper utilizes a single assem-bled magnetic medium to understand the relationship between the geometry of the assembled magnetic medium and its magnetic field distribution characteristics. The results show that high magnetic field, regional field, magnetic field gradient, and magnetic force formed by the different sections of the assem-bled magnetic medium in the same background magnetic field reduce in turn based on the triangle, square, hexagonal, octagon, dodecagon, and round. Based on the magnetic field characteristics analytic results, the magnetic separation tests of the ilmenite are carried out. The results indicate that the section shape of the toothed plate compared with the section shape of cylinder can improve the recovery of ilme-nite up to 45%in the same magnetizing current condition of 2 A, which is consistent with magnetic field characteristics analysis of different assembled magnetic medium section shapes.

  19. The Magnetic Field of Solar Spicules

    CERN Document Server

    Centeno, R; Ramos, A Asensio

    2009-01-01

    Determining the magnetic field of solar spicules is vital for developing adequate models of these plasma jets, which are thought to play a key role in the thermal, dynamic, and magnetic structure of the chromosphere. Here we report on magnetic spicule properties in a very quiet region of the off-limb solar atmosphere, as inferred from new spectropolarimetric observations in the HeI 10830 A triplet. We have used a novel inversion code for Stokes profiles caused by the joint action of atomic level polarization and the Hanle and Zeeman effects (HAZEL) to interpret the observations. Magnetic fields as strong as 40G were unambiguously detected in a very localized area of the slit, which may represent a possible lower value of the field strength of organized network spicules.

  20. Field-structured composite studies.

    Energy Technology Data Exchange (ETDEWEB)

    Martin, James Ellis; Williamson, Rodney L.

    2004-04-01

    Field-structured composites (FSCs) were produced by hosting micron-sized gold-coated nickel particles in a pre-polymer and allowing the mixture to cure in a magnetic field environment. The feasibility of controlling a composite's electrical conductivity using feedback control applied to the field coils was investigated. It was discovered that conductivity in FSCs is primarily determined by stresses in the polymer host matrix due to cure shrinkage. Thus, in cases where the structuring field was uniform and unidirectional so as to produce chainlike structures in the composite, no electrical conductivity was measured until well after the structuring field was turned off at the gel point. In situations where complex, rotating fields were used to generate complex, three-dimensional structures in a composite, very small, but measurable, conductivity was observed prior to the gel point. Responsive, sensitive prototype chemical sensors were developed based on this technology with initial tests showing very promising results.

  1. Magnetic Field Generation in Stars

    CERN Document Server

    Ferrario, Lilia; Zrake, Jonathan

    2015-01-01

    Enormous progress has been made on observing stellar magnetism in stars from the main sequence through to compact objects. Recent data have thrown into sharper relief the vexed question of the origin of stellar magnetic fields, which remains one of the main unanswered questions in astrophysics. In this chapter we review recent work in this area of research. In particular, we look at the fossil field hypothesis which links magnetism in compact stars to magnetism in main sequence and pre-main sequence stars and we consider why its feasibility has now been questioned particularly in the context of highly magnetic white dwarfs. We also review the fossil versus dynamo debate in the context of neutron stars and the roles played by key physical processes such as buoyancy, helicity, and superfluid turbulence,in the generation and stability of neutron star fields. Independent information on the internal magnetic field of neutron stars will come from future gravitational wave detections. Thus we maybe at the dawn of a ...

  2. Band structure of a 2D photonic crystal based on ferrofluids of Co(1-x)Znx Fe2O4 nanoparticles under perpendicular applied magnetic field

    Science.gov (United States)

    Lopez, Javier; Gonzalez, Luz Esther; Quinonez, Mario; Porras, Nelson; Zambrano, Gustavo; Gomez, Maria Elena

    2014-03-01

    Using a ferrfluid of cobalt-zinc ferrite nanoparticles Co(1 - x)ZnxFe2O4 coated with oleic acid and suspended in ethanol, we have fabricated a 2D photonic crystal (PC) by the application of an external magnetic field perpendicular to the plane of the ferrofluid. The 2D PC is made by rods of nanoparticles organized in a hexagonal structure. By means of the plane-wave expansion method, we study its photonic band structure (PBS) which depends on the effective permittivity and on the area ratio of the liquid phase. Additionaly, taking into account the Maxwell-Garnett theory we calculated the effective permittivity of the rods. We have found that the effective refractive index of the ferrofluid increases with its magnetization. Using these results we calculate the band structure of the photonic crystal at different applied magnetic fields, finding that the increase of the applied magnetic field shifts the band structure to lower frequencies with the appearance of more band gaps. Departamento de Física, Universidad del Valle, A.A. 25360, Cali, Colombia

  3. Measurements of Photospheric and Chromospheric Magnetic Fields

    Science.gov (United States)

    Lagg, Andreas; Lites, Bruce; Harvey, Jack; Gosain, Sanjay; Centeno, Rebecca

    2017-09-01

    The Sun is replete with magnetic fields, with sunspots, pores and plage regions being their most prominent representatives on the solar surface. But even far away from these active regions, magnetic fields are ubiquitous. To a large extent, their importance for the thermodynamics in the solar photosphere is determined by the total magnetic flux. Whereas in low-flux quiet Sun regions, magnetic structures are shuffled around by the motion of granules, the high-flux areas like sunspots or pores effectively suppress convection, leading to a temperature decrease of up to 3000 K. The importance of magnetic fields to the conditions in higher atmospheric layers, the chromosphere and corona, is indisputable. Magnetic fields in both active and quiet regions are the main coupling agent between the outer layers of the solar atmosphere, and are therefore not only involved in the structuring of these layers, but also for the transport of energy from the solar surface through the corona to the interplanetary space. Consequently, inference of magnetic fields in the photosphere, and especially in the chromosphere, is crucial to deepen our understanding not only for solar phenomena such as chromospheric and coronal heating, flares or coronal mass ejections, but also for fundamental physical topics like dynamo theory or atomic physics. In this review, we present an overview of significant advances during the last decades in measurement techniques, analysis methods, and the availability of observatories, together with some selected results. We discuss the problems of determining magnetic fields at smallest spatial scales, connected with increasing demands on polarimetric sensitivity and temporal resolution, and highlight some promising future developments for their solution.

  4. Simulating magnetic fields in the Antennae galaxies

    CERN Document Server

    Kotarba, H; Naab, T; Johansson, P H; Dolag, K; Lesch, H

    2009-01-01

    We present self-consistent high-resolution simulations of NGC4038/4039 (the "Antennae galaxies") including star formation, supernova feedback and magnetic fields performed with the N-body/SPH code Gadget, in which hydrodynamics and magnetohydrodynamics are followed with the SPH method. We vary the initial magnetic field in the progenitor disks from 1 nG to 1 muG. At the time of the best match with the central region of the Antennae system the magnetic field has been amplified by compression and shear flows to an equilibrium field of approximately 10 muG, independent of the initial seed field. This simulations are a proof of the principle that galaxy mergers are efficient drivers for the cosmic evolution of magnetic fields. We present a detailed analysis of the magnetic field structure in the central overlap region. Simulated radio and polarization maps are in good morphological and quantitative agreement with the observations. In particular, the two cores with the highest synchrotron intensity and ridges of r...

  5. Magnetic structure of Bayonnaise knoll caldera including Hakurei hydrothermal site obtained from near-bottom magnetic vector field mapping by autonomous underwater vehicle

    Science.gov (United States)

    Honsho, C.; Ura, T.; Kim, K.

    2012-12-01

    The Bayonnaise knoll caldera is one of the silicic submarine calderas in the Izu-Ogasawara Arc in Japan. In 2003, a large-scale hydrothermal deposit was found in the caldera, called the Hakurei deposit. The caldera had been explored by four surveys using autonomous underwater vehicles (AUVs) from 2008 to 2011, and the near-bottom magnetic field was mapped over about 75% of the caldera floor. We carried out detailed correction for the magnetic field produced by the vehicle body, which allowed us to take advantage of the vector anomaly instead of the total anomaly for the magnetic inversion. We applied the inversion method using the block model together with the Akaike's Bayesian information criterion (ABIC). One remarkable thing is that we recognized significant difference between the magnetic inversion result using the vector anomaly and that using the total anomaly: the latter result explains the observed total anomalies excellently, but does not explain the vector anomalies adequately. Except for a rare case where the vector anomaly is perpendicular to the main field throughout, the total anomaly should be sufficient for evaluating the entire field, provided that the data is collected in sufficiently high density. In fact, the track lines of our survey sometimes separate from each other by about twice the altitude of the vehicle (100 m), which can lead to considerable aliasing in the sampled field. The vector anomaly can provide vital information in such a situation. The obtained magnetization distribution is well correlated with the topography. The caldera rim and central cone have weak magnetization, which is consistent with the fact that they consist of dacite rocks. On the other hand, the caldera floor shows high magnetization, which implies the existence of basaltic rocks. The high magnetization appears to continue north and south beyond the caldera rim, forming an NS-trending high magnetization zone. Because the caldera floor is generally covered with

  6. Magnetic field of the Earth

    Science.gov (United States)

    Popov, Aleksey

    2013-04-01

    The magnetic field of the Earth has global meaning for a life on the Earth. The world geophysical science explains: - occurrence of a magnetic field of the Earth it is transformation of kinetic energy of movements of the fused iron in the liquid core of Earth - into the magnetic energy; - the warming up of a kernel of the Earth occurs due to radioactive disintegration of elements, with excretion of thermal energy. The world science does not define the reasons: - drift of a magnetic dipole on 0,2 a year to the West; - drift of lithospheric slabs and continents. The author offers: an alternative variant existing in a world science the theories "Geodynamo" - it is the theory « the Magnetic field of the Earth », created on the basis of physical laws. Education of a magnetic field of the Earth occurs at moving the electric charge located in a liquid kernel, at rotation of the Earth. At calculation of a magnetic field is used law the Bio Savara for a ring electric current: dB = . Magnetic induction in a kernel of the Earth: B = 2,58 Gs. According to the law of electromagnetic induction the Faradey, rotation of a iron kernel of the Earth in magnetic field causes occurrence of an electric field Emf which moves electrons from the center of a kernel towards the mantle. So of arise the radial electric currents. The magnetic field amplifies the iron of mantle and a kernel of the Earth. As a result of action of a radial electric field the electrons will flow from the center of a kernel in a layer of an electric charge. The central part of a kernel represents the field with a positive electric charge, which creates inverse magnetic field Binv and Emfinv When ?mfinv = ?mf ; ?inv = B, there will be an inversion a magnetic field of the Earth. It is a fact: drift of a magnetic dipole of the Earth in the western direction approximately 0,2 longitude, into a year. Radial electric currents a actions with the basic magnetic field of a Earth - it turn a kernel. It coincides with laws

  7. Effect of microgravity and magnetic field on the metallic and crystalline structure of magnetostrictive SmFe2 synthesized by unidirectional solidification.

    Science.gov (United States)

    Okutani, Takeshi; Nagai, Hideaki; Mamiya, Mikito; Shibuya, Masachika; Castillo, Martin

    2006-09-01

    The Sm-2Fe molten alloy with 1:2 molar ratio was unidirectionally solidified in both microgravity and normal gravity in concurrence with a magnetic flux (0-0.12 T). The compound SmFe2 was produced by the unidirectional solidification in microgravity with a magnetic flux of 0T and exhibited a lamellar microstructure. The average lamellar thickness was 30 mum and each lamella possessed a crystallographic alignment along major axis aligned in the direction of cooling. Unidirectional solidification in microgravity with a magnetic field of 0.04 T produced crystalline SmFe2 and Fe phases. The microstructure of this product was lamellar with an average lamellar thickness of 17 mum and no crystalline alignment. Unidirectional solidification in microgravity with a magnetic flux ranging from 0.06 to 0.12 T and in normal gravity with a magnetic flux ranging from 0 to 0.12 T produced crystalline Sm2Fe17 and Fe. During unidirectional solidification in microgravity without a magnetic flux, few nucleation sites were formed and rapid crystal growth occurred, consequently forming large-grain SmFe2. The produced SmFe2 had a lamellar structure with a dominant crystallographic alignment in the direction of cooling. Convection in the molten state and where a magnetic flux was present caused homogeneous nucleation, forming Sm2Fe17 with a disordered structure and crystalline alignment coinciding with the formation of the dendritic Fe.

  8. Magnetohydrodynamic experiments on cosmic magnetic fields

    CERN Document Server

    Stefani, Frank; Gerbeth, Gunter

    2008-01-01

    It is widely known that cosmic magnetic fields, including the fields of planets, stars, and galaxies, are produced by the hydromagnetic dynamo effect in moving electrically conducting fluids. It is less well known that cosmic magnetic fields play also an active role in cosmic structure formation by enabling outward transport of angular momentum in accretion disks via the magnetorotational instability (MRI). Considerable theoretical and computational progress has been made in understanding both processes. In addition to this, the last ten years have seen tremendous efforts in studying both effects in liquid metal experiments. In 1999, magnetic field self-excitation was observed in the large scale liquid sodium facilities in Riga and Karlsruhe. Recently, self-excitation was also obtained in the French "von Karman sodium" (VKS) experiment. An MRI-like mode was found on the background of a turbulent spherical Couette flow at the University of Maryland. Evidence for MRI as the first instability of an hydrodynamica...

  9. Cosmic Magnetic Fields: Observations and Prospects

    CERN Document Server

    Beck, Rainer

    2011-01-01

    Synchrotron emission, its polarization and its Faraday rotation at radio frequencies of 0.2-10 GHz are powerful tools to study the strength and structure of cosmic magnetic fields. The observational results are reviewed for spiral, barred and flocculent galaxies, the Milky Way, halos and relics of galaxy clusters, and for the intergalactic medium. Polarization observations with the forthcoming large radio telescopes will open a new era in the observation of cosmic magnetic fields and will help to understand their origin. At low frequencies, LOFAR (10-250 MHz) will allow us to map the structure of weak magnetic fields in the outer regions and halos of galaxies and galaxy clusters. Polarization at higher frequencies (1-10 GHz), as observed with the EVLA, ASKAP, MeerKAT, APERTIF and the SKA, will trace magnetic fields in the disks and central regions of nearby galaxies in unprecedented detail. Surveys of Faraday rotation measures of pulsars will map the Milky Way's magnetic field with high precision. All-sky sur...

  10. Jovian plasma torus interaction with Europa. Plasma wake structure and effect of inductive magnetic field: 3D Hybrid kinetic simulation

    CERN Document Server

    Lipatov, A S; Paterson, W R; Sittler, E C; Hartle, R E; Simpson, D G

    2012-01-01

    The hybrid kinetic model supports comprehensive simulation of the interaction between different spatial and energetic elements of the Europa moon-magnetosphere system with respect a to variable upstream magnetic field and flux or density distributions of plasma and energetic ions, electrons, and neutral atoms. This capability is critical for improving the interpretation of the existing Europa flyby measurements from the Galileo Orbiter mission, and for planning flyby and orbital measurements (including the surface and atmospheric compositions) for future missions. The simulations are based on recent models of the atmosphere of Europa (Cassidy et al., 2007; Shematovich et al., 2005). In contrast to previous approaches with MHD simulations, the hybrid model allows us to fully take into account the finite gyroradius effect and electron pressure, and to correctly estimate the ion velocity distribution and the fluxes along the magnetic field (assuming an initial Maxwellian velocity distribution for upstream backgr...

  11. Magnetic fields during galaxy mergers

    CERN Document Server

    Rodenbeck, Kai

    2016-01-01

    Galaxy mergers are expected to play a central role for the evolution of galaxies, and may have a strong impact on their magnetic fields. We present the first grid-based 3D magneto-hydrodynamical simulations investigating the evolution of magnetic fields during merger events. For this purpose, we employ a simplified model considering the merger event of magnetized gaseous disks in the absence of stellar feedback and without a stellar or dark matter component. We show that our model naturally leads to the production of two peaks in the evolution of the average magnetic field strength within 5 kpc, within 25 kpc and on scales in between 5 and 25 kpc. The latter is consistent with the peak in the magnetic field strength reported by Drzazga et al. (2011) in a merger sequence of observed galaxies. We show that the peak on the galactic scale and in the outer regions is likely due to geometrical effects, as the core of one galaxy enters the outskirts of the other one. In addition, there is a physical enhancement of t...

  12. Magnetic field control of the neutral and charged exciton fine structure in single quantum dashes emitting at 1.55 μm

    Energy Technology Data Exchange (ETDEWEB)

    Mrowiński, P.; Musiał, A.; Maryński, A.; Syperek, M.; Misiewicz, J.; Sęk, G. [Laboratory for Optical Spectroscopy of Nanostructures, Department of Experimental Physics, Wrocław University of Technology, Wybrzeże Wyspiańskiego 27, Wrocław (Poland); Somers, A. [Technische Physik, University of Würzburg and Wilhelm-Conrad-Röntgen-Research Center for Complex Material Systems, Am Hubland, D-97074 Würzburg (Germany); Reithmaier, J. P. [Technische Physik, University of Würzburg and Wilhelm-Conrad-Röntgen-Research Center for Complex Material Systems, Am Hubland, D-97074 Würzburg (Germany); Institute of Nanostructure Technologies and Analytics (INA), CINSaT, University of Kassel, Heinrich-Plett-Str. 40, 34132 Kassel (Germany); Höfling, S. [Technische Physik, University of Würzburg and Wilhelm-Conrad-Röntgen-Research Center for Complex Material Systems, Am Hubland, D-97074 Würzburg (Germany); SUPA, School of Physics and Astronomy, University of St. Andrews, North Haugh, KY16 9SS St. Andrews (United Kingdom)

    2015-02-02

    We investigated the neutral and charged exciton fine structure in single InAs/InGaAlAs/InP quantum dashes emitting at 1.55 μm using polarization-resolved microphotoluminescence in a magnetic field. Inverted spin configuration of horizontally [1–10] and vertically [110] polarized transitions has been observed. An in-plane magnetic field of up to 5 Tesla has been applied to tailor the fine structure, and eventually to reduce the splitting of the bright exciton states down to zero. This inverted structure has been observed for all the investigated excitons, making it a characteristic feature for this class of nanostructures with the largest splitting reduction of 170 μeV.

  13. Zero magnetic field type magnetic field sensor. Reijikaigata jikai sensor

    Energy Technology Data Exchange (ETDEWEB)

    Sonoda, T.; Ueda, R. (Kyushu Institute of Technology, Fukuoka (Japan))

    1990-11-20

    It is shown in this paper that a new type of sensor with excellent characteristics can be made by demagnetizing the sensor core toward a zero field state and then detecting an unknown field to be detected by the demagnetizing current. The core operates equivalently in a zero magnetic field so that the detection sensitivity is determined by the coil constant including the number of turns of the solenoid for demagnetization required to offset the field to be detected. Therefore the detection sensitivity does not depend on its configuration and magnetization characteristics and does not depend on the temperature. It is thereby considered that these characteristics can largely reduce such problems at present as the aging deterioration of magnetic materials or the quality control accompanied by manufacturing. In addition, the following points have been clarified: (1) The upper limit of the detectable range does not exist in principle. (2) The accuracy of the detection is 0.02% to the full scale 20kA/m. (3) The magnetization property required to the core used as a sensor is that it has a rectangular B-H loop which is as sharp as possible. 14 refs., 13 figs., 2 tabs.

  14. Magnetic resonance of field-frozen and zero-field-frozen magnetic fluids

    Energy Technology Data Exchange (ETDEWEB)

    Pereira, A.R. E-mail: anarita@fis.ufg.br; Pelegrini, F.; Neto, K. Skeff; Buske, N.; Morais, P.C. E-mail: pcmor@unb.br

    2004-05-01

    In this study magnetic resonance was used to investigate magnetic fluid samples frozen under zero and non-zero (15 kG) external fields. The magnetite-based sample containing 2x10{sup 17} particle/cm{sup 3} was investigated from 100 to 400 K. Analysis of the temperature dependence of the resonance field revealed bigger magnetic structures in the frozen state than in the liquid phase. Also, differences in the mesoscopic organization in the frozen state may explain the data obtained from samples frozen under zero and non-zero fields.

  15. Plasma properties and magnetic field structure of the solar corona, based on coordinated Max 1991 observations from SERTS, the VLA, and magnetographs

    Science.gov (United States)

    Brosius, Jeffrey W.

    1995-01-01

    The purposes of this investigation are to determine the plasma properties and magnetic field structure of the solar corona using coordinated observations obtained with NASA/GSFC's Solar EUV rocket Telescope and Spectrograph (SERTS), the Very Large Array (VLA), and magnetographs. The observations were obtained under the auspices of NASA's Max '91 program. The methods of achieving the stated purposes of this investigation are: (1) to use SERTS spectra and spectroheliograms to determine coronal plasma properties such as temperature, density, and emission measure; (2) to use the coronal plasma properties to calculate the intensity of the thermal bremsstrahlung microwave emission from the coronal plasma (the minimum microwave intensity expected from the emitting plasma); (3) to establish which emission mechanism(s) contribute to the observed microwave emission by comparing the calculated thermal bremsstrahlung intensity with the observed microwave intensity; (4) to derive the coronal magnetic field for regions in which gyroemission contributes to the microwave emission by determining the appropriate harmonic of the local electron gyrofrequency; (5) to derive the coronal magnetic field for regions in which thermal bremsstrahlung emission alone is responsible for the observed microwave emission by calculating the magnetic field which yields the observed microwave polarization; (6) to derive three-dimensional models of the coronal plasma and magnetic field which are consistent with all of the EUV spectra and spectroheliograms, as well as with the intensity and polarization maps at all of the microwave observing frequencies; and (7) to compare the coronal magnetic field derived from the coordinated multiwaveband observations with extrapolations from photospheric magnetograms.

  16. Effects of static magnetic fields on plants.

    Science.gov (United States)

    Kuznetsov, O.

    In our recent experiment on STS-107 (MFA-Biotube) we took advantage of the magnetic heterogeneity of the gravity receptor cells of flax roots, namely stronger diamagnetism of starch-filled amyloplasts compared to cytoplasm (Δ ≊ HGMF, grad(H2/2) up to 109-1010 Oe2/cm) of the experimental chambers (MFCs) repelled amyloplasts from the zones of stronger field thus providing a directional stimulus for plant gravisensing system in microgravity, and causing the roots to react. Such reaction was observed in the video downlink pictures. Unfortunately, the ``Columbia'' tragedy caused loss of the plant material and most of the images, thus preventing us from detailed studies of the results. Currently we are looking for a possibility to repeat this experiment. Therefore, it is very important to understand, what other effects (besides displacing amyloplasts) static magnetic fields with intensities 0 to 2.5104 Oe, and with the size of the area of non-uniformity 10-3 to 1 cm. These effects were estimated theoretically and tested experimentally. No statistically significant differences in growth rates or rates of gravicurvature were observed in experiments with Linum, Arabidopsis, Hordeum, Avena, Ceratodon and Chara between the plants grown in uniform magnetic fields of various intensities (102 to 2.5104 Oe) and those grown in the Earth's magnetic field. Microscopic studies also did not detect any structural differences between test and control plants. The magnitudes of possible effects of static magnetic fields on plant cells and organs (including effects on ion currents, magneto-hydrodynamic effects in moving cytoplasm, ponderomotive forces on other cellular structures, effects on some biochemical reactions and biomolecules) were estimated theoretically. The estimations have shown, that these effects are small compared to the thermodynamic noise and thus are insignificant. Both theoretical estimations and control experiments confirm, that intracellular magnetophoresis of

  17. A deep dynamo generating Mercury's magnetic field.

    Science.gov (United States)

    Christensen, Ulrich R

    2006-12-21

    Mercury has a global magnetic field of internal origin and it is thought that a dynamo operating in the fluid part of Mercury's large iron core is the most probable cause. However, the low intensity of Mercury's magnetic field--about 1% the strength of the Earth's field--cannot be reconciled with an Earth-like dynamo. With the common assumption that Coriolis and Lorentz forces balance in planetary dynamos, a field thirty times stronger is expected. Here I present a numerical model of a dynamo driven by thermo-compositional convection associated with inner core solidification. The thermal gradient at the core-mantle boundary is subadiabatic, and hence the outer region of the liquid core is stably stratified with the dynamo operating only at depth, where a strong field is generated. Because of the planet's slow rotation the resulting magnetic field is dominated by small-scale components that fluctuate rapidly with time. The dynamo field diffuses through the stable conducting region, where rapidly varying parts are strongly attenuated by the skin effect, while the slowly varying dipole and quadrupole components pass to some degree. The model explains the observed structure and strength of Mercury's surface magnetic field and makes predictions that are testable with space missions both presently flying and planned.

  18. Physics of semiconductors in high magnetic fields

    CERN Document Server

    Miura, Noboru

    2008-01-01

    This book summarizes most of the fundamental physical phenomena which semiconductors and their modulated structures exhibit in high magnetic fields. Readers can learn not only the basic theoretical background but also the present state of the art from the most advanced data in this rapidly growing research area.

  19. High-field magnetization in transuranium compound

    Energy Technology Data Exchange (ETDEWEB)

    Sugiyama, K. [Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043 (Japan) and KYOKUGEN, Osaka University, Osaka 560-8531 (Japan)]. E-mail: sugiyama@phys.sci.osaka-u.ac.jp; Nakashima, H. [Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043 (Japan); Aoki, D. [Institute of Material Research, Tohoku University, Oarai, Ibaraki 311-1313 (Japan); Ikeda, S. [Institute of Material Research, Tohoku University, Oarai, Ibaraki 311-1313 (Japan); Haga, Y. [Advanced Science and Research Centerer, JAEA, Tokai, Ibaraki 319-1195 (Japan); Yamamoto, E. [Advanced Science and Research Centerer, JAEA, Tokai, Ibaraki 319-1195 (Japan); Nakamura, A. [Advanced Science and Research Centerer, JAEA, Tokai, Ibaraki 319-1195 (Japan); Homma, Y. [Institute of Material Research, Tohoku University, Oarai, Ibaraki 311-1313 (Japan); Shiokawa, Y. [Institute of Material Research, Tohoku University, Oarai, Ibaraki 311-1313 (Japan); Kindo, K. [Institite of Solid State Physics, University of Tokyo, Kashiwanoha 5-1-5, Kashiwa, Chiba 277-8581 (Japan); Hagiwara, M. [KYOKUGEN, Osaka University, Osaka 560-8531 (Japan); Onuki, Y. [Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043 (Japan); Advanced Science and Research Centerer, JAEA, Tokai, Ibaraki 319-1195 (Japan)

    2007-03-15

    We measured the high-field magnetization up to 55T and constructed a magnetic phase diagram for a transuranium antiferromagnet NpRhGa{sub 5} with the tetragonal structure. The magnetization at 4.2K for H(parallel) [100] indicates a sharp metamagnetic transition with a step at H{sub c}=26T and saturates above H{sub s}=38T, reaching 0.43{mu}{sub B}/Np. An ordered moment of 0.96{mu}{sub B}/Np at zero field, which was determined from the neutron scattering experiment, is found to be reduced to 0.43{mu}{sub B}/Np at H{sub s}, together with an orientation of the magnetic moment from the (001) plane to the (100) plane.

  20. Primordial Magnetic Fields and Causality

    CERN Document Server

    Durrer, R; Durrer, Ruth; Caprini, Chiara

    2003-01-01

    In this letter we discuss the implications of causality on a primordial magnetic field. We show that the residual field on large scales is much stronger suppressed than usually assumed and that a helical component is even suppressed even more than the parity even part. We show that due to this strong suppression, even maximal primordial fields generated at the electroweak phase transition can just marginally seed the fields in galaxies and clusters, but they cannot leave any detectable imprint on the cosmic microwave background.

  1. Magnetic field structure in single late-type giants: The weak G-band giant 37 Comae from 2008 to 2011

    Science.gov (United States)

    Tsvetkova, S.; Petit, P.; Konstantinova-Antova, R.; Aurière, M.; Wade, G. A.; Palacios, A.; Charbonnel, C.; Drake, N. A.

    2017-03-01

    Aims: This work studies the magnetic activity of the late-type giant 37 Com. This star belongs to the group of weak G-band stars that present very strong carbon deficiency in their photospheres. The paper is a part of a global investigation into the properties and origin of magnetic fields in cool giants. Methods: We use spectropolarimetric data, which allows the simultaneous measurement of the longitudinal magnetic field Bl, line activity indicators (Hα, Ca ii IRT, S-index) and radial velocity of the star, and consequently perform a direct comparison of their time variability. Mean Stokes V profiles are extracted using the least squares deconvolution (LSD) method. One map of the surface magnetic field of the star is reconstructed via the Zeeman Doppler imaging (ZDI) inversion technique. Results: A periodogram analysis is performed on our dataset and it reveals a rotation period of 111 days. We interpret this period to be the rotation period of 37 Com. The reconstructed magnetic map reveals that the structure of the surface magnetic field is complex and features a significant toroidal component. The time variability of the line activity indicators, radial velocity and magnetic field Bl indicates a possible evolution of the surface magnetic structures in the period from 2008 to 2011. For completeness of our study, we use customized stellar evolutionary models suited to a weak G-band star. Synthetic spectra are also calculated to confirm the peculiar abundance of 37 Com. Conclusions: We deduce that 37 Com is a 6.5 M⊙ weak G-band star located in the Hertzsprung gap, whose magnetic activity is probably due to dynamo action. Based on observations obtained at the Télescope Bernard Lyot (TBL, Pic du Midi, France) of the Midi-Pyrénées Observatory which is operated by the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique of France and Université de Toulouse, and at the Canada-France-Hawaii Telescope (CFHT) which is

  2. Magnetic fields around black holes

    Science.gov (United States)

    Garofalo, David A. G.

    Active Galactic Nuclei are the most powerful long-lived objects in the universe. They are thought to harbor supermassive black holes that range from 1 million solar masses to 1000 times that value and possibly greater. Theory and observation are converging on a model for these objects that involves the conversion of gravitational potential energy of accreting gas to radiation as well as Poynting flux produced by the interaction of the rotating spacetime and the electromagnetic fields originating in the ionized accretion flow. The presence of black holes in astrophysics is taking center stage, with the output from AGN in various forms such as winds and jets influencing the formation and evolution of the host galaxy. This dissertation addresses some of the basic unanswered questions that plague our current understanding of how rotating black holes interact with their surrounding magnetized accretion disks to produce the enormous observed energy. Two magnetic configurations are examined. The first involves magnetic fields connecting the black hole with the inner accretion disk and the other involves large scale magnetic fields threading the disk and the hole. We study the effects of the former type by establishing the consequences that magnetic torques between the black hole and the inner accretion disk have on the energy dissipation profile. We attempt a plausible explanation to the observed "Deep Minimum" state in the Seyfert galaxy MCG-6- 30-15. For the latter type of magnetic geometry, we study the effects of the strength of the magnetic field threading the black hole within the context of the cherished Blandford & Znajek mechanism for black hole spin energy extraction. We begin by addressing the problem in the non-relativistic regime where we find that the black hole-threading magnetic field is stronger for greater disk thickness, larger magnetic Prandtl number, and for a larger accretion disk. We then study the problem in full relativity where we show that our

  3. Magnetic fields of green.

    Science.gov (United States)

    Branton, Scott; Lile, Lawrence

    2011-01-01

    By incorporating even the basic elements of a more environmentally friendly, "green"construction and design in an MRI setting can create a safer, more pleasant space for the patients and staff, better images, and operational cost savings. Using building systems that have reduced amounts of steel can decrease construction time, increase thermal insulation, and reduce the weight of the structure meaning less energy required to transport and install. HVAC systems and lighting design can also play a major role in creating a "green"MRI suite. LEED certification places a focus on quality of the built environment, life cycle cost, and a productive indoor environment, as well as impact on the exterior environment. An LEED certified building considers costs and benefits for the lifetime of the building.

  4. Magnetostriction of field-structured magnetoelastomers.

    Energy Technology Data Exchange (ETDEWEB)

    Gulley, Gerald L. (Dominican University, River Forest, IL); Read, Douglas H.; Martin, James Ellis; Huber, Dale L.; Anderson, Robert Alan; Frankamp, Benjamin L.

    2005-12-01

    Field-structured magnetic particle composites are an important new class of materials that have great potential as both sensors and actuators. These materials are synthesized by suspending magnetic particles in a polymeric resin and subjecting these to magnetic fields while the resin polymerizes. If a simple uniaxial magnetic field is used, the particles will form chains, yielding composites whose magnetic susceptibility is enhanced along a single direction. A biaxial magnetic field, comprised of two orthogonal ac fields, forms particle sheets, yielding composites whose magnetic susceptibility is enhanced along two principal directions. A balanced triaxial magnetic field can be used to enhance the susceptibility in all directions, and biased heterodyned triaxial magnetic fields are especially effective for producing composites with a greatly enhanced susceptibility along a single axis. Magnetostriction is quadratic in the susceptibility, so increasing the composite susceptibility is important to developing actuators that function well at modest fields. To investigate magnetostriction in these field-structured composites we have constructed a sensitive, constant-stress apparatus capable of 1 ppm strain resolution. The sample geometry is designed to minimize demagnetizing field effects. With this apparatus we have demonstrated field-structured composites with nearly 10,000 ppm strain.

  5. Magnetic field-induced ferroelectric domain structure evolution and magnetoelectric coupling for [110]-oriented PMN-PT/Terfenol-D multiferroic composites

    Science.gov (United States)

    Fang, F.; Jing, W. Q.

    2016-01-01

    Magnetic field-induced polarization rotation and magnetoelectric coupling effects are studied for [110]-oriented (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3/Tb0.3Dy0.7Fe2(PMN-xPT/Terfenol-D) multiferroic composites. Two compositions of the [110]-oriented relaxor ferroelectric single crystals, PMN-28PT and PMN-33PT, are used. In [110]-oriented PMN-28PT, domains of rhombohedral (R) and monoclinic (MB) phases coexist prior to the magnetic loadings. Upon the applied magnetic loadings, phase transition from monoclinic MB to R phase occurs. In [110]-oriented PMN-33PT, domains are initially of mixed orthorhombic (O) and MB phases, and the phase transition from O to MB phase takes place upon the external magnetic loading. Compared to PMN-28PT, the PMN-33PT single crystal exhibits much finer domain boundary structure prior to the magnetic loadings. Upon the magnetic loadings, more domain variants are induced via the phase transition in PMN-33PT than that in PMN-28PT single crystal. The finer domain band structure and more domain variants contribute to stronger piezoelectric activity. As a result, the composite of PMN-33PT/Terfenol-D manifests a stronger ME coupling than PMN-28PT/Terfenol-D composite.

  6. Magnetic field-induced ferroelectric domain structure evolution and magnetoelectric coupling for [110]-oriented PMN-PT/Terfenol-D multiferroic composites

    Directory of Open Access Journals (Sweden)

    F. Fang

    2016-01-01

    Full Text Available Magnetic field-induced polarization rotation and magnetoelectric coupling effects are studied for [110]-oriented (1-xPb(Mg1/3Nb2/3O3-xPbTiO3/Tb0.3Dy0.7Fe2(PMN-xPT/Terfenol-D multiferroic composites. Two compositions of the [110]-oriented relaxor ferroelectric single crystals, PMN-28PT and PMN-33PT, are used. In [110]-oriented PMN-28PT, domains of rhombohedral (R and monoclinic (MB phases coexist prior to the magnetic loadings. Upon the applied magnetic loadings, phase transition from monoclinic MB to R phase occurs. In [110]-oriented PMN-33PT, domains are initially of mixed orthorhombic (O and MB phases, and the phase transition from O to MB phase takes place upon the external magnetic loading. Compared to PMN-28PT, the PMN-33PT single crystal exhibits much finer domain boundary structure prior to the magnetic loadings. Upon the magnetic loadings, more domain variants are induced via the phase transition in PMN-33PT than that in PMN-28PT single crystal. The finer domain band structure and more domain variants contribute to stronger piezoelectric activity. As a result, the composite of PMN-33PT/Terfenol-D manifests a stronger ME coupling than PMN-28PT/Terfenol-D composite.

  7. Chiral transition with magnetic fields

    CERN Document Server

    Ayala, Alejandro; Mizher, Ana Julia; Rojas, Juan Cristobal; Villavicencio, Cristian

    2014-01-01

    We study the nature of the chiral transition for an effective theory with spontaneous breaking of symmetry, where charged bosons and fermions are subject to the effects of a constant external magnetic field. The problem is studied in terms of the relative intensity of the magnetic field with respect to the mass and the temperature. When the former is the smallest of the scales, we present a suitable method to obtain magnetic and thermal corrections up to ring order at high temperature. By these means, we solve the problem of the instability in the boson sector for these theories, where the squared masses, taken as functions of the order parameter, can vanish and even become negative. The solution is found by considering the screening properties of the plasma, encoded in the resummation of the ring diagrams at high temperature. We also study the case where the magnetic field is the intermediate of the three scales and explore the nature of the chiral transition as we vary the field strength, the coupling const...

  8. Magnetic Fields of Neutron Stars

    Indian Academy of Sciences (India)

    Sushan Konar

    2017-09-01

    This article briefly reviews our current understanding of the evolution of magnetic fields in neutron stars, which basically defines the evolutionary pathways between different observational classes of neutron stars. The emphasis here is on the evolution in binary systems and the newly emergent classes of millisecond pulsars.

  9. Planck intermediate results. XLIV. The structure of the Galactic magnetic field from dust polarization maps of the southern Galactic cap

    CERN Document Server

    Aghanim, N; Arzoumanian, D; Aumont, J; Baccigalupi, C; Ballardini, M; Banday, A J; Barreiro, R B; Bartolo, N; Basak, S; Benabed, K; Bernard, J -P; Bersanelli, M; Bielewicz, P; Bonavera, L; Bond, J R; Borrill, J; Bouchet, F R; Boulanger, F; Bracco, A; Bucher, M; Burigana, C; Calabrese, E; Cardoso, J -F; Chiang, H C; Colombo, L P L; Combet, C; Comis, B; Couchot, F; Coulais, A; Crill, B P; Curto, A; Cuttaia, F; Davis, R J; de Bernardis, P; de Rosa, A; de Zotti, G; Delabrouille, J; Delouis, J -M; Di Valentino, E; Dickinson, C; Diego, J M; Doré, O; Douspis, M; Ducout, A; Dupac, X; Dusini, S; Efstathiou, G; Elsner, F; Enßlin, T A; Eriksen, H K; Falgarone, E; Fantaye, Y; Ferrière, K; Finelli, F; Frailis, M; Fraisse, A A; Franceschi, E; Frolov, A; Galeotta, S; Galli, S; Ganga, K; Génova-Santos, R T; Gerbino, M; Ghosh, T; González-Nuevo, J; Górski, K M; Gratton, S; Gregorio, A; Gruppuso, A; Gudmundsson, J E; Guillet, V; Hansen, F K; Helou, G; Henrot-Versillé, S; Herranz, D; Hivon, E; Huang, Z; Jaffe, A H; Jaffe, T R; Jones, W C; Keihänen, E; Keskitalo, R; Kisner, T S; Krachmalnicoff, N; Kunz, M; Kurki-Suonio, H; Lagache, G; Lähteenmäki, A; Lamarre, J -M; Langer, M; Lasenby, A; Lattanzi, M; Jeune, M Le; Levrier, F; Liguori, M; Lilje, P B; López-Caniego, M; Lubin, P M; Macías-Pérez, J F; Maggio, G; Maino, D; Mandolesi, N; Mangilli, A; Maris, M; Martin, P G; Martínez-González, E; Matarrese, S; Mauri, N; McEwen, J D; Melchiorri, A; Mennella, A; Migliaccio, M; Miville-Deschênes, M -A; Molinari, D; Moneti, A; Montier, L; Morgante, G; Moss, A; Naselsky, P; Natoli, P; Neveu, J; Nørgaard-Nielsen, H U; Oppermann, N; Oxborrow, C A; Pagano, L; Paoletti, D; Partridge, B; Perdereau, O; Perotto, L; Pettorino, V; Piacentini, F; Plaszczynski, S; Polenta, G; Rachen, J P; Rebolo, R; Reinecke, M; Remazeilles, M; Renzi, A; Ristorcelli, I; Rocha, G; Rossetti, M; Roudier, G; Ruiz-Granados, B; Salvati, L; Sandri, M; Savelainen, M; Scott, D; Sirignano, C; Soler, J D; Suur-Uski, A -S; Tauber, J A; Tavagnacco, D; Tenti, M; Toffolatti, L; Tomasi, M; Tristram, M; Trombetti, T; Valiviita, J; Vansyngel, F; Van Tent, F; Vielva, P; Villa, F; Wandelt, B D; Wehus, I K; Zacchei, A; Zonca, A

    2016-01-01

    We study the statistical properties of interstellar dust polarization at high Galactic latitude, using the Stokes parameter Planck maps at 353 GHz. Our aim is to advance the understanding of the magnetized interstellar medium (ISM), and to provide a model of the polarized dust foreground for cosmic microwave background component-separation procedures. Focusing on the southern Galactic cap, we examine the statistical distributions of the polarization fraction ($p$) and angle ($\\psi$) to characterize the ordered and turbulent components of the Galactic magnetic field (GMF) in the solar neighbourhood. We relate patterns at large angular scales in polarization to the orientation of the mean (ordered) GMF towards Galactic coordinates $(l_0,b_0)=(70^\\circ \\pm 5^\\circ,24^\\circ \\pm 5^\\circ)$. The histogram of $p$ shows a wide dispersion up to 25 %. The histogram of $\\psi$ has a standard deviation of $12^\\circ$ about the regular pattern expected from the ordered GMF. We use these histograms to build a phenomenological...

  10. Imaging of the magnetic field structure in megagauss plasmas by combining pulsed polarimetry with an optical Kerr effect shutter technique.

    Science.gov (United States)

    Smith, R J

    2010-10-01

    Pulsed polarimetry in combination with a high speed photographic technique based on the optical Kerr effect is described. The backscatter in a pulsed polarimeter is directed through a scattering cell and photographed using an ∼1 ps shutter, essentially freezing the intensity pattern. The image provides both the local electron density and magnetic field distributions along and transverse to the laser sightline. Submillimeter spatial resolution is possible for probing wavelengths in the visible due to the high densities and strong optical activity. Pulsed polarimetry is thereby extended to centimeter-sized plasmas with n(e)>10(19)-10(20) cm(-3) and B>20-100 T (MG) produced by multiterawatt, multimega-ampere electrical drivers, wire Z pinches, and liner imploded magnetized plasmas.

  11. Magnetic Fields in the Interstellar Medium

    Science.gov (United States)

    Clark, Susan

    2017-01-01

    The Milky Way is magnetized. Invisible magnetic fields thread the Galaxy on all scales and play a vital but still poorly understood role in regulating flows of gas in the interstellar medium and the formation of stars. I will present highlights from my thesis work on magnetic fields in the diffuse interstellar gas and in accretion disks. At high Galactic latitudes, diffuse neutral hydrogen is organized into an intricate network of slender linear features. I will show that these neutral hydrogen “fibers” are extremely well aligned with the ambient magnetic field as traced by both starlight polarization (Clark et al. 2014) and Planck 353 GHz polarized dust emission (Clark et al. 2015). The structure of the neutral interstellar medium is more tightly coupled to the magnetic field than previously known. Because the orientation of neutral hydrogen is an independent predictor of the local dust polarization angle, our work provides a new tool in the search for inflationary gravitational wave B-mode polarization in the cosmic microwave background, which is currently limited by dust foreground contamination. Magnetic fields also drive accretion in astrophysical disks via the magnetorotational instability (MRI). I analytically derive the behavior of this instability in the weakly nonlinear regime and show that the saturated state of the instability depends on the geometry of the background magnetic field. The analytical model describes the behavior of the MRI in a Taylor-Couette flow, a set-up used by experimentalists in the ongoing quest to observe MRI in the laboratory (Clark & Oishi 2016a, 2016b).

  12. Primordial Magnetic Fields that Last?

    CERN Document Server

    Carroll, S M; Carroll, Sean M.; Field, George B.

    1998-01-01

    The magnetic fields we observe in galaxies today may have their origins in the very early universe. While a number of mechanisms have been proposed which lead to an appreciable field amplitude at early times, the subsequent evolution of the field is of crucial importance, especially whether the correlation length of the field can grow as large as the size of a protogalaxy. This talk is a report on work in progress, in which we consider the fate of one specific primordial field scenario, driven by pseudoscalar effects near the electroweak phase transition. We argue that such a scenario has a number of attractive features, although it is still uncertain whether a field of appropriate size can survive until late times.

  13. Magnetic Properties of Erbium Gallium Gallate under High Magnetic Field

    Institute of Scientific and Technical Information of China (English)

    Zhang Xijuan; Cheng Haiying; Yang Cuihong; Wang Wei

    2004-01-01

    A theoretical investigation on the magnetic properties of rare-earth Er3+ in Er3 Ga5 O12 was reported. The average magnetic moments(M) for applied magnetic field H parallel to the [001 ], [ 100], [ 110], [ 111 ] direction was studied based on the quantum theory. Temperature dependence of the magnetic properties is analyzed for H applied parallel to the [ 100] and [ 111 ] crystallographic directions. The magnetization decreases with increasing temperature,showing good agreement with thermal effect. A strong anisotropy of the magnetization is found under high magnetic field, but when the magnetic field is small, M and H are proportional.

  14. Zero-Field Nuclear Magnetic Resonance

    OpenAIRE

    Weitekamp, D.P.; Bielecki, A.; Zax, D.; Zilm, K.; Pines, A.

    1983-01-01

    In polycrystalline samples, NMR "powder spectra" are broad and much structural information is lost as a result of the orientational disorder. In this Letter Fourier-transform NMR in zero magnetic field is described. With no preferred direction in space, all crystallites contribute equivalently and resolved dipolar splittings can be interpreted directly in terms of internuclear distances. This opens the possiblity of molecular structure determination without the need for single crystals or ori...

  15. Zero-field nuclear magnetic resonance

    Energy Technology Data Exchange (ETDEWEB)

    Weitekamp, D.P.; Bielecki, A.; Zax, D.; Zilm, K.; Pines, A.

    1983-05-30

    In polycrystalline samples, NMR ''powder spectra'' are broad and much structural information is lost as a result of the orientational disorder. In this Letter Fourier transform NMR in zero magnetic field is described. With no preferred direction in space, all crystallites contribute equivalently and resolved dipolar splittings can be interpreted directly in terms of internuclear distances. This opens the possibility of molecular structure determination without the need for single crystals or oriented samples.

  16. The Oscillator Strength of the Quantum Transitions in Multi-Resonant-Tunneling Structures Tours as Basic Elements of Quantum Cascade Lasers and Detectors in a Transverse Magnetic Field

    Directory of Open Access Journals (Sweden)

    I.V. Boyko

    2014-04-01

    Full Text Available Using the model of a closed resonant tunneling structure developed the theory of the electron energy spectrum and oscillator strengths of the quantum electronic transitions between energy levels of this nanostructure. It is shown that by changing the intensity of the magnetic field can be in a wide range of electromagnetic waves to adjust the operating frequency of the radiation of a quantum cascade laser or detector, working on quantum transitions between the first and the third energy electronic states.

  17. Modeling and analysis of magnetic dipoles in weak magnetic field

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The magnetic leakage field distribution resulting from linear defects of a tube sample in the geomagnetic field is modeled according to the magnetic dipole theory.The formula to compute the normal component of the weak magnetic field is deduced based on the spatial distribution of the magnetic dipole.The shape and characteristics of the zero line (an important criterion for magnetic memory testing) of the normal field is analyzed under different longitudinal magnetizations.Results show that the characteristics of the zero line should be considered when the metal magnetic memory testing method is used to find and locate the defect.

  18. Magnetic fields in early-type stars

    CERN Document Server

    Grunhut, Jason H

    2015-01-01

    For several decades we have been cognizant of the presence of magnetic fields in early-type stars, but our understanding of their magnetic properties has recently (over the last decade) expanded due to the new generation of high-resolution spectropolarimeters (ESPaDOnS at CFHT, Narval at TBL, HARPSpol at ESO). The most detailed surface magnetic field maps of intermediate-mass stars have been obtained through Doppler imaging techniques, allowing us to probe the small-scale structure of these stars. Thanks to the effort of large programmes (e.g. the MiMeS project), we have, for the first time, addressed key issues regarding our understanding of the magnetic properties of massive (M > 8 M_sun) stars, whose magnetic fields were only first detected about fifteen years ago. In this proceedings article we review the spectropolarimetric observations and statistics derived in recent years that have formed our general understanding of stellar magnetism in early-type stars. We also discuss how these observations have fu...

  19. Low-temperature high magnetic field powder x-ray diffraction setup for field-induced structural phase transition studies from 2 to 300 K and at 0 to 8-T field

    Science.gov (United States)

    Shahee, Aga; Sharma, Shivani; Kumar, Dhirendra; Yadav, Poonam; Bhardwaj, Preeti; Ghodke, Nandkishor; Singh, Kiran; Lalla, N. P.; Chaddah, P.

    2016-10-01

    A low-temperature and high magnetic field powder x-ray diffractometer (XRD) has been developed at UGC-DAE CSR (UGC: University Grant Commission, DAE: Department of Atomic Energy, and CSR: Consortium for scientific research), Indore, India. The setup has been developed around an 18 kW rotating anode x-ray source delivering Cu-Kα x-rays coming from a vertical line source. It works in a symmetric θ-2θ parallel beam geometry. It consists of a liquid helium cryostat with an 8 T split-pair Nb-Ti superconducting magnet comprising two x-ray windows each covering an angular range of 65°. This is mounted on a non-magnetic type heavy duty goniometer equipped with all necessary motions along with data collection accessories. The incident x-ray beam has been made parallel using a parabolic multilayer mirror. The scattered x-ray is detected using a NaI detector through a 0.1° acceptance solar collimator. To control the motions of the goniometer, a computer programme has been developed. The wide-angle scattering data can be collected in a range of 2°-115° of 2θ with a resolution of ˜0.1°. The whole setup is tightly shielded for the scattered x-rays using a lead hutch. The functioning of the goniometer and the artifacts arising possibly due to the effect of stray magnetic field on the goniometer motions, on the x-ray source, and on the detector have been characterized by collecting powder XRD data of a National Institute of Standards and Technology certified standard reference material LaB6 (SRM-660b) and Si powder in zero-field and in-field conditions. Occurrence of field induced structural-phase transitions has been demonstrated on various samples like Pr0.5Sr0.5MnO3, Nd0.49Sr0.51MnO3-δ and La0.175Pr0.45Ca0.375MnO3 by collecting data in zero field cool and field cool conditions.

  20. Galactic and intergalactic magnetic fields

    CERN Document Server

    Klein, Ulrich

    2014-01-01

    This course-tested textbook conveys the fundamentals of magnetic fields and relativistic plasma in diffuse cosmic media, with a primary focus on phenomena that have been observed at different wavelengths. Theoretical concepts are addressed wherever necessary, with derivations presented in sufficient detail to be generally accessible.In the first few chapters the authors present an introduction to various astrophysical phenomena related to cosmic magnetism, with scales ranging from molecular clouds in star-forming regions and supernova remnants in the Milky Way, to clusters of galaxies. Later c

  1. The perturbed magnetic fields caused by mechanical stress

    Institute of Scientific and Technical Information of China (English)

    QIN Fei; YAN Dong-mei

    2006-01-01

    In the framework of the linearized magnetoelastic theory,the perturbed magnetic fields caused by mechanical stress and deformation were investigated theoretically.Governing equations and boundary conditions to determine the perturbed fields were derived.The effect of mechanical deformation on the magnetic fields was taken into account by coupling structural displacement into the perturbed magnetic field continuous conditions on the boundary of the structure.As an example,the perturbed field of a half-plane magnetized structure caused by a point force was calculated by the Fourier transform method.The results show that the calculated magnetic intensity component normal to the boundary of the structure reaches its maximum at the point force acted while the component tangent to the boundary inverses its direction sharply.The magnetic induction of the perturbed field is proportional to the applied force.Magnitude analysis proved that since the applied magnetic field has a relative weak intensity such as the Earth's magnetic field, influence of the magnetic field on deformation of the structure can be neglected.

  2. Holographic fermions in external magnetic fields

    CERN Document Server

    Gubankova, E; Cubrovic, M; Schalm, K; Schijven, P; Zaanen, J

    2011-01-01

    We study the Fermi level structure of 2+1-dimensional strongly interacting electron systems in external magnetic field using the AdS/CFT correspondence. The gravity dual of a finite density fermion system is a Dirac field in the background of the dyonic AdS-Reissner-Nordstrom black hole. In the probe limit the magnetic system can be reduced to the non-magnetic one, with Landau-quantized momenta and rescaled thermodynamical variables. We find that at strong enough magnetic fields, the Fermi surface vanishes and the quasiparticle is lost either through a crossover to conformal regime or through a phase transition to an unstable Fermi surface. In the latter case, the vanishing Fermi velocity at the critical magnetic field triggers the non-Fermi liquid regime with unstable quasiparticles and a change in transport properties of the system. We associate it with a metal-"strange metal" phase transition. Next we compute compute the DC Hall and longitudinal conductivities using the gravity-dressed fermion propagators....

  3. Stress Field of Straight Edge Dislocation in Magnetic Field

    Institute of Scientific and Technical Information of China (English)

    LIU Zhao-long; HU Hai-yun; FAN Tian-you

    2007-01-01

    To study the changes in mechanical properties of materials within magnetic fields and the motion of dislocations,stress fields of dislocation in magnetic field need to be calculated.The straight edge dislocation is of basic importance in various defects.The stress field of straight edge dislocation in an external static magnetic field is determined by the theory of elasticity and electrodynamics according to the Volterra dislocation model for continuous media.This reduces to the known stress field when the magnet field is zero.The results can be used for further study on the strain energy of dislocations and the interactions between dislocations in magnetic fields.

  4. Evolution of structure and local magnetic fields during crystallization of HITPERM glassy alloys studied by in situ diffraction and nuclear forward scattering of synchrotron radiation.

    Science.gov (United States)

    Miglierini, Marcel; Pavlovič, Márius; Procházka, Vít; Hatala, Tomáš; Schumacher, Gerhard; Rüffer, Rudolf

    2015-11-14

    Evolution of structure and local magnetic fields in (Fe(1-x)Co(x))76Mo8Cu1B15 (HITPERM) metallic glass ribbons with various amounts of Co (x = 0, 0.25, 0.5) were studied in situ using diffraction and nuclear forward scattering of synchrotron radiation. It was found that crystallization of all three glasses proceeds in two stages. In the first stage, bcc (Fe,Co) nanocrystals are formed, while in the second stage additional crystalline phases evolve. For all three glasses, the crystallization temperatures at the wheel side were found to be lower than at the air side of the ribbon. The crystallization temperatures were found to decrease with increasing Co content. The lattice parameters of the bcc nanocrystals decrease up to about 550 °C and then increase pointing to squeezing Mo atoms out of the nanograins or to interface effects between the nanocrystals and the glassy matrix. Nuclear forward scattering enabled separate evaluation of the contributions that stem from structurally different regions within the investigated samples including the newly formed nanocrystals and the residual amorphous matrix. Even minor Co content (x = 0.25) has a substantial effect not only upon the magnetic behaviour of the alloy but also upon its structure. Making use of hyperfine magnetic fields, it was possible to unveil structurally diverse positions of Fe atoms that reside in a nanocrystalline lattice with different numbers of Co nearest neighbours.

  5. Diagnosis of solar chromospheric magnetic field

    Institute of Scientific and Technical Information of China (English)

    ZHANG; Hongqi(张洪起)

    2002-01-01

    This paper discusses the measurements of the chromospheric magnetic field and the spatial configuration of the field at the lower solar atmosphere inferred by the distribution of the solar photospheric and chromospheric magnetic fields. Some questions in the study of the chromospheric magnetic field are also presented.

  6. The HMI Magnetic Field Pipeline

    Science.gov (United States)

    Hoeksema, Jon Todd; Liu, Y.; Schou, J.; Scherrer, P.; HMI Science Team

    2009-05-01

    The Helioseismic and Magnetic Imager (HMI) will provide frequent full-disk magnetic field data after launch of the Solar Dynamics Observatory (SDO), currently scheduled for fall 2009. 16 megapixel line-of-sight magnetograms (Blos) will be recorded every 45 seconds. A full set of polarized filtergrams needed to determine the vector magnetic field requires 90 seconds. Quick-look data will be available within a few minutes of observation. Quick-look space weather and browse products must have identified users, and the list currently includes full disk magnetograms, feature identification and movies, 12-minute disambiguated vector fields in active region patches, time evolution of AR indices, synoptic synchronic frames, potential and MHD model results, and 1 AU predictions. A more complete set of definitive science data products will be offered about a day later and come in three types. "Pipeline” products, such as full disk vector magnetograms, will be computed for all data on an appropriate cadence. A larger menu of "On Demand” products, such as Non-Linear Force Free Field snapshots of an evolving active region, will be produced whenever a user wants them. Less commonly needed "On Request” products that require significant project resources, such as a high resolution MHD simulation of the global corona, will be created subject to availability of resources. Further information can be found at the SDO Joint Science Operations Center web page, jsoc.stanford.edu

  7. A Vorticity-Magnetic Field Dynamo Instability

    OpenAIRE

    1997-01-01

    We generalize the mean field magnetic dynamo to include local evolution of the mean vorticity in addition to the mean magnetic field. The coupled equations exhibit a general mean field dynamo instability that enables the transfer of turbulent energy to the magnetic field and vorticity on larger scales. The growth of the vorticity and magnetic field both require helical turbulence which can be supplied by an underlying global rotation. The dynamo coefficients are derived including the backreac...

  8. Milestones in the Observations of Cosmic Magnetic Fields

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Magnetic fields are observed everywhere in the universe. In this review,we concentrate on the observational aspects of the magnetic fields of Galactic and extragalactic objects. Readers can follow the milestones in the observations of cosmic magnetic fields obtained from the most important tracers of magnetic fields,namely, the star-light polarization, the Zeeman effect, the rotation measures (RMs,hereafter) of extragalactic radio sources, the pulsar RMs, radio polarization observations, as well as the newly implemented sub-mm and mm polarization capabilities.The magnetic field of the Galaxy was first discovered in 1949 by optical polarization observations. The local magnetic fields within one or two kpc have been well delineated by starlight polarization data. The polarization observations of diffuse Galactic radio background emission in 1962 confirmed unequivocally the existence of a Galactic magnetic field. The bulk of the present information about the magnetic fields in the Galaxy comes from analysis of rotation measures of extragalactic radio sources and pulsars, which can be used to construct the 3-D magnetic field structure in the Galactic halo and Galactic disk. Radio synchrotron spurs in the Galactic center show a poloidal field, and the polarization mapping of dust emission and Zeeman observation in the central molecular zone reveal a toroidal magnetic field parallel to the Galactic plane. For nearby galaxies, both optical polarization and multifrequency radio polarization data clearly show the large-scale magnetic field following the spiral arms or dust lanes. For more distant objects, radio polarization is the only approach available to show the magnetic fields in the jets or lobes of radio galaxies or quasars. Clusters of galaxies also contain widely distributed magnetic fields, which are reflected by radio halos or the RM distribution of background objects. The intergalactic space could have been magnetized by outflows or galactic superwinds even in

  9. Decoupling of hyperfine structure of Cs $D_1$ line in strong magnetic field studied by selective reflection from a nanocell

    CERN Document Server

    Sargsyan, Armen; Hakhumyan, Grant; Tonoyan, Ara; Papoyan, Aram; Leroy, Claude; Sarkisyan, David

    2016-01-01

    Decoupling of total electronic and nuclear spin moments of Cs atoms in external magnetic field for the case of atomic $D_1$ line, leading to onset of the hyperfine Paschen-Back regime has been studied theoretically and experimentally. Selective reflection of laser radiation from an interface of dielectric window and atomic vapor confined in a nanocell with 300 nm gap thickness was implemented for the experimental studies. The real time derivative of selective reflection signal with a frequency position coinciding with atomic transitions was used in measurements, providing $\\sim$ 40 MHz spectral resolution and linearity of signal response in respect to transition probability. Behavior of 28 individual Zeeman transitions in a wide range of longitudinal magnetic field (0 - 6 kG) has been tracked under excitation of Cs vapor by a low-intensity $\\sigma^+$- polarized cw laser radiation. For $B\\ge 6~$kG, only 8 transitions with nearly equal probabilities and the same frequency slope remained in the spectrum, which i...

  10. ANALYTIC EXPRESSION OF MAGNETIC FIELD DISTRIBUTION OF RECTANGULAR PERMANENT MAGNETS

    Institute of Scientific and Technical Information of China (English)

    苟晓凡; 杨勇; 郑晓静

    2004-01-01

    From the molecular current viewpoint,an analytic expression exactly describing magnetic field distribution of rectangular permanent magnets magnetized sufficiently in one direction was derived from the Biot-Savart's law. This expression is useful not only for the case of one rectangular permanent magnet bulk, but also for that of several rectangular permanent magnet bulks. By using this expression,the relations between magnetic field distribution and the size of rectangular permanent magnets as well as the magnitude of magnetic field and the distance from the point in the space to the top (or bottom) surface of rectangular permanent magnets were discussed in detail. All the calculating results are consistent with experimental ones. For transverse magnetic field which is a main magnetic field of rectangular permanent magnets,in order to describe its distribution,two quantities,one is the uniformity in magnitude and the other is the uniformity in distribution of magnetic field,were defined. Furthermore, the relations between them and the geometric size of the magnet as well as the distance from the surface of permanent magnets were investigated by these formulas. The numerical results show that the geometric size and the distance have a visible influence on the uniformity in magnitude and the uniformity in distribution of the magnetic field.

  11. Evolution and structure of the plasma of current sheets forming in two-dimensional magnetic fields with a null line at low initial gas ionization and their interpretation

    Science.gov (United States)

    Ostrovskaya, G. V.; Frank, A. G.

    2012-04-01

    An analysis of the experimental data obtained by holographic interferometry in our work [1] makes it possible to explain most of the observed specific features of the structure and evolution of the plasma sheets developing in a two-dimensional magnetic field with a null line in a plasma with a low initial degree of ionization (≈10-4). The following two processes are shown to play a key role here: additional gas ionization in an electric field and the peculiarities of plasma dynamics in a current sheet expanding in time.

  12. Building Magnetic Fields in White Dwarfs

    Science.gov (United States)

    Kohler, Susanna

    2017-03-01

    White dwarfs, the compact remnants left over at the end of low- and medium-mass stars lifetimes, are often found to have magnetic fields with strengths ranging from thousands to billions of times that of Earth. But how do these fields form?MultiplePossibilitiesAround 1020% of white dwarfs have been observed to have measurable magnetic fields with a wide range of strengths. There are several theories as to how these fields might be generated:The fields are fossil.The original weak magnetic fields of the progenitor stars were amplified as the stars cores evolved into white dwarfs.The fields are caused by binary interactions.White dwarfs that formed in the merger of a binary pair might have had a magnetic field amplified as a result of a dynamo that was generated during the merger.The fields were produced by some other internal physical mechanism during the cooling of the white dwarf itself.In a recent publication, a team of authors led by Jordi Isern (Institute of Space Sciences, CSIC, and Institute for Space Studies of Catalonia, Spain) explored this third possibility.Dynamos from CrystallizationThe inner and outer boundaries of the convective mantle of carbon/oxygen white dwarfs of two different masses (top vs. bottom panel) as a function of luminosity. As the white dwarf cools (toward the right), the mantle grows thinner due to the crystallization and settling of material. [Isern et al. 2017]As white dwarfs have no nuclear fusion at their centers, they simply radiate heat and gradually cool over time. The structure of the white dwarf undergoes an interesting change as it cools, however: though the object begins as a fluid composed primarily of an ionized mixture of carbon and oxygen (and a few minor species like nickel and iron), it gradually crystallizes as its temperature drops.The crystallized phase of the white dwarf is oxygen-rich which is denser than the liquid, so the crystallized material sinks to the center of the dwarf as it solidifies. As a result, the

  13. Chromospheric magnetic field and density structure measurements using hard X-rays in a flaring coronal loop

    CERN Document Server

    Kontar, E P; MacKinnon, A L

    2008-01-01

    A novel method of using hard X-rays as a diagnostic for chromospheric density and magnetic structures is developed to infer sub-arcsecond vertical variation of magnetic flux tube size and neutral gas density.Using Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) X-ray data and the newly developed X-ray visibilities forward fitting technique we find the FWHM and centroid positions of hard X-ray sources with sub-arcsecond resolution ($\\sim 0.2"$) for a solar limb flare. We show that the height variations of the chromospheric density and the magnetic flux densities can be found with unprecedented vertical resolution of $\\sim$ 150 km by mapping 18-250 keV X-ray emission of energetic electrons propagating in the loop at chromospheric heights of 400-1500 km. Our observations suggest that the density of the neutral gas is in good agreement with hydrostatic models with a scale height of around $140\\pm 30$ km. FWHM sizes of the X-ray sources decrease with energy suggesting the expansion (fanning out) of m...

  14. Field and Thermal Characteristics of Magnetizing Fixture

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    This paper describes field modeling and thermal modeling for magnetizing fixture. As the detailed characteristics of magnetizing fixture can be obtained, the efficient design of magnetizer which produce desired magnet will be possible using our modeling. For field modeling finite-element analysis is used as part of the design and analysis process for magnetizing fixture. The thermal modeling method of magnetizing fixture resistor uses multi-lumped model with equivalent thermal resistance and thermal capacitance.

  15. Laboratory Measurements of Astrophysical Magnetic Fields

    Science.gov (United States)

    Murphy, C. D.; Miniati, F.; Edwards, M.; Mithen, J.; Bell, A. R.; Constantin, C.; Everson, E.; Schaeffer, D.; Niemann, C.; Ravasio, A.; Brambrink, E.; Benuzzi-Mounaix, A.; Koenig, M.; Gregory, C.; Woolsey, N.; Park, H.-S.; Remington, B.; Ryutov, D.; Bingham, R.; Gargate, L.; Spitkovsky, A.; Gregori, G.

    2010-11-01

    It has been proposed that high Mach number collisionless shocks propagating in an initially unmagnetized plasma play a major role in the magnetization of large scale structures in the Universe. A detailed study of the experimental configuration necessary to scale such environments down to laboratory dimensions will be presented. We will show initial results from preliminary experiments conducted at the Phoenix laser (UCLA) and the LULI laser (Ecole Polytechnique) where collisionless shocks are generated by the expansion of exploding foils driven by energetic laser beams. The time evolution of the magnetic field is probed with induction coils placed at 10 cm from the laser focus. We will discuss various mechanisms of magnetic field generation and compare them with the experimental results.

  16. Heavy meson spectroscopy under strong magnetic field

    CERN Document Server

    Yoshida, Tetsuya

    2016-01-01

    Spectra of the neutral heavy mesons, $\\eta_c(1S,2S)$, $J/psi$, $\\psi(2S)$, $\\eta_b(1S,2S,3S)$, $\\Upsilon(1S,2S,3S)$, $D$, $D^\\ast$, $B$, $B^\\ast$, $B_s$ and $B_s^\\ast$, in a homogeneous magnetic field are analyzed in a potential model of constituent quarks. To obtain anisotropic wave functions and the corresponding eigenvalues, the cylindrical Gaussian expansion method is applied, where the wave functions for transverse and longitudinal directions in the cylindrical coordinate are expanded by the Gaussian bases separately. Energy level structures in the wide range of magnetic field are obtained and the deformation of the wave functions is shown, which reflects effects of the spin mixing, the Zeeman splitting and quark Landau levels. The contribution from the magnetic catalysis in heavy-light mesons is discussed as a change of the light constituent quark mass.

  17. Magnetic fields for fluid motion.

    Science.gov (United States)

    Weston, Melissa C; Gerner, Matthew D; Fritsch, Ingrid

    2010-05-01

    Three forces induced by magnetic fields offer unique control of fluid motion and new opportunities in microfluidics. This article describes magnetoconvective phenomena in terms of the theory and controversy, tuning by redox processes at electrodes, early-stage applications in analytical chemistry, mature applications in disciplines far afield, and future directions for micro total analysis systems. (To listen to a podcast about this article, please go to the Analytical Chemistry multimedia page at pubs.acs.org/page/ancham/audio/index.html .).

  18. Thermodynamic study of gap structure and pair-breaking effect by magnetic field in the heavy-fermion superconductor CeCu2Si2

    Science.gov (United States)

    Kittaka, Shunichiro; Aoki, Yuya; Shimura, Yasuyuki; Sakakibara, Toshiro; Seiro, Silvia; Geibel, Christoph; Steglich, Frank; Tsutsumi, Yasumasa; Ikeda, Hiroaki; Machida, Kazushige

    2016-08-01

    This paper presents the results of specific-heat and magnetization measurements, in particular their field-orientation dependence, on the first discovered heavy-fermion superconductor CeCu2Si2 (Tc˜0.6 K). We discuss the superconducting gap structure and the origin of the anomalous pair-breaking phenomena, leading, e.g., to the suppression of the upper critical field Hc 2, found in the high-field region. The data show that the anomalous pair breaking becomes prominent below about 0.15 K in any field direction, but occurs closer to Hc 2 for H ∥c . The presence of this anomaly is confirmed by the fact that the specific-heat and magnetization data satisfy standard thermodynamic relations. Concerning the gap structure, field-angle dependencies of the low-temperature specific heat within the a b and a c planes do not show any evidence for gap nodes. From microscopic calculations in the framework of a two-band full-gap model, the power-law-like temperature dependencies of C and 1 /T1 , reminiscent of nodal superconductivity, have been reproduced reasonably. These facts further support multiband full-gap superconductivity in CeCu2Si2 .

  19. Magnetic-Field-Assisted Assembly of Anisotropic Superstructures by Iron Oxide Nanoparticles and Their Enhanced Magnetism.

    Science.gov (United States)

    Jiang, Chengpeng; Leung, Chi Wah; Pong, Philip W T

    2016-12-01

    Magnetic nanoparticle superstructures with controlled magnetic alignment and desired structural anisotropy hold promise for applications in data storage and energy storage. Assembly of monodisperse magnetic nanoparticles under a magnetic field could lead to highly ordered superstructures, providing distinctive magnetic properties. In this work, a low-cost fabrication technique was demonstrated to assemble sub-20-nm iron oxide nanoparticles into crystalline superstructures under an in-plane magnetic field. The gradient of the applied magnetic field contributes to the anisotropic formation of micron-sized superstructures. The magnitude of the applied magnetic field promotes the alignment of magnetic moments of the nanoparticles. The strong dipole-dipole interactions between the neighboring nanoparticles lead to a close-packed pattern as an energetically favorable configuration. Rod-shaped and spindle-shaped superstructures with uniform size and controlled spacing were obtained using spherical and polyhedral nanoparticles, respectively. The arrangement and alignment of the superstructures can be tuned by changing the experimental conditions. The two types of superstructures both show enhancement of coercivity and saturation magnetization along the applied field direction, which is presumably associated with the magnetic anisotropy and magnetic dipole interactions of the constituent nanoparticles and the increased shape anisotropy of the superstructures. Our results show that the magnetic-field-assisted assembly technique could be used for fabricating nanomaterial-based structures with controlled geometric dimensions and enhanced magnetic properties for magnetic and energy storage applications.

  20. Engineered Magnetic Core-Shell Structures.

    Science.gov (United States)

    Alavi Nikje, Mir Mohammad; Vakili, Maryam

    2015-01-01

    In recent years, engineered magnetic core-shell structures are playing an important role in the wide range of various applications. These magnetic core-shell structures have attracted considerable attention because of their unique properties and various applications. Also, the synthesis of engineered magnetic core-shell structures has attracted practical interest because of potential applications in areas such as ferrofluids, medical imaging, drug targeting and delivery, cancer therapy, separations, and catalysis. So far a large number of engineered magnetic core-shell structures have been successfully synthesized. This review article focuses on the recent progress in synthesis and characterization of engineered magnetic core-shell structures. Also, this review gives a brief description of the various application of these structures. It is hoped that this review will play some small part in helping future developments in important field.

  1. Formation of HI Clouds in Shock-compressed Interstellar Medium: Physical Origin of Angular Correlation Between Filamentary Structure and Magnetic Field

    CERN Document Server

    Inoue, Tsuyoshi

    2016-01-01

    Recent observations of neutral Galactic interstellar medium showed that filamentary structures of HI clouds are aligned with the interstellar magnetic field. Many interesting applications are proposed based on the alignment such as measurement of magnetic field strength through the Chandrasekhar-Fermi method and removal of polarized foreground dust emissions for the detection of inflationary polarized emission in the cosmic microwave background radiation. However, the physical origin of the alignment remains to be explained. To understand the alignment mechanism, we examine formation of HI clouds triggered by shock compression of diffuse warm neutral medium using three-dimensional magnetohydrodynamic simulations with the effects of optically thin cooling and heating. We show that the shock-compressed diffuse interstellar medium of density n~1 cm^-3 evolves into HI clouds with typical density n~50 cm^-3 via thermal instability driven by cooling, which is consistent with previous studies. We apply a machine vis...

  2. Deformation of Water by a Magnetic Field

    Science.gov (United States)

    Chen, Zijun; Dahlberg, E. Dan

    2011-03-01

    After the discovery that superconducting magnets could levitate diamagnetic objects,1,2 researchers became interested in measuring the repulsion of diamagnetic fluids in strong magnetic fields,3-5 which was given the name "The Moses Effect."5 Both for the levitation experiments and the quantitative studies on liquids, the large magnetic fields necessary were produced by superconducting magnets.

  3. POLARIZED SCATTERING OF LIGHT FOR ARBITRARY MAGNETIC FIELDS WITH LEVEL-CROSSINGS FROM THE COMBINATION OF HYPERFINE AND FINE STRUCTURE SPLITTINGS

    Energy Technology Data Exchange (ETDEWEB)

    Sowmya, K.; Nagendra, K. N.; Sampoorna, M. [Indian Institute of Astrophysics, Koramangala, Bengaluru (India); Stenflo, J. O., E-mail: ksowmya@iiap.res.in, E-mail: knn@iiap.res.in, E-mail: sampoorna@iiap.res.in, E-mail: stenflo@astro.phys.ethz.ch [Institute of Astronomy, ETH Zurich, CH-8093 Zurich (Switzerland)

    2015-12-01

    Interference between magnetic substates of the hyperfine structure states belonging to different fine structure states of the same term influences the polarization for some of the diagnostically important lines of the Sun's spectrum, like the sodium and lithium doublets. The polarization signatures of this combined interference contain information on the properties of the solar magnetic fields. Motivated by this, in the present paper, we study the problem of polarized scattering on a two-term atom with hyperfine structure by accounting for the partial redistribution in the photon frequencies arising due to the Doppler motions of the atoms. We consider the scattering atoms to be under the influence of a magnetic field of arbitrary strength and develop a formalism based on the Kramers–Heisenberg approach to calculate the scattering cross section for this process. We explore the rich polarization effects that arise from various level-crossings in the Paschen–Back regime in a single scattering case using the lithium atomic system as a concrete example that is relevant to the Sun.

  4. Polarized Scattering of Light for Arbitrary Magnetic Fields with Level-crossings from the Combination of Hyperfine and Fine Structure Splittings

    Science.gov (United States)

    Sowmya, K.; Nagendra, K. N.; Sampoorna, M.; Stenflo, J. O.

    2015-12-01

    Interference between magnetic substates of the hyperfine structure states belonging to different fine structure states of the same term influences the polarization for some of the diagnostically important lines of the Sun's spectrum, like the sodium and lithium doublets. The polarization signatures of this combined interference contain information on the properties of the solar magnetic fields. Motivated by this, in the present paper, we study the problem of polarized scattering on a two-term atom with hyperfine structure by accounting for the partial redistribution in the photon frequencies arising due to the Doppler motions of the atoms. We consider the scattering atoms to be under the influence of a magnetic field of arbitrary strength and develop a formalism based on the Kramers-Heisenberg approach to calculate the scattering cross section for this process. We explore the rich polarization effects that arise from various level-crossings in the Paschen-Back regime in a single scattering case using the lithium atomic system as a concrete example that is relevant to the Sun.

  5. Passive Magnetic Shielding in Gradient Fields

    CERN Document Server

    Bidinosti, C P

    2013-01-01

    The effect of passive magnetic shielding on dc magnetic field gradients imposed by both external and internal sources is studied. It is found that for concentric cylindrical or spherical shells of high permeability material, higher order multipoles in the magnetic field are shielded progressively better, by a factor related to the order of the multipole. In regard to the design of internal coil systems for the generation of uniform internal fields, we show how one can take advantage of the coupling of the coils to the innermost magnetic shield to further optimize the uniformity of the field. These results demonstrate quantitatively a phenomenon that was previously well-known qualitatively: that the resultant magnetic field within a passively magnetically shielded region can be much more uniform than the applied magnetic field itself. Furthermore we provide formulae relevant to active magnetic compensation systems which attempt to stabilize the interior fields by sensing and cancelling the exterior fields clos...

  6. Parahydrogen enhanced zero-field nuclear magnetic resonance

    OpenAIRE

    Theis, Thomas; Ganssle, Paul; Kervern, Gwendal; Knappe, Svenja; Kitching, John; Ledbetter, Micah; Budker, Dmitry; Pines, Alex

    2011-01-01

    Nuclear magnetic resonance (NMR), conventionally detected in multi-tesla magnetic fields, is a powerful analytical tool for the determination of molecular identity, structure, and function. With the advent of prepolarization methods and alternative detection schemes using atomic magnetometers or superconducting quantum interference devices (SQUIDs), NMR in very low- (~earth's field), and even zero-field, has recently attracted considerable attention. Despite the use of SQUIDs or atomic magnet...

  7. Hanle Effect Diagnostics of the Coronal Magnetic Field - A Test Using Realistic Magnetic Field Configurations

    CERN Document Server

    Raouafi, N -E; Wiegelmann, T

    2008-01-01

    Our understanding of coronal phenomena, such as coronal plasma thermodynamics, faces a major handicap caused by missing coronal magnetic field measurements. Several lines in the UV wavelength range present suitable sensitivity to determine the coronal magnetic field via the Hanle effect. The latter is a largely unexplored diagnostic of coronal magnetic fields with a very high potential. Here we study the magnitude of the Hanle-effect signal to be expected outside the solar limb due to the Hanle effect in polarized radiation from the H {\\sc{i}} Ly$\\alpha$ and $\\beta$ lines, which are among the brightest lines in the off-limb coronal FUV spectrum. For this purpose we use a magnetic field structure obtained by extrapolating the magnetic field starting from photospheric magnetograms. The diagnostic potential of these lines for determining the coronal magnetic field, as well as their limitations are studied. We show that these lines, in particular H {\\sc{i}} Ly$\\beta$, are useful for such measurements.

  8. Transformation from an easy-plane to an easy-axis antiferromagnetic structure in the mixed rare-earth ferroborates Pr x Y1-x Fe3(BO3)4: magnetic properties and crystal field calculations.

    Science.gov (United States)

    Pankrats, A I; Demidov, A A; Ritter, C; Velikanov, D A; Semenov, S V; Tugarinov, V I; Temerov, V L; Gudim, I A

    2016-10-05

    The magnetic structure of the mixed rare-earth system Pr x Y1-x Fe3(BO3)4 (x  =  0.75, 0.67, 0.55, 0.45, 0.25) was studied via magnetic and resonance measurements. These data evidence the successive spin reorientation from the easy-axis antiferromagnetic structure formed in PrFe3(BO3)4 to the easy-plane one of YFe3(BO3)4 associated with the weakening of the magnetic anisotropy of the Pr subsystem due to its diamagnetic dilution by nonmagnetic Y. This reorientation occurs through the formation of an inclined magnetic structure, as was confirmed by our previous neutron research in the range of x  =  0.67 ÷ 0.45. In the compounds with x  =  0.75 and 0.67 whose magnetic structure is close to the easy-axis one, a two-step spin reorientation takes place in the magnetic field H||c. Such a peculiarity is explained by the formation of an interjacent inclined magnetic structure with magnetic moments of Fe ions located closer to the basal plane than in the initial state, with these intermediate states remaining stable in some ranges of the magnetic field. An approach based on a crystal field model for the Pr(3+) ion and the molecular-field approximation is used to describe the magnetic characteristics of the system Pr x Y1-x Fe3(BO3)4. With the parameters of the d-d and f-d exchange interactions, of the magnetic anisotropy of the iron subsystem and of the crystal field parameters of praseodymium thus determined, it is possible to achieve a good agreement between the experimental and calculated temperature and field dependences of the magnetization curves (up to 90 kOe) and magnetic susceptibilities (2-300 K).

  9. Magnetic fields around AGNs at large and small scales

    Science.gov (United States)

    Tyul'bashev, S. A.

    2002-06-01

    The dipole structure of the magnetic field on distances ge 1 kpc from an active galactic nucleus is discussed. Two different models of the magnetic field around a supermassive black hole on the scale of the accretion disk are tested. The first model suggests a superstrong field of the order of 1010 Gauss (Kardashev \\cite{Kardashev95}), the other one proposed by Field & Rodgers (\\cite{Field93}) predicts much lower values ( ~ 104 Gauss).

  10. High-Field Magnetization of Some Mn Alloys(Magnetism)

    OpenAIRE

    Tomiei, Hori; Hiroshi, Shiraishi; Hiroshi, Niida; Hiroaki, Kato; Giyuu, Kido; Yasuo, Yamaguchi; Yasuaki, Nakagawa; Shibaura Institute of Technology; Institute for Materials Research, Tohoku University

    1993-01-01

    We have made high-field magnetization measurements for some Mn alloys : ε-Mn_Ga with δ= -0.30, ε-(Mn_Fe_x)_3Sn with x=0.1 and 0.3, Fe_3Mn_4Ge_ and γ-(Mn_Fe_x)_Ga_y with x=0.44 and y=0.27. The ε-Mn_Ga has the hexagonal D0_ type structure and a distorted triangular antiferromagnetic spin structure. The hexagonal lattice is slightly distorted to an orthorhombic lattice at T_d of about 290 K with large magnetization. Pseudo-binary ε-(Mn_Fe_x)_3Sn has also the D0_ type structure, and the alloys wi...

  11. Spontaneous magnetic fluctuations in ultrathin magnetic films at zero field

    Science.gov (United States)

    Balk, Andrew; Unguris, John

    2014-03-01

    We use magneto optical Kerr effect (MOKE) microscopy to observe room temperature, zero field magnetic fluctuations in perpendicularly magnetized cobalt films at thicknesses near the in-plane to out-of-plane spin reorientation transition. The magnetic behavior of our films resembles that of collections of superparamagnetic particles, in that globally they exhibit zero net moment, while local areas continually undergo thermal magnetic fluctuations between saturated states of the maze-like domain structure. Unlike superparamagnetic particles, the fluctuations are not constrained by particle boundaries and thus are subject to both exchange and magnetostatic interactions. Due to this we can observe temporal and spatial correlations in the fluctuations. Furthermore, we observe that the fluctuations obey dynamics distinct from field-driven Barkhausen jumps. We also determine scaling exponents of the fluctuations, finding their areas follow a power law distribution (t =1.5), and their temporal noise power spectrum is close to 1/f (a = 1.04). Based on these observations, we discuss these films as possible candidates for exhibiting magnetic self-organized criticality.

  12. Electronic structure and magnetism in actinide compounds

    Energy Technology Data Exchange (ETDEWEB)

    Durakiewicz, T. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)]. E-mail: tomasz@lanl.gov; Joyce, J.J. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Lander, G.H. [JRC, Institute of Transuranium Elements, Postfach 2340, 76125 Karlsruhe (Germany); Olson, C.G. [Ames Laboratory, Iowa State University, Ames, Iowa 5011 (United States); Butterfield, M.T. [Lawrence Livermoore National Laboratory, Livermoore, CA 94550 (United States); Guziewicz, E. [Institute of Physics, Polish Academy of Sciences, 02-668 Warsaw (Poland); Batista, C.D. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Arko, A.J. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Morales, L. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Mattenberger, K. [Laboratorium fur Festkorperphysik, ETH, CH-8093, Zurich (Switzerland); Vogt, O. [Laboratorium fur Festkorperphysik, ETH, CH-8093, Zurich (Switzerland)

    2006-05-01

    A close relationship between electronic structure and magnetic properties is observed in actinide compounds. The exact nature of this relationship is under investigation. We present examples of a direct link between electronic structure and ordered magnetic moment and/or magnetization. Specifically, results obtained for cubic U, Np and Pu compounds and quasi-2D U compounds are be presented. In the case of cubic compounds, a direct relationship between binding energy of valence band features and magnetic moment will be discussed. A Stoner-like mechanism and simple mean-field explanation is proposed for ferromagnetic UTe.

  13. Field dependence of the magnetic correlations of the frustrated magnet SrDy2O4

    Science.gov (United States)

    Gauthier, N.; Fennell, A.; Prévost, B.; Désilets-Benoit, A.; Dabkowska, H. A.; Zaharko, O.; Frontzek, M.; Sibille, R.; Bianchi, A. D.; Kenzelmann, M.

    2017-05-01

    The frustrated magnet SrDy2O4 exhibits a field-induced phase with a magnetization plateau at 1 /3 of the saturation value for magnetic fields applied along the b axis. We report here a neutron scattering study of the nature and symmetry of the magnetic order in this field-induced phase. Below T ≈0.5 K, there are strong hysteretic effects, and the order is short- or long-ranged for zero-field and field cooling, respectively. We find that the long-range ordered magnetic structure within the zigzag chains is identical to that expected for the one-dimensional axial next-nearest neighbor Ising (ANNNI) model in longitudinal fields. The long-range ordered structure in field contrasts with the short-range order found at zero field, and is probably reached through enhanced quantum fluctuations with increasing fields.

  14. Magnetic fields of the W4 superbubble

    CERN Document Server

    Gao, X Y; Reich, P; Han, J L; Kothes, R

    2015-01-01

    Superbubbles and supershells are the channels for transferring mass and energy from the Galactic disk to the halo. Magnetic fields are believed to play a vital role in their evolution. We study the radio continuum and polarized emission properties of the W4 superbubble to determine its magnetic field strength. New sensitive radio continuum observations were made at 6 cm, 11 cm, and 21 cm. The total intensity measurements were used to derive the radio spectrum of the W4 superbubble. The linear polarization data were analysed to determine the magnetic field properties within the bubble shells. The observations show a multi-shell structure of the W4 superbubble. A flat radio continuum spectrum that stems from optically thin thermal emission is derived from 1.4 GHz to 4.8 GHz. By fitting a passive Faraday screen model and considering the filling factor fne , we obtain the thermal electron density ne = 1.0/\\sqrt{fne} (\\pm5%) cm^-3 and the strength of the line-of-sight component of the magnetic field B// = -5.0/\\sq...

  15. Homogeneous Magnetic Field Source For Attenuated Total Reflection

    Directory of Open Access Journals (Sweden)

    Lesňák Michal

    2014-07-01

    Full Text Available The paper is focused on the study of two-dimensional magnetic field distribution used for an analysis of samples containing magnetically active films by means of the Attenuated Total Reflection (ATR method. The design of a proposed electromagnet and the magnetic field model computation are presented together with the results obtained from magnetic field distribution measurement. The ATR method can provide information about a thin film thickness, refractive index, and attenuation in addition to the perfunctory coupling of an optical wave into and off a waveguide [1, 2]. The prism coupling conditions are determined for magnetic structures with induced anisotropy.

  16. Focus on Materials Analysis and Processing in Magnetic Fields

    Directory of Open Access Journals (Sweden)

    Yoshio Sakka, Noriyuki Hirota, Shigeru Horii and Tsutomu Ando

    2009-01-01

    Full Text Available Recently, interest in the applications of feeble (diamagnetic and paramagnetic magnetic materials has grown, whereas the popularity of ferromagnetic materials remains steady and high. This trend is due to the progress of superconducting magnet technology, particularly liquid-helium-free superconducting magnets that can generate magnetic fields of 10 T and higher. As the magnetic energy is proportional to the square of the applied magnetic field, the magnetic energy of such 10 T magnets is in excess of 10 000 times that of conventional 0.1 T permanent magnets. Consequently, many interesting phenomena have been observed over the last decade, such as the Moses effect, magnetic levitation and the alignment of feeble magnetic materials. Researchers in this area are widely spread around the world, but their number in Japan is relatively high, which might explain the success of magnetic field science and technology in Japan.Processing in magnetic fields is a rapidly expanding research area with a wide range of promising applications in materials science. The 3rd International Workshop on Materials Analysis and Processing in Magnetic Fields (MAP3, which was held on 14–16 May 2008 at the University of Tokyo, Japan, focused on various topics including magnetic field effects on chemical, physical, biological, electrochemical, thermodynamic and hydrodynamic phenomena; magnetic field effects on the crystal growth and processing of materials; diamagnetic levitation, the magneto-Archimedes effect, spin chemistry, magnetic orientation, control of structure by magnetic fields, magnetic separation and purification, magnetic-field-induced phase transitions, properties of materials in high magnetic fields, the development of NMR and MRI, medical applications of magnetic fields, novel magnetic phenomena, physical property measurement by magnetic fields, and the generation of high magnetic fields.This focus issue compiles 13 key papers selected from the proceedings

  17. Bats respond to very weak magnetic fields.

    Directory of Open Access Journals (Sweden)

    Lan-Xiang Tian

    Full Text Available How animals, including mammals, can respond to and utilize the direction and intensity of the Earth's magnetic field for orientation and navigation is contentious. In this study, we experimentally tested whether the Chinese Noctule, Nyctalus plancyi (Vespertilionidae can sense magnetic field strengths that were even lower than those of the present-day geomagnetic field. Such field strengths occurred during geomagnetic excursions or polarity reversals and thus may have played an important role in the evolution of a magnetic sense. We found that in a present-day local geomagnetic field, the bats showed a clear preference for positioning themselves at the magnetic north. As the field intensity decreased to only 1/5th of the natural intensity (i.e., 10 μT; the lowest field strength tested here, the bats still responded by positioning themselves at the magnetic north. When the field polarity was artificially reversed, the bats still preferred the new magnetic north, even at the lowest field strength tested (10 μT, despite the fact that the artificial field orientation was opposite to the natural geomagnetic field (P<0.05. Hence, N. plancyi is able to detect the direction of a magnetic field even at 1/5th of the present-day field strength. This high sensitivity to magnetic fields may explain how magnetic orientation could have evolved in bats even as the Earth's magnetic field strength varied and the polarity reversed tens of times over the past fifty million years.

  18. Hybrid Shielding for Magnetic Fields

    Science.gov (United States)

    Mullins, David; Royal, Kevin

    2017-01-01

    Precision symmetry measurements such as the search for the electric dipole moment of the neutron require magnetic shielding rooms to reduce the ambient field to the pT scale. The massive mu-metal sheets and large separation between layers make these shield rooms bulky and expensive. Active field cancellation systems used to reduce the surrounding field are limited in uniformity of cancellation. A novel approach to reducing the space between shield layers and increasing the effectiveness of active cancellation is to combine the two systems into a hybrid system, with active and passive layers interspersed. We demonstrate this idea in a prototype with an active layer sandwiched between two passive layers of shielding.

  19. Manifestations of Magnetic Field Inhomogeneities

    Indian Academy of Sciences (India)

    Lawrence Rudnick

    2011-12-01

    Both observations and simulations reveal large inhomogeneities in magnetic field distributions in diffuse plasmas. Incorporating these inhomogeneities into various calculations can significantly change the inferred physical conditions. In extragalactic sources, e.g., these can compromise analyses of spectral ageing, which I will illustrate with some current work on cluster relics. I also briefly re-examine the old issue of how inhomogeneous fields affect particle lifetimes; perhaps not surprisingly, the next generation of radio telescopes are unlikely to find many sources that can extend their lifetimes from putting relativistic electrons into a low-field ‘freezer’. Finally, I preview some new EVLA results on the complex relic in Abell 2256, with implications for the interspersing of its relativistic and thermal plasmas.

  20. Effects of magnetic field on fluidization properties of magnetic pearls

    Institute of Scientific and Technical Information of China (English)

    Maoming Fan; Zhenfu Luo; Yuemin Zhao; Qingru Chen; Daniel Tao; Xiuxiang Tao; Zhenqiang Chen

    2007-01-01

    An experimental study of the influence of external magnetic field on the fluidization behavior of magnetic pearls was carried out. Magnetic pearls are a magnetic form of iron oxide that mainly consists of Fe2O3 which are recovered from a high-volume power plant fly ash from pulverized coal combustion. Due to its abundance, low price and particular physical and chemical properties, magnetic pearls can be used as a heavy medium for minerals or solid waste dry separation based on density difference. This paper introduces the properties of magnetic pearls and compares the performance of magnetic pearls fluidised bed operation with or without an external magnetic field. Experimental results show that an external magnetic field significantly improves the fluidization performance of magnetic pearls such as uniformity and stability.

  1. Stabilization of helical magnetic structures in thin multilayers

    OpenAIRE

    Dzemiantsova, L. V.; Meier, G.; R. Röhlsberger

    2014-01-01

    Based on micromagnetic simulations, we report on a novel helical magnetic structure in a soft magnetic film that is sandwiched between and exchange-coupled to two hard magnetic layers. Confined between antiparallel hard magnetic moments, a helix with a turn of 180$^{\\circ}$ is stable without the presence of an external magnetic field. The magnetic stability is determined by the energy minimization and is a result of an internal field created by exchange interaction and anisotropy. Since the i...

  2. Interaction between two magnetic dipoles in a uniform magnetic field

    Directory of Open Access Journals (Sweden)

    J. G. Ku

    2016-02-01

    Full Text Available A new formula for the interaction force between two magnetic dipoles in a uniform magnetic field is derived taking their mutual magnetic interaction into consideration and used to simulate their relative motion. Results show that when the angle β between the direction of external magnetic field and the centerline of two magnetic dipoles is 0 ° or 90 °, magnetic dipoles approach each other or move away from each other in a straight line, respectively. And the time required for them to contact each other from the initial position is related to the specific susceptibility and the diameter of magnetic particles, medium viscosity and magnetic field strength. When β is between 0 ° and 90 °, magnetic dipole pair performs approximate elliptical motion, and the motion trajectory is affected by the specific susceptibility, diameter and medium viscosity but not magnetic field strength. However, time required for magnetic dipoles to complete the same motion trajectory is shorter when adopting stronger magnetic field. Moreover, the subsequent motion trajectory of magnetic dipoles is ascertained once the initial position is set in a predetermined motion trajectory. Additionally, magnetic potential energy of magnetic dipole pairs is transformed into kinetic energy and friction energy during the motion.

  3. Band-Structure Effects in the High-Field Magnetization of Pd and Dilute Pd-Rh and Pd-Ag Alloys

    DEFF Research Database (Denmark)

    Andersen, O. Krogh

    1970-01-01

    be derived solely from the band density of states N(E). The previously reported Pd band-structure calculations, which were in excellent agreement with the de Haas-van Alphen data, have been extended to yield DeltaB(sigma) for Pd and, using the rigid band model, also for dilute Pd[Single Bond]Rh and Pd......From Stoner theory we show that the magnetic field-vs-spin magnetization has the form B(sigma)=sigma/chi(0)+DeltaB(sigma). The low-field susceptibility chi(0) is exchange-enhanced but, if the effective exchange potential does not depend on magnetization, the deviation from linearity DeltaB may......; moreover, the experimental data have previously been analyzed according to a power series expansion of sigma(B) that neither separates the effect of band structure from that of exchange enhancement nor applies when van Hove singularities are important. Our formulation suggests a way of analyzing...

  4. Effective magnetic moment of neutrinos in strong magnetic fields

    CERN Document Server

    Pérez, A; Masood, S S; Gaitan, R; Rodríguez, S

    2002-01-01

    In this paper we compute the effective magnetic moment of neutrinos propagating in dense high magnetized medium. Taking typical values of magnetic field and densities of astrophysical objects (such as the cores of supernovae and neutron stars) we obtain an effective type of dipole magnetic moment in agreement with astrophysical and cosmological bounds. (Author)

  5. Collisionless reconnection: magnetic field line interaction

    Directory of Open Access Journals (Sweden)

    R. A. Treumann

    2012-10-01

    Full Text Available Magnetic field lines are quantum objects carrying one quantum Φ0 = 2πh/e of magnetic flux and have finite radius λm. Here we argue that they possess a very specific dynamical interaction. Parallel field lines reject each other. When confined to a certain area they form two-dimensional lattices of hexagonal structure. We estimate the filling factor of such an area. Anti-parallel field lines, on the other hand, attract each other. We identify the physical mechanism as being due to the action of the gauge potential field, which we determine quantum mechanically for two parallel and two anti-parallel field lines. The distortion of the quantum electrodynamic vacuum causes a cloud of virtual pairs. We calculate the virtual pair production rate from quantum electrodynamics and estimate the virtual pair cloud density, pair current and Lorentz force density acting on the field lines via the pair cloud. These properties of field line dynamics become important in collisionless reconnection, consistently explaining why and how reconnection can spontaneously set on in the field-free centre of a current sheet below the electron-inertial scale.

  6. Long-term Trends in Interplanetary Magnetic Field Strength and Solar Wind Structure during the 20th Century

    Science.gov (United States)

    Richardson, I. G.; Cliver, E. W.; Cane, H. V.; White, Nicholas E. (Technical Monitor)

    2002-01-01

    Lockwood et al have recently reported an approximately 40% increase in the radial component of the interplanetary magnetic field (IMF) at Earth between 1964 and 1996. We argue that this increase does not constitute a secular trend but is largely the consequence of lower than average fields during solar cycle 20 (1964-1976) in comparison with surrounding cycles. For times after 1976 the average IMF strength has actually decreased slightly. Examination of the cosmic ray intensity, an indirect measure of the IMF strength, over the last five solar cycles (19-23) also indicates that cycle averages of the IMF strength have been relatively constant since approximately 1954. We also consider the origin of the well-documented increase in the geomagnetic alphaalpha index that occurred primarily during the first half of the twentieth century. We surmise that the coronal mass ejection (CME) rate for recent solar cycles was approximately twice as high as that for solar cycles 100 years ago. However, this change in the CME rate and the accompanying increase in 27-day recurrent storm activity reported by others are unable to account completely for the increase in alphaalpha. Rather, the CMEs and recurrent high-speed streams at the beginning of the twentieth century must have been embedded in a background of slow solar wind that was less geoeffective (having, for example, lower IMF strength and/or flow speed) than its modern counterpart.

  7. An FDTD Study of Errors in Magnetic Direction Finding of Lightning Due to the Presence of Conducting Structure Near the Field Measuring Station

    Directory of Open Access Journals (Sweden)

    Yosuke Suzuki

    2016-07-01

    Full Text Available Lightning electromagnetic fields in the presence of conducting (grounded structure having a height of 60 m and a square cross-section of 40 m × 40 m within about 100 m of the observation point are analyzed using the 3D finite-difference time-domain (FDTD method. Influence of the conducting structure on the two orthogonal components of magnetic field is analyzed, and resultant errors in the estimated lightning azimuth are evaluated. Influences of ground conductivity and lightning current waveshape parameters are also examined. When the azimuth vector passes through the center of conducting structure diagonally (e.g., azimuth angle is 45° or parallel to its walls (e.g., azimuth angle is 0°, the presence of conducting structure equally influences Hx and Hy, so that Hx/Hy is the same as in the absence of structure. Therefore, no azimuth error occurs in those configurations. When the conducting structure is not located on the azimuth vector, the structure influences Hx and Hy differently, with the resultant direction finding error being greater when the structure is located closer to the observation point.

  8. Magnetic field penetration of erosion switch plasmas

    Science.gov (United States)

    Mason, Rodney J.; Jones, Michael E.; Grossmann, John M.; Ottinger, Paul F.

    1988-10-01

    Computer simulations demonstrate that the entrainment (or advection) of magnetic field with the flow of cathode-emitted electrons can constitute a dominant mechanism for the magnetic field penetration of erosion switch plasmas. Cross-field drift in the accelerating electric field near the cathode starts the penetration process. Plasma erosion propagates the point for emission and magnetic field injection along the cathode toward the load-for the possibility of rapid switch opening.

  9. Magnetic field reversals and galactic dynamos

    OpenAIRE

    2012-01-01

    We argue that global magnetic field reversals similar to those observed in the Milky Way occur quite frequently in mean-field galactic dynamo models that have relatively strong, random, seed magnetic fields that are localized in discrete regions. The number of reversals decreases to zero with reduction of the seed strength, efficiency of the galactic dynamo and size of the spots of the seed field. A systematic observational search for magnetic field reversals in a representative sample of spi...

  10. Observation of spin diffusion in zero-field magnetic resonance

    Energy Technology Data Exchange (ETDEWEB)

    Suter, D.; Jarvie, T.P.; Sun, B.; Pines, A.

    1987-07-06

    We report the measurement of spin diffusion at zero field, observed by two-dimensional deuterium magnetic resonance of a polycrystalline sample. This demonstrates for the first time an appealing feature of pulsed zero-field magnetic resonance, namely the potential for structure determination in solids without the need for single crystals or oriented samples.

  11. Ultrathin magnetic structures III fundamentals of nanomagnetism

    CERN Document Server

    Bland, JAC

    2004-01-01

    The ability to understand and control the unique properties of interfaces has created an entirely new field of magnetism which already has a profound impact in technology and is providing the basis for a revolution in electronics. The last decade has seen dramatic progress in the development of magnetic devices for information technology but also in the basic understanding of the physics of magnetic nanostructures. This volume describes thin film magnetic properties and methods for characterising thin film structure topics that underpin the present 'spintronics' revolution in which devices are based on combined magnetic materials and semiconductors. Volume IV deals with the fundamentals of spintronics: magnetoelectronic materials, spin injection and detection, micromagnetics and the development of magnetic random access memory based on GMR and tunnel junction devices. Together these books provide readers with a comprehensive account of an exciting and rapidly developing field. The treatment is designed to be ...

  12. Ultrathin magnetic structures IV applications of nanomagnetism

    CERN Document Server

    Heinrich, Bretislav

    2004-01-01

    The ability to understand and control the unique properties of interfaces has created an entirely new field of magnetism which already has a profound impact in technology and is providing the basis for a revolution in electronics. The last decade has seen dramatic progress in the development of magnetic devices for information technology but also in the basic understanding of the physics of magnetic nanostructures. Volume III describes thin film magnetic properties and methods for characterising thin film structure topics that underpin the present 'spintronics' revolution in which devices are based on combined magnetic materials and semiconductors. The present volume (IV) deals with the fundamentals of spintronics: magnetoelectronic materials, spin injection and detection, micromagnetics and the development of magnetic random access memory based on GMR and tunnel junction devices. Together these books provide readers with a comprehensive account of an exciting and rapidly developing field. The treatment is de...

  13. Near-Field Magnetic Dipole Moment Analysis

    Science.gov (United States)

    Harris, Patrick K.

    2003-01-01

    This paper describes the data analysis technique used for magnetic testing at the NASA Goddard Space Flight Center (GSFC). Excellent results have been obtained using this technique to convert a spacecraft s measured magnetic field data into its respective magnetic dipole moment model. The model is most accurate with the earth s geomagnetic field cancelled in a spherical region bounded by the measurement magnetometers with a minimum radius large enough to enclose the magnetic source. Considerably enhanced spacecraft magnetic testing is offered by using this technique in conjunction with a computer-controlled magnetic field measurement system. Such a system, with real-time magnetic field display capabilities, has been incorporated into other existing magnetic measurement facilities and is also used at remote locations where transport to a magnetics test facility is impractical.

  14. Magnetic Fields from the Electroweak Phase Transition

    CERN Document Server

    Törnkvist, O

    1998-01-01

    I review some of the mechanisms through which primordial magnetic fields may be created in the electroweak phase transition. I show that no magnetic fields are produced initially from two-bubble collisions in a first-order transition. The initial field produced in a three-bubble collision is computed. The evolution of fields at later times is discussed.

  15. Synthesis by molten salt method of the AFeO{sub 3} system (A=La, Gd) and its structural, vibrational and internal hyperfine magnetic field characterization

    Energy Technology Data Exchange (ETDEWEB)

    Romero, M.; Gómez, R.W. [Facultad de Ciencias, Universidad Nacional Autónoma de México, Apartado Postal 70-399, México D. F. 04510 (Mexico); Marquina, V., E-mail: marquina@unam.mx [Facultad de Ciencias, Universidad Nacional Autónoma de México, Apartado Postal 70-399, México D. F. 04510 (Mexico); Pérez-Mazariego, J.L. [Facultad de Ciencias, Universidad Nacional Autónoma de México, Apartado Postal 70-399, México D. F. 04510 (Mexico); Escamilla, R. [Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, Apartado Postal 70-360, México D. F. 04510 (Mexico)

    2014-06-15

    Polycrystalline samples of LaFeO{sub 3} and GdFeO{sub 3} were synthesized by the molten salt method. Some properties and the quality of the resulting compounds were investigated. The crystal structure and purity of the samples were determined through X-ray diffraction and Rietveld analysis. The vibrational properties were characterized by Raman and IR spectroscopy. Mössbauer spectroscopy was used to determine the ionic state of the Fe ions and the internal hyperfine magnetic fields. Considerable reduction of the heat treatment (temperature and time) for the reaction to take place was achieved without detriment of the quality of the compounds.

  16. Strong and superstrong pulsed magnetic fields generation

    CERN Document Server

    Shneerson, German A; Krivosheev, Sergey I

    2014-01-01

    Strong pulsed magnetic fields are important for several fields in physics and engineering, such as power generation and accelerator facilities. Basic aspects of the generation of strong and superstrong pulsed magnetic fields technique are given, including the physics and hydrodynamics of the conductors interacting with the field as well as an account of the significant progress in generation of strong magnetic fields using the magnetic accumulation technique. Results of computer simulations as well as a survey of available field technology are completing the volume.

  17. Influence of stress and unidirectional field annealing on structural and magnetic performance of PtMn bottom spin-filter spin valves

    Science.gov (United States)

    Öksüzoglu, R. Mustafa; Schug, Christoph; York, Brian

    2004-09-01

    The influence of unidirectional field annealing (UDA) and subsequent stress annealing (SA) on the structure and magnetic response of PtMn bottom spin-filter spin-valve sensors with a NiFeCr/NiFe seed layer was investigated. A time constant of 1.17 h for the FCC-FCT phase transition of the PtMn layer was obtained upon UDA at 265°C in an external magnet field of 13 kOe, which is consistent with 1.1 h observed for the GMR. A lower time constant of 0.7 h was determined for the exchange interaction field. The SA with similar conditions as in the manufacturing environment leads to a UDA time-dependent alteration of sensor performance. A SA up to 38 h causes a GMR value reduction, which becomes more pronounced with increasing UDA duration prior to SA. Furthermore, SA causes a progressive oxidation of the Ta cap layer; in contrast, the exchange field remains nearly unaffected, particularly for the sensors with 5 or 6 h UDA. From the point view of application, an UDA treatment of (5-6) h yields the optimal sensor performance for the finished read-write head.

  18. Magnetic stochasticity in magnetically confined fusion plasmas chaos of field lines and charged particle dynamics

    CERN Document Server

    Abdullaev, Sadrilla

    2014-01-01

    This is the first book to systematically consider the modern aspects of chaotic dynamics of magnetic field lines and charged particles in magnetically confined fusion plasmas.  The analytical models describing the generic features of equilibrium magnetic fields and  magnetic perturbations in modern fusion devices are presented. It describes mathematical and physical aspects of onset of chaos, generic properties of the structure of stochastic magnetic fields, transport of charged particles in tokamaks induced by magnetic perturbations, new aspects of particle turbulent transport, etc. The presentation is based on the classical and new unique mathematical tools of Hamiltonian dynamics, like the action--angle formalism, classical perturbation theory, canonical transformations of variables, symplectic mappings, the Poincaré-Melnikov integrals. They are extensively used for analytical studies as well as for numerical simulations of magnetic field lines, particle dynamics, their spatial structures and  statisti...

  19. 3D Field Simulation of Magnetic Thin Film Inductor

    OpenAIRE

    FUJIWARA, Toshiyasu; CHOI, Kyung-Ku; SATO, SHIGEKI

    2006-01-01

    The 3D magnetic field simulations with FEM (finite element method) have been performed to predictand understand the performance of Magnetic Thin Film Inductor (MTFl). Inductor structures of planar electroplated Cu spiralcoil, which are sandwiched and underlaid with magnetic thin films, are considered as the simulation models. The inductance increment of 300% compared to air-core inductor was predicted when the sandwiched 5μm thickness magnetic thin film with relative permeability of 600 was a...

  20. Deformation of Water by a Magnetic Field

    Science.gov (United States)

    Chen, Zijun; Dahlberg, E. Dan

    2011-01-01

    After the discovery that superconducting magnets could levitate diamagnetic objects, researchers became interested in measuring the repulsion of diamagnetic fluids in strong magnetic fields, which was given the name "The Moses Effect." Both for the levitation experiments and the quantitative studies on liquids, the large magnetic fields necessary…

  1. Exploring Magnetic Fields with a Compass

    Science.gov (United States)

    Lunk, Brandon; Beichner, Robert

    2011-01-01

    A compass is an excellent classroom tool for the exploration of magnetic fields. Any student can tell you that a compass is used to determine which direction is north, but when paired with some basic trigonometry, the compass can be used to actually measure the strength of the magnetic field due to a nearby magnet or current-carrying wire. In this…

  2. Planck intermediate results: XLIV. Structure of the Galactic magnetic field from dust polarization maps of the southern Galactic cap

    DEFF Research Database (Denmark)

    Aghanim, N.; Alves, M. I R; Arzoumanian, D.

    2016-01-01

    components of the Galactic magnetic field (GMF) in the solar neighbourhood. The Q and U maps show patterns at large angular scales, which we relate to the mean orientation of the GMF towards Galactic coordinates (l0,b0) = (70° ± 5°,24° ± 5°). The histogram of the observed p values shows a wide dispersion up...... fraction (p0) of dust emission. To compute the Stokes parameters, we approximate the integration along the line of sight (LOS) as a sum over a set of N independent polarization layers, in each of which the turbulent component of the GMF is obtained from Gaussian realizations of a power-law power spectrum....... We are able to reproduce the observed p and ψ distributions using a p0 value of 26%, a ratio of 0.9 between the strengths of the turbulent and mean components of the GMF, and a small value of N. The mean value of p (inferred from the fit of the large-scale patterns in the Stokes maps) is 12 ± 1%. We...

  3. Influence of Magnetic Field on the Mesoporous Structure of Fe-Cu Compounds in Dye-Sensitized Photovoltaic Cells

    Science.gov (United States)

    Alami, Abdul Hai; Zhang, Di; Aokal, Camilia; Abed, Jehad; Abdoun, Ideisan Abu; Alawadhi, Hussain

    2016-03-01

    This paper investigates the effect of applying static and dynamic magnetic fields on the deposition of Fe-Cu compound on the working electrode of a dye-sensitized solar cell. The deposition of this compound on glass is complicated due to the fact that it cannot be evaporated or sintered beyond the dissociation temperature of 973 K (700 °C), and the doctor blade technique causes detrimental layer inconsistencies. The Fe-Cu compound is relatively easy to produce and is significantly cheaper and more absorptive (>81 pct) in the Vis-NIR than the standard TiO2 mesoporous material used for solar cells. It also behaves as a semiconductor due to the high diffusion of the Fe into the Cu lattice that a bandgap of 1.8 eV is obtained. The use of a Schiff base dye with a compatible bandgap of 1.68 eV is used as a sensitizer for the production of a test cell that generated more photocurrent than its TiO2 counterpart, which is a promising result for an alternative mesoporous layer in solar cells.

  4. Biological Effect of Magnetic Field in Mice

    Institute of Scientific and Technical Information of China (English)

    Zhao-Wei ZENG

    2005-01-01

    Objective: To study the biological effect of magnetic field in mice bodies. Method: With a piece of permanent magnet embeded in mice bodies beside the femoral artery and vein to measure the electrophoretic velocity(um/s). Result: The magnetic field in mice bodies on the experiment group that the electrophoretic velocity is faster more than control and free group.Conclusion:The magnetic field in animal's body can raise the negative electric charges on the surface of erythrocyte to improve the microcirculation, this is the biological effect of magnetic field.

  5. The origin, evolution and signatures of primordial magnetic fields.

    Science.gov (United States)

    Subramanian, Kandaswamy

    2016-07-01

    The universe is magnetized on all scales probed so far. On the largest scales, galaxies and galaxy clusters host magnetic fields at the micro Gauss level coherent on scales up to ten kpc. Recent observational evidence suggests that even the intergalactic medium in voids could host a weak  ∼  10(-16) Gauss magnetic field, coherent on Mpc scales. An intriguing possibility is that these observed magnetic fields are a relic from the early universe, albeit one which has been subsequently amplified and maintained by a dynamo in collapsed objects. We review here the origin, evolution and signatures of primordial magnetic fields. After a brief summary of magnetohydrodynamics in the expanding universe, we turn to magnetic field generation during inflation and phase transitions. We trace the linear and nonlinear evolution of the generated primordial fields through the radiation era, including viscous effects. Sensitive observational signatures of primordial magnetic fields on the cosmic microwave background, including current constraints from Planck, are discussed. After recombination, primordial magnetic fields could strongly influence structure formation, especially on dwarf galaxy scales. The resulting signatures on reionization, the redshifted 21 cm line, weak lensing and the Lyman-α forest are outlined. Constraints from radio and γ-ray astronomy are summarized. Astrophysical batteries and the role of dynamos in reshaping the primordial field are briefly considered. The review ends with some final thoughts on primordial magnetic fields.

  6. The origin, evolution and signatures of primordial magnetic fields

    Science.gov (United States)

    Subramanian, Kandaswamy

    2016-07-01

    The universe is magnetized on all scales probed so far. On the largest scales, galaxies and galaxy clusters host magnetic fields at the micro Gauss level coherent on scales up to ten kpc. Recent observational evidence suggests that even the intergalactic medium in voids could host a weak  ˜  10-16 Gauss magnetic field, coherent on Mpc scales. An intriguing possibility is that these observed magnetic fields are a relic from the early universe, albeit one which has been subsequently amplified and maintained by a dynamo in collapsed objects. We review here the origin, evolution and signatures of primordial magnetic fields. After a brief summary of magnetohydrodynamics in the expanding universe, we turn to magnetic field generation during inflation and phase transitions. We trace the linear and nonlinear evolution of the generated primordial fields through the radiation era, including viscous effects. Sensitive observational signatures of primordial magnetic fields on the cosmic microwave background, including current constraints from Planck, are discussed. After recombination, primordial magnetic fields could strongly influence structure formation, especially on dwarf galaxy scales. The resulting signatures on reionization, the redshifted 21 cm line, weak lensing and the Lyman-α forest are outlined. Constraints from radio and γ-ray astronomy are summarized. Astrophysical batteries and the role of dynamos in reshaping the primordial field are briefly considered. The review ends with some final thoughts on primordial magnetic fields.

  7. Magnetic field concentrator for probing optical magnetic metamaterials.

    Science.gov (United States)

    Antosiewicz, Tomasz J; Wróbel, Piotr; Szoplik, Tomasz

    2010-12-06

    Development of all dielectric and plasmonic metamaterials with a tunable optical frequency magnetic response creates a need for new inspection techniques. We propose a method of measuring magnetic responses of such metamaterials within a wide range of optical frequencies with a single probe. A tapered fiber probe with a radially corrugated metal coating concentrates azimuthally polarized light in the near-field into a subwavelength spot the longitudinal magnetic field component which is much stronger than the perpendicular electric one. The active probe may be used in a future scanning near-field magnetic microscope for studies of magnetic responses of subwavelength elementary cells of metamaterials.

  8. Magnetic anisotropy in Fe-25Cr-12Co-1Si alloy induced by external magnetic field

    Institute of Scientific and Technical Information of China (English)

    ZHEN Liang; SUN Xue-yin; XU Cheng-yan; GAO Run-sheng; XU Ren-gen; QIN Lu-chang

    2007-01-01

    Structural and magnetic properties of Fe-25Cr-12Co-1Si alloy thermo-magnetically treated under different external magnetic field conditions were investigated. Orientation and morphology of the ferromagnetic α1 phase embedded in α2 phase matrix before and after step ageing are characterized by transmission electron microscope(TEM). The results show that the ellipsoidal particles of ferromagnetic α1 phase are aligned along the direction of external magnetic field during isothermal magnetic ageing. Approximately 28% of the total coercivity can be attributed to the shape anisotropy of α1 phase particles induced by external magnetic field for Fe-25Cr-12Co-1Si alloy thermo-magnetically treated with a parallel magnetic field.

  9. Electrolytic tiltmeters inside magnetic fields: Some observations

    Energy Technology Data Exchange (ETDEWEB)

    Alberdi, J. [CIEMAT, Madrid (Spain); Arce, P. [CIEMAT, Madrid (Spain); Barcala, J.M. [CIEMAT, Madrid (Spain); Calvo, E. [CIEMAT, Madrid (Spain); Ferrando, A. [CIEMAT, Madrid (Spain)]. E-mail: antonio.ferrando@ciemat.es; Josa, M.I. [CIEMAT, Madrid (Spain); Luque, J.M. [CIEMAT, Madrid (Spain); Molinero, A. [CIEMAT, Madrid (Spain); Navarrete, J. [CIEMAT, Madrid (Spain); Oller, J.C. [CIEMAT, Madrid (Spain); Yuste, C. [CIEMAT, Madrid (Spain); Calderon, A. [Instituto de Fisica de Cantabria, CSIC-University of Cantabria, Santander (Spain); Garcia-Moral, L.A. [Instituto de Fisica de Cantabria, CSIC-University of Cantabria, Santander (Spain); Gomez, G. [Instituto de Fisica de Cantabria, CSIC-University of Cantabria, Santander (Spain); Gonzalez-Sanchez, F.J. [Instituto de Fisica de Cantabria, CSIC-University of Cantabria, Santander (Spain); Martinez-Rivero, C. [Instituto de Fisica de Cantabria, CSIC-University of Cantabria, Santander (Spain); Matorras, F. [Instituto de Fisica de Cantabria, CSIC-University of Cantabria, Santander (Spain); Rodrigo, T. [Instituto de Fisica de Cantabria, CSIC-University of Cantabria, Santander (Spain); Ruiz-Arbol, P. [Instituto de Fisica de Cantabria, CSIC-University of Cantabria, Santander (Spain); Scodellaro, L. [Instituto de Fisica de Cantabria, CSIC-University of Cantabria, Santander (Spain); Sobron, M. [Instituto de Fisica de Cantabria, CSIC-University of Cantabria, Santander (Spain); Vila, I. [Instituto de Fisica de Cantabria, CSIC-University of Cantabria, Santander (Spain); Virto, A.L. [Instituto de Fisica de Cantabria, CSIC-University of Cantabria, Santander (Spain)

    2007-04-21

    We present observations of the electrolytic clinometers behaviour inside magnetic field environments introducing phenomenological expressions to account for the measured output voltage variations as functions of field gradients and field strengths.

  10. From Inverse to Delayed Magnetic Catalysis in Strong Magnetic Field

    CERN Document Server

    Mao, Shijun

    2016-01-01

    We study magnetic field effect on chiral phase transition in a Nambu--Jona-Lasinio model. In comparison with mean field approximation containing quarks only, including mesons as quantum fluctuations in the model leads to a transition from inverse to delayed magnetic catalysis at finite temperature and delays the transition at finite baryon chemical potential. The location of the critical end point depends on the the magnetic field non-monotonously.

  11. Chiral spiral induced by a strong magnetic field

    Directory of Open Access Journals (Sweden)

    Abuki Hiroaki

    2016-01-01

    Full Text Available We study the modification of the chiral phase structure of QCD due to an external magnetic field. We first demonstrate how the effect of magnetic field can systematically be incorporated into a generalized Ginzburg-Landau framework. We then analyze the phase structure in the vicinity of the chiral critical point. In the chiral limit, the effect is found to be so drastic that it brings a “continent” of chiral spiral in the phase diagram, by which the chiral tricritical point is totally washed out. This is the case no matter how small the intensity of magnetic field is. On the other hand, the current quark mass protects the chiral critical point from a weak magnetic field. However, the critical point will eventually be covered by the chiral spiral phase as the magnetic field grows.

  12. Chiral spiral induced by a strong magnetic field

    CERN Document Server

    Abuki, H

    2016-01-01

    We study the modification of the chiral phase structure of QCD due to an external magnetic field. We first demonstrate how the effect of magnetic field can systematically be incorporated into a generalized Ginzburg-Landau framework. We then analyze the phase structure in the vicinity of the chiral critical point. In the chiral limit, the effect is found to be so drastic that it totally washes the tricritical point out of the phase diagram, bringing the continent for the chiral spiral. This is the case no matter how small is the intensity of the magnetic field. On the other hand, the current quark mass protects the chiral critical point from a weak magnetic field. However the critical point will eventually be covered by the chiral spiral phase as the magnetic field grows.

  13. Fields with Analytic Structure

    CERN Document Server

    Cluckers, Raf

    2009-01-01

    We present a unifying theory of fields with certain classes of analytic functions, called fields with analytic structure. Both real closed fields and Henselian valued fields are considered. For real closed fields with analytic structure, o-minimality is shown. For Henselian valued fields, both the model theory and the analytic theory are developed. We give a list of examples that comprises, to our knowledge, all principal, previously studied, analytic structures on Henselian valued fields, as well as new ones. The b-minimality is shown, as well as other properties useful for motivic integration on valued fields. The paper is reminiscent of [Denef, van den Dries, "p-adic and real subanalytic sets" Ann. of Math. (2) 128 (1988) 79--138], of [Cohen, Paul J. "Decision procedures for real and p-adic fields" Comm. Pure Appl. Math. 22 (1969) 131--151, and of [Fresnel, van der Put, "Rigid analytic geometry and its applications" Progress in Mathematics, 218 Birkhauser (2004)], and unifies work by van den Dries, Haskell...

  14. The Galactic Magnetic Field and UHECR Optics

    CERN Document Server

    Farrar, Glennys R; Khurana, Deepak; Sutherland, Michael

    2015-01-01

    A good model of the Galactic magnetic field is crucial for estimating the Galactic contribution in dark matter and CMB-cosmology studies, determining the sources of UHECRs, and also modeling the transport of Galactic CRs since the halo field provides an important escape route for by diffusion along its field lines. We briefly review the observational foundations of the Jansson-Farrar 2012 model for the large scale structure of the GMF, underscoring the robust evidence for a N-to-S directed, spiraling halo field. New results on the lensing effect of the GMF on UHECRs are presented, displaying multiple images and dramatic magnification and demagnification that varies with source direction and CR rigidity.

  15. Dynamic shielding of the magnetic fields

    Directory of Open Access Journals (Sweden)

    RAU, M.

    2010-11-01

    Full Text Available The paper presents a comparative study of the methods used to control and compensate the direct and alternative magnetic fields. Two frequently used methods in the electromagnetic compatibility of the complex biomagnetism installations were analyzed. The two methods refer to the use of inductive magnetic field sensors (only for alternative fields and of fluxgate magnetometers as active transducers which measures both the direct and alternative components of the magnetic field. The applications of the dynamic control of the magnetic field are: control of the magnetic field of the military ships, control of parasite magnetic field produced by power transformers and the electrical networks, protection of the mass spectrometers, electronic microscopes, SQUID and optical pumping magnetometers for applications in biomagnetism.

  16. Self-organization of topological defects for a triangular-lattice magnetic dots array subject to a perpendicular magnetic field

    Directory of Open Access Journals (Sweden)

    R.S. Khymyn

    2014-09-01

    Full Text Available The regular array of magnetic particles (magnetic dots of the form of a two-dimensional triangular lattice in the presence of external magnetic field demonstrates complicated magnetic structures. The magnetic symmetry of the ground state for such a system is lower than that for the underlying lattice. Long range dipole-dipole interaction leads to a specific antiferromagnetic order in small fields, whereas a set of linear topological defects appears with the growth of the magnetic field. Self-organization of such defects determines the magnetization process for a system within a wide range of external magnetic fields.

  17. Magnetic Fields Structures and Turbulent Components in the Star Forming Molecular Clouds OMC-2 and OMC-3

    CERN Document Server

    Poidevin, Frederick; Matthews, Brenda C

    2010-01-01

    The SCUBA polarized 850 microns thermal emission data of the region OMC-2 in Orion A are added to and homogeneously reduced with data already available in the region OMC-3. The data set shows that OMC-2 is a region generally less polarized than OMC-3. Where coincident, most of the 850 microns polarization pattern is similar to that measured in 350 microns polarization data. Only 850 microns polarimetry data have been obtained in and around MMS7, FIR1 & FIR2, and in the region south of FIR6. A realignment of the polarization vectors with the filament can be seen near FIR1 in the region south of OMC-3. An analysis shows that the energy injected by CO outflows and H2 jets associated to OMC-2 and OMC-3 does not appear to alter the polarization patterns at a scale of the 14'' resolution beam. A second order structure function analysis of the polarization position angles shows that OMC-2 is a more turbulent region than OMC-3. OMC-3 appears to be a clear case of a magnetically dominated region with respect to th...

  18. Spin Structures in Magnetic Nanoparticles

    DEFF Research Database (Denmark)

    Mørup, Steen; Brok, Erik; Frandsen, Cathrine

    2013-01-01

    Spin structures in nanoparticles of ferrimagnetic materials may deviate locally in a nontrivial way from ideal collinear spin structures. For instance, magnetic frustration due to the reduced numbers of magnetic neighbors at the particle surface or around defects in the interior can lead to spin...... canting and hence a reduced magnetization. Moreover, relaxation between almost degenerate canted spin states can lead to anomalous temperature dependences of the magnetization at low temperatures. In ensembles of nanoparticles, interparticle exchange interactions can also result in spin reorientation....... Here, we give a short review of anomalous spin structures in nanoparticles....

  19. Field free line magnetic particle imaging

    CERN Document Server

    Erbe, Marlitt

    2014-01-01

    Marlitt Erbe provides a detailed introduction into the young research field of Magnetic Particle Imaging (MPI) and field free line (FFL) imaging in particular. She derives a mathematical description of magnetic field generation for FFL imaging in MPI. To substantiate the simulation studies on magnetic FFL generation with a proof-of-concept, the author introduces the FFL field demonstrator, which provides the world's first experimentally generated rotated and translated magnetic FFL field complying with the requirements for FFL reconstruction. Furthermore, she proposes a scanner design of consi

  20. A Model of Mercury's Magnetospheric Magnetic Field with Dependence on Magnetic Activity

    Science.gov (United States)

    Korth, H.; Tsyganenko, N. A.; Johnson, C. L.; Philpott, L. C.; Anderson, B. J.; Solomon, S. C.; McNutt, R. L., Jr.

    2015-12-01

    Accurate knowledge of Mercury's magnetospheric magnetic field is required to characterize the planet's internal field and the structure of the magnetosphere. We present the first model of Mercury's magnetospheric magnetic field that includes a dependence on magnetic activity. The model consists of individual modules for magnetic fields of internal origin, approximated by a dipole of magnitude 190 nT RM3, where RM is Mercury's radius, offset northward by 479 km along the spin axis, and of external origin resulting from currents flowing on the magnetopause boundary and in the cross-tail current sheet. The magnetic field is confined within a magnetopause shape derived from Magnetometer observations by the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft and dependent on magnetic activity. The cross-tail current is prescribed having a disk shape near the planet and extending into a sheet at larger distances. The magnitude of the tail current, which also depends on magnetic activity, is fit to minimize the root-mean-square residual between the model magnetic field and the field within the magnetosphere observed by MESSENGER. The model was fit separately for magnetic field observations within distinct levels of magnetic activity. Linear fits of model parameters versus magnetic activity allows continuous scaling of the model to magnetic activity. The magnetic field contribution from each module is shielded individually by a scalar potential function, which was fit to minimize the root-mean-square normal magnetic field component at the magnetopause. The resulting model reproduces the dependence of the magnetospheric size and tail current intensity on magnetic activity, and allows more accurate characterization of the internal field.

  1. On the origin of cosmic magnetic fields

    Science.gov (United States)

    Kulsrud, Russell M.; Zweibel, Ellen G.

    2008-04-01

    We review the extensive and controversial literature concerning how the cosmic magnetic fields pervading nearly all galaxies and clusters of galaxies actually got started. Some observational evidence supports a hypothesis that the field is already moderately strong at the beginning of the life of a galaxy and its disc. One argument involves the chemical abundance of the light elements Be and B, while a second one is based on the detection of strong magnetic fields in very young high red shift galaxies. Since this problem of initial amplification of cosmic magnetic fields involves important plasma problems it is obvious that one must know the plasma in which the amplification occurs. Most of this review is devoted to this basic problem and for this it is necessary to devote ourselves to reviewing studies that take place in environments in which the plasma properties are most clearly understood. For this reason the authors have chosen to restrict themselves almost completely to studies of dynamos in our Galaxy. It is true that one can get a much better idea of the grand scope of galactic fields in extragalactic systems. However, most mature galaxies share the same dilemma as ours of overcoming important plasma problems. Since the authors are both trained in plasma physics we may be biased in pursuing this approach, but we feel it is justified by the above argument. In addition we feel we can produce a better review by staying close to that which we know best. In addition we have chosen not to consider the saturation problem of the galactic magnetic field since if the original dynamo amplification fails the saturation question does not arise. It is generally accepted that seed fields, whose strength is of order 10-20 G, easily spring up in the era preceding galaxy formation. Several mechanisms have been proposed to amplify these seed magnetic fields to a coherent structure with the microgauss strengths of the currently observed galactic magnetic fields. The standard

  2. A Moving Coordinate Numerical Method for Analyses of Electromagneto-Mechanical Coupled Behavior of Structures in a Strong Magnetic Field Aiming at Application to Tokamak Structures

    Science.gov (United States)

    Li, Weixin; Yuan, Zhensheng; Chen, Zhenmao

    2014-12-01

    Analysis of the electromagneto-mechanical coupling effect contributes greatly to the high accuracy estimation of the EM load of many EM devices, such as a tokamak structure during plasma disruption. This paper presents a method for the numerical analysis of the electromagneto-mechanical coupling effect on the basis of Maxwell's equations in the Lagrangian description and staggered load transfer scheme, which can treat the coupled behaviors of magnetic damping and magnetic stiffness effects at the same time. Codes were developed based on the ANSYS development platform and were applied to solve two typical numerical examples: the TEAM Problem 16 and dynamic behavior analysis of a shallow arch under electromagnetic force. The good consistency of numerical results and experimental data demonstrates the validity and accuracy of the proposed method and the related numerical codes.

  3. Gravitational redshift from rotating body having intense magnetic field

    CERN Document Server

    Dubey, Anuj Kumar

    2016-01-01

    It is well known fact that gravitational field can alter the space-time structure and gravitational redshift is its one example. Electromagnetic field can also alter the space-time similar to gravitational field. So electromagnetic field can give rise to an additional effect on gravitational redshift. There are many objects in nature, like neutron stars, magnetars etc which have high amount of rotation and magnetic field. In the present paper we will derive the expression of gravitational redshift from rotating body having intense magnetic field by using the action function of the electromagnetic fields.

  4. Magnetic field mapper based on rotating coils

    CERN Document Server

    AUTHOR|(CDS)2087244; Arpaia, Pasquale

    This thesis presents a magnetic field mapper based on rotating coils. The requirements, the architecture, the conceptual design, and the prototype for straight magnets were shown. The proposed system is made up of a rotating coil transducer and a train-like system for longitudinal motion and positioning inside magnet bore. The mapper allows a localized measurement of magnetic fields and the variation of the harmonic multipole content in the magnet ends. The proof-of-principle demonstration and the experimental characterization of the rotating-coil transducer specifically conceived for mapping validated the main objective of satisfying the magnetic measurement needs of the next generation of compact accelerators.

  5. Bistability between equatorial and axial dipoles during magnetic field reversals

    CERN Document Server

    Gissinger, Christophe; Schrinner, Martin; Dormy, Emmanuel

    2012-01-01

    Numerical simulations of the geodynamo in presence of an heterogeneous heating are presented. We study the dynamics and the structure of the magnetic field when the equatorial symmetry of the flow is broken. If the symmetry breaking is sufficiently strong, the m = 0 axial dipolar field is replaced by an hemispherical magnetic field, dominated by an oscillating m = 1 magnetic field. Moreover, for moderate symmetry breaking, a bistability between the axial and the equatorial dipole is observed. In this bistable regime, the axial magnetic field exhibits chaotic switches of its polarity, involving the equatorial dipole during the transition period. This new scenario for magnetic field reversals is discussed within the framework of the Earth's dynamo.

  6. Bistability between equatorial and axial dipoles during magnetic field reversals.

    Science.gov (United States)

    Gissinger, Christophe; Petitdemange, Ludovic; Schrinner, Martin; Dormy, Emmanuel

    2012-06-08

    Numerical simulations of the geodynamo in the presence of heterogeneous heating are presented. We study the dynamics and the structure of the magnetic field when the equatorial symmetry of the flow is broken. If the symmetry breaking is sufficiently strong, the m=0 axial dipolar field is replaced by a hemispherical magnetic field, dominated by an oscillating m=1 magnetic field. Moreover, for moderate symmetry breaking, a bistability between the axial and the equatorial dipole is observed. In this bistable regime, the axial magnetic field exhibits chaotic switches of its polarity, involving the equatorial dipole during the transition period. This new scenario for magnetic field reversals is discussed within the framework of Earth's dynamo.

  7. Magnetic microscopy of layered structures

    CERN Document Server

    Kuch, Wolfgang; Fischer, Peter; Hillebrecht, Franz Ulrich

    2015-01-01

    This book presents the important analytical technique of magnetic microscopy. This method is applied to analyze layered structures with high resolution. This book presents a number of layer-resolving magnetic imaging techniques that have evolved recently. Many exciting new developments in magnetism rely on the ability to independently control the magnetization in two or more magnetic layers in micro- or nanostructures. This in turn requires techniques with the appropriate spatial resolution and magnetic sensitivity. The book begins with an introductory overview, explains then the principles of the various techniques and gives guidance to their use. Selected examples demonstrate the specific strengths of each method. Thus the book is a valuable resource for all scientists and practitioners investigating and applying magnetic layered structures.

  8. Magnetic Fields and Star Formation

    CERN Document Server

    Van Loo, S; Falle, S A E G

    2012-01-01

    Research performed in the 1950s and 1960s by Leon Mestel on the roles of magnetic fields in star formation established the framework within which he and other key figures have conducted subsequent investigations on the subject. This short tribute to Leon contains a brief summary of some, but not all, of his ground breaking contributions in the area. It also mentions of some of the relevant problems that have received attention in the last few years. The coverage is not comprehensive, and the authors have drawn on their own results more and touched more briefly on those of others than they would in a normal review. Theirs is a personal contribution to the issue honouring Leon, one of the truly great gentlemen, wits, and most insightful of astrophysicists.

  9. DC-based magnetic field controller

    Energy Technology Data Exchange (ETDEWEB)

    Kotter, Dale K. (Shelley, ID); Rankin, Richard A. (Ammon, ID); Morgan, John P,. (Idaho Falls, ID)

    1994-01-01

    A magnetic field controller for laboratory devices and in particular to dc operated magnetic field controllers for mass spectrometers, comprising a dc power supply in combination with improvements to a hall probe subsystem, display subsystem, preamplifier, field control subsystem, and an output stage.

  10. DC-based magnetic field controller

    Energy Technology Data Exchange (ETDEWEB)

    Kotter, D.K.; Rankin, R.A.; Morgan, J.P.

    1994-05-31

    A magnetic field controller is described for laboratory devices and in particular to dc operated magnetic field controllers for mass spectrometers, comprising a dc power supply in combination with improvements to a Hall probe subsystem, display subsystem, preamplifier, field control subsystem, and an output stage. 1 fig.

  11. High magnetic fields science and technology

    CERN Document Server

    Miura, Noboru

    2003-01-01

    This three-volume book provides a comprehensive review of experiments in very strong magnetic fields that can only be generated with very special magnets. The first volume is entirely devoted to the technology of laboratory magnets: permanent, superconducting, high-power water-cooled and hybrid; pulsed magnets, both nondestructive and destructive (megagauss fields). Volumes 2 and 3 contain reviews of the different areas of research where strong magnetic fields are an essential research tool. These volumes deal primarily with solid-state physics; other research areas covered are biological syst

  12. [Magnetic field numerical calculation and analysis for magnetic coupling of centrifugal blood pump for extracorporeal circulation].

    Science.gov (United States)

    Hu, Zhaoyan; Lu, Lijun; Zhang, Tianyi; Chen, Zhenglong; Zhang, Tao

    2013-12-01

    This paper mainly studies the driving system of centrifugal blood pump for extracorporeal circulation, with the core being disc magnetic coupling. Structure parameters of disc magnetic coupling are related to the ability of transferring magnetic torque. Therefore, it is necessary to carry out disc magnetic coupling permanent magnet pole number (n), air gap length (L(g)), permanent magnet thickness (L(m)), permanent magnet body inside diameter (R(i)) and outside diameter (R(o)), etc. thoroughly. This paper adopts the three-dimensional static magnetic field edge element method of Ansys for numerical calculation, and analyses the relations of magnetic coupling each parameter to transmission magnetic torque. It provides a good theory basis and calculation method for further optimization of the disc magnetic coupling.

  13. Trapped magnetic field measurements on HTS bulk by peak controlled pulsed field magnetization

    Energy Technology Data Exchange (ETDEWEB)

    Ida, Tetsuya; Watasaki, Masahiro [Department of Electronic Control Engineering, Hiroshima National College of Maritime Technology, 4272-1, Higashino, Ohsakikamijima-cho, Toyota-gun, Hiroshima 725-0231 (Japan); Kimura, Yosuke [Kawasaki Heavy Industries, Ltd. Technical Institute System Technology Development Centre 1-1, Kawasaki-cho, Akashi-shi, Hyogo 673-8666 (Japan); Miki, Motohiro; Izumi, Mitsuru, E-mail: ida@hiroshima-cmt.ac.j [Department of Marine Electronics and Mechanical Engineering, Tokyo University of Marine Science and Technology, 2-1-6, Etchu-jima, Koto-ku, Tokyo 135-8533 (Japan)

    2010-06-01

    For the past several years, we have studied the high-temperature superconducting (HTS) synchronous motor assembled with melt-textured Gd-Ba-Cu-O bulk magnets. If the single pulse field magnetizes a bulk effectively, size of electrical motor will become small for the strong magnetic field of the HTS magnets without reducing output power of motor. In the previous study, we showed that the HTS bulk was magnetized to excellent cone-shape magnetic field distribution by using the waveform control pulse magnetization (WCPM) method. The WCPM technique made possible the active control of the waveform on which magnetic flux motion depended. We generated the pulse waveform with controlled risetime for HTS bulk magnetization to suppress the magnetic flux motion which decreases magnetization efficiency. The pulsed maximum magnetic flux density with slow risetime is not beyond the maximum magnetic flux density which is trapped by the static field magnetization. But, as for applying the pulse which has fast risetime, the magnetic flux which exceed greatly the threshold penetrates the bulk and causes the disorder of the trapped magnetic distribution. This fact suggests the possibility that the threshold at pulsed magnetization influences the dynamic magnetic flux motion. In this study, Gd-Ba-Cu-O bulk is magnetized by the controlled arbitrary trapezoidal shape pulse, of which the maximum magnetic flux density is controlled not to exceed the threshold. We will present the trapped magnetic characteristics and the technique to generate the controlled pulsed field.

  14. Magnetic field evolution in tidal disruption events

    CERN Document Server

    Bonnerot, Clément; Lodato, Giuseppe; Rossi, Elena M

    2016-01-01

    When a star gets tidally disrupted by a supermassive black hole, its magnetic field is expected to be transmitted to the debris. In this paper, we study this process via smoothed particle magnetohydrodynamical simulations of the disruption and early debris evolution including the stellar magnetic field. As the gas stretches into a stream, we show that the magnetic field evolution is strongly dependent on its orientation with respect to the stretching direction. In particular, an alignment of the field lines with the direction of stretching induces an increase of the magnetic energy. For disruptions happening well within the tidal radius, the star compression causes the magnetic field strength to sharply increase by an order of magnitude at the time of pericentre passage. If the disruption is partial, we find evidence for a dynamo process occurring inside the surviving core due to the formation of vortices. This causes an amplification of the magnetic field strength by a factor of $\\sim 10$. However, this valu...

  15. Synchrotron Applications of High Magnetic Fields

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2006-07-01

    This workshop aims at discussing the scientific potential of X-ray diffraction and spectroscopy in magnetic fields above 30 T. Pulsed magnetic fields in the range of 30 to 40 T have recently become available at Spring-8 and the ESRF (European synchrotron radiation facility). This document gathers the transparencies of the 6 following presentations: 1) pulsed magnetic fields at ESRF: first results; 2) X-ray spectroscopy and diffraction experiments by using mini-coils: applications to valence state transition and frustrated magnet; 3) R{sub 5}(Si{sub x}Ge{sub 1-x}){sub 4}: an ideal system to be studied in X-ray under high magnetic field?; 4) high field studies at the Advanced Photon Source: present status and future plans; 5) synchrotron X-ray diffraction studies under extreme conditions; and 6) projects for pulsed and steady high magnetic fields at the ESRF.

  16. Demagnetizing fields in active magnetic regenerators

    DEFF Research Database (Denmark)

    Nielsen, Kaspar Kirstein; Bahl, Christian R.H.; Smith, Anders

    2014-01-01

    is in general both a function of the overall shape of the regenerator and its morphology (packed particles, parallel plates etc.) as well as the magnetization of the material. Due to the pronounced temperature dependence of the magnetization near the Curie temperature, the demagnetization field is also......A magnetic material in an externally applied magnetic field will in general experience a spatially varying internal magnetic field due to demagnetizing effects. When the performance of active magnetic regenerators (AMRs) is evaluated using numerical models the internal field is often assumed...... temperature dependent. We propose a relatively straightforward method to correct sufficiently for the demagnetizing field in AMR models. We discuss how the demagnetizing field behaves in regenerators made of packed spheres under realistic operation conditions....

  17. New knowledge of the Galactic magnetic fields

    CERN Document Server

    Han, J L

    2009-01-01

    The magnetic fields of our Milky Way galaxy are the main agent for cosmic rays to transport. In the last decade, much new knowledge has been gained from measurements of the Galactic magnetic fields. In the Galactic disk, from the RMs of a large number of newly discovered pulsars, the large-scale magnetic fields along the spiral arms have been delineated in a much larger region than ever before, with alternating directions in the arm and interarm regions. The toroidal fields in the Galactic halo were revealed to have opposite directions below and above the Galactic plane, which is an indication of an A0 mode dynamo operating in the halo. The strength of large-scale fields obtained from pulsar RM data has been found to increase exponentially towards the Galactic center. Compared to the steep Kolmogorov spectrum of magnetic energy at small scales, the large-scale magnetic fields show a shallow broken spatial magnetic energy spectrum.

  18. Behaviour of ferrocholesterics under external magnetic fields

    Science.gov (United States)

    Petrescu, Emil; Motoc, Cornelia

    2001-08-01

    The influence of an external magnetic field on the orientational behaviour of a ferrocholesteric with a positive magnetic anisotropy is investigated. Both the phenomena arising when the field was switched on or switched off are considered. It is found that the field needed for a ferrocholesteric-ferronematic transition BFC↑ is higher when compared to that obtained for the pure cholesteric ( BC↑). A similar result was obtained when estimating the critical field for the homeotropic ferronematic-ferrocholesteric (focal conic) transition, occurring when the magnetic field was decreased or switched off. We found that BFC↓> BC↓. These results are explained when considering that the magnetic moments of the magnetic powder are not oriented parallel to the liquid crystal molecular directors, therefore hindering their orientation under a magnetic field.

  19. Coulomb crystals in the magnetic field

    CERN Document Server

    Baiko, D A

    2009-01-01

    The body-centered cubic Coulomb crystal of ions in the presence of a uniform magnetic field is studied using the rigid electron background approximation. The phonon mode spectra are calculated for a wide range of magnetic field strengths and for several orientations of the field in the crystal. The phonon spectra are used to calculate the phonon contribution to the crystal