Sample records for magnetic field configurations

  1. Earth-directed ICME magnetic field configuration

    NASA Astrophysics Data System (ADS)

    Nieves-Chinchilla, Teresa; Vourlidas, Angelos; Adam, Szabo; Neel, Savani; Mays Leila, M.; Hidalgo Miguel, A.; Wenyuan, Yu

    2015-04-01

    It is known that the geoeffectiveness of interplanetary coronal mass ejections (ICMEs) depends on their magnetic field configuration. However, it remains unclear how the ICME interactions with the solar wind or other solar transient structures affect their magnetic configuration through, say, distortion of their cross-section, or deformation of their front. Obviously, precise space weather forecasting is depended on precise understanding of the evolution of the ICME internal magnetic topology. The goal of this study is to identify the ambient solar wind parameters that affect the flux-rope geometry and magnetic field configuration.

  2. Magnetic helicity injection for configurations with field errors

    Microsoft Academic Search

    John M. Finn; Thomas M. Antonsen Jr.

    1988-01-01

    The relative magnetic helicity and its rate of injection are computed for several examples of configurations representing magnetic fusion experiments, specifically reversed field pinches (RFP's) with field errors. Field errors, here defined to be normal components of magnetic field at the wall, are believed to have a significant effect on the loop voltage, and therefore the volt-second consumption, in RFP's.

  3. Magnetic Field Configuration in the Magnetotail Near 60 R E

    Microsoft Academic Search

    C.-I. Meng; K. A. Anderson

    1974-01-01

    The magnetic field line configuration in the geomagnetic tail near 60 RE is examined on the basis of nearly 3 years of magnetometer data from the lunar-orbiting Explorer 35 satellite. The magnetotail field line characteristics inside the plasma sheet and in the high-latitude tail, i.e., outside the plasma sheet, are separately examined. In the high-latitude tail the magnetic field lines

  4. Steady state magnetic field configurations for the earth's magnetotail

    NASA Technical Reports Server (NTRS)

    Hau, L.-N.; Wolf, R. A.; Voigt, G.-H.; Wu, C. C.

    1989-01-01

    A two-dimensional, force-balance magnetic field model is presented. The theoretical existence of a steady state magnetic field configuration that is force-balanced and consistent with slow, lossless, adiabatic, earthward convection within the limit of the ideal MHD is demonstrated. A numerical solution is obtained for a two-dimensional magnetosphere with a rectangular magnetopause and nonflaring tail. The results are consistent with the convection time sequences reported by Erickson (1985).

  5. Magnetic helicity injection for configurations with field errors

    SciTech Connect

    Finn, J.M.; Antonsen T.M. Jr.

    1988-10-01

    The relative magnetic helicity and its rate of injection are computed for several examples of configurations representing magnetic fusion experiments, specifically reversed field pinches (RFP's) with field errors. Field errors, here defined to be normal components of magnetic field at the wall, are believed to have a significant effect on the loop voltage, and therefore the volt-second consumption, in RFP's. The perturbations producing these errors can arise from imbalance of the vertical field, leakage of Ohmic transformer flux, or toroidal field ripple. In the examples given, the relative helicity is the difference between two terms, which are called, respectively, the plasma linkage and the vacuum linkage. The latter quantity, which is zero for the simplified configurations studied previously, represents the linkage between vacuum fluxes occurring within the region of interest. On the other hand, the plasma linkage is the part of the relative helicity directly related to the instantaneous state of the plasma. It is found that the rate of change of the plasma linkage in the presence of poloidal field errors contains a new term proportional to the time rate of change of toroidal flux.

  6. The magnetic field configurations of AM Herculis binaries

    NASA Technical Reports Server (NTRS)

    Wu, Kinwah; Wickramasinghe, Dayal T.

    1993-01-01

    We have considered equilibrium configurations of a white dwarf and a red dwarf companion in AM Herculis type binary system where the red dwarf is assumed to have an intrinsic centered dipole field, and the white dwarf an offset dipole or a centered dipole plus a quadrupole field, and the interaction is purely magnetic. The restoring torque, due to the system being perturbed from its stable equilibrium configuration, is compared with the accretion torque. The results are used to show that the observed alignment of the main cyclotron emission region relative to the red star can be explained quite simply by these models without having to invoke gravitational torques. We also provide a possible explanation of the observation that the more strongly accreting pole has the weaker field strength in the few systems where fields have been determined at both poles.

  7. Hamiltonian description of closed configurations of the vacuum magnetic field

    NASA Astrophysics Data System (ADS)

    Skovoroda, A. A.

    2015-05-01

    Methods of obtaining and using the Hamiltonians of closed vacuum magnetic configurations of fusion research systems are reviewed. Various approaches to calculate the flux functions determining the Hamiltonian are discussed. It is shown that the Hamiltonian description allows one not only to reproduce all traditional results, but also to study the behavior of magnetic field lines by using the theory of dynamic systems. The potentialities of the Hamiltonian formalism and its close relation to traditional methods are demonstrated using a large number of classical examples adopted from the fundamental works by A.I. Morozov, L.S. Solov'ev, and V.D. Shafranov.

  8. Observations of improved confinement in field reversed configurations sustained by antisymmetric rotating magnetic fields

    Microsoft Academic Search

    H. Y. Guo; A. L. Hoffman; L. C. Steinhauer

    2005-01-01

    Rotating magnetic fields (RMF) have been employed to both form and sustain currents in field reversed configurations (FRC). A major concern about this method has been the fear of opening up magnetic field lines with even small ratios of vacuum RMF B? to external confinement field Be. A recently proposed innovation was to use an antisymmetric arrangement of RMF, but

  9. Observations of improved confinement in field reversed configurations sustained by antisymmetric rotating magnetic fields

    Microsoft Academic Search

    H. Y. Guo; A. L. Hoffman; L. C. Steinhauer

    2005-01-01

    Rotating magnetic fields (RMF) have been employed to both form and sustain currents in field reversed configurations (FRC). A major concern about this method has been the fear of opening up magnetic field lines with even small ratios of vacuum RMF Bomega to external confinement field Be. A recently proposed innovation was to use an antisymmetric arrangement of RMF, but

  10. Error-field penetration in reversed magnetic shear configurations

    SciTech Connect

    Wang, H. H.; Wang, Z. X.; Wang, X. Q. [MOE Key Laboratory of Materials Modification by Beams of the Ministry of Education, School of Physics and Optoelectronic Engineering, Dalian University of Technology, Dalian 116024 (China)] [MOE Key Laboratory of Materials Modification by Beams of the Ministry of Education, School of Physics and Optoelectronic Engineering, Dalian University of Technology, Dalian 116024 (China); Wang, X. G. [School of Physics, Peking University, Beijing 100871 (China)] [School of Physics, Peking University, Beijing 100871 (China)

    2013-06-15

    Error-field penetration in reversed magnetic shear (RMS) configurations is numerically investigated by using a two-dimensional resistive magnetohydrodynamic model in slab geometry. To explore different dynamic processes in locked modes, three equilibrium states are adopted. Stable, marginal, and unstable current profiles for double tearing modes are designed by varying the current intensity between two resonant surfaces separated by a certain distance. Further, the dynamic characteristics of locked modes in the three RMS states are identified, and the relevant physics mechanisms are elucidated. The scaling behavior of critical perturbation value with initial plasma velocity is numerically obtained, which obeys previously established relevant analytical theory in the viscoresistive regime.

  11. Field Reversed Configuration Translation and the Magnetized Target Fusion Collaboration

    NASA Astrophysics Data System (ADS)

    Intrator, T. P.; Wurden, G. A.; Sieck, P. E.; Waganaar, W. J.; Dorf, L.; Kostora, M.; Cortez, R. J.; Degnan, J. H.; Ruden, E. L.; Domonkos, M.; Adamson, P.; Grabowski, C.; Gale, D. G.; Kostora, M.; Sommars, W.; Frese, M.; Frese, S.; Camacho, J. F.; Parks, P.; Siemon, R. E.; Awe, T.; Lynn, A. G.; Gribble, R.

    2009-06-01

    After considerable design and construction, we describe the status of a physics exploration of magnetized target fusion (MTF) that will be carried out with the first flux conserving compression of a high pressure field-reversed configuration (FRC). The upgraded Los Alamos (LANL) high density FRC experiment FRXL has demonstrated that an appropriate FRC plasma target can be created and translated on a time scale fast enough to be useful for MTF. Compression to kilovolt temperature is expected to form a Mbar pressure, high energy density laboratory plasma (HEDLP). Integrated hardware on the new Field Reversed Compression and Heating Experiment (FRCHX) at the Air Force Research Laboratory Shiva Star facility, has formed initial FRC's and will radially compress them within a cylindrically symmetric aluminum "liner". FRXL has shown that time scales for FRC translation to the target region are significantly shorter than the typical FRC lifetime. The hardware, diagnostics, and design rationales are presented. Pre-compression plasma formation and trapping experimental data from FRXL and FRCHX are shown.

  12. Magnetic Field Configurations Due to Air Core Coils

    Microsoft Academic Search

    John P. Blewett

    1947-01-01

    The field configurations around a circular loop of wire bearing current are discussed, and a tabulation is presented for the field component parallel to the axis of the loop. Formulae are derived for the current distribution which must obtain in cylindrical and ellipsoidal coils in order that the field inside be uniform. Several special cases are noted. The energy storage

  13. Resonance and Chaotic Trajectories in Magnetic Field Reversed Configuration

    SciTech Connect

    A.S. Landsman; S.A. Cohen; M. Edelman; G.M. Zaslavsky

    2005-04-13

    The nonlinear dynamics of a single ion in a field-reversed configuration (FRC) were investigated. FRC is a toroidal fusion device which uses a specific type of magnetic field to confine ions. As a result of angular invariance, the full three-dimensional Hamiltonian system can be expressed as two coupled, highly nonlinear oscillators. Due to the high nonlinearity in the equations of motion, the behavior of the system is extremely complex, showing different regimes, depending on the values of the conserved canonical angular momentum and the geometry of the fusion vessel. Perturbation theory and averaging were used to derive the unperturbed Hamiltonian and frequencies of the two degrees of freedom. The derived equations were then used to find resonances and compare to Poincar{copyright} surface-of-section plots. A regime was found where the nonlinear resonances were clearly separated by KAM [Kolmogorov-Arnold-Mosher] curves. The structure of the observed island chains was explained. The condition for the destruction of KAM curves and the onset of strong chaos was derived, using Chirikov island overlap criterion, and shown qualitatively to depend both on the canonical angular momentum and geometry of the device. After a brief discussion of the adiabatic regime the paper goes on to explore the degenerate regime that sets in at higher values of angular momenta. In this regime, the unperturbed Hamiltonian can be approximated as two uncoupled linear oscillators. In this case, the system is near-integrable, except in cases of a universal resonance, which results in large island structures, due to the smallness of nonlinear terms, which bound the resonance. The linear force constants, dominant in this regime, were derived and the geometry for a large one-to-one resonance identified. The above analysis showed good agreement with numerical simulations and was able to explain characteristic features of the dynamics.

  14. Spin rectification for collinear and noncollinear magnetization and external magnetic field configurations

    NASA Astrophysics Data System (ADS)

    Huo, Y.; Bai, L. H.; Hyde, P.; Wu, Y. Z.; Hu, C.-M.

    2015-05-01

    Spin rectification in a single crystal Fe/Au/Fe sandwich is electrically detected for collinear and noncollinear magnetization and external magnetic field configurations. The line shape, linewidth, and signal polarity are analyzed. The spin rectification theory has been much extended by taking the magnetocrystalline anisotropy and shape anisotropy into account, which explains noncollinear resonances and agrees very well with experimental data. Thus, a comprehensive understanding of spin rectification in ferromagnetic metal is demonstrated in this work.

  15. The magnetic field and magnetospheric configuration of Uranus

    NASA Technical Reports Server (NTRS)

    Ness, Norman F.; Connerney, John E. P.; Lepping, Ronald P.; Schulz, Michael; Voigt, Gerd-Hannes

    1991-01-01

    A significant and unique planetary magnetic field discovered by Voyager 2 is presented. A large tilt of 58.6 deg of the magnetic-dipole axis from the rotation axis was found. Combined with a large offset of 0.3 RU of the magnetic dipole from the center of the planet, the moment of 0.23 gauss-RU3 leads to field magnitudes at the surface which vary widely between 0.1 and 1.0 gauss. A simple diagram illustrating the offset tilted dipole of Uranus and some field lines is shown. A more exact and accurate spherical-harmonic model of the planetary field, which includes both dipole and quadrupole moments, is derived. There exists a well-developed bipolar magnetic tail on the night side of the planet which rotates daily about the extended planet-sunline with Uranus because of the large obliquity of the Uranian rotation axis.

  16. Effects of magnetic field configuration on thrust performance in a miniature microwave discharge ion thruster

    Microsoft Academic Search

    Naoji Yamamoto; Shinya Kondo; Takayuki Chikaoka; Hideki Nakashima; Hirokazu Masui

    2007-01-01

    The effects of magnetic field configuration on thrust performance in a miniature microwave discharge ion thruster were investigated in order to improve thrust performance. First, the extracted ion beam current was measured for various levels of strength of the magnetic field. It was found that there is an optimum magnitude of the magnetic field. That this is due to the

  17. Equilibrium configuration of the 1u state of hydrogen molecular ion in a magnetic field

    NASA Astrophysics Data System (ADS)

    Song, Xuanyu; Gong, Cheng; Wang, Xiaofeng; Qiao, Haoxue

    2013-08-01

    Using the variational method based on the Gaussian basis set, the authors investigate the 1u state of hydrogen molecular ion in a non-parallel magnetic field with respect to the fixed molecular axis. At sufficiently small field strength, the equilibrium configuration prefers the perpendicular orientation, in which the (relative) orientation ? between the magnetic field and the molecular axis is 90°. With increasing field strength, the orientation ? of the equilibrium configuration decreases, and is neither the parallel orientation nor the perpendicular orientation at field strength between 109 G and 2.35 × 1010 G. Meanwhile, more and more configurations with large orientations become unstable with respect to the dissociation H + p.

  18. Field Reversed Configuration (FRC) Formation Studies with Variable Magnetic Geometry

    NASA Astrophysics Data System (ADS)

    Wurden, G. A.; Intrator, T. P.; Sieck, P. E.; Cortez, R. J.; Waganaar, W. J.

    2008-11-01

    FRX-L has been recently rebuilt with conical theta pinch coils, fast cusp coils, and a translation/capture coils. We report on studies of optimizing the formation of FRC's in the 4 degree conical theta pinch region, while doing parameter scans of the adjacent fast cusp coil B fields, and downstream translation coils. The visible interferometer is configured for 7 chords, and is located at the exit of the theta coil region, for quantitative density information. Filtered visible light fibers provide positional information, while sets of B-dot and flux loop probes yield excluded flux. This work is supported by the Office of Fusion Energy Sciences, and DOE/LANL contract DE- AC52-06NA25396.

  19. Study on Axially Distributed Divertor Magnetic Field Configuration in a Mirror Cell

    SciTech Connect

    Islam, M.K.; Nakashima, Y.; Higashizono, Y.; Katanuma, I.; Cho, T

    2005-01-15

    A mirror magnetic field configuration (MFC) is studied in which a divertor is distributed axially using multipole coils. Both configurations of divertor and minimum-B are obtained in a mirror cell. Magnetohydrodynamic (MHD) instability of a mirror cell can be eliminated in this way. Concept of the design and properties of the MFC are discussed.

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

    SciTech Connect

    Velas, K. M. [William E. Boeing Department of Aeronautics and Astronautics, University of Washington, Box 352250, Seattle, Washington 98195-2250 (United States)] [William E. Boeing Department of Aeronautics and Astronautics, University of Washington, Box 352250, Seattle, Washington 98195-2250 (United States); Milroy, R. D. [Plasma Science and Innovation-Center, William E. Boeing Department of Aeronautics and Astronautics, University of Washington, Box 352250, Seattle, Washington 98195-2250 (United States)] [Plasma Science and Innovation-Center, William E. Boeing Department of Aeronautics and Astronautics, University of Washington, Box 352250, Seattle, Washington 98195-2250 (United States)

    2014-01-15

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-01-01

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

  2. Enhanced Confinement and Stability of a Field-Reversed Configuration with Rotating Magnetic Field Current Drive

    NASA Astrophysics Data System (ADS)

    Slough, J. T.; Miller, K. E.

    2000-08-01

    A new experiment has been constructed to study the sustainment of a field-reversed configuration (FRC) with a rotating magnetic field (RMF). FRCs were formed with cold, unmagnetized ions and thus without a kinetic ion component that was believed to provide stability to internal tilt modes. No destructive instabilities were observed for the RMF FRC. Only peripheral radial penetration of the RMF was observed. The radially inward flow arising from axial screening currents at the FRC edge reduced convective and conductive losses to the measurement limit of the diagnostics.

  3. Passive Superconducting Flux Conservers for Rotating-Magnetic-Field-Driven Field-Reversed Configurations

    SciTech Connect

    Oz, E.; Myers, C. E.; Edwards, M. R.; Berlinger, B.; Brooks, A.; Cohen, S. A.

    2011-01-05

    The Princeton Field-Reversed Configuration (PFRC) experiment employs an odd-parity rotating magnetic field (RMFo) current drive and plasma heating system to form and sustain high-? plasmas. For radial confinement, an array of coaxial, internal, passive, flux-conserving (FC) rings applies magnetic pressure to the plasma while still allowing radio-frequency RMFo from external coils to reach the plasma. The 3 ms pulse duration of the present experiment is limited by the skin time (?fc) of its room-temperature copper FC rings. To explore plasma phenomena with longer characteristic times, the pulse duration of the next-generation PFRC-2 device will exceed 100 ms, necessitating FC rings with (?fc > 300 ms. In this paper we review the physics of internal, discrete, passive FCs and describe the evolution of the PFRC's FC array. We then detail new experiments that have produced higher performance FC rings that contain embedded high-temperature superconducting (HTS) tapes. Several HTS tape winding configurations have been studied and a wide range of extended skin times, from 0.4 s to over 103 s, has been achieved. The new FC rings must carry up to 3 kA of current to balance the expected PFRC-2 plasma pressure, so the dependence of the HTS-FC critical current on the winding configuration and temperature was also studied. From these experiments, the key HTS-FC design considerations have been identified and HTS-FC rings with the desired performance characteristics have been produced.

  4. Flux generation and sustainment of a field reversed configuration with rotating magnetic field current drive

    NASA Astrophysics Data System (ADS)

    Slough, J. T.; Miller, K. E.

    2000-05-01

    A new experimental device has been constructed to study the flux build-up and sustainment of a field reversed configuration (FRC) with a rotating magnetic field (RMF). Even though complete penetration was expected from RMF theory, the RMF field was observed to penetrate only a few centimeters inside the FRC separatrix. Despite the limited penetration, significantly larger toroidal currents (40 kA) were driven than in previous experiments (˜2 kA) with the same RMF field. The high currents and lack of deep penetration allowed the axial field to be the dominant field throughout the FRC. The radially inward pondermotive force arising from axial screening currents at the FRC edge had a significant influence on energy and particle confinement, reducing convective losses to the limit of observability. With only ohmic heating, the measured low ion temperatures (2 eV) left the ions unmagnetized while the electrons (˜40 eV) were well magnetized. No destructive instability was observed for the RMF driven FRC despite the lack of a strong kinetic ion component.

  5. Radial current density effects on rotating magnetic field current drive in field-reversed configurations

    SciTech Connect

    Clemente, R. A.; Gilli, M. [Instituto de Fisica Gleb Wataghin, Universidade Estadual de Campinas, 13083-970 Campinas, SP (Brazil); Farengo, R. [Centro Atomico Bariloche and Instituto Balseiro, San Carlos de Bariloche (8400), RN (Argentina)

    2008-10-15

    Steady state solutions, suitable for field-reversed configurations (FRCs) sustained by rotating magnetic fields (RMFs) are obtained by properly including three-dimensional effects, in the limit of large FRC elongation, and the radial component of Ohm's law. The steady electrostatic potential, necessary to satisfy Ohm's law, is considered to be a surface function. The problem is analyzed at the midplane of the configuration and it is reduced to the solution of two coupled nonlinear differential equations for the real and imaginary parts of the phasor associated to the longitudinal component of the vector potential. Additional constraints are obtained by requesting that the steady radial current density and poloidal magnetic flux vanish at the plasma boundary which is set at the time-averaged separatrix. The results are presented in terms of the degree of synchronism of the electrons with the RMF and compared with those obtained when radial current effects are neglected. Three important differences are observed when compared with the case without radial current density. First, at low penetration of the RMF into the plasma there is a significant increase in the driven azimuthal current. Second, the RMF amplitude necessary to access the high synchronism regime, starting from low synchronism, is larger and the difference appears to increase as the separatrix to classical skin depth ratio increases. Third, the minimum RMF amplitude necessary to sustain almost full synchronism is reduced.

  6. Stochastic Ion Heating in a Field-reversed Configuration Geometry by Rotating Magnetic Fields

    SciTech Connect

    S.A. Cohen, A.S. Landsman, and A.H. Glasser

    2007-06-25

    Ion heating by application of rotating magnetic fields (RMF) to a prolate field-reversed configuration(FRC) is explored by analytical and numerical techniques. For odd-parity RMF (RMFo), perturbation analysis shows ions in figure-8 orbits gain energy at resonances of the RMFo frequency, ?R, with the figure-8 orbital frequency, ?. Since figure-8 orbits tend to gain the most energy from the RMF and are unlikely to escape in the cusp region (where most losses occur), they are optimal candidates for rapid stochastic heating, as compared to cyclotron and betatron orbits. Comparisons are made between heating caused by even- and odd-parity RMFs and between heating in currently operating and in reactor-scale FRC devices.

  7. Power deposition and field penetration in a field-reversed configuration generated by rotating magnetic fields

    NASA Astrophysics Data System (ADS)

    Kuthi, A.; Zwi, H.; Wells, B.; Wong, A. Y.

    1989-07-01

    Power deposition profiles derived from measured equlibrium and field-penetration profiles in the RACETRACK rotating magnetic field drived FRC are presented. It is found, that significantly higher RF power can be deposited in the plasma than what is necessary to maintain the diamagnetic current. The Klima relations are reconciled with the higher power input because the excess power is delivered by waves possessing zero net angular momentum. Only the right-hand rotating component of the RF field penetrates fully, and this results in correct circular polarization of the fields on axis regardless of the imposed polarization by the antennas.

  8. Penetration and radial force balance in field-reversed configuration with large rotating magnetic field

    SciTech Connect

    Ohnishi, M.; Fukuhara, M.; Masaki, T.; Osawa, H.; Chikano, T. [Department of Electrical Engineering and Computer Science, Kansai University, 3-3-35 Yamate-cho, Suita-shi, Osaka 564-8680 (Japan); Hugrass, W. [School of Computing, University of Tasmania, Locked Bag 1359, Launceston, Tasmania 7250 (Australia)

    2008-10-15

    A field-reversed configuration (FRC) is formed by applying a rotating magnetic field (RMF) much larger than the axial magnetic field to a cylindrical glass vacuum chamber filled with 10 Pa argon gas without a preionization. The FRC with the plasma density 2.2x10{sup 19} m{sup -3}, the temperature 8.0 eV, the separatrix length 0.45 m, and the separatrix radius 0.035 m is sustained for the notably long period of 40 ms. It is observed that the antenna current which produces the RMF is reduced by about half after the FRC is formed. The interaction between the plasma and the antenna circuit increases the antenna resistance and changes the inductance of the antenna so that the circuit becomes nonresonant. The RMF is sufficiently large to fully penetrate to the center during the period and drive the current with a rigid rotor profile. The RMF is shown to play a major role in sustaining the plasma pressure.

  9. Ion heating in the field-reversed configuration by rotating magnetic fields near the ion-cyclotron resonance

    PubMed

    Cohen; Glasser

    2000-12-11

    The trajectories of ions confined in a field-reversed configuration (FRC) equilibrium magnetic geometry and heated with a small-amplitude, odd-parity rotating magnetic field (RMF) have been studied with a Hamiltonian computer code. When the RMF frequency is in the ion-cyclotron range, explosive heating occurs. Higher-energy ions are found to have betatron-type orbits, preferentially localized near the FRC's midplane. These results are relevant to a compact magnetic-fusion-reactor design. PMID:11102199

  10. MHD simulations of the flapping instability in tail-like magnetic configurations with guide field

    NASA Astrophysics Data System (ADS)

    Korovinskiy, Daniil; Divin, Andrey; Ivanov, Ivan; Semenov, Vladimir; Erkaev, Nikolay; Artemiev, Anton; Markidis, Stefano; Lapenta, Giovanni; Ivanova, Viktoria; Kubyshkina, Darya

    2014-05-01

    The flapping (kink) mode developing in the magnetotail-like magnetic configuration with tailward growing normal magnetic component and finite guide field is studied by means of linearized 2-dimensional and non-linear 3-dimensional MHD modeling. We consider a particular case of a weak normal magnetic component (that is, small radius of the magnetic field line curvature), which makes the configuration unstable to a special branch of ballooning instability known as "double-gradient" mode, introduced recently to describe the magnetotail flapping oscillations. The initial tail-like equilibrium is provided by conventional Grad-Shafranov equation. The results of the 2D linearized MHD code are in agreement with the analytical predictions, and the growth rate is found to be close to the peak value provided by an analytical estimate. Both 2D and 3D calculations confirm that the double-gradient mode is excited in a region of large curvature of the magnetic field lines. In agreement with the analytical predictions, non-zero guide field reduces the growth rate significantly for large (compare to the current sheet width L) wave numbers k, hence the modes kL ~ 1 are the fastest growing. Thus, the non-zero guide field introduces a characteristic wavelength corresponding to the dispersion curve peak. For the guide field of ~ 0.5 (in the lobe magnetic field units), the mode decays totally.

  11. Formation of a field reversed configuration for magnetic and electrostatic confinement of plasma

    DOEpatents

    Rostoker, Norman; Binderbauer, Michl; Qerushi, Artan; Tahsiri, Hooshang

    2007-02-20

    A system and method for containing plasma and forming a Field Reversed Configuration (FRC) magnetic topology are described in which plasma ions are contained magnetically in stable, non-adiabatic orbits in the FRC. Further, the electrons are contained electrostatically in a deep energy well, created by tuning an externally applied magnetic field. The simultaneous electrostatic confinement of electrons and magnetic confinement of ions avoids anomalous transport and facilitates classical containment of both electrons and ions. In this configuration, ions and electrons may have adequate density and temperature so that upon collisions they are fused together by nuclear force, thus releasing fusion energy. Moreover, the fusion fuel plasmas that can be used with the present confinement system and method are not limited to neutronic fuels only, but also advantageously include advanced fuels.

  12. Formation of a field reversed configuration for magnetic and electrostatic confinement of plasma

    DOEpatents

    Rostoker, Norman; Binderbauer, Michl; Qerushi, Artan; Tahsiri, Hooshang

    2006-02-07

    A system and method for containing plasma and forming a Field Reversed Configuration (FRC) magnetic topology are described in which plasma ions are contained magnetically in stable, non-adiabatic orbits in the FRC. Further, the electrons are contained electrostatically in a deep energy well, created by tuning an externally applied magnetic field. The simultaneous electrostatic confinement of electrons and magnetic confinement of ions avoids anomalous transport and facilitates classical containment of both electrons and ions. In this configuration, ions and electrons may have adequate density and temperature so that upon collisions they are fused together by nuclear force, thus releasing fusion energy. Moreover, the fusion fuel plasmas that can be used with the present confinement system and method are not limited to neutronic fuels only, but also advantageously include advanced fuels.

  13. Applied magnetic field design for the field reversed configuration compression heating experiment.

    PubMed

    Domonkos, M T; Amdahl, D; Camacho, J F; Coffey, S K; Degnan, J H; Delaney, R; Frese, M; Gale, D; Grabowski, T C; Gribble, R; Intrator, T P; McCullough, J; Montano, N; Robinson, P R; Wurden, G

    2013-04-01

    Detailed calculations of the formation, guide, and mirror applied magnetic fields in the FRC compression-heating experiment (FRCHX) were conducted using a commercially available generalized finite element solver, COMSOL Multiphysics(®). In FRCHX, an applied magnetic field forms, translates, and finally captures the FRC in the liner region sufficiently long to enable compression. Large single turn coils generate the fast magnetic fields necessary for FRC formation. Solenoidal coils produce the magnetic field for translation and capture of the FRC prior to liner implosion. Due to the limited FRC lifetime, liner implosion is initiated before the FRC is injected, and the magnetic flux that diffuses into the liner is compressed. Two-dimensional axisymmetric magnetohydrodynamic simulations using MACH2 were used to specify optimal magnetic field characteristics, and this paper describes the simulations conducted to design magnetic field coils and compression hardware for FRCHX. This paper presents the vacuum solution for the magnetic field. PMID:23635196

  14. Particle Diffusion in Chaotic Magnetic Fields Generated by Asymmetric Current Configurations

    NASA Astrophysics Data System (ADS)

    Ram, A. K.; Dasgupta, B.

    2008-12-01

    The observed cross-field diffusion of charged particles in cosmic rays is assumed to be due to the chaotic nature of the interplanetary/intergalactic magnetic fields. Among the classic works on this subject have been those of Parker [1] and Jokipii [2]. Parker considered the passage of cosmic ray particles and energetic solar particles in a large scale magnetic field containing small scale irregularities. In the context of cosmic ray propagation, Jokipii considered a small fluctuating component, added on to a uniform magnetic field, to study the spatial transport of particles. In these studies the irregular component of the magnetic field is prescribed in an ad hoc fashion. In contrast, we consider asymmetric, nonlinear, steady-state magnetic fields, in three spatial dimensions, generated by currents flowing in circular loops and straight lines [3]. These magnetic fields are completely deterministic and, for certain range of parameters, chaotic. We will present analytical and numerical studies on the spatial characteristics of these fields. The motion of charged particles in the nonlinear and chaotic magnetic fields is determined using the Lorentz equation. A particle moving in a deterministic chaotic magnetic field superposed on a uniform background magnetic field is found to undergo spatial transport. This shows that chaotic magnetic fields generated by simple current configurations can produce cross-field diffusion. A detailed analysis of particle motion and diffusion along with application to space plasmas will be presented. [1] E.N. Parker, Planet. Space Sci. 13, 9 (1965). [2] J.R. Jokipii, Astrophys. J. 146, 480 (1966), and J.R. Jokipii, Astrophys. J. 149, 405 (1967). [3] A.K. Ram and B. Dasgupta, Eos Trans. AGU 87 (52), Fall Meet. Suppl. Abstract NG31B-1593 (2006); and Eos Trans. AGU 88 (52), Fall Meet. Suppl. Abstract NG21B-0522 (2007).

  15. Equilibrium configurations of Vlasov plasmas carrying a current component along an external magnetic field.

    NASA Technical Reports Server (NTRS)

    Kan, J. R.

    1972-01-01

    A model of equilibrium configurations of Vlasov plasmas is considered which represents a combination of the models of Harris (1962) and Nicholson (1963). These plasma configurations carry a current component along an external magnetic field. The considered slab model contains a diamagnetic current and a field-aligned current for an arbitrary ratio of particle pressure to magnetic pressure of the applied constant field. For a fixed pressure ratio and field-aligned current, the model admits a family of equilibrium solutions in which the diamagnetic currents range from zero to a maximum value. The amount of diamagnetic current flowing in a machine depends on the width of the machine, the field-aligned current and other plasma parameters.

  16. Thermally induced magnetization switching in Fe/MnAs/GaAs(001): selectable magnetic configurations by temperature and field control

    PubMed Central

    Spezzani, Carlo; Vidal, Franck; Delaunay, Renaud; Eddrief, Mahmoud; Marangolo, Massimiliano; Etgens, Victor H.; Popescu, Horia; Sacchi, Maurizio

    2015-01-01

    Spintronic devices currently rely on magnetization control by external magnetic fields or spin-polarized currents. Developing temperature-driven magnetization control has potential for achieving enhanced device functionalities. Recently, there has been much interest in thermally induced magnetisation switching (TIMS), where the temperature control of intrinsic material properties drives a deterministic switching without applying external fields. TIMS, mainly investigated in rare-earth–transition-metal ferrimagnets, has also been observed in epitaxial Fe/MnAs/GaAs(001), where it stems from a completely different physical mechanism. In Fe/MnAs temperature actually modifies the surface dipolar fields associated with the MnAs magnetic microstructure. This in turn determines the effective magnetic field acting on the Fe overlayer. In this way one can reverse the Fe magnetization direction by performing thermal cycles at ambient temperatures. Here we use element selective magnetization measurements to demonstrate that various magnetic configurations of the Fe/MnAs/GaAs(001) system are stabilized predictably by acting on the thermal cycle parameters and on the presence of a bias field. We show in particular that the maximum temperature reached during the cycle affects the final magnetic configuration. Our findings show that applications are possible for fast magnetization switching, where local temperature changes are induced by laser excitations. PMID:25631753

  17. Thermally induced magnetization switching in Fe/MnAs/GaAs(001): selectable magnetic configurations by temperature and field control.

    PubMed

    Spezzani, Carlo; Vidal, Franck; Delaunay, Renaud; Eddrief, Mahmoud; Marangolo, Massimiliano; Etgens, Victor H; Popescu, Horia; Sacchi, Maurizio

    2015-01-01

    Spintronic devices currently rely on magnetization control by external magnetic fields or spin-polarized currents. Developing temperature-driven magnetization control has potential for achieving enhanced device functionalities. Recently, there has been much interest in thermally induced magnetisation switching (TIMS), where the temperature control of intrinsic material properties drives a deterministic switching without applying external fields. TIMS, mainly investigated in rare-earth-transition-metal ferrimagnets, has also been observed in epitaxial Fe/MnAs/GaAs(001), where it stems from a completely different physical mechanism. In Fe/MnAs temperature actually modifies the surface dipolar fields associated with the MnAs magnetic microstructure. This in turn determines the effective magnetic field acting on the Fe overlayer. In this way one can reverse the Fe magnetization direction by performing thermal cycles at ambient temperatures. Here we use element selective magnetization measurements to demonstrate that various magnetic configurations of the Fe/MnAs/GaAs(001) system are stabilized predictably by acting on the thermal cycle parameters and on the presence of a bias field. We show in particular that the maximum temperature reached during the cycle affects the final magnetic configuration. Our findings show that applications are possible for fast magnetization switching, where local temperature changes are induced by laser excitations. PMID:25631753

  18. Radial expansion of an ideal MHD configuration and the temporal development of the magnetic field. [in magnetic cloud velocity profiles

    NASA Technical Reports Server (NTRS)

    Farrugia, C. J.; Osherovich, V. A.; Burlaga, L. F.; Lepping, R. P.; Freeman, M. P.

    1992-01-01

    We study the free radial expansion of a 3-component magnetic configuration. The emphasis of this paper is on the behavior of a field undergoing non-self-similar expansion. Comparing our results with the evolution of a magnetic configuration expanding self-similarly, we find that self-similar expansion appears as the asymptotic limit (with time) of the general case. Using a model field we show that a non-self-similar velocity profile need not have a strict monotonic decrease with time.

  19. Magnetic field effects on the optical properties of superlattices in the Voigt configuration

    NASA Astrophysics Data System (ADS)

    García-Serrano, R.; Martínez, G.; Hernández, P. H.; Cocoletzi, Gregorio H.

    2004-01-01

    Optical responses of magnetoplasmons in superlattices are investigated accounting for an external magnetic B0 field in the Voigt configuration. Two-layer period superlattices are considered to study magnetoplasma normal modes in the infinite superlattice and the optical response Rp when p-polarized light is incident onto the truncated system. The dispersion relation and reflectivity curves display minibands and minigaps of bulk magnetoplasmons. The resonances of both Bloch wave vector and Rp experience a blue shift when the magnetic field strength increases. Comparisons with the structures obtained in the perpendicular and Faraday geometries show that the perpendicular case yields the most important effects.

  20. Flux generation and sustainment of a field reversed configuration with rotating magnetic field current drive*

    E-print Network

    Washington at Seattle, University of

    simplest, most compact, and high- est power density of all currently studied magnetic fusion confinement of Physics. S1070-664X 00 96305-5 I. INTRODUCTION Fusion research in recent years has focused on the toka, expensive reactor designs. This dictates exploring novel, simpler and less costly configurations. A leading

  1. Non-thermal Plasmas Around Massive Black Holes: Collective Modes, Ring Configurations and Magnetic Field Generation

    NASA Astrophysics Data System (ADS)

    Coppi, B.

    2013-10-01

    The discovered gamma-ray bubbles emanating from the center of Our Galaxy are a new motivation to develop theories for large scale structures in the Universe in terms of plasmas for which electromagnetic interactions are no less important than the relevant (e.g. density wave theory of spirals) gravitational interactions. Moreover, considering the observed emission spectra, the particle distributions in phase space cannot be represented by isotropic Maxwellian in significant cases. The consequent theory of plasmas surrounding rotating massive black holes has led to identify new stationary plasma and field configurations (in particular Solitary Rings) and modes, emerging from conventional (currentless) disks, that depend on the existence of temperature anisotropies. These modes, which produce outward transport of angular momentum at a significant rate, involve large amplifications of a seed magnetic field. In the related (by the envisioned non-linear mode evolution) stationary configurations, without a seed magnetic field, the field energy densities are of the order of the particle thermal energy densities. Thus a clear sequence of processes for the generation of magnetic fields in the Universe is identified. The discovered gamma-ray bubbles emanating from the center of Our Galaxy are a new motivation to develop theories for large scale structures in the Universe in terms of plasmas for which electromagnetic interactions are no less important than the relevant (e.g. density wave theory of spirals) gravitational interactions. Moreover, considering the observed emission spectra, the particle distributions in phase space cannot be represented by isotropic Maxwellian in significant cases. The consequent theory of plasmas surrounding rotating massive black holes has led to identify new stationary plasma and field configurations (in particular Solitary Rings) and modes, emerging from conventional (currentless) disks, that depend on the existence of temperature anisotropies. These modes, which produce outward transport of angular momentum at a significant rate, involve large amplifications of a seed magnetic field. In the related (by the envisioned non-linear mode evolution) stationary configurations, without a seed magnetic field, the field energy densities are of the order of the particle thermal energy densities. Thus a clear sequence of processes for the generation of magnetic fields in the Universe is identified. US DOE partly sponsored.

  2. H3+ molecular ion in a magnetic field: Linear parallel configuration

    NASA Astrophysics Data System (ADS)

    Turbiner, A. V.; Guevara, N. L.; López Vieyra, J. C.

    2007-05-01

    A detailed study of the ground state of the H3+ molecular ion in linear configuration, parallel to the magnetic field direction, and its low-lying ? , ? , and ? states is carried out for magnetic fields B=0-4.414×1013G in the Born-Oppenheimer approximation. The variational method is employed with a single trial function which includes electronic correlation in the form exp(?r12) , where ? is a variational parameter. It is shown that the quantum numbers of the state of the lowest total energy (ground state) depend on the magnetic field strength. The ground state evolves from the spin-singlet ?g1 state for weak magnetic fields B?5×108G to a weakly bound spin-triplet ?u3 state for intermediate fields and, eventually, to a spin-triplet ?u3 state for 5×1010?B?4.414×1013G . Local stability of the linear parallel configuration with respect to possible small deviations is checked.

  3. Inductrack magnet configuration

    DOEpatents

    Post, Richard Freeman

    2003-10-14

    A magnet configuration comprising a pair of Halbach arrays magnetically and structurally connected together are positioned with respect to each other so that a first component of their fields substantially cancels at a first plane between them, and a second component of their fields substantially adds at this first plane. A track of windings is located between the pair of Halbach arrays and a propulsion mechanism is provided for moving the pair of Halbach arrays along the track. When the pair of Halbach arrays move along the track and the track is not located at the first plane, a current is induced in the windings and a restoring force is exerted on the pair of Halbach arrays.

  4. Inductrack magnet configuration

    DOEpatents

    Post, Richard Freeman

    2003-12-16

    A magnet configuration comprising a pair of Halbach arrays magnetically and structurally connected together are positioned with respect to each other so that a first component of their fields substantially cancels at a first plane between them, and a second component of their fields substantially adds at this first plane. A track of windings is located between the pair of Halbach arrays and a propulsion mechanism is provided for moving the pair of Halbach arrays along the track. When the pair of Halbach arrays move along the track and the track is not located at the first plane, a current is induced in the windings and a restoring force is exerted on the pair of Halbach arrays.

  5. Asymmetric configurations of a thin current sheet with a constant normal magnetic field component

    SciTech Connect

    Mingalev, O. V.; Mingalev, I. V. [Russian Academy of Sciences, Polar Geophysics Institute, Kola Scientific Center (Russian Federation); Malova, Kh. V. [Moscow State University, Skobeltsyn Institute of Nuclear Physics (Russian Federation); Zelenyi, L. M.; Artem'ev, A. V. [Russian Academy of Sciences, Space Research Institute (Russian Federation)

    2009-01-15

    A possible mechanism for the formation of a quasi-equilibrium asymmetric current sheet in the magnetospheric tail due to the asymmetry of peripheral plasma sources is analyzed using a self-consistent particle- in-cell model of a thin collisionless current sheet with a constant normal magnetic field component. For the case in which the current sheet is produced by only one source, quasi-equilibrium sheet configurations with maximum possible asymmetry are obtained for different input parameters of the model. In such configurations, the equilibrium force balance is satisfied with high accuracy and the shape of the current density profile remains nearly symmetric, but the current sheet itself is slightly shifted from the source as compared to the symmetric case. The configurations obtained using numerical simulations are compared with those calculated using the previous analytical model of a thin current sheet. It is found that the results provided by these models agree well both qualitatively and quantitatively.

  6. Magnetic Field Configuration Models and Reconstruction Methods for Interplanetary Coronal Mass Ejections

    E-print Network

    Al-Haddad, N; Savani, N P; Möstl, C; Marubashi, K; Hidalgo, M; Roussev, I I; Poedts, S; Farrugia, C J

    2012-01-01

    This study aims to provide a reference to different magnetic field models and reconstruction methods for interplanetary coronal mass ejections (ICMEs). In order to understand the differences in the outputs of those models and codes, we analyze 59 events from the Coordinated Data Analysis Workshop (CDAW) list, using four different magnetic field models and reconstruction techniques; force-free fitting (Goldstein,1983,Burlaga,1988,Lepping et al.,1990), magnetostatic reconstruction using a numerical solution to the Grad-Shafranov equation (Hu and Sonnerup, 2001), fitting to a self-similarly expanding cylindrical configuration (Marubashi and Lepping, 2007) and elliptical, non-force free fitting (Hidalgo,2003). The resulting parameters of the reconstructions for the 59 events are compared statistically, as well as in selected case studies. The ability of a method to fit or reconstruct an event is found to vary greatly: the Grad-Shafranov reconstruction is successful for most magnetic clouds (MCs) but for less than...

  7. Plasma-dominated magnetic field configurations for the magnetosphere of Uranus

    NASA Technical Reports Server (NTRS)

    Ip, A. K.; Voigt, G.-H.

    1985-01-01

    There is significant indirect evidence that the planet Uranus possesses a magnetic field. This evidence is based on the observation of hydrogen Lyman alpha emission from Uranus with the aid of the International Ultraviolet Explorer (IUE) spacecraft. The detection of water ice on the Uranian moons led Cheng (1984) to suggest that charged particle sputtering of the icy satellites could provide a significant internal source of oxygen ions and protons to the Uranian magnetosphere. Cheng concluded that this mechanism would predict aurorae around both magnetic poles of Uranus. Cheng's idea of the presence of a continuous internal plasma supply to the Uranian magnetosphere is further pursued in the present investigation. Questions are considered regarding the evolution of Uranus' magnetosphere from a vacuum configuration toward a plasma pressure dominated equilibrium configuration, taking into account the amount of the thermal plasma pressure as a free parameter.

  8. Effect of magnetic field configuration on the multiply charged ion and plume characteristics in Hall thruster plasmas

    NASA Astrophysics Data System (ADS)

    Kim, Holak; Lim, Youbong; Choe, Wonho; Park, Sanghoo; Seon, Jongho

    2015-04-01

    Multiply charged ions and plume characteristics in Hall thruster plasmas are investigated with regard to magnetic field configuration. Differences in the plume shape and the fraction of ions with different charge states are demonstrated by the counter-current and co-current magnetic field configurations, respectively. The significantly larger number of multiply charged and higher charge state ions including Xe4+ are observed in the co-current configuration than in the counter-current configuration. The large fraction of multiply charged ions and high ion currents in this experiment may be related to the strong electron confinement, which is due to the strong magnetic mirror effect in the co-current magnetic field configuration.

  9. Ion and electron cyclotron wall conditioning in stellarator and tokamak magnetic field configuration on WEGA

    SciTech Connect

    Wauters, T.; Louche, F. [Association Euratom-Belgian State, LPP-ERM/KMS, 1000 Brussels (Belgium); Laqua, H. P.; Otte, M.; Preynas, M.; Stange, T.; Altenburg, Y.; Aßmus, D.; Birus, D. [Max Planck Institute for Plasma Physics, EURATOM Association, 17491 Greifswald (Germany); Urlings, P. [Max Planck Institute for Plasma Physics, EURATOM Association, 17491 Greifswald, Germany and University of Technology, Department of Applied Physics, Eindhoven (Netherlands)

    2014-02-12

    Discharge wall conditioning is an effective tool to improve plasma performance in tokamaks and stellarators. RF Discharge Conditioning (RFDC) techniques are envisaged for use during operational campaigns on superconducting devices like the ITER tokamak and W7-X stellarator, as alternative to DC Glow Discharge Conditioning which is inefficient in presence of magnetic fields. This contribution investigates RFDC in both the ion and electron cyclotron range of frequencies (ICRF and ECRF) on the WEGA device (Max-Planck-Institute for Plasma Physics, Greifswald, Germany) as preparation for W7-X operation. ECRF discharges produced by localised absorption of RF power at EC resonance layers suffer from poor radial discharge homogeneity in the tokamak vacuum magnetic field configuration, severely limiting the plasma wetted wall areas and consequently the conditioning efficiency. The non-localised production of ICRF discharges by collisional RF power absorption features much improved discharge homogeneity making Ion Cyclotron Wall Conditioning (ICWC) the favoured RFDC technique for superconducting tokamaks. RFDC with the stellarator vacuum magnetic field needs to aim at sufficient plasma densities at and outside the last closed flux surface (LCFS), maximising the convective plasma flux along the open field lines to the wall. Whereas for ICRF discharges this condition is easily fulfilled, on WEGA for He-ECRF discharges this could be achieved as well by off axis heating close to the LCFS. In stellarator magnetic field configuration it is found that He-ICWC for wall desaturation is at least one order of magnitude more efficient than He-ECWC. Novel ECWC methods are proposed that can decrease this efficiency gap with ICWC to a factor 2-3. The efficiency difference is less pronounced in case of H{sub 2}-ICWC and ECWC for isotopic exchange.

  10. Kinetic description of quasi-stationary axisymmetric collisionless accretion disk plasmas with arbitrary magnetic field configurations

    NASA Astrophysics Data System (ADS)

    Cremaschini, Claudio; Miller, John C.; Tessarotto, Massimo

    2011-06-01

    A kinetic treatment is developed for collisionless magnetized plasmas occurring in high-temperature, low-density astrophysical accretion disks, such as are thought to be present in some radiatively inefficient accretion flows onto black holes. Quasi-stationary configurations are investigated, within the framework of a Vlasov-Maxwell description. The plasma is taken to be axisymmetric and subject to the action of slowly time-varying gravitational and electromagnetic fields. The magnetic field is assumed to be characterized by a family of locally nested but open magnetic surfaces. The slow collisionless dynamics of these plasmas is investigated, yielding a reduced gyrokinetic Vlasov equation for the kinetic distribution function. For doing this, an asymptotic quasi-stationary solution is first determined, represented by a generalized bi-Maxwellian distribution expressed in terms of the relevant adiabatic invariants. The existence of the solution is shown to depend on having suitable kinetic constraints and conditions leading to particle trapping phenomena. With this solution, one can treat temperature anisotropy, toroidal and poloidal flow velocities, and finite Larmor-radius effects. An asymptotic expansion for the distribution function permits analytic evaluation of all the relevant fluid fields. Basic theoretical features of the solution and their astrophysical implications are discussed. As an application, the possibility of describing the dynamics of slowly time-varying accretion flows and the self-generation of magnetic field by means of a ``kinetic dynamo effect'' are discussed. Both effects are shown to be related to intrinsically kinetic physical mechanisms.

  11. Kinetic description of quasi-stationary axisymmetric collisionless accretion disk plasmas with arbitrary magnetic field configurations

    SciTech Connect

    Cremaschini, Claudio [International School for Advanced Studies (SISSA), Trieste 34136 (Italy); Miller, John C. [International School for Advanced Studies (SISSA) and INFN, Trieste 34136, Italy and Department of Physics (Astrophysics), University of Oxford, Oxford OX1 3RH (United Kingdom); Tessarotto, Massimo [Department of Mathematics and Informatics, University of Trieste, Trieste 34127 (Italy)

    2011-06-15

    A kinetic treatment is developed for collisionless magnetized plasmas occurring in high-temperature, low-density astrophysical accretion disks, such as are thought to be present in some radiatively inefficient accretion flows onto black holes. Quasi-stationary configurations are investigated, within the framework of a Vlasov-Maxwell description. The plasma is taken to be axisymmetric and subject to the action of slowly time-varying gravitational and electromagnetic fields. The magnetic field is assumed to be characterized by a family of locally nested but open magnetic surfaces. The slow collisionless dynamics of these plasmas is investigated, yielding a reduced gyrokinetic Vlasov equation for the kinetic distribution function. For doing this, an asymptotic quasi-stationary solution is first determined, represented by a generalized bi-Maxwellian distribution expressed in terms of the relevant adiabatic invariants. The existence of the solution is shown to depend on having suitable kinetic constraints and conditions leading to particle trapping phenomena. With this solution, one can treat temperature anisotropy, toroidal and poloidal flow velocities, and finite Larmor-radius effects. An asymptotic expansion for the distribution function permits analytic evaluation of all the relevant fluid fields. Basic theoretical features of the solution and their astrophysical implications are discussed. As an application, the possibility of describing the dynamics of slowly time-varying accretion flows and the self-generation of magnetic field by means of a ''kinetic dynamo effect'' are discussed. Both effects are shown to be related to intrinsically kinetic physical mechanisms.

  12. Translation and Capture of High-Density Field Reversed Configurations for Magnetized Target Fusion

    NASA Astrophysics Data System (ADS)

    Sieck, P. E.; Intrator, T. P.; Wurden, G. A.; Waganaar, W. J.; Cortez, R. J.; Oberto, R. J.

    2009-11-01

    A physics demonstration of Magnetized Target Fusion (MTF) is being pursued by a collaborative team from Los Alamos National Laboratory and Air Force Research Laboratory. The LANL facility, known as the Field Reversed eXperiment --- Liner (FRX-L), focuses on the physics of producing high-density Field Reversed Configurations (FRCs), translating them, and capturing them in a static flux conserver. Observations of FRCs in translation and capture will be presented. The data suggest FRCs are formed at density above 10^22/m^3, translate over the one meter chamber at 97 km/s, and a captured portion having radius 4 cm lives for 10?s. The repeatability of FRC capture will be discussed in context of that necessary for MTF. This work is supported by the Office of Fusion Energy Sciences, and DOE/LANL contract DE-AC52-06NA25396.

  13. Comparison of Ar electron-cyclotron-resonance plasmas in three magnetic field configurations. I. Electron temperature and plasma density

    SciTech Connect

    Junck, K.L. (Department of Nuclear Engineering, University of Michigan, Ann Arbor, Michigan 48109 (United States)); Getty, W.D. (Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan 48109 (United States))

    1994-09-01

    Optical emission spectroscopy, Langmuir probe, and microwave interferometry measurements have been used to characterize the electron temperature and plasma density of electron-cyclotron-resonance (ECR) heated Ar plasmas in a magnetic-mirror plasma tool. The magnetic field was operated in a symmetric mirror, asymmetric mirror, and minimum-B configuration. The dependency of the plasma parameters upon microwave power, pressure, and magnetic field configuration have been examined. Plasma densities up to 2[times]10[sup 12] cm[sup [minus]3] at the midplane and 5[times]10[sup 12] cm[sup [minus]3] at the ECR zone for a symmetric mirror configuration of the magnetic field have been measured. Operation of the minimum-B magnetic field configuration was found to increase the plasma stability with comparable plasma density while an asymmetric mirror magnetic field configuration, similar to other devices recently studied, yielded densities in the 2--8[times]10[sup 11] cm[sup [minus]3] range. Radial uniformity was found to be [plus minus]25% over the 4 cm radius of the microwave window.

  14. Field-dependent spin chirality and frustration in V and Cu nanomagnets in transverse magnetic field. 2. Spin configurations, chirality and intermediate spin magnetization in distorted trimers

    NASA Astrophysics Data System (ADS)

    Belinsky, Moisey I.

    2014-05-01

    Correlated spin configurations, magnetizations, frustration, vector ? and scalar ?¯ chiralities are considered for distorted V, /Cu/ anisotropic DM nanomagnets in transverse Bx?X and longitudinal B?Z fields. Different planar configurations in the ground and excited states of distorted nanomagnets in Bx determine different field behavior of the vector chiralities and the degenerate frustration in these states correlated with the M?˜12±(Bx) intermediate spin (IS) magnetization which describes the S12 characteristics, ?=0. Distortion results in the reduced ?<1 chirality in the ground distorted configuration and in the maximum ?z=±1 in the excited states with the planar 120° configurations at avoided level crossing. In B?Z, distorted longitudinal spin-collinear configurations are characterized by the reduced degenerate frustration, out-of-plane staggered and IS M?˜12±(Bz) magnetizations, and in-plane toroidal moments, correlated with the ?, ?¯ chiralities, ?¯=±|?|. The chiralities and IS magnetization in EPR, INS and NMR spectra are considered. The quantitative correlations describe variable spin chirality, frustration and field manipulation of chiralities in nanomagnets.

  15. Magnetoreflectance of films with corrugated surfaces, with magnetic fields applied in the perpendicular configuration

    NASA Astrophysics Data System (ADS)

    Jacobo-Escobar, J. H.; Martínez, G.; Cocoletzi, Gregorio H.

    1999-03-01

    The effects of external magnetic 0953-8984/11/8/009/img1-fields on the scattering of p-polarized light from metallic films with corrugated surfaces are investigated, with 0953-8984/11/8/009/img1 along the growth axis (in the perpendicular configuration). The Rayleigh-Fano and transfer-matrix approaches are applied to obtain 0953-8984/11/8/009/img3 for the scattered fields, with the specular magnetoreflection 0953-8984/11/8/009/img4 displaying minima due to the coupling of the incident light with the surface magnetoplasmons at frequencies in the range 0953-8984/11/8/009/img5, where 0953-8984/11/8/009/img6 and 0953-8984/11/8/009/img7 are the cyclotron and hybrid frequencies, respectively, with the gap of the splitting decreasing as the magnetic field strength increases. The presence of a metallic superlattice inhibits the gap between the minima of the surface magnetoplasmon polaritons. In addition, a pseudosurface magnetoplasmon polariton is manifested for both geometries for 0953-8984/11/8/009/img8.

  16. Global Perturbation Configurations in a Composite Disc System with an Isopedic Magnetic Field

    E-print Network

    Y. -Q. Lou; Y. Wu

    2005-08-28

    We construct stationary global configurations of both aligned and unaligned logarithmic spiral perturbations in a composite disc system of stellar and isopedically magnetized gaseous singular isothermal discs (SIDs) coupled by gravity. The thin gaseous SID is threaded across by a vertical magnetic field B_z with a constant ratio of the surface gas mass density to B_z. There exist two classes of stationary magnetohydrodynamic (MHD) solutions with in-phase and out-of-phase density perturbations. For both aligned and unaligned cases with azimuthal periodicities |m|\\geq 2 (m is an integer), there may be two, one, and no solution situations, depending on the chosen parameters. For the transition criteria from an axisymmetric equilibrium to aligned secular bar-like instabilities, the corresponding T/|W| ratio can be much lower than the oft-quoted value of T/|W|\\sim 0.14, where T is the total rotational kinetic energy and W is the total gravitational potential energy plus the magnetic energy. The T/|W| ratios for the two sets of solutions in different ranges are separated by m/(4m+4). For the unaligned cases, we study marginal stabilities for axisymmetric (m=0) and non-axisymmetric (m\

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

    SciTech Connect

    Deards, C. L. [Lockheed Martin, 1011 Lockheed Way, Palmdale, California 93599 (United States); Hoffman, A. L.; Steinhauer, L. C. [Redmond Plasma Physics Laboratory, University of Washington, 14700 NE 95th Street, Suite 100, Redmond, Washington 98052 (United States)

    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.

  18. Enhanced absorption Hanle effect in the configuration of crossed laser beam and magnetic field F. Renzoni,1,

    E-print Network

    -field-created Zeeman coherences. The Hanle effect investigations of Refs. 11,12 were based on a linearly polarizedEnhanced absorption Hanle effect in the configuration of crossed laser beam and magnetic field F 2001 We have analyzed the Hanle effect on the closed Fg 3Fe 4 D2-line transition of 85 Rb. Exciting

  19. Three-Dimensional MHD Simulation of FTEs Produced by Merging at an Isolated Point in a Sheared Magnetic Field Configuration

    NASA Technical Reports Server (NTRS)

    Santos, J. C.; Sibeck, D. G.; Buchner, J.; Gonzalez, W. D.; Ferreira, J. L.

    2014-01-01

    We present predictions for the evolution of FTEs generated by localized bursts of reconnection on a planar magnetopause that separates a magnetosheath region of high densities and weak magnetic field from a magnetospheric region of low densities and strong magnetic field. The magnetic fields present a shear angle of 105 degrees. Reconnection forms a pair of FTEs each crossing the magnetopause in the field reversal region and bulging into the magnetosphere and magnetosheath. At their initial stage they can be characterized as flux tubes since the newly reconnected magnetic field lines are not twisted. Reconnection launches Alfvenic perturbations that propagate along the FTEs generating high-speed jets, which move the pair of FTEs in opposite directions. As the FTE moves, it displaces the ambient magnetic field and plasma producing bipolar magnetic field and plasma velocity signatures normal to the nominal magnetopause in the regions surrounding the FTE. The combination of the ambient plasma with the FTE flows generates a vortical velocity pattern around the reconnected field lines. During its evolution the FTE evolves to a flux rope configuration due to the twist of the magnetic field lines. The alfvenic perturbations propagate faster along the part of the FTE bulging into the magnetosphere than in the magnetosheath, and due to the differences between the plasma and magnetic field properties the perturbations have slightly different signatures in the two regions. As a consequence, the FTEs have different signatures depending on whether the satellite encounters the part bulging into the magnetosphere or into the magnetosheath.

  20. A Configurable Component-Based Software System for Magnetic Field Measurements

    Microsoft Academic Search

    J. M. Nogiec; J. DiMarco; S. Kotelnikov; K. Trombly-Freytag; D. Walbridge; M. Tartaglia

    2006-01-01

    A new software system to test accelerator magnets has been developed at Fermilab. The magnetic measurement technique involved employs a single stretched wire to measure alignment parameters and magnetic field strength. The software for the system is built on top of a flexible component-based framework, which allows for easy reconfiguration and runtime modification. Various user interface, data acquisition, analysis, and

  1. Flux buildup in field reversed configurations using rotating magnetic fields Alan L. Hoffman

    E-print Network

    Washington at Seattle, University of

    , neither the ions nor electrons are tied to the rotating field lines. Rather, an effective azimuthal University of Washington, Redmond Plasma Physics Laboratory, Seattle, Washington 98195 Received 14 August with the plasma currents and particle orbits produced in one-dimensional cylinders with the rotating field

  2. The TITAN magnet configuration

    SciTech Connect

    Bathke, C.G.

    1987-01-01

    The TITAN study uses copper-alloy ohmic-heating coils (OHC) to startup inductively a reversed-field-pinch (RFP) fusion reactor. The plasma equilibrium is maintained with a pair of superconducting equilibrium-field coils (EFCs). A second pair of copper EFCs provides the necessary trimming of the equilibrium field during plasma transients. A compact toroidal-field-coil (TFC) set is provided by an integrated blanket/coil (IBC). The IBC concept also is applied to the toroidal-field divertor coils. Steady-state operation is achieved with oscillating-field current drive, which oscillates at low amplitude and frequency the OHCs, EFCs, the TFCs, and divertor coils about their steady-state currents. An integrated magnet design, which uses low-field, low technology coils, and the related design basis is given. 18 refs.

  3. On the Role of Global Magnetic Field Configuration in Affecting Ring Current Dynamics

    NASA Technical Reports Server (NTRS)

    Zheng, Y.; Zaharia, S. G.; Fok, M. H.

    2010-01-01

    Plasma and field interaction is one important aspect of inner magnetospheric physics. The magnetic field controls particle motion through gradient, curvature drifts and E cross B drift. In this presentation, we show how the global magnetic field affects dynamics of the ring current through simulations of two moderate geomagnetic storms (20 November 2007 and 8-9 March 2008). Preliminary results of coupling the Comprehensive Ring Current Model (CRCM) with a three-dimensional plasma force balance code (to achieve self-consistency in both E and B fields) indicate that inclusion of self-consistency in B tends to mitigate the intensification of the ring current as other similar coupling efforts have shown. In our approach, self-consistency in the electric field is already an existing capability of the CRCM. The magnetic self-consistency is achieved by computing the three-dimensional magnetic field in force balance with anisotropic ring current ion distributions. We discuss the coupling methodology and its further improvement. In addition, comparative studies by using various magnetic field models will be shown. Simulation results will be put into a global context by analyzing the morphology of the ring current, its anisotropy and characteristics ofthe interconnected region 2 field-aligned currents.

  4. Effect of Expansion and Magnetic Field Configuration on Mass Entrainment of Jets

    E-print Network

    A. Rosen; P. E. Hardee

    1999-09-03

    We investigate the growth of jet plus entrained mass in simulations of supermagnetosonic cylindrical and expanding jets. The entrained mass spatially grows in three stages: from an initially slow spatial rate to a faster rate and finally at a flatter rate. These stages roughly coincide with the similar rates of expansion in simulated radio intensity maps, and also appear related to the growth of the Kelvin-Helmholtz instability through linear, nonlinear, and saturated regimes. In the supermagnetosonic cylindrical jets, we found that a jet with an embedded primarily toroidal magnetic field is more stable than a jet with a primarily axial magnetic field. Also, pressure-matched expanding jets are more stable and entrain less mass than cylindrical jets with equivalent inlet conditions.

  5. Field-dependent spin chirality and frustration in V3 and Cu3 nanomagnets in transverse magnetic field. 1. Correlations between variable planar spin configurations, vector and scalar chiralities and magnetization

    NASA Astrophysics Data System (ADS)

    Belinsky, Moisey I.

    2014-05-01

    Correlations between field-dependent planar spin configurations, degenerate frustration, energy, vector ?z and scalar ? chiralities, spin canting, total, in-plane staggered and intermediate spin (IS) magnetizations are considered for the V3, Cu nanomagnets in transverse B?Z magnetic field. The planar spin configurations in Bx?X are characterized by the variable axial ?z(Bx) vector chirality correlated with the total in-plane magnetization Mx(Bx) and the IS magnetization M?12±(Bx), which describes the IS S12 behavior, ?(B?)=0. The in-plane staggered magnetization determines the magnitude of the vector chirality ?z. The low-field frustrated planar 120° configurations are transformed by increasing Bx field into the high-field achiral planar spin-collinear configurations. This transition is accompanied by the reduction of the vector chirality ?z and simultaneous increase of the total Mx(Bx) and IS M?12±(Bx) magnetizations. The spin configurations, chiralities and magnetization are highly anisotropic. In longitudinal B?Z field, the frustrated longitudinal spin-collinear configurations are characterized by the correlated maximal vector and scalar chiralities, ?=2?zMz.

  6. Mitigation of rotational instability of high-beta field-reversed configuration by double-sided magnetized plasmoid injection

    SciTech Connect

    Itagaki, H.; Inomoto, M. [Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8561 (Japan)] [Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8561 (Japan); Asai, T.; Takahashi, Ts. [College of Science and Technology, Nihon University, 1-8-14 Kanda Surugadai, Chiyoda-ku, Tokyo 101-8308 (Japan)] [College of Science and Technology, Nihon University, 1-8-14 Kanda Surugadai, Chiyoda-ku, Tokyo 101-8308 (Japan)

    2014-03-15

    Active control of destructive rotational instability in a high-beta field-reversed configuration (FRC) plasma was demonstrated by using double-sided plasmoid injection technique. The elliptical deformation of the FRC's cross section was mitigated as a result of substantial suppression of spontaneous spin-up by the plasmoid injection. It was found that the injected plasmoid provided better stability against the rotational mode, suggesting that the compensation of the FRC's decaying magnetic flux might help to suppress its spin-up.

  7. Switching ferroelectric domain configurations using both electric and magnetic fields in Pb(Zr,Ti)O3–Pb(Fe,Ta)O3 single-crystal lamellae

    PubMed Central

    Evans, D. M.; Schilling, A.; Kumar, Ashok; Sanchez, D.; Ortega, N.; Katiyar, R. S.; Scott, J. F.; Gregg, J. M.

    2014-01-01

    Thin single-crystal lamellae cut from Pb(Zr,Ti)O3–Pb(Fe,Ta)O3 ceramic samples have been integrated into simple coplanar capacitor devices. The influence of applied electric and magnetic fields on ferroelectric domain configurations has been mapped, using piezoresponse force microscopy. The extent to which magnetic fields alter the ferroelectric domains was found to be strongly history dependent: after switching had been induced by applying electric fields, the susceptibility of the domains to change under a magnetic field (the effective magnetoelectric coupling parameter) was large. Such large, magnetic field-induced changes resulted in a remanent domain state very similar to the remanent state induced by an electric field. Subsequent magnetic field reversal induced more modest ferroelectric switching. PMID:24421376

  8. Three-dimensional instability of thermal convection in a vertical Bridgman growth configuration under traveling magnetic field

    NASA Astrophysics Data System (ADS)

    Wang, Bo-Fu; Li, Yan-Hui; Zhou, Lin; Deng, An-Li; Ma, Dong-Jun; Sun, De-Jun; Jiang, Jin

    2015-06-01

    Thermal convection in a vertical Bridgman growth configuration under the effect of a traveling magnetic field (TMF) is investigated numerically. The vertical Bridgman growth configuration is approximated by convection in a cylinder with a parabolic heated sidewall and isothermal-cooled end walls. The TMF effect is introduced as a usual approximation under low frequency and a low induction assumption to use the analytical expression for the Lorentz force applied in the fluid volume. The strength of the TMF force is measured by the parameter Ft. The cylinder aspect ratio (height/radius) is fixed to ? =1, and the Prandtl number considered is fixed to Pr = 0.02. The base flow simultaneously excited by buoyancy and TMF is axisymmetric. Our primary goal is to determine how the flow loses stability to three-dimensional flow. An extremely multiple valued stability curve in the (Ft,Ra) plane is revealed by linear stability analysis. Three distinct flow regimes are classified, i.e., buoyancy dominated regime, buoyancy and TMF-counterbalanced regime, and TMF-dominated regime. Typical steady and unsteady three-dimensional flows are illustrated.

  9. High Performance Field Reversed Configurations

    NASA Astrophysics Data System (ADS)

    Binderbauer, Michl

    2014-10-01

    The field-reversed configuration (FRC) is a prolate compact toroid with poloidal magnetic fields. FRCs could lead to economic fusion reactors with high power density, simple geometry, natural divertor, ease of translation, and possibly capable of burning aneutronic fuels. However, as in other high-beta plasmas, there are stability and confinement concerns. These concerns can be addressed by introducing and maintaining a significant fast ion population in the system. This is the approach adopted by TAE and implemented for the first time in the C-2 device. Studying the physics of FRCs driven by Neutral Beam (NB) injection, significant improvements were made in confinement and stability. Early C-2 discharges had relatively good confinement, but global power losses exceeded the available NB input power. The addition of axially streaming plasma guns, magnetic end plugs as well as advanced surface conditioning leads to dramatic reductions in turbulence driven losses and greatly improved stability. As a result, fast ion confinement significantly improved and allowed for build-up of a dominant fast particle population. Under such appropriate conditions we achieved highly reproducible, long-lived, macroscopically stable FRCs with record lifetimes. This demonstrated many beneficial effects of large orbit particles and their performance impact on FRCs Together these achievements point to the prospect of beam-driven FRCs as a path toward fusion reactors. This presentation will review and expand on key results and present context for their interpretation.

  10. Final Report on Development of Optimized Field-Reversed Configuration Plasma Formation Techniques for Magnetized Target Fusion

    SciTech Connect

    Lynn, Alan

    2013-11-01

    The University of New Mexico (UNM) proposed a collaboration with Los Alamos National Laboratory (LANL) to develop and test methods for improved formation of field-reversed configuration (FRC) plasmas relevant to magnetized target fusion (MTF) energy research. MTF is an innovative approach for a relatively fast and cheap path to the production of fusion energy that utilizes magnetic confinement to assist in the compression of a hot plasma to thermonuclear conditions by an external driver. LANL is currently pursing demonstration of the MTF concept via compression of an FRC plasma by a metal liner z-pinch in conjunction with the Air Force Research Laboratory in Albuquerque, NM. A key physics issue for the FRC's ultimate success as an MTF target lies in the initial pre-ionization (PI) stage. The PI plasma sets the initial conditions from which the FRC is created. In particular, the PI formation process determines the amount of magnetic flux that can be trapped to form the FRC. A ringing theta pinch ionization (RTPI) technique, such as currently used by the FRX-L device at LANL, has the advantages of high ionization fraction, simplicity (since no additional coils are required), and does not require internal electrodes which can introduce impurities into the plasma. However RTPI has been shown to only trap #24;50% of the initial bias flux at best and imposes additional engineering constraints on the capacitor banks. The amount of trapped flux plays an important role in the FRC's final equilibrium, transport, and stability properties, and provides increased ohmic heating of the FRC through induced currents as the magnetic field decays. Increasing the trapped flux also provides the route to greatest potential gains in FRC lifetime, which is essential to provide enough time to translate and compress the FRC effectively. In conjunction with LANL we initially planned to develop and test a microwave break- down system to improve the initial PI plasma formation. The UNM team would design the microwave optics and oversee the fabrication and assembly of all components and assist with integration into the FRX-L machine control system. LANL would provide a preexisting 65 kW X-band microwave source and some associated waveguide hardware. Once constructed and installed, UNM would take the lead in operating the microwave breakdown system and conducting studies to optimize its use in FRC PI formation in close cooperation with the needs of the LANL MTF team. In conjunction with our LANL collaborators, we decided after starting the project to switch from a microwave plasma breakdown approach to a plasma gun technology to use for enhanced plasma formation in the FRX-L field-reversed configuration experiment at LANL. Plasma guns would be able to provide significantly higher density plasma with greater control over its distribution in time and space within the experiment. This would allow greater control and #12;ne-tuning of the PI plasma formed in the experiment. Multiple plasma guns would be employed to fill a Pyrex glass test chamber (built at UNM) with plasma which would then be characterized and optimized for the MTF effort.

  11. Effect of the latitudinal distribution of temperature at the coronal base on the interplanetary magnetic field configuration and the solar wind flow

    Microsoft Academic Search

    Bo Li; Shadia Rifai Habbal; Xing Li; Chris Mountford

    2005-01-01

    Received 22 July 2005; revised 13 September 2005; accepted 26 October 2005; published 30 December 2005. (1) Using a two-dimensional MHD model of the corona and solar wind, we investigate the role of the temperature distribution with latitude at the coronal base on the global magnetic field configuration and solar wind properties at 1 AU. The latitudinal distribution of temperature

  12. Effect of the latitudinal distribution of temperature at the coronal base on the interplanetary magnetic field configuration and the solar wind flow

    Microsoft Academic Search

    Bo Li; Shadia Rifai Habbal; Xing Li; Chris Mountford

    2005-01-01

    Using a two-dimensional MHD model of the corona and solar wind, we investigate the role of the temperature distribution with latitude at the coronal base on the global magnetic field configuration and solar wind properties at 1 AU. The latitudinal distribution of temperature is aimed at modeling the transition in electron temperature at the Sun from a polar coronal hole

  13. Magnetic Fields

    NSDL National Science Digital Library

    2014-09-18

    Students visualize the magnetic field of a strong permanent magnet using a compass. The lesson begins with an analogy to the effect of the Earth's magnetic field on a compass. Students see the connection that the compass simply responds to the Earth's magnetic field since it is the closest, strongest field, and thus the compass responds to the field of the permanent magnets, allowing them the ability to map the field of that magnet in the activity. This information will be important in designing a solution to the grand challenge in activity 4 of the unit.

  14. Field-Reversed Configurations in an Unmagnetized Plasma

    SciTech Connect

    Stenzel, R. L.; Urrutia, J. M.; Strohmaier, K. D. [Department of Physics and Astronomy, University of California, Los Angeles, California 90095-1547 (United States)

    2008-09-26

    An oscillating magnetic field is applied with a loop antenna to an unmagnetized plasma. At small amplitudes the field is evanescent. At large amplitudes the field magnetizes the electrons, which allows deeper field penetration in the whistler modes. Field-reversed configurations are formed at each half cycle. Electrons are energized. Transient whistler instabilities produce high-frequency oscillations in the magnetized plasma volume.

  15. Magnetic Fields

    E-print Network

    Schöller, Markus

    2015-01-01

    In this chapter, we give a brief introduction into the use of the Zeeman effect in astronomy and the general detection of magnetic fields in stars, concentrating on the use of FORS2 for longitudinal magnetic field measurements.

  16. Controlling precise magnetic field configuration around electron cyclotron resonance zone for enhancing plasma parameters and beam current

    SciTech Connect

    Yano, Keisuke, E-mail: yano@i-beam.jp; Kurisu, Yosuke; Nozaki, Dai; Kimura, Daiju; Imai, Youta; Kumakura, Sho; Sato, Fuminobu; Kato, Yushi; Iida, Toshiyuki [Division of Electrical, Electronic and Information Engineering, Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita-shi, Osaka 565-0871 (Japan)] [Division of Electrical, Electronic and Information Engineering, Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita-shi, Osaka 565-0871 (Japan)

    2014-02-15

    Multi-charged ion source which has wide operating conditions is required in various application fields. We have constructed tandem type ECR ion source (ECRIS); one of the features of its main stage is an additional coil for controlling magnetic field distribution around the mirror bottom precisely. Here the effect of magnetic field variation caused by the additional coil is experimentally considered in terms of plasma parameters and beam current as the first investigation of the main stage plasma. Furthermore, behavior of magnetic lines of force flowing from the ECR zone is calculated, and is compared with measurement results aiming for better understanding of interrelationship between plasma production and ion beam generation on the ECRIS.

  17. The Magnetic Field

    NSDL National Science Digital Library

    Windows to the Universe

    1997-12-03

    This webpage is part of the University Corporation for Atmospheric Research (UCAR) Windows to the Universe program. It describes the nature and configuration of magnetic fields, which are the result of moving electric charges, including how they cause magnetic objects to orient themselves along the direction of the magnetic force points, which are illustrated as lines. Magnetic field lines by convention point outwards at the north magnetic pole and inward at the south magnetic pole. The site features text, scientific illustrations and an animation. Text and vocabulary are selectable for the beginning, intermediate, or advanced reader.

  18. Fast electron bremsstrahlung in axisymmetric magnetic configuration

    SciTech Connect

    Peysson, Y.; Decker, J. [Association Euratom-CEA, CEA, IRFM, F-13108 Saint-Paul-lez-Durance (France)

    2008-09-15

    The nonthermal bremsstrahlung is calculated in a plasma with arbitrary axisymmetric magnetic configuration, taking into account the relativistic angular anisotropy of the radiation cross section at high photon energies, the helical winding of the field lines on the magnetic flux surfaces, and the poloidal variation of the electron distribution function including particle trapping effects. The fast electron dynamics during current drive in tokamaks and reverse field pinches can be investigated in detail by coupling this calculation to a bounce-averaged relativistic Fokker-Planck solver, which calculates the electron distribution function. The asymmetry between high- and low-field side hard x-ray emission intensity that has been measured on the Tore-Supra tokamak [Equipe TORE SUPRA, in Proceedings of the 15th Conference on Plasma Physics and Controlled Nuclear Fusion Research, Seville (International Atomic Energy Agency, Vienna, 1995) Vol. 1, IAEA-CN-60/A1-5 (Institute of Physics, Bristol, U.K., 1995), p. 105] is explained for the first time by the role of trapped electrons. A much stronger poloidal asymmetry is predicted for the line-integrated fast electron bremsstrahlung in the poloidal plane of the Madison Symmetric Torus [R. N. Dexter et al., Fusion Tech. 19, 131 (1991)], since the helical winding of the magnetic field lines is much larger for a reverse field pinch configuration. In this case, the hard x-ray emission is no longer a flux surface quantity, which prevents local reconstructions using a standard Abel inversion, whatever the geometrical arrangement of the lines of sight.

  19. Magnetic Field Safety Magnetic Field Safety

    E-print Network

    McQuade, D. Tyler

    Magnetic Field Safety Training #12;Magnetic Field Safety Strong Magnetic Fields exist around energized magnets. High magnetic fields alone are a recognized hazard only for personnel with certain fields will rapidly accelerate any magnetic material towards the magnet. § Magnetic material is commonly

  20. Magnetic Field Configuration of Active Region NOAA 6555 at the Time of a Long Duration Flare on 23 March 1991: An Exception to Standard Flare Reconnection Model

    NASA Technical Reports Server (NTRS)

    Choudhary, Debi Prasad; Gary, Allen G.

    1998-01-01

    The high-resolution H(sub alpha) images observed during the decay phase of a long duration flare on 23 March 1991 are used to study the three-dimensional magnetic field configuration of the active region NOAA 6555. Whereas, all the large flares in NOAA 6555 occurred at the location of high magnetic shear and flux emergence, this long duration flare was observed in the region of low magnetic shear at the photosphere. The H(sub alpha) loop activity started soon after the maximum phase of the flare. There were few long loop at the initial phase of the activity. Some of these were sheared in the chromosphere at an angle of about 45 deg with the east-west axis. Gradually, increasing number of shorter loops, oriented along the east-west axis, started appearing. The chromospheric Dopplergrams show blue-shifts at the end points of the loops. By using different magnetic field models, we have extrapolated the photospheric magnetograms to the chromospheric heights. The magnetic field lines computed by using the potential field model correspond to most of the observed H(sub alpha) loops. The height of the H(sub alpha) loops were derived by comparing them with the computed field lines. From the temporal evolution of the H(sub alpha) loop activity, we derive the negative rate of appearance of H(sub alpha) features as a function of height. It is found that the field lines oriented along one of the neutral lines was sheared and low lying. The higher field lines were mostly potential. The paper also outlines a possible scenario for describing the post-flare stage of the observed long duration flare.

  1. An automated approach to magnetic divertor configuration design

    NASA Astrophysics Data System (ADS)

    Blommaert, M.; Dekeyser, W.; Baelmans, M.; Gauger, N. R.; Reiter, D.

    2015-01-01

    Automated methods based on optimization can greatly assist computational engineering design in many areas. In this paper an optimization approach to the magnetic design of a nuclear fusion reactor divertor is proposed and applied to a tokamak edge magnetic configuration in a first feasibility study. The approach is based on reduced models for magnetic field and plasma edge, which are integrated with a grid generator into one sensitivity code. The design objective chosen here for demonstrative purposes is to spread the divertor target heat load as much as possible over the entire target area. Constraints on the separatrix position are introduced to eliminate physically irrelevant magnetic field configurations during the optimization cycle. A gradient projection method is used to ensure stable cost function evaluations during optimization. The concept is applied to a configuration with typical Joint European Torus (JET) parameters and it automatically provides plausible configurations with reduced heat load.

  2. High Energy Electron Confinement in a Magnetic Cusp Configuration

    E-print Network

    Park, Jaeyoung; Sieck, Paul E; Offermann, Dustin T; Skillicorn, Michael; Sanchez, Andrew; Davis, Kevin; Alderson, Eric; Lapenta, Giovanni

    2014-01-01

    We report experimental results validating the concept that plasma confinement is enhanced in a magnetic cusp configuration when beta (plasma pressure/magnetic field pressure) is order of unity. This enhancement is required for a fusion power reactor based on cusp confinement to be feasible. The magnetic cusp configuration possesses a critical advantage: the plasma is stable to large scale perturbations. However, early work indicated that plasma loss rates in a reactor based on a cusp configuration were too large for net power production. Grad and others theorized that at high beta a sharp boundary would form between the plasma and the magnetic field, leading to substantially smaller loss rates. The current experiment validates this theoretical conjecture for the first time and represents critical progress toward the Polywell fusion concept which combines a high beta cusp configuration with an electrostatic fusion for a compact, economical, power-producing nuclear fusion reactor.

  3. Average configuration of the distant (less than 220-earth-radii) magnetotail - Initial ISEE-3 magnetic field results

    NASA Technical Reports Server (NTRS)

    Slavin, J. A.; Tsurutani, B. T.; Smith, E. J.; Jones, D. E.; Sibeck, D. G.

    1983-01-01

    Magnetic field measurements from the first two passes of the ISEE-3 GEOTAIL Mission have been used to study the structure of the trans-lunar tail. Good agreement was found between the ISEE-3 magnetopause crossings and the Explorer 33, 35 model of Howe and Binsack (1972). Neutral sheet location was well ordered by the hinged current sheet models based upon near earth measurements. Between X = -20 and -120 earth radii the radius of the tail increases by about 30 percent while the lobe field strength decreases by approximately 60 percent. Beyond X = -100 to -1200 earth radii the tail diameter and lobe field magnitude become nearly constant at terminal values of approximately 60 earth radii and 9 nT, respectively. The distance at which the tail was observed to cease flaring, 100-120 earth radii, is in close agreement with the predictions of the analytic tail model of Coroniti and Kennel (1972). Overall, the findings of this study suggest that the magnetotail retains much of its near earth structure out to X = -220 earth radii.

  4. Review of field-reversed configurations

    SciTech Connect

    Steinhauer, Loren C. [Department of Aeronautics and Astronautics, University of Washington, Seattle, Washington 98195 (United States)

    2011-07-15

    This review addresses field-reversed configurations (FRCs), which are compact-toroidal magnetic systems with little or no toroidal field and very high {beta} (ratio of plasma pressure to magnetic pressure). Although enthusiasm for the FRC has primarily been driven by its potential for an attractive fusion reactor, this review focuses on the physics rather than on technological or engineering aspects. Major advances in both theory and experiment have taken place since the previous comprehensive FRC review in 1988. Even so many questions remain. In particular, even though FRC experiments have exhibited remarkable stability, how well this extrapolates to larger systems remains unresolved. The review considers FRCs under familiar topical categories: equilibrium, global stability, self-organization, transport, formation, and sustainment.

  5. Field-reversed configuration high power density fusion reactor

    Microsoft Academic Search

    Hoffman

    1986-01-01

    A field-reversed-configuration (FRC) is a compact toroidal plasma confined solely by poloidal fields. Its naturally high ..beta.. (<..beta..> greater than or equal to 0.5), and the simple cylindrical vacuum chamber and magnetic field configuration needed to confine it offer significant engineering advantages in constructing compact, small unit size, economic fusion reactors. The FRC's demonstrated ability to be translated opens many

  6. 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.

  7. Evolution of heliospheric magnetized configurations via topological invariants

    NASA Astrophysics Data System (ADS)

    Roth, Ilan

    2013-07-01

    The analogy between magnetohydrodynamics (MHD) and knot theory is utilized in presenting a new method for an analysis of stability and evolution of complex magnetic heliospheric flux tubes. Planar projection of a three-dimensional magnetic configuration depicts the structure as a two-dimensional diagram with crossings, to which one may assign mathematical operations leading to robust topological invariants. These invariants enrich the topological information of magnetic configurations beyond helicity. It is conjectured that the field which emerges from the solar photosphere is structured as one of the simplest knots-unknot or prime knot-and these flux ropes are then stretched while carried by the solar wind into the interplanetary medium. Preservation of invariants for small diffusivity and large cross section of the emerging magnetic flux makes them impervious to large scale reconnection, allowing us to predict the observed structures at 1 AU as elongated prime knots. Similar structures may be observed in magnetic clouds which got disconnected from their footpoints and in ion drop-out configurations from a compact flare source in solar impulsive solar events. Observation of small scale magnetic features consistent with prime knots may indicate spatial intermittency and non-Gaussian statistics in the turbulent cascade process. For flux tubes with higher resistivity, magnetic energy decay rate should decrease with increased knot complexity as the invariants are then harder to be violated. These observations could be confirmed if adjacent satellites happen to measure distinctly oriented magnetic fields with directionally varying suprathermal particle fluxes.

  8. Configuration Interaction in Crystal Field Theory

    Microsoft Academic Search

    K. Rajnak; B. G. Wybourne

    1964-01-01

    The effect of configuration interaction on the validity of the usual method of expanding the crystal field potential in terms of spherical harmonics is examined using second-order perturbation theory. It is found that for a configuration of equivalent electrons lN most mechanisms of configuration interaction lead to a simple scaling of the crystal field parameters Bqk. However, one-electron excitations, either

  9. High-Energy Electron Confinement in a Magnetic Cusp Configuration

    NASA Astrophysics Data System (ADS)

    Park, Jaeyoung; Krall, Nicholas A.; Sieck, Paul E.; Offermann, Dustin T.; Skillicorn, Michael; Sanchez, Andrew; Davis, Kevin; Alderson, Eric; Lapenta, Giovanni

    2015-04-01

    We report experimental results validating the concept that plasma confinement is enhanced in a magnetic cusp configuration when ? (plasma pressure/magnetic field pressure) is of order unity. This enhancement is required for a fusion power reactor based on cusp confinement to be feasible. The magnetic cusp configuration possesses a critical advantage: the plasma is stable to large scale perturbations. However, early work indicated that plasma loss rates in a reactor based on a cusp configuration were too large for net power production. Grad and others theorized that at high ? a sharp boundary would form between the plasma and the magnetic field, leading to substantially smaller loss rates. While not able to confirm the details of Grad's work, the current experiment does validate, for the first time, the conjecture that confinement is substantially improved at high ? . This represents critical progress toward an understanding of the plasma dynamics in a high-? cusp system. We hope that these results will stimulate a renewed interest in the cusp configuration as a fusion confinement candidate. In addition, the enhanced high-energy electron confinement resolves a key impediment to progress of the Polywell fusion concept, which combines a high-? cusp configuration with electrostatic fusion for a compact, power-producing nuclear fusion reactor.

  10. Multichord optical interferometry of FRX-L's field reversed configuration

    Microsoft Academic Search

    E. L. Ruden; Shouyin Zhang; G. A. Wurden; T. P. Intrator; R. Renneke; W. J. Waganaar; F. T. Analla; T. C. Grabowski

    2006-01-01

    A 0.633 mum laser interferometer provides detailed time resolved information about the spatial distribution of the plasma density of field reversed configurations (FRC's) produced by the FRX-L experiment at Los Alamos National Laboratory. This experiment is an effort to produce a magnetized plasma with closed field lines suitable for compression by a solid metal liner imploded by the Shiva Star

  11. Equilibrium rotation in field-reversed configurations

    SciTech Connect

    Steinhauer, Loren [Redmond Plasma Physics Laboratory, University of Washington, 4700 N. E. 95th Street, Suite 100, Redmond, Washington 98052 (United States)

    2008-01-15

    The turbulence that drives anomalous transport in field-reversed configurations (FRCs) is believed to break the otherwise closed magnetic surfaces inside the separatrix. This places electrons in the core of the plasma in electrical contact with those in the periphery. This effect was proposed and investigated in the context of spheromaks [D. D. Ryutov, Phys. Plasmas 14, 022506 (2007)]. The opening up of internal magnetic field lines serves to regulate the electrostatic potential in the interior of the plasma, and in turn drives ion rotation. In effect, 'end-shorting', a well-known phenomenon in the FRC scrape-off layer, also extends into the plasma interior. For conditions relevant to experiments, the ion rotation can be expressed in terms of equilibrium properties (density and temperature gradients) and as such is the 'equilibrium' rotation. This theory is incomplete in that it neglects evolving, transport-related effects that modify the equilibrium and, indirectly, the rotation rate. Consequently, the equilibrium rotation theory is only partially successful in predicting experimental results: although it predicts the average rotation well, the estimated degree of rotational shear seems unlikely, especially at late times in the plasma lifetime.

  12. Shear angle of magnetic fields.

    NASA Astrophysics Data System (ADS)

    Yanping, Lü; Wang, Jingxiu; Wang, Huaning

    1993-11-01

    The authors introduce a new parameter, the shear angle of vector magnetic fields, ??, to describe the non-potentiality of magnetic fields in active regions, which is defined as the angle between the observed vector magnetic field and its corresponding current-free field. In the case of highly inclined field configurations, this angle is approximately equal to the "angular shear", ??, defined by Hagyard et al. (1984). ?? can be considered as the projection of the shear angle, ??, on the photosphere. For the active region studied, the shear angle, ??, seems to have a better and neater correspondence with flare activity than does ??. It gives a clearer explanation of the non-potentiality of magnetic fields. It is a better measure of the deviation of the observed magnetic field from a potential field, and is directly related to the magnetic free energy stored in non-potential fields.

  13. Chaotic motion of charged particles in toroidal magnetic configurations

    SciTech Connect

    Cambon, Benjamin; Leoncini, Xavier; Vittot, Michel [Aix Marseille Université, Université de Toulon, CNRS, CPT UMR 7332, 13288 Marseille (France); Dumont, Rémi; Garbet, Xavier [CEA, IRFM, F-13108 Saint-Paul-lez-Durance (France)

    2014-09-01

    We study the motion of a charged particle in a tokamak magnetic field and discuss its chaotic nature. Contrary to most of recent studies, we do not make any assumption on any constant of the motion and solve numerically the cyclotron gyration using Hamiltonian formalism. We take advantage of a symplectic integrator allowing us to make long-time simulations. First considering an idealized magnetic configuration, we add a nongeneric perturbation corresponding to a magnetic ripple, breaking one of the invariant of the motion. Chaotic motion is then observed and opens questions about the link between chaos of magnetic field lines and chaos of particle trajectories. Second, we return to an axisymmetric configuration and tune the safety factor (magnetic configuration) in order to recover chaotic motion. In this last setting with two constants of the motion, the presence of chaos implies that no third global constant exists, we highlight this fact by looking at variations of the first order of the magnetic moment in this chaotic setting. We are facing a mixed phase space with both regular and chaotic regions and point out the difficulties in performing a global reduction such as gyrokinetics.

  14. Chaotic motion of charged particles in toroidal magnetic configurations.

    PubMed

    Cambon, Benjamin; Leoncini, Xavier; Vittot, Michel; Dumont, Rémi; Garbet, Xavier

    2014-09-01

    We study the motion of a charged particle in a tokamak magnetic field and discuss its chaotic nature. Contrary to most of recent studies, we do not make any assumption on any constant of the motion and solve numerically the cyclotron gyration using Hamiltonian formalism. We take advantage of a symplectic integrator allowing us to make long-time simulations. First considering an idealized magnetic configuration, we add a nongeneric perturbation corresponding to a magnetic ripple, breaking one of the invariant of the motion. Chaotic motion is then observed and opens questions about the link between chaos of magnetic field lines and chaos of particle trajectories. Second, we return to an axisymmetric configuration and tune the safety factor (magnetic configuration) in order to recover chaotic motion. In this last setting with two constants of the motion, the presence of chaos implies that no third global constant exists, we highlight this fact by looking at variations of the first order of the magnetic moment in this chaotic setting. We are facing a mixed phase space with both regular and chaotic regions and point out the difficulties in performing a global reduction such as gyrokinetics. PMID:25273181

  15. Chaotic motion of charged particles in toroidal magnetic configurations

    E-print Network

    Benjamin Cambon; Xavier Leoncini; Michel Vittot; Rémi Dumont; Xavier Garbet

    2014-12-04

    We study the motion of a charged particle in a tokamak magnetic field and discuss its chaotic nature. Contrary to most of recent studies, we do not make any assumption on any constant of the motion and solve numerically the cyclotron gyration using Hamiltonian formalism. We take advantage of a symplectic integrator allowing us to make long-time simulations. First considering an idealized magnetic configuration, we add a non generic perturbation corresponding to a magnetic ripple, breaking one of the invariant of the motion. Chaotic motion is then observed and opens questions about the link between chaos of magnetic field lines and chaos of particle trajectories. Second, we return to a axi-symmetric configuration and tune the safety factor (magnetic configuration) in order to recover chaotic motion. In this last setting with two constants of the motion, the presence of chaos implies that no third global constant exists, we highlight this fact by looking at variations of the first order of the magnetic moment in this chaotic setting. We are facing a mixed phase space with both regular and chaotic regions and point out the difficulties in performing a global reduction such as gyrokinetics.

  16. Sympathetic solar eruptions in quadrupolar magnetic configurations

    NASA Astrophysics Data System (ADS)

    Torok, T.; Titov, V. S.; Panasenco, O.

    2014-12-01

    Observations by SDO/AIA have renewed the interest in sympathetic solareruptions, i.e., of eruptions that occur simultaneously (or in shortsuccession) at different source regions in the corona. Recently, Toroket al. (2011) developed an idealized numerical model for the triggermechanisms of sympathetic eruptions in so-called pseudo-streamers, whichconsist of a tri-polar magnetic configuration with a parasitic polarityin their center. Here we extend the work by Torok et al. by investigating sympathetic eruptions in (the topologically somewhat more complex) quadrupolar configurations, using MHD simulations. We consider both symmetric and asymmetric initial configurations that contain two or three flux ropes within the quadrupole. We find, differentto Torok et al. (2011), that magnetic reconnection induced by a firsteruption cannot just trigger, but also prevent subsequent eruptions. In addition, a (relatively modest) asymmetry of the configuration may fully suppress the occurrence of successive full eruptions, i.e., of coronal mass ejections. We discuss the implications of these results for our understanding of sympathetic eruptions.

  17. Ferrofilm in a magnetic field

    NASA Astrophysics Data System (ADS)

    Back, Randy; Beckham, J. Regan

    2012-10-01

    A vertically draining thin ferrofilm under the influence of gravity and a nonuniform magnetic field is considered. It is observed experimentally that the presence of the magnetic field greatly alters the drainage of the film. A mathematical model is developed to describe the behavior. Experiments are conducted for multiple magnetic field configurations. The model is solved for two different sets of boundary conditions and results are compared to experiments. It is shown that the magnetic field structure, the concentration of magnetite in the solution, and the boundary conditions all have noticeable affects on the evolution of the thinning film. Good qualitative agreement between the model and the experiments is observed.

  18. Compact toroid experiments: spheromaks and field-reversed configurations

    SciTech Connect

    Quinn, W.E.

    1982-01-01

    Compact toroids (CT) containing both poloidal and toroidal magnetic field spheromaks, are generated in the CTX experiment using a magnetized coaxial plasma gun, and are trapped and stably confined in an oblate flux conserver. Total configuration lifetimes are observed up to approx. 0.8 ms, consistent with classical resistive decay. The field reversed configuration (FRC) is a high beta, axisymmetric, highly prolate compact toroid, containing only poloidal magnetic field, formed in a field-reversed theta pinch. A quiescent confinement period of 30 to 90 ..mu..s with T/sub i/ approx. 200 to 500 eV and n approx. 5 x 10/sup 15/ cm/sup -3/ is terminated by an n = 2 rotational instability. The FRC is stable to MHD modes including the tilting instability.

  19. The effects of magnetic nozzle configurations on plasma thrusters

    NASA Technical Reports Server (NTRS)

    York, Thomas M.

    1989-01-01

    Plasma thrusters have been operated at power levels from 10kW to 0.1MW. When these devices have had magnetic fields applied to them which form a nozzle configuration for the expanding plasma, they have shown marked increases in exhaust velocity which is in direct proportion to the magnitude of the applied field. Further, recent results have shown that electrode erosion may be influenced by applied magnetic fields. This research is directed to the experimental and computational study of the effects of applied magnetic field nozzles in the acceleration of plasma flows. Plasma source devices which eliminate the plasma interaction in normal thrusters are studied as most basic. Normal thruster configurations will be studied without applied fields and with applied magnetic nozzle fields. Unique computational studies will utilize existing codes which accurately include transport processes. Unique diagnostic studies will support the experimental studies to generate new data. Both computation and diagnostics will be combined to indicate the physical mechanisms and transport properties that are operative in order to allow scaling and accurate prediction of thruster performance.

  20. The effects of magnetic nozzle configurations on plasma thrusters

    NASA Technical Reports Server (NTRS)

    York, Thomas M.

    1990-01-01

    Plasma thrusters have been operated at power levels from 10 kw to 0.1 MW. When these devices have had magnetic fields applied to them which form a nozzle configuration for the expanding plasma, they have shown marked increases in exhaust velocity which is in direct proportion to the magnitude of the applied field. Further, recent results have shown that electrode erosion may be influenced by applied magnetic fields. This research effort is directed to the experimental and computational study of the effects of applied magnetic field nozzles in the acceleration of plasma flows. Plasma source devices which eliminate the plasma interaction in normal thrusters are studied as most basic. Normal thruster configurations were studied without applied fields and with applied magnetic nozzle fields. Unique computational studies utilize existing codes which accurately include transport processes. Unique diagnostic studies supported the experimental studies to generate new data. Both computation and diagnostics were combined to indicate the physical mechanisms and transport properties that are operative in order to allow scaling and accurate prediction of thruster performance.

  1. Magnetic fields in astrophysics

    Microsoft Academic Search

    Ia. B. Zeldovich; A. A. Ruzmaikin; D. D. Sokolov

    1983-01-01

    The evidence of cosmic magnetism is examined, taking into account the Zeeman effect, beats in atomic transitions, the Hanle effect, Faraday rotation, gyro-lines, and the strength and scale of magnetic fields in astrophysics. The origin of magnetic fields is considered along with dynamos, the conditions for magnetic field generation, the topology of flows, magnetic fields in stationary flows, kinematic turbulent

  2. Magnetic fields in anisotropic relativistic stars

    NASA Astrophysics Data System (ADS)

    Folomeev, Vladimir; Dzhunushaliev, Vladimir

    2015-02-01

    Relativistic, spherically symmetric configurations consisting of a gravitating magnetized anisotropic fluid are studied. For such configurations, we obtain static equilibrium solutions with an axisymmetric, poloidal magnetic field produced by toroidal electric currents. The presence of such a field results in small deviations of the shape of the configuration from spherical symmetry. This in turn leads to the modification of an equation for the current and correspondingly to changes in the structure of the internal magnetic field for the systems supported by the anisotropic fluid, in contrast to the case of an isotropic fluid, where such deviations do not affect the magnetic field.

  3. Magnetic fields in anisotropic relativistic stars

    E-print Network

    Vladimir Folomeev; Vladimir Dzhunushaliev

    2015-02-28

    Relativistic, spherically symmetric configurations consisting of a gravitating magnetized anisotropic fluid are studied. For such configurations, we obtain static equilibrium solutions with an axisymmetric, poloidal magnetic field produced by toroidal electric currents. The presence of such a field results in small deviations of the shape of the configuration from spherical symmetry. This in turn leads to the modification of an equation for the current and correspondingly to changes in the structure of the internal magnetic field for the systems supported by the anisotropic fluid, in contrast to the case of an isotropic fluid, where such deviations do not affect the magnetic field.

  4. Field-reversed Configuration Plasma for Magnetized Target Fusion Manuscript received September 8, 2005. Revised January 16, 2006. This work was supported by the Department of Energy--

    E-print Network

    to implode (compress) the target FRC plasma with a liner is planned on the Shiva-Star facility of Air Force. Ruden and James H. Degnan are with the Air Force Research Laboratory, Albuquerque, NM 87117, USA. Chris; he is contracted with the Air Force Research Laboratory. High-Density Field-Reversed Configuration

  5. Magnetic shielding by soft magnetic materials in alternating magnetic field

    Microsoft Academic Search

    Yasuo Okazaki; Kiyoshi Ueno

    1992-01-01

    The magnetic shielding effect of an alternating field up to 20 kHz was examined in 3% Si steel sheets and amorphous ribbons. Not only the permeability but also the domain configuration was found to affect the shielding effects. The annealed Fe-based amorphous shield without field showed exceedingly high shielding effectiveness for higher frequencies.

  6. Ideal compact fusion reactor based on a field-reversed configuration

    Microsoft Academic Search

    Hoffman

    1996-01-01

    Field-reversed configurations (FRC) have been recognized as possessing almost ideal fusion reactor characteristics from the point of view of engineering simplicity and maintainability. The external geometry is cylindrical while the internal magnetic field configuration is toroidal, allowing for both a simple magnetic confinement design and the possibility of good plasma confinement. FRCs are unique among all toroidal confinement concepts in

  7. Exploring Magnetic Field Lines

    NSDL National Science Digital Library

    NASA

    2012-06-26

    In this activity, learners explore the magnetic field of a bar magnet as an introduction to understanding Earth's magnetic field. First, learners explore and play with magnets and compasses. Then, learners trace the field lines of the magnet using the compass on a large piece of paper. This activity will also demonstrate why prominences are always "loops."

  8. 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.

  9. Electric and magnetic fields

    Microsoft Academic Search

    K. B. Maracas

    1994-01-01

    Increasing electrification brings increased human exposures to electric and magnetic fields, commonly called EMFs, and growing evidence suggests that exposure to even low frequency, low energy, electric and magnetic fields may be related to adverse health effects. This paper focuses on magnetic fields and strategies that address them. The challenges faced by scientists in understanding magnetic field interactions with humans,

  10. Magnetic Fields Matter

    NSDL National Science Digital Library

    2014-09-18

    This lesson introduces students to the effects of magnetic fields in matter addressing permanent magnets, diamagnetism, paramagnetism, ferromagnetism, and magnetization. First students must compare the magnetic field of a solenoid to the magnetic field of a permanent magnet. Students then learn the response of diamagnetic, paramagnetic, and ferromagnetic material to a magnetic field. Now aware of the mechanism causing a solid to respond to a field, students learn how to measure the response by looking at the net magnetic moment per unit volume of the material.

  11. Exploring Magnetic Fields

    NSDL National Science Digital Library

    In this activity, students investigate the presence of magnetic fields around magnets, the sun and the earth. They will explore magnetic field lines, understand that magnetic lines of force show the strength and direction of magnetic fields, determine how field lines interact between attracting and repelling magnetic poles, and discover that the earth and sun have magnetic properties. They will also discover that magnetic force is invisible and that a "field of force" is a region or space in which one object can attract or repel another.

  12. Planar permanent magnet multipoles: measurements and configurations

    Microsoft Academic Search

    T. Cremer; R. Tatchyn

    1995-01-01

    Biplanar arrays of N rectangular permanent magnet (PM) blocks can be used to generate high quality N-pole fields in close proximity to the array axis. In applications featuring small-diameter charged particle beams, N-poles of adequate quality can be realized at relatively low cost using small volumes of PM material. In this paper we report on recent measurements performed on planar

  13. Planar permanent magnet multipoles: Measurements and configurations

    SciTech Connect

    Cremer, T.; Tatchyn, R. [Stanford Univ., Stanford, CA (United States)

    1995-05-01

    Biplanar arrays of N rectangular permanent magnet (PM) blocks can be used to generate high quality N-pole fields in close proximity to the array axis. In applications featuring small-diameter charged particle beams, N-poles of adequate quality can be realized at relatively low cost using small volumes of PM material. In this paper we report on recent measurements performed on planar PM multipoles, and discuss techniques for improving the field quality of such devices at distances appreciably far away from the axis. Applications to hybrid/PM insertion device designs for linac-driven Free Electron Laser (FEL) operation in the x-ray range are described.

  14. What are Magnetic Fields?

    NSDL National Science Digital Library

    2012-08-03

    This is an activity about magnetic fields. Using iron filings, learners will observe magnets in various arrangements to investigate the magnetic field lines of force. This information is then related to magnetic loops on the Sun's surface and the magnetic field of the Earth. This is the second activity in the Magnetic Math booklet; this booklet can be found on the Space Math@NASA website.

  15. Visualizing Magnetic Field Lines

    NSDL National Science Digital Library

    2014-09-18

    In this activity, students take the age old concept of etch-a-sketch a step further. Using iron filings, students begin visualizing magnetic field lines. To do so, students use a compass to read the direction of the magnet's magnetic field. Then, students observe the behavior of iron filings near that magnet as they rotate the filings about the magnet. Finally, students study the behavior of iron filings suspended in mineral oil which displays the magnetic field in three dimensions.

  16. Magnetic fields of galaxies

    Microsoft Academic Search

    Aleksandr A. Ruzmaikin; Dmitrii D. Sokolov; Anvar M. Shukurov

    1988-01-01

    The current state of the understanding of the magnetic fields of galaxies is reviewed. A simple model of the turbulent dynamo is developed which explains the main observational features of the global magnetic fields of spiral galaxies. The generation of small-scale chaotic magnetic fields in the interstellar medium is also examined. Attention is also given to the role of magnetic

  17. FNAS: The magnetic configuration leading to solar flares

    NASA Technical Reports Server (NTRS)

    Fontenla, Juan M.

    1992-01-01

    We present a method for solving plasma magnetohydrodynamic (MHD) problems arising from the interaction of plasmas with magnetic fields in stellar atmospheres. Our approach, in contrast to previous methods, is not based on solving equations for the magnetic field and plasma velocity but rather studies the evolution of the electric current and density (and the related gas pressure). We have applied the method to several studies involving linearized departures from static, current-free equilibria. The applications show explicit solutions for cases found in astrophysics and to problems encountered with earlier studies where the gas pressure was neglected. The method is particularly well suited for studying situations which involve a transition between high and low plasma-beta regions. It shows precisely how electric currents, and magnetic free-energy, build up in the plasma as a result of the slow stressing of a potential magnetic field configuration. The method also demonstrates how transverse-current waves, a mix of Alfven and magneto-acoustic modes, propagate in a low-beta plasma for any density stratification and background field geometry.

  18. Force-free configurations in reversed-field pinches

    SciTech Connect

    Emets, Y.P.; Zamidra, A.I.; Kovbasenko, Y.P.

    1988-03-01

    The structure of reversed-field pinches is analyzed on the basis of analytic solutions of equations describing force-free configurations. A model with a constant coefficient of the proportionality between the current density and the magnetic field is used to analyze the effect of the toroidal geometry on the field distribution and the F--THETA diagrams. A modified model is proposed in which the ratio of the current density to the magnetic field tends toward zero near the wall of the discharge chamber. This model yields a more accurate description of the experiments F--THETA diagrams and of the field distributions. It is preferable to the Bessel-function model from the energy standpoint.

  19. Plasma flow processes within magnetic nozzle configurations

    NASA Technical Reports Server (NTRS)

    York, Thomas M.; Mikellides, Pavlos; Jacoby, Barry A.

    1989-01-01

    An attempt is made to separate the interactive processes occurring in electromagnetic devices and to examine the acceleration of ionized gas within magnetic fields which can guide it through an expansion process. The plasma was generated in a single turn coil 50 cm long with a radius of 5.25 cm which surrounded a quartz tube with an internal radius of 3.81 cm and a length of 100 cm. Choking was found to occur at both sonic and cusp velocities which were coincident in the present experiment.

  20. Facility Measures Magnetic Fields

    NASA Technical Reports Server (NTRS)

    Honess, Shawn B.; Narvaez, Pablo; Mcauley, James M.

    1991-01-01

    Partly automated facility measures and computes steady near magnetic field produced by object. Designed to determine magnetic fields of equipment to be installed on spacecraft including sensitive magnetometers, with view toward application of compensating fields to reduce interfernece with spacecraft-magnetometer readings. Because of its convenient operating features and sensitivity of its measurements, facility serves as prototype for similar facilities devoted to magnetic characterization of medical equipment, magnets for high-energy particle accelerators, and magnetic materials.

  1. Graphene Nanoribbon in Sharply Localized Magnetic Fields

    E-print Network

    Abdulaziz D. Alhaidari; Hocine Bahlouli; Abderrahim El Mouhafid; Ahmed Jellal

    2013-03-20

    We study the effect of a sharply localized magnetic field on the electron transport in a strip (ribbon) of graphene sheet, which allows to give results for the transmission and reflection probability through magnetic barriers. The magnetic field is taken as a single and double delta type localized functions, which are treated later as the zero width limit of gaussian fields. For both field configurations, we evaluate analytically and numerically their transmission and reflection coefficients. The possibility of spacial confinement due to the inhomogeneous field configuration is also investigated.

  2. The Declining Magnetic Field

    NSDL National Science Digital Library

    2012-08-03

    This is an activity about the declining strength of Earth's magnetic field. Learners will review a graph of magnetic field intensity and calculate the amount by which the field has changed its intensity in the last century, the rate of change of its intensity, and when the field should decrease to zero strength at the current rate of change. Learners will also use evidence from relevant sources to create a conjecture on the effects on Earth of a vanished magnetic field. Access to information sources about Earth's magnetic field strength is needed for this activity. This is Activity 7 in the Exploring Magnetism on Earth teachers guide.

  3. 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

  4. Magnetic Fields on the Surface of the Sun

    NSDL National Science Digital Library

    This is a lesson about magnetism in solar flares. Learners will map magnetic fields around bar magnets and investigate how this configuration relates to magnetic fields of sunspots. This activity requires compasses, bar magnets, and a equipment for the instructor to project a PowerPoint or pdf lecture presentation. This is Activity 1 in the Exploring Magnetism in Solar Flares teachers guide.

  5. Magnetic Fields Analogous to electric field, a magnet

    E-print Network

    Bertulani, Carlos A. - Department of Physics and Astronomy, Texas A&M University

    Magnetic Fields Analogous to electric field, a magnet produces a magnetic field, B Set up a B field two ways: Moving electrically charged particles Current in a wire Intrinsic magnetic field Basic characteristic of elementary particles such as an electron #12;Magnetic Fields Magnetic field lines Direction

  6. The Magnetic Field

    NSDL National Science Digital Library

    Jeffrey Barker

    This demonstration of the magnetic field lines of Earth uses a bar magnet, iron filings, and a compass. The site explains how to measure the magnetic field of the Earth by measuring the direction a compass points from various points on the surface. There is also an explanation of why the north magnetic pole on Earth is actually, by definition, the south pole of a magnet.

  7. Electricity and Magnetic Fields

    NSDL National Science Digital Library

    VU Bioengineering RET Program,

    The grand challenge for this legacy cycle unit is for students to design a way to help a recycler separate aluminum from steel scrap metal. In previous lessons, they have looked at how magnetism might be utilized. In this lesson, students think about how they might use magnets and how they might confront the problem of turning the magnetic field off. Through the accompanying activity students explore the nature of an electrically induced magnetic field and its applicability to the needed magnet.

  8. Drawing Magnetic Fields

    NSDL National Science Digital Library

    VU Bioengineering RET Program,

    Students use a compass and a permanent magnet to trace the magnetic field lines produced by the magnet. By positioning the compass in enough spots around the magnet, the overall magnet field will be evident from the collection of arrows representing the direction of the compass needle. In activities 3 and 4 of this unit, students will use this information to design a way to solve the grand challenge of separating metal for a recycling company.

  9. Three-dimensional prominence-hosting magnetic configurations: Creating a helical magnetic flux rope

    SciTech Connect

    Xia, C.; Keppens, R. [Centre for Mathematical Plasma Astrophysics, Department of Mathematics, KU Leuven, Celestijnenlaan 200B, B-3001 Leuven (Belgium); Guo, Y. [School of Astronomy and Space Science, Nanjing University, Nanjing 210093 (China)

    2014-01-10

    The magnetic configuration hosting prominences and their surrounding coronal structure is a key research topic in solar physics. Recent theoretical and observational studies strongly suggest that a helical magnetic flux rope is an essential ingredient to fulfill most of the theoretical and observational requirements for hosting prominences. To understand flux rope formation details and obtain magnetic configurations suitable for future prominence formation studies, we here report on three-dimensional isothermal magnetohydrodynamic simulations including finite gas pressure and gravity. Starting from a magnetohydrostatic corona with a linear force-free bipolar magnetic field, we follow its evolution when introducing vortex flows around the main polarities and converging flows toward the polarity inversion line near the bottom of the corona. The converging flows bring the feet of different loops together at the polarity inversion line, where magnetic reconnection and flux cancellation happen. Inflow and outflow signatures of the magnetic reconnection process are identified, and thereby the newly formed helical loops wind around preexisting ones so that a complete flux rope grows and ascends. When a macroscopic flux rope is formed, we switch off the driving flows and find that the system relaxes to a stable state containing a helical magnetic flux rope embedded in an overlying arcade structure. A major part of the formed flux rope is threaded by dipped field lines that can stably support prominence matter, while the total mass of the flux rope is in the order of 4-5× 10{sup 14} g.

  10. Circuits and Magnetic Fields

    NSDL National Science Digital Library

    VU Bioengineering RET Program,

    Students use the same method as in the activity from lesson 2 of this unit to explore the magnetism due to electric current instead of a permanent magnet. Students use a compass and circuit to trace the magnetic field lines induced by the electric current moving through the wire. Students develop an understanding of the effect of the electrical current on the compass needle through the induced magnetic field and understand the complexity of a three dimensional field system.

  11. Magnetic fields at Neptune

    Microsoft Academic Search

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

    1989-01-01

    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 = 10⁻⁵ gauss) was observed near closest approach, at a

  12. Kinetic Stability of the Field Reversed Configuration

    SciTech Connect

    E.V. Belova; R.C. Davidson; H. Ji; and M. Yamada

    2002-07-09

    New computational results are presented which advance the understanding of the stability properties of the Field-Reversed Configuration (FRC). The FRC is an innovative confinement approach that offers a unique fusion reactor potential because of its compact and simple geometry, translation properties, and high plasma beta. One of the most important issues is FRC stability with respect to low-n (toroidal mode number) MHD modes. There is a clear discrepancy between the predictions of standard MHD theory that many modes should be unstable on the MHD time scale, and the observed macroscopic resilience of FRCs in experiments.

  13. 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.

  14. Magnetic Field Problem

    NSDL National Science Digital Library

    Wolfgang Christian

    The above animations represent two typical bar magnets each with a North and South pole. The arrows represent the direction of the magnetic field. The color of the arrows represents the magnitude of the field with magnitude increasing as the color changes from blue to green to red to black. You may drag either magnet and double-click anywhere inside the animation to add a magnetic field line, and mouse-down to read the magnitude of the magnetic field at that point.

  15. The configuration of the Brazilian scientific field.

    PubMed

    Barata, Rita B; Aragão, Erika; de Sousa, Luis E P Fernandes; Santana, Taris M; Barreto, Mauricio L

    2014-03-01

    This article describes the configuration of the scientific field in Brazil, characterizing the scientific communities in every major area of knowledge in terms of installed capacity, ability to train new researchers, and capacity for academic production. Empirical data from several sources of information are used to characterize the different communities. Articulating the theoretical contributions of Pierre Bourdieu, Ludwik Fleck, and Thomas Kuhn, the following types of capital are analyzed for each community: social capital (scientific prestige), symbolic capital (dominant paradigm), political capital (leadership in S & T policy), and economic capital (resources). Scientific prestige is analyzed by taking into account the volume of production, activity index, citations, and other indicators. To characterize symbolic capital, the dominant paradigms that distinguish the natural sciences, the humanities, applied sciences, and technology development are analyzed theoretically. Political capital is measured by presidency in one of the main agencies in the S & T national system, and research resources and fellowships define the economic capital. The article discusses the composition of these different types of capital and their correspondence to structural capacities in various communities with the aim of describing the configuration of the Brazilian scientific field. PMID:24676181

  16. Mapping Magnetic Field Lines

    NSDL National Science Digital Library

    This is a lesson about the magnetic field of a bar magnet. The lesson begins with an introductory discussion with learners about magnetism to draw out any misconceptions that may be in their minds. Then, learners freely experiment with bar magnets and various materials, such as paper clips, rulers, copper or aluminum wire, and pencils, to discover that magnets attract metals containing iron, nickel, and/or cobalt but not most other materials. Next, learners experiment with using a magnetic compass to discover how it is affected by the magnet and then draw the magnetic field lines of the magnet by putting dots at the location of the compass arrow. This is the first lesson in the first session of the Exploring Magnetism teacher guide.

  17. A new discrete packaging configuration of bidirectional power switch with less magnetic interference

    Microsoft Academic Search

    Handy Blanchette; Kamal Al-Haddad

    2005-01-01

    This paper presents a new discrete packaging configuration and an electromagnetic modeling of a bidirectional MOSFET power switch with less magnetic interference used in matrix converter application. The study is based on computing the magnetic field inside a specific new proposed low losses switching cell in order to incorporate gates drivers' circuit inside the power module space volume. The novelty

  18. Melatonin and magnetic fields.

    PubMed

    Karasek, Michal; Lerchl, Alexander

    2002-04-01

    There is public health concern raised by epidemiological studies indicating that extremely low frequency electric and magnetic fields generated by electric power distribution systems in the environment may be hazardous. Possible carcinogenic effects of magnetic field in combination with suggested oncostatic action of melatonin lead to the hypothesis that the primary effects of electric and magnetic fields exposure is a reduction of melatonin synthesis which, in turn, may promote cancer growth. In this review the data on the influence of magnetic fields on melatonin synthesis, both in the animals and humans, are briefly presented and discussed. PMID:12019358

  19. Hybrid equilibria of field-reversed configurations

    SciTech Connect

    Steinhauer, Loren C. [Department of Aeronautics and Astronautics, University of Washington, Seattle, Washington 98195 (United States)

    2011-11-15

    This paper presents the first detailed model of hybrid equilibria relevant to field-reversed configuration experiments, leading to a system of equations that are solved for a range of fully two-dimensional equilibria. Several features of these highly kinetic objects are explored. The range of equilibria is primarily dependent on a single free parameter related to the flow shear. The level of flow shear has a profound effect on the structure, especially near the separatrix. This likely has a strong influence on both stability and transport properties. Higher flow shear is favorable in every respect. The key factor behind the influence of flow shear is the relatively rapid end loss of unconfined ions. Differences between hybrid and static-fluid equilibrium models are highlighted, including the integrity of surface functions, the effect of flow shear, and the scrape-off layer thickness.

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

    SciTech Connect

    Mauel, M; Ryutov, D; Kesner, J

    2003-12-02

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

  1. Magnetic fields in neutron stars

    NASA Astrophysics Data System (ADS)

    Viganò, Daniele

    2013-09-01

    This work aims at studying how magnetic fields affect the observational properties and the long-term evolution of isolated neutron stars, which are the strongest magnets in the universe. The extreme physical conditions met inside these astronomical sources complicate their theoretical study, but, thanks to the increasing wealth of radio and X-ray data, great advances have been made over the last years. A neutron star is surrounded by magnetized plasma, the so-called magnetosphere. Modeling its global configuration is important to understand the observational properties of the most magnetized neutron stars, magnetars. On the other hand, magnetic fields in the interior are thought to evolve on long time-scales, from thousands to millions of years. The magnetic evolution is coupled to the thermal one, which has been the subject of study in the last decades. An important part of this thesis presents the state-of-the-art of the magneto-thermal evolution models of neutron stars during the first million of years, studied by means of detailed simulations. The numerical code here described is the first one to consistently consider the coupling of magnetic field and temperature, with the inclusion of both the Ohmic dissipation and the Hall drift in the crust.

  2. 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.

  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. Magnetic Field Viewing Cards

    NASA Astrophysics Data System (ADS)

    Kanim, Stephen; Thompson, John R.

    2005-09-01

    For some years now laminated cards containing a green, magnetically sensitive film have been available from science education suppliers. When held near a magnet, these cards appear dark green in regions where the field is perpendicular to the card and light green where the field is parallel to the card. The cards can be used to explore the magnetic field near a variety of magnets as well as near wire loops. In this paper we describe how to make these cards and how we have used them in our physics classrooms and labs.

  5. Magnetic field line Hamiltonian

    SciTech Connect

    Boozer, A.H.

    1984-03-01

    The magnetic field line Hamiltonian and the associated canonical form for the magnetic field are important concepts both for understanding toroidal plasma physics and for practical calculations. A number of important properties of the canonical or Hamiltonian representation are derived and their importance is explained.

  6. Cosmic Magnetic Fields

    Microsoft Academic Search

    Elisabete M. de Gouveia Dal Pino; Dal Pino

    2006-01-01

    Most of the visible matter in the Universe is in a plasma state, or more specifically is composed of ionized or partially ionized gas permeated by magnetic fields. Thanks to recent advances on the theory and detection of cosmic magnetic fields there has been a worldwide growing interest in the study of their role on the formation of astrophysical sources

  7. Novel magnets configuration toward a high performance electrodynamic micro-electro-mechanical-systems microspeaker

    NASA Astrophysics Data System (ADS)

    Sassine, G.; Shahosseini, I.; Woytasik, M.; Martincic, E.; Moulin, J.; Lefeuvre, E.

    2014-05-01

    This paper presents a study of different configurations of permanent magnets' to maximize microspeakers' electroacoustic performances. The proposed theoretical approach is based on an analytical model allowing the calculation of the magnetic field created by cylindrical and ring-shaped permanent magnet, making thus possible to analyze different magnetic structures. Several combinations of cylindrical and rings were analyzed in view of maximizing the magnetic field in the vicinity of the voice coil. Taking into account the whole electro-mechano-acoustic behavior of the microspeaker, we present two optimized magnets configurations which increase the efficiency by factors between 2.7 and 5 comparing to previously optimized microspeakers. Moreover, we show that it is possible to get devices twice smaller with efficiencies increased by factors between 1.2 and 3.4.

  8. Magnetic Fields Classroom Activity

    NSDL National Science Digital Library

    Reinhart, Rose

    In this lesson from Math Machines, students will learn about the effects of magnetic fields on moving, electrically charged particles. The activity consists of two exercises. The first involves analyzing how a robot is controlled in a magnetic field. The second has students design and test a "magnetic bottle."A participant handout (including worksheets) and facilitator notes are made available for download in DOC file format. A link to a required calculator program is also provided.

  9. Overview of C-2 Field Reversed Configuration Experiments

    NASA Astrophysics Data System (ADS)

    Guo, Houyang; TAE Team

    2013-10-01

    The C-2 compact toroid merging (CT) facility was built to form and sustain high temperature Field Reversed Configurations (FRC) with extremely high beta (i.e., with the ratio of confined plasma to external total magnetic pressure approaching 100%). Significant progress has been made in C-2 on both technology and physics fronts, achieving stable plasmas up to 5 ms with a dramatic improvement in confinement, far beyond the prediction from the conventional FRC scaling. The key approaches to these exciting achievements are (1) dynamic FRC formation by collisional merging of super-Alfvénic CTs, (2) effective control of stability and transport by plasma guns and neutral beam injection, and (3) active wall conditioning. The emerging confinement scaling for this new plasma regime shows a strong dependence on temperature in contrast to the usually observed Bohm or gyro-Bohm scaling in other magnetic confinement systems. This presentation highlights these recent advances.

  10. 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 (Gómez 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.

  11. Interplanetary Magnetic Field Lines

    NSDL National Science Digital Library

    Mendez, J.

    This web page, authored and curated by David P. Stern, provides information and a graphical exercise for students regarding the interaction between magnetic field lines and a plasma. The activity involves tracing a typical interplanetary magnetic field line, dragged out of a location on the Sun by the radial flow of the solar wind. This illustrates the way magnetic field lines are "frozen to the plasma" and the wrapping of field lines due to the rotation of the sun. This is part of the work "The Exploration of the Earth's Magnetosphere". A Spanish translation is available.

  12. Damping of cosmic magnetic fields

    SciTech Connect

    Jedamzik, K. [Max-Planck-Institut fuer Astrophysik, 85748 Garching bei Muenchen (Germany)] [Max-Planck-Institut fuer Astrophysik, 85748 Garching bei Muenchen (Germany); Katalinic, V.; Olinto, A.V. [Department of Astronomy and Astrophysics and Enrico Fermi Institute, University of Chicago, 5640 S. Ellis Ave., Chicago, Illinois 60637 (United States)] [Department of Astronomy and Astrophysics and Enrico Fermi Institute, University of Chicago, 5640 S. Ellis Ave., Chicago, Illinois 60637 (United States)

    1998-03-01

    We examine the evolution of magnetic fields in an expanding fluid composed of matter and radiation with particular interest in the evolution of cosmic magnetic fields. We derive the propagation velocities and damping rates for relativistic and non-relativistic fast and slow magnetosonic and Alfv{acute e}n waves in the presence of viscous and heat conducting processes. The analysis covers all magnetohydrodynamics modes in the radiation diffusion and the free-streaming regimes. When our results are applied to the evolution of magnetic fields in the early universe, we find that cosmic magnetic fields are damped from prior to the epoch of neutrino decoupling up to recombination. Similar to the case of sound waves propagating in a demagnetized plasma, fast magnetosonic waves are damped by radiation diffusion on all scales smaller than the radiation diffusion length. The characteristic damping scales are the horizon scale at neutrino decoupling (M{sub {nu}}{approx}10{sup {minus}4}M{sub {circle_dot}} in baryons) and the Silk mass at recombination (M{sub {gamma}}{approx}10{sup 13}M{sub {circle_dot}} in baryons). In contrast, the oscillations of slow magnetosonic and Alfv{acute e}n waves get overdamped in the radiation diffusion regime, resulting in frozen-in magnetic field perturbations. Further damping of these perturbations is possible only if before recombination the wave enters a regime in which radiation free-streams on the scale of the perturbation. The maximum damping scale of slow magnetosonic and Alfv{acute e}n modes is always smaller than or equal to the damping scale of fast magnetosonic waves, and depends on the magnetic field strength and its direction relative to the wave vector. Our findings have multifold implications for cosmology. The dissipation of magnetic field energy into heat during the epoch of neutrino decoupling ensures that most magnetic field configurations generated in the very early universe satisfy big bang nucleosynthesis constraints. Further dissipation before recombination constrains models in which primordial magnetic fields give rise to galactic magnetic fields or density perturbations. Finally, the survival of Alfv{acute e}n and slow magnetosonic modes on scales well below the Silk mass may be of significance for the formation of structure on small scales. {copyright} {ital 1998} {ital The American Physical Society}

  13. The outer magnetic field

    NASA Technical Reports Server (NTRS)

    Hoeksema, J. T.; Suess, S. T.

    1990-01-01

    The magnetic field of the sun extends outward through the photosphere into the corona. The resulting coronal and interplanetary magnetic fields therefore respond to and evolve with the solar cycle, as well as on shorter and longer time scales. These fields are modeled using photospheric magnetic field observations under the assumption that the coronal field is current free, becomes radial at a 'source surface' placed at 2.5 solar radii from the center of the sun, and is passively advected by the solar wind beyond the source surface. This review covers the computation of such models and their applications to characterize the morphology, evolution, and rotation of coronal and interplanetary magnetic fields using data collected between 1976 and the present at the Wilcox Solar Observatory.

  14. Nonlinear electron magnetohydrodynamics physics. I. Whistler spheromaks, mirrors, and field reversed configurations

    SciTech Connect

    Stenzel, R. L.; Urrutia, J. M.; Strohmaier, K. D. [Department of Physics and Astronomy, University of California, Los Angeles, California 90095-1547 (United States)

    2008-04-15

    The nonlinear interactions of time-varying magnetic fields with plasmas is investigated in the regime of electron magnetohydrodynamics. Simple magnetic field geometries are excited in a large laboratory plasma with a loop antenna driven with large oscillatory currents. When the axial loop field opposes the ambient field, the net field can be reversed to create a field-reversed configuration (FRC). In the opposite polarity, a strong field enhancement is produced. The time-varying antenna field excites whistler modes with wave magnetic fields exceeding the ambient magnetic field. The resulting magnetic field topologies have been measured. As the magnetic topology is changed from FRC to strong enhancement, two propagating field configurations resembling spheromaks are excited, one with positive and the other with negative helicity. Such 'whistler spheromaks' propagate with their null points along the weaker ambient magnetic field, with the current density localized around its O-line. In contrast, 'whistler mirrors' which have topologies similar to linear whistlers, except with B{sub wave}>B{sub 0}, have no null regions and, therefore, broad current layers. This paper describes the basic field topologies of whistler spheromaks and mirrors, while companion papers discuss the associated nonlinear phenomena as well as the interaction between them.

  15. Magnetic fields and rotation of spiral galaxies

    E-print Network

    E. Battaner; H. Lesch; E. Florido

    1998-02-02

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

  16. Magnetic field tomography, helical magnetic fields and Faraday depolarization

    NASA Astrophysics Data System (ADS)

    Horellou, C.; Fletcher, A.

    2014-07-01

    Wide-band radio polarization observations offer the possibility to recover information about the magnetic fields in synchrotron sources, such as details of their three-dimensional configuration, that has previously been inaccessible. The key physical process involved is the Faraday rotation of the polarized emission in the source (and elsewhere along the wave's propagation path to the observer). In order to proceed, reliable methods are required for inverting the signals observed in wavelength space into useful data in Faraday space, with robust estimates of their uncertainty. In this paper, we examine how variations of the intrinsic angle of polarized emission ?0 with the Faraday depth ? within a source affect the observable quantities. Using simple models for the Faraday dispersion F(?) and ?0(?), along with the current and planned properties of the main radio interferometers, we demonstrate how degeneracies among the parameters describing the magneto-ionic medium can be minimized by combining observations in different wavebands. We also discuss how depolarization by Faraday dispersion due to a random component of the magnetic field attenuates the variations in the spectral energy distribution of the polarization and shifts its peak towards shorter wavelengths. This additional effect reduces the prospect of recovering the characteristics of the magnetic field helicity in magneto-ionic media dominated by the turbulent component of the magnetic field.

  17. Dynamic processes in field-reversed-configuration compact toroids

    SciTech Connect

    Rej, D.J.

    1987-01-01

    In this lecture, the dynamic processes involved in field-reversed configuration (FRC) formation, translation, and compression will be reviewed. Though the FRC is related to the field-reversed mirror concept, the formation method used in most experiments is a variant of the field-reversed THETA-pinch. Formation of the FRC eqilibrium occurs rapidly, usually in less than 20 ..mu..s. The formation sequence consists of several coupled processes: preionization; radial implosion and compression; magnetic field line closure; axial contraction; equilibrium formation. Recent experiments and theory have led to a significantly improved understanding of these processes; however, the experimental method still relies on a somewhat empirical approach which involves the optimization of initial preionization plasma parameters and symmetry. New improvements in FRC formation methods include the use of lower voltages which extrapolate better to larger devices. The axial translation of compact toroid plasmas offers an attractive engineering convenience in a fusion reactor. FRC translation has been demonstrated in several experiments worldwide, and these plasmas are found to be robust, moving at speeds up to the Alfven velocity over distances of up to 16 m, with no degradation in the confinement. Compact toroids are ideal for magnetic compression. Translated FRCs have been compressed and heated by imploding liners. Upcoming experiments will rely on external flux compression to heat a translater FRC at 1-GW power levels. 39 refs.

  18. Magnetic fields in spiral galaxies

    NASA Astrophysics Data System (ADS)

    Chiba, Masashi

    The magnetic-field characteristics in spiral galaxies are investigated, with emphasis on the Milky Way. The dynamo theory is considered, and axisymmetric spiral (ASS) and bisymmetric spiral (BSS) magnetic fields are analyzed. Toroidal and poloidal magnetic fields are discussed.

  19. Detecting Exoplanetary Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Llama, Joe

    2015-01-01

    Asymmetries in exoplanet transits are proving to be a useful tool for furthering our understanding of magnetic activity on both stars and planets outside our Solar System.Near-UV observations of the WASP-12 system have revealed asymmetries in the timing of the transit when compared with the optical light curve. A number of possible explanations have been suggested for this variation, including the presence of a magnetospheric bow shock arising from the interaction of the planet's magnetic field with the stellar wind from it's host star. Such observations provide the first method for directly detecting the presence of a magnetic field on exoplanets.The shape and size of such asymmetries is highly dependent on the structure of the host stars magnetic field at the time of observation. This implies we may observe highly varying near-UV transit light curves for the same system. These variations can then be used to learn about the geometry of the host star's magnetic field.In this presentation I will show modelling a bow shock around an exoplanet can help us to not only detect, but also also place constraints on the magnetic field strength of hot Jupiters. For some systems, such as HD 189733, we have maps of the surface magnetic field of the star at various epochs. I will also show how incorporating these maps into a stellar wind model, I can model the formation of a bow shock around the planet and hence demonstrate the variability of the near-UV transits.

  20. Mapping Magnetic Field Lines

    NSDL National Science Digital Library

    This is an activity about electromagnetism. Learners will use a compass to map the magnetic field lines surrounding a coil of wire that is connected to a battery. This activity requires a large coil or spool of wire, a source of electricity such as 3 D-cell batteries or an AC to DC power adapter, alligator-clipped wire, and magnetic compasses. This is the third lesson in the second session of the Exploring Magnetism teachers guide.

  1. 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.

  2. Configuration and temperature dependence of magnetic damping in spin valves

    NASA Astrophysics Data System (ADS)

    Joyeux, X.; Devolder, T.; Kim, Joo-Von; Gomez de la Torre, Y.; Eimer, S.; Chappert, C.

    2011-09-01

    Using vector-analyzer ferromagnetic resonance, we have studied the microwave susceptibility of a Py/Co/Cu/Co/MnIr spin valve over a large temperature range (5-450 K) and as a function of the magnetic configuration. An effective magnetization and Gilbert damping constant of 1.1 T and 0.021, respectively, are found for the permalloy free layer, with no discernible variation in temperature observed for either quantities. In contrast, the pinned layer magnetization is reduced by heating, and the exchange bias collapses near a temperature of 450 K. The ferromagnetic resonance linewidth of the free layer increases by 500 MHz when the layer magnetizations are aligned in antiparallel, which is attributed to a configuration-dependent contribution to the damping from spin pumping effects.

  3. Configuration and temperature dependence of magnetic damping in spin valves

    SciTech Connect

    Joyeux, X.; Devolder, T.; Kim, Joo-Von; Gomez de la Torre, Y.; Eimer, S.; Chappert, C. [Institut d'Electronique Fondamentale, University Paris-Sud, 91405 Orsay (France); UMR8622, CNRS, University Paris-Sud, 91405 Orsay (France)

    2011-09-15

    Using vector-analyzer ferromagnetic resonance, we have studied the microwave susceptibility of a Py/Co/Cu/Co/MnIr spin valve over a large temperature range (5-450 K) and as a function of the magnetic configuration. An effective magnetization and Gilbert damping constant of 1.1 T and 0.021, respectively, are found for the permalloy free layer, with no discernible variation in temperature observed for either quantities. In contrast, the pinned layer magnetization is reduced by heating, and the exchange bias collapses near a temperature of 450 K. The ferromagnetic resonance linewidth of the free layer increases by 500 MHz when the layer magnetizations are aligned in antiparallel, which is attributed to a configuration-dependent contribution to the damping from spin pumping effects.

  4. Movements and magnetic fields on the sun

    Microsoft Academic Search

    V. A. Krat

    1977-01-01

    Studies of mass motions and magnetic-field configurations on the sun are reviewed. The intensity of the photospheric magnetic field is estimated from photographs of the granulation network obtained during stratospheric flights, and the behavior of the H-alpha line in stratospheric spectrograms is compared with that of metallic lines and the continuum. H-alpha filtergrams are also used to discern the forms

  5. Adiabatic model and design of a translating field reversed configuration

    SciTech Connect

    Intrator, T. P. [Los Alamos National Laboratory, M.S. E526, Los Alamos, New Mexico 87545 (United States); Siemon, R. E. [Department of Physics, University of Nevada, Reno, Reno, Nevada 89557 (United States); Sieck, P. E. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

    2008-04-15

    We apply an adiabatic evolution model to predict the behavior of a field reversed configuration (FRC) during decompression and translation, as well as during boundary compression. Semi-empirical scaling laws, which were developed and benchmarked primarily for collisionless FRCs, are expected to remain valid even for the collisional regime of FRX-L experiment. We use this approach to outline the design implications for FRX-L, the high density translated FRC experiment at Los Alamos National Laboratory. A conical theta coil is used to accelerate the FRC to the largest practical velocity so it can enter a mirror bounded compression region, where it must be a suitable target for a magnetized target fusion (MTF) implosion. FRX-L provides the physics basis for the integrated MTF plasma compression experiment at the Shiva-Star pulsed power facility at Kirtland Air Force Research Laboratory, where the FRC will be compressed inside a flux conserving cylindrical shell.

  6. Electronic configurations and magnetic anisotropy in organometallic metallocenes

    NASA Astrophysics Data System (ADS)

    Nawa, Kenji; Kitaoka, Yukie; Nakamura, Kohji; Akiyama, Toru; Ito, Tomonori

    2015-05-01

    Electronic configurations and magnetic anisotropy of organometallic metallocenes (MCp2s) were investigated by means of first principles calculations based on the constraint density functional theory. The results predict that the ground states for M = Cr, Mn, Fe, Co, and Ni are the 3E2 g, 2E2 g, 1A1 g, 2E1 g, and 3A2 g states, respectively. The magnetizations of the CoCp2 and NiCp2 energetically favor highly orienting along the perpendicular and parallel directions to the cyclopentadienyl (Cp) plane, respectively, and the others show almost no preference for the magnetic easy axis.

  7. Magnetic Field Problem: Current

    NSDL National Science Digital Library

    Wolfgang Christian

    A cross section of a circular wire loop carrying an unknown current is shown above. The arrows represent the direction of the magnetic field. The color of the arrows represents the magnitude of the field with magnitude increasing as the color changes from blue to green to red to black. You can double-click in the animation to add magnetic field lines, click-drag the center of the loop to reposition it, and click-drag the top or bottom of the loop to change its size.

  8. Hidden Magnetic Configuration in Epitaxial La1-x SrxMnO3 Films

    SciTech Connect

    Lee, J.S.; Arena, D.A.; Yu, P.; Nelson, C.S.; Fan, R.; Kinane, C.J.; Langridge, S.; Rossell, M.D.; Ramesh, R.; Kao, C.C.

    2010-12-17

    We present an unreported magnetic configuration in epitaxial La{sub 1-x}Sr{sub x}MnO{sub 3} (x {approx} 0.3) (LSMO) films grown on strontium titanate (STO). X-ray magnetic circular dichroism indicates that the remanent magnetic state of thick LSMO films is opposite to the direction of the applied magnetic field. Spectroscopic and scattering measurements reveal that the average Mn valence varies from mixed Mn{sup 3+}/Mn{sup 4+} to an enriched Mn{sup 3+} region near the STO interface, resulting in a compressive lattice along the a, b axis and a possible electronic reconstruction in the Mn e{sub g} orbital (d{sub 3z{sup 2}-r{sup 2}}). This reconstruction may provide a mechanism for coupling the Mn{sup 3+} moments antiferromagnetically along the surface normal direction, and in turn may lead to the observed reversed magnetic configuration.

  9. Magnetic susceptibility of a model for valence fluctuations between two magnetic configurations: Renormalization-group approach

    Microsoft Academic Search

    Roberto Allub; Horacio Ceva; Blas R. Alascio

    1984-01-01

    We use Wilson's renormalization-group technique to calculate the magnetic susceptibility of an impurity model describing fluctuations between two magnetic configurations. We find a magnetic ground state and a divergent susceptibility at low temperatures. When the configuration with larger degeneracy is more stable than the other, the model can be reduced to a spin-1 Kondo model and its low-temperature behavior exhibits

  10. Experimental configuration for isentropic compression of solids using pulsed magnetic loading

    NASA Astrophysics Data System (ADS)

    Hall, C. A.; Asay, J. R.; Knudson, M. D.; Stygar, W. A.; Spielman, R. B.; Pointon, T. D.; Reisman, D. B.; Toor, A.; Cauble, R. C.

    2001-09-01

    A capability to produce quasi-isentropic compression of solids using pulsed magnetic loading on the Z accelerator has recently been developed and demonstrated [C. A. Hall, Phys. Plasmas 7, 2069 (2000)]. This technique allows planar, continuous compression of materials to stresses approaching 1.5 Mbar. In initial stages of development, the experimental configuration used a magnetically loaded material cup or disk as the sample of interest pressed into a conductor. This installation caused distortions that limited the ability to attach interferometer windows or other materials to the rear of the sample. In addition, magnetic pressure was not completely uniform over sample dimensions of interest. A new modular configuration is described that improves the uniformity of loading over the sample surface, allows materials to be easily attached to the magnetically loaded sample, and improves the quality of data obtained. Electromagnetic simulations of the magnetic field uniformity for this new configuration will also be presented. Comparisons between data on copper to ˜300 kbar using the old and new experimental configurations will also be made. Results indicate that to within experimental error, the configurations produce similar results in the pressure-volume plane.

  11. HMI Magnetic Field Products

    NASA Astrophysics Data System (ADS)

    Hoeksema, Jon T.; HMI Magnetic Field Team

    2013-07-01

    The Helioseismic and Magnetic Imager (HMI) on SDO has measured magnetic field, velocity, and intensity in the photosphere over the full disk continuously since May 2010 with arc-second resolution. Scalar images are measured every 45 seconds. From these basic observables the pipeline automatically identifies and tracks active regions on the solar disk. The vector magnetic field and a variety of summary quantities are determined every 720s in these tracked Space-weather HMI Active Region Patches (SHARPS). Synoptic and synchronic maps are constructed daily and after each Carrington Rotation Most data products are available with definitive scientific calibration after a few day deal at and in a quick-look near-real-time version a few minutes after the observations are made. Uncertainties are determined for the derived products. All of the magnetic field products along with movies and images suitable for browsing are available at http:://Hmi.stanford.edu/magnetic. Other products, e.g. coronal field over active regions, can be computed on demand.

  12. 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 ?G) and in central starburst regions (50-100 ?G). 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 ?G 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 ? -? 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.

  13. Use of high magnetic fields at the study of magnetism and superconductivity in intermetallic compounds

    Microsoft Academic Search

    J. J. M. Franse; F. R. Deboer; P. H. Frings; A. Devisser

    1994-01-01

    Magnetic fields have a large impact on the magnetic and superconducting properties of solids. High magnetic fields are required to reach magnetic saturation along a hard magnetic direction in a variety of rare-earth intermetallics, to break the ferrimagnetic moment configuration in specific 3d-4f intermetallics, to quench the strongly correlated electron states in heavy-fermion compounds, to reach the upper critical fields

  14. The use of high magnetic fields for the study of magnetism and superconductivity in intermetallic compounds

    Microsoft Academic Search

    J. J. M. Franse; F. R. De Boer; P. H. Frings; A. De Visser

    1994-01-01

    Magnetic fields have a large impact on the magnetic and superconducting properties of solids. High magnetic fields are required to reach magnetic saturation along a hard magnetic direction in a variety of rare-earth intermetallics, to break the ferrimagnetic moment configuration in specific 3d-4f intermetallics, to quench the strongly correlated electron states in heavy-fermion compounds, to reach the upper critical fields

  15. Magnetic Field Measurements in Beam Guiding Magnets

    Microsoft Academic Search

    K. N. Henrichsen

    1998-01-01

    Electromagnets used as beam guiding elements in particle accelerators and colliders require very tight tole-rances on their magnetic fields and on their alignment along the particle path. This article describes the methods and equipment used for magnetic measurements in beam transport magnets. Descriptions are given of magnetic resonance techniques, various induction coil methods, Hall generator measurements, the fluxgate magnetometer as

  16. The Primordial Origin Model of Magnetic Fields in Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Sofue, Yoshiaki; Machida, Mami; Kudoh, Takahiro

    2010-10-01

    We propose a primordial-origin model for composite configurations of global magnetic fields in spiral galaxies. We show that a uniform tilted magnetic field wound up into a rotating disk galaxy can evolve into composite magnetic configurations comprising bisymmetric spiral (S = BSS), axisymmetric spiral (A = ASS), plane-reversed spiral (PR), and/or ring (R) fields in the disk, and vertical (V) fields in the center. By MHD simulations we show that these composite galactic fields are indeed created from a weak primordial uniform field, and that different configurations can co-exist in the same galaxy. We show that spiral fields trigger the growth of two-armed gaseous arms. The centrally accumulated vertical fields are twisted and produce a jet toward the halo. We found that the more vertical was the initial uniform field, the stronger was the formed magnetic field in the galactic disk.

  17. Multichord optical interferometry of FRX-L's field reversed configuration

    NASA Astrophysics Data System (ADS)

    Ruden, E. L.; Zhang, Shouyin; Wurden, G. A.; Intrator, T. P.; Renneke, R.; Waganaar, W. J.; Analla, F. T.; Grabowski, T. C.

    2006-10-01

    A 0.633?m laser interferometer provides detailed time resolved information about the spatial distribution of the plasma density of field reversed configurations (FRC's) produced by the FRX-L experiment at Los Alamos National Laboratory. This experiment is an effort to produce a magnetized plasma with closed field lines suitable for compression by a solid metal liner imploded by the Shiva Star capacitor bank at the Air Force Research Laboratory. The interferometer probes a fanned array of eight chords through the FRC midplane, measuring the line integrated free electron density via its effect on optical phase shift relative to eight reference beams as a function of time. The reference beams are given nominally identical optical paths, except that they are folded for compactness and given an 80MHz higher optical frequency by use of a Bragg cell beam splitter. After the beams are recombined, interference results in 80MHz electromagnetic beat waves with dynamic phase shifts equal to those of the corresponding optical probes. Quadrature mixing of the electronically monitored light is then performed with rf components. Noteworthy features of the interferometer's design are the unique compact folding scheme of the reference paths, inclusion of a fused quartz tube in the reference path similar to that of the FRC's vacuum vessel to compensate for cylindrical lensing, and transmission of the interfering light via optical fibers to a rf shielded room for processing. Extraneous contributions to the phase shift due to vibration resulting from the system's pulsed magnetic field, and dynamic refractive changes in or near the fused quartz tube wall (possibly due to radiation heating) are corrected for.

  18. Multichord optical interferometry of FRX-L's field reversed configuration

    SciTech Connect

    Ruden, E. L.; Zhang, Shouyin; Wurden, G. A.; Intrator, T. P.; Renneke, R.; Waganaar, W. J.; Analla, F. T.; Grabowski, T. C. [Air Force Research Laboratory, Directed Energy Directorate, Kirtland AFB, New Mexico 87117 (United States); Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Science Applications International Corporation, Albuquerque, New Mexico 87106 (United States)

    2006-10-15

    A 0.633 {mu}m laser interferometer provides detailed time resolved information about the spatial distribution of the plasma density of field reversed configurations (FRC's) produced by the FRX-L experiment at Los Alamos National Laboratory. This experiment is an effort to produce a magnetized plasma with closed field lines suitable for compression by a solid metal liner imploded by the Shiva Star capacitor bank at the Air Force Research Laboratory. The interferometer probes a fanned array of eight chords through the FRC midplane, measuring the line integrated free electron density via its effect on optical phase shift relative to eight reference beams as a function of time. The reference beams are given nominally identical optical paths, except that they are folded for compactness and given an 80 MHz higher optical frequency by use of a Bragg cell beam splitter. After the beams are recombined, interference results in 80 MHz electromagnetic beat waves with dynamic phase shifts equal to those of the corresponding optical probes. Quadrature mixing of the electronically monitored light is then performed with rf components. Noteworthy features of the interferometer's design are the unique compact folding scheme of the reference paths, inclusion of a fused quartz tube in the reference path similar to that of the FRC's vacuum vessel to compensate for cylindrical lensing, and transmission of the interfering light via optical fibers to a rf shielded room for processing. Extraneous contributions to the phase shift due to vibration resulting from the system's pulsed magnetic field, and dynamic refractive changes in or near the fused quartz tube wall (possibly due to radiation heating) are corrected for.

  19. Relativistic stars with purely toroidal magnetic fields

    SciTech Connect

    Kiuchi, Kenta [Department of Physics, Waseda University, 3-4-1 Okubo, Shinjuku-ku, Tokyo 169-8555 (Japan); Yoshida, Shijun [Astronomical Institute, Tohoku University, Sendai 980-8578 (Japan)

    2008-08-15

    We investigate the effects of the purely toroidal magnetic field on the equilibrium structures of the relativistic stars. The basic equations for obtaining equilibrium solutions of relativistic rotating stars containing purely toroidal magnetic fields are derived for the first time. To solve these basic equations numerically, we extend the Cook-Shapiro-Teukolsky scheme for calculating relativistic rotating stars containing no magnetic field to incorporate the effects of the purely toroidal magnetic fields. By using the numerical scheme, we then calculate a large number of the equilibrium configurations for a particular distribution of the magnetic field in order to explore the equilibrium properties. We also construct the equilibrium sequences of the constant baryon mass and/or the constant magnetic flux, which model the evolution of an isolated neutron star as it loses angular momentum via the gravitational waves. Important properties of the equilibrium configurations of the magnetized stars obtained in this study are summarized as follows: (1) For the nonrotating stars, the matter distribution of the stars is prolately distorted due to the toroidal magnetic fields. (2) For the rapidly rotating stars, the shape of the stellar surface becomes oblate because of the centrifugal force. But, the matter distribution deep inside the star is sufficiently prolate for the mean matter distribution of the star to be prolate. (3) The stronger toroidal magnetic fields lead to the mass shedding of the stars at the lower angular velocity. (4) For some equilibrium sequences of the constant baryon mass and magnetic flux, the stars can spin up as they lose angular momentum.

  20. Chaotic magnetic fields: Particle motion and energization

    SciTech Connect

    Dasgupta, Brahmananda [CSPAR, University of Alabama in Huntsville, Huntsville, AL 35805 (United States); Ram, Abhay K. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Li, Gang [Department of Physics, University of Alabama in Huntsville, Huntsville, AL 35899 and CSPAR, University of Alabama in Huntsville, Huntsville, AL 35805 (United States); Li, Xiaocan [Department of Physics, University of Alabama in Huntsville, Huntsville, AL 35899 (United States)

    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.

  1. The Earth's Magnetic Field

    NSDL National Science Digital Library

    Roberta Johnson

    2000-07-01

    This section of the Windows to the Universe website provides information and images about Earth's magnetic field (the magnetosphere), including detailed information about the aurora borealis, magnets, and solar wind. Windows to the Universe is a user-friendly learning system pertaining to the Earth and Space sciences. The objective of this project is to develop an innovative and engaging website that includes a rich array of documents, including images, movies, animations, and data sets that explore the Earth and Space sciences and the historical and cultural ties between science, exploration and the human experience. Links at the top of each page allow users to navigate between beginner, intermediate and advanced levels.

  2. 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.

  3. A flexible and configurable system to test accelerator magnets

    SciTech Connect

    Jerzy M. Nogiec et al.

    2001-07-20

    Fermilab's accelerator magnet R and D programs, including production of superconducting high gradient quadrupoles for the LHC insertion regions, require rigorous yet flexible magnetic measurement systems. Measurement systems must be capable of handling various types of hardware and extensible to all measurement technologies and analysis algorithms. A tailorable software system that satisfies these requirements is discussed. This single system, capable of distributed parallel signal processing, is built on top of a flexible component-based framework that allows for easy reconfiguration and run-time modification. Both core and domain-specific components can be assembled into various magnet test or analysis systems. The system configured to comprise a rotating coil harmonics measurement is presented. Technologies as Java, OODB, XML, JavaBeans, software bus and component-based architectures are used.

  4. Magnetic fields in mixed neutron-star-plus-wormhole systems

    E-print Network

    Ascar Aringazin; Vladimir Dzhunushaliev; Vladimir Folomeev; Burkhard Kleihaus; Jutta Kunz

    2015-04-09

    We consider mixed configurations consisting of a wormhole filled by a strongly magnetized isotropic or anisotropic neutron fluid. The nontrivial topology of the spacetime is allowed by the presence of exotic matter. By comparing these configurations with ordinary magnetized neutron stars, we clarify the question of how the presence of the nontrivial topology influences the magnetic field distribution inside the fluid. In the case of an anisotropic fluid, we find new solutions describing configurations, where the maximum of the fluid density is shifted from the center. A linear stability analysis shows that these mixed configurations are unstable.

  5. CSEM-steel hybrid wiggler/undulator magnetic field studies

    SciTech Connect

    Halbach, K.; Hoyer, E.; Marks, S.; Plate, D.; Shuman, D.

    1985-05-01

    Current design of permanent magnet wiggler/undulators use either pure charge sheet equivalent material (CSEM) or the CSEM-Steel hybrid configuration. Hybrid configurations offer higher field strength at small gaps, field distributions dominated by the pole surfaces and pole tuning. Nominal performance of the hybrid is generally predicted using a 2-D magnetic design code neglecting transverse geometry. Magnetic measurements are presented showing transverse configuration influence on performance, from a combination of models using CSEMs, REC (H/sub c/ = 9.2 kOe) and NdFe (H/sub c/ = 10.7 kOe), different pole widths and end configurations. Results show peak field improvement using NdFe in place of REC in identical models, gap peak field decrease with pole width decrease (all results less than computed 2-D fields), transverse gap field distributions, and importance of CSEM material overhanging the poles in the transverse direction for highest gap fields.

  6. Magnetic field induced rearrangement of the electric field domains in weakly coupled superlattices

    Microsoft Academic Search

    W. H. M. Feu; D. C. Elias; L. A. Cury; G. S. Vieira; M. P. Pires; S. M. Landi; P. L. Souza

    2007-01-01

    We present an investigation of the electric field domain configuration in the sequential tunneling regime in weakly coupled superlattices in the presence of a magnetic field applied parallel to the quantum well layers. We show that, for an applied bias such that two electric field domains are present in the sample, as the magnetic field is increased a succession of

  7. 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.

  8. Simulation of lightning magnetic field

    Microsoft Academic Search

    Chen Yazhou; Wu Xiaorong; Liu Shanghe; Zhang Feizhou

    2002-01-01

    The lightning magnetic field is simulated when a pulse current is injected into the loop from the lightning surge generator. Different waveforms of lightning magnetic field can be simulated by regulating the parameters of the loop according to the relation between the parameters of the loop and the simulated wave. The dot loop is made to measure the magnetic field

  9. The WIND magnetic field investigation

    Microsoft Academic Search

    R. P. Lepping; M. H. Ac?na; L. F. Burlaga; W. M. Farrell; J. A. Slavin; K. H. Schatten; F. Mariani; N. F. Ness; F. M. Neubauer; Y. C. Whang; J. B. Byrnes; R. S. Kennon; P. V. Panetta; J. Scheifele; E. M. Worley

    1995-01-01

    The magnetic field experiment on WIND will provide data for studies of a broad range of scales of structures and fluctuation characteristics of the interplanetary magnetic field throughout the mission, and, where appropriate, relate them to the statics and dynamics of the magnetosphere. The basic instrument of the Magnetic Field Investigation (MFI) is a boom-mounted dual triaxial fluxgate magnetometer and

  10. AC Magnetic Field Survey Report

    E-print Network

    Krstic, Miroslav

    AC Magnetic Field Survey Report of Literature Building - 3000 University of California San Diego:..........................................................................................................2 ELF OR AC MAGNETIC FIELD CHARACTERISTICS:...............................................2 UNITS of California San Diego La Jolla, California PROJECT: AC Magnetic Field Survey SCOPE: The scope of this project

  11. Stray Field Magnetic Resonance Imaging

    Microsoft Academic Search

    K. Zick

    1994-01-01

    In many applications of magnetic resonance imaging large linewidths means that to achieve useful resolution in the image large magnetic field gradients should be employed. This paper outlines the principles of stray field imaging that utilises the large gradients intrinsic to the fringe field of superconducting solenoidal magnets. Examples of images from strongly broadened everyday objects are given.

  12. Classical field configurations and infrared slavery

    NASA Astrophysics Data System (ADS)

    Swanson, Mark S.

    1987-09-01

    The problem of determining the energy of two spinor particles interacting through massless-particle exchange is analyzed using the path-integral method. A form for the long-range interaction energy is obtained by analyzing an abridged vertex derived from the parent theory. This abridged vertex describes the radiation of zero-momentum particles by pointlike sources. A path-integral formalism for calculating the energy of the radiation field associated with this abridged vertex is developed and applications are made to determine the energy necessary for adiabatic separation of two sources in quantum electrodynamics and for an SU(2) Yang-Mills theory. The latter theory is shown to be consistent with confinement via infrared slavery.

  13. Plasma transport in a simulated magnetic-divertor configuration

    SciTech Connect

    Strawitch, C. M.

    1981-03-01

    The transport properties of plasma on magnetic field lines that intersect a conducting plate are studied experimentally in the Wisconsin internal ring D.C. machine. The magnetic geometry is intended to simulate certain aspects of plasma phenomena that may take place in a tokamak divertor. It is found by a variety of measurements that the cross field transport is non-ambipolar; this may have important implications in heat loading considerations in tokamak divertors. The undesirable effects of nonambipolar flow make it preferable to be able to eliminate it. However, we find that though the non-ambipolarity may be reduced, it is difficult to eliminate entirely. The plasma flow velocity parallel to the magnetic field is found to be near the ion acoustic velocity in all cases. The experimental density and electron temperature profiles are compared to the solutions to a one dimensional transport model that is commonly used in divertor theory.

  14. The Astromag Superconducting Magnet Facility Configured for a FreeFlying Satellite

    SciTech Connect

    Green, M.A.; Smoot, George F.

    1991-06-01

    ASTROMAG is a particle astrophysics facility that was originally configured for the Space Station. The heart of the ASTROMAG facility is a large superconducting magnet which is cooled using superfluid helium. The task of resizing the facility so that it will fly in a satellite in. a high angle of inclination orbit is driven by the launch weight capability of the launch rocket and the desire to be able to do nearly the same physics as the Space Station version of ASTROMAG. In order to reduce the launch weight, the magnet and its cryogenic system had to be downsized, yet the integrated field generated by the magnet in the particle detectors has to match the Space Station version of the magnet. The use of aluminum matrix superconductor and oriented composite materials in the magnet insulation permits one to achieve this goal. The net magnetic dipole moment from the ASTROMAG magnet must be small to minimize the torque due to interaction with the earth's magnetic field. The ASTROMAG magnet consists of identical two coils 1.67 meters apart. The two coils are connected in series in persistent mode. Each coil is designed to carry 2.34 million ampere turns. Both coils are mounted on the same magnetic axis and they operate at opposite polarity. This reduces the dipole moment by a factor of more than 1000. This is tolerable for the Space Station version of the magnet. A magnet operating on a free flying satellite requires additional compensation. This report presents the magnet parameters of a free flying version of ASTROMAG and the parameters of the space cryogenic system for the magnet.

  15. The ASTROMAG superconducting magnet facility configured for a free flying satellite

    SciTech Connect

    Green, M.A.; Smoot, G.F.

    1991-06-01

    ASTROMAG is a particle astrophysics facility that was originally configured for the Space Station. The heart of the ASTROMAG facility is a large superconducting magnet which is cooled using superfluid helium. The task of resizing the facility so that it will fly in a satellite in a high angle of inclination orbit is driven by the launch weight capability of the launch rocket and the desire to be able to do nearly the same physics as the Space Station version of ASTROMAG. In order to reduce the launch weight, the magnet and its cryogenic system had to be downsized, yet the integrated field generated by the magnet in the particle detectors has to match the Space Station version of the magnet. The use of aluminum matrix superconductor and oriented composite materials in the magnet insulation permits one to achieve this goal. The net magnetic dipole moment from the ASTROMAG magnet must be small to minimize the torque due to interaction with the earth's magnetic field. The ASTROMAG magnet consists of identical two coils 1.67 meters apart. The two coils are connected in series in persistent mode. Each coil is designed to carry 2.34 million ampere turns. Both coils are mounted on the same magnetic axis and they operate at opposite polarity. This reduces the dipole moment by a factor of more than 1000. This is tolerable for the Space Station version of the magnet. A magnet operating on a free flying satellite requires additional compensation. This report presents the magnet parameters of a free flying version of ASTROMAG and the parameters of the space cryogenic system for the magnet. 12 refs., 6 figs.

  16. Compact low field magnetic resonance imaging magnet: Design and optimization

    NASA Astrophysics Data System (ADS)

    Sciandrone, M.; Placidi, G.; Testa, L.; Sotgiu, A.

    2000-03-01

    Magnetic resonance imaging (MRI) is performed with a very large instrument that allows the patient to be inserted into a region of uniform magnetic field. The field is generated either by an electromagnet (resistive or superconductive) or by a permanent magnet. Electromagnets are designed as air cored solenoids of cylindrical symmetry, with an inner bore of 80-100 cm in diameter. In clinical analysis of peripheral regions of the body (legs, arms, foot, knee, etc.) it would be better to adopt much less expensive magnets leaving the most expensive instruments to applications that require the insertion of the patient in the magnet (head, thorax, abdomen, etc.). These "dedicated" apparati could be smaller and based on resistive magnets that are manufactured and operated at very low cost, particularly if they utilize an iron yoke to reduce power requirements. In order to obtain good field uniformity without the use of a set of shimming coils, we propose both particular construction of a dedicated magnet, using four independently controlled pairs of coils, and an optimization-based strategy for computing, a posteriori, the optimal current values. The optimization phase could be viewed as a low-cost shimming procedure for obtaining the desired magnetic field configuration. Some experimental measurements, confirming the effectiveness of the proposed approach (construction and optimization), have also been reported. In particular, it has been shown that the adoption of the proposed optimization based strategy has allowed the achievement of good uniformity of the magnetic field in about one fourth of the magnet length and about one half of its bore. On the basis of the good experimental results, the dedicated magnet can be used for MRI of peripheral regions of the body and for animal experimentation at very low cost.

  17. 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.

  18. Experimental evidence of skyrmion-like configurations in bilayer nanodisks with perpendicular magnetic anisotropy

    NASA Astrophysics Data System (ADS)

    Stebliy, Maxim E.; Kolesnikov, Alexander G.; Davydenko, Alexander V.; Ognev, Alexey V.; Samardak, Alexander S.; Chebotkevich, Ludmila A.

    2015-05-01

    Formation and existence of magnetic skyrmion-like configurations in bilayer nanodisks {Ta(3 nm)/[Co(0.37 nm)/Ni(0.58 nm)]10}2 with perpendicular magnetic anisotropy are shown experimentally at room temperature. Magnetization reversal through the skyrmion state is studied using magnetic hysteresis measurements. An evolution of skyrmion configurations in the nanodisk structure is analyzed. Experimental methods and micromagnetic simulations help to understand the magnetization reversal processes occurring through the stable skyrmion-like configurations. Formation of the intermediate C-states during magnetization reversal is demonstrated. The skyrmion number for all possible spin configurations is calculated.

  19. Multichord optical interferometry of FRX-L’s field reversed configuration

    Microsoft Academic Search

    E. L. Ruden; Shouyin Zhang; G. A. Wurden; T. P. Intrator; R. Renneke; W. J. Waganaar; F. T. Analla; T. C. Grabowski

    2006-01-01

    A 0.633 ?m laser interferometer provides detailed time resolved information about the spatial distribution of the plasma density of field reversed configurations (FRC’s) produced by the FRX-L experiment at Los Alamos National Laboratory. This experiment is an effort to produce a magnetized plasma with closed field lines suitable for compression by a solid metal liner imploded by the Shiva Star

  20. Similarity of Edge Turbulence in Various Magnetic Configurations of HSX

    NASA Astrophysics Data System (ADS)

    Guttenfelder, Walter

    2005-10-01

    Multi-pin Langmuir probes have been used to measure the edge and SOL characteristics of HSX plasmas in multiple locations and under various magnetic configurations. Auxiliary coils provide the flexibility to change the vacuum magnetic spectrum, well depth, rotational transform, and effective minor radius. The ion saturation current and floating potential probes measure broadband, large level fluctuations (10 -- 40%) in the edge and SOL. Poloidal wavenumbers, measured via two displaced probes, are in the range of 0.5 -- 1.5 cm-1, with ?sk? = 0.1 -- 0.2. From the estimated density gradient scale lengths in the edge (Ln = 2 -- 5 cm), these fluctuation levels are consistent with mixing length type arguments (n`/n ˜ 1/k?Ln). The phase velocities of the fluctuations follow the ExB velocities inferred from floating potential profiles. The measured turbulent features are similar for the quasi-symmetric and non-symmetric configurations. This work is supported by DOE grant number DE-FG02-93ER54222.

  1. Magnetic field studies at Jupiter by Voyager 1: preliminary results

    Microsoft Academic Search

    N. F. Ness; M. H. Acuna; R. P. Lepping; L. F. Burlaga; K. W. Behannon; F. M. Neubauer

    1979-01-01

    Results obtained by the Goddard Space Flight Center magnetometers on Voyager 1 concerning the large scale configuration of the Jovian bow shock and magnetopause, and the magnetic field in both the inner and outer magnetosphere are highlighted. There is evidence that a magnetic tail extending away from the planet on the nightside is formed by the solar wind-Jovian field interaction.

  2. 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.

  3. (version 6/26/06) Magnetic Fields

    E-print Network

    Collins, Gary S.

    (version 6/26/06) Magnetic Fields GOALS (1) To visualize the magnetic fields produced by several to trace out the magnetic field lines of a single bar magnet on a large sheet of paper. (3) To calculate where the magnetic fields of the Earth and the bar magnet sum to zero. INTRODUCTION A magnetic field

  4. Physics and Engineering Assessments ?of the K-DEMO Magnet Configuration

    SciTech Connect

    Neilson, George H. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Brown, Thomas [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)

    2014-09-01

    Increased attention is being given now to studies of next-step fusion facilities with nuclear missions. Among these, South Korea's K DEMO is unique in its focus on a high toroidal magnetic field, large major radius, steady-state tokamak design for the core of a facility to test fusion nuclear components in Phase I and, after upgrades, produce 500 MW of electricity in a Phase II. Innovative features of the K DEMO magnet set include the use of two toroidal field (TF) coil winding packs with conductor grading and a machine configuration designed for vertical maintenance. The magnet arrangement features large TF coils and widelyspaced poloidal field (PF) coils to accommodate removal of in-vessel components as large modules. Physics and engineering assessments of the pre-conceptual K-DEMO magnet configuration are reported, including: 1) design point and operating space assessment, 2) conductor assessment, and 3) structural assessment. It is found that a reference design point at 6.8 m major radius and 7.4 T toroidal field provides sufficient operating margins for the 500 MWe Phase II mission. Analyses of candidate cable-in-conduit conductors provide predictions of critical current degradation, both in the initial load cycle and an additionally with cyclic loading. A first-pass global analysis of the magnet system found minimal out-of-plane deformations of the TF coil, but an overstress condition in the inner leg of the TF coil. However an analysis taking into account elastic-plastic behavior, frictional sliding, and displacement shows that the structure can safely carry the load. Although the design evolution is still at an early stage, these assessments support the design point choices to date and the expectation that a feasible solution for the high-field K DEMO magnet system can be found.

  5. Formation of Non-Potential Magnetic Field and Flare-CMEs Eruption

    Microsoft Academic Search

    Hongqi Zhang

    2005-01-01

    We analyze the formation process of delta configuration in some well-known super active regions based on the photospheric vector magnetogram observations. It is found that the magnetic field in the initial developing stage of some delta active regions shows the potential-like configuration in the solar atmosphere, the magnetic shear develops mainly near the magnetic neutral line with the magnetic islands

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

    SciTech Connect

    Stenzel, R.L.; Urrutia, J.M.; Strohmaier, K.D. [Department of Physics and Astronomy, University of California, Los Angeles, California 90095-1547 (United States)

    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.

  7. The external magnetic field environment

    NASA Technical Reports Server (NTRS)

    1977-01-01

    Calculations were made to predict magnetic field intensities surrounding an aircraft following a lightning strike. Aircraft design and aircraft structural geometry were considered in the computations. A wire grid aircraft model was used to aid in magnetic flux estimation.

  8. Equilibrium rotation in field-reversed configurations Loren Steinhauer

    E-print Network

    Washington at Seattle, University of

    of spheromaks D. D. Ryutov, Phys. Plasmas 14, 022506 2007 . The opening up of internal magnetic field lines was recently investigated by Ryutov in the context of spheromaks.1 The same effect is expected to appear

  9. Magnetic fields of degenerate stars

    NASA Astrophysics Data System (ADS)

    Chanmugam, G.

    The magnetic fields of degenerate stars are discussed with emphasis on such basic issues as how their magnetic field strengths are determined, their origin, and evolution. The magnetic fields of both white dwarfs and neutron stars are discussed together, and it is speculated that the origin and evolution of their fields may be related. It is also suggested that it may be possible to apply and test models for the evolution of the magnetic fields in neutron stars by using white dwarfs and vice versa.

  10. 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.

  11. 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.

  12. Domain configuration and magnetization switching in arrays of permalloy nanostripes

    NASA Astrophysics Data System (ADS)

    Iglesias-Freire, Ó.; Jaafar, M.; Pérez, L.; de Abril, O.; Vázquez, M.; Asenjo, A.

    2014-04-01

    The proximity effect in the collective behavior of arrays of magnetic nanostripes is currently a subject of intensive research. The imperative of reducing the size and distances between elements in order to achieve higher storage capacity, faster access to the information as well as low energy consumption, brings consequences about the isolated behavior of the elements and devices. Parallel to each other permalloy nanostripes with high aspect ratio have been prepared by the nanolithography technique. The evolution of the closure domains and the magnetization direction in individual nanostructures has been imaged under applied magnetic fields using Variable Field Magnetic Force Microscopy. Moreover, the magnetostatic interactions between neighboring elements and the proximity effects in arrays of such nanostructures have been quantitatively analyzed by Magnetic Force Microscopy and micromagnetic simulations. The agreement between simulations and the experimental results allows us to conclude the relevance of those interactions depending on the geometry characteristics. In particular, results suggest that the magnetostatic coupling between adjacent nanostripes vanishes for separation distances higher than 500 nm.

  13. Evolution of twisted magnetic fields

    SciTech Connect

    Zweibel, E.G.; Boozer, A.H.

    1985-02-01

    The magnetic field of the solar corona evolves quasistatically in response to slowly changing photospheric boundary conditions. The magnetic topology is preserved by the low resistivity of the solar atmosphere. We show that a magnetic flux coordinate system simplifies the problem of calculating field evolution with invariant topology. As an example, we calculate the equilibrium of a thin magnetic flux tube with small twist per unit length.

  14. Cyclical magnetic field flow fractionation

    NASA Astrophysics Data System (ADS)

    Tasci, T. O.; Johnson, W. P.; Gale, B. K.

    2012-04-01

    In this study, a new magnetic field flow fractionation (FFF) system was designed and modeled by using finite element simulations. Other than current magnetic FFF systems, which use static magnetic fields, our system uses cyclical magnetic fields. Results of the simulations show that our cyclical magnetic FFF system can be used effectively for the separation of magnetic nanoparticles. Cyclical magnetic FFF system is composed of a microfluidic channel (length = 5 cm, height = 30 ?m) and 2 coils. Square wave currents of 1 Hz (with 90 deg of phase difference) were applied to the coils. By using Comsol Multiphysics 3.5a, magnetic field profile and corresponding magnetic force exerted on the magnetite nanoparticles were calculated. The magnetic force data were exported from Comsol to Matlab. In Matlab, a parabolic flow profile with maximum flow speed of 0.4 mL/h was defined. Particle trajectories were obtained by the calculation of the particle speeds resulted from both magnetic and hydrodynamic forces. Particle trajectories of the particles with sizes ranging from 10 to 50 nm were simulated and elution times of the particles were calculated. Results show that there is a significant difference between the elution times of the particles so that baseline separation of the particles can be obtained. In this work, it is shown that by the application of cyclical magnetic fields, the separation of magnetic nanoparticles can be done efficiently.

  15. Magnetic field fluctuations in SC dipole magnet

    SciTech Connect

    Vladimir Shiltsev et al.

    2001-08-15

    Magnetic field fluctuations at the betatron frequency can lead to emittance growth in circular accelerators. Tolerances are extremely tight for large hadron colliders like LHC and VLHC[1]. We performed experimental studies of the fluctuations in a stand-alone superconducting Tevatron magnet. Here we give a general description of the experimental set-up, present main results and discuss consequences for the colliders.

  16. 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.

  17. Textbook (non-) adoption motives, legitimizing strategies and academic field configuration

    Microsoft Academic Search

    Mark Palmer; Geoff Simmons; Matthew Hall

    2011-01-01

    Textbooks are an integral part of structured syllabus coverage in higher education. The argument advanced in this article is that textbooks are not simply products of inscription and embodied scholarly labour for pedagogical purposes, but embedded institutional artefacts that configure entire academic subject fields. Empirically, this article shows the various ways that motives of the (non-) adoption of textbooks have

  18. Implosion of solid liner for compression of field reversed configuration

    Microsoft Academic Search

    J. H. Degnan; J. M. Taccetti; T. Cavazos; D. Clark; S. K. Coffey; R. J. Faehl; M. H. Frese; D. Fulton; J. C. Gueits; D. Gale; T. W. Hussey; T. P. Intrator; R. C. Kirkpatrick; G. H. Kiuttu; F. M. Lehr; J. D. Letterio; I. Lindemuth; W. F. McCullough; R. Moses; R. E. Reinovsky; N. F. Roderick; E. L. Ruden; J. S. Shlachter; K. F. Schoenberg; R. E. Siemon; W. Sommars; P. J. Turchi; G. A. Wurden; F. Wysocki

    2001-01-01

    The design and first successful demonstration of an imploding solid liner with height to diameter ratio, radial convergence, and uniformity suitable for compressing a field reversed configuration is discussed. Radiographs indicated a very symmetric implosion with no instability growth, with ~13x radial compression of the inner liner surface prior to impacting a central measurement unit. The implosion kinetic energy was

  19. Transport in a stochastic magnetic field

    SciTech Connect

    White, R.B.; Wu, Yanlin (Princeton Univ., NJ (United States). Plasma Physics Lab.); Rax, J.M. (Association Euratom-CEA, Centre d'Etudes Nucleaires de Cadarache, 13 -Saint-Paul-lez-Durance (France). Dept. de Recherches sur la Fusion Controlee)

    1992-01-01

    Collisional heat transport in a stochastic magnetic field configuration is investigated. Well above stochastic threshold, a numerical solution of a Chirikov-Taylor model shows a short-time nonlocal regime, but at large time the Rechester-Rosenbluth effective diffusion is confirmed. Near stochastic threshold, subdiffusive behavior is observed for short mean free paths. The nature of this subdiffusive behavior is understood in terms of the spectrum of islands in the stochastic sea.

  20. Transport in a stochastic magnetic field

    SciTech Connect

    White, R.B.; Wu, Yanlin [Princeton Univ., NJ (United States). Plasma Physics Lab.; Rax, J.M. [Association Euratom-CEA, Centre d`Etudes Nucleaires de Cadarache, 13 -Saint-Paul-lez-Durance (France). Dept. de Recherches sur la Fusion Controlee

    1992-09-01

    Collisional heat transport in a stochastic magnetic field configuration is investigated. Well above stochastic threshold, a numerical solution of a Chirikov-Taylor model shows a short-time nonlocal regime, but at large time the Rechester-Rosenbluth effective diffusion is confirmed. Near stochastic threshold, subdiffusive behavior is observed for short mean free paths. The nature of this subdiffusive behavior is understood in terms of the spectrum of islands in the stochastic sea.

  1. Magnetic-field-dosimetry system

    DOEpatents

    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.

  2. Magnetic field draping about coronal mass ejecta

    SciTech Connect

    McComas, D.J.; Gosling, J.T.

    1987-01-01

    Fast coronal mass ejecta (CMEs) accelerate and deflect the slower moving solar wind plasma which piles up ahead of them as they propagate out through the heliosphere. This acceleration and deflection, in turn, causes the interplanetary magnetic field (IMF) imbedded in the upstream solar wind to drape about the ejecta. Draping should cause substantial out-of-the-ecliptic magnetic fields at some locations ahead of CMEs, and radial fields behind and along the flanks. At the Earth, draping can be an important factor in the generation of some magnetic storms and substorms, while in the outer heliosphere draping may produce very large magnetotail-like configurations, somewhat analogous to those observed behind Venus and comets. 17 refs.

  3. Heat pipes for use in a magnetic field

    DOEpatents

    Werner, Richard W. (San Ramon, CA); Hoffman, Myron A. (Davis, CA)

    1983-01-01

    A heat pipe configuration for use in a magnetic field environment of a fusion reactor. Heat pipes for operation in a magnetic field when liquid metal working fluids are used are optimized by flattening of the heat pipes having an unobstructed annulus which significantly reduces the adverse side region effect of the prior known cylindrically configured heat pipes. The flattened heat pipes operating in a magnetic field can remove 2--3 times the heat as a cylindrical heat pipe of the same cross sectional area.

  4. Switching field variation in patterned submicron magnetic film elements

    Microsoft Academic Search

    Youfeng Zheng; Jian-Gang Zhu

    1997-01-01

    In this article, a micromagnetic study of magnetic switching properties on submicron scale single layer and multilayer thin film elements is presented. Even at deep submicron scale, there exist various edge domain configurations at the saturation remanent state. It is found that the switching field of these patterned film elements can strongly depend on these edge domain configurations. If the

  5. Hydrogen-molecule ion in a strong magnetic field

    Microsoft Academic Search

    V. K. Khersonskii

    1983-01-01

    The potential energy functions of a molecular ion of hydrogen H\\/sup +\\/â are calculated in a strong magnetic field B approx. = 10¹°⁻⁻¹°sup 13\\/ G. The calculations were carried out for symmetric and antisymmetric configurations. Equilibrium internuclear separations and dissociation energies were determined for the symmetric configuration, and quadrupole moments were calculated.

  6. Hydrogen-molecule ion in a strong magnetic field

    SciTech Connect

    Khersonskii, V.K.

    1983-11-01

    The potential energy functions of a molecular ion of hydrogen H/sup +//sub 2/ are calculated in a strong magnetic field B approx. = 10/sup 10/--10/sup 13/ G. The calculations were carried out for symmetric and antisymmetric configurations. Equilibrium internuclear separations and dissociation energies were determined for the symmetric configuration, and quadrupole moments were calculated.

  7. (Revised December 30, 2013) Magnetic Fields

    E-print Network

    Collins, Gary S.

    (Revised December 30, 2013) Magnetic Fields GOALS (1) To visualize the magnetic fields produced compasses to trace out the magnetic field lines of a single bar magnet on a large sheet of paper. (3 of the points where the magnetic fields of the Earth and the bar magnet sum to zero. INTRODUCTION A magnetic

  8. 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.

  9. On sunspot magnetic field diffusion.

    NASA Astrophysics Data System (ADS)

    Krivodubskij, V. N.

    The efficiency of different mechanisms of sunspot magnetic field dissipation depending on the stage of sunspot decay and optical depth is investigated. The highest rate of the magnetic field diffusion has place at the initial stage of sunspot decay, when the turbulence motion in the sunspot umbra takes a two-dimensional structure due to the strong magnetic field (B ? 3000 G). The turbulence degeneracy withdraws at the later stage of the sunspot decay (B ? 2000 G) and the dissipation slows down.

  10. An atlas of photospheric magnetic field observations and computed coronal magnetic fields: 1976-1985

    NASA Technical Reports Server (NTRS)

    Hoeksema, J. T.; Scherrer, P. H.

    1986-01-01

    Daily magnetogram observations of the large-scale photospheric magnetic field have been made at the John M. Wilcox Solar Observatory at Stanford since May of 1976. These measurements provide a homogeneous record of the changing solar field through most of solar cycle 21. Using the photospheric data, the configuration of the coronal and heliospheric fields can be calculated using a Potential Field-Source Surface model. This provides a three-dimensional picture of the heliospheric field evolution during the solar cycle. This paper announces the publication of UAG Report No. 94, an Atlas containing the complete set of synoptic charts of the measured photospheric magnetic field, the computed field at the source surface, and the coefficients of the multipole expansion of the coronal field. The general underlying structures of the solar and heliospheric fields, which determine the environment for solar-terrestrial relations and provide the context within which solar activity related events occur, can be approximated from these data.

  11. Quasilinear theory of interchange modes in a closed field line configuration

    SciTech Connect

    Kouznetsov, A.; Freidberg, J. P.; Kesner, J. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

    2007-10-15

    Two important issues for any magnetic fusion configuration are the maximum achievable values of {beta} and energy confinement time when ideal magnetohydrodynamic (MHD) modes are excited. It is well known that the excitation of the MHD unstable modes typically can lead to violent restructuring of the plasma profiles. The particle and energy transport associated with these modes normally dominates all other transport mechanisms and can lead to plasma disruptions and a rapid loss of energy. This paper analytically investigates the transport of particle density, energy, and magnetic field due to the ideal MHD interchange mode in a closed-line system using the quasilinear approximation. The transport equations are derived for a static plasma in a hardcore Z-pinch configuration and generalized to an arbitrary axisymmetric toroidal closed poloidal field line configuration. It is shown that violation of the marginal stability criterion leads to rapid quasilinear transport that drives the pressure profile back to its marginal profile and forces the particle density to be inversely proportional to {integral}dl/B. The applicability of the quasilinear approximation is numerically tested for the hardcore Z-pinch magnetic configuration using a full nonlinear code.

  12. Quasilinear theory of interchange modes in a closed field line configuration

    NASA Astrophysics Data System (ADS)

    Kouznetsov, A.; Freidberg, J. P.; Kesner, J.

    2007-10-01

    Two important issues for any magnetic fusion configuration are the maximum achievable values of ? and energy confinement time when ideal magnetohydrodynamic (MHD) modes are excited. It is well known that the excitation of the MHD unstable modes typically can lead to violent restructuring of the plasma profiles. The particle and energy transport associated with these modes normally dominates all other transport mechanisms and can lead to plasma disruptions and a rapid loss of energy. This paper analytically investigates the transport of particle density, energy, and magnetic field due to the ideal MHD interchange mode in a closed-line system using the quasilinear approximation. The transport equations are derived for a static plasma in a hardcore Z-pinch configuration and generalized to an arbitrary axisymmetric toroidal closed poloidal field line configuration. It is shown that violation of the marginal stability criterion leads to rapid quasilinear transport that drives the pressure profile back to its marginal profile and forces the particle density to be inversely proportional to ?dl/B. The applicability of the quasilinear approximation is numerically tested for the hardcore Z-pinch magnetic configuration using a full nonlinear code.

  13. The Sun's global magnetic field.

    PubMed

    Mackay, Duncan H

    2012-07-13

    Our present-day understanding of solar and stellar magnetic fields is discussed from both an observational and theoretical viewpoint. To begin with, observations of the Sun's large-scale magnetic field are described, along with recent advances in measuring the spatial distribution of magnetic fields on other stars. Following this, magnetic flux transport models used to simulate photospheric magnetic fields and the wide variety of techniques used to deduce global coronal magnetic fields are considered. The application and comparison of these models to the Sun's open flux, hemispheric pattern of solar filaments and coronal mass ejections are then discussed. Finally, recent developments in the construction of steady-state global magnetohydrodynamic models are considered, along with key areas of future research. PMID:22665897

  14. 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.

  15. Axial magnetic field contacts with nonuniform distributed axial magnetic fields

    Microsoft Academic Search

    Zongqian Shi; Shenli Jia; Jun Fu; Zheng Wang

    2003-01-01

    It is well known that axial magnetic fields (AMFs) can keep vacuum arc in diffuse mode at high current. According to our recent research and other published papers, it has been found that vacuum arc can be maintained in high-current diffuse mode at much higher current if nonuniform AMF is applied, that the axial magnetic field is higher at contact

  16. CHAPTER 3. STRUCTURE OF MAGNETIC FIELDS 1 Structure of Magnetic

    E-print Network

    Callen, James D.

    CHAPTER 3. STRUCTURE OF MAGNETIC FIELDS 1 Chapter 3 Structure of Magnetic Fields Many of the most interesting plasmas are permeated by or imbedded in magnetic fields.1 As shown in Fig. 3.1, the magnetic field properties of magnetic fields in plasmas can be discussed without specifying a model for the plasma

  17. 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.

  18. Laboratory Measurements of Astrophysical Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Murphy, C. D.; Miniati, F.; Edwards, M.; Mithen, J.; Bell, A. R.; Constantin, C.; Everson, E.; Schaeffer, D.; Niemann, C.; Ravasio, A.; Brambrink, E.; Benuzzi-Mounaix, A.; Koenig, M.; Gregory, C.; Woolsey, N.; Park, H.-S.; Remington, B.; Ryutov, D.; Bingham, R.; Gargate, L.; Spitkovsky, A.; Gregori, G.

    2010-11-01

    It has been proposed that high Mach number collisionless shocks propagating in an initially unmagnetized plasma play a major role in the magnetization of large scale structures in the Universe. A detailed study of the experimental configuration necessary to scale such environments down to laboratory dimensions will be presented. We will show initial results from preliminary experiments conducted at the Phoenix laser (UCLA) and the LULI laser (Ecole Polytechnique) where collisionless shocks are generated by the expansion of exploding foils driven by energetic laser beams. The time evolution of the magnetic field is probed with induction coils placed at 10 cm from the laser focus. We will discuss various mechanisms of magnetic field generation and compare them with the experimental results.

  19. Apparatus for storing high magnetic fields having reduced mechanical forces and reduced magnetic pollution

    DOEpatents

    Prueitt, M.L.; Mueller, F.M.; Smith, J.L.

    1991-04-09

    The present invention identifies several configurations of conducting elements capable of storing extremely high magnetic fields for the purpose of energy storage or for other uses, wherein forces experienced by the conducting elements and the magnetic field pollution produced at locations away from the configuration are both significantly reduced over those which are present as a result of the generation of such high fields by currently proposed techniques. It is anticipated that the use of superconducting materials will both permit the attainment of such high fields and further permit such fields to be generated with vastly improved efficiency. 15 figures.

  20. 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.

    2015-06-01

    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.

  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. Field reversed configuration confinement enhancement through edge biasing and neutral beam injection.

    PubMed

    Tuszewski, M; Smirnov, A; Thompson, M C; Korepanov, S; Akhmetov, T; Ivanov, A; Voskoboynikov, R; Schmitz, L; Barnes, D; Binderbauer, M W; Brown, R; Bui, D Q; Clary, R; Conroy, K D; Deng, B H; Dettrick, S A; Douglass, J D; Garate, E; Glass, F J; Gota, H; Guo, H Y; Gupta, D; Gupta, S; Kinley, J S; Knapp, K; Longman, A; Hollins, M; Li, X L; Luo, Y; Mendoza, R; Mok, Y; Necas, A; Primavera, S; Ruskov, E; Schroeder, J H; Sevier, L; Sibley, A; Song, Y; Sun, X; Trask, E; Van Drie, A D; Walters, J K; Wyman, M D

    2012-06-22

    Field reversed configurations (FRCs) with high confinement are obtained in the C-2 device by combining plasma gun edge biasing and neutral beam injection. The plasma gun creates an inward radial electric field that counters the usual FRC spin-up. The n = 2 rotational instability is stabilized without applying quadrupole magnetic fields. The FRCs are nearly axisymmetric, which enables fast ion confinement. The plasma gun also produces E × B shear in the FRC edge layer, which may explain the observed improved particle transport. The FRC confinement times are improved by factors 2 to 4, and the plasma lifetimes are extended from 1 to up to 4 ms. PMID:23004613

  3. Zero-dimensional model for field-reversed configurations

    SciTech Connect

    Rej, D.J.; Tuszewski, M.

    1982-01-01

    A 0-D model has been developed to study energy, particle, and internal flux confinement during the equilibrium phase in field-reversed configurations (FRC's). Earlier work has been extended to include: (1) a 1-D radial equilibrium pressure profile consistent with particle transport calculations; (2) a time-dependent treatment of impurity radiation losses; (3) a more consistent treatment of ohmic power. The 0-D model is described. Example numerical solutions are presented.

  4. Topology, magnetic field, and strongly interacting matter

    E-print Network

    Kharzeev, Dmitri E

    2015-01-01

    Gauge theories with compact symmetry groups possess topologically non-trivial configurations of gauge field. This has dramatic implications for the vacuum structure of Quantum Chromo-Dynamics (QCD) and for the behavior of QCD plasma, as well as for condensed matter systems with chiral quasiparticles. I review the current status of the problem with an emphasis on the interplay of chirality with a background magnetic field, and on the observable manifestations of topology in heavy ion collisions, Dirac semimetals, neutron stars, and in the Early Universe.

  5. High latitude solar magnetic fields

    NASA Technical Reports Server (NTRS)

    Murray, Norman

    1992-01-01

    Kitt Peak magnetograms are used to measure polar magnetic fields. The polar mean absolute field increases at the same time as the polar mean field decreases. That is, the polar mean absolute field varies in phase with solar activity, in contrast to the out of phase variation of the mean polar field. It is found that the polar fields have a large bipolar component even at solar minimum, with a magnitude equal to that found at low latitudes outside the active latitude bands.

  6. Observation of an Effective Magnetic field for Light

    E-print Network

    Tzuang, Lawrence D; Nussenzveig, Paulo; Fan, Shanhui; Lipson, Michal

    2013-01-01

    Photons are neutral particles that do not interact directly with a magnetic field. However, recent theoretical work has shown that an effective magnetic field for photons can exist if the phase of light would change with its propagating direction. This direction-dependent phase indicates the presence of an effective magnetic field as shown for electrons experimentally in the Aharonov-Bohm experiment. Here we replicate this experiment using photons. In order to create this effective magnetic field, we construct an on-chip silicon-based Ramsey-type interferometer. This interferometer has been traditionally used to probe the phase of atomic states, and here we apply it to probe the phase of photonic states. We experimentally observe a phase change, i.e. an effective magnetic field flux from 0 to 2pi. In an Aharonov-Bohm configuration for electrons, considering the device geometry, this flux corresponds to an effective magnetic field of 0.2 Gauss.

  7. Computer simulation of a novel electron gun with a magnetic reversal field

    Microsoft Academic Search

    Xinhui Wu; Jiayin Li

    2010-01-01

    Efficient operation of gyro-devices depends critically on the quality of the beam. Single-particle motion of relativistic electrons in a cusped magnetic field has been studied analytically. The Lagrangian formulation is used to solve for the electron trajectories in a general magnetic cusp configurations. The exact configurations of the solenoid coils and pole pieces were designed to generate the magnetic reversal

  8. Impurity entanglement through electron scattering in a magnetic field

    NASA Astrophysics Data System (ADS)

    Metavitsiadis, Alexandros; Dillenschneider, Raoul; Eggert, Sebastian

    2014-04-01

    We study the entanglement of magnetic impurities in an environment of electrons through successive scattering while an external magnetic field is applied. We show that the dynamics of the problem can be approximately described by a reduced model of three interacting spins, which reveals an intuitive view on how spins can be entangled by controlled electron scattering. The role of the magnetic field is rather crucial. Depending on the initial state configuration, the magnetic field can either increase or decrease the resulting entanglement but more importantly it can allow the impurities to be maximally entangled.

  9. NUMERICAL SIMULATION OF SOLAR MICROFLARES IN A CANOPY-TYPE MAGNETIC CONFIGURATION

    SciTech Connect

    Jiang, R.-L.; Fang, C.; Chen, P.-F., E-mail: rljiang@nju.edu.cn [School of Astronomy and Space Science, Nanjing University, Nanjing 210093 (China)

    2012-06-01

    Microflares are small activities in the solar low atmosphere; some are in the low corona while others are in the chromosphere. Observations show that some of the microflares are triggered by magnetic reconnection between the emerging flux and a pre-existing background magnetic field. We perform 2.5-dimensional, compressible, resistive magnetohydrodynamic simulations of the magnetic reconnection with gravity considered. The background magnetic field is a canopy-type configuration that is rooted at the boundary of the solar supergranule. By changing the bottom boundary conditions in the simulation, a new magnetic flux emerges at the center of the supergranule and reconnects with the canopy-type magnetic field. We successfully simulate the coronal and chromospheric microflares whose current sheets are located at the corona and the chromosphere, respectively. The microflare with a coronal origin has a larger size and a higher temperature enhancement than the microflare with a chromospheric origin. In the microflares with coronal origins, we also found a hot jet ({approx}1.8 Multiplication-Sign 10{sup 6} K), which is probably related to the observational extreme ultraviolet or soft X-ray jets, and a cold jet ({approx}10{sup 4} K), which is similar to the observational H{alpha}/Ca surges. However, there is only a H{alpha}/Ca bright point in the microflares that have chromospheric origins. The study of parameter dependence shows that the size and strength of the emerging magnetic flux are the key parameters that determine the height of the reconnection location, and they further determine the different observational features of the microflares.

  10. 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

  11. Low-magnetic-field magnetars

    E-print Network

    Turolla, R

    2013-01-01

    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 (~4.4E+13 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.

  12. 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.

  13. Primordial Magnetic Fields in Cosmology

    E-print Network

    Iain A. Brown

    2008-12-09

    Magnetic fields have been observed in galaxies, clusters of galaxies and probably in superclusters. While mechanisms exist to generate these in the late universe, it is possible that magnetic fields have existed since very early times. This thesis is concerned with methods to predict the form of such imprints. We review in detail a standard, linearised cosmology before introducing an electromagnetic field. We then consider the intrinsic statistics of the magnetic stresses in two ways, analytically and via static realisations. We construct the power spectra, some of which we present for the first time. At the one- and three-point level we find significant intrinsic non-Gaussianities. Finally we turn to the observable impacts a primordial magnetic field. Assuming coherence, the statistics of the source can be mapped onto the CMB in a simple manner. We demonstrate that our approach is valid by reproducing the signals for Gaussian power law fields on the microwave sky. [ABRIDGED

  14. Studying the magnetic fields of cool stars

    NASA Astrophysics Data System (ADS)

    Lynch, Christene Rene

    Magnetic fields are prevalent in a wide variety of low mass stellar systems and play an important role in their evolution. Yet the process through which these fields are generated is not well understood. To understand how such systems can generate strong field structures characterization of these fields is required. Radio emission traces the fields directly and the properties of this emission can be modeled leading to constraints on the field geometry and magnetic parameters. The new Karl Jansky Very Large Array (VLA) provides highly sensitive radio observations. My thesis involves combining VLA observations with the development of magnetospheric emission models in order to characterize the magnetic fields in two fully convective cool star systems: (1) Young Stellar Objects (YSOs); (2) Ultracool dwarf stars. I conducted multi epoch observations of DG Tau, a YSO with a highly active, collimated outflow. The radio emission observed from this source was found to be optically thick thermal emission with no indication of the magnetic activity observed in X-rays. I determined that the outflow is highly collimated very close to the central source, in agreement with jet launching models. Additionally, I constrained the mass loss of the ionized component of the jet and found that close to the central source the majority of mass is lost through this component. Using lower angular resolution observations, I detected shock formations in the extended jet of DG Tau and modeled their evolution with time. Taking full advantage of the upgraded bandwidth on the VLA, I made wideband observations of two UCDs, TVLM513-46 and 2M 0746+20. Combining these observations with previously published and archival VLA observations I was able to fully characterize the spectral and temporal properties of the radio emission. I found that the emission is dominated by a mildly polarized, non-thermal quiescent component with periodic strongly polarized flare emission. The spectral energy distribution and polarization of the quiescent emission is well modeled using gyrosynchrotron emission with a mean field B ˜100 G, mildly relativistic power-law electrons with a density ne ˜ 105-6 cm-3, and source size of R ˜ 2R*. We were able to model the pulsed emission by coherent electron cyclotron radiation from a small number of isolated loops of high magnetic field (2-3 kG) with scale heights˜1.2-2.7 stellar radii. The loops are well-separated in magnetic longitude, and are not part of a single dipolar magnetosphere. The overall magnetic configuration of both stars appears to confirm recent suggestions that radio over-luminous UCD's have `weak field' non-axisymmetric topologies, but with isolated regions of high magnetic field.

  15. Investigating Magnetic Force Fields

    NSDL National Science Digital Library

    Daryl ("Tish") Monjeau, Bancroft Elementary School, Minneapolis, MN

    2012-03-18

    In this classroom activity, the students will investigate the magnetic pull of a bar magnet at varying distances with the use of paper clips. Students will hypothesize, conduct the experiment, collect the data, and draw conclusions that support their data. Each student will record the experiment and their findings in their science journals. As a class, students will compare each groups' data and their interpretation of the results.

  16. Mathematical modeling of transformation process of structurally unstable magnetic configurations into structurally stable ones in two-dimensional and three-dimensional geometry

    NASA Astrophysics Data System (ADS)

    Inovenkov, Igor; Echkina, Eugenia; Ponomarenko, Loubov

    Magnetic reconnection is a fundamental process in astrophysical, space and laboratory plasma. In essence, it represents a change of topology of the magnetic field caused by readjustment of the structure of the magnetic field lines. This change leads to release of energy accumulated in the field. We consider transformation process of structurally unstable magnetic configurations into the structurally steady ones from the point of view of the ?atastrophe theory. Special attention is paid to modeling of evolution of the structurally unstable three-dimensional magnetic fields.

  17. Magnetic field properties of the ISABELLE Project superconducting dipole magnets

    SciTech Connect

    Kirk, H.G.; Engelmann, R.; Herrera, J.; Jaeger, K.; Robins, K.; Willen, E.

    1981-01-01

    A series of prototype superconducting dipole magnets have been constructed and tested as part of the ISABELLE Project research and development program. Results of magnetic field measurements are presented with emphasis placed on the DC and AC components of the main field. Magnetization and the effects of the magnetic fields at the ends of the magnet are displayed.

  18. Intrinsic trapping of stochastic sheared magnetic field lines

    SciTech Connect

    Negrea, M.; Petrisor, I.; Balescu, R. [Department of Physics, University of Craiova, A.I. Cuza str. 13, Craiova, Dolj 1100, Romania Association Euratom-MEC (Romania); Department of Statistical Physics and Plasma, Association Euratom-Etat Belge-sur la Fusion, CP 231, Universite Libre de Bruxelles, Campus Plaine, 1050 Brussels (Belgium)

    2004-10-01

    The decorrelation trajectory method is applied to the diffusion of magnetic field lines in a perturbed sheared slab magnetic configuration. Some interesting decorrelation trajectories for several values of the magnetic Kubo number and of the shear parameter are exhibited. The asymmetry of the decorrelation trajectories appears in comparison with those obtained in the purely electrostatic case studied in earlier work. The running and asymptotic diffusion tensor components are calculated and displayed.

  19. Demonstration of current drive by a rotating magnetic dipole field

    NASA Astrophysics Data System (ADS)

    Giersch, L.; Slough, J. T.; Winglee, R.

    2007-04-01

    Abstract.A dipole-like rotating magnetic field was produced by a pair of circular, orthogonal coils inside a metal vacuum chamber. When these coils were immersed in plasma, large currents were driven outside the coils: the currents in the plasma were generated and sustained by the rotating magnetic dipole (RMD) field. The peak RMD-driven current was at roughly two RMD coil radii, and this current (60 kA m-) was sufficient to reverse the ambient magnetic field (33 G). Plasma density, electron temperature, magnetic field and current probes indicated that plasma formed inside the coils, then expanded outward until the plasma reached equilibrium. This equilibrium configuration was adequately described by single-fluid magnetohydrodynamic equilibrium, wherein the cross product of the driven current and magnetic filed was approximately equal to the pressure gradient. The ratio of plasma pressure to magnetic field pressure, ?, was locally greater than unity.

  20. RELATIVISTIC TWO-FLUID SIMULATIONS OF GUIDE FIELD MAGNETIC RECONNECTION

    SciTech Connect

    Zenitani, Seiji; Hesse, Michael; Klimas, Alex, E-mail: Seiji.Zenitani-1@nasa.go [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

    2009-11-01

    The nonlinear evolution of relativistic magnetic reconnection in sheared magnetic configuration (with a guide field) is investigated by using two-dimensional relativistic two-fluid simulations. Relativistic guide field reconnection features the charge separation and the guide field compression in and around the outflow channel. As the guide field increases, the composition of the outgoing energy changes from enthalpy-dominated to Poynting-dominated. The inertial effects of the two-fluid model play an important role to sustain magnetic reconnection. Implications for the single-fluid magnetohydrodynamic approach and the physics models of relativistic reconnection are briefly addressed.

  1. The generation and stability of magnetic fields in CP stars

    E-print Network

    R. Arlt

    2008-01-29

    A variety of magnetohydrodynamic mechanisms that may play a role in magnetic, chemically peculiar (mCP) stars is reviewed. These involve dynamo mechanisms in laminar flows as well as turbulent environments, and magnetic instabilities of poloidal and toroidal fields as well as combinations of the two. While the proto-stellar phase makes the survival of primordial fields difficult, the variety of magnetic field configurations on mCP stars may be an indication for that they are instability remnants, but there is no process which is clearly superior in explaining the strong fields.

  2. Tilt stability and compression heating studies of field-reversed configurations

    SciTech Connect

    Rej, D.J.; Tuszewski, M.; Barnes, D.C.; Barnes, G.A.; Chrien, R.E.; Siemon, R.E.; Taggart, D.P.; Webster, R.B.; Wright, B.L. (Los Alamos National Lab., NM (USA)); Milroy, R.D.; Crawford, E.A.; Slough, J.T.; Steinhauer, L.C. (Spectra Technology, Inc., Bellevue, WA (USA)); Bailey, A.D. (California Inst. of Tech., Pasadena, CA (USA)); Baron, M.H. (Auburn Univ., AL (USA)); Cobb, J.W. (Texas Univ., Austin, TX (U

    1990-01-01

    The first observations of internal tilt instabilities in field-reversed configurations (FRCs) are reported. Detailed comparisons with theory establish that data from an array of external magnetic probes are signatures of these destructive plasma instabilities. This work reconciles theory and experiments and suggests that grossly stable FRCs are restricted to very kinetic and elongated plasmas. Self-consistent three-dimensional numerical simulations demonstrate tilt stabilization by the addition of a beam ion component. High-power compression heating experiments with stable equilibrium FRCs are also reported. Plasmas formed in a tapered theta-pinch coil have been translated along a guide magnetic field into a new single-turn compression coil where the external field is increased up to 7 times the initial value in 55 {mu}s. Substantial heating is observed accompanied by a decrease in confinement time. 17 refs.

  3. 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)

  4. The contrasting magnetic fields of superconducting pulsars and magnetars

    NASA Astrophysics Data System (ADS)

    Lander, S. K.

    2014-01-01

    We study equilibrium magnetic field configurations in a neutron star (NS) whose core has type-II superconducting protons. Unlike the equations for normal matter, which feature no special field strength, those for superconductors contain the lower critical field, of the order of 1015 G. We find that the ratio of this critical field to the smooth-averaged stellar field at the crust-core boundary is the key feature dictating the field geometry. Our results suggest that pulsar- and magnetar-strength fields have notably different configurations. Field decay for NSs with Bpole ˜ 1014 G could thus result in substantial internal rearrangements, pushing the toroidal field component out of the core; this may be related to observed magnetar activity. In addition, we calculate the magnetically induced ellipticities of our models.

  5. The HeH+ molecular ion in a magnetic field

    NASA Astrophysics Data System (ADS)

    Turbiner, A. V.; Guevara, N. L.

    2007-08-01

    A detailed study of the low-lying electronic states 1?, 3?, 3?, 3? of the HeH+ molecular ion in parallel to a magnetic field configuration (when ?-particle and proton are situated on the same magnetic line) is carried out for B = 0 - 4.414 × 1013 G in the Born-Oppenheimer approximation. The variational method is employed using a physically adequate trial function. It is shown that for the ? states the parallel configuration is stable with respect to small deviations. The quantum numbers of the ground state depend on the magnetic field strength. The ground state evolves from the spin-singlet 1? state for small magnetic fields B <~ 0.5 au to the spin-triplet 3? (unbound or weakly bound) state for intermediate fields and to the spin-triplet strongly bound 3? state for B >~ 15 au. When the HeH+ molecular ion exists, it is stable with respect to dissociation.

  6. The magnetic field of Mercury

    NASA Technical Reports Server (NTRS)

    Ness, N. F.

    1977-01-01

    The Mariner 10 spacecraft encountered Mercury three times in 1974-1975. The first and third encounters provided detailed observations of a well-developed detached bow shock wave which results from the interaction of the solar wind. The planet possesses a global magnetic field and a modest magnetosphere, which deflects the solar wind. The field is approximately dipolar, with orientation in the same sense as earth, tilted 12 deg from the rotation axis. The magnetic moment corresponds to an undistorted equatorial field intensity of 350 gammas, approximately 1% of earth's. The field, while unequivocally intrinsic to the planet, may be due to remanent magnetization acquired from an extinct dynamo or a primordial magnetic field or due to a presently active dynamo. The latter possibility appears more plausible at present. In any case, the existence of the magnetic field provides very strong evidence of a mature differentiated planetary interior with a large core (core radius about 0.7 Mercury radius) and a record of the history of planetary formation in the magnetization of the crustal rocks.

  7. 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.

  8. Primordial Magnetic Fields and Causality

    E-print Network

    Ruth Durrer; Chiara Caprini

    2003-10-29

    We discuss the implications of causality on a primordial magnetic field. We show that the residual field on large scales is much more suppressed than usually assumed and that a helical component is even more reduced. Due to this strong suppression, even maximal primordial fields generated at the electroweak phase transition can just marginally seed the fields in clusters, but they cannot leave any detectable imprint on the cosmic microwave background.

  9. Coherent population trapping in a ? configuration coupled by magnetic dipole interactions

    NASA Astrophysics Data System (ADS)

    Kim, Huidong; Han, Hyok Sang; Yoon, Tai Hyun; Cho, D.

    2014-03-01

    We report our study on coherent population trapping (CPT) in a ? configuration coupled by magnetic dipole interactions. The ? configuration is formed by bichromatic radio-frequency fields coupling a pair of Zeeman sublevels in one hyperfine level of an alkali-metal atom to another sublevel in the other hyperfine level. The Zeeman sublevel at the apex is coupled to a state in the nP manifold via an optical transition on one of the spectroscopic D lines to induce optical pumping to a dark state. The configuration is closed without leakage to other Zeeman sublevels. We use lithium atoms in an optical trap for our experimental study. The system allows independent control of the main parameters characterizing CPT, which include the upper-state decay rate and the decoherence rate as well as the Rabi frequencies. By turning off the applied fields, the system is frozen so that its quantum state can be measured precisely. We studied the line shapes and dynamics of the CPT system, and measured the phase relation of the dark superposition state to find excellent agreement with theory. The possible application of the scheme as a method to cool optically trapped atoms below the recoil limit in a manner analogous to velocity-selective coherent population trapping is discussed.

  10. Magnetic field induced dynamical chaos

    SciTech Connect

    Ray, Somrita; Baura, Alendu; Bag, Bidhan Chandra, E-mail: bidhanchandra.bag@visva-bharati.ac.in [Department of Chemistry, Visva-Bharati, Santiniketan 731 235 (India)

    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.

  11. Photoluminescence spectra of GaP\\/AlP short-period superlattices under high magnetic fields

    Microsoft Academic Search

    Kazuhito Uchida; Noboru Miura; Jun Kitamura; Hiroshi Kukimoto

    1996-01-01

    Photoluminescence spectra in a series of GaP\\/AlP short-period superlattices were measured under high magnetic fields up to 40 T in the Faraday and the Voigt configurations. A large dependence of the photoluminescence intensity upon the magnetic-field direction relative to the superlattice layers was found. Namely, in the Faraday configuration, the peak intensity decreased dramatically with increasing applied magnetic field perpendicular

  12. Manipulation of magnetic state in nanostructures by perpendicular anisotropy and magnetic field

    SciTech Connect

    Chen, J. P.; Xie, Y. L.; Chu, P.; Wang, Y. L. [Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093 (China); Wang, Z. Q.; Gao, X. S. [Institute for Advanced Materials and Laboratory of Quantum Engineering and Quantum Materials, South China Normal University, Guangzhou 510006 (China); Liu, J.-M. [Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093 (China); Institute for Advanced Materials and Laboratory of Quantum Engineering and Quantum Materials, South China Normal University, Guangzhou 510006 (China)

    2014-06-28

    We investigate the transitions of spin configurations in ultrathin nanostructures by tuning the perpendicular anisotropy (K{sub z}) and out-of-plane magnetic field (H), using the Monte Carlo simulation. It is revealed that enhancing the anisotropy K{sub z} can drive the evolution of in-plane vortex state into intriguing saturated magnetization states under various H, such as the bubble domain state and quadruple-block-domain state etc. The spin configurations of these states exhibit remarkable H-dependence. In addition, the strong effects of geometry and size on the spin configurations of nanostructures are observed. In particular, a series of edged states occur in the circular disk-shaped lattices, and rich intricate saturated magnetization patterns appear in big lattices. It is suggested that the magnetic states can be manipulated by varying the perpendicular anisotropy, magnetic field, and geometry/size of the nanostructures. Furthermore, the stability (retention capacity) of the saturated magnetization states upon varying magnetic field is predicted, suggesting the potential applications of these saturated magnetization states in magnetic field-controlled data storages.

  13. Capture of a high density field reversed configuration in a flux conserver

    NASA Astrophysics Data System (ADS)

    Sieck, P. E.; Intrator, T. P.; Wurden, G. A.; Sun, X.; Cortez, R. J.; Waganaar, W. J.

    2008-11-01

    A physics demonstration of Magnetized Target Fusion (MTF) is being pursued by a collaborative team from Los Alamos National Laboratory and Air Force Research Laboratory. The approach is to form a high density Field Reversed Configuration (FRC), translate it into a liner, and adiabatically compress the FRC by imploding the liner. Capture of the FRC in the liner is critical to the success of the experiment. Several interesting phenomena are possible. The FRC can undergo heating when it bounces off the end mirror. Also, partial capture of the FRC can occur such that a smaller FRC remains captured while some plasma and magnetic energy ejects from the liner. Magnetic mirrors at both the upstream and downstream ends of the capture section help to determine the prominence of these behaviors. The translation and capture regions of the experiment are instrumented with flux loops and surface magnetic field diagnostics. Plans will be presented for internal magnetic field probes in these regions. Implications for optimum capture geometry for compression experiments will be discussed. This work is supported by the Office of Fusion Energy Sciences, and DOE/LANL contract DE-AC52-06NA25396.

  14. Effect of magnetic yoke on magnetic field distribution and intercepting effect of multi-channel cascading magnet arrays

    NASA Astrophysics Data System (ADS)

    Zhang, S. P.; Wu, P.; Wang, L.; Li, F. C.; Chen, S.; Sun, S. F.

    2010-03-01

    `Magnetic-Sieve' possesses a potential use in oxygen separation. The effect of a magnetic yoke on magnetic field distribution and intercepting effect of multi-channel cascading magnet arrays in a `Magnetic-Sieve' configuration is studied by ANSYS finite element software. The multi-channel cascading magnet arrays consist of cuboid neodymium-iron-boron permanent magnets. The size of the magnets is W×H = 38 mm×5 mm, and the clearance between two adjacent magnets is 1 mm. The results show that the intercepting effect tends to decrease from the central channel to the most lateral channels in multi-channel cascading magnet arrays. Compared with the simulation result of two magnets, the central magnetic inductions of the center channel and the most lateral channels in the multi-channel cascading magnet array including 14 magnets decrease respectively 10% and 31%, and the intercepting effects of the center channel and the most lateral channels decrease 19% and 60%, respectively. When the magnetic yoke is added on the multi-channel cascading magnet array, the above-mentioned four values are increased by 28%, 29%, 63% and 65%, respectively. The simulation study shows that the introducing of magnetic yokes can enhance the central magnetic induction and the intercepting effect of the gradient magnetic field, and moreover, reduce the disparities of intercepting effect among the channels.

  15. Effect of magnetic configuration on frequency of NBI-driven Alfvén modes in TJ-II

    NASA Astrophysics Data System (ADS)

    Melnikov, A. V.; Ochando, M.; Ascasibar, E.; Castejon, F.; Cappa, A.; Eliseev, L. G.; Hidalgo, C.; Krupnik, L. I.; Lopez-Fraguas, A.; Liniers, M.; Lysenko, S. E.; de Pablos, J. L.; Perfilov, S. V.; Sharapov, S. E.; Spong, D. A.; Jimenez, J. A.; Ufimtsev, M. V.; Breizman, B. N.; HIBP group; the TJ-II team

    2014-12-01

    Excitation of modes in the Alfvénic frequency range, 30 kHz < fAE < 300 kHz, was observed in hydrogen plasma heated by hydrogen neutral beam injection (NBI) in the TJ-II heliac. Co-field and counter-field NBI were injected, and the components of the poloidal magnetic field were varied one by one and in combinations, in order to investigate the beam-driven modes over an extended range of the rotational transform values, 1.51<\\unicode{7548} (0)<1.67 . Taking advantage of the unique TJ-II capabilities, a dynamic magnetic configuration experiment with \\unicode{7548} (? , t) variation during discharges has shown strong effects on the mode frequency via both vacuum \\unicode{7548} changes and induced net plasma current. A drastic frequency increase from ˜50 to ˜250 kHz was observed for some modes when plasma current as low as ±2 kA was induced by small (10%) changes in the vertical field. A comprehensive set of diagnostics including a heavy ion beam probe, magnetic probes and a multi-chord bolometer made it possible to identify the spatial spread of the modes and deduce the internal amplitudes of their plasma density and magnetic field perturbations. A simple analytical model for fAE, based on the local Alfvén eigenmode (AE) dispersion relation, was proposed to characterize the observation. It was shown that all the observations, including vacuum iota and plasma current variations, may be fitted by the model, so the linear mode frequency dependence on \\unicode{7548} (plasma current) and one over square root density dependence present the major features of the NBI-induced AEs in TJ-II, and provide the framework for further experiment-to-theory comparison.

  16. Safety concerns related to magnetic field exposure

    Microsoft Academic Search

    Amanda K. Andriola Silva; Érica L. Silva; E. Sócrates T. Egito; Artur S. Carriço

    2006-01-01

    The recent development of superconducting magnets has resulted in a huge increase in human exposure to very large static magnetic fields of up to several teslas (T). Considering the rapid advances in applications and the great increases in the strength of magnetic fields used, especially in magnetic resonance imaging, safety concerns about magnetic field exposure have become a key issue.

  17. Apparatus having reduced mechanical forces for supporting high magnetic fields

    DOEpatents

    Prueitt, Melvin L. (Los Alamos, NM); Mueller, Fred M. (Los Alamos, NM); Smith, James L. (Los Alamos, NM)

    1991-01-01

    The present invention identifies several configurations of conducting elements capable of supporting extremely high magnetic fields suitable for plasma confinement, wherein forces experienced by the conducting elements are significantly reduced over those which are present as a result of the generation of such high fields by conventional techniques. It is anticipated that the use of superconducting materials will both permit the attainment of such high fields and further permit such fields to be generated with vastly improved efficiency.

  18. Electric and magnetic field exposure

    Microsoft Academic Search

    S. S. Sussman

    1988-01-01

    The possible health hazards of low-level, power line frequency (50\\/60 Hz) electric and magnetic fields are considered. The historical background to this concern is briefly discussed. The types of studies being carried out and the results so far are summarized. It is concluded that while the scientific evidence on field effects is inconclusive, inferences of health effects justify further evaluation

  19. Magnetic fields and coronal heating

    NASA Technical Reports Server (NTRS)

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

    1980-01-01

    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.

  20. Magnetic properties of TbFe2 particles prepared by magnetic field assisted ball milling

    NASA Astrophysics Data System (ADS)

    Arout Chelvane, J.; Palit, Mithun; Basumatary, Himalay; Pandian, S.

    2013-10-01

    The alloy of TbFe2 was studied by ball milling with and without the presence of external magnetic field. While the structure and powder morphology of the alloy were investigated using scanning electron microscope and X-ray diffraction, the magnetization was investigated using vibrating sample and superconducting quantum interference device magnetometers. The rate of particle reduction with ball milling is comparatively higher in the presence of external magnetic field than without it. Consequently, owing to a large fraction of particles acquiring near single domain configuration under the field assisted milling condition, the coercivity derived from these particles are as high as 6500 Oe than that of particles obtained without the aid of external magnetic field which is around 3850 Oe. The field cooled low temperature magnetization exhibits a large coercivity and skew in the shape of the magnetization curve due to the large anisotropy.

  1. Magnetically Driven Accretion Flows in the Kerr Metric II: Structure of the Magnetic Field

    E-print Network

    Shigenobu Hirose; Julian H. Krolik; Jean-Pierre De Villiers; John F. Hawley

    2003-11-21

    We present a detailed analysis of the magnetic field structure found in general relativistic 3D MHD simulations of accreting tori in the Kerr metric with different black hole spins. Among the properties analyzed are the field strength as a function of position and black hole spin, the shapes of field lines, the degree to which they connect different regions, and their degree of tangling. We investigate prior speculations about the structure of the magnetic fields and discuss how frequently certain configurations are seen in the simulations. We also analyze the distribution of current density, with a view toward identifying possible locations for magnetic energy dissipation.

  2. MAGNETIC FIELD MEASUREMENTS FOR FAST-CHANGING MAGNETIC FIELDS.

    SciTech Connect

    JAIN, A.; ESCALLIER, J.; GANETIS, G.; LOUIE, W.; MARONE, A.; THOMAS. R.; WANDERER, P.

    2004-10-03

    Several recent applications for fast ramped magnets have been found that require rapid measurement of the field quality during the ramp. (In one instance, accelerator dipoles will be ramped at 1 T/sec, with measurements needed to the accuracy typically required for accelerators.) We have built and tested a new type of magnetic field measuring system to meet this need. The system consists of 16 stationary pickup windings mounted on a cylinder. The signals induced in the windings in a changing magnetic field are sampled and analyzed to obtain the field harmonics. To minimize costs, printed circuit boards were used for the pickup windings and a combination of amplifiers and ADPs used for the voltage readout system. New software was developed for the analysis. Magnetic field measurements of a model dipole developed for the SIS200 accelerator at GSI are presented. The measurements are needed to insure that eddy currents induced by the fast ramps do not impact the field quality needed for successful accelerator operation.

  3. Observations of Improved Stability and Confinement in a High-Self-Organized Spherical-Torus-Like Field-Reversed Configuration

    E-print Network

    Washington at Seattle, University of

    chamber for confine- ment and sustainment, which offers engineering advan- tages for a fusion reactor.55.Lf, 52.35.Py, 52.55.Fa A field-reversed configuration (FRC) is a compact toroid with little connected magnetic geometry. This strongly self- organized compact toroid (CT) has been produced by various

  4. Shear-induced inflation of coronal magnetic fields

    NASA Technical Reports Server (NTRS)

    Klimchuk, James A.

    1989-01-01

    Using numerical models of force-free magnetic fields, the shearing of footprints in arcade geometries leading to an inflation of the coronal magnetic field was examined. For each of the shear profiles considered, all of the field lines become elevated compared with the potential field. This includes cases where the shear is concentrated well away from the arcade axis, such that B(sub z), the component of field parallel to the axis, increases outward to produce an inward B(sub z)squared/8 pi magnetic pressure gradient force. These results contrast with an earlier claim, shown to be incorrect, that field lines can sometimes become depressed as a result of shear. It is conjectured that an inflation of the entire field will always result from the shearing of simple arcade configurations. These results have implications for prominence formation, the interplanetary magnetic flux, and possibly also coronal holes.

  5. Magnetic field studies at Jupiter by Voyager 1: Preliminary results

    NASA Technical Reports Server (NTRS)

    Ness, N. F.; Acuna, M. H.; Lepping, R. P.; Burlaga, L. F.; Behannon, K. W.; Neubauer, F. M.

    1979-01-01

    Results obtained by the Goddard Space Flight Center magnetometers on Voyager 1 concerning the large scale configuration of the Jovian bow shock and magnetopause, and the magnetic field in both the inner and outer magnetosphere are highlighted. There is evidence that a magnetic tail extending away from the planet on the nightside is formed by the solar wind-Jovian field interaction. This is much like Earth's magnetosphere but is a new configuration for Jupiter's magnetosphere not previously considered from earlier Pioneer data. Magnetic field perturbations associated with intense electrical currents (approximately 5 x 10 to the 6th power amps) flowing near or in the magnetic flux tube linking Jupiter with the satellite Io and induced by the relative motion between Io and the co-rotating Jovian magnetosphere are analyzed and interpreted. These currents may be an important source of heating the ionosphere and interior of Io through Joule dissipation.

  6. Rotation of the coronal magnetic field

    NASA Technical Reports Server (NTRS)

    Hoeksema, J. T.; Scherrer, P. H.

    1987-01-01

    The coronal magnetic field rotates differently than the photosphere. The field configuration of the corona can be calculated from the observed photosphpere field using a potential field model. Correlation of the field patterns at different latitudes with a lag near one solar rotation shows much less differential rotation than observed in the photospheric field; however, the peak is very broad and determines the rotation rate rather poorly. Consideration of longer lags reveals a more complex rotational structure and indicates different rotation rates in the Northern and Southern Hemispheres. Spectral analysis of the equatorial dipole component of the coronal field reveals an organization into just a few discrete rotation frequencies which are apparently present simultaneously. Spectral analysis of the field at different latitudes shows that the frequencies are present simultaneously. Spectra analysis of the field at different latitudes shows that the frequencies are present simultaneously, but in different hemispheres, and that the Southern Hemisphere fields rotate more slowly than those in the north in solar cycle 21.

  7. A new high performance field reversed configuration operating regime in the C-2 device

    SciTech Connect

    Tuszewski, M.; Smirnov, A.; Thompson, M. C.; Barnes, D.; Binderbauer, M. W.; Brown, R.; Bui, D. Q.; Clary, R.; Conroy, K. D.; Deng, B. H.; Dettrick, S. A.; Douglass, J. D.; Garate, E.; Glass, F. J.; Gota, H.; Guo, H.Y.; Gupta, D.; Gupta, S.; Kinley, J. S.; Knapp, K. [Tri Alpha Energy, Inc., P.O. Box 7010, Rancho Santa Margarita, California 92688 (United States); and others

    2012-05-15

    Large field reversed configurations (FRCs) are produced in the C-2 device by combining dynamic formation and merging processes. The good confinement of these FRCs must be further improved to achieve sustainment with neutral beam (NB) injection and pellet fuelling. A plasma gun is installed at one end of the C-2 device to attempt electric field control of the FRC edge layer. The gun inward radial electric field counters the usual FRC spin-up and mitigates the n = 2 rotational instability without applying quadrupole magnetic fields. Better plasma centering is also obtained, presumably from line-tying to the gun electrodes. The combined effects of the plasma gun and of neutral beam injection lead to the high performance FRC operating regime, with FRC lifetimes up to 3 ms and with FRC confinement times improved by factors 2 to 4.

  8. Pinning features of the magnetic flux trapped by YBCO single crystals in weak constant magnetic fields

    NASA Astrophysics Data System (ADS)

    Monarkha, V. Yu.; Paschenko, V. A.; Timofeev, V. P.

    2013-02-01

    The dynamics of Abrikosov vortices and their bundles was experimentally investigated in weak constant magnetic fields, in the range of Earth's magnetic field. Characteristics of the isothermal magnetization relaxation in YBCO single-crystal samples with strong pinning centers were studied for different sample-field orientation. The obtained values of normalized relaxation rate S allowed us to estimate the effective pinning potential U in the bulk of the YBCO sample and its temperature dependence, as well as the critical current density Jc. A comparison between the data obtained and the results of similar measurements in significantly higher magnetic fields was performed. To compare different techniques for evaluation of Jc, the magnetization loop measurements M(H), which relate the loop width to the critical current, were carried out. These measurements provided important parameters of the samples under study (penetration field Hp and first critical field Hc1), which involve the geometrical configuration of the samples.

  9. Theorem on magnet fringe field

    Microsoft Academic Search

    Jie Wei; R. Talman

    1995-01-01

    Transverse particle motion in particle accelerators is governed almost totally by non-solenoidal magnets for which the body magnetic field can be expressed as a series expansion of the normal (b{sub n}) and skew (a{sub n}) multipoles, B{sub y} + iBâ = â(b{sub n} + ia{sub n})(x + iy)ⁿ, where x, y, and z denote horizontal, vertical, and longitudinal (along the

  10. Three-dimensional magnetic field analysis of superconducting 180° bending magnets

    Microsoft Academic Search

    J. Nakata; M. Nakajima; T. Hosokawa; T. Kitayama

    1990-01-01

    Large-scale three-dimensional magnetic field analyses were performed in order to design the superconducting 180° bending for compact electron storage rings used in SOR lithography. Three types of magnets-air core, iron yoke, and iron pole-were computed. Optimizing the coil positions and iron yoke configurations, the proper parameters for obtaining wide good field regions along the electron orbit were found for all

  11. Tearing relaxation and the globalization of transport in field-reversed configurations

    SciTech Connect

    Steinhauer, Loren [Redmond Plasma Physics Laboratory, University of Washington, Redmond, Washington 98052 (United States); Barnes, D. C. [Coronado Consulting, 146 Bishop Lamy Rd., Lamy, New Mexico 87540 (United States)

    2009-09-15

    Tearing instability of field-reversed configurations (FRC) is investigated using the method of neighboring equilibria. It is shown that the conducting wall position in experiment lies very close to the location needed for tearing stability. This strongly suggests that vigorous but benign tearing modes, acting globally, are the engine of continual self-organization in FRCs, i.e., tearing relaxation. It also explains the ''profile consistency'' and anomalous loss rate of magnetic flux. In effect, tearing globalizes the effect of edge-driven transport.

  12. 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.

  13. Tunneling in a magnetic field

    SciTech Connect

    Ivlev, B. [Department of Physics and Astronomy and NanoCenter, University of South Carolina, Columbia, South Carolina 29208 (United States) and Instituto de Fisica, Universidad Autonoma de San Luis Potosi, San Luis Potosi, San Luis Potosi 78000 Mexico

    2006-05-15

    Quantum tunneling across a static potential barrier in a static magnetic field is very sensitive to an analytical form of the potential barrier. Depending on that, the oscillatory structure of the modulus of the wave function can be formed in the direction of tunneling. Due to an underbarrier interference, the probability of tunneling through a higher barrier can be larger than through a lower one. For some barriers the quantum interference of underbarrier cyclotron paths results in a strong enhancement of tunneling. This occurs in the vicinity of the certain magnetic field and is referred to as Euclidean resonance. This strongly contrasts to the Wentzel, Kramers, and Brillouin type tunneling which occurs with no magnetic field.

  14. Protogalactic evolution and magnetic fields

    E-print Network

    Harald Lesch; Masashi Chiba

    1994-11-17

    We show that the relatively strong magnetic fields ($\\ge 1 \\mu$G) in high redshift objects can be explained by the combined action of an evolving protogalactic fluctuation and electrodynamic processes providing the magnetic seed fields. Three different seed field mechanisms are reviewed and incorporated into a spherical "top-hat" model and tidal torque theory for the fate of a forming galaxy in an expanding universe. Very weak fields $10^{-19} \\sim 10^{-23}$G created in an expanding over-dense region are strongly enhanced due to the dissipative disk formation by a factor $\\sim 10^4$, and subsequently amplified by strong non-axisymmetric flow by a factor $\\sim 10^{6-10}$, depending on the cosmological parameters and the epoch of galaxy formation. The resulting field strength at $z \\sim 0.395$ can be of the order of a few $\\mu$G and be close to this value at $z \\sim 2$.

  15. Magnetic Forces and Field Line Density

    NSDL National Science Digital Library

    2012-08-03

    This is an activity about depicting the relative strength of magnetic fields using field line density. Learners will use the magnetic field line drawing of six magnetic poles created in a previous activity and identify the areas of strong, weak, and medium magnetic intensity using the density of magnetic field lines. This is the fifth activity in the Magnetic Math booklet; this booklet can be found on the Space Math@NASA website. How to Draw Magnetic Fields - II in the Magnetic Math booklet must be completed prior to this activity.

  16. Simulations of magnetic fields in filaments

    E-print Network

    M. Bruggen; M. Ruszkowski; A. Simionescu; M. Hoeft; C. Dalla Vecchia

    2005-08-10

    The intergalactic magnetic field within filaments should be less polluted by magnetised outflows from active galaxies than magnetic fields in clusters. Therefore, filaments may be a better laboratory to study magnetic field amplification by structure formation than galaxy clusters which typically host many more active galaxies. We present highly resolved cosmological AMR simulations of magnetic fields in the cosmos and make predictions about the evolution and structure of magnetic fields in filaments. Comparing our results to observational evidence for magnetic fields in filaments suggests that amplification of seed fields by gravitational collapse is not sufficient to produce IGM fields. Finally, implications for cosmic ray transport are discussed.

  17. Multi-Object Spectroscopy Field Configuration by Simulated Annealing

    E-print Network

    Brent Miszalski; Keith Shortridge; Will Saunders; Quentin A. Parker; Scott M. Croom

    2006-07-07

    Multi-object spectroscopy (MOS) instruments, such as the Two-degree Field (2dF) facility of the Anglo-Australian Observatory (AAO), have facilitated large-scale redshift surveys. Yet despite their acclaim, instrument design has been suspected of introducing subtle selection effects into surveys. Investigation into these selection effects has been overshadowed by instrument complexity. We identify the field configuration algorithm (FCA) used to select targets for observation as mainly responsible for such effects. A FCA can imprint artificial structure on observed target distributions, which may accrue over large angular scales, potentially to the detriment of statistical analyses applied to such surveys. We present here a new FCA developed for 2dF that is based on simulated annealing (SA), a generic method commonly used to solve constrained optimisation problems. We generate synthetic fields and utilise mock 2dF volumes to contrast the behaviour of previous strategies with the SA FCA. The angular two-point correlation function and other sensitive techniques reveal that the new FCA achieves unprecedented sampling uniformity and target yield with improved target priority handling and observational flexibility over current FCAs. The SA FCA is generic enough to be used by current 2dF-like and potentially next-generation MOS instruments with little modification.

  18. Origin of primordial magnetic fields

    SciTech Connect

    Souza, Rafael S. de; Opher, Reuven [IAG, Universidade de Sao Paulo, Rua do Matao 1226, Cidade Universitaria, CEP 05508-900, Sao Paulo, SP (Brazil)

    2008-02-15

    Magnetic fields of intensities similar to those in our galaxy are also observed in high redshift galaxies, where a mean field dynamo would not have had time to produce them. Therefore, a primordial origin is indicated. It has been suggested that magnetic fields were created at various primordial eras: during inflation, the electroweak phase transition, the quark-hadron phase transition (QHPT), during the formation of the first objects, and during reionization. We suggest here that the large-scale fields {approx}{mu}G, observed in galaxies at both high and low redshifts by Faraday rotation measurements (FRMs), have their origin in the electromagnetic fluctuations that naturally occurred in the dense hot plasma that existed just after the QHPT. We evolve the predicted fields to the present time. The size of the region containing a coherent magnetic field increased due to the fusion of smaller regions. Magnetic fields (MFs) {approx}10 {mu}G over a comoving {approx}1 pc region are predicted at redshift z{approx}10. These fields are orders of magnitude greater than those predicted in previous scenarios for creating primordial magnetic fields. Line-of-sight average MFs {approx}10{sup -2} {mu}G, valid for FRMs, are obtained over a 1 Mpc comoving region at the redshift z{approx}10. In the collapse to a galaxy (comoving size {approx}30 kpc) at z{approx}10, the fields are amplified to {approx}10 {mu}G. This indicates that the MFs created immediately after the QHPT (10{sup -4} s), predicted by the fluctuation-dissipation theorem, could be the origin of the {approx}{mu}G fields observed by FRMs in galaxies at both high and low redshifts. Our predicted MFs are shown to be consistent with present observations. We discuss the possibility that the predicted MFs could cause non-negligible deflections of ultrahigh energy cosmic rays and help create the observed isotropic distribution of their incoming directions. We also discuss the importance of the volume average magnetic field predicted by our model in producing the first stars and in reionizing the Universe.

  19. Bethe ansatz solution of a model for valence fluctuations between two magnetic configurations

    Microsoft Academic Search

    A. A. Aligia; C. R. Proetto; C. A. Balseiro

    1985-01-01

    We consider a model describing an intermediate-valence impurity fluctuating between two magnetic configurations. The model includes spin-(1\\/2) and spin-1 configurations hybridized through the promotion of an electron to the conduction band. The Hamiltonian is diagonalized by means of the Bethe ansatz and the ground-state properties are calculated.

  20. Reduced MHD in Nearly Potential Magnetic Fields

    E-print Network

    Strauss, Hank

    Reduced MHD in Nearly Potential Magnetic Fields H.R. Strauss Courant Institute of Mathematical that the magnetic field is close to a potential field. The potential field can have an arbitrary three dimensional of equations have essentially the same structure. The main time dependent variables are the magnetic field

  1. Bosonic Casimir effect in external magnetic field

    NASA Astrophysics Data System (ADS)

    Cougo-Pinto, M. V.; Farina, C.; Negrão, M. R.; Tort, A. C.

    1999-06-01

    We compute the influence of an external magnetic field on the Casimir energy of a massive charged scalar field confined between two parallel infinite plates. For this case the obtained result shows that the magnetic field inhibits the Casimir effect.

  2. Photospheric and coronal magnetic fields

    SciTech Connect

    Sheeley, N.R., Jr. (USAF, Geophysics Laboratory, Hanscom AFB, MA (United States))

    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.

  3. DIVERT: a divertor magnetic field line following code

    SciTech Connect

    Morris, R N; Bateman, G

    1980-05-01

    The computer code DIVERT has been written to trace magnetic field lines in the presence of a divertor. Its purpose is to allow a user to estimate the thickness of the plasma scrapeoff region and to provide a visual mapping of the magnetic field lines near the divertor. Included in the code is the capability to provide auxiliary graphics and compute the field ripple. The code can handle a divertor made up of any arrangement of straight line coil segments and will provide a graph of the field line configuration on output.

  4. Interplanetary Magnetic Field Guiding Relativistic Particles

    NASA Technical Reports Server (NTRS)

    Masson, S.; Demoulin, P.; Dasso, S.; Klein, K. L.

    2011-01-01

    The origin and the propagation of relativistic solar particles (0.5 to few Ge V) in the interplanetary medium remains a debated topic. These relativistic particles, detected at the Earth by neutron monitors have been previously accelerated close to the Sun and are guided by the interplanetary magnetic field (IMF) lines, connecting the acceleration site and the Earth. Usually, the nominal Parker spiral is considered for ensuring the magnetic connection to the Earth. However, in most GLEs the IMF is highly disturbed, and the active regions associated to the GLEs are not always located close to the solar footprint of the nominal Parker spiral. A possible explanation is that relativistic particles are propagating in transient magnetic structures, such as Interplanetary Coronal Mass Ejections (ICMEs). In order to check this interpretation, we studied in detail the interplanetary medium where the particles propagate for 10 GLEs of the last solar cycle. Using the magnetic field and the plasma parameter measurements (ACE/MAG and ACE/SWEPAM), we found widely different IMF configurations. In an independent approach we develop and apply an improved method of the velocity dispersion analysis to energetic protons measured by SoHO/ERNE. We determined the effective path length and the solar release time of protons from these data and also combined them with the neutron monitor data. We found that in most of the GLEs, protons propagate in transient magnetic structures. Moreover, the comparison between the interplanetary magnetic structure and the interplanetary length suggest that the timing of particle arrival at Earth is dominantly determined by the type of IMF in which high energetic particles are propagating. Finally we find that these energetic protons are not significantly scattered during their transport to Earth.

  5. How to Draw Magnetic Fields - I

    NSDL National Science Digital Library

    2012-08-03

    This is an activity about depicting magnetic fields. Learners will observe two provided drawings of magnetic field line patterns for bar magnets in simple orientations of like and unlike polarities and carefully draw the field lines for both orientations. This is the third activity in the Magnetic Math booklet; this booklet can be found on the Space Math@NASA website.

  6. Cancellation of the ion deflection due to electron-suppression magnetic field in a negative-ion accelerator

    SciTech Connect

    Chitarin, G., E-mail: chitarin@igi.cnr.it [Consorzio RFX, Association EURATOM-ENEA, Corso Stati Uniti 4, 35127 Padova (Italy); Dept. of Management and Engineering, University of Padova, Strad. S. Nicola 3, 36100 Vicenza (Italy); Agostinetti, P.; Aprile, D.; Marconato, N.; Veltri, P. [Consorzio RFX, Association EURATOM-ENEA, Corso Stati Uniti 4, 35127 Padova (Italy)] [Consorzio RFX, Association EURATOM-ENEA, Corso Stati Uniti 4, 35127 Padova (Italy)

    2014-02-15

    A new magnetic configuration is proposed for the suppression of co-extracted electrons in a negative-ion accelerator. This configuration is produced by an arrangement of permanent magnets embedded in one accelerator grid and creates an asymmetric local magnetic field on the upstream and downstream sides of this grid. Thanks to the “concentration” of the magnetic field on the upstream side of the grid, the resulting deflection of the ions due to magnetic field can be “intrinsically” cancelled by calibrating the configuration of permanent magnets. At the same time, the suppression of co-extracted electrons can be improved.

  7. EXPLORER 10 MAGNETIC FIELD MEASUREMENTS

    Microsoft Academic Search

    J. P. Heppner; N. F. Ness; C. S. Scearce; T. L. Skillman

    1963-01-01

    Magnetic field measurements made by means of Explorer 10 over geocentric ; distances of 1.8 to 42.6R\\/sub e\\/ on March 25experiment on the same satellite are ; referenced in interpretations. The close-in data are consistent with the ; existence of a very weak ring current below 3R\\/sub e\\/ along the trajectory, but ; alternative explanations for the field deviations are

  8. 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.

  9. Levin and Ernst, DC Magnetic Field Effects on Development Applied DC Magnetic Fields Cause Alterations in the

    E-print Network

    Levin, Michael

    Levin and Ernst, DC Magnetic Field Effects on Development Applied DC Magnetic Fields Cause urchin, static magnetic field, gastrulation, development, mitotic cycle, teratogenic effects running title: static Magnetic Field Effects on Development #12;Levin and Ernst, DC Magnetic Field Effects

  10. Note: Manipulation of supersonic atomic beams with static magnetic fields.

    PubMed

    Gardner, Jamie; Castillo-Garza, Rodrigo; Raizen, Mark G

    2013-09-01

    The inhomogeneous magnetic field of a permanent-magnet planar Halbach array is used to either deflect or to specularly reflect a supersonic beam of neutral atoms. Metastable neon and helium beams are tested to experimentally evaluate the performance of this array in a range of configurations. Results are compared with numerical simulations and the device is presented as a high precision tool for the manipulation of neutral atom beams. PMID:24028135

  11. Separation of magnetic field lines

    SciTech Connect

    Boozer, Allen H. [Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027 (United States)

    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.

  12. 3-D mesoscale MHD simulations of a cusp-like magnetic configuration: method and first results

    NASA Astrophysics Data System (ADS)

    Adamson, E.; Nykyri, K.

    2011-05-01

    We present a local mesoscale model of the magnetospheric cusp region with high resolution (up to 300 km). We discuss the construction and implementation of the initial configuration and give a detailed description of the numerical simulation. An overview of simulation results for the case of strongly northward interplanetary magnetic field (IMF) is then presented and compared with data from Cluster 2 spacecraft from 14 February 2003. Results show a cusp diamagnetic cavity (CDC) with depth normal to the magnetospheric boundary on the order of 1-2 RE and a much larger extent of ~5-9 RE tangential to the boundary, bounded by a gradual inner boundary with the magnetospheric lobe and a more distinct exterior boundary with the magnetosheath. These results are qualitatively consistent with observational data.

  13. 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).

  14. 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.

  15. 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 as 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 G. 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.

  16. A new method of asymmetric Abel inversion for magnetic equilibrium configuration state in tokamaks

    Microsoft Academic Search

    Chong-Li Tian; Yan Zhou; Zhong-Bing Shi; Ying-Liang Li

    2007-01-01

    It is difficult to obtain the asymmetrical factor along the observation direction parallel to the plasma mid-plane when the detected radiation is also in the mid-plane. This paper considers the magnetic surfaces and Grad-Shafranov shift, and develops a new method for inverse asymmetric electron density information, during magnetic equilibrium configuration in a tokamak.

  17. Magnetic Field Line Simulation Using a Microcomputer.

    ERIC Educational Resources Information Center

    Kirkup, L.

    1986-01-01

    Describes the implementation of a computer simulation of magnetic field lines. Discusses properties of magnetic fields and the calculation of magnetic fields at points. Provides a program listing (additional programs and teaching notes available from the author) and gives examples of several field plots. (JM)

  18. Comparison between planar magnetocrystaline and shape anisotropies in the magnetic vortex configuration of nanostructured particles

    NASA Astrophysics Data System (ADS)

    Parreiras, Sofia; Souza, Rafael; Martins, Maximiliano

    2015-03-01

    Soft ferromagnetic dots with sub-micrometer size can exhibit in the ground state a curling spin configuration known as magnetic vortex. In the case of soft ferromagnetic materials in micron and submicron scales, small changes in shape, size and material's anisotropy can modify the energy equilibrium that defines the stable spin structure. In this work, we investigated the magnetic configuration of micron-sized Co60Fe40 and Permalloy disks and elipses, prepared by lift-off lithography process, by comparing the results of micromagnetic simulations and magnetic force microscopy (MFM) measurements. By comparing the results for Co60Fe40 and Permalloy it is possible to elucidate the effect of the planar magnetocrystaline anisotropy in the stability of the magnetic vortex configuration and this effect is compared with the effect of the shape anisotropy induced by the elliptical shape. The results for disks with diameters between 0.5 and 8 ?m showed that the anisotropy favors spins alignment and domains division, reducing vortex stability. The results showed different magnetic configurations for each disk diameter. Additionally, a statistical analysis of the magnetic configuration distribution observed in MFM experiments was performed and compared with the simulation results. Acknowledgements: CAPES, CNPq and FAPEMIG.

  19. Electric and magnetic fields at power frequencies.

    PubMed

    Miller, Anthony B; Green, Lois M

    2010-01-01

    Exposures to electric and magnetic fields are among the most ubiquitous exposures that the Canadian population experiences. Sources of electric and magnetic field exposures may be occupational or residential and include proximity to certain types of electrical equipment, transmission and distribution power lines as well as appliance use. The early studies of children tended toward a consistent association between risks for leukemia and brain cancer and residential proximity to power lines having high wire configuration. More recent studies-and studies which have attempted to improve upon the measurement of exposure by using calculated fields, point-in-time or personal monitoring-have been inconsistent, with some suggesting increased risk and others not. Occupational exposures have suggested an increase in risk for leukemia, and to a lesser extent brain cancer and Non-Hodgkin lymphoma. However, studies of residential exposures and cancer in adults generally have suggested no effect. Laboratory work has been unable to demonstrate a biological mechanism which might explain the epidemiological findings. In spite of extensive efforts over the past 20 years and many expert reviews, it has been difficult to reach consensus regarding the carcinogenic effects of electric and magnetic fields. Exposure assessment has proven to be complex, and agreement on the relevant exposure metric has not yet been obtained. There is justification to question whether point-in-time measures in homes are appropriate indices of the relevant etiological exposure, as they fail to account for changes over time, peak exposures or time-varying fields. Nevertheless, it is probably desirable to err on the side of caution in not placing too much weight on the inconsistencies. The IARC has classified EMF as a "possible carcinogen" which refers to the circumstances where there is limited evidence of carcinogenicity in humans and inadequate evidence in experimental animals. The IARC review indicated limited evidence for the carcinogenicity of extremely low-frequency magnetic fields in relation to childhood leukemia at high level exposure in the residential environment (average residential magnetic field strength >0.4 ?T). Even higher levels of exposure in the occupational environment may increase the risk of leukemia in adults. PMID:21199600

  20. Effect of magnetic field on ball milled hard magnetic particles

    NASA Astrophysics Data System (ADS)

    Altuncevahir, B.; Poudyal, N.; Chakka, V. M.; Chen, K. H.; Black, T. D.; Liu, T. D.

    2004-03-01

    In this investigation, the powder particles of NdFeB and SmCo based alloys prepared by the ball milling in a uniform magnetic field are compared to those milled without an applied magnetic field. The ball milling was carried out for a total of 100 hours, and the powders were sampled every 25 hours. The particle size after 100 hours of milling was around 100 nm and the grain size in the particles was below 20 nm. The particles were then aligned in a magnetic field in hardening epoxy. It was found that the remanence ratios of the samples milled in an applied magnetic field were remarkably higher than those milled without field. XRD patterns also showed that the powder milled in magnetic field has better alignment than those milled without magnetic field. This technique is a novel approach to preparing anisotropic magnetic nanoparticles and has potential for producing high energy-product nanocomposite permanent magnets.

  1. CORRELATION OF MAGNETIC FIELDS AND ENERGETIC ELECTRONS ON THE IMP 1 SATELLITE

    Microsoft Academic Search

    K. A. ANDERSON; N. F. NESS

    1966-01-01

    A study of simultaneous magnetic field and energetic particle records from the IMP 1 satellite on the dark side of the earth has shown several distinct correlations that can be understood as diamagnetic effects of charged particle populations. Depression of the mag- netic field in the closed magnetic field line configuration of the particle cusp region is ob- served on

  2. Fusion proton diagnostic for the C-2 field reversed configuration

    SciTech Connect

    Magee, R. M., E-mail: rmagee@trialphaenergy.com; Clary, R.; Korepanov, S.; Smirnov, A.; Garate, E.; Knapp, K. [Tri Alpha Energy, Inc., Rancho Santa Margarita, California 92688 (United States); Tkachev, A. [Budker Institute of Nuclear Physics, Novosibirsk (Russian Federation)

    2014-11-15

    Measurements of the flux of fusion products from high temperature plasmas provide valuable insights into the ion energy distribution, as the fusion reaction rate is a very sensitive function of ion energy. In C-2, where field reversed configuration plasmas are formed by the collision of two compact toroids and partially sustained by high power neutral beam injection [M. Binderbauer et al., Phys. Rev. Lett. 105, 045003 (2010); M. Tuszewski et al., Phys. Rev. Lett. 108, 255008 (2012)], measurements of DD fusion neutron flux are used to diagnose ion temperature and study fast ion confinement and dynamics. In this paper, we will describe the development of a new 3 MeV proton detector that will complement existing neutron detectors. The detector is a large area (50?cm{sup 2}), partially depleted, ion implanted silicon diode operated in a pulse counting regime. While the scintillator-based neutron detectors allow for high time resolution measurements (?100 kHz), they have no spatial or energy resolution. The proton detector will provide 10 cm spatial resolution, allowing us to determine if the axial distribution of fast ions is consistent with classical fast ion theory or whether anomalous scattering mechanisms are active. We will describe in detail the diagnostic design and present initial data from a neutral beam test chamber.

  3. Dynamic formation of a hot field reversed configuration with improved confinement by supersonic merging of two colliding high-? compact toroids.

    PubMed

    Binderbauer, M W; Guo, H Y; Tuszewski, M; Putvinski, S; Sevier, L; Barnes, D; Rostoker, N; Anderson, M G; Andow, R; Bonelli, L; Brandi, F; Brown, R; Bui, D Q; Bystritskii, V; Ceccherini, F; Clary, R; Cheung, A H; Conroy, K D; Deng, B H; Dettrick, S A; Douglass, J D; Feng, P; Galeotti, L; Garate, E; Giammanco, F; Glass, F J; Gornostaeva, O; Gota, H; Gupta, D; Gupta, S; Kinley, J S; Knapp, K; Korepanov, S; Hollins, M; Isakov, I; Jose, V A; Li, X L; Luo, Y; Marsili, P; Mendoza, R; Meekins, M; Mok, Y; Necas, A; Paganini, E; Pegoraro, F; Pousa-Hijos, R; Primavera, S; Ruskov, E; Qerushi, A; Schmitz, L; Schroeder, J H; Sibley, A; Smirnov, A; Song, Y; Sun, X; Thompson, M C; Van Drie, A D; Walters, J K; Wyman, M D

    2010-07-23

    A hot stable field-reversed configuration (FRC) has been produced in the C-2 experiment by colliding and merging two high-? plasmoids preformed by the dynamic version of field-reversed ?-pinch technology. The merging process exhibits the highest poloidal flux amplification obtained in a magnetic confinement system (over tenfold increase). Most of the kinetic energy is converted into thermal energy with total temperature (T{i}+T{e}) exceeding 0.5 keV. The final FRC state exhibits a record FRC lifetime with flux confinement approaching classical values. These findings should have significant implications for fusion research and the physics of magnetic reconnection. PMID:20867853

  4. The Magnetism of Meteorites and Early Solar System Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Collinson, D. W.

    1994-11-01

    The characteristics of the remanent magnetization of chondrite, achondrite and shergottite, nakhlite and chassignite (SNC) meteorites are described, and interpretation in terms of magnetizing fields in the ancient Solar System discussed. The magnetism of ordinary chondrites is commonly scattered in direction within samples, implying magnetization of constituent fragments before accumulation. The magnetic history of these meteorites is uncertain because of lack of knowledge of the origin and properties of tetrataenite, an ordered FeNi alloy often carrying the bulk of the magnetization. Achondrites also often possess scattered magnetization, the primary component probably being acquired during cooling after differentiation of the parent body. A magnetizing field of internal origin is possible. Estimates of magnetizing field strength are in the approximate range 5-100 ? T, with carbonaceous chondrites showing the highest values. The SNC meteorites, probably originating on Mars, provide evidence for a weak, ancient Martian magnetic field of the order 1 ? T.

  5. MAGNETIC FIELD CONFINEMENT IN THE SOLAR CORONA. I. FORCE-FREE MAGNETIC FIELDS B. Fornberg,2

    E-print Network

    Fornberg, Bengt

    MAGNETIC FIELD CONFINEMENT IN THE SOLAR CORONA. I. FORCE-FREE MAGNETIC FIELDS N. Flyer,1 B Axisymmetric force-free magnetic fields external to a unit sphere are studied as solutions to boundary value to the formation of an azimuthal rope of twisted magnetic field embedded within the global field, and to the energy

  6. 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.

  7. Variability in Martian Magnetic Field Topology

    NASA Astrophysics Data System (ADS)

    Brain, D. A.; Halekas, J. S.; Eastwood, J. P.; Ulusen, D.; Lillis, R. J.

    2014-07-01

    We have determined the locations of open and closed magnetic field lines at Mars as a function of four different controlling influences: solar wind magnetic field direction, solar wind pressure, martian season, and solar EUV flux.

  8. Passive Magnetic Shielding in Gradient Fields

    E-print Network

    Bidinosti, C P

    2013-01-01

    The effect of passive magnetic shielding on dc magnetic field gradients imposed by both external and internal sources is studied. It is found that for concentric cylindrical or spherical shells of high permeability material, higher order multipoles in the magnetic field are shielded progressively better, by a factor related to the order of the multipole. In regard to the design of internal coil systems for the generation of uniform internal fields, we show how one can take advantage of the coupling of the coils to the innermost magnetic shield to further optimize the uniformity of the field. These results demonstrate quantitatively a phenomenon that was previously well-known qualitatively: that the resultant magnetic field within a passively magnetically shielded region can be much more uniform than the applied magnetic field itself. Furthermore we provide formulae relevant to active magnetic compensation systems which attempt to stabilize the interior fields by sensing and cancelling the exterior fields clos...

  9. Plasma stability in a dipole magnetic field

    E-print Network

    Simakov, Andrei N., 1974-

    2001-01-01

    The MHD and kinetic stability of an axially symmetric plasma, confined by a poloidal magnetic field with closed lines, is considered. In such a system the stabilizing effects of plasma compression and magnetic field ...

  10. Three-dimensional magnetic field analysis of superconducting 180 degrees bending magnets

    SciTech Connect

    Nakata, J.; Nakajima, M.; Hosokawa, T.; Kitayama, T. (Nippon Telegraph and Telephone Corp., NTT LSI Lab., 3-1 Morinosato, Wakamiya, Atugi-shi, Kanagawa 243-01 (JP))

    1990-03-01

    To design the superconducting 180{degrees} bending magnets for compact electron storage rings used in SOR lithography, large-scale 3-dimensional (3-D) magnetic field analyses were performed. Three types of magnets, -- air core, iron yoke, and iron pole -- were minutely computed. Optimizing the coil positions and iron yoke configurations, were found the proper parameters for obtaining wide good field regions along the electron orbit, for all three types. This paper discusses how the iron yoke type was minutely studied an very low liquid helium consumption, wide good field regions that were not changed from low to high field, very low stray fields around the magnet and good tracking controllability could be obtained.

  11. Near-field magnetic communication

    Microsoft Academic Search

    R. Bansal

    2004-01-01

    Even as cell phones have shrunk in size while boasting an ever-increasing array of features, two things about them haven't changed much: they still sprout a stubby antenna and, if you want a headset, you have to put up with an unwieldy wire connecting the headset and the phone. Thanks to a patented technology called near-field magnetic communication (NFMC), from

  12. Rotating copper plasmoid in external magnetic field

    SciTech Connect

    Pandey, Pramod K.; Thareja, Raj K. [Department of Physics, Indian Institute of Technology Kanpur, Uttar Pradesh 208 016 (India)

    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.

  13. Magnetic field effect for cellulose nanofiber alignment

    NASA Astrophysics Data System (ADS)

    Kim, Jaehwan; Chen, Yi; Kang, Kwang-Sun; Park, Young-Bin; Schwartz, Mark

    2008-11-01

    Regenerated cellulose formed into cellulose nanofibers under strong magnetic field and aligned perpendicularly to the magnetic field. Well-aligned microfibrils were found as the exposure time of the magnetic field increased. Better alignment and more crystalline structure of the cellulose resulted in the increased decomposition temperature of the material. X-ray crystallograms showed that crystallinity index of the cellulose increased as the exposure time of the magnetic field increased.

  14. Extraterrestrial magnetic fields - Achievements and opportunities

    Microsoft Academic Search

    E. J. Smith; C. P. Sonett

    1976-01-01

    The major scientific achievements associated with the measurement of magnetic fields in space over the past decade and a half are reviewed. Aspects of space technology relevant to magnetic-field observations are discussed: magnetometers and how they operate, problems arising from spacecraft-generated magnetic fields and appropriate countermeasures and on-board processing of magnetometer data. The solar wind and interplanetary magnetic field, the

  15. Energy buildup in sheared force-free magnetic fields

    NASA Technical Reports Server (NTRS)

    Wolfson, Richard; Low, Boon C.

    1992-01-01

    Photospheric displacement of the footpoints of solar magnetic field lines results in shearing and twisting of the field, and consequently in the buildup of electric currents and magnetic free energy in the corona. The sudden release of this free energy may be the origin of eruptive events like coronal mass ejections, prominence eruptions, and flares. An important question is whether such an energy release may be accompanied by the opening of magnetic field lines that were previously closed, for such open field lines can provide a route for matter frozen into the field to escape the sun altogether. This paper presents the results of numerical calculations showing that opening of the magnetic field is permitted energetically, in that it is possible to build up more free energy in a sheared, closed, force-free magnetic field than is in a related magnetic configuration having both closed and open field lines. Whether or not the closed force-free field attains enough energy to become partially open depends on the form of the shear profile; the results presented compare the energy buildup for different shear profiles. Implications for solar activity are discussed briefly.

  16. Comments on s-rule violating configurations in field theory

    NASA Astrophysics Data System (ADS)

    Cottrell, William; Hashimoto, Akikazu; Pillai, Mohandas

    2015-06-01

    We explicitly construct a configuration of N = 4 supersymmetry Yang-Mills theory with gauge group U (N) on an interval on length L with a D5-like boundary condition on one end and an NS5-like boundary condition on the other. For N > 1, such a configuration violates the s-rule and is non-supersymmetric. We compute the energy relative to the BPS bound of these configurations and find that it is proportional to N (N2 - 1) gYM4- 2 L-3.

  17. Van der Waals torque induced by external magnetic fields

    NASA Astrophysics Data System (ADS)

    Esquivel-Sirvent, R.; Cocoletzi, G. H.; Palomino-Ovando, M.

    2010-12-01

    We present a method for inducing and controlling van der Waals torques between two parallel slabs using a constant magnetic field. The torque is calculated using the Barash theory of dispersive torques. In III-IV semiconductors such as InSb, the effect of an external magnetic field is to induce an optical anisotropy, in an otherwise isotropic material, that will in turn induce a torque. The calculations of the torque are done in the Voigt configuration, with the magnetic field parallel to the surface of the slabs. As a case study we consider a slab made of calcite and a second slab made of InSb. In the absence of magnetic field there is no torque. As the magnetic field increases, the optical anisotropy of InSb increases and the torque becomes different from zero, increasing with the magnetic field. The resulting torque is of the same order of magnitude as that calculated using permanent anisotropic materials when the magnetic fields is close to 1 T.

  18. Pulsed-Field Gradient Nuclear Magnetic

    E-print Network

    Duncan, James S.

    Pulsed-Field Gradient Nuclear Magnetic Resonance as a Tool for Studying Translational Diffusion and biochemical systems. Pulsed-field gradient nuclear magnetic resonance pro- vides a convenient and noninvasive spin-echo pulse sequence contain- ing a magnetic field gradient pulse in each period is used to measure

  19. Primordial magnetic field limits from cosmological data

    SciTech Connect

    Kahniashvili, Tina [McWilliams Center for Cosmology and Department of Physics, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, Pennsylvania 15213 (United States); Department of Physics, Laurentian University, Ramsey Lake Road, Sudbury, Ontario P3E 2C (Canada); Abastumani Astrophysical Observatory, Ilia State University, 2A Kazbegi Ave, Tbilisi, GE-0160 (Georgia); Tevzadze, Alexander G. [Abastumani Astrophysical Observatory, Ilia State University, 2A Kazbegi Ave, Tbilisi, GE-0160 (Georgia); Faculty of Exact and Natural Sciences, Tbilisi State University, 1 Chavchavadze Avenue, Tbilisi, GE-0128 (Georgia); Sethi, Shiv K. [McWilliams Center for Cosmology and Department of Physics, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, Pennsylvania 15213 (United States); Raman Research Institute, Sadashivanagar, Bangalore 560080 (India); Pandey, Kanhaiya [Raman Research Institute, Sadashivanagar, Bangalore 560080 (India); Ratra, Bharat [Department of Physics, Kansas State University, 116 Cardwell Hall, Manhattan, Kansas 66506 (United States)

    2010-10-15

    We study limits on a primordial magnetic field arising from cosmological data, including that from big bang nucleosynthesis, cosmic microwave background polarization plane Faraday rotation limits, and large-scale structure formation. We show that the physically relevant quantity is the value of the effective magnetic field, and limits on it are independent of how the magnetic field was generated.

  20. Wormholes supported by the kink-like configuration of a scalar field

    E-print Network

    S. V. Sushkov; S. -W. Kim

    2002-08-23

    We study the problem of existence of static spherically symmetric wormholes supported by the kink-like configuration of a scalar field. With this aim we consider a self-consistent, real, nonlinear, nonminimally coupled scalar field $\\phi$ in general relativity with the symmetry-breaking potential $V(\\phi)$ possessing two minima. We classify all possible field configurations ruling out those of them for which wormhole solutions are impossible. Field configurations admitting wormholes are investigated numerically. Such the configurations represent a spherical domain wall localized near the wormhole throat.

  1. Magnetism

    NSDL National Science Digital Library

    University Corporation for Atmospheric Research Windows to the Universe team

    2007-12-12

    This webpage is part of the University Corporation for Atmospheric Research (UCAR) Windows to the Universe program. It describes the nature and configuration of magnetic fields, which are the result of moving electric charges, including how they cause magnetic objects to orient themselves along the direction of the magnetic force points, which are illustrated as lines. Magnetic field lines by convention point outwards at the north magnetic pole and inward at the south magnetic pole. The site features text, scientific illustrations and an animation. Text and vocabulary are selectable for the beginning, intermediate, or advanced reader.

  2. Magnetic field response sensor for conductive media

    NASA Technical Reports Server (NTRS)

    Woodard, Stanley E. (Inventor); Taylor, Bryant Douglas (Inventor)

    2010-01-01

    A magnetic field response sensor comprises an inductor placed at a fixed separation distance from a conductive surface to address the low RF transmissivity of conductive surfaces. The minimum distance for separation is determined by the sensor response. The inductor should be separated from the conductive surface so that the response amplitude exceeds noise level by a recommended 10 dB. An embodiment for closed cavity measurements comprises a capacitor internal to said cavity and an inductor mounted external to the cavity and at a fixed distance from the cavity's wall. An additional embodiment includes a closed cavity configuration wherein multiple sensors and corresponding antenna are positioned inside the cavity, with the antenna and inductors maintained at a fixed distance from the cavity's wall.

  3. Magnetic field response sensor for conductive media

    NASA Technical Reports Server (NTRS)

    Woodard, Stanley E. (Inventor); Taylor, Bryant D. (Inventor)

    2009-01-01

    A magnetic field response sensor comprises an inductor placed at a fixed separation distance from a conductive surface to address the low RF transmissivity of conductive surfaces. The minimum distance for separation is determined by the sensor response. The inductor should be separated from the conductive surface so that the response amplitude exceeds noise level by a recommended 10 dB. An embodiment for closed cavity measurements comprises a capacitor internal to said cavity and an inductor mounted external to the cavity and at a fixed distance from the cavity's wall. An additional embodiment includes a closed cavity configuration wherein multiple sensors and corresponding antenna are positioned inside the cavity, with the antenna and inductors maintained at a fixed distance from the cavity's wall.

  4. Magnetic monopole and the nature of the static magnetic field

    E-print Network

    Xiuqing Huang

    2008-12-10

    We investigate the factuality of the hypothetical magnetic monopole and the nature of the static magnetic field. It is shown from many aspects that the concept of the massive magnetic monopoles clearly is physically untrue. We argue that the static magnetic field of a bar magnet, in fact, is the static electric field of the periodically quasi-one-dimensional electric-dipole superlattice, which can be well established in some transition metals with the localized d-electron. This research may shed light on the perfect unification of magnetic and electrical phenomena.

  5. Cluster Magnetic Fields from Galactic Outflows

    E-print Network

    J. Donnert; K. Dolag; H. Lesch; E. Müller

    2008-10-24

    We performed cosmological, magneto-hydrodynamical simulations to follow the evolution of magnetic fields in galaxy clusters, exploring the possibility that the origin of the magnetic seed fields are galactic outflows during the star-burst phase of galactic evolution. To do this we coupled a semi-analytical model for magnetized galactic winds as suggested by \\citet{2006MNRAS.370..319B} to our cosmological simulation. We find that the strength and structure of magnetic fields observed in galaxy clusters are well reproduced for a wide range of model parameters for the magnetized, galactic winds and do only weakly depend on the exact magnetic structure within the assumed galactic outflows. Although the evolution of a primordial magnetic seed field shows no significant differences to that of galaxy clusters fields from previous studies, we find that the magnetic field pollution in the diffuse medium within filaments is below the level predicted by scenarios with pure primordial magnetic seed field. We therefore conclude that magnetized galactic outflows and their subsequent evolution within the intra-cluster medium can fully account for the observed magnetic fields in galaxy clusters. Our findings also suggest that measuring cosmological magnetic fields in low-density environments such as filaments is much more useful than observing cluster magnetic fields to infer their possible origin.

  6. 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

  7. Calculations of the field distribution of a spectrometric magnet

    NASA Astrophysics Data System (ADS)

    Polyakova, R. V.; Perepelkin, E. E.; Shavrina, T. V.; Yudin, I. P.

    2006-12-01

    The design and construction of magnetic systems of electrophysical installations require preliminary mathematical modeling. Mathematical modeling is necessary in the process of adjustment and subsequent operation of an installation. Calculations of fields of magnetic systems, although performed on the basis of the solution of direct magnetostatic problems, are related to the class of inverse magnetostatic problems, since they actually include the search for optimal design of current elements and an iron yoke for a given magnetic field distribution. In this work, the method of numerical solution of the magnetostatic problem for domains with boundaries containing cusps is proposed. Using this numerical method, magnetic systems of rectangular configuration were modeled with high accuracy. In particular, the calculations of several modifications of the magnetic system SP-94 used in certain experimental installations are presented.

  8. Suppression of magnetic relaxation by a transverse alternating magnetic field

    SciTech Connect

    Voloshin, I. F.; Kalinov, A. V.; Fisher, L. M. [All-Russia Electrical Engineering Institute (Russian Federation)], E-mail: fisher@vei.ru; Yampol'skii, V. A. [National Academy of Sciences of Ukraine, Institute of Radiophysics and Electronics (Ukraine)], E-mail: yam@vk.kharkov.ua

    2007-07-15

    The evolution of the spatial distribution of the magnetic induction in a superconductor after the action of the alternating magnetic field perpendicular to the trapped magnetic flux has been analyzed. The observed stabilization of the magnetic induction profile is attributed to the increase in the pinning force, so that the screening current density becomes subcritical. The last statement is corroborated by direct measurements.

  9. 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.

  10. Pull-in control due to Casimir forces using external magnetic fields

    NASA Astrophysics Data System (ADS)

    Esquivel-Sirvent, R.; Palomino-Ovando, M. A.; Cocoletzi, G. H.

    2009-08-01

    We present a theoretical calculation of the pull-in control in capacitive microswitches actuated by Casimir forces using external magnetic fields. The external magnetic fields induce an optical anisotropy due to the excitation of magnetoplasmons that reduces the Casimir force. The calculations are performed in the Voigt configuration and the results show that as the magnetic field increases the system becomes more stable. The detachment length for a cantilever is also calculated for a cantilever, showing that it increases with increasing magnetic field. At the pull-in separation, the stiffness of the system decreases with the increasing magnetic field.

  11. Pull-in control due to Casimir forces using external magnetic fields

    E-print Network

    R. Esquivel-Sirvent; M. A. Palomino-Ovando; G. H. Cocoletzi

    2009-07-13

    We present a theoretical calculation of the pull-in control in capacitive micro switches actuated by Casimir forces, using external magnetic fields. The external magnetic fields induces an optical anisotropy due to the excitation of magneto plasmons, that reduces the Casimir force. The calculations are performed in the Voigt configuration, and the results show that as the magnetic field increases the system becomes more stable. The detachment length for a cantilever is also calculated for a cantilever, showing that it increases with increasing magnetic field. At the pull-in separation, the stiffness of the system decreases with increasing magnetic field.

  12. Compact low field magnetic resonance imaging magnet: Design and optimization

    Microsoft Academic Search

    M. Sciandrone; G. Placidi; L. Testa; A. Sotgiu

    2000-01-01

    Magnetic resonance imaging (MRI) is performed with a very large instrument that allows the patient to be inserted into a region of uniform magnetic field. The field is generated either by an electromagnet (resistive or superconductive) or by a permanent magnet. Electromagnets are designed as air cored solenoids of cylindrical symmetry, with an inner bore of 80-100 cm in diameter.

  13. Magnetic Fields1 Increasingly, instruments that generate large static magnetic fields (e.g., NMR spectrometers,

    E-print Network

    Shull, Kenneth R.

    Magnetic Fields1 Increasingly, instruments that generate large static magnetic fields (e.g., NMR spectrometers, MRI) are present in research laboratories. Such magnets typically have fields of 14,000 to 235,000 G (1.4 to 23.5 T), far above that of Earth's magnetic field, which is approximately 0.5 G

  14. Magnetic field perturbations in the systems where only poloidal magnetic field is present*

    E-print Network

    1 Magnetic field perturbations in the systems where only poloidal magnetic field is present* D In some plasma confinement systems the confinement is provided by a poloidal magnetic field (no toroidal magnetic field is present). Examples include FRC, levitated dipoles, and long diffuse pinches. We consider

  15. Deformable homeotropic nematic droplets in a magnetic field

    NASA Astrophysics Data System (ADS)

    Otten, Ronald H. J.; van der Schoot, Paul

    2012-10-01

    We present a Frank-Oseen elasticity theory for the shape and structure of deformable nematic droplets with homeotropic surface anchoring in the presence of a magnetic field. Inspired by recent experimental observations, we focus on the case where the magnetic susceptibility is negative, and find that small drops have a lens shape with a homogeneous director field for any magnetic-field strength, whereas larger drops are spherical and have a radial director field, at least if the magnetic field is weak. For strong magnetic fields the hedgehog configuration transforms into a split-core line defect that, depending on the anchoring strength, can be accompanied by an elongation of the tactoid itself. We present a three-dimensional phase diagram that shows the tactoid shape and director field for a given anchoring strength, tactoid size, and magnetic-field strength. Our findings rationalize the different shapes and structures that recently have been observed experimentally for nematic droplets found in dispersions of gibbsite platelets in two types of solvent.

  16. Deformable homeotropic nematic droplets in a magnetic field.

    PubMed

    Otten, Ronald H J; van der Schoot, Paul

    2012-10-21

    We present a Frank-Oseen elasticity theory for the shape and structure of deformable nematic droplets with homeotropic surface anchoring in the presence of a magnetic field. Inspired by recent experimental observations, we focus on the case where the magnetic susceptibility is negative, and find that small drops have a lens shape with a homogeneous director field for any magnetic-field strength, whereas larger drops are spherical and have a radial director field, at least if the magnetic field is weak. For strong magnetic fields the hedgehog configuration transforms into a split-core line defect that, depending on the anchoring strength, can be accompanied by an elongation of the tactoid itself. We present a three-dimensional phase diagram that shows the tactoid shape and director field for a given anchoring strength, tactoid size, and magnetic-field strength. Our findings rationalize the different shapes and structures that recently have been observed experimentally for nematic droplets found in dispersions of gibbsite platelets in two types of solvent. PMID:23083185

  17. Asymptotic analysis of force-free magnetic fields of cylindrical symmetry

    NASA Technical Reports Server (NTRS)

    Sturrock, P. A.; Antiochos, S. K.; Roumeliotis, G.

    1995-01-01

    It is known from computer calculations that if a force-free magnetic-field configuration is stressed progressively by footpoint displacements, the configuration expands and approaches the open configuration with the same surface flux distribution, and, in the process, the energy of the field increases progressively. Analysis of a simple model of force-free fields of cylindrical symmetry leads to simple asymptotic expressions for the extent and energy of such a configuration. The analysis is carried through for both spherical and planar source surfaces. According to this model, the field evolves in a well-behaved manner with no indication of instability or loss of equilibrium.

  18. How to Draw Magnetic Fields - II

    NSDL National Science Digital Library

    This is an activity about depicting magnetic polarity. Learners will observe several provided drawings of magnetic field line patterns for bar magnets in simple orientations of like and unlike polarities and carefully draw the field lines and depict the polarities for several orientations, including an arrangement of six magnetic poles. This is the fourth activity in the Magnetic Math booklet; this booklet can be found on the Space Math@NASA website.

  19. Magnetic Configuration Effects on Fast Ion Losses Induced by Fast Ion Driven Toroidal Alfven Eigenmodes in the Large Helical Device

    SciTech Connect

    Ogawa, K. [Nagoya University, Japan; Isobe, M. [National Institute for Fusion Science, Toki, Japan; Watanabe, F. [Kyoto University, Japan; Spong, Donald A [ORNL; Shimizu, A. [National Institute for Fusion Science, Toki, Japan; Osakabe, M. [National Institute for Fusion Science, Toki, Japan; Ohdachi, S. [National Institute for Fusion Science, Toki, Japan; Sakakibara, S. [National Institute for Fusion Science, Toki, Japan

    2012-01-01

    Beam-ion losses induced by fast-ion-driven toroidal Alfven eigenmodes (TAE) were measured with a scintillator-based lost fast-ion probe (SLIP) in the large helical device (LHD). The SLIP gave simultaneously the energy E and the pitch angle chi = arccos(v(parallel to)/v) distribution of the lost fast ions. The loss fluxes were investigated for three typical magnetic configurations of R{sub ax{_}vac} = 3.60 m, 3.75 m, and 3.90 m, where R{sub ax{_}vac} is the magnetic axis position of the vacuum field. Dominant losses induced by TAEs in these three configurations were observed in the E/chi regions of 50 similar to 190 keV/40 degrees, 40 similar to 170 keV/25 degrees, and 30 similar to 190 keV/30 degrees, respectively. Lost-ion fluxes induced by TAEs depend clearly on the amplitude of TAE magnetic fluctuations, R{sub ax{_}vac} and the toroidal field strength B{sub t}. The increment of the loss fluxes has the dependence of (b{sub TAE}/B{sub t}){sup s}. The power s increases from s = 1 to 3 with the increase of the magnetic axis position in finite beta plasmas.

  20. Force-free magnetic fields - The magneto-frictional method

    NASA Technical Reports Server (NTRS)

    Yang, W. H.; Sturrock, P. A.; Antiochos, S. K.

    1986-01-01

    The problem under discussion is that of calculating magnetic field configurations in which the Lorentz force j x B is everywhere zero, subject to specified boundary conditions. We choose to represent the magnetic field in terms of Clebsch variables in the form B = grad alpha x grad beta. These variables are constant on any field line so that each field line is labeled by the corresponding values of alpha and beta. When the field is described in this way, the most appropriate choice of boundary conditions is to specify the values of alpha and beta on the bounding surface. We show that such field configurations may be calculated by a magneto-frictional method. We imagine that the field lines move through a stationary medium, and that each element of magnetic field is subject to a frictional force parallel to and opposing the velocity of the field line. This concept leads to an iteration procedure for modifying the variables alpha and beta, that tends asymptotically towards the force-free state. We apply the method first to a simple problem in two rectangular dimensions, and then to a problem of cylindrical symmetry that was previously discussed by Barnes and Sturrock (1972). In one important respect, our new results differ from the earlier results of Barnes and Sturrock, and we conclude that the earlier article was in error.

  1. 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.

  2. DIFFUSION OF MAGNETIC FIELD AND REMOVAL OF MAGNETIC FLUX FROM CLOUDS VIA TURBULENT RECONNECTION

    SciTech Connect

    Santos-Lima, R.; De Gouveia Dal Pino, E. M. [Instituto de Astronomia, Geofisica e Ciencias Atmosfericas, Universidade de Sao Paulo, R. do Matao, 1226, Sao Paulo, SP 05508-090 (Brazil); Lazarian, A.; Cho, J. [Department of Astronomy, University of Wisconsin, Madison, WI 53706 (United States)

    2010-05-01

    The diffusion of astrophysical magnetic fields in conducting fluids in the presence of turbulence depends on whether magnetic fields can change their topology via reconnection in highly conducting media. Recent progress in understanding fast magnetic reconnection in the presence of turbulence reassures that the magnetic field behavior in computer simulations and turbulent astrophysical environments is similar, as far as magnetic reconnection is concerned. This makes it meaningful to perform MHD simulations of turbulent flows in order to understand the diffusion of magnetic field in astrophysical environments. Our studies of magnetic field diffusion in turbulent medium reveal interesting new phenomena. First of all, our three-dimensional MHD simulations initiated with anti-correlating magnetic field and gaseous density exhibit at later times a de-correlation of the magnetic field and density, which corresponds well to the observations of the interstellar media. While earlier studies stressed the role of either ambipolar diffusion or time-dependent turbulent fluctuations for de-correlating magnetic field and density, we get the effect of permanent de-correlation with one fluid code, i.e., without invoking ambipolar diffusion. In addition, in the presence of gravity and turbulence, our three-dimensional simulations show the decrease of the magnetic flux-to-mass ratio as the gaseous density at the center of the gravitational potential increases. We observe this effect both in the situations when we start with equilibrium distributions of gas and magnetic field and when we follow the evolution of collapsing dynamically unstable configurations. Thus, the process of turbulent magnetic field removal should be applicable both to quasi-static subcritical molecular clouds and cores and violently collapsing supercritical entities. The increase of the gravitational potential as well as the magnetization of the gas increases the segregation of the mass and magnetic flux in the saturated final state of the simulations, supporting the notion that the reconnection-enabled diffusivity relaxes the magnetic field + gas system in the gravitational field to its minimal energy state. This effect is expected to play an important role in star formation, from its initial stages of concentrating interstellar gas to the final stages of the accretion to the forming protostar. In addition, we benchmark our codes by studying the heat transfer in magnetized compressible fluids and confirm the high rates of turbulent advection of heat obtained in an earlier study.

  3. Magnetic field driven domain-wall propagation in magnetic nanowires

    SciTech Connect

    Wang, X.R. [Physics Department, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong (China); Yan, P. [Physics Department, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong (China)], E-mail: yanpeng@ust.hk; Lu, J.; He, C. [Physics Department, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong (China)

    2009-08-15

    The mechanism of magnetic field induced magnetic domain-wall (DW) propagation in a nanowire is revealed: A static DW cannot exist in a homogeneous magnetic nanowire when an external magnetic field is applied. Thus, a DW must vary with time under a static magnetic field. A moving DW must dissipate energy due to the Gilbert damping. As a result, the wire has to release its Zeeman energy through the DW propagation along the field direction. The DW propagation speed is proportional to the energy dissipation rate that is determined by the DW structure. The negative differential mobility in the intermediate field is due to the transition from high energy dissipation at low field to low energy dissipation at high field. For the field larger than the so-called Walker breakdown field, DW plane precesses around the wire, leading to the propagation speed oscillation.

  4. Characteristics of geometric distortion correction with increasing field-of-view in open-configuration MRI.

    PubMed

    Hong, Cheolpyo; Lee, Dong-Hoon; Han, Bong Soo

    2014-07-01

    Open-configuration magnetic resonance imaging (MRI) systems are becoming increasingly desirable for musculoskeletal imaging and image-guided radiotherapy because of their non-claustrophobic configuration. However, geometric image distortion in large fields-of-view (FOV) due to field inhomogeneity and gradient nonlinearity hinders the practical applications of open-type MRI. We demonstrated the use of geometric distortion correction for increasing FOV in open MRI. Geometric distortion was modeled and corrected as a global polynomial function. The appropriate polynomial order was identified as the minimum difference between the coordinates of control points in the distorted MR image space and those predicted by polynomial modeling. The sixth order polynomial function was found to give the optimal value for geometric distortion correction. The area of maximum distortion was<1 pixel with an FOV of 285mm. The correction performance error was increased at most 1.2% and 2.9% for FOVs of 340mm and~400mm compared with the FOV of 285mm. In particular, unresolved distortion was generated by local deformation near the gradient coil center. PMID:24698340

  5. Correcting field harmonics after design in superconducting magnets

    SciTech Connect

    Gupta, R.C.

    1992-10-01

    For a variety of reasons the actual field harmonics, as measured, in the superconducting magnets come out to be somewhat different than what were intended at the time of design. In this paper we shall discuss the schemes which can be used to correct them in the magnets. We shall discuss them for both the allowed and non-allowed harmonics. Since the deviation in field harmonics from their design value is mainly related to the mechanical properties of the coil cross section, in order for a scheme to work as planned, the mechanical configuration of the coil should not be changed significantly while this correction is being implemented.

  6. Correcting field harmonics after design in superconducting magnets

    SciTech Connect

    Gupta, R.C.

    1992-01-01

    For a variety of reasons the actual field harmonics, as measured, in the superconducting magnets come out to be somewhat different than what were intended at the time of design. In this paper we shall discuss the schemes which can be used to correct them in the magnets. We shall discuss them for both the allowed and non-allowed harmonics. Since the deviation in field harmonics from their design value is mainly related to the mechanical properties of the coil cross section, in order for a scheme to work as planned, the mechanical configuration of the coil should not be changed significantly while this correction is being implemented.

  7. Particle acceleration and transport in a chaotic magnetic field

    NASA Astrophysics Data System (ADS)

    Li, X.; Li, G.; Dasgupta, B.

    2012-12-01

    Time-dependent chaotic magnetic field can arise from a simple asymmetric current wire-loop system (CWLS). Such simple CWLSs exist, for example, in solar flares. Indeed one can use an ensemble of such systems to model solar active region magnetic field [1,2]. Here we use test particle simulation to investigate particle transport and energization in such a time-dependent chaotic magnetic field, and through induction, a chaotic electric field. We first construct an ensemble of simple systems based on the estimated size and field strength of solar active region. By following the trajectories of single charged particles, we will examine how particle energy is changed. Diffusion coefficients in both real space and momentum space can be calculated as well as the average trapped time of the particles within chaotic field region. Particle energy spectrum as a function of time will be examined. [1] Dasgupta, B. and Abhay K. Ram, (2007) Chaotic magnetic fields due to asymmetric current configurations -application to cross field diffusion of particles in cosmic rays, (Presented at the 49th Annual Meeting of the DPP, APS, Abstract # BP8.00102) [2] G. Li, B. Dasgupta, G. Webb, and A. K. Ram, (2009) Particle Motion and Energization in a Chaotic Magnetic Field, AIP Conf. Proc. 1183, pp. 201-211; doi: http://dx.doi.org/10.1063/1.3266777

  8. The origin of magnetic fields in hot stars

    E-print Network

    Neiner, C; Alecian, E; Emeriau, C; Grunhut, J; BinaMIcS, the

    2015-01-01

    Observations of stable mainly dipolar magnetic fields at the surface of ~7% of single hot stars indicate that these fields are of fossil origin, i.e. they descend from the seed field in the molecular clouds from which the stars were formed. Recent results confort this theory. First, theoretical work and numerical simulations confirm that the properties of the observed fields correspond to those expected from fossil fields. They also showed that rapid rotation does not modify the surfacic dipolar magnetic configurations, but hinders the stability of fossil fields. This explains the lack of correlation between the magnetic field properties and stellar properties in massive stars. It may also explain the lack of detections of magnetic fields in Be stars, which rotate close to their break-up velocity. In addition, observations by the BinaMIcS collaboration of hot stars in binary systems show that the fraction of those hosting detectable magnetic fields is much smaller than for single hot stars. This could be rela...

  9. Characterizing the quiet time magnetic field at geostationary orbit

    NASA Astrophysics Data System (ADS)

    Skone, S. H.; Donovan, E. F.; Rostoker, G.

    1995-12-01

    There is now an increasing body of evidence which suggests that the onset of a substorm expansive phase is triggered in the near-Earth tail region, inside X~-12RE [Samson et al., 1992]. For this reason, it is necessary to characterize the magnetic field in the near-Earth region, particularly the quiet time reference field. We have therefore carried out a detailed study of the magnetic field at geostationary orbit, using data acquired during quiet times from the GOES 5 and GOES 6 satellites which operated simultaneously during 1986. Diurnal and seasonal variations of the total field, and the perturbation magnetic field with the IGRF removed, have been identified and attributed to variations in the position of the neutral sheet with respect to the satellite. We have processed the data to remove seasonal effects by using the semiempirical expression developed by Lopez [1990] to express the displacement of the neutral sheet with respect to the magnetic equatorial plane. We then use our magnetic field model, recently developed by Donovan [1993a], to model the observed quiet time magnetic field at geostationary orbit, and also determine the quiet time current configuration.

  10. Performance of electret ionization chambers in magnetic field.

    PubMed

    Kotrappa, P; Stieff, L R; Mengers, T F; Shull, R D

    2006-04-01

    Electret ionization chambers are widely used for measuring radon and radiation. The radiation measured includes alpha, beta, and gamma radiation. These detectors do not have any electronics and as such can be introduced into magnetic field regions. It is of interest to study the effect of magnetic fields on the performance of these detectors. Relative responses are measured with and without magnetic fields present. Quantitative responses are measured as the magnetic field is varied from 8 kA/m to 716 kA/m (100 to 9,000 gauss). No significant effect is observed for measuring alpha radiation and gamma radiation. However, a significant systematic effect is observed while measuring beta radiation from a 90Sr-Y source. Depending upon the field orientation, the relative response increased from 1.0 to 2.7 (vertical position) and decreased from 1.0 to 0.60 (horizontal position). This is explained as due to the setting up of a circular motion for the electrons by the magnetic field, which may increase or decrease the path length in air depending upon the experimental configuration. It is concluded that these ionization chambers can be used for measuring alpha (and hence radon) and gamma radiation in the range of magnetic fields studied. However, caution must be exercised if measuring beta radiation. PMID:16538144

  11. Large-scale magnetic fields in magnetohydrodynamic turbulence.

    PubMed

    Alexakis, Alexandros

    2013-02-22

    High Reynolds number magnetohydrodynamic turbulence in the presence of zero-flux large-scale magnetic fields is investigated as a function of the magnetic field strength. For a variety of flow configurations, the energy dissipation rate [symbol: see text] follows the scaling [Symbol: see text] proportional U(rms)(3)/? even when the large-scale magnetic field energy is twenty times larger than the kinetic energy. A further increase of the magnetic energy showed a transition to the [Symbol: see text] proportional U(rms)(2) B(rms)/? scaling implying that magnetic shear becomes more efficient at this point at cascading the energy than the velocity fluctuations. Strongly helical configurations form nonturbulent helicity condensates that deviate from these scalings. Weak turbulence scaling was absent from the investigation. Finally, the magnetic energy spectra support the Kolmogorov spectrum k(-5/3) while kinetic energy spectra are closer to the Iroshnikov-Kraichnan spectrum k(-3/2) as observed in the solar wind. PMID:23473153

  12. Adiabatic compression of a closed-field-line configuration by a centimeter-size liner

    Microsoft Academic Search

    R. P. Drake; J. H. Hammer; C. W. Hartman; L. J. Perkins; D. D. Ryutov

    1995-01-01

    The paper considers adiabatic compression of a pre-formed closed field line configuration by an imploding liner. Three configurations are discussed: the field-reversed configuration, the spheromak and the Z-pinch. It is shown that, by employing a 2D-compression, one can reach a break-even condition with an energy input as low as 100 kJ. It is emphasized that the possibility of performing crucial

  13. Josephson junction interferometer device for detection of curl-free magnetic vector potential fields

    SciTech Connect

    Gelinas, R.C.

    1985-01-01

    A device for detecting and/or measuring the presence of a magnetic vector potential ''field'' including two Josephson devices in a Josephson interferometer configuration, a magnetic shielding envelope with apertures arranged so that the magnetic vector potential is confined to the vicinity of one of the two Josephson devices (but not the interferometer loop region) and a means for detecting magnetic flux induced by the interaction of the Josephson device and the magnetic vector potential ''field''. The detection of the magnetic vector potential offers a more advantageous range of dependence than the magnetic flux density.

  14. Numerical calculation of equilibria for the field-reversed configuration

    Microsoft Academic Search

    Shumaker

    1986-01-01

    A two-dimensional magnetohydrodynamic equilibria code is used to demonstrate how the properties of the equilibria depend on the input quantities. This code uses adiabatic quantities as inputs, which are entropy and magnetic flux. With the magnetic flux held constant, it is shown that the length of the separatrix is a smooth function of the total entropy. It is shown that

  15. Magnetic field calculation and measurement of active magnetic bearings

    NASA Astrophysics Data System (ADS)

    Ding, Guoping; Zhou, Zude; Hu, Yefa

    2006-11-01

    Magnetic Bearings are typical devices in which electric energy and mechanical energy convert mutually. Magnetic Field indicates the relationship between 2 of the most important parameters in a magnetic bearing - current and force. This paper presents calculation and measurement of the magnetic field distribution of a self-designed magnetic bearing. Firstly, the static Maxwell's equations of the magnetic bearing are presented and a Finite Element Analysis (FEA) is found to solve the equations and get post-process results by means of ANSYS software. Secondly, to confirm the calculation results a Lakeshore460 3-channel Gaussmeter is used to measure the magnetic flux density of the magnetic bearing in X, Y, Z directions accurately. According to the measurement data the author constructs a 3D magnetic field distribution digital model by means of MATLAB software. Thirdly, the calculation results and the measurement data are compared and analyzed; the comparing result indicates that the calculation results are consistent with the measurement data in allowable dimension variation, which means that the FEA calculation method of the magnetic bearing has high precision. Finally, it is concluded that the magnetic field calculation and measurement can accurately reflect the real magnetic distribution in the magnetic bearing and the result can guide the design and analysis of the magnetic bearing effectively.

  16. 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.

  17. Stepped Impedance Resonators for High Field Magnetic Resonance Imaging

    PubMed Central

    Akgun, Can E.; DelaBarre, Lance; Yoo, Hyoungsuk; Sohn, Sung-Min; Snyder, Carl J.; Adriany, Gregor; Ugurbil, Kamil; Gopinath, Anand; Vaughan, J. Thomas

    2014-01-01

    Multi-element volume radio-frequency (RF) coils are an integral aspect of the growing field of high field magnetic resonance imaging (MRI). In these systems, a popular volume coil of choice has become the transverse electromagnetic (TEM) multi-element transceiver coil consisting of microstrip resonators. In this paper, to further advance this design approach, a new microstrip resonator strategy in which the transmission line is segmented into alternating impedance sections referred to as stepped impedance resonators (SIRs) is investigated. Single element simulation results in free space and in a phantom at 7 tesla (298 MHz) demonstrate the rationale and feasibility of the SIR design strategy. Simulation and image results at 7 tesla in a phantom and human head illustrate the improvements in transmit magnetic field, as well as, RF efficiency (transmit magnetic field versus SAR) when two different SIR designs are incorporated in 8-element volume coil configurations and compared to a volume coil consisting of microstrip elements. PMID:23508243

  18. 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

  19. Full 180° magnetization reversal with electric fields.

    PubMed

    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

  20. Full 180° Magnetization Reversal with Electric Fields

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    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.

  1. Vlasov Equation In Magnetic Field

    E-print Network

    Biao Wu

    1999-09-07

    The linearized Vlasov equation for a plasma system in a uniform magnetic field and the corresponding linear Vlasov operator are studied. The spectrum and the corresponding eigenfunctions of the Vlasov operator are found. The spectrum of this operator consists of two parts: one is continuous and real; the other is discrete and complex. Interestingly, the real eigenvalues are infinitely degenerate, which causes difficulty solving this initial value problem by using the conventional eigenfunction expansion method. Finally, the Vlasov equation is solved by the resolvent method.

  2. Overview of C-2 field-reversed configuration experiment plasma diagnosticsa)

    NASA Astrophysics Data System (ADS)

    Gota, H.; Thompson, M. C.; Tuszewski, M.; Binderbauer, M. W.

    2014-11-01

    A comprehensive diagnostic suite for field-reversed configuration (FRC) plasmas has been developed and installed on the C-2 device at Tri Alpha Energy to investigate the dynamics of FRC formation as well as to understand key FRC physics properties, e.g., confinement and stability, throughout a discharge. C-2 is a unique, large compact-toroid merging device that produces FRC plasmas partially sustained for up to ˜5 ms by neutral-beam (NB) injection and end-on plasma-guns for stability control. Fundamental C-2 FRC properties are diagnosed by magnetics, interferometry, Thomson scattering, spectroscopy, bolometry, reflectometry, and NB-related fast-ion/neutral diagnostics. These diagnostics (totaling >50 systems) are essential to support the primary goal of developing a deep understanding of NB-driven FRCs.

  3. Overview of C-2 field-reversed configuration experiment plasma diagnostics.

    PubMed

    Gota, H; Thompson, M C; Tuszewski, M; Binderbauer, M W

    2014-11-01

    A comprehensive diagnostic suite for field-reversed configuration (FRC) plasmas has been developed and installed on the C-2 device at Tri Alpha Energy to investigate the dynamics of FRC formation as well as to understand key FRC physics properties, e.g., confinement and stability, throughout a discharge. C-2 is a unique, large compact-toroid merging device that produces FRC plasmas partially sustained for up to ?5 ms by neutral-beam (NB) injection and end-on plasma-guns for stability control. Fundamental C-2 FRC properties are diagnosed by magnetics, interferometry, Thomson scattering, spectroscopy, bolometry, reflectometry, and NB-related fast-ion/neutral diagnostics. These diagnostics (totaling >50 systems) are essential to support the primary goal of developing a deep understanding of NB-driven FRCs. PMID:25430249

  4. Studies of global stability of field-reversed configuration plasmas using a rigid body model

    E-print Network

    Ji, Hantao

    Studies of global stability of field-reversed configuration plasmas using a rigid body model H. Ji stability of field-reversed configuration FRC plasmas has been studied using a simple rigid body model of motion for each global mode is formulated and analyzed using a rigid body model of the FRC plasma

  5. Plasma Magnet: Using a Rotating Magnetic Field to Couple Thrust From the Solar Wind

    NASA Astrophysics Data System (ADS)

    Giersch, Louis; Slough, John; Winglee, Robert; Andreason, Samuel

    2004-11-01

    The Plasma Magnet concept aims to provide a large magnetic barrier to couple thrust from the solar wind. A spacecraft using Plasma Magnet propulsion would be able to move throughout the solar system faster and more efficiently than possible using conventional chemical or electric propulsion. This dramatic improvement in performance is made possible by coupling thrust from the solar wind. The Plasma Magnet drives electrical currents in plasma surrounding the spacecraft using a rotating magnetic field (RMF). RMF has been successfully used to drive currents of several thousand amps in Field Reversed Configurations (FRC) and Rotamak plasma configurations during the course of international fusion research efforts. However, these experiments have used RMF current drive in the region inside the RMF coils. For the Plasma Magnet concept to be successful, RMF current drive must be successfully used to drive currents external to and at large distances from the RMF coils. Preliminary computer simulations indicate that RMF can drive currents outside the RMF coils. Preliminary experimental investigations of the Plasma Magnet concept are also underway. The poster presented will feature these results and a description of the Plasma Magnet concept in the context of advanced spacecraft propulsion.

  6. Laboratory experiments on the magnetic field and neutral density limits on CIV interaction

    Microsoft Academic Search

    I. Axnaes; N. Brenning

    1990-01-01

    Laboratory experiments are reported which determine the magnetic field and neutral density limits for Critical Ionization Velocity (CIV) interaction in the impact configuration. A combination of microwave interferometry and spectroscopy was used to measure how the electron energy distribution varies with the neutral density and the magnetic field strength. The efficiency of the CIV process is evaluated in terms of

  7. CIV interaction: laboratory experiments on the magnetic field and neutral density limits

    Microsoft Academic Search

    I. Axnas; N. Brenning

    1991-01-01

    Laboratory experiments are reported which determine the magnetic field and neutral density limits for critical ionization velocity (CIV) interaction in the impact configuration. A combination of microwave interferometry and spectroscopy has been used to measure how the electron energy distribution varies with the neutral density and the magnetic field strength. The efficiency of the CIV process is evaluated in terms

  8. A coupling between electric circuits and 2D magnetic field modeling

    Microsoft Academic Search

    A. Nicolet; F. Delince; N. Bamps; A. Genon; W. Legros

    1993-01-01

    A method which enables coupling between equations of electric circuits consisting of a lumped element RLC configuration and a magnetic field model is presented. The coupling between the finite-element and the boundary-element methods is used to compute the magnetic field produced by conductors excited by an electric circuit. The conductors involved in this computation may be connected according to any

  9. Modification of interdendritic convection in directional solidification by a uniform magnetic field

    Microsoft Academic Search

    P. Lehmann; R. Moreau; D. Camel; R. Bolcato

    1998-01-01

    Because of thermoelectric effects, a local current density appears in the dendritic network during the solidification of a metallic alloy. Thus, when a magnetic field is applied, a Lorentz force is created. Two alloys are solidified directionally in the horizontal configuration under a transverse magnetic field with the result that this force opposes the natural solutal buoyancy force. The experimental

  10. The Magnetic Field Geometry in Pulsar Wind Nebulae: Thoughts from an Observer's Point of View

    NASA Astrophysics Data System (ADS)

    Kothes, Roland

    There has been a lot of debate lately about the large-scale magnetic field configuration inside pulsar wind nebulae and the number of studies of individual sources is steadily increasing. I will present a careful investigation of all the observational evidence regarding the magnetic field structure inside these synchrotron nebulae and try to create a coherent picture of the magnetic field geometry and its development during the different phases of PWN and SNR evolution.

  11. Parallel heat transport in integrable and chaotic magnetic fields

    SciTech Connect

    Castillo-Negrete, D. del; Chacon, L. [Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-8071 (United States)

    2012-05-15

    The study of transport in magnetized plasmas is a problem of fundamental interest in controlled fusion, space plasmas, and astrophysics research. Three issues make this problem particularly challenging: (i) The extreme anisotropy between the parallel (i.e., along the magnetic field), {chi}{sub ||} , and the perpendicular, {chi}{sub Up-Tack }, conductivities ({chi}{sub ||} /{chi}{sub Up-Tack} may exceed 10{sup 10} in fusion plasmas); (ii) Nonlocal parallel transport in the limit of small collisionality; and (iii) Magnetic field lines chaos which in general complicates (and may preclude) the construction of magnetic field line coordinates. Motivated by these issues, we present a Lagrangian Green's function method to solve the local and non-local parallel transport equation applicable to integrable and chaotic magnetic fields in arbitrary geometry. The method avoids by construction the numerical pollution issues of grid-based algorithms. The potential of the approach is demonstrated with nontrivial applications to integrable (magnetic island), weakly chaotic (Devil's staircase), and fully chaotic magnetic field configurations. For the latter, numerical solutions of the parallel heat transport equation show that the effective radial transport, with local and non-local parallel closures, is non-diffusive, thus casting doubts on the applicability of quasilinear diffusion descriptions. General conditions for the existence of non-diffusive, multivalued flux-gradient relations in the temperature evolution are derived.

  12. Parallel heat transport in integrable and chaotic magnetic fields

    SciTech Connect

    Del-Castillo-Negrete, Diego B [ORNL; Chacon, Luis [ORNL

    2012-01-01

    The study of transport in magnetized plasmas is a problem of fundamental interest in controlled fusion, space plasmas, and astrophysics research. Three issues make this problem particularly chal- lenging: (i) The extreme anisotropy between the parallel (i.e., along the magnetic field), , and the perpendicular, , conductivities ( / may exceed 1010 in fusion plasmas); (ii) Magnetic field lines chaos which in general complicates (and may preclude) the construction of magnetic field line coordinates; and (iii) Nonlocal parallel transport in the limit of small collisionality. Motivated by these issues, we present a Lagrangian Green s function method to solve the local and non-local parallel transport equation applicable to integrable and chaotic magnetic fields in arbitrary geom- etry. The method avoids by construction the numerical pollution issues of grid-based algorithms. The potential of the approach is demonstrated with nontrivial applications to integrable (magnetic island chain), weakly chaotic (devil s staircase), and fully chaotic magnetic field configurations. For the latter, numerical solutions of the parallel heat transport equation show that the effective radial transport, with local and non-local closures, is non-diffusive, thus casting doubts on the appropriateness of the applicability of quasilinear diffusion descriptions. General conditions for the existence of non-diffusive, multivalued flux-gradient relations in the temperature evolution are derived.

  13. 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…

  14. Coupled Field Synthesis in Magnetic Fluid Hyperthermia

    Microsoft Academic Search

    Paolo Di Barba; Fabrizio Dughiero; Elisabetta Sieni; Alessandro Candeo

    2011-01-01

    AGNETIC fluid hyperthermia (MFH) uses magnetic nanoparticles (NPs) excited by an ac magnetic field to destroy cancer tissues (i.e., the target tissue) by means of induced heat [1]. In general, this kind of device exhibits a large iron core. For instance, at the Charité hospital in Berlin, Germany, the equipment for this kind of technique has a magnetic field source

  15. Field Corrections of Open MRI Superconducting Magnets

    Microsoft Academic Search

    Tetsuya Matsuda; Akihiko Ariyoshi; Hajime Tanabe

    2005-01-01

    We constructed open MRI superconducting magnets with an iron yoke that generates a 0.7T highly uniform magnetic field. A program that compensates for the error field of those magnets was developed that uses linear programming to achieve an optimal arrangement of a large number of small iron shims. Since additional homogeneity compensation near the target value becomes difficult, we also

  16. Neutrinos with Mixing in Twisting Magnetic Fields

    E-print Network

    E. Kh. Akhmedov; S. T. Petcov; A. Yu. Smirnov

    1993-01-06

    Transitions in a system of neutrinos with vacuum mixing and magnetic moments, propagating in matter and transverse magnetic field, are considered. It is shown that in the realistic case of magnetic field direction varying along the neutrino path qualitatively new phenomena become possible: permutation of neutrino conversion resonances, appearance of resonances in the neutrino-antineutrino ($\

  17. Helicity of the Solar Magnetic Field

    Microsoft Academic Search

    Sanjiv Kumar Tiwari

    2009-01-01

    Magnetic helicity is a physical quantity that measures the degree of linkages and twistedness in the field lines. It is given by a volume integral over the scalar product of magnetic field B and its vector potential A. Direct computation of magnetic helicity in the solar atmosphere is not possible due to two reasons. First, we do not have the

  18. ELECTRON SPECTROMETER WITH TOROIDAL MAGNETIC FIELD

    Microsoft Academic Search

    A. E. Dubinov; N. V. Minashkin; V. D. Selemir; N. V. Stepanov; V. E. Vatrunin

    1993-01-01

    The spectrometer allows to measure the spectrum of the electron beam, generated in the magnetized diode. Principle of the spectrometer's operation consists in spatial separation of Merent energies particles in gradient static magnetic field. Numerical integration of electron movement equations in the toroidal magnetic field %l\\/r -manner, is consistent with the experimental results received at 1-3000 accelerator. The results of

  19. Instantaneous configuration of the geomagnetic field inferred from the low-altitude isotropic boundaries: modeling and observations

    NASA Astrophysics Data System (ADS)

    Ilie, Raluca; Ganushkina, Natalia; Toth, Gabor; Liemohn, Michael

    2015-04-01

    Understanding the interplay between ionospheric, auroral and magnetospheric phenomena requires detailed knowledge of Earth’s magnetic field geometry under various solar wind conditions. This geometry is directly relevant to the magnetic field mapping between different regions of near-Earth space.To evaluate the instantaneous geomagnetic field configuration we probe the isotropic boundaries (IB) of energetic particles measured at low altitudes. Those are interpreted as the boundary between the regions of adiabatic and stochastic particle motion in the equatorial magnetotail and provide information regarding the degree of magnetic field stretching.We investigate the topology and dynamics of the magnetotail current during active and quiet times as de- pendent on solar wind and IMF parameters based on NOAA/POES MEPED and DMSP SSJ/4 measurements in combination with global magnetospheric simulations using the Space Weather Modeling Framework (SWMF).The extensive NOAA/POES MEPED low-altitude data sets give the locations of isotropic boundaries, which are used to extract information regarding particle distributions and field structure in the source regions in the magnetosphere.We present a comparison between the magnetic field lines with the observed IB latitude and those com- puted from the SWMF using the theoretical relation for IB locations in the magnetotail, i.e. where the ratio between curvature radius and Larmor radius is close to 8. This investigation assesses the accuracy of the model magnetic field and the structure of the magnetotail. The results are examined in relation to the solar wind and IMF conditions to determine the corresponding configuration and dynamics of the magnetotail.

  20. Deriving Potential Coronal Magnetic Fields from Vector Magnetograms

    E-print Network

    Welsch, Brian T

    2015-01-01

    The minimum-energy configuration for the magnetic field above the solar photosphere is curl-free (hence, by Ampere's law, also current-free), so can be represented as the gradient of a scalar potential. Since magnetic fields are divergence free, this scalar potential obeys Laplace's equation, given an appropriate boundary condition (BC). With measurements of the full magnetic vector at the photosphere, it is possible to employ either Neumann or Dirichlet BCs there. Historically, the Neumann BC was used, since available line-of-sight magnetic field measurements approximated the radial field needed for the Neumann BC. Since each BC fully determines the 3D vector magnetic field, either choice will, in general, be inconsistent with some aspect of the observed field on the boundary, due to the presence of both currents and noise in the observed field. We present a method to combine solutions from both Dirichlet and Neumann BCs to determine a hybrid potential field that minimizes the integrated square of the residu...

  1. ECE 390 Electric & Magnetic Fields Catalog Description: Static and quasi-static electric and magnetic fields.

    E-print Network

    ECE 390 ­ Electric & Magnetic Fields Catalog Description: Static and quasi-static electric and magnetic fields. Credits: 4 Terms Offered: Fall Prerequisites: MTH 255, ENGR 203 (concurrent enrollment fields in free space, Ampere's circuital law, vector magnetic potential · Biot-Savart law, magnetic

  2. A Method for Evaluating the Magnetic Field Homogeneity of a Radiofrequency Coil by Its Field Histogram

    NASA Astrophysics Data System (ADS)

    Yang, Q. X.; Li, S. H.; Smith, M. B.

    The magnetic field homogeneity of a radiofrequency coil is very important in both magnetic resonance imaging and spectroscopy. In this report, a method is proposed for quantitatively evaluating the RF magnetic field homogeneity from its histogram, which is obtained by either experimental measurement or theoretical calculation. The experimental histogram and theoretical histogram can be compared directly to verify the theoretical findings. The RF field homogeneities of the bird-cage coil, slotted-tube resonator, cosine wire coil, and a new radial plate coil design were evaluated using this method. The results showed that the experimental histograms and the corresponding theoretical histograms are consistent. This method provides an easy and sensitive way of evaluating the magnetic field homogeneity and facilitates the design and evaluation of new RF coil configurations.

  3. Magnetic, nonmagnetic, and non-Fermi-liquid ground state of an impurity fluctuating between two magnetic configurations

    Microsoft Academic Search

    A. A. Aligia

    1995-01-01

    The ground state of a generalized Anderson model for valence fluctuations between two magnetic p, d, or f configurations is discussed. In the isotropic limit, in contrast to the ordinary Anderson model, the localized problem (limit of zero bandwidth) does not correspond to a stable fixed point, except in the extreme case of j-j coupling. Taking the simplest possible case

  4. The flexible magnetic field thruster

    NASA Technical Reports Server (NTRS)

    Brophy, J. R.; Wilbur, P. J.

    1982-01-01

    The thruster is designed so that ion currents to various internal surfaces can be measured directly; these measurements facilitate calculations of the distribution of ion currents inside the discharge chamber. Experiments are described suggesting that the distribution of ion currents inside the discharge chamber is strongly dependent on the shape and strength of the magnetic field but independent of the discharge current, discharge voltage, and neutral flow rate. Measurements of the energy cost per plasma ion suggest that this cost decreases with increasing magnetic field strength as a consequence of increased anode shielding from the primary electrons. Energy costs per argon plasma ion as low as 50 eV are measured. The energy cost per beam ion is found to be a function of the energy cost per plasma ion, extracted ion fraction, and discharge voltage. Part of the energy cost per beam ion has to do with creating many ions in the plasma and then extracting only a fraction of them into the beam. The balance of the energy goes into accelerating the remaining plasma ions into the walls of the discharge chamber.

  5. Hall equilibria and stability of magnetic field structure in neutron star crusts

    NASA Astrophysics Data System (ADS)

    Gourgouliatos, K.

    2012-01-01

    We consider the Hall dynamics of the magnetic fields in the electron plasma of solid neutron star crusts. Stationary configurations satisfy a Grad-Shafranov type equation for magnetic flux surfaces, where the poloidal electrical current is a function of magnetic flux. The non-vanishing Lorentz force is balanced by gravity, pressure and tensile stresses. We present the general separable solution for the linear approximation. We investigate their stability and we find that although purely poloidal magnetic field configuration is stable to internal modes it is not if the perturbation does not vanish on the boundaries and energy is exchanged between the crust a nd the magnetosphere.

  6. Phase-field simulation of electric-field-induced in-plane magnetic domain switching in magnetic/ferroelectric layered heterostructures

    NASA Astrophysics Data System (ADS)

    Hu, Jia-Mian; Sheng, G.; Zhang, J. X.; Nan, C. W.; Chen, L. Q.

    2011-06-01

    The electric-field-induced in-plane magnetic domain switching in magnetic/ferroelectric (FE) layered heterostructures was studied using phase-field simulations. In particular, we chose the CoFe2O4 (CFO) magnetic film and the Pb(Zn1/3Nb2/3)O3-PbTiO3 (PZN-PT) FE layer as a representative example due to their strong respective magnetoelastic and piezoelectric couplings. In-plane 90° magnetic domain switching in the CFO film was observed when a transverse electric field was applied to the PZN-PT layer. The detailed switching behaviors as well as the corresponding magnetic domain structures are presented for CFO films with different geometric sizes and initial magnetization configurations. The effect of a dynamic electric field on the switching process, i.e., a time-dependent electric-field-induced magnetic domain switching, is also discussed.

  7. 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.

  8. Transonic Flow Field Analysis for Wing-Fuselage Configurations

    NASA Technical Reports Server (NTRS)

    Boppe, C. W.

    1980-01-01

    A computational method for simulating the aerodynamics of wing-fuselage configurations at transonic speeds is developed. The finite difference scheme is characterized by a multiple embedded mesh system coupled with a modified or extended small disturbance flow equation. This approach permits a high degree of computational resolution in addition to coordinate system flexibility for treating complex realistic aircraft shapes. To augment the analysis method and permit applications to a wide range of practical engineering design problems, an arbitrary fuselage geometry modeling system is incorporated as well as methodology for computing wing viscous effects. Configuration drag is broken down into its friction, wave, and lift induced components. Typical computed results for isolated bodies, isolated wings, and wing-body combinations are presented. The results are correlated with experimental data. A computer code which employs this methodology is described.

  9. Model of the influence of magnetic fields on a plasma electrode Pockels cell

    SciTech Connect

    Boley, C.D.; Rhodes, M.A.

    1996-10-01

    We describe a model which gives the effects of magnetic fields on a plasma electrode Pockels cell. The fields arise from the return currents to the cathode as well as from neighboring devices such as amplifier flashlamps. In effect, electrons are treated as a static, planar fluid moving under the influence of magnetic fields, the electric field of the discharge, electron pressure gradients, and electron-atom elastic collisions. This leads to a closed two- dimensional equation for the electron density, which is solved subject to appropriate boundary collisions. The model is applied to four cases-. the baseline NIF configuration with magnetic fields due to balanced return currents; a case with unbalanced return currents; the reverser configuration containing an external field parallel to the main plasma current; and a configuration with a field perpendicular to both the current and the optical direction.

  10. Exploring Magnetic Fields in Your Environment

    NSDL National Science Digital Library

    This is a lesson about measuring magnetic field directions of Earth and in the environment. First, learners go outside, far away from buildings, power lines, or anything electrical or metal, and use compasses to identify magnetic North. Next, they use the compasses to probe whether there are any sources of magnetic fields in the local environment, including around electronic equipment such as a CD player and speakers. This is the first lesson in the second session of the Exploring Magnetism teacher guide.

  11. A carpet cloak for static magnetic field

    NASA Astrophysics Data System (ADS)

    Wang, Rongfeng; Lei Mei, Zhong; Jun Cui, Tie

    2013-05-01

    We present a two-dimensional carpet cloak for static magnetic field, a design that renders the magnetic response of a given volume invisible from its exterior, without altering the external magnetic fields. The device is designed using transformation optics method and can be implemented with alternating superconducting and magnetic material layers. Through the proper design of the constitutive tensors and relative thicknesses of each slab, we achieve the perfect performance of invisibility. Full wave numerical simulations confirm our design.

  12. Magnetic Fields and Rotations of Protostars

    E-print Network

    Masahiro N. Machida; Shu-ichiro Inutsuka; Tomoaki Matsumoto

    2007-07-21

    The evolution of the magnetic field and angular momentum in the collapsing cloud core is studied using three-dimensional resistive MHD nested grid simulations. Starting with a Bonnor-Ebert isothermal cloud rotating in a uniform magnetic field, we calculate the cloud evolution from the molecular cloud core (n=10^4 cm^-3) to the stellar core (n \\simeq 10^22 cm^-3). The magnetic field strengths at the center of the clouds converge to a certain value as the clouds collapse, when the clouds have the same angular momenta but different strengths of the magnetic fields at the initial state. For 10^12 cm^-3 magnetic field from the collapsing cloud core, and the magnetic field lines, which are strongly twisted for n magnetic field lines are twisted and amplified again for nc > 10^16 cm^-3, because the magnetic field is recoupled with the warm gas. Finally, protostars at their formation epoch have 0.1-1kG of the magnetic fields, which are comparable to observations. The magnetic field strength of protostar slightly depends on the angular momentum of the host cloud. The protostar formed from the slowly rotating cloud core has a stronger magnetic field. The evolution of the angular momentum is closely related to the evolution of the magnetic field. The angular momentum in the collapsing cloud is removed by the magnetic effect. The formed protostars have 0.1-2 days of the rotation period at their formation epoch, which are slightly shorter than the observation. This indicates that the further removal mechanism of the angular momentum such as interaction between the protostar and disk, wind gas or jet is important in further evolution of the protostar.

  13. Efficient gradient field generation providing a multi-dimensional arbitrary shifted field-free point for magnetic particle imaging

    NASA Astrophysics Data System (ADS)

    Kaethner, Christian; Ahlborg, Mandy; Knopp, Tobias; Sattel, Timo F.; Buzug, Thorsten M.

    2014-01-01

    Magnetic Particle Imaging (MPI) is a tomographic imaging modality capable to visualize tracers using magnetic fields. A high magnetic gradient strength is mandatory, to achieve a reasonable image quality. Therefore, a power optimization of the coil configuration is essential. In order to realize a multi-dimensional efficient gradient field generator, the following improvements compared to conventionally used Maxwell coil configurations are proposed: (i) curved rectangular coils, (ii) interleaved coils, and (iii) multi-layered coils. Combining these adaptions results in total power reduction of three orders of magnitude, which is an essential step for the feasibility of building full-body human MPI scanners.

  14. Plasma and Magnetic Field Inside Magnetic Clouds: a Global Study

    Microsoft Academic Search

    C. Cid; M. A. Hidalgo; T. Nieves-Chinchilla; J. Sequeiros; A. F. Viñas

    2002-01-01

    Data observed during spacecraft encounters with magnetic clouds have been extensively analyzed in the literature. Moreover, several models have been proposed for the magnetic topology of these events, and fitted to the observations. Although these interplanetary events present well-defined plasma features, none of those models have included a simultaneous analysis of magnetic field and plasma data. Using as a starting

  15. The magnetic field in the disk of our Galaxy

    NASA Astrophysics Data System (ADS)

    Han, J. L.; Qiao, G. J.

    1994-08-01

    The magnetic field in the disk of our Galaxy is investigated by using the Rotation Measures (RMs) of pulsars and Extragalactic Radio Sources (ERSes). Through analyses of the RMs of carefully selected pulsar samples, it is found that the Galaxy has a global field of BiSymmetric Spiral (BSS) configuration, rather than a concentric ring or an AxiSymmetric Spiral (ASS) configuration. The Galactic magnetic field of BSS structure is supposed to be of primordial origin. The pitch angle of the BSS structure is -8.2deg+/-0.5deg. The field geometry shows that the field goes along the Carina-Sagittarius arm, which is delineated by Giant Molecular Clouds (GMCs). The amplitude of the BSS field is 1.8+/-0.3?G. The first field strength maximum is at r_0_=11.9+/-0.15 kpc in the direction of l=180deg. The field is strong in the interarm regions and it reverses in the arm regions. In the vicinity of the Sun, it has a strength of ~1.4?G and reverses at 0.2-0.3kpc in the direction of l=0deg. Because of the unknown electron distribution of the Galaxy and other difficulties, it is impossible to derive the galactic field from the RMs of ERSes very quantitatively. Nevertheless, the RMs of ERSes located in the region of the two galactic poles are used to estimate the vertical component of the local galactic field, which is found to have a strength of 0.2-0.3?G and is directed from the south galactic pole to the north galactic pole. The scale height of the magnetic disk of the Galaxy is estimated from the RMs of all-sky distributed ERSes, being about 1.2+/-0.4pc. The regular magnetic field of our Galaxy, which is probably similar to that of M81, extends far from the optical disk.

  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. Nonlocal heat transport in a stochastic magnetic field

    SciTech Connect

    Rax, J.M.; White, R.B.

    1991-12-01

    Heat transport in a stochastic magnetic field configuration is shown to be nonlocal. Collisional transport processes, in such a disordered media, cannot always be reduced to a standard diffusion process, and the concept of a diffusion coefficient is meaningless for a wide range of typical tokamak parameters. In the nonlocal regime the relaxation of a gradient is described by an integral equation, involving a nonlocal propagator. This propagator is calculated, and the relation to previous results is elucidated. 15 refs.

  18. Field-like spin torque in magnetic tunnel junctions

    NASA Astrophysics Data System (ADS)

    Tang, Y.-H.; Kioussis, N.; Kalitsov, A.; Butler, W. H.; Car, R.

    2010-01-01

    We show that the exchange splitting asymmetry between the left and right ferromagnetic leads in non-collinear magnetic tunnel junctions (MTJ) tunes the bias behavior of the field-like spin torque, T?. These results can be understood by our recently derived general expression, which relates the non-collinear T? to the algebraic sum of four independent non-equilibrium interlayer exchange couplings (IEC) solely in collinear configurations.

  19. 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.

  20. 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.

  1. Static uniform magnetic fields and amoebae

    SciTech Connect

    Berk, S.G.; Srikanth, S.; Mahajan, S.M.; Ventrice, C.A. [Tennessee Technological Univ., Cookeville, TN (United States)] [Tennessee Technological Univ., Cookeville, TN (United States)

    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.

  2. Confinement of Nonneutral Plasmas in a Trap Composed of a Cusped Magnetic Field and an Electrostatic Octapole Field

    NASA Astrophysics Data System (ADS)

    Mohri, Akihiro; Yuyama, Tetsumori; Kiwamoto, Yasuhito; Yamazawa, Yohei; Michishita, Toshinori

    1998-12-01

    The field configuration formed by the superposition of a cuspedmagnetic field and an electrostatic octapole field provides a closedsystem of confinement for a charged particle. In a cusped magneticfield, the Störmer region which constrains a charged particle isopen, but it is closed by adding a potential barrier made by theoctapole field. One-component plasmas are thus expected to beconfined in this configuration, preserving superior characteristicsof the cusp field for plasma stability. A preliminary experiment was performed on the confinement of electrons in thisfield configuration. An electron plasma was confinedfor 3 s in a magnetic field as weak as B=50 G at thecircular line cusp. The confinement time was roughly proportionalto B2, suggesting that the confinement would be improved substantially ina higher magnetic field.

  3. Extraterrestrial Magnetic Fields: Achievements and Opportunities

    Microsoft Academic Search

    EDWARD J. SMITHAND; Charles Sonett

    1976-01-01

    The major scientific achievements associated with the measurement of magnetic fields in space over the past decade and a half are reviewed. Aspects of space technology relevant to magnetic-field observations are discussed, including the different types of magnetometers used and how they operate, problems arising from spacecraft-generated magnetic fields and the appropriate countermeasures that have been developed and on-board processing

  4. 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.

  5. Origin of magnetic fields in galaxies

    Microsoft Academic Search

    Rafael S. de Souza; Reuven Opher

    2010-01-01

    Microgauss magnetic fields are observed in all galaxies at low and high redshifts. The origin of these intense magnetic fields is a challenging question in astrophysics. We show here that the natural plasma fluctuations in the primordial Universe (assumed to be random), predicted by the fluctuation -dissipation theorem, predicts ˜0.034muG fields over ˜0.3kpc regions in galaxies. If the dipole magnetic

  6. Magnetic field sensor utilizing bent fiber taper and magnetic fluid

    NASA Astrophysics Data System (ADS)

    Li, Jie; Tian, Zhuang; Sun, Li-Peng; Guan, Bai-Ou

    2014-05-01

    A magnetic field sensor is demonstrated by placing a bent-fiber taper modal interferometer inside a magnetic fluid sealed with an organic glass base. Owing to the strong refractive index dependency of the interferometer and magneto-optics property of the fluid, our sensor exhibits high sensitivity to the external magnetic field change. A linear wavelength dependency of ~58pm/Oe is experimentally obtained within a magnetic field range from 30 to 80 Oe. Our structure is featured of high sensitivity, fiber-compatibility, compactness, and robustness.

  7. 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.

  8. Minimizing magnetic fields for precision experiments

    E-print Network

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

    2015-01-01

    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 linear improvement in the systematic reach and a 40 % improvement of the statistical reach of the measurement. However, this versatile procedure can improve the performance of any MSR for any application.

  9. Magnetic field properties of SSC model dipole magnets

    SciTech Connect

    Wake, M.; Bossert, R.; Carson, J.; Delchamps, S.; Jaffery, T.S.; Kinney, W.; Koska, W.; Lamm, M.J.; Strait, J. (Fermi National Accelerator Lab., Batavia, IL (United States)); Butteris, J.; Sims, R.; Winters, M. (Superconducting Super Collider Lab., Dallas, TX (United States))

    1992-09-01

    SSC 1.5m model dipole magnets were built and tested at Fermilab. Magnetic field properties were studied in term of transfer function variation and multipole components. The results were satisfactory. Observation of periodicity of remanent field along the axis is also reported.

  10. Magnetic Resonance Imaging System Based on Earth's Magnetic Field

    E-print Network

    Stepi?nik, Janez

    of the magnetic field enables scanning of very large volume samples. Reduction in S/N ratio due to the weak in the case of strong magnetic fields, detection and processing of low frequency signal are less 655 DOI: 10 Vol. 32, No. 6, pp. 655­667, 2004 #12;demanding for the electronics. The techniques used

  11. 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.

  12. Magnetic monopole field exposed by electrons

    NASA Astrophysics Data System (ADS)

    Béché, Armand; van Boxem, Ruben; van Tendeloo, Gustaaf; Verbeeck, Jo

    2014-01-01

    The experimental search for magnetic monopole particles has, so far, been in vain. Nevertheless, these elusive particles of magnetic charge have fuelled a rich field of theoretical study. Here, we created an approximation of a magnetic monopole in free space at the end of a long, nanoscopically thin magnetic needle. We experimentally demonstrate that the interaction of this approximate magnetic monopole field with a beam of electrons produces an electron vortex state, as theoretically predicted for a true magnetic monopole. This fundamental quantum mechanical scattering experiment is independent of the speed of the electrons and has consequences for all situations where electrons meet such monopole magnetic fields, as, for example, in solids. The set-up not only shows an attractive way to produce electron vortex states but also provides a unique insight into monopole fields and shows that electron vortices might well occur in unexplored solid-state physics situations.

  13. 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.

  14. 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.

  15. Magnetic field spectrum at cosmological recombination revisited

    NASA Astrophysics Data System (ADS)

    Saga, Shohei; Ichiki, Kiyotomo; Takahashi, Keitaro; Sugiyama, Naoshi

    2015-06-01

    If vector type perturbations are present in the primordial plasma before recombination, the generation of magnetic fields is known to be inevitable through the Harrison mechanism. In the context of the standard cosmological perturbation theory, nonlinear couplings of first-order scalar perturbations create second-order vector perturbations, which generate magnetic fields. Here we reinvestigate the generation of magnetic fields at second-order in cosmological perturbations on the basis of our previous study, and extend it by newly taking into account the time evolution of purely second-order vector perturbations with a newly developed second-order Boltzmann code. We confirm that the amplitude of magnetic fields from the product-terms of the first-order scalar modes is consistent with the result in our previous study. However, we find, both numerically and analytically, that the magnetic fields from the purely second-order vector perturbations partially cancel out the magnetic fields from one of the product-terms of the first-order scalar modes, in the tight coupling regime in the radiation dominated era. Therefore, the amplitude of the magnetic fields on small scales, k ?10 h Mpc-1 , is smaller than the previous estimates. The amplitude of the generated magnetic fields at cosmological recombination is about Brec=5.0 ×10-24 Gauss on k =5.0 ×10-1 h Mpc-1 . Finally, we discuss the reason for the discrepancies that exist in estimates of the amplitude of magnetic fields among other authors.

  16. Nuclear magnetic resonances in weak fields

    E-print Network

    Mitchell, Richard Warren

    1953-01-01

    ?s technique involves ~ su41ng a molecular beam through tuo sueeessive static magnetic fields shish have gradients in opposite direotions, While passing from ene magnetic field ts tho other~ the beam is irradiated eith electro-mag- nstio ?nsrgy? When tho...Lgneto The ssmple was placed in, the best pert of the field Then a permanent magnet was brought close to the solenoid& snd pointed to a spot gust beyond the sample in such a manner that, the field of the permanent magnet was roughly opposibx to that...

  17. Magnetic field in the end region of the SSC quadrupole magnet

    SciTech Connect

    Caspi, S.; Helm, M.; Laslett, L.J.

    1991-06-01

    Recent advances in methods of computing magnetic fields have made it possible to study the field in the end region of the SS quadrupole magnet in detail. The placement of conductor in the straight section, away from the ends, was designed to produce a practically pure quadrupole field in the two-dimensional sense. The ends of the coils were designed to produce a practically pure quadrupole field in the integral sense using a method that ignores the presence of the iron yoke. Subsequently, the effect of presence of the yoke on the field was analyzed. The paper presents the end configuration together with the computed integrated multipole components, local multipole components, and local field components. A comparison with measurements is included. 5 refs., 5 figs., 1 tab.

  18. Magnetic field in the end region of the SSC quadrupole magnet

    SciTech Connect

    Caspi, S.; Helm, M.; Laslett, L.J. (Lawrence Berkeley Lab., CA (United States))

    1992-01-01

    Recent advances in methods of computing magnetic fields have made it possible to study the field in the end region of the SSC quadrupole magnet in detail. The placement of conductor in the straight section, away from the ends, was designed to produce a practically pure quadrupole field in the two-dimensional sense. The ends of the coils were designed to produce a practically pure quadrupole field in the integral sense using a method that ignores the presence of the iron yoke. Subsequently, the effect of the presence of the yoke on the field was analyzed. The paper presents the end configuration together with the computer integrated multipole components, local multipole components, and local field components. A comparison with measurements is included.

  19. Generation of the magnetic field in jets

    E-print Network

    V. Urpin

    2006-05-22

    We consider dynamo action under the combined influence of turbulence and large-scale shear in sheared jets. Shear can stretch turbulent magnetic field lines in such a way that even turbulent motions showing mirror symmetry become suitable for generation of a large-scale magnetic field. We derive the integral induction equation governing the behaviour of the mean field in jets. The main result is that sheared jets may generate a large-scale magnetic field if shear is sufficiently strong. The generated mean field is mainly concentrated in a magnetic sheath surrounding the central region of a jet, and it exhibits sign reversals in the direction of the jet axis. Typically, the magnetic field in a sheath is dominated by the component along the jet that can reach equipartition with the kinetic energy of particles, The field in the central region of jets has a more disordered structure.

  20. Modeling of field-reversed configuration experiment with large safety factor

    SciTech Connect

    Steinhauer, Loren; Guo Houyang; Hoffman, Alan; Ishida, Akio; Ryutov, Dmitri [University of Washington, Redmond Plasma Physics Laboratory, Redmond, Washington 98052 (United States); Department of Environmental Science, Faculty of Science Niigata University, Niigata 950-2181 (Japan); Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)

    2006-05-15

    The Translation-Confinement-Sustainment facility has been operated in the 'translation-formation' mode in which a plasma is ejected at high-speed from a {theta}-pinch-like source into a confinement chamber where it settles into a field-reversed-configuration state. Measurements of the poloidal and toroidal field have been the basis of modeling to infer the safety factor. It is found that the edge safety factor exceeds two, and that there is strong forward magnetic shear. The high-q arises because the large elongation compensates for the modest ratio of toroidal-to-poloidal field in the plasma. This is the first known instance of a very high-{beta} plasma with a safety factor greater than unity. Two-fluid modeling of the measurements also indicate several other significant features: a broad 'transition layer' at the plasma boundary with probable line-tying effects, complex high-speed flows, and the appearance of a two-fluid minimum-energy state in the plasma core. All these features may contribute to both the stability and good confinement of the plasma.

  1. Modelling of Field-Reversed Configuration Experiment with Large Safety Factor

    SciTech Connect

    Steinhauer, L; Guo, H; Hoffman, A; Ishida, A; Ryutov, D D

    2005-11-28

    The Translation-Confinement-Sustainment facility has been operated in the 'translation-formation' mode in which a plasma is ejected at high-speed from a {theta}-pinch-like source into a confinement chamber where it settles into a field-reversed-configuration state. Measurements of the poloidal and toroidal field have been the basis of modeling to infer the safety factor. It is found that the edge safety factor exceeds two, and that there is strong forward magnetic shear. The high-q arises because the large elongation compensates for the modest ratio of toroidal-to-poloidal field in the plasma. This is the first known instance of a very high-{beta} plasma with a safety factor greater than unity. Two-fluid modeling of the measurements also indicate several other significant features: a broad 'transition layer' at the plasma boundary with probable line-tying effects, complex high-speed flows, and the appearance of a two-fluid minimum-energy state in the plasma core. All these features may contribute to both the stability and good confinement of the plasma.

  2. Differential Magnetic Field Shear in an Active Region

    NASA Technical Reports Server (NTRS)

    Schmeider, B.; DeMoulin, P.; Aulanier, G.; Golub, Leon

    1997-01-01

    The three-dimensional extrapolation of magnetic field lines from a magnetogram obtained at Kitt Peak allows us to understand the global structure of the NOAA active region 6718, as observed in X-rays with the Normal Incidence X-ray Telescope (NIXT) and in Ha with the Multichannel Subtractive Double Pass spectrograph (MSDP) in Meudon on 1991 July 11. This active region was in a quiet stage. Bright X-ray loops connect plages having field strengths of approx. 300 G, while H-alpha fibriles connect penumbrae having strong spot fields to the surrounding network. Small, intense X-ray features in the moat region around a large spot, which could be called X-ray-bright points, are due mainly to the emergence of magnetic flux and merging of these fields with surrounding ones. A set of large-scale, sheared X-ray loops is observed in the central part of the active region. Based on the fit between the observed coronal structure and the field configurations (and assuming a linear force-free field), we propose a differential magnetic field shear model for this active region. The decreasing shear in outer portions of the active region may indicate a continual relaxation of the magnetic field to a lower energy state in the progressively older portions of the AR.

  3. FIRST SIMULTANEOUS DETECTION OF MOVING MAGNETIC FEATURES IN PHOTOSPHERIC INTENSITY AND MAGNETIC FIELD DATA

    SciTech Connect

    Lim, Eun-Kyung; Yurchyshyn, Vasyl; Goode, Philip, E-mail: eklim@bbso.njit.edu [Big Bear Solar Observatory, New Jersey Institute of Technology, 40386 North Shore Lane, Big Bear City, CA 92314-9672 (United States)

    2012-07-01

    The formation and the temporal evolution of a bipolar moving magnetic feature (MMF) was studied with high-spatial and temporal resolution. The photometric properties were observed with the New Solar Telescope at Big Bear Solar Observatory using a broadband TiO filter (705.7 nm), while the magnetic field was analyzed using the spectropolarimetric data obtained by Hinode. For the first time, we observed a bipolar MMF simultaneously in intensity images and magnetic field data, and studied the details of its structure. The vector magnetic field and the Doppler velocity of the MMF were also studied. A bipolar MMF with its positive polarity closer to the negative penumbra formed, accompanied by a bright, filamentary structure in the TiO data connecting the MMF and a dark penumbral filament. A fast downflow ({<=}2 km s{sup -1}) was detected at the positive polarity. The vector magnetic field obtained from the full Stokes inversion revealed that a bipolar MMF has a U-shaped magnetic field configuration. Our observations provide a clear intensity counterpart of the observed MMF in the photosphere, and strong evidence of the connection between the MMF and the penumbral filament as a serpentine field.

  4. Studies of Global Stability of FieldReversed Configuration Plasmas Using A Rigid Body Model

    E-print Network

    Studies of Global Stability of Field­Reversed Configuration Plasmas Using A Rigid Body Model H. Ji­reversed configuration (FRC) plasmas has been stud­ ied using a simple rigid body model in the parameter space of motion for each global mode is formulated and analyzed using a rigid body model of the FRC plasma

  5. Optimal electro-optic sensor configuration for phase noise limited, remote field sensing applications

    Microsoft Academic Search

    A. Garzarella; S. B. Qadri; Dong Ho Wu

    2009-01-01

    Electro-optic (EO) sensors, used for the nonperturbative detection of electric fields, are typically configured to modulate an optical probe beam along a crystal direction in which the EO tensor coefficient is largest. However in fiber optic EO sensors, such configurations can be strongly limited by phase noise and cumbersome compensation optics. Our results demonstrate that a greater signal to noise

  6. Numerical calculation of equilibria for the field-reversed configuration

    SciTech Connect

    Shumaker, D.E.

    1986-01-01

    A two-dimensional magnetohydrodynamic equilibria code is used to demonstrate how the properties of the equilibria depend on the input quantities. This code uses adiabatic quantities as inputs, which are entropy and magnetic flux. With the magnetic flux held constant, it is shown that the length of the separatrix is a smooth function of the total entropy. It is shown that the shape of the separatrix can be changed from eliptical to racetrack by changing the profile of the entropy function. This code can also be used for flux and wall compression since the equilibria are determined by adiabatic quantities. Examples of flux and wall compression are presented. An equilibrium is compared with data from the FRX-C experiment.

  7. Electric field detectors in a coupled ring configuration: preliminary results

    Microsoft Academic Search

    Bruno Ando; Salvatore Baglio; Alberto Ascia; Adi R. Bulsara

    2007-01-01

    A novel architecture for sensing weak dc magneticfields exploits the co- operation between nonlinear coupled systems and ferroelectric devices. Sensors for static electric fields (E-fields) based on unidirection- ally coupled nonlinear dynamical systems1 are currently un- der development. They will exploit the synergic use of bistable ferroelectric materials, micromachining technologies, and novel sensing strategies. Considerable practical interest in such de-

  8. Magnetic Field Variations with a Rotational Period on Solar-like Star xi Bootis A

    Microsoft Academic Search

    S. I. Plachinda; T. N. Tarasova

    2000-01-01

    We examine the global configuration of the magnetic field of the active dwarf xi Boo A as a function of stellar rotation phase (P=6.1455+\\/-0.0003 days), using direct high-precision spectropolarimetric measurements. The magnetic field varies from -10 G up to +30 G. Integrated magnetic flux on the surface changes polarity during a single rotation period on xi Boo A, resulting in

  9. Laboratory Measurements of Astrophysical Magnetic Fields

    Microsoft Academic Search

    C. D. Murphy; F. Miniati; M. Edwards; J. Mithen; A. R. Bell; C. Constantin; E. Everson; D. Schaeffer; C. Niemann; A. Ravasio; E. Brambrink; A. Benuzzi-Mounaix; M. Koenig; C. Gregory; N. Woolsey; H.-S. Park; B. Remington; D. Ryutov; R. Bingham; L. Gargate; A. Spitkovsky; G. Gregori

    2010-01-01

    It has been proposed that high Mach number collisionless shocks propagating in an initially unmagnetized plasma play a major role in the magnetization of large scale structures in the Universe. A detailed study of the experimental configuration necessary to scale such environments down to laboratory dimensions will be presented. We will show initial results from preliminary experiments conducted at the

  10. MAGNETOHYDRODYNAMIC SHOCK-CLUMP EVOLUTION WITH SELF-CONTAINED MAGNETIC FIELDS

    SciTech Connect

    Li Shule; Frank, Adam; Blackman, Eric G., E-mail: shuleli@pas.rochester.edu [Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627 (United States)

    2013-09-10

    We study the interaction of strong shock waves with magnetized clumps. Previous numerical work focused on a simplified scenario in which shocked clumps are immersed in a globally uniform magnetic field that extends through both the clump and the ambient medium. Here, we consider the complementary circumstance in which the field is completely self-contained within the clumps. This situation could arise naturally during clump formation via dynamical or thermal instabilities, for example, as a magnetic field pinches off from the ambient medium. Using our adaptive mesh refinement magnetohydrodynamics code AstroBEAR, we carry out a series of simulations with magnetized clumps that have different self-contained magnetic field configurations. We find that the clump and magnetic evolution are sensitive to the fraction of the magnetic field aligned with, or perpendicular to, the shock normal. The relative strength of magnetic pressure and tension in the different field configurations allows us to analytically understand the different cases of post-shock evolution. We also show how turbulence and the mixing it implies depends of the initial field configuration and suggest ways in which the observed shock-clump morphology may be used as a proxy for identifying internal field topologies a posteriori.

  11. Creation of a high-temperature plasma through merging and compression of supersonic field reversed configuration plasmoids

    NASA Astrophysics Data System (ADS)

    Slough, John; Votroubek, George; Pihl, Chris

    2011-05-01

    A new device, the Inductive Plasma Accelerator, was employed to simultaneously form and accelerate two oppositely directed field reversed configurations (FRCs) where the relative velocity (600 km s-1) of the plasmoids was much larger than their internal thermal motion. Upon collision all of the FRC directional energy was observed to be rapidly thermalized concurrent with complete magnetic reconnection of the two FRCs. Upon merging, the resulting FRC was compressed to kilovolt ion temperatures exhibiting a configuration lifetime better than predicted by past scaling of in situ formed FRCs. With the improved FRC confinement scaling, a pulsed plasma device based on this approach capable of achieving fusion gain is examined. For an FRC with a poloidal flux 20 mWb or greater, the fusion energy yield per pulse exceeds the plasma energy for compression fields of 10 T or more. The scaling is insensitive to the compression chamber radial scale, providing for the possibility of a very compact fusion neutron source.

  12. Magnetic phase control by an electric field

    Microsoft Academic Search

    Thomas Lottermoser; Thomas Lonkai; Uwe Amann; Dietmar Hohlwein; Jörg Ihringer; Manfred Fiebig

    2004-01-01

    The quest for higher data density in information storage is motivating investigations into approaches for manipulating magnetization by means other than magnetic fields. This is evidenced by the recent boom in magnetoelectronics and `spintronics', where phenomena such as carrier effects in magnetic semiconductors and high-correlation effects in colossal magnetoresistive compounds are studied for their device potential. The linear magnetoelectric effect-the

  13. Magnetic Field Mapping by Selective Equipotential Excitation

    Microsoft Academic Search

    Ouajdi Felfoul; Michelle Raimbert; Sylvain Martel

    2006-01-01

    A new magnetic field mapping method in MRI is presented. This technique is ideal for severe inhomogeneities where plane warp cannot be ignored. The present study employs a ferromagnetic ball to create a perturbation within the imaged volume. The magnetic moment and position of the device are acquired experimentally with a new technique that excites magnetic equipotentials within a volume.

  14. LABORATORY VI MAGNETIC FIELDS AND FORCES

    E-print Network

    Minnesota, University of

    . · Calculate the motion of a particle with a constant acceleration. · Calculate the motion of a particle of the universe, the atomic structure of materials, and the quark structure of elementary particles. Magnetic; · Calculate the magnetic force on a charged particle moving in a uniform magnetic field and describe its

  15. A two-dimensional model for a solar prominence - Effect of an external magnetic field

    NASA Astrophysics Data System (ADS)

    Oliver, R.; Ballester, J. L.; Priest, E. R.

    1991-07-01

    Analytical approximations are here used to study the effects of different external magnetic configurations on the half-width, mass, and internal magnetic structure of a quiescent solar prominence, modeled as a thin vertical sheet of cool plasma. A zeroth-order model is used to analyze the effects produced by a potential coronal field or a constant-alpha force-free field. This model allows us to obtain the half-width and mass of the prominence for different values of the external field, pressure and shear angle. The effects of these external magnetic configurations on a two-dimensional model proposed by Ballester and Priest (1987) are studied. The main effects are a change of the half-width with height, an increase of the mass, a decrease of the magnetic field strength with height and a change in the shape of the magnetic field lines.

  16. The Physics of Attraction and Repulsion: Magnetism and Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Nakotte, Heinz

    2001-11-01

    The development of new materials with improved magnetic properties completely changed the modern world in the past decades. Recent progress is predominantly due to a better understanding of magnetism that has gone far beyond compass needles rotating in a magnetic field and bar magnets attracting or repelling each other. New magnetic materials are used to build smaller and smaller read/write heads and hard disks with increased storage capacity, developments that are responsible the revolution in the computer industry. Another example is the field of magnetic levitation that became feasible for commercial applications with the discovery of new superconducting materials, and a prototype train is under development in Japan. In medicine, the development of magnetic resonance imaging (MRI) provides an alternative to other (destructive) radiation techniques.

  17. Self-magnetic-field-limiting current of intense relativistic electron beam under externally applied magnetic field

    Microsoft Academic Search

    Liu Guo-zhi; Song Xiao-xin

    1998-01-01

    The self-magnetic-field-limiting current of intense relativistic electron beam (IREB) without an externally applied magnetic field is reported and briefly commented in this paper. By using dynamic balance method the self-magnetic-field-limiting current of IREB under externally applied magnetic field is derived, showing that in this case it will increase. This result is obtained for the first time, so far as we

  18. 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.

  19. Resonances of the helium atom in a strong magnetic field

    NASA Astrophysics Data System (ADS)

    Lühr, Armin; Al-Hujaj, Omar-Alexander; Schmelcher, Peter

    2007-01-01

    We present an investigation of the resonances of a doubly excited helium atom in a strong magnetic field covering the regime B=0-100a.u. A full-interaction approach which is based on an anisotropic Gaussian basis set of one-particle functions being nonlinearly optimized for each field strength is employed. Accurate results for a total of 17 resonances below the threshold consisting of He+ in the N=2 state are reported in this work. This includes states with total magnetic quantum numbers M=0,-1,-2 and even z parity. The corresponding binding energies are compared to approximate energies of two-particle configurations consisting of two hydrogenlike electrons in the strong-field regime, thereby providing an understanding of the behavior of the energies of the resonances with varying field strength.

  20. Three-dimensional photogrammetric measurement of magnetic field lines in the WEGA stellarator

    SciTech Connect

    Drewelow, Peter; Braeuer, Torsten; Otte, Matthias; Wagner, Friedrich; Werner, Andreas [Max-Planck-Institut fuer Plasmaphysik, EURATOM Association, Wendelsteinstr. 1, D-17491 Greifswald (Germany)

    2009-12-15

    The magnetic confinement of plasmas in fusion experiments can significantly degrade due to perturbations of the magnetic field. A precise analysis of the magnetic field in a stellarator-type experiment utilizes electrons as test particles following the magnetic field line. The usual fluorescent detector for this electron beam limits the provided information to two-dimensional cut views at certain toroidal positions. However, the technique described in this article allows measuring the three-dimensional structure of the magnetic field by means of close-range photogrammetry. After testing and optimizing the main diagnostic components, measurements of the magnetic field lines were accomplished with a spatial resolution of 5 mm. The results agree with numeric calculations, qualifying this technique as an additional tool to investigate magnetic field configurations in a stellarator. For a possible future application, ways are indicated on how to reduce experimental error sources.

  1. An analytical methodology for magnetic field control in unilateral NMR

    NASA Astrophysics Data System (ADS)

    Marble, Andrew E.; Mastikhin, Igor V.; Colpitts, Bruce G.; Balcom, Bruce J.

    2005-05-01

    Traditionally, unilateral NMR systems such as the NMR-MOUSE have used the fringe field between two bar magnets joined with a yoke in a 'U' geometry. This allows NMR signals to be acquired from a sensitive volume displaced from the magnets, permitting large samples to be investigated. The drawback of this approach is that the static field ( B0) generated in this configuration is inhomogeneous, and has a large, nonlinear, gradient. As a consequence, the sensitive volume of the instrument is both small and ill defined. Empirical redesign of the permanent magnet array producing the B0 field has yielded instruments with magnetic field topologies acceptable for varying applications. The drawback of current approaches is the lack of formalism in the control of B0. Rather than tailoring the magnet geometry to NMR investigations, measurements must be tailored to the available magnet geometry. In this work, we present a design procedure whereby the size, shape, field strength, homogeneity, and gradients in the sensitive spot of a unilateral NMR sensor can be controlled. Our design uses high permeability pole pieces, shaped according to the contours of an analytical expression, to control B0, allowing unilateral NMR instruments to be designed to generate a controlled static field topology. We discuss the approach in the context of previously published design techniques, and explain the advantages inherent in our strategy as compared to other optimization methods. We detail the design, simulation, and construction of a unilateral magnet array using our approach. It is shown that the fabricated array exhibits a B0 topology consistent with the design. The utility of the design is demonstrated in a sample nondestructive testing application. Our design methodology is general, and defines a class of unilateral permanent magnet arrays in which the strength and shape of B0 within the sensitive volume can be controlled.

  2. An analytical methodology for magnetic field control in unilateral NMR.

    PubMed

    Marble, Andrew E; Mastikhin, Igor V; Colpitts, Bruce G; Balcom, Bruce J

    2005-05-01

    Traditionally, unilateral NMR systems such as the NMR-MOUSE have used the fringe field between two bar magnets joined with a yoke in a 'U' geometry. This allows NMR signals to be acquired from a sensitive volume displaced from the magnets, permitting large samples to be investigated. The drawback of this approach is that the static field (B0) generated in this configuration is inhomogeneous, and has a large, nonlinear, gradient. As a consequence, the sensitive volume of the instrument is both small and ill defined. Empirical redesign of the permanent magnet array producing the B0 field has yielded instruments with magnetic field topologies acceptable for varying applications. The drawback of current approaches is the lack of formalism in the control of B0. Rather than tailoring the magnet geometry to NMR investigations, measurements must be tailored to the available magnet geometry. In this work, we present a design procedure whereby the size, shape, field strength, homogeneity, and gradients in the sensitive spot of a unilateral NMR sensor can be controlled. Our design uses high permeability pole pieces, shaped according to the contours of an analytical expression, to control B0, allowing unilateral NMR instruments to be designed to generate a controlled static field topology. We discuss the approach in the context of previously published design techniques, and explain the advantages inherent in our strategy as compared to other optimization methods. We detail the design, simulation, and construction of a unilateral magnet array using our approach. It is shown that the fabricated array exhibits a B0 topology consistent with the design. The utility of the design is demonstrated in a sample nondestructive testing application. Our design methodology is general, and defines a class of unilateral permanent magnet arrays in which the strength and shape of B0 within the sensitive volume can be controlled. PMID:15809175

  3. Inclination angle of vector magnetic fields.

    NASA Astrophysics Data System (ADS)

    Yanping, Lü; Wang, Jingxiu

    1994-11-01

    The authors further elaborate on an empirical method to improve the consistency of the line-of-sight and transverse field calibration. The method can also be used to check the transverse field calibration. Furthermore, based on the correction, the authors calculate the inclination angle of the vector magnetic field related to the solar surface, which can give some information on how the vector magnetic field is distributed in space.

  4. 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.

  5. Single-layer high field dipole magnets

    SciTech Connect

    Vadim V. Kashikhin and Alexander V. Zlobin

    2001-07-30

    Fermilab is developing high field dipole magnets for post-LHC hadron colliders. Several designs with a nominal field of 10-12 T, coil bore size of 40-50 mm based on both shell-type and block-type coil geometry are currently under consideration. This paper presents a new approach to magnet design, based on simple and robust single-layer coils optimized for the maximum field, good field quality and minimum number of turns.

  6. Field Corrections of Open MRI Superconducting Magnets

    NASA Astrophysics Data System (ADS)

    Matsuda, Tetsuya; Ariyoshi, Akihiko; Tanabe, Hajime

    We constructed open MRI superconducting magnets with an iron yoke that generates a 0.7T highly uniform magnetic field. A program that compensates for the error field of those magnets was developed that uses linear programming to achieve an optimal arrangement of a large number of small iron shims. Since additional homogeneity compensation near the target value becomes difficult, we also used nonlinear programming. We must evaluate all shim magnetizations precisely by making a 3D finite element shim model. Since, it is impossible to make such shims in a large magnet model, we describe a fast calculation method of shim magnetizations without that model. Homogeneity of 0.35ppm (Vrms) at 35cm Diameter Spherical Volume (DSV), which is the top value of an open MRI magnet, is obtained by applying these methods. The number of correction times were reduced by half of initial manufactured magnets.

  7. Equivalence of periodic magnetic field to uniform magnetic field in electron beam focusing

    Microsoft Academic Search

    K. Ura; M. Terada

    1966-01-01

    The general solution of the electron trajectory equation in a periodic magnetic field is derived in the form of series expansion, assuming laminar electron flow and small perturbation. It is concluded that if the cathode is not very heavily immersed in a magnetic field, beam focusing by a periodic magnetic field would be almost equivalent to that by a uniform

  8. The National High Magnetic Field Laboratory

    NASA Astrophysics Data System (ADS)

    Jaime, M.; Lacerda, A.; Takano, Y.; Boebinger, G. S.

    2006-11-01

    The National High Magnetic Field Laboratory, established in 1990 with support from the National Science Foundation, the State of Florida, and the US Department of Energy, is a facility open to external users around the world. The experimental capabilities are distributed in three campuses. In Tallahassee, Florida, continuous magnetic fields are produced by means of superconducting and resistive magnets reaching fields of up to 33T (resistive), and 45T (hybrid). EMR, ICR, and a 900MHz wide bore NMR magnet are also available. The facility in Gainesville, Florida, is devoted to generating extremely low temperatures in the presence of external magnetic fields (15T, down to 0.4mK), and large MRI imaging capabilities. In Los Alamos, New Mexico, a 9 kV-capable capacitor bank and a number of different liquid Nitrogen-cooled resistive magnets produce repetitive pulses up to 75 T and now a single-shot pulsed up to 300T.

  9. 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.

  10. Coronal holes and solar magnetic fields

    NASA Technical Reports Server (NTRS)

    Harvey, J. W.; Sheeley, N. R., Jr.

    1979-01-01

    Since 1972 nearly continuous observations of coronal holes and their associated photospheric magnetic fields have been made using a variety of satellite and ground-based equipment. The present paper reviews the results of comparisons of these data and shows that the structure and evolution of coronal holes is basically governed by the large-scale distribution of photospheric magnetic flux. Nonpolar holes form in the decaying remnants of bipolar magnetic regions in areas with a large-scale flux imbalance. In addition, there is strong indirect evidence that the magnetic field in coronal holes is always open to interplanetary space, but not all open-field regions have associated coronal holes.

  11. High concentration ferronematics in low magnetic fields

    E-print Network

    T. Tóth-Katona; P. Salamon; N. Éber; N. Tomašovi?ová; Z. Mitróová; P. Kop?anský

    2014-09-05

    We investigated experimentally the magneto-optical and dielectric properties of magnetic-nanoparticle-doped nematic liquid crystals (ferronematics). Our studies focus on the effect of the very small orienting bias magnetic field $B_{bias}$, and that of the nematic director pretilt at the boundary surfaces in our systems sensitive to low magnetic fields. Based on the results we assert that $B_{bias}$ is not necessarily required for a detectable response to low magnetic fields, and that the initial pretilt, as well as the aggregation of the nanoparticles play an important (though not yet explored enough) role.

  12. Domain structures in complex 3D magnetic fields

    NASA Astrophysics Data System (ADS)

    Close, R. M.; Parnell, C. E.; Priest, E. R.

    The numerous magnetic fragments that populate the mixed-polarity, quiet-Sun photosphere give rise to many interesting topological features in the corona. In light of this, much recent work has gone into classifying the configurations that arise from simple, point-source potential-field models in efforts to determine the nature of the quiet-Sun magnetic field. These studies have ranged from systematic and detailed examinations of magnetic fields arising from only a handful of sources, involving classifying the configurations that arise (and how some states may bifurcate into other states), to statistical studies of the overall properties of fields arising from hundreds of magnetic sources. Such studies have greatly increased our understanding of what we might expect the magnetic field over the quiet Sun to behave like; the purpose of the study presented here is to extend this understanding further by examining the structure of the individual domains (the regions in space through which pairs of opposite-polarity sources are connected). In particular, the features of lesser-known domain structures that are absent from fields arising from only a few sources and overlooked by sweeping statistical studies are documented. In spite of the incredible complexity of the coronal field, previous studies have shown that there are only two types of building block in a potential field arising from coplanar point sources: namely, an isolated dome, bounded by a single unbroken separatrix surface, and a separator-ring domain, engirdled by a ring of separators. However, it is demonstrated here how both isolated domains and separator-ring domains may be categorised further depending upon their particular geometrical and topological traits. As many models predict coronal heating at topologically distinct features in magnetic fields such as null points, separators and separatrices, for any such models to be applied to general fields would require a scheme for identifying which topological features are related to a given domain. The study here explores some of the issues that would need to be taken into account by such a scheme, and in particular the problems associated with trying to deduce the properties of a general magnetic field from knowledge of domain footprints alone. Animated 3D-rotational views of some of the figures in this manuscript may be viewed in AVI, MPEG and animated-GIF formats by visiting http://www-solar.mcs.st-and.ac.uk/robertc/animations/blocks.html and following the desired link.

  13. Fluctuating magnetic field induced resonant activation.

    PubMed

    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. PMID:25494726

  14. Plasma Equilibrium in a Magnetic Field with Stochastic Regions

    SciTech Connect

    J.A. Krommes and Allan H. Reiman

    2009-04-23

    The nature of plasma equilibrium in a magnetic field with stochastic regions is examined. It is shown that the magnetic differential equation that determines the equilibrium Pfirsch-Schluter currents can be cast in a form similar to various nonlinear equations for a turbulent plasma, allowing application of the mathematical methods of statistical turbulence theory. An analytically tractable model, previously studied in the context of resonance-broadening theory, is applied with particular attention paid to the periodicity constraints required in toroidal configurations. It is shown that even a very weak radial diffusion of the magnetic field lines can have a significant effect on the equilibrium in the neighborhood of the rational surfaces, strongly modifying the near-resonant Pfirsch-Schluter currents. Implications for the numerical calculation of 3D equilibria are discussed

  15. The nature of the sunspot phenomenon. III - Energy consumption and energy transport. IV - The intrinsic instability of the magnetic configuration

    NASA Technical Reports Server (NTRS)

    Parker, E. N.

    1975-01-01

    The basic relation is described between conversion of thermal energy into convective fluid motion and convective transport of thermal energy, and the equilibrium configuration of a sunspot's magnetic field is shown to be unstable to the hydromagnetic exchange instability. It is determined that heat transport necessarily accompanies convective driving of fluid motion and that the formation of cool sunspots requires convection extending coherently over several scale heights, a distance of at least 500 km. Several theoretical possibilities for sunspot stabilization are reviewed, and it is suggested that a suitable redistribution of cooling in the umbra may be the stabilization mechanism. It is believed that if cooling extends to a great depth in an elongated portion of a sunspot, the magnetic pressure on the boundary will be reduced, tending to reduce the elongation.

  16. 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.

  17. Decay of positronium in strong magnetic fields

    Microsoft Academic Search

    G. Wunner; H. Herold

    1979-01-01

    We investigate the decay of bound electron-positron pairs (positronium) in strong magnetic fields (of order 1012 Gauss, which are assumed for neutron stars) on the basis of a correct treatment of the two-body problem, thus improving previous work by Carr and Sutherland (1978). We find that, even in the presence of a strong magnetic field, the decay of the ground

  18. Ensemble Solar Global Magnetic Field Modeling

    Microsoft Academic Search

    C. J. Henney; C. N. Arge; J. Koller; W. A. Toussaint; S. L. Young; J. W. Harvey

    2010-01-01

    The ability to forecast geoeffective space weather events is critically dependent on the estimation of the global solar photospheric magnetic field distribution as input to coronal and heliospheric models. Currently, the solar magnetic field can only be recorded for approximately half of the solar surface at any given time. Since the rotation period of the Sun as observed from Earth

  19. Photon-neutrino interactions in magnetic fields

    E-print Network

    Shaisultanov R

    1998-02-28

    The low-energy two neutrino-two photon interactions in the presence of homogeneous magnetic field are studied. The cross sections in external magnetic field are shown to be larger than in vacuum by factor $\\sim (m_W /m_e) ^4(B/B_c) ^2$. The energy-loss rate due to the process $\\gamma \\gamma \\to \

  20. Lengthwise field variation in CBA magnets

    Microsoft Academic Search

    Willen

    1984-01-01

    The multipole content of the magnetic field in accelerator superconducting magnets built with a cos theta current distribution inside an iron yoke is determined by the placement of the individual current-carrying turns in the coil, by the location of the coil inside the iron yoke and by the amount of iron saturation at high field. Differences in these parameters cause

  1. Coulomb crystals in the magnetic field

    SciTech Connect

    Baiko, D. A. [A.F. Ioffe Physical-Technical Institute, Politekhnicheskaya 26, 194021 St. Petersburg (Russian Federation)

    2009-10-15

    The body-centered-cubic Coulomb crystal of ions in the presence of a uniform magnetic field is studied using the rigid electron background approximation. The phonon mode spectra are calculated for a wide range of magnetic-field strengths and for several orientations of the field in the crystal. The phonon spectra are used to calculate the phonon contribution to the crystal energy, entropy, specific heat, Debye-Waller factor of ions, and the rms ion displacements from the lattice nodes for a broad range of densities, temperatures, chemical compositions, and magnetic fields. Strong magnetic field dramatically alters the properties of quantum crystals. The phonon specific heat increases by many orders of magnitude. The ion displacements from their equilibrium positions become strongly anisotropic. The results can be relevant for dusty plasmas, ion plasmas in Penning traps, and especially for the crust of magnetars (neutron stars with superstrong magnetic fields B > or approx. 10{sup 14} G). The effect of the magnetic field on ion displacements in a strongly magnetized neutron star crust can suppress the nuclear reaction rates and make them extremely sensitive to the magnetic-field direction.

  2. Line Sink in Uniform Magnetic Field

    Microsoft Academic Search

    Jai Prakash Narain; Mahinder S. Uberoi

    1971-01-01

    The motion of an inviscid, incompressible, and conducting fluid due to a line sink in a uniform strong magnetic field is considered. The solutions show that motion is confined in a narrow region parallel to the magnetic field. Such a motion for a point sink has erroneously been named as a wake or backward jet flow. Finally, the known solution

  3. Directional discontinuities in the interplanetary magnetic field

    Microsoft Academic Search

    Leonard F. Burlaga

    1969-01-01

    It is shown that the interplanetary magnetic field has different characteristics on different scales, and it is noted that a given physical theory may not be applicable or relevant on all scales. Four scales are defined in terms of time intervals on which the data may be viewed. Many discontinuities in the magnetic-field direction are seen on the mesoscale (˜

  4. On the origins of galactic magnetic fields

    E-print Network

    A. Borzou; H. R. Sepangi; R. Yousefi; A. H. Ziaie

    2009-11-18

    We present a five dimensional unified theory of gravity and electromagnetism which leads to modified Maxwell equations, suggesting a new origin for galactic magnetic fields. It is shown that a region with nonzero scalar curvature would amplify the magnetic fields under certain conditions.

  5. Magnetic fields, branes, and noncommutative geometry

    Microsoft Academic Search

    Daniela Bigatti; Leonard Susskind

    2000-01-01

    We construct a simple physical model of a particle moving on the infinite noncommutative 2-plane. The model consists of a pair of opposite charges moving in a strong magnetic field. In addition, the charges are connected by a spring. In the limit of large magnetic field, the charges are frozen into the lowest Landau levels. Interactions of such particles include

  6. Electronic and magnetic properties of AGNRs with different edge configurations of 558 grain boundary

    NASA Astrophysics Data System (ADS)

    Han, L. P.; Dai, Q. Q.

    2015-03-01

    In this paper, finite length 558 grain boundaries (GBs) with different edge configurations are introduced in armchair graphene nanoribbons (AGNRs). By using first-principles calculations, the variations of electronic and magnetic properties with two adjustable parameters W (ribbons widths) and NZ (the distances between neighboring 558 GBs) are investigated for each group. The impurity states introduced by 558 GB have a dominating effect on AGNRs. Different transitions of the electronic and magnetic phases with W and NZ occur for different groups. Furthermore, a ferromagnetic ordering between the two zigzag chains of 558 GB appears for the ferromagnetic systems.

  7. Electromagnet configurations for extreme attitude testing in magnetic suspension and balance systems

    NASA Technical Reports Server (NTRS)

    Britcher, C. P.

    1980-01-01

    The inclusion of adequate versatility into the electromagnet array configuration requires sizing the electromagnets to satisfy particular absolute force and moment requirements. Magnetic performance of a permanent magnet model core, air cored electromagnet may easily and reliably be computed by using the FORCE program which calculates model forces and moments via representations of the model as an assembly of dipoles and the electromagnets as an assembly of line currents. Some aspects of the performance of an ellipsoidal iron cored model may be inferred from the above under certain circumstances.

  8. Magnetic Fields in Stars: Origin and Impact

    NASA Astrophysics Data System (ADS)

    Langer, N.

    2014-08-01

    Various types of magnetic fields occur in stars: small scale fields, large scale fields, and internal toroidal fields. While the latter may be ubiquitous in stars due to differential rotation, small scale fields (spots) may be associated with envelop convection in all low and high mass stars. The stable large scale fields found in only about 10% of intermediate mass and massive stars may be understood as a consequence of dynamical binary interaction, e.g., the merging of two stars in a binary. We relate these ideas to magnetic fields in white dwarfs and neutron stars, and to their role in core-collapse and thermonuclear supernova explosions.

  9. Solar Mean Magnetic Field Observed by GONG

    Microsoft Academic Search

    J. W. Harvey; G. Petrie; R. Clark

    2009-01-01

    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

  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. Low loss pole configuration for multi-pole homopolar magnetic bearings

    NASA Technical Reports Server (NTRS)

    Blumenstock, Kenneth A. (Inventor); Hakun, Claef F. (Inventor)

    2001-01-01

    A new pole configuration for multi-pole homopolar bearings proposed in this invention reduces rotational losses caused by eddy-currents generated when non-uniform flux distributions exist along the rotor surfaces. The new homopolar magnetic bearing includes a stator with reduced pole-to-pole and exhibits a much more uniform rotor flux than with large pole-to-pole gaps. A pole feature called a pole-link is incorporated into the low-loss poles to provide a uniform pole-to-pole gap and a controlled path for pole-to-pole flux. In order to implement the low-loss pole configuration of magnetic bearings with small pole-to-pole gaps, a new stator configuration was developed to facilitate installation of coil windings. The stator was divided into sector shaped pieces, as many pieces as there are poles. Each sector-shaped pole-piece can be wound on a standard coil winding machine, and it is practical to wind precision layer wound coils. To achieve maximum actuation efficiency, it is desirable to use all the available space for the coil formed by the natural geometric configuration. Then, the coils can be wound in a tapered shape. After winding, the sectored-pole-pieces are installed into and fastened by bonding or other means, to a ring of material which encloses the sectored-pole-pieces, forming a complete stator.

  12. Tunable configurational anisotropy in collective magnetization dynamics of Ni80Fe20 nanodot arrays with varying dot shapes

    NASA Astrophysics Data System (ADS)

    Mahato, B. K.; Choudhury, S.; Mandal, R.; Barman, S.; Otani, Y.; Barman, A.

    2015-06-01

    We present broadband ferromagnetic resonance measurements of tunable spin wave anisotropy in arrays of nanodots with different dot shapes. Magnetization dynamics of the circular dot array shows two modes, while square, diamond, and triangular dot arrays show three, three, and four modes, respectively. Various distinct rotational symmetries in the configurational anisotropy of the nanodot arrays are observed with the variation of dot shape. The observed spin wave modes are reproduced by micromagnetic simulations and the calculated mode profiles show different collective modes determined by internal and stray magnetic fields. Effects of dot shapes are observed in combination with the effects of lattice symmetry and the shape of the boundary of the array. The collective behaviour is observed to be weakest in the diamond shaped dots and strongest in circular shaped dots. This is further confirmed by the stray field calculation. The large variation of spin wave mode frequencies and their configurational anisotropies with dot shapes are important for selection of suitable basis structures for future magnonic crystals.

  13. Configuration Mixing Effects in Magnetic Moments and in Gamow-Teller Matrix Elements of Mirror Nuclei

    Microsoft Academic Search

    Renzo Leonardi; Marco Rosa-Clot

    1970-01-01

    Phenomenological analysis of Gamow-Teller transitions and magnetic moments is done for the ground states of the mirror nuclei, putting in evidence the linear quenching of the matrix elements and . Configuration mixing techniques in the j-j coupling scheme are discussed and used to explain the quenching and to fit the experimental data.

  14. Design and Construction of Field Reversed Configuration Plasma Chamber for Plasma Material Interaction Studies

    NASA Astrophysics Data System (ADS)

    Smith, DuWayne L.

    A Field Reversed Configuration (FRC) plasma source was designed and constructed to conduct high energy plasma-materials interaction studies. The purpose of these studies is the development of advanced materials for use in plasma based electric propulsion systems and nuclear fusion containment vessels. Outlined within this thesis is the basic concept of FRC plasmoid creation, an overview of the device design and integration of various diagnostics systems for plasma conditions and characterization, discussion on the variety of material defects resulting from the plasma exposure with methods and tools designed for characterization. Using a Michelson interferometer it was determined that the FRC plasma densities are on the order of ~1021 m-3. A novel dynamic pressure probe was created to measure ion velocities averaging 300 km/s. Compensating flux loop arrays were used to measure magnetic field strength and verify the existence of the FRC plasmoid and when used in combination with density measurements it was determined that the average ion temperatures are ~130 eV. X-ray Photoelectron Spectroscopy (XPS) was employed as a means of characterizing the size and shape of the plasma jet in the sample exposure positions. SEM results from preliminary studies reveal significant morphological changes on plasma facing material surfaces, and use of XRD to elucidate fuel gas-ion implantation strain rates correlated to plasma exposure energies.

  15. Manipulation of Raman Resonances Using Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Desavage, Sara A.; Davis, Jon P.; Narducci, Frank A.

    2012-06-01

    We have theoretically and experimentally studied Raman resonances in multi-level atoms (specifically ^85Rb). Our emphasis has been on varying the relative orientation of the magnetic field with respect to the propagation direction of the Raman fields. We find that, in general, the spectrum consists of up to 11 peaks. By considering selection rules, we show that it is possible to orient the magnetic field so that either a 6 peak spectrum or 5 peak spectrum results, depending on whether the Raman fields contain a polarization component along the magnetic field direction or not. Furthermore, we find that the spectrum is not always symmetric with respect to the magnetically insensitive transition (clock transition). We explore the origins of the asymmetry and the overall shape of the spectra. We will discuss applications to magnetically sensitive atom interferometry.

  16. Processing of polymers in high magnetic fields

    SciTech Connect

    Douglas, E.P.; Smith, M.E.; Benicewicz, B.C. [Los Alamos National Lab., NM (United States); Earls, J.D.; Priester, R.D. Jr. [Dow Chemical Co., Freeport, TX (United States)

    1996-05-01

    Many organic molecules and polymers have an anisotropic diamagnetic susceptibility, and thus can be aligned in high magnetic fields. The presence of liquid crystallinity allows cooperative motions of the individual molecules, and thus the magnetic energy becomes greater than the thermal energy at experimentally obtainable field strengths. This work has determined the effect of magnetic field alignment on the thermal expansion and mechanical properties of liquid crystalline thermosets in the laboratory. Further advances in magnet design are needed to make magnetic field alignment a commercially viable approach to polymer processing. The liquid crystal thermoset chosen for this study is the diglycidyl ether of dihydroxy-{alpha}-methylstilbene cured with the diamine sulfamilamide. This thermoset has been cured at field strengths up to 18 Tesla.

  17. Experiments on the critical ionization velocity interaction in weak magnetic fields

    Microsoft Academic Search

    N. Brenning

    1981-01-01

    The critical ionization velocity interaction is investigated experimentally in a configuration with a magnetized plasma stream colliding with a stationary neutral gas cloud. It is noted that in all previous experiments of this kind the magnetic field (1) has had a component transverse to the plasma flow and (2) has been strong in the sense that the electron gyro frequency

  18. Experiments on the critical ionization velocity interaction in weak magnetic fields

    Microsoft Academic Search

    N. Brenning

    1980-01-01

    The critical ionization velocity interaction was studied in a configuration with a magnetized plasma stream colliding with a stationary neutral gas cloud. An electrodeless plasma gun of the conical pinch type was used. In all previous experiments of this kind the magnetic field has had a component transverse to the plasma flow and has been strong in the sense that

  19. Quark condensate in a magnetic field

    E-print Network

    Shushpanov, I A

    1997-01-01

    We study the dependence of quark condensate $\\Sigma$ on an external magnetic field. For weak fields, it rises linearly with the field. Pion mass and residue are also shifted so that the Gell-Mann - Oakes - Renner relation is satisfied. In the strong field region, $\\Sigma(H) \\propto (eH)^{3/2}$.

  20. Magnetic field observations during the ulysses flyby of jupiter.

    PubMed

    Balogh, A; Dougherty, M K; Forsyth, R J; Southwood, D J; Smith, E J; Tsurutani, B T; Murphy, N; Burton, M E

    1992-09-11

    The Jovian flyby of the Ulysses spacecraft presented the opportunity to confirm and complement the findings of the four previous missions that investigated the structure and dynamics of the Jovian magnetosphere and magnetic field, as well as to explore for the first time the high-latitude dusk side of the magnetosphere and its boundary regions. In addition to confirming the general structure of the dayside magnetosphere, the Ulysses magnetic field measurements also showed that the importance of the current sheet dynamics extends well into the middle and outer magnetosphere. On the dusk side, the magnetic field is swept back significantly toward the magnetotail. The importance of current systems, both azimuthal and field-aligned, in determining the configuration of the field has been strongly highlighted by the Ulysses data. No significant changes have been found in the internal planetary field; however, the need to modify the external current densities with respect to previous observations on the inbound pass shows that Jovian magnetic and magnetospheric models are highly sensitive to both the intensity and the structure assumed for the current sheet and to any time dependence that may be assigned to these. The observations show that all boundaries and boundary layers in the magnetosphere have a very complex microstructure. Waves and wave-like structures were observed throughout the magnetosphere; these included the longest lasting mirror-mode wave trains observed in space. PMID:17776160