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Sample records for magnetic field drag

  1. Axisymmetric Two-Dimensional Computation of Magnetic Field Dragging in Accretion Disks

    NASA Technical Reports Server (NTRS)

    Reyes-Ruiz, Mauricio; Stepinski, Tomasz F.

    1996-01-01

    In this paper we model a geometrically thin accretion disk interacting with an externally imposed, uniform, vertical magnetic field. The accretion flow in the disk drags and distorts field lines, amplifying the magnetic field in the process. Inside the disk the radial component of the field is sheared into a toroidal component. The aim of this work is to establish the character of the resultant magnetic field and its dependence on the disk's parameters. We concentrate on alpha-disks driven by turbulent viscosity. Axisymmetric, two-dimensional solutions are obtained without taking into account the back-reaction of the magnetic field on the structure of the disk. The character of the magnetic field depends strongly on the magnitude of the magnetic Prandtl number, P . We present two illustrative examples of viscous disks: a so-called 'standard' steady state model of a disk around a compact star (e.g., cataclysmic variable), and a steady state model of a proto-planetary disk. In both cases, P = 1, P = 10(sup -1), and P = 10(sup -2) scenarios are calculated. Significant bending and magnification of the magnetic field is possible only for disks characterized by P of the order of 10(sup -2). In such a case, the field lines are bent sufficiently to allow the development of a centrifugally driven wind. Inside the disk the field is dominated by its toroidal component. We also investigate the dragging of the magnetic field by a nonviscous protoplanetary disk described by a phenomenological model. This scenario leads to large distortion and magnification of the magnetic field.

  2. Oblique Magnetic Fields and the Role of Frame Dragging near Rotating Black Hole

    NASA Astrophysics Data System (ADS)

    Karas, V.; Kopacek, O.; Kunneriath, D.; Hamersky, J.

    2014-12-01

    Magnetic null points can develop near the ergosphere boundary of a rotating black hole by the combined effects of strong gravitational field and the frame-dragging mechanism. The induced electric component does not vanish in the magnetic null and an efficient process of particle acceleration can occur in its immediate vicinity. Furthermore, the effect of imposed (weak) magnetic field can trigger an onset of chaos in the motion of electrically charged particles. The model set-up appears to be relevant for low-accretion-rate nuclei of some galaxies which exhibit episodic accretion events (such as the Milky Way's supermassive black hole) embedded in a large-scale magnetic field of external origin with respect to the central black hole. In this contribution we summarise recent results and we give an outlook for future work with the focus on the role of gravito-magnetic effects caused by rotation of the black hole.

  3. MAGNETIC DRAG ON HOT JUPITER ATMOSPHERIC WINDS

    SciTech Connect

    Perna, Rosalba; Menou, Kristen; Rauscher, Emily

    2010-08-20

    Hot Jupiters, with atmospheric temperatures T {approx}> 1000 K, have residual thermal ionization levels sufficient for the interaction of ions with the planetary magnetic field to result in a sizable magnetic drag on the (neutral) atmospheric winds. We evaluate the magnitude of magnetic drag in a representative three-dimensional atmospheric model of the hot Jupiter HD 209458b and find that it is a plausible mechanism to limit wind speeds in this class of atmospheres. Magnetic drag has a strong geometrical dependence, both meridionally and from the dayside to the nightside (in the upper atmosphere), which could have interesting consequences for the atmospheric flow pattern. By extension, close-in eccentric planets with transiently heated atmospheres will experience time-variable levels of magnetic drag. A robust treatment of magnetic drag in circulation models for hot atmospheres may require iterated solutions to the magnetic induction and Saha equations as the hydrodynamic flow is evolved.

  4. Computational analysis of magnetic field induced deposition of magnetic particles in lung alveolus in comparison to deposition produced with viscous drag and gravitational force

    NASA Astrophysics Data System (ADS)

    Krafcik, Andrej; Babinec, Peter; Frollo, Ivan

    2015-04-01

    Magnetic targeting of drugs attached to magnetic nanoparticles with diameter ? 100 nm after their intravenous administration is an interesting method of drug delivery widely investigated both theoretically as well as experimentally. Our aim in this study is theoretical analysis of a magnetic aerosol targeting to the lung. Due to lung anatomy magnetic particles up to 5 ?m can be safely used, therefore the magnetic force would be stronger, moreover drag force exerted on the particle is according to Stokes law linearly dependent on the viscosity, would be weaker, because the viscosity of the air in the lung is approximately 200 fold smaller than viscosity of the blood. Lung therefore represents unique opportunity for magnetic drug targeting, as we have shown in this study by the analysis of magnetic particle dynamics in a rhythmically expanding and contracting distal and proximal alveolus subjected to high-gradient magnetic field generated by quadrupolar permanent Halbach magnet array.

  5. The influence of the magnetic field on the effect of drag of electrons by phonons in n-Cd{sub x}Hg{sub 1-x}Te

    SciTech Connect

    Aliyev, S. A.; Zulfigarov, E. I.; Selim-Zade, R. I.; Agayev, Z. F.

    2009-09-15

    Thermopower in n-Cd{sub 0.2}Hg{sub 0.8}Te (6-100 K) is studied. A large effect of drag of the charge carriers by phonons {alpha}{sub ph} is found. The influence of the magnetic field H on the drag thermopower is considered. It is established that the magnetic field exerts the effect mainly on the electron component of {alpha}{sub ph}. The data are interpreted in the context of the theory taking into account the effect of H on thermopower {alpha}{sub ph}, in which parameter A({epsilon}) proportional to the static force of the drag effect is introduced. By the experimental data {alpha}{sub ph}(T, H), T, and H dependences A({epsilon}) are determined. It is shown that, as H increases, A({epsilon}) sharply decreases. This explains a decrease in {alpha}{sub ph} in the magnetic field, power index k in dependence {alpha}{sub ph} {proportional_to} T{sup -}{kappa}, and narrowing the region of manifestation of the drag effect. It is established that at classically high fields, the drag effect in n-Cd{sub 0.2}Hg{sub 0.8}Te does not vanish.

  6. Dragging Human Mesenchymal Stem Cells with the Aid of Supramolecular Assemblies of Single-Walled Carbon Nanotubes, Molecular Magnets, and Peptides in a Magnetic Field

    PubMed Central

    de Paula, Ana Cludia C.; Sfar, Gustavo A. M.; Ges, Alfredo M.; Bemquerer, Marcelo P.; Ribeiro, Marcos A.; Stumpf, Humberto O.

    2015-01-01

    Human adipose-derived stem cells (hASCs) are an attractive cell source for therapeutic applicability in diverse fields for the repair and regeneration of damaged or malfunctioning tissues and organs. There is a growing number of cell therapies using stem cells due to their characteristics of modulation of immune system and reduction of acute rejection. So a challenge in stem cells therapy is the delivery of cells to the organ of interest, a specific site. The aim of this paper was to investigate the effects of a supramolecular assembly composed of single-walled carbon nanotubes (SWCNT), molecular magnets (lawsone-Co-phenanthroline), and a synthetic peptide (FWYANHYWFHNAFWYANHYWFHNA) in the hASCs cultures. The hASCs were isolated, characterized, expanded, and cultured with the SWCNT supramolecular assembly (SWCNT-MA). The assembly developed did not impair the cell characteristics, viability, or proliferation. During growth, the cells were strongly attached to the assembly and they could be dragged by an applied magnetic field of less than 0.3?T. These assemblies were narrower than their related allotropic forms, that is, multiwalled carbon nanotubes, and they could therefore be used to guide cells through thin blood capillaries within the human body. This strategy seems to be useful as noninvasive and nontoxic stem cells delivery/guidance and tracking during cell therapy. PMID:25688350

  7. GAS KINEMATICS AND THE DRAGGED MAGNETIC FIELD IN THE HIGH-MASS MOLECULAR OUTFLOW SOURCE G192.16-3.84: AN SMA VIEW

    SciTech Connect

    Liu Hauyu Baobab; Ho, Paul T. P.; Qiu Keping; Zhang Qizhou; Girart, Josep M.

    2013-07-01

    We report Submillimeter Array (SMA) observations of polarized 0.88 mm thermal dust emission and various molecular line transitions toward the early B-type (L{sub *} {approx} 2 Multiplication-Sign 10{sup 3} L{sub Sun }) star-forming region G192.16-3.84 (IRAS 05553+1631). The peak of the continuum Stokes-I emission coincides with a hot rotating disk/envelope (SO{sub 2} rotational temperature T{sub rot}{sup SO{sub 2}}{approx}84{sup +18}{sub -13} K), with a north-south velocity gradient. Joint analysis of the rotation curve traced by HCO{sup +} 4-3 and SO{sub 2} 19{sub 1,19}-18{sub 0,18} suggests that the dense molecular gas is undergoing a spinning-up rotation, marginally bound by the gravitational force of an enclosed mass M{sub *+gas+dust} {approx} 11.2-25.2 M{sub Sun }. Perpendicular to the rotational plane, a {approx}>100/cos (i) km s{sup -1} (i {approx} 63 Degree-Sign ) high velocity molecular jet and a {approx}15-20 km s{sup -1} expanding biconical cavity were revealed in the CO 3-2 emission. The polarization percentage of the 0.88 mm continuum emission decreases toward the central rotating disk/envelope. The polarization angle in the inner {approx}2'' (0.015 pc) disk/envelope is perpendicular to the plane of the rotation. The magnetic field lines, which are predominantly in the toroidal direction along the disk plane, are likely to be dragged by the gravitationally accelerated rotation.

  8. Effect of guideway discontinuities on magnetic levitation and drag forces

    SciTech Connect

    Rossing, T.D.; Korte, R. Northern Illinois Univ., De Kalb, IL . Dept. of Physics); Hull, J.R. )

    1991-01-01

    Transients in the lift and drag forces on a NdFeB permanent magnet were observed as the magnet passed over various discontinuities in a rotating aluminum disk at velocities of 4 to 25 m/s. For full cuts in the disk, the amplitude of the lift and drag transients and the waveform of the drag transient depend on the width, and the amplitudes are much larger than for partial cuts. The use of a backing plate to join two cut segments is ineffective. 2 refs., 3 figs.

  9. Superconductor-Magnet Bearings With Inherent Stability and Velocity-Independent Drag Torque

    NASA Technical Reports Server (NTRS)

    Lee, Eun-Jeong; Ma, Ki Bui; Wilson, Thomas L.; Chu, Wei-Kan

    1999-01-01

    A hybrid superconductor magnet bearing system has been developed based on passive magnetic levitation and the flux pinning effect of high-temperature superconductivity. The rationale lies in the unique capability of a high-temperature superconductor (HTS) to enhance system stability passively without power consumption. Characterization experiments have been conducted to understand its dynamic behavior and to estimate the required motor torque for its driving system design. These experiments show that the hybrid HTS-magnet bearing system has a periodic oscillation of drag torque due mainly to the nonuniform magnetic field density of permanent magnets. Furthermore, such a system also suffers from a small superimposed periodic oscillation introduced by the use of multiple HTS disks rather than a uniform annulus of HTS material. The magnitude of drag torque is velocity independent and very small. These results make this bearing system appealing for high-speed application. Finally, design guidelines for superconducting bearing systems are suggested based on these experimental results.

  10. Drag measurements on a body of revolution in Langley's 13-inch Magnetic Suspension and Balance System

    NASA Technical Reports Server (NTRS)

    Dress, David A.

    1988-01-01

    NASA Langley's 13-inch Magnetic Suspension and Balance System (MSBS) has been used to conduct low-speed wind tunnel drag force measurements on a laminar-flow body-of-revolution free of support system interference, in order to verify the drag force measurement capabilities of the MSBS. The drag force calibrations and wind-on repeatability data obtained have verified the design capabilities for this system. A drag-prediction code has been used to assess the MSBS's usefulness in body drag estimation.

  11. Frame-dragging fields and spin 1 gravitomagnetic radiation

    NASA Astrophysics Data System (ADS)

    Tolstoy, Ivan

    2012-12-01

    Experimental results published in 2004 (Ciufolini and Pavlis in Nature 431:958-960, 2004) and 2011 (Everitt et al. in Phys Rev Lett 106:221101, 1-5, 2011) have confirmed the frame-dragging phenomenon for a spinning earth predicted by Einstein's field equations. Since this is observed as a precession caused by the gravitomagnetic (GM) field of the rotating body, these experiments may be viewed as measurements of a GM field. The effect is encapsulated in the classic steady state solution for the vector potential field ? of a spinning sphere-a solution applying to a sphere with angular momentum J and describing a field filling space for all time (Weinberg in Gravitation and Cosmology, Wiley, New York, 1972). In a laboratory setting one may visualise the case of a sphere at rest (? =0, { t}<0), being spun up by an external torque at { t}=0 to the angular momentum J: the ? field of the textbook solution cannot establish itself instantaneously over all space at { t}=0, but must propagate with the velocity c, implying the existence of a travelling GM wave field yielding the textbook ? field for large enough t (Tolstoy in Int J Theor Phys 40(5):1021-1031, 2001). The linearized GM field equations of the post-Newtonian approximation being isomorphic with Maxwell's equations (Braginsky et al. in Phys Rev D 15(6):2047-2060, 1977), such GM waves are dipole waves of spin 1. It is well known that in purely gravitating systems conservation of angular momentum forbids the existence of dipole radiation (Misner et al. in Gravitation, Freeman & Co., New York, 1997); but this rule does not prohibit the insertion of angular momentum into the system from an external source-e.g., by applying a torque to our laboratory sphere.

  12. Magnetic field sensor

    NASA Astrophysics Data System (ADS)

    Silva, Nicolas

    2012-09-01

    Earlier papers1-3 in this journal have described experiments on measuring the magnetic fields of current-carrying wires and permanent magnets using magnetic field probes of various kinds. This paper explains how to use an iPad and the free app MagnetMeter-3D Vector Magnetometer and Accelerometer4 (compass HD) to measure the magnetic fields.

  13. Magnetic field line Hamiltonian

    SciTech Connect

    Boozer, A.H.

    1985-02-01

    The basic properties of the Hamiltonian representation of magnetic fields in canonical form are reviewed. The theory of canonical magnetic perturbation theory is then developed and applied to the time evolution of a magnetic field embedded in a toroidal plasma. Finally, the extension of the energy principle to tearing modes, utilizing the magnetic field line Hamiltonian, is outlined.

  14. Magnetic field mapper

    NASA Technical Reports Server (NTRS)

    Masters, R. M.; Stenger, F. J.

    1969-01-01

    Magnetic field mapper locates imperfections in cadmium sulphide solar cells by detecting and displaying the variations of the normal component of the magnetic field resulting from current density variations. It can also inspect for nonuniformities in other electrically conductive materials.

  15. Resonances of an Oscillating Conductive Pipe Driven by an Alternating Magnetic Field in the Presence of a Static Magnetic Field

    ERIC Educational Resources Information Center

    Ladera, Celso L.; Donoso, Guillermo

    2011-01-01

    A short conducting pipe that hangs from a weak spring is forced to oscillate by the magnetic field of a surrounding coaxial coil that has been excited by a low-frequency current source in the presence of an additional static magnetic field. Induced oscillating currents appear in the pipe. The pipe motion becomes damped by the dragging forces

  16. Photospheric magnetic fields

    NASA Technical Reports Server (NTRS)

    Howard, R.

    1972-01-01

    Knowledge on the nature of magnetic fields on the solar surface is reviewed. At least a large part of the magnetic flux in the solar surface is confined to small bundles of lines of force within which the field strength is of the order of 500 gauss. Magnetic fields are closely associated with all types of solar activity. Magnetic flux appears at the surface at the clearly defined birth or regeneration of activity of an active region. As the region ages, the magnetic flux migrates to form large-scale patterns and the polar fields. Some manifestations of the large-scale distribution are discussed.

  17. Magnetic Fields and Plasmas

    SciTech Connect

    Schep, T.J.

    2004-03-15

    Plasmas and magnetic fields are inseparably related in numerous physical circumstances. This is not only the case in natural occurring plasmas like the solar corona and the earth magnetic tail, but also in laboratory plasmas like tokamaks and stellarators.

  18. Exploiting Size-Dependent Drag and Magnetic Forces for Size-Specific Separation of Magnetic Nanoparticles.

    PubMed

    Rogers, Hunter B; Anani, Tareq; Choi, Young Suk; Beyers, Ronald J; David, Allan E

    2015-01-01

    Realizing the full potential of magnetic nanoparticles (MNPs) in nanomedicine requires the optimization of their physical and chemical properties. Elucidation of the effects of these properties on clinical diagnostic or therapeutic properties, however, requires the synthesis or purification of homogenous samples, which has proved to be difficult. While initial simulations indicated that size-selective separation could be achieved by flowing magnetic nanoparticles through a magnetic field, subsequent in vitro experiments were unable to reproduce the predicted results. Magnetic field-flow fractionation, however, was found to be an effective method for the separation of polydisperse suspensions of iron oxide nanoparticles with diameters greater than 20 nm. While similar methods have been used to separate magnetic nanoparticles before, no previous work has been done with magnetic nanoparticles between 20 and 200 nm. Both transmission electron microscopy (TEM) and dynamic light scattering (DLS) analysis were used to confirm the size of the MNPs. Further development of this work could lead to MNPs with the narrow size distributions necessary for their in vitro and in vivo optimization. PMID:26307980

  19. Exploiting Size-Dependent Drag and Magnetic Forces for Size-Specific Separation of Magnetic Nanoparticles

    PubMed Central

    Rogers, Hunter B.; Anani, Tareq; Choi, Young Suk; Beyers, Ronald J.; David, Allan E.

    2015-01-01

    Realizing the full potential of magnetic nanoparticles (MNPs) in nanomedicine requires the optimization of their physical and chemical properties. Elucidation of the effects of these properties on clinical diagnostic or therapeutic properties, however, requires the synthesis or purification of homogenous samples, which has proved to be difficult. While initial simulations indicated that size-selective separation could be achieved by flowing magnetic nanoparticles through a magnetic field, subsequent in vitro experiments were unable to reproduce the predicted results. Magnetic field-flow fractionation, however, was found to be an effective method for the separation of polydisperse suspensions of iron oxide nanoparticles with diameters greater than 20 nm. While similar methods have been used to separate magnetic nanoparticles before, no previous work has been done with magnetic nanoparticles between 20 and 200 nm. Both transmission electron microscopy (TEM) and dynamic light scattering (DLS) analysis were used to confirm the size of the MNPs. Further development of this work could lead to MNPs with the narrow size distributions necessary for their in vitro and in vivo optimization. PMID:26307980

  20. Magnetic field generator

    DOEpatents

    Krienin, Frank

    1990-01-01

    A magnetic field generating device provides a useful magnetic field within a specific retgion, while keeping nearby surrounding regions virtually field free. By placing an appropriate current density along a flux line of the source, the stray field effects of the generator may be contained. One current carrying structure may support a truncated cosine distribution, and it may be surrounded by a current structure which follows a flux line that would occur in a full coaxial double cosine distribution. Strong magnetic fields may be generated and contained using superconducting cables to approximate required current surfaces.

  1. Drag measurements on a laminar-flow body of revolution in the 13-inch magnetic suspension and balance system

    NASA Technical Reports Server (NTRS)

    Dress, David A.

    1989-01-01

    Low speed wind tunnel drag force measurements were taken on a laminar flow body of revolution free of support interference. This body was tested at zero incidence in the NASA Langley 13 in. Magnetic Suspension and Balance System (MSBS). The primary objective of these tests was to substantiate the drag force measuring capabilities of the 13 in. MSBS. The drag force calibrations and wind-on repeatability data provide a means of assessing these capabilities. Additional investigations include: (1) the effects of fixing transition; (2) the effects of fins installed in the tail; and (3) surface flow visualization using both liquid crystals and oil flow. Also two simple drag prediction codes were used to assess their usefulness in estimating overall body drag.

  2. On Cosmic Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Florido, E.; Battaner, E.

    2010-12-01

    Magnetic fields are present in all astrophysical media. However, many models and interpretations of observations often ignore them, because magnetic fields are difficult to handle and because they produce complicated morphological features. Here we will comment on the basic intuitive properties, which even if not completely true, provide a first guiding insight on the physics of a particular astrophysical problem. These magnetic properties are not mathematically demonstrated here. How magnetic fields evolve and how they introduce dynamical effects are considered, also including a short comment on General Relativity Magnetohydrodynamics. In a second part we consider some audacious and speculative matters. They are answers to three questions: a) How draw a cube without lifting the pencil from the paper so that when the pen passes through the same side do in the same direction? B) Are MILAGRO anisotropies miraculous? C) Do cosmic magnetic lenses exist?. The last two questions deal with issues related with the interplay between magnetic fields and cosmic ray propagation.

  3. Magnetic Fields in Galaxies

    NASA Astrophysics Data System (ADS)

    Beck, Rainer

    Magnetic fields are a major agent in the interstellar medium. They contribute significantly to the total pressure which balances the gas disk against gravitation. They affect the gas flows in spiral arms (Gmez and Cox, 2002). The effective sound speed of the gas is increased by the presence of strong fields which reduce the shock strength. The interstellar fields are closely connected to gas clouds. They affect the dynamics of the gas clouds (Elmegreen, 1981; de Avillez and Breitschwerdt, 2004). The stability and evolution of gas clouds are also influenced by magnetic fields, but it is not understood how (Crutcher, 1999; see Chap. 7). Magnetic fields are essential for the onset of star formation as they enable the removal of angular momentum from the protostellar cloud during its collapse (magnetic braking, Mouschovias, 1990). Strong fields may shift the stellar mass spectrum towards the more massive stars (Mestel, 1990). MHD turbulence distributes energy from supernova explosions within the ISM (Subramanian, 1998) and regenerates the field via the dynamo process (Wielebinski, R., Krause, 1993, Beck et al., 1996; Sect. 6). Magnetic reconnection is a possible heating source for the ISM and halo gas (Birk et al., 1998). Magnetic fields also control the density and distribution of cosmic rays in the ISM. A realistic model for any process in the ISM needs basic information about the magnetic field which has to be provided by observations.

  4. Inverse-Compton drag on a highly magnetized GRB jet in stellar envelope

    NASA Astrophysics Data System (ADS)

    Ceccobello, Chiara; Kumar, Pawan

    2015-05-01

    The collimation and evolution of relativistic outflows in ?-ray bursts are determined by their interaction with the stellar envelope through which they travel before reaching the much larger distance where the energy is dissipated and ?-rays are produced. We consider the case of a Poynting-flux-dominated relativistic outflow and show that it suffers strong inverse-Compton (IC) scattering drag near the stellar surface and the jet is slowed down to sub-relativistic speed if its initial magnetization parameter (?0) is larger than about 105. If the temperature of the cocoon surrounding the jet were to be larger than about 10 keV, then an optically thick layer of electrons and positrons forms at the interface of the cocoon and the jet, and one might expect this pair screen to protect the interior of the jet from IC drag. However, the pair screen turns out to be ephemeral, and instead of shielding the jet it speeds up the IC drag on it. Although a high ?0 jet might not survive its passage through the star, a fraction of its energy is converted to 1-100 MeV radiation that escapes the star and appears as a bright flash lasting for about 10 s.

  5. Magnetic fields at Neptune

    SciTech Connect

    Ness, N.F. ); Acuna, M.H.; Burlaga, L.F.; Connerney, J.E.P.; Lepping, R.P. ); Neubauer, F.M. )

    1989-12-15

    The National Aeronautics and Space Administration Goddard Space Flight Center-University of Delaware Bartol Research Institute magnetic field experiment on the Voyager 2 spacecraft discovered a strong and complex intrinsic magnetic field of Neptune and an associated magnetosphere and magnetic tail. A maximum magnetic field of nearly 10,000 nanoteslas (1 nanotesla = 10{sup {minus}5} gauss) was observed near closest approach, at a distance of 1.18 R{sub N}. The planetary magnetic field between 4 and 15 R{sub N} can be well represented by an offset tilted magnetic dipole (OTD), displaced from the center of Neptune by the surprisingly large amount of 0.55 R{sub N} and inclined by 47{degrees} with respect to the rotation axis. Within 4 R{sub N}, the magnetic field representation must include localized sources or higher order magnetic multipoles, or both, which are not yet well determined. As the spacecraft exited the magnetosphere, the magnetic tail appeared to be monopolar, and no crossings of an imbedded magnetic field reversal or plasma neutral sheet were observed. The auroral zones are most likely located far from the rotation poles and may have a complicated geometry. The rings and all the known moons of Neptune are imbedded deep inside the magnetosphere, except for Nereid, which is outside when sunward of the planet. The radiation belts will have a complex structure owing to the absorption of energetic particles by the moons and rings of Neptune and losses associated with the significant changes in the diurnally varying magnetosphere configuration. In an astrophysical context, the magnetic field of Neptune, like that of Uranus, may be described as that of an oblique rotator.

  6. Concurrent field measurements of turbulent velocities, plant reconfiguration and drag forces on Ranunculus penicillatus

    NASA Astrophysics Data System (ADS)

    Paul, Maike; Thomas, Robert E.; Keevil, Gareth M.

    2013-04-01

    In lowland rivers, seasonal patterns of in-stream macrophyte growth and decay have significant implications for flood risk. For a given discharge, flood risk is increased when dense macrophyte canopies reduce flow areas, increase blockage ratios and alter reach-scale roughness values. These factors combine and can increase the flow depth. Conversely, submerged vegetation is exposed to drag forces exerted by the flow, which may be sufficient to damage limbs or dislodge plants. The classical drag equation suggests that the force exerted by fluid flows upon submerged vegetation is a function of the fluid properties, the projected area of the vegetation, and the square of the flow velocity. However, very few studies have simultaneously monitored all of these parameters, resulting in significant uncertainty in the estimation of the coefficient that relates these parameters to the drag force and also the related roughness parameters that control the flow depth for a given discharge. To our knowledge, this study presents the first concurrent field measurements of turbulent velocities, plant reconfigurations and drag forces acting on Ranunculus penicillatus ssp. pseudofluitans (Syme) S.D.Webster. Measurements were undertaken in an artificially straightened reach of the chalk-bed River Wylye, near Longbridge Deverill, Wiltshire, UK. The reach is 5.7 m wide and during measurements there was a mean flow depth of 0.28 m and an average discharge of 0.28 m³s-1. The reach is cleared of vegetation up to three times a year for flood defence purposes, but Ranunculus p. grows back within several weeks. Measurements were carried out after re-growth, when plants were fully developed with a mean length of 0.75 m and on average 6 nodes along the stem. The distances between the nodes increased from the base towards the tip and each node produced a capillary leaf, sometimes in conjunction with a branch. Floating leaves and flowers were not present. Plants were attached to a custom-made drag sensor that was deployed flush with the streambed. Simultaneously, a profiling Acoustic Doppler Velocimeter (Nortek Vectrino-II) was deployed 0.5 m upstream of the plants. Also, a video camera was installed with its field of view perpendicular to the mean flow direction, in order to record plant motion and reconfiguration associated with turbulent velocity and drag fluctuations. Measurements were repeated while the Vectrino-II was consecutively deployed at four vertical positions to: 1. obtain a velocity profile through the entire water column and 2. study which vertical position correlated most strongly to the drag force. Velocity measurements confirmed that turbulent structures were present throughout the water column and a response to these fluctuations was observed in the drag measurements. Responses lagged in time due to the horizontal distance between Vectrino-II and drag sensor position. Additionally, spectral analysis showed that the drag fluctuates with a frequency of 0.5 Hz which corresponds well with the undulating, quasi-sinusoidal, plant motion observed on the video footage. This motion was associated with the downstream propagation of coherent eddies.

  7. Training-induced changes in drag-flick technique in female field hockey players.

    PubMed

    de Subijana, C L; Gmez, M; Martn-Casado, L; Navarro, E

    2012-12-01

    The penalty corner is one of the most important goal plays in field hockey. The drag-flick is used less by women than men in a penalty corner. The aim of this study was to describe training-induced changes in the drag-flick technique in female field hockey players. Four female players participated in the study. The VICON optoelectronic system (Oxford Metrics, Oxford, UK) measured the kinematic parameters of the drag-flick with six cameras sampling at 250 Hz, prior to and after training. Fifteen shots were captured for each subject. A Wilcoxon test assessed the differences between pre-training and post-training parameters. Two players received specific training twice a week for 8 weeks; the other two players did not train. The proposed drills improved the position of the stick at the beginning of the shot (p < 0.05), the total distance of the shot (p < 0.05) and the rotation radius at ball release (p < 0.01). It was noted that all players had lost speed of the previous run. Further studies should include a larger sample, in order to provide more information on field hockey performance. PMID:24868116

  8. TRAINING-INDUCED CHANGES IN DRAG-FLICK TECHNIQUE IN FEMALE FIELD HOCKEY PLAYERS

    PubMed Central

    Gmez, M.; Martn-Casado, L.; Navarro, E.

    2012-01-01

    The penalty corner is one of the most important goal plays in field hockey. The drag-flick is used less by women than men in a penalty corner. The aim of this study was to describe training-induced changes in the drag-flick technique in female field hockey players. Four female players participated in the study. The VICON optoelectronic system (Oxford Metrics, Oxford, UK) measured the kinematic parameters of the drag-flick with six cameras sampling at 250 Hz, prior to and after training. Fifteen shots were captured for each subject. A Wilcoxon test assessed the differences between pre-training and post-training parameters. Two players received specific training twice a week for 8 weeks; the other two players did not train. The proposed drills improved the position of the stick at the beginning of the shot (p < 0.05), the total distance of the shot (p < 0.05) and the rotation radius at ball release (p < 0.01). It was noted that all players had lost speed of the previous run. Further studies should include a larger sample, in order to provide more information on field hockey performance. PMID:24868116

  9. Magnetic field dosimeter development

    SciTech Connect

    Lemon, D.K.; Skorpik, J.R.; Eick, J.L.

    1980-09-01

    In recent years there has been increased concern over potential health hazards related to exposure of personnel to magnetic fields. If exposure standards are to be established, then a means for measuring magnetic field dose must be available. To meet this need, the Department of Energy has funded development of prototype dosimeters at the Battelle Pacific Northwest Laboratory. This manual reviews the principle of operation of the dosimeter and also contains step-by-step instructions for its operation.

  10. Magnetosheath magnetic field variability

    NASA Technical Reports Server (NTRS)

    Sibeck, D. G.

    1994-01-01

    A case study using simulations IRM and CCE observations demonstrates that transient magnetospheric events correspond to pressure pulses in the magnetosheath, inward bow shock motion, and magnetopause compression. Statistical surveys indicate that the magnetosheath magnetic field orientation rarely remains constant during periods of magnetopause and bow shock motion (both characterized by periods of 1 to 10 min). There is no tendency for bow shock motion to occur for southward interplanetary magnetic field (IMF) orientations.

  11. Solar Wind Magnetic Fields

    NASA Technical Reports Server (NTRS)

    Smith, E. J.

    1995-01-01

    The magnetic fields originate as coronal fields that are converted into space by the supersonic, infinitely conducting, solar wind. On average, the sun's rotation causes the field to wind up and form an Archimedes Spiral. However, the field direction changes almost continuously on a variety of scales and the irregular nature of these changes is often interpreted as evidence that the solar wind flow is turbulent.

  12. Magnetic Field Measurement System

    SciTech Connect

    Kulesza, Joe; Johnson, Eric; Lyndaker, Aaron; Deyhim, Alex; Waterman, Dave; Blomqvist, K. Ingvar; Dunn, Jonathan Hunter

    2007-01-19

    A magnetic field measurement system was designed, built and installed at MAX Lab, Sweden for the purpose of characterizing the magnetic field produced by Insertion Devices (see Figure 1). The measurement system consists of a large granite beam roughly 2 feet square and 14 feet long that has been polished beyond laboratory grade for flatness and straightness. The granite precision coupled with the design of the carriage yielded minimum position deviations as measured at the probe tip. The Hall probe data collection and compensation technique allows exceptional resolution and range while taking data on the fly to programmable sample spacing. Additional flip coil provides field integral data.

  13. Magnetic Field Solver

    NASA Technical Reports Server (NTRS)

    Ilin, Andrew V.

    2006-01-01

    The Magnetic Field Solver computer program calculates the magnetic field generated by a group of collinear, cylindrical axisymmetric electromagnet coils. Given the current flowing in, and the number of turns, axial position, and axial and radial dimensions of each coil, the program calculates matrix coefficients for a finite-difference system of equations that approximates a two-dimensional partial differential equation for the magnetic potential contributed by the coil. The program iteratively solves these finite-difference equations by use of the modified incomplete Cholesky preconditioned-conjugate-gradient method. The total magnetic potential as a function of axial (z) and radial (r) position is then calculated as a sum of the magnetic potentials of the individual coils, using a high-accuracy interpolation scheme. Then the r and z components of the magnetic field as functions of r and z are calculated from the total magnetic potential by use of a high-accuracy finite-difference scheme. Notably, for the finite-difference calculations, the program generates nonuniform two-dimensional computational meshes from nonuniform one-dimensional meshes. Each mesh is generated in such a way as to minimize the numerical error for a benchmark one-dimensional magnetostatic problem.

  14. Magnetic fields at neptune.

    PubMed

    Ness, N F; Acua, M H; Burlaga, L F; Connerney, J E; Lepping, R P; Neubauer, F M

    1989-12-15

    The National Aeronautics and Space Administration Goddard Space Flight Center-University of Delaware Bartol Research Institute magnetic field experiment on the Voyager 2 spacecraft discovered a strong and complex intrinsic magnetic field of Neptune and an associated magnetosphere and magnetic tail. The detached bow shock wave in the supersonic solar wind flow was detected upstream at 34.9 Neptune radii (R(N)), and the magnetopause boundary was tentatively identified at 26.5 R(N) near the planet-sun line (1 R(N) = 24,765 kilometers). A maximum magnetic field of nearly 10,000 nanoteslas (1 nanotesla = 10(-5) gauss) was observed near closest approach, at a distance of 1.18 R(N). The planetary magnetic field between 4 and 15 R(N) can be well represented by an offset tilted magnetic dipole (OTD), displaced from the center of Neptune by the surprisingly large amount of 0.55 R(N) and inclined by 47 degrees with respect to the rotation axis. The OTD dipole moment is 0.133 gauss-R(N)(3). Within 4 R(N), the magnetic field representation must include localized sources or higher order magnetic multipoles, or both, which are not yet well determined. The obliquity of Neptune and the phase of its rotation at encounter combined serendipitously so that the spacecraft entered the magnetosphere at a time when the polar cusp region was directed almost precisely sunward. As the spacecraft exited the magnetosphere, the magnetic tail appeared to be monopolar, and no crossings of an imbedded magnetic field reversal or plasma neutral sheet were observed. The auroral zones are most likely located far from the rotation poles and may have a complicated geometry. The rings and all the known moons of Neptune are imbedded deep inside the magnetosphere, except for Nereid, which is outside when sunward of the planet. The radiation belts will have a complex structure owing to the absorption of energetic particles by the moons and rings of Neptune and losses associated with the significant changes in the diurnally varying magnetosphere configuration. In an astrophysical context, the magnetic field of Neptune, like that of Uranus, may be described as that of an "oblique" rotator. PMID:17756002

  15. Magnetic propulsion of intense lithium streams in a tokamak magnetic field.

    PubMed

    Zakharov, Leonid E

    2003-01-31

    This paper describes the effect and gives the theory of magnetic propulsion which allows driving free surface plasma facing liquid lithium streams in tokamaks. In the approximation of a thin flowing layer the MHD equations are reduced to one integrodifferential equation which takes into account the propulsion effect, viscosity, and the drag force due to magnetic pumping and other interactions with the magnetic field. A stability criterion is obtained for stabilization of the "sausage" instability of the streams by centrifugal force. PMID:12570428

  16. Magnetic Propulsion of Intense Lithium Streams in a Tokamak Magnetic Field

    SciTech Connect

    Leonid E. Zakharov

    2002-03-13

    The paper gives the theory of magnetic propulsion of liquid lithium streams and their stability in tokamaks. In the approximation of a thin flowing layer the MHD equations are reduced to one integro-differential equation which takes into account the propulsion effect, viscosity and the drag force due to magnetic pumping and other interactions with the magnetic field. A criterion is obtained for the stabilization of the ''sausage'' instability of the streams by centrifugal force.

  17. Gas rotation in discharges in a longitudinal magnetic field

    NASA Astrophysics Data System (ADS)

    Nedospasov, A. V.

    2015-06-01

    This paper reviews theoretical and experimental work on gas rotation in discharges ignited in a longitudinal magnetic field. There is abundant evidence that such a field causes plasma-dust structures to rotate in the plane perpendicular to itself. This rotation cannot be explained solely by the dragging action of azimuthally moving ions. Drag is also exerted by the gas rotating under the moment produced by the Ampere force that arises in discharge regions with a nonuniform magnetic field near solenoid end faces and due to the narrowing of the discharge channel cross section. In a stratified discharge in a uniform magnetic field, an eddy electric current due to the noncollinearity of the plasma-density and temperature gradients brings the gas to rotation.

  18. Magnetic fields at uranus.

    PubMed

    Ness, N F; Acua, M H; Behannon, K W; Burlaga, L F; Connerney, J E; Lepping, R P; Neubauer, F M

    1986-07-01

    The magnetic field experiment on the Voyager 2 spacecraft revealed a strong planetary magnetic field of Uranus and an associated magnetosphere and fully developed bipolar masnetic tail. The detached bow shock wave in the solar wind supersonic flow was observed upstream at 23.7 Uranus radii (1 R(U) = 25,600 km) and the magnetopause boundary at 18.0 R(U), near the planet-sun line. A miaximum magnetic field of 413 nanotesla was observed at 4.19 R(U ), just before closest approach. Initial analyses reveal that the planetary magnetic field is well represented by that of a dipole offset from the center of the planet by 0.3 R(U). The angle between Uranus' angular momentum vector and the dipole moment vector has the surprisingly large value of 60 degrees. Thus, in an astrophysical context, the field of Uranus may be described as that of an oblique rotator. The dipole moment of 0.23 gauss R(3)(U), combined with the large spatial offset, leads to minimum and maximum magnetic fields on the surface of the planet of approximately 0.1 and 1.1 gauss, respectively. The rotation period of the magnetic field and hence that of the interior of the planet is estimated to be 17.29+/- 0.10 hours; the magnetotail rotates about the planet-sun line with the same period. Thelarge offset and tilt lead to auroral zones far from the planetary rotation axis poles. The rings and the moons are embedded deep within the magnetosphere, and, because of the large dipole tilt, they will have a profound and diurnally varying influence as absorbers of the trapped radiation belt particles. PMID:17812894

  19. Mercury's Magnetic Field

    NASA Astrophysics Data System (ADS)

    Johnson, C. L.

    2014-12-01

    Mercury is the only inner solar system body other than Earth to possess an active core dynamo-driven magnetic field and the only planet with a small, highly dynamic magnetosphere. Measurements made by the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft have provided a wealth of data on Mercury's magnetic field environment. Mercury's weak magnetic field was discovered 40 years ago by the Mariner 10 spacecraft, but its large-scale geometry, strength and origin could not be definitively established. MESSENGER data have shown that the field is dynamo-generated and can be described as an offset axisymmetric dipole field (hereafter OAD): the magnetic equator lies ~0.2 RM (RM = 2440 km) north of the geographic equator and the dipole moment is 2.8 x1019 Am2 (~0.03% that of Earth's). The weak internal field and the high, but variable, solar wind ram pressure drive vigorous magnetospheric dynamics and result in an average distance from the planet center to the sub-solar magnetopause of only 1.42 RM. Magnetospheric models developed with MESSENGER data have allowed re-analysis of the Mariner 10 observations, establishing that there has been no measureable secular variation in the internal field over 40 years. Together with spatial power spectra for the OAD, this provides critical constraints for viable dynamo models. Time-varying magnetopause fields induce secondary core fields, the magnitudes of which confirm the core radius estimated from MESSENGER gravity and Earth-based radar data. After accounting for large-scale magnetospheric fields, residual signatures are dominated by additional external fields that are organized in the local time frame and that vary with magnetospheric activity. Birkeland currents have been identified, which likely close in the planetary interior at depths below the base of the crust. Near-periapsis magnetic field measurements at altitudes greater than 200 km have tantalizing hints of crustal fields, but crustal sources cannot be distinguished from core fields, nor cleanly separated from external fields. I will report on recent data acquired at altitudes as low as 25 km that have the potential to resolve these issues. The presence of remanent crustal fields would have profound implications for Mercury's thermal and dynamical histories.

  20. Eruptive solar magnetic fields

    NASA Technical Reports Server (NTRS)

    Low, B. C.

    1981-01-01

    The quasi-steady evolution of solar magnetic fields in response to gradual photospheric changes is considered, with particular attention given to the threshold of a sudden eruption in the solar atmosphere. The formal model of an evolving, force-free field dependent on two Cartesian coordinates is extended to a field which is not force free but in static equilibrium with plasma pressure and gravity. The basic physics is illustrated through the evolution of a loop-shaped electric current sheet enclosing a potential bipolar field with footpoints rooted in the photosphere. A free-boundary problem is posed and then solved for the equilibrium configuration of the current sheet in a hydrostatically supported isothermal atmosphere. As the footpoints move apart to spread a constant photospheric magnetic flux over a larger region, the equilibria available extend the field to increasing heights.

  1. Radiation drag in the field of a non-spherical source

    NASA Astrophysics Data System (ADS)

    Bini, D.; Geralico, A.; Passamonti, A.

    2015-01-01

    The motion of a test particle in the gravitational field of a non-spherical source endowed with both mass and mass quadrupole moment is investigated when a test radiation field is also present. The background is described by the Erez-Rosen solution, which is a static space-time belonging to the Weyl class of solutions to the vacuum Einstein's field equations, and reduces to the familiar Schwarzschild solution when the quadrupole parameter vanishes. The radiation flux has a fixed but arbitrary (non-zero) angular momentum. The interaction with the radiation field is assumed to be Thomson-like, i.e. the particles absorb and re-emit radiation, thus suffering for a friction-like drag force. Such an additional force is responsible for the Poynting-Robertson effect, which is well established in the framework of Newtonian gravity and has been recently extended to the general theory of relativity. The balance between gravitational attraction, centrifugal force and radiation drag leads to the occurrence of equilibrium circular orbits which are attractors for the surrounding matter for every fixed value of the interaction strength. The presence of the quadrupolar structure of the source introduces a further degree of freedom: there exists a whole family of equilibrium orbits parametrized by the quadrupole parameter, generalizing previous works. This scenario is expected to play a role in the context of accretion matter around compact objects.

  2. Magnetic Fields in Galaxies

    NASA Astrophysics Data System (ADS)

    Beck, Rainer

    The origin and evolution of cosmic magnetic fields, their strength and structure in intergalactic space, their first occurrence in young galaxies, and their dynamical importance for galaxy evolution remain widely unknown. Radio synchrotron emission, its polarization and its Faraday rotation are powerful tools to study the strength and structure of magnetic fields in galaxies. Unpolarized radio synchrotron emission traces isotropic turbulent fields which are strongest in spiral arms and bars (20-30 μG) and in central starburst regions (50-100 μG). Such fields are dynamically important; they can affect gas flows and drive gas inflows in central regions. Polarized radio emission traces ordered fields which can be regular or anisotropic turbulent, generated from isotropic turbulent fields by compression or shear. The strongest ordered fields of 10-15 μG strength are generally found in interarm regions and follow the orientation of adjacent gas spiral arms. In galaxies with strong density waves, ordered (anisotropic turbulent) fields are also observed at the inner edges of the spiral arms. Ordered fields with spiral patterns exist in grand-design, barred and flocculent galaxies, and in central regions of starburst galaxies. Ordered fields in interacting galaxies have asymmetric distributions and are an excellent tracer of past interactions between galaxies or with the intergalactic medium. Irregular galaxies host isotropic turbulent fields often of similar strength as in spiral galaxies, but only weak ordered fields. Faraday rotation measures (RM) of the diffuse polarized radio emission from the disks of several galaxies reveal large-scale spiral patterns that can be described by the superposition of azimuthal modes; these are signatures of regular fields generated by a mean-field α -Ω dynamo. So far no indications were found in external galaxies of large-scale field reversals, like the one in the Milky Way. Ordered magnetic fields are also observed in radio halos around edge-on galaxies out to large distances from the plane, with X-shaped patterns. In the outflow cone above a starburst region of NGC 253, RM data indicate a helical magnetic field.

  3. High field superconducting magnets

    NASA Technical Reports Server (NTRS)

    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.

  4. Planetary magnetic fields

    NASA Technical Reports Server (NTRS)

    Stevenson, D. J.

    1983-01-01

    Observations of planetary magnetic fields are synthesized with current knowledge of the composition and evolution of planets and the sources of planetary magnetism. The observations for earth, Jupiter, Saturn, Mercury, Venus, the moon, Mars, and small bodies and meteorites are summarized. The evolution and structure of the terrestrial planets, of Jupiter and Saturn, and of Uranus and Neptune are discussed in detail. Possible sources of planetary magnetism are discussed, and estimates are established which are sufficient in most cases to identify whether an observed field is likely to be the consequence of dynamo generation. Predictions of the existence or nonexistence of dynamos are offered for each large planet or satellite in the solar system.

  5. Magnetic Signatures on Planets Without Magnetic Fields

    NASA Astrophysics Data System (ADS)

    McEnroe, S. A.; Dyar, M. D.; Brown, L. B.

    2002-03-01

    On extraterrestrial bodies with no present day magnetic fields, the majority of the magnetic signature must come from high coercivity phases such as hemo-ilmenite, ilmenohematite, or very fine-grained magnetite.

  6. Crustal Magnetic Fields

    NASA Technical Reports Server (NTRS)

    Taylor, Patrick T.; Ravat, D.; Frawley, James J.

    1999-01-01

    Cosmos 49, Polar Orbit Geophysical Observatory (POGO) (Orbiting Geophysical Observatory (OGO-2, 4 and 6)) and Magsat have been the only low-earth orbiting satellites to measure the crustal magnetic field on a global scale. These missions revealed the presence of long- wavelength (> 500 km) crustal anomalies predominantly located over continents. Ground based methods were, for the most part, unable to record these very large-scale features; no doubt due to the problems of assembling continental scale maps from numerous smaller surveys acquired over many years. Questions arose as to the source and nature of these long-wave length anomalies. As a result there was a great stimulant given to the study of the magnetic properties of the lower crust and upper mantle. Some indication as to the nature of these deep sources has been provided by the recent results from the deep crustal drilling programs. In addition, the mechanism of magnetization, induced or remanent, was largely unknown. For computational ease these anomalies were considered to result solely from induced magnetization. However, recent results from Mars Orbiter Laser Altimeter (MOLA), a magnetometer-bearing mission to Mars, have revealed crustal anomalies with dimensions similar to the largest anomalies on Earth. These Martian features could only have been produced by remanent magnetization, since Mars lacks an inducing field. The origin of long-wavelength crustal anomalies, however, has not been completely determined. Several large crustal magnetic anomalies (e.g., Bangui, Kursk, Kiruna and Central Europe) will be discussed and the role of future satellite magnetometer missions (Orsted, SUNSAT and Champ) in their interpretation evaluated.

  7. A Topology for the Penumbral Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Snchez Almeida, J.

    We describe a scenario for the topology of the magnetic field in penumbrae that accounts for recent observations showing upflows, downflows, and reverse magnetic polarities. According to our conjecture, short narrow magnetic loops fill the penumbral photosphere. Flows along these arched field lines are responsible for both the Evershed effect and the convective transport. This scenario seems to be qualitatively consistent with most existing observations, including the dark cores in penumbral filaments reported by Scharmer et al. Each bright filament with dark core would be a system of two paired convective rolls with the dark core tracing the common lane where the plasma sinks down. The magnetic loops would have a hot footpoint in one of the bright filament and a cold footpoint in the dark core. The scenario fits in most of our theoretical prejudices (siphon flows along field lines, presence of overturning convection, drag of field lines by downdrafts, etc). If the conjecture turns out to be correct, the mild upward and downward velocities observed in penumbrae must increase upon improving the resolution. This and other observational tests to support or disprove the scenario are put forward.

  8. Chiral drag force

    NASA Astrophysics Data System (ADS)

    Rajagopal, Krishna; Sadofyev, Andrey V.

    2015-10-01

    We provide a holographic evaluation of novel contributions to the drag force acting on a heavy quark moving through strongly interacting plasma. The new contributions are chiral in the sense that they act in opposite directions in plasmas containing an excess of left- or right-handed quarks. The new contributions are proportional to the coefficient of the axial anomaly, and in this sense also are chiral. These new contributions to the drag force act either parallel to or antiparallel to an external magnetic field or to the vorticity of the fluid plasma. In all these respects, these contributions to the drag force felt by a heavy quark are analogous to the chiral magnetic effect (CME) on light quarks. However, the new contribution to the drag force is independent of the electric charge of the heavy quark and is the same for heavy quarks and antiquarks, meaning that these novel effects do not in fact contribute to the CME current. We show that although the chiral drag force can be non-vanishing for heavy quarks that are at rest in the local fluid rest frame, it does vanish for heavy quarks that are at rest in a suitably chosen frame. In this frame, the heavy quark at rest sees counterpropagating momentum and charge currents, both proportional to the axial anomaly coefficient, but feels no drag force. This provides strong concrete evidence for the absence of dissipation in chiral transport, something that has been predicted previously via consideration of symmetries. Along the way to our principal results, we provide a general calculation of the corrections to the drag force due to the presence of gradients in the flowing fluid in the presence of a nonzero chemical potential. We close with a consequence of our result that is at least in principle observable in heavy ion collisions, namely an anticorrelation between the direction of the CME current for light quarks in a given event and the direction of the kick given to the momentum of all the heavy quarks and antiquarks in that event.

  9. External Electromagnetic Fields of a Slowly Rotating Magnetized Star with Nonvanishing Gravitomagnetic Charge

    NASA Astrophysics Data System (ADS)

    Ahmedov, B. J.; Khugaev, A. V.; Rakhmatov, N. I.

    2008-09-01

    We write Maxwell equations in the external background spacetime of a slowly rotating magnetized NUT star and find analytical solutions after separating them into angular and radial parts. The star is considered isolated and in vacuum, with monopolar configuration model for the stellar magnetic field. The contribution to the external field from the NUT charge and frame-dragging effect are considered in detail.

  10. Coronal Magnetic Field Models

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

    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.

  11. THE GALACTIC MAGNETIC FIELD

    SciTech Connect

    Jansson, Ronnie; Farrar, Glennys R.

    2012-12-10

    With this Letter, we complete our model of the Galactic magnetic field (GMF), by using the WMAP7 22 GHz total synchrotron intensity map and our earlier results to obtain a 13-parameter model of the Galactic random field, and to determine the strength of the striated random field. In combination with our 22-parameter description of the regular GMF, we obtain a very good fit to more than 40,000 extragalactic Faraday rotation measures and the WMAP7 22 GHz polarized and total intensity synchrotron emission maps. The data call for a striated component to the random field whose orientation is aligned with the regular field, having zero mean and rms strength Almost-Equal-To 20% larger than the regular field. A noteworthy feature of the new model is that the regular field has a significant out-of-plane component, which had not been considered earlier. The new GMF model gives a much better description of the totality of data than previous models in the literature.

  12. The Galactic Magnetic Field

    NASA Astrophysics Data System (ADS)

    Jansson, Ronnie; Farrar, Glennys R.

    2012-12-01

    With this Letter, we complete our model of the Galactic magnetic field (GMF), by using the WMAP7 22 GHz total synchrotron intensity map and our earlier results to obtain a 13-parameter model of the Galactic random field, and to determine the strength of the striated random field. In combination with our 22-parameter description of the regular GMF, we obtain a very good fit to more than 40,000 extragalactic Faraday rotation measures and the WMAP7 22 GHz polarized and total intensity synchrotron emission maps. The data call for a striated component to the random field whose orientation is aligned with the regular field, having zero mean and rms strength ?20% larger than the regular field. A noteworthy feature of the new model is that the regular field has a significant out-of-plane component, which had not been considered earlier. The new GMF model gives a much better description of the totality of data than previous models in the literature.

  13. Global solar magnetic fields

    NASA Astrophysics Data System (ADS)

    Hoeksema, J. T.

    The global solar magnetic field greatly affects the corona, heliosphere, and terrestrial environment as well as revealing much about the Sun itself. It may be useful to think of the global field in two ways: as an aggregate of many small scale processes and as an entity. When considering the origin and evolution of the global field, one immediately focuses on the smaller-scale features and processes that it comprises. These include the emergence of active regions, the interaction of new and existing flux patterns, the distortion and dispersal of flux over the surface by convective motions, the phenomena that produce the emergence of patterns with various periods, and the influence of convection and rotation at various depths on flux tubes. When contemplating the effects of the global field, one often focuses on it as an entity or on its large-scale features. Examples are the reversal of the polar fields, the asymmetry between the north and south hemispheres, the dipole or quadrupole structure of the coronal field and its observation of the Earth as 2 or 4 polarity sectors, and the rigid rotation seen in coronal holes. Both views help us appreciate the significance of the global field.

  14. Superhorizon magnetic fields

    NASA Astrophysics Data System (ADS)

    Campanelli, Leonardo

    2016-03-01

    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 wave number k evolves, after inflation, according to the values of k ηe , nk , and Ωk , where ηe is the conformal time at the end of inflation, nk is the number density spectrum of inflation-produced photons, and Ωk is the phase difference between the two Bogoliubov coefficients which characterize the state of that mode at the end of inflation. For any realistic inflationary magnetogenesis scenario, we find that nk-1≪|k ηe|≪1 , and three evolutionary scenarios are possible: (i) |Ωk∓π |=O (1 ) , in which case the evolution of the magnetic spectrum Bk(η ) is adiabatic, a2Bk(η )=const , with a being the expansion parameter; (ii) |Ωk∓π |≪|k ηe| , in which case the evolution is superadiabatic, a2Bk(η )∝η ; (iii) |k ηe|≪|Ωk∓π |≪1 or |k ηe|˜|Ωk∓π |≪1 , in which case an early phase of adiabatic evolution is followed, after a time η⋆˜|Ωk∓π |/k , by a superadiabatic evolution. Once a given mode reenters the horizon, it remains frozen into the plasma and then evolves adiabatically till today. As a corollary of our results, we find that inflation-generated magnetic fields evolve adiabatically on all scales and for all times in conformal-invariant free Maxwell theory, while they evolve superadiabatically after inflation on superhorizon scales in the nonconformal-invariant Ratra model, where the inflaton is kinematically coupled to the electromagnetic field. The latter result supports and, somehow, clarifies our recent claim that the Ratra model can account for the presence of cosmic magnetic fields without suffering from both backreaction and strong-coupling problems.

  15. Low field magnetic resonance imaging

    DOEpatents

    Pines, Alexander (Berkeley, CA); Sakellariou, Dimitrios (Billancourt, FR); Meriles, Carlos A. (Fort Lee, NJ); Trabesinger, Andreas H. (London, GB)

    2010-07-13

    A method and system of magnetic resonance imaging does not need a large homogenous field to truncate a gradient field. Spatial information is encoded into the spin magnetization by allowing the magnetization to evolve in a non-truncated gradient field and inducing a set of 180 degree rotations prior to signal acquisition.

  16. Electric and magnetic fields

    NASA Technical Reports Server (NTRS)

    Kaufman, H. R.; Robinson, R. S.; Etters, R. D.

    1982-01-01

    A number of energy momentum anomalies are described that result from the use of Abraham-Lorentz electromagnetic theory. These anomalies have in common the motion of charged bodies or current carrying conductors relative to the observer. The anomalies can be avoided by using the nonflow approach, based on internal energy of the electromagnetic field. The anomalies can also be avoided by using the flow approach, if all contributions to flow work are included. The general objective of this research is a fundamental physical understanding of electric and magnetic fields which, in turn, might promote the development of new concepts in electric space propulsion. The approach taken is to investigate quantum representations of these fields.

  17. Drag measurements on a laminar flow body of revolution in Langley's 13 inch magnetic suspension and balance system. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Dress, David A.

    1988-01-01

    Low-speed wind tunnel drag force measurements were taken on a laminar flow body of revolution free of support interference. This body was tested at zero incidence in the NASA Langley 13 inch Magnetic Suspension and Balance System (MSBS). The primary objective of these tests was to substantiate the drag force measuring capabilities of the 13 inch MSBS. A secondary objective was to obtain support interference free drag measurements on an axisymmetric body of interest. Both objectives were met. The drag force calibrations and wind-on repeatability data provide a means of assessing the drag force measuring capabilities of the 13 inch MSBS. The measured drag coefficients for this body are of interest to researchers actively involved in designing minimum drag fuselage shapes. Additional investigations included: the effects of fixing transition; the effects of fins installed in the tail; surface flow visualizations using both liquid crystals and oil flow; and base pressure measurements using a one-channel telemetry system. Two drag prediction codes were used to assess their usefulness in estimating overall body drag. These theoretical results did not compare well with the measured values because of the following: incorrect or non-existent modeling of a laminar separation bubble on the body and incorrect of non-existent estimates of base pressure drag.

  18. Magnetic nanoparticle motion in external magnetic field

    NASA Astrophysics Data System (ADS)

    Usov, N. A.; Liubimov, B. Ya

    2015-07-01

    A set of equations describing the motion of a free magnetic nanoparticle in an external magnetic field in a vacuum, or in a medium with negligibly small friction forces is postulated. The conservation of the total particle momentum, i.e. the sum of the mechanical and the total spin momentum of the nanoparticle is taken into account explicitly. It is shown that for the motion of a nanoparticle in uniform magnetic field there are three different modes of precession of the unit magnetization vector and the director that is parallel the particle easy anisotropy axis. These modes differ significantly in the precession frequency. For the high-frequency mode the director points approximately along the external magnetic field, whereas the frequency and the characteristic relaxation time of the precession of the unit magnetization vector are close to the corresponding values for conventional ferromagnetic resonance. On the other hand, for the low-frequency modes the unit magnetization vector and the director are nearly parallel and rotate in unison around the external magnetic field. The characteristic relaxation time for the low-frequency modes is remarkably long. This means that in a rare assembly of magnetic nanoparticles there is a possibility of additional resonant absorption of the energy of alternating magnetic field at a frequency that is much smaller compared to conventional ferromagnetic resonance frequency. The scattering of a beam of magnetic nanoparticles in a vacuum in a non-uniform external magnetic field is also considered taking into account the precession of the unit magnetization vector and director.

  19. Polar Magnetic Field Experiment

    NASA Technical Reports Server (NTRS)

    Russell, C. T.

    1999-01-01

    This grant covers the initial data reduction and analysis of the magnetic field measurements of the Polar spacecraft. At this writing data for the first three years of the mission have been processed and deposited in the key parameter database. These data are also available in a variety of time resolutions and coordinate systems via a webserver at UCLA that provides both plots and digital data. The flight software has twice been reprogrammed: once to remove a glitch in the data where there were rare collisions between commands in the central processing unit and once to provide burst mode data at 100 samples per second on a regular basis. The instrument continues to function as described in the instrument paper (1.1 in the bibliography attached below). The early observations were compared with observations on the same field lines at lower altitude. The polar magnetic measurements also proved to be most useful for testing the accuracy of MHD models. WE also made important contributions to study of waves and turbulence.

  20. Photonic Magnetic Field Sensor

    NASA Astrophysics Data System (ADS)

    Wyntjes, Geert

    2002-02-01

    Small, in-line polarization rotators or isolators to reduce feedback in fiber optic links can be the basis for excellent magnetic field sensors. Based on the giant magneto-optical (GMO) or Faraday effect in iron garnets, they with a magnetic field of a few hundred Gauss, (20 mT) for an interaction length for an optical beam of a few millimeters achieve a polarization rotation or phase shift of 45 deg (1/8 cycle). When powered by a small laser diode, with the induced linear phase shift recovered at the shot noise limit, we have demonstrated sensitivities at the 3.3 nT/Hz1/2 level for frequencies from less than 1 Hz to frequencies into the high kHz range. Through further improvements; an increase in interaction length, better materials and by far the greatest factor, the addition of a flux concentrator, sensitivities at the pT/Hz1/2 level appear to be within reach. We will detail such a design and discuss the issues that may limit achieving these goals.

  1. Magnetic Fields: Visible and Permanent.

    ERIC Educational Resources Information Center

    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)

  2. Magnetic field therapy: a review.

    PubMed

    Markov, Marko S

    2007-01-01

    There is increasing interest in using permanent magnets for therapeutic purposes encouraged by basic science publications and clinical reports. Magnetotherapy provides a non invasive, safe, and easy method to directly treat the site of injury, the source of pain and inflammation, and other types of disease. The physiological bases for the use of magnetic fields for tissue repair as well as physical principles of dosimetry and application of various magnetic fields are subjects of this review. Analysis of the magnetic and electromagnetic stimulation is followed by a discussion of the advantage of magnetic field stimulation compared with electric current and electric field stimulation. PMID:17454079

  3. Leptogenesis and primordial magnetic fields

    SciTech Connect

    Long, Andrew J.; Sabancilar, Eray; Vachaspati, Tanmay E-mail: eray.sabancilar@asu.edu

    2014-02-01

    The anomalous conversion of leptons into baryons during leptogenesis is shown to produce a right-handed helical magnetic field; in contrast, the magnetic field produced during electroweak baryogenesis is known to be left-handed. If the cosmological medium is turbulent, the magnetic field evolves to have a present day coherence scale ? 10pc and field strength ? 10{sup ?18}Gauss. This result is insensitive to the energy scale at which leptogenesis took place. Observations of the amplitude, coherence scale, and helicity of the intergalactic magnetic field promise to provide a powerful probe of physics beyond the Standard Model and the very early universe.

  4. Fast superconducting magnetic field switch

    DOEpatents

    Goren, Y.; Mahale, N.K.

    1996-08-06

    The superconducting magnetic switch or fast kicker magnet is employed with electron stream or a bunch of electrons to rapidly change the direction of flow of the electron stream or bunch of electrons. The apparatus employs a beam tube which is coated with a film of superconducting material. The tube is cooled to a temperature below the superconducting transition temperature and is subjected to a constant magnetic field which is produced by an external dc magnet. The magnetic field produced by the dc magnet is less than the critical field for the superconducting material, thus, creating a Meissner Effect condition. A controllable fast electromagnet is used to provide a magnetic field which supplements that of the dc magnet so that when the fast magnet is energized the combined magnetic field is now greater that the critical field and the superconducting material returns to its normal state allowing the magnetic field to penetrate the tube. This produces an internal field which effects the direction of motion and of the electron stream or electron bunch. The switch can also operate as a switching mechanism for charged particles. 6 figs.

  5. Fast superconducting magnetic field switch

    DOEpatents

    Goren, Yehuda (Mountain View, CA); Mahale, Narayan K. (The Woodlands, TX)

    1996-01-01

    The superconducting magnetic switch or fast kicker magnet is employed with electron stream or a bunch of electrons to rapidly change the direction of flow of the electron stream or bunch of electrons. The apparatus employs a beam tube which is coated with a film of superconducting material. The tube is cooled to a temperature below the superconducting transition temperature and is subjected to a constant magnetic field which is produced by an external dc magnet. The magnetic field produced by the dc magnet is less than the critical field for the superconducting material, thus, creating a Meissner Effect condition. A controllable fast electromagnet is used to provide a magnetic field which supplements that of the dc magnet so that when the fast magnet is energized the combined magnetic field is now greater that the critical field and the superconducting material returns to its normal state allowing the magnetic field to penetrate the tube. This produces an internal field which effects the direction of motion and of the electron stream or electron bunch. The switch can also operate as a switching mechanism for charged particles.

  6. Martian external magnetic field proxies

    NASA Astrophysics Data System (ADS)

    Langlais, Benoit; Civet, Francois

    2015-04-01

    Mars possesses no dynamic magnetic field of internal origin as it is the case for the Earth or for Mercury. Instead Mars is characterized by an intense and localized magnetic field of crustal origin. This field is the result of past magnetization and demagnetization processes, and reflects its evolution. The Interplanetary Magnetic Field (IMF) interacts with Mars' ionized environment to create an external magnetic field. This external field is weak compared to lithospheric one but very dynamic, and may hamper the detailed analysis of the internal magnetic field at some places or times. Because there are currently no magnetic field measurements made at Mars' surface, it is not possible to directly monitor the external field temporal variability as it is done in Earth's ground magnetic observatories. In this study we examine to indirect ways of quantifying this external field. First we use the Advanced Composition Explorer (ACE) mission which measures the solar wind about one hour upstream of the bow-shock resulting from the interaction between the solar wind and the Earth's internal magnetic field. These measurements are extrapolated to Mars' position taking into account the orbital configurations of the Mars-Earth system and the velocity of particles carrying the IMF. Second we directly use Mars Global Surveyor magnetic field measurements to quantify the level of variability of the external field. We subtract from the measurements the internal field which is otherwise modeled, and bin the residuals first on a spatial and then on a temporal mesh. This allows to compute daily or semi daily index. We present a comparison of these two proxies and demonstrate their complementarity. We also illustrate our analysis by comparing our Martian external field proxies to terrestrial index at epochs of known strong activity. These proxies will especially be useful for upcoming magnetic field measurements made around or at the surface of Mars.

  7. DYNAMICAL FRICTION IN A GASEOUS MEDIUM WITH A LARGE-SCALE MAGNETIC FIELD

    SciTech Connect

    Sanchez-Salcedo, F. J.

    2012-02-01

    The dynamical friction force experienced by a massive gravitating body moving through a gaseous medium is modified by sufficiently strong large-scale magnetic fields. Using linear perturbation theory, we calculate the structure of the wake generated by, and the gravitational drag force on, a body traveling in a straight-line trajectory in a uniformly magnetized medium. The functional form of the drag force as a function of the Mach number ({identical_to} V{sub 0}/c{sub s} , where V{sub 0} is the velocity of the body and c{sub s} is the sound speed) depends on the strength of the magnetic field and on the angle between the velocity of the perturber and the direction of the magnetic field. In particular, the peak value of the drag force is not near Mach number {approx}1 for a perturber moving in a sufficiently magnetized medium. As a rule of thumb, we may state that for supersonic motion, magnetic fields act to suppress dynamical friction; for subsonic motion, they tend to enhance dynamical friction. For perturbers moving along the magnetic field lines, the drag force at some subsonic Mach numbers may be stronger than at supersonic velocities. We also mention the relevance of our findings to black hole coalescence in galactic nuclei.

  8. Exposure guidelines for magnetic fields

    SciTech Connect

    Miller, G.

    1987-12-01

    The powerful magnetic fields produced by a controlled fusion experiment at Lawrence Livermore National Laboratory (LLNL) necessitated the development of personnel-exposure guidelines for steady magnetic fields. A literature search and conversations with active researchers showed that it is currently possible to develop preliminary exposure guidelines for steady magnetic fields. An overview of the results of past research into the bioeffects of magnetic fields was compiled, along with a discussion of hazards that may be encountered by people with sickle-cell anemia or medical electronic and prosthetic implants. The LLNL steady magnetic-field exposure guidelines along with a review of developments concerning the safety of time-varying fields were also presented in this compilation. Guidelines developed elsewhere for time varying fields were also given. Further research is needed to develop exposure standards for both steady or time-varying fields.

  9. Magnetic field modification of optical magnetic dipoles.

    PubMed

    Armelles, Gaspar; Caballero, Blanca; Cebollada, Alfonso; Garcia-Martin, Antonio; Meneses-Rodríguez, David

    2015-03-11

    Acting on optical magnetic dipoles opens novel routes to govern light-matter interaction. We demonstrate magnetic field modification of the magnetic dipolar moment characteristic of resonant nanoholes in thin magnetoplasmonic films. This is experimentally shown through the demonstration of the magneto-optical analogue of Babinet's principle, where mirror imaged MO spectral dependencies are obtained for two complementary magnetoplasmonic systems: holes in a perforated metallic layer and a layer of disks on a substrate. PMID:25646869

  10. Magnetic-field-dosimetry system

    SciTech Connect

    Lemon, D.K.; Skorpik, J.R.; Eick, J.L.

    1981-01-21

    A device is provided for measuring the magnetic field dose and peak field exposure. The device includes three Hall-effect sensors all perpendicular to each other, sensing the three dimensional magnetic field and associated electronics for data storage, calculating, retrieving and display.

  11. Solvent-drag bending motion of polymer gel induced by an electric field

    NASA Astrophysics Data System (ADS)

    Hirai, Toshihiro; Zheng, Jianming; Watanabe, Masashi

    1999-05-01

    Non-ionic polymer gel was found to bend and scrawl much faster than conventional polymer gels by applying d.c. electric field. The motion looks like to be an action of a biological muscle in a sense. The dimensions of the gel were 2 mm in thickness, and 7 X 5 mm2 in area. Both surface of the gel sheet was coated with thin gold film whose thickness is 0.1 (mu) . Bending angle reaches 180 degrees within 90 ms when electric field of 500 V/mm was applied. The current was around 0.03 mA under the field, suggesting that the heat generated in the motion be negligible. The gel was composed of chemically crosslinked poly(vinyl alcohol) (PVA) swollen with dimethyl sulfoxide (DMSO). Solvent loss from the gel in the action was negligible. DMSO orientation by an electric field was investigated by Raman spectroscopy. DMSO was found to flow or to generate a pressure gap under an electric field over 60 V/mm. It turned out that the orientation of DMSO does not directly induce the motion of a gel, but the electrically induced DMSO flow plays a critical role in the actuation. The electrically induced solvent flow implied that the solvent was enforced to flow from an anode side to a cathode side. The results are consistent to the observation of the bending or scrawling motion in which the cathode side is expanded much more than the anode side. As a conclusion, the concept of the 'electrically-induced solvent-drag' gel actuator provides the most promising way to a high power artificial muscle, a soft actuator, at this moment.

  12. Mercury's magnetic field and interior

    NASA Technical Reports Server (NTRS)

    Connerney, J. E. P.; Ness, N. F.

    1988-01-01

    The magnetic-field data collected on Mercury by the Mariner-10 spacecraft present substantial evidence for an intrinsic global magnetic field. However, studies of Mercury's thermal evolution show that it is most likely that the inner core region of Mercury solidified or froze early in the planet's history. Thus, the explanation of Mercury's magnetic field in the framework of the traditional planetary dynamo is less than certain.

  13. Electromagnetically induced frame dragging around astrophysical objects

    NASA Astrophysics Data System (ADS)

    Gutiérrez-Ruiz, Andrés F.; Pachón, Leonardo A.

    2015-06-01

    Frame dragging (Lense-Thirring effect) is generally associated with rotating astrophysical objects. However, it can also be generated by electromagnetic fields if electric and magnetic fields are simultaneously present. In most models of astrophysical objects, macroscopic charge neutrality is assumed and the entire electromagnetic field is characterized in terms of a magnetic dipole component. Hence, the purely electromagnetic contribution to the frame dragging vanishes. However, strange stars may possess independent electric dipole and neutron stars independent electric quadrupole moments that may lead to the presence of purely electromagnetic contributions to the frame dragging. Moreover, recent observations have shown that in stars with strong electromagnetic fields, the magnetic quadrupole may have a significant contribution to the dynamics of stellar processes. As an attempt to characterize and quantify the effect of electromagnetic frame dragging in these kinds of astrophysical objects, an analytic solution to the Einstein-Maxwell equations is constructed here on the basis that the electromagnetic field is generated by the combination of arbitrary magnetic and electric dipoles plus arbitrary magnetic and electric quadrupole moments. The effect of each multipole contribution on the vorticity scalar and the Poynting vector is described in detail. Corrections on important quantities such the innermost stable circular orbit (ISCO) and the epicyclic frequencies are also considered.

  14. Can We Predict CME Deflections Based on Solar Magnetic Field Configuration Alone?

    NASA Astrophysics Data System (ADS)

    Kay, C.; Opher, M.; Evans, R. M.

    2013-12-01

    Accurate space weather forecasting requires knowledge of the trajectory of coronal mass ejections (CMEs), including predicting CME deflections close to the Sun and through interplanetary space. Deflections of CMEs occur due to variations in the background magnetic field or solar wind speed, magnetic reconnection, and interactions with other CMEs. Using our newly developed model of CME deflections due to gradients in the background solar magnetic field, ForeCAT (Kay et al. 2013), we explore the questions: (a) do all simulated CMEs ultimately deflect to the minimum in the background solar magnetic field? (b) does the majority of the deflection occur in the lower corona below 4 Rs? ForeCAT does not include temporal variations in the magnetic field of active regions (ARs), spatial variations in the background solar wind speed, magnetic reconnection, or interactions with other CMEs. Therefore we focus on the effects of the steady state solar magnetic field. We explore two different Carrington Rotations (CRs): CR 2029 (April-May 2005) and CR 2077 (November-December 2008). Little is known about how the density and magnetic field fall with distance in the lower corona. We consider four density models derived from observations (Chen 1996, Mann et al. 2003, Guhathakurta et al. 2006, Leblanc et al. 1996) and two magnetic field models (PFSS and a scaled model). ForeCAT includes drag resulting from both CME propagation and deflection through the background solar wind. We vary the drag coefficient to explore the effect of drag on the deflection at 1 AU.

  15. Magnetic fields around evolved stars

    NASA Astrophysics Data System (ADS)

    Leal-Ferreira, M.; Vlemmings, W.; Kemball, A.; Amiri, N.; Maercker, M.; Ramstedt, S.; Olofsson, G.

    2014-04-01

    A number of mechanisms, such as magnetic fields, (binary) companions and circumstellar disks have been suggested to be the cause of non-spherical PNe and in particular collimated outflows. This work investigates one of these mechanisms: the magnetic fields. While MHD simulations show that the fields can indeed be important, few observations of magnetic fields have been done so far. We used the VLBA to observe five evolved stars, with the goal of detecting the magnetic field by means of water maser polarization. The sample consists in four AGB stars (IK Tau, RT Vir, IRC+60370 and AP Lyn) and one pPN (OH231.8+4.2). In four of the five sources, several strong maser features were detected allowing us to measure the linear and/or circular polarization. Based on the circular polarization detections, we infer the strength of the component of the field along the line of sight to be between ~30 mG and ~330 mG in the water maser regions of these four sources. When extrapolated to the surface of the stars, the magnetic field strength would be between a few hundred mG and a few Gauss when assuming a toroidal field geometry and higher when assuming more complex magnetic fields. We conclude that the magnetic energy we derived in the water maser regions is higher than the thermal and kinetic energy, leading to the conclusion that, indeed, magnetic fields probably play an important role in shaping Planetary Nebulae.

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

    NASA Astrophysics Data System (ADS)

    Adorno, T. C.; Gitman, D. M.; Shabad, A. E.

    2014-04-01

    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 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.

  17. Strain-assisted current-induced magnetization reversal in magnetic tunnel junctions: A micromagnetic study with phase-field microelasticity

    SciTech Connect

    Huang, H. B.; Hu, J. M.; Yang, T. N.; Chen, L. Q.; Ma, X. Q.

    2014-09-22

    Effect of substrate misfit strain on current-induced in-plane magnetization reversal in CoFeB-MgO based magnetic tunnel junctions is investigated by combining micromagnetic simulations with phase-field microelasticity theory. It is found that the critical current density for in-plane magnetization reversal decreases dramatically with an increasing substrate strain, since the effective elastic field can drag the magnetization to one of the four in-plane diagonal directions. A potential strain-assisted multilevel bit spin transfer magnetization switching device using substrate misfit strain is also proposed.

  18. Theory of fossil magnetic field

    NASA Astrophysics Data System (ADS)

    Dudorov, Alexander E.; Khaibrakhmanov, Sergey A.

    2015-02-01

    Theory of fossil magnetic field is based on the observations, analytical estimations and numerical simulations of magnetic flux evolution during star formation in the magnetized cores of molecular clouds. Basic goals, main features of the theory and manifestations of MHD effects in young stellar objects are discussed.

  19. Origin of cosmic magnetic fields.

    PubMed

    Campanelli, Leonardo

    2013-08-01

    We calculate, in the free Maxwell theory, the renormalized quantum vacuum expectation value of the two-point magnetic correlation function in de Sitter inflation. We find that quantum magnetic fluctuations remain constant during inflation instead of being washed out adiabatically, as usually assumed in the literature. The quantum-to-classical transition of super-Hubble magnetic modes during inflation allow us to treat the magnetic field classically after reheating, when it is coupled to the primeval plasma. The actual magnetic field is scale independent and has an intensity of few10(-12)??G if the energy scale of inflation is few10(16)??GeV. Such a field accounts for galactic and galaxy cluster magnetic fields. PMID:23971556

  20. Measurements of magnetic field alignment

    SciTech Connect

    Kuchnir, M.; Schmidt, E.E.

    1987-11-06

    The procedure for installing Superconducting Super Collider (SSC) dipoles in their respective cryostats involves aligning the average direction of their field with the vertical to an accuracy of 0.5 mrad. The equipment developed for carrying on these measurements is described and the measurements performed on the first few prototypes SSC magnets are presented. The field angle as a function of position in these 16.6 m long magnets is a characteristic of the individual magnet with possible feedback information to its manufacturing procedure. A comparison of this vertical alignment characteristic with a magnetic field intensity (by NMR) characteristic for one of the prototypes is also presented. 5 refs., 7 figs.

  1. The MAVEN Magnetic Field Investigation

    NASA Technical Reports Server (NTRS)

    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.

  2. The MAVEN Magnetic Field Investigation

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    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 resolution 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.

  3. Field-measured drag area is a key correlate of level cycling time trial performance

    PubMed Central

    Peterman, James E.; Lim, Allen C.; Ignatz, Ryan I.; Edwards, Andrew G.

    2015-01-01

    Drag area (Ad) is a primary factor determining aerodynamic resistance during level cycling and is therefore a key determinant of level time trial performance. However, Ad has traditionally been difficult to measure. Our purpose was to determine the value of adding field-measured Ad as a correlate of level cycling time trial performance. In the field, 19 male cyclists performed a level (22.1 km) time trial. Separately, field-determined Ad and rolling resistance were calculated for subjects along with projected frontal area assessed directly (AP) and indirectly (Est AP). Also, a graded exercise test was performed to determine \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{upgreek} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} }{}$\\dot {V}{O}_{2}$\\end{document}V˙O2 peak, lactate threshold (LT), and economy. \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{upgreek} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} }{}$\\dot {V}{O}_{2}$\\end{document}V˙O2 peak (\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{upgreek} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} }{}$\\mathrm{l}~\\min ^{-1}$\\end{document}lmin−1) and power at LT were significantly correlated to power measured during the time trial (r = 0.83 and 0.69, respectively) but were not significantly correlated to performance time (r = − 0.42 and −0.45). The correlation with performance time improved significantly (p < 0.05) when these variables were normalized to Ad. Of note, Ad alone was better correlated to performance time (r = 0.85, p < 0.001) than any combination of non-normalized physiological measure. The best correlate with performance time was field-measured power output during the time trial normalized to Ad (r = − 0.92). AP only accounted for 54% of the variability in Ad. Accordingly, the correlation to performance time was significantly lower using power normalized to AP (r = − 0.75) or Est AP (r = − 0.71). In conclusion, unless normalized to Ad, level time trial performance in the field was not highly correlated to common laboratory measures. Furthermore, our field-measured Ad is easy to determine and was the single best predictor of level time trial performance. PMID:26290797

  4. Cosmic Magnetic Fields - An Overview

    NASA Astrophysics Data System (ADS)

    Wielebinski, Richard; Beck, Rainer

    Magnetic fields have been known in antiquity. Aristotle attributes the first of what could be called a scientific discussion on magnetism to Thales, who lived from about 625 BC. In China “magnetic carts” were in use to help the Emperor in his journeys of inspection. Plinius comments that in the Asia Minor province of Magnesia shepherds' staffs get at times “glued” to a stone, a alodestone. In Europe the magnetic compass came through the Arab sailors who met the Portuguese explorers. The first scientific treatise on magnetism, “De Magnete”, was published by William Gilbert who in 1600 described his experiments and suggested that the Earth was a huge magnet. Johannes Kepler was a correspondent of Gilbert and at times suggested that planetary motion was due to magnetic forces. Alas, this concept was demolished by Isaac Newton,who seeing the falling apple decided that gravity was enough. This concept of dealing with gravitational forces only remains en vogue even today. The explanations why magnetic effects must be neglected go from “magnetic energy is only 1% of gravitation” to “magnetic fields only complicate the beautiful computer solutions”. What is disregarded is the fact that magnetic effects are very directional(not omni-directional as gravity) and also the fact that magnetic fields are seen every where in our cosmic universe.

  5. The effect of sting interference at low speeds on the drag coefficient of an ellipsoidal body using a magnetic suspension and balance system

    NASA Technical Reports Server (NTRS)

    Newcomb, A. W.

    1988-01-01

    A Boltz body of revolution (fineness ratio 7.5:1) was tested in the Southampton University Magnetic Suspension and Balance System. The effects of sting interference on the drag coefficient of the model at zero angle of attack were noted as well as the effects on drag coefficient values at boundary layer trips. The drag coefficient values were compared with other sources and seemed to show agreement. The pressure distribution over the rear of the model with no sting interference was investigated including the use of boundary layer trips.

  6. PREPROCESSING MAGNETIC FIELDS WITH CHROMOSPHERIC LONGITUDINAL FIELDS

    SciTech Connect

    Yamamoto, Tetsuya T.; Kusano, K.

    2012-06-20

    Nonlinear force-free field (NLFFF) extrapolation is a powerful tool for the modeling of the magnetic field in the solar corona. However, since the photospheric magnetic field does not in general satisfy the force-free condition, some kind of processing is required to assimilate data into the model. In this paper, we report the results of new preprocessing for the NLFFF extrapolation. Through this preprocessing, we expect to obtain magnetic field data similar to those in the chromosphere. In our preprocessing, we add a new term concerning chromospheric longitudinal fields into the optimization function proposed by Wiegelmann et al. We perform a parameter survey of six free parameters to find minimum force- and torque-freeness with the simulated-annealing method. Analyzed data are a photospheric vector magnetogram of AR 10953 observed with the Hinode spectropolarimeter and a chromospheric longitudinal magnetogram observed with SOLIS spectropolarimeter. It is found that some preprocessed fields show the smallest force- and torque-freeness and are very similar to the chromospheric longitudinal fields. On the other hand, other preprocessed fields show noisy maps, although the force- and torque-freeness are of the same order. By analyzing preprocessed noisy maps in the wave number space, we found that small and large wave number components balance out on the force-free index. We also discuss our iteration limit of the simulated-annealing method and magnetic structure broadening in the chromosphere.

  7. Mathematical modelling for trajectories of magnetic nanoparticles in a blood vessel under magnetic field

    NASA Astrophysics Data System (ADS)

    Sharma, Shashi; Katiyar, V. K.; Singh, Uaday

    2015-04-01

    A mathematical model is developed to describe the trajectories of a cluster of magnetic nanoparticles in a blood vessel for the application of magnetic drug targeting (MDT). The magnetic nanoparticles are injected into a blood vessel upstream from a malignant tissue and are captured at the tumour site with help of an applied magnetic field. The applied field is produced by a rare earth cylindrical magnet positioned outside the body. All forces expected to significantly affect the transport of nanoparticles were incorporated, including magnetization force, drag force and buoyancy force. The results show that particles are slow down and captured under the influence of magnetic force, which is responsible to attract the magnetic particles towards the magnet. It is optimized that all particles are captured either before or at the centre of the magnet (z≤0) when blood vessel is very close proximity to the magnet (d=2.5 cm). However, as the distance between blood vessel and magnet (d) increases (above 4.5 cm), the magnetic nanoparticles particles become free and they flow away down the blood vessel. Further, the present model results are validated by the simulations performed using the finite element based COMSOL software.

  8. Thermometers in Low Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Gerak, G.; Begu, S.

    2010-09-01

    In this article the effect of low amplitude DC magnetic fields on different types of thermometers is discussed. By means of a precision water-cooled electromagnet, the effect of a magnetic field on platinum resistance thermometers, thermistors, and type T, J, and K thermocouples was investigated, while thermometers were thermally stabilized in thermostatic baths. Four different baths were used for temperatures from 77 K (-196 C) to 353 K (80 C): liquid nitrogen bath (nitrogen boiling point at atmospheric pressure), ice-point bath, room-temperature air bath, and hot-water bath. The generated DC magnetic field of high relative precision (2 10-4 at 1 T, 4 10-5 short-term stability) and high relative uniformity (2 10-5 over 1 cm2, 10 mm gap) had a magnetic flux density of 1 T in the center of the gap between the magnet pole caps. The results indicate a magnetic effect of up to 100 mK due to a 1 T magnetic field for the types of thermocouples composed of ferromagnetic materials (Fe, Cr, Ni). For platinum resistance thermometers, thermistors, and non-magnetic type T thermocouples, the detected magnetic effect was weaker, i.e., under 10 mK.

  9. Low-Magnetic-Field Magnetars

    NASA Astrophysics Data System (ADS)

    Turolla, Roberto; Esposito, Paolo

    2013-11-01

    It is now widely accepted that soft gamma repeaters and anomalous X-ray pulsars are the observational manifestations of magnetars, i.e. sources powered by their own magnetic energy. This view was supported by the fact that these "magnetar candidates" exhibited, without exception, a surface dipole magnetic field (as inferred from the spin-down rate) in excess of the electron critical field (≃ 4.4×1013 G). The recent discovery of fully qualified magnetars, SGR 0418+5729 and Swift J1822.3-1606, with dipole magnetic field well in the range of ordinary radio pulsars posed a challenge to the standard picture, showing that a very strong field is not necessary for the onset of magnetar activity (chiefly bursts and outbursts). Here we summarize the observational status of the low-magnetic-field magnetars and discuss their properties in the context of the mainstream magnetar model and its main alternatives.

  10. The magnetic field of Neptune

    NASA Technical Reports Server (NTRS)

    Connerney, J. E. P.; Acuna, Mario H.; Ness, Norman F.

    1992-01-01

    A model is given of the planetary magnetic field of Neptune based on a spherical harmonic analysis of the observations obtained by the Voyager 2. Generalized inverse techniques are used to partially solve a severely underdetermined inverse problem, and the resulting model is nonunique since the observations are limited in spatial distribution. Dipole, quadrupole, and octupole coefficients are estimated independently of other terms, and the parameters are shown to be well constrained by the measurement data. The large-scale features of the magnetic field including dipole tilt, offset, and harmonic content are found to characterize a magnetic field that is similar to that of Uranus. The traits of Neptune's magnetic field are theorized to relate to the 'ice' interior of the planet, and the dynamo-field generation reflects this poorly conducting planet.

  11. Preflare magnetic and velocity fields

    NASA Technical Reports Server (NTRS)

    Hagyard, M. J.; Gaizauskas, V.; Chapman, G. A.; Deloach, A. C.; Gary, G. A.; Jones, H. P.; Karpen, J. T.; Martres, M.-J.; Porter, J. G.; Schmeider, B.

    1986-01-01

    A characterization is given of the preflare magnetic field, using theoretical models of force free fields together with observed field structure to determine the general morphology. Direct observational evidence for sheared magnetic fields is presented. The role of this magnetic shear in the flare process is considered within the context of a MHD model that describes the buildup of magnetic energy, and the concept of a critical value of shear is explored. The related subject of electric currents in the preflare state is discussed next, with emphasis on new insights provided by direct calculations of the vertical electric current density from vector magnetograph data and on the role of these currents in producing preflare brightenings. Results from investigations concerning velocity fields in flaring active regions, describing observations and analyses of preflare ejecta, sheared velocities, and vortical motions near flaring sites are given. This is followed by a critical review of prevalent concepts concerning the association of flux emergence with flares

  12. Three-dimensional Atmospheric Circulation Models of HD 189733b and HD 209458b with Consistent Magnetic Drag and Ohmic Dissipation

    NASA Astrophysics Data System (ADS)

    Rauscher, Emily; Menou, Kristen

    2013-02-01

    We present the first three-dimensional circulation models for extrasolar gas giant atmospheres with geometrically and energetically consistent treatments of magnetic drag and ohmic dissipation. Atmospheric resistivities are continuously updated and calculated directly from the flow structure, strongly coupling the magnetic effects with the circulation pattern. We model the hot Jupiters HD 189733b (T eq ≈ 1200 K) and HD 209458b (T eq ≈ 1500 K) and test planetary magnetic field strengths from 0 to 30 G. We find that even at B = 3 G the atmospheric structure and circulation of HD 209458b are strongly influenced by magnetic effects, while the cooler HD 189733b remains largely unaffected, even in the case of B = 30 G and super-solar metallicities. Our models of HD 209458b indicate that magnetic effects can substantially slow down atmospheric winds, change circulation and temperature patterns, and alter observable properties. These models establish that longitudinal and latitudinal hot spot offsets, day-night flux contrasts, and planetary radius inflation are interrelated diagnostics of the magnetic induction process occurring in the atmospheres of hot Jupiters and other similarly forced exoplanets. Most of the ohmic heating occurs high in the atmosphere and on the dayside of the planet, while the heating at depth is strongly dependent on the internal heat flux assumed for the planet, with more heating when the deep atmosphere is hot. We compare the ohmic power at depth in our models, and estimates of the ohmic dissipation in the bulk interior (from general scaling laws), to evolutionary models that constrain the amount of heating necessary to explain the inflated radius of HD 209458b. Our results suggest that deep ohmic heating can successfully inflate the radius of HD 209458b for planetary magnetic field strengths of B >= 3-10 G.

  13. THREE-DIMENSIONAL ATMOSPHERIC CIRCULATION MODELS OF HD 189733b AND HD 209458b WITH CONSISTENT MAGNETIC DRAG AND OHMIC DISSIPATION

    SciTech Connect

    Rauscher, Emily; Menou, Kristen

    2013-02-10

    We present the first three-dimensional circulation models for extrasolar gas giant atmospheres with geometrically and energetically consistent treatments of magnetic drag and ohmic dissipation. Atmospheric resistivities are continuously updated and calculated directly from the flow structure, strongly coupling the magnetic effects with the circulation pattern. We model the hot Jupiters HD 189733b (T {sub eq} Almost-Equal-To 1200 K) and HD 209458b (T {sub eq} Almost-Equal-To 1500 K) and test planetary magnetic field strengths from 0 to 30 G. We find that even at B = 3 G the atmospheric structure and circulation of HD 209458b are strongly influenced by magnetic effects, while the cooler HD 189733b remains largely unaffected, even in the case of B = 30 G and super-solar metallicities. Our models of HD 209458b indicate that magnetic effects can substantially slow down atmospheric winds, change circulation and temperature patterns, and alter observable properties. These models establish that longitudinal and latitudinal hot spot offsets, day-night flux contrasts, and planetary radius inflation are interrelated diagnostics of the magnetic induction process occurring in the atmospheres of hot Jupiters and other similarly forced exoplanets. Most of the ohmic heating occurs high in the atmosphere and on the dayside of the planet, while the heating at depth is strongly dependent on the internal heat flux assumed for the planet, with more heating when the deep atmosphere is hot. We compare the ohmic power at depth in our models, and estimates of the ohmic dissipation in the bulk interior (from general scaling laws), to evolutionary models that constrain the amount of heating necessary to explain the inflated radius of HD 209458b. Our results suggest that deep ohmic heating can successfully inflate the radius of HD 209458b for planetary magnetic field strengths of B {>=} 3-10 G.

  14. AC photovoltaic module magnetic fields

    SciTech Connect

    Jennings, C.; Chang, G.J.; Reyes, A.B.; Whitaker, C.M.

    1997-12-31

    Implementation of alternating current (AC) photovoltaic (PV) modules, particularly for distributed applications such as PV rooftops and facades, may be slowed by public concern about electric and magnetic fields (EMF). This paper documents magnetic field measurements on an AC PV module, complementing EMF research on direct-current PV modules conducted by PG and E in 1993. Although not comprehensive, the PV EMF data indicate that 60 Hz magnetic fields (the EMF type of greatest public concern) from PV modules are comparable to, or significantly less than, those from household appliances. Given the present EMF research knowledge, AC PV module EMF may not merit considerable concern.

  15. Magnetic fields and scintillator performance

    SciTech Connect

    Green, D.; Ronzhin, A.; Hagopian, V.

    1995-06-01

    Experimental data have shown that the light output of a scintillator depends on the magnitude of the externally applied magnetic fields, and that this variation can affect the calorimeter calibration and possibly resolution. The goal of the measurements presented here is to study the light yield of scintillators in high magnetic fields in conditions that are similar to those anticipated for the LHC CMS detector. Two independent measurements were performed, the first at Fermilab and the second at the National High Magnetic Field Laboratory at Florida State University.

  16. Magnetoconvection in sheared magnetic fields

    SciTech Connect

    Bian, N. H.; Garcia, O. E.

    2008-10-15

    The development of magnetoconvection in a sheared magnetic field is investigated. The equilibrium magnetic field B{sub 0} is horizontal and its orientation varies linearly along the vertical axis. Preliminary consideration of the transition from the inertial to the viscous regime of the gravitational resistive interchange instability, reveals that the latter is characterized by the existence of viscoresistive boundary layers of vertical width which scales as Q{sup -1/6}, where Q is the Chandrasekhar number. The situation is analogous to the one encountered in magnetically confined laboratory plasmas, where convective flows are constrained by the magnetic shear to develop in boundary layers located around resonant magnetic surfaces in order to fulfill the 'interchange condition'k{center_dot}B{sub 0}=0, where k is the wave vector of the magnetic perturbation. It follows that when the effect of thermal diffusion is taken into account in the process, convection can only occur above a certain critical value of the Rayleigh number which scales as Q{sup 2/3} for large Q. At the onset, the convection pattern is a superposition of identically thin convective rolls everywhere aligned with the local magnetic field lines and which therefore adopt the magnetic field geometry, a situation also reminiscent of the penumbra of sunspots. Using this degeneracy, equations describing the weakly nonlinear state are obtained and discussed. A reduced magnetohydrodynamic description of magnetoconvection is introduced. Since it is valid for arbitrary magnetic field configurations, it allows a simple extension to the case where there exists an inclination between the direction of gravity and the plane spanned by the equilibrium magnetic field. These reduced magnetohydrodynamic equations are proposed as a powerful tool for further investigations of magnetoconvection in more complex field line geometries.

  17. Magnetic field structure of Mercury

    NASA Astrophysics Data System (ADS)

    Hiremath, K. M.

    2012-04-01

    Recently planet Mercury - an unexplored territory in our solar system - has been of much interest to the scientific community due to recent flybys of the spacecraft MESSENGER that discovered its intrinsic stationary and large-scale dipole like magnetic field structure with an intensity of 300nT confirming Mariner 10 observations. In the present study, with the observed constraint of Mercury's atmospheric magnetic field structure, internal magnetic field structure is modeled as a solution of magnetic diffusion equation. In this study, Mercury's internal structure mainly consists of a stable stratified fluid core and the convective mantle. For simplicity, magnetic diffusivity in both parts of the structure is considered to be uniform and constant with a value represented by a suitable averages. It is further assumed that vigorous convection in the mantle disposes of the electric currents leading to a very high diffusivity in that region. Thus, in order to satisfy observed atmospheric magnetic field structure, Mercury's most likely magnetic field structure consists of a solution of MHD diffusion equation in the core and a combined multipolar (dipole and quadrupole like magnetic field structures embedded in the uniform field) solution of a current free like magnetic field structure in the mantle and in the atmosphere. With imposition of appropriate boundary conditions at the core-mantle boundary for the first two diffusion eigen modes, in order to satisfy the observed field structure, present study puts the constraint on Mercury's core radius to be 2000km. From the estimated magnetic diffusivity and the core radius, it is also possible to estimate the two diffusion eigen modes with their diffusion time scales of 8.6 and 3.7 billion years respectively suggesting that the planet inherits its present-day magnetic field structure from the solar Nebula. It is proposed that permanency of such a large-scale magnetic field structure of the planet is attained during Mercury's early evolutionary history of heavy bombardments by the asteroids and comets supporting the giant impact hypothesis for the formation of Mercury.

  18. Magnetic Field Generation in Stars

    NASA Astrophysics Data System (ADS)

    Ferrario, Lilia; Melatos, Andrew; Zrake, Jonathan

    2015-10-01

    Enormous progress has been made on observing stellar magnetism in stars from the main sequence (particularly thanks to the MiMeS, MAGORI and BOB surveys) 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.

  19. The polar heliospheric magnetic field

    NASA Technical Reports Server (NTRS)

    Jokipii, J. R.; Kota, J.

    1989-01-01

    It is suggested that the polar heliospheric magnetic field, at large heliocentric distances, may deviate considerably from the generally accepted Archimedean spiral. Instead, it is suggested that the large-scale field near the poles may be dominated by randomly-oriented transverse magnetic fields with magnitude much larger than the average spiral. The average vector field is still the spiral, but the average magnitude may be much larger. In addition, the field direction is transverse to the radial direction most of the time instead of being nearly radial. This magnetic-field structure has important consequences for the transport of cosmic rays. Preliminary model calculations suggest changes in the radial gradient of galactic cosmic rays which may improve agreement with observations.

  20. Measuring Earth's Magnetic Field Simply.

    ERIC Educational Resources Information Center

    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)

  1. Galactic dynamics with magnetic fields

    NASA Astrophysics Data System (ADS)

    Howes, Gregory Gershom

    Contributing to the effort to unravel the origin and understand the evolution of magnetic fields in the universe, this dissertation focuses on the evolution of the Galactic magnetic field through analytical and numerical approaches. The current state of research into magnetism in the universe is reviewed, with particular emphasis on synthesizing a unified view of the various environments in which magnetic fields have been observed. An analytical examination of the stability of magnetic fields in a sheared flow is presented. Gradient Particle Magnetohydro-dynamics is a new computational algorithm for MHD simulation developed here with validation tests of the method to display its capabilities. Adaptive Particle Refinement provides a general adaptive framework into which this new algorithm can be fit, promising improved computational efficiency and better stability characteristics. A model for numerical evolution of the magnetized Galactic disk is described. Preliminary results of two-dimensional Galactic disk simulations are analyzed to demonstrate the potential of this new computational tool and lend insight into the evolution of the Galactic magnetic field.

  2. Magnetic fields on the Sun

    NASA Astrophysics Data System (ADS)

    Howard, R.

    1982-02-01

    Synoptic observations of solar magnetic fields are discussed. Seen in long-term averages, the magnetic fields of the Sun show distinctive behavior. The active-region latitudes are characterized by magnetic fields of preceding polarity. The flow of following polarity fields to make up the polar fields is episodic, not continuous. This field motion is a directed poleward flow and is not due to diffusion. The total magnetic flux on the solar surface, which is related linearly to the calcium emission in integrated sunlight, varies from activity minimum to maximum by a factor of 2 or 3. Nearly all this flux is seen at active-region latitudes-only about 1% is at the poles. The total flux of the Sun disappears from the surface at a very rapid rate and is replaced by new flux. All the field and flux patterns that we see originate in active-region latitudes. The polar magnetic fields of the Sun were observed to change polarity recently. The variations of the full-disk solar flux are shown to lead to the proper rotation rate of the Sun, but the phase of the variations is constant for only a year or two at most.

  3. The magnetic field of Neptune

    NASA Technical Reports Server (NTRS)

    Connerney, J. E. P.; Acuna, Mario H.; Ness, Norman F.

    1991-01-01

    The Voyager 2 observations obtained during the Neptune encounter are used to develop a spherical harmonic model of the planetary magnetic field of Neptune. The model yields a dipole of magnitude 0.14 G R(N) exp 3, tilted by 47 deg toward 72 deg west longitude. Neptune's quadrupole is equal to or exceeding in magnitude the surface dipole field; the octupole is also very large, although less well constrained. The characteristics of the Neptune's magnetic field are illustrated using contour maps of the field on the planet's surface.

  4. Optical sensor of magnetic fields

    DOEpatents

    Butler, M.A.; Martin, S.J.

    1986-03-25

    An optical magnetic field strength sensor for measuring the field strength of a magnetic field comprising a dilute magnetic semi-conductor probe having first and second ends, longitudinally positioned in the magnetic field for providing Faraday polarization rotation of light passing therethrough relative to the strength of the magnetic field. Light provided by a remote light source is propagated through an optical fiber coupler and a single optical fiber strand between the probe and the light source for providing a light path therebetween. A polarizer and an apparatus for rotating the polarization of the light is provided in the light path and a reflector is carried by the second end of the probe for reflecting the light back through the probe and thence through the polarizer to the optical coupler. A photo detector apparatus is operably connected to the optical coupler for detecting and measuring the intensity of the reflected light and comparing same to the light source intensity whereby the magnetic field strength may be calculated.

  5. Magnetic field induced dynamical chaos

    SciTech Connect

    Ray, Somrita; Baura, Alendu; Bag, Bidhan Chandra

    2013-12-15

    In this article, we have studied the dynamics of a particle having charge in the presence of a magnetic field. The motion of the particle is confined in the xy plane under a two dimensional nonlinear potential. We have shown that constant magnetic field induced dynamical chaos is possible even for a force which is derived from a simple potential. For a given strength of the magnetic field, initial position, and velocity of the particle, the dynamics may be regular, but it may become chaotic when the field is time dependent. Chaotic dynamics is very often if the field is time dependent. Origin of chaos has been explored using the Hamiltonian function of the dynamics in terms of action and angle variables. Applicability of the present study has been discussed with a few examples.

  6. Magnetic field induced dynamical chaos

    SciTech Connect

    Ray, Somrita; Baura, Alendu; Bag, Bidhan Chandra

    2013-12-15

    In this article, we have studied the dynamics of a particle having charge in the presence of a magnetic field. The motion of the particle is confined in the x–y plane under a two dimensional nonlinear potential. We have shown that constant magnetic field induced dynamical chaos is possible even for a force which is derived from a simple potential. For a given strength of the magnetic field, initial position, and velocity of the particle, the dynamics may be regular, but it may become chaotic when the field is time dependent. Chaotic dynamics is very often if the field is time dependent. Origin of chaos has been explored using the Hamiltonian function of the dynamics in terms of action and angle variables. Applicability of the present study has been discussed with a few examples.

  7. Magnetic fields in spiral galaxies

    NASA Astrophysics Data System (ADS)

    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 forthcoming radio telescopes like the Square Kilometre Array.

  8. Magnetic field effect on hemin

    NASA Astrophysics Data System (ADS)

    Bartoszek, Mariola; Balanda, Maria; Skrzypek, Danuta; Drzazga, Zofia

    2001-12-01

    Magnetic behaviour of hemin has been investigated by means of magnetostatic methods, AC-susceptibility measurements and EPR spectroscopy. The measurements were made using polycrystalline and oriented samples of hemin in the temperature range 2.3-292 K and in magnetic fields up to 6 T. In the paramagnetic region, the susceptibility obeys the Curie-Weiss law with positive Curie-Weiss temperature. At low temperature, a rapid increase of the susceptibility is noticed but up to 2 K no long-range correlations are observed. The studies show that the iron ion in hemin exists in two spin states ( S= {5}/{2} and {1}/{2}). The applied magnetic field increases the occupation of the low-spin state. Hemin shows high-field-induced magnetic anisotropy which, similar to the susceptibility, increases with decreasing temperature.

  9. Magnetic fields in quiescent prominences

    NASA Technical Reports Server (NTRS)

    Van Ballegooijen, A. A.; Martens, P. C. H.

    1990-01-01

    The origin of the axial fields in high-latitude quiescent prominences is considered. The fact that almost all quiescent prominences obey the same hemisphere-dependent rule strongly suggests that the solar differential rotation plays an important role in producing the axial fields. However, the observations are inconsistent with the hypothesis that the axial fields are produced by differential rotation acting on an existing coronal magnetic field. Several possible explanations for this discrepancy are considered. The possibility that the sign of the axial field depends on the topology of the magnetic field in which the prominence is embedded is examined, as is the possibility that the neutral line is tilted with respect to the east-west direction, so that differential rotation causes the neutral line also to rotate with time. The possibility that the axial fields of quiescent prominences have their origin below the solar surface is also considered.

  10. The magnetic field of Uranus

    NASA Technical Reports Server (NTRS)

    Connerney, J. E. P.; Acuna, Mario H.; Ness, Norman F.

    1987-01-01

    Aspherical harmonic model of the planetary magnetic field of Uranus is obtained from the Voyager 2 encounter observations using generalized inverse techniques which allow partial solutions to complex (underdetermined) problems. The Goddard Space Flight Center 'Q3' model is characterized by a large dipole tilt (58.6 deg) relative to the rotation axis, a dipole moment of 0.228 G R(Uranus radii cubed) and an unusually large quadrupole moment. Characteristics of this complex model magnetic field are illustrated using contour maps of the field on the planet's surface and discussed in the context of possible dynamo generation in the relatively poorly conducting 'ice' mantle.

  11. Magnetic fields and coronal heating

    NASA Astrophysics Data System (ADS)

    Golub, L.; Maxson, C.; Rosner, R.; Vaiana, G. S.; Serio, S.

    1980-05-01

    General considerations concerning the scaling properties of magnetic-field-related coronal heating mechanisms are used to build a two-parameter model for the heating of closed coronal regions. The model predicts the way in which coronal temperature and electron density are related to photospheric magnetic field strength and the size of the region, using the additional constraint provided by the scaling law of Rosner, Tucker, and Vaiana. The model duplicates the observed scaling of total thermal energy content with total longitudinal flux; it also predicts a relation between the coronal energy density (or pressure) and the longitudinal field strength modified by the region scale size.

  12. Magnetic Fields in Molecular Clouds

    NASA Astrophysics Data System (ADS)

    Bourke, T. L.; Goodman, A. A.

    2004-09-01

    Magnetic fields are believed to play an important role in the evolution of molecular clouds, from their large scale structure to dense cores, protostellar envelopes, and protoplanetary disks. How important is unclear, and whether magnetic fields are the dominant force driving star formation at any scale is also unclear. In this review we examine the observational data which address these questions, with particular emphasis on high angular resolution observations. Unfortunately the data do not clarify the situation. It is clear that the fields are important, but to what degree we don't yet know. Observations to date have been limited by the sensitivity of available telescopes and instrumentation. In the future ALMA and the SKA in particular should provide great advances in observational studies of magnetic fields, and we discuss which observations are most desirable when they become available.

  13. The magnetic field of Mercury

    NASA Technical Reports Server (NTRS)

    Ness, N. F.

    1979-01-01

    The paper examines the magnetic field observations and their analyses relating to the determination of the Mercury magnetic field. Methods of analyzing data included: (1) comparison of bow shock and magnetopause relative positions at Mercury to the earth, (2) direct spherical harmonic analysis, (3) magnetosphere modeling by an image dipole, and (4) scaling of a mathematical model for the terrestrial magnetosphere. Dipole moments were determined using partial quadrupole and octupole terms to improve the least-square fit of models to observations; analyses by method (2) yield a convergent series of dipole moments values considered to best represent the intrinsic planetary field. Finally, it is suggested that the origin of the magnetic field of Mercury cannot be uniquely determined, but the sources of convective energy may be radiogenic decay and heat release, gravitational settling, and differentiation of processional torques.

  14. Fibrillation of solar magnetic fields

    NASA Astrophysics Data System (ADS)

    Ashbourn, J. M. A.; Woods, L. C.

    2009-06-01

    Solar magnetic structures are often observed in the form of flux tubes composed of a number of smaller elements called fibres or threads, although theoretically such concentrations should not appear but should be flattened by magnetic diffusivity into a uniform, low intensity field. In this paper we describe a mechanism which may be responsible for the fibrillation and also for the very large diffusivity which dissipates magnetic flux tubes in hours instead of years. Firstly, the electric current associated with magnetic field gradients usually increases the local electron temperature and reduces the resistivity, so that the current becomes concentrated into sheets or streamers. Secondly, the magnetic field gradients continue to increase until the current magnitude reaches its limit, which is determined by the electron-ion streaming instability. Then with appropriate temperature and number densities, the Larmor radius of the ions overlaps the near discontinuity in Bz and generates a sharply peaked fluid motion at the edge that is close to the thermal speed. Finally, the resulting vorticity generates an axial magnetic field opposing Bz in the term partial B_z/partial t, and if this is sufficient to change the sign of this term, the very unstable backward heat equation results. This instability repeatedly switches on and off and maintains the magnetic structure in the fibrillated form. Such structures are eventually eliminated by magnetic diffusivity in the usual way, but because of the fluctuations in Bz, this occurs at a vastly increased rate. We show that this phenomenon increases the magnetic diffusivity, D, by a factor 108 in agreement with some observations of plasma loops and supergranules.

  15. Phonon-drag magnetothermopower in Rashba spin-split two-dimensional electron systems.

    PubMed

    Biswas, Tutul; Ghosh, Tarun Kanti

    2013-10-16

    We study the phonon-drag contribution to the thermoelectric power in a quasi-two-dimensional electron system confined in GaAs/AlGaAs heterostructure in the presence of both Rashba spin-orbit interaction and perpendicular magnetic field at very low temperature. It is observed that the peaks in the phonon-drag thermopower split into two when the Rashba spin-orbit coupling constant is strong. This splitting is a direct consequence of the Rashba spin-orbit interaction. We show the dependence of phonon-drag thermopower on both magnetic field and temperature numerically. A power-law dependence of phonon-drag magnetothermopower on the temperature in the Bloch-Gruneisen regime is found. We also extract the exponent of the temperature dependence of phonon-drag thermopower for different parameters like electron density, magnetic field, and the spin-orbit coupling constant. PMID:24047679

  16. Radial Transport of Large-scale Magnetic Fields in Accretion Disks. II. Relaxation to Steady States

    NASA Astrophysics Data System (ADS)

    Takeuchi, Taku; Okuzumi, Satoshi

    2014-12-01

    We study the time evolution of a large-scale magnetic flux threading an accretion disk. The induction equation of the mean poloidal field is solved under the standard viscous disk model. Magnetic flux evolution is controlled by two timescales: one is the timescale of the inward advection of the magnetic flux, ?adv. This is induced by the dragging of the flux by the accreting gas. The other is the outward diffusion timescale of the magnetic flux ?dif. We consider diffusion due to the Ohmic resistivity. These timescales can be significantly different from the disk viscous timescale ?disk. The behaviors of the magnetic flux evolution are quite different depending on the magnitude relationship of the timescales ?adv, ?dif, and ?disk. The most interesting phenomena occur when ?adv Lt ?dif, ?disk. In such a case, the magnetic flux distribution approaches a quasi-steady profile much faster than the viscous evolution of the gas disk, and the magnetic flux has also been tightly bundled to the inner part of the disk. In the inner part, although the poloidal magnetic field becomes much stronger than the interstellar magnetic field, the field strength is limited to the maximum value that is analytically given by our previous work. We also find a condition for the initial large magnetic flux, which is a fossil of the magnetic field dragging during the early phase of star formation that survives for a duration in which significant gas disk evolution proceeds.

  17. Magnetic field fluctuations during substorms

    NASA Technical Reports Server (NTRS)

    Fairfield, D. H.

    1971-01-01

    Before a magnetospheric substorm and during its early phases the magnetic field magnitude in the geomagnetic tail increases and field lines in the nighttime hemisphere assume a more tail-like configuration. Before the substorm onset a minimum amount of magnetic flux is observed to cross the neutral sheet which means that the neutral sheet currents attain their most earthward locations and their greatest current densities. This configuration apparently results from an increased transport of magnetic flux to the tail caused by a southward interplanetary magnetic field. The field begins relaxing toward a more dipolar configuration at the time of a substorm onset with the recovery probably occurring first between 6 and 10 R sub E. This recovery must be associated with magnetospheric convection which restores magnetic flux to the dayside hemisphere. Field aligned currents appear to be required to connect magnetospheric currents to the auroral electrojets, implying that a net current flows in a limited range of longitudes. Space measurements supporting current systems are limited. More evidence exists for the occurrence of double current sheets which do not involve net current at a given longitude.

  18. Computer program documentation for a subcritical wing design code using higher order far-field drag minimization

    NASA Technical Reports Server (NTRS)

    Kuhlman, J. M.; Shu, J. Y.

    1981-01-01

    A subsonic, linearized aerodynamic theory, wing design program for one or two planforms was developed which uses a vortex lattice near field model and a higher order panel method in the far field. The theoretical development of the wake model and its implementation in the vortex lattice design code are summarized and sample results are given. Detailed program usage instructions, sample input and output data, and a program listing are presented in the Appendixes. The far field wake model assumes a wake vortex sheet whose strength varies piecewise linearly in the spanwise direction. From this model analytical expressions for lift coefficient, induced drag coefficient, pitching moment coefficient, and bending moment coefficient were developed. From these relationships a direct optimization scheme is used to determine the optimum wake vorticity distribution for minimum induced drag, subject to constraints on lift, and pitching or bending moment. Integration spanwise yields the bound circulation, which is interpolated in the near field vortex lattice to obtain the design camber surface(s).

  19. Indoor localization using magnetic fields

    NASA Astrophysics Data System (ADS)

    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 hallways with different kinds of pillars, doors and elevators. All in all, this dissertation contributes the following: 1) provides a framework for understanding the presence of ambient magnetic fields indoors and utilizing them to solve the indoor localization problem; 2) develops an application that is independent of the user and the smart phones and 3) requires no other infrastructure since it is deployed on a device that encapsulates the sensing, computing and inferring functionalities, thereby making it a novel contribution to the mobile and pervasive computing domain.

  20. Magnetic field of the Earth

    NASA Astrophysics Data System (ADS)

    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 of electromagnetism. According to a rule of the left hand: if the magnetic field in a kernel is directed to drawing, electric current are directed to an axis of rotation of the Earth, - a action of force clockwise (to West). Definition of the force causing drift a kernel according to the law of Ampere F = IBlsin. Powerful force 3,5 × 1012 Nyton, what makes drift of the central part of a kernel of the Earth on 0,2 the longitude in year to West, and also it is engine of the mechanism of movement of slabs together with continents. Movement of a core of the Earth carry out around of a terrestrial axis one circulation in the western direction in 2000 of years. Linear speed of rotation of a kernel concerning a mantle on border the mantle a kernel: V = × 3,471 × 10 = 3,818 × 10 m/s = 33 m/day = 12 km/years. Considering greater viscosity of a mantle, the powerful energy at rotation of a kernel seize a mantle and lithospheric slabs and makes their collisions as a result of which there are earthquakes and volcano. Continents Northern and Southern America every year separate from the Europe and Africa on several centimeters. Atlantic ocean as a result of movement of these slabs with such speed was formed for 200 million years, that in comparison with the age of the Earth - several billions years, not so long time. Drift of a kernel in the western direction is a principal cause of delay of speed of rotation of the Earth. Flow of radial electric currents allot according to the law of Joule - Lenz, the quantity of warmth : Q = I2Rt = IUt, of thermal energy 6,92 × 1017 calories/year. This defines heating of a kernel and the Earth as a whole. In the valley of the median-Atlantic ridge having numerous volcanos, the lava flow constantly thus warm up waters of Atlantic ocean. It is a fact the warm current Gulf Stream. Thawing of a permafrost and ices of Arctic ocean, of glaciers of Greenland and Antarctica is acknowledgement: the warmth of earth defines character of thawing of glaciers and a permafrost. This is a global warming. The version of the author: the periods of inversion of a magnetic field of the Earth determine cycles of the Ice Age. At inversions of a magnetic field when B=0, radial electric currents are small or are absent, excretion of thermal energy minimally or an equal to zero,it is the beginning of the cooling the Earth and offensive of the Ice Age. Disappearance warm current Gulf Stream warming the north of the Europe and Canada. Drift of a magnetic dipole of the Earth in a rotation the opposite to rotation of the Earth, is acknowledgement of drift of a kernel of the Earth in a rotation the opposite to rotation of the Earth and is acknowledgement of the theory « the Magnetic field of the Earth ». The author continues to develop the theory « the Magnetic field of the Earth » and invites geophysicists to accept in it participation in it.

  1. Observations of Mercury's magnetic field

    NASA Technical Reports Server (NTRS)

    Ness, N. F.; Behannon, K. W.; Lepping, R. P.; Whang, Y. C.

    1975-01-01

    Magnetic field data obtained by Mariner 10 during the third and final encounter with the planet Mercury on 16 March 1975 were studied. A well developed bow shock and modest magnetosphere, previously observed at first encounter on 29 March 1974, were again observed. In addition, a much stronger magnetic field near closest approach, 400 gamma versus 98 gamma, was observed at an altitude of 327 km and approximately 70 deg north Mercurian latitude. Spherical harmonic analysis of the data provide an estimate of the centered planetary magnetic dipole of 4.7 x 10 to the 22nd power Gauss/cu cm with the axis tilted 12 deg to the rotation axis and in the same sense as Earth's. The interplanetary field was sufficiently different between first and third encounters that in addition to the very large field magnitude observed, it argues strongly against a complex induction process generating the observed planetary field. While a possibility exists that Mercury possesses a remanent field due to magnetization early in its formation, a present day active dynamo seems to be a more likely candidate for its origin.

  2. Satellite to study earth's magnetic field

    NASA Technical Reports Server (NTRS)

    1979-01-01

    The Magnetic Field Satellite (Magsat) designed to measure the near earth magnetic field and crustal anomalies is briefly described. A scalar magnetometer to measure the magnitude of the earth's crustal magnetic field and a vector magnetometer to measure magnetic field direction as well as magnitude are included. The mission and its objectives are summarized along with the data collection and processing system.

  3. The effects of radiation drag on radial, relativistic hydromagnetic winds

    NASA Astrophysics Data System (ADS)

    Li, Zhi-Yun; Begelman, Mitchell C.; Chiueh, Tzihong

    1992-01-01

    The effects of drag on an idealized relativistic MHD wind of radial geometry are studied. The astrophysical motivation is to understand the effects of radiation drag on the dynamics of a jet or wind passing through the intense radiation field of an accreting compact object. From a critical point analysis, it is found that a slow magnetosonic point can appear in a dragged flow even in the absence of gravitational force, as a result of a balance between the drag force and the combination of thermal pressure and centrifugal forces. As in the undragged case, the Alfven point does not impose any constraints on the flow. Although it is formally possible for a dragged flow to possess more than one fast magnetosonic point, it is shown that this is unlikely in practice. In the limit of a 'cold', centrifugally driven flow, it is shown that the fast magnetosonic point moves to infinite radius, just as in the drag-free case. For a given mass flux, the total energy output carried to infinity, and the final partition between the kinetic energy and the Poynting flux, are the same for the dragged and the drag-free flows. The main effects of radiation drag are to increase the amount of energy and angular momentum extracted from the source and to redistribute the regions where acceleration occurs in the flow. This is accomplished through the storage and release of magnetic energy, as a result of additional winding and compression of the field caused by the action of the drag. For a relativistic wind, the dissipated energy can exceed the final kinetic energy of the flow and may be comparable to the total flow energy (which is dominated by Poynting flux). The energy lost to radiation drag will appear as a Doppler-boosted beam of scattered radiation, which could dominate the background radiation if the flow is well-collimated.

  4. Photospheric and coronal magnetic fields

    SciTech Connect

    Sheeley, N.R., Jr. )

    1991-01-01

    Research on small-scale and large-scale photospheric and coronal magnetic fields during 1987-1990 is reviewed, focusing on observational studies. Particular attention is given to the new techniques, which include the correlation tracking of granules, the use of highly Zeeman-sensitive infrared spectral lines and multiple lines to deduce small-scale field strength, the application of long integration times coupled with good seeing conditions to study weak fields, and the use of high-resolution CCD detectors together with computer image-processing techniques to obtain images with unsurpassed spatial resolution. Synoptic observations of large-scale fields during the sunspot cycle are also discussed. 101 refs.

  5. ALIGNMENT BETWEEN FLATTENED PROTOSTELLAR INFALL ENVELOPES AND AMBIENT MAGNETIC FIELDS

    SciTech Connect

    Chapman, Nicholas L.; Matthews, Tristan G.; Novak, Giles; Davidson, Jacqueline A.; Goldsmith, Paul F.; Houde, Martin; Kwon, Woojin; Looney, Leslie W.; Li Zhiyun; Matthews, Brenda; Peng Ruisheng; Vaillancourt, John E.; Volgenau, Nikolaus H.

    2013-06-20

    We present 350 {mu}m polarization observations of four low-mass cores containing Class 0 protostars: L483, L1157, L1448-IRS2, and Serp-FIR1. This is the second paper in a larger survey aimed at testing magnetically regulated models for core-collapse. One key prediction of these models is that the mean magnetic field in a core should be aligned with the symmetry axis (minor axis) of the flattened young stellar object inner envelope (aka pseudodisk). Furthermore, the field should exhibit a pinched or hourglass-shaped morphology as gravity drags the field inward toward the central protostar. We combine our results for the four cores with results for three similar cores that were published in the first paper from our survey. An analysis of the 350 {mu}m polarization data for the seven cores yields evidence of a positive correlation between mean field direction and pseudodisk symmetry axis. Our rough estimate for the probability of obtaining by pure chance a correlation as strong as the one we found is about 5%. In addition, we combine together data for multiple cores to create a source-averaged magnetic field map having improved signal-to-noise ratio, and this map shows good agreement between mean field direction and pseudodisk axis (they are within 15 Degree-Sign ). We also see hints of a magnetic pinch in the source-averaged map. We conclude that core-scale magnetic fields appear to be strong enough to guide gas infall, as predicted by the magnetically regulated models. Finally, we find evidence of a positive correlation between core magnetic field direction and bipolar outflow axis.

  6. Crystal field and magnetic properties

    NASA Technical Reports Server (NTRS)

    Flood, D. J.

    1977-01-01

    Magnetization and magnetic susceptibility measurements have been made in the temperature range 1.3 to 4.2 K on powdered samples of ErH3. The susceptibility exhibits Curie-Weiss behavior from 4.2 to 2 K, and intercepts the negative temperature axis at theta = 1.05 + or - 0.05 K, indicating that the material is antiferromagnetic. The low field effective moment is 6.77 + or - 0.27 Bohr magnetons per ion. The magnetization exhibits a temperature independent contribution, the slope of which is (5 + or - 1.2) x 10 to the -6th Weber m/kg Tesla. The saturation moment is 3.84 + or - 1 - 0.15 Bohr magnetons per ion. The results can be qualitatively explained by the effects of crystal fields on the magnetic ions. No definitive assignment of a crystal field ground state can be given, nor can a clear choice between cubically or hexagonally symmetric crystal fields be made. For hexagonal symmetry, the first excited state is estimated to be 86 to 100 K above the ground state. For cubic symmetry, the splitting is on the order of 160 to 180 K.

  7. Transverse Magnetic Field Propellant Isolator

    NASA Technical Reports Server (NTRS)

    Foster, John E.

    2000-01-01

    An alternative high voltage isolator for electric propulsion and ground-based ion source applications has been designed and tested. This design employs a transverse magnetic field that increases the breakdown voltage. The design can greatly enhance the operating range of laboratory isolators used for high voltage applications.

  8. Separation of magnetic field lines

    SciTech Connect

    Boozer, Allen H.

    2012-11-15

    The field lines of magnetic fields that depend on three spatial coordinates are shown to have a fundamentally different behavior from those that depend on two coordinates. Unlike two-coordinate cases, a flux tube in a magnetic field that depends on all three spatial coordinates that has a circular cross section at one location along the tube characteristically has a highly distorted cross section at other locations. In an ideal evolution of a magnetic field, the current densities typically increase. Crudely stated, if the current densities increase by a factor {sigma}, the ratio of the long to the short distance across a cross section of a flux tube characteristically increases by e{sup 2{sigma}}, and the ratio of the longer distance to the initial radius increases as e{sup {sigma}}. Electron inertia prevents a plasma from isolating two magnetic field structures on a distance scale shorter than c/{omega}{sub pe}, which is about 10 cm in the solar corona, and reconnection must be triggered if {sigma} becomes sufficiently large. The radius of the sun, R{sub Circled-Dot-Operator }=7 Multiplication-Sign 10{sup 10}cm is about e{sup 23} times larger, so when {sigma} Greater-Than-Or-Equivalent-To 23, two lines separated by c/{omega}{sub pe} at one location can be separated by the full scale of any magnetic structures in the corona at another. The conditions for achieving a large exponentiation, {sigma}, are derived, and the importance of exponentiation is discussed.

  9. Magnetic fields in spiral galaxies

    NASA Astrophysics Data System (ADS)

    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 ?6 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).

  10. Magnetic fields in the sun

    NASA Technical Reports Server (NTRS)

    Mullan, D. J.

    1974-01-01

    The observed properties of solar magnetic fields are reviewed, with particular reference to the complexities imposed on the field by motions of the highly conducting gas. Turbulent interactions between gas and field lead to heating or cooling of the gas according to whether the field energy density is less or greater than the maximum kinetic energy density in the convection zone. The field strength above which cooling sets in is 700 gauss. A weak solar dipole field may be primeval, but dynamo action is also important in generating new flux. The dynamo is probably not confined to the convection zone, but extends throughout most of the volume of the sun. Planetary tides appear to play a role in driving the dynamo.

  11. The magnetic field of Jupiter

    NASA Technical Reports Server (NTRS)

    Acuna, M. H.; Ness, N. F.

    1976-01-01

    The paper is concerned mainly with the intrinsic planetary field which dominates the inner magnetosphere up to a distance of 10 to 12 Jovian radii where other phenomena, such as ring currents and diamagnetic effects of trapped charged particles, become significant. The main magnetic field of Jupiter as determined by in-situ observations by Pioner 10 and 11 is found to be relatively more complex than a simple offset tilted dipole. Deviations from a simple dipole geometry lead to distortions of the charged particle L shells and warping of the magnetic equator. Enhanced absorption effects associated with Io and Amalthea are predicted. The results are consistent with the conclusions derived from extensive radio observations at decimetric and decametric wavelengths for the planetary field.

  12. Oxide superconductors under magnetic field

    NASA Technical Reports Server (NTRS)

    Kitazawa, K.

    1991-01-01

    One of the current most serious problems for the oxide superconductors from the standpoint of practical application is the various novel features derived mainly from their extremely short coherence. In particular, the coherence length so far observed in the cuprate superconductors is in the range of 0.1 nm perpendicular to the CuO2 plane. This seems to be creating most of the difficulties in the device fabrication and in the performance under the magnetic field. Some of the superconducting properties under the magnetic field will be discussed in terms of the short coherence length. A model will be presented based on the gradual strengthening of the pinning force with decrease in temperature and the weak coupling at the grain boundaries. Secondly, the broadening of the superconducting transition under the magnetic field is discussed. This is observed significantly only when the field is applied perpendicular to the basal plane and the relative orientation of the current to the field is insignificant in determining the extent of broadening. Besides, the change in the strength of the pinning force does not affect the width of the broadening. From these observations discussions will be made on a model based on the giant fluctuation. Based on this model, it is predicted that the coherence length along the c-axis will be the single most important material parameter to determine the performance of the superconductor under a strong magnetic field. It seems that BYCO is superior in this regard to Bi- or Tl-systems as far as the performance at 77 K is considered, although another material with the coherence length slightly longer along the c-axis is still highly desired.

  13. Oxide superconductors under magnetic field

    NASA Technical Reports Server (NTRS)

    Kitazawa, K.

    1990-01-01

    One of the current most serious problems for the oxide superconductors from the standpoint of practical application is the various novel features derived mainly from their extremely short coherence. In particular, the coherence length so far observed in the cuprate superconductors is in the range of 0.1 nm perpendicular to the CuO2 plane. This seems to be creating most of the difficulties in the device fabrication and in the performance under the magnetic field. Some of the superconducting properties under the magnetic field will be discussed in terms of the short coherence length. A model will be presented based on the gradual strengthening of the pinning force with decrease in temperature and the weak coupling at the grain boundaries. Secondly, the broadening of the superconducting transition under the magnetic field is discussed. This is observed significantly only when the field is applied perpendicular to the basal plane and the relative orientation of the current to the field is insignificant in determining the extent of the broadening. Besides, the change in the strength of the pinning force does not affect the width of the broadening. From these observations discussions will be made on a model based on the giant fluctuation. Based on this model, it is predicted that the coherence length along the c-axis will be the single most important material parameter to determine the performance of the superconductor under a strong magnetic field. It seems that BYCO is superior in this regard to Bi- or Tl-systems as far as the performance at 77 K is considered, although another material with the coherence length slightly longer along the c-axis is still highly desired.

  14. A high-field superferric NMR magnet.

    PubMed

    Huson, F R; Bryan, R N; MacKay, W W; Herrick, R C; Colvin, J; Ford, J J; Pissanetzky, S; Plishker, G A; Rocha, R; Schmidt, W

    1993-01-01

    Strong, extensive magnetic fringe fields are a significant problem with magnetic resonance imaging magnets. This is particularly acute with 4-T, whole-body research magnets. To date this problem has been addressed by restricting an extensive zone around the unshielded magnet or by placing external unsaturated iron shielding around the magnet. This paper describes a solution to this problem which uses superconducting coils closely integrated with fully saturated iron elements. A 4-T, 30-cm-bore prototype, based on this design principle, was built and tested. The 5 G fringe field is contained within 1 meter of the magnet bore along the z axis. Homogeneity of the raw magnetic field is 10 ppm over 30% of the magnet's diameter after passive shimming. Compared with an unshielded magnet, 20% less superconductor is required to generate the magnetic field. Images and spectra are presented to demonstrate the magnet's viability for magnetic resonance imaging and spectroscopy. PMID:8419740

  15. The HMI Magnetic Field Pipeline

    NASA Astrophysics Data System (ADS)

    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

  16. Magnetic fields and coronal heating

    SciTech Connect

    Golub, L.; Maxson, C.; Rosner, R.; Serio, S.; Vaiana, G.S.

    1980-05-15

    General considerations concerning the scaling properties of magnetic-field--related colonal heating mechanisms are used to build a two-parameter model for the heating of closed coronal regions. The model perdicts the way in which coronal temperature and electron density are related to photospheric magnetic field strength and the size of the region, using the additional constraint provided by the scaling law of rosner, tucker, and Viaiana. The model successfully duplicates the observed scaling of total thermal energy content with total longitudinal flux; it also predict a relation between the coronal energy density (or pressure) and the longitudinal field strength modified by the region scale size. The observational data yield a similar relation, pproportional/sup 1.6/. A parameter of the theory, which is evaluated by fitting to the data, is the product ..cap alpha..upsilon/sub phi/, where ..cap alpha.. is the ratio of azimuthal to longitudinal magnetic field and upsilon/sub phi/ is the effective twisting velocity of the loop footpoints, which supplies the energy for coronal heating.

  17. Explaining Mercury's peculiar magnetic field

    NASA Astrophysics Data System (ADS)

    Wicht, Johannes; Cao, Hao; Heyner, Daniel; Dietrich, Wieland; Christensen, Ulrich R.

    2014-05-01

    MESSENGER magnetometer data revealed that Mercury's magnetic field is not only particularly weak but also has a peculiar geometry. The MESSENGER team finds that the location of the magnetic equator always lies significantly north of the geographic equator, is largely independent of the distance to the planet, and also varies only weakly with longitude. The field is best described by an axial dipole that is offset to the north by about 20% of the planetary radius. In terms of classical Gauss coefficients, this translates into a low axial dipole component of g10= -190 nT but a relatively large axial quadrupole contribution that amounts to roughly 40% of this value. The axial octupole is also sizable while higher harmonic contributions are much weaker. Very remarkable is also the fact that the equatorial dipole contribution is very small, consistent with a dipole tilt below 0.8 degree, and this is also true for the other non-axisymmetic field contributions. We analyze several numerical dynamos concerning their capability of explaining Mercury's magnetic field. Classical schemes geared to model the geomagnetic field typically show a much weaker quadrupole component and thus a smaller offset. The onset only becomes larger when the dynamo operates in the multipolar regime at higher Rayleigh numbers. However, since the more complex dynamics generally promotes all higher multipole contributions the location of the magnetic equator varies strongly with longitude and distance to the planet. The situation improves when introducing a stably stratified outer layer in the dynamo region, representing either a rigid FeS layer or a sub-adiabatic core-mantle boundary heat flux. This layer filters out the higher harmonic contributions and the field not only becomes sufficiently weak but also assumes a Mercury like offset geometry during a few percent of the simulation time. To increase the likelihood for the offset configuration, the north-south symmetry must be permanently broken and we explore two scenarios. Increasing the heat flux through the northern hemisphere of the core-mantle boundary is an obvious choice but is not supported by current models for Mercury's mantle. We find that a combination of internal rather than bottom driving and an increased heat flux through the equatorial region of the core-mantle boundary also promotes the required symmetry breaking and results in very Mercury like fields. The reason is that the imposed heat flux pattern, though being equatorially symmetric, lowers the critical Rayleigh number for the onset of equatorially anti-symmetric convection modes. In both scenarios, a stably stratified layer or a feedback coupling to the magnetospheric field is required for lowering the field strength to Mercury-like values.

  18. Field errors in superconducting magnets

    SciTech Connect

    Barton, M.Q.

    1982-01-01

    The mission of this workshop is a discussion of the techniques for tracking particles through arbitrary accelerator field configurations to look for dynamical effects that are suggested by various theoretical models but are not amenable to detailed analysis. A major motivation for this type of study is that many of our accelerator projects are based on the use of superconducting magnets which have field imperfections that are larger and of a more complex nature than those of conventional magnets. Questions such as resonances, uncorrectable closed orbit effects, coupling between planes, and diffusion mechanisms all assume new importance. Since, simultaneously, we are trying to do sophisticated beam manipulations such as stacking, high current accelerator, long life storage, and low loss extraction, we clearly need efficient and accurate tracking programs to proceed with confidence.

  19. High Steady Magnetic Field Processing of Functional Magnetic Materials

    NASA Astrophysics Data System (ADS)

    Rivoirard, Sophie

    2013-07-01

    The materials science community has been enriched for some decades now by the "magneto-science" approach, which consists of applying a magnetic field during material processing. The development of anisotropic properties by applying a steady magnetic field is now a well-established effect in the material processing of magnetic substances, which benefits from the unidirectional and static nature of the field delivered by superconducting magnets. Among other effects, magnetic anisotropy in functional magnetic materials, which arises from the alignment of magnetic moments under external field, can be developed at various structural scales. Magnetic ordering, magnetic patterning, and texturation are at the origin of this anisotropy development. Texture is developed in materials from magnetic orientation due to magnetic forces and torques or from stored energy. In metals and alloys, for instance, this effect can occur either in their liquid state or during solid-state thermomagnetic treatments and can thus impact significantly the material functional magnetic properties. Today's improved superconducting magnet technology allows higher field intensities to be delivered more easily (1 T up to several tens of Teslas) and enables researchers to gather evidence on magnetic field effects that were formerly thought to be negligible. The magneto-thermodynamic effect is one of them and involves the magnetization energy as an additional parameter to tailor microstructures. Control of functional properties can thus result from magnetic monitoring of the phase transformation, and kinetics can be impacted by the magnetic energy contribution.

  20. Lift, Drag and Flow-field Measurements around a Single-degree-of-freedom Toy Ornithopter

    NASA Astrophysics Data System (ADS)

    Chavez Alarcon, Ramiro; Balakumar, B. J.; Allen, James

    2010-11-01

    The aerodynamics of a flight-worthy toy ornithopter under laminar inflow conditions are studied using a combination of load cell, flow visualization, high speed camera and PIV experiments. All the experiments were performed in the large wind tunnel facility at New Mexico State University, with the exception of a free flight test of the model. Measurements from a six-axis load cell were used to capture the variation of the lift and drag forces at various angles of attack, flapping frequencies and free-speed velocities. Smoke visualization is used to clearly demonstrate that the momentum flux in the downward direction during downstroke exceeds the upward momentum flux during upstroke due to the flexion of the wing and its angle of attack. This net surplus creates the lift in such ornithopter designs despite the stroke symmetry. PIV measurements are then performed at suitable locations to identify flow structures around the wing at various spanwise locations. A control volume analysis is performed to compare the momentum deficit in the wake to the load cell measurements.

  1. Field quality aspects of CBA superconducting magnets

    SciTech Connect

    Kahn, S.; Engelmann, R.; Fernow, R.; Greene, A.F.; Herrera, J.; Kirk, H.; Skaritka, J.; Wanderer, P.; Willen, E.

    1983-01-01

    A series of superconducting dipole magnets for the BNL Colliding Beam Accelerator which were manufactured to have the proper field quality characteristics has been tested. This report presents the analysis of the field harmonics of these magnets.

  2. Anisotropic Magnetism in Field-Structured Composites

    SciTech Connect

    Anderson, Robert A.; Martin, James E.; Odinek, Judy; Venturini, Eugene

    1999-06-24

    Magnetic field-structured-composites (FSCs) are made by structuring magnetic particle suspensions in uniaxial or biaxial (e.g. rotating) magnetic fields, while polymerizing the suspending resin. A uniaxial field produces chain-like particle structures, and a biaxial field produces sheet-like particle structures. In either case, these anisotropic structures affect the measured magnetic hysteresis loops, with the magnetic remanence and susceptibility increased significantly along the axis of the structuring field, and decreased slightly orthogonal to the structuring field, relative to the unstructured particle composite. The coercivity is essentially unaffected by structuring. We present data for FSCs of magnetically soft particles, and demonstrate that the altered magnetism can be accounted for by considering the large local fields that occur in FSCs. FSCS of magnetically hard particles show unexpectedly large anisotropies in the remanence, and this is due to the local field effects in combination with the large crystalline anisotropy of this material.

  3. Measurements of Solar Vector Magnetic Fields

    NASA Technical Reports Server (NTRS)

    Hagyard, M. J. (Editor)

    1985-01-01

    Various aspects of the measurement of solar magnetic fields are presented. The four major subdivisions of the study are: (1) theoretical understanding of solar vector magnetic fields; (3) techniques for interpretation of observational data; and (4) techniques for data display.

  4. Magnetic holes in the solar wind. [(interplanetary magnetic fields)

    NASA Technical Reports Server (NTRS)

    Turner, J. M.; Burlaga, L. F.; Ness, N. F.; Lemaire, J. F.

    1976-01-01

    An analysis is presented of high resolution interplanetary magnetic field measurements from the magnetometer on Explorer 43 which showed that low magnetic field intensities in the solar wind at 1 AU occur as distinct depressions or 'holes'. These magnetic holes are new kinetic-scale phenomena, having a characteristic dimension on the order of 20,000 km. They occurred at a rate of 1.5/day in the 18-day time span (March 18 to April 6, 1971) that was analyzed. Most of the magnetic holes are characterized by both a depression in the absolute value of the magnetic field, and a change in the magnetic field direction; some of these are possibly the result of magnetic merging. However, in other cases the magnetic field direction does not change; such holes are not due to magnetic merging, but might be a diamagnetic effect due to localized plasma inhomogeneities.

  5. Rotating copper plasmoid in external magnetic field

    SciTech Connect

    Pandey, Pramod K.; Thareja, Raj K.

    2013-02-15

    Effect of nonuniform magnetic field on the expanding copper plasmoid in helium and argon gases using optical emission spectroscopy and fast imaging is presented. We report a peculiar oscillatory rotation of plasmoid in magnetic field and argon ambient. The temporal variation and appearance of the dip in the electron temperature show a direct evidence of the threading and expulsion of the magnetic field lines from the plasmoid. Rayleigh Taylor instability produced at the interface separating magnetic field and plasma is discussed.

  6. Minireview: Biological effects of magnetic fields

    SciTech Connect

    Villa, M.; Mustarelli, P. ); Caprotti, M. )

    1991-01-01

    The literature about the biological effects of magnetic fields is reviewed. The authors begin by discussing the weak and/or time variable fields, responsible for subtle changes in the circadian rhythms of superior animals, which are believed to be induced by same sort of resonant mechanism. The safety issues related with the strong magnetic fields and gradients generated by clinical NMR magnets are then considered. The last portion summarizes the debate about the biological effects of strong and uniform magnetic fields.

  7. Penetration of plasma across a magnetic field

    NASA Astrophysics Data System (ADS)

    Plechaty, C.; Presura, R.; Wright, S.; Neff, S.; Haboub, A.

    2009-08-01

    Experiments were performed at the Nevada Terawatt Facility to investigate the plasma penetration across an externally applied magnetic field. In experiment, a short-pulse laser ablates a polyethylene laser target, producing a plasma which interacts with an external magnetic field. The mechanism which allows the plasma to penetrate the applied magnetic field in experiment will be discussed.

  8. Superposition of DC magnetic fields by cascading multiple magnets in magnetic loops

    NASA Astrophysics Data System (ADS)

    Sun, Fei; He, Sailing

    2015-09-01

    A novel method that can effectively collect the DC magnetic field produced by multiple separated magnets is proposed. With the proposed idea of a magnetic loop, the DC magnetic field produced by these separated magnets can be effectively superimposed together. The separated magnets can be cascaded in series or in parallel. A novel nested magnetic loop is also proposed to achieve a higher DC magnetic field in the common air region without increasing the DC magnetic field in each magnetic loop. The magnetic loop can be made by a magnetic hose, which is designed by transformation optics and can be realized by the combination of super-conductors and ferromagnetic materials.

  9. Superparamagnetic particle dynamics and mixing in a rotating capillary tube with a stationary magnetic field

    PubMed Central

    Lee, Jun-Tae; Abid, Aamir; Cheung, Ka Ho; Sudheendra, L.; Kennedy, Ian M.

    2012-01-01

    The dynamics of superparamagnetic particles subject to competing magnetic and viscous drag forces have been examined with a uniform, stationary, external magnetic field. In this approach, competing drag and magnetic forces were created in a fluid suspension of superparamagnetic particles that was confined in a capillary tube; competing viscous drag and magnetic forces were established by rotating the tube. A critical Mason number was determined for conditions under which the rotation of the capillary prevents the formation of chains from individual particles. The statistics of chain length were investigated by image analysis while varying parameters such as the rotation speed and the viscosity of the liquid. The measurements showed that the rate of particle chain formation was decreased with increased viscosity and rotation speed ; the particle dynamics could be quantified by the same dimensionless Mason number that has been demonstrated for rotating magnetic fields. The potential for enhancement of mixing in a bioassay was assessed using a fast chemical reaction that was diffusion-limited. Reducing the Mason below the critical value, so that chains were formed in the fluid, gave rise to a modest improvement in the time to completion of the reaction. PMID:23066382

  10. Interplanetary magnetic field data book

    NASA Technical Reports Server (NTRS)

    King, J. H.

    1975-01-01

    An interplanetary magnetic field (IMF) data set is presented that is uniform with respect to inclusion of cislunar IMF data only, and which has as complete time coverage as presently possible over a full solar cycle. Macroscale phenomena in the interplanetary medium (sector structure, heliolatitude variations, solar cycle variations, etc.) and other phenomena (e.g., ground level cosmic-ray events) for which knowledge of the IMF with hourly resolution is necessary, are discussed. Listings and plots of cislunar hourly averaged IMP parameters over the period November 27, 1963, to May 17, 1974, are presented along with discussion of the mutual consistency of the IMF data used herein. The magnetic tape from which the plots and listings were generated, which is available from the National Space Science Data Center (NSSDC), is also discussed.

  11. The Giotto magnetic field investigation

    NASA Technical Reports Server (NTRS)

    Neubauer, F. M.; Musmann, G.; Acuna, M. H.; Burlaga, L. F.; Ness, N. F.; Mariani, F.; Wallis, M.; Ungstrup, E.; Schmidt, H.

    1983-01-01

    The Giotto spacecraft will carry sensors for investigating the interplanetary magnetic field while en route and the interaction between the solar wind magnetoplasma and Halley's Comet neutral gas outflow during close approach. Giotto will carry an outboard biaxial fluxgate system and inboard electronics. The instrumentation draws 1.2 kW and weighs 1.31 kg. Sampling rates will be 28/sec during close encounter, covering selectable ranges from 16 nT to 65,535 nT. In-flight calibration techniques are under development to ensure magnetic cleanliness will be obtained. Measurements are also planned of the inbound bow shock, the magnetosheath and the cometary ionopause. The data will be collected as close as 1000 km from the comet surface.

  12. Bats respond to very weak magnetic fields.

    PubMed

    Tian, Lan-Xiang; Pan, Yong-Xin; Metzner, Walter; Zhang, Jin-Shuo; Zhang, Bing-Fang

    2015-01-01

    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 ?T; 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 ?T), 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. PMID:25922944

  13. Control of auroral-zone dynamics and thermodynamics by the interplanetary magnetic field dawn-dusk (Y) component

    SciTech Connect

    Sica, R.J.; Hernandez, G.; Emery, B.A.; Roble, R.G.; Smith, R.W.

    1989-09-01

    It is well known that ion drag momentum forcing is one of the primary drivers of the thermospheric wind at high latitudes. Previous theoretical and experimental studies have shown that the dawn-dusk component of the interplanetary magnetic field (IMF By) expands the classical symmetric two-cell convection pattern toward dusk (By negative) or toward dawn (By positive) in the northern hemisphere, altering the ion drag forcing on the neutral atmosphere. Measurements of the neutral dynamics associated with these convection patterns have been presented primarily at magnetic latitudes greater than 70 deg. in the polar cap.

  14. Free-solution electrophoretic separations of DNA–drag-tag conjugates on glass microchips with no polymer network and no loss of resolution at increased electric field strength

    PubMed Central

    Albrecht, Jennifer Coyne; Kerby, Matthew B.; Niedringhaus, Thomas P.; Lin, Jennifer S.; Wang, Xiaoxiao; Barron, Annelise E.

    2012-01-01

    Here, we demonstrate the potential for high-resolution electrophoretic separations of ssDNA-protein conjugates in borosilicate glass microfluidic chips, with no sieving media and excellent repeatability. Using polynucleotides of two different lengths conjugated to moderately cationic protein polymer drag-tags, we measured separation efficiency as a function of applied electric field. In excellent agreement with prior theoretical predictions of Slater et al., resolution is found to remain constant as applied field is increased up to 700 V/cm, the highest field we were able to apply. This remarkable result illustrates the fundamentally different physical limitations of Free-Solution Conjugate Electrophoresis (FSCE)-based DNA separations relative to matrix-based DNA electrophoresis. Single-stranded DNA separations in “gels” have always shown rapidly declining resolution as the field strength is increased; this is especially true for ssDNA > 400 bases in length. FSCE’s ability to decouple DNA peak resolution from applied electric field suggests the future possibility of ultra-rapid FSCE sequencing on chips. We investigated sources of peak broadening for FSCE separations on borosilicate glass microchips, using six different protein polymer drag-tags. For drag-tags with four or more positive charges, electrostatic and adsorptive interactions with pHEA-coated microchannel walls led to appreciable band-broadening, while much sharper peaks were seen for bioconjugates with nearly charge-neutral protein drag-tags. PMID:21500207

  15. Dust particles under the influence of crossed electric and magnetic fields in the sheath of an rf discharge

    NASA Astrophysics Data System (ADS)

    Puttscher, M.; Melzer, A.

    2014-12-01

    Experimental studies on the interaction of micron-sized dust particles in plasmas with external magnetic fields are presented. The particles are levitated in the sheath region of an rf discharge by gravity and electric field force under the presence of a horizontal magnetic field of up to 50 mT. It is observed that the dust particles are pushed either in the E → × B → - or in the opposite direction depending on magnetic field strength, particle properties, and discharge conditions. This transport behavior is described by a competition between horizontal ambipolar electric field force and ion and neutral drag.

  16. Dust particles under the influence of crossed electric and magnetic fields in the sheath of an rf discharge

    SciTech Connect

    Puttscher, M. Melzer, A.

    2014-12-15

    Experimental studies on the interaction of micron-sized dust particles in plasmas with external magnetic fields are presented. The particles are levitated in the sheath region of an rf discharge by gravity and electric field force under the presence of a horizontal magnetic field of up to 50 mT. It is observed that the dust particles are pushed either in the E{sup →}×B{sup →}- or in the opposite direction depending on magnetic field strength, particle properties, and discharge conditions. This transport behavior is described by a competition between horizontal ambipolar electric field force and ion and neutral drag.

  17. Graphene in high magnetic fields

    NASA Astrophysics Data System (ADS)

    Orlita, Milan; Escoffier, Walter; Plochocka, Paulina; Raquet, Bertrand; Zeitler, Uli

    2013-01-01

    Carbon-based nano-materials, such as graphene and carbon nanotubes, represent a fascinating research area aiming at exploring their remarkable physical and electronic properties. These materials not only constitute a playground for physicists, they are also very promising for practical applications and are envisioned as elementary bricks of the future of the nano-electronics. As for graphene, its potential already lies in the domain of opto-electronics where its unique electronic and optical properties can be fully exploited. Indeed, recent technological advances have demonstrated its effectiveness in the fabrication of solar cells and ultra-fast lasers, as well as touch-screens and sensitive photo-detectors. Although the photo-voltaic technology is now dominated by silicon-based devices, the use of graphene could very well provide higher efficiency. However, before the applied research to take place, one must first demonstrates the operativeness of carbon-based nano-materials, and this is where the fundamental research comes into play. In this context, the use of magnetic field has been proven extremely useful for addressing their fundamental properties as it provides an external and adjustable parameter which drastically modifies their electronic band structure. In order to induce some significant changes, very high magnetic fields are required and can be provided using both DC and pulsed technology, depending of the experimental constraints. In this article, we review some of the challenging experiments on single nano-objects performed in high magnetic and low temperature. We shall mainly focus on the high-field magneto-optical and magneto-transport experiments which provided comprehensive understanding of the peculiar Landau level quantization of the Dirac-type charge carriers in graphene and thin graphite.

  18. Magnetic field sources and their threat to magnetic media

    NASA Technical Reports Server (NTRS)

    Jewell, Steve

    1993-01-01

    Magnetic storage media (tapes, disks, cards, etc.) may be damaged by external magnetic fields. The potential for such damage has been researched, but no objective standard exists for the protection of such media. This paper summarizes a magnetic storage facility standard, Publication 933, that ensures magnetic protection of data storage media.

  19. Harmonic undulator radiations with constant magnetic field

    NASA Astrophysics Data System (ADS)

    Jeevakhan, Hussain; Mishra, G.

    2015-01-01

    Harmonic undulators has been analysed in the presence of constant magnetic field along the direction of main undulator field. The spectrum modifications in harmonic undulator radiations and intensity degradation as a function of constant magnetic field magnitude at fundamental and third harmonics have been evaluated with a numerical integration method and generalised Bessel function. The role of harmonic field to overcome the intensity reduction due to constant magnetic field and energy spread in electron beam has also been demonstrated.

  20. Magnetic Field Diagnostic for Sonoluminescence

    NASA Astrophysics Data System (ADS)

    Chou, Tom; Blackman, Eric G.

    1996-02-01

    This study is motivated by the extraordinary process of single bubble sonoluminescence (SBSL), where an acoustically driven spherical shock is thought to power the emitted radiation. We propose new experiments using an external magnetic field which can induce anisotropies in both the shock propagation and radiation pattern. The effects will depend on the temperature, density, conductivity, and size of the radiating region. Our predictions suggest that such an experiment could serve as an important diagnostic in placing bounds on experimental parameters and understanding the physics of SBSL.

  1. Nuclear magnetic resonance apparatus for pulsed high magnetic fields.

    PubMed

    Meier, Benno; Kohlrautz, Jonas; Haase, Jrgen; Braun, Marco; Wolff-Fabris, Frederik; Kampert, Erik; Herrmannsdrfer, Thomas; Wosnitza, Joachim

    2012-08-01

    A nuclear magnetic resonance apparatus for experiments in pulsed high magnetic fields is described. The magnetic field pulses created together with various magnet coils determine the requirements such an apparatus has to fulfill to be operated successfully in pulsed fields. Independent of the chosen coil it is desirable to operate the entire experiment at the highest possible bandwidth such that a correspondingly large temporal fraction of the magnetic field pulse can be used to probe a given sample. Our apparatus offers a bandwidth of up to 20 MHz and has been tested successfully at the Hochfeld-Magnetlabor Dresden, even in a very fast dual coil magnet that has produced a peak field of 94.2 T. Using a medium-sized single coil with a significantly slower dependence, it is possible to perform advanced multi-pulse nuclear magnetic resonance experiments. As an example we discuss a Carr-Purcell spin echo sequence at a field of 62 T. PMID:22938280

  2. Magnetic field of the magnetosheath

    NASA Technical Reports Server (NTRS)

    Fairfield, D. H.

    1975-01-01

    The magnetic field of the magnetosheath is most naturally discussed in terms of its steady state and its fluctuating components. Theory of the steady state field is quite well developed and its essential features have been confirmed by observations. The interplanetary field is convected through the bow shock where its magnitude is increased and its direction changed by the minimal amount necessary to preserve the normal component across the shock. Convection within the magnetosheath usually increases the magnitude still further near the subsolar point and further distortes the direction until the field is aligned approximately tangent to the magnetopause. Fluctuations of the magnetosheath field are very complex, variable and not well understood. Spectral peaks are common features which occur at different frequencies at various times. Perturbation vectors of hydromagnetic waves tend to be aligned with the shock and magnetopause surfaces. Magnetosheath waves may be generated upstream, within the magnetosheath, at the bow shock, or at the magnetopause, but the relative importance of these sources is not known.

  3. The synchronous orbit magnetic field data set

    NASA Technical Reports Server (NTRS)

    Mcpherron, R. L.

    1979-01-01

    The magnetic field at synchronous orbit is the result of superposition of fields from many sources such as the earth, the magnetopause, the geomagnetic tail, the ring current and field-aligned currents. In addition, seasonal changes in the orientation of the earth's dipole axis causes significant changes in each of the external sources. Main reasons for which the synchronous orbit magnetic field data set is a potentially valuable resource are outlined. The primary reason why synchronous magnetic field data have not been used more extensively in magnetic field modeling is the presence of absolute errors in the measured fields. Nevertheless, there exists a reasonably large collection of synchronous orbit magnetic field data. Some of these data can be useful in quantitative modeling of the earth's magnetic field. A brief description is given of the spacecraft, the magnetometers, the standard graphical data displays, and the digital data files.

  4. Permanent Magnet Ecr Plasma Source With Magnetic Field Optimization

    DOEpatents

    Doughty, Frank C. (Plano, TX); Spencer, John E. (Plano, TX)

    2000-12-19

    In a plasma-producing device, an optimized magnet field for electron cyclotron resonance plasma generation is provided by a shaped pole piece. The shaped pole piece adjusts spacing between the magnet and the resonance zone, creates a convex or concave resonance zone, and decreases stray fields between the resonance zone and the workpiece. For a cylindrical permanent magnet, the pole piece includes a disk adjacent the magnet together with an annular cylindrical sidewall structure axially aligned with the magnet and extending from the base around the permanent magnet. The pole piece directs magnetic field lines into the resonance zone, moving the resonance zone further from the face of the magnet. Additional permanent magnets or magnet arrays may be utilized to control field contours on a local scale. Rather than a permeable material, the sidewall structure may be composed of an annular cylindrical magnetic material having a polarity opposite that of the permanent magnet, creating convex regions in the resonance zone. An annular disk-shaped recurve section at the end of the sidewall structure forms magnetic mirrors keeping the plasma off the pole piece. A recurve section composed of magnetic material having a radial polarity forms convex regions and/or magnetic mirrors within the resonance zone.

  5. Magnetic field generation by rotating black holes

    NASA Technical Reports Server (NTRS)

    Leahy, D. A.; Vilenkin, A.

    1981-01-01

    A new mechanism of cosmic magnetic field generation is discussed. Neutrinos asymmetrically emitted by rotating black holes scatter on protons and produce a proton current which generates the magnetic field. It is shown that this mechanism can in principle produce a seed field sufficiently strong to account for present galactic fields.

  6. Near-Field Magnetic Dipole Moment Analysis

    NASA Technical Reports Server (NTRS)

    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.

  7. Magnetic field waves at Uranus

    NASA Technical Reports Server (NTRS)

    Smith, Charles W.; Goldstein, Melvyn L.; Lepping, Ronald P.; Mish, William H.; Wong, Hung K.

    1994-01-01

    The research efforts funded by the Uranus Data Analysis Program (UDAP) grant to the Bartol Research Institute (BRI) involved the study of magnetic field waves associated with the Uranian bow shock. Upstream wave studies are motivated as a study of the physics of collisionless shocks. Collisionless shocks in plasmas are capable of 'reflecting' a fraction of the incoming thermal particle distribution and directing the resulting energetic particle motion back into the upstream region. Once within the upstream region, the backward streaming energetic particles convey information of the approaching shock to the supersonic flow. This particle population is responsible for the generation of upstream magnetic and electrostatic fluctuations known as 'upstream waves', for slowing the incoming wind prior to the formation of the shock ramp, and for heating of the upstream plasma. The waves produced at Uranus not only differed in several regards from the observations at other planetary bow shocks, but also gave new information regarding the nature of the reflected particle populations which were largely unmeasurable by the particle instruments. Four distinct magnetic field wave types were observed upstream of the Uranian bow shock: low-frequency Alfven or fast magnetosonic waves excited by energetic protons originating at or behind the bow shock; whistler wave bursts driven by gyrating ion distributions within the shock ramp; and two whistler wave types simultaneously observed upstream of the flanks of the shock and argued to arise from resonance with energetic electrons. In addition, observations of energetic particle distributions by the LECP experiment, thermal particle populations observed by the PLS experiment, and electron plasma oscillations recorded by the PWS experiment proved instrumental to this study and are included to some degree in the papers and presentations supported by this grant.

  8. Magnetic field gradient effects on magnetic fluid stabilization

    NASA Astrophysics Data System (ADS)

    Zahn, Markus; Rosensweig, R. E.

    1987-03-01

    The penetrating finger instability which develops when a less viscous fluid pushes a more viscous fluid can be stabilized through the use of a magnetizable fluid in the presence of a magnetic field tangential to the interface. A uniform magnetic field only stabilizes suitably short waves travelling along the field lines. Transverse waves of all wavelengths and orientations are also stabilized if the tangential magnetic field is non-uniform with field decreasing in the direction away from the magnetically permeable fluid. Confirming experiments are described using laboratory sandpacks.

  9. Magnetic field observations in Comet Halley's coma

    NASA Astrophysics Data System (ADS)

    Riedler, W.; Schwingenschuh, K.; Yeroshenko, Ye. G.; Styashkin, V. A.; Russell, C. T.

    1986-05-01

    During the encounter with Comet Halley, the magnetometer (MISCHA) aboard the Vega 1 spacecraft observed an increased level of magnetic field turbulence, resulting from an upstream bow wave. Both Vega spacecraft measured a peak field strength of 70-80 nT and observed draping of magnetic field lines around the cometary obstacle. An unexpected rotation of the magnetic field vector was observed, which may reflect either penetration of magnetic field lines into a diffuse layer related to the contact surface separating the solar-wind and cometary plasma, or the persistence of pre-existing interplanetary field structures.

  10. Full 180 Magnetization Reversal with Electric Fields

    PubMed Central

    Wang, J. J.; Hu, J. M.; Ma, J.; Zhang, J. X.; Chen, L. Q.; Nan, C. W.

    2014-01-01

    Achieving 180 magnetization reversal with an electric field rather than a current or magnetic field is a fundamental challenge and represents a technological breakthrough towards new memory cell designs. Here we propose a mesoscale morphological engineering approach to accomplishing full 180 magnetization reversals with electric fields by utilizing both the in-plane piezostrains and magnetic shape anisotropy of a multiferroic heterostructure. Using phase-field simulations, we examined a patterned single-domain nanomagnet with four-fold magnetic axis on a ferroelectric layer with electric-field-induced uniaxial strains. We demonstrated that the uniaxial piezostrains, if non-collinear to the magnetic easy axis of the nanomagnet at certain angles, induce two successive, deterministic 90 magnetization rotations, thereby leading to full 180 magnetization reversals. PMID:25512070

  11. Magnetic field effects on microwave absorbing materials

    NASA Technical Reports Server (NTRS)

    Goldberg, Ira; Hollingsworth, Charles S.; Mckinney, Ted M.

    1991-01-01

    The objective of this program was to gather information to formulate a microwave absorber that can work in the presence of strong constant direct current (DC) magnetic fields. The program was conducted in four steps. The first step was to investigate the electrical and magnetic properties of magnetic and ferrite microwave absorbers in the presence of strong magnetic fields. This included both experimental measurements and a literature survey of properties that may be applicable to finding an appropriate absorbing material. The second step was to identify those material properties that will produce desirable absorptive properties in the presence of intense magnetic fields and determine the range of magnetic field in which the absorbers remain effective. The third step was to establish ferrite absorber designs that will produce low reflection and adequate absorption in the presence of intense inhomogeneous static magnetic fields. The fourth and final step was to prepare and test samples of such magnetic microwave absorbers if such designs seem practical.

  12. Magnetohydrodynamic simulations of global accretion disks with vertical magnetic fields

    SciTech Connect

    Suzuki, Takeru K.; Inutsuka, Shu-ichiro

    2014-04-01

    We report results of three-dimensional magnetohydrodynamical (MHD) simulations of global accretion disks threaded with weak vertical magnetic fields. We perform the simulations in the spherical coordinates with different temperature profiles and accordingly different rotation profiles. In the cases with a spatially constant temperature, because the rotation frequency is vertically constant in the equilibrium condition, general properties of the turbulence excited by magnetorotational instability are quantitatively similar to those obtained in local shearing box simulations. On the other hand, in the cases with a radially variable temperature profile, the vertical differential rotation, which is inevitable in the equilibrium condition, winds up the magnetic field lines in addition to the usual radial differential rotation. As a result, the coherent wound magnetic fields contribute to the Maxwell stress in the surface regions. We obtain nondimensional density and velocity fluctuations ∼0.1-0.2 at the midplane. The azimuthal power spectra of the magnetic fields show shallower slopes, ∼m {sup 0} – m {sup –1}, than those of velocity and density. The Poynting flux associated with the MHD turbulence drives intermittent and structured disk winds as well as sound-like waves toward the midplane. The mass accretion mainly occurs near the surfaces, and the gas near the midplane slowly moves outward in the time domain of the present simulations. The vertical magnetic fields are also dragged inward in the surface regions, while they stochastically move outward and inward around the midplane. We also discuss an observational implication of induced spiral structure in the simulated turbulent disks.

  13. Accelerated immunoassays based on magnetic particle dynamics in a rotating capillary tube with stationary magnetic field

    PubMed Central

    Lee, Jun-Tae; Sudheendra, L.; Kennedy, Ian M.

    2012-01-01

    A rapid and simple magnetic particle-based immunoassay has been demonstrated in a capillary mixing system. Antibody-coated micrometer size super-paramagnetic polystyrene (SPP) particles were used in an assay for rabbit IgG in a sandwich (non-competitive) format. The kinetics of the assay was compared between a plate – based system and a single capillary tube. The interaction between the antigen (R-IgG) and the antibody (anti-R-IgG) that was carried by the SPP particles in a rotating capillary was tested under a stationary magnetic field. Competing magnetic and viscous drag forces helped to enhance the interaction between the analyte and the capture antibodies on the particles. The dimensionless Mason number (Mn) was employed to characterize the magnetic particle dynamics – a previously determined critical Mason number (Mnc) was employed as a guide to the appropriate experimental conditions of magnetic field strength and rotational speed of the capillary. The advantage of the rotating capillary system included a short assay time and a reduced reactive volume (20μl). The results show that the immunoassay kinetics were improved by the formation of chains of the SPP particles for the conditions that corresponded to the critical Mason number. PMID:22931580

  14. Exploring Magnetic Fields with a Compass

    ERIC Educational Resources Information Center

    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…

  15. Deformation of Water by a Magnetic Field

    ERIC Educational Resources Information Center

    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…

  16. Magnetic field inhomogeneity in superconducting composites

    NASA Astrophysics Data System (ADS)

    Golosovsky, M.; Bontemps, N.; Davidov, D.; Waysand, G.

    1996-03-01

    The distribution of a static magnetic field in the composites consisting of YBCO powder in paraffin wax as function of temperature and volume fraction of YBCO is studied using ESR and magnetization techniques. We show that the field distribution is determined by the magnetization and the demagnetizing factor of the superconducting particles.

  17. Exploring Magnetic Fields with a Compass

    ERIC Educational Resources Information Center

    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

  18. Deformation of Water by a Magnetic Field

    ERIC Educational Resources Information Center

    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

  19. Baryon onset in a magnetic field

    NASA Astrophysics Data System (ADS)

    Haber, Alexander; Preis, Florian; Schmitt, Andreas

    2016-01-01

    The critical baryon chemical potential for the onset of nuclear matter is a function of the vacuum mass and the binding energy. Both quantities are affected by an external magnetic field. We show within two relativistic mean-field models - including magnetic catalysis, but omitting the anomalous magnetic moment - that a magnetic field increases both the vacuum mass and the binding energy. For sufficiently large magnetic fields, the effect on the vacuum mass dominates and as a result the critical baryon chemical potential is increased.

  20. Magnetic field effect on charged Brownian swimmers

    NASA Astrophysics Data System (ADS)

    Sandoval, M.; Velasco, R. M.; Jiménez-Aquino, J. I.

    2016-01-01

    We calculate the effective diffusion of a spherical self-propelled charged particle swimming at low Reynolds number, and subject to a time-dependent magnetic field and thermal agitation. We find that the presence of an external magnetic field may reduce or enhance (depending on the type of swimming and magnetic field applied) the swimmer's effective diffusion, hence we get another possible strategy to control its displacement. For swimmers performing reciprocal motion, and under an oscillating time-dependent magnetic field, mechanical resonance appears when the swimmer and magnetic frequencies coincide, thus enhancing the particle's effective diffusion. Our analytical results are compared with Brownian Dynamics simulations and we obtain excellent agreement.

  1. Analysis of magnetic field levels at KSC

    NASA Technical Reports Server (NTRS)

    Christodoulou, Christos G.

    1994-01-01

    The scope of this work is to evaluate the magnetic field levels of distribution systems and other equipment at Kennedy Space Center (KSC). Magnetic fields levels in several operational areas and various facilities are investigated. Three dimensional mappings and contour are provided along with the measured data. Furthermore, the portion of magnetic fields generated by the 60 Hz fundamental frequency and the portion generated by harmonics are examined. Finally, possible mitigation techniques for attenuating fields from electric panels are discussed.

  2. Abnormal Magnetic Field Effects on Electrogenerated Chemiluminescence

    NASA Astrophysics Data System (ADS)

    Pan, Haiping; Shen, Yan; Wang, Hongfeng; He, Lei; Hu, Bin

    2015-03-01

    We report abnormal magnetic field effects on electrogenerated chemiluminescence (MFEECL) based on triplet emission from the Ru(bpy)3Cl2-TPrA electrochemical system: the appearance of MFEECL after magnetic field ceases. In early studies the normal MFEECL have been observed from electrochemical systems during the application of magnetic field. Here, the abnormal MFEECL suggest that the activated charge-transfer [Ru(bpy)33+ TPrA] complexes may become magnetized in magnetic field and experience a long magnetic relaxation after removing magnetic field. Our analysis indicates that the magnetic relaxation can gradually increase the density of charge-transfer complexes within reaction region due to decayed magnetic interactions, leading to a positive component in the abnormal MFEECL. On the other hand, the magnetic relaxation facilitates an inverse conversion from triplets to singlets within charge-transfer complexes. The inverse triplet --> singlet conversion reduces the density of triplet light-emitting states through charge-transfer complexes and gives rise to a negative component in the abnormal MFEECL. The combination of positive and negative components can essentially lead to a non-monotonic profile in the abnormal MFEECL after ceasing magnetic field. Nevertheless, our experimental studies may reveal un-usual magnetic behaviors with long magnetic relaxation from the activated charge-transfer [Ru(bpy)33+ TPrA] complexes in solution at room temperature.

  3. RADIAL TRANSPORT OF LARGE-SCALE MAGNETIC FIELDS IN ACCRETION DISKS. II. RELAXATION TO STEADY STATES

    SciTech Connect

    Takeuchi, Taku; Okuzumi, Satoshi

    2014-12-20

    We study the time evolution of a large-scale magnetic flux threading an accretion disk. The induction equation of the mean poloidal field is solved under the standard viscous disk model. Magnetic flux evolution is controlled by two timescales: one is the timescale of the inward advection of the magnetic flux, τ{sub adv}. This is induced by the dragging of the flux by the accreting gas. The other is the outward diffusion timescale of the magnetic flux τ{sub dif}. We consider diffusion due to the Ohmic resistivity. These timescales can be significantly different from the disk viscous timescale τ{sub disk}. The behaviors of the magnetic flux evolution are quite different depending on the magnitude relationship of the timescales τ{sub adv}, τ{sub dif}, and τ{sub disk}. The most interesting phenomena occur when τ{sub adv} << τ{sub dif}, τ{sub disk}. In such a case, the magnetic flux distribution approaches a quasi-steady profile much faster than the viscous evolution of the gas disk, and the magnetic flux has also been tightly bundled to the inner part of the disk. In the inner part, although the poloidal magnetic field becomes much stronger than the interstellar magnetic field, the field strength is limited to the maximum value that is analytically given by our previous work. We also find a condition for the initial large magnetic flux, which is a fossil of the magnetic field dragging during the early phase of star formation that survives for a duration in which significant gas disk evolution proceeds.

  4. Bipolar pulse field for magnetic refrigeration

    DOEpatents

    Lubell, M.S.

    1994-10-25

    A magnetic refrigeration apparatus includes first and second steady state magnets, each having a field of substantially equal strength and opposite polarity, first and second bodies made of magnetocaloric material disposed respectively in the influence of the fields of the first and second steady state magnets, and a pulsed magnet, concentric with the first and second steady state magnets, and having a field which cycles between the fields of the first and second steady state magnets, thereby cyclically magnetizing and demagnetizing and thus heating and cooling the first and second bodies. Heat exchange apparatus of suitable design can be used to expose a working fluid to the first and second bodies of magnetocaloric material. A controller is provided to synchronize the flow of working fluid with the changing states of magnetization of the first and second bodies. 2 figs.

  5. Bipolar pulse field for magnetic refrigeration

    DOEpatents

    Lubell, Martin S. (Oak Ridge, TN)

    1994-01-01

    A magnetic refrigeration apparatus includes first and second steady state magnets, each having a field of substantially equal strength and opposite polarity, first and second bodies made of magnetocaloric material disposed respectively in the influence of the fields of the first and second steady state magnets, and a pulsed magnet, concentric with the first and second steady state magnets, and having a field which cycles between the fields of the first and second steady state magnets, thereby cyclically magnetizing and demagnetizing and thus heating and cooling the first and second bodies. Heat exchange apparatus of suitable design can be used to expose a working fluid to the first and second bodies of magnetocaloric material. A controller is provided to synchronize the flow of working fluid with the changing states of magnetization of the first and second bodies.

  6. On Magnetic Field Generation Mechanisms in Astrophysics

    NASA Astrophysics Data System (ADS)

    Cherny, O. G.

    Magnetic chemically peculiar stars (CP stars) are characterized by a strong magnetic field, peculiar chemical composition and slow rotation. Since the origin and evolution of CP stars may be responsible for such unusual features, understanding the mechanisms of generation of the magnetic field is one of the ways to learn more about the CP star characteristics. At present there are two mechanisms of magnetic field generation considered in astrophysics, a fossil field hypothesis and turbulent dynamo theory. However, there is another mechanism of magnetic field generation. All the elementary particles including the most abundant, i. e. the protons, electrons, neutrons, have their own angular momenta and the corresponding magnetic momenta. Microscopic magnetic fields are determined generally by these magnetic momenta. Provided that microscopic magnetic fields are aligned, large-scale magnetic fields may be generated, which has been proved in the experiments of Barnett, Einstein and de Haas. This phenomenon is best illustrated by the experiments with iron. Analysis performed in the current study showed that all the large bodies of the Solar System have both an iron-nickel core and a magnetic field, which is proportional to the planet's core volume and its rotational velocity. We hypothesize that the reason for this phenomenon is a magnetic interaction of ferromagnetic materials, which occurred during the formation of the Solar System. We show that the magnitude of the magnetic field of the Earth and a change of magnetic field polarity can be explained by the gyromagnetic effect. In the beginning of formation of the Solar System the prospective Sun was the main attractive center. Therefore, there is a possibility that the Sun contains a massive (relative to the Earth) iron-nickel core.

  7. Application peculiarities of magnetic materials for protection from magnetic fields

    NASA Astrophysics Data System (ADS)

    Wai, P.; Dmitrenko, V.; Grabchikov, S.; Vlasik, K.; Novikov, A.; Petrenko, D.; Trukhanov, V.; Ulin, S.; Uteshev, Z.; Chernysheva, V.; Shustov, A.

    2016-02-01

    In different materials for magnetic shields, the maximum permeability is achieved for different values of the magnetic field. This determines the choice of material. So for protection from magnetic fields strength of 10 - 150 A/m it is advisable to apply the amorphous ribbon 84KXCP. For stronger fields (more than 400 A/m) it is recommended to use MFS based on Ni20Fe80. Use of these materials allows creating an effective shield working in a wide range of magnetic field strengths.

  8. Magnetic field waves at Uranus

    NASA Technical Reports Server (NTRS)

    Smith, Charles W.; Goldstein, Melvyn L.; Lepping, Ronald P.; Mish, William H.; Wong, Hung K.

    1991-01-01

    The proposed research efforts funded by the UDAP grant to the BRI involve the study of magnetic field waves associated with the Uranian bow shock. This is a collaborative venture bringing together investigators at the BRI, Southwest Research Institute (SwRI), and Goddard Space Flight Center (GSFC). In addition, other collaborations have been formed with investigators granted UDAP funds for similar studies and with investigators affiliated with other Voyager experiments. These investigations and the corresponding collaborations are included in the report. The proposed effort as originally conceived included an examination of waves downstream from the shock within the magnetosheath. However, the observations of unexpected complexity and diversity within the upstream region have necessitated that we confine our efforts to those observations recorded upstream of the bow shock on the inbound and outbound legs of the encounter by the Voyager 2 spacecraft.

  9. Swarm: ESA's Magnetic Field Mission

    NASA Astrophysics Data System (ADS)

    Plank, G.; Floberghagen, R.; Menard, Y.; Haagmans, R.

    2013-12-01

    Swarm is the fifth Earth Explorer mission in ESA's Living Planet Programme, and is scheduled for launch in fall 2013. The objective of the Swarm mission is to provide the best-ever survey of the geomagnetic field and its temporal evolution using a constellation of three identical satellites. The mission shall deliver data that allow access to new insights into the Earth system by improved scientific understanding of the Earth's interior and near-Earth electromagnetic environment. After launch and triple satellite release at an initial altitude of about 490 km, a pair of the satellites will fly side-by-side with slowly decaying altitude, while the third satellite will be lifted to 530 km to complete the Swarm constellation. High-precision and high-resolution measurements of the strength, direction and variation of the magnetic field, complemented by precise navigation, accelerometer and electric field measurements, will provide the observations required to separate and model various sources of the geomagnetic field and near-Earth current systems. The mission science goals are to provide a unique view into Earth's core dynamics, mantle conductivity, crustal magnetisation, ionospheric and magnetospheric current systems and upper atmosphere dynamics - ranging from understanding the geodynamo to contributing to space weather. The scientific objectives and results from recent scientific studies will be presented. In addition the current status of the project, which is presently in the final stage of the development phase, will be addressed. A consortium of European scientific institutes is developing a distributed processing system to produce geophysical (Level 2) data products for the Swarm user community. The setup of the Swarm ground segment and the contents of the data products will be addressed. In case the Swarm satellites are already in orbit, a summary of the on-going mission operations activities will be given. More information on Swarm can be found at www.esa.int/esaLP/LPswarm.html.

  10. DC-based magnetic field controller

    DOEpatents

    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.

  11. DC-based magnetic field controller

    DOEpatents

    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.

  12. Representation of magnetic fields in space

    NASA Technical Reports Server (NTRS)

    Stern, D. P.

    1975-01-01

    Several methods by which a magnetic field in space can be represented are reviewed with particular attention to problems of the observed geomagnetic field. Time dependence is assumed to be negligible, and five main classes of representation are described by vector potential, scalar potential, orthogonal vectors, Euler potentials, and expanded magnetic field.

  13. Static uniform magnetic fields and amoebae

    SciTech Connect

    Berk, S.G.; Srikanth, S.; Mahajan, S.M.; Ventrice, C.A.

    1997-03-01

    Three species of potentially pathogenic amoebae were exposed to 71 and 106.5 mT from constant homogeneous magnetic fields and examined for inhibition of population growth. The number of amoebae for three species was significantly less than controls after a 72 h exposure to the magnetic fields when the temperature was 20 C or above. Axenic cultures, i.e., cultures grown without bacteria, were significantly affected after only 24 h. In 20 of 21 tests using the three species, the magnetic field significantly inhibited the growth of amoebae. In one test in which the temperature was 20 C for 48 h, exposure to the magnetic field was not inhibitory. Final numbers of magnetic field-exposed amoebae ranged from 9 to 72% lower than the final numbers of unexposed controls, depending on the species. This research may lead to disinfection strategies utilizing magnetic fields for surfaces on which pathogenic amoebae may proliferate.

  14. Magnon drag thermopile

    NASA Astrophysics Data System (ADS)

    Valenzuela, Sergio O.

    2013-03-01

    Thermoelectric effects in spintronics are gathering increasing attention as a means of controlling spin information by using heat flow. Thermal magnons (spin-wave quanta) are expected to play a major role, however, the coupling between electrons and magnons in ferromagnetic metals remains poorly understood. We demonstrate a conceptually new device that enables us to gather information on magnon-electron scattering and magnon-drag effects. The device resembles a thermopile formed by a large number of pairs of ferromagnetic wires placed between a hot and a cold source and connected thermally in parallel and electrically in series. By controlling the relative orientation of the magnetization in pairs of wires, the magnon drag can be studied independently of the electron and phonon drag thermoelectric effects. Measurements as a function of temperature reveal the effect on magnon drag following a variation of magnon and phonon populations. These results demonstrate the feasibility of directly converting magnon dynamics of nanomagnets into an electrical signal and could pave the way to novel thermoelectric devices for energy harvesting. This research was supported by the Spanish Ministerio de Ciencia e Innovacin, MICINN (MAT2010-18065) and by the European Community's Seventh Framework Programme (FP7/2007-2013) under grant agreement NANOFUNCTION no 257375.

  15. Magnon-drag thermopile.

    PubMed

    Costache, Marius V; Bridoux, German; Neumann, Ingmar; Valenzuela, Sergio O

    2012-03-01

    Thermoelectric effects in spintronics are gathering increasing attention as a means of managing heat in nanoscale structures and of controlling spin information by using heat flow. Thermal magnons (spin-wave quanta) are expected to play a major role; however, little is known about the underlying physical mechanisms involved. The reason is the lack of information about magnon interactions and of reliable methods to obtain it, in particular for electrical conductors because of the intricate influence of electrons. Here, we demonstrate a conceptually new device that enables us to gather information on magnon-electron scattering and magnon-drag effects. The device resembles a thermopile formed by a large number of pairs of ferromagnetic wires placed between a hot and a cold source and connected thermally in parallel and electrically in series. By controlling the relative orientation of the magnetization in pairs of wires, the magnon drag can be studied independently of the electron and phonon-drag thermoelectric effects. Measurements as a function of temperature reveal the effect on magnon drag following a variation of magnon and phonon populations. This information is crucial to understand the physics of electron-magnon interactions, magnon dynamics and thermal spin transport. PMID:22179396

  16. Magnetic field sensor for isotropically sensing an incident magnetic field in a sensor plane

    NASA Technical Reports Server (NTRS)

    Pant, Bharat B. (Inventor); Wan, Hong (Inventor)

    2001-01-01

    A magnetic field sensor that isotropically senses an incident magnetic field. This is preferably accomplished by providing a magnetic field sensor device that has one or more circular shaped magnetoresistive sensor elements for sensing the incident magnetic field. The magnetoresistive material used is preferably isotropic, and may be a CMR material or some form of a GMR material. Because the sensor elements are circular in shape, shape anisotropy is eliminated. Thus, the resulting magnetic field sensor device provides an output that is relatively independent of the direction of the incident magnetic field in the sensor plane.

  17. Magnetic field effects on plasma ionization balance

    SciTech Connect

    Weisheit, J.C.

    1995-12-31

    Magnetic fields give rise to several phenomena that can significantly affect ionization balance in a plasma. Theoretical models commonly used to determine the charge state distribution (viz., ) of ions in non-magnetized plasmas are reviewed first, for both equilibrium and non-equilibrium situations. Then, after a brief survey of laboratory and cosmic plasmas with strong fields, B > 10{sup 6} Gauss, some of the ways such magnetic fields influence are highlighted. Most key problems have yet to be tackled.

  18. Nonlinear energy dissipation of magnetic nanoparticles in oscillating magnetic fields

    NASA Astrophysics Data System (ADS)

    Soto-Aquino, D.; Rinaldi, C.

    2015-11-01

    The heating of magnetic nanoparticle suspensions subjected to alternating magnetic fields enables a variety of emerging applications such as magnetic fluid hyperthermia and triggered drug release. Rosensweig (2002) [25] obtained a model for the heat dissipation rate of a collection of non-interacting particles. However, the assumptions made in this analysis make it rigorously valid only in the limit of small applied magnetic field amplitude and frequency (i.e., values of the Langevin parameter that are much less than unity and frequencies below the inverse relaxation time). In this contribution we approach the problem from an alternative point of view by solving the phenomenological magnetization relaxation equation exactly for the case of arbitrary magnetic field amplitude and frequency and by solving a more accurate magnetization relaxation equation numerically. We also use rotational Brownian dynamics simulations of non-interacting magnetic nanoparticles subjected to an alternating magnetic field to estimate the rate of energy dissipation and compare the results of the phenomenological theories to the particle-scale simulations. The results are summarized in terms of a normalized energy dissipation rate and show that Rosensweig's expression provides an upper bound on the energy dissipation rate achieved at high field frequency and amplitude. Estimates of the predicted dependence of energy dissipation rate, quantified as specific absorption rate (SAR), on magnetic field amplitude and frequency, and particle core and hydrodynamic diameter, are also given.

  19. Minimizing magnetic fields for precision experiments

    NASA Astrophysics Data System (ADS)

    Altarev, I.; Fierlinger, P.; Lins, T.; Marino, M. G.; Nießen, B.; Petzoldt, G.; Reisner, M.; Stuiber, S.; Sturm, M.; Taggart Singh, J.; Taubenheim, B.; Rohrer, H. K.; Schläpfer, U.

    2015-06-01

    An increasing number of measurements in fundamental and applied physics rely on magnetically shielded environments with sub nano-Tesla residual magnetic fields. State of the art magnetically shielded rooms (MSRs) consist of up to seven layers of high permeability materials in combination with highly conductive shields. Proper magnetic equilibration is crucial to obtain such low magnetic fields with small gradients in any MSR. Here, we report on a scheme to magnetically equilibrate MSRs with a 10 times reduced duration of the magnetic equilibration sequence and a significantly lower magnetic field with improved homogeneity. For the search of the neutron's electric dipole moment, our finding corresponds to a 40% improvement of the statistical reach of the measurement. However, this versatile procedure can improve the performance of any MSR for any application.

  20. Bats Respond to Very Weak Magnetic Fields

    PubMed Central

    Tian, Lan-Xiang; Pan, Yong-Xin; Metzner, Walter; Zhang, Jin-Shuo; Zhang, Bing-Fang

    2015-01-01

    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. PMID:25922944

  1. Measurement of magnetic fields in stars

    SciTech Connect

    Landstreet, J.D.

    1980-05-01

    A review is presented of techniques of measuring magnetic fields in nondegenerate stars. The strengths and limitations of the classical photographic field measurement technique are compared to those of various photoelectric methods developed during the past decade, particularly the Balmer-line Zeeman analyzer technique. The problem of modeling magnetic data to infer the magnetic field geometry of an observed star is discussed. In the few cases where sufficient data are available to test the centered dipole geometry, it is found to be inadequate. It appears that most magnetic stars have field geometries at least as complex as the oblique decentered dipole (or dipole plus parallel linear quadrupole) model.

  2. Ferroelectric Cathodes in Transverse Magnetic Fields

    SciTech Connect

    Alexander Dunaevsky; Yevgeny Raitses; Nathaniel J. Fisch

    2002-07-29

    Experimental investigations of a planar ferroelectric cathode in a transverse magnetic field up to 3 kGs are presented. It is shown that the transverse magnetic field affects differently the operation of ferroelectric plasma cathodes in ''bright'' and ''dark'' modes in vacuum. In the ''bright'' mode, when the surface plasma is formed, the application of the transverse magnetic field leads to an increase of the surface plasma density. In the ''dark'' mode, the magnetic field inhibits the development of electron avalanches along the surface, as it does similarly in other kinds of surface discharges in the pre-breakdown mode.

  3. Magnetic Fields in the Milky Way

    NASA Astrophysics Data System (ADS)

    Haverkorn, Marijke

    This chapter presents a review of observational studies to determine the magnetic field in the Milky Way, both in the disk and in the halo, focused on recent developments and on magnetic fields in the diffuse interstellar medium. I discuss some terminology which is confusingly or inconsistently used and try to summarize current status of our knowledge on magnetic field configurations and strengths in the Milky Way. Although many open questions still exist, more and more conclusions can be drawn on the large-scale and small-scale components of the Galactic magnetic field. The chapter is concluded with a brief outlook to observational projects in the near future.

  4. Quark matter in a strong magnetic field

    SciTech Connect

    Chakrabarty, S.

    1996-07-01

    The effect of a strong magnetic field on the stability and gross properties of bulk as well as quasibulk quark matter is investigated using the conventional MIT bag model. Both the Landau diamagnetism and the paramagnetism of quark matter are studied. How the quark hadron phase transition is affected by the presence of a strong magnetic field is also investigated. The equation of state of strange quark matter changes significantly in a strong magnetic field. It is also shown that the thermal nucleation of quark bubbles in a compact metastable state of neutron matter is completely forbidden in the presence of a strong magnetic field. {copyright} {ital 1996 The American Physical Society.}

  5. Flow Transitions in a Rotating Magnetic Field

    NASA Technical Reports Server (NTRS)

    Volz, M. P.; Mazuruk, K.

    1996-01-01

    Critical Rayleigh numbers have been measured in a liquid metal cylinder of finite height in the presence of a rotating magnetic field. Several different stability regimes were observed, which were determined by the values of the Rayleigh and Hartmann numbers. For weak rotating magnetic fields and small Rayleigh numbers, the experimental observations can be explained by the existence of a single non-axisymmetric meridional roll rotating around the cylinder, driven by the azimuthal component of the magnetic field. The measured dependence of rotational velocity on magnetic field strength is consistent with the existence of laminar flow in this regime.

  6. Magnetic vector field tag and seal

    DOEpatents

    Johnston, Roger G.; Garcia, Anthony R.

    2004-08-31

    One or more magnets are placed in a container (preferably on objects inside the container) and the magnetic field strength and vector direction are measured with a magnetometer from at least one location near the container to provide the container with a magnetic vector field tag and seal. The location(s) of the magnetometer relative to the container are also noted. If the position of any magnet inside the container changes, then the measured vector fields at the these locations also change, indicating that the tag has been removed, the seal has broken, and therefore that the container and objects inside may have been tampered with. A hollow wheel with magnets inside may also provide a similar magnetic vector field tag and seal. As the wheel turns, the magnets tumble randomly inside, removing the tag and breaking the seal.

  7. Operating a magnetic nozzle helicon thruster with strong magnetic field

    NASA Astrophysics Data System (ADS)

    Takahashi, Kazunori; Komuro, Atsushi; Ando, Akira

    2016-03-01

    A pulsed axial magnetic field up to ˜2.8 kG is applied to a 26-mm-inner-diameter helicon plasma thruster immersed in a vacuum chamber, and the thrust is measured using a pendulum target. The pendulum is located 30-cm-downstream of the thruster, and the thruster rf power and argon flow rate are fixed at 1 kW and 70 sccm (which gives a chamber pressure of 0.7 mTorr). The imparted thrust increases as the applied magnetic field is increased and saturates at a maximum value of ˜9.5 mN for magnetic field above ˜2 kG. At the maximum magnetic field, it is demonstrated that the normalized plasma density, and the ion flow energy in the magnetic nozzle, agree within ˜50% and of 10%, respectively, with a one-dimensional model that ignores radial losses from the nozzle. This magnetic nozzle model is combined with a simple global model of the thruster source that incorporates an artificially controlled factor α, to account for radial plasma losses to the walls, where α = 0 and 1 correspond to zero losses and no magnetic field, respectively. Comparison between the experiments and the model implies that the radial losses in the thruster source are experimentally reduced by the applied magnetic field to about 10% of that obtained from the no magnetic field model.

  8. Pulsed magnetic field magnetic force microscope and evaluation of magnetic properties of soft magnetic tips

    NASA Astrophysics Data System (ADS)

    Zheng, Yangdong; Yoshimura, Satoru; Egawa, Genta; Zheng, Fu; Kinoshita, Yukinori; Saito, Hitoshi

    2015-08-01

    A pulsed magnetic field magnetic force microscope (PMF-MFM) is developed for evaluation of the magnetic properties of nano-scale materials and devices, as well as the characteristics of MFM tips. We present the setup of the PMF-MFM system, and focus on the evaluation of a FeCo soft magnetic tip by PMF-MFM. We find a new theoretical method to calculate tip magnetization curves (M-H curves) using MFM phase signals. We measure the MFM phase and amplitude signals for the FeCo tip during the presence of the pulsed magnetic fields oriented parallel and antiparallel to the initial tip magnetization direction, and acquire the tip coercivity H c ~ 1.1?kOe. The tip M-H curves are also calculated using the MFM phase signals data. We obtain the basic features of the tip magnetic properties from the tip M-H curves.

  9. Magnetized quark matter with a magnetic-field dependent coupling

    NASA Astrophysics Data System (ADS)

    Li, Chang-Feng; Yang, Li; Wen, Xin-Jian; Peng, Guang-Xiong

    2016-03-01

    It was recently derived that the QCD running coupling is a function of the magnetic field strength under the strong magnetic field approximation. Inspired by this progress and based on the self-consistent solutions of gap equations, the properties of two-flavor and three-flavor quark matter are studied in the framework of the Nambu-Jona-Lasinio model with a magnetic-field-dependent running coupling. We find that the dynamical quark masses as functions of the magnetic field strength are not monotonous in the fully chirally broken phase. Furthermore, the stability of magnetized quark matter with the running coupling is enhanced by lowering the free energy per baryon, which is expected to be more stable than that of the conventional constant coupling case. It is concluded that the magnetized strange quark matter described by running coupling can be absolutely stable.

  10. Numerical analysis of magnetic field in superconducting magnetic energy storage

    SciTech Connect

    Kanamaru, Y. ); Amemiya, Y. )

    1991-09-01

    This paper reports that the superconducting magnetic energy storage (SMES) is more useful than the other systems of electric energy storage because of larger stored energy and higher efficiency. The other systems are the battery, the flywheel, the pumped-storage power station. Some models of solenoid type SMES are designed in U.S.A. and Japan. But a high magnetic field happens by the large scale SMES in the living environment, and makes the erroneous operations of the computer display, the pacemaker of the heart and the electronic equipments. We study some fit designs of magnetic shielding of the solenoidal type SMES for reduction of the magnetic field in living environment. When some superconducting shielding coils are over the main storage coil, magnetic field reduces remarkably than the case of non shielding coil. The calculated results of the magnetic field are obtained y the finite element method.

  11. Reducing Field Distortion in Magnetic Resonance Imaging

    NASA Technical Reports Server (NTRS)

    Eom, Byeong Ho; Penanen, Konstantin; Hahn, Inseob

    2010-01-01

    A concept for a magnetic resonance imaging (MRI) system that would utilize a relatively weak magnetic field provides for several design features that differ significantly from the corresponding features of conventional MRI systems. Notable among these features are a magnetic-field configuration that reduces (relative to the conventional configuration) distortion and blurring of the image, the use of a superconducting quantum interference device (SQUID) magnetometer as the detector, and an imaging procedure suited for the unconventional field configuration and sensor. In a typical application of MRI, a radio-frequency pulse is used to excite precession of the magnetic moments of protons in an applied magnetic field, and the decaying precession is detected for a short time following the pulse. The precession occurs at a resonance frequency proportional to the strengths of the magnetic field and the proton magnetic moment. The magnetic field is configured to vary with position in a known way; hence, by virtue of the aforesaid proportionality, the resonance frequency varies with position in a known way. In other words, position is encoded as resonance frequency. MRI using magnetic fields weaker than those of conventional MRI offers several advantages, including cheaper and smaller equipment, greater compatibility with metallic objects, and higher image quality because of low susceptibility distortion and enhanced spin-lattice-relaxation- time contrast. SQUID MRI is being developed into a practical MRI method for applied magnetic flux densities of the order of only 100 T

  12. Magnetic field evolution in interacting galaxies

    NASA Astrophysics Data System (ADS)

    Drzazga, R. T.; Chy?y, K. T.; Jurusik, W.; Wirkiewicz, K.

    2011-09-01

    Aims: Violent gravitational interactions can change the morphologies of galaxies and, by means of merging, transform them into elliptical galaxies. We aim to investigate how they affect the evolution of galactic magnetic fields. Methods: We selected 16 systems of interacting galaxies with available VLA archive radio data at 4.86 and 1.4 GHz and compared their radio emission and estimated magnetic field strengths with their star-forming activity, far-infrared emission, and the stage of tidal interaction. Results: The estimated mean of total magnetic field strength for our sample of interacting galaxies is 14 5 ?G, which is larger than for the non-interacting objects. The field regularity (of 0.27 0.09) is lower than in typical spirals and indicates enhanced production of random magnetic fields in the interacting objects. We find a general evolution of magnetic fields: for weak interactions the strength of magnetic field is almost constant (10-15 ?G) as interaction advances, then it increases up to 2 , peaks at the nuclear coalescence (25 ?G), and decreases again, down to 5-6 ?G, for the post-merger remnants. The main production of magnetic fields in colliding galaxies thus terminates somewhere close to the nuclear coalescence, after which magnetic field diffuses. The magnetic field strength for whole galaxies is weakly affected by the star formation rate (SFR), while the dependence is higher for galactic centres. We show that the morphological distortions visible in the radio total and polarized emission do not depend statistically on the global or local SFRs, while they do increase (especially in the polarization) with the advance of interaction. The constructed radio-far-infrared relations for interacting and non-interacting galaxies display a similar balance between the generation of cosmic rays, magnetic fields, and the production of the thermal energy and dust radiation. Conclusions: The regular magnetic fields are much more sensitive to morphological distortions induced by tidal interactions than are the random fields. As a result the polarized emission could be yet another indicator of an ongoing merging process. The found evolution of magnetic field with advancing interaction would definitely imply a stronger effect of magnetic fields on the galaxy surroundings in the earlier cosmological epochs. The process of strong gravitational interactions can efficiently magnetize the merger's surroundings, having a similar magnetizing effect on intergalactic medium as supernova explosions or galactic winds. If interacting galaxies generate some ultra-high energy cosmic rays (UHECRs), the disk or magnetized outflows can deflect them (up to 23), and make an association of the observed UHECRs with the sites of their origin very uncertain.

  13. High-field magnetization of polycrystalline praseodymium

    SciTech Connect

    Leyarovski, E.; Mrachkov, J.; Gilewski, A.; Mydlarz, T.

    1987-06-01

    The field dependence of the induced magnetic moment in polycrystalline Pr is studied in impulse magnetic fields up to 45 T at 4.2 K and in stationary magnetic fields up to 18 T at 20 and 30 K. No anomalies in the magnetization have been observed which might be associated with the metamagnetic phase transition in single crystals at 31.5 T (K. A. McEwen, G. J. Cock, L. W. Roeland, and A. R. Mackinstosh, Phys. Rev. Lett. 30, 287 (1973)), as well as with any changes of the orientation of the magnetic moments characteristic for an antiferromagnetic. The observed magnetization is satisfactorily described using a molecular field Hamiltonian including the crystal electric field potential, exchange interactions, and Zeeman-effect term.

  14. High-field magnetization of polycrystalline praseodymium

    NASA Astrophysics Data System (ADS)

    Leyarovski, E.; Mrachkov, J.; Gilewski, A.; Mydlarz, T.

    1987-06-01

    The field dependence of the induced magnetic moment in polycrystalline Pr is studied in impulse magnetic fields up to 45 T at 4.2 K and in stationary magnetic fields up to 18 T at 20 and 30 K. No anomalies in the magnetization have been observed which might be associated with the metamagnetic phase transition in single crystals at 31.5 T [K. A. McEwen, G. J. Cock, L. W. Roeland, and A. R. Mackinstosh, Phys. Rev. Lett. 30, 287 (1973)], as well as with any changes of the orientation of the magnetic moments characteristic for an antiferromagnetic. The observed magnetization is satisfactorily described using a molecular field Hamiltonian including the crystal electric field potential, exchange interactions, and Zeeman-effect term.

  15. Magnetic field optimization of permanent magnet undulators for arbitrary polarization

    NASA Astrophysics Data System (ADS)

    Bahrdt, J.; Frentrup, W.; Gaupp, A.; Scheer, M.; Englisch, U.

    2004-01-01

    Techniques for improving the magnetic field quality of APPLE II undulators are discussed. Individual block characterization including the inhomogeneities of the magnetization permits a precise prediction of field integrals as required for sorting. Specific shimming procedures adapted to the magnetic design of APPLE II undulators have to be employed in order to meet the stringent requirements of insertion devices in third generation synchrotron radiation sources as demonstrated for BESSY.

  16. Magnetic field decay in model SSC dipoles

    SciTech Connect

    Gilbert, W.S.; Althaus, R.F.; Barale, P.J.; Benjegerdes, R.W.; Green, M.A.; Green, M.I.; Scanlan, R.M.

    1988-08-01

    We have observed that some of our model SSC dipoles have long time constant decays of the magnetic field harmonics with amplitudes large enough to result in significant beam loss, if they are not corrected. The magnets were run at constant current at the SSC injection field level of 0.3 tesla for one to three hours and changes in the magnetic field were observed. One explanation for the observed field decay is time dependent superconductor magnetization. Another explanation involves flux creep or flux flow. Data are presented on how the decay changes with previous flux history. Similar magnets with different Nb-Ti filament spacings and matrix materials have different long time field decay. A theoretical model using proximity coupling and flux creep for the observed field decay is discussed. 10 refs., 5 figs., 2 tabs.

  17. The Evolution of the Earth's Magnetic Field.

    ERIC Educational Resources Information Center

    Bloxham, Jeremy; Gubbins, David

    1989-01-01

    Describes the change of earth's magnetic field at the boundary between the outer core and the mantle. Measurement techniques used during the last 300 years are considered. Discusses the theories and research for explaining the field change. (YP)

  18. Cantilever magnetometry in pulsed magnetic fields

    NASA Astrophysics Data System (ADS)

    Naughton, M. J.; Ulmet, J. P.; Narjis, A.; Askenazy, S.; Chaparala, M. V.; Hope, A. P.

    1997-11-01

    The technique of cantilever magnetometry is shown to be functional in pulsed magnetic fields. Employing micromachined single crystal silicon cantilevers and capacitance detection, we demonstrated a utilizable sensitivity to magnetic moment of 2.510-12 Am2 in magnetic fields to 36 T, representing an improvement of more than a factor of 10 over competing technologies. Torque magnetization measurements on microcrystals of anisotropic superconductors are presented as evidence of the feasibility of the technique in long pulse magnets of pulse duration 0.1-1 s.

  19. Asymmetric drag in oscillatory motion: ratchet effect without an asymmetric potential.

    PubMed

    Fomin, Vladimir M; Smith, Elliot J; Karnaushenko, Dmitriy D; Makarov, Denys; Schmidt, Oliver G

    2013-05-01

    Asymmetry of magnetic objects in a fluid under an oscillating magnetic field leads to a wealth of nonequilibrium dynamics phenomena including a novel ratchet effect without an asymmetric substrate. These nonlinear dynamics are explained in the framework of the Stokes' model by a drag coefficient, which depends on the direction of motion. This approach is general and is independent of the physical mechanism responsible for this directional dependence of the drag coefficient as well as the size of the object. The theoretical model is experimentally verified for two systems, a nonrigid magnetic microcoil and a chiral magnetic macroobject immersed in a bounded fluid. PMID:23767502

  20. Control of magnetism by electric fields

    NASA Astrophysics Data System (ADS)

    Matsukura, Fumihiro; Tokura, Yoshinori; Ohno, Hideo

    2015-03-01

    The electrical manipulation of magnetism and magnetic properties has been achieved across a number of different material systems. For example, applying an electric field to a ferromagnetic material through an insulator alters its charge-carrier population. In the case of thin films of ferromagnetic semiconductors, this change in carrier density in turn affects the magnetic exchange interaction and magnetic anisotropy; in ferromagnetic metals, it instead changes the Fermi level position at the interface that governs the magnetic anisotropy of the metal. In multiferroics, an applied electric field couples with the magnetization through electrical polarization. This Review summarizes the experimental progress made in the electrical manipulation of magnetization in such materials, discusses our current understanding of the mechanisms, and finally presents the future prospects of the field.

  1. Magnetic field evolution of accreting neutron stars

    NASA Astrophysics Data System (ADS)

    Istomin, Y. N.; Semerikov, I. A.

    2016-01-01

    The flow of a matter, accreting on to a magnetized neutron star, is accompanied by an electric current. The closing of the electric current occurs in the crust of a neutron stars in the polar region across the magnetic field. But the conductivity of the crust along the magnetic field greatly exceeds the conductivity across the field, so the current penetrates deep into the crust down up to the superconducting core. The magnetic field, generated by the accretion current, increases greatly with the depth of penetration due to the Hall conductivity of the crust is also much larger than the transverse conductivity. As a result, the current begins to flow mainly in the toroidal direction, creating a strong longitudinal magnetic field, far exceeding an initial dipole field. This field exists only in the narrow polar tube of r width, narrowing with the depth, i.e. with increasing of the crust density ?, r ? ?-1/4. Accordingly, the magnetic field B in the tube increases with the depth, B??1/2, and reaches the value of about 1017 Gauss in the core. It destroys superconducting vortices in the core of a star in the narrow region of the size of the order of 10 cm. Because of generated density gradient of vortices, they constantly flow into this dead zone and the number of vortices decreases, the magnetic field of a star decreases as well. The attenuation of the magnetic field is exponential, B = B0(1 + t/?)-1. The characteristic time of decreasing of the magnetic field ? is equal to ? ? 103 yr. Thus, the magnetic field of accreted neutron stars decreases to values of 108-109 Gauss during 107-106 yr.

  2. Coronal magnetic fields produced by photospheric shear

    NASA Technical Reports Server (NTRS)

    Sturrock, P. A.; Yang, W.-H.

    1987-01-01

    The magneto-frictional method is used for computing force free fields to examine the evolution of the magnetic field of a line dipole, when there is relative shearing motion between the two polarities. It found that the energy of the sheared field can be arbitrarily large compared with the potential field. It is also found that it is possible to fit the magnetic energy, as a function of shear, by a simple functional form.

  3. Relaxed plasmas in external magnetic fields

    SciTech Connect

    Spies, G.O. ); Li, J. )

    1994-09-01

    The extension of the theory of relaxed plasmas to external magnetic fields whose field lines intersect the wall is concisely formulated and then applied to the Extrap experiment [J. R. Drake, Plasma Phys. Controlled Fusion [bold 26], 387 (1984)]. It is found that the external octupole field, though not affecting the phenomenon of current saturation, inhibits field reversal at parts of the wall if it is sufficiently strong to generate magnetic x points within the plasma.

  4. Magnetic fields in Neutron Stars

    NASA Astrophysics Data System (ADS)

    Viganò, D.; Pons, J. A.; Miralles, J. A.; Rea, N.

    2015-05-01

    Isolated neutron stars show a diversity in timing and spectral properties, which has historically led to a classification in different sub-classes. The magnetic field plays a key role in many aspects of the neutron star phenomenology: it regulates the braking torque responsible for their timing properties and, for magnetars, it provides the energy budget for the outburst activity and high quiescent luminosities (usually well above the rotational energy budget). We aim at unifying this observational variety by linking the results of the state-of-the-art 2D magneto-thermal simulations with observational data. The comparison between theory and observations allows to place two strong constraints on the physical properties of the inner crust. First, strong electrical currents must circulate in the crust, rather than in the star core. Second, the innermost part of the crust must be highly resistive, which is in principle in agreement with the presence of a novel phase of matter so-called nuclear pasta phase.

  5. Two-axis magnetic field sensor

    NASA Technical Reports Server (NTRS)

    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.

  6. Fluctuating magnetic field induced resonant activation

    SciTech Connect

    Mondal, Shrabani; Das, Sudip; Baura, Alendu; Bag, Bidhan Chandra

    2014-12-14

    In this paper, we have studied the properties of a Brownian particle at stationary state in the presence of a fluctuating magnetic field. Time dependence of the field makes the system thermodynamically open. As a signature of that the steady state distribution function becomes function of damping strength, intensity of fluctuations and constant parts of the applied magnetic field. It also depends on the correlation time of the fluctuating magnetic field. Our another observation is that the random magnetic field can induce the resonant activation phenomenon. Here correlation time is increased under the fixed variance of the fluctuating field. But if the correlation time (?) increases under the fixed field strength then the mean first passage time rapidly grows at low ? and it almost converges at other limit. This is sharp contrast to the usual colored noise driven open system case where the mean first passage time diverges exponentially. We have also observed that a giant enhancement of barrier crossing rate occurs particularly at large strength of constant parts of the applied magnetic field even for very weak fluctuating magnetic field. Finally, break down of the Arrhenius result and disappearance of the Kramers turn over phenomenon may occur in the presence of a fluctuating magnetic field.

  7. Magnetic Fields at the Center of Coils

    ERIC Educational Resources Information Center

    Binder, Philippe; Hui, Kaleonui; Goldman, Jesse

    2014-01-01

    In this note we synthesize and extend expressions for the magnetic field at the center of very short and very long current-carrying coils. Elementary physics textbooks present the following equation for the magnetic field inside a very long current-carrying coil (solenoid): B[subscript sol] = [subscript 0] (N/L) I, (1) where I is the current, N

  8. Magnetic Fields at the Center of Coils

    ERIC Educational Resources Information Center

    Binder, Philippe; Hui, Kaleonui; Goldman, Jesse

    2014-01-01

    In this note we synthesize and extend expressions for the magnetic field at the center of very short and very long current-carrying coils. Elementary physics textbooks present the following equation for the magnetic field inside a very long current-carrying coil (solenoid): B[subscript sol] = µ[subscript 0] (N/L) I, (1) where I is the current, N…

  9. Permanent magnet edge-field quadrupole

    DOEpatents

    Tatchyn, R.O.

    1997-01-21

    Planar permanent magnet edge-field quadrupoles for use in particle accelerating machines and in insertion devices designed to generate spontaneous or coherent radiation from moving charged particles are disclosed. The invention comprises four magnetized rectangular pieces of permanent magnet material with substantially similar dimensions arranged into two planar arrays situated to generate a field with a substantially dominant quadrupole component in regions close to the device axis. 10 figs.

  10. Permanent magnet edge-field quadrupole

    DOEpatents

    Tatchyn, Roman O. (Mountain View, CA)

    1997-01-01

    Planar permanent magnet edge-field quadrupoles for use in particle accelerating machines and in insertion devices designed to generate spontaneous or coherent radiation from moving charged particles are disclosed. The invention comprises four magnetized rectangular pieces of permanent magnet material with substantially similar dimensions arranged into two planar arrays situated to generate a field with a substantially dominant quadrupole component in regions close to the device axis.

  11. Pair annihilation in superstrong magnetic fields

    NASA Technical Reports Server (NTRS)

    Daugherty, J. K.; Bussard, R. W.

    1980-01-01

    The kinematical and dynamical aspects of the annihilation processes in superstrong magnetic fields are studied. The feasibility and potential significance of detecting from magnetic neutron stars are discussed. The discussion proceeds from the derivation of the fully relativistic differential cross sections and annihilation rates for both one- and two-photon emission from a ground-state gas of electrons and positrons in a static, uniform magnetic field.

  12. Interplanetary stream magnetism: Kinematic effects. [solar magnetic fields and wind

    NASA Technical Reports Server (NTRS)

    Burlaga, L. F.; Barouch, E.

    1974-01-01

    The particle density, and the magnetic field intensity and direction are calculated in corotating streams of the solar wind, assuming that the solar wind velocity is constant and radial and that its azimuthal variations are not two rapid. The effects of the radial velocity profile in corotating streams on the magnetic fields were examined using kinematic approximation and a variety of field configurations on the inner boundary. Kinematic and dynamic effects are discussed.

  13. Ionospheric electric fields, currents, and resulting magnetic fields variations

    NASA Astrophysics Data System (ADS)

    Du, Junhu

    This thesis uses an equivalent circuit model to calculate ionospheric electric fields, current densities and introduced magnetic fields variations on the ground. The role of the field aligned current is examined. Using different wind models, we studied the electric field variations with altitude, season and solar activity. The ionospheric eastward electric field changes very little within the whole ionosphere. The southward (equatorward) electric field is large and changes quickly with height in the E region although it is nearly constant in the F region. The prereversal enhancement of the eastward electric field is produced by the F region dynamo. We conclude that the Forbes and Gillette tidal wind can reproduce most features of the Jicamarca experiment and the AE-E and DE-2 satellite observations of the electric fields. The HWM90 empirical wind model failed to produce the observed electric field and it seems the semidiurnal wind in HWM90 is too strong. The field aligned current is located mainly in the E and low F region. The non-coincidence of the geomagnetic and geographic equators has a strong effect on the field aligned current in the equatorial zone. The field aligned currents driven by Forbes' winds for March equinox and December solstice flow mainly from the southern to northern hemisphere in the morning and vice versa in the afternoon at F region heights. The observed magnetic field variations on the ground are well reproduced in our simulations. The field aligned current is the main contributor to the eastward magnetic field component in the equatorial zone. The longitudinal inequality of the northward magnetic field is introduced mainly by the variations of the local magnetic field intensity. The electric field variations have only a minor effect. The northward magnetic field variations with the solar activity are introduced by changes of the E region equatorward electric field and the Hall conductivity.

  14. Comparison of adjustable permanent magnetic field sources

    NASA Astrophysics Data System (ADS)

    Bjørk, R.; Bahl, C. R. H.; Smith, A.; Pryds, N.

    2010-11-01

    A permanent magnet assembly in which the flux density can be altered by a mechanical operation is often significantly smaller than comparable electromagnets and also requires no electrical power to operate. In this paper five permanent magnet designs in which the magnetic flux density can be altered are analyzed using numerical simulations, and compared based on the generated magnetic flux density in a sample volume and the amount of magnet material used. The designs are the concentric Halbach cylinder, the two half Halbach cylinders, the two linear Halbach arrays and the four and six rod mangle. The concentric Halbach cylinder design is found to be the best performing design, i.e. the design that provides the most magnetic flux density using the least amount of magnet material. A concentric Halbach cylinder has been constructed and the magnetic flux density, the homogeneity and the direction of the magnetic field are measured and compared with numerical simulation and a good agrement is found.

  15. Energy of magnetic moment of superconducting current in magnetic field

    NASA Astrophysics Data System (ADS)

    Gurtovoi, V. L.; Nikulov, A. V.

    2015-09-01

    The energy of magnetic moment of the persistent current circulating in superconducting loop in an externally produced magnetic field is not taken into account in the theory of quantization effects because of identification of the Hamiltonian with the energy. This identification misleads if, in accordance with the conservation law, the energy of a state is the energy expended for its creation. The energy of magnetic moment is deduced from a creation history of the current state in magnetic field both in the classical and quantum case. But taking this energy into account demolishes the agreement between theory and experiment. Impartial consideration of this problem discovers the contradiction both in theory and experiment.

  16. Levitation of a magnet by an alternating magnetic field

    NASA Astrophysics Data System (ADS)

    Gough, W.; Hunt, M. O.; Summerskill, W. S. H.

    2013-01-01

    An experiment is described in which a small strong cylindrical magnet is levitated by a vertical non-uniform alternating magnetic field. Surprisingly, no superimposed constant field is necessary, but the levitation can be explained when the vertical motion of the magnet is taken into account. The theoretical mean levitation force is (0.26 0.06) N, which is in good agreement with the levitated weight of (0.239 0.001) N. This experiment is suitable for an undergraduate laboratory, particularly as a final year project. Students have found it interesting, and it sharpens up knowledge of basic magnetism.

  17. Structure of magnetic fields in intracluster cavities

    NASA Astrophysics Data System (ADS)

    Gourgouliatos, Konstantinos Nektarios; Braithwaite, Jonathan; Lyutikov, Maxim

    2010-12-01

    Observations of clusters of galaxies show ubiquitous presence of X-ray cavities, presumably blown by the active galactic nuclei (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 we evaluate the rotation measure for radiation transversing the bubble.

  18. Organic Superconductors at Extremely High Magnetic Fields

    SciTech Connect

    Mielke, Charles H.

    2002-02-27

    Intense magnetic fields are an essential tool for understanding layered superconductors. Fundamental electronic properties of organic superconductors are revealed in intense (60 tesla) magnetic fields. Properties such as the topology of the Fermi surface and the nature of the superconducting order parameter are revealed. With modest maximum critical temperatures {approx}13K the charge transfer salt organic superconductors prove to be incredibly valuable materials as their electronically clean nature and layered (highly anisotropic) structures yield insights to the high temperature superconductors. Observation of de Haas-van Alphen and Shubnikov-de Haas quantum oscillatory phenomena, magnetic field induced superconductivity and re-entrant superconductivity are some of the physical phenomena observed in the charge transfer organic superconductors. In this talk, I will discuss the nature of organic superconductors and give an overview of the generation of intense magnetic fields; from the 60 tesla millisecond duration to the extreme 1000 tesla microsecond pulsed magnetic fields.

  19. Orienting Paramecium with intense static magnetic fields

    NASA Astrophysics Data System (ADS)

    Valles, James M., Jr.; Guevorkian, Karine; Quindel, Carl

    2004-03-01

    Recent experiments on cell division suggest the application of intense static magnetic fields as a novel tool for the manipulation of biological systems [1]. The magnetic field appears to couple to the intrinsic anisotropies in the diamagnetic components of the cells. Here, we present measurements of the intrinsic average diamagnetic anisotropy of the whole single celled ciliate, Paramecium Caudatum. Magnetic fields, 2.5 T < B < 8 T were applied to immobilized (non-swimming) Paramecium Caudatum that were suspended in a density matched medium. The organisms align with their long axis parallel to the applied magnetic field. Their intrinsic diamagnetic anisotropy is 3x10-11 in cgs units. We will discuss the implications of these results for employing magnetic fields to probe the behavior of swimming Paramecium. [1] J. M. Valles, Jr. et al., Expt. Cell Res.274, 112-118 (2002).

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

    NASA Astrophysics Data System (ADS)

    Blackman, Eric G.

    2015-05-01

    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. Here I discuss how magnetic helicity has come to help us understand the saturation of and sustenance of large scale dynamos, the need for either local or global helicity fluxes to avoid dynamo quenching, and the associated observational consequences. I also discuss how magnetic helicity acts as a hindrance to turbulent diffusion of large scale fields, and thus a helper for fossil remnant large scale field origin models in some contexts. I briefly discuss the connection between large scale fields and accretion disk theory as well. The goal here is to provide a conceptual primer to help the reader efficiently penetrate the literature.

  1. Chaotic magnetic fields: Particle motion and energization

    SciTech Connect

    Dasgupta, Brahmananda; Ram, Abhay K.; Li, Gang; Li, Xiaocan

    2014-02-11

    Magnetic field line equations correspond to a Hamiltonian dynamical system, so the features of a Hamiltonian systems can easily be adopted for discussing some essential features of magnetic field lines. The integrability of the magnetic field line equations are discussed by various authors and it can be shown that these equations are, in general, not integrable. We demonstrate several examples of realistic chaotic magnetic fields, produced by asymmetric current configurations. Particular examples of chaotic force-free field and non force-free fields are shown. We have studied, for the first time, the motion of a charged particle in chaotic magnetic fields. It is found that the motion of a charged particle in a chaotic magnetic field is not necessarily chaotic. We also showed that charged particles moving in a time-dependent chaotic magnetic field are energized. Such energization processes could play a dominant role in particle energization in several astrophysical environments including solar corona, solar flares and cosmic ray propagation in space.

  2. Measurement of AC magnetic field distribution using magnetic resonance imaging.

    PubMed

    Ider, Y Z; Muftuler, L T

    1997-10-01

    Electric currents are applied to body in numerous applications in medicine such as electrical impedance tomography, cardiac defibrillation, electrocautery, and physiotherapy. If the magnetic field within a region is measured, the currents generating these fields can be calculated using the curl operator. In this study, magnetic fields generated within a phantom by currents passing through an external wire is measured using a magnetic resonance imaging (MRI) system. A pulse sequence that is originally designed for mapping static magnetic field inhomogeneity is adapted. AC current in the form of a burst sine wave is applied synchronously with the pulse sequence. The frequency of the applied current is in the audio range with an amplitude of 175-mA rms. It is shown that each voxel value of sequential images obtained by the proposed pulse sequence is modulated similar to a single tone broadband frequency modulated (FM) waveform with the ac magnetic field strength determining the modulation index. An algorithm is developed to calculate the ac magnetic field intensity at each voxel using the frequency spectrum of the voxel signal. Experimental results show that the proposed algorithm can be used to calculate ac magnetic field distribution within a conducting sample that is placed in an MRI system. PMID:9368117

  3. Exoplanet Magnetic Fields and Their Detectability

    NASA Astrophysics Data System (ADS)

    Stanley, S.; Tian, B. Y.; Vilim, R.

    2014-12-01

    The investigation of planetary magnetic fields in our solar system provides a wealth of information on planetary interior structure and dynamics. Satellite magnetic data demonstrates that planetary dynamos can produce a range of magnetic field morphologies and intensities. Numerical dynamo simulations are working towards determining relationships between planetary properties and the resulting magnetic field characteristics. However, with only a handful of planetary dynamos in our solar system, it is challenging to determine specific dependence of magnetic field properties on planetary characteristics. Extrasolar planets therefore provide a unique opportunity by significantly increasing the number of planets for study as well as offering a much larger range of planetary properties to investigate. Although detection of exoplanet magnetic fields is challenging at present, the increasing sophistication of observational tools available to astronomers implies these extrasolar planetary magnetic fields may eventually be detectable. This presentation will discuss potential observational trends for magnetic field strength and morphology for exoplanets based on numerical simulations and interior structure modeling. We will focus on the influence of planetary age, environment, composition and structure.

  4. Physics in Very Strong Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Lai, Dong

    2015-10-01

    This paper provides an introduction to a number of astrophysics problems related to strong magnetic fields. The first part deals with issues related to atoms, condensed matter and high-energy processes in very strong magnetic fields, and how these issues influence various aspects of neutron star astrophysics. The second part deals with classical astrophysical effects of magnetic fields: Even relatively "weak" fields can play a strong role in various astrophysical problems, ranging from stars, accretion disks and outflows, to the formation and merger of compact objects.

  5. Warm inflation in presence of magnetic fields

    SciTech Connect

    Piccinelli, Gabriella; Ayala, Alejandro; Mizher, Ana Julia

    2013-07-23

    We present preliminary results on the possible effects that primordial magnetic fields can have for a warm inflation scenario, based on global supersymmetry, with a new-inflation-type potential. This work is motivated by two considerations: first, magnetic fields seem to be present in the universe on all scales which rises de possibility that they could also permeate the early universe; second, the recent emergence of inflationary models where the inflaton is not assumed to be isolated but instead it is taken as an interacting field, even during the inflationary expansion. The effects of magnetic fields are included resorting to Schwinger's proper time method.

  6. Femtotesla Magnetic Field Measurement with Magnetoresistive Sensors

    NASA Astrophysics Data System (ADS)

    Pannetier, Myriam; Fermon, Claude; Le Goff, Gerald; Simola, Juha; Kerr, Emma

    2004-06-01

    The measurement of magnetic fields in the femtotesla (fT, 10-15 tesla) range is important for applications such as magnetometry, quantum computing, solid-state nuclear magnetic resonance, and magnetoencephalography. The only sensors capable of detecting these very small fields have been based on low-temperature superconducting quantum interference devices operating at 4.2 kelvin. We present a magnetic field sensor that combines a superconducting flux-to-field transformer with a low-noise giant magnetoresistive sensor. The sensor can be operated up to 77 kelvin. Our small-size prototype provides the capability of measuring 32 fT.

  7. Femtotesla magnetic field measurement with magnetoresistive sensors.

    PubMed

    Pannetier, Myriam; Fermon, Claude; Le Goff, Gerald; Simola, Juha; Kerr, Emma

    2004-06-11

    The measurement of magnetic fields in the femtotesla (fT, 10(-15) tesla) range is important for applications such as magnetometry, quantum computing, solid-state nuclear magnetic resonance, and magnetoencephalography. The only sensors capable of detecting these very small fields have been based on low-temperature superconducting quantum interference devices operating at 4.2 kelvin. We present a magnetic field sensor that combines a superconducting flux-to-field transformer with a low-noise giant magnetoresistive sensor. The sensor can be operated up to 77 kelvin. Our small-size prototype provides the capability of measuring 32 fT. PMID:15192222

  8. The magnetic field of ζ Orionis A

    NASA Astrophysics Data System (ADS)

    Blazère, A.; Neiner, C.; Tkachenko, A.; Bouret, J.-C.; Rivinius, Th.

    2015-10-01

    Context. ζ Ori A is a hot star claimed to host a weak magnetic field, but no clear magnetic detection was obtained so far. In addition, it was recently shown to be a binary system composed of a O9.5I supergiant and a B1IV star. Aims: We aim at verifying the presence of a magnetic field in ζ Ori A, identifying to which of the two binary components it belongs (or whether both stars are magnetic), and characterizing the field. Methods: Very high signal-to-noise spectropolarimetric data were obtained with Narval at the Bernard Lyot Telescope (TBL) in France. Archival HEROS, FEROS and UVES spectroscopic data were also used. The data were first disentangled to separate the two components. We then analyzed them with the least-squares deconvolution technique to extract the magnetic information. Results: We confirm that ζ Ori A is magnetic. We find that the supergiant component ζ Ori Aa is the magnetic component: Zeeman signatures are observed and rotational modulation of the longitudinal magnetic field is clearly detected with a period of 6.829 d. This is the only magnetic O supergiant known as of today. With an oblique dipole field model of the Stokes V profiles, we show that the polar field strength is ~140 G. Because the magnetic field is weak and the stellar wind is strong, ζ Ori Aa does not host a centrifugally supported magnetosphere. It may host a dynamical magnetosphere. Its companion ζ Ori Ab does not show any magnetic signature, with an upper limit on the undetected field of ~300 G. Based on observations obtained at the Télescope Bernard Lyot (USR5026) operated by the Observatoire Midi-Pyrénées, Université de Toulouse (Paul Sabatier), Centre National de la Recherche Scientifique of France.Appendix A is available in electronic form at http://www.aanda.org

  9. The Measurement of Magnetic Fields

    ERIC Educational Resources Information Center

    Berridge, H. J. J.

    1973-01-01

    Discusses five experimental methods used by senior high school students to provide an accurate calibration curve of magnet current against the magnetic flux density produced by an electromagnet. Compares the relative merits of the five methods, both as measurements and from an educational viewpoint. (JR)

  10. Magnetic fields in noninvasive brain stimulation.

    PubMed

    Vidal-Dourado, Marcos; Conforto, Adriana Bastos; Caboclo, Luis Otvio Sales Ferreira; Scaff, Milberto; Guilhoto, Laura Maria de Figueiredo Ferreira; Yacubian, Elza Mrcia Targas

    2014-04-01

    The idea that magnetic fields could be used therapeutically arose 2000 years ago. These therapeutic possibilities were expanded after the discovery of electromagnetic induction by the Englishman Michael Faraday and the American Joseph Henry. In 1896, Arsne d'Arsonval reported his experience with noninvasive brain magnetic stimulation to the scientific French community. In the second half of the 20th century, changing magnetic fields emerged as a noninvasive tool to study the nervous system and to modulate neural function. In 1985, Barker, Jalinous, and Freeston presented transcranial magnetic stimulation, a relatively focal and painless technique. Transcranial magnetic stimulation has been proposed as a clinical neurophysiology tool and as a potential adjuvant treatment for psychiatric and neurologic conditions. This article aims to contextualize the progress of use of magnetic fields in the history of neuroscience and medical sciences, until 1985. PMID:23787954

  11. Field Mapping System for Solenoid Magnet

    NASA Astrophysics Data System (ADS)

    Park, K. H.; Jung, Y. K.; Kim, D. E.; Lee, H. G.; Park, S. J.; Chung, C. W.; Kang, B. K.

    2007-01-01

    A three-dimensional Hall probe mapping system for measuring the solenoid magnet of PLS photo-cathode RF e-gun has been developed. It can map the solenoid field either in Cartesian or in cylindrical coordinate system with a measurement reproducibility better than 5 10-5 T. The system has three axis motors: one for the azimuthal direction and the other two for the x and z direction. This architecture makes the measuring system simple in fabrication. The magnetic center was calculated using the measured axial component of magnetic field Bz in Cartesian coordinate system because the accuracy of magnetic axis measurement could be improved significantly by using Bz, instead of the radial component of magnetic field Br. This paper describes the measurement system and summarizes the measurement results for the solenoid magnetic of PLS photo-cathode RF e-gun.

  12. Magnetic-field-controlled reconfigurable semiconductor logic.

    PubMed

    Joo, Sungjung; Kim, Taeyueb; Shin, Sang Hoon; Lim, Ju Young; Hong, Jinki; Song, Jin Dong; Chang, Joonyeon; Lee, Hyun-Woo; Rhie, Kungwon; Han, Suk Hee; Shin, Kyung-Ho; Johnson, Mark

    2013-02-01

    Logic devices based on magnetism show promise for increasing computational efficiency while decreasing consumed power. They offer zero quiescent power and yet combine novel functions such as programmable logic operation and non-volatile built-in memory. However, practical efforts to adapt a magnetic device to logic suffer from a low signal-to-noise ratio and other performance attributes that are not adequate for logic gates. Rather than exploiting magnetoresistive effects that result from spin-dependent transport of carriers, we have approached the development of a magnetic logic device in a different way: we use the phenomenon of large magnetoresistance found in non-magnetic semiconductors in high electric fields. Here we report a device showing a strong diode characteristic that is highly sensitive to both the sign and the magnitude of an external magnetic field, offering a reversible change between two different characteristic states by the application of a magnetic field. This feature results from magnetic control of carrier generation and recombination in an InSb p-n bilayer channel. Simple circuits combining such elementary devices are fabricated and tested, and Boolean logic functions including AND, OR, NAND and NOR are performed. They are programmed dynamically by external electric or magnetic signals, demonstrating magnetic-field-controlled semiconductor reconfigurable logic at room temperature. This magnetic technology permits a new kind of spintronic device, characterized as a current switch rather than a voltage switch, and provides a simple and compact platform for non-volatile reconfigurable logic devices. PMID:23364687

  13. Particle Acceleration, Magnetic Field Generation and Emission from Relativistic Jets and Supernova Remnants

    NASA Technical Reports Server (NTRS)

    Nishikawa, K.-I.; Hartmann, D. H.; Hardee, P.; Hededal, C.; Mizunno, Y.; Fishman, G. J.

    2006-01-01

    We performed numerical simulations of particle acceleration, magnetic field generation, and emission from shocks in order to understand the observed emission from relativistic jets and supernova remnants. The investigation involves the study of collisionless shocks, where the Weibel instability is responsible for particle acceleration as well as magnetic field generation. A 3-D relativistic particle-in-cell (RPIC) code has been used to investigate the shock processes in electron-positron plasmas. The evolution of theWeibe1 instability and its associated magnetic field generation and particle acceleration are studied with two different jet velocities (0 = 2,5 - slow, fast) corresponding to either outflows in supernova remnants or relativistic jets, such as those found in AGNs and microquasars. Slow jets have intrinsically different structures in both the generated magnetic fields and the accelerated particle spectrum. In particular, the jet head has a very weak magnetic field and the ambient electrons are strongly accelerated and dragged by the jet particles. The simulation results exhibit jitter radiation from inhomogeneous magnetic fields, generated by the Weibel instability, which has different spectral properties than standard synchrotron emission in a homogeneous magnetic field.

  14. Dynamic Magnetic Field Applications for Materials Processing

    NASA Technical Reports Server (NTRS)

    Mazuruk, K.; Grugel, Richard N.; Motakef, S.; Whitaker, Ann F. (Technical Monitor)

    2001-01-01

    Magnetic fields, variable in time and space, can be used to control convection in electrically conducting melts. Flow induced by these fields has been found to be beneficial for crystal growth applications. It allows increased crystal growth rates, and improves homogeneity and quality. Particularly beneficial is the natural convection damping capability of alternating magnetic fields. One well-known example is the rotating magnetic field (RMF) configuration. RMF induces liquid motion consisting of a swirling basic flow and a meridional secondary flow. In addition to crystal growth applications, RMF can also be used for mixing non-homogeneous melts in continuous metal castings. These applied aspects have stimulated increasing research on RMF-induced fluid dynamics. A novel type of magnetic field configuration consisting of an axisymmetric magnetostatic wave, designated the traveling magnetic field (TMF), has been recently proposed. It induces a basic flow in the form of a single vortex. TMF may find use in crystal growth techniques such as the vertical Bridgman (VB), float zone (FZ), and the traveling heater method. In this review, both methods, RMF and TMF are presented. Our recent theoretical and experimental results include such topics as localized TMF, natural convection dumping using TMF in a vertical Bridgman configuration, the traveling heater method, and the Lorentz force induced by TMF as a function of frequency. Experimentally, alloy mixing results, with and without applied TMF, will be presented. Finally, advantages of the traveling magnetic field, in comparison to the more mature rotating magnetic field method, will be discussed.

  15. Interplanetary magnetic field and geomagnetic Dst variations.

    NASA Technical Reports Server (NTRS)

    Patel, V. L.; Desai, U. D.

    1973-01-01

    The interplanetary magnetic field has been shown to influence the ring current field represented by Dst. Explorer 28 hourly magnetic field observations have been used with the hourly Dst values. The moderate geomagnetic storms of 60 gammas and quiet-time fluctuations of 10 to 30 gammas are correlated with the north to south change of the interplanetary field component perpendicular to the ecliptic. This change in the interplanetary field occurs one to three hours earlier than the corresponding change in the Dst field.

  16. External-field-free magnetic biosensor

    SciTech Connect

    Li, Yuanpeng; Wang, Yi; Klein, Todd; Wang, Jian-Ping

    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.

  17. Polarized radiation diagnostics of stellar magnetic fields

    NASA Astrophysics Data System (ADS)

    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 geometric structure of these fields. How this can possibly be achieved is briefly discussed. An overview of the current status of polarimetric studies of magnetic fields in non-degenerate stars of other types is presented. The final section is devoted to magnetic fields of white dwarfs. Current knowledge of magnetic fields of isolated white dwarfs is briefly reviewed. Diagnostic techniques are discussed, with particular emphasis on the variety of physical processes to be considered for understanding of spectral line formation over the broad range of magnetic field strengths encountered in these stars.

  18. Ohm's law for mean magnetic fields

    SciTech Connect

    Boozer, A.H.

    1986-05-01

    The magnetic fields associated with plasmas frequently exhibit small amplitude MHD fluctuations. It is useful to have equations for the magnetic field averaged over these fluctuations, the so-called mean field equations. Under very general assumptions it is shown that the effect of MHD fluctuations on a force-free plasma can be represented by one parameter in Ohm's law, which is effectively the coefficient of electric current viscosity.

  19. Surface magnetic fields across the HR Diagram

    NASA Astrophysics Data System (ADS)

    Landstreet, John D.

    2015-10-01

    The past 20 years have seen remarkable advances in spectropolarimetric instrumentation that have allowed us, for the first time, to identify some magnetic stars in most major stages of stellar evolution. We are beginning to see the broad outline of how such fields change during stellar evolution, to confront theoretical hypotheses and models of magnetic field structure and evolution with detailed data, and to understand more of the ways in which the presence of a field in turn affects stellar structure and evolution.

  20. Emittance measurement in a magnetic field

    SciTech Connect

    Boyd, J.K.

    1991-04-15

    Emittance can be measured by intercepting an electron beam on a range thick plate and then observing the expansion of beamlets transmitted through small holes. The hole size is selected to minimize space charge effects. In the presence of a magnetic field the beamlets have a spiral trajectory and the usual field free formulation must be modified. To interpret emittance in the presence of a magnetic field an envelope equation is derived in the appropriate rotating frame. 1 ref.

  1. Quantitative modeling of planetary magnetospheric magnetic fields

    NASA Technical Reports Server (NTRS)

    Walker, R. J.

    1979-01-01

    Three new quantitative models of the earth's magnetospheric magnetic field have recently been presented: the Olson-Pfitzer model, the Tsyganenko model, and the Voigt model. The paper reviews these models in some detail with emphasis on the extent to which they have succeeded in improving on earlier models. The models are compared with the observed field in both magnitude and direction. Finally, the application to other planetary magnetospheres of the techniques used to model the earth's magnetospheric magnetic field is briefly discussed.

  2. Manipulating Cells with Static Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Valles, J. M.; Guevorkian, K.

    2005-07-01

    We review our investigations of the use of static magnetic fields, B, for manipulating cells and cellular processes. We describe how B fields modify the cell division pattern of frog embryos and consequently can be used to probe the pattern determinants. We also observe that magnetic fields modify the swimming behavior of Paramecium Caudatum. We describe these modifications and their potential application to investigations of their swimming behavior.

  3. Biological effects of high DC magnetic fields

    SciTech Connect

    Tenforde, T.S.

    1981-06-01

    The principal focus of the program is the analysis of magnetic field effects on physiological functions in experimental animals and selected organ and tissue systems. A major research effort has involved the use of electrical recording techniques to detect functional alterations in the cardiovascular, neural, and visual systems during the application of DC magnetic fields. These systems involve ionic conduction processes, and are therefore potentially sensitive to electrodynamic interactions with an applied magnetic field. In the specific case of the visual system, magnetic interactions could also arise through orientational effects on the magnetically anisotropic photopigment molecules within retinal photoreceptor cells. In addition to studies with potentially sensitive target tissues, an evaluation is being made of magnetic field effects on a broad range of other physiological functions in laboratory mammals, including the measurement of circadian rhythms using noninvasive recording techniques. Results of investigations of magnetic field effects on the conformation of DNA, and on the growth and development of plants and insects are also reported. Figures and tables provide a brief summary of some representative observations in each of the research areas described. No significant alterations were observed in any of the physiological parameters examined to date, with the exception of major changes that occur in the electrocardiogram during magnetic field exposure. Studies with several species of animals have provided evidence that this phenomenon is attributable to electrical potentials that are induced during pulsatile blood flow in the aorta and in other major vessels of the circulatory system.

  4. Field mapping system for cyclotron magnet

    NASA Astrophysics Data System (ADS)

    Park, K. H.; Jung, Y. G.; Kim, D. E.; Kang, B. K.; Yoon, M.; Chai, J. S.; Kim, Y. S.

    2005-06-01

    This paper presents a Hall probe mapping system for measuring a cyclotron magnet, which has been fabricated for the 13 MeV cyclotron at the Korea Institute of Radiological and Medical Sciences. Two Hall probes are mounted on a precision mechanical x- y stage and map magnetic field in the Cartesian coordinate system. The mapping system uses the 'flying' mode field mapping method to reduce data-acquisition time. The time required for mapping the whole gap-area of the cyclotron magnet is ˜60 min. The relative measurement error for the averaged magnetic field along beam orbit is less than 0.02%. The cyclotron magnet has been corrected using field measurement data, and the achieved total phase excursion of the cyclotron after correction is less than ±15°, which is within the tolerance of ±20° for the total phase excursion.

  5. An Extraordinary Magnetic Field Map of Mars

    NASA Technical Reports Server (NTRS)

    Connerney, J. E. P.; Acuna, M. H.; Ness, N. F.; Mitchell, D. L.; Lin, R. P.

    2004-01-01

    The Mars Global Surveyor spacecraft has completed two Mars years in nearly circular polar orbit at a nominal altitude of 400 km. The Mars crust is at least an order of magnitude more intensely magnetized than that of the Earth [1], and intriguing in both its global distribution and geometric properties [2,3]. Measurements of the vector magnetic field have been used to map the magnetic field of crustal origin to high accuracy [4]. We present here a new map of the magnetic field with an order of magnitude increased sensitivity to crustal magnetization. The map is assembled from > 2 full years of MGS night-side observations, and uses along-track filtering to greatly reduce noise due to external field variations.

  6. Vector Magnetic Field in Emerging Flux Regions

    NASA Astrophysics Data System (ADS)

    Schmieder, B.; Pariat, E.

    A crucial phase in magnetic flux emergence is the rise of magnetic flux tubes through the solar photosphere, which represents a severe transition between the very different environments of the solar interior and corona. Multi-wavelength observations with Flare Genesis, TRACE, SoHO, and more recently with the vector magnetographs at THEMIS and Hida (DST) led to the following conclusions. The fragmented magnetic field in the emergence region - with dipped field lines or bald patches - is directly related with Ellerman bombs, arch filament systems, and overlying coronal loops. Measurements of vector magnetic fields have given evidence that undulating "serpentine" fields are present while magnetic flux tubes cross the photosphere. See the sketch below, and for more detail see Pariat et al. (2004, 2007); Watanabe et al. (2008):

  7. Magnetic fields near Mars - First results

    NASA Technical Reports Server (NTRS)

    Riedler, W.; Schwingenschuh, K.; Moehlmann, D.; Oraevskii, V. N.; Eroshenko, E.; Slavin, J.

    1989-01-01

    The magnetic fields of Mars have been measured from Phobos 2 with high temporal resolution in the tail and down to an 850-km altitude. During four successive highly elliptical orbits, the position of the bow shock as well as that of a transition layer, the 'planetopause', were identified. Subsequent circular orbits at 6000-km altitude provided the first high-resolution data in the planetary tail and indicate that the interplanetary magnetic field mainly controls the magnetic tail. Magnetic turbulence was also detected when the spacecraft crossed the orbit of Phobos, indicating the possible existence of a torus near the orbit of this moon.

  8. Particle Transport in Therapeutic Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Puri, Ishwar K.; Ganguly, Ranjan

    2014-01-01

    Iron oxide magnetic nanoparticles, in ferrofluids or as magnetic microspheres, offer magnetic maneuverability, biochemical surface functionalization, and magnetic relaxation under the influence of an alternating field. The use of these properties for clinical applications requires an understanding of particles, forces, and scalar transport at various length scales. This review explains the behavior of magnetic nano- and microparticles during magnetic drug targeting and magnetic fluid hyperthermia, and the microfluidic transport of these particles in bioMEMS (biomedical microelectromechanical systems) devices for ex vivo therapeutic and diagnostic applications. Magnetic particle transport, the momentum interaction of these particles with a host fluid in a flow, and thermal transport in a particle-infused tissue are characterized through the governing electrodynamic, hydrodynamic, and scalar transport equations.

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

    PubMed

    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. PMID:24316186

  10. Magnetic field homogeneity perturbations in finite Halbach dipole magnets

    NASA Astrophysics Data System (ADS)

    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.

  11. Polarization Diagnostics of Solar Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Manso Sainz, R.

    2011-12-01

    The solar atmosphere is a highly ionized medium which is the playground of magnetic fields. In the deepest layer (the photosphere), magnetic fields disturb the 'normal' fluid motions forcing the plasma to behave incounterintuitive ways; in the outer layers (the chromosphere and the corona) magnetic fields rule, making the plasma levitate or even ejecting it out of the gravitational well of the Sun, with important consequences for us here on Earth. However, magnetic fields are elusive. The only quantitative evidence of their presence is through the polarization state of the light emitted by the plasma they are playing with. Remote sensing of magnetic fields from 150 million km away through spectropolarimetry is a challenge on applied physics as well as an art. It requires the application of quantum mechanics, radiative transfer theory, and advanced optics to the interpretation and analysis of spectropolarimetric observations. I will review standard diagnostic techniques and recent developments on this field. I will discuss their limitations and how to overcome them through the complementary aspects of different diagnostic techniques, spectral regions, and statistical analysis. Finally, I will review what are the main areas for progress in this regard: most notably, the 'measurement' of magnetic fields in the extremely dilute and weakly magnetized outer layers of the sun.

  12. Magnetic reconnection at the edge of Uranus's magnetic field

    NASA Astrophysics Data System (ADS)

    Balcerak, Ernie

    2014-09-01

    A new modeling study sheds light on how the magnetosphere of Uranus compares to those of other planets. Magnetospheres around the inner planets Mercury and Earth are primarily driven by the solar wind—the charged particles spewed out from the Sun—through magnetic reconnection, in which the planet's magnetic field lines break and reconnect, releasing energy in the process.

  13. State transitions triggered by inverse magnetic field: probably applied in high-mass X-ray binaries?

    NASA Astrophysics Data System (ADS)

    Li, Shuang-Liang; Yan, Zhen

    2016-03-01

    Previous works suggested that the state transitions in an X-ray binary can be triggered by accreting an inverse magnetic field from its companion star. A key point of this mechanism is the accretion and magnification of large-scale magnetic fields from the outer boundary of a thin disk. However, how such a process can be realized is still an open question. In this work, we check this issue in a realistic X-ray binary system. According to our calculations, a quite strong initial magnetic field, B ∼ 102 ‑ 103 G, is required in order to assure that the large-scale magnetic field can be effectively dragged inward and magnified with the accretion of gas. Thus, such a picture probably can be present in high-mass X-ray binaries possessing a strong stellar magnetic field, e.g., Cyg X-1.

  14. The magnetic field of Mercury, part 1

    NASA Technical Reports Server (NTRS)

    Ness, N. F.; Behannon, K. W.; Lepping, R. P.; Whang, Y. C.

    1974-01-01

    An updated analysis and interpretation is presented of the magnetic field observations obtained during the Mariner 10 encounter with the planet Mercury. The combination of data relating to position of the detached bow shock wave and magnetopause, and the geometry and magnitude of the magnetic field within the magnetosphere-like region surrounding Mercury, lead to the conclusion that an internal planetary field exists with dipole moment approximately 5.1 x 10 the 22nd power Gauss sq cm. The dipole axis has a polarity sense similar to earth's and is tilted 7 deg from the normal to Mercury's orbital plane. The magnetic field observations reveal a significant distortion of the modest Hermean field (350 Gamma at the equator) by the solar wind flow and the formation of a magnetic tail and neutral sheet which begins close to the planet on the night side. The composite data is not consistent with a complex induction process driven by the solar wind flow.

  15. Electric-field guiding of magnetic skyrmions

    NASA Astrophysics Data System (ADS)

    Upadhyaya, Pramey; Yu, Guoqiang; Amiri, Pedram Khalili; Wang, Kang L.

    2015-10-01

    We theoretically study equilibrium and dynamic properties of nanosized magnetic skyrmions in thin magnetic films with broken inversion symmetry, where an electric field couples to magnetization via spin-orbit coupling. Based on a symmetry-based phenomenology and micromagnetic simulations we show that this electric-field coupling, via renormalizing the micromagnetic energy, modifies the equilibrium properties of the skyrmion. This change, in turn, results in a significant alteration of the current-induced skyrmion motion. Particularly, the speed and direction of the skyrmion can be manipulated by designing a desired energy landscape electrically, which we describe within Thiele's analytical model and demonstrate in micromagnetic simulations including electric-field-controlled magnetic anisotropy. We additionally use this electric-field control to construct gates for controlling skyrmion motion exhibiting a transistorlike and multiplexerlike function. The proposed electric-field effect can thus provide a low-energy electrical knob to extend the reach of information processing with skyrmions.

  16. How are static magnetic fields detected biologically?

    NASA Astrophysics Data System (ADS)

    Finegold, Leonard

    2009-03-01

    There is overwhelming evidence that life, from bacteria to birds to bats, detects magnetic fields, using the fields for orientation or navigation. Indeed there are recent reports (based on Google Earth imagery) that cattle and deer align themselves with the earth's magnetic field. [1]. The development of frog and insect eggs are changed by high magnetic fields, probably through known physical mechanisms. However, the mechanisms for eukaryotic navigation and alignment are not clear. Persuasive published models will be discussed. Evidence, that static magnetic fields might produce therapeutic effects, will be updated [2]. [4pt] [1] S. Begall, et al., Proc Natl Acad Sci USA, 105:13451 (2008). [0pt] [2] L. Finegold and B.L. Flamm, BMJ, 332:4 (2006).

  17. ASYMMETRIC DIFFUSION OF MAGNETIC FIELD LINES

    SciTech Connect

    Beresnyak, Andrey

    2013-04-20

    Stochasticity of magnetic field lines is important for particle transport properties. Magnetic field lines separate faster than diffusively in turbulent plasma, which is called superdiffusion. We discovered that this superdiffusion is pronouncedly asymmetric, so that the separation of field lines along the magnetic field direction is different from the separation in the opposite direction. While the symmetry of the flow is broken by the so-called imbalance or cross-helicity, the difference between forward and backward diffusion is not directly due to imbalance, but a non-trivial consequence of both imbalance and non-reversibility of turbulence. The asymmetric diffusion perpendicular to the mean magnetic field entails a variety of new physical phenomena, such as the production of parallel particle streaming in the presence of perpendicular particle gradients. Such streaming and associated instabilities could be significant for particle transport in laboratory, space, and astrophysical plasmas.

  18. Normal glow discharge in axial magnetic field

    NASA Astrophysics Data System (ADS)

    Surzhikov, S.; Shang, J.

    2014-10-01

    Theory and results of mathematical modeling of a glow discharge in a parallel-plate configuration with axial magnetic field is presented. The model consists of continuity equations for electron and ion fluids, the Poisson equation for the self-consistent electric field. Numerical simulation results are presented for two-dimensional glow discharge at various initial conditions. The results are obtained for molecular nitrogen at pressure 1-5 Torr, emf of power supply 1-2 kV, and magnetic field induction B = 0-0.5 T. It is shown that in the presence of the axial magnetic field the glow discharge is rotated around its axis of symmetry. Nevertheless it is shown that in the investigated range of discharge parameters in an axial magnetic field the law of the normal current density is retained.

  19. Theory of cosmological seed magnetic fields

    SciTech Connect

    Saleem, H.

    2007-07-15

    A theory for the generation of seed magnetic field and plasma flow on cosmological scales driven by externally given baroclinic vectors is presented. The Beltrami-like plasma fields can grow from zero values at initial time t=0 from a nonequilibrium state. Exact analytical solutions of the set of two-fluid equations are obtained that are valid for large plasma {beta}-values as well. Weaknesses of previous models for seed magnetic field generation are also pointed out. The analytical calculations predict the galactic seed magnetic field generated by this mechanism to be of the order of 10{sup -14} G, which may be amplified later by the {alpha}{omega} dynamo (or by some other mechanism) to the present observed values of the order of {approx}(2-10) {mu}G. The theory has been applied to laser-induced plasmas as well and the estimate of the magnetic field's magnitude is in agreement with the experimentally observed values.

  20. Ultracold atoms in strong synthetic magnetic fields

    NASA Astrophysics Data System (ADS)

    Ketterle, Wolfgang

    2015-03-01

    The Harper Hofstadter Hamiltonian describes charged particles in the lowest band of a lattice at high magnetic fields. This Hamiltonian can be realized with ultracold atoms using laser assisted tunneling which imprints the same phase into the wavefunction of neutral atoms as a magnetic field dose for electrons. I will describe our observation of a bosonic superfluid in a magnetic field with half a flux quantum per lattice unit cell, and discuss new possibilities for implementing spin-orbit coupling. Work done in collaboration with C.J. Kennedy, G.A. Siviloglou, H. Miyake, W.C. Burton, and Woo Chang Chung.

  1. Magnetic fields of the terrestrial planets

    NASA Technical Reports Server (NTRS)

    Russell, C. T.

    1993-01-01

    The four terrestrial planets, together with the Earth's Moon, provide a significant range of conditions under which dynamo action could occur. All five bodies have been visited by spacecraft, and from three of the five bodies (Earth, Moon and Mars) we have samples of planetary material upon which paleomagnetic studies have been undertaken. At the present time, only the Earth and Mercury appear to have a significant dipole magnetic field. However, the Moon, and possibly Mars, appear to have had ancient planetary dynamos. Venus does not now have a significant planetary magnetic field, and the high surface temperatures should have prevented the recording of evidence of any ancient magnetic field. Since the solidification of the solid inner core is thought to be the energy source for the terrestrial magnetic field, and since smaller bodies evolve thermally more rapidly than larger bodies, we conjecture that the terrestrial planets are today in three different phases of magnetic activity. Venus is in a predynamo phase, not having cooled to the point of core solidification. Mercury and the Earth are in the middle of their dynamo phase, with Mercury perhaps near the end of its activity. Mars and the Moon seem to be well past their dynamo phase. Much needs to be done in the study of the magnetism of the terrestrial planets. We need to characterize the multipole harmonic structure of the Mercury magnetic field plus its secular variation, and we need to analyze returned samples to attempt to unfold the long-term history of Mercury's dynamo. We need to more thoroughly map the magnetism of the lunar surface and to analyze samples obtained from a wider area of the lunar surface. We need a more complete survey of the present Martian magnetic field and samples from a range of different ages of Martian surface material. Finally, a better characterization of the secular variation of the terrestrial magnetic field is needed in order to unfold the workings of the terrestrial dynamo.

  2. Environmental magnetic fields: Influences on early embryogenesis

    SciTech Connect

    Cameron, I.L.; Hardman, W.E.; Winters, W.D.; Zimmerman, S.; Zimmerman, A.M. )

    1993-04-01

    A 10-mG, 50 to 60-Hz magnetic field is in the intensity and frequency range that people worldwide are often exposed to in homes and in the workplace. Studies about the effects of 50- to 100-Hz electromagnetic fields on various species of animal embryos (fish, chick, fly, sea urchin, rat, and mouse) indicate that early stages of embryonic development are responsive to fluctuating magnetic fields. Chick, sea urchin, and mouse embryos are responsive to magnetic field intensities of 10-100 mG. Results from studies on sea urchin embryos indicate that exposure to conditions of rotating 60-Hz magnetic fields, e.g., similar to those in our environment, interferes with cell proliferation at the morula stage in a manner dependent on field intensity. The cleavage stages, prior to the 64-cell stage, were not delayed by this rotating 60-Hz magnetic field suggesting that the ionic surges, DNA replication, and translational events essential for early cleavage stages were not significantly altered. Studies of histone synthesis in early sea urchin embryos indicated that the rotating 60-Hz magnetic field decreased zygotic expression of early histone genes at the morula stage and suggests that this decrease in early histone production was limiting to cell proliferation. Whether these comparative observations from animal development studies will be paralleled by results from studies of human embryogenesis, as suggested by some epidemiology studies, has yet to be established. 38 refs.

  3. The field of a screened magnetic dipole

    NASA Technical Reports Server (NTRS)

    Greene, J. M.; Miller, R. L.

    1994-01-01

    The purpose of this note is to quantitatively study the asymptotic behavior of the dipole magnetic field in the tail region of a paraboloidal or cylindrical model of the magnetosphere, assuming the complete screening of the internal field by magnetopause currents. This screening assumption is equivalent to imposing the boundary condition that the normal component of the magnetic field is zero at the magnetopause. With this boundary condition, the screened dipole field falls off exponentially with distance down the tail, in sharp constrast to the bare dipole field. Analytic expressions for a cylindrical and paraboloidal magnetopause are given.

  4. Aurora and magnetic field of Uranus

    NASA Astrophysics Data System (ADS)

    Herbert, Floyd

    2009-11-01

    Resolution of the details of a planetary magnetic field from magnetometer measurements made during a single flyby can be severely limited because of the incomplete geometrical sampling of the planetary neighborhood by the flyby trajectory. This problem was especially severe for the only spacecraft encounter with Uranus, that of Voyager 2 in 1986. Fortunately, auroras at the magnetic field line footprints serve as additional constraints that may be used to determine the higher multipole moments of planetary fields (Connerney et al.'s (1998) VIP-4 model of for Jupiter). In the present work, this approach is applied to improving the resolution of the magnetic field of Uranus. The auroral emission distribution at Uranus is determined from scans by the Voyager 2 Ultraviolet Spectrometer (UVS), enhancing an earlier analysis by Herbert and Sandel (1994) by incorporating more observations and by using more powerful analysis techniques. The resulting new determination of the auroral ovals is well correlated with the field lines associated with the strongest plasma wave and radio emissions but differs from model ovals computed by Connerney et al. (1987) from the Q3 magnetic field model for Uranus. Consequently, a search has been initiated for model coefficients of the planetary magnetic field that agree both with the magnetic field observations and also with the reasonable assumption that the newly determined auroral emissions lie at the magnetic footprints of an equidistant circum-Uranian region of the magnetosphere. The dipole and quadrupole terms of the new field model, termed AH5, are similar to those of the dipole + quadrupole Q3 model, but the AH5 higher multipole terms diverge from the dipole + quadrupole + octupole I3E1 model of Connerney et al. (1987), from which the Q3 model was derived. Inasmuch as the I3E1 octupole terms were not resolved, the AH5 model derived here comprises a first estimate of the higher multipole moments of Uranus's magnetic field.

  5. Some Structural Properties of Solar Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Ioshpa, B.; Mogilevskii, E.; Obridko, V.

    2007-05-01

    We discuss some results of the study of spatial characteristics of solar magnetic fields. The analysis is based on the magnetic field data obtained with a new spectromagnetograph installed on the IZMIRAN Tower Telescope (Fe I 6302.5 Å) (Kozhevatov et al., 2002), the data of the MSFC solar vector magnetograph (Fe I 5250.2 Å) and the data of longitudinal magnetic 96 m daily maps of SOHO/MDI magnetograph (Ni I 6768 Å) downloaded through Internet. Our study was directed in some different ways: the fractal properties of sunspots; fractal properties of space distribution of the magnetic fields along great distances comparable with the size of active regions or active complexes; fractal properties of active and quiet regions as global entities. To do it we used some different methods, particularly, the well known method using the relation between the area and the perimeter of magnetic field lines (see (Feder, 1988; Meunier, 1999; Nesme-Ribes at al., 1996; Balke et al., 1993)) and technique developed by Higuchi (1988), who applied it to the investigation of long time series. Note also that magnetic structure in terms of the fractal models was developed earlier in (Zelenyi & Milovanov, 1991; Milovanov & Zelenyi, 1993; Mogilevskii, 1994; Mogilevskii, 2001; Abramenko et al., 2002; Abramenko, 2005; Salakhudinova & Golovko, 2005). The main results are: 1. Fractal analysis of sunspot magnetic field indicated the existence of three families of self-similar contour lines roughly belonging to the umbra, penumbra and the ambient photosphere correspondingly. The greatest fractal dimension corresponds to the regions of weakest fields (ambient photosphere), the least one corresponds to the intermediate region (penumbra). 2. More detailed analysis shows that the fractal coefficient has a maximum (about 1.50) near the umbra--penumbra interface. 3. The global fractal numbers of space distribution of magnetic field on solar surface is closely connected with the mean absolute values of the longitudinal magnetic field for this surface. The fractal numbers diminish with the rising of mean magnetic field (from values about 2.0 for the relatively quiet region to 1- 1.2 for very active regions). 4. The dependences of fractal numbers of the space distribution of longitudinal and transversal fields versus mean longitudinal field are similar by their character but the fractal values for transversal field are higher than the corresponding factor values for longitudinal field by factor about 1.5. This means that the distribution of transversal field along the space is more chaotic than the distribution of longitudinal field.

  6. The theory of the Galactic magnetic field

    NASA Technical Reports Server (NTRS)

    Zweibel, Ellen G.

    1987-01-01

    The paper discusses the role of the magnetic field in determining the large scale structure and dynamics of the interstellar medium. It then discusses the origin and maintenance of the Galactic field. The two major competing theories are that the field is primordial and connected to an intergalactic field or that the field is removed from and regenerated within the Galaxy. Finally, cosmic ray acceleration and confinement in the interstellar medium are discussed.

  7. Magnetic Field Strengths in Photodissociation Regions

    NASA Astrophysics Data System (ADS)

    Balser, Dana S.; Anish Roshi, D.; Jeyakumar, S.; Bania, T. M.; Montet, Benjamin T.; Shitanishi, J. A.

    2016-01-01

    We measure carbon radio recombination line (RRL) emission at 5.3 {{GHz}} toward four H ii regions with the Green Bank Telescope to determine the magnetic field strength in the photodissociation region (PDR) that surrounds the ionized gas. Roshi suggests that the non-thermal line widths of carbon RRLs from PDRs are predominantly due to magneto-hydrodynamic waves, thus allowing the magnetic field strength to be derived. We model the PDR with a simple geometry and perform the non-LTE radiative transfer of the carbon RRL emission to solve for the PDR physical properties. Using the PDR mass density from these models and the carbon RRL non-thermal line width we estimate total magnetic field strengths of B? 100{--}300 ? {{G}} in W3 and NGC 6334A. Our results for W49 and NGC 6334D are less well constrained with total magnetic field strengths between B? 200{--}1000 ? {{G}}. H i and OH Zeeman measurements of the line of sight magnetic field strength ({B}{{los}}), taken from the literature, are between a factor of ? 0.5{--}1 of the lower bound of our carbon RRL magnetic field strength estimates. Since | {B}{{los}}| ?slant B, our results are consistent with the magnetic origin of the non-thermal component of carbon RRL widths.

  8. Directed Plasma Flow across Magnetic Field

    NASA Astrophysics Data System (ADS)

    Presura, R.; Stepanenko, Y.; Neff, S.; Sotnikov, V. I.

    2008-04-01

    The Hall effect plays a significant role in the penetration of plasma flows across magnetic field. For example, its effect may become dominant in the solar wind penetration into the magnetosphere, in the magnetic field advection in wire array z-pinch precursors, or in the arcing of magnetically insulated transmission lines. An experiment performed at the Nevada Terawatt Facility explored the penetration of plasma with large Hall parameter (˜10) across ambient magnetic field. The plasma was produced by ablation with the short pulse high intensity laser Leopard (0.35 ps, 10^17W/cm^2) and the magnetic field with the pulsed power generator Zebra (50 T). The expanding plasma assumed a jet configuration and propagated beyond a distance consistent with a diamagnetic bubble model. Without magnetic field, the plasma expansion was close to hemispherical. The ability to produce the plasma and the magnetic field with distinct generators allows a controlled, quasi-continuous variation of the Hall parameter and other plasma parameters making the experiments useful for benchmarking numerical simulations.

  9. Space applications of superconductivity - High field magnets

    NASA Technical Reports Server (NTRS)

    Fickett, F. R.

    1979-01-01

    The paper discusses developments in superconducting magnets and their applications in space technology. Superconducting magnets are characterized by high fields (to 15T and higher) and high current densities combined with low mass and small size. The superconducting materials and coil design are being improved and new high-strength composites are being used for magnet structural components. Such problems as maintaining low cooling temperatures (near 4 K) for long periods of time and degradation of existing high-field superconductors at low strain levels can be remedied by research and engineering. Some of the proposed space applications of superconducting magnets include: cosmic ray analysis with magnetic spectrometers, energy storage and conversion, energy generation by magnetohydrodynamic and thermonuclear fusion techniques, and propulsion. Several operational superconducting magnet systems are detailed.

  10. Tracing Magnetic Fields by Atomic Alignment in Extended Radiation Fields

    NASA Astrophysics Data System (ADS)

    Zhang, Heshou; Yan, Huirong; Dong, Le

    2015-05-01

    Tracing magnetic field is crucial as magnetic field plays an important role in many astrophysical processes. Earlier studies have demonstrated that ground state alignment (GSA) is an effective way to detect a weak magnetic field (1G? B? {{10}-15} G) in a diffuse medium. We explore the atomic alignment in the presence of an extended radiation field for both absorption lines and emission lines. The alignment in the circumstellar medium, binary systems, disks, and the local interstellar medium are considered in order to study the alignment in the radiation field where the pumping source has a clear geometric structure. Furthermore, the multipole expansion method is adopted to study GSA induced in the radiation field with unidentified pumping sources. We study the alignment in the dominant radiation components of the general radiation field: the dipole and quadrupole radiation field. We discuss the approximation of GSA in a general radiation field by summing the contribution from the dipole and quadrupole radiation field. We conclude that GSA is a powerful tool for detecting weak magnetic fields in the diffuse medium in general radiation fields.

  11. Compact Electric- And Magnetic-Field Sensor

    NASA Technical Reports Server (NTRS)

    Winterhalter, Daniel; Smith, Edward

    1994-01-01

    Compact sensor measures both electric and magnetic fields. Includes both short electric-field dipole and search-coil magnetometer. Three mounted orthogonally providing triaxial measurements of electromagnetic field at frequencies ranging from near 0 to about 10 kHz.

  12. Effect of magnetic field inhomogeneity on ion cyclotron motion coherence at high magnetic field.

    PubMed

    Vladimirov, Gleb; Kostyukevich, Yury; Hendrickson, Christopher L; Blakney, Greg T; Nikolaev, Eugene

    2015-01-01

    A three-dimensional code based on the particle-in-cell algorithm modified to account for the inhomogeneity of the magnetic field was applied to determine the effect of Z(1), Z(2), Z(3), Z(4), X, Y, ZX, ZY, XZ(2) YZ(2), XY and X(2)-Y(2) components of an orthogonal magnetic field expansion on ion motion during detection in an FT-ICR cell. Simulations were performed for magnetic field strengths of 4.7, 7, 14.5 and 21 Tesla, including experimentally determined magnetic field spatial distributions for existing 4.7 T and 14.5 T magnets. The effect of magnetic field inhomogeneity on ion cloud stabilization ("ion condensation") at high numbers of ions was investigated by direct simulations of individual ion trajectories. Z(1), Z(2), Z(3) and Z(4) components have the largest effect (especially Z(1)) on ion cloud stability. Higher magnetic field strength and lower m/z demand higher relative magnetic field homogeneity to maintain cloud coherence for a fixed time period. The dependence of mass resolving power upper limit on Z(1) inhomogeneity is evaluated for different magnetic fields and m/z. The results serve to set the homogeneity requirements for various orthogonal magnetic field components (shims) for future FT-ICR magnet design. PMID:26307725

  13. Magnetic monopoles in field theory and cosmology.

    PubMed

    Rajantie, Arttu

    2012-12-28

    The existence of magnetic monopoles is predicted by many theories of particle physics beyond the standard model. However, in spite of extensive searches, there is no experimental or observational sign of them. I review the role of magnetic monopoles in quantum field theory and discuss their implications for particle physics and cosmology. I also highlight their differences and similarities with monopoles found in frustrated magnetic systems. PMID:23166376

  14. High Field Pulse Magnets with New Materials

    NASA Astrophysics Data System (ADS)

    Li, L.; Lesch, B.; Cochran, V. G.; Eyssa, Y.; Tozer, S.; Mielke, C. H.; Rickel, D.; van Sciver, S. W.; Schneider-Muntau, H. J.

    2004-11-01

    High performance pulse magnets using the combination of CuNb conductor and Zylon fiber composite reinforcement with bore sizes of 24, 15 and 10 mm have been designed, manufactured and tested to destruction. The magnets successfully reached the peak fields of 64, 70 and 77.8 T respectively with no destruction. Failures occurred near the end flanges at the layer. The magnet design, manufacturing and testing, and the mode of the failure are described and analyzed.

  15. On the helicity of open magnetic fields

    SciTech Connect

    Prior, C.; Yeates, A. R.

    2014-06-01

    We reconsider the topological interpretation of magnetic helicity for magnetic fields in open domains, and relate this to the relative helicity. Specifically, our domains stretch between two parallel planes, and each of these ends may be magnetically open. It is demonstrated that, while the magnetic helicity is gauge-dependent, its value in any gauge may be physically interpreted as the average winding number among all pairs of field lines with respect to some orthonormal frame field. In fact, the choice of gauge is equivalent to the choice of reference field in the relative helicity, meaning that the magnetic helicity is no less physically meaningful. We prove that a particular gauge always measures the winding with respect to a fixed frame, and propose that this is normally the best choice. For periodic fields, this choice is equivalent to measuring relative helicity with respect to a potential reference field. However, for aperiodic fields, we show that the potential field can be twisted. We prove by construction that there always exists a possible untwisted reference field.

  16. Constraints on primordial magnetic fields from inflation

    NASA Astrophysics Data System (ADS)

    Green, Daniel; Kobayashi, Takeshi

    2016-03-01

    We present generic bounds on magnetic fields produced from cosmic inflation. By investigating field bounds on the vector potential, we constrain both the quantum mechanical production of magnetic fields and their classical growth in a model independent way. For classical growth, we show that only if the reheating temperature is as low as Treh lesssim 102 MeV can magnetic fields of 10‑15 G be produced on Mpc scales in the present universe. For purely quantum mechanical scenarios, even stronger constraints are derived. Our bounds on classical and quantum mechanical scenarios apply to generic theories of inflationary magnetogenesis with a two-derivative time kinetic term for the vector potential. In both cases, the magnetic field strength is limited by the gravitational back-reaction of the electric fields that are produced simultaneously. As an example of quantum mechanical scenarios, we construct vector field theories whose time diffeomorphisms are spontaneously broken, and explore magnetic field generation in theories with a variable speed of light. Transitions of quantum vector field fluctuations into classical fluctuations are also analyzed in the examples.

  17. Juno and Jupiter's Magnetic Field (Invited)

    NASA Astrophysics Data System (ADS)

    Bloxham, J.; Connerney, J. E.; Jorgensen, J. L.

    2013-12-01

    The Juno spacecraft, launched in August 2011, will reach Jupiter in early July 2016, where it will enter a polar orbit, with an 11 day period and a perijove altitude of approximately 5000 km. The baseline mission will last for one year during which Juno will complete 32 orbits, evenly spaced in longitude. The baseline mission presents an unparalleled opportunity for investigating Jupiter's magnetic field. In many ways Jupiter is a better planet for studying dynamo-generated magnetic fields than the Earth: there are no crustal fields, of course, which otherwise mask the dynamo-generated field at high degree; and an orbiting spacecraft can get proportionately much closer to the dynamo region. Assuming Jupiter's dynamo extends to 0.8 Rj, Juno at closet approach is only 0.3 Rc above the dynamo, while Earth orbiting magnetic field missions sample the field at least 1 Rc above the dynamo (where Rc is the respective outer core or dynamo region radius). Juno's MAG Investigation delivers magnetic measurements with exceptional vector accuracy (100 ppm) via two FGM sensors, each co-located with a dedicated pair of non-magnetic star cameras for attitude determination at the sensor. We expect to image Jupiter's dynamo with unsurpassed resolution. Accordingly, we anticipate that the Juno magnetic field investigation may place important constraints on Jupiter's interior structure, and hence on the formation and evolution of Jupiter.

  18. Laser-Driven Magnetic Field Compression

    NASA Astrophysics Data System (ADS)

    Jang, N.

    2005-10-01

    An experiment was designed to compress magnetic fields to ultrahigh intensities through laser-driven implosions. A seed axial magnetic field is produced through two Helmholtz coils using a capacitor charged by the hot electrons produced by an intense laser pulse as a power supply. The seed-field generation circuit is designed to produce an initial field of several Tesla (5--10 T) inside a cylindrical CH shell. The plastic shell is then imploded by direct laser irradiation with a 23-kJ laser pulse. Two implosion pulse shapes have been considered: a square pulse and a shaped, low-adiabat pulse. One-dimensional simulations of the magnetic field compression resulting from the shell convergence show magnetic field amplifications of 300 for the square pulse and 1000 for the shaped pulse, thus leading to peak magnetic fields of 3 x 10^3 T and 10^4 T, respectively (for a 10-T seed). Details of the experimental design and simulations are presented, and the experimental plans for implementation are outlined. This experiment is intended to study ways to improve the hot-spot energy confinement through magnetic insulation. This work has been supported by the US-DOE under grant ER54768 and under cooperative agreement DE-FC52-92SF19460.

  19. Studies of the interaction between drag-reducing polymers and a turbulent flow field using PIV and FENE bead-spring model

    NASA Astrophysics Data System (ADS)

    Massahbavani, Heshmatollah

    An understanding of polymer drag-reduction has remained a challenge to researchers in turbulence and polymer fluid mechanics. The intriguing aspect of this phenomenon is that the addition of high molecular weight, long chain polymer molecules in amounts as small as 1 ppm can reduce the drag of a turbulent flow on a wall by as much as 25 percent. A popular argument is that drag-reduction is associated with the unraveling of polymer molecules by the turbulent velocity fluctuations causing an increase in the viscosity in the buffer zone but not in the viscous sublayer. This increase in the viscosity results in damping of small eddies and an increase in the thickness of the buffer layer, reducing the drag. This thesis addresses two basic questions underlying this phenomenon. What is the effect of turbulence on polymers? What is the effect of polymers on turbulence? A 3-D direct numerical simulation of turbulent channel flow and a particle tracking code were utilized to follow the paths of fluid particles and to record the changes of flow field. A FENE (finitely extendable nonlinear elastic) bead-spring model was used to calculate the changes in the average configuration of polymer molecules affined to the fluid particles whose path were being followed. Stresses created by polymers were calculated. For future work, it is suggested that these stresses be added to the Navier-Stokes equations in order to simulate turbulent flow of a dilute solution of polymers. Pulsed image velocimetry (PIV) measurements were carried out to compare the flow fields between water and a polymer solution of 3 ppm concentration, in planes parallel and perpendicular to the top wall of a 2 in. x 24 in. channel. The computer experiments show that polymer molecules unravel the most in the viscous sublayer and orient in the direction of flow. They add, mainly, elongational stress to the flow in this region. In the buffer zone, polymers unravel and orient in different directions and create both elongational and shear stresses. Therefore, the flow becomes more dissipative and eddies increase in size. This results in a thickening of the viscous wall region and a reduction of drag. PIV measurements show that the similarities between flow fields with and without polymers are more than the differences; both flows are highly turbulent. However, in the polymeric regime, spanwise fluctuations are significantly dampened and the streaky structures appear farther away from the wall. This, also, indicates that the viscous wall region has been thickened as a result of polymer injection.

  20. Laminated magnet field coil sheath

    DOEpatents

    Skaritka, J.R.

    1987-05-15

    A method for manufacturing a magnetic cable trim coil in a sheath assembly for use in a cryogenic particle accelerator. A precisely positioned pattern of trim coil turns is bonded to a flexible substrate sheath that is capable of withstanding cryogenic operating conditions. In the method of the invention the flexible substrate sheath, with the trim coil pattern precisely location relative to a bore tube assembly of an accelerator and is then bonded to the bore tube with a tape suitable for cryogenic application. The resultant assembly can be readily handled and installed within an iron magnet yoke assembly of a suitable cryogenic particle accelerator. 1 fig.

  1. Laminated magnet field coil sheath

    DOEpatents

    Skaritka, John R. (Coram, NY)

    1987-12-01

    a method for manufacturing a magnet cable trim coil in a sheath assembly for use in a cryogenic particle accelerator. A precisely positioned pattern of trim coil turns is bonded to a flexible substrate sheath that is capable of withstanding cryogenic operating conditions. In the method of the invention the flexible sheath, with the trim coil pattern precisely positioned thereon, is accurately positioned at a precise location relative to a bore tube assembly of an accelerator and is then bonded to the bore tube with a tape suitable for cryogenic application. The resultant assembly can be readily handled and installed within an iron magnet yoke assembly of a suitable cryogenic particle accelerator.

  2. High-field superconducting nested coil magnet

    NASA Technical Reports Server (NTRS)

    Laverick, C.; Lobell, G. M.

    1970-01-01

    Superconducting magnet, employed in conjunction with five types of superconducting cables in a nested solenoid configuration, produces total, central magnetic field strengths approaching 70 kG. The multiple coils permit maximum information on cable characteristics to be gathered from one test.

  3. MRS photodiode in strong magnetic field

    SciTech Connect

    Beznosko, D.; Blazey, G.; Dyshkant, A.; Francis, K.; Kubik, D.; Rykalin, V.; Tartaglia, M.A.; Zutshi, v.; /Northern Illinois U.

    2004-12-01

    The experimental results on the performance of the MRS (Metal/Resistor/Semiconductor) photodiode in the strong magnetic field of 4.4T, and the possible impact of the quench of the magnet at 4.5T on sensor's operation are reported.

  4. Estimating the magnetic field strength from magnetograms

    NASA Astrophysics Data System (ADS)

    Asensio Ramos, A.; Martnez Gonzlez, M. J.; Manso Sainz, R.

    2015-05-01

    A properly calibrated longitudinal magnetograph is an instrument that measures circular polarization and gives an estimation of the magnetic flux density in each observed resolution element. This usually constitutes a lower bound of the field strength in the resolution element, given that it can be made arbitrarily large as long as it occupies a proportionally smaller area of the resolution element and/or becomes more transversal to the observer while still produce the same magnetic signal. However, we know that arbitrarily stronger fields are less likely - hG fields are more probable than kG fields, with fields above several kG virtually absent - and we may even have partial information about their angular distribution. Based on a set of sensible considerations, we derive simple formulae based on a Bayesian analysis to give an improved estimation of the magnetic field strength for magnetographs.

  5. Magnetic space-based field measurements

    NASA Technical Reports Server (NTRS)

    Langel, R. A.

    1981-01-01

    Satellite measurements of the geomagnetic field began with the launch of Sputnik 3 in May 1958 and have continued sporadically in the intervening years. A list of spacecraft that have made significant contributions to an understanding of the near-earth geomagnetic field is presented. A new era in near-earth magnetic field measurements began with NASA's launch of Magsat in October 1979. Attention is given to geomagnetic field modeling, crustal magnetic anomaly studies, and investigations of the inner earth. It is concluded that satellite-based magnetic field measurements make global surveys practical for both field modeling and for the mapping of large-scale crustal anomalies. They are the only practical method of accurately modeling the global secular variation. Magsat is providing a significant contribution, both because of the timeliness of the survey and because its vector measurement capability represents an advance in the technology of such measurements.

  6. Magnetic Field Response Measurement Acquisition System

    NASA Technical Reports Server (NTRS)

    Woodard, Stanley E.; Taylor, Bryant D.; Shams, Qamar A.; Fox, Robert L.

    2005-01-01

    A measurement acquisition method that alleviates many shortcomings of traditional measurement systems is presented in this paper. The shortcomings are a finite number of measurement channels, weight penalty associated with measurements, electrical arcing, wire degradations due to wear or chemical decay and the logistics needed to add new sensors. The key to this method is the use of sensors designed as passive inductor-capacitor circuits that produce magnetic field responses. The response attributes correspond to states of physical properties for which the sensors measure. A radio frequency antenna produces a time-varying magnetic field used to power the sensor and receive the magnetic field response of the sensor. An interrogation system for discerning changes in the sensor response is presented herein. Multiple sensors can be interrogated using this method. The method eliminates the need for a data acquisition channel dedicated to each sensor. Methods of developing magnetic field response sensors and the influence of key parameters on measurement acquisition are discussed.

  7. Magnetic field, chiral transition and Pauli interaction

    NASA Astrophysics Data System (ADS)

    Partyka, Tomasz L.

    2014-04-01

    The possibility that the Pauli interaction could influence the critical temperature of chiral transition is investigated. We work within the Nambu-Jona-Lasinio model at the mean field level, with quark anomalous magnetic moment as a parameter.

  8. Fractal structure of the interplanetary magnetic field

    NASA Technical Reports Server (NTRS)

    Burlaga, L. F.; Klein, L. W.

    1985-01-01

    Under some conditions, time series of the interplanetary magnetic field strength and components have the properties of fractal curves. Magnetic field measurements made near 8.5 AU by Voyager 2 from June 5 to August 24, 1981 were self-similar over time scales from approximately 20 sec to approximately 3 x 100,000 sec, and the fractal dimension of the time series of the strength and components of the magnetic field was D = 5/3, corresponding to a power spectrum P(f) approximately f sup -5/3. Since the Kolmogorov spectrum for homogeneous, isotropic, stationary turbulence is also f sup -5/3, the Voyager 2 measurements are consistent with the observation of an inertial range of turbulence extending over approximately four decades in frequency. Interaction regions probably contributed most of the power in this interval. As an example, one interaction region is discussed in which the magnetic field had a fractal dimension D = 5/3.

  9. Heat Capacity Measurements in Pulsed Magnetic Fields

    SciTech Connect

    Jaime, M.; Movshovich, R.; Sarrao, J.L.; Kim, J.; Stewart, G.; Beyermann, W.P.; Canfield, P.C.

    1998-10-23

    The new NHMFL 60T quasi-continuous magnet produces a flat-top field for a period of 100 ms at 60 Tesla, and for longer time at lower fields, e.g. 0.5 s at 45 Tesla. We have developed for the first time the capability to measure heat capacity at very high magnetic fields in the NHMFL 60T quasi-continuous magnet at LANL, using a probe built out of various plastic materials. The field plateau allows us to utilize a heat-pulse method to obtain heat capacity data. Proof-of-principle heat capacity experiments were performed on a variety of correlated electron systems. Both magnet performance characteristics and physical properties of various materials studied hold out a promise of wide application of this new tool.

  10. Magnetic Field Response Measurement Acquisition System

    NASA Technical Reports Server (NTRS)

    Woodard, Stanley E. (Inventor); Taylor, Bryant D. (Inventor); Shams, Qamar A. (Inventor); Fox, Robert L. (Inventor); Fox, Christopher L. (Inventor); Fox, Melanie L. (Inventor); Bryant, Robert G. (Inventor)

    2006-01-01

    Magnetic field response sensors designed as passive inductor-capacitor circuits produce magnetic field responses whose harmonic frequencies correspond to states of physical properties for which the sensors measure. Power to the sensing element is acquired using Faraday induction. A radio frequency antenna produces the time varying magnetic field used for powering the sensor, as well as receiving the magnetic field response of the sensor. An interrogation architecture for discerning changes in sensor s response kequency, resistance and amplitude is integral to the method thus enabling a variety of measurements. Multiple sensors can be interrogated using this method, thus eliminating the need to have a data acquisition channel dedicated to each sensor. The method does not require the sensors to be in proximity to any form of acquisition hardware. A vast array of sensors can be used as interchangeable parts in an overall sensing system.

  11. THE SNS RING DIPOLE MAGNETIC FIELD QUALITY.

    SciTech Connect

    WANDERER,P.; JACKSON,J.; JAIN,A.; LEE,Y.Y.; MENG,W.; PAPAPHILIPPOU,I.; SPATARO,C.; TEPIKIAN,S.; TSOUPAS,N.; WEI,J.

    2002-06-03

    The large acceptance and compact size of the Spallation Neutron Source (SNS) ring implies the use of short, large aperture dipole magnets, with significant end field errors. The SNS will contain 32 such dipoles. We report magnetic field measurements of the first 16 magnets. The end field errors have been successfully compensated by the use of iron bumps. For 1.0 GeV protons, the magnets have been shimmed to meet the 0.01% specification for rms variation of the integral field. At 1.3 GeV, the rms variation is 0.036%. The load on the corrector system at 1.3 GeV will be reduced by the use of sorting.

  12. Comparing modified vertical gradient freezing with rotating magnetic fields or with steady magnetic and electric fields

    NASA Astrophysics Data System (ADS)

    Wang, X.; Ma, N.; Bliss, D. F.; Iseler, G. W.; Becla, P.

    2006-01-01

    This investigation treats the flow of molten gallium-antimonide and the dopant transport during the vertical gradient freezing process using submerged heater growth. A rotating magnetic field or a combination of steady magnetic and steady electric fields is used to control the melt motion. This paper compares the effects of these externally applied fields on the transport in the melt and on the dopant segregation in the crystal. Crystal growth in a combination of steady magnetic and electric fields produces a crystal with more radial and axial dopant homogeneity than growth in a rotating magnetic field.

  13. High-Field Superconducting Magnets Supporting PTOLEMY

    NASA Astrophysics Data System (ADS)

    Hopkins, Ann; Luo, Audrey; Osherson, Benjamin; Gentile, Charles; Tully, Chris; Cohen, Adam

    2013-10-01

    The Princeton Tritium Observatory for Light, Early Universe, Massive Neutrino Yield (PTOLEMY) is an experiment planned to collect data on Big Bang relic neutrinos, which are predicted to be amongst the oldest and smallest particles in the universe. Currently, a proof-of-principle prototype is being developed at Princeton Plasma Physics Laboratory to test key technologies associated with the experiment. A prominent technology in the experiment is the Magnetic Adiabatic Collimation with an Electrostatic Filter (MAC-E filter), which guides tritium betas along magnetic field lines generated by superconducting magnets while deflecting those of lower energies. B field mapping is performed to ensure the magnets produce a minimum field at the midpoint of the configuration of the magnets and to verify accuracy of existing models. Preliminary tests indicate the required rapid decrease in B field strength from the bore of the more powerful 3.35 T magnet, with the field dropping to 0.18 T approximately 0.5 feet from the outermost surface of the magnet.

  14. Nondissipative drag of superflow in a two-component Bose gas

    SciTech Connect

    Fil, D.V.; Shevchenko, S.I.

    2005-07-15

    A microscopic theory of a nondissipative drag in a two-component superfluid Bose gas is developed. The expression for the drag current in the system with the components of different atomic masses, densities, and scattering lengths is derived. It is shown that the drag current is proportional to the square root of the gas parameter. The temperature dependence of the drag current is studied and it is shown that at temperature of order or smaller than the interaction energy the temperature reduction of the drag current is rather small. A possible way of measuring the drag factor is proposed. A toroidal system with the drag component confined in two half-ring wells separated by two Josephson barriers is considered. Under certain condition such a system can be treated as a Bose-Einstein counterpart of the Josephson charge qubit in an external magnetic field. It is shown that the measurement of the difference of number of atoms in two wells under a controlled evolution of the state of the qubit allows one to determine the drag factor.

  15. Magnetic Fields and Massive Star Formation

    NASA Astrophysics Data System (ADS)

    Zhang, Qizhou; Qiu, Keping; Girart, Josep M.; (Baobab Liu, Hauyu; Tang, Ya-Wen; Koch, Patrick M.; Li, Zhi-Yun; Keto, Eric; Ho, Paul T. P.; Rao, Ramprasad; Lai, Shih-Ping; Ching, Tao-Chung; Frau, Pau; Chen, How-Huan; Li, Hua-Bai; Padovani, Marco; Bontemps, Sylvain; Csengeri, Timea; Jurez, Carmen

    2014-09-01

    Massive stars (M > 8 M ?) typically form in parsec-scale molecular clumps that collapse and fragment, leading to the birth of a cluster of stellar objects. We investigate the role of magnetic fields in this process through dust polarization at 870 ?m obtained with the Submillimeter Array (SMA). The SMA observations reveal polarization at scales of lsim0.1 pc. The polarization pattern in these objects ranges from ordered hour-glass configurations to more chaotic distributions. By comparing the SMA data with the single dish data at parsec scales, we found that magnetic fields at dense core scales are either aligned within 40 of or perpendicular to the parsec-scale magnetic fields. This finding indicates that magnetic fields play an important role during the collapse and fragmentation of massive molecular clumps and the formation of dense cores. We further compare magnetic fields in dense cores with the major axis of molecular outflows. Despite a limited number of outflows, we found that the outflow axis appears to be randomly oriented with respect to the magnetic field in the core. This result suggests that at the scale of accretion disks (lsim 103 AU), angular momentum and dynamic interactions possibly due to close binary or multiple systems dominate over magnetic fields. With this unprecedentedly large sample of massive clumps, we argue on a statistical basis that magnetic fields play an important role during the formation of dense cores at spatial scales of 0.01-0.1 pc in the context of massive star and cluster star formation.

  16. Magnetic fields and massive star formation

    SciTech Connect

    Zhang, Qizhou; Keto, Eric; Ho, Paul T. P.; Ching, Tao-Chung; Chen, How-Huan; Qiu, Keping; Girart, Josep M.; Juárez, Carmen; Liu, Hauyu; Tang, Ya-Wen; Koch, Patrick M.; Rao, Ramprasad; Lai, Shih-Ping; Li, Zhi-Yun; Frau, Pau; Li, Hua-Bai; Padovani, Marco; Bontemps, Sylvain

    2014-09-10

    Massive stars (M > 8 M {sub ☉}) typically form in parsec-scale molecular clumps that collapse and fragment, leading to the birth of a cluster of stellar objects. We investigate the role of magnetic fields in this process through dust polarization at 870 μm obtained with the Submillimeter Array (SMA). The SMA observations reveal polarization at scales of ≲0.1 pc. The polarization pattern in these objects ranges from ordered hour-glass configurations to more chaotic distributions. By comparing the SMA data with the single dish data at parsec scales, we found that magnetic fields at dense core scales are either aligned within 40° of or perpendicular to the parsec-scale magnetic fields. This finding indicates that magnetic fields play an important role during the collapse and fragmentation of massive molecular clumps and the formation of dense cores. We further compare magnetic fields in dense cores with the major axis of molecular outflows. Despite a limited number of outflows, we found that the outflow axis appears to be randomly oriented with respect to the magnetic field in the core. This result suggests that at the scale of accretion disks (≲ 10{sup 3} AU), angular momentum and dynamic interactions possibly due to close binary or multiple systems dominate over magnetic fields. With this unprecedentedly large sample of massive clumps, we argue on a statistical basis that magnetic fields play an important role during the formation of dense cores at spatial scales of 0.01-0.1 pc in the context of massive star and cluster star formation.

  17. Nonlinear diffusion waves in high magnetic fields

    NASA Astrophysics Data System (ADS)

    Oreshkin, V. I.; Chaikovsky, S. A.; Labetskaya, N. A.; Datsko, I. M.; Rybka, D. V.; Ratakhin, N. A.; Khishchenko, K. V.

    2015-11-01

    The nonlinear diffusion of a magnetic field and the large-scale instabilities arising upon an electrical explosion of conductors in a superstrong (2-3 MG) magnetic field were investigated experimentally on the MIG high-current generator (up to 2.5 peak current, 100 ns current rise time). It was observed that in the nonlinear stage of the process, the wavelength of thermal instabilities (striations) increased with a rate of 1.5-3 km/s.

  18. Muon photodecay in a magnetic field

    NASA Astrophysics Data System (ADS)

    Zhukovskii, V. Ch.; Kormiltsev, G. V.; Eminov, P. A.

    1985-08-01

    Spectral-angular and spectral probability distributions of relativistic-lepton photodecay in a magnetic field are calculated. Specific attention is given to the gamma + mu reaction, leading to the formation of an electron and a neutrino-antineutrino pair. An analysis is made of the dependence of the probability of the process on the magnetic field strength, the lepton spin orientation, the mass ratio of the initial and final leptons, and the circular-polarization direction of the electromagnetic wave.

  19. The determination of the coronal magnetic field

    NASA Astrophysics Data System (ADS)

    Arnaud, J.

    Measurements of magnetic fields in the solar corona are needed to improve our understanding of structures, dynamics and heating of the corona and of the acceleration of the fast and slow modes of the solar wind expending into the heliosphere. However, those measurements are very difficult and still very scarce. I revue the main methods proposed to access the direction and the strength of the coronal magnetic field and discuss what seem the main avenues to improve its determination in the future.

  20. Interstellar magnetic fields: An observational perspective

    SciTech Connect

    Goodman, A.A.

    1989-01-01

    The plausibility of magnetic molecular clouds is established. It is shown that the empirically known relations between spectral line width, density, and cloud size can be derived from a virial equilibrium model where gravity is balanced by the sum of magnetic and pressure support. It is shown that substitution of measured density, cloud size, and line width measurements into the model can predict observed field strength to within a factor of two. The Zeeman effect is discussed and new measurements are presented for magnetic field strength based on OH and HI Zeeman observations at the Arecibo and Green Bank telescopes. The Barnard 1 (B1) region, in the Perseus Molecular Cloud Complex, is discussed in detail. OH spectral line intensity maps are presented for the regions where the OH Zeeman effect was observed, which allow, for the first time, comparison of observed field strength values with predicted field strength values, using emission from a single molecular species. Spatial structure of magnetic fields in molecular clouds are investigated. New optical polarization maps are presented for the dark clouds in Perseus, Taurus, and Ophiuchus. The polarization observed is attributed to preferential extinction of background starlight by magnetically aligned dust grains in the clouds, and we analyze the polarization maps as maps of the projection of the magnetic field onto the plane of the sky.

  1. Magnetic field transfer device and method

    DOEpatents

    Wipf, Stefan L. (Hamburg, DE)

    1990-01-01

    A magnetic field transfer device includes a pair of oppositely wound inner coils which each include at least one winding around an inner coil axis, and an outer coil which includes at least one winding around an outer coil axis. The windings may be formed of superconductors. The axes of the two inner coils are parallel and laterally spaced from each other so that the inner coils are positioned in side-by-side relation. The outer coil is outwardly positioned from the inner coils and rotatable relative to the inner coils about a rotational axis substantially perpendicular to the inner coil axes to generate a hypothetical surface which substantially encloses the inner coils. The outer coil rotates relative to the inner coils between a first position in which the outer coil axis is substantially parallel to the inner coil axes and the outer coil augments the magnetic field formed in one of the inner coils, and a second position 180.degree. from the first position, in which the augmented magnetic field is transferred into the other inner coil and reoriented 180.degree. from the original magnetic field. The magnetic field transfer device allows a magnetic field to be transferred between volumes with negligible work being required to rotate the outer coil with respect to the inner coils.

  2. Magnetic field transfer device and method

    DOEpatents

    Wipf, S.L.

    1990-02-13

    A magnetic field transfer device includes a pair of oppositely wound inner coils which each include at least one winding around an inner coil axis, and an outer coil which includes at least one winding around an outer coil axis. The windings may be formed of superconductors. The axes of the two inner coils are parallel and laterally spaced from each other so that the inner coils are positioned in side-by-side relation. The outer coil is outwardly positioned from the inner coils and rotatable relative to the inner coils about a rotational axis substantially perpendicular to the inner coil axes to generate a hypothetical surface which substantially encloses the inner coils. The outer coil rotates relative to the inner coils between a first position in which the outer coil axis is substantially parallel to the inner coil axes and the outer coil augments the magnetic field formed in one of the inner coils, and a second position 180[degree] from the first position, in which the augmented magnetic field is transferred into the other inner coil and reoriented 180[degree] from the original magnetic field. The magnetic field transfer device allows a magnetic field to be transferred between volumes with negligible work being required to rotate the outer coil with respect to the inner coils. 16 figs.

  3. Solar Mean Magnetic Field Observed by GONG

    NASA Astrophysics Data System (ADS)

    Harvey, J. W.; Petrie, G.; Clark, R.; GONG Team

    2009-05-01

    The average line-of-sight (LOS) magnetic field of the Sun has been observed for decades, either by measuring the circular polarization across a selected spectrum line using integrated sunlight or by averaging such measurements in spatially resolved images. The GONG instruments produce full-disk LOS magnetic images every minute, which can be averaged to yield the mean magnetic field nearly continuously. Such measurements are well correlated with the heliospheric magnetic field observed near Earth about 4 days later. They are also a measure of solar activity on long and short time scales. Averaging a GONG magnetogram, with nominal noise of 3 G per pixel, results in a noise level of about 4 mG. This is low enough that flare-related field changes have been seen in the mean field signal with time resolution of 1 minute. Longer time scales readily show variations associated with rotation of magnetic patterns across the solar disk. Annual changes due to the varying visibility of the polar magnetic fields may also be seen. Systematic effects associated with modulator non-uniformity require correction and limit the absolute accuracy of the GONG measurements. Comparison of the measurements with those from other instruments shows high correlation but suggest that GONG measurements of field strength are low by a factor of about two. The source of this discrepancy is not clear. Fourier analysis of 2007 and 2008 time series of the GONG mean field measurements shows strong signals at 27.75 and 26.84/2 day (synodic) periods with the later period showing more power. The heliospheric magnetic field near Earth shows the same periods but with reversed power dominance. The Global Oscillation Network Group (GONG) project is managed by NSO, which is operated by AURA, Inc. under a cooperative agreement with the National Science Foundation.

  4. The magnetic field of a permanent hollow cylindrical magnet

    NASA Astrophysics Data System (ADS)

    Reich, Felix A.; Stahn, Oliver; Müller, Wolfgang H.

    2015-12-01

    Based on the rational version of Muc(AXWELL)'s equations according to Tuc(RUESDELL) and Tuc(OUPIN) or KOVETZ, cf. (Kovetz in Electromagnetic theory, Oxford University Press, Oxford, 2000; Truesdell and Toupin in Handbuch der Physik, Bd. III/1, Springer, Berlin, pp 226-793; appendix, pp 794-858, 2000), we present, for stationary processes, a closed-form solution for the magnetic flux density of a hollow cylindrical magnet. Its magnetization is constant in axial direction. We consider Muc(AXWELL)'s equations in regular and singular points that are obtained by rational electrodynamics, adapted to stationary processes. The magnetic flux density is calculated analytically by means of a vector potential. We obtain a solution in terms of complete elliptic integrals. Therefore, numerical evaluation can be performed in a computationally efficient manner. The solution is written in dimensionless form and can easily be applied to cylinders of arbitrary shape. The relation between the magnetic flux density and the magnetic field is linear, and an explicit relation for the field is presented. With a slight modification the result can be used to obtain the field of a solid cylindrical magnet. The mathematical structure of the solution and, in particular, singularities are discussed.

  5. Dynamic signatures of quiet sun magnetic fields

    NASA Technical Reports Server (NTRS)

    Martin, S. F.

    1983-01-01

    The collision and disappearance of opposite polarity fields is observed most frequently at the borders of network cells. Due to observational limitations, the frequency, magnitude, and spatial distribution of magnetic flux loss have not yet been quantitatively determined at the borders or within the interiors of the cells. However, in agreement with published hypotheses of other authors, the disapperance of magnetic flux is speculated to be a consequence of either gradual or rapid magnetic reconnection which could be the means of converting magnetic energy into the kinetic, thermal, and nonthermal sources of energy for microflares, spicules, the solar wind, and the heating of the solar corona.

  6. Hanle Effect Diagnostics of the Coronal Magnetic Field: A Test Using Realistic Magnetic Field Configurations

    NASA Astrophysics Data System (ADS)

    Raouafi, N.-E.; Solanki, S. K.; Wiegelmann, T.

    2009-06-01

    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 I Ly? and ? 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 I Ly?, are useful for such measurements.

  7. Research of weak pulsed magnetic field system derived from the time, displacement, and static magnetic field

    NASA Astrophysics Data System (ADS)

    Zhao, Xiao-Dong; Qian, Zheng

    2015-10-01

    The accurate measurement of dynamic characteristics in weak magnetic sensors is urgently required as a greater number of applications for these devices are found. In this paper, a novel weak pulsed magnetic field system is presented. The underlying principle is to drive a permanent magnet passing another magnet rapidly, producing a pulsed weak magnetic field. The magnitude of the field can be adjusted by changing the velocity and distance between the two magnets. The standard value of the pulsed dynamic magnetic field can be traced back to the accurate measurement of time, displacement, and static magnetic field. In this study a detailed procedure for producing a pulse magnetic field system using the above method is outlined after which a theoretical analysis of the permanent magnet movement is discussed. Using the described apparatus a milli-second level pulse-width with a milli-Tesla magnetic field magnitude is used to study the dynamic characteristics of a giant magnetoresistance sensor. We conclude by suggesting possible improvements to the described apparatus.

  8. Research of weak pulsed magnetic field system derived from the time, displacement, and static magnetic field.

    PubMed

    Zhao, Xiao-Dong; Qian, Zheng

    2015-10-01

    The accurate measurement of dynamic characteristics in weak magnetic sensors is urgently required as a greater number of applications for these devices are found. In this paper, a novel weak pulsed magnetic field system is presented. The underlying principle is to drive a permanent magnet passing another magnet rapidly, producing a pulsed weak magnetic field. The magnitude of the field can be adjusted by changing the velocity and distance between the two magnets. The standard value of the pulsed dynamic magnetic field can be traced back to the accurate measurement of time, displacement, and static magnetic field. In this study a detailed procedure for producing a pulse magnetic field system using the above method is outlined after which a theoretical analysis of the permanent magnet movement is discussed. Using the described apparatus a milli-second level pulse-width with a milli-Tesla magnetic field magnitude is used to study the dynamic characteristics of a giant magnetoresistance sensor. We conclude by suggesting possible improvements to the described apparatus. PMID:26520987

  9. Magnetic Field Apparatus (MFA) Hardware Test

    NASA Technical Reports Server (NTRS)

    Anderson, Ken; Boody, April; Reed, Dave; Wang, Chung; Stuckey, Bob; Cox, Dave

    1999-01-01

    The objectives of this study are threefold: (1) Provide insight into water delivery in microgravity and determine optimal germination paper wetting for subsequent seed germination in microgravity; (2) Observe the behavior of water exposed to a strong localized magnetic field in microgravity; and (3) Simulate the flow of fixative (using water) through the hardware. The Magnetic Field Apparatus (MFA) is a new piece of hardware slated to fly on the Space Shuttle in early 2001. MFA is designed to expose plant tissue to magnets in a microgravity environment, deliver water to the plant tissue, record photographic images of plant tissue, and deliver fixative to the plant tissue.

  10. Parameterization and measurements of helical magnetic fields

    SciTech Connect

    Fischer, W.; Okamura, M.

    1997-07-01

    Magnetic fields with helical symmetry can be parameterized using multipole coefficients (a{sub n}, b{sub n}). We present a parameterization that gives the familiar multipole coefficients (a{sub n}, b{sub n}) for straight magnets when the helical wavelength tends to infinity. To measure helical fields all methods used for straight magnets can be employed. We show how to convert the results of those measurements to obtain the desired helical multipole coefficients (a{sub n}, b{sub n}).

  11. Superconductivity in Strong Magnetic Field (Greater Than Upper Critical Field)

    SciTech Connect

    Tessema, G.X.; Gamble, B.K.; Skove, M.J.; Lacerda, A.H.; Mielke, C.H.

    1998-08-22

    The National High Magnetic Field Laboratory, funded by the National Science Foundation and other US federal Agencies, has in recent years built a wide range of magnetic fields, DC 25 to 35 Tesla, short pulse 50 - 60 Tesla, and quasi-continuous 60 Tesla. Future plans are to push the frontiers to 45 Tesla DC and 70 to 100 Tesla pulse. This user facility, is open for national and international users, and creates an excellent tool for materials research (metals, semiconductors, superconductors, biological systems ..., etc). Here we present results of a systematic study of the upper critical field of a novel superconducting material which is considered a promising candidate for the search for superconductivity beyond H{sub c2} as proposed by several new theories. These theories predict that superconductors with low carrier density can reenter the superconducting phase beyond the conventional upper critical field H{sub c2}. This negates the conventional thinking that superconductivity and magnetic fields are antagonistic.

  12. Critical Magnetic Field Determination of Superconducting Materials

    SciTech Connect

    Canabal, A.; Tajima, T.; Dolgashev, V.A.; Tantawi, S.G.; Yamamoto, T.; /Tsukuba, Natl. Res. Lab. Metrol.

    2011-11-04

    Superconducting RF technology is becoming more and more important. With some recent cavity test results showing close to or even higher than the critical magnetic field of 170-180 mT that had been considered a limit, it is very important to develop a way to correctly measure the critical magnetic field (H{sup RF}{sub c}) of superconductors in the RF regime. Using a 11.4 GHz, 50-MW, <1 {mu}s, pulsed power source and a TE013-like mode copper cavity, we have been measuring critical magnetic fields of superconductors for accelerator cavity applications. This device can eliminate both thermal and field emission effects due to a short pulse and no electric field at the sample surface. A model of the system is presented in this paper along with a discussion of preliminary experimental data.

  13. NIST Undulator Magnetic Field Characterization

    NASA Astrophysics Data System (ADS)

    Johnson, L. E.; Denbeaux, G.; Madey, J. M. J.; Straub, K. D.

    1997-05-01

    A 3.64 m undulator was constructed by the Brobeck Division of Maxwell Laboratories for FEL experiments at NIST in Washington, DC. The Duke University FEL Lab has since acquired the undulator for use as a soft x-ray source. We report on our effort to transform the undulator into a high performance soft x-ray insertion device through careful characterization of the existing magnet blocks, sorting and trimming.

  14. Fast Reconnection of Weak Magnetic Fields

    NASA Technical Reports Server (NTRS)

    Zweibel, Ellen G.

    1998-01-01

    Fast magnetic reconnection refers to annihilation or topological rearrangement of magnetic fields on a timescale that is independent (or nearly independent) of the plasma resistivity. The resistivity of astrophysical plasmas is so low that reconnection is of little practical interest unless it is fast. Yet, the theory of fast magnetic reconnection is on uncertain ground, as models must avoid the tendency of magnetic fields to pile up at the reconnection layer, slowing down the flow. In this paper it is shown that these problems can be avoided to some extent if the flow is three dimensional. On the other hand, it is shown that in the limited but important case of incompressible stagnation point flows, every flow will amplify most magnetic fields. Although examples of fast magnetic reconnection abound, a weak, disordered magnetic field embedded in stagnation point flow will in general be amplified, and should eventually modify the flow. These results support recent arguments against the operation of turbulent resistivity in highly conducting fluids.

  15. Magnetic fields in early-type stars

    NASA Astrophysics Data System (ADS)

    Grunhut, Jason H.; Neiner, Coralie

    2015-10-01

    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 ?) 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 furthered our understanding of the interactions between the magnetic field and stellar wind, as well as the consequences and connections of this interaction with other observed phenomena.

  16. Measurements accounting for the impediment of ion spin-up in rotating magnetic field driven field reversed configurations

    SciTech Connect

    Deards, C. L.; Hoffman, A. L.; Steinhauer, L. C.

    2011-11-15

    Improved vacuum hygiene, wall conditioning, and reduced recycling in the rotating magnetic field (RMF) driven translation, confinement, and sustainment-upgrade (TCSU) field reversed configuration experiment have made possible a more accurate assessment of the forces affecting ion spin-up. This issue is critical in plasmas sustained by RMFs, such as TCSU since ion spin-up can substantially reduce or cancel the RMF current drive effect. Several diagnostics are brought to bear, including a 3-axis translatable magnetic probe allowing the first experimental measurement of the end shorting effect. These results show that the ion rotation is determined by a balance between electron-ion friction, the end shorting effect, and ion drag against neutrals.

  17. Measurements accounting for the impediment of ion spin-up in rotating magnetic field driven field reversed configurations

    NASA Astrophysics Data System (ADS)

    Deards, C. L.; Hoffman, A. L.; Steinhauer, L. C.

    2011-11-01

    Improved vacuum hygiene, wall conditioning, and reduced recycling in the rotating magnetic field (RMF) driven translation, confinement, and sustainment-upgrade (TCSU) field reversed configuration experiment have made possible a more accurate assessment of the forces affecting ion spin-up. This issue is critical in plasmas sustained by RMFs, such as TCSU since ion spin-up can substantially reduce or cancel the RMF current drive effect. Several diagnostics are brought to bear, including a 3-axis translatable magnetic probe allowing the first experimental measurement of the end shorting effect. These results show that the ion rotation is determined by a balance between electron-ion friction, the end shorting effect, and ion drag against neutrals.

  18. TANGLED MAGNETIC FIELDS IN SOLAR PROMINENCES

    SciTech Connect

    Van Ballegooijen, A. A.; Cranmer, S. R.

    2010-03-01

    Solar prominences are an important tool for studying the structure and evolution of the coronal magnetic field. Here we consider so-called hedgerow prominences, which consist of thin vertical threads. We explore the possibility that such prominences are supported by tangled magnetic fields. A variety of different approaches are used. First, the dynamics of plasma within a tangled field is considered. We find that the contorted shape of the flux tubes significantly reduces the flow velocity compared to the supersonic free fall that would occur in a straight vertical tube. Second, linear force-free models of tangled fields are developed, and the elastic response of such fields to gravitational forces is considered. We demonstrate that the prominence plasma can be supported by the magnetic pressure of a tangled field that pervades not only the observed dense threads but also their local surroundings. Tangled fields with field strengths of about 10 G are able to support prominence threads with observed hydrogen density of the order of 10{sup 11} cm{sup -3}. Finally, we suggest that the observed vertical threads are the result of Rayleigh-Taylor instability. Simulations of the density distribution within a prominence thread indicate that the peak density is much larger than the average density. We conclude that tangled fields provide a viable mechanism for magnetic support of hedgerow prominences.

  19. Undirected response transducer of magnetic field induction

    NASA Astrophysics Data System (ADS)

    Skubis, Tadeusz; Gonscz, Damian

    2001-08-01

    This paper present the concept of the transducer for shape reconstruction and magnetic induction measurement of periodic arbitrary shape wave magnetic field. The measuring head consists of three coils with separated leads. Coils are fixed perpendicularly one to the other. Coil output voltages are synchronously sampled and the input samples are processed according to the algorithm developed. The characteristic curve of the transducer is theoretically deduced. Algorithm fixing signs of currently reproduced output samples of reconstructed shape wave is commented. Most significant uncertainty sources of the circuit thrust by essential blocks of signal processing path are analyzed. It was confirmed by simulation that the reconstructed wave shape and calculated induction value are independent of angle setting of measuring head in magnetic field. The transducer sensitivity to the angle setting in the magnetic field is very small.

  20. Mechanical propulsion from unsymmetrical magnetic induction fields

    SciTech Connect

    Schlicher, R.L.; Biggs, A.W.; Tedeschi, W.J.

    1995-06-01

    A method is reported for generating mechanical spacecraft propulsion from unsymmetrical magnetic induction fields. It is based on an unsymmetrical three-dimensional loop antenna structure driven by a repetitively-pulsed high-current power supply. Antenna geometry is optimized for generating propulsive thrust rather than radiating electromagnetic energy. Part of this antenna consists of flat electrical conductors, which form a partially-closed quasi-cylindrical volume around a center conductor. Magnetic flux concentrates at the closed end of the quasicylindrical volume thereby creating a magnetic field flux density gradient along a single axis collinear to the Center Conductor. This magnetic field density gradient imbalances the magneto-mechanical forces that result from the interactions of the internal magnetic induction field with the current in the conductors of the antenna structure, in accordance with Lorentz`s Force Law. Also, there are electrically isolated prismatic conductor surfaces attached to the inside surface of the flat conductors which form the closed end of the quasi-cylindrical volume. Mechanical pressures occur on these conductor prisms because of the changing internal magnetic field and are a consequence of Faraday`s Induction Law and Lenz`s Law. Input current rise time and wave shape are crucial to maximizing spacecraft propulsive thrust.

  1. Maneuvering thermal conductivity of magnetic nanofluids by tunable magnetic fields

    NASA Astrophysics Data System (ADS)

    Patel, Jaykumar; Parekh, Kinnari; Upadhyay, R. V.

    2015-06-01

    We report an experimental investigation of magnetic field dependent thermal conductivity of a transformer oil base magnetic fluid as a function of volume fractions. In the absence of magnetic field, thermal conductivity increases linearly with an increase in volume fraction, and magnitude of thermal conductivity thus obtained is lower than that predicted by Maxwell's theory. This reveals the presence of clusters/oligomers in the system. On application of magnetic field, it exhibits a non-monotonous increase in thermal conductivity. The results are interpreted using the concept of a two-step homogenization method (which is based on differential effective medium theory). The results show a transformation of particle cluster configuration from long chain like prolate shape to the aggregated drop-like structure with increasing concentration as well as a magnetic field. The aggregated drop-like structure for concentrated system is supported by optical microscopic images. This shape change of clusters reduces thermal conductivity enhancement. Moreover, this structure formation is observed as a dynamic phenomenon, and at 226 mT field, the length of the structure extends with time, becomes maximum, and then reduces. This change results in the increase or decrease of thermal conductivity.

  2. Review of magnetic field observations.

    NASA Technical Reports Server (NTRS)

    Ness, N. F.

    1972-01-01

    Recent observations in previously unexplored regions of the magnetosphere, particularly in the polar-cusp region, compliment and reinforce emphasis on particle access to the plasma sheet via the polar neutral points. Significant distortions of the geomagnetic field in the polar-cusp region suggest field-aligned currents at large geocentric distances which can be related to low-altitude polar-cap phenomena. Studies of the microstructure of the field reversal region of the plasma sheet embedded in the geomagnetic tail suggest a periodic structure of more complexity than earlier assumed simplified single neutral-line models.

  3. Measurements of Photospheric and Chromospheric Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Lagg, Andreas; Lites, Bruce; Harvey, Jack; Gosain, Sanjay; Centeno, Rebecca

    2015-12-01

    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. Secondary resonance magnetic force microscopy using an external magnetic field for characterization of magnetic thin films

    NASA Astrophysics Data System (ADS)

    Liu, Dongzi; Mo, Kangxin; Ding, Xidong; Zhao, Liangbing; Lin, Guocong; Zhang, Yueli; Chen, Dihu

    2015-09-01

    A bimodal magnetic force microscopy (MFM) that uses an external magnetic field for the detection and imaging of magnetic thin films is developed. By applying the external modulation magnetic field, the vibration of a cantilever probe is excited by its magnetic tip at its higher eigenmode. Using magnetic nanoparticle samples, the capacity of the technique which allows single-pass imaging of topography and magnetic forces is demonstrated. For the detection of magnetic properties of thin film materials, its signal-to-noise ratio and sensitivity are demonstrated to be superior to conventional MFM in lift mode. The secondary resonance MFM technique provides a promising tool for the characterization of nanoscale magnetic properties of various materials, especially of magnetic thin films with weak magnetism.

  5. Electric/magnetic field sensor

    DOEpatents

    Schill, Jr., Robert A.; Popek, Marc [Las Vegas, NV

    2009-01-27

    A UNLV novel electric/magnetic dot sensor includes a loop of conductor having two ends to the loop, a first end and a second end; the first end of the conductor seamlessly secured to a first conductor within a first sheath; the second end of the conductor seamlessly secured to a second conductor within a second sheath; and the first sheath and the second sheath positioned adjacent each other. The UNLV novel sensor can be made by removing outer layers in a segment of coaxial cable, leaving a continuous link of essentially uncovered conductor between two coaxial cable legs.

  6. Primordial magnetic fields from self-ordering scalar fields

    NASA Astrophysics Data System (ADS)

    Horiguchi, Kouichirou; Ichiki, Kiyotomo; Sekiguchi, Toyokazu; Sugiyama, Naoshi

    2015-04-01

    A symmetry-breaking phase transition in the early universe could have led to the formation of cosmic defects. Because these defects dynamically excite not only scalar and tensor type cosmological perturbations but also vector type ones, they may serve as a source of primordial magnetic fields. In this study, we calculate the time evolution and the spectrum of magnetic fields that are generated by a type of cosmic defects, called global textures, using the non-linear sigma (NLSM) model. Based on the standard cosmological perturbation theory, we show, both analytically and numerically, that a vector-mode relative velocity between photon and baryon fluids is induced by textures, which inevitably leads to the generation of magnetic fields over a wide range of scales. We find that the amplitude of the magnetic fields is given by B~10?9((1+z)/103)?2.5(v/mpl)2(k/Mpc?1)3.5/?N Gauss in the radiation dominated era for klesssim 1 Mpc?1, with v being the vacuum expectation value of the O(N) symmetric scalar fields. By extrapolating our numerical result toward smaller scales, we expect that B~ 10?14.5((1+z)/103)1/2(v/mpl)2(k/Mpc?1)1/2/?N Gauss on scales of kgtrsim 1 Mpc?1 at redshift 0zgtrsim 110. This might be a seed of the magnetic fields observed on large scales today.

  7. UNDERSTANDING THE GEOMETRY OF ASTROPHYSICAL MAGNETIC FIELDS

    SciTech Connect

    Broderick, Avery E.; Blandford, Roger D.

    2010-08-01

    Faraday rotation measurements have provided an invaluable technique for probing the properties of astrophysical magnetized plasmas. Unfortunately, typical observations provide information only about the density-weighted average of the magnetic field component parallel to the line of sight. As a result, the magnetic field geometry along the line of sight, and in many cases even the location of the rotating material, is poorly constrained. Frequently, interpretations of Faraday rotation observations are dependent upon underlying models of the magnetic field being probed (e.g., uniform, turbulent, equipartition). However, we show that at sufficiently low frequencies, specifically below roughly 13(RM/1 rad m{sup -2}){sup 1/4}(B/1 G){sup 1/2} MHz, the character of Faraday rotation changes, entering what we term the 'super-adiabatic regime' in which the rotation measure (RM) is proportional to the integrated absolute value of the line-of-sight component of the field. As a consequence, comparing RMs at high frequencies with those in this new regime provides direct information about the geometry of the magnetic field along the line of sight. Furthermore, the frequency defining the transition to this new regime, {nu}{sub SA}, depends directly upon the local electron density and magnetic field strength where the magnetic field is perpendicular to the line of sight, allowing the unambiguous distinction between Faraday rotation within and in front of the emission region. Typical values of {nu}{sub SA} range from 10 kHz (below the ionospheric cutoff, but above the heliospheric cutoff) to 10 GHz, depending upon the details of the Faraday rotating environment. In particular, for resolved active galactic nuclei, including the black holes at the center of the Milky Way (Sgr A*) and M81, {nu}{sub SA} ranges from roughly 10 MHz to 10 GHz, and thus can be probed via existing and up-coming ground-based radio observatories.

  8. Magnetic nanoparticle sensing: decoupling the magnetization from the excitation field

    PubMed Central

    Reeves, Daniel B.; Weaver, John B.

    2014-01-01

    Remote sensing of magnetic nanoparticles has exciting applications for magnetic nanoparticle hyperthermia and molecular detection. We introduce, simulate, and experimentally demonstrate an innovationa sensing coil that is geometrically decoupled from the excitation fieldfor magnetic nanoparticle spectroscopy that increases the flexibility and capabilities of remote detection. The decoupling enhances the sensitivity absolutely; to small amounts of nanoparticles, and relatively; to small changes in the nanoparticle dynamics. We adapt a previous spectroscopic method that measures the relaxation time of nanoparticles and demonstrate a new measurement of nanoparticle temperature that could potentially be used concurrently during hyperthermia. PMID:24610961

  9. Magnetic nanoparticles for applications in oscillating magnetic field

    SciTech Connect

    Peeraphatdit, Chorthip

    2010-12-15

    Enzymatic and thermochemical catalysis are both important industrial processes. However, the thermal requirements for each process often render them mutually exclusive: thermochemical catalysis requires high temperature that denatures enzymes. One of the long-term goals of this project is to design a thermocatalytic system that could be used with enzymatic systems in situ to catalyze reaction sequences in one pot; this system would be useful for numerous applications e.g. conversion of biomass to biofuel and other commodity products. The desired thermocatalytic system would need to supply enough thermal energy to catalyze thermochemical reactions, while keeping the enzymes from high temperature denaturation. Magnetic nanoparticles are known to generate heat in an oscillating magnetic field through mechanisms including hysteresis and relaxational losses. We envisioned using these magnetic nanoparticles as the local heat source embedded in sub-micron size mesoporous support to spatially separate the particles from the enzymes. In this study, we set out to find the magnetic materials and instrumental conditions that are sufficient for this purpose. Magnetite was chosen as the first model magnetic material in this study because of its high magnetization values, synthetic control over particle size, shape, functionalization and proven biocompatibility. Our experimental designs were guided by a series of theoretical calculations, which provided clues to the effects of particle size, size distribution, magnetic field, frequency and reaction medium. Materials of theoretically optimal size were synthesized, functionalized, and their effects in the oscillating magnetic field were subsequently investigated. Under our conditions, the materials that clustered e.g. silica-coated and PNIPAM-coated iron oxides exhibited the highest heat generation, while iron oxides embedded in MSNs and mesoporous iron oxides exhibited the least bulk heating. It is worth noting that the specific loss power of PNIPAM-coated Fe{sub 3}O{sub 4} was peculiarly high, and the heat loss mechanism of this material remains to be elucidated. Since thermocatalysis is a long-term goal of this project, we also investigated the effects of the oscillating magnetic field system for the synthesis of 7-hydroxycoumarin-3-carboxylic acid. Application of an oscillating magnetic field in the presence of magnetic particles with high thermal response was found to effectively increase the reaction rate of the uncatalyzed synthesis of the coumarin derivative compared to the room temperature control.

  10. Primordial magnetic fields and nonlinear electrodynamics

    SciTech Connect

    Kunze, Kerstin E.

    2008-01-15

    The creation of large scale magnetic fields is studied in an inflationary universe where electrodynamics is assumed to be nonlinear. After inflation ends electrodynamics becomes linear and thus the description of reheating and the subsequent radiation dominated stage are unaltered. The nonlinear regime of electrodynamics is described by Lagrangians having a power-law dependence on one of the invariants of the electromagnetic field. It is found that there is a range of parameters for which primordial magnetic fields of cosmologically interesting strengths can be created.

  11. Constructing the Coronal Magnetic Field: by Correlating Parameterized Magnetic Field Lines with Observed Coronal Plasma Structures

    NASA Technical Reports Server (NTRS)

    Gary, G. A.

    1998-01-01

    The reconstruction of the coronal magnetic field is carried out using a perturbation procedure. A set of magnetic field lines generated from magnetogram data is parameterized and then deformed by varying the parameterized values. The coronal fluxtubes associated with this field are adjusted until the correlation between the field lines and the observed coronal loops is maximized. A mathematical formulation is described which ensures (1) that the normal component of the photospheric field remains unchanged, (2) that the field is given in the entire corona, (3) that the field remains divergence free, and (4) that electrical currents are introduced into the field. It is demonstrated that a simple radial parameterization of a potential field, comprising a radial stretching of the field, can provide a match for a simple bipolar active region, AR 7999, which crossed the central meridian on 1996 Nov 26. At a coronal height of 30 km, the resulting magnetic field is a non-force free magnetic field with the maximum Lorentz force being on the order of 2.6 x 10(exp -9) dyn resulting from an electric current density of $0.13 mu A/ sq m. This scheme is an important tool in generating a magnetic field solution consistent with the coronal flux tube observations and the observed photospheric magnetic field.

  12. Probing Magnetic Fields with GALFACTS

    NASA Astrophysics Data System (ADS)

    George, S. J.; Stil, J. M.; Andrecut, M.; Taylor, A. R.

    2012-09-01

    GALFACTS is a large-area spectro-polarimetric survey on the Arecibo Radio telescope. It uses the seven-beam focal plane feed array receiver system (ALFA) to carry out an imaging survey project of the 12,700 square degrees of sky visible from Arecibo at 1.4 GHz with 8192 spectral channels over a bandwidth of 300 MHz sampled at 1 millisecond. The aggregate data rate is 875 MB/s. GALFACTS observations will create full-Stokes image cubes at an angular resolution of 3.5' with a band-averaged sensitivity of 90 μJy, allowing sensitive imaging of polarized radiation and Faraday Rotation Measure from both diffuse emission and extragalactic sources. GALFACTS is a scientific pathfinder to the SKA in the area of cosmic magnetism. Key to magnetism science with the SKA is the technique of RM synthesis. The technique of RM synthesis is introduced and we discuss practical aspects of RM synthesis including efficient computational techniques and detection thresholds in the resulting Faraday spectrum. We illustrate the use of the technique by presenting the current development of the RM synthesis pipeline for GALFACTS and present early results.

  13. Evaluation of Electromagnetic Force and Magnetic Laval Nozzle Acceleration in an Applied-Field MPD Thruster

    NASA Astrophysics Data System (ADS)

    Tobari, Hiroyuki; Sato, Ryuichi; Harata, Kenji; Hattori, Kunihiko; Ando, Akira; Inutake, Masaaki

    2003-10-01

    A magneto-plasma-dynamic thruster (MPDT) is expected as one of the promising electric propulsion systems owing to features of a relatively large thrust, high specific impulse that is unattainable by conventional chemical or nuclear propulsion required for space missions such as a manned Mars mission. To clarify the electromagnetic acceleration mechanism of a plasma flow in an applied-field MPDT, detailed flow field and electromagnetic force field are evaluated experimentally with spectroscopic technique and magnetic probe array. It is found that an axial drag force generated by an interaction between azimuthal plasma current and radial magnetic field cancels an acceleration force in a uniform magnetic field. A thermal energy component is much larger than a flow energy component in Bernoulli's equation and ion acoustic Mach number is limited less than unity in the muzzle region of MPD arcjet. In order to convert the thermal energy to the flow energy, magnetic Laval nozzle acceleration with a local magnetic coil is attempted. The ion Mach number after passing through the nozzle throat exceeds unity and a production of supersonic plasma flow is achieved. An optimum magnetic nozzle configuration is discussed with the experimental results.

  14. Impurity coupled to an artificial magnetic field in a Fermi gas in a ring trap

    NASA Astrophysics Data System (ADS)

    nal, F. Nur; Hetnyi, B.; Oktel, M. .-.

    2015-05-01

    The dynamics of a single impurity interacting with a many-particle background is one of the central problems of condensed-matter physics. Recent progress in ultracold-atom experiments makes it possible to control this dynamics by coupling an artificial gauge field specifically to the impurity. In this paper, we consider a narrow toroidal trap in which a Fermi gas is interacting with a single atom. We show that an external magnetic field coupled to the impurity is a versatile tool to probe the impurity dynamics. Using a Bethe ansatz, we calculate the eigenstates and corresponding energies exactly as a function of the flux through the trap. Adiabatic change of flux connects the ground state to excited states due to flux quantization. For repulsive interactions, the impurity disturbs the Fermi sea by dragging the fermions whose momentum matches the flux. This drag transfers momentum from the impurity to the background and increases the effective mass. The effective mass saturates to the total mass of the system for infinitely repulsive interactions. For attractive interactions, the drag again increases the effective mass which quickly saturates to twice the mass of a single particle as a dimer of the impurity and one fermion is formed. For excited states with momentum comparable to number of particles, effective mass shows a resonant behavior. We argue that standard tools in cold-atom experiments can be used to test these predictions.

  15. Magnetic field generation from cosmological perturbations.

    PubMed

    Takahashi, Keitaro; Ichiki, Kiyotomo; Ohno, Hiroshi; Hanayama, Hidekazu

    2005-09-16

    In this Letter, we discuss the generation of magnetic field from cosmological perturbations. We consider the evolution of three component plasma (electron, proton, and photon) evaluating the collision term between electrons and photons up to the second order. The collision term is shown to induce electric current, which then generates magnetic field. There are three contributions, two of which can be evaluated from the first-order quantities, while the other one is fluid vorticity, which is purely second order. We estimate the magnitudes of the former contributions and show that the amplitude of the produced magnetic field is about approximately 10(-19) G at 10 Mpc comoving scale at the decoupling. Compared to astrophysical and inflationary mechanisms for seed-field generation, our study suffers from much less ambiguities concerning unknown physics and/or processes. PMID:16197062

  16. A holographic bound on cosmic magnetic fields

    NASA Astrophysics Data System (ADS)

    McInnes, Brett

    2015-03-01

    Magnetic fields large enough to be observable are ubiquitous in astrophysics, even at extremely large length scales. This has led to the suggestion that such fields are seeded at very early (inflationary) times, and subsequently amplified by various processes involving, for example, dynamo effects. Many such mechanisms give rise to extremely large magnetic fields at the end of inflationary reheating, and therefore also during the quark-gluon plasma epoch of the early universe. Such plasmas have a well-known holographic description in terms of a thermal asymptotically AdS black hole. We show that holography imposes an upper bound on the intensity of magnetic fields (? 3.6 1018gauss at the hadronization temperature) in these circumstances; this is above, but not far above, the values expected in some models of cosmic magnetogenesis.

  17. Magnetic field dissipation in D-sheets

    NASA Technical Reports Server (NTRS)

    Burlaga, L. F.; Scudder, J. D.

    1973-01-01

    The effects of magnetic field annihilation at a tangential or rotational discontinuity in a resistive plasma are examined. The magnetic field intensity profile depends on (1) the field intensities far from the current sheet (+ and - infinity), (2) the angle between the two intensities, and (3) the electrical resistivity. For a tangential discontinuity, the theory predicts a depression in B, centered at the discontinuity, and it predicts a monotonic transition. The theory provides satisfactory fits to the magnetic field intensity and proton temperature profiles observed for two extremely broad D-sheets in the solar wind. Assuming a diffusion time 10 days, one obtains effective resistivities or approximately = 3 x 10 to the 12th power and 2 x 10 to the 13th power emu for the D-sheets. Either resistivity at directional discontinuities is much lower than 10 to the 12th power emu or annihilation does not always occur at discontinuities.

  18. Measuring vector magnetic fields in solar prominences

    NASA Astrophysics Data System (ADS)

    Orozco Surez, D.; Asensio Ramos, A.; Trujillo Bueno, J.

    2013-05-01

    We present spectropolarimetric observations in the He I 1083.0 nm multiplet of a quiescent, hedgerow solar prominence. The data were taken with the Tenerife Infrared Polarimeter attached to the German Vacuum Tower Telescope at the Observatorio del Teide (Tenerife; Canary Islands; Spain). The observed He I circular and linear polarization signals are dominated by the Zeeman effect and by atomic level polarization and the Hanle effect, respectively. These observables are sensitive to the strength and orientation of the magnetic field vector at each spatial point of the field of view. We determine the magnetic field vector of the prominence by applying the HAZEL inversion code to the observed Stokes profiles. We briefly discuss the retrieved magnetic field vector configuration.

  19. Magnetic fields in superconducting neutron stars.

    PubMed

    Lander, S K

    2013-02-15

    The interior of a neutron star is likely to be predominantly a mixture of superfluid neutrons and superconducting protons. This results in the quantization of the star's magnetic field into an array of thin flux tubes, producing a macroscopic force very different from the Lorentz force of normal matter. We show that in an axisymmetric superconducting equilibrium the behavior of a magnetic field is governed by a single differential equation. Solving this, we present the first self-consistent superconducting neutron star equilibria with poloidal and mixed poloidal-toroidal fields and also give the first quantitative results for the corresponding magnetically induced distortions to the star. The poloidal component is dominant in all our configurations. We suggest that the transition from normal to superconducting matter in a young neutron star may cause a large-scale field rearrangement. PMID:25166363

  20. Magnetic Fields at the Center of Coils

    NASA Astrophysics Data System (ADS)

    Binder, Philippe; Hui, Kaleonui; Goldman, Jesse

    2014-12-01

    In this note we synthesize and extend expressions for the magnetic field at the center of very short and very long current-carrying coils. Elementary physics textbooks present the following equation for the magnetic field inside a very long current-carrying coil (solenoid): Bsol=?0(N/L)I, (1) where I is the current, N the number of windings, and L the coil length. It is obtained directly from Ampre's law, ignores end effects (hence it assumes an infinite coil), and is valid over the entire cross-section of the coil. The field is in the axial direction and it follows the right-hand rule convention. For N superposed loops of radius R each carrying current I, the multi-loop magnetic field at the center is given by Bml=?0(N/2 R) I. (2)

  1. Coulomb drag in graphene quantum Hall bilayer systems

    NASA Astrophysics Data System (ADS)

    Liu, Xiaomeng; Wang, Lei; Fong, Kin Chung; Gao, Yuanda; Maher, Patrick; Watanabe, Kenji; Taniguchi, Takashi; Hone, James; Dean, Cory; Kim, Philip

    2015-03-01

    Coulomb drag between electrons in closely spaced two-dimensional electron systems has provided an exciting avenue for research on quantum Hall bilayer systems. Employing dual-gated, encapsulated graphene double layers separated by a thin hBN dielectric, we investigate density tunable magneto and Hall drag in quantum Hall bilayer systems. Large variations of magneto-drag and Hall-drag are observed, which can be related to the Landau level (LL) filling status of both driving and drag layers. The measured drag resistivity tensor can be associated with the tensor product of the differential magneto-resistivity tensors of the drive and drag layers. The temperature and field dependence of magneto-drag can be described in terms of the phase space for Coulomb scattering between LLs in the drag and drive layers. In the strong interaction regime and ultra-low temperature, we observe the effect of symmetry broken integer quantum Hall States in magneto and Hall drag signals.

  2. Whistler Modes with Wave Magnetic Fields Exceeding the Ambient Field

    SciTech Connect

    Stenzel, R.L.; Urrutia, J.M.; Strohmaier, K.D.

    2006-03-10

    Whistler-mode wave packets with fields exceeding the ambient dc magnetic field have been excited in a large, high electron-beta plasma. The waves are induced with a loop antenna with dipole moment either along or opposite to the dc field. In the latter case the excited wave packets have the topology of a spheromak but are propagating in the whistler mode along and opposite to the dc magnetic field. Field-reversed configurations with net zero helicity have also been produced. The electron magnetohydrodynamics fields are force free, have wave energy density exceeding the particle energy density, and propagate stably at subelectron thermal velocities through a nearly uniform stationary ion density background.

  3. Whistler modes with wave magnetic fields exceeding the ambient field.

    PubMed

    Stenzel, R L; Urrutia, J M; Strohmaier, K D

    2006-03-10

    Whistler-mode wave packets with fields exceeding the ambient dc magnetic field have been excited in a large, high electron-beta plasma. The waves are induced with a loop antenna with dipole moment either along or opposite to the dc field. In the latter case the excited wave packets have the topology of a spheromak but are propagating in the whistler mode along and opposite to the dc magnetic field. Field-reversed configurations with net zero helicity have also been produced. The electron magnetohydrodynamics fields are force free, have wave energy density exceeding the particle energy density, and propagate stably at subelectron thermal velocities through a nearly uniform stationary ion density background. PMID:16606272

  4. Near-Zero-Field Nuclear Magnetic Resonance

    NASA Astrophysics Data System (ADS)

    Ledbetter, M. P.; Theis, T.; Blanchard, J. W.; Ring, H.; Ganssle, P.; Appelt, S.; Blmich, B.; Pines, A.; Budker, D.

    2011-09-01

    We investigate nuclear magnetic resonance (NMR) in near zero field, where the Zeeman interaction can be treated as a perturbation to the electron mediated scalar interaction (J coupling). This is in stark contrast to the high-field case, where heteronuclear J couplings are normally treated as a small perturbation. We show that the presence of very small magnetic fields results in splitting of the zero-field NMR lines, imparting considerable additional information to the pure zero-field spectra. Experimental results are in good agreement with first-order perturbation theory and with full numerical simulation when perturbation theory breaks down. We present simple rules for understanding the splitting patterns in near-zero-field NMR, which can be applied to molecules with nontrivial spectra.

  5. Simulation of interplanetary magnetic field B{sub y} penetration into the magnetotail

    SciTech Connect

    Guo, Jiuling; Shen, Chao; Liu, Zhenxing

    2014-07-15

    Based on our global 3D magnetospheric MHD simulation model, we investigate the phenomena and physical mechanism of the B{sub y} component of the interplanetary magnetic field (IMF) penetrating into the magnetotail. We find that the dayside reconnected magnetic field lines move to the magnetotail, get added to the lobe fields, and are dragged in the IMF direction. However, the B{sub y} component in the plasma sheet mainly originates from the tilt and relative slippage of the south and north lobes caused by plasma convection, which results in the original B{sub z} component in the plasma sheet rotating into a B{sub y} component. Our research also shows that the penetration effect of plasma sheet B{sub y} from the IMF B{sub y} during periods of northward IMF is larger than that during periods of southward IMF.

  6. Topology of magnetic fields from MDI data: Background field

    NASA Astrophysics Data System (ADS)

    Knyazeva, I. S.; Makarenko, N. G.; Karimova, L. M.

    2010-08-01

    A quantitative description of the geometry and topology of the magnetic field of the Sun is given in terms of Minkowski functionals: the Euler characteristic and the perimeter of excursion sets for specified levels. Methods of mathematical morphology are applied to background fragments of magnetograms for the entire solar disk. The results obtained show that the topological characteristics of the background field are stable in time and correspond to log-normal, intermittent random fields.

  7. Refocusing properties of periodic magnetic fields

    NASA Technical Reports Server (NTRS)

    Stankiewicz, N.

    1976-01-01

    The use of depressed collectors for the efficient collection of spent beams from linear-beam microwave tubes depends on a refocusing procedure in which the space charge forces and transverse velocity components are reduced. The refocusing properties are evaluated of permanent magnet configurations whose axial fields are approximated by constant plateaus or linearly varying fields. The results provide design criteria and show that the refocusing properties can be determined from the plateau fields alone.

  8. Magnetic Field Response Measurement Acquisition System

    NASA Technical Reports Server (NTRS)

    Woodard, Stanley E.; Taylor,Bryant D.; Shams, Qamar A.; Fox, Robert L.

    2007-01-01

    This paper presents a measurement acquisition method that alleviates many shortcomings of traditional measurement systems. The shortcomings are a finite number of measurement channels, weight penalty associated with measurements, electrical arcing, wire degradations due to wear or chemical decay and the logistics needed to add new sensors. Wire degradation has resulted in aircraft fatalities and critical space launches being delayed. The key to this method is the use of sensors designed as passive inductor-capacitor circuits that produce magnetic field responses. The response attributes correspond to states of physical properties for which the sensors measure. Power is wirelessly provided to the sensing element by using Faraday induction. A radio frequency antenna produces a time-varying magnetic field used to power the sensor and receive the magnetic field response of the sensor. An interrogation system for discerning changes in the sensor response frequency, resistance and amplitude has been developed and is presented herein. Multiple sensors can be interrogated using this method. The method eliminates the need for a data acquisition channel dedicated to each sensor. The method does not require the sensors to be near the acquisition hardware. Methods of developing magnetic field response sensors and the influence of key parameters on measurement acquisition are discussed. Examples of magnetic field response sensors and the respective measurement characterizations are presented. Implementation of this method on an aerospace system is discussed.

  9. Magnetic field generation in relativistic shocks

    NASA Astrophysics Data System (ADS)

    Wiersma, J.; Achterberg, A.

    2005-05-01

    Linear theory of the Weibel instability cannot explain magnetic field generation in relativistic shock fronts in electron-proton plasmas. The fireball model for Gamma-ray Burst afterglows requires a magnetic field in similar shock fronts between the fireball and the surrounding matter to explain the detected non-thermal afterglow radiation. We consider an analytical model of pre-shock protons penetrating the hot post-shock electron plasma. The linear Weibel instability produces magnetic fields through self-enhancing current channels. Perturbations with a length-scale comparable to the electron skin depth reach the highest magnetic field before the linear theory breaks down. The electrons quench the linear proton instability so that it cannot randomize the proton velocity distribution and only converts a small fraction of the available kinetic energy of the protons into magnetic fields. We conclude that the linear Weibel instability that dominates in pair plasmas is relatively unimportant in electron-proton plasmas and that non-linear processes are probably much more important.

  10. Dissipation function in a magnetic field (Review)

    NASA Astrophysics Data System (ADS)

    Gurevich, V. L.

    2015-07-01

    The dissipation function is introduced to describe the behavior of the system of harmonic oscillations interacting with the environment (thermostat). This is a quadratic function of generalized velocities, which determines the rate of dissipation of the mechanical energy in the system. It was assumed earlier (Landau, Lifshitz) that the dissipation function can be introduced only in the absence of magnetic field. In the present review based on the author's studies, it has been shown how the dissipation function can be introduced in the presence of a magnetic field B. In a magnetic field, both dissipative and nondissipative responses arise as a response to perturbation and are expressed in terms of kinetic coefficients. The matrix of nondissipative coefficients can be obtained to determine an additional term formally including it into the equations of motion, which still satisfy the energy conservation law. Then, the dissipative part of the matrix can be considered in exactly the same way as without magnetic field, i.e., it defines the dissipation loss. As examples, the propagation and absorption of ultrasound in a metal or a semiconductor in a magnetic field have been considered using two methods: (i) the method based on the phenomenological theory using the equations of the theory of elasticity and (ii) the method based on the microscopic approach by analyzing and solving the kinetic equation. Both examples are used to illustrate the approach with the dissipation function.

  11. Magnetic fields of the outer planets

    NASA Technical Reports Server (NTRS)

    Connerney, J. E. P.

    1993-01-01

    It is difficult to imagine a group of planetary dynamos more diverse than those visited by the Pioneer and Voyager spacecraft. The magnetic field of Jupiter is large in magnitude and has a dipole axis within 10 deg of its rotation axis, comfortably consistent with the paleomagnetic history of the geodynamo. Saturn's remarkable (zonal harmonic) magnetic field has an axis of symmetry that is indistinguishable from its rotation axis (mush less than 1 deg angular separation); it is also highly antisymmetric with respect to the equator plane. According to one hypothesis, the spin symmetry may arise from the differential rotation of an electrically conducting and stably stratified layer above the dynamo. The magnetic fields of Uranus and Neptune are very much alike, and equally unlike those of the other known magnetized planets. These two planets are characterized by a large dipole tilts (59 deg and 47 deg, respectively) and quadrupole moments (Schmidt-normalized quadrupole/dipole ratio approximately equal 1.0). These properties may be characteristic of dynamo generation in the relatively poorly conducting 'ice' interiors of Uranus and Neptune. Characteristics of these planetary magnetic fields are illustrated using contour maps of the field on the planet's surface and discussed in the context of planetary interiors and dynamo generation.

  12. The Magnetic Field in Tapia's Globule 2

    NASA Astrophysics Data System (ADS)

    Andersson, B.-G.; Carretti, Ettore; Bhat, Ramesh; Robishaw, Timothy; Crutcher, Richard; Vaillancourt, John

    2014-04-01

    We propose to measure the magnetic field in the Southern Coalsack using the Zeeman effect in OH at 1665 and 1667 MHz. This is motivated by (1) the measurement of a large magnetic field (B~90 uG) in the Coalsack region from optical and near infrared polarimetry and (2) a very low magnetic field (B~1 uG) measured ~30' from the cloud edge using pulsar Faraday rotation measurements. While the derived field strength in the cloud is significantly larger than usually seen in the interstellar medium, the existence of an X-ray emitting envelope around the cloud that contains significant amounts of O VI ions puts the magnetic pressure at approximate equipartition with the thermal pressure of such gas. A chain of observational results indicate that the Coalsack might be a unique, nearby example of externally triggered star formation. This chain starts with the passage of the Upper Centaurus-Lupus super bubble over the cloud, eventually causing triggered star formation. Probing the high magnetic field strength and providing accurate constraints for the interpretation of the observations of the cloud is therefore of great importance for testing this hypothesis.

  13. Reionization constraints on primordial magnetic fields

    NASA Astrophysics Data System (ADS)

    Pandey, Kanhaiya L.; Choudhury, T. Roy; Sethi, Shiv K.; Ferrara, Andrea

    2015-08-01

    We study the impact of the extra density fluctuations induced by primordial magnetic fields on the reionization history in the redshift range: 6 < z < 10. We perform a comprehensive Markov chain Monte Carlo (MCMC) physical analysis allowing the variation of parameters related to primordial magnetic fields (strength, B0, and power-spectrum index n_{B}), reionization and Λ cold dark matter cosmological model. We find that magnetic field strengths in the range: B0 ≃ 0.05-0.3 nG (for nearly scale-free power spectra) can significantly alter the reionization history in the above redshift range and can relieve the tension between the Wilkinson Microwave Anisotropy Probe and quasar absorption spectra data. Our analysis puts upper limits on the magnetic field strength B0 < 0.358, 0.120 and 0.059 nG (95 per cent c.l.) for n_{B} = -2.95, -2.9 and -2.85, respectively. These represent the strongest magnetic field constraints among those available from other cosmological observables.

  14. Reducing blood viscosity with magnetic fields

    NASA Astrophysics Data System (ADS)

    Tao, R.; Huang, K.

    2011-07-01

    Blood viscosity is a major factor in heart disease. When blood viscosity increases, it damages blood vessels and increases the risk of heart attacks. Currently, the only method of treatment is to take drugs such as aspirin, which has, however, several unwanted side effects. Here we report our finding that blood viscosity can be reduced with magnetic fields of 1 T or above in the blood flow direction. One magnetic field pulse of 1.3 T lasting ˜1 min can reduce the blood viscosity by 20%-30%. After the exposure, in the absence of magnetic field, the blood viscosity slowly moves up, but takes a couple of hours to return to the original value. The process is repeatable. Reapplying the magnetic field reduces the blood viscosity again. By selecting the magnetic field strength and duration, we can keep the blood viscosity within the normal range. In addition, such viscosity reduction does not affect the red blood cells’ normal function. This technology has much potential for physical therapy.

  15. Magnetic fields in primordial accretion disks

    NASA Astrophysics Data System (ADS)

    Latif, M. A.; Schleicher, D. R. G.

    2016-01-01

    Magnetic fields are considered a vital ingredient of contemporary star formation and may have been important during the formation of the first stars in the presence of an efficient amplification mechanism. Initial seed fields are provided via plasma fluctuations and are subsequently amplified by the small-scale dynamo, leading to a strong, tangled magnetic field. We explore how the magnetic field provided by the small-scale dynamo is further amplified via the α-Ω dynamo in a protostellar disk and assess its implications. For this purpose, we consider two characteristic cases, a typical Pop. III star with 10M⊙ and an accretion rate of 10-3M⊙ yr-1, and a supermassive star with 105M⊙ and an accretion rate of 10-1M⊙ yr-1. For the 10M⊙ Pop. III star, we find that coherent magnetic fields can be produced on scales of at least 100 AU, which are sufficient to drive a jet with a luminosity of 100L⊙ and a mass outflow rate of 10-3.7M⊙ yr-1. For the supermassive star, the dynamical timescales in its environment are even shorter, implying smaller orbital timescales and an efficient magnetization out to at least 1000 AU. The jet luminosity corresponds to ~106.0L⊙ and a mass outflow rate of 10-2.1M⊙ yr-1. We expect that the feedback from the supermassive star can have a relevant impact on its host galaxy.

  16. Charmonia and bottomonia in a magnetic field

    NASA Astrophysics Data System (ADS)

    Alford, Jeremy; Strickland, Michael

    2013-11-01

    We study the effect of a static homogeneous external magnetic field on charmonium and bottomonium states. In an external magnetic field, quarkonium states do not have a conserved center-of-mass momentum. Instead there is a new conserved quantity called the pseudomomentum which takes into account the Lorentz force on the particles in the system. When written in terms of the pseudomomentum, the internal and center-of-mass motions do not decouple and, as a result, the properties of quarkonia depend on the states center-of-mass momentum. We analyze the behavior of heavy particle-antiparticle pairs subject to an external magnetic field assuming a three-dimensional harmonic potential and Cornell potential plus spin-spin interaction. In the case of the Cornell potential, we also take into account the mixing of the ?c and J/? states and ?b and ? states due to the background magnetic field. We then numerically calculate the dependence of the masses and mixing fractions on the magnitude of the background magnetic field and center-of-mass momentum of the state.

  17. Exploring Magnetic Fields with a Compass

    NASA Astrophysics Data System (ADS)

    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 paper, we present a series of simple activities adapted from the Matter & Interactions textbook for doing just this. Interestingly, these simple measurements are comparable to predictions made by the Bohr model of the atom. Although antiquated, Bohr's atom can lead the way to a deeper analysis of the atomic properties of magnets. Although originally developed for an introductory calculus-based course, these activities can easily be adapted for use in an algebra-based class or even at the high school level.

  18. Magnetic field configuration of the theta aurora

    NASA Technical Reports Server (NTRS)

    Toffoletto, F. R.; Hill, T. W.

    1990-01-01

    A magnetic configuration of the open magnetosphere is described which is conducive to the formation of the theta aurora when the IMF has a significant northward component. A magnetic field topology and polar cap configuration, derived from a quantitative model of the open magnetosphere that incorporates Crooker's antiparallel merging hypothesis, are presented. Under this hypothesis, when the IMF has a northward component, the dayside merging line bifurcates, leaving a large fraction of the subsolar magnetopause untouched by the merging process. The polar cap, defined by tracing magnetic field lines that connect from the solar wind to the earth, is similarly bifurcated, leaving a sun-aligned stagnation region that is not magnetically connected to the solar wind and may plausibly be associated with the sun-aligned 'bar' of the theta aurora. The model provides testable predictions with regard to the position of this 'convection gap' in both Northern and Southern Hemispheres as functions of IMF direction.

  19. Magnetic Field Effects on Plasma Plumes

    NASA Technical Reports Server (NTRS)

    Ebersohn, F.; Shebalin, J.; Girimaji, S.; Staack, D.

    2012-01-01

    Here, we will discuss our numerical studies of plasma jets and loops, of basic interest for plasma propulsion and plasma astrophysics. Space plasma propulsion systems require strong guiding magnetic fields known as magnetic nozzles to control plasma flow and produce thrust. Propulsion methods currently being developed that require magnetic nozzles include the VAriable Specific Impulse Magnetoplasma Rocket (VASIMR) [1] and magnetoplasmadynamic thrusters. Magnetic nozzles are functionally similar to de Laval nozzles, but are inherently more complex due to electromagnetic field interactions. The two crucial physical phenomenon are thrust production and plasma detachment. Thrust production encompasses the energy conversion within the nozzle and momentum transfer to a spacecraft. Plasma detachment through magnetic reconnection addresses the problem of the fluid separating efficiently from the magnetic field lines to produce maximum thrust. Plasma jets similar to those of VASIMR will be studied with particular interest in dual jet configurations, which begin as a plasma loops between two nozzles. This research strives to fulfill a need for computational study of these systems and should culminate with a greater understanding of the crucial physics of magnetic nozzles with dual jet plasma thrusters, as well as astrophysics problems such as magnetic reconnection and dynamics of coronal loops.[2] To study this problem a novel, hybrid kinetic theory and single fluid magnetohydrodynamic (MHD) solver known as the Magneto-Gas Kinetic Method is used.[3] The solver is comprised of a "hydrodynamic" portion based on the Gas Kinetic Method and a "magnetic" portion that accounts for the electromagnetic behaviour of the fluid through source terms based on the resistive MHD equations. This method is being further developed to include additional physics such as the Hall effect. Here, we will discuss the current level of code development, as well as numerical simulation results

  20. Magnetic Fields in Early Protostellar Disk Formation

    NASA Astrophysics Data System (ADS)

    González-Casanova, Diego F.; Lazarian, Alexander; Santos-Lima, Reinaldo

    2016-03-01

    We consider formation of accretion disks from a realistically turbulent molecular gas using 3D MHD simulations. In particular, we analyze the effect of the fast turbulent reconnection described by the Lazarian & Vishniac model for the removal of magnetic flux from a disk. With our numerical simulations we demonstrate how the fast reconnection enables protostellar disk formation resolving the so-called “magnetic braking catastrophe.” In particular, we provide a detailed study of the dynamics of a 0.5 M⊙ protostar and the formation of its disk for up to several thousands years. We measure the evolution of the mass, angular momentum, magnetic field, and turbulence around the star. We consider effects of two processes that strongly affect the magnetic transfer of angular momentum, both of which are based on turbulent reconnection: the first, “reconnection diffusion,” removes the magnetic flux from the disk; the other involves the change of the magnetic field's topology, but does not change the absolute value of the magnetic flux through the disk. We demonstrate that for the first mechanism, turbulence causes a magnetic flux transport outward from the inner disk to the ambient medium, thus decreasing the coupling of the disk to the ambient material. A similar effect is achieved through the change of the magnetic field's topology from a split monopole configuration to a dipole configuration. We explore how both mechanisms prevent the catastrophic loss of disk angular momentum and compare both above turbulent reconnection mechanisms with alternative mechanisms from the literature.

  1. Intrinsic Josephson junctions in a magnetic field

    NASA Astrophysics Data System (ADS)

    Yurgens, A.

    2004-05-01

    Measurements of the c-axis tunneling characteristics across mesas patterned on the surfaces of Bi2212 single crystals are discussed. The measurements provide information on the magnetic phase diagram, vortex pinning and the interplanar pancake correlations at different temperatures and magnetic fields. The pancake correlations and/or pinning can be effectively controlled by: (i) carrier concentration (oxygen content), (ii) columnar defects via heavy-ion irradiation, (iii) changes of the tunneling-barriers' width via intercalation of inert molecules or pressure.

  2. On flow of electrically conducting fluids over a flat plate in the presence of a transverse magnetic field

    NASA Technical Reports Server (NTRS)

    Rossow, Vernon J

    1958-01-01

    The use of a magnetic field to control the motion of electrically conducting fluids is studied. The incompressible boundary-layer solutions are found for flow over a flat plate when the magnetic field is fixed relative to the plate or to the fluid. The equations are integrated numerically for the effect of the transverse magnetic field on the velocity and temperature profiles, and hence, the skin friction and rate of heat transfer. It is concluded that the skin friction and the heat-transfer rate are reduced when the transverse magnetic field is fixed relative to the plate and increased when fixed relative to the fluid. The total drag is increased in all of the areas.

  3. Mechanical Response of Elastomers to Magnetic Fields

    NASA Technical Reports Server (NTRS)

    Munoz, B. C.; Jolly, M. R.

    1996-01-01

    Elastomeric materials represent an important class of engineering materials, which are widely used to make components of structures, machinery, and devices for vibration and noise control. Elastomeric material possessing conductive or magnetic properties have been widely used in applications such as conductive and magnetic tapes, sensors, flexible permanent magnets, etc. Our interest in these materials has focussed on understanding and controlling the magnitude and directionality of their response to applied magnetic fields. The effect of magnetic fields on the mechanical properties of these materials has not been the subject of many published studies. Our interest and expertise in controllable fluids have given us the foundation to make a transition to controllable elastomers. Controllable elastomers are materials that exhibit a change in mechanical properties upon application of an external stimuli, in this case a magnetic field. Controllable elastomers promise to have more functionality than conventional elastomers and therefore could share the broad industrial application base with conventional elastomers. As such, these materials represent an attractive class of smart materials, and may well be a link that brings the applications of modern control technologies, intelligent structures and smart materials to a very broad industrial area. This presentation will cover our research work in the area of controllable elastomers at the Thomas Lord Research Center. More specifically, the presentation will discuss the control of mechanical properties and mathematical modeling of the new materials prepared in our laboratories along with experiments to achieve adaptive vibration control using the new materials.

  4. Drag bit construction

    DOEpatents

    Hood, M.

    1986-02-11

    A mounting movable with respect to an adjacent hard face has a projecting drag bit adapted to engage the hard face. The drag bit is disposed for movement relative to the mounting by encounter of the drag bit with the hard face. That relative movement regulates a valve in a water passageway, preferably extending through the drag bit, to play a stream of water in the area of contact of the drag bit and the hard face and to prevent such water play when the drag bit is out of contact with the hard face. 4 figs.

  5. Drag bit construction

    DOEpatents

    Hood, Michael (Lafayette, CA)

    1986-01-01

    A mounting movable with respect to an adjacent hard face has a projecting drag bit adapted to engage the hard face. The drag bit is disposed for movement relative to the mounting by encounter of the drag bit with the hard face. That relative movement regulates a valve in a water passageway, preferably extending through the drag bit, to play a stream of water in the area of contact of the drag bit and the hard face and to prevent such water play when the drag bit is out of contact with the hard face.

  6. Drag reduction in nature

    NASA Technical Reports Server (NTRS)

    Bushnell, D. M.; Moore, K. J.

    1991-01-01

    Recent studies on the drag-reducing shapes, structures, and behaviors of swimming and flying animals are reviewed, with an emphasis on potential analogs in vehicle design. Consideration is given to form drag reduction (turbulent flow, vortex generation, mass transfer, and adaptations for body-intersection regions), skin-friction drag reduction (polymers, surfactants, and bubbles as surface 'additives'), reduction of the drag due to lift, drag-reduction studies on porpoises, and drag-reducing animal behavior (e.g., leaping out of the water by porpoises). The need for further research is stressed.

  7. Modeling Solar Magnetic Fields Using Satellite Data

    NASA Astrophysics Data System (ADS)

    Lee, G.; Malanushenko, A. V.; DeRosa, M. L.

    2014-12-01

    Previous research reconstructed a three-dimensional model of the magnetic field of an active region on the Sun from using solar coronal loops as guides for modeling(Malanushenko et al., ApJ,2009, 707:1044). In this study, we test the consistency of such reconstructions with data from the Atmospheric Imaging Assembly (AIA) and the Helioseismic and Magnetic Imager (HMI) by applying the aformentioned method to additional active regions with varying amounts of solar activity. To create an initial model of a magnetic field surrounding an active region, we first manually trace the coronal loops on the coronal images in the following wavelengths: 171Å, 193Å, 211Å, 94Å, 131Å, and 335Å. The manually traced loops are then used as a guide for a computer reconstruction of the individual three-dimensional field lines with differing heights and degrees of local twist. The reconstructed field lines are then adjusted by a partially automated algorithm, so that the constructed field line would correspond to a coronal loop on the Sun. These fitted loops serve as a skeleton to create a model of the magnetic field of the active region. We expect that our modeling can be used in future works to predict future solar events. Implications of this ability include being able to prepare a response for a solar event before it happens.

  8. Field determination of drag forces and shear stress partitioning effects for a desert shrub (Sarcobatus vermiculatus, greasewood)

    NASA Astrophysics Data System (ADS)

    Gillies, J. A.; Lancaster, N.; Nickling, W. G.; Crawley, D. M.

    2000-10-01

    Drag coefficients (Cd) for the desert shrub greasewood (Sarcobatus vermiculatus) were developed from force versus wind speed data collected with an omnidirectional force balance. The average Cd for a small (0.6 m high, 0.5 m wide) shrub and a larger (1.6 m high, 1.3 m wide) shrub were 1.425 (±0.103) and 0.435 (±0.200), respectively. These values are much larger than similarly shaped solid elements and previously reported values for creosote bush (Larrea tridentata, Cd = 0.485) and an artificial tree (0.4). The greater Cd value for greasewood probably results from factors related to porosity and vegetation structure that gives this shrub-type greater momentum extracting potential. The drag coefficients for the greasewood shrubs were found to show dependence upon flow Reynolds numbers >6×105, corresponding to wind speeds greater than 18 m s-1 at 10 m. The developed greasewood Cd values were used in a shear stress partitioning model that indicated they would be extremely effective at reducing wind-generated sediment transport at low-percent coverage.

  9. Human melatonin during continuous magnetic field exposure

    SciTech Connect

    Graham, C.; Cook, M.R.; Riffle, D.W.

    1997-05-01

    This report describes the third in a series of double-blind, laboratory-based studies that were aimed at determining the effects of nocturnal exposure to power frequency magnetic fields on blood levels of melatonin in human volunteers. The two earlier studies evaluated effects on melatonin of intermittent exposure to 60 Hz circularly polarized magnetic fields at 10 and 200 mG. No overall effects on melatonin levels were found. In the present study, men were exposed continuously rather than intermittently through the night to the same 200 mG magnetic field condition that was used previously; again, no overall effects on melatonin levels were found. The authors conclude that the intermittent and continuous exposure conditions used in the laboratory to date are not effective in altering nocturnal blood levels of melatonin in human volunteers.

  10. Configuration of the local interstellar magnetic field

    NASA Astrophysics Data System (ADS)

    Frisch, Priscilla C.; Andersson, B.; Berdhyugin, A.; Funsten, H. O.; DeMajistre, R.; Magalhaes, A.; McComas, D.; Piirola, V.; Schwadron, N.; Seriacopi, D.; Slavin, J. D.; Wiktorowicz, S.; IBEX Team

    2014-01-01

    The discovery of the Ribbon of energetic neutral atoms by the Interstellar Boundary Explorer (IBEX) provides a new and unexpected diagnostic of the direction of the local interstellar magnetic field (ISMF). The IBEX Ribbon forms where the interstellar magnetic field draping over the heliosphere is perpendicular to the sightline. We have shown that the direction of the interstellar magnetic field close to the Sun, obtained from starlight polarized in the interstellar medium (ISM), is consistent with the ISMF direction that is traced by the IBEX Ribbon. In this presentation we show that new optical polarization data indicate that the local ISMF has a smoothly varying component stretching from the first to the third galactic quadrant. Both the ISMF direction and the kinematics of local interstellar gas within tens of parsecs support an interpretation where the local interstellar clouds are a fragment of the expanding Loop I superbubble.

  11. Behavior of a Single Langmuir Probe in a Magnetic Field.

    ERIC Educational Resources Information Center

    Pytlinski, J. T.; And Others

    1978-01-01

    Describes an experiment to demonstrate the influence of a magnetic field on the behavior of a single Langmuir probe. The experiment introduces the student to magnetically supported plasma and particle behavior in a magnetic field. (GA)

  12. Vertical gradients of sunspot magnetic fields

    NASA Technical Reports Server (NTRS)

    Hagyard, M. J.; Teuber, D.; West, E. A.; Tandberg-Hanssen, E.; Henze, W., Jr.; Beckers, J. M.; Bruner, M.; Hyder, C. L.; Woodgate, B. E.

    1983-01-01

    The results of a Solar Maximum Mission (SMM) guest investigation to determine the vertical gradients of sunspot magnetic fields for the first time from coordinated observations of photospheric and transition-region fields are described. Descriptions are given of both the photospheric vector field of a sunspot, derived from observations using the NASA Marshall Space Flight Center vector magnetograph, and of the line-of-sight component in the transition region, obtained from the SMM Ultraviolet Spectrometer and Polarimeter instrument. On the basis of these data, vertical gradients of the line-of-sight magnetic field component are calculated using three methods. It is found that the vertical gradient of Bz is lower than values from previous studies and that the transition-region field occurs at a height of approximately 4000-6000 km above the photosphere.

  13. The symmetry properties of planetary magnetic fields

    NASA Technical Reports Server (NTRS)

    Raedler, Karl-Heinz; Ness, Norman F.

    1990-01-01

    This paper provides a comparative study of the geometrical structures of the magnetic fields of earth, Jupiter, Saturn, and Uranus, starting from the traditional multipolar representations of these fields. For earth, Jupiter, and Saturn, the centered dipole, quadrupole, and octupole contributions are included, while at Uranus only the dipole and quadrupole contributions are considered. It is found that there are a number of common features of the magnetic fields of earth and Jupiter. Compared to earth and Jupiter, the Saturnian field exhibits not only a high degree of symmetry about the rotation axis but also a high degree of antisymmetry about the equatorial plane. The Uranian field shows strong deviations from both such symmetries. Nevertheless, there remain features common to all four planets.

  14. Neutrino dispersion in external magnetic fields

    SciTech Connect

    Kuznetsov, A. V.; Mikheev, N. V.; Vassilevskaya, L. A.; Raffelt, G. G.

    2006-01-15

    We calculate the neutrino self-energy operator {sigma}(p) in the presence of a magnetic field B. In particular, we consider the weak-field limit eB<field' m{sub l}{sup 2}<field, we show that it is crucial to include the contributions from all Landau levels of the intermediate charged lepton, not just the ground state. For the conditions of the early universe where the background medium consists of a charge-symmetric plasma, the pure B-field contribution to the neutrino dispersion relation is proportional to (eB){sup 2} and thus comparable to the contribution of the magnetized plasma.

  15. Magnetic resonance signal moment determination using the Earth's magnetic field

    NASA Astrophysics Data System (ADS)

    Fridjonsson, E. O.; Creber, S. A.; Vrouwenvelder, J. S.; Johns, M. L.

    2015-03-01

    We demonstrate a method to manipulate magnetic resonance data such that the moments of the signal spatial distribution are readily accessible. Usually, magnetic resonance imaging relies on data acquired in so-called k-space which is subsequently Fourier transformed to render an image. Here, via analysis of the complex signal in the vicinity of the centre of k-space we are able to access the first three moments of the signal spatial distribution, ultimately in multiple directions. This is demonstrated for biofouling of a reverse osmosis (RO) membrane module, rendering unique information and an early warning of the onset of fouling. The analysis is particularly applicable for the use of mobile magnetic resonance spectrometers; here we demonstrate it using an Earth's magnetic field system.

  16. Effect of magnetic field in malaria diagnosis using magnetic nanoparticles

    NASA Astrophysics Data System (ADS)

    Liu, Quan; Yuen, Clement

    2011-07-01

    The current gold standard method of Malaria diagnosis relies on the blood smears examination. The method is laborintensive, time consuming and requires the expertise for data interpretation. In contrast, Raman scattering from a metabolic byproduct of the malaria parasite (Hemozoin) shows the possibility of rapid and objective diagnosis of malaria. However, hemozoin concentration is usually extremely low especially at the early stage of malaria infection, rendering weak Raman signal. In this work, we propose the sensitive detection of enriched ?-hematin, whose spectroscopic properties are equivalent to hemozoin, based on surface enhanced Raman spectroscopy (SERS) by using magnetic nanoparticles. A few orders of magnitude enhancement in the Raman signal of ?-hematin can be achieved using magnetic nanoparticles. Furthermore, the effect of magnetic field on SERS enhancement is investigated. Our result demonstrates the potential of SERS using magnetic nanoparticles in the effective detection of hemozoin for malaria diagnosis.

  17. The symmetry properties of planetary magnetic fields

    SciTech Connect

    Raedler, K.H. ); Ness, N.F. )

    1990-03-01

    This paper provides a comparative study of the geometrical structures of the magnetic fields of Earth, Jupiter, Saturn, and Uranus, starting from the traditional multipolar representations of these fields. For Earth, Jupiter, and Saturn the centered dipole, quadrupole, and octupole contributions are included, while at Uranus, only the dipole and quadrupole contributoins are considered. The magnetic fields are analyzed by decomposing them into those parts which have simple symmetry properties with respect to the rotation axis and the equatorial plane. It is found that there are a number of common features of the magnetic fields of Earth and Jupiter. Compared to Earth and Jupiter, the Saturnian field exhibits not only a high degree of symmetry about the rotation axis, by now rather well known, but also a high degree of antisymmetry about the equatorial plane. The Uranian field shows strong deviations from both such symmetries. Nevertheless, there remain features common to all four planets. The implications of these results for dynamo models are discussed. With a vgiew to Cowling's theorem the symmetry of the fields is investigated with respect to not only the rotation axis but also to other axes intersecting the plaentary center. Surprisingly, the high degree of asymmetry of the Uranian field that is observed with respect to the rotation axis reduces considerably to being compare to that for Earth or Jupiter when the appropriate axis is employed.

  18. A magnetically field-controllable phononic crystal

    NASA Astrophysics Data System (ADS)

    Bayat, Alireza; Gordaninejad, Faramarz

    2014-04-01

    Phononic crystals are periodic structures consist of different materials in an elastic medium designed to interact with elastic waves. These crystals have practical applications, such as, frequency filters, beam splitters, sound or vibration protectors, acoustic lasers, acoustic mirrors and elastic waveguides. In this study, the wave propagation in a tunable phononic crystal is investigated. The magnetically controllable phononic crystal consists of a soft magnetorheological elastic medium undergoing large deformations upon the application of a magnetic field. Finite deformations and induced magnetic fields influence wave propagation characteristics in the periodic structure. The soft matrix is modeled as a hyperelastic elastomer to take into account the material nonlinearity. The integrated effects of material properties, transformation of the geometry of the unit cell, and the induced magnetic field, are used to tune the band structure of the periodic structure. Both analytical and finite element methods are employed to evaluate the dispersion diagrams considering Bloch boundary conditions. Results show that the applied magnetic field significantly affect the width and the position of band-gaps.

  19. Lunar magnetic permeability, magnetic fields, and electrical conductivity temperature

    NASA Technical Reports Server (NTRS)

    Parkin, C. W.

    1978-01-01

    In the time period 1969-1972 a total of five magnetometers were deployed on the lunar surface during four Apollo missions. Data from these instruments, along with simultaneous measurements from other experiments on the moon and in lunar orbit, were used to study properties of the lunar interior and the lunar environment. The principal scientific results from analyses of the magnetic field data are discussed. The results are presented in the following main categories: (1) lunar electrical conductivity, temperature, and structure; (2) lunar magnetic permeability, iron abundance, and core size limits; (3) the local remnant magnetic fields, their interaction with the solar wind, and a thermoelectric generator model for their origin. Relevant publications and presented papers are listed.

  20. High magnetic field ohmically decoupled non-contact technology

    DOEpatents

    Wilgen, John [Oak Ridge, TN; Kisner, Roger [Knoxville, TN; Ludtka, Gerard [Oak Ridge, TN; Ludtka, Gail [Oak Ridge, TN; Jaramillo, Roger [Knoxville, TN

    2009-05-19

    Methods and apparatus are described for high magnetic field ohmically decoupled non-contact treatment of conductive materials in a high magnetic field. A method includes applying a high magnetic field to at least a portion of a conductive material; and applying an inductive magnetic field to at least a fraction of the conductive material to induce a surface current within the fraction of the conductive material, the surface current generating a substantially bi-directional force that defines a vibration. The high magnetic field and the inductive magnetic field are substantially confocal, the fraction of the conductive material is located within the portion of the conductive material and ohmic heating from the surface current is ohmically decoupled from the vibration. An apparatus includes a high magnetic field coil defining an applied high magnetic field; an inductive magnetic field coil coupled to the high magnetic field coil, the inductive magnetic field coil defining an applied inductive magnetic field; and a processing zone located within both the applied high magnetic field and the applied inductive magnetic field. The high magnetic field and the inductive magnetic field are substantially confocal, and ohmic heating of a conductive material located in the processing zone is ohmically decoupled from a vibration of the conductive material.

  1. Permanent Magnet Spiral Motor for Magnetic Gradient Energy Utilization: Axial Magnetic Field

    NASA Astrophysics Data System (ADS)

    Valone, Thomas F.

    2010-01-01

    The Spiral Magnetic Motor, which can accelerate a magnetized rotor through 90% of its cycle with only permanent magnets, was an energy milestone for the 20th century patents by Kure Tekkosho in the 1970's. However, the Japanese company used old ferrite magnets which are relatively weak and an electrically-powered coil to jump start every cycle, which defeated the primary benefit of the permanent magnet motor design. The principle of applying an inhomogeneous, anisotropic magnetic field gradient force Fz = ? cos ? dB/dz, with permanent magnets is well-known in physics, e.g., Stern-Gerlach experiment, which exploits the interaction of a magnetic moment with the aligned electron spins of magnetic domains. In this case, it is applied to dB/d? in polar coordinates, where the force F? depends equally on the magnetic moment, the cosine of the angle between the magnetic moment and the field gradient. The radial magnetic field increases in strength (in the attractive mode) or decreases in strength (in the repulsive mode) as the rotor turns through one complete cycle. An electromagnetic pulsed switching has been historically used to help the rotor traverse the gap (detent) between the end of the magnetic stator arc and the beginning (Kure Tekko, 1980). However, alternative magnetic pulse and switching designs have been developed, as well as strategic eddy current creation. This work focuses on the switching mechanism, novel magnetic pulse methods and advantageous angular momentum improvements. For example, a collaborative effort has begun with Toshiyuki Ueno (University of Tokyo) who has invented an extremely low power, combination magnetostrictive-piezoelectric (MS-PZT) device for generating low frequency magnetic fields and consumes "zero power" for static magnetic field production (Ueno, 2004 and 2007a). Utilizing a pickup coil such as an ultra-miniature millihenry inductor with a piezoelectric actuator or simply Wiegand wire geometry, it is shown that the necessary power for magnetic field switching device can be achieved in order to deflect the rotor magnet in transit. The Wiegand effect itself (bistable FeCoV wire called "Vicalloy") invented by John Wiegand (Switchable Magnetic Device, US Patent ?4,247,601), utilizing Barkhausen jumps of magnetic domains, is also applied for a similar achievement (Dilatush, 1977). Conventional approaches for spiral magnetic gradient force production have not been adequate for magnetostatic motors to perform useful work. It is proposed that integrating a magnetic force control device with a spiral stator inhomogeneous axial magnetic field motor is a viable approach to add a sufficient nonlinear boundary shift to apply the angular momentum and potential energy gained in 315 degrees of the motor cycle.

  2. A Compact Disk Type Plasma Propulsion System with Modulated Magnetic Field for Nanoscale Space Vehicles

    SciTech Connect

    Fukuda, Takeshi; Ueda, Satoshi; Ohnishi, Yukihiro; Inomoto, Michiaki

    2008-12-31

    A compact 5 mm disk type plasma thruster simply composed of only a set of antenna windings and bias field coil which produces significant thrust of 0.74 mN with rotating magnetic field has been proposed and successfully developed for future applications to low altitude nanosatellites. The key technology issue is that the rotating speed is set above the ion plasma frequency but far below the electron plasma frequency, in order to produce the electron drag current and axial electric field as a consequence of the interaction with the bias field. The formation of axial electric field was confirmed and the produced plasma density was >6x10{sup 18} m{sup -3}, whereas the power consumption is 500 W in the inductively coupled mode of operation. The anticipated thrust density and specific thrust could potentially be extended to 7.64 Nm{sup -2} and 850 s, respectively, which is comparable to conventional Hall effect thrusters.

  3. Broadband antenna systems for lightning magnetic fields

    NASA Technical Reports Server (NTRS)

    Krider, E. P.; Noggle, R. C.

    1975-01-01

    Broadband magnetic antenna systems suitable for recording submicrosecond field changes are described, and typical data from distant lightning are presented. Two types of systems are described, one with a high-impedance antenna loop connected to the integrator by a twisted pair of coaxial cables and another with the antenna loop and twisted signal loops formed from a single piece of coaxial cable. Data for correlated magnetic and electric field waveforms from lightning at a distance of 50 to 100 km are presented and are shown to be almost identical.

  4. High magnetic field MHD generator program

    NASA Astrophysics Data System (ADS)

    1980-10-01

    The MHD channel phenomena which are important at high magnetic fields are investigated. Nonuniformity effects, boundary layers, Hall field breakdown, the effects on electrode configuration and current concentrations, and studies of steady state combustion disk and linear channels in an existing 6 Tesla magnet of small dimensions are discussed. In the study of the effects of nonuniformities and instabilities, theoretical models were developed and tested against available data. Boundary layer measurements and calculations of velocity, temperature, and electron density were systematically assessed; by accounting for the effect of free stream turbulence, good agreement is obtained between measurement and theory. An improved laser Doppler anemometer was developed for turbulence damping and velocity profile measurements.

  5. The Magnetic Field in the Outer Heliosphere

    NASA Technical Reports Server (NTRS)

    Suess, S. T.

    2004-01-01

    One of the great achievements of Parker was the prediction that the solar magnetic field would be drawn into Archimedian spirals as it is carried away from the Sun by the solar wind. This prediction has been amply confirmed by many in situ measurements in the intervening four decades. But, Parker made his prediction for a solar wind that expands into infinite space while we now know that the local interstellar medium (LISM) is far from empty and, in fact, confines the solar wind to a finite volume, known as the heliosphere, that extends to approximately 100 AU in the upstream direction (the solar system is moving through the LISM). Voyagers 1/2, presently at -80 AU, are approaching the upstream boundaries of the heliosphere and returning data on the properties of the magnetic field. This is important for understanding how galactic cosmic rays (GCRs) reach the Earth. Voyagers show that the IMF at 10-80 AU behaves much as Parker predicted - with two important exceptions. This is not surprising since the field is essentially passively advected by the solar wind out to 80 AU. But, new models say that nearer the heliosphere boundaries the field plays a major role in the solar wind-LISM interaction. However, of the many physical ingredients that constitute the outer heliosphere, the magnetic field poses some of the most interesting and difficult numerical modeling problems. Presently, only a few results have been published and much remains to be done. Here I will summarize the expected and measured behavior of the magnetic field at 80 AU. Then I will describe modeling predictions beyond 80 AU: magnetic "tornadoes", polarity envelopes, the Axford-Cranfill effect, inner and outer magnetic walls and more. I will also list what I believe to be important new modeling objectives. Finally, I will speculate on what is happening with the magnetic field near the nose of the heliosphere. My conclusion is that models of GCR modulation rarely incorporate even crudely realistic magnetic fields so it is a wonder that they are as successful as they are and no surprise that there are still important discrepancies between GCR modulation observations and the models.

  6. Possible production mechanisms of lunar magnetic fields.

    NASA Technical Reports Server (NTRS)

    Cap, F. F.

    1972-01-01

    Demonstration of the impossibility of the production of local surface magnetic fields on the moon by conduction currents in the lunar soil and in local lunar atmospheres by volcanic eruption. However, it is suggested that convection currents produced by the ionization (by radiation and/or by triboelectric effects) of volcanic-ash-particle flows may produce the local magnetic fields of about 1000 gamma that are believed to have existed on the moon about 3.5 x 10 to the 9th years ago. A simple electrogasdynamic model for such flows and experiments for further investigation of this hypothesis are discussed.

  7. Measurements of magnetic fields in solar prominences

    NASA Technical Reports Server (NTRS)

    Deglinnocenti, Egidio Landi

    1986-01-01

    Magnetic fields can be measured, in solar prominences, by means of two different basic mechanisms that are responsible for the introduction (or the reduction) of a given amount of polarization in spectral lines: these are the Zeeman effect and the Hanle effect. Through the splitting of the magnetic components of a spectral line, the Zeeman effect is capable of introducing a certain amount of circular polarization across the line profile. The Hanle effect consist of a modification of the linear polarization that is induced in spectral lines by the anisotropic illumination of the prominence plasma by the photospheric radiation field. These two effects are briefly discussed.

  8. Magnetic fields of HgMn stars⋆

    NASA Astrophysics Data System (ADS)

    Hubrig, S.; González, J. F.; Ilyin, I.; Korhonen, H.; Schöller, M.; Savanov, I.; Arlt, R.; Castelli, F.; Lo Curto, G.; Briquet, M.; Dall, T. H.

    2012-11-01

    Context. The frequent presence of weak magnetic fields on the surface of spotted late-B stars with HgMn peculiarity in binary systems has been controversial during the two last decades. Recent studies of magnetic fields in these stars using the least-squares deconvolution (LSD) technique have failed to detect magnetic fields, indicating an upper limit on the longitudinal field between 8 and 15 G. In these LSD studies, assumptions were made that all spectral lines are identical in shape and can be described by a scaled mean profile. Aims: We re-analyse the available spectropolarimetric material by applying the moment technique on spectral lines of inhomogeneously distributed elements separately. Furthermore, we present new determinations of the mean longitudinal magnetic field for the HgMn star HD 65949 and the hotter analog of HgMn stars, the PGa star HD 19400, using FORS 2 installed at the VLT. We also give new measurements of the eclipsing system AR Aur with a primary star of HgMn peculiarity, which were obtained with the SOFIN spectropolarimeter installed at the Nordic Optical Telescope. Methods: We downloaded from the European Southern Observatory (ESO) archive the publically available HARPS spectra for eight HgMn stars and one normal and one superficially normal B-type star obtained in 2010. Out of this sample, three HgMn stars belong to spectroscopic double-lined systems. The application of the moment technique to the HARPS and SOFIN spectra allowed us to study the presence of the longitudinal magnetic field, the crossover effect, and quadratic magnetic fields. Results for the HgMn star HD 65949 and the PGa star HD 19400 are based on a linear regression analysis of low-resolution spectra obtained with FORS 2 in spectropolarimetric mode. Results: Our measurements of the magnetic field with the moment technique using spectral lines of several elements separately reveal the presence of a weak longitudinal magnetic field, a quadratic magnetic field, and the crossover effect on the surface of several HgMn stars as well as normal and superficially normal B-type stars. Furthermore, our analysis suggests the existence of intriguing correlations between the strength of the magnetic field, abundance anomalies, and binary properties. The results are discussed in the context of possible mechanisms responsible for the development of the element patches and complex magnetic fields on the surface of late B-type stars. Based on observations obtained at the European Southern Observatory (ESO programmes 076.D-0169(A), 076.D-0172(A), 084.D-0338(A), 085.D-0296(A), 085.D-0296(B), 087.D-0049(A), 088.D-0284(A)), SOFIN observations at the 2.56 m Nordic Optical Telescope on La Palma, and observations obtained with the CORALIE Echelle Spectrograph on the 1.2 m Euler Swiss telescope on La Silla, Chile.Tables 2-7, 9, 10 are only available in electronic form at http://www.aanda.org

  9. THE EFFECT OF MAGNETIC FIELD ERRORS ON DYNAMICAL FRICTION IN ELECTRON COOLERS.

    SciTech Connect

    FEDOTOV, A.V.; LITVINENKO, V.N.

    2005-05-16

    A proposed luminosity upgrade to the Relativistic Heavy Ion Collider (RHIC) includes a novel electron cooling section [1], which would use -55 MeV electrons to cool fully-ionized 100 GeV/nucleon gold ions. A strong (1-5 T) solenoidal field will be used to magnetize the electrons and thus enhance the dynamical friction force on the ions. The physics of magnetized friction is being simulated for RHIC parameters [2,3,4], using the VORPAL code [5]. Most theoretical treatments for magnetized dynamical friction do not consider the effect of magnetic field errors, except in a parametric fashion. However, field errors can in some cases dramatically reduce the velocity drag and corresponding cooling rate. We present two simple analytical models for the magnetic field errors. The simulated dynamical friction for the case of a perfect solenoidal field is compared with results from these new models. We simulate parameters for the existing cooler of the CELSIUS ring, because recent experiments [6] provide data that will later be used for code validation.

  10. Impact-generated magnetic fields on the Moon : a magnetohydrodynamic numerical investigation

    NASA Astrophysics Data System (ADS)

    Oran, Rona; Shprits, Yuri; Weiss, Benjamin; Gombosi, Tamas

    2015-04-01

    Natural remanent magnetization has been identified in lunar rocks, the lunar crust, and a diversity of meteorites. Much of this magnetization is thought to have been produced by cooling a core dynamo mag-netic field. However, the identification of lunar crustal magnetic anomalies at the antipodes of four of the five youngest large (>600 km diameter) impact basins has motivated the alternative hypothesis that the lunar crust could have been magnetized by the impacts. In particular, it has been proposed that highly conducting ionized vapor produced by a basin-forming impact interacts with the ambient solar wind plasma surrounding the Moon to amplify the ambient solar wind magnetic field or any core dynamo field. In this picture, as the ionized vapor cloud expands around the Moon, it pushes and compresses the solar wind plasma into a small region at the antipodal point. The conservation of magnetic flux then leads to an enhanced magnetic field in the compressed plasma. This field can then be recorded as shock remanent magnetization by crustal materials at the antipodal point following the impact of converging basin ejecta. A key requirement for the impact-generated fields hypothesis is that the compressed field be suffi-ciently strong to explain the lunar paleointensities (at least tens of μT) and maintained at the antipodal point for a sufficiently long time (several hours) for the ejecta to arrive and impact the surface. Previous simulations of the expansion of the vapor cloud found that the enhanced field will be strong enough (per-haps reaching hundreds of μT) and will remain at the antipodal site for a sufficiently long time (>1 day) for the arrival of incoming ejecta. However, these studies did not include an explicit calculation of the interaction of the magnetized solar wind plasma with the vapor cloud. Rather, the cloud evolution under the lunar gravity was simulated in the purely hydrodynamic regime. The vapor cloud structure at certain times was used to derive a simplified picture of what the effects would be on an ambient magnetized plasma using general magnetohydrodynamic (MHD) arguments. The solar wind drag acting on the cloud, as well as MHD effects such as field lines stretching and magnetic reconnection were not taken into ac-count. With the advances made in computational MHD models in recent years, we can now revisit these ear-lier important models. Our goal is to perform the first MHD simulations of an impact-generated vapor cloud expanding in the solar wind around the Moon, using BATSRUS, a 3D highly-parallelized versatile MHD code developed at the University of Michigan, in order to self-consistently test the previous estima-tions of the strength and duration of the magnetic field enhancement at the antipodal points. We will con-sider different MHD processes, such as: 1) the finite resistivity of the lunar mantle 2) magnetic diffusion between the solar wind and the initially non-magnetized cloud, 3) magnetic reconnection at the antipode, and 4) viscous drag and the transport of magnetic flux due to solar wind motion, and 4) MHD instabili-ties. This will allow us to systematically examine whether impact-generated fields can indeed be respon-sible for the formation of crustal field enhancements on the Moon.

  11. Skyrmion motion driven by oscillating magnetic field

    PubMed Central

    Moon, Kyoung-Woong; Kim, Duck-Ho; Je, Soong-Geun; Chun, Byong Sun; Kim, Wondong; Qiu, Z.Q.; Choe, Sug-Bong; Hwang, Chanyong

    2016-01-01

    The one-dimensional magnetic skyrmion motion induced by an electric current has attracted much interest because of its application potential in next-generation magnetic memory devices. Recently, the unidirectional motion of large (20 μm in diameter) magnetic bubbles with two-dimensional skyrmion topology, driven by an oscillating magnetic field, has also been demonstrated. For application in high-density memory devices, it is preferable to reduce the size of skyrmion. Here we show by numerical simulation that a skyrmion of a few tens of nanometres can also be driven by high-frequency field oscillations, but with a different direction of motion from the in-plane component of the tilted oscillating field. We found that a high-frequency field for small skyrmions can excite skyrmion resonant modes and that a combination of different modes results in a final skyrmion motion with a helical trajectory. Because this helical motion depends on the frequency of the field, we can control both the speed and the direction of the skyrmion motion, which is a distinguishable characteristic compared with other methods. PMID:26847334

  12. Magnetic field exposure of commercial airline pilots.

    PubMed

    Hood; Nicholas; Butler; Lackland; Hoel; Mohr

    2000-10-01

    PURPOSE: Airline pilots are exposed to magnetic fields generated by the aircraft's electrical and electronic systems. The purpose of this study was to directly measure the flight deck magnetic fields to which commercial airline pilots are exposed when flying on different aircraft types over a 75-hour flight-duty month.METHODS: Magentic field measurements were taken using personal dosimeters capable of measuring magnetic fields in the 40-800 Hz frequency range. Dosimeters were carried by either the Captain or the First Officer on Boeing 737/200, Boeing 747/400, Boeing 767/300ER, and Airbus 320 aircraft. The data were analyzed by aircraft type, with statistics based on block hours. Block hours begin when the aircraft departs the gate prior to take off and end when the aircraft returns to the gate after landing.RESULTS: Approximately 1008 block hours were recorded at a sampling rate of 3 seconds. Total block time exposure to the pilots ranged from a harmonic geometric mean of 6.7 milliGauss (mG) for the Boeing 767/300ER to 12.7 mG for the Boeing 737/200.CONCLUSIONS: Measured flight deck magnetic field levels were substantially above the 0.8 to 1 mG level typically found in the home or office and suggest the need for further study to evaluate potential health effects of long-term exposure. PMID:11018425

  13. Magnetic fields and galactic star formation rates

    SciTech Connect

    Loo, Sven Van; Tan, Jonathan C.; Falle, Sam A. E. G.

    2015-02-10

    The regulation of galactic-scale star formation rates (SFRs) is a basic problem for theories of galaxy formation and evolution: which processes are responsible for making observed star formation rates so inefficient compared to maximal rates of gas content divided by dynamical timescale? Here we study the effect of magnetic fields of different strengths on the evolution of giant molecular clouds (GMCs) within a kiloparsec patch of a disk galaxy and resolving scales down to ≃0.5 pc. Including an empirically motivated prescription for star formation from dense gas (n{sub H}>10{sup 5} cm{sup −3}) at an efficiency of 2% per local free-fall time, we derive the amount of suppression of star formation by magnetic fields compared to the nonmagnetized case. We find GMC fragmentation, dense clump formation, and SFR can be significantly affected by the inclusion of magnetic fields, especially in our strongest investigated B-field case of 80 μG. However, our chosen kiloparsec-scale region, extracted from a global galaxy simulation, happens to contain a starbursting cloud complex that is only modestly affected by these magnetic fields and likely requires internal star formation feedback to regulate its SFR.

  14. Skyrmion motion driven by oscillating magnetic field

    NASA Astrophysics Data System (ADS)

    Moon, Kyoung-Woong; Kim, Duck-Ho; Je, Soong-Geun; Chun, Byong Sun; Kim, Wondong; Qiu, Z. Q.; Choe, Sug-Bong; Hwang, Chanyong

    2016-02-01

    The one-dimensional magnetic skyrmion motion induced by an electric current has attracted much interest because of its application potential in next-generation magnetic memory devices. Recently, the unidirectional motion of large (20 μm in diameter) magnetic bubbles with two-dimensional skyrmion topology, driven by an oscillating magnetic field, has also been demonstrated. For application in high-density memory devices, it is preferable to reduce the size of skyrmion. Here we show by numerical simulation that a skyrmion of a few tens of nanometres can also be driven by high-frequency field oscillations, but with a different direction of motion from the in-plane component of the tilted oscillating field. We found that a high-frequency field for small skyrmions can excite skyrmion resonant modes and that a combination of different modes results in a final skyrmion motion with a helical trajectory. Because this helical motion depends on the frequency of the field, we can control both the speed and the direction of the skyrmion motion, which is a distinguishable characteristic compared with other methods.

  15. Skyrmion motion driven by oscillating magnetic field.

    PubMed

    Moon, Kyoung-Woong; Kim, Duck-Ho; Je, Soong-Geun; Chun, Byong Sun; Kim, Wondong; Qiu, Z Q; Choe, Sug-Bong; Hwang, Chanyong

    2016-01-01

    The one-dimensional magnetic skyrmion motion induced by an electric current has attracted much interest because of its application potential in next-generation magnetic memory devices. Recently, the unidirectional motion of large (20??m in diameter) magnetic bubbles with two-dimensional skyrmion topology, driven by an oscillating magnetic field, has also been demonstrated. For application in high-density memory devices, it is preferable to reduce the size of skyrmion. Here we show by numerical simulation that a skyrmion of a few tens of nanometres can also be driven by high-frequency field oscillations, but with a different direction of motion from the in-plane component of the tilted oscillating field. We found that a high-frequency field for small skyrmions can excite skyrmion resonant modes and that a combination of different modes results in a final skyrmion motion with a helical trajectory. Because this helical motion depends on the frequency of the field, we can control both the speed and the direction of the skyrmion motion, which is a distinguishable characteristic compared with other methods. PMID:26847334

  16. Riblet drag reduction at flight conditions

    NASA Technical Reports Server (NTRS)

    Walsh, Michael J.; Sellers, William L., III; Mcginley, Catherine B.

    1988-01-01

    Paper describes perforated and nonperforated riblet tests on the fuselage of a modified Learjet Model 28/29 twin-engine business jet at Reynolds numbers 1.0-2.75 x 10 to the 6th/ft and Mach numbers 0.3-0.7. Drag reductions of the order of 6 percent at nondimensional wall spacings of 12 were obtained using boundary-layer rakes and direct drag balances. At the measurement locations the Reynolds number based on distance was 1.0-46 x 10 to the 6th. The nondimensional wall spacing for maximum drag reduction was well-predicted by low-speed wind-tunnel data, but the maximum drag reduction was lower. The low drag is tentatively ascribed to various instrumentation difficulties and the flow field on the aircraft. Riblets with 0.010-in. perforations at center spacings of 0.25 in. were found to give the same drag reduction as nonperforated riblets.

  17. Tracing the Magnetic Field in Orion A

    NASA Technical Reports Server (NTRS)

    Dowell, C. Darren; Hildebrand, Roger H.; Dotson, Jessie L.; Vaillancourt, John E.; Phillips, Thomas G.; Peng, Rui-Sheng; Bastien, Pierre

    2003-01-01

    We use extensive 350 micron polarimetry and continuum maps obtained with Hertz and SHARC II along with HCN and HCO(sup +) spectroscopic data to trace the orientation of the magnetic field in the Orion A star-forming region. Using the polarimetry data, we find that the direction of the projection of the magnetic field in the plane of the sky relative to the orientation of the integral-shaped filament varies considerably as one moves from north to south. While in IRAS 05327-0457 and OMC-3 MMS 1-6 the projection of the field is primarily perpendicular to the filament it becomes better aligned with it at OMC-3 MMS 8-9 and well aligned with it at OMC-2 FIR 6. The OMC-2 FIR 4 cloud, located between the last two, is a peculiar object where we find almost no polarization. There is a relatively sharp boundary within its core where two adjacent regions exhibiting differing polarization angles merge. The projected angle of the field is more complicated in OMC-1 where it exhibits smooth variations in its orientation across the face of this massive complex. We also note that while the relative orientation of the projected angle of the magnetic field to the filament varies significantly in the OMC-3 and OMC-2 regions, its orientation relative to a fixed position on the sky shows much more stability. This suggests that, perhaps, the orientation of the field is relatively unaffected by the mass condensations present in these parts of the molecular cloud. By combining the polarimetry and spectroscopic data we were able to measure a set of average d u e s for the inclination angle of the magnetic field relative to the line of sight. We find that the field is oriented quite close to the plane of the sky in most places. More precisely, the inclination of the magnetic field is approx. = 73 deg around OMC-3 MMS 6, approx. = 74 deg at OMC-3 MMS 8-9, approx. = 80 deg at OMC-2 FIR 4, approx. = 65 deg in the northeastern part of OMC-1, and approx. = 49 deg in the Bas. The small difference in the inclination of the field between OMC-3 and OMC-2 seems to strengthen the idea that the orientation of the magnetic field is relatively unaffected by the agglomeration of matter located in these regions. We also present polarimetry data for the OMC-4 region located some 13 min. south of OMC-1.

  18. Biomaterials and Magnetic fields for Cancer Therapy

    NASA Technical Reports Server (NTRS)

    Ramachandran, Narayanan; Mazuruk, Konstanty

    2003-01-01

    The field of biomaterials has emerged as an important topic in the purview of NASA s new vision of research activities in the Microgravity Research Division. Although this area has an extensive track record in the medical field as borne out by the routine use of polymeric sutures, implant devices, and prosthetics, novel applications such as tissue engineering, artificial heart valves and controlled drug delivery are beginning to be developed. Besides the medical field, biomaterials and bio-inspired technologies are finding use in a host of emerging interdisciplinary fields such as self-healing and self-assembling structures, biosensors, fuel systems etc. The field of magnetic fluid technology has several potential applications in medicine. One of the emerging fields is the area of controlled drug delivery, which has seen its evolution from the basic oral delivery system to pulmonary to transdermal to direct inoculations. In cancer treatment by chemotherapy for example, targeted and controlled drug delivery has received vast scrutiny and substantial research and development effort, due to the high potency of the drugs involved and the resulting requirement to keep the exposure of the drugs to surrounding healthy tissue to a minimum. The use of magnetic particles in conjunction with a static magnetic field allows smart targeting and retention of the particles at a desired site within the body with the material transport provided by blood perfusion. Once so located, the therapeutical aspect (radiation, chemotherapy, hyperthermia, etc.) of the treatment, now highly localized, can be implemented.

  19. Pulsar studies and magnetic fields in galaxies

    NASA Astrophysics Data System (ADS)

    Han, Jinlin

    2001-06-01

    In recent years, I have mainly worked on the two research areas: pulsar polarization and magnetic fields in galaxies. Together with my cooperators, we have observed about 150 pulsars in total and will do another 100 in near future. We did systematical studies on circular polarization of pulsars and obtained several intriguing results. Using pulsars as probes, we detected the magnetic field reversals from spiral arm to arm in our Galaxy. We found that the B-field has a bi-symmetric structure in the disk. We also obtained the unique measurements of the vertical component of the B-field in the solar vicinity. From the anti-symmetric distribution of Galactic rotation measure sky, we identified the B-field structure produced by A0 dynamo in the Galactic halo or thick disk. The magnetic fields in the disk of our Galaxy and M31 were found to be very extended. The spiral B-field we detected from NGC 2997 suggests that there may be two kinds of dynamos operating in one galaxy.

  20. Unusual Magnetic Fields of Uranus and Neptune

    NASA Astrophysics Data System (ADS)

    Nellis, W. J.

    2015-06-01

    Voyager 2 discovered the unusual non-dipolar and non-axisymmetric magnetic fields of the Ice Giants Uranus and Neptune (U/N) in the 1980's. The cause of those unique fields has been a major scientific question ever since. The answer lies in physical properties of fluids that generate planetary magnetic fields by dynamo action: convecting, electrically conducting fluids at high pressures P and temperatures T. Properties of fluids at planetary P/Ts are measured under adiabatic shock compression and quasi-isentropic multiple-shock compression up to a few 100 GPa and several 1000 K. Dynamic-compression and Voyager 2 data measured over three decades indicate (i) There is little ``Ice'' in the Ice Giants. (ii) Magnetic fields of U/N are made by metallic fluid H close to outer planetary radii. (iii) Thus, it is reasonable to observe non-dipolar non-axisymmetric fields. (iv) Those fields are probably caused by decoupling of rotational motion of U/N from convective motions in their dynamos, unlike Earth with strong coupling between those motions and a dipolar field. The full paper on this work is published.

  1. Coronal and interplanetary magnetic field models

    NASA Astrophysics Data System (ADS)

    Schatten, Kenneth H.

    1999-06-01

    We provide an historical perspective of coronal and interplanetary field models. The structure of the interplanetary medium is controlled by the coronal magnetic field from which the solar wind emanates. This field has been described with ``Source Surface'' (SS) and ``Heliospheric Current Sheet'' (HCS) models. The ``Source Surface'' model was the first to open the solar field into interplanetary space using volumetric coronal currents, which were a ``source'' for the IMF. The Heliospheric Current Sheet (HCS) model provided a more physically realistic solution. The field structure was primarily a dipole, however, without regard to sign, the shape appeared to be a monopole pattern (uniform field stress). Ulysses has observed this behavior. Recently, Sheeley and Wang have utilized the HCS field model to calculate solar wind structures fairly accurately. Fisk, Schwadron, and Zurbuchen have investigated small differences from the SS model. These differences allow field line motions reminiscent of a ``timeline'' or moving ``streakline'' in a flow field, similar to the smoke pattern generated by a skywriting plane. Differences exist in the magnetic field geometry, from the Parker ``garden hose'' model affecting both the ``winding angle'' as well as the amount of latitudinal ``wandering.''

  2. Magnetic resonance imaging without field cycling at less than earth's magnetic field

    SciTech Connect

    Lee, Seong-Joo Shim, Jeong Hyun; Kim, Kiwoong; Yu, Kwon Kyu; Hwang, Seong-min

    2015-03-09

    A strong pre-polarization field, usually tenths of a milli-tesla in magnitude, is used to increase the signal-to-noise ratio in ordinary superconducting quantum interference device-based nuclear magnetic resonance/magnetic resonance imaging experiments. Here, we introduce an experimental approach using two techniques to remove the need for the pre-polarization field. A dynamic nuclear polarization (DNP) technique enables us to measure an enhanced resonance signal. In combination with a π/2 pulse to avoid the Bloch-Siegert effect in a micro-tesla field, we obtained an enhanced magnetic resonance image by using DNP technique with a 34.5 μT static external magnetic field without field cycling. In this approach, the problems of eddy current and flux trapping in the superconducting pickup coil, both due to the strong pre-polarization field, become negligible.

  3. Sensor for detecting changes in magnetic fields

    DOEpatents

    Praeg, Walter F. (Palos Park, IL)

    1981-01-01

    A sensor for detecting changes in the magnetic field of the equilibrium-field coil of a Tokamak plasma device comprises a pair of bifilar wires disposed circumferentially, one inside and one outside the equilibrium-field coil. Each is shorted at one end. The difference between the voltages detected at the other ends of the bifilar wires provides a measure of changing flux in the equilibrium-field coil. This difference can be used to detect faults in the coil in time to take action to protect the coil.

  4. Sensor for detecting changes in magnetic fields

    DOEpatents

    Praeg, W.F.

    1980-02-26

    A sensor is described for detecting changes in the magnetic field of the equilibrium-field coil of a Tokamak plasma device that comprises a pair of bifilar wires disposed circumferentially, one inside and one outside the equilibrium-field coil. Each is shorted at one end. The difference between the voltages detected at the other ends of the bifilar wires provides a measure of changing flux in the equilibrium-field coil. This difference can be used to detect faults in the coil in time to take action to protect the coil.

  5. Magnetic field generated resistivity maximum in graphite

    NASA Technical Reports Server (NTRS)

    Woollam, J. A.; Kreps, L. W.; Rojeski, M.; Vold, T.; Devaty, R.

    1976-01-01

    In a zero magnetic field, the electrical resistivity of highly oriented pyrolytic (polycrystalline) graphite drops smoothly with decreasing temperature, becoming constant below 4 K. However, in a fixed applied magnetic field, the resistivity goes through a maximum as a function of temperature, with a larger maximum for a larger field intensity. The temperature of the maximum increases with field intensity, but saturates to a constant value near 25 K (the exact temperature depends on the sample) at high intensity. In single-crystal graphite, a maximum in resistivity as a function of temperature is also present, but has the effects of Landau level quantization superimposed. Several possible explanations for the resistivity maximum are proposed, but a complete explanation awaits detailed calculations involving the energy band structure of graphite, and the particular scattering mechanisms involved.

  6. Terrestrial magnetic field effects on large photomultipliers

    NASA Astrophysics Data System (ADS)

    Leonora, E.; KM3NeT Consortium

    2013-10-01

    The effects of the Earth's magnetic field on the performance of large PMTs for a cubic-kilometer-scale neutrino telescope has been studied. Measurements were performed for three Hamamatsu PMTs: two 8? R5912 types; one with a standard and the other with a super bialkali photocathode, and a 10? R7081 type with a standard bialkali photocathode. The main characteristics of the PMTs, such as detection efficiency, transit time, transit time spread, gain, peak-to-valley ratio, charge resolution and fractions of spurious pulses were measured while varying the PMT orientations with respect to the Earth's magnetic field. The measurements were performed both with and without a mu-metal cage magnetic shielding. For the 8? PMTs the impact of the magnetic field was found to be smaller than for the 10? PMT. The magnetic shielding strongly reduced the orientation-dependent variations measured for the 10? PMT and even improved the performance. Although less pronounced, improvements were also measured for the 8? PMTs.

  7. Magnetic fields of spherical compact stars in a braneworld

    SciTech Connect

    Ahmedov, B. J.; Fattoyev, F. J.

    2008-08-15

    We study the stellar magnetic field configuration in dependence on brane tension and present solutions of Maxwell equations in the external background space-time of a magnetized spherical star in a Randall-Sundrum II type braneworld. The star is modeled as a sphere consisting of perfect highly magnetized fluid with infinite conductivity and a frozen-in magnetic field. With respect to solutions for magnetic fields found in the Schwarzschild space-time, brane tension introduces enhancing corrections to the exterior magnetic field which could be relevant for the magnetic fields of magnetized compact objects as pulsars and magnetars and may provide observational evidence for the brane tension.

  8. 'Clean' Observations of Magnetic Field Fluctuations on Planetary Surfaces

    NASA Astrophysics Data System (ADS)

    Schwingenschuh, K.; Prattes, G.; Delva, M.; Eichelberger, H. U.; Berghofer, G.; Magnes, W.; Vellante, M.; Nenovski, P.; Wesztergom, V.; Auster, H. U.; Fornacon, K.-H.

    2012-05-01

    Magnetic field measurements on planetary surfaces are disturbed by various internal and external sources. We discuss methods to reduce their influence on the quality of magnetic field experiments aboard surface stations. Our major emphasis is on terrestrial seismo-magnetic measurements, but magnetic cleanliness procedures for the ROSETTA lander magnetic field experiment is discussed too. We consider not only disturbing magnetic field sources as magnetized material or current loops but also environmental sources as the vibration of the magnetic field sensors and eddy currents in conducting material.

  9. The ULF Magnetic Fields Generated by Thunderstorms

    NASA Astrophysics Data System (ADS)

    Fraser-Smith, A. C.; Kjono, S. N.

    2013-12-01

    It has long been known that thunderstorms produce strong electric field fluctuations in their immediate vicinity but it has been little recognized that these storms are also a source of strong ULF magnetic field fluctuations (ULF; frequencies less than 5 Hz). Some characteristics of the magnetic field fluctuations were documented for a thunderstorm occurring in 1990 [Fraser-Smith, Geophys. Res. Letts., 20, 467-470, 1993]. We now describe further measurements of these magnetic field changes for an additional intense thunderstorm that passed over the San Francisco Bay area on 8-9 September 1999. The thunderstorm is further characterized by measurements of its associated lightning by the National Lightning Detection Network (NLDN). As compared with the results reported for the 1990 thunderstorm, the new measurements were made by two separate and independently-operated measurement systems. In addition, they have greater time resolution and more components of the magnetic field changes are measured. These thunderstorm-related ULF magnetic field changes must extend up through the electromagnetic-phenomena-rich space between the thunderstorms and the ionosphere and they have the potential to generate both ULF electric currents and ULF hydromagnetic waves in the lower ionosphere. This latter possibility suggests, once again, that thunderstorms may be an important and little studied source of ULF energy in the magnetosphere. In this context, it is important to note that although thunderstorms tend to occur predominantly in the equatorial regions, there can be substantial activity at middle latitudes and even, on occasion, at higher latitudes. As a result, the thunderstorm-related ULF hydromagnetic waves can be injected into the magnetosphere over a broad range of geomagnetic latitudes and not just confined to low latitudes.

  10. High magnetic field facilities in Latin America

    NASA Astrophysics Data System (ADS)

    Sato, R.; Grssinger, R.; Bertorello, H.; Broto, J. M.; Davies, H. A.; Estevez-Rams, E.; Gonzalez, J.; Matutes, J.; Sinnecker, J. P.; Sagredo, V.

    2006-11-01

    The EC supported a network (under the Framework 5 ALFA Programme) designated HIFIELD (Project number II0147FI) and entitled: "Measurement methods involving high magnetic fields for advanced and novel materials". As a result, high field facilities were initiated, constructed or extended at the following laboratories in Latin America: University Cordoba (Argentina), CES, Merida (Venezuela), CIMAV, Chihuahua (Mexico), University Federal de Rio de Janeiro (Brazil).

  11. Magnetic field influence on paramecium motility

    SciTech Connect

    Rosen, M.F.; Rosen, A.D. )

    1990-01-01

    The influence of a moderately intense static magnetic field on movement patterns of free swimming Paramecium was studied. When exposed to fields of 0.126 T, these ciliated protozoa exhibited significant reduction in velocity as well as a disorganization of movement pattern. It is suggested that these findings may be explained on the basis of alteration in function of ion specific channels within the cell membrane.

  12. Trapped field recovery of bulk superconductor magnets by static field magnetization

    NASA Astrophysics Data System (ADS)

    Deng, Z.; Tsuzuki, K.; Miki, M.; Felder, B.; Hara, S.; Izumi, M.

    2011-11-01

    Thanks to the trapped field of bulk high-temperature superconductors, they can be used as field-pole magnets in the high temperature superconducting (HTS) rotating machines. For example, an output power of 10 kW at 720 rpm was realized by an average trapped field of 0.56 T of eight melt-textured GdBa 2Cu 3O y (Gd-123) bulks at liquid nitrogen temperature in TUMSAT in 2004. Similarly to the HTS machines involving 1G or 2G wires, the trapped field of the bulk is possibly sensitive and even can be attenuated by the AC component field during the operation. Hence, it is necessary to recover the trapped field once being decreased to some extent in the practical application. From this point, we have investigated the trapped field recovery of HTS bulk magnets by static field magnetization in the paper. A series of different initial trapped fields after zero-field-cooling or field-cooling magnetization are used to simulate the attenuated trapped field. By comparing the trapped field peak and its distribution, the trapped field was found to be able to recover by the static field magnetization method with a stronger excitation field and the initial trapped flux inside the bulk also has an influence on the recovery process. The optimum recovery field was found to be about 2.5 times the saturated trapped field of the bulk at liquid nitrogen temperature, by which the bulk can regain the former best trapped field performance.

  13. Mechanical response of elastomers to magnetic fields

    SciTech Connect

    Munoz, B.C.; Jolly, M.R.

    1995-12-31

    Elastomeric materials represent an important class of engineering materials, which are widely used to make components of structures, machinery, and devices for vibration and noise control. Elastomeric materials possessing conductive or magnetic properties are used in applications such as conductive and magnetic tapes, sensors, flexible permanent magnets, etc. Our interest in these materials has focused on understanding and controlling the magnitude and directionality of their mechanical response to applied magnetic fields. This presentation will discuss the control of mechanical properties and mathematical modeling of the new materials prepared in our laboratories along with experiments to achieve adaptive vibration control using the new materials. Such controllable elastomers promise to have more functionality than conventional elastomers and therefore could be a link that brings the applications of modern control technologies, intelligent structures, and smart materials to a very broad industrial area.

  14. Global Solar Photospheric Magnetic Field Modeling (Invited)

    NASA Astrophysics Data System (ADS)

    Henney, C. J.; Arge, C. N.; Toussaint, W.; Gonzalez-Hernandez, I. E.; Koller, J.; Godinez, H. C.; Macdonald, G. A.

    2013-12-01

    Estimation of the global photospheric magnetic field distribution is currently difficult since only approximately half of the solar surface is magnetically observed at any given time. With the solar rotational period relative to Earth at approximately 27 days, these global maps include observed data that are more than 13 days old. Data assimilation between old and new observations can result in spatial polarity discontinuities that result in monopole signals. To help minimize these large discontinuities we have developed the ADAPT (Air Force Data Assimilative Photospheric flux Transport) model, which incorporates data assimilation using an Ensemble Least Squares (EnLS) estimation method with photospheric magnetic flux transport. The ADAPT transport model evolves the solar magnetic flux for an ensemble of realizations using different parameter values for rotational, meridional, and super-granular diffusive transport processes. New data assimilative methods, along with recent progress to incorporate solar farside and subsurface nearside data inferred from helioseismology, will be discussed in this presentation.

  15. Pulsed-field magnetometry for rock magnetism

    NASA Astrophysics Data System (ADS)

    Kodama, Kazuto

    2015-07-01

    An improved method is proposed for measuring dynamic magnetizations of bulk volcanic rock samples induced by a pulsed-field of 0.7 T and a duration of 10 ms. The transient magnetization is measured by a sensing system that consists of a pair of inductive differential coils, an analog preamplifier and integrator, and a high-speed digital storage scope. The system was calibrated using a paramagnetic salt (Gd2O3) and was tested to different kinds of volcanic rocks with their magnetic properties well-documented previously. The results were comparable with those measured by a quasi-static method using a vibrating sample magnetometer, although there were small discrepancies in hysteresis parameters suggesting the time-dependence of the magnetic properties. The proposed system provides not only the magnetization over the short interval of a pulse but also the rapid (~3 ms) exponential decay after a pulse. The decay time constant was different among the samples under study, indicating the variations of their magnetic relaxation time. Although the present system is not sensitive enough to characterize varieties of natural samples including sediments, it has the potential as a versatile and convenient tool for rock magnetism.

  16. Structural alloys for high field superconducting magnets

    SciTech Connect

    Morris, J.W. Jr.

    1985-08-01

    Research toward structural alloys for use in high field superconducting magnets is international in scope, and has three principal objectives: the selection or development of suitable structural alloys for the magnet support structure, the identification of mechanical phenomena and failure modes that may influence service behavior, and the design of suitable testing procedures to provide engineering design data. This paper reviews recent progress toward the first two of these objectives. The structural alloy needs depend on the magnet design and superconductor type and differ between magnets that use monolithic and those that employ force-cooled or ICCS conductors. In the former case the central requirement is for high strength, high toughness, weldable alloys that are used in thick sections for the magnet case. In the latter case the need is for high strength, high toughness alloys that are used in thin welded sections for the conductor conduit. There is productive current research on both alloy types. The service behavior of these alloys is influenced by mechanical phenomena that are peculiar to the magnet environment, including cryogenic fatigue, magnetic effects, and cryogenic creep. The design of appropriate mechanical tests is complicated by the need for testing at 4/sup 0/K and by rate effects associated with adiabatic heating during the tests. 46 refs.

  17. Magnetic fields and density functional theory

    SciTech Connect

    Salsbury Jr., Freddie

    1999-02-01

    A major focus of this dissertation is the development of functionals for the magnetic susceptibility and the chemical shielding within the context of magnetic field density functional theory (BDFT). These functionals depend on the electron density in the absence of the field, which is unlike any other treatment of these responses. There have been several advances made within this theory. The first of which is the development of local density functionals for chemical shieldings and magnetic susceptibilities. There are the first such functionals ever proposed. These parameters have been studied by constructing functionals for the current density and then using the Biot-Savart equations to obtain the responses. In order to examine the advantages and disadvantages of the local functionals, they were tested numerically on some small molecules.

  18. Dynamical Field Line Connectivity in Magnetic Turbulence

    NASA Astrophysics Data System (ADS)

    Ruffolo, D. J.; Matthaeus, W. H.

    2014-12-01

    Point-to-point magnetic connectivity has a stochastic character whenever magnetic fluctuations cause a field line random walk, with observable manifestations such as dropouts of solar energetic particles and upstream events at Earth's bow shock. This can also change due to dynamical activity. Comparing the instantaneous magnetic connectivity to the same point at two different times, we provide a nonperturbative analytic theory for the ensemble average perpendicular displacement of the magnetic field line, given the power spectrum of magnetic fluctuations. For simplicity, the theory is developed in the context of transverse turbulence, and is numerically evaluated for two specific models: reduced magnetohydrodynanmics (RMHD), a quasi-two dimensional model of anisotropic turbulence that is applicable to low-beta plasmas, and two-dimensional (2D) plus slab turbulence, which is a good parameterization for solar wind turbulence. We take into account the dynamical decorrelation of magnetic fluctuations due to wave propagation, nonlinear distortion, random sweeping, and convection by a bulk wind flow relative to the observer. The mean squared time-differenced displacement increases with time and with parallel distance, becoming twice the field line random walk displacement at long distances and/or times, corresponding to a pair of uncorrelated random walks. These results are relevant to a variety of astrophysical processes, such as electron transport and heating patterns in coronal loops and the solar transition region, changing magnetic connection to particle sources near the Sun or at a planetary bow shock, and thickening of coronal hole boundaries. Partially supported by the Thailand Research Fund, the US NSF (AGS-1063439 and SHINE AGS-1156094), NASA (Heliophysics Theory NNX11AJ44G), and by the Solar Probe Plus Project through the ISIS Theory team.

  19. A proposed concept for the extraction of energy stored in magnetic or electric fields in space

    NASA Technical Reports Server (NTRS)

    Papailiou, D. D.

    1976-01-01

    It is known that enormous energy resources associated with electric, magnetic, gravitational, and other fields exist in space. It is also known that the major difficulty in 'tapping' this energy arises from the extremely low density level at which this energy exists. An analytical study has been made of a particular scheme that appears promising for an efficient utilization of some of these energy resources in propulsion. The principle involves the exchange of energy between a fluctuating magnetic field and a velocity field of electrically conducting fluid in turbulent motion located onboard a spacecraft. Under certain conditions the total energy of the turbulent flow field onboard the spacecraft can be increased and this increase appears in the form of Joulean heat. The utilization of the fluctuating part of the magnetic field, in the form of Joulean dissipation (because of its random character) does not introduce any drag on the spacecraft. The application appears promising for flights in the vicinity of Jupiter and other planets. The rate at which energy is gained by the conducting fluid is of the order of 100 watts when the rms value of the fluctuating magnetic field strength is about 1 gauss.

  20. Magnetic fields of the Ap stars

    SciTech Connect

    Borra, E.F.; Landstreet, J.D.

    1980-03-01

    We have conducted a survey of longitudinal magnetic fields (B/sub e/) among bright northern and southern Ap stars. The photoelectric technique used involves circular Zeeman polarimetry in the wings of H..beta... We find that the photoelectric B/sub e/ curves tend to be more harmonic than the photographic B/sub e/ curves. We have discovered magnetic fields in several rapidly rotating Ap stars. There is marginal statistical evidence to suggest that the rapid rotators might have surface magnetic fields smaller than the slow rotators; however, some very rapid rotators (P=0.5 days) can clearly have B/sub e/ extrema (approx.1 kilogauss) comparable to the extrema of slow rotators. We do not find serious evidence for irregular B/sub e/ variations, although we cannot exclude irregular variations of the order of 200 gauss in some stars. The astrophysical implications of our findings are briefly discussed. We have observed several Am and Hg-Mn stars, finding no evidence of magnetic fields.

  1. A dynamo model of Jupiter's magnetic field

    NASA Astrophysics Data System (ADS)

    Jones, C. A.

    2014-10-01

    Jupiter's dynamo is modelled using the anelastic convection-driven dynamo equations. The reference state model is taken from French et al. [2012]. Astrophys. J. Suppl. 202, 5, (11pp), which used density functional theory to compute the equation of state and the electrical conductivity in Jupiter's interior. Jupiter's magnetic field is approximately dipolar, but self-consistent dipolar dynamo models are rather rare when the large variation in density and the effective internal heating are taken into account. Jupiter-like dipolar magnetic fields were found here at small Prandtl number, Pr=0.1. Strong differential rotation in the dynamo region tends to destroy a dominant dipolar component, but when the convection is sufficiently supercritical it generates a strong magnetic field, and the differential rotation in the electrically conducting region is suppressed by the Lorentz force. This allows a magnetic field to develop which is dominated by a steady dipolar component. This suggests that the strong zonal winds seen at Jupiter's surface cannot penetrate significantly into the dynamo region, which starts approximately 7000 km below the surface.

  2. Current Collection in a Magnetic Field

    NASA Technical Reports Server (NTRS)

    Krivorutsky, E. N.

    1997-01-01

    It is found that the upper-bound limit for current collection in the case of strong magnetic field from the current is close to that given by the Parker-Murphy formula. This conclusion is consistent with the results obtained in laboratory experiments. This limit weakly depends on the shape of the wire. The adiabatic limit in this case will be easily surpassed due to strong magnetic field gradients near the separatrix. The calculations can be done using the kinetic equation in the drift approximation. Analytical results are obtained for the region where the Earth's magnetic field is dominant. The current collection can be calculated (neglecting scattering) using a particle simulation code. Dr. Singh has agreed to collaborate, allowing the use of his particle code. The code can be adapted for the case when the current magnetic field is strong. The needed dm for these modifications is 3-4 months. The analytical description and essential part of the program is prepared for the calculation of the current in the region where the adiabatic description can be used. This was completed with the collaboration of Drs. Khazanov and Liemohn. A scheme of measuring the end body position is also proposed. The scheme was discussed in the laboratory (with Dr. Stone) and it was concluded that it can be proposed for engineering analysis.

  3. Magnetic fields and SDC endcap scintillator performance

    SciTech Connect

    Green, D.

    1993-01-01

    Many detectors designed to operate in colliders contain both magnetic fields, usually solenoids, and scintillators. The former is known to influence the operation of the latter. A first look is taken in this note at the implications of that influence for the SDC detector.

  4. Charm production in a strong magnetic field

    SciTech Connect

    Machado, C. S.; Navarra, F. S.; Noronha, J.; Oliveira, E. G. de; Strickland, M.

    2014-11-11

    We discuss the effects of a strong magnetic field on B and D mesons, focusing on the changes of the energy levels and the masses of the bound states. Using the Color Evaporation Model we discuss the possible changes in the production of J/? and ?. We briefly comment the recent experimental data.

  5. Historic Methods for Capturing Magnetic Field Images

    ERIC Educational Resources Information Center

    Kwan, Alistair

    2016-01-01

    I investigated two late 19th-century methods for capturing magnetic field images from iron filings for historical insight into the pedagogy of hands-on physics education methods, and to flesh out teaching and learning practicalities tacit in the historical record. Both methods offer opportunities for close sensory engagement in data-collection…

  6. Passive levitation in alternating magnetic fields

    DOEpatents

    Romero, Louis; Christenson, Todd; Aronson, Eugene A.

    2009-06-16

    Stable levitation of an object in an alternating magnetic field can be achieved by eliminating coupling between the rotational and translational forces acting on the object. Stable levitation can also be achieved by varying the coupling between the rotational and translational forces acting on the object, while maintaining one or more of the rotational and translational forces steady in time.

  7. Passive levitation in alternating magnetic fields

    DOEpatents

    Romero, Louis; Christenson, Todd; Aronson, Eugene A.

    2010-09-14

    Stable levitation of an object in an alternating magnetic field can be achieved by eliminating coupling between the rotational and translational forces acting on the object. Stable levitation can also be achieved by varying the coupling between the rotational and translational forces acting on the object, while maintaining one or more of the rotational and translational forces steady in time.

  8. Enzyme Substrate Reactions in High Magnetic Fields

    PubMed Central

    Maling, J. E.; Weissbluth, M.; Jacobs, E. E.

    1965-01-01

    The reaction rates of two enzyme substrate systems, ribonuclease-RNA and succinate-cytochrome c reductase, were followed as a function of magnetic field from zero to 48,000 gauss. The reaction rates remained constant to within 10 per cent. PMID:5884011

  9. Historic Methods for Capturing Magnetic Field Images

    NASA Astrophysics Data System (ADS)

    Kwan, Alistair

    2016-03-01

    I investigated two late 19th-century methods for capturing magnetic field images from iron filings for historical insight into the pedagogy of hands-on physics education methods, and to flesh out teaching and learning practicalities tacit in the historical record. Both methods offer opportunities for close sensory engagement in data-collection processes.

  10. Starspots Magnetic field by transit mapping

    NASA Astrophysics Data System (ADS)

    Vlio, Adriana; Spagiari, Eduardo

    2014-08-01

    Sunspots are important signatures of the global solar magnetic field cycle. It is believed that other stars also present these same phenomena. However, today it is not possible to observe directly star spots due to their very small sizes. The method applied here studies star spots by detecting small variations in the stellar light curve during a planetary transit. When the planet passes in front of its host star, there is a chance of it occulting, at least partially, a spot. This allows the determination of the spots physical characteristics, such as size, temperature, and location on the stellar surface. In the case of the Sun, there exists a relation between the magnetic field and the spot temperature. We estimate the magnetic field component along the line-of-sight and the intensity of sunspots using data from the MDI instrument on board of the SOHO satellite. Assuming that the same relation applies to other stars, we estimate spots magnetic fields of CoRoT-2 and Kepler-17 stars.

  11. Strain sensors for high field pulse magnets

    SciTech Connect

    Martinez, Christian; Zheng, Yan; Easton, Daniel; Farinholt, Kevin M; Park, Gyuhae

    2009-01-01

    In this paper we present an investigation into several strain sensing technologies that are being considered to monitor mechanical deformation within the steel reinforcement shells used in high field pulsed magnets. Such systems generally operate at cryogenic temperatures to mitigate heating issues that are inherent in the coils of nondestructive, high field pulsed magnets. The objective of this preliminary study is to characterize the performance of various strain sensing technologies at liquid nitrogen temperatures (-196 C). Four sensor types are considered in this investigation: fiber Bragg gratings (FBG), resistive foil strain gauges (RFSG), piezoelectric polymers (PVDF), and piezoceramics (PZT). Three operational conditions are considered for each sensor: bond integrity, sensitivity as a function of temperature, and thermal cycling effects. Several experiments were conducted as part of this study, investigating adhesion with various substrate materials (stainless steel, aluminum, and carbon fiber), sensitivity to static (FBG and RFSG) and dynamic (RFSG, PVDF and PZT) load conditions, and sensor diagnostics using PZT sensors. This work has been conducted in collaboration with the National High Magnetic Field Laboratory (NHMFL), and the results of this study will be used to identify the set of sensing technologies that would be best suited for integration within high field pulsed magnets at the NHMFL facility.

  12. Magnetic fields in gaps surrounding giant protoplanets

    NASA Astrophysics Data System (ADS)

    Keith, Sarah L.; Wardle, Mark

    2015-07-01

    Giant protoplanets evacuate a gap in their host protoplanetary disc, which gas must cross before it can be accreted. A magnetic field is likely carried into the gap, potentially influencing the flow. Gap crossing has been simulated with varying degrees of attention to field evolution [pure hydrodynamical, ideal, and resistive magnetohydrodynamical (MHD)], but as yet there has been no detailed assessment of the role of the field accounting for all three key non-ideal MHD effects: Ohmic resistivity, ambipolar diffusion, and Hall drift. We present a detailed investigation of gap magnetic field structure as determined by non-ideal effects. We assess susceptibility to turbulence induced by the magnetorotational instability (MRI) and angular momentum loss from large-scale fields. As full non-ideal simulations are computationally expensive, we take an a posteriori approach, estimating MHD quantities from the pure hydrodynamical gap-crossing simulation by Tanigawa, Ohtsuki & Machida. We calculate the ionization fraction and estimate field strength and geometry to determine the strength of non-ideal effects. We find that the protoplanetary disc field would be easily drawn into the gap and circumplanetary disc. Hall drift dominates, so that much of the gap is conditionally MRI unstable depending on the alignment of the field and disc rotation axes. Field alignment also influences the strong toroidal field component permeating the gap. Large-scale magnetic forces are small in the circumplanetary disc, indicating that they cannot drive accretion there. However, turbulence will be key during satellite growth as it affects critical disc features, such as the location of the ice line.

  13. Lunar Magnetic Fields: Implications for Resource Utilization

    NASA Technical Reports Server (NTRS)

    Hood, L. L.

    1992-01-01

    It is well known that solar-wind-implanted hydrogen and helium-3 in lunar soils are potentially usable resources for future manned activities. For economical mining of these implanted gases, it is desirable that relative concentrations exceed that of typical soils. It has previously been noted that the monthly variation of solar wind flux on the surface due to lunar immersion in the geomagnetic tail may have measurable consequences for resource utilization. It is pointed out that, for a constant external flux, locally strong lunar crustal magnetic fields will exert the dominant influence on solar wind volatile implantation rates. In particular, the strongest lunar crustal magnetic fields will both deflect and focus incident ions in local regions leading to local enhancements of the incident ion flux. Thus, the most economical sites for extraction of solar-wind-implanted volatiles may be within or adjacent to strong crustal magnetic fields. In addition, solar wind ion deflection by crustal magnetic fields must be considered in evaluating the issue of whether remnant cometary ice or water-bearing minerals have survived in permanently shadowed regions near the lunar poles. This is because sputter erosion of water ice by solar wind ions has been suggested to be an important ice loss mechanism within permanently shadowed regions. Thus, permanently shadowed regions that are also shielded from the solar wind by locally strong crustal fields could be the most promising locations for the survival of cometary ice. Additional numerical simulations are employed to show that solar wind ion deflection by strong lunar magnetic anomalies can produce local increases in the implantation rate of solar wind gases such as hydrogen.

  14. Measuring the Earth's Magnetic Field in a Laboratory

    ERIC Educational Resources Information Center

    Cartacci, A.; Straulino, S.

    2008-01-01

    Two methods for measuring the Earth's magnetic field are described. In the former, according to Gauss, the Earth's magnetic field is compared with that of a permanent magnet; in the latter, a well-known method, the comparison is made with the magnetic field generated by a current. As all the used instruments are available off the shelf, both…

  15. Measuring the Earth's Magnetic Field in a Laboratory

    ERIC Educational Resources Information Center

    Cartacci, A.; Straulino, S.

    2008-01-01

    Two methods for measuring the Earth's magnetic field are described. In the former, according to Gauss, the Earth's magnetic field is compared with that of a permanent magnet; in the latter, a well-known method, the comparison is made with the magnetic field generated by a current. As all the used instruments are available off the shelf, both

  16. Core shifts, magnetic fields and magnetization of extragalactic jets

    NASA Astrophysics Data System (ADS)

    Zdziarski, Andrzej A.; Sikora, Marek; Pjanka, Patryk; Tchekhovskoy, Alexander

    2015-07-01

    We study the effect of radio-jet core shift, which is a dependence of the position of the jet radio core on the observational frequency. We derive a new method of measuring the jet magnetic field based on both the value of the shift and the observed radio flux, which complements the standard method that assumes equipartition. Using both methods, we re-analyse the blazar sample of Zamaninasab et al. We find that equipartition is satisfied only if the jet opening angle in the radio core region is close to the values found observationally, ?0.1-0.2 divided by the bulk Lorentz factor, ?j. Larger values, e.g. 1/?j, would imply magnetic fields much above equipartition. A small jet opening angle implies in turn the magnetization parameter of ?1. We determine the jet magnetic flux taking into account this effect. We find that the transverse-averaged jet magnetic flux is fully compatible with the model of jet formation due to black hole (BH) spin-energy extraction and the accretion being a magnetically arrested disc (MAD). We calculate the jet average mass-flow rate corresponding to this model and find it consists of a substantial fraction of the mass accretion rate. This suggests the jet composition with a large fraction of baryons. We also calculate the average jet power, and find it moderately exceeds the accretion power, dot{M} c^2, reflecting BH spin energy extraction. We find our results for radio galaxies at low Eddington ratios are compatible with MADs but require a low radiative efficiency, as predicted by standard accretion models.

  17. A Linear Magnetic Field Scan Driver

    PubMed Central

    QUINE, RICHARD W.; CZECHOWSKI, TOMASZ; EATON, GARETH R.

    2009-01-01

    A linear magnetic field scan driver was developed to provide a rapidly scanning magnetic field for use in electron paramagnetic resonance (EPR) spectroscopy. The driver consists of two parts: a digitally synthesized ramp waveform generator and a power amplifier to drive the magnetic field coils. Additionally, the driver provides a trigger signal to a data collection digitizer that is synchronized to the ramp waveform. The driver can also drive an arbitrary current waveform supplied from an external source. The waveform generator is computer controlled through a serial data interface. Additional functions are controlled by the user from the driver front panel. The frequency and amplitude of the waveform are each separately controlled with 12-bit resolution (one part in 4,096). Several versions of the driver have been built with different frequency and amplitude ranges. Frequencies range from 500 to 20,000 Hz. Field sweep amplitudes range up to 80 Gpp. This article also gives a brief description of the field coils that are driven by the driver. PMID:19838315

  18. Dynamic nuclear polarization at high magnetic fields

    PubMed Central

    Maly, Thorsten; Debelouchina, Galia T.; Bajaj, Vikram S.; Hu, Kan-Nian; Joo, Chan-Gyu; MakJurkauskas, Melody L.; Sirigiri, Jagadishwar R.; van der Wel, Patrick C. A.; Herzfeld, Judith; Temkin, Richard J.; Griffin, Robert G.

    2009-01-01

    Dynamic nuclear polarization (DNP) is a method that permits NMR signal intensities of solids and liquids to be enhanced significantly, and is therefore potentially an important tool in structural and mechanistic studies of biologically relevant molecules. During a DNP experiment, the large polarization of an exogeneous or endogeneous unpaired electron is transferred to the nuclei of interest (I) by microwave (?w) irradiation of the sample. The maximum theoretical enhancement achievable is given by the gyromagnetic ratios (?e/?l), being ?660 for protons. In the early 1950s, the DNP phenomenon was demonstrated experimentally, and intensively investigated in the following four decades, primarily at low magnetic fields. This review focuses on recent developments in the field of DNP with a special emphasis on work done at high magnetic fields (?5 T), the regime where contemporary NMR experiments are performed. After a brief historical survey, we present a review of the classical continuous wave (cw) DNP mechanismsthe Overhauser effect, the solid effect, the cross effect, and thermal mixing. A special section is devoted to the theory of coherent polarization transfer mechanisms, since they are potentially more efficient at high fields than classical polarization schemes. The implementation of DNP at high magnetic fields has required the development and improvement of new and existing instrumentation. Therefore, we also review some recent developments in ?w and probe technology, followed by an overview of DNP applications in biological solids and liquids. Finally, we outline some possible areas for future developments. PMID:18266416

  19. Magnetic field regulation control system analysis

    SciTech Connect

    Badelt, Steven W.

    1996-05-01

    This study comprises (1) an analytical characterization of the Cameca ion microscope`s magnetic field regulation circuitry and (2) comparisons between the analytical predictions and the measured performance of the control system. It is the first step in a project to achieve routine field regulation better than 10ppm. The control loop was decomposed into functional subcircuits and simulated in SPICE to determine DC, AC, and transient response. Transfer functions were extracted from SPICE, simplified, and analyzed in MATLAB. Both SPICE and MATLAB simulations were calculated for step inputs, and these results were compared to actual measurements. Magnetic field fluctuations were measured at high mass resolving power. The frequency spectrum of the fluctuations was analyzed by FFT. Difficulties encountered and implications for future work are discussed.

  20. The ESRF Miniature Pulsed Magnetic Field System

    SciTech Connect

    Linden, Peter J. E. M. van der; Strohm, Cornelius; Roth, Thomas; Detlefs, Carsten; Mathon, Olivier

    2010-06-23

    We have developed a portable system to provide pulsed magnetic fields on the ESRF X-ray beamlines. The complete system consists of a power supply, liquid Helium and liquid Nitrogen dewars with a siphon each, control electronics and a double cryostat for separate coil and sample cooling. The liquid nitrogen cooled solenoids reach a maximum field of 30 Tesla for a total pulse duration of one milisecond. They are constructed for optimised cooling rate after the pulse to obtain a high duty cycle, the repetition rate is five pulses per minute at maximum field. The sample is cooled in an independent Helium flow cryostat which is inserted into the bore of the magnet. The flow cryostat has a temperature range from 5 to 250 Kelvin with a direct contact between the sample and Helium flow. This overview gives a general presentation of the system and we will show recent results.

  1. The ESRF Miniature Pulsed Magnetic Field System

    NASA Astrophysics Data System (ADS)

    van der Linden, Peter J. E. M.; Strohm, Cornelius; Roth, Thomas; Detlefs, Carsten; Mathon, Olivier

    2010-06-01

    We have developed a portable system to provide pulsed magnetic fields on the ESRF X-ray beamlines. The complete system consists of a power supply, liquid Helium and liquid Nitrogen dewars with a siphon each, control electronics and a double cryostat for separate coil and sample cooling. The liquid nitrogen cooled solenoids reach a maximum field of 30 Tesla for a total pulse duration of one milisecond. They are constructed for optimised cooling rate after the pulse to obtain a high duty cycle, the repetition rate is five pulses per minute at maximum field. The sample is cooled in an independent Helium flow cryostat which is inserted into the bore of the magnet. The flow cryostat has a temperature range from 5 to 250 Kelvin with a direct contact between the sample and Helium flow. This overview gives a general presentation of the system and we will show recent results.

  2. Non-Gaussianity from cosmic magnetic fields

    SciTech Connect

    Brown, Iain; Crittenden, Robert

    2005-09-15

    Magnetic fields in the early Universe could have played an important role in sourcing cosmological perturbations. While not the dominant source, even a small contribution might be traceable through its intrinsic non-Gaussianity. Here we calculate analytically the one-, two-, and three-point statistics of the magnetic stress energy resulting from tangled Gaussian fields, and confirm these with numerical realizations of the fields. We find significant non-Gaussianity, and importantly predict higher order moments that will appear between the scalar, vector, and tensor parts of the stress energy (e.g., scalar-tensor-tensor moments). Such higher order cross correlations are a generic feature of nonlinear theories and could prove to be an important probe of the early Universe.

  3. Magnetic field contribution to the Lorentz model.

    PubMed

    Oughstun, Kurt E; Albanese, Richard A

    2006-07-01

    The classical Lorentz model of dielectric dispersion is based on the microscopic Lorentz force relation and Newton's second law of motion for an ensemble of harmonically bound electrons. The magnetic field contribution in the Lorentz force relation is neglected because it is typically small in comparison with the electric field contribution. Inclusion of this term leads to a microscopic polarization density that contains both perpendicular and parallel components relative to the plane wave propagation vector. The modified parallel and perpendicular polarizabilities are both nonlinear in the local electric field strength. PMID:16783441

  4. Ponderomotive ratchet in a uniform magnetic field.

    PubMed

    Dodin, I Y; Fisch, N J

    2005-10-01

    We show how a ratchet effect, generally used in systems with periodic potentials, can also be practiced on charged particles by an ac field alone, in a background magnetic field near the cyclotron resonance. The effect relies entirely on the spatial inhomogeneity of the high-frequency drive, which produces a deterministic asymmetric ponderomotive barrier for undamped particles. Such a barrier can reflect particles incident from one side while transmitting those incident from the opposite side, hence acting somewhat like a Maxwell demon. The necessary fields are perhaps most easily realized in a plasma, though the effect is more general. PMID:16383549

  5. Ponderomotive ratchet in a uniform magnetic field

    SciTech Connect

    Dodin, I.Y.; Fisch, N.J.

    2005-10-01

    We show how a ratchet effect, generally used in systems with periodic potentials, can also be practiced on charged particles by an ac field alone, in a background magnetic field near the cyclotron resonance. The effect relies entirely on the spatial inhomogeneity of the high-frequency drive, which produces a deterministic asymmetric ponderomotive barrier for undamped particles. Such a barrier can reflect particles incident from one side while transmitting those incident from the opposite side, hence acting somewhat like a Maxwell demon. The necessary fields are perhaps most easily realized in a plasma, though the effect is more general.

  6. Quantum cascade lasers in high magnetic fields

    NASA Astrophysics Data System (ADS)

    Wade, Aaron

    The frontier of the rapidly emerging field of nano-optoelectronics relies on the understanding and control of intersubband transitions in low-dimensional systems. The continual search for new optoelectronics concepts and materials (including, but not limited to, III-V semiconductors, nitrides, and Si/Ge) has resulted in a rapid expansion of the field of intersubband physics and quantum cascade devices. A quantum cascade (QC) structure is a general concept of an optoelectronic device (laser, LED, frequency mixer, or detector) based on a cascade of radiative transitions between size-quantized energy levels in a multi-quantum-well structure. Today, Quantum Cascade Lasers (QCL), which are the only semiconductor devices operating from the mid-infrared (MIR) to the THz range of frequencies, represent one of the most striking outcomes of intersubband structure engineering, and provide a state-of-the-art model structure to study the basic properties of low-dimensional semiconductor systems. This dissertation concerns the experimental study of MIR and THz QC structures in high magnetic fields. Because of the similar energy and size scales of the spatial and magnetic confinements, the application of an external magnetic field offers a unique experimental tool to control and understand the most basic processes determining the performance of QC nanostructures: quantum confinement and intersubband relaxation. Specific issues addressed in this thesis are (i) mechanisms of intersubband electron relaxation, including electron-phonon, electron-electron, and interface effects; (ii) intersubband transitions in the effective zero-dimensional system ("magnetic" quantum box system); and (iii) intersubband radiative transitions in tilted magnetic fields. First we present detailed studies of GaAs/AlGaAs and GaInAs/AlInAs mid-IR QCLs. By comparing the experimental data and the model of the electron lifetime in the presence of a strong magnetic field, the lifetimes of the elastic and inelastic scattering processes are determined. Ultimately this results in the development (formulation) of a new powerful spectroscopic tool to study the scattering mechanisms in QC structures---intersubband magneto-spectroscopy. Secondly, a study of InAs/AlSb mid-IR QC structures is performed. By applying the method of the intersubband magneto-spectroscopy, we directly measured the quantum efficiency of intersubband processes in a model two-level system, and then obtain electron lifetimes of the upper-state of the radiative transition. Thirdly, GaAs/AlGaAs THz QCLs are studied. Here, a magnetic field was used as a tool to controllably transform a 2D multi-QW structure into effective 0D system with reduced (eventually quenched) non-radiative intersubband scattering. This allowed us to achieve laser emission from a single device in an unprecedented range of frequencies from 0.68 THz to 3.33 THz. Moreover, the device shows 1 THz lasing at temperatures up to 215 K, and 3 THz lasing up to 225 K. This is the longest wavelength, the widest spectral coverage, and the highest operational temperatures of any single THz solid state laser to date. The last chapter discusses QCL angular-resolved magneto-spectroscopy. At tilted magnetic fields, additional optical transitions, never observed in QC structures, are allowed as a result of the intersubband-cyclotron coupling. Also, angular field measurements are an effective tool to study the effects related to cyclotron- and spin-splitting phenomena. Here we demonstrated the feasibility of QCL angular measurements at high magnetic fields, and discuss the first results.

  7. Warm Magnetic Field Measurements of LARP HQ Magnet

    SciTech Connect

    Caspi, S; Cheng, D; Deitderich, D; Felice, H; Ferracin, P; Hafalia, R; Joseph, J; Lizarazo, J; Martchevskii, M; Nash, C; Sabbi, G L; Vu, C; Schmalzle, J; Ambrosio, G; Bossert, R; Chlachidze, G; DiMarco, J; Kashikhin, V

    2011-03-28

    The US-LHC Accelerator Research Program is developing and testing a high-gradient quadrupole (HQ) magnet, aiming at demonstrating the feasibility of Nb{sub 3}Sn technologies for the LHC luminosity upgrade. The 1 m long HQ magnet has a 120 mm bore with a conductor-limited gradient of 219 T/m at 1.9 K and a peak field of 15 T. HQ includes accelerator features such as alignment and field quality. Here we present the magnetic measurement results obtained at LBNL with a constant current of 30 A. A 100 mm long circuit-board rotating coil developed by FNAL was used and the induced voltage and flux increment were acquired. The measured b{sub 6} ranges from 0.3 to 0.5 units in the magnet straight section at a reference radius of 21.55 mm. The data reduced from the numerical integration of the raw voltage agree with those from the fast digital integrators.

  8. Magnetic Field Gradient Waveform Monitoring for Magnetic Resonance

    NASA Astrophysics Data System (ADS)

    Han, Hui

    Linear magnetic field gradients have played a central role in Magnetic Resonance Imaging (MRI) since Fourier Transform MRI was proposed three decades ago. Their primary function is to encode spatial information into MR signals. Magnetic field gradients are also used to sensitize the image contrast to coherent and/or incoherent motion, to selectively enhance an MR signal, and to minimize image artifacts. Modern MR imaging techniques increasingly rely on the implementation of complex gradient waveforms for the manipulation of spin dynamics. However, gradient system infidelities caused by eddy currents, gradient amplifier imperfections and group delays, often result in image artifacts and other errors (e.g., phase and intensity errors). This remains a critical problem for a wide range of MRI techniques on modern commercial systems, but is of particular concern for advanced MRI pulse sequences. Measuring the real magnetic field gradients, i.e., characterizing eddy currents, is critical to addressing and remedying this problem. Gradient measurement and eddy current calibration are therefore a general topic of importance to the science of MRI. The Magnetic Field Gradient Monitor (MFGM) idea was proposed and developed specifically to meet these challenges. The MFGM method is the heart of this thesis. MFGM methods permit a variety of magnetic field gradient problems to be investigated and systematically remedied. Eddy current effects associated with MR compatible metallic pressure vessels were analyzed, simulated, measured and corrected. The appropriate correction of eddy currents may enable most MR/MRI applications with metallic pressure vessels. Quantitative imaging (1D/2D) with model pressure vessels was successfully achieved by combining image reconstruction with MFGM determined gradient waveform behaviour. Other categories of MR applications with metallic vessels, including diffusion measurement and spin echo SPI T2 mapping, cannot be realized solely by MFGM guided image reconstruction. A new 'demand compensation' gradient waveform adjustment method was proposed to address this particular challenge. This idea was verified in this thesis. It should also be noted that, in a general sense, this new waveform compensation method will potentially provide a novel solution to a variety of gradient related problems in MRI.

  9. Magnetic-Field-Tunable Superconducting Rectifier

    NASA Technical Reports Server (NTRS)

    Sadleir, John E.

    2009-01-01

    Superconducting electronic components have been developed that provide current rectification that is tunable by design and with an externally applied magnetic field to the circuit component. The superconducting material used in the device is relatively free of pinning sites with its critical current determined by a geometric energy barrier to vortex entry. The ability of the vortices to move freely inside the device means this innovation does not suffer from magnetic hysteresis effects changing the state of the superconductor. The invention requires a superconductor geometry with opposite edges along the direction of current flow. In order for the critical current asymmetry effect to occur, the device must have different vortex nucleation conditions at opposite edges. Alternative embodiments producing the necessary conditions include edges being held at different temperatures, at different local magnetic fields, with different current-injection geometries, and structural differences between opposite edges causing changes in the size of the geometric energy barrier. An edge fabricated with indentations of the order of the coherence length will significantly lower the geometric energy barrier to vortex entry, meaning vortex passage across the device at lower currents causing resistive dissipation. The existing prototype is a two-terminal device consisting of a thin-film su - perconducting strip operating at a temperature below its superconducting transition temperature (Tc). Opposite ends of the strip are connected to electrical leads made of a higher Tc superconductor. The thin-film lithographic process provides an easy means to alter edge-structures, current-injection geo - metries, and magnetic-field conditions at the edges. The edge-field conditions can be altered by using local field(s) generated from dedicated higher Tc leads or even using the device s own higher Tc superconducting leads.

  10. Magnetic field diffusion and dissipation in reversed-field plasmas

    NASA Technical Reports Server (NTRS)

    Drake, J. F.; Gladd, N. T.; Huba, J. D.

    1981-01-01

    A diffusion equation is derived which describes the evolution of a magnetic field in a plasma of arbitrary beta and resistivity. The equation is valid for a one-dimensional slab geometry, assumes the plasma remains in quasi-equilibrium throughout its evolution and does not include thermal transport. Scaling laws governing the rate of change of the magnetic energy, particle drift energy, and magnetic flux are calculated. It is found that the magnetic free energy can be substantially larger than the particle drift energy and can be an important energy reservoir in driving plasma instabilities (e.g., the lower-hybrid-drift instability). In addition, the effect of a spatially varying resistivity on the evolution of a reversed-field plasma is studied. The resistivity model used is based upon the anomalous transport properties associated with the nonlocal mode structure of the lower-hybrid-drift instability. The relevance of this research to laboratory plasmas (e.g., theta pinches, reversed-field theta pinches) and space plasmas (e.g., the earth's magnetotail) is discussed.

  11. Spherical compression of a magnetic field

    SciTech Connect

    Fowler, C.M.

    1996-09-01

    In an interesting paper, Rutkevich obtained the electromagnetic wave solution for the compression of a magnetic field contained by an imploding, perfectly conducting cylindrical shell or liner. The magnetic and electric susceptibilities were taken as constant. The solution was obtained by Laplace transforms. In his paper, he also considered the corresponding plane problem when driving together two perfectly conducting, parallel plates that confine a magnetic field. He compared the method of solution obtained by Laplace transforms with that obtained by the method of characteristics which was used to obtain the original solution. He concluded his paper by noting that the transform method is more versatile that the characteristic method. Somewhat later, Bodulinskii and Medvedev obtained a solution for the wave structure generated when an initial magnetic field is compressed by the implosion of a conducting spherical liner. Again, the solution was obtained by transform methods. In this paper, we outline the solution to the spherical problem using the method of characteristics. The utility of this method is described for some other situations.

  12. Jerks in Stochastic Synthetic Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Brown, W. J.; Mound, J. E.; Livermore, P. W.

    2014-12-01

    The geomagnetic field is generated by the constant motion of the fluid outer core and varies on timescales from months to millions of years. Geomagnetic jerks are rapid changes in the secular variation of Earth's magnetic field, attributed primarily to changing flows near the surface of the outer core. Various generation mechanisms have been suggested for these rapid changes but none have conclusively explained the phenomena. Jerks can be seen in magnetic observatory records over the last 170~years and in satellite data of the last 15~years. This data coverage, spatially limited and/or temporally restricted, makes it difficult to interpret the true character of jerks at the surface or their origins in the core. This leads us to investigate what further insight we can gain from synthetic magnetic fields such as those which are described by modelling stochastic processes. Such fields are not restricted by the temporal smoothing of most magnetic field models and can better represent rapid variations such as jerks. We compare the characteristics of the synthetic fields with those of observatory and satellite data and hence, finding great similarity, study the presence of jerks in stochastic synthetic fields. Synthetic jerks are seen which resemble observed jerks, occurring frequently with regional periodic variations in amplitudes. These synthetic jerks occur without related features in the large scale secular acceleration power at the CMB. The flexible spatial and temporal sampling of the models creates a means of validating the robustness of observed features in the real field, which suffer from limited sampling. Initial results suggest that the distribution of magnetic observatories is sufficient to accurately recover the large scale features of jerks. As such comparisons between jerks seen in observatory and satellite data may be drawn. We further investigate the spectral properties of jerks in the synthetic fields using spherical harmonic analysis with a view to assessing possible dynamic patterns responsible for jerk features. Such insights could help to interpret the core flows inferred from high-resolution SWARM data to understand the generation process behind jerks.

  13. Magnetic Reconnection in Field-Reversed Configurations

    NASA Astrophysics Data System (ADS)

    Sevillano, Evelio

    Internal magnetic field probes are used to study the magnetic field-line reconnection during the formation of Field-Reversed Configurations (FRC's) in a low-compression theta-pinch. Measurements of the reversed trapped flux indicated that most of the loss of the initial bias flux occurs during the radial implosion. Therefore the flux loss is not a consequence of plasma-wall contact during field-reversal. An operating boundary in the parameter space of filling pressure, bias field and external field is found for formation of FRC's with equilibrium lengths shorter than the coil. Measurements of the internal magnetic fields near the ends of the theta-pinch indicate that FRC formation can be delayed by plasma flow out the ends. The addition of independently driven magnetic mirrors extends the operating boundary. An axial array of magnetic islands forms during the early stages of the discharge. These islands then coalesce into large units. Several possible explanations of their formation are given. In addition, the growth rate for coalescence obtained from MHD simulations is compared with the experimental results. With the addition of a third magnetic mirror near the midplane of the device the formation of a two-cell FRC is observed. These experiments provide a proof-of -principle for possible future multiple-cell experiments. It was discovered that the reconnection in the region of the X-point between the cells consisted of two phases. A slow phase, where flux is dissipated slowly, is followed by the onset of a fast reconnection phase which leads to the formation of the two independent cells. The FRC's created are different than those in most other experiments in that neither an n = 2 rotational instability nor a strong axial contraction are observed. Simultaneous measurements of the density and excluded-flux radius indicate that the configurations terminate as a result of a radial collapse. This collapse may be a consequence of loss of the reversed flux as a barrier of radiation energy loss is crossed and the plasma resistivity consequently increases.

  14. Circular polarization of obliquely propagating whistler wave magnetic field

    SciTech Connect

    Bellan, P. M.

    2013-08-15

    The circular polarization of the magnetic field of obliquely propagating whistler waves is derived using a basis set associated with the wave partial differential equation. The wave energy is mainly magnetic and the wave propagation consists of this magnetic energy sloshing back and forth between two orthogonal components of magnetic field in quadrature. The wave electric field energy is small compared to the magnetic field energy.

  15. Axial magnetic field interrupters in autorecloser applications

    SciTech Connect

    Bestel, E.F.; Stoving, P.N.

    1996-12-31

    Application of vacuum interruption in distribution switchgear, especially in autoreclosers, which have uniquely high demands on vacuum fault interrupters, will be discussed. The fast open-close-open sequence and its associated highly asymmetrical waveforms are some of the difficulties encountered. The authors will present their solution to these problems in the form of an economical axial magnetic field interrupter that realizes current densities of up to 1.68 kA/cm{sup 2} - the most efficient axial magnetic interrupter that is in production today. Actual design test data per ANSI C37.60 will be shown.

  16. Laser plasma in a magnetic field

    SciTech Connect

    Kondo,K.; Kanesue, T.; Tamura, J.; Dabrowski, R.; Okamura, M.

    2009-09-20

    Laser Ion Source (LIS) is a candidate among various heavy ion sources. A high density plasma produced by Nd:YAG laser with drift velocity realizes high current and high charge state ion beams. In order to obtain higher charged particle ions, we had test experiments of LIS with a magnetic field by which a connement effect can make higher charged beams. We measured total current by Faraday Cup (FC) and analyzed charge distribution by Electrostatic Ion Analyzer (EIA). It is shown that the ion beam charge state is higher by a permanent magnet.

  17. Crustal Magnetic Field Anomalies and Global Tectonics

    NASA Astrophysics Data System (ADS)

    Storetvedt, Karsten

    2014-05-01

    A wide variety of evidence suggests that the ruling isochron (geomagnetic polarity versus age) hypothesis of marine magnetic lineations has no merit - undermining therefore one of the central tenets of plate tectonics. Instead, variable induction by the ambient geomagnetic field is likely to be the principal agent for mega-scale crustal magnetic features - in both oceanic and continental settings. This revitalizes the fault-controlled susceptibility-contrast model of marine magnetic lineations, originally proposed in the late 1960s. Thus, the marine magnetic 'striping' may be ascribed to tectonic shearing and related, but variable, disintegration of the original iron-oxide mineralogy, having developed primarily along one of the two pan-global sets of orthogonal fractures and faults. In this way, fault zones (having the more advanced mineral alteration) would be characterized by relatively low susceptibility, while more moderately affected crustal sections (located between principal fault zones) would be likely to have less altered oxide mineralogy and therefore higher magnetic susceptibility. On this basis, induction by the present geomagnetic field is likely to produce oscillating magnetic field anomalies with axis along the principal shear grain. The modus operandi of the alternative magneto-tectonic interpretation is inertia-driven wrenching of the global Alpine age palaeo-lithosphere - triggered by changes in Earth's rotation. Increasing sub-crustal loss to the upper mantle during the Upper Mesozoic had left the ensuing Alpine Earth in a tectonically unstable state. Thus, sub-crustal eclogitization and associated gravity-driven delamination to the upper mantle led to a certain degree of planetary acceleration which in turn gave rise to latitude-dependent, westward inertial wrenching of the global palaeo-lithosphere. During this process, 1) the thin and mechanically fragile oceanic crust were deformed into a new type of broad fold belts, and 2) the continents were subjected to relative 'in situ' rotations (mostly moderate). Examples of marine magnetic lineations with landward continuation along prominent transcurrent fault zones, and the fact that striped marine magnetic anomalies may display orthogonal networks - concordant with the ubiquitous system of rectilinear fractures, faults and joints - corroborate the wrench tectonic interpretation of crustal field anomalies.

  18. Instrument Records Magnetic Fields Generated By Lightning

    NASA Technical Reports Server (NTRS)

    Medelius, Pedro J.; Simpson, Howard James

    1995-01-01

    Portable, self-contained, compact instrument measures and records transient magnetic fields particularly those generated by nearby lightning strikes. Designed to be placed near sensitive electronic equipment in anticipation of thunderstorms. Data recorded during thunderstorms analyzed afterward to determine whether magnetic effects of lightning strong enough to have damaged and/or affected operation of sensitive equipment. Provides data helping engineers decide whether sensitive equipment should be tested for damage and/or other effects caused by lightning. Typical installations in which instrument beneficial include outdoor sensing equipment, computer rooms, broadcasting stations, and powerplant control rooms.

  19. Coronal magnetic field modeling using stereoscopy constraints

    NASA Astrophysics Data System (ADS)

    Chifu, I.; Inhester, B.; Wiegelmann, T.

    2015-05-01

    Aims: Nonlinear force-free field (NLFFF) extrapolation has been used extensively in the past to extrapolate solar surface magnetograms to stationary coronal field models. In theoretical tests with known boundary conditions, the nonlinear boundary value problem can be solved reliably. However, if the magnetogram is measured with errors, the extrapolation often yields field lines that disagree with the shapes of simultaneously observed and stereoscopically reconstructed coronal loops. We here propose an extension to an NLFFF extrapolation scheme that remedies this deficiency in that it incorporates the loop information in the extrapolation procedure. Methods: We extended the variational formulation of the NLFFF optimization code by an additional term that monitors and minimizes the difference of the local magnetic field direction and the orientation of 3D plasma loops. We tested the performance of the new code with a previously reported semi-analytical force-free solution. Results: We demonstrate that there is a range of force-free and divergence-free solutions that comply with the boundary measurements within some error bound. With our new approach we can obtain the solution out of this set the coronal fields which is well aligned with given loops. Conclusions: We conclude that the shape of coronal loops reconstructed by stereoscopy may lead to an important stabilization of coronal NLFFF field solutions when, as is typically the case, magnetic surface measurements with limited precision do not allow determining the solution solely from photospheric field measurements.

  20. The energy budget of stellar magnetic fields

    NASA Astrophysics Data System (ADS)

    See, V.; Jardine, M.; Vidotto, A. A.; Donati, J.-F.; Folsom, C. P.; Boro Saikia, S.; Bouvier, J.; Fares, R.; Gregory, S. G.; Hussain, G.; Jeffers, S. V.; Marsden, S. C.; Morin, J.; Moutou, C.; do Nascimento, J. D.; Petit, P.; Rosn, L.; Waite, I. A.

    2015-11-01

    Spectropolarimetric observations have been used to map stellar magnetic fields, many of which display strong bands of azimuthal fields that are toroidal. A number of explanations have been proposed to explain how such fields might be generated though none are definitive. In this paper, we examine the toroidal fields of a sample of 55 stars with magnetic maps, with masses in the range 0.1-1.5 M?. We find that the energy contained in toroidal fields has a power-law dependence on the energy contained in poloidal fields. However the power index is not constant across our sample, with stars less and more massive than 0.5 M? having power indices of 0.72 0.08 and 1.25 0.06, respectively. There is some evidence that these two power laws correspond to stars in the saturated and unsaturated regimes of the rotation-activity relation. Additionally, our sample shows that strong toroidal fields must be generated axisymmetrically. The latitudes at which these bands appear depend on the stellar rotation period with fast rotators displaying higher latitude bands than slow rotators. The results in this paper present new constraints for future dynamo studies.

  1. Primordial magnetic field amplification from turbulent reheating

    SciTech Connect

    Calzetta, Esteban; Kandus, Alejandra E-mail: kandus@uesc.br

    2010-08-01

    We analyze the possibility of primordial magnetic field amplification by a stochastic large scale kinematic dynamo during reheating. We consider a charged scalar field minimally coupled to gravity. During inflation this field is assumed to be in its vacuum state. At the transition to reheating the state of the field changes to a many particle/anti-particle state. We characterize that state as a fluid flow of zero mean velocity but with a stochastic velocity field. We compute the scale-dependent Reynolds number Re(k), and the characteristic times for decay of turbulence, t{sub d} and pair annihilation t{sub a}, finding t{sub a} << t{sub d}. We calculate the rms value of the kinetic helicity of the flow over a scale L and show that it does not vanish. We use this result to estimate the amplification factor of a seed field from the stochastic kinematic dynamo equations. Although this effect is weak, it shows that the evolution of the cosmic magnetic field from reheating to galaxy formation may well be more complex than as dictated by simple flux freezing.

  2. Orientation and Magnitude of Mars' Magnetic Field

    NASA Technical Reports Server (NTRS)

    1997-01-01

    This image shows the orientation and magnitude of the magnetic field measured by the MGS magnetometer as it sped over the surface of Mars during an early aerobraking pass (Day of the year, 264; 'P6' periapsis pass). At each point along the spacecraft trajectory we've drawn vectors in the direction of the magnetic field measured at that instant; the length of the line is scaled to show the relative magnitude of the field. Imagine traveling along with the MGS spacecraft, holding a string with a magnetized needle on one end: this essentially a compass with a needle that is free to spin in all directions. As you pass over the surface the needle would swing rapidly, first pointing towards the planet and then rotating quickly towards 'up' and back down again. All in a relatively short span of time, say a minute or two, during which time the spacecraft has traveled a couple of hundred miles. You've just passed over one of many 'magnetic anomalies' thus far detected near the surface of Mars. A second major anomaly appears a little later along the spacecraft track, about 1/4 the magnitude of the first - can you find it? The short scale length of the magnetic field signature locates the source near the surface of Mars, perhaps in the crust, a 10 to 75 kilometer thick outer shell of the planet (radius 3397 km).

    The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO. JPL is an operating division of California Institute of Technology (Caltech).

  3. Mystery of the magnetic field of Mars

    NASA Astrophysics Data System (ADS)

    Mordovskaya, V.

    Research of interaction of the solar wind with bodies of Solar System is one of methods, which allows us to make the conclusion about substance of the bodies and about its magnetization. The investigation of the solar wind interaction with Mars and Phobos has been carried out using the data of the Soviet expedition "Phobos - 2" and the kinetic approach to study the data. It is shown, that the size of the Martian obstacle to the solar wind is actually the size of Mars, as a physical body. The weak ionosphere and crystal magnetic anomalies at Mars result in inelastic dispersion of particles of the solar wind on the Martian obstacle, which give additional accumulation of the plasma and magnetic field in front of the Martian obstacle. The more the density of the solar wind, the more will the pileup of the plasma in front of Mars. Mars has not magnetospheres, neither own, nor induced to give the additional size for the obstacle like the Earth. The tail inherent in the interaction of magnetized bodies with the solar wind plasma, practically, is absent at Mars. The magnetic topology of the Martian wake is a result of the flow by the warm plasma of the solar wind around Mars. The Phobos interaction with the solar wind has been investigated. Dependence of the pileup of the solar wind plasma ahead of Phobos from the ion skin-depth has been found, which shows the existence of an effective obstacle of Phobos with the sizes about 150-170 km. Source with equivalent magnetic moment as order 1015A m2 in Phobos leads to the development of such obstacle for the solar wind flow around Phobos. Thus the received results: absence of the intrinsic global magnetic field of Mars, the magnetization of the Martian moon of Phobos and so the crystal magnetic anomalies revealed by the MGS satellite on surface of Mars give the primal magnetic mystery of Mars. If we will understand it we may probably approach to the problem of lifelessness of Mars. It is necessary to remind that evidence of biological origin has been revealed in the Martian meteorite ALH84001 with chains of magnetite crystals.

  4. The Magnetic Field of Planet Earth

    NASA Astrophysics Data System (ADS)

    Hulot, G.; Finlay, C. C.; Constable, C. G.; Olsen, N.; Mandea, M.

    2010-05-01

    The magnetic field of the Earth is by far the best documented magnetic field of all known planets. Considerable progress has been made in our understanding of its characteristics and properties, thanks to the convergence of many different approaches and to the remarkable fact that surface rocks have quietly recorded much of its history. The usefulness of magnetic field charts for navigation and the dedication of a few individuals have also led to the patient construction of some of the longest series of quantitative observations in the history of science. More recently even more systematic observations have been made possible from space, leading to the possibility of observing the Earths magnetic field in much more details than was previously possible. The progressive increase in computer power was also crucial, leading to advanced ways of handling and analyzing this considerable corpus of data. This possibility, together with the recent development of numerical simulations, has led to the development of a very active field in Earth science. In this paper, we make an attempt to provide an overview of where the scientific community currently stands in terms of observing, interpreting and understanding the past and present behavior of the so-called main magnetic field produced within the Earths core. The various types of data are introduced and their specific properties explained. The way those data can be used to derive the time evolution of the core field, when this is possible, or statistical information, when no other option is available, is next described. Special care is taken to explain how information derived from each type of data can be patched together into a consistent description of how the core field has been behaving in the past. Interpretations of this behavior, from the shortest (1 yr) to the longest (virtually the age of the Earth) time scales are finally reviewed, underlining the respective roles of the magnetohydodynamics at work in the core, and of the slow dynamic evolution of the planet as a whole.

  5. Precision measurement of magnetic characteristics of an article with nullification of external magnetic fields

    NASA Technical Reports Server (NTRS)

    Honess, Shawn B. (Inventor); Narvaez, Pablo (Inventor); Mcauley, James M. (Inventor)

    1992-01-01

    An apparatus for characterizing the magnetic field of a device under test is discussed. The apparatus is comprised of five separate devices: (1) a device for nullifying the ambient magnetic fields in a test environment area with a constant applied magnetic field; (2) a device for rotating the device under test in the test environment area; (3) a device for sensing the magnetic field (to obtain a profile of the magnetic field) at a sensor location which is along the circumference of rotation; (4) a memory for storing the profiles; and (5) a processor coupled to the memory for characterizing the magnetic field of the device from the magnetic field profiles thus obtained.

  6. Ultrafast time domain demonstration of bulk magnetization precession at zero magnetic field ferromagnetic resonance induced by terahertz magnetic field.

    PubMed

    Nakajima, M; Namai, A; Ohkoshi, S; Suemoto, T

    2010-08-16

    We report the first observation of sub-terahertz bulk-magnetization precession, using terahertz time-domain spectroscopy. The magnetization precession in gallium-substituted epsilon-iron oxide nano-ferromagnets under zero magnetic field is induced by the impulsive magnetic field of the THz wave through the gyromagnetic effect. Just at the resonance frequency, the linear to circular polarized wave conversion is realized. This is understood as the free induction decay signal radiated from a rotating magnetic dipole corresponding to the natural resonance. Furthermore, this demonstration reveals that the series of gallium-substituted epsilon-iron oxide nano-ferromagnets is very prospective for magneto-optic devices, which work at room temperature without external magnetic field, in next-generation wireless communication. PMID:20721218

  7. MAGNETIC FIELDS IN POPULATION III STAR FORMATION

    SciTech Connect

    Turk, Matthew J.; Bryan, Greg L.; Oishi, Jeffrey S.; Abel, Tom

    2012-02-01

    We study the buildup of magnetic fields during the formation of Population III star-forming regions by conducting cosmological simulations from realistic initial conditions and varying the Jeans resolution. To investigate this in detail, we start simulations from identical initial conditions, mandating 16, 32, and 64 zones per Jeans length, and study the variation in their magnetic field amplification. We find that, while compression results in some amplification, turbulent velocity fluctuations driven by the collapse can further amplify an initially weak seed field via dynamo action, provided there is sufficient numerical resolution to capture vortical motions (we find this requirement to be 64 zones per Jeans length, slightly larger than but consistent with previous work run with more idealized collapse scenarios). We explore saturation of amplification of the magnetic field, which could potentially become dynamically important in subsequent, fully resolved calculations. We have also identified a relatively surprising phenomenon that is purely hydrodynamic: the higher-resolved simulations possess substantially different characteristics, including higher infall velocity, increased temperatures inside 1000 AU, and decreased molecular hydrogen content in the innermost region. Furthermore, we find that disk formation is suppressed in higher-resolution calculations, at least at the times that we can follow the calculation. We discuss the effect this may have on the buildup of disks over the accretion history of the first clump to form as well as the potential for gravitational instabilities to develop and induce fragmentation.

  8. Magnetic Fields in Population III Star Formation

    SciTech Connect

    Turk, Matthew J.; Oishi, Jeffrey S.; Abel, Tom; Bryan, Greg

    2012-02-22

    We study the buildup of magnetic fields during the formation of Population III star-forming regions, by conducting cosmological simulations from realistic initial conditions and varying the Jeans resolution. To investigate this in detail, we start simulations from identical initial conditions, mandating 16, 32 and 64 zones per Jeans length, and studied the variation in their magnetic field amplification. We find that, while compression results in some amplification, turbulent velocity fluctuations driven by the collapse can further amplify an initially weak seed field via dynamo action, provided there is sufficient numerical resolution to capture vortical motions (we find this requirement to be 64 zones per Jeans length, slightly larger than, but consistent with previous work run with more idealized collapse scenarios). We explore saturation of amplification of the magnetic field, which could potentially become dynamically important in subsequent, fully-resolved calculations. We have also identified a relatively surprising phenomena that is purely hydrodynamic: the higher-resolved simulations possess substantially different characteristics, including higher infall-velocity, increased temperatures inside 1000 AU, and decreased molecular hydrogen content in the innermost region. Furthermore, we find that disk formation is suppressed in higher-resolution calculations, at least at the times that we can follow the calculation. We discuss the effect this may have on the buildup of disks over the accretion history of the first clump to form as well as the potential for gravitational instabilities to develop and induce fragmentation.

  9. Magnetic field effects in hybrid perovskite devices

    NASA Astrophysics Data System (ADS)

    Zhang, C.; Sun, D.; Sheng, C.-X.; Zhai, Y. X.; Mielczarek, K.; Zakhidov, A.; Vardeny, Z. V.

    2015-05-01

    Magnetic field effects have been a successful tool for studying carrier dynamics in organic semiconductors as the weak spin-orbit coupling in these materials gives rise to long spin relaxation times. As the spin-orbit coupling is strong in organic-inorganic hybrid perovskites, which are promising materials for photovoltaic and light-emitting applications, magnetic field effects are expected to be negligible in these optoelectronic devices. We measured significant magneto-photocurrent, magneto-electroluminescence and magneto-photoluminescence responses in hybrid perovskite devices and thin films, where the amplitude and shape are correlated to each other through the electron-hole lifetime, which depends on the perovskite film morphology. We attribute these responses to magnetic-field-induced spin-mixing of the photogenerated electron-hole pairs with different g-factors--the Δg model. We validate this model by measuring large Δg (~ 0.65) using field-induced circularly polarized photoluminescence, and electron-hole pair lifetime using picosecond pump-probe spectroscopy.

  10. The main magnetic field of Jupiter

    NASA Technical Reports Server (NTRS)

    Acuna, M. H.; Ness, N. F.

    1976-01-01

    The main magnetic field of Jupiter has been measured by the Goddard Space Flight Center flux gate magnetometer on Pioneer 11. Analysis of the data yields a more detailed model than that obtained from Pioneer 10 results. In a spherical harmonic octupole representation the dipole term (with opposite polarity to earth's) has a magnitude of 4.28 G times the radial distance cubed at a tilt angle of 9.6 deg and a system 111 longitude of 232 deg. The quadrupole and octupole moments are 24% and 21% of the dipole, respectively. This leads to a significant deviation of the planetary magnetic field from a simple offset dipole topology at distances of less than three times the radial distance. The north polar field strength is 14 G, and in the Northern Hemisphere the 'footprint' of the Io associated flux tube traverses the magnetic polar region. Associated L shell splitting in the radiation belts, warping of the charged particle equatorial planes, and enhanced absorption effects due to the satellites Amalthea and Io are expected as a result of the field complexity.

  11. Magnetic field depression within electron holes

    NASA Astrophysics Data System (ADS)

    Vasko, I. Y.; Agapitov, O. V.; Mozer, F.; Artemyev, A. V.; Jovanovic, D.

    2015-04-01

    We analyze electron holes that are spikes of the electrostatic field (up to 500 mV/m) observed by Van Allen Probes in the outer radiation belt. The unexpected feature is the magnetic field depression of about several tens of picotesla within many of the spikes. The earlier observations showed amplification or negligible perturbations of the magnetic field within the electron holes. We suggest that the observed magnetic field depression is due to the diamagnetic current of hot and highly anisotropic population of electrons trapped within the electron holes. The required trapped population should have a density up to 65% of the background plasma density, a temperature up to several keV, and a temperature anisotropy T⊥/T∥˜2. We argue that the observed electron holes could be generated due to injections of highly anisotropic plasma sheet electrons into the outer radiation belt. These electron holes may present a source of the seed population due to transport of trapped electrons to higher latitudes and can be potentially used for distant probing of plasma properties in their source region.

  12. Fast magnetic reconnection with large guide fields

    SciTech Connect

    Stanier, A. Simakov, Andrei N.; Chacn, L.; Daughton, W.

    2015-01-15

    In this letter, it is demonstrated using two-fluid simulations that low-? magnetic reconnection remains fast, regardless of the presence of fast dispersive waves, which have been previously suggested to play a critical role. To understand these results, a discrete model is constructed that offers scaling relationships for the reconnection rate and dissipation region (DR) thickness in terms of the upstream magnetic field and DR length. We verify these scalings numerically and show how the DR self-adjusts to process magnetic flux at the same rate that it is supplied to a larger region where two-fluid effects become important. The rate is therefore independent of the DR physics and is in good agreement with kinetic results.

  13. A compact high field magnetic force microscope.

    PubMed

    Zhou, Haibiao; Wang, Ze; Hou, Yubin; Lu, Qingyou

    2014-12-01

    We present the design and performance of a simple and compact magnetic force microscope (MFM), whose tip-sample coarse approach is implemented by the piezoelectric tube scanner (PTS) itself. In brief, a square rod shaft is axially spring-clamped on the inner wall of a metal tube which is glued inside the free end of the PTS. The shaft can thus be driven by the PTS to realize image scan and inertial stepping coarse approach. To enhance the inertial force, each of the four outer electrodes of the PTS is driven by an independent port of the controller. The MFM scan head is so compact that it can easily fit into the 52mm low temperature bore of a 20T superconducting magnet. The performance of the MFM is demonstrated by imaging a manganite thin film at low temperature and in magnetic fields up to 15T. PMID:25189114

  14. Internal magnetic fields and supersymmetry in orientifolds

    NASA Astrophysics Data System (ADS)

    Dudas, E.; Timirgaziu, C.

    2005-06-01

    Within the context of type I strings, we show the equivalence between BPS D9-branes with internal magnetic fluxes H in the three torii and non-BPS D3-branes with inverted internal magnetic fluxes 1/H. We then construct new supersymmetric examples of ZZ orientifolds with discrete torsion which in the past had only non-supersymmetric solutions and emphasize the role of new twisted tadpole cancellation conditions, arising in the presence of magnetic fields, in order to get a consistent spectrum. In a second and independent part of the paper, we construct a new nine-dimensional type IIB orientifold with Scherk-Schwarz deformation which has the peculiarity of introducing a new type of non-BPS O9-planes and which contains as top branes a Scherk-Schwarz deformation of non-BPS D9-branes. The model contains charged D7- and D3-branes with a soft supersymmetry breaking spectrum.

  15. NMR in rotating magnetic fields: Magic angle field spinning

    SciTech Connect

    Sakellariou, D.; Meriles, C.; Martin, R.; Pines, A.

    2004-09-10

    Magic angle sample spinning has been one of the cornerstones in high-resolution solid state NMR. Spinning frequencies nowadays have increased by at least one order of magnitude over the ones used in the first experiments and the technique has gained tremendous popularity. It is currently a routine procedure in solid-state NMR, high-resolution liquid-state NMR and solid-state MRI. The technique enhances the spectral resolution by averaging away rank 2 anisotropic spin interactions thereby producing isotropic-like spectra with resolved chemical shifts and scalar couplings. Andrew proposed that it should be possible to induce similar effects in a static sample if the direction of the magnetic field is varied, e.g., magic-angle rotation of the B0 field (B0-MAS) and this has been recently demonstrated using electromagnetic field rotation. Here we discuss on the possibilities to perform field rotation using alternative hardware, together with spectroscopic methods to recover isotropic resolution even in cases where the field is not rotating at the magic angle. Extension to higher magnetic fields would be beneficial in situations where the physical manipulation of the sample is inconvenient or impossible. Such situations occur often in materials or biomedical samples where ''ex-situ'' NMR spectroscopy and imaging analysis is needed.

  16. Magnetic Field in the Outer Heliosphere

    NASA Technical Reports Server (NTRS)

    Smith, Edward J.

    2004-01-01

    Observed properties of the magnetic field in the outer heliosphere are generally well described by the Parker model but evidence has accumulated of significant departures in the components and field magnitude. The radial component is independent of solar latitude at both solar minimum and maximum implying non-radial solar wind flow near the Sun driven by differential magnetic pressure. The azimuthal component deviates from the Parker values at high latitudes as a result of the non-radial flow near the Sun that causes fields to originate at higher latitudes than those at which they are observed far from the Sun. A turning of the spiral angle toward the radial direction by tens of degrees is often observed inside co-rotating rarefaction regions (dwells). A recent model attributes this effect to a motion of the field across polar coronal hole boundaries that results in different solar wind speeds along parts of the field line. The north-south component can depart from zero for many days as a result of the tilting of the interface between fast and slow streams. Recent Voyager observations show that, during solar minimum, the field magnitude is smaller than extrapolations outward from 1 AU. This 'flux deficit,' seen earlier in Pioneer data, may be explained by any of several physical models.

  17. Numerical simulation of solar coronal magnetic fields

    NASA Technical Reports Server (NTRS)

    Dahlburg, Russell B.; Antiochos, Spiro K.; Zang, T. A.

    1990-01-01

    Many aspects of solar activity are believed to be due to the stressing of the coronal magnetic field by footpoint motions at the photosphere. The results are presented of a fully spectral numerical simulation which is the first 3-D time dependent simulation of footpoint stressing in a geometry appropriate for the corona. An arcade is considered that is initially current-free and impose a smooth footpoint motion that produces a twist in the field of approx 2 pi. The footprints were fixed and the evolution was followed until the field relaxes to another current-free state. No evidence was seen for any instability, either ideal or resistive and no evidence for current sheet formation. The most striking feature of the evolution is that in response to photospheric motions, the field expands rapidly upward to minimize the stress. The expansion has two important effects. First, it suppresses the development of dips in the field that could support dense, cool material. For the motions assumed, the magnetic field does not develop a geometry suitable for prominence formation. Second, the expansion inhibits ideal instabilities such as kinking. The results indicate that simple stearing of a single arcade is unlikely to lead to solar activity such as flares or prominences. Effects are discussed that might possibly lead to such activity.

  18. Magnetic Fields at Largest Universal Strengths: Overview

    NASA Astrophysics Data System (ADS)

    Beskin, V. S.; Balogh, A.; Falanga, M.; Treumann, R. A.

    2015-10-01

    A brief review is given about the role strong magnetic fields play in the universe. We list the main observational and theoretical achievements treated in the following chapters including a number of open questions which future research is going to attack. Strong fields in the universe exceed any large scale fields by several orders of magnitude, at first glance suggesting that their generation mechanisms would be different. However, it is believed that gravitational collapse and magnetic flux conservation is responsible for the amplification of fields generated in the progenitors to the observed strengths. In this sense the extremely strong fields are mainly fossil, and their variety confirms the different masses and stages where the collapse comes to rest, at the lightest in white dwarfs and at the strongest in magnetars, which are a particular class of neutron stars with strongly inhomogeneous particularly structured crust. Various effects related to the detection of such fields, radiation generation and consequences for the environment are pointed out and referred to the relevant chapters in this volume.

  19. Reconstructing magnetic fields of spiral galaxies from radiopolarimetric observations

    NASA Astrophysics Data System (ADS)

    Shneider, C.

    2015-12-01

    We live in a magnetic universe with magnetic fields spanning an enormous range of spatial and temporal scales. In particular, magnetic fields at the scale of a galaxy are known as galactic magnetic fields and are the focus of this PhD thesis. These galactic magnetic fields are very important since they affect the dynamics of the interstellar gas as well as the gas distribution. The presence of these magnetic fields induces a certain type of radiation to occur at radio frequencies known as synchrotron radiation. The observed polarization properties of this synchrotron radiation then serves to record the imprint of these magnetic fields. The goal of this thesis has been to infer the structure of the magnetic field across various spatial scales in our own Galaxy as well as the strength and structure of the magnetic field in other galaxies using radiopolarimetric observations.

  20. On turbulent diffusion of magnetic fields and the loss of magnetic flux from stars

    NASA Technical Reports Server (NTRS)

    Vainshtein, Samuel I.; Rosner, Robert

    1991-01-01

    The turbulent diffusion of magnetic fields in astrophysical objects, and the processes leading to magnetic field flux loss from such objects are discussed with attention to the suppression of turbulent diffusion by back-reaction of magnetic fields on small spatial scales, and on the constraint imposed on magnetic flux loss by flux-freezing within stars. Turbulent magnetic diffusion can be suppressed even for very weak large-scale magnetic fields, so that 'standard' turbulent diffusion is incapable of significant magnetic flux destruction within a star. Finally, magnetic flux loss via winds is shown to be generally ineffective, no matter what the value of the effective magnetic Reynolds number is.