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Sample records for magnetic flux distributions

  1. Solar Intranetwork Magnetic Elements: Flux Distributions

    NASA Astrophysics Data System (ADS)

    Zhou, Guiping; Wang, Jingxiu; Jin, Chunlan

    2013-04-01

    The current study aims at quantifying the flux distributions of solar intranetwork (IN) magnetic field based on the data taken in four quiet and two enhanced network areas with the Narrow-band Filter Imager of the Solar Optical Telescope on board the Hinode satellite. More than 14000 IN elements and 3000 NT elements were visually identified. They exhibit a flux distribution function with a peak at 1 - 3×1016 Mx (maxwell) and 2 - 3×1017 Mx, respectively. We found that the IN elements contribute approximately to 52 % of the total flux and an average flux density of 12.4 gauss of the quiet region at any given time. By taking the lifetime of IN elements of about 3 min (Zhou et al., Solar Phys. 267, 63, 2010) into account, the IN fields are estimated to have total contributions to the solar magnetic flux up to 3.8×1026 Mx per day. No fundamental distinction can be identified in IN fields between the quiet and enhanced network areas.

  2. Size and energy distributions of interplanetary magnetic flux ropes

    NASA Astrophysics Data System (ADS)

    Feng, H. Q.; Wu, D. J.; Chao, J. K.

    2007-02-01

    In observations from 1995 to 2001 from the Wind spacecraft, 144 interplanetary magnetic flux ropes were identified in the solar wind around 1 AU. Their durations vary from tens of minutes to tens of hours. These magnetic flux ropes include many small- and intermediate-sized structures and display a continuous distribution in size. Energies of these flux ropes are estimated and it is found that the distribution of their energies is a good power law spectrum with an index ~-0.87. The possible relationship between them and solar eruptions is discussed. It is suggested that like interplanetary magnetic clouds are interplanetary coronal mass ejections, the small- and intermediate-sized interplanetary magnetic flux ropes are the interplanetary manifestations of small coronal mass ejections produced in small solar eruptions. However, these small coronal mass ejections are too weak to appear clearly in the coronagraph observations as an ordinary coronal mass ejection.

  3. Magnetic flux invasion in REBCO bulk magnets with varying pre-magnetized flux distributions in multiple-PFM processes

    NASA Astrophysics Data System (ADS)

    Oka, T.; Hara, K.; Takeda, A.; Ogawa, J.; Fukui, S.; Sato, T.; Yokoyama, K.; Murakami, A.

    2017-07-01

    The motion of magnetic flux invading into the HTS bulk magnets were experimentally studied in their pulsed field magnetization processes. The authors paid attention to the effects of the shapes of the pre-magnetized trapped flux distributions before the successive field applications by means of varying the M-shaped distribution. We estimated the differences of the magnetic flux motions between the Dy123 and Gd123 systems, which might have different J c properties of each sample. As for the Dy123 system, the increase of remaining flux in the periphery region of the M-shaped distribution resulted in the decrease of flux-trapping according to the promotion of flux invasion. On the other hand, trapped flux density has been raised to 3.4 T owing to the effective suppression of flux invasion for the Gd123 bulk magnet. The experiments showed that the peak heights and the positions of the formerly trapped M-shaped fluxes precisely affect the heat generation and the trapped field performance.

  4. Statistical Distribution of Magnetic Flux Concentrations in an Active Region

    NASA Astrophysics Data System (ADS)

    Abramenko, V. I.

    2004-05-01

    Probability distribution functions (PDFs) of the unsigned magnetic flux content in flux concentrations in a mature active region NOAA 9077 were calculated by using a set of 248 high resolution SOHO/MDI magnetograms. Two independent routines to outline magnetic flux concentrations were elaborated. The analysis was performed with 4 different values of the threshold, p, of the magnetic flux density (p=25, 50, 75, 100 G). We have found that: i) the best analytical approximation of the observed PDFs in the range of low flux (1 x 1018 Mx < F < 150 x 1018 Mx ) is a lognormal distribution, LN(m ,s2), with the expected value m=(0.7-5) x 1018 Mx and the standard deviation s = (10-45) x 1018 Mx. The peak of the lognormal distribution tends to shift toward the lower flux as the threshold p decreases. This tendency suggests that the real expected value may be even smaller than 0.7 x 1018 Mx; ii) for the flux F > 150 x 1018 Mx the observed PDFs fall off slower than the lognormal approximation predicts. In this flux range, the power law is found to be the best analytical approximation with the power law index approximately equal to 2. The transition region between the lognormality and the power law shifts toward the lower flux as the threshold p is lowered. This implies that the functional form of the distribution changes continuously with the scale. The above findings are consistent with the concept of highly intermittent (or multifractal) nature of photospheric magnetic fields and offer a new tool to study their multifractality. SOHO is a project of international cooperation between ESA and NASA. This work was supported by NSF-ATM 0076602, 9903515 and NASA NAG5-12782 grants.

  5. Magnetic flux distribution in the amorphous modular transformers

    NASA Astrophysics Data System (ADS)

    Tomczuk, B.; Koteras, D.

    2011-06-01

    3D magnetic fluxes in one-phase and three-phase transformers with amorphous modular cores have been studied. Scalar potentials were implemented for the 3D Finite Element field calculation. Due to the inability to simulate each thin amorphous layer, we introduced supplementary permeabilities along the main directions of magnetization. The calculated fluxes in the cores were tested on the prototypes.

  6. Magnetic flux distribution and magnetic relaxation in polycrystalline Bi,PbSrCaCuO superconductors

    NASA Astrophysics Data System (ADS)

    Paasi, J.; Polák, M.; Lahtinen, M.; Plecháček, V.; Söderlund, L.

    We have studied magnetic flux distribution and magnetic relaxation in polycrystalline (Bi,Pb) 2Sr 2Ca 2Cu 3O 10+ x superconductors at 77 K using a movable miniature Hall sensor. Flux distribution was studied by measuring magnetic field profiles as a function of external field and time. The effects of inter- and intragrain shielding currents on magnetic flux distribution were distinguished using these measurements. The intergrain critical current density can be calculated from the field profile also in the case where intragrain currents are present. The relaxation of inter- and intragrain currents was distinguished and studied. The relaxation was logarithmic in both current systems. The relaxation rates of intergrain currents were remarkably higher than the rates of intragrain currents. When neither internor intragrain currents dominated, the total relaxation was non-logarithmic.

  7. Enhancement of magnetic flux distribution in a DC superconducting electric motor

    NASA Astrophysics Data System (ADS)

    Hamid, N. A.; Ewe, L. S.; Chin, K. M.

    2013-06-01

    Most motor designs require an air gap between the rotor and stator to enable the armature to rotate freely. The interaction of magnetic flux from rotor and stator within the air gap will provide the thrust for rotational motion. Thus, the understanding of magnetic flux in the vicinity of the air gap is very important to mathematically calculate the magnetic flux generated in the area. In this work, a finite element analysis was employed to study the behavior of the magnetic flux in view of designing a synchronous DC superconducting electric motor. The analysis provides an ideal magnetic flux distribution within the components of the motor. From the flux plot analysis, it indicates that flux losses are mainly in the forms of leakage and fringe effect. The analysis also shows that the flux density is high at the area around the air gap and the rotor. The high flux density will provide a high force area that enables the rotor to rotate. In contrast, the other parts of the motor body do not show high flux density indicating low distribution of flux. Consequently, a bench top model of a DC superconducting motor was developed where by motor with a 2-pole type winding was chosen. Each field coil was designed with a racetrack-shaped double pancake wound using DI-BSCCO Bi-2223 superconducting tapes. The performance and energy efficiency of the superconducting motor was superior when compared to the conventional motor with similar capacity.

  8. Morphology and magnetic flux distribution in superparamagnetic, single-crystalline Fe3O4 nanoparticle rings

    NASA Astrophysics Data System (ADS)

    Takeno, Yumu; Murakami, Yasukazu; Sato, Takeshi; Tanigaki, Toshiaki; Park, Hyun Soon; Shindo, Daisuke; Ferguson, R. Matthew; Krishnan, Kannan M.

    2014-11-01

    This study reports on the correlation between crystal orientation and magnetic flux distribution of Fe3O4 nanoparticles in the form of self-assembled rings. High-resolution transmission electron microscopy demonstrated that the nanoparticles were single-crystalline, highly monodispersed, (25 nm average diameter), and showed no appreciable lattice imperfections such as twins or stacking faults. Electron holography studies of these superparamagnetic nanoparticle rings indicated significant fluctuations in the magnetic flux lines, consistent with variations in the magnetocrystalline anisotropy of the nanoparticles. The observations provide useful information for a deeper understanding of the micromagnetics of ultrasmall nanoparticles, where the magnetic dipolar interaction competes with the magnetic anisotropy.

  9. Morphology and magnetic flux distribution in superparamagnetic, single-crystalline Fe3O4 nanoparticle rings

    PubMed Central

    Takeno, Yumu; Murakami, Yasukazu; Sato, Takeshi; Tanigaki, Toshiaki; Park, Hyun Soon; Shindo, Daisuke; Ferguson, R. Matthew

    2014-01-01

    This study reports on the correlation between crystal orientation and magnetic flux distribution of Fe3O4 nanoparticles in the form of self-assembled rings. High-resolution transmission electron microscopy demonstrated that the nanoparticles were single-crystalline, highly monodispersed, (25 nm average diameter), and showed no appreciable lattice imperfections such as twins or stacking faults. Electron holography studies of these superparamagnetic nanoparticle rings indicated significant fluctuations in the magnetic flux lines, consistent with variations in the magnetocrystalline anisotropy of the nanoparticles. The observations provide useful information for a deeper understanding of the micromagnetics of ultrasmall nanoparticles, where the magnetic dipolar interaction competes with the magnetic anisotropy. PMID:25422526

  10. High-resolution dichroic imaging of magnetic flux distributions in superconductors with scanning x-ray microscopy

    SciTech Connect

    Ruoß, S. Stahl, C.; Weigand, M.; Schütz, G.; Albrecht, J.

    2015-01-12

    The penetration of magnetic flux into high-temperature superconductors has been observed using a high-resolution technique based on x-ray magnetic circular dichroism. Superconductors coated with thin soft-magnetic layers are observed in a scanning x-ray microscope under the influence of external magnetic fields. Resulting electric currents in the superconductor create an inhomogeneous magnetic field distribution above the superconductor and lead to a local reorientation of the ferromagnetic layer. Measuring the local magnetization of the ferromagnet by x-ray absorption microscopy with circular-polarized radiation allows the analysis of the magnetic flux distribution in the superconductor with a spatial resolution on the nanoscale.

  11. Quantitative comparison of dynamic flux distribution of magnetic couplers for roadway electric vehicle wireless charging system

    NASA Astrophysics Data System (ADS)

    Qiu, Chun; Chau, K. T.; Liu, Chunhua; Li, Wenlong; Lin, Fei

    2014-05-01

    This paper gives a quantitative comparison of magnetic couplers for electric vehicle (EV) wireless charging applications. Circular pad with ferrite spokes and coreless rectangular coils are specially selected for analysis. The dynamic flux density between couplers under high misalignment is studied by calculating the uncompensated power of the pick-up coupler. By using finite element analysis, the performance of each type of coupler is evaluated, and its adaptation to on-road EV charging are compared according to the flux distribution and effective charging area.

  12. Magnetic-flux pump

    NASA Technical Reports Server (NTRS)

    Hildebrandt, A. F.; Elleman, D. D.; Whitmore, F. C. (Inventor)

    1966-01-01

    A magnetic flux pump is described for increasing the intensity of a magnetic field by transferring flux from one location to the magnetic field. The device includes a pair of communicating cavities formed in a block of superconducting material, and a piston for displacing the trapped magnetic flux into the secondary cavity producing a field having an intense flux density.

  13. Evaluation of magnetic flux distribution from magnetic domains in [Co/Pd] nanowires by magnetic domain scope method using contact-scanning of tunneling magnetoresistive sensor

    SciTech Connect

    Okuda, Mitsunobu Miyamoto, Yasuyoshi; Miyashita, Eiichi; Hayashi, Naoto

    2014-05-07

    Current-driven magnetic domain wall motions in magnetic nanowires have attracted great interests for physical studies and engineering applications. The magnetic force microscope (MFM) is widely used for indirect verification of domain locations in nanowires, where relative magnetic force between the local domains and the MFM probe is used for detection. However, there is an occasional problem that the magnetic moments of MFM probe influenced and/or rotated the magnetic states in the low-moment nanowires. To solve this issue, the “magnetic domain scope for wide area with nano-order resolution (nano-MDS)” method has been proposed recently that could detect the magnetic flux distribution from the specimen directly by scanning of tunneling magnetoresistive field sensor. In this study, magnetic domain structure in nanowires was investigated by both MFM and nano-MDS, and the leakage magnetic flux density from the nanowires was measured quantitatively by nano-MDS. Specimen nanowires consisted from [Co (0.3)/Pd (1.2)]{sub 21}/Ru(3) films (units in nm) with perpendicular magnetic anisotropy were fabricated onto Si substrates by dual ion beam sputtering and e-beam lithography. The length and the width of the fabricated nanowires are 20 μm and 150 nm. We have succeeded to obtain not only the remanent domain images with the detection of up and down magnetizations as similar as those by MFM but also magnetic flux density distribution from nanowires directly by nano-MDS. The obtained value of maximum leakage magnetic flux by nano-MDS is in good agreement with that of coercivity by magneto-optical Kerr effect microscopy. By changing the protective diamond-like-carbon film thickness on tunneling magnetoresistive sensor, the three-dimensional spatial distribution of leakage magnetic flux could be evaluated.

  14. Magnetic x-ray microscopy at low temperatures – Visualization of flux distributions in superconductors

    SciTech Connect

    Stahl, Claudia Ruoß, Stephen; Weigand, Markus; Bechtel, Michael; Schütz, Gisela; Albrecht, Joachim

    2016-01-28

    X-ray Magnetic Circular Dichroism (XMCD) microscopy at liquid nitrogen temperature has been performed on bilayers of high-T{sub c} superconducting YBCO (YBa{sub 2}Cu{sub 3}O{sub 7-δ}) and soft-magnetic Co{sub 40}Fe{sub 40}B{sub 20}. This should allow us to map the magnetic flux density distribution in the current-carrying state of the superconductor with high spatial resolution. For that purpose the UHV scanning X-ray microscope MAXYMUS has been upgraded by a MMR Micro Miniature Joule-Thompson cryostat capable of temperatures between 75 K and 580 K. Resulting XMCD images of the magnetic flux density in the superconductor with a field of view ranging from millimeters to micrometers are presented. The microscope’s unique combination of total electron yield (TEY) measurements together with low temperatures offers novel possibilities concerning the current transport in superconductors on small length scales.

  15. Excessive magnetic field flux density distribution from overhead isolated powerline conductors due to neutral line current.

    PubMed

    Netzer, Moshe

    2013-06-01

    Overhead isolated powerline conductors (hereinafter: "OIPLC") are the most compact form for distributing low voltage currents. From the known physics of magnetic field emission from 3-phase power lines, it is expected that excellent symmetry of the 120° shifted phase currents and where compact configuration of the 3-phase+neutral line exist, the phase current vectorial summation of the magnetic field flux density (MFFD) is expected to be extremely low. However, despite this estimation, an unexpectedly very high MFFD was found in at least three towns in Israel. This paper explains the reasons leading to high MFFD emissions from compact OIPLC and the proper technique to fix it. Analysis and measurement results had led to the failure hypothsis of neutral line poor connection design and poor grounding design of the HV-LV utility transformers. The paper elaborates on the low MFFD exposure level setup by the Israeli Environmental Protection Office which adopted a rather conservative precaution principal exposure level (2 mG averaged over 24 h).

  16. Morphology and magnetic flux distribution in superparamagnetic, single-crystalline Fe{sub 3}O{sub 4} nanoparticle rings

    SciTech Connect

    Takeno, Yumu; Murakami, Yasukazu E-mail: kannanmk@uw.edu; Shindo, Daisuke; Sato, Takeshi; Tanigaki, Toshiaki; Park, Hyun Soon; Ferguson, R. Matthew; Krishnan, Kannan M. E-mail: kannanmk@uw.edu

    2014-11-03

    This study reports on the correlation between crystal orientation and magnetic flux distribution of Fe{sub 3}O{sub 4} nanoparticles in the form of self-assembled rings. High-resolution transmission electron microscopy demonstrated that the nanoparticles were single-crystalline, highly monodispersed, (25 nm average diameter), and showed no appreciable lattice imperfections such as twins or stacking faults. Electron holography studies of these superparamagnetic nanoparticle rings indicated significant fluctuations in the magnetic flux lines, consistent with variations in the magnetocrystalline anisotropy of the nanoparticles. The observations provide useful information for a deeper understanding of the micromagnetics of ultrasmall nanoparticles, where the magnetic dipolar interaction competes with the magnetic anisotropy.

  17. Flux Compression Magnetic Nozzle

    NASA Technical Reports Server (NTRS)

    Thio, Y. C. Francis; Schafer, Charles (Technical Monitor)

    2001-01-01

    In pulsed fusion propulsion schemes in which the fusion energy creates a radially expanding plasma, a magnetic nozzle is required to redirect the radially diverging flow of the expanding fusion plasma into a rearward axial flow, thereby producing a forward axial impulse to the vehicle. In a highly electrically conducting plasma, the presence of a magnetic field B in the plasma creates a pressure B(exp 2)/2(mu) in the plasma, the magnetic pressure. A gradient in the magnetic pressure can be used to decelerate the plasma traveling in the direction of increasing magnetic field, or to accelerate a plasma from rest in the direction of decreasing magnetic pressure. In principle, ignoring dissipative processes, it is possible to design magnetic configurations to produce an 'elastic' deflection of a plasma beam. In particular, it is conceivable that, by an appropriate arrangement of a set of coils, a good approximation to a parabolic 'magnetic mirror' may be formed, such that a beam of charged particles emanating from the focal point of the parabolic mirror would be reflected by the mirror to travel axially away from the mirror. The degree to which this may be accomplished depends on the degree of control one has over the flux surface of the magnetic field, which changes as a result of its interaction with a moving plasma.

  18. The calculation of force-free fields from discrete flux distributions. [for chromospheric magnetic fields

    NASA Technical Reports Server (NTRS)

    Sheeley, N. R., Jr.; Harvey, J. W.

    1975-01-01

    This paper presents particularly simple mathematical formulas for the calculation of force-free fields of constant alpha from the distribution of discrete sources on a flat surface. The advantage of these formulas lies in their physical simplicity and the fact that they can be easily used in practice to calculate the fields. The disadvantage is that they are limited to fields of 'sufficiently small alpha'. These formulas may be useful in the study of chromospheric magnetic fields by the comparison of high-resolution H-alpha photographs and photospheric magnetograms.

  19. Magnetic flux amplification by Lenz lenses

    NASA Astrophysics Data System (ADS)

    Schoenmaker, J.; Pirota, K. R.; Teixeira, J. C.

    2013-08-01

    Tailoring magnetic flux distribution is highly desirable in a wide range of applications such as magnetic sensors and biomedicine. In this paper we study the manipulation of induced currents in passive devices in order to engineer the distribution of magnetic flux intensity in a given region. We propose two different approaches, one based on especially designed wire loops (Lenz law) and the other based on solid conductive pieces (eddy currents). The gain of such devices is mainly determined by geometry giving perspective of high amplification. We consistently modeled, simulated, and executed the proposed devices. Doubled magnetic flux intensity is demonstrated experimentally for a moderate aspect ratio.

  20. Permanent magnet flux-biased magnetic actuator with flux feedback

    NASA Technical Reports Server (NTRS)

    Groom, Nelson J. (Inventor)

    1991-01-01

    The invention is a permanent magnet flux-biased magnetic actuator with flux feedback for adjustably suspending an element on a single axis. The magnetic actuator includes a pair of opposing electromagnets and provides bi-directional forces along the single axis to the suspended element. Permanent magnets in flux feedback loops from the opposing electromagnets establish a reference permanent magnet flux-bias to linearize the force characteristics of the electromagnets to extend the linear range of the actuator without the need for continuous bias currents in the electromagnets.

  1. Magnetized retarding field energy analyzer measuring the particle flux and ion energy distribution of both positive and negative ions

    SciTech Connect

    Rafalskyi, Dmytro; Aanesland, Ane; Dudin, Stanislav

    2015-05-15

    This paper presents the development of a magnetized retarding field energy analyzer (MRFEA) used for positive and negative ion analysis. The two-stage analyzer combines a magnetic electron barrier and an electrostatic ion energy barrier allowing both positive and negative ions to be analyzed without the influence of electrons (co-extracted or created downstream). An optimal design of the MRFEA for ion-ion beams has been achieved by a comparative study of three different MRFEA configurations, and from this, scaling laws of an optimal magnetic field strength and topology have been deduced. The optimal design consists of a uniform magnetic field barrier created in a rectangular channel and an electrostatic barrier consisting of a single grid and a collector placed behind the magnetic field. The magnetic barrier alone provides an electron suppression ratio inside the analyzer of up to 6000, while keeping the ion energy resolution below 5 eV. The effective ion transparency combining the magnetic and electrostatic sections of the MRFEA is measured as a function of the ion energy. It is found that the ion transparency of the magnetic barrier increases almost linearly with increasing ion energy in the low-energy range (below 200 eV) and saturates at high ion energies. The ion transparency of the electrostatic section is almost constant and close to the optical transparency of the entrance grid. We show here that the MRFEA can provide both accurate ion flux and ion energy distribution measurements in various experimental setups with ion beams or plasmas run at low pressure and with ion energies above 10 eV.

  2. Magnetized retarding field energy analyzer measuring the particle flux and ion energy distribution of both positive and negative ions.

    PubMed

    Rafalskyi, Dmytro; Dudin, Stanislav; Aanesland, Ane

    2015-05-01

    This paper presents the development of a magnetized retarding field energy analyzer (MRFEA) used for positive and negative ion analysis. The two-stage analyzer combines a magnetic electron barrier and an electrostatic ion energy barrier allowing both positive and negative ions to be analyzed without the influence of electrons (co-extracted or created downstream). An optimal design of the MRFEA for ion-ion beams has been achieved by a comparative study of three different MRFEA configurations, and from this, scaling laws of an optimal magnetic field strength and topology have been deduced. The optimal design consists of a uniform magnetic field barrier created in a rectangular channel and an electrostatic barrier consisting of a single grid and a collector placed behind the magnetic field. The magnetic barrier alone provides an electron suppression ratio inside the analyzer of up to 6000, while keeping the ion energy resolution below 5 eV. The effective ion transparency combining the magnetic and electrostatic sections of the MRFEA is measured as a function of the ion energy. It is found that the ion transparency of the magnetic barrier increases almost linearly with increasing ion energy in the low-energy range (below 200 eV) and saturates at high ion energies. The ion transparency of the electrostatic section is almost constant and close to the optical transparency of the entrance grid. We show here that the MRFEA can provide both accurate ion flux and ion energy distribution measurements in various experimental setups with ion beams or plasmas run at low pressure and with ion energies above 10 eV.

  3. Physics of magnetic flux ropes

    NASA Astrophysics Data System (ADS)

    Russell, C. T.; Priest, E. R.; Lee, L. C.

    The present work encompasses papers on the structure, waves, and instabilities of magnetic flux ropes (MFRs), photospheric flux tubes (PFTs), the structure and heating of coronal loops, solar prominences, coronal mass ejections and magnetic clouds, flux ropes in planetary ionospheres, the magnetopause, magnetospheric field-aligned currents and flux tubes, and the magnetotail. Attention is given to the equilibrium of MFRs, resistive instability, magnetic reconnection and turbulence in current sheets, dynamical effects and energy transport in intense flux tubes, waves in solar PFTs, twisted flux ropes in the solar corona, an electrodynamical model of solar flares, filament cooling and condensation in a sheared magnetic field, the magnetopause, the generation of twisted MFRs during magnetic reconnection, ionospheric flux ropes above the South Pole, substorms and MFR structures, evidence for flux ropes in the earth magnetotail, and MFRs in 3D MHD simulations.

  4. Reconstruction of current density distributions in axially symmetric cylindrical sections using one component of magnetic flux density: computer simulation study.

    PubMed

    Seo, Jin Keun; Kwon, Ohin; Lee, Byung Il; Woo, Eung Je

    2003-05-01

    In magnetic resonance current density imaging (MRCDI), we inject current into a subject through surface electrodes and measure the induced magnetic flux density B inside the subject using an MRI scanner. Once we have obtained all three components of B, we can reconstruct the internal current density distribution J = inverted triangle x B/mu0). This technique, however, requires subject rotation since the MRI scanner can measure only one component of B that is parallel to the direction of its main magnetic field. In this paper, under the assumption that the out-of-plane current density Jz is negligible in an imaging slice belonging to the xy-plane, we developed an imaging technique of current density distributions using only Bz, the z-component of B. The technique described in this paper does not require a subject rotation but the quality of reconstructed images depends on the amount of out-of-plane current density Jz. From numerical simulations, we found that the new algorithm could be applied to subjects such as human limbs using longitudinal electrodes.

  5. Magnetic balltracking: Tracking the photospheric magnetic flux

    NASA Astrophysics Data System (ADS)

    Attie, R.; Innes, D. E.

    2015-02-01

    Context. One aspect of understanding the dynamics of the quiet Sun is to quantify the evolution of the flux within small-scale magnetic features. These features are routinely observed in the quiet photosphere and were given various names, such as pores, knots, magnetic patches. Aims: This work presents a new algorithm for tracking the evolution of the broad variety of small-scale magnetic features in the photosphere, with a precision equal to the instrumental resolution. Methods: We have developed a new technique to track the evolution of the individual magnetic features from magnetograms, called "magnetic balltracking". It quantifies the flux of the tracked features, and it can track the footpoints of magnetic field lines inferred from magnetic field extrapolation. The algorithm can detect and quantify flux emergence, as well as flux cancellation. Results: The capabilities of magnetic balltracking are demonstrated with the detection and the tracking of two cases of magnetic flux emergence that lead to the brightening of X-ray loops. The maximum emerged flux ranges from 1018 Mx to 1019 Mx (unsigned flux) when the X-ray loops are observed. Movies associated to Figs. 6 and 18 are available in electronic form at http://www.aanda.org

  6. Magnetic reconnection during eruptive magnetic flux ropes

    NASA Astrophysics Data System (ADS)

    Mei, Z. X.; Keppens, R.; Roussev, I. I.; Lin, J.

    2017-08-01

    Aims: We perform a three-dimensional (3D) high resolution numerical simulation in isothermal magnetohydrodynamics to study the magnetic reconnection process in a current sheet (CS) formed during an eruption of a twisted magnetic flux rope (MFR). Because the twist distribution violates the Kruskal-Shafranov condition, the kink instability occurs, and the MFR is distorted. The centre part of the MFR loses its equilibrium and erupts upward, which leads to the formation of a 3D CS underneath it. Methods: In order to study the magnetic reconnection inside the CS in detail, mesh refinement has been used to reduce the numerical diffusion and we estimate a Lundquist number S = 104 in the vicinity of the CS. Results: The refined mesh allows us to resolve fine structures inside the 3D CS: a bifurcating sheet structure signaling the 3D generalization of Petschek slow shocks, some distorted-cylindrical substructures due to the tearing mode instabilities, and two turbulence regions near the upper and the lower tips of the CS. The topological characteristics of the MFR depend sensitively on the observer's viewing angle: it presents as a sigmoid structure, an outwardly expanding MFR with helical distortion, or a flare-CS-coronal mass ejection symbiosis as in 2D flux-rope models when observed from the top, the front, or the side. The movie associated to Fig. 2 is available at http://www.aanda.org

  7. Scanning micro-Hall probe mapping of magnetic flux distributions and current densities in YBa{sub 2}Cu{sub 3}O{sub 7}

    SciTech Connect

    Xing, W.; Heinrich, B.; Zhou, H.

    1994-12-31

    Mapping of the magnetic flux density B{sub z} (perpendicular to the film plane) for a YBa{sub 2}Cu{sub 3}O{sub 7} thin-film sample was carried out using a scanning micro-Hall probe. The sheet magnetization and sheet current densities were calculated from the B{sub z} distributions. From the known sheet magnetization, the tangential (B{sub x,y}) and normal components of the flux density B were calculated in the vicinity of the film. It was found that the sheet current density was mostly determined by 2B{sub x,y}/d, where d is the film thickness. The evolution of flux penetration as a function of applied field will be shown.

  8. Scanning micro-Hall probe mapping of magnetic flux distributions and current densities in YBa2Cu3O7 thin films

    NASA Technical Reports Server (NTRS)

    Xing, W.; Heinrich, B.; Zhou, HU; Fife, A. A.; Cragg, A. R.; Grant, P. D.

    1995-01-01

    Mapping of the magnetic flux density B(sub z) (perpendicular to the film plane) for a YBa2Cu3O7 thin-film sample was carried out using a scanning micro-Hall probe. The sheet magnetization and sheet current densities were calculated from the B(sub z) distributions. From the known sheet magnetization, the tangential (B(sub x,y)) and normal components of the flux density B were calculated in the vicinity of the film. It was found that the sheet current density was mostly determined by 2B(sub x,y)/d, where d is the film thickness. The evolution of flux penetration as a function of applied field will be shown.

  9. In situ observations of domain structures and magnetic flux distributions in Mn-Zn and Ni-Zn ferrites by Lorentz microscopy and electron holography.

    PubMed

    Kasahara, Takehiro; Shindo, Daisuke; Yoshikawa, Hideyuki; Sato, Takafumi; Kondo, Koichi

    2007-01-01

    Domain structures and magnetic flux distributions in Mn-Zn and Ni-Zn ferrites are investigated by in situ observations with Lorentz microscopy and electron holography. In situ Lorentz microscopic observation with the magnetic field applied reveals that the domain walls in Mn-Zn ferrite move easily across the grain boundary. On the other hand, each grain of Ni-Zn ferrite is magnetized by domain wall motion inside the grain. By taking a series of holograms with adjustment of the optical axis and astigmatism while the magnetic field is applied, we succeeded in observing the change in magnetic flux distribution quantitatively. Eventually, it is clarified that magnetization rotation does not take place in the magnetization process of Ni-Zn ferrite. The domain wall widths delta in Mn-Zn and Ni-Zn ferrites are evaluated to be 73 and 58 nm, respectively. Furthermore, through direct observation of the domain structure in Ni-Cu-Zn ferrite with Lorentz microscopy, it is found that the grains with size below 1.5 microm diameter are single domain.

  10. Triode for Magnetic Flux Quanta

    SciTech Connect

    Vlasko-Vlasov, V. K.; Colauto, F.; Benseman, T.; Rosenmann, D.; Kwok, W. -K.

    2016-11-15

    In an electronic triode, the electron current emanating from the cathode is regulated by the electric potential on a grid between the cathode and the anode. Here we demonstrate a triode for single quantum magnetic field carriers, where the flow of individual magnetic vortices in a superconducting film is regulated by the magnetic potential of striae of soft magnetic strips deposited on the film surface. By rotating an applied in-plane field, the magnetic strip potential can be varied due to changes in the magnetic charges at the strip edges, allowing accelerated or retarded motion of magnetic vortices inside the superconductor. Scaling down our design and reducing the gap width between the magnetic stripes will enable controlled manipulation of individual vortices and creation of single flux quantum circuitry for novel high-speed low-power superconducting electronics.

  11. Triode for Magnetic Flux Quanta

    DOE PAGES

    Vlasko-Vlasov, V. K.; Colauto, F.; Benseman, T.; ...

    2016-11-15

    In an electronic triode, the electron current emanating from the cathode is regulated by the electric potential on a grid between the cathode and the anode. Here we demonstrate a triode for single quantum magnetic field carriers, where the flow of individual magnetic vortices in a superconducting film is regulated by the magnetic potential of striae of soft magnetic strips deposited on the film surface. By rotating an applied in-plane field, the magnetic strip potential can be varied due to changes in the magnetic charges at the strip edges, allowing accelerated or retarded motion of magnetic vortices inside the superconductor.more » Scaling down our design and reducing the gap width between the magnetic stripes will enable controlled manipulation of individual vortices and creation of single flux quantum circuitry for novel high-speed low-power superconducting electronics.« less

  12. Triode for Magnetic Flux Quanta

    NASA Astrophysics Data System (ADS)

    Vlasko-Vlasov, V. K.; Colauto, F.; Benseman, T.; Rosenmann, D.; Kwok, W.-K.

    2016-11-01

    In an electronic triode, the electron current emanating from the cathode is regulated by the electric potential on a grid between the cathode and the anode. Here we demonstrate a triode for single quantum magnetic field carriers, where the flow of individual magnetic vortices in a superconducting film is regulated by the magnetic potential of striae of soft magnetic strips deposited on the film surface. By rotating an applied in-plane field, the magnetic strip potential can be varied due to changes in the magnetic charges at the strip edges, allowing accelerated or retarded motion of magnetic vortices inside the superconductor. Scaling down our design and reducing the gap width between the magnetic stripes will enable controlled manipulation of individual vortices and creation of single flux quantum circuitry for novel high-speed low-power superconducting electronics.

  13. Triode for Magnetic Flux Quanta.

    PubMed

    Vlasko-Vlasov, V K; Colauto, F; Benseman, T; Rosenmann, D; Kwok, W-K

    2016-11-15

    In an electronic triode, the electron current emanating from the cathode is regulated by the electric potential on a grid between the cathode and the anode. Here we demonstrate a triode for single quantum magnetic field carriers, where the flow of individual magnetic vortices in a superconducting film is regulated by the magnetic potential of striae of soft magnetic strips deposited on the film surface. By rotating an applied in-plane field, the magnetic strip potential can be varied due to changes in the magnetic charges at the strip edges, allowing accelerated or retarded motion of magnetic vortices inside the superconductor. Scaling down our design and reducing the gap width between the magnetic stripes will enable controlled manipulation of individual vortices and creation of single flux quantum circuitry for novel high-speed low-power superconducting electronics.

  14. Triode for Magnetic Flux Quanta

    PubMed Central

    Vlasko-Vlasov, V. K.; Colauto, F.; Benseman, T.; Rosenmann, D.; Kwok, W.-K.

    2016-01-01

    In an electronic triode, the electron current emanating from the cathode is regulated by the electric potential on a grid between the cathode and the anode. Here we demonstrate a triode for single quantum magnetic field carriers, where the flow of individual magnetic vortices in a superconducting film is regulated by the magnetic potential of striae of soft magnetic strips deposited on the film surface. By rotating an applied in-plane field, the magnetic strip potential can be varied due to changes in the magnetic charges at the strip edges, allowing accelerated or retarded motion of magnetic vortices inside the superconductor. Scaling down our design and reducing the gap width between the magnetic stripes will enable controlled manipulation of individual vortices and creation of single flux quantum circuitry for novel high-speed low-power superconducting electronics. PMID:27845375

  15. Magnetic field line lengths inside interplanetary magnetic flux ropes

    NASA Astrophysics Data System (ADS)

    Hu, Qiang; Qiu, Jiong; Krucker, Sam

    2015-07-01

    We report on the detailed and systematic study of field line twist and length distributions within magnetic flux ropes embedded in interplanetary coronal mass ejections (ICMEs). The Grad-Shafranov reconstruction method is utilized together with a constant-twist nonlinear force-free (Gold-Hoyle) flux rope model to reveal the close relation between the field line twist and length in cylindrical flux ropes, based on in situ Wind spacecraft measurements. We show that the field line twist distributions within interplanetary flux ropes are inconsistent with the Lundquist model. In particular, we utilize the unique measurements of magnetic field line lengths within selected ICME events as provided by Kahler et al. () based on energetic electron burst observations at 1 AU and the associated type III radio emissions detected by the Wind spacecraft. These direct measurements are compared with our model calculations to help assess the flux rope interpretation of the embedded magnetic structures. By using the different flux rope models, we show that the in situ direct measurements of field line lengths are consistent with a flux rope structure with spiral field lines of constant and low twist, largely different from that of the Lundquist model, especially for relatively large-scale flux ropes.

  16. Force sensor using changes in magnetic flux

    NASA Technical Reports Server (NTRS)

    Pickens, Herman L. (Inventor); Richard, James A. (Inventor)

    2012-01-01

    A force sensor includes a magnetostrictive material and a magnetic field generator positioned in proximity thereto. A magnetic field is induced in and surrounding the magnetostrictive material such that lines of magnetic flux pass through the magnetostrictive material. A sensor positioned in the vicinity of the magnetostrictive material measures changes in one of flux angle and flux density when the magnetostrictive material experiences an applied force that is aligned with the lines of magnetic flux.

  17. Power distribution of a co-axial dual-mechanical-port flux-switching permanent magnet machine for fuel-based extended range electric vehicles

    NASA Astrophysics Data System (ADS)

    Zhou, Lingkang; Hua, Wei; Zhang, Gan

    2017-05-01

    In this paper, power distribution between the inner and outer machines of a co-axial dual-mechanical-port flux-switching permanent magnet (CADMP-FSPM) machine is investigated for fuel-based extended range electric vehicle (ER-EV). Firstly, the topology and operation principle of the CADMP-FSPM machine are introduced, which consist of an inner FSPM machine used for high-speed, an outer FSPM machine for low-speed, and a magnetic isolation ring between them. Then, the magnetic field coupling of the inner and outer FSPM machines is analyzed with more attention paid to the optimization of the isolation ring thickness. Thirdly, the power-dimension (PD) equations of the inner and outer FSPM machines are derived, respectively, and thereafter, the PD equation of the whole CADMP-FSPM machine can be given. Finally, the PD equations are validated by finite element analysis, which supplies the guidance on the design of this type of machines.

  18. Transport of magnetic flux in Saturn’s inner magnetosphere

    NASA Astrophysics Data System (ADS)

    Russell, Christopher T.; Lai, H. R.; Wei, H. Y.; Jia, Y. D.; Dougherty, M. K.

    2015-11-01

    The dynamics of the Saturnian magnetosphere, which rotates rapidly with an internal plasma source provided by Enceladus, qualitatively resembles those of the jovian magnetosphere powered by Io. The newly added plasma is accelerated to the corotation speed and moves outward together with the magnetic flux. In the near tail region, reconnection cuts the magnetic flux, reconnects it into plasma-depleted inward moving flux tubes and outward moving massive plasmoids. The buoyant empty tubes then convect inward against the outward flow to conserve the total magnetic flux established by the internal dynamo. In both jovian and saturnian magnetospheres, flux tubes with enhanced field strength relative to their surroundings are detected in the equatorial region. Recent observations show that there are flux tubes with reduced field strength off the equator in the saturnian magnetosphere. To understand the formation mechanism of both types of flux tubes, we have surveyed all the available 1-sec magnetic field data from Cassini. The systematic statistical study confirms the different latitudinal distributions of the two types of flux tubes. In addition, enhanced-field flux tubes are closer to the planet while reduced-field flux tubes can be detected at larger distances; both types of flux tubes become indistinguishable from the background magnetic flux inside an L-value of about 4; the local time distribution of both types of flux tubes are similar and they contain about the same amount of magnetic flux. Therefore, the two types of flux tubes are the same phenomena with different manifestations in different plasma environments. When the surrounding plasma density is high (near the equator and closer to the plasma source region), the flux tubes are compressed and have enhanced field strength inside; while in the low-plasma density region (off the equator and further from the plasma source region), the flux tubes expand and have reduced field strength inside.

  19. Magnetic Flux Compression in Plasmas

    NASA Astrophysics Data System (ADS)

    Velikovich, A. L.

    2012-10-01

    Magnetic flux compression (MFC) as a method for producing ultra-high pulsed magnetic fields had been originated in the 1950s by Sakharov et al. at Arzamas in the USSR (now VNIIEF, Russia) and by Fowler et al. at Los Alamos in the US. The highest magnetic field produced by explosively driven MFC generator, 28 MG, was reported by Boyko et al. of VNIIEF. The idea of using MFC to increase the magnetic field in a magnetically confined plasma to 3-10 MG, relaxing the strict requirements on the plasma density and Lawson time, gave rise to the research area known as MTF in the US and MAGO in Russia. To make a difference in ICF, a magnetic field of ˜100 MG should be generated via MFC by a plasma liner as a part of the capsule compression scenario on a laser or pulsed power facility. This approach was first suggested in mid-1980s by Liberman and Velikovich in the USSR and Felber in the US. It has not been obvious from the start that it could work at all, given that so many mechanisms exist for anomalously fast penetration of magnetic field through plasma. And yet, many experiments stimulated by this proposal since 1986, mostly using pulsed-power drivers, demonstrated reasonably good flux compression up to ˜42 MG, although diagnostics of magnetic fields of such magnitude in HED plasmas is still problematic. The new interest of MFC in plasmas emerged with the advancement of new drivers, diagnostic methods and simulation tools. Experiments on MFC in a deuterium plasma filling a cylindrical plastic liner imploded by OMEGA laser beam led by Knauer, Betti et al. at LLE produced peak fields of 36 MG. The novel MagLIF approach to low-cost, high-efficiency ICF pursued by Herrmann, Slutz, Vesey et al. at Sandia involves pulsed-power-driven MFC to a peak field of ˜130 MG in a DT plasma. A review of the progress, current status and future prospects of MFC in plasmas is presented.

  20. Chaos in Magnetic Flux Ropes

    NASA Astrophysics Data System (ADS)

    Gekelman, W. N.; DeHaas, T.; Van Compernolle, B.

    2013-12-01

    Magnetic Flux Ropes Immersed in a uniform magnetoplasma are observed to twist about themselves, writhe about each other and rotate about a central axis. They are kink unstable and smash into one another as they move. Full three dimensional magnetic field and flows are measured at thousands of time steps. Each collision results in magnetic field line generation and the generation of a quasi-seperatrix layer and induced electric fields. Three dimensional magnetic field lines are computed by conditionally averaging the data using correlation techniques. The permutation entropy1 ,which is related to the Lyapunov exponent, can be calculated from the the time series of the magnetic field data (this is also done with flows) and used to calculate the positions of the data on a Jensen Shannon complexity map2. The location of data on this map indicates if the magnetic fields are stochastic, or fall into regions of minimal or maximal complexity. The complexity is a function of space and time. The complexity map, and analysis will be explained in the course of the talk. Other types of chaotic dynamical models such as the Lorentz, Gissinger and Henon process also fall on the map and can give a clue to the nature of the flux rope turbulence. The ropes fall in the region of the C-H plane where chaotic systems lie. The entropy and complexity change in space and time which reflects the change and possibly type of chaos associated with the ropes. The maps give insight as to the type of chaos (deterministic chaos, fractional diffusion , Levi flights..) and underlying dynamical process. The power spectra of much of the magnetic and flow data is exponential and Lorentzian structures in the time domain are embedded in them. Other quantities such as the Hurst exponent are evaluated for both magnetic fields and plasma flow. Work Supported by a UC-LANL Lab fund and the Basic Plasma Science Facility which is funded by DOE and NSF. 1) C. Bandt, B. Pompe, Phys. Rev. Lett., 88,174102 (2007) 2

  1. Flux trapping in superconducting thin films in weak magnetic fields

    NASA Astrophysics Data System (ADS)

    Geng, Q.; Goto, E.

    1993-11-01

    Magnetic-field distribution measurements over a patterned superconducting strip line sample were conducted using a superconducting quantum interference device pickup coil, showing that, in the range of 500 μG-50 mG of perpendicular magnetic field B⊥,i, the superconducting films record previous magnetic histories precisely. The magnetic-field distribution with a field B⊥,i applied at all times is identical to one with no field applied at any time. A calculation based on the flux trapping model explains these results indicating that all the magnetic fluxes penetrate the superconducting thin films.

  2. A time-varying magnetic flux concentrator

    NASA Astrophysics Data System (ADS)

    Kibret, B.; Premaratne, M.; Lewis, P. M.; Thomson, R.; Fitzgerald, P. B.

    2016-08-01

    It is known that diverse technological applications require the use of focused magnetic fields. This has driven the quest for controlling the magnetic field. Recently, the principles in transformation optics and metamaterials have allowed the realization of practical static magnetic flux concentrators. Extending such progress, here, we propose a time-varying magnetic flux concentrator cylindrical shell that uses electric conductors and ferromagnetic materials to guide magnetic flux to its center. Its performance is discussed based on finite-element simulation results. Our proposed design has potential applications in magnetic sensors, medical devices, wireless power transfer, and near-field wireless communications.

  3. Magnetic Flux Circulation in the Saturnian Magnetosphere Revisited

    NASA Astrophysics Data System (ADS)

    Lai, H.; Russell, C. T.; Jia, Y. D.; Masters, A.; Dougherty, M. K.

    2016-12-01

    The magnetic flux circulation in the magnetosphere of Saturn is driven by the plasma sources in the inner magnetosphere. The magnetic flux convects outward with the loaded cold plasma originated from Enceladus and the plasma torus, is emptied of plasma during tail reconnection events, and returns buoyantly to conserve the magnetic flux in the inner magnetosphere. Returning magnetic flux can be recognized in magnetic field data by the sharp changes in the field strength and in plasma data by the absence of cold plasma and appearance of hot particles. These hot particles are subject to gradient and curvature drift as they convect inward. This results in a dispersion of the hot particles that can be recognized in the energy-time spectrograms. Here we model the time evolution of the electron distribution. By comparing these models with Cassini observations, we can determine the age of the flux tubes, and can constrain the magnetic flux return. This greatly improves our quantitative understanding of the magnetic flux circulation at Saturn. This same model can be applied to Jovian magnetosphere, which is also a fast rotator driven by internal mass-loading. We compare the inferred magnetic flux transport in the two systems.

  4. Self-organization in magnetic flux ropes

    NASA Astrophysics Data System (ADS)

    Lukin, Vyacheslav S.

    2014-06-01

    This cross-disciplinary special issue on 'Self-organization in magnetic flux ropes' follows in the footsteps of another collection of manuscripts dedicated to the subject of magnetic flux ropes, a volume on 'Physics of magnetic flux ropes' published in the American Geophysical Union's Geophysical Monograph Series in 1990 [1]. Twenty-four years later, this special issue, composed of invited original contributions highlighting ongoing research on the physics of magnetic flux ropes in astrophysical, space and laboratory plasmas, can be considered an update on our state of understanding of this fundamental constituent of any magnetized plasma. Furthermore, by inviting contributions from research groups focused on the study of the origins and properties of magnetic flux ropes in a variety of different environments, we have attempted to underline both the diversity of and the commonalities among magnetic flux ropes throughout the solar system and, indeed, the universe. So, what is a magnetic flux rope? The answer will undoubtedly depend on whom you ask. A flux rope can be as narrow as a few Larmor radii and as wide as the Sun (see, e.g., the contributions by Heli Hietala et al and by Angelous Vourlidas). As described below by Ward Manchester IV et al , they can stretch from the Sun to the Earth in the form of interplanetary coronal mass ejections. Or, as in the Swarthmore Spheromak Experiment described by David Schaffner et al , they can fit into a meter-long laboratory device tended by college students. They can be helical and line-tied (see, e.g., Walter Gekelman et al or J Sears et al ), or toroidal and periodic (see, e.g., John O'Bryan et al or Philippa Browning et al ). They can form in the low plasma beta environment of the solar corona (Tibor Török et al ), the order unity beta plasmas of the solar wind (Stefan Eriksson et al ) and the plasma pressure dominated stellar convection zones (Nicholas Nelson and Mark Miesch). In this special issue, Setthivoine You

  5. Magnetic-Flux-Compression Cooling Using Superconductors

    NASA Technical Reports Server (NTRS)

    Strayer, Donald M.; Israelsson, Ulf E.; Elleman, Daniel D.

    1989-01-01

    Proposed magnetic-flux-compression refrigeration system produces final-stage temperatures below 4.2 K. More efficient than mechanical and sorption refrigerators at temperatures in this range. Weighs less than comparable liquid-helium-cooled superconducting magnetic refrigeration systems operating below 4.2 K. Magnetic-flux-compression cooling stage combines advantages of newly discovered superconductors with those of cooling by magnetization and demagnetization of paramagnetic salts.

  6. How the Saturnian Magnetosphere Conserves Magnetic Flux

    NASA Astrophysics Data System (ADS)

    Powell, R. L.; Wei, H.; Russell, C. T.; Arridge, C. S.; Dougherty, M. K.

    2012-12-01

    The magnetospheric dynamics at Saturn are driven by the centrifugal force of near co-rotating water group ions released at a rate of hundreds of kilograms per second by Saturn's moon Enceladus. The plasma is accelerated up to co-rotation speed by the magnetospheric magnetic field coupled to the Saturnian ionosphere. The plasma is lost ultimately through the process of magnetic reconnection in the tail. Conservation of magnetic flux requires that plasma-depleted, "empty" flux tubes return magnetic flux to the inner magnetosphere. After completion of the initial inrush of the reconnected and largely emptied flux tubes inward of the reconnection point, the flux tubes face the outflowing plasma and must move inward against the flow. Observations of such flux tubes have been identified in the eight years of Cassini magnetometer data. The occurrence of these tubes is observed at all local times indicating slow inward transport of the tubes relative to the co-rotation speed. Depleted flux tubes observed in the equatorial region appear as an enhancement in the magnitude of the magnetic field, whereas the same flux tubes observed at higher latitudes appear as decreased field strength. The difference in appearance of the low latitude and the high latitude tubes is due to the plasma environment just outside the tube. Warm low-density plasma fills the inside of the flux tube at all latitudes. This flux tube thus will expand in the less dense regions away from the magnetic equator and will be observed as a decrease in the magnitude of the magnetic field from the background. These flux tubes near the equator, where the plasma density outside of the flux tube is much greater, will be observed as an enhancement in the magnitude of the magnetic field. Cassini magnetometer and CAPS data are examined to understand the properties of these flux tubes and their radial and latitudinal evolution throughout the Saturnian magnetospheric environment.

  7. Magnetic hysteresis and magnetic flux patterns measured by acoustically stimulated electromagnetic response in a steel plate

    NASA Astrophysics Data System (ADS)

    Yamada, Hisato; Watanabe, Kakeru; Ikushima, Kenji

    2015-08-01

    Magnetic hysteresis loops are measured by ultrasonic techniques and used in visualizing the magnetic-flux distribution in a steel plate. The piezomagnetic coefficient determines the amplitude of acoustically stimulated electromagnetic (ASEM) fields, yielding the hysteresis behavior of the intensity of the ASEM response. By utilizing the high correspondence of the ASEM response to the magnetic-flux density, we image the specific spatial patterns of the flux density formed by an artificial defect in a steel plate specimen. Magnetic-flux probing by ultrasonic waves is thus shown to be a viable method of nondestructive material inspection.

  8. Regulation of the interplanetary magnetic flux

    SciTech Connect

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

    1991-01-01

    In this study we use a recently developed technique for measuring the 2-D magnetic flux in the ecliptic plane to examine (1) the long term variation of the magnetic flux in interplanetary space and (2) the apparent rate at which coronal mass ejections (CMEs) may be opening new flux from the Sun. Since there is a substantial variation ({approximately}50%) of the flux in the ecliptic plane over the solar cycle, we conclude that there must be some means whereby new flux can be opened from the Sun and previously open magnetic flux can be closed off. We briefly describe recently discovered coronal disconnections events which could serve to close off previously open magnetic flux. CMEs appear to retain at least partial magnetic connection to the Sun and hence open new flux, while disconnections appear to be likely signatures of the process that returns closed flux to the Sun; the combination of these processes could regulate the amount of open magnetic flux in interplanetary space. 6 refs., 3 figs.

  9. Magnetic flux noise in copper oxide superconductors

    SciTech Connect

    Ferrari, M.J.

    1991-11-01

    Magnetic flux noise and flux creep in thin films and single crystals of YBa{sub 2}Cu{sub 3}O{sub 7-x}, Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+x}, Tl{sub 2}Ca{sub 2}Ba{sub 2}Cu{sub 3}O{sub x}, and TlCa{sub 2}Ba{sub 2}Cu{sub 3}O{sub x} are measured with a superconducting quantum interference device (SQUID). The noise power spectrum generally scales as 1/f (f is frequency) from 1 Hz to 1 kHz, increases with temperature, and decreases in higher-quality films. It is proportional to the magnetic field B in which the sample is cooled, at least in the range 0.1 mT < B < 3 mT. A model of thermally activated vortex motion is developed which explains the dependence of the noise on frequency, temperature, current, and applied magnetic field. The pinning potential is idealized as an ensemble of double wells, each with a different activation energy separating the two states. From the noise measurements, this model yields the distribution of pinning energies in the samples, the vortex hopping distance, the number density of mobile vortices, and the restoring force on a vortex at a typical pinning site. The distribution of pinning energies in YBa{sub 2}Cu{sub 3}O{sub 7-x} shows a broad peak below 0.1 eV. The small ambient magnetic field, and the detection of noise even in the absence of a driving force, insure that the measured pinning energies are characteristic of isolated vortices near thermal equilibrium. The observed vortex density in fields much less than 0.1 mT is too large to be explained by the ambient field, suggesting a mechanism intrinsic to the sample which produces trapped vortices.

  10. Interplanetary magnetic flux: Measurement and balance

    SciTech Connect

    McComas, D.J.; Gosling, J.T.; Phillips, J.L. )

    1992-01-01

    The authors have developed a new method for determining the approximate magnetic flux content of the various solar wind structures in the ecliptic plane, using single-spacecraft measurements. The two-dimensional magnetic flux in a region of the solar wind is given by the integral of the radial magnetic field component over an arc perpendicular to the radial. Unfortunately, such measurements cannot be achieved with single (or even several) spacecraft in the solar wind. They will show that the desired two-dimensional, ecliptic plane magnetic flux integral, at least for regions with simple magnetic topologies, is equivalent to {phi} = {integral} B{sub y}{vert bar}v{vert bar}dt, where B{sub y} is the ecliptic plane field component perpendicular to the solar wind velocity vector v. Thus {phi} can be determined entirely from measured quantities. In this study they examine variations in the magnetic flux in the ecliptic plane over a 16-year interval. In addition, they address the question of the opening and closing of interplanetary magnetic flux by comparing the ecliptic plane flux content of both coronal mass ejections (CMEs) and heat flux droplets (HFDs). If CMEs remain at least partially attached to the Sun, they would serve to open new magnetic flux to the interplanetary medium. In contrast, flux could be closed off by reconnection across helmet streamers in the corona, leading to the release of U-shaped magnetic structures open to the outer heliosphere at both ends and to the return of closed arches to the Sun.

  11. Magnetic Flux Cancellation and Formation of Prominence

    NASA Astrophysics Data System (ADS)

    Miley, George; Kim, Mun Song; Chon Nam, Sok; Kim, Kyong Chol

    2015-08-01

    Magnetic flux cancellation appears to be closely related to various kinds of solar activities such as flares, microflares/surges/jets, X-ray bright points, erupting mini-filaments, transition region explosive events, filament formation, filament activation and eruption, and coronal mass ejections. It is commonly believed that magnetic reconnections in the low atmosphere are responsible for canceling magnetic features, and magnetic fragments are observed to originate as bipoles. According to the Sweet-Parker type reconnection model, the inflow speed closely corresponds to the converging speed of each pole in a canceling magnetic feature and the rate of flux cancellation must be explained by the observed converging speed. As distinct from the corona, the efficiency of photospheric magnetic reconnection may be due to the small Cowling conductivity, instead of the Spitzer, of weakly ionized and magnetized plasma in the low atmosphere of the sun. Using the VAL-C atmospheric model and Cowling conductivity, we have computed the parameters describing Sweet-Parker type reconnecting current sheets in the plasma of the solar photosphere and chromosphere, and particularly for the phenomena of magnetic flux cancellation and dark filament formation which occurred on July 2, 1994 we have estimated the rate of flux cancellation, the inflow speed(the converging speed) and the upward mass flux to compare with the observation. The results show that when taking account of the Cowling conductivity in the low atmosphere, large flux cancellation rates(>1019Mxhr-1) in solar active regions are better explained than by the Spitzer conductivity-considered reconnection model. Particularly for the flux cancellation event on July 2, 1994, the inflow speed(0.26kms-1)is almost similar to the converging speed(0.22kms-1)and the upward mass flux(3.3X1012gs-1) in the model is sufficient for the large dark filament formation in a time of several hours through magnetic flux cancellation process.

  12. Magnetic flux biasing of magnetostrictive sensors

    NASA Astrophysics Data System (ADS)

    Deng, Zhangxian; Dapino, Marcelo J.

    2017-05-01

    The performance of magnetostrictive materials, especially those with high initial magnetic permeability and associated low magnetic reluctance, is sensitive to not just the amount of magnetic bias but also how the bias is applied. Terfenol-D and Galfenol have been characterized under constant magnetic field and constant magnetomotive force, which require active control. The application of a magnetic flux bias utilizing permanent magnets allows for robust magnetostrictive systems that require no active control. However, this biasing configuration has not been thoroughly investigated. This study presents flux density versus stress major loops of Terfenol-D and Galfenol at various magnetic flux biases. A new piezomagnetic coefficient {d}33φ is defined as the locally-averaged slope of flux density versus stress. Considering the materials alone, the maximum {d}33φ is 18.42 T GPa-1 and 19.53 T GPa-1 for Terfenol-D and Galfenol, respectively. Compared with the peak piezomagnetic coefficient {d}33* measured under controlled magnetic fields, the piezomagnetic coefficient {d}33φ is 26% and 74% smaller for Terfenol-D and Galfenol, respectively. This study shows that adding parallel magnetic flux paths to low-reluctance magnetostrictive components can partially compensate for the performance loss. With a low carbon steel flux path in parallel to the Galfenol specimen, the maximum {d}33φ increased to 28.33 T GPa-1 corresponding to a 45% improvement compared with the case without a flux path. Due to its low magnetic permeability, Terfenol-D does not benefit from the addition of a parallel flux path.

  13. Strongly magnetized accretion discs require poloidal flux

    NASA Astrophysics Data System (ADS)

    Salvesen, Greg; Armitage, Philip J.; Simon, Jacob B.; Begelman, Mitchell C.

    2016-08-01

    Motivated by indirect observational evidence for strongly magnetized accretion discs around black holes, and the novel theoretical properties of such solutions, we investigate how a strong magnetization state can develop and persist. To this end, we perform local simulations of accretion discs with an initially purely toroidal magnetic field of equipartition strength. We demonstrate that discs with zero net vertical magnetic flux and realistic boundary conditions cannot sustain a strong toroidal field. However, a magnetic pressure-dominated disc can form from an initial configuration with a sufficient amount of net vertical flux and realistic boundary conditions. Our results suggest that poloidal flux is a necessary prerequisite for the sustainability of strongly magnetized accretion discs.

  14. Magnetic flux, Wilson line, and orbifold

    SciTech Connect

    Abe, Hiroyuki; Choi, Kang-Sin; Kobayashi, Tatsuo; Ohki, Hiroshi

    2009-12-15

    We study torus/orbifold models with magnetic flux and Wilson line backgrounds. The number of zero modes and their profiles depend on those backgrounds. That has interesting implications from the viewpoint of particle phenomenology.

  15. FLUX EMERGENCE IN A MAGNETIZED CONVECTION ZONE

    SciTech Connect

    Pinto, R. F.; Brun, A. S.

    2013-07-20

    We study the influence of a dynamo magnetic field on the buoyant rise and emergence of twisted magnetic flux ropes and their influence on the global external magnetic field. We ran three-dimensional MHD numerical simulations using the ASH code (anelastic spherical harmonics) and analyzed the dynamical evolution of such buoyant flux ropes from the bottom of the convection zone until the post-emergence phases. The global nature of this model can only very crudely and inaccurately represent the local dynamics of the buoyant rise of the implanted magnetic structure, but nonetheless allows us to study the influence of global effects, such as self-consistently generated differential rotation and meridional circulation, and of Coriolis forces. Although motivated by the solar context, this model cannot be thought of as a realistic model of the rise of magnetic structures and their emergence in the Sun, where the local dynamics are completely different. The properties of initial phases of the buoyant rise are determined essentially by the flux-rope's properties and the convective flows and consequently are in good agreement with previous studies. However, the effects of the interaction of the background dynamo field become increasingly strong as the flux ropes evolve. During the buoyant rise across the convection zone, the flux-rope's magnetic field strength scales as B{proportional_to}{rho}{sup {alpha}}, with {alpha} {approx}< 1. An increase of radial velocity, density, and current density is observed to precede flux emergence at all longitudes. The geometry, latitude, and relative orientation of the flux ropes with respect to the background magnetic field influences the resulting rise speeds, zonal flow amplitudes (which develop within the flux ropes), and the corresponding surface signatures. This influences the morphology, duration and amplitude of the surface shearing, and the Poynting flux associated with magnetic flux-rope emergence. The emerged magnetic flux

  16. Vector Magnetic Field in Emerging Flux Regions

    NASA Astrophysics Data System (ADS)

    Schmieder, B.; Pariat, E.

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

  17. Magnetohydrodynamic simulations of the ejection of a magnetic flux rope

    NASA Astrophysics Data System (ADS)

    Pagano, P.; Mackay, D. H.; Poedts, S.

    2013-06-01

    Context. Coronal mass ejections (CME's) are one of the most violent phenomena found on the Sun. One model to explain their occurrence is the flux rope ejection model. In this model, magnetic flux ropes form slowly over time periods of days to weeks. They then lose equilibrium and are ejected from the solar corona over a few hours. The contrasting time scales of formation and ejection pose a serious problem for numerical simulations. Aims: We simulate the whole life span of a flux rope from slow formation to rapid ejection and investigate whether magnetic flux ropes formed from a continuous magnetic field distribution, during a quasi-static evolution, can erupt to produce a CME. Methods: To model the full life span of magnetic flux ropes we couple two models. The global non-linear force-free field (GNLFFF) evolution model is used to follow the quasi-static formation of a flux rope. The MHD code ARMVAC is used to simulate the production of a CME through the loss of equilibrium and ejection of this flux rope. Results: We show that the two distinct models may be successfully coupled and that the flux rope is ejected out of our simulation box, where the outer boundary is placed at 2.5 R⊙. The plasma expelled during the flux rope ejection travels outward at a speed of 100 km s-1, which is consistent with the observed speed of CMEs in the low corona. Conclusions: Our work shows that flux ropes formed in the GNLFFF can lead to the ejection of a mass loaded magnetic flux rope in full MHD simulations. Coupling the two distinct models opens up a new avenue of research to investigate phenomena where different phases of their evolution occur on drastically different time scales. Movies are available in electronic form at http://www.aanda.org

  18. Magnetic refrigeration using flux compression in superconductors

    NASA Technical Reports Server (NTRS)

    Israelsson, U. E.; Strayer, D. M.; Jackson, H. W.; Petrac, D.

    1990-01-01

    The feasibility of using flux compression in high-temperature superconductors to produce the large time-varying magnetic fields required in a field cycled magnetic refrigerator operating between 20 K and 4 K is presently investigated. This paper describes the refrigerator concept and lists limitations and advantages in comparison with conventional refrigeration techniques. The maximum fields obtainable by flux compression in high-temperature supercoductor materials, as presently prepared, are too low to serve in such a refrigerator. However, reports exist of critical current values that are near usable levels for flux pumps in refrigerator applications.

  19. Magnetic flux ropes at planetary magnetopauses

    NASA Astrophysics Data System (ADS)

    Hasegawa, H.

    2015-12-01

    Magnetic flux ropes at the magnetopause are generated as a result of magnetopause reconnection involving more than one X-line, and constitute a subgroup of flux transfer events which are believed to result from transient, localized, and/or multiple X-line reconnection, i.e., time-dependent forms of magnetopause reconnection. Single X-line reconnection at the low-latitude magnetopause erodes the dayside closed field lines and contributes to magnetic flux transport into the magnetotail, which forms the basis for dynamic phenomena in the magnetosphere such as substorms and storms. On the other hand, multiple X-line reconnection can produce the field lines of various topologies and/or can cause complex interactions of reconnection jets or reconnected flux tubes, thus possibly reducing the efficiency of magnetic energy transfer into the tail. This presentation discusses in situ observations at the terrestrial, Hermean, and Kronian magnetopauses and models for the generation, of magnetic flux ropes. In particular, we emphasize that magnetic field (e.g., bipolar) signatures alone cannot be taken as evidence for the flux ropes, and plasma signatures (Alfvenic ion jets, electron pitch-angle anisotropy, etc.) help identify their topological structure. We also present our recent studies using multi-spacecraft (Cluster or THEMIS) measurements at the terrestrial magnetopause for the reconstruction of their two-dimensional and three-dimensional structures based on the Grad-Shafranov and magneto-hydrostatic equations, respectively.

  20. Heat flux viscosity in collisional magnetized plasmas

    SciTech Connect

    Liu, C.; Fox, W.; Bhattacharjee, A.

    2015-05-15

    Momentum transport in collisional magnetized plasmas due to gradients in the heat flux, a “heat flux viscosity,” is demonstrated. Even though no net particle flux is associated with a heat flux, in a plasma there can still be momentum transport owing to the velocity dependence of the Coulomb collision frequency, analogous to the thermal force. This heat-flux viscosity may play an important role in numerous plasma environments, in particular, in strongly driven high-energy-density plasma, where strong heat flux can dominate over ordinary plasma flows. The heat flux viscosity can influence the dynamics of the magnetic field in plasmas through the generalized Ohm's law and may therefore play an important role as a dissipation mechanism allowing magnetic field line reconnection. The heat flux viscosity is calculated directly using the finite-difference method of Epperlein and Haines [Phys. Fluids 29, 1029 (1986)], which is shown to be more accurate than Braginskii's method [S. I. Braginskii, Rev. Plasma Phys. 1, 205 (1965)], and confirmed with one-dimensional collisional particle-in-cell simulations. The resulting transport coefficients are tabulated for ease of application.

  1. Magnetic flux noise in copper oxide superconductors

    SciTech Connect

    Ferrari, Mark Joseph

    1991-11-01

    Magnetic flux noise and flux creep in thin films and single crystals of YBa2Cu3O7-x, Bi2Sr2CaCu2O8+x, Tl2Ca2Ba2Cu3Ox, and TlCa2Ba2Cu3Ox are measured with a superconducting quantum interference device (SQUID). The noise power spectrum generally scales as 1/f (f is frequency) from 1 Hz to 1 kHz, increases with temperature, and decreases in higher-quality films. It is proportional to the magnetic field B in which the sample is cooled, at least in the range 0.1 mT < B < 3 mT. A model of thermally activated vortex motion is developed which explains the dependence of the noise on frequency, temperature, current, and applied magnetic field. The pinning potential is idealized as an ensemble of double wells, each with a different activation energy separating the two states. From the noise measurements, this model yields the distribution of pinning energies in the samples, the vortex hopping distance, the number density of mobile vortices, and the restoring force on a vortex at a typical pinning site. The distribution of pinning energies in YBa2Cu3O7-x shows a broad peak below 0.1 eV. The small ambient magnetic field, and the detection of noise even in the absence of a driving force, insure that the measured pinning energies are characteristic of isolated vortices near thermal equilibrium. The observed vortex density in fields much less than 0.1 mT is too large to be explained by the ambient field, suggesting a mechanism intrinsic to the sample which produces trapped vortices.

  2. Magnetic Field Distribution for Massive Stars

    NASA Astrophysics Data System (ADS)

    Medvedev, A.; Kholtygin, A.

    2017-06-01

    A model of the evolution of an ensemble of magnetic massive stars on the main sequence is developed. We use our own population synthesis code, which allows us to obtain distributions of stars by radii, ages, masses, temperatures, effective magnetic fields, and magnetic fluxes from the pre-main sequence up to the TAMS stages. We assume that magnetic fields in massive stars decrease with time. The rate of magnetic field dissipation may depend on the mass of a star on ZAMS. The distribution of magnetic fluxes of the ZAMS stars is assumed to be log-normal. We show that such kind of distribution may be a result of the dynamo action occurring at the pre-MS evolutionary stage of magnetic stars. Our model also includes capabilities for statistical simulations and parameter estimation necessary for the analysis of real data. Comparison of model magnetic field distributions with those obtained from recent measurements of stellar magnetic fields allows us to conclude that the evolution of magnetic fields of massive stars is very slow if not absent. The shape of the real magnetic field distribution has no indications of the “magnetic desert,” previously suggested by Lignieres et al. (2014). Based on those findings we argue that the observed fraction of magnetic stars is determined only by physical conditions at early stages of stellar evolution.

  3. Flux-Feedback Magnetic-Suspension Actuator

    NASA Technical Reports Server (NTRS)

    Groom, Nelson J.

    1990-01-01

    Flux-feedback magnetic-suspension actuator provides magnetic suspension and control forces having linear transfer characteristics between force command and force output over large range of gaps. Hall-effect devices used as sensors for electronic feedback circuit controlling currents flowing in electromagnetic windings to maintain flux linking suspended element at substantially constant value independent of changes in length of gap. Technique provides effective method for maintenance of constant flux density in gap and simpler than previous methods. Applications include magnetic actuators for control of shapes and figures of antennas and of precise segmented reflectors, magnetic suspensions in devices for storage of angular momentum and/or kinetic energy, and systems for control, pointing, and isolation of instruments.

  4. Magnetic topology of emerging flux regions

    NASA Astrophysics Data System (ADS)

    Pariat, Etienne

    Coronal magnetic fields structure and governs the dynamics of the solar atmosphere. These magnetic fields are often complex, composed of multiples domains of magnetic-field-lines connectivity. The topology of the magnetic field allows a synthetic description of these complex magnetic field by highlighting the structural elements that are important for the dynamic and the activity of the corona. Topology identifies the key elements where magnetic reconnection will preferentially occurs, and allows to explain and predict the evolution of the coronal plasma. However the topological elements - such as null points, separatrices, separators - do not appear out of thin air. Along with energy, and helicity, the magnetic topology of an active region is build up as the consequence of flux emergence. Some topological elements, such as bald-patches, are even fully part of the mechanism of flux emergence mechanism and drive the evolution and the structuration of the coronal magnetic field as it crosses the lower layer of the solar atmosphere. In the present talk I will therefore review our current understanding of the formation of active region in terms of magnetic topology. I will speak on how the topological structures which are key to solar activity are formed. Meanwhile I'll also discus the topological properties of emerging active region and how topology influences the very process of flux emergence.

  5. Magnetic flux density in the heliosphere through several solar cycles

    SciTech Connect

    Erdős, G.; Balogh, A.

    2014-01-20

    We studied the magnetic flux density carried by solar wind to various locations in the heliosphere, covering a heliospheric distance range of 0.3-5.4 AU and a heliolatitudinal range from 80° south to 80° north. Distributions of the radial component of the magnetic field, B{sub R} , were determined over long intervals from the Helios, ACE, STEREO, and Ulysses missions, as well as from using the 1 AU OMNI data set. We show that at larger distances from the Sun, the fluctuations of the magnetic field around the average Parker field line distort the distribution of B{sub R} to such an extent that the determination of the unsigned, open solar magnetic flux density from the average (|B{sub R} |) is no longer justified. We analyze in detail two methods for reducing the effect of fluctuations. The two methods are tested using magnetic field and plasma velocity measurements in the OMNI database and in the Ulysses observations, normalized to 1 AU. It is shown that without such corrections for the fluctuations, the magnetic flux density measured by Ulysses around the aphelion phase of the orbit is significantly overestimated. However, the matching between the in-ecliptic magnetic flux density at 1 AU (OMNI data) and the off-ecliptic, more distant, normalized flux density by Ulysses is remarkably good if corrections are made for the fluctuations using either method. The main finding of the analysis is that the magnetic flux density in the heliosphere is fairly uniform, with no significant variations having been observed either in heliocentric distance or heliographic latitude.

  6. Radiation-induced magnetization reversal causing a large flux loss in undulator permanent magnets

    NASA Astrophysics Data System (ADS)

    Bizen, Teruhiko; Kinjo, Ryota; Hasegawa, Teruaki; Kagamihata, Akihiro; Kida, Yuichiro; Seike, Takamitsu; Watanabe, Takahiro; Hara, Toru; Itoga, Toshiro; Asano, Yoshihiro; Tanaka, Takashi

    2016-11-01

    We report an unexpectedly large flux loss observed in permanent magnets in one of the undulators operated in SACLA, the x-ray free electron laser facility in Japan. Characterizations of individual magnets extracted from the relevant undulator have revealed that the flux loss was caused by a homogeneous magnetization reversal extending over a wide area, but not by demagnetization of individual magnets damaged by radiation. We show that the estimated flux-loss rate is much higher than what is reported in previous papers, and its distribution is much more localized to the upstream side. Results of numerical and experimental studies carried out to validate the magnetization reversal and quantify the flux loss are presented, together with possible countermeasures against rapid degradation of the undulator performance.

  7. Radiation-induced magnetization reversal causing a large flux loss in undulator permanent magnets

    PubMed Central

    Bizen, Teruhiko; Kinjo, Ryota; Hasegawa, Teruaki; Kagamihata, Akihiro; Kida, Yuichiro; Seike, Takamitsu; Watanabe, Takahiro; Hara, Toru; Itoga, Toshiro; Asano, Yoshihiro; Tanaka, Takashi

    2016-01-01

    We report an unexpectedly large flux loss observed in permanent magnets in one of the undulators operated in SACLA, the x-ray free electron laser facility in Japan. Characterizations of individual magnets extracted from the relevant undulator have revealed that the flux loss was caused by a homogeneous magnetization reversal extending over a wide area, but not by demagnetization of individual magnets damaged by radiation. We show that the estimated flux-loss rate is much higher than what is reported in previous papers, and its distribution is much more localized to the upstream side. Results of numerical and experimental studies carried out to validate the magnetization reversal and quantify the flux loss are presented, together with possible countermeasures against rapid degradation of the undulator performance. PMID:27897218

  8. Radiation-induced magnetization reversal causing a large flux loss in undulator permanent magnets.

    PubMed

    Bizen, Teruhiko; Kinjo, Ryota; Hasegawa, Teruaki; Kagamihata, Akihiro; Kida, Yuichiro; Seike, Takamitsu; Watanabe, Takahiro; Hara, Toru; Itoga, Toshiro; Asano, Yoshihiro; Tanaka, Takashi

    2016-11-29

    We report an unexpectedly large flux loss observed in permanent magnets in one of the undulators operated in SACLA, the x-ray free electron laser facility in Japan. Characterizations of individual magnets extracted from the relevant undulator have revealed that the flux loss was caused by a homogeneous magnetization reversal extending over a wide area, but not by demagnetization of individual magnets damaged by radiation. We show that the estimated flux-loss rate is much higher than what is reported in previous papers, and its distribution is much more localized to the upstream side. Results of numerical and experimental studies carried out to validate the magnetization reversal and quantify the flux loss are presented, together with possible countermeasures against rapid degradation of the undulator performance.

  9. Plasmas fluxes to surfaces for an oblique magnetic field

    SciTech Connect

    Pitcher, C.S. ); Stangeby, P.C.; Elder, J.D. ); Bell, M.G.; Kilpatrick, S.J.; Manos, D.M.; Medley, S.S.; Owens, D.K.; Ramsey, A.T.; Ulrickson, M. . Plasma Physics Lab.)

    1992-07-01

    The poloidal and toroidal spatial distributions of D{sub {alpha}}, He I and C II emission have been obtained in the vicinity of the TFTR bumper limiter and are compared with models of ion flow to the surface. The distributions are found not to agree with a model (the Cosine'' model) which determines the incident flux density using only the parallel fluxes in the scrape-off layer and the projected area of the surface perpendicular to the field lines. In particular, the Cosine model is not able to explain the significant fluxes observed at locations on the surface which are oblique to the magnetic field. It is further shown that these fluxes cannot be explained by the finite Larmor radius of impinging ions. Finally, it is demonstrated, with the use of Monte Carlo codes, that the distributions can be explained by including both parallel and cross-field transport onto the limiter surface.

  10. Plasmas fluxes to surfaces for an oblique magnetic field

    SciTech Connect

    Pitcher, C.S.; Stangeby, P.C.; Elder, J.D.; Bell, M.G.; Kilpatrick, S.J.; Manos, D.M.; Medley, S.S.; Owens, D.K.; Ramsey, A.T.; Ulrickson, M.

    1992-07-01

    The poloidal and toroidal spatial distributions of D{sub {alpha}}, He I and C II emission have been obtained in the vicinity of the TFTR bumper limiter and are compared with models of ion flow to the surface. The distributions are found not to agree with a model (the ``Cosine`` model) which determines the incident flux density using only the parallel fluxes in the scrape-off layer and the projected area of the surface perpendicular to the field lines. In particular, the Cosine model is not able to explain the significant fluxes observed at locations on the surface which are oblique to the magnetic field. It is further shown that these fluxes cannot be explained by the finite Larmor radius of impinging ions. Finally, it is demonstrated, with the use of Monte Carlo codes, that the distributions can be explained by including both parallel and cross-field transport onto the limiter surface.

  11. Color magnetic flux tubes in dense QCD

    SciTech Connect

    Eto, Minoru; Nitta, Muneto

    2009-12-15

    QCD is expected to be in the color-flavor locking phase in high baryon density, which exhibits color superconductivity. The most fundamental topological objects in the color superconductor are non-Abelian vortices which are topologically stable color magnetic flux tubes. We present numerical solutions of the color magnetic flux tube for diverse choices of the coupling constants based on the Ginzburg-Landau Lagrangian. We also analytically study its asymptotic profiles and find that they are different from the case of usual superconductors. We propose the width of color magnetic fluxes and find that it is larger than naive expectation of the Compton wavelength of the massive gluon when the gluon mass is larger than the scalar mass.

  12. Solar cycle variation of magnetic flux emergence

    NASA Technical Reports Server (NTRS)

    Davis, J. M.; Golub, L.; Kreiger, A. S.

    1977-01-01

    The number of X-ray bright points (XBP) has been measured from solar X-ray images obtained during two rocket flights in 1976. When compared with the data obtained during the Skylab mission (1973), the number is found to be higher by a factor of 2. As the probability of obtaining the result by chance is less than 1 in 5 million, it is concluded that the number of XBP has increased in the three year interval. As all other indicators of activity have decreased between 1973 and 1976, the cyclical variation of the short-lifetime end of the magnetic-flux-emergence spectrum is out of phase with the solar cycle as defined by active regions or sunspots. Since XBP in 1973 contributed more to the emerging magnetic flux than did active regions, the possibility exists that the total amount of emerging magnetic flux may be maximized at a sunspot minimum.

  13. Magnetic flux reconstruction methods for shaped tokamaks

    NASA Astrophysics Data System (ADS)

    Tsui, Chi-Wa

    1993-12-01

    The use of a variational method permits the Grad-Shafranov (GS) equation to be solved by reducing the problem of solving the two dimensional nonlinear partial differential equation to the problem of minimizing a function of several variables. This high speed algorithm approximately solves the GS equation given a parameterization of the plasma boundary and the current profile (p' and FF' functions). The current profile parameters are treated as unknowns. The goal is to reconstruct the internal magnetic flux surfaces of a tokamak plasma and the toroidal current density profile from the external magnetic measurements. This is a classic problem of inverse equilibrium determination. The current profile parameters can be evaluated by several different matching procedures. Matching of magnetic flux and field at the probe locations using the Biot-Savart law and magnetic Green's function provides a robust method of magnetic reconstruction. The matching of poloidal magnetic field on the plasma surface provides a unique method of identifying the plasma current profile. However, the power of this method is greatly compromised by the experimental errors of the magnetic signals. The Casing principle provides a very fast way to evaluate the plasma contribution to the magnetic signals. It has the potential of being a fast matching method. The performance of this method is hindered by the accuracy of the poloidal magnetic field computed from the equilibrium solver. A flux reconstruction package has been implemented which integrates a vacuum field solver using a filament model for the plasma, a multilayer perception neural network as an interface, and the volume integration of plasma current density using Green's functions as a matching method for the current profile parameters. The flux reconstruction package is applied to compare with the ASEQ and EFIT data.

  14. MAGNETIC FLUX SUPPLEMENT TO CORONAL BRIGHT POINTS

    SciTech Connect

    Mou, Chaozhou; Huang, Zhenghua; Xia, Lidong; Li, Bo; Fu, Hui; Jiao, Fangran; Hou, Zhenyong; Madjarska, Maria S.

    2016-02-10

    Coronal bright points (BPs) are associated with magnetic bipolar features (MBFs) and magnetic cancellation. Here we investigate how BP-associated MBFs form and how the consequent magnetic cancellation occurs. We analyze longitudinal magnetograms from the Helioseismic and Magnetic Imager to investigate the photospheric magnetic flux evolution of 70 BPs. From images taken in the 193 Å passband of the Atmospheric Imaging Assembly (AIA) we dermine that the BPs’ lifetimes vary from 2.7 to 58.8 hr. The formation of the BP MBFs is found to involve three processes, namely, emergence, convergence, and local coalescence of the magnetic fluxes. The formation of an MBF can involve more than one of these processes. Out of the 70 cases, flux emergence is the main process of an MBF buildup of 52 BPs, mainly convergence is seen in 28, and 14 cases are associated with local coalescence. For MBFs formed by bipolar emergence, the time difference between the flux emergence and the BP appearance in the AIA 193 Å passband varies from 0.1 to 3.2 hr with an average of 1.3 hr. While magnetic cancellation is found in all 70 BPs, it can occur in three different ways: (I) between an MBF and small weak magnetic features (in 33 BPs); (II) within an MBF with the two polarities moving toward each other from a large distance (34 BPs); (III) within an MBF whose two main polarities emerge in the same place simultaneously (3 BPs). While an MBF builds up the skeleton of a BP, we find that the magnetic activities responsible for the BP heating may involve small weak fields.

  15. Magnetic Flux Supplement to Coronal Bright Points

    NASA Astrophysics Data System (ADS)

    Mou, Chaozhou; Huang, Zhenghua; Xia, Lidong; Madjarska, Maria S.; Li, Bo; Fu, Hui; Jiao, Fangran; Hou, Zhenyong

    2016-02-01

    Coronal bright points (BPs) are associated with magnetic bipolar features (MBFs) and magnetic cancellation. Here we investigate how BP-associated MBFs form and how the consequent magnetic cancellation occurs. We analyze longitudinal magnetograms from the Helioseismic and Magnetic Imager to investigate the photospheric magnetic flux evolution of 70 BPs. From images taken in the 193 Å passband of the Atmospheric Imaging Assembly (AIA) we dermine that the BPs’ lifetimes vary from 2.7 to 58.8 hr. The formation of the BP MBFs is found to involve three processes, namely, emergence, convergence, and local coalescence of the magnetic fluxes. The formation of an MBF can involve more than one of these processes. Out of the 70 cases, flux emergence is the main process of an MBF buildup of 52 BPs, mainly convergence is seen in 28, and 14 cases are associated with local coalescence. For MBFs formed by bipolar emergence, the time difference between the flux emergence and the BP appearance in the AIA 193 Å passband varies from 0.1 to 3.2 hr with an average of 1.3 hr. While magnetic cancellation is found in all 70 BPs, it can occur in three different ways: (I) between an MBF and small weak magnetic features (in 33 BPs); (II) within an MBF with the two polarities moving toward each other from a large distance (34 BPs); (III) within an MBF whose two main polarities emerge in the same place simultaneously (3 BPs). While an MBF builds up the skeleton of a BP, we find that the magnetic activities responsible for the BP heating may involve small weak fields.

  16. Magnetic flux reconstruction methods for shaped tokamaks

    SciTech Connect

    Tsui, Chi-Wa

    1993-12-01

    The use of a variational method permits the Grad-Shafranov (GS) equation to be solved by reducing the problem of solving the 2D non-linear partial differential equation to the problem of minimizing a function of several variables. This high speed algorithm approximately solves the GS equation given a parameterization of the plasma boundary and the current profile (p` and FF` functions). The author treats the current profile parameters as unknowns. The goal is to reconstruct the internal magnetic flux surfaces of a tokamak plasma and the toroidal current density profile from the external magnetic measurements. This is a classic problem of inverse equilibrium determination. The current profile parameters can be evaluated by several different matching procedures. Matching of magnetic flux and field at the probe locations using the Biot-Savart law and magnetic Green`s function provides a robust method of magnetic reconstruction. The matching of poloidal magnetic field on the plasma surface provides a unique method of identifying the plasma current profile. However, the power of this method is greatly compromised by the experimental errors of the magnetic signals. The Casing Principle provides a very fast way to evaluate the plasma contribution to the magnetic signals. It has the potential of being a fast matching method. The performance of this method is hindered by the accuracy of the poloidal magnetic field computed from the equilibrium solver. A flux reconstruction package has been implemented which integrates a vacuum field solver using a filament model for the plasma, a multi-layer perception neural network as an interface, and the volume integration of plasma current density using Green`s functions as a matching method for the current profile parameters. The flux reconstruction package is applied to compare with the ASEQ and EFIT data. The results are promising.

  17. MAGNETIC FLUX TUBE INTERCHANGE AT THE HELIOPAUSE

    SciTech Connect

    Florinski, V.

    2015-11-01

    The magnetic field measured by Voyager 1 prior to its heliocliff encounter on 2012.65 showed an unexpectedly complex transition from the primarily azimuthal inner-heliosheath field to the draped interstellar field tilted by some 20° to the nominal azimuthal direction. Most prominent were two regions of enhanced magnetic field strength depleted in energetic charged particles of heliospheric origin. These regions were interpreted as magnetic flux tubes connected to the outer heliosheath that provided a path for the particles to escape. Despite large increases in strength, the field’s direction did not change appreciably at the boundaries of these flux tubes. Rather, the field’s direction changed gradually over several months prior to the heliocliff crossing. It is shown theoretically that the heliopause, as a pressure equilibrium layer, can become unstable to interchange of magnetic fields between the inner and the outer heliosheaths. The curvature of magnetic field lines and the anti-sunward gradient in plasma kinetic pressure provide conditions favorable for an interchange. Magnetic shear between the heliosheath and the interstellar fields reduces the growth rates, but does not fully stabilize the heliopause against perturbations propagating in the latitudinal direction. The instability could create a transition layer permeated by magnetic flux tubes, oriented parallel to each other and alternately connected to the heliosheath or the interstellar regions.

  18. The dynamics of magnetic flux rings

    NASA Technical Reports Server (NTRS)

    Deluca, E. E.; Fisher, G. H.; Patten, B. M.

    1993-01-01

    The evolution of magnetic fields in the presence of turbulent convection is examined using results of numerical simulations of closed magnetic flux tubes embedded in a steady 'ABC' flow field, which approximate some of the important characteristics of a turbulent convecting flow field. Three different evolutionary scenarios were found: expansion to a steady deformed ring; collapse to a compact fat flux ring, separated from the expansion type of behavior by a critical length scale; and, occasionally, evolution toward an advecting, oscillatory state. The work suggests that small-scale flows will not have a strong effect on large-scale, strong fields.

  19. Magnetic flux penetration into superconducting thin films.

    NASA Technical Reports Server (NTRS)

    Peabody, G. E.; Meservey, R.

    1972-01-01

    The quantum-interference technique developed by Meservey (1965) is used to measure directly the absolute value of the penetration depth in lead in tin superconducting thin films. The technique assumes that the change in phase of the superconducting wave function around any contour within the superconductor must be 2 pi n, where n is a nonnegative integer. Results show that the critical current of a superconducting interferometer with two parallel junctions is not strictly periodic in the applied magnetic flux with a period equal to the flux quantum because of the magnetic field dependence of the critical currents of the junctions.

  20. Magnetic Flux Cancellation in Ellerman Bombs

    NASA Astrophysics Data System (ADS)

    Reid, A.; Mathioudakis, M.; Doyle, J. G.; Scullion, E.; Nelson, C. J.; Henriques, V.; Ray, T.

    2016-06-01

    Ellerman Bombs (EBs) are often found to be co-spatial with bipolar photospheric magnetic fields. We use Hα imaging spectroscopy along with Fe i 6302.5 Å spectropolarimetry from the Swedish 1 m Solar Telescope (SST), combined with data from the Solar Dynamic Observatory, to study EBs and the evolution of the local magnetic fields at EB locations. EBs are found via an EB detection and tracking algorithm. Using NICOLE inversions of the spectropolarimetric data, we find that, on average, (3.43 ± 0.49) × 1024 erg of stored magnetic energy disappears from the bipolar region during EB burning. The inversions also show flux cancellation rates of 1014-1015 Mx s-1 and temperature enhancements of 200 K at the detection footpoints. We investigate the near-simultaneous flaring of EBs due to co-temporal flux emergence from a sunspot, which shows a decrease in transverse velocity when interacting with an existing, stationary area of opposite polarity magnetic flux, resulting in the formation of the EBs. We also show that these EBs can be fueled further by additional, faster moving, negative magnetic flux regions.

  1. Photospheric Magnetic Flux Transport - Supergranules Rule

    NASA Technical Reports Server (NTRS)

    Hathaway, David H.; Rightmire-Upton, Lisa

    2012-01-01

    Observations of the transport of magnetic flux in the Sun's photosphere show that active region magnetic flux is carried far from its origin by a combination of flows. These flows have previously been identified and modeled as separate axisymmetric processes: differential rotation, meridional flow, and supergranule diffusion. Experiments with a surface convective flow model reveal that the true nature of this transport is advection by the non-axisymmetric cellular flows themselves - supergranules. Magnetic elements are transported to the boundaries of the cells and then follow the evolving boundaries. The convective flows in supergranules have peak velocities near 500 m/s. These flows completely overpower the superimposed 20 m/s meridional flow and 100 m/s differential rotation. The magnetic elements remain pinned at the supergranule boundaries. Experiments with and without the superimposed axisymmetric photospheric flows show that the axisymmetric transport of magnetic flux is controlled by the advection of the cellular pattern by underlying flows representative of deeper layers. The magnetic elements follow the differential rotation and meridional flow associated with the convection cells themselves -- supergranules rule!

  2. Magnetic Flux Transients during Solar Flares

    NASA Astrophysics Data System (ADS)

    Balasubramaniam, K. S.; Delgado, F.; Hock, R. A.

    2013-12-01

    Solar flares result from the sudden release of energy stored in the magnetic field of the solar atmosphere, attributed to magnetic reconnection. In this work, we use line-of-sight magnetograms to study the changes in photospheric magnetic field during large solar flares. The magnetograms are derived from observations using NASA's Helioseismic and Magnetic Imager onboard the Solar Dynamics Observatory, and have a cadence of 3 minutes at a 0.5 arcsecond spatial resolution. We studied the inferred magnetic flux changes in 11 X-class flares from (2011-2012) and 26 M-class flares (2011). Of the 37 flares, 32 exhibited short-lived (less than 30 minutes) magnetic flux transients (MFTs) during the progress of the flare, similar to those by Maurya et al. (2012). We note that MFTs were co-temporal with GOES X-ray peaks. Flares with rapid rises (impulsive flares) had stronger transients while those with slower rises (gradual flares) had weak or no MFTs. Finally, flares with stronger GOES X-ray peaks (flare class) showed stronger MFTs. We believe that these changes are non-physical because the changes in the magnetic field are transient (the magnetic field returns to the pre-flare state) and coincide with the impulsive phase of the flare. This work supported by the US Airforce Office of Scientific Research and the AFRL/RV Space Scholar Program.

  3. Synthetic magnetic fluxes on the honeycomb lattice

    SciTech Connect

    Gorecka, Agnieszka; Gremaud, Benoit; Miniatura, Christian

    2011-08-15

    We devise experimental schemes that are able to mimic uniform and staggered magnetic fluxes acting on ultracold two-electron atoms, such as ytterbium atoms, propagating in a honeycomb lattice. The atoms are first trapped into two independent state-selective triangular lattices and then further exposed to a suitable configuration of resonant Raman laser beams. These beams induce hops between the two triangular lattices and make atoms move in a honeycomb lattice. Atoms traveling around each unit cell of this honeycomb lattice pick up a nonzero phase. In the uniform case, the artificial magnetic flux sustained by each cell can reach about two flux quanta, thereby realizing a cold-atom analog of the Harper model with its notorious Hofstadter's butterfly structure. Different condensed-matter phenomena such as the relativistic integer and fractional quantum Hall effects, as observed in graphene samples, could be targeted with this scheme.

  4. Synthetic magnetic fluxes on the honeycomb lattice

    NASA Astrophysics Data System (ADS)

    Górecka, Agnieszka; Grémaud, Benoît; Miniatura, Christian

    2011-08-01

    We devise experimental schemes that are able to mimic uniform and staggered magnetic fluxes acting on ultracold two-electron atoms, such as ytterbium atoms, propagating in a honeycomb lattice. The atoms are first trapped into two independent state-selective triangular lattices and then further exposed to a suitable configuration of resonant Raman laser beams. These beams induce hops between the two triangular lattices and make atoms move in a honeycomb lattice. Atoms traveling around each unit cell of this honeycomb lattice pick up a nonzero phase. In the uniform case, the artificial magnetic flux sustained by each cell can reach about two flux quanta, thereby realizing a cold-atom analog of the Harper model with its notorious Hofstadter’s butterfly structure. Different condensed-matter phenomena such as the relativistic integer and fractional quantum Hall effects, as observed in graphene samples, could be targeted with this scheme.

  5. Magnetic flux noise in strongly anisotropic superconductors

    NASA Astrophysics Data System (ADS)

    Ashkenazy, V. D.; Jung, G.; Shapiro, B. Ya.

    1995-04-01

    Magnetic noise due to thermally activated movements of flux vortices has been calculated taking into account fluctuations modes of nonrigid vortices. It has been shown that at low frequencies, below the crossover frequency, the noise spectrum of a layered superconductor is identical to that of a continuous material. Three regimes of spectral behavior, lnω, ω-1/2, and ω-3/2, have been predicted to be present in this frequency range. Characteristic frequencies separating different regimes depend on the geometry of the flux pickup loop. At high frequencies, above the crossover frequency, bending of vortices leads to a Lorentzian shape of noise spectra. The value of the crossover frquency is not influenced by the particularities of the flux-measuring arrangement and depends only on the material properties and applied magnetic field.

  6. Magnetic flux concentrations in a polytropic atmosphere

    NASA Astrophysics Data System (ADS)

    Losada, I. R.; Brandenburg, A.; Kleeorin, N.; Rogachevskii, I.

    2014-04-01

    Context. Strongly stratified hydromagnetic turbulence has recently been identified as a candidate for explaining the spontaneous formation of magnetic flux concentrations by the negative effective magnetic pressure instability (NEMPI). Much of this work has been done for isothermal layers, in which the density scale height is constant throughout. Aims: We now want to know whether earlier conclusions regarding the size of magnetic structures and their growth rates carry over to the case of polytropic layers, in which the scale height decreases sharply as one approaches the surface. Methods: To allow for a continuous transition from isothermal to polytropic layers, we employ a generalization of the exponential function known as the q-exponential. This implies that the top of the polytropic layer shifts with changing polytropic index such that the scale height is always the same at some reference height. We used both mean-field simulations (MFS) and direct numerical simulations (DNS) of forced stratified turbulence to determine the resulting flux concentrations in polytropic layers. Cases of both horizontal and vertical applied magnetic fields were considered. Results: Magnetic structures begin to form at a depth where the magnetic field strength is a small fraction of the local equipartition field strength with respect to the turbulent kinetic energy. Unlike the isothermal case where stronger fields can give rise to magnetic flux concentrations at larger depths, in the polytropic case the growth rate of NEMPI decreases for structures deeper down. Moreover, the structures that form higher up have a smaller horizontal scale of about four times their local depth. For vertical fields, magnetic structures of super-equipartition strengths are formed, because such fields survive downward advection that causes NEMPI with horizontal magnetic fields to reach premature nonlinear saturation by what is called the "potato-sack" effect. The horizontal cross-section of such

  7. Helioseismic Detection of Emerging Magnetic Flux

    NASA Astrophysics Data System (ADS)

    Ilonidis, S.; Zhao, J.; Kosovichev, A. G.

    2012-09-01

    Investigating the properties of magnetic flux emergence is one of the most important problems of solar physics. In this study we present a newly developed deep-focus time-distance measurement scheme which is able to detect strong emerging flux events in the deep solar interior, before the flux becomes visible on the surface. We discuss in detail the differences between our method and previous methods, and demonstrate step-by-step how the signal-to-noise (S/N) ratio is increased. The method is based on detection of perturbations in acoustic phase travel times determined from cross-covariances of solar oscillations observed on the surface. We detect strong acoustic travel-time reductions of an order of 12 - 16 seconds at a depth of 42 - 75 Mm. These acoustic anomalies are detected 1 - 2 days before high peaks in the photospheric magnetic flux rate implying that the average emerging speed is 0.3 - 0.6 km s-1. The results of this work contribute to our understanding of solar magnetism and benefit space weather forecasting.

  8. Ion and electron velocity distributions within flux transfer events

    NASA Technical Reports Server (NTRS)

    Thomsen, M. F.; Stansberry, J. A.; Bame, S. J.; Fuselier, S. A.; Gosling, J. T.

    1987-01-01

    The detailed nature of the thermal and suprathermal ion and electron distributions within magnetic flux transfer events (FTEs) is examined. Examples of both magnetosheath FTEs and magnetospheric FTEs are discussed. The detailed distributions confirm that FTEs contain a mixture of magnetosheath and magnetospheric plasmas. To lowest order, the distributions are consistent with a simple superposition of the two interpenetrating populations, with no strong interactions between them. To first order, some interesting differences appear, especially in the electron distributions, suggesting that considerable pitch angle scattering and some electron energy diffusion are also occurring. These observations should provide a useful test of analytical and numerical studies of interpenetrating plasmas.

  9. Coronal Magnetic Flux Ropes in Quadrupolar Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Zhang, Yingzhi; Hu, Youqiu; Wang, Jingxiu

    Using a 2.5-D, time-dependent ideal MHD model in spherical coordinates, we carry out a numerical study of the equilibrium properties of coronal magnetic flux ropes in a quadrupolar background magnetic field. For such a flux rope system, a catastrophic occurs: the flux rope is detached from the photosphere and jumps to a finite altitude with a vertical current sheet below. There is a transversal current sheet formed above the rope, and the whole system stays in quasi-equilibrium. We argue that the additional Lorentz force provided by the transversal current sheet on the flux rope plays an important role in keeping the system in quasi-equilibrium in the corona.

  10. Interplanetary magnetic flux - Measurement and balance

    NASA Technical Reports Server (NTRS)

    Mccomas, D. J.; Gosling, J. T.; Phillips, J. L.

    1992-01-01

    A new method for determining the approximate amount of magnetic flux in various solar wind structures in the ecliptic (and solar rotation) plane is developed using single-spacecraft measurements in interplanetary space and making certain simplifying assumptions. The method removes the effect of solar wind velocity variations and can be applied to specific, limited-extent solar wind structures as well as to long-term variations. Over the 18-month interval studied, the ecliptic plane flux of coronal mass ejections was determined to be about 4 times greater than that of HFDs.

  11. Stochastic flux freezing and magnetic dynamo

    SciTech Connect

    Eyink, Gregory L.

    2011-05-15

    Magnetic flux conservation in turbulent plasmas at high magnetic Reynolds numbers is argued neither to hold in the conventional sense nor to be entirely broken, but instead to be valid in a statistical sense associated to the ''spontaneous stochasticity'' of Lagrangian particle trajectories. The latter phenomenon is due to the explosive separation of particles undergoing turbulent Richardson diffusion, which leads to a breakdown of Laplacian determinism for classical dynamics. Empirical evidence is presented for spontaneous stochasticity, including numerical results. A Lagrangian path-integral approach is then exploited to establish stochastic flux freezing for resistive hydromagnetic equations and to argue, based on the properties of Richardson diffusion, that flux conservation must remain stochastic at infinite magnetic Reynolds number. An important application of these results is the kinematic, fluctuation dynamo in nonhelical, incompressible turbulence at magnetic Prandtl number (Pr{sub m}) equal to unity. Numerical results on the Lagrangian dynamo mechanisms by a stochastic particle method demonstrate a strong similarity between the Pr{sub m}=1 and 0 dynamos. Stochasticity of field-line motion is an essential ingredient of both. Finally, some consequences for nonlinear magnetohydrodynamic turbulence, dynamo, and reconnection are briefly considered.

  12. Characteristics of soft magnetic composite material under rotating magnetic fluxes

    NASA Astrophysics Data System (ADS)

    Zhong, J. J.; Guo, Y. G.; Zhu, J. G.; Lin, Z. W.

    2006-04-01

    This paper reports the measurement of magnetic properties of the soft magnetic composite material SOMALOY TM 500 in a square sample under different patterns of flux density with 2D magnetic excitations. The test system, principle of measurement, magnetic power loss calculation, and methods of correction for misalignment of H surface sensing coils are presented. The experimental results show that although nominally isotropic, the SOMALOY TM 500 sample exhibits some anisotropy. The results are useful in the design and performance analysis of rotating electrical machines.

  13. Magnetic Flux Reconstruction Methods for Shaped Tokamaks

    NASA Astrophysics Data System (ADS)

    Tsui, Chi-Wa.

    The use of a variational method permits the Grad -Shafranov (GS) equation to be solved by reducing the problem of solving the 2D non-linear partial differential equation to the problem of minimizing a function of several variables. This high speed algorithm approximately solves the GS equation given a pararmeterization of the plasma boundary and the current profile (p^' and FF^' functions). We treat the current profile parameters as unknowns. The goal is to reconstruct the internal magnetic flux surfaces of a tokamak plasma and the toroidal current density profile from the external magnetic measurements. This is a classic problem of inverse equilibrium determination. The current profile parameters can be evaluated by several different matching procedures. We found that the matching of magnetic flux and field at the probe locations using the Biot-Savart law and magnetic Green's function provides a robust method of magnetic reconstruction. The matching of poloidal magnetic field on the plasma surface provides a unique method of identifying the plasma current profile. However, the power of this method is greatly compromised by the experimental errors of the magnetic signals. The Casing Principle (60) provides a very fast way to evaluate the plasma contribution to the magnetic signals. It has the potential of being a fast matching method. We found that the performance of this method is hindered by the accuracy of the poloidal magnetic field computed from the equilibrium solver. A flux reconstruction package have been implemented which integrates a vacuum field solver using a filament model for the plasma, a multi-layer perceptron neural network as a interface, and the volume integration of plasma current density using Green's functions as a matching method for the current profile parameters. The flux reconstruction package is applied to compare with the ASEQ and EFIT data. The results are promising. Also, we found that some plasmas in the tokamak Alcator C-Mod lie

  14. Magnetic Flux Compression Experiments Using Plasma Armatures

    NASA Technical Reports Server (NTRS)

    Turner, M. W.; Hawk, C. W.; Litchford, R. J.

    2003-01-01

    Magnetic flux compression reaction chambers offer considerable promise for controlling the plasma flow associated with various micronuclear/chemical pulse propulsion and power schemes, primarily because they avoid thermalization with wall structures and permit multicycle operation modes. The major physical effects of concern are the diffusion of magnetic flux into the rapidly expanding plasma cloud and the development of Rayleigh-Taylor instabilities at the plasma surface, both of which can severely degrade reactor efficiency and lead to plasma-wall impact. A physical parameter of critical importance to these underlying magnetohydrodynamic (MHD) processes is the magnetic Reynolds number (R(sub m), the value of which depends upon the product of plasma electrical conductivity and velocity. Efficient flux compression requires R(sub m) less than 1, and a thorough understanding of MHD phenomena at high magnetic Reynolds numbers is essential to the reliable design and operation of practical reactors. As a means of improving this understanding, a simplified laboratory experiment has been constructed in which the plasma jet ejected from an ablative pulse plasma gun is used to investigate plasma armature interaction with magnetic fields. As a prelude to intensive study, exploratory experiments were carried out to quantify the magnetic Reynolds number characteristics of the plasma jet source. Jet velocity was deduced from time-of-flight measurements using optical probes, and electrical conductivity was measured using an inductive probing technique. Using air at 27-inHg vacuum, measured velocities approached 4.5 km/s and measured conductivities were in the range of 30 to 40 kS/m.

  15. Nonlinear nanodevices using magnetic flux quanta.

    PubMed

    Ooi, S; Savel'ev, Sergey; Gaifullin, M B; Mochiku, T; Hirata, K; Nori, Franco

    2007-11-16

    All devices realized so far that control the motion of magnetic flux quanta employ either samples with nanofabricated spatially-asymmetric potentials (which strongly limit controllability), or pristine superconductors rectifying with low-efficiency time-asymmetric oscillations of an external magnetic field. Using layered Bi2Sr2CaCu2O8+delta materials, here we fabricate and simulate two efficient nonlinear superconducting devices with no spatial asymmetry. These devices can rectify with high-efficiency a two-harmonic external current dragging vortices in target directions by changing either the relative phase or the frequency ratio of the two harmonics.

  16. Noisy dynamics of magnetic flux in mesoscopic cylinders

    NASA Astrophysics Data System (ADS)

    Dajka, J.; Luczka, J.; Mierzejewski, M.; Hänggi, P.

    2006-02-01

    We study magnetic fluxes and currents in mesoscopic systems of cylindrical symmetry like rings, toroids and cylinders. We analyze the time evolution of the magnetic flux and the characteristic time of a formation of the ordered state. We investigate how, starting from some symmetric initial state, the magnetic flux or the current approach their corresponding asymptotic state.

  17. Magnetic-Flux-Compensated Voltage Divider

    NASA Technical Reports Server (NTRS)

    Mata, Carlos T.

    2005-01-01

    A magnetic-flux-compensated voltage-divider circuit has been proposed for use in measuring the true potential across a component that is exposed to large, rapidly varying electric currents like those produced by lightning strikes. An example of such a component is a lightning arrester, which is typically exposed to currents of the order of tens of kiloamperes, having rise times of the order of hundreds of nanoseconds. Traditional voltage-divider circuits are not designed for magnetic-flux-compensation: They contain uncompensated loops having areas large enough that the transient magnetic fluxes associated with large transient currents induce spurious voltages large enough to distort voltage-divider outputs significantly. A drawing of the proposed circuit was not available at the time of receipt of information for this article. What is known from a summary textual description is that the proposed circuit would contain a total of four voltage dividers: There would be two mixed dividers in parallel with each other and with the component of interest (e.g., a lightning arrester), plus two mixed dividers in parallel with each other and in series with the component of interest in the same plane. The electrical and geometric configuration would provide compensation for induced voltages, including those attributable to asymmetry in the volumetric density of the lightning or other transient current, canceling out the spurious voltages and measuring the true voltage across the component.

  18. Magnetic flux concentrations from turbulent stratified convection

    NASA Astrophysics Data System (ADS)

    Käpylä, P. J.; Brandenburg, A.; Kleeorin, N.; Käpylä, M. J.; Rogachevskii, I.

    2016-04-01

    Context. The formation of magnetic flux concentrations within the solar convection zone leading to sunspot formation is unexplained. Aims: We study the self-organization of initially uniform sub-equipartition magnetic fields by highly stratified turbulent convection. Methods: We perform simulations of magnetoconvection in Cartesian domains representing the uppermost 8.5-24 Mm of the solar convection zone with the horizontal size of the domain varying between 34 and 96 Mm. The density contrast in the 24 Mm deep models is more than 3 × 103 or eight density scale heights, corresponding to a little over 12 pressure scale heights. We impose either a vertical or a horizontal uniform magnetic field in a convection-driven turbulent flow in set-ups where no small-scale dynamos are present. In the most highly stratified cases we employ the reduced sound speed method to relax the time step constraint arising from the high sound speed in the deep layers. We model radiation via the diffusion approximation and neglect detailed radiative transfer in order to concentrate on purely magnetohydrodynamic effects. Results: We find that super-equipartition magnetic flux concentrations are formed near the surface in cases with moderate and high density stratification, corresponding to domain depths of 12.5 and 24 Mm. The size of the concentrations increases as the box size increases and the largest structures (20 Mm horizontally near the surface) are obtained in the models that are 24 Mm deep. The field strength in the concentrations is in the range of 3-5 kG, almost independent of the magnitude of the imposed field. The amplitude of the concentrations grows approximately linearly in time. The effective magnetic pressure measured in the simulations is positive near the surface and negative in the bulk of the convection zone. Its derivative with respect to the mean magnetic field, however, is positive in most of the domain, which is unfavourable for the operation of the negative

  19. Stop of magnetic flux movement in levitating superconductor

    NASA Astrophysics Data System (ADS)

    Smolyak, B. M.; Zakharov, M. S.

    2017-01-01

    A phenomenon of magnetic relaxation stopping in a levitating superconductor was studied. It was experimentally shown that magnetic flux creep (diffusion of flux lines to regions with lower vortex density) is absent in magnetic suspension of the superconductor. Magnetic relaxation arises, when a rigid constraint that fixes a position of the superconductor relative to a magnet is imposed on a levitating object. It is assumed that oscillations of magnetic structure, which is due to free oscillations of the levitating superconductor, stop magnetic relaxation.

  20. Statistical Flux Tube Properties of 3D Magnetic Carpet Fields

    NASA Astrophysics Data System (ADS)

    Close, R. M.; Parnell, C. E.; Mackay, D. H.; Priest, E. R.

    2003-02-01

    The quiet-Sun photosphere consists of numerous magnetic flux fragments of both polarities that evolve with granular and supergranular flow fields. These concentrations give rise to a web of intermingled magnetic flux tubes which characterise the coronal magnetic field. Here, the nature of these flux tubes is studied. The photosphere is taken to be the source plane and each photospheric fragment is represented by a series of point sources. By analysing the potential field produced by these sources, it is found that the distribution of flux tube lengths obtained by (i) integrating forward from positive sources and (ii) tracing back from negative sources is highly dependent on the total flux imbalance within the region of interest. It is established that the relation between the footpoint separation of a flux tube and its height cannot be assumed to be linear. Where there is a significant imbalance of flux within a region, it is found that fragments of the dominant polarity will have noticeably more connections, on average, than the minority polarity fragments. Despite this difference, the flux from a single fragment of either polarity is typically divided such that (i) 60-70% connects to one opposite-polarity fragment, (ii) 25-30% goes to a further 1 to 2 opposite-polarity fragments, and (iii) any remaining flux may connect to as many as another 50 or more other opposite-polarity fragments. This is true regardless of any flux imbalance within the region. It is found that fragments connect preferentially to their nearest neighbours, with, on average, around 60-70% of flux closing down within 10 Mm of a typical fragment. Only 50% of the flux in a quiet region extends higher than 2.5 Mm above the solar surface and 5-10% extends higher than 25 Mm. The fragments that contribute to the field above this height cover a range of sizes, with even the smallest of fragments contributing to the field at heights of over 50 Mm.

  1. Magnetic flux stabilizing thin accretion discs

    NASA Astrophysics Data System (ADS)

    Sądowski, Aleksander

    2016-10-01

    We calculate the minimal amount of large-scale poloidal magnetic field that has to thread the inner, radiation-over-gas pressure dominated region of a thin disc for its thermal stability. Such a net field amplifies the magnetization of the saturated turbulent state and makes it locally stable. For a 10 M⊙ black hole the minimal magnetic flux is 10^{24}(dot{M}/dot{M}_Edd)^{20/21} G cm2. This amount is compared with the amount of uniform magnetic flux that can be provided by the companion star - estimated to be in the range 1022-1024 G cm2. If accretion rate is large enough, the companion is not able to provide the required amount and such a system, if still sub-Eddington, must be thermally unstable. The peculiar variability of GRS 1915+105, an X-ray binary with the exceptionally high BH mass and near-Eddington luminosity, may result from the shortage of large-scale poloidal field of uniform polarity.

  2. Slip Running Reconnection in Magnetic Flux Ropes

    NASA Astrophysics Data System (ADS)

    Gekelman, W. N.; Van Compernolle, B.; Vincena, S. T.; De Hass, T.

    2012-12-01

    Magnetic flux ropes are due to helical currents and form a dense carpet of arches on the surface of the sun. Occasionally one tears loose as a coronal mass ejection and its rope structure can be detected by satellites close to the earth. Current sheets can tear into filaments and these are nothing other than flux ropes. Ropes are not static, they exert mutual ěc{J}×ěc{B} forces causing them to twist about each other and eventually merge. Kink instabilities cause them to violently smash into each other and reconnect at the point of contact. We report on experiments on two adjacent ropes done in the large plasma device (LAPD) at UCLA ( ne ˜ 1012, Te ˜ 6 eV, B0z=330G, Brope}\\cong{10G,trep=1 Hz). The currents and magnetic fields form exotic shapes with no ignorable direction and no magnetic nulls. Volumetric space-time data (70,600 spatial locations) show multiple reconnection sites with time-dependent locations. The concept of a quasi-separatrix layer (QSL), a tool to understand and visualize 3D magnetic field lines reconnection without null points is introduced. Three-dimensional measurements of the QSL derived from magnetic field data are presented. Within the QSL field lines that start close to one another rapidly diverge as they pass through one or more reconnection regions. The motion of magnetic field lines are traced as reconnection proceeds and they are observed to slip through the regions of space where the QSL is largest. As the interaction proceeds we double the current in the ropes. This accompanied by intense heating as observed in uv light and plasma flows measured by Mach probes. The interaction of the ropes is clearly seen by vislaulizng magnetic field data , as well as in images from a fast framing camera. Work supported by the Dept. of Energy and The National Science Foundation, done at the Basic Plasma Science Facility at UCLA.Magnetic Field lines (measured) of three flux ropes and the plasma currents associated with them

  3. SEED BANKS FOR MAGNETIC FLUX COMPRESSION GENERATORS

    SciTech Connect

    Fulkerson, E S

    2008-05-14

    In recent years the Lawrence Livermore National Laboratory (LLNL) has been conducting experiments that require pulsed high currents to be delivered into inductive loads. The loads fall into two categories (1) pulsed high field magnets and (2) the input stage of Magnetic Flux Compression Generators (MFCG). Three capacitor banks of increasing energy storage and controls sophistication have been designed and constructed to drive these loads. One bank was developed for the magnet driving application (20kV {approx} 30kJ maximum stored energy.) Two banks where constructed as MFCG seed banks (12kV {approx} 43kJ and 26kV {approx} 450kJ). This paper will describe the design of each bank including switching, controls, circuit protection and safety.

  4. Exploring ISEE-3 magnetic cloud polarities with electron heat fluxes

    NASA Astrophysics Data System (ADS)

    Kahler, S. W.; Crooker, N. U.; Gosling, J. T.

    1999-06-01

    We have used solar wind electron heat fluxes to determine the magnetic polarities of the interplanetary magnetic fields (IMF) during the ISEE-3 observations in 1978-1982. That period included 14 magnetic clouds (MCs) identified by Zhang and Burlaga. The MCs have been modeled as single magnetic flux ropes, and it is generally assumed that they are magnetically closed structures with each end of the flux rope connected to the Sun. The flux rope model is valid only if the magnetic polarity of each MC does not change during the passage of ISEE-3 through the MC. We test this model with the heat flux data, using the dominant heat flux in bidirectional electron heat fluxes to determine the MC polarities. The polarity changes within at least 2, and possibly 6, of the 14 MCs, meaning that those MCs can not fit the model of a single flux rope.

  5. Linear magnetic motor/generator. [to generate electric energy using magnetic flux for spacecraft power supply

    NASA Technical Reports Server (NTRS)

    Studer, P. A. (Inventor)

    1982-01-01

    A linear magnetic motor/generator is disclosed which uses magnetic flux to provide mechanical motion or electrical energy. The linear magnetic motor/generator includes an axially movable actuator mechanism. A permament magnet mechanism defines a first magnetic flux path which passes through a first end portion of the actuator mechanism. Another permament magnet mechanism defines a second magnetic flux path which passes through a second end portion of the actuator mechanism. A drive coil defines a third magnetic flux path passing through a third central portion of the actuator mechanism. A drive coil selectively adds magnetic flux to and subtracts magnetic flux from magnetic flux flowing in the first and second magnetic flux path.

  6. Nonlinear oscillations of coalescing magnetic flux ropes

    NASA Astrophysics Data System (ADS)

    Kolotkov, Dmitrii Y.; Nakariakov, Valery M.; Rowlands, George

    2016-05-01

    An analytical model of highly nonlinear oscillations occurring during a coalescence of two magnetic flux ropes, based upon two-fluid hydrodynamics, is developed. The model accounts for the effect of electric charge separation, and describes perpendicular oscillations of the current sheet formed by the coalescence. The oscillation period is determined by the current sheet thickness, the plasma parameter β , and the oscillation amplitude. The oscillation periods are typically greater or about the ion plasma oscillation period. In the nonlinear regime, the oscillations of the ion and electron concentrations have a shape of a narrow symmetric spikes.

  7. Permanent-magnet switched-flux machine

    DOEpatents

    Trzynadlowski, Andrzej M.; Qin, Ling

    2011-06-14

    A permanent-magnet switched-flux (PMSF) device has an outer rotor mounted to a shaft about a central axis extending axially through the PMSF device. First and second pluralities of permanent-magnets (PMs) are respectively mounted in first and second circles, radially outwardly in first and second transverse planes extending from first and second sections of the central axis adjacent to an inner surface of the outer rotor. An inner stator is coupled to the shaft and has i) a stator core having a core axis co-axial with the central axis; and ii) first and second pluralities of stator poles mounted in first and second circles, radially outwardly from the stator core axis in the first and second transverse planes. The first and second pluralities of PMs each include PMs of alternating polarity.

  8. Permanent-magnet switched-flux machine

    DOEpatents

    Trzynadlowski, Andrzej M.; Qin, Ling

    2010-01-12

    A permanent-magnet switched-flux (PMSF) device has a ferromagnetic outer stator mounted to a shaft about a central axis extending axially through the PMSF device. Pluralities of top and bottom stator poles are respectively mounted in first and second circles, radially outwardly in first and second transverse planes extending from first and second sections of the central axis adjacent to an inner surface of the ferromagnetic outer stator. A ferromagnetic inner rotor is coupled to the shaft and has i) a rotor core having a core axis co-axial with the central axis; and ii) first and second discs having respective outer edges with first and second pluralities of permanent magnets (PMs) mounted in first and second circles, radially outwardly from the rotor core axis in the first and second transverse planes. The first and second pluralities of PMs each include PMs of alternating polarity.

  9. Permanent-magnet switched-flux machine

    DOEpatents

    Trzynadlowski, Andrzej M.; Qin, Ling

    2012-02-21

    A permanent-magnet switched-flux (PMSF) device has an outer rotor mounted to a shaft about a central axis extending axially through the PMSF device. First and second pluralities of permanent-magnets (PMs) are respectively mounted in first and second circles, radially outwardly in first and second transverse planes extending from first and second sections of the central axis adjacent to an inner surface of the outer rotor. An inner stator is coupled to the shaft and has i) a stator core having a core axis co-axial with the central axis; and ii) first and second pluralities of stator poles mounted in first and second circles, radially outwardly from the stator core axis in the first and second transverse planes. The first and second pluralities of PMs each include PMs of alternating polarity.

  10. Downward Catastrophe of Solar Magnetic Flux Ropes

    NASA Astrophysics Data System (ADS)

    Zhang, Quanhao; Wang, Yuming; Hu, Youqiu; Liu, Rui

    2016-07-01

    2.5-dimensional time-dependent ideal magnetohydrodynamic (MHD) models in Cartesian coordinates were used in previous studies to seek MHD equilibria involving a magnetic flux rope embedded in a bipolar, partially open background field. As demonstrated by these studies, the equilibrium solutions of the system are separated into two branches: the flux rope sticks to the photosphere for solutions at the lower branch but is suspended in the corona for those at the upper branch. Moreover, a solution originally at the lower branch jumps to the upper, as the related control parameter increases and reaches a critical value, and the associated jump is here referred to as an upward catastrophe. The present paper advances these studies in three aspects. First, the magnetic field is changed to be force-free; the system still experiences an upward catastrophe with an increase in each control parameter. Second, under the force-free approximation, there also exists a downward catastrophe, characterized by the jump of a solution from the upper branch to the lower. Both catastrophes are irreversible processes connecting the two branches of equilibrium solutions so as to form a cycle. Finally, the magnetic energy in the numerical domain is calculated. It is found that there exists a magnetic energy release for both catastrophes. The Ampère's force, which vanishes everywhere for force-free fields, appears only during the catastrophes and does positive work, which serves as a major mechanism for the energy release. The implications of the downward catastrophe and its relevance to solar activities are briefly discussed.

  11. Automatic magnetic flux measurement of micro plastic-magnetic rotors

    NASA Astrophysics Data System (ADS)

    Wang, Qingdong; Lin, Mingxing; Song, Aiwei

    2015-07-01

    Micro plastic-magnetic rotors of various sizes and shapes are widely used in industry, their magnetic flux measurement is one of the most important links in the production process, and therefore some technologies should be adopted to improve the measurement precision and efficiency. In this paper, the automatic measurement principle of micro plastic-magnetic rotors is proposed and the integration time constant and the integrator drift’s suppression and compensation in the measurement circuit are analyzed. Two other factors influencing the measurement precision are also analyzed, including the relative angles between the rotor magnetic poles and the measurement coil, and the starting point of the rotors in the coil where the measurement begins. An instrument is designed to measure the magnetic flux of the rotors. Measurement results show that the measurement error is within  ±1%, which meets the basic requirements in industry application, and the measurement efficiency is increased by 10 times, which can cut down labor cost and management cost when compared with manual measurement.

  12. Magnetohydrostatic Equilibrium. II. Three-dimensional Multiple Open Magnetic Flux Tubes in the Stratified Solar Atmosphere

    NASA Astrophysics Data System (ADS)

    Gent, F. A.; Fedun, V.; Erdélyi, R.

    2014-07-01

    A system of multiple open magnetic flux tubes spanning the solar photosphere and lower corona is modeled analytically, within a realistic stratified atmosphere subject to solar gravity. This extends results for a single magnetic flux tube in magnetohydrostatic equilibrium, described in Gent et al. Self-similar magnetic flux tubes are combined to form magnetic structures, which are consistent with high-resolution observations. The observational evidence supports the existence of strands of open flux tubes and loops persisting in a relatively steady state. Self-similar magnetic flux tubes, for which an analytic solution to the plasma density and pressure distribution is possible, are combined. We calculate the appropriate balancing forces, applying to the equations of momentum and energy conservation to preserve equilibrium. Multiplex flux tube configurations are observed to remain relatively stable for up to a day or more, and it is our aim to apply our model as the background condition for numerical studies of energy transport mechanisms from the solar surface to the corona. We apply magnetic field strength, plasma density, pressure, and temperature distributions consistent with observational and theoretical estimates for the lower solar atmosphere. Although each flux tube is identical in construction apart from the location of the radial axis, combinations can be applied to generate a non-axisymmetric magnetic field with multiple non-uniform flux tubes. This is a considerable step forward in modeling the realistic magnetized three-dimensional equilibria of the solar atmosphere.

  13. Magnetohydrostatic equilibrium. II. Three-dimensional multiple open magnetic flux tubes in the stratified solar atmosphere

    SciTech Connect

    Gent, F. A.; Erdélyi, R.; Fedun, V.

    2014-07-01

    A system of multiple open magnetic flux tubes spanning the solar photosphere and lower corona is modeled analytically, within a realistic stratified atmosphere subject to solar gravity. This extends results for a single magnetic flux tube in magnetohydrostatic equilibrium, described in Gent et al. Self-similar magnetic flux tubes are combined to form magnetic structures, which are consistent with high-resolution observations. The observational evidence supports the existence of strands of open flux tubes and loops persisting in a relatively steady state. Self-similar magnetic flux tubes, for which an analytic solution to the plasma density and pressure distribution is possible, are combined. We calculate the appropriate balancing forces, applying to the equations of momentum and energy conservation to preserve equilibrium. Multiplex flux tube configurations are observed to remain relatively stable for up to a day or more, and it is our aim to apply our model as the background condition for numerical studies of energy transport mechanisms from the solar surface to the corona. We apply magnetic field strength, plasma density, pressure, and temperature distributions consistent with observational and theoretical estimates for the lower solar atmosphere. Although each flux tube is identical in construction apart from the location of the radial axis, combinations can be applied to generate a non-axisymmetric magnetic field with multiple non-uniform flux tubes. This is a considerable step forward in modeling the realistic magnetized three-dimensional equilibria of the solar atmosphere.

  14. Topology of magnetic flux ropes and formation of fossil flux transfer events and boundary layer plasmas

    NASA Technical Reports Server (NTRS)

    Lee, L. C.; Ma, Z. W.; Fu, Z. F.; Otto, A.

    1993-01-01

    A mechanism for the formation of fossil flux transfer events and the low-level boundary layer within the framework of multiple X-line reconnection is proposed. Attention is given to conditions for which the bulk of magnetic flux in a flux rope of finite extent has a simple magnetic topology, where the four possible connections of magnetic field lines are: IMF to MSP, MSP to IMF, IMF to IMF, and MSP to MSP. For a sufficient relative shift of the X lines, magnetic flux may enter a flux rope from the magnetosphere and exit into the magnetosphere. This process leads to the formation of magnetic flux ropes which contain a considerable amount of magnetosheath plasma on closed magnetospheric field lines. This process is discussed as a possible explanation for the formation of fossil flux transfer events in the magnetosphere and the formation of the low-latitude boundary layer.

  15. Topology of magnetic flux ropes and formation of fossil flux transfer events and boundary layer plasmas

    NASA Technical Reports Server (NTRS)

    Lee, L. C.; Ma, Z. W.; Fu, Z. F.; Otto, A.

    1993-01-01

    A mechanism for the formation of fossil flux transfer events and the low-level boundary layer within the framework of multiple X-line reconnection is proposed. Attention is given to conditions for which the bulk of magnetic flux in a flux rope of finite extent has a simple magnetic topology, where the four possible connections of magnetic field lines are: IMF to MSP, MSP to IMF, IMF to IMF, and MSP to MSP. For a sufficient relative shift of the X lines, magnetic flux may enter a flux rope from the magnetosphere and exit into the magnetosphere. This process leads to the formation of magnetic flux ropes which contain a considerable amount of magnetosheath plasma on closed magnetospheric field lines. This process is discussed as a possible explanation for the formation of fossil flux transfer events in the magnetosphere and the formation of the low-latitude boundary layer.

  16. Magnetic-flux quanta in superconducting thin films observed by electron holography and digital phase analysis

    SciTech Connect

    Hasegawa, S.; Matsuda, T.; Endo, J.; Osakabe, N.; Igarashi, M.; Kobayashi, T.; Naito, M.; Tonomura, A. ); Aoki, R. )

    1991-04-01

    Singly quantized magnetic fluxes in superconducting lead films have been directly observed in the form of magnetic-flux-line distributions by using an electron-holography technique. Combining this with the digital-phase-analysis method, we were able to determine the flux quantum {ital h}/2{ital e} for individual fluxes with a precision of {similar to}{ital h}/100{ital e}, and analyze the distributions of field-vector components around the fluxon centers. The internal-field distributions obtained were compared with those calculated from the Ginzburg-Landau equations with use of some models, and an overall agreement was found between them. We also observed the changes of the magnetic-flux structures of lead thin films as a function of their thickness. Fluxon pairs were observed in 0.2-{mu}m-thick films, which may correspond to those suggested by Kosterlitz-Thouless theory.

  17. Flux distributions and colors of accretion disks

    NASA Technical Reports Server (NTRS)

    Pacharintanakul, P.; Katz, J. I.

    1980-01-01

    The disk model of Shakura and Sunyaev (1973) and Novikov and Thorne (1973) is used to calculate temperature distributions and integrated spectral fluxes for disks around a typical white dwarf and a typical neutron star, under the assumption that each element of the disk locally radiates as a blackbody. In addition, the disks' integrated UBV colors are calculated using the grid colors for real model atmospheres calculated by Buser and Kurucz (1978) and the observed colors given by Allen (1973). In all the calculations the effect of radiation from one part of the disk on all the other parts is included.

  18. Peculiarities of the magnetic flux emerging in the equatorial solar zone

    NASA Astrophysics Data System (ADS)

    Merzlyakov, V. L.; Starkova, L. I.

    2016-12-01

    The magnetic flux longitudinal distribution in the equatorial solar zone has been studied. The magnetic synoptic maps of the Wilcox Solar Observatory (WSO) during Carrington rotations (CRs) 2052-2068 in 2007 and early 2008 have been analyzed. The longitudinal distributions of the area of the zones where the photospheric magnetic field locally enhanced have been constructed for each CR. The obtained distributions indicate that the zones are located discretely and that a clearly defined one narrow longitudinal interval with the maximum flux is present. The longitudinal position of this maximum shifted discretely by ≈130° at an interval of 5.5 ± 0.5 CRs. A longitudinal shift of the zones with an increased magnetic flux multiple of 60° was observed between the hemispheres. In addition, a time shift of ≈2.5 CRs existed between the instants when the position of maximum fluxes in different hemispheres shifted. The established peculiarities of the magnetic flux longitudinal distribution and time dynamics are interpreted as an action of supergiant convection cells. These actions result in that magnetic fields are removed from the generation region through the channels that are formed between such cells at a longitudinal interval of 120°. The average synodic rotation velocity of the considered equatorial channels, through which the magnetic flux emerges, is 13.43° day-1.

  19. Magnetic Flux Emergence into the Solar Corona. I. Its Role for the Reversal of Global Coronal Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Zhang, M.; Low, B. C.

    2001-11-01

    Some physical insights into how the corona reverses its global magnetic field are described in this paper based on a set of elementary hydromagnetic calculations. We assume that a fresh magnetic field of opposite polarity has emerged into a corona containing a preexisting magnetic field. The inevitable magnetic reconnection that takes place between the two magnetic flux systems may result in an expulsion of magnetic flux to infinity. Our calculations suggest the following physical story of the coronal reversal process: When the emerged flux exceeds the preexisting flux by a critical amount, the corona will reverse its polarity. Before this critical ratio is attained, the field with the emerged flux may have enough energy to let only one or two bipolar parts of the multipolar field open up. This opening-up process, taking place as a coronal mass ejection (CME), may take some of the preexisting flux out of the corona and thus increase the emerged-to-preexisting flux ratio and bring the corona closer to the critical value for its global magnetic reversal. Our calculations also indicate that it is possible that the position where the field opens up may be different from that where the new flux emerges. This may help explain the difference in the latitude distribution of active regions and CMEs during a solar cycle as observed by Hundhausen.

  20. Compressed magnetic flux amplifier with capacitive load

    SciTech Connect

    Stuetzer, O.M.

    1980-03-01

    A first-order analysis is presented for a compressed magnetic flux (CMF) current amplifier working into a load with a capacitive component. Since the purpose of the investigation was to gain a general understanding of the arrangement, a number of approximations and limitations were accepted. The inductance of the transducer varies with time; the inductance/resistance/capacitance (LRC) circuit therefore is parametric and solutions are different for the stable regime (high C), the oscillation regime (low C), and the transition case. Solutions and performance depend strongly on circuit boundary conditions, i.e., energization of the circuit by either an injected current or by an applied capacitor charge. The behavior of current and energy amplification for the various cases are discussed in detail. A number of experiments with small CMF devices showed that the first-order theory presented predicts transducer performance well in the linear regime.

  1. Magnetic nerve stimulation without interlinkage between nerve and magnetic flux

    SciTech Connect

    Ueno, S.; Harada, K.; Ji, C.; Oomura, Y.

    1984-09-01

    A new method of magnetic stimulation of nerves is proposed. Nerves are located on a core aperture outside the core which is implanted in the body. Nerves can be stimulated by the secondary currents which flow in the body fluids around the core when the magnetic flux in the core is changed. One of the advantages in this method is to be able to avoid the interlinkage between the core and nerves. The equivalent resistance of tissues around the core is calculated, and current density for nerve excitation is estimated. The validity of the new method is demonstrated by experiments using frog nerve-muscle preparations. The results show that the nerve can be excited by a change of magnetic flux which generates an EMF of 0.8-volts peak amplitude and 0.8-ms duration in a monitor wire. The current density in the vicinity of the core aperture for nerve excitation is 3.2 mA/cm/sup 2/.

  2. Relationships of a growing magnetic flux region to flares

    NASA Technical Reports Server (NTRS)

    Martin, S. F.; Bentley, R. D.; Schadee, A.; Antalova, A.; Kucera, A.; Dezso, L.; Gesztelyi, L.; Harvey, K. L.; Jones, H.; Livi, S. H. B.

    1984-01-01

    The evolution of flare sites at the boundaries of major new and growing magnetic flux regions within complexes of active regions has been analyzed using H-alpha images. A spectrum of possible relationships of growing flux regions to flares is described. An 'intimate' interaction between old and new flux and flare sites occurs at the boundaries of their regions. Forced or 'intimidated' interaction involves new flux pushing older, lower flux density fields toward a neighboring old polarity inversion line, followed by the occurrence of a flare. In 'influential' interaction, magnetic lines of force over an old polarity inversion line reconnect to new emerging flux, and a flare occurs when the magnetic field overlying the filament becomes too weak to prevent its eruption. 'Inconsequential' interaction occurs when a new flux region is too small or has the wrong orientation for creating flare conditions. 'Incidental' interaction involves a flare occurring without any significant relationship to new flux regions.

  3. Relationships of a growing magnetic flux region to flares

    NASA Technical Reports Server (NTRS)

    Martin, S. F.; Bentley, R. D.; Schadee, A.; Antalova, A.; Kucera, A.; Dezso, L.; Gesztelyi, L.; Harvey, K. L.; Jones, H.; Livi, S. H. B.

    1984-01-01

    The evolution of flare sites at the boundaries of major new and growing magnetic flux regions within complexes of active regions has been analyzed using H-alpha images. A spectrum of possible relationships of growing flux regions to flares is described. An 'intimate' interaction between old and new flux and flare sites occurs at the boundaries of their regions. Forced or 'intimidated' interaction involves new flux pushing older, lower flux density fields toward a neighboring old polarity inversion line, followed by the occurrence of a flare. In 'influential' interaction, magnetic lines of force over an old polarity inversion line reconnect to new emerging flux, and a flare occurs when the magnetic field overlying the filament becomes too weak to prevent its eruption. 'Inconsequential' interaction occurs when a new flux region is too small or has the wrong orientation for creating flare conditions. 'Incidental' interaction involves a flare occurring without any significant relationship to new flux regions.

  4. Structures of interplanetary magnetic flux ropes and comparison with their solar sources

    SciTech Connect

    Hu, Qiang; Dasgupta, B.; Khare, A.; Webb, G. M. E-mail: qiu@physics.montana.edu

    2014-09-20

    Whether a magnetic flux rope is pre-existing or formed in situ in the Sun's atmosphere, there is little doubt that magnetic reconnection is essential to release the flux rope during its ejection. During this process, the question remains: how does magnetic reconnection change the flux-rope structure? In this work, we continue with the original study of Qiu et al. by using a larger sample of flare-coronal mass ejection (CME)-interplanetary CME (ICME) events to compare properties of ICME/magnetic cloud (MC) flux ropes measured at 1 AU and properties of associated solar progenitors including flares, filaments, and CMEs. In particular, the magnetic field-line twist distribution within interplanetary magnetic flux ropes is systematically derived and examined. Our analysis shows that, similar to what was found before, for most of these events, the amount of twisted flux per AU in MCs is comparable with the total reconnection flux on the Sun, and the sign of the MC helicity is consistent with the sign of the helicity of the solar source region judged from the geometry of post-flare loops. Remarkably, we find that about half of the 18 magnetic flux ropes, most of them associated with erupting filaments, have a nearly uniform and relatively low twist distribution from the axis to the edge, and the majority of the other flux ropes exhibit very high twist near the axis, up to ≳ 5 turns per AU, which decreases toward the edge. The flux ropes are therefore not linearly force-free. We also conduct detailed case studies showing the contrast of two events with distinct twist distribution in MCs as well as different flare and dimming characteristics in solar source regions, and discuss how reconnection geometry reflected in flare morphology may be related to the structure of the flux rope formed on the Sun.

  5. Magnetic flux ropes in 3-dimensional MHD simulations

    NASA Technical Reports Server (NTRS)

    Ogino, Tatsuki; Walker, Raymond J.; Ashour-Abdalla, Maha

    1990-01-01

    The interaction of the solar wind and the earth's magnetosphere is presently simulated by a 3D, time-dependent, global MHD method in order to model the magnetopause and magnetotail generation of magnetic flux ropes. It is noted that strongly twisted and localized magnetic flux tubes simular to magnetic flux ropes appear at the subpolar magnetopause when the IMF has a large azimuthal component, as well as a southward component. Plasmoids are generated in the magnetotail after the formation of a near-earth magnetic neutral line; the magnetic field lines have a helical structure that is connected from dawn to dusk.

  6. Magnetic flux ropes in 3-dimensional MHD simulations

    NASA Technical Reports Server (NTRS)

    Ogino, Tatsuki; Walker, Raymond J.; Ashour-Abdalla, Maha

    1990-01-01

    The interaction of the solar wind and the earth's magnetosphere is presently simulated by a 3D, time-dependent, global MHD method in order to model the magnetopause and magnetotail generation of magnetic flux ropes. It is noted that strongly twisted and localized magnetic flux tubes simular to magnetic flux ropes appear at the subpolar magnetopause when the IMF has a large azimuthal component, as well as a southward component. Plasmoids are generated in the magnetotail after the formation of a near-earth magnetic neutral line; the magnetic field lines have a helical structure that is connected from dawn to dusk.

  7. Study on Crystallization Properties of Mold Flux in Magnetic Field

    NASA Astrophysics Data System (ADS)

    Zhang, Congjing; Wang, Yu; Hu, Lang; Zhu, Mingmei; Wang, Hongpo

    Magnetic field has a great effect on the crystallization behavior of mold flux and properties of the flux film between mold and strand, on which the surface quality of strand was deeply depended in continuous casting process. Therefore, studying the change law of the crystallization properties of mold flux in magnetic field is of great significant. In the present work, based on intensity of the applied magnetic field with the range from 0mT to 60mT, the crystallization ratio, crystal size and mineralogical phases of the flux film were discussed. The results show that crystallization ratio increases with the increasing magnetic field intensity, and the crystal size becomes bigger at the same time. The magnetic field promotes the crystallization ratio and growth speed of the crystallized grains of mold flux. However, magnetic field doesn't change types of the mineralogical phases.

  8. Complexity and diffusion of magnetic flux surfaces in anisotropic turbulence

    SciTech Connect

    Servidio, S.; Matthaeus, W. H.; Wan, M.; Rappazzo, A. F.; Ruffolo, D.; Oughton, S.

    2014-04-10

    The complexity of magnetic flux surfaces is investigated analytically and numerically in static homogeneous magnetic turbulence. Magnetic surfaces are computed to large distances in magnetic fields derived from a reduced magnetohydrodynamic model. The question addressed is whether one can define magnetic surfaces over large distances when turbulence is present. Using a flux surface spectral analysis, we show that magnetic surfaces become complex at small scales, experiencing an exponential thinning that is quantified here. The computation of a flux surface is of either exponential or nondeterministic polynomial complexity, which has the conceptual implication that global identification of magnetic flux surfaces and flux exchange, e.g., in magnetic reconnection, can be intractable in three dimensions. The coarse-grained large-scale magnetic flux experiences diffusive behavior. The link between the diffusion of the coarse-grained flux and field-line random walk is established explicitly through multiple scale analysis. The Kubo number controls both large and small scale limits. These results have consequences for interpreting processes such as magnetic reconnection and field-line diffusion in astrophysical plasmas.

  9. Hall Effect-Mediated Magnetic Flux Transport in Protoplanetary Disks

    NASA Astrophysics Data System (ADS)

    Bai, Xue-Ning; Stone, James M.

    2017-02-01

    The global evolution of protoplanetary disks (PPDs) has recently been shown to be largely controlled by the amount of poloidal magnetic flux threading the disk. The amount of magnetic flux must also coevolve with the disk, as a result of magnetic flux transport, a process that is poorly understood. In weakly ionized gas as in PPDs, magnetic flux is largely frozen in the electron fluid, except when resistivity is large. When the disk is largely laminar, we show that the relative drift between the electrons and ions (the Hall drift), and the ions and neutral fluids (ambipolar drift) can play a dominant role on the transport of magnetic flux. Using two-dimensional simulations that incorporate the Hall effect and ambipolar diffusion (AD) with prescribed diffusivities, we show that when large-scale poloidal field is aligned with disk rotation, the Hall effect rapidly drags magnetic flux inward at the midplane region, while it slowly pushes flux outward above/below the midplane. This leads to a highly radially elongated field configuration as a global manifestation of the Hall-shear instability. This field configuration further promotes rapid outward flux transport by AD at the midplane, leading to instability saturation. In quasi-steady state, magnetic flux is transported outward at approximately the same rate at all heights, and the rate is comparable to the Hall-free case. For anti-aligned field polarity, the Hall effect consistently transports magnetic flux outward, leading to a largely vertical field configuration in the midplane region. The field lines in the upper layer first bend radially inward and then outward to launch a disk wind. Overall, the net rate of outward flux transport is about twice as fast as that of the aligned case. In addition, the rate of flux transport increases with increasing disk magnetization. The absolute rate of transport is sensitive to disk microphysics, which remains to be explored in future studies.

  10. PROTOSTELLAR ACCRETION FLOWS DESTABILIZED BY MAGNETIC FLUX REDISTRIBUTION

    SciTech Connect

    Krasnopolsky, Ruben; Shang, Hsien; Li Zhiyun; Zhao Bo

    2012-09-20

    Magnetic flux redistribution lies at the heart of the problem of star formation in dense cores of molecular clouds that are magnetized to a realistic level. If all of the magnetic flux of a typical core were to be dragged into the central star, the stellar field strength would be orders of magnitude higher than the observed values. This well-known magnetic flux problem can in principle be resolved through non-ideal MHD effects. Two-dimensional (axisymmetric) calculations have shown that ambipolar diffusion, in particular, can transport magnetic flux outward relative to matter, allowing material to enter the central object without dragging the field lines along. We show through simulations that such axisymmetric protostellar accretion flows are unstable in three dimensions to magnetic interchange instability in the azimuthal direction. The instability is driven by the magnetic flux redistributed from the matter that enters the central object. It typically starts to develop during the transition from the prestellar phase of star formation to the protostellar mass accretion phase. In the latter phase, the magnetic flux is transported outward mainly through advection by strongly magnetized low-density regions that expand against the collapsing inflow. The tussle between the gravity-driven infall and magnetically driven expansion leads to a highly filamentary inner accretion flow that is more disordered than previously envisioned. The efficient outward transport of magnetic flux by advection lowers the field strength at small radii, making the magnetic braking less efficient and the formation of rotationally supported disks easier in principle. However, we find no evidence for such disks in any of our rotating collapse simulations. We conclude that the inner protostellar accretion flow is shaped to a large extent by the flux redistribution-driven magnetic interchange instability. How disks form in such an environment is unclear.

  11. Avalanche dynamics of magnetic flux in a two-dimensional discrete superconductor

    SciTech Connect

    Ginzburg, S. L.; Nakin, A. V.; Savitskaya, N. E.

    2006-11-15

    The critical state of a two-dimensional discrete superconductor in an external magnetic field is studied. This state is found to be self-organized in the generalized sense, i.e., is a set of metastable states that transform to each other by means of avalanches. An avalanche is characterized by the penetration of a magnetic flux to the system. The sizes of the occurring avalanches, i.e., changes in the magnetic flux, exhibit the power-law distribution. It is also shown that the size of the avalanche occurring in the critical state and the external magnetic field causing its change are statistically independent quantities.

  12. Shifted orbifold models with magnetic flux

    NASA Astrophysics Data System (ADS)

    Fujimoto, Yukihiro; Kobayashi, Tatsuo; Miura, Takashi; Nishiwaki, Kenji; Sakamoto, Makoto

    2013-04-01

    We propose a mechanism to obtain the generation of matter in the standard model. We start from the analysis of the T2/ZN shifted orbifold with magnetic flux, which imposes a ZN symmetry on torus. We also consider several orbifolds such as (T2×T2)/ZN, (T2×T2×T2)/(ZN×ZN') and (T2×T2×T2)/(ZN×ZN'×ZN''). On such orbifolds, we study the behavior of fermions in two different means—the operator formalism and the explicit analysis of wave functions. For an interesting result, it is found that the number of zero-mode fermions is related to N of the ZN symmetry. In other words, the generation of matter relates to the type of orbifolds. Moreover, we find that shifted orbifold models are severely restricted from realizing three generations. For example, the three-generation model on the type of M4×(T2×T2)/ZN is unique. One can also construct other types of three-generation orbifold models with rich flavor structure. Those results may bring us a realistic model with desired Yukawa structure.

  13. EFFECT OF FINITE LARMOR RADIUS ON COSMIC-RAY PENETRATION INTO AN INTERPLANETARY MAGNETIC FLUX ROPE

    SciTech Connect

    Kubo, Yuki; Shimazu, Hironori

    2010-09-01

    We discuss a mechanism for cosmic-ray penetration into an interplanetary magnetic flux rope, particularly the effect of the finite Larmor radius and magnetic field irregularities. First, we derive analytical solutions for cosmic-ray behavior inside a magnetic flux rope, on the basis of the Newton-Lorentz equation of a particle, to investigate how cosmic rays penetrate magnetic flux ropes under an assumption of there being no scattering by small-scale magnetic field irregularities. The results show that the behavior of a particle is determined by only one parameter f{sub 0}, that is, the ratio of the Larmor radius at the flux rope axis to the flux rope radius. The analytical solutions show that cosmic rays cannot penetrate into the inner region of a flux rope by only gyration and gradient-curvature drift in the case of small f{sub 0}. Next, we perform a numerical simulation of a cosmic-ray penetration into an interplanetary magnetic flux rope by adding small-scale magnetic field irregularities. The results show that cosmic rays can penetrate into a magnetic flux rope even in the case of small f{sub 0} because of the effect of small-scale magnetic field irregularities. This simulation also shows that a cosmic-ray density distribution is greatly different from that deduced from a guiding center approximation because of the effect of the finite Larmor radius and magnetic field irregularities for the case of a moderate to large Larmor radius compared to the flux rope radius.

  14. Influence of the crustal magnetic field on the Mars aurora electron flux and UV brightness

    NASA Astrophysics Data System (ADS)

    Bisikalo, D. V.; Shematovich, V. I.; Gérard, J.-C.; Hubert, B.

    2017-01-01

    Observations with the SPICAM instrument on board Mars Express have shown the occasional presence of localized ultraviolet nightside emissions associated with enhanced energetic electron fluxes. These features generally occur in regions with significant radial crustal magnetic field. We use a Monte-Carlo electron transport model to investigate the role of the magnetic field on the downward and upward electron fluxes, the brightness and the emitted power of auroral emissions. Simulations based on an ASPERA-3 measured auroral electron precipitation indicate that magnetic mirroring leads to an intensification of the energy flux carried by upward moving electrons- from about 20% in the absence of crustal magnetic field up to 33-78% when magnetic field is included depending on magnetic field topology. Conservation of the particle flux in a flux tube implies that the presence of the B-field does not appreciably modify the emission rate profiles for an initially isotropic pitch angle distribution. However, we find that crustal magnetic field results in increase of the upward electron flux, and, consequently, in reduction of the total auroral brightness for given energy flux of precipitating electrons.

  15. Flux Transport and the Sun's Global Magnetic Field

    NASA Technical Reports Server (NTRS)

    Hathaway, David H.

    2010-01-01

    The Sun s global magnetic field is produced and evolved through the emergence of magnetic flux in active regions and its transport across the solar surface by the axisymmetric differential rotation and meridional flow and the non-axisymmetric convective flows of granulation, supergranulation, and giant cell convection. Maps of the global magnetic field serve as the inner boundary condition for space weather. The photospheric magnetic field and its evolution determine the coronal and solar wind structures through which CMEs must propagate and in which solar energetic particles are accelerated and propagate. Producing magnetic maps which best represent the actual field configuration at any instant requires knowing the magnetic field over the observed hemisphere as well as knowing the flows that transport flux. From our Earth-based vantage point we only observe the front-side hemisphere and each pole is observable for only six months of the year at best. Models for the surface magnetic flux transport can be used to provide updates to the magnetic field configuration in those unseen regions. In this presentation I will describe successes and failures of surface flux transport and present new observations on the structure, the solar cycle variability, and the evolution of the flows involved in magnetic flux transport. I find that supergranules play the dominant role due to their strong flow velocities and long lifetimes. Flux is transported by differential rotation and meridional flow only to the extent that the supergranules participate in those two flows.

  16. Distribution Functions of Sizes and Fluxes Determined from Supra-Arcade Downflows

    NASA Technical Reports Server (NTRS)

    McKenzie, D.; Savage, S.

    2011-01-01

    The frequency distributions of sizes and fluxes of supra-arcade downflows (SADs) provide information about the process of their creation. For example, a fractal creation process may be expected to yield a power-law distribution of sizes and/or fluxes. We examine 120 cross-sectional areas and magnetic flux estimates found by Savage & McKenzie for SADs, and find that (1) the areas are consistent with a log-normal distribution and (2) the fluxes are consistent with both a log-normal and an exponential distribution. Neither set of measurements is compatible with a power-law distribution nor a normal distribution. As a demonstration of the applicability of these findings to improved understanding of reconnection, we consider a simple SAD growth scenario with minimal assumptions, capable of producing a log-normal distribution.

  17. Bimodal Distribution of Magnetic Fields and Areas of Sunspots

    NASA Astrophysics Data System (ADS)

    Tlatov, Andrey G.; Pevtsov, Alexei A.

    2014-04-01

    We applied automatic identification of sunspot umbrae and penumbrae to daily observations from the Helioseismic Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO) to study their magnetic flux density ( B) and area ( A). The results confirm an already known logarithmic relationship between the area of sunspots and their maximum flux density. In addition, we find that the relation between average magnetic flux density () and sunspot area shows a bimodal distribution: for small sunspots and pores ( A≤20 millionth of solar hemisphere, MSH), (gauss), and for large sunspots ( A≥100 MSH), is about 600 G. For intermediate sunspots, average flux density linearly decreases from about 800 G to 600 G. A similar bimodal distribution was found in several other integral parameters of sunspots. We show that this bimodality can be related to different stages of sunspot penumbra formation and can be explained by the difference in average inclination of magnetic fields at the periphery of small and large sunspots.

  18. Helicity charging and eruption of magnetic flux from the Sun

    NASA Technical Reports Server (NTRS)

    Rust, David M.; Kumar, A.

    1994-01-01

    The ejection of helical toroidal fields from the solar atmosphere and their detection in interplanetary space are described. The discovery that solar magnetic fields are twisted and that they are segregated by hemisphere according to their chirality has important implications for the escape process. The roles played by erupting prominences, coronal mass ejections (CME's) and active region (AR) loops in expressing the escape of magnetic flux and helicity are discussed. Sporadic flux escape associated with filament eruptions accounts for less than one-tenth the flux loss. Azimuthal flux loss by CME's could account for more, but the major contributor to flux escape may be AR loop expansion. It is shown how the transfer of magnetic helicity from the sun's interior into emerged loops ('helicity charging') could be the effective driver of solar eruptions and of flux loss from the sun.

  19. Siphon flows in isolated magnetic flux tubes. II - Adiabatic flows

    NASA Technical Reports Server (NTRS)

    Montesinos, Benjamin; Thomas, John H.

    1989-01-01

    This paper extends the study of steady siphon flows in isolated magnetic flux tubes surrounded by field-free gas to the case of adiabatic flows. The basic equations governing steady adiabatic siphon flows in a thin, isolated magnetic flux tube are summarized, and qualitative features of adiabatic flows in elevated, arched flux tubes are discussed. The equations are then cast in nondimensional form and the results of numerical computations of adiabatic siphon flows in arched flux tubes are presented along with comparisons between isothermal and adiabatic flows. The effects of making the interior of the flux tube hotter or colder than the surrounding atmosphere at the upstream footpoint of the arch is considered. In this case, is it found that the adiabatic flows are qualitatively similar to the isothermal flows, with adiabatic cooling producing quantitative differences. Critical flows can produce a bulge point in the rising part of the arch and a concentration of magnetic flux above the bulge point.

  20. Flux-limitation of the Nernst effect in magnetized ICF

    NASA Astrophysics Data System (ADS)

    Ridgers, Christopher; Barrois, Rion; Wengraf, Joshua; Bissell, John; Brodrick, Jonathan; Kingham, Robert; Read, Martin

    2016-10-01

    Magnetized ICF is a promising scheme which combines the advantages of magnetic and inertial confinement fusion. In the relevant high-energy density plasmas magnetic field evolution is often controlled by the Nernst effect where the magnetic field advects with the electron heat flow. It is well known that non-local thermal transport necessitates a flux-limiter on the heat flow. This suggests that a flux-limiter should also be applied to the Nernst effect. We have shown that this is the case using Vlasov-Fokker-Planck simulations and that the flux-limter is not the same as that required for the heat flow itself, for example when a NIF-relevant flux-limiter of 0.15 is required to limit the heat flow a Nernst flux limiter of 0.08 is required. We acknowledge support from EPSRC Grant No. EPM011372/1.

  1. Studying the Formation and Evolution of Eruptive Magnetic Flux Ropes

    NASA Astrophysics Data System (ADS)

    Linton, Mark

    2017-08-01

    Solar magnetic eruptions are dramatic sources of solar activity, and dangerous sources of space weather hazards. Many of these eruptions take the form of magnetic flux ropes, i.e., magnetic fieldlines wrapping around a core magnetic flux tube. Investigating the processes which form these flux ropes both prior to and during eruption, and investigating their evolution after eruption, can give us a critical window into understanding the sources of and processes involved in these eruptions. This presentation will discuss modeling and observational investigations into these various phases of flux rope formation, eruption, and evolution, and will discuss how these different explorations can be used to develop a more complete picture of erupting flux rope dynamics.

  2. OBSERVATIONS OF A SMALL INTERPLANETARY MAGNETIC FLUX ROPE ASSOCIATED WITH A MAGNETIC RECONNECTION EXHAUST

    SciTech Connect

    Feng, H. Q.; Wu, D. J.

    2009-11-10

    A small interplanetary magnetic flux rope prior to an X-line magnetic reconnection exhaust was observed on 1998 March 25 at 1 AU. The X-line magnetic reconnection exhaust has been identified and reported by Gosling et al. The duration of this small magnetic flux rope is about 2 hr. We fitted the constant alpha force-free model to the observed magnetic fields. The model fitting results show that the spacecraft crosses the magnetic flux rope well away from the axis, with d {sub 0}/R {sub 0} being 0.76. The fitting results also show that its magnetic configuration is a right-handed helical flux rope, that the estimated field intensity at the axis is 16.3 nT, and that its diameter is 0.0190 AU. In addition, the axial direction of this rope is (theta = 6 deg., phi = 214 deg.), namely, this magnetic flux rope is lying nearly in the ecliptic plane. According to the geometric relation of the small flux rope and the reconnection exhaust, it is very possible that the small magnetic flux rope has a larger scale initially and comes from the corona; its magnetic fields are peeled off when moving from the Sun to the Earth and at last it reaches a small scale. Though magnetic reconnection can produce a flux-rope topology, in this case the X-line magnetic reconnection is destroying rather than generating the small magnetic flux rope.

  3. Performance analysis of a new radial-axial flux machine with SMC cores and ferrite magnets

    NASA Astrophysics Data System (ADS)

    Liu, Chengcheng; Wang, Youhua; Lei, Gang; Guo, Youguang; Zhu, Jianguo

    2017-05-01

    Soft magnetic composite (SMC) is a popular material in designing of new 3D flux electrical machines nowadays for it has the merits of isotropic magnetic characteristic, low eddy current loss and high design flexibility over the electric steel. The axial flux machine (AFM) with the extended stator tooth tip both in the radial and circumferential direction is a good example, which has been investigated in the last years. Based on the 3D flux AFM and radial flux machine, this paper proposes a new radial-axial flux machine (RAFM) with SMC cores and ferrite magnets, which has very high torque density though the low cost low magnetic energy ferrite magnet is utilized. Moreover, the cost of RAFM is quite low since the manufacturing cost can be reduced by using the SMC cores and the material cost will be decreased due to the adoption of the ferrite magnets. The 3D finite element method (FEM) is used to calculate the magnetic flux density distribution and electromagnetic parameters. For the core loss calculation, the rotational core loss computation method is used based on the experiment results from previous 3D magnetic tester.

  4. Magnetic Flux Rope Identification and Characterization from Observationally Driven Solar Coronal Models

    NASA Astrophysics Data System (ADS)

    Lowder, Chris; Yeates, Anthony

    2017-09-01

    Formed through magnetic field shearing and reconnection in the solar corona, magnetic flux ropes are structures of twisted magnetic field, threaded along an axis. Their evolution and potential eruption are of great importance for space weather. Here we describe a new methodology for the automated detection of flux ropes in simulated magnetic fields, utilizing field-line helicity. Our Flux Rope Detection and Organization (FRoDO) code, which measures the magnetic flux and helicity content of pre-erupting flux ropes over time, as well as detecting eruptions, is publicly available. As a first demonstration, the code is applied to the output from a time-dependent magnetofrictional model, spanning 1996 June 15–2014 February 10. Over this period, 1561 erupting and 2099 non-erupting magnetic flux ropes are detected, tracked, and characterized. For this particular model data, erupting flux ropes have a mean net helicity magnitude of 2.66× {10}43 Mx2, while non-erupting flux ropes have a significantly lower mean of 4.04× {10}42 Mx2, although there is overlap between the two distributions. Similarly, the mean unsigned magnetic flux for erupting flux ropes is 4.04× {10}21 Mx, significantly higher than the mean value of 7.05× {10}20 Mx for non-erupting ropes. These values for erupting flux ropes are within the broad range expected from observational and theoretical estimates, although the eruption rate in this particular model is lower than that of observed coronal mass ejections. In the future, the FRoDO code will prove to be a valuable tool for assessing the performance of different non-potential coronal simulations and comparing them with observations.

  5. Experimental results for 2D magnetic resonance electrical impedance tomography (MR-EIT) using magnetic flux density in one direction.

    PubMed

    Birgül, Ozlem; Eyüboğlu, B Murat; Ider, Y Ziya

    2003-11-07

    Magnetic resonance electrical impedance tomography (MR-EIT) is an emerging imaging technique that reconstructs conductivity images using magnetic flux density measurements acquired employing MRI together with conventional EIT measurements. In this study, experimental MR-EIT images from phantoms with conducting and insulator objects are presented. The technique is implemented using the 0.15 T Middle East Technical University MRI system. The dc current method used in magnetic resonance current density imaging is adopted. A reconstruction algorithm based on the sensitivity matrix relation between conductivity and only one component of magnetic flux distribution is used. Therefore, the requirement for object rotation is eliminated. Once the relative conductivity distribution is found, it is scaled using the peripheral voltage measurements to obtain the absolute conductivity distribution. Images of several insulator and conductor objects in saline filled phantoms are reconstructed. The L2 norm of relative error in conductivity values is found to be 13%, 17% and 14% for three different conductivity distributions.

  6. Magnetic Flux Density of Different Types of New Generation Magnetic Attachment Systems.

    PubMed

    Akin, Hakan

    2015-07-01

    The purpose of this study was to analyze the static magnetic flux density of different types of new generation laser-welded magnetic attachments in the single position and the attractive position and to determine the effect of different corrosive environments on magnetic flux density. Magnetic flux densities of four magnetic attachment systems (Hyper slim, Hicorex slim, Dyna, and Steco) were measured with a gaussmeter. Then magnetic attachment systems were immersed in two different media, namely 1% lactic acid solution (pH 2.3), and 0.9% NaCl solution (pH 7.3). Magnetic flux densities of the attachment systems were measured with a gaussmeter after immersion to compare with measurements before immersion (α = 0.05). The data were statistically evaluated with one-way ANOVA, paired-samples t-test, and post hoc Tukey-Kramer multiple comparisons tests (α = 0.05). The highest magnetic flux density was found in Dyna magnets for both single and attractive positions. In addition, after the magnets were in the corrosive environments for 2 weeks, they had a significant decrease in magnetic flux density (p < 0.05). No significant differences were found between corrosive environments (p > 0.05). The leakage flux of all the magnetic attachments did not exceed the WHO's guideline of 40 mT. The magnets exhibited a significant decrease in magnetic flux density after aging in corrosive environments including lactic acid and NaCl. © 2014 by the American College of Prosthodontists.

  7. Coronal mass ejections and magnetic flux ropes in interplanetary space

    NASA Technical Reports Server (NTRS)

    Gosling, J. T.

    1990-01-01

    Coronal mass ejections (CMEs) are formed in the solar corona by the ejection of material from closed field regions that were not previously participating in the solar wind expansion. CMEs commonly exhibit a signature consisting of a counterstreaming flux of suprathermal electrons with energies above about 80 eV, indicating closed field structures that are either rooted at both ends in the sun or entirely disconnected from it. About 30 percent of all CME events at 1 AU exhibit large, coherent internal field rotations typical of magnetic flux ropes. It is suggested that interplanetary magnetic flux ropes form as a result of reconnection within rising, previously sheared coronal magnetic loops.

  8. Magnetic flux rope type structures in the geomagnetic tail

    NASA Astrophysics Data System (ADS)

    Antonova, A. E.; Kropotkin, A. P.

    1991-12-01

    Some structures in the geomagnetic tail observed by the Prognoz 9 and ISEE spacecraft as 'magnetic flux ropes' are identified, and new features are emphasized. The structures are associated with considerable fluxes of energetic ions and electrons. Particles are effectively energized at magnetic field discontinuities, resulting in the generation of spectra extending up to MeV energies. An external field source (i.e., the interplanetary magnetic field) may be of essential importance for the generation of the flux ropes whose axes lie in the cross-tail direction.

  9. MAGNETIC FLUX TRANSPORT AND THE LONG-TERM EVOLUTION OF SOLAR ACTIVE REGIONS

    SciTech Connect

    Ugarte-Urra, Ignacio; Upton, Lisa; Warren, Harry P.; Hathaway, David H.

    2015-12-20

    With multiple vantage points around the Sun, Solar Terrestrial Relations Observatory (STEREO) and Solar Dynamics Observatory imaging observations provide a unique opportunity to view the solar surface continuously. We use He ii 304 Å data from these observatories to isolate and track ten active regions and study their long-term evolution. We find that active regions typically follow a standard pattern of emergence over several days followed by a slower decay that is proportional in time to the peak intensity in the region. Since STEREO does not make direct observations of the magnetic field, we employ a flux-luminosity relationship to infer the total unsigned magnetic flux evolution. To investigate this magnetic flux decay over several rotations we use a surface flux transport model, the Advective Flux Transport model, that simulates convective flows using a time-varying velocity field and find that the model provides realistic predictions when information about the active region's magnetic field strength and distribution at peak flux is available. Finally, we illustrate how 304 Å images can be used as a proxy for magnetic flux measurements when magnetic field data is not accessible.

  10. Magnetic Flux Transport and the Long-term Evolution of Solar Active Regions

    NASA Astrophysics Data System (ADS)

    Ugarte-Urra, Ignacio; Upton, Lisa; Warren, Harry P.; Hathaway, David H.

    2015-12-01

    With multiple vantage points around the Sun, Solar Terrestrial Relations Observatory (STEREO) and Solar Dynamics Observatory imaging observations provide a unique opportunity to view the solar surface continuously. We use He ii 304 Å data from these observatories to isolate and track ten active regions and study their long-term evolution. We find that active regions typically follow a standard pattern of emergence over several days followed by a slower decay that is proportional in time to the peak intensity in the region. Since STEREO does not make direct observations of the magnetic field, we employ a flux-luminosity relationship to infer the total unsigned magnetic flux evolution. To investigate this magnetic flux decay over several rotations we use a surface flux transport model, the Advective Flux Transport model, that simulates convective flows using a time-varying velocity field and find that the model provides realistic predictions when information about the active region's magnetic field strength and distribution at peak flux is available. Finally, we illustrate how 304 Å images can be used as a proxy for magnetic flux measurements when magnetic field data is not accessible.

  11. MAGNETIC FLUX PARADIGM FOR RADIO LOUDNESS OF ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Sikora, Marek; Begelman, Mitchell C. E-mail: mitch@jila.colorado.edu

    2013-02-20

    We argue that the magnetic flux threading the black hole (BH), rather than BH spin or Eddington ratio, is the dominant factor in launching powerful jets and thus determining the radio loudness of active galactic nuclei (AGNs). Most AGNs are radio quiet because the thin accretion disks that feed them are inefficient in depositing magnetic flux close to the BH. Flux accumulation is more likely to occur during a hot accretion (or thick disk) phase, and we argue that radio-loud quasars and strong emission-line radio galaxies occur only when a massive, cold accretion event follows an episode of hot accretion. Such an event might be triggered by the merger of a giant elliptical galaxy with a disk galaxy. This picture supports the idea that flux accumulation can lead to the formation of a so-called magnetically choked accretion flow. The large observed range in radio loudness reflects not only the magnitude of the flux pressed against the BH, but also the decrease in UV flux from the disk, due to its disruption by the ''magnetosphere'' associated with the accumulated flux. While the strongest jets result from the secular accumulation of flux, moderate jet activity can also be triggered by fluctuations in the magnetic flux deposited by turbulent, hot inner regions of otherwise thin accretion disks, or by the dissipation of turbulent fields in accretion disk coronae. These processes could be responsible for jet production in Seyferts and low-luminosity AGNs, as well as jets associated with X-ray binaries.

  12. Unsteady wandering magnetic field lines, turbulence and laboratory flux ropes

    NASA Astrophysics Data System (ADS)

    Intrator, T.; Sears, J.; Weber, T.; Liu, D.; Pulliam, D.; Lazarian, A.

    2011-12-01

    We describe earth bound laboratory experiment investigations of patchy, unsteady, bursty, patchy magnetic field structures that are unifying features of magnetic reconnection and turbulence in helio, space and astro physics. Macroscopic field lines occupy cross sectional areas, fill up three dimensional (3D) volumes as flux tubes. They contain mass with Newtonian dynamics that follow magneto-hydro-dynamic (MHD) equations of motion. Flux rope geometry can be ubiquitous in laminar reconnection sheet geometries that are themselves unstable to formation of secondary "islands" that in 3D are really flux ropes. Flux ropes are ubiquitous structures on the sun and the rest of the heliosphere. Understanding the dynamics of flux ropes and their mutual interactions offers the key to many important astrophysical phenomena, including magnetic reconnection and turbulence. We describe laboratory investigations on RSX, where 3D interaction of flux ropes can be studied in great detail. We use experimental probes inside the the flux ropes to measure the magnetic and electric fields, current density, density, temperatures, pressure, and electrostatic and vector plasma potentials. Macroscopic magnetic field lines, unsteady wandering characteristics, and dynamic objects with structure down to the dissipation scale length can be traced from data sets in a 3D volume. Computational approaches are finally able to tackle simple 3D systems and we sketch some intriguing simulation results that are consistent with 3D extensions of typical 2D cartoons for magnetic reconnection and turbulence.

  13. Catastrophe of Coronal Magnetic Flux Ropes Caused by Photospheric Motions

    NASA Astrophysics Data System (ADS)

    Hu, Y. Q.; Jiang, Y. W.

    2001-11-01

    Using a 2.5-D, time-dependent ideal MHD model in Cartesian coordinates, we carried out numerical simulations to investigate the equilibrium and evolution properties of a magnetic configuration that consists of a coronal magnetic flux rope and a partly open photospheric background field, which is equivalent to that produced by a two-patch magnetic source on the photospheric surface. The axial and annular magnetic fluxes of the flux rope are given and fixed. The global magnetic configuration evolves in response to three types of changes of the background field: decreasing of the distance between the two sources, shrinking of the size of each source, and increasing of the shear in the closed component of the background field. As a result, the geometrical parameters of the flux rope, i.e. the height of the rope axis, the half-width of the rope and the length of the vertical current sheet below the rope, change due to the variation of the background field. It is shown that for a given coronal magnetic flux rope in a partly open background field, the variation of the geometrical parameters of the flux rope displays a catastrophic behavior, namely, there exists a critical point for each case, at which an infinitesimal change of the background field leads to a loss of equilibrium, and thus a jump of the flux rope. The implication of such a catastrophe in solar active phenomena is briefly discussed.

  14. Quantum transport in coupled resonators enclosed synthetic magnetic flux

    SciTech Connect

    Jin, L.

    2016-07-15

    Quantum transport properties are instrumental to understanding quantum coherent transport processes. Potential applications of quantum transport are widespread, in areas ranging from quantum information science to quantum engineering, and not restricted to quantum state transfer, control and manipulation. Here, we study light transport in a ring array of coupled resonators enclosed synthetic magnetic flux. The ring configuration, with an arbitrary number of resonators embedded, forms a two-arm Aharonov–Bohm interferometer. The influence of magnetic flux on light transport is investigated. Tuning the magnetic flux can lead to resonant transmission, while half-integer magnetic flux quantum leads to completely destructive interference and transmission zeros in an interferometer with two equal arms. -- Highlights: •The light transport is investigated through ring array of coupled resonators enclosed synthetic magnetic field. •Aharonov–Bohm ring interferometer of arbitrary configuration is investigated. •The half-integer magnetic flux quantum leads to destructive interference and transmission zeros for two-arm at equal length. •Complete transmission is available via tuning synthetic magnetic flux.

  15. Magnetic flux studies in horizontally cooled elliptical superconducting cavities

    SciTech Connect

    Martinello, M. Checchin, M.; Grassellino, A. Crawford, A. C.; Melnychuk, O.; Romanenko, A.; Sergatskov, D. A.

    2015-07-28

    Previous studies on magnetic flux expulsion as a function of cooldown procedures for elliptical superconducting radio frequency (SRF) niobium cavities showed that when the cavity beam axis is placed parallel to the helium cooling flow and sufficiently large thermal gradients are achieved, all magnetic flux could be expelled and very low residual resistance could be achieved. In this paper, we investigate flux trapping for the case of resonators positioned perpendicularly to the helium cooling flow, which is more representative of how SRF cavities are cooled in accelerators and for different directions of the applied magnetic field surrounding the resonator. We show that different field components have a different impact on the surface resistance, and several parameters have to be considered to fully understand the flux dynamics. A newly discovered phenomenon of concentration of flux lines at the cavity top leading to temperature rise at the cavity equator is presented.

  16. Magnetic flux studies in horizontally cooled elliptical superconducting cavities

    DOE PAGES

    Martinello, M.; Checchin, M.; Grassellino, A.; ...

    2015-07-29

    Previous studies on magnetic flux expulsion as a function of cooldown procedures for elliptical superconducting radio frequency (SRF) niobium cavities showed that when the cavity beam axis is placed parallel to the helium cooling flow and sufficiently large thermal gradients are achieved, all magnetic flux could be expelled and very low residual resistance could be achieved. In this paper, we investigate flux trapping for the case of resonators positioned perpendicularly to the helium cooling flow, which is more representative of how SRF cavities are cooled in accelerators and for different directions of the applied magnetic field surrounding the resonator. Wemore » show that different field components have a different impact on the surface resistance, and several parameters have to be considered to fully understand the flux dynamics. A newly discovered phenomenon of concentration of flux lines at the cavity top leading to temperature rise at the cavity equator is presented.« less

  17. Photospheric and Subphotospheric Dynamics of Emerging Magnetic Flux

    NASA Astrophysics Data System (ADS)

    Kosovichev, A. G.

    Magnetic fields emerging from the Sun's interior carry information about physical processes of magnetic field generation and transport in the convection zone. Soon after appearance on the solar surface the magnetic flux gets concentrated in sunspot regions and causes numerous active phenomena on the Sun. This paper discusses some properties of the emerging magnetic flux observed on the solar surface and in the interior. A statistical analysis of variations of the tilt angle of bipolar magnetic regions during the emergence shows that the systematic tilt with respect to the equator (the Joy's law) is most likely established below the surface. However, no evidence of the dependence of the tilt angle on the amount of emerging magnetic flux, predicted by the rising magnetic flux rope theories, is found. Analysis of surface plasma flows in a large emerging active region reveals strong localized upflows and downflows at the initial phase of emergence but finds no evidence for large-scale flows indicating future appearance a large-scale magnetic structure. Local helioseismology provides important tools for mapping perturbations of the wave speed and mass flows below the surface. Initial results from SOHO/MDI and GONG reveal strong diverging flows during the flux emergence, and also localized converging flows around stable sunspots. The wave speed images obtained during the process of formation of a large active region, NOAA 10488, indicate that the magnetic flux gets concentrated in strong field structures just below the surface. Further studies of magnetic flux emergence require systematic helioseismic observations from the ground and space, and realistic MHD simulations of the subsurface dynamics.

  18. Photospheric and Subphotospheric Dynamics of Emerging Magnetic Flux

    NASA Astrophysics Data System (ADS)

    Kosovichev, A. G.

    2009-04-01

    Magnetic fields emerging from the Sun’s interior carry information about physical processes of magnetic field generation and transport in the convection zone. Soon after appearance on the solar surface the magnetic flux gets concentrated in sunspot regions and causes numerous active phenomena on the Sun. This paper discusses some properties of the emerging magnetic flux observed on the solar surface and in the interior. A statistical analysis of variations of the tilt angle of bipolar magnetic regions during the emergence shows that the systematic tilt with respect to the equator (the Joy’s law) is most likely established below the surface. However, no evidence of the dependence of the tilt angle on the amount of emerging magnetic flux, predicted by the rising magnetic flux rope theories, is found. Analysis of surface plasma flows in a large emerging active region reveals strong localized upflows and downflows at the initial phase of emergence but finds no evidence for large-scale flows indicating future appearance a large-scale magnetic structure. Local helioseismology provides important tools for mapping perturbations of the wave speed and mass flows below the surface. Initial results from SOHO/MDI and GONG reveal strong diverging flows during the flux emergence, and also localized converging flows around stable sunspots. The wave speed images obtained during the process of formation of a large active region, NOAA 10488, indicate that the magnetic flux gets concentrated in strong field structures just below the surface. Further studies of magnetic flux emergence require systematic helioseismic observations from the ground and space, and realistic MHD simulations of the subsurface dynamics.

  19. Multifield measurement of magnetic fluctuation-induced particle flux in a high-temperature toroidal plasma

    NASA Astrophysics Data System (ADS)

    Lin, L.; Ding, W. X.; Brower, D. L.

    2016-12-01

    Magnetic fluctuation-induced particle transport is explored in the high-temperature, high-beta interior of the Madison symmetric torus (MST) reversed-field pinch by performing a multifield measurement of the correlated product of magnetic and density fluctuations associated with global resistive tearing modes. Local density fluctuations are obtained by inverting the line-integrated interferometry data after resolving the mode helicity through correlation techniques. The local magnetic and current density fluctuations are then reconstructed using a parameterized fit of Faraday-effect polarimetry measurements. Reconstructed 2D images of density and current density perturbations in a poloidal cross section exhibit significantly different spatial structure. Combined with their relative phase, the magnetic-fluctuation-induced particle transport flux and its spatial distribution are resolved. The convective magnetic fluctuation-induced particle flux profile is measured for both standard and high-performance plasmas in MST with tokamak-like confinement, showing large reduction in the flux during improved confinement.

  20. Quantum transport in coupled resonators enclosed synthetic magnetic flux

    NASA Astrophysics Data System (ADS)

    Jin, L.

    2016-07-01

    Quantum transport properties are instrumental to understanding quantum coherent transport processes. Potential applications of quantum transport are widespread, in areas ranging from quantum information science to quantum engineering, and not restricted to quantum state transfer, control and manipulation. Here, we study light transport in a ring array of coupled resonators enclosed synthetic magnetic flux. The ring configuration, with an arbitrary number of resonators embedded, forms a two-arm Aharonov-Bohm interferometer. The influence of magnetic flux on light transport is investigated. Tuning the magnetic flux can lead to resonant transmission, while half-integer magnetic flux quantum leads to completely destructive interference and transmission zeros in an interferometer with two equal arms.

  1. Detection of magnetic flux with superconducting quantum interference gratings

    NASA Astrophysics Data System (ADS)

    Miller, J. H., Jr.; Gunaratne, G. H.; Zou, Z.

    1993-03-01

    The authors have carried out finite-inductance calculations of the critical vs. flux (Ic-Phi) and voltage vs. flux (V-Phi) characteristics of superconducting interferometers with many Josephson junctions in parallel. At least two features of the calculations suggest that many junction interferometers, called superconducting quantum interference gratings, might be advantageous for the detection of magnetic flux. First, the voltage noise can be reduced significantly for a given flux-to-voltage transfer coefficient, a feature which is likely to improve the magnetic flux sensitivity of both low- and high-Tc superconducting devices. In addition, nonuniformity of the junction critical currents appears to have little adverse effect on the predicted diffraction grating such as enhancement and narrowing of the peaks in the Ic-Phi characteristic. Specific schemes for efficiently coupling flux into the device are proposed.

  2. Evolution of the magnetic helicity flux during the formation and eruption of flux ropes

    SciTech Connect

    Romano, P.; Zuccarello, F. P.; Guglielmino, S. L.; Zuccarello, F.

    2014-10-20

    We describe the evolution and the magnetic helicity flux for two active regions (ARs) since their appearance on the solar disk: NOAA 11318 and NOAA 11675. Both ARs hosted the formation and destabilization of magnetic flux ropes. In the former AR, the formation of the flux rope culminated in a flare of C2.3 GOES class and a coronal mass ejection (CME) observed by Large Angle and Spectrometric Coronagraph Experiment. In the latter AR, the region hosting the flux rope was involved in several flares, but only a partial eruption with signatures of a minor plasma outflow was observed. We found a different behavior in the accumulation of the magnetic helicity flux in the corona, depending on the magnetic configuration and on the location of the flux ropes in the ARs. Our results suggest that the complexity and strength of the photospheric magnetic field is only a partial indicator of the real likelihood of an AR producing the eruption of a flux rope and a subsequent CME.

  3. Double Catastrophe of Coronal Flux Rope in Quadrupolar Magnetic Field

    NASA Astrophysics Data System (ADS)

    Zhang, Y. Z.; Hu, Y. Q.; Wang, J. X.

    2005-06-01

    Using a relaxation method based on time-dependent ideal magnetohydrodynamic simulations, we find 2.5-dimensional force-free field solutions in spherical geometry, which are associated with an isolated flux rope embedded in a quadrupolar background magnetic field. The background field is of Antiochos type, consisting of a dipolar and an octopolar component with a neutral point somewhere in the equatorial plane. The flux rope is characterized by its magnetic fluxes, including the annular flux Φp and the axial magnetic flux Φϕ, and its geometric features described by the height of the rope axis and the length of the vertical current sheet below the rope. It is found that for a given Φp, the force-free field exhibits a complex catastrophic behavior with respect to increasing Φϕ. There exist two catastrophic points, and the catastrophic amplitude, measured by the jump in the height of the rope axis, is finite for both catastrophes. As a result, the flux rope may levitate stably in the corona after catastrophe, with a transverse current sheet above and a vertical current sheet below. The magnetic energy threshold for the two successive catastrophes are found to be larger than the corresponding partly open field energy. We argue that it is the transverse current sheet formed above the flux rope that provides a downward Lorentz force on the flux rope and thus keeps the rope levitating stably in the corona.

  4. Spatial Transport of Magnetic Flux Surfaces in Strongly Anisotropic Turbulence

    NASA Astrophysics Data System (ADS)

    Matthaeus, W. H.; Servidio, S.; Wan, M.; Ruffolo, D. J.; Rappazzo, A. F.; Oughton, S.

    2013-12-01

    Magnetic flux surfaces afford familiar descriptions of spatial structure, dynamics, and connectivity of magnetic fields, with particular relevance in contexts such as solar coronal flux tubes, magnetic field connectivity in the interplanetary and interstellar medium, as well as in laboratory plasmas and dynamo problems [1-4]. Typical models assume that field-lines are orderly, and flux tubes remain identifiable over macroscopic distances; however, a previous study has shown that flux tubes shred in the presence of fluctuations, typically losing identity after several correlation scales [5]. Here, the structure of magnetic flux surfaces is numerically investigated in a reduced magnetohydrodynamic (RMHD) model of homogeneous turbulence. Short and long-wavelength behavior is studied statistically by propagating magnetic surfaces along the mean field. At small scales magnetic surfaces become complex, experiencing an exponential thinning. At large scales, instead, the magnetic flux undergoes a diffusive behavior. The link between the diffusion of the coarse-grained flux and field-line random walk is established by means of a multiple scale analysis. Both large and small scales limits are controlled by the Kubo number. These results have consequences for understanding and interpreting processes such as magnetic reconnection and field-line diffusion in plasmas [6]. [1] E. N. Parker, Cosmical Magnetic Fields (Oxford Univ. Press, New York, 1979). [2] J. R. Jokipii and E. N. Parker, Phys. Rev. Lett. 21, 44 (1968). [3] R. Bruno et al., Planet. Space Sci. 49, 1201 (2001). [4] M. N. Rosenbluth et al., Nuclear Fusion 6, 297 (1966). [5] W. H. Matthaeus et al., Phys. Rev. Lett. 75, 2136 (1995). [6] S. Servidio et al., submitted (2013).

  5. CONDITIONS FOR TRANSVERSE WAVES PROPAGATION ALONG THIN MAGNETIC FLUX TUBES ON THE SUN

    SciTech Connect

    Lopin, Igor; Nagorny, Ivan

    2013-09-10

    The propagation of kink waves in the thin gravity stratified flux tubes with a generalized magnetic field distribution model is considered in cylindrical geometry. The new kink wave equations for both wave variables are obtained. It is shown that the inclusion of the radial component of an unperturbed tube magnetic field sufficiently transforms the conditions for the propagation of transverse waves. It is demonstrated that, for the models of isothermal and polytropic atmosphere in the tube and its environment, the propagation of kink waves along thin magnetic flux tubes is cutoff-free.

  6. Line-of-sight magnetic flux imbalances caused by electric currents

    NASA Technical Reports Server (NTRS)

    Gary, G. Allen; Rabin, Douglas

    1995-01-01

    Several physical and observational effects contribute to the significant imbalances of magnetic flux that are often observed in active regions. We consider an effect not previously treated: the influence of electric currents in the photosphere. Electric currents can cause a line-of-sight flux imbalance because of the directionality of the magnetic field they produce. Currents associated with magnetic flux tubes produce larger imbalances than do smoothly-varying distributions of flux and current. We estimate the magnitude of this effect for current densities, total currents, and magnetic geometry consistent with observations. The expected imbalances lie approximately in the range 0-15%, depending on the character of the current-carying fields and the angle from which they are viewed. Observationally, current-induced flux imbalances could be indicated by a statistical dependence of the imbalance on angular distance from disk center. A general study of magnetic flux balance in active regions is needed to determine the relative importance of other- probably larger- effects such as dilute flux (too weak to measure or rendered invisible by radiative transfer effects), merging with weak background fields, and long-range connections between active regions.

  7. Magnetic moment distribution of magnetic cataclysmic variables

    NASA Technical Reports Server (NTRS)

    Wu, Kinwah; Wickramasinghe, Dayal T.

    1991-01-01

    A simulation study is made of the relative numbers of the AM Herculis binaries and the intermediate polars as a function of the orbital period using random variables subject to suitable constraints to describe the various parameters. It is shown that the observations can be matched by a single distribution in the magnetic moment equals 0.7 +/- 0.3. For such an ensemble, the intermediate polars are distributed in the log(Porb) - log(Ps) diagram about the critical disk line but with a larger scatter than observed.

  8. The global distribution of magnetic helicity in the solar corona

    NASA Astrophysics Data System (ADS)

    Yeates, A. R.; Hornig, G.

    2016-10-01

    By defining an appropriate field line helicity, we apply the powerful concept of magnetic helicity to the problem of global magnetic field evolution in the Sun's corona. As an ideal-magnetohydrodynamic invariant, the field line helicity is a meaningful measure of how magnetic helicity is distributed within the coronal volume. It may be interpreted, for each magnetic field line, as a magnetic flux linking with that field line. Using magneto-frictional simulations, we investigate how field line helicity evolves in the non-potential corona as a result of shearing by large-scale motions on the solar surface. On open magnetic field lines, the helicity injected by the Sun is largely output to the solar wind, provided that the coronal relaxation is sufficiently fast. But on closed magnetic field lines, helicity is able to build up. We find that the field line helicity is non-uniformly distributed, and is highly concentrated in twisted magnetic flux ropes. Eruption of these flux ropes is shown to lead to sudden bursts of helicity output, in contrast to the steady flux along the open magnetic field lines. Movies are available at http://www.aanda.org

  9. Correlations Between Magnetic Flux and Levitation Force of HTS Bulk Above a Permanent Magnet Guideway

    NASA Astrophysics Data System (ADS)

    Huang, Huan; Zheng, Jun; Zheng, Botian; Qian, Nan; Li, Haitao; Li, Jipeng; Deng, Zigang

    2017-06-01

    In order to clarify the correlations between magnetic flux and levitation force of the high-temperature superconducting (HTS) bulk, we measured the magnetic flux density on bottom and top surfaces of a bulk superconductor while vertically moving above a permanent magnet guideway (PMG). The levitation force of the bulk superconductor was measured simultaneously. In this study, the HTS bulk was moved down and up for three times between field-cooling position and working position above the PMG, followed by a relaxation measurement of 300 s at the minimum height position. During the whole processes, the magnetic flux density and levitation force of the bulk superconductor were recorded and collected by a multipoint magnetic field measurement platform and a self-developed maglev measurement system, respectively. The magnetic flux density on the bottom surface reflected the induced field in the superconductor bulk, while on the top, it reveals the penetrated magnetic flux. The results show that the magnetic flux density and levitation force of the bulk superconductor are in direct correlation from the viewpoint of inner supercurrent. In general, this work is instructive for understanding the connection of the magnetic flux density, the inner current density and the levitation behavior of HTS bulk employed in a maglev system. Meanwhile, this magnetic flux density measurement method has enriched present experimental evaluation methods of maglev system.

  10. Correlations Between Magnetic Flux and Levitation Force of HTS Bulk Above a Permanent Magnet Guideway

    NASA Astrophysics Data System (ADS)

    Huang, Huan; Zheng, Jun; Zheng, Botian; Qian, Nan; Li, Haitao; Li, Jipeng; Deng, Zigang

    2017-10-01

    In order to clarify the correlations between magnetic flux and levitation force of the high-temperature superconducting (HTS) bulk, we measured the magnetic flux density on bottom and top surfaces of a bulk superconductor while vertically moving above a permanent magnet guideway (PMG). The levitation force of the bulk superconductor was measured simultaneously. In this study, the HTS bulk was moved down and up for three times between field-cooling position and working position above the PMG, followed by a relaxation measurement of 300 s at the minimum height position. During the whole processes, the magnetic flux density and levitation force of the bulk superconductor were recorded and collected by a multipoint magnetic field measurement platform and a self-developed maglev measurement system, respectively. The magnetic flux density on the bottom surface reflected the induced field in the superconductor bulk, while on the top, it reveals the penetrated magnetic flux. The results show that the magnetic flux density and levitation force of the bulk superconductor are in direct correlation from the viewpoint of inner supercurrent. In general, this work is instructive for understanding the connection of the magnetic flux density, the inner current density and the levitation behavior of HTS bulk employed in a maglev system. Meanwhile, this magnetic flux density measurement method has enriched present experimental evaluation methods of maglev system.

  11. SEPARATION OF THE INTERSTELLAR BOUNDARY EXPLORER RIBBON FROM GLOBALLY DISTRIBUTED ENERGETIC NEUTRAL ATOM FLUX

    SciTech Connect

    Schwadron, N. A.; Kucharek, H.; Moebius, E. E-mail: harald.kucharek@unh.edu

    2011-04-10

    The Interstellar Boundary Explorer (IBEX) observes a remarkable feature, the IBEX ribbon, which has energetic neutral atom (ENA) flux over a narrow region {approx}20{sup 0} wide, a factor of 2-3 higher than the more globally distributed ENA flux. Here, we separate ENA emissions in the ribbon from the distributed flux by applying a transparency mask over the ribbon and regions of high emissions, and then solve for the distributed flux using an interpolation scheme. Our analysis shows that the energy spectrum and spatial distribution of the ribbon are distinct from the surrounding globally distributed flux. The ribbon energy spectrum shows a knee between {approx}1 and 4 keV, and the angular distribution is approximately independent of energy. In contrast, the distributed flux does not show a clear knee and more closely conforms to a power law over much of the sky. Consistent with previous analyses, the slope of the power law steepens from the nose to tail, suggesting a weaker termination shock toward the tail as compared to the nose. The knee in the energy spectrum of the ribbon suggests that its source plasma population is generated via a distinct physical process. Both the slope in the energy distribution of the distributed flux and the knee in the energy distribution of the ribbon are ordered by latitude. The heliotail may be identified in maps of globally distributed flux as a broad region of low flux centered {approx}44{sup 0}W of the interstellar downwind direction, suggesting heliotail deflection by the interstellar magnetic field.

  12. Quantized Chiral Magnetic Current from Reconnections of Magnetic Flux

    SciTech Connect

    Hirono, Yuji; Kharzeev, Dmitri E.; Yin, Yi

    2016-10-20

    We introduce a new mechanism for the chiral magnetic e ect that does not require an initial chirality imbalance. The chiral magnetic current is generated by reconnections of magnetic ux that change the magnetic helicity of the system. The resulting current is entirely determined by the change of magnetic helicity, and it is quantized.

  13. SQUIDs De-fluxing Using a Decaying AC Magnetic Field

    SciTech Connect

    Matlashov, Andrei Nikolaevich; Semenov, Vasili Kirilovich; Anderson, Bill

    2016-06-08

    Flux trapping is the Achilles’ heel of all superconductor electronics. The most direct way to avoid flux trapping is a prevention of superconductor circuits from exposure to magnetic fields. Unfortunately this is not feasible if the circuits must be exposed to a strong DC magnetic field even for a short period of time. For example, such unavoidable exposures take place in superparamagnetic relaxation measurements (SPMR) and ultra-low field magnetic resonance imaging (ULF MRI) using unshielded thin-film SQUID-based gradiometers. Unshielded SQUIDs stop working after being exposed to DC magnetic fields of only a few Gauss in strength. In this paper we present experimental results with de-fluxing of planar thin-film LTS SQUID-based gradiometers using a strong decaying AC magnetic field. We used four commercial G136 gradiometers for SPMR measurements with up to a 10 mT magnetizing field. Strong 12.9 kHz decaying magnetic field pulses reliably return SQUIDs to normal operation 50 ms after zeroing the DC magnetizing field. This new AC de-fluxing method was also successfully tested with seven other different types of LTS SQUID sensors and has been shown to dissipate extremely low energy.

  14. SIGNATURES OF MAGNETIC RECONNECTION AT BOUNDARIES OF INTERPLANETARY SMALL-SCALE MAGNETIC FLUX ROPES

    SciTech Connect

    Tian Hui; Yao Shuo; Zong Qiugang; Qi Yu; He Jiansen

    2010-09-01

    The interaction between interplanetary small-scale magnetic flux ropes and the magnetic field in the ambient solar wind is an important topic in the understanding of the evolution of magnetic structures in the heliosphere. Through a survey of 125 previously reported small flux ropes from 1995 to 2005, we find that 44 of them reveal clear signatures of Alfvenic fluctuations and thus classify them as Alfven wave trains rather than flux ropes. Signatures of magnetic reconnection, generally including a plasma jet of {approx}30 km s{sup -1} within a magnetic field rotational region, are clearly present at boundaries of about 42% of the flux ropes and 14% of the wave trains. The reconnection exhausts are often observed to show a local increase in the proton temperature, density, and plasma beta. About 66% of the reconnection events at flux rope boundaries are associated with a magnetic field shear angle larger than 90{sup 0} and 73% of them reveal a decrease of 20% or more in the magnetic field magnitude, suggesting a dominance of anti-parallel reconnection at flux rope boundaries. The occurrence rate of magnetic reconnection at flux rope boundaries through the years 1995-2005 is also investigated and we find that it is relatively low around the solar maximum and much higher when approaching solar minima. The average magnetic field depression and shear angle for reconnection events at flux rope boundaries also reveal a similar trend from 1995 to 2005. Our results demonstrate for the first time that boundaries of a substantial fraction of small-scale flux ropes have properties similar to those of magnetic clouds, in the sense that both of them exhibit signatures of magnetic reconnection. The observed reconnection signatures could be related either to the formation of small flux ropes or to the interaction between flux ropes and the interplanetary magnetic fields.

  15. AN ANALYSIS OF MAGNETOHYDRODYNAMIC INVARIANTS OF MAGNETIC FLUCTUATIONS WITHIN INTERPLANETARY FLUX ROPES

    SciTech Connect

    Telloni, D.; Perri, S.; Carbone, V.; Bruno, R.; D Amicis, R.

    2013-10-10

    A statistical analysis of magnetic flux ropes, identified by large-amplitude, smooth rotations of the magnetic field vector and a low level of both proton density and temperature, has been performed by computing the invariants of the ideal magnetohydrodynamic (MHD) equations, namely the magnetic helicity, the cross-helicity, and the total energy, via magnetic field and plasma fluctuations in the interplanetary medium. A technique based on the wavelet spectrograms of the MHD invariants allows the localization and characterization of those structures in both scales and time: it has been observed that flux ropes show, as expected, high magnetic helicity states (|σ{sub m}| in [0.6: 1]), but extremely variable cross-helicity states (|σ{sub c}| in [0: 0.8]), which, however, are not independent of the magnetic helicity content of the flux rope itself. The two normalized MHD invariants observed within the flux ropes tend indeed to distribute, neither trivially nor automatically, along the √(σ{sub m}{sup 2}+σ{sub c}{sup 2})=1 curve, thus suggesting that some constraint should exist between the magnetic and cross-helicity content of the structures. The analysis carried out has further showed that the flux rope properties are totally independent of their time duration and that they are detected either as a sort of interface between different portions of solar wind or as isolated structures embedded in the same stream.

  16. Sigmoidal equilibria and eruptive instabilities in laboratory magnetic flux ropes

    NASA Astrophysics Data System (ADS)

    Myers, C. E.; Yamada, M.; Belova, E.; Ji, H.; Yoo, J.

    2013-12-01

    The Magnetic Reconnection Experiment (MRX) has recently been modified to study quasi-statically driven line-tied magnetic flux ropes in the context of storage-and-release eruptions in the corona. Detailed in situ magnetic measurements and supporting MHD simulations permit quantitative analysis of the plasma behavior. We find that the behavior of these flux ropes depends strongly on the properties of the applied potential magnetic field arcade. For example, when the arcade is aligned parallel to the flux rope footpoints, force free currents induced in the expanding rope modify the pressure and tension in the arcade, resulting in a confined, quiescent discharge with a saturated kink instability. When the arcade is obliquely aligned to the footpoints, on the other hand, a highly sigmoidal equilibrium forms that can dynamically erupt (see Fig. 1 and Fig. 2). To our knowledge, these storage-and-release eruptions are the first of their kind to be produced in the laboratory. A new 2D magnetic probe array is used to map out the internal structure of the flux ropes during both the storage and the release phases of the discharge. The kink instability and the torus instability are studied as candidate eruptive mechanisms--the latter by varying the vertical gradient of the potential field arcade. We also investigate magnetic reconnection events that accompany the eruptions. The long-term objective of this work is to use internal magnetic measurements of the flux rope structure to better understand the evolution and eruption of comparable structures in the corona. This research is supported by DoE Contract Number DE-AC02-09CH11466 and by the Center for Magnetic Self-Organization (CMSO). Qualitative sketches of flux ropes formed in (1) a parallel potential field arcade; and (2) an oblique potential field arcade. One-dimensional magnetic measurements from (1) a parallel arcade discharge that is confined; and (2) an oblique arcade discharge that erupts.

  17. Siphon flows in isolated magnetic flux tubes. 3: The equilibrium path of the flux tube arch

    NASA Technical Reports Server (NTRS)

    Thomas, John H.; Montesinis, Benjamin

    1989-01-01

    The arched equilibrium path of a thin magnetic flux tube in a plane-stratified, nonmagnetic atmosphere is calculated for cases in which the flux tube contains a steady siphon flow. The large scale mechanical equilibrium of the flux tube involves a balance among the magnetic buoyancy force, the net magnetic tension force due to the curvature of the flux tube axis, and the inertial (centrifugal) force due to the siphon flow along curved streamlines. The ends of the flux tube are assumed to be pinned down by some other external force. Both isothermal and adiabatic siphon flows are considered for flux tubes in an isothermal external atmosphere. For the isothermal case, in the absence of a siphon flow the equilibrium path reduces to the static arch calculated by Parker (1975, 1979). The presence of a siphon flow causes the flux tube arch to bend more sharply, so that magnetic tension can overcome the additional straightening effect of the inertial force, and reduces the maximum width of the arch. The curvature of the arch increases as the siphon flow speed increases. For a critical siphon flow, with supercritical flow in the downstream leg, the arch is asymmetric, with greater curvature in the downstream leg of the arch. Adiabatic flow have qualitatively similar effects, except that adiabatic cooling reduces the buoyancy of the flux tube and thus leads to significantly wider arches. In some cases the cooling is strong enough to create negative buoyancy along sections of the flux tube, requiring upward curvature of the flux tube path along these sections and sometimes leading to unusual equilibrium paths of periodic, sinusoidal form.

  18. Siphon flows in isolated magnetic flux tubes. 3: The equilibrium path of the flux tube arch

    NASA Astrophysics Data System (ADS)

    Thomas, John H.; Montesinis, Benjamin

    1989-09-01

    The arched equilibrium path of a thin magnetic flux tube in a plane-stratified, nonmagnetic atmosphere is calculated for cases in which the flux tube contains a steady siphon flow. The large scale mechanical equilibrium of the flux tube involves a balance among the magnetic buoyancy force, the net magnetic tension force due to the curvature of the flux tube axis, and the inertial (centrifugal) force due to the siphon flow along curved streamlines. The ends of the flux tube are assumed to be pinned down by some other external force. Both isothermal and adiabatic siphon flows are considered for flux tubes in an isothermal external atmosphere. For the isothermal case, in the absence of a siphon flow the equilibrium path reduces to the static arch calculated by Parker (1975, 1979). The presence of a siphon flow causes the flux tube arch to bend more sharply, so that magnetic tension can overcome the additional straightening effect of the inertial force, and reduces the maximum width of the arch. The curvature of the arch increases as the siphon flow speed increases. For a critical siphon flow, with supercritical flow in the downstream leg, the arch is asymmetric, with greater curvature in the downstream leg of the arch. Adiabatic flow have qualitatively similar effects, except that adiabatic cooling reduces the buoyancy of the flux tube and thus leads to significantly wider arches. In some cases the cooling is strong enough to create negative buoyancy along sections of the flux tube, requiring upward curvature of the flux tube path along these sections and sometimes leading to unusual equilibrium paths of periodic, sinusoidal form.

  19. Coronal Heating and the Magnetic Flux Content of the Network

    NASA Astrophysics Data System (ADS)

    Moore, R. L.; Falconer, D. A.; Porter, J. G.; Hathaway, D. H.

    2003-05-01

    We investigate the heating of the quiet corona by measuring the increase of coronal luminosity with the amount of magnetic flux in the underlying network at solar minimum when there were no active regions on the face of the Sun. The coronal luminosity is measured from Fe IX/X-Fe XII pairs of coronal images from SOHO/EIT. The network magnetic flux content is measured from SOHO/MDI magnetograms. We find that the luminosity of the corona in our quiet regions increases roughly in proportion to the square root of the magnetic flux content of the network and roughly in proportion to the length of the perimeter of the network magnetic flux clumps. From (1) this result, (2) other observations of many fine-scale explosive events at the edges of network flux clumps, and (3) a demonstration that it is energetically feasible for the heating of the corona in quiet regions to be driven by explosions of granule-sized sheared-core magnetic bipoles embedded in the edges of network flux clumps, we infer that in quiet regions that are not influenced by active regions the corona is mainly heated by such magnetic activity in the edges of the network flux clumps. Our observational results together with our feasibility analysis allow us to predict that (1) at the edges of the network flux clumps there are many transient sheared-core bipoles of the size and lifetime of granules and having transverse field strengths > 100 G, (2) 30 of these bipoles are present per supergranule, and (3) most spicules are produced by explosions of these bipoles. This work was supported by NASA's Office of Space Science through its Solar and Heliospheric Physics Supporting Research and Technology Program and its Sun-Earth Connection Guest Investigator Program.

  20. Structure of sunspot penumbrae - Fallen magnetic flux tubes

    NASA Technical Reports Server (NTRS)

    Wentzel, Donat G.

    1992-01-01

    A model is presented of a sunspot penumbra involving magnetic flux tubes that have fallen into the photosphere and float there. An upwelling at the inner end of a fallen tube continuously provides additional gas. This gas flows along and lengthens the tube and is observable as the Evershed flow. Fallen flux tubes may appear as bright streaks near the upwelling, but they become dark filaments further out. The model is corroborated by recent optical high-resolution magnetic data regarding the penumbral filaments, by the 12-micron magnetic measurements relevant to the height of the temperature minimum, and by photographs of the umbra/penumbra boundary.

  1. Re-direction of dc magnetic flux in magnetically isotropic multilayered structures

    NASA Astrophysics Data System (ADS)

    Tarkhanyan, Roland H.; Niarchos, Dimitris G.

    2016-07-01

    Analytical design of a periodic composite structure allowing re-direction (bending) of dc magnetic flux with respect to applied external field is presented using methods of transformation optics. The composite structure is made of micrometer scale alternating layers of two different homogeneous and magnetically isotropic materials. Dependence of the magnetic flux bending angle on geometrical orientation of the layers as well as on the magnetic permeability ratio is examined. Such structures can find use in various devices based on the control and manipulations of the magnetic flux.

  2. Vacuum magnetic fields with dense flux surfaces

    SciTech Connect

    Cary, J R

    1982-05-01

    A procedure is given for eliminating resonances and stochasticity in nonaxisymmetric vacuum toroidal magnetic field. The results of this procedure are tested by the surface of section method. It is found that one can obtain magnetic fields with increased rotational transform and decreased island structure while retaining basically the same winding law.

  3. The Solar Internetwork. I. Contribution to the Network Magnetic Flux

    NASA Astrophysics Data System (ADS)

    Gošić, M.; Bellot Rubio, L. R.; Orozco Suárez, D.; Katsukawa, Y.; del Toro Iniesta, J. C.

    2014-12-01

    The magnetic network (NE) observed on the solar surface harbors a sizable fraction of the total quiet Sun flux. However, its origin and maintenance are not well known. Here we investigate the contribution of internetwork (IN) magnetic fields to the NE flux. IN fields permeate the interior of supergranular cells and show large emergence rates. We use long-duration sequences of magnetograms acquired by Hinode and an automatic feature tracking algorithm to follow the evolution of NE and IN flux elements. We find that 14% of the quiet Sun (QS) flux is in the form of IN fields with little temporal variations. IN elements interact with NE patches and modify the flux budget of the NE either by adding flux (through merging processes) or by removing it (through cancellation events). Mergings appear to be dominant, so the net flux contribution of the IN is positive. The observed rate of flux transfer to the NE is 1.5 × 1024 Mx day-1 over the entire solar surface. Thus, the IN supplies as much flux as is present in the NE in only 9-13 hr. Taking into account that not all the transferred flux is incorporated into the NE, we find that the IN would be able to replace the entire NE flux in approximately 18-24 hr. This renders the IN the most important contributor to the NE, challenging the view that ephemeral regions are the main source of flux in the QS. About 40% of the total IN flux eventually ends up in the NE.

  4. Magnetic flux noise in MgB2 superconductor

    NASA Astrophysics Data System (ADS)

    Khare, Neeraj; Singh, D. P.; Gupta, Ajai K.

    2008-05-01

    Magnetic flux noise in MgB2 polycrystalline sample is measured using a high-TC rf-superconducting quantum interference device in the temperature range of 6-40K. A small magnetic field (˜200mG ) was applied while cooling the sample. The flux noise exhibits 1/fα type of behavior with α ˜1.0-1.3 and shows enhanced noise around 24 and 37K. The flux noise seems to originate from thermally activated vortex hopping. The large magnetic noise at 24K indicates the presence of larger density of pinning sites with energies ˜0.061eV leading to enhanced magnetic fluctuations at temperatures much below TC.

  5. A novel flux-switching permanent magnet machine with v-shaped magnets

    NASA Astrophysics Data System (ADS)

    Zhao, Guishu; Hua, Wei

    2017-05-01

    In this paper, firstly a novel 6-stator-coil/17-rotor-pole (6/17) flux-switching permanent magnet (FSPM) machine with V-shaped magnets, deduced from conventional 12/17 FSPM machines is proposed to achieve more symmetrical phase back-electromotive force (back-EMF), and smaller torque ripple by comparing with an existing 6/10 V-shaped FSPM machine. Then, to obtain larger electromagnetic torque, less torque ripple, and easier mechanical processing, two improved variants based on the original 6/17 V-shaped topology are proposed. For the first variant, the separate stator-core segments located on the stator yoke are connected into a united stator yoke, while for the second variant the stator core is a whole entity by adding magnetic bridges at the ends of permanent magnets (PMs). Consequently, the performances of the three 6/17 V-shaped FSPM machines, namely, the original one and the two variants, are conducted by finite element analysis (FEA). The results reveal that the first variant exhibits significantly larger torque and considerably improved torque per magnet volume, i.e., the magnet utilization ratio than the original one, and the second variant exhibits the smallest torque ripple, least total harmonic distribution (THD) of phase back-EMF, and easiest mechanical processing for manufacturing.

  6. Magnetized Black Hole Accretion Disks with Poloidal Flux

    NASA Astrophysics Data System (ADS)

    Salvesen, Greg; Simon, Jacob B.; Armitage, Philip J.; Begelman, Mitchell C.

    2017-08-01

    Observations of blueshifted absorption lines associated with black hole X-ray binary accretion disk winds sometimes imply a magnetic driving mechansim. To study the properties of magnetized disks, we performed shearing box simulations (stratified, isothermal, ideal MHD) with different amounts of net vertical magnetic flux, spanning essentially the entire range over which the MRI is linearly unstable. This net vertical flux sets the strength of the dominant toroidal field that is generated by the MRI-dynamo. Given sufficiently large net vertical flux, magnetic pressure support against gravity dominates throughout the vertical column of the disk. Without net poloidal flux, a strongly magnetized state cannot persist because the toroidal field buoyantly escapes faster than it can be replenished. With increasing disk magnetization: (1) toroidal field reversals characteristic of the MRI-dynamo become less frequent and more sporadic and (2) gas density becomes more inhomogeneous, with field concentrating in low-density regions. We are currently investigating whether magnetic pressure support in the disk atmosphere alters the disk continuum spectrum, which would bring the robustness of black hole spin measurements into question.

  7. DRIFT ORBITS OF ENERGETIC PARTICLES IN AN INTERPLANETARY MAGNETIC FLUX ROPE

    SciTech Connect

    Krittinatham, W.; Ruffolo, D. E-mail: scdjr@mahidol.ac.t

    2009-10-10

    Interplanetary magnetic flux ropes have significant effects on the distribution of energetic particles in space. Flux ropes can confine solar energetic particles (SEPs) for hours, and have relatively low densities of Galactic cosmic rays (GCRs), as seen during second-stage Forbush decreases. As particle diffusion is apparently inhibited across the flux rope boundary, we suggest that guiding center drifts could play a significant role in particle motion into and out of the flux ropes. We develop an analytic model of the magnetic field in an interplanetary magnetic flux rope attached to the Sun at both ends, in quasi-toroidal coordinates, with the realistic features of a flux rope cross section that is small near the Sun, expanding with distance from the Sun, and field lines that are wound less tightly close to the Sun due to stretching by the solar wind. We calculate the particle drift velocity field due to the magnetic field curvature and gradient as a function of position and pitch-angle cosine, and trace particle guiding center orbits numerically, assuming conservation of the first adiabatic invariant. We find that SEPs in the interior of a flux rope can have drift orbits that are trapped for long times, as in a tokamak configuration, with resonant escape features as a function of the winding number. For Forbush decreases of GCRs, the drifts should contribute to a unidirectional anisotropy and net flow from one leg of the loop to the other, in a direction determined by the poloidal field direction.

  8. Vacuum currents induced by a magnetic flux around a cosmic string with finite core

    NASA Astrophysics Data System (ADS)

    Bezerra de Mello, E. R.; Bezerra, V. B.; Saharian, A. A.; Harutyunyan, H. H.

    2015-03-01

    We evaluate the Hadamard function and the vacuum expectation value of the current density for a massive complex scalar field in the generalized geometry of a straight cosmic string with a finite core enclosing an arbitrary distributed magnetic flux along the string axis. For the interior geometry, a general cylindrically symmetric static metric tensor is used with finite support. In the region outside the core, both the Hadamard function and the current density are decomposed into the idealized zero-thickness cosmic string and core-induced contributions. The only nonzero component corresponds to the azimuthal current. The zero-thickness part of the latter is a periodic function of the magnetic flux inside the core, with the period equal to the quantum flux. As a consequence of the direct interaction of the quantum field with the magnetic field inside the penetrable core, the core-induced contribution, in general, is not a periodic function of the flux. In addition, the vacuum current, in general, is not a monotonic function of the distance from the string and may change the sign. For a general model of the core interior, we also evaluate the magnetic fields generated by the vacuum current. As applications of the general results, we have considered an impenetrable core modeled by Robin boundary condition, a core with the Minkowski-like interior and a core with a constant positive curvature space. Various exactly solvable distributions of the magnetic flux are discussed.

  9. Magnetic field characters of returning flux tubes in Saturn's magnetosphere

    NASA Astrophysics Data System (ADS)

    Lai, Hairong; Russell, Christopher; Jia, Yingdong; Wei, Hanying

    2016-04-01

    Deep in the Saturnian magnetosphere, water-group neutrals are ionized after being released from the plume of Enceladus at 4 RS. This forms a plasma disk from 2.5 to 8 RS around Saturn and the typical source rate is 12~250 kg/s. Such plasma addition must be shed to the solar wind ultimately to maintain the plasma density in the magnetosphere in long term average. In this plasma transfer process, the magnetic flux also convects outward. To conserve the total magnetic flux imposed on the magnetosphere by the planet's internal dynamo, the magnetic flux has to return to the inner magnetosphere. Flux tubes are found to be the major form of such return. Determining such flux tubes is essential in understanding the breathing of Saturn magnetosphere. We investigated 10 years of Cassini magnetometer data to identify over six hundred flux-returning events between 4 and 18 in L. Statistical properties are presented, to constrain the origin, transport and evolution of these flux tubes.

  10. Dynamics of local isolated magnetic flux tubes in a fast-rotating stellar atmosphere

    SciTech Connect

    Chou, W.; Tajima, C.T.; Matsumoto, R. |; Shibata, K.

    1998-01-01

    Dynamics of magnetic flux tubes in the fast rotating stellar atmosphere is studied. We focus on the effects and signatures of the instability of the flux tube emergence influenced by the Coriolis force. We present the result from a linear stability analysis and discuss its possible signatures in the course of the evolution of G-type and M-type stars. We present a three dimensional magnetohydrodynamical simulation of local isolated magnetic flux tubes under a magnetic buoyancy instability in co-rotating Cartesian coordinates. We find that the combination of the buoyancy instability and the Coriolis effect gives rise to a mechanism, to twist the emerging magnetic flux tube into a helical structure. The tilt angle, east-west asymmetry and magnetic helicity of the Twisted flux tubes in the simulations are studied in detail. The linear and nonlinear analyses provide hints as to what kind of pattern of large spots in young M-type main-sequence stars might be observed. We find that young and old G-type stars may have different distributions of spots while M-type stars may always have low latitudes spots. The size of stellar spots may decrease when a star becomes older, due to the decreasing of magnetic field. A qualitative comparison with solar observations is also presented.

  11. Flux distribution in Fe-based superconducting materials by magneto-optical imaging

    NASA Astrophysics Data System (ADS)

    Lin, Zhi Wei; Zhu, Jian Guo; Guo, You Guang; Wang, Xiao Lin; Dou, Shi Xue; Johansen, Tom H.; Shi, Xun; Choi, K. Y.

    2012-04-01

    This paper presents the magnetic flux distributions in Fe-based superconducting materials including single crystal of Ba(Fe1.9Ni0.1)As2 and Ba(Fe1.8Co0.2)As2, as well as polycrystalline SmFeO0.75F0.2As by means of magneto-optical imaging (MOI) technique. The single crystals were grown out of FeAs flux while polycrystalline sample was grown by hot-press. A MOI film with in-plan magnetization was used to visualize flux distributions at the sample surface. A series of magneto-optical images was taken when the samples were zero-field cooled and field cooled. The flux behavior, including penetration into and expelling from the samples, as well as pinning properties were studied. When external fields increase, flux is completely shielded from the crystals, then, gradually penetrates toward the crystal center from the edge. For polycrystalline sample, Meissner state was observed at very low field. With increasing the field further, flux penetrates into the sample easily along grain boundary, then into grain. Compared with high-Tc cuprates, it is found that the flux distributions in Fe-based superconducting materials are very similar to that in high-Tc cuprates with strong pinning strength.

  12. The Return of Magnetic Flux to the Inner Saturnian Magnetosphere

    NASA Astrophysics Data System (ADS)

    Lai, Hairong; Russell, Christopher T.; Jia, Yingdong; Masters, Adam; Dougherty, Michele K.

    2017-04-01

    The addition of plasma to the rotating inner Saturnian magnetosphere drives the circulation of the magnetic flux. The magnetic flux is loaded with cold plasma originating from Enceladus and its plasma torus. It then convects outward to the tail region, is emptied of plasma during reconnection events, and returns buoyantly to the inner magnetosphere. Returning flux tubes carry hot and tenuous plasma that serves as a marker of this type of flux tube. The plasma inside the tubes drifts at different rates depending on energy in the curved and inhomogeneous magnetosphere when the tubes convect inward. This energy dispersion can be used to track the flux tube. With data from MAG and CAPS, we model the energy dispersion of the electrons to determine the age and the point of return of the 'empty' flux tubes. The results show that even the 'fresh' flux tubes are several hours old when seen and they start to return at 19 Saturn radii, near Titan's orbit. This supports the hypothesis that returning flux tubes generated by reconnection in the far-tail region are injected directly into the inner magnetosphere.

  13. Mechanisms of the outer radiation belt electron flux variation during magnetic storms

    NASA Astrophysics Data System (ADS)

    Nakamura, M.; Obara, T.; Koshiishi, H.; Koga, K.; Matsumoto, H.; Goka, T.

    2003-12-01

    We have investigated variations of the energetic electron flux (> 0.4 MeV) and the magnetic field in the outer radiation belt obtained from the Standard DOse Monitor (SDOM) and the MAgnetoMeter (MAM) of the Space Environment Data Acquisition equipment (SEDA) onboard Tsubasa (Mission Demonstration Test Satellite (MDS)-1). Since Tsubasa operates in geostationary transfer orbit (GTO) with an orbital period of 10 hours and an inclination of 28.5 degrees, it has provided a rare opportunity for directly observing near-equatorial radiation belt plasma particles and the magnetic field during magnetic storms. The decreases of the energetic electron flux during the main phase of the magnetic storms, and the subsequent recoveries and enhancements during the recovery phase in the outer radiation belt are linked respectively to typical variations of the magnetic field. At the moment that the outer radiation belt flux sharply drops during the main phase of the 17 April 2002 magnetic storm, the butterfly distribution is observed at L=5 and the magnetic equator where the magnitude of magnetic field is much smaller than the IGRF model. Calculating the drift motions of the energetic electrons in the Tyganenko 2001 magnetospheric magnetic field model, shows that the drift-shell splitting mechanism could generate the butterfly distribution due to loss of the near-equatorially mirroring electrons through dayside magnetopause boundary. We evaluate roles and contributions of the other possible mechanisms to explain the flux decreases. We discuss the three-dimensional field configuration in the magnetopause to compare with the low earth orbital observation of the outer radiation belt flux.

  14. Magnetic clouds, helicity conservation, and intrinsic scale flux ropes

    NASA Technical Reports Server (NTRS)

    Kumar, A.; Rust, D. M.

    1995-01-01

    An intrinsic-scale flux-rope model for interplanetary magnetic clouds, incorporating conservation of magnetic helicity, flux and mass is found to adequately explain clouds' average thermodynamic and magnetic properties. In spite their continuous expansion as they balloon into interplanetary space, magnetic clouds maintain high temperatures. This is shown to be due to magnetic energy dissipation. The temperature of an expanding cloud is shown to pass through a maximum above its starting temperature if the initial plasma beta in the cloud is less than 2/3. Excess magnetic pressure inside the cloud is not an important driver of the expansion as it is almost balanced by the tension in the helical field lines. It is conservation of magnetic helicity and flux that requires that clouds expand radially as they move away from the Sun. Comparison with published data shows good agreement between measured cloud properties and theory. Parameters determined from theoretical fits to the data, when extended back to the Sun, are consistent with the origin of interplanetary magnetic clouds in solar filament eruptions. A possible extension of the heating mechanism discussed here to heating of the solar corona is discussed.

  15. THE EVOLUTION OF OPEN MAGNETIC FLUX DRIVEN BY PHOTOSPHERIC DYNAMICS

    SciTech Connect

    Linker, Jon A.; Lionello, Roberto; Mikic, Zoran; Titov, Viacheslav S.; Antiochos, Spiro K. E-mail: lionel@predsci.com E-mail: titovv@predsci.com

    2011-04-20

    The coronal magnetic field is of paramount importance in solar and heliospheric physics. Two profoundly different views of the coronal magnetic field have emerged. In quasi-steady models, the predominant source of open magnetic field is in coronal holes. In contrast, in the interchange model, the open magnetic flux is conserved, and the coronal magnetic field can only respond to the photospheric evolution via interchange reconnection. In this view, the open magnetic flux diffuses through the closed, streamer belt fields, and substantial open flux is present in the streamer belt during solar minimum. However, Antiochos and coworkers, in the form of a conjecture, argued that truly isolated open flux cannot exist in a configuration with one heliospheric current sheet-it will connect via narrow corridors to the polar coronal hole of the same polarity. This contradicts the requirements of the interchange model. We have performed an MHD simulation of the solar corona up to 20 R{sub sun} to test both the interchange model and the Antiochos conjecture. We use a synoptic map for Carrington rotation 1913 as the boundary condition for the model, with two small bipoles introduced into the region where a positive polarity extended coronal hole forms. We introduce flows at the photospheric boundary surface to see if open flux associated with the bipoles can be moved into the closed-field region. Interchange reconnection does occur in response to these motions. However, we find that the open magnetic flux cannot be simply injected into closed-field regions-the flux eventually closes down and disconnected flux is created. Flux either opens or closes, as required, to maintain topologically distinct open- and closed-field regions, with no indiscriminate mixing of the two. The early evolution conforms to the Antiochos conjecture in that a narrow corridor of open flux connects the portion of the coronal hole that is nearly detached by one of the bipoles. In the later evolution, a

  16. The Evolution of Open Magnetic Flux Driven by Photospheric Dynamics

    NASA Technical Reports Server (NTRS)

    Linker, Jon A.; Lionello, Roberto; Mikic, Zoran; Titov, Viacheslav S.; Antiochos, Spiro K.

    2010-01-01

    The coronal magnetic field is of paramount importance in solar and heliospheric physics. Two profoundly different views of the coronal magnetic field have emerged. In quasi-steady models, the predominant source of open magnetic field is in coronal holes. In contrast, in the interchange model, the open magnetic flux is conserved, and the coronal magnetic field can only respond to the photospheric evolution via interchange reconnection. In this view the open magnetic flux diffuses through the closed, streamer belt fields, and substantial open flux is present in the streamer belt during solar minimum. However, Antiochos and co-workers, in the form of a conjecture, argued that truly isolated open flux cannot exist in a configuration with one heliospheric current sheet (HCS) - it will connect via narrow corridors to the polar coronal hole of the same polarity. This contradicts the requirements of the interchange model. We have performed an MHD simulation of the solar corona up to 20R solar to test both the interchange model and the Antiochos conjecture. We use a synoptic map for Carrington Rotation 1913 as the boundary condition for the model, with two small bipoles introduced into the region where a positive polarity extended coronal hole forms. We introduce flows at the photospheric boundary surface to see if open flux associated with the bipoles can be moved into the closed-field region. Interchange reconnection does occur in response to these motions. However, we find that the open magnetic flux cannot be simply injected into closed-field regions - the flux eventually closes down and disconnected flux is created. Flux either opens or closes, as required, to maintain topologically distinct open and closed field regions, with no indiscriminate mixing of the two. The early evolution conforms to the Antiochos conjecture in that a narrow corridor of open flux connects the portion of the coronal hole that is nearly detached by one of the bipoles. In the later evolution, a

  17. Determination of meteor flux distribution over the celestial sphere

    NASA Technical Reports Server (NTRS)

    Andreev, V. V.; Belkovich, O. I.; Filimonova, T. K.; Sidorov, V. V.

    1992-01-01

    A new method of determination of meteor flux density distribution over the celestial sphere is discussed. The flux density was derived from observations by radar together with measurements of angles of arrival of radio waves reflected from meteor trails. The role of small meteor showers over the sporadic background is shown.

  18. Instantaneous flux distribution on a solar central receiver

    NASA Astrophysics Data System (ADS)

    vant-Hull, L. L.

    1984-02-01

    An important aspect in the design of a Solar Central Receiver system is the distribution of the solar flux on the receiver. In this paper, information for the Central Receiver Pilot Plant, Solar One, at Barstow, California, on the time variation of the receiver flux during cloud passage, at sunrise and during the day, is presented.

  19. Dual-stage trapped-flux magnet cryostat for measurements at high magnetic fields

    DOEpatents

    Islam, Zahirul; Das, Ritesh K.; Weinstein, Roy

    2015-04-14

    A method and a dual-stage trapped-flux magnet cryostat apparatus are provided for implementing enhanced measurements at high magnetic fields. The dual-stage trapped-flux magnet cryostat system includes a trapped-flux magnet (TFM). A sample, for example, a single crystal, is adjustably positioned proximate to the surface of the TFM, using a translation stage such that the distance between the sample and the surface is selectively adjusted. A cryostat is provided with a first separate thermal stage provided for cooling the TFM and with a second separate thermal stage provided for cooling sample.

  20. Controlling the motion of magnetic flux quanta.

    PubMed

    Zhu, B Y; Marchesoni, F; Nori, Franco

    2004-05-07

    We study the transport of vortices in superconductors with triangular arrays of boomerang- or V-shaped asymmetric pinning wells, when applying an alternating electrical current. The asymmetry of the pinning landscape induces a very efficient "diode" effect, that allows the sculpting at will of the magnetic field profile inside the sample. We present the first quantitative study of magnetic "lensing" of fluxons inside superconductors. Our proposed vortex lens provides a near threefold increase of the vortex density at its "focus" regions. The main numerical features have been derived analytically.

  1. Effect of uncertainties in solar synoptic magnetic flux maps in modeling of solar wind

    NASA Astrophysics Data System (ADS)

    Pevtsov, Alexei A.; Bertello, Luca; MacNeice, Peter

    2015-12-01

    Recently, the NSO/SOLIS team developed variance (error) maps that represent uncertainties in magnetic flux synoptic charts. These uncertainties are determined by the spatial variances of the magnetic flux distribution from full disk magnetograms that contribute to each bin in the synoptic chart. Here we present a study of the effects of variances on solar wind parameters (wind speed, density, magnetic field, and temperature) derived using the WSA-ENLIL model and ensemble modeling approach. We compare the results of the modeling with near-Earth solar wind magnetic field and plasma data as extracted from NASA/GSFC's OMNI data set. We show that analysis of uncertainties may be useful for understanding the sensitivity of the model predictions to short-term evolution of magnetic field and noise in the synoptic magnetograms.

  2. Magnetic Flux Expulsion Studies in Niobium SRF Cavities

    SciTech Connect

    Posen, Sam; Checchin, Mattia; Crawford, Anthony; Grassellino, Anna; Martinello, Martina; Melnychuk, Oleksandr; Romanenko, Alexander; Sergatskov, Dmitri; Trenikhina, Yulia

    2016-06-01

    With the recent discovery of nitrogen doping treatment for SRF cavities, ultra-high quality factors at medium accelerating fields are regularly achieved in vertical RF tests. To preserve these quality factors into the cryomodule, it is important to consider background magnetic fields, which can become trapped in the surface of the cavity during cooldown and cause Q₀ degradation. Building on the recent discovery that spatial thermal gradients during cooldown can significantly improve expulsion of magnetic flux, a detailed study was performed of flux expulsion on two cavities with different furnace treatments that are cooled in magnetic fields amplitudes representative of what is expected in a realistic cryomodule. In this contribution, we summarize these cavity results, in order to improve understanding of the impact of flux expulsion on cavity performance.

  3. Z N twisted orbifold models with magnetic flux

    NASA Astrophysics Data System (ADS)

    Abe, Tomo-hiro; Fujimoto, Yukihiro; Kobayashi, Tatsuo; Miura, Takashi; Nishiwaki, Kenji; Sakamoto, Makoto

    2014-01-01

    We propose new backgrounds of extra dimensions to lead to four-dimensional chiral models with three generations of matter fermions, that is T 2 /Z N twisted orbifolds with magnetic fluxes. We consider gauge theory on six-dimensional space-time, which contains the T 2 /Z N orbifold with magnetic flux, Scherk-Schwarz phases and Wilson line phases. We classify all the possible Scherk-Schwarz and Wilson line phases on T 2 /Z N orbifolds with magnetic fluxes. The behavior of zero modes is studied. We derive the number of zero modes for each eigenvalue of the Z N twist, showing explicitly examples of wave functions. We also investigate Kaluza-Klein mode functions and mass spectra.

  4. The Pressure Limitations on Flux Pile-Up Magnetic Reconnection

    NASA Astrophysics Data System (ADS)

    Litvinenko, Y. E.

    1999-05-01

    Flux pile-up magnetic reconnection was thought to be able to provide fast energy dissipation a strongly magnetized plasma, for example, in solar flares. We examine the problem of the plasma pressure limitations on the rapidity of flux pile-up reconnection. It is shown that for a two-dimensional stagnation point flow with nonzero vorticity the magnetic merging rate cannot exceed the Sweet-Parker scaling in a low-beta plasma, which is too slow to explain flares. Moreover, the solution has some undesireable properties such as a diffusion layer at the external boundary and the massively increasing inflow speed. The pressure limitation appears to be somewhat less restrictive for three-dimensional flux pile-up. This work was supported by NSF grant ATM-9813933.

  5. DO THE LEGS OF MAGNETIC CLOUDS CONTAIN TWISTED FLUX-ROPE MAGNETIC FIELDS?

    SciTech Connect

    Owens, M. J.

    2016-02-20

    Magnetic clouds (MCs) are a subset of interplanetary coronal mass ejections (ICMEs) characterized primarily by a smooth rotation in the magnetic field direction indicative of the presence of a magnetic flux rope. Energetic particle signatures suggest MC flux ropes remain magnetically connected to the Sun at both ends, leading to widely used model of global MC structure as an extended flux rope, with a loop-like axis stretching out from the Sun into the heliosphere and back to the Sun. The time of flight of energetic particles, however, suggests shorter magnetic field line lengths than such a continuous twisted flux rope would produce. In this study, two simple models are compared with observed flux rope axis orientations of 196 MCs to show that the flux rope structure is confined to the MC leading edge. The MC “legs,” which magnetically connect the flux rope to the Sun, are not recognizable as MCs and thus are unlikely to contain twisted flux rope fields. Spacecraft encounters with these non-flux rope legs may provide an explanation for the frequent observation of non-MC ICMEs.

  6. Do the Legs of Magnetic Clouds Contain Twisted Flux-rope Magnetic Fields?

    NASA Astrophysics Data System (ADS)

    Owens, M. J.

    2016-02-01

    Magnetic clouds (MCs) are a subset of interplanetary coronal mass ejections (ICMEs) characterized primarily by a smooth rotation in the magnetic field direction indicative of the presence of a magnetic flux rope. Energetic particle signatures suggest MC flux ropes remain magnetically connected to the Sun at both ends, leading to widely used model of global MC structure as an extended flux rope, with a loop-like axis stretching out from the Sun into the heliosphere and back to the Sun. The time of flight of energetic particles, however, suggests shorter magnetic field line lengths than such a continuous twisted flux rope would produce. In this study, two simple models are compared with observed flux rope axis orientations of 196 MCs to show that the flux rope structure is confined to the MC leading edge. The MC “legs,” which magnetically connect the flux rope to the Sun, are not recognizable as MCs and thus are unlikely to contain twisted flux rope fields. Spacecraft encounters with these non-flux rope legs may provide an explanation for the frequent observation of non-MC ICMEs.

  7. Measurement of magnetic fluctuation-induced particle flux (invited).

    PubMed

    Ding, W X; Brower, D L; Yates, T Y

    2008-10-01

    Magnetic field fluctuation-induced particle transport has been directly measured in the high-temperature core of the MST reversed field pinch plasma. Measurement of radial particle transport is achieved by combining various interferometry techniques, including Faraday rotation, conventional interferometry, and differential interferometry. It is observed that electron convective particle flux and its divergence exhibit a significant increase during a sawtooth crash. In this paper, we describe the basic techniques employed to determine the particle flux.

  8. Equilibrium model of thin magnetic flux tubes. [solar atmosphere

    NASA Technical Reports Server (NTRS)

    Bodo, G.; Ferrari, A.; Massaglia, S.; Kalkofen, W.; Rosner, R.

    1984-01-01

    The existence of a physically realizable domain in which approximations that lead to a self consistent solution for flux tube stratification in the solar atmosphere, without ad hoc hypotheses, is proved. The transfer equation is solved assuming that no energy transport other than radiative is present. Convective motions inside the tube are assumed to be suppressed by magnetic forces. Only one parameter, the plasma beta at tau = 0, must be specified, and this can be estimated from observations of spatially resolved flux tubes.

  9. Theory and Application of Magnetic Flux Leakage Pipeline Detection.

    PubMed

    Shi, Yan; Zhang, Chao; Li, Rui; Cai, Maolin; Jia, Guanwei

    2015-12-10

    Magnetic flux leakage (MFL) detection is one of the most popular methods of pipeline inspection. It is a nondestructive testing technique which uses magnetic sensitive sensors to detect the magnetic leakage field of defects on both the internal and external surfaces of pipelines. This paper introduces the main principles, measurement and processing of MFL data. As the key point of a quantitative analysis of MFL detection, the identification of the leakage magnetic signal is also discussed. In addition, the advantages and disadvantages of different identification methods are analyzed. Then the paper briefly introduces the expert systems used. At the end of this paper, future developments in pipeline MFL detection are predicted.

  10. Theory and Application of Magnetic Flux Leakage Pipeline Detection

    PubMed Central

    Shi, Yan; Zhang, Chao; Li, Rui; Cai, Maolin; Jia, Guanwei

    2015-01-01

    Magnetic flux leakage (MFL) detection is one of the most popular methods of pipeline inspection. It is a nondestructive testing technique which uses magnetic sensitive sensors to detect the magnetic leakage field of defects on both the internal and external surfaces of pipelines. This paper introduces the main principles, measurement and processing of MFL data. As the key point of a quantitative analysis of MFL detection, the identification of the leakage magnetic signal is also discussed. In addition, the advantages and disadvantages of different identification methods are analyzed. Then the paper briefly introduces the expert systems used. At the end of this paper, future developments in pipeline MFL detection are predicted. PMID:26690435

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

    SciTech Connect

    Xia, C.; Keppens, R.; Guo, Y.

    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.

  12. Flux theory for Poisson distributed pores with Gaussian permeability.

    PubMed

    Salinas, Dino G

    2016-01-01

    The mean of the solute flux through membrane pores depends on the random distribution and permeability of the pores. Mathematical models including such randomness factors make it possible to obtain statistical parameters for pore characterization. Here, assuming that pores follow a Poisson distribution in the lipid phase and that their permeabilities follow a Gaussian distribution, a mathematical model for solute dynamics is obtained by applying a general result from a previous work regarding any number of different kinds of randomly distributed pores. The new proposed theory is studied using experimental parameters obtained elsewhere, and a method for finding the mean single pore flux rate from liposome flux assays is suggested. This method is useful for pores without requiring studies by patch-clamp in single cells or single-channel recordings. However, it does not apply in the case of ion-selective channels, in which a more complex flux law combining the concentration and electrical gradient is required.

  13. Determining the axis orientation of cylindrical magnetic flux rope

    NASA Astrophysics Data System (ADS)

    Rong, Zhaojin; Wan, Weixing; Shen, Chao; Zhang, Tielong; Lui, Anthony; Wang, Yuming; Dunlop, malcolm; Zhang, Yongcun; Zong, Qiugang

    2013-04-01

    We develop a new simple method for inferring the orientation of a magnetic flux rope, which is assumed to be a time-independent cylindrically symmetric structure via the direct single-point analysis of magnetic field structure. The model tests demonstrate that, for the cylindrical flux rope regardless of whether it is force-free or not, the method can consistently yield the axis orientation of the flux rope with higher accuracy and stability than the minimum variance analysis of the magnetic field and the Grad-Shafranov reconstruction technique. Moreover, the radial distance to the axis center and the current density can also be estimated consistently. Application to two actual flux transfer events observed by the four satellites of the Cluster mission demonstrates that the method is more appropriate to be used for the inner part of flux rope, which might be closer to the cylindrical structure, showing good agreement with the results obtained from the optimal Grad-Shafranov reconstruction and the least squares technique of Faraday's law, but fails to produce such agreement for the outer satellite that grazes the flux rope. Therefore, the method must be used with caution.

  14. Hamiltonian magnetic reconnection with parallel electron heat flux dynamics

    NASA Astrophysics Data System (ADS)

    Grasso, D.; Tassi, E.

    2015-10-01

    > We analyse, both analytically and numerically, a two-dimensional six-field fluid model for collisionless magnetic reconnection, accounting for temperature and heat flux fluctuations along the direction of the magnetic guide field. We show that the model possesses a Hamiltonian structure with a non-canonical Poisson bracket. This bracket is characterized by the presence of six infinite families of Casimirs, associated with Lagrangian invariants. This reveals that the model can be reformulated as a system of advection equations, thus generalizing previous results obtained for Hamiltonian isothermal fluid models for reconnection. Numerical simulations indicate that the presence of heat flux and temperature fluctuations yields slightly larger growth rates and similar saturated island amplitudes, with respect to the isothermal models. For values of the sonic Larmor radius much smaller than the electron skin depth, heat flux fluctuations tend to be suppressed and temperature fluctuations follow density fluctuations. Increasing the sonic Larmor radius results in an increasing fraction of magnetic energy converted into heat flux, at the expense of temperature fluctuations. In particular, heat flux fluctuations tend to become relevant along the magnetic island separatrices. The qualitative structures associated with the electron field variables are also reinterpreted in terms of the rotation of the Lagrangian invariants of the system.

  15. Chromospheric and Coronal Wave Generation in a Magnetic Flux Sheath

    NASA Astrophysics Data System (ADS)

    Kato, Yoshiaki; Steiner, Oskar; Hansteen, Viggo; Gudiksen, Boris; Wedemeyer, Sven; Carlsson, Mats

    2016-08-01

    Using radiation magnetohydrodynamic simulations of the solar atmospheric layers from the upper convection zone to the lower corona, we investigate the self-consistent excitation of slow magneto-acoustic body waves (slow modes) in a magnetic flux concentration. We find that the convective downdrafts in the close surroundings of a two-dimensional flux slab “pump” the plasma inside it in the downward direction. This action produces a downflow inside the flux slab, which encompasses ever higher layers, causing an upwardly propagating rarefaction wave. The slow mode, excited by the adiabatic compression of the downflow near the optical surface, travels along the magnetic field in the upward direction at the tube speed. It develops into a shock wave at chromospheric heights, where it dissipates, lifts the transition region, and produces an offspring in the form of a compressive wave that propagates further into the corona. In the wake of downflows and propagating shock waves, the atmosphere inside the flux slab in the chromosphere and higher tends to oscillate with a period of ν ≈ 4 mHz. We conclude that this process of “magnetic pumping” is a most plausible mechanism for the direct generation of longitudinal chromospheric and coronal compressive waves within magnetic flux concentrations, and it may provide an important heat source in the chromosphere. It may also be responsible for certain types of dynamic fibrils.

  16. Data Mining Solar X-Ray Flares Triggered by Emerging Magnetic Flux

    NASA Astrophysics Data System (ADS)

    Loftus, Kaitlyn; Saar, Steven H.; Schanche, Nicole

    2017-01-01

    We investigate the association between emerging magnetic flux and solar X-ray flares to identify, and if possible quantify, distinguishing physical properties of flares triggered by flux emergence versus those triggered by other sources. Our study uses as its basis GOES-classified solar flares from March 2011 through June 2016 that have been identified by the Space Weather Prediction Center’s flare detection algorithm. The basic X-ray flare data is then enriched with data about related EUV-spectrum flares, emerging fluxes, active regions, eruptions, and sigmoids, which are all characterized by event-specific keywords, identified via SDO feature finding tools, and archived in the Heliophysics Events Knowledgebase (HEK). Using appropriate spatial and temporal parameters for each event type to determine association, we create a catalogue of solar events associated with each GOES-classified flare. After accounting for the primitive state of many of these event detection algorithms, we statistically analyze the compiled dataset to determine the effects of an emerging flux trigger on flare properties. A two-sample Kolmogorov-Smirnov test confirms with 99.9% confidence that flares triggered by emerging flux have a different peak flux distribution than non-emerging-flux-associated flares. We observe no linear or logarithmic correlations between flares’ and their associated emerging fluxes’ individual properties and find flares triggered by emerging flux are ~ 10% more likely to cause an eruption inside an active region while outside of an active region, the flare’s association with emerging flux has no effect on its likeliness to cause an eruption. We also compare the morphologies of the flares triggered by emerging flux and flares not via a superposed epoch analysis of lightcurves. Our results will be of interest for predicting flare behavior as a function of magnetic activity (where we can use enhanced rates of emerging flux as a proxy for heightened stellar

  17. Simulations of emerging magnetic flux. I. The formation of stable coronal flux ropes

    SciTech Connect

    Leake, James E.; Linton, Mark G.; Török, Tibor

    2013-12-01

    We present results from three-dimensional visco-resistive magnetohydrodynamic simulations of the emergence of a convection zone magnetic flux tube into a solar atmosphere containing a pre-existing dipole coronal field, which is orientated to minimize reconnection with the emerging field. We observe that the emergence process is capable of producing a coronal flux rope by the transfer of twist from the convection zone, as found in previous simulations. We find that this flux rope is stable, with no evidence of a fast rise, and that its ultimate height in the corona is determined by the strength of the pre-existing dipole field. We also find that although the electric currents in the initial convection zone flux tube are almost perfectly neutralized, the resultant coronal flux rope carries a significant net current. These results suggest that flux tube emergence is capable of creating non-current-neutralized stable flux ropes in the corona, tethered by overlying potential fields, a magnetic configuration that is believed to be the source of coronal mass ejections.

  18. Explosive instability and erupting flux tubes in a magnetized plasma

    PubMed Central

    Cowley, S. C.; Cowley, B.; Henneberg, S. A.; Wilson, H. R.

    2015-01-01

    The eruption of multiple flux tubes in a magnetized plasma is proposed as a mechanism for explosive release of energy in plasmas. A significant fraction of the linearly stable isolated flux tubes are shown to be metastable in a box model magnetized atmosphere in which ends of the field lines are embedded in conducting walls. The energy released by destabilizing such field lines can be a large proportion of the gravitational energy stored in the system. This energy can be released in a fast dynamical time. PMID:26339193

  19. Magnetic field generation from shear flow in flux ropes

    NASA Astrophysics Data System (ADS)

    Intrator, T. P.; Sears, J.; Gao, K.; Klarenbeek, J.; Yoo, C.

    2012-10-01

    In the Reconnection Scaling Experiment (RSX) we have measured out of plane quadrupole magnetic field structure in situations where magnetic reconnection was minimal. This quadrupole out of plane magnetic signature has historically been presumed to be the smoking gun harbinger of reconnection. On the other hand, we showed that when flux ropes bounced instead of merging and reconnecting, this signature could evolve. This can follow from sheared fluid flows in the context of a generalized Ohms Law. We reconstruct a shear flow model from experimental data for flux ropes that have been experimentally well characterized in RSX as screw pinch equilibria, including plasma ion and electron flow, with self consistent profiles for magnetic field, pressure, and current density. The data can account for the quadrupole field structure.

  20. Magnetic Helicity Density and Its Flux in Weakly Inhomogeneous Turbulence

    NASA Astrophysics Data System (ADS)

    Subramanian, Kandaswamy; Brandenburg, Axel

    2006-09-01

    A gauge-invariant and hence physically meaningful definition of magnetic helicity density for random fields is proposed, using the Gauss linking formula, as the density of correlated field line linkages. This definition is applied to the random small-scale field in weakly inhomogeneous turbulence, whose correlation length is small compared with the scale on which the turbulence varies. For inhomogeneous systems, with or without boundaries, our technique then allows one to study the local magnetic helicity density evolution in a gauge-independent fashion, which was not possible earlier. This evolution equation is governed by local sources (owing to the mean field) and by the divergence of a magnetic helicity flux density. The role of magnetic helicity fluxes in alleviating catastrophic quenching of mean field dynamos is discussed.

  1. A magnetic flux leakage NDE system for CANDU feeder pipes

    NASA Astrophysics Data System (ADS)

    Mak, Thomas Don

    This work examines the application of different magnetic flux leakage (MFL) inspection concepts to the non destructive evaluation (NDE) of residual (elastic) stresses in CANDURTM reactor feeder pipes. The stress sensitivity of three MFL inspection techniques was examined with flat plate samples, with stress-induced magnetic anisotropy (SMA) demonstrating the greatest stress sensitivity. A prototype SMA testing system was developed to apply magnetic NDE to feeders. The system consists of a flux controller that incorporates feedback from a wire coil and a Hall sensor (FCV2), and a magnetic anisotropy prototype (MAP) probe. The combination of FCV2 and the MAP probe was shown to provide SMA measurements on feeder pipe samples and predict stresses from SMA measurements with a mean accuracy of +/-38MPa.

  2. Magnetic flux-load current interactions in ferrous conductors

    NASA Astrophysics Data System (ADS)

    Cannell, Michael J.; McConnell, Richard A.

    1992-06-01

    A modeling technique has been developed to account for interactions between load current and magnetic flux in an iron conductor. Such a conductor would be used in the active region of a normally conducting homopolar machine. This approach has been experimentally verified and its application to a real machine demonstrated. Additionally, measurements of the resistivity of steel under the combined effects of magnetic field and current have been conducted.

  3. Experimental Results from Railgun Firings Involving Magnetic Flux Probes.

    DTIC Science & Technology

    1986-12-01

    of railgun firings, the voltages induced in small solenoidal probes mounted in different positions and orientations along the barrel were measured to...different positions and orientations along the barrel were measured to gain a better understanding of the current density and magnetic field in a...ACKNOWLEDGEMENTS 7. REFERENCES 10 I’. 4¢ EXPERIMENTAL RESULTS FROM RAILGUN FIRINGS INVOLVING MAGNETIC FLUX PROBES 1. INTRODUCTION The Lorentz force acting on the

  4. Estimating the Global Solar Magnetic Field Distribution Using ADAPT

    NASA Astrophysics Data System (ADS)

    Arge, C. N.; Henney, C. J.; Toussaint, W. A.; Godinez, H. C.; Hickmann, K. S.

    2014-12-01

    Estimation of the global solar photospheric magnetic field distribution is currently difficult, since only approximately half of the solar surface is magnetically observed at any given time. With the solar rotational period relative to Earth at approximately 27 days, these global maps include observed data that are more than 13 days old. Data assimilation between old and new observations can result in spatial polarity discontinuities that result in significant monopole signals. To help minimize these large discontinuities and to specify the global state of the photospheric magnetic flux distribution as accurately as possible, we have developed the ADAPT (Air Force Data Assimilative Photospheric flux Transport) model, which is comprised of a photospheric magnetic flux transport model that makes use of data assimilation methods. The ADAPT transport model evolves the solar magnetic flux for an ensemble of realizations using different model parameter values, e.g., for rotational, meridional, and super-granular diffusive transport processes. In this presentation, the ADAPT model and the data assimilative methods used within it will be reviewed. Coronal, solar wind, F10.7, and EUV model predictions based on ADAPT global photospheric magnetic field maps as input will be discussed.

  5. Manipulation of magnetic flux landscapes in superconducting BSCCO crystals

    NASA Astrophysics Data System (ADS)

    Cole, David

    We present data showing the exploration of the dynamic behaviour of vortices in the high critical temperature. Type II superconductor Bi2Sr2CaCu2O8+5. Under tilted magnetic fields the flux penetration in a layered superconductor is composed of a complex and rich series of ground states. The existence of interacting orthogonal crossing lattices has led to the proposal of two techniques for the manipulation of vortices and the control of micromagnetic profiles. We show that we can manipulate the local PV density via a variation in the in-plane field, H//. This technique involves moving Josephson vortices that drag pancake vortex stacks, and allows us to manipulate the magnetic profile, Bz(x), across the entire sample. Depending on the magnetic history and the temperature we can increase or decrease the magnetic flux density at the center and near the edges of the crystal by as much as 40%, realising both "convex" and "concave" magnetic flux lenses. A requirement of many recently proposed nanodevices for the control of the motion of tiny particles is a nanoengineered, spatially-asymmetric substrate. However, using recent theoretical ideas, we demonstrate experimentally how to guide flux quanta using a drive that is asymmetric in time instead of being asymmetric in space. By varying the time-asymmetry of the drive, we are able experimentally to increase or decrease the density of magnetic flux at the centre of superconducting samples that have no spatial ratchet substrate. This is the first ratchet that depends upon a temporal rather than a spatial ratchet potential. These two techniques involve no permanent nanofabrication of the sample and are non-invasive and flexible. The manipulation of magnetic flux quanta could be used to reduce flux noise in sensitive superconducting devices such as SQUIDs and high frequency filters and has possible future applications in the manipulation of flux bits in superconducting quantum computers. The experimental results are well

  6. Turbulent transport of Small-scale magnetic flux elements on Solar Photosphere

    NASA Astrophysics Data System (ADS)

    Agrawal, Piyush; Rempel, Matthias; Bellot Rubio, Luis; Rast, Mark

    2016-05-01

    We study the transport of small-scale magnetic elements on the solar photosphere using both observations and simulations. Observational data was obtained from Hinode - Solar Optical Telescope (SOT/SP) instrument and simulations from MURaM code. The magnetic flux elements were tracked in both data sets and statistics were obtained. We compute the probability density of the Eulerian distances traveled by the flux elements along Lagrangian trajectories. For a two-dimensional random walk process this distribution should be Rayleigh. Preliminary results show that the measured probability distribution in both the observed and simulated data approximates a random walk, on time scale close to the lifetime of granules, but deviates from it for longer times. This implies that diffusion may not be an appropriate framework for transport in the solar photosphere. We explore the roles of flux cancelation and element trapping in producing this result. Work is ongoing.

  7. The distribution of ion orbit loss fluxes of ions and energy from the plasma edge across the last closed flux surface into the scrape-off layer

    SciTech Connect

    Stacey, Weston M.; Schumann, Matthew T.

    2015-04-15

    A more detailed calculation strategy for the evaluation of ion orbit loss of thermalized plasma ions in the edge of tokamaks is presented. In both this and previous papers, the direct loss of particles from internal flux surfaces is calculated from the conservation of canonical angular momentum, energy, and magnetic moment. The previous result that almost all of the ion energy and particle fluxes crossing the last closed flux surface are in the form of ion orbit fluxes is confirmed, and the new result that the distributions of these fluxes crossing the last closed flux surface into the scrape-off layer are very strongly peaked about the outboard midplane is demonstrated. Previous results of a preferential loss of counter current particles leading to a co-current intrinsic rotation peaking just inside of the last closed flux surface are confirmed. Various physical details are discussed.

  8. Evolution of the magnetic field distribution of active regions

    NASA Astrophysics Data System (ADS)

    Dacie, S.; Démoulin, P.; van Driel-Gesztelyi, L.; Long, D. M.; Baker, D.; Janvier, M.; Yardley, S. L.; Pérez-Suárez, D.

    2016-12-01

    Aims: Although the temporal evolution of active regions (ARs) is relatively well understood, the processes involved continue to be the subject of investigation. We study how the magnetic field of a series of ARs evolves with time to better characterise how ARs emerge and disperse. Methods: We examined the temporal variation in the magnetic field distribution of 37 emerging ARs. A kernel density estimation plot of the field distribution was created on a log-log scale for each AR at each time step. We found that the central portion of the distribution is typically linear, and its slope was used to characterise the evolution of the magnetic field. Results: The slopes were seen to evolve with time, becoming less steep as the fragmented emerging flux coalesces. The slopes reached a maximum value of -1.5 just before the time of maximum flux before becoming steeper during the decay phase towards the quiet-Sun value of -3. This behaviour differs significantly from a classical diffusion model, which produces a slope of -1. These results suggest that simple classical diffusion is not responsible for the observed changes in field distribution, but that other processes play a significant role in flux dispersion. Conclusions: We propose that the steep negative slope seen during the late-decay phase is due to magnetic flux reprocessing by (super)granular convective cells.

  9. Turbulent transport of fast ions due to magnetic flux ropes

    NASA Astrophysics Data System (ADS)

    Preiwisch, Adam

    The transport of fast ions in magnetic flux ropes in a laboratory plasma is studied. Strong perturbing flux ropes (deltaE ~175 V/m, deltaB ~7 G) are generated by secondary cathode-anode pair at the upgraded LArge Plasma Device (LAPD). A 500-1000 eV lithium ion test beam is passed through the turbulent region and recollected by a gridded collimated analyzer, revealing enhanced fast ion broadening attributable to flux rope perturbations. The broadening is observed to be well in excess of Coulomb scattering levels. Monte Carlo simulation is performed with model electrostatic and magnetic fields, revealing negligible spreading as a result of the magnetic perturbations. Modeled electrostatic perturbations are observed to broaden the beam by 3.0 mm2 at the closest recollection plane, increasing as the transit time squared further downstream. Transport attributed to electrostatic fluctuations has been shown to decrease with energy while magnetic transport does not. Enhanced fast ion transport observed during the flux rope off phase is presently unexplained.

  10. Miniature solenoid for the production of confined magnetic flux

    SciTech Connect

    Walker, I.R.

    1984-11-01

    For experiments involving SQUID's it is sometimes desirable to have a small source of confined magnetic field in order to provide a dc or RF flux bias. This has been done by closely winding number50 AWG copper wire on a 250-..mu..m-diam optical fiber. The resulting solenoid is very small and has excellent mechanical and electrical properties at 4 K.

  11. Magnetic helicity distribution in the solar atmosphere

    NASA Astrophysics Data System (ADS)

    Yang, Shangbin; Büchner, Jörg; Zhang, Hongqi

    We have developed a method to derive the relative magnetic helicity in the solar corona based on the magnetic helicity flux at the solar photosphere. We apply the method to the two newly emerging active regions (ARs) with simple and complex magnetic structures respectively. It is found that the helicity change rate in the solar corona is consistent with the helicity flux at the solar photosphere. However, the accumulated magnetic helicity in the solar corona for the simple one reverse sign as time changed. For the complex one, there is a continuous magnetic helicity accumulated just before the occurrence of solar storm, which may reflect the formation of the magnetic flux rope. It is also found that 90% of magnetic helicity is accumulated in less than 1.1 solar radius both for the two ARs After discussing the different sources of magnetic helicity, we suggested that the long term of differential rotations could play an important role to the accumulation of magnetic helicity in the solar corona and the interplanetary space, together with strong magnetic flux emergency at the solar photosphere.

  12. Mass ablation and magnetic flux losses through a magnetized plasma-liner wall interface

    NASA Astrophysics Data System (ADS)

    García-Rubio, F.; Sanz, J.

    2017-07-01

    The understanding of energy and magnetic flux losses in a magnetized plasma medium confined by a cold wall is of great interest in the success of magnetized liner inertial fusion (MagLIF). In a MagLIF scheme, the fuel is magnetized and subsonically compressed by a cylindrical liner. Magnetic flux conservation is degraded by the presence of gradient-driven transport processes such as thermoelectric effects (Nernst) and magnetic field diffusion. In previous publications [Velikovich et al., Phys. Plasmas 22, 042702 (2015)], the evolution of a hot magnetized plasma in contact with a cold solid wall (liner) was studied using the classical collisional Braginskii's plasma transport equations in one dimension. The Nernst term degraded the magnetic flux conservation, while both thermal energy and magnetic flux losses were reduced with the electron Hall parameter ωeτe with a power-law asymptotic scaling (ωeτe)-1/2. In the analysis made in the present paper, we consider a similar situation, but with the liner being treated differently. Instead of a cold solid wall acting as a heat sink, we model the liner as a cold dense plasma with low thermal conduction (that could represent the cryogenic fuel layer added on the inner surface of the liner in a high-gain MagLIF configuration). Mass ablation comes into play, which adds notably differences to the previous analysis. The direction of the plasma motion is inverted, but the Nernst term still convects the magnetic field towards the liner. Magnetization suppresses the Nernst velocity and improves the magnetic flux conservation. Thermal energy in the hot plasma is lost in heating the ablated material. When the electron Hall parameter is large, mass ablation scales as (ωeτe)-3/10, while both the energy and magnetic flux losses are reduced with a power-law asymptotic scaling (ωeτe)-7/10.

  13. Nitrogen Flux in Watersheds: The Role of Soil Distributions in Nitrogen Flux to the Coastal Ecosystems

    NASA Astrophysics Data System (ADS)

    Showers, W. J.; Gurley, W.; O'Conner, J. W.

    2010-12-01

    Quantifying the flux of nitrate from different landscape sources in watersheds is important to understand the increased flux of nitrogen to coastal ecosystems. The RiverNet program has measured the nitrate flux in the Neuse River Basin, NC on a 15 minute interval over the past ten years. Discharge and N flux in the basin also has significant inter-annual variations associated with El Nino oscillations modified by the North Atlantic oscillation. To understand how climate oscillations affect discharge and nutrient fluxes, we have continuously mapped nitrate concentrations, with Chlorophyll a and CDOM to understand how nitrogen is transported across landscapes to the coastal ecosystems. Hydric soil spatial distributions are an excellent predictor of nutrient transport in watersheds, and are related to the distribution of biogeochemical “hotspots”. Detailed spatial analysis indicates that nitrate, Chlorophyll a, and CDOM are not spatially coherent and one concentration cannot be used to predict the distribution of the other parameters as suggested by some regulatory agencies. These results also indicate that the contribution of wastewater treatment plants from urban watersheds has been greatly under-estimated in current models while the transport of agricultural nitrogen is controlled by hydric soil distributions and riparian buffer size. Prediction of future changes in discharge and nutrient flux by the modeling of climate oscillations has important implications for water resources policy and drought management for public policy and utility managers.

  14. On the Magnetic Flux Conservation in the Partially Ionzied Plasma

    NASA Astrophysics Data System (ADS)

    Tsap, Yu.; Kopylova, Yu.

    2014-12-01

    The Ohm, Hall, and ambipolar diffusions in the partially ionized plasma are considered. It has been shown that the statement of Pandey and Wardle that only the Ohm diffusion is capable to decrease the magnetic flux is not sufficiently correct due to the formal dependence of the magnetic diffusion on a selected frame of reference. Thes ignificance of understanding of the physical nature for the dissipation and diffusion of the magnetic field in the partially ionized plasma as well as consequences of obtained results are discussed.

  15. Regularized Biot-Savart Laws for Modeling Magnetic Flux Ropes

    NASA Astrophysics Data System (ADS)

    Titov, Viacheslav; Downs, Cooper; Mikic, Zoran; Torok, Tibor; Linker, Jon A.

    2017-08-01

    Many existing models assume that magnetic flux ropes play a key role in solar flares and coronal mass ejections (CMEs). It is therefore important to develop efficient methods for constructing flux-rope configurations constrained by observed magnetic data and the initial morphology of CMEs. As our new step in this direction, we have derived and implemented a compact analytical form that represents the magnetic field of a thin flux rope with an axis of arbitrary shape and a circular cross-section. This form implies that the flux rope carries axial current I and axial flux F, so that the respective magnetic field is a curl of the sum of toroidal and poloidal vector potentials proportional to I and F, respectively. The vector potentials are expressed in terms of Biot-Savart laws whose kernels are regularized at the rope axis. We regularized them in such a way that for a straight-line axis the form provides a cylindrical force-free flux rope with a parabolic profile of the axial current density. So far, we set the shape of the rope axis by tracking the polarity inversion lines of observed magnetograms and estimating its height and other parameters of the rope from a calculated potential field above these lines. In spite of this heuristic approach, we were able to successfully construct pre-eruption configurations for the 2009 February13 and 2011 October 1 CME events. These applications demonstrate that our regularized Biot-Savart laws are indeed a very flexible and efficient method for energizing initial configurations in MHD simulations of CMEs. We discuss possible ways of optimizing the axis paths and other extensions of the method in order to make it more useful and robust.Research supported by NSF, NASA's HSR and LWS Programs, and AFOSR.

  16. Frozen flux violation, electron demagnetization and magnetic reconnection

    SciTech Connect

    Scudder, J. D.; Karimabadi, H.; Roytershteyn, V.; Daughton, W.

    2015-10-15

    We argue that the analogue in collisionless plasma of the collisional diffusion region of magnetic reconnection is properly defined in terms of the demagnetization of the plasma electrons that enable “frozen flux” slippage to occur. This condition differs from the violation of the “frozen-in” condition, which only implies that two fluid effects are involved, rather than the necessary slippage of magnetic flux as viewed in the electron frame. Using 2D Particle In Cell (PIC) simulations, this approach properly finds the saddle point region of the flux function. Our demagnetization conditions are the dimensionless guiding center approximation expansion parameters for electrons which we show are observable and determined locally by the ratio of non-ideal electric to magnetic field strengths. Proxies for frozen flux slippage are developed that (a) are measurable on a single spacecraft, (b) are dimensionless with theoretically justified threshold values of significance, and (c) are shown in 2D simulations to recover distinctions theoretically possible with the (unmeasurable) flux function. A new potentially observable dimensionless frozen flux rate, Λ{sub Φ}, differentiates significant from anecdotal frozen flux slippage. A single spacecraft observable, ϒ, is shown with PIC simulations to be essentially proportional to the unobservable local Maxwell frozen flux rate. This relationship theoretically establishes electron demagnetization in 3D as the general cause of frozen flux slippage. In simple 2D cases with an isolated central diffusion region surrounded by separatrices, these diagnostics uniquely identify the traditional diffusion region (without confusing it with the two fluid “ion-diffusion” region) and clarify the role of the separatrices where frozen flux violations do occur but are not substantial. In the more complicated guide and asymmetric 2D cases, substantial flux slippage regions extend out along, but inside of, the preferred separatrices

  17. Minnealloy: a new magnetic material with high saturation flux density and low magnetic anisotropy

    NASA Astrophysics Data System (ADS)

    Mehedi, Md; Jiang, Yanfeng; Suri, Pranav Kumar; Flannigan, David J.; Wang, Jian-Ping

    2017-09-01

    We are reporting a new soft magnetic material with high saturation magnetic flux density, and low magnetic anisotropy. The new material is a compound of iron, nitrogen and carbon, α‧-Fe8(NC), which has saturation flux density of 2.8  ±  0.15 T and magnetic anisotropy of 46 kJ m-3. The saturation flux density is 27% higher than pure iron, a widely used soft magnetic material. Soft magnetic materials are very important building blocks of motors, generators, inductors, transformers, sensors and write heads of hard disk. The new material will help in the miniaturization and efficiency increment of the next generation of electronic devices.

  18. Incompressible magnetohydrodynamic modes in the thin magnetically twisted flux tube

    NASA Astrophysics Data System (ADS)

    Cheremnykh, O. K.; Fedun, V.; Kryshtal, A. N.; Verth, G.

    2017-08-01

    Context. Observations have shown that twisted magnetic fields naturally occur, and indeed are omnipresent in the Sun's atmosphere. It is therefore of great theoretical interest in solar atmospheric waves research to investigate the types of magnetohydrodynamic (MHD) wave modes that can propagate along twisted magnetic flux tubes. Aims: Within the framework of ideal MHD, the main aim of this work is to investigate small amplitude incompressible wave modes of twisted magnetic flux tubes with m ≥ 1. The axial magnetic field strength inside and outside the tube will be allowed to vary, to ensure the results will not be restricted to only cold plasma equilibria conditions. Methods: The dispersion equation for these incompressible linear MHD wave modes was derived analytically by implementing the long wavelength approximation. Results: It is shown, in the long wavelength limit, that both the frequency and radial velocity profile of the m = 1 kink mode are completely unaffected by the choice of internal background magnetic twist. However, fluting modes with m ≥ 2 are sensitive to the particular radial profile of magnetic twist chosen. Furthermore, due to background twist, a low frequency cut-off is introduced for fluting modes that is not present for kink modes. From an observational point of view, although magnetic twist does not affect the propagation of long wavelength kink modes, for fluting modes it will either work for or against the propagation, depending on the direction of wave travel relative to the sign of the background twist.

  19. Materials for efficient high-flux magnetic bearing actuators

    NASA Technical Reports Server (NTRS)

    Williams, M. E.; Trumper, D. L.

    1994-01-01

    Magnetic bearings have demonstrated the capability for achieving positioning accuracies at the nanometer level in precision motion control stages. This makes possible the positioning of a wafer in six degrees of freedom with the precision necessary for photolithography. To control the position of an object at the nanometer level, a model of the magnetic bearing actuator force-current-airgap relationship must be accurately obtained. Additionally, to reduce thermal effects the design of the actuator should be optimized to achieve maximum power efficiency and flux density. Optimization of the actuator is accomplished by proper pole face sizing and utilizing a magnetic core material which can be magnetized to the highest flux density with low magnetic loss properties. This paper describes the construction of a magnetic bearing calibration fixture designed for experimental measurement of the actuator force characteristics. The results of a material study that review the force properties of nickel-steel, silicon-steel, and cobalt-vanadium-iron, as they apply to magnetic bearing applications are also presented.

  20. Flux line depinning in a magnet-superconductor levitation system

    NASA Astrophysics Data System (ADS)

    Terentiev, A. N.; Hull, J. R.; De Long, L. E.

    The AC loss characteristics of a magnet-superconductor system were studied with the magnet fixed to the free end of an oscillating cantilever located near a stationary melt-textured YBCO pellet. Below a threshold AC field amplitude ≈2 Oe, the dissipation of the oscillator is amplitude-independent, characteristic of a linear, non-hysteretic regime. Above threshold, dissipation increases with amplitude, reflecting the depinning and hysteretic motion of flux lines. The threshold AC field is an order of magnitude higher than that measured for the same YBCO material via AC susceptometry in a uniform DC magnetic field. A partial lock-in of flux lines between YBCO ab planes is proposed as the mechanism for the substantial increase of the depinning threshold.

  1. Non-Force-Free Magnetic Flux Ropes with Minimum Complexity in anAmbient Medium: A Parameter Study

    DTIC Science & Technology

    2012-10-16

    the solar corona and interplanetary medium. A flux rope is a self-organized magnetized plasma structure consisting of an electric current distribution J... Solar plasma physics Interplanetary plasma physics The structure and properties of non-force-free (NFF) equilibrium magnetic flux ropes in an ambient...rope becomes highly NFF in this limit with Dp → ∞. In the solar physics literature, the common adage is that the coronal plasma β is so small (β → 0

  2. MAGNETIC FLUX DENSITY MEASURED IN FAST AND SLOW SOLAR WIND STREAMS

    SciTech Connect

    Erdos, G.; Balogh, A.

    2012-07-10

    The radial component of the heliospheric magnetic field vector is used to estimate the open magnetic flux density of the Sun. This parameter has been calculated using observations from the Ulysses mission that covered heliolatitudes from 80 Degree-Sign S to 80 Degree-Sign N, from 1990 to 2009 and distances from 1 to 5.4 AU, the Advanced Composition Explorer mission at 1 AU from 1997 to 2010, the OMNI interplanetary database from 1971, and the Helios 1 and 2 missions that covered the distance range from 0.3 to 1 AU. The flux density was found to be much affected by fluctuations in the magnetic field which make its calculated value dependent on heliospheric location, type of solar wind (fast or slow), and the level of solar activity. However, fluctuations are distributed symmetrically perpendicular to the average Parker direction. Therefore, distributions of the field vector in the two-dimensional plane defined by the radial and azimuthal directions in heliospheric coordinates provide a way to reduce the effects of the fluctuations on the measurement of the flux density. This leads to a better defined flux density parameter; the distributions modified by removing the effects of fluctuations then allow a clearer assessment of the dependence of the flux density on heliospheric location, solar wind type, and solar activity. This assessment indicates that the flux density normalized to 1 AU is independent of location and solar wind type (fast or slow). However, there is a residual dependence on solar activity which can be studied using the modified flux density measurements.

  3. Which sets of elementary flux modes form thermodynamically feasible flux distributions?

    PubMed

    Gerstl, Matthias P; Jungreuthmayer, Christian; Müller, Stefan; Zanghellini, Jürgen

    2016-05-01

    Elementary flux modes (EFMs) are non-decomposable steady-state fluxes through metabolic networks. Every possible flux through a network can be described as a superposition of EFMs. The definition of EFMs is based on the stoichiometry of the network, and it has been shown previously that not all EFMs are thermodynamically feasible. These infeasible EFMs cannot contribute to a biologically meaningful flux distribution. In this work, we show that a set of thermodynamically feasible EFMs need not be thermodynamically consistent. We use first principles of thermodynamics to define the feasibility of a flux distribution and present a method to compute the largest thermodynamically consistent sets (LTCSs) of EFMs. An LTCS contains the maximum number of EFMs that can be combined to form a thermodynamically feasible flux distribution. As a case study we analyze all LTCSs found in Escherichia coli when grown on glucose and show that only one LTCS shows the required phenotypical properties. Using our method, we find that in our E. coli model < 10% of all EFMs are thermodynamically relevant.

  4. Quasi-static and dynamic magnetic tension forces in arched, line-tied magnetic flux ropes

    SciTech Connect

    Myers, C. E.; Yamada, M.; Ji, H.; Yoo, J.; Jara-Almonte, J.; Fox, W.

    2016-11-22

    Solar eruptions are often driven by magnetohydrodynamic instabilities such as the torus and kink instabilities that act on line-tied magnetic flux ropes. We designed our recent laboratory experiments to study these eruptive instabilities which have demonstrated the key role of both dynamic (Myers et al 2015 Nature 528 526) and quasi-static (Myers et al 2016 Phys. Plasmas 23 112102) magnetic tension forces in contributing to the equilibrium and stability of line-tied magnetic flux ropes. In our paper, we synthesize these laboratory results and explore the relationship between the dynamic and quasi-static tension forces. And while the quasi-static tension force is found to contribute to the flux rope equilibrium in a number of regimes, the dynamic tension force is substantial mostly in the so-called failed torus regime where magnetic self-organization events prevent the flux rope from erupting.

  5. Quasi-static and dynamic magnetic tension forces in arched, line-tied magnetic flux ropes

    DOE PAGES

    Myers, C. E.; Yamada, M.; Ji, H.; ...

    2016-11-22

    Solar eruptions are often driven by magnetohydrodynamic instabilities such as the torus and kink instabilities that act on line-tied magnetic flux ropes. We designed our recent laboratory experiments to study these eruptive instabilities which have demonstrated the key role of both dynamic (Myers et al 2015 Nature 528 526) and quasi-static (Myers et al 2016 Phys. Plasmas 23 112102) magnetic tension forces in contributing to the equilibrium and stability of line-tied magnetic flux ropes. In our paper, we synthesize these laboratory results and explore the relationship between the dynamic and quasi-static tension forces. And while the quasi-static tension force ismore » found to contribute to the flux rope equilibrium in a number of regimes, the dynamic tension force is substantial mostly in the so-called failed torus regime where magnetic self-organization events prevent the flux rope from erupting.« less

  6. Quasi-static and dynamic magnetic tension forces in arched, line-tied magnetic flux ropes

    NASA Astrophysics Data System (ADS)

    Myers, C. E.; Yamada, M.; Ji, H.; Yoo, J.; Jara-Almonte, J.; Fox, W.

    2017-01-01

    Solar eruptions are often driven by magnetohydrodynamic instabilities such as the torus and kink instabilities that act on line-tied magnetic flux ropes. Recent laboratory experiments designed to study these eruptive instabilities have demonstrated the key role of both dynamic (Myers et al 2015 Nature 528 526) and quasi-static (Myers et al 2016 Phys. Plasmas 23 112102) magnetic tension forces in contributing to the equilibrium and stability of line-tied magnetic flux ropes. In this paper, we synthesize these laboratory results and explore the relationship between the dynamic and quasi-static tension forces. While the quasi-static tension force is found to contribute to the flux rope equilibrium in a number of regimes, the dynamic tension force is substantial mostly in the so-called failed torus regime where magnetic self-organization events prevent the flux rope from erupting.

  7. C 4 fluxes from the sun as a star and the correlation with magnetic flux

    NASA Technical Reports Server (NTRS)

    Schrijver, C. J.; Linsky, J. L.; Bennett, J.; Brown, A.; Saar, S. H.

    1988-01-01

    A total of 144 C 4 wavelength 1548 SMM-UVSP spectroheliograms of solar plages were analyzed, some of which are series of exposures of the same region on the same day. Also analyzed were C 4 wavelength 1551 rasters of plages and C 4 1548 rasters of the quiet sun. The sample contains data on 17 different plages, observed on 50 different days. The center-to-limb variations of the active regions show that the optical thickness effects in the C 4 wavelength 1548 line can be neglected in the conversion from intensity to flux density. As expected for the nearly optically thin situation, the C 4 1548 line is twice as bright as the C 4 wavelength 1551 line. The average C 4 wavelength 1548 flux density for a quiet is 2700 erg/cm/s and, with surprisingly little scatter, 18,000 erg/cm/s for plages. The intensity histograms of rasters obtained at disk centers can be separated into characteristic plage and quiet-sun contributions with variable relative filling factors. The disk-averaged flux density in the C 4 doublet and the disk-averaged magnitude of the magnetic flux density are related. The relationship between the C 4 and magnetic flux densities for spatially resolved data is inferred to be almost the same, with only an additional factor of order unity in the constant of proportionality.

  8. Contagious Coronal Heating from Recurring Emergence of Magnetic Flux

    NASA Astrophysics Data System (ADS)

    Moore, R. L.; Falconer, D. A.; Sterling, A. C.

    2002-01-01

    For each of six old bipolar active regions, we present and interpret Yohkoh/SXT and SOHO/MDI observations of the development, over several days, of enhanced coronal heating in and around the old bipole in response to new magnetic flux emergence within the old bipole. The observations show: 1. In each active region, new flux emerges in the equatorward side of the old bipole, around a lone remaining leading sunspot and/or on the equatorward end of the neutral line of the old bipole. 2. The emerging field is marked by intense internal coronal heating, and enhanced coronal heating occurs in extended loops stemming from the emergence site. 3. In five of the six cases, a "rooster tail" of coronal loops in the poleward extent of the old bipole also brightens in response to the flux emergence. 4. There are episodes of enhanced coronal heating in surrounding magnetic fields that are contiguous with the old bipole but are not directly connected to the emerging field. From these observations, we suggest that the accommodation of localized newly emerged flux within an old active region entails far reaching adjustments in the 3D magnetic field throughout the active region and in surrounding fields in which the active region is embedded, and that these adjustments produce the extensive enhanced coronal heating. We Also Note That The Reason For The recurrence of flux emergence in old active regions may be that active-region flux tends to emerge in giant-cell convection downflows. If so, the poleward "rooster tail" is a coronal flag of a long-lasting downflow in the convection zone. This work was funded by NASA's Office of Space Science through the Solar Physics Supporting Research and Technology Program and the Sun-Earth Connection Guest Investigator Program.

  9. Contagious Coronal Heating from Recurring Emergence of Magnetic Flux

    NASA Technical Reports Server (NTRS)

    Moore, Ronald L.; Falconer, David; Sterling, Alphonse; Whitaker, Ann F. (Technical Monitor)

    2001-01-01

    For each of six old bipolar active regions, we present and interpret Yohkoh/SXT and SOHO/MDI observations of the development, over several days, of enhanced coronal heating in and around the old bipole in response to new magnetic flux emerge= within the old bipole. The observations show: 1. In each active region, new flux emerges in the equatorward side of the old bipole, around a lone remaining leading sunspot and/or on the equatorward end of the neutral line of the old bipole. 2. The emerging field is marked by intense internal coronal heating, and enhanced coronal heating occurs in extended loops stemming from the emergence site. 3. In five of the six cases, a "rooster tail" of coronal loops in the poleward extent of the old bipole also brightens in response to the flux emergence. 4. There are episodes of enhanced coronal heating in surrounding magnetic fields that are contiguous with the old bipole but are not directly connected to the emerging field. From these observations, we suggest that the accommodation of localized newly emerged flux within an old active region entails far reaching adjustments in the 3D magnetic field throughout the active region and in surrounding fields in which the active region is embedded, and that these adjustments produce the extensive enhanced coronal heating. We also note that the reason for the recurrence of flux emergence in old active regions may be that active region flux tends to emerge in giant-cell convection downflows. If so, the poleward "rooster tail" is a coronal flag of a long-lasting downflow in the convection zone. This work was funded by NASA's Office of Space Science through the Solar Physics Supporting Research and Technology Program and the Sun-Earth Connection Guest Investigator Program.

  10. Contagious Coronal Heating from Recurring Emergence of Magnetic Flux

    NASA Technical Reports Server (NTRS)

    Moore, Ronald L.; Falconer, David; Sterling, Alphonse; Whitaker, Ann F. (Technical Monitor)

    2001-01-01

    For each of six old bipolar active regions, we present and interpret Yohkoh/SXT and SOHO/MDI observations of the development, over several days, of enhanced coronal heating in and around the old bipole in response to new magnetic flux emerge= within the old bipole. The observations show: 1. In each active region, new flux emerges in the equatorward side of the old bipole, around a lone remaining leading sunspot and/or on the equatorward end of the neutral line of the old bipole. 2. The emerging field is marked by intense internal coronal heating, and enhanced coronal heating occurs in extended loops stemming from the emergence site. 3. In five of the six cases, a "rooster tail" of coronal loops in the poleward extent of the old bipole also brightens in response to the flux emergence. 4. There are episodes of enhanced coronal heating in surrounding magnetic fields that are contiguous with the old bipole but are not directly connected to the emerging field. From these observations, we suggest that the accommodation of localized newly emerged flux within an old active region entails far reaching adjustments in the 3D magnetic field throughout the active region and in surrounding fields in which the active region is embedded, and that these adjustments produce the extensive enhanced coronal heating. We also note that the reason for the recurrence of flux emergence in old active regions may be that active region flux tends to emerge in giant-cell convection downflows. If so, the poleward "rooster tail" is a coronal flag of a long-lasting downflow in the convection zone. This work was funded by NASA's Office of Space Science through the Solar Physics Supporting Research and Technology Program and the Sun-Earth Connection Guest Investigator Program.

  11. TWISTED MAGNETIC FLUX TUBES IN THE SOLAR WIND

    SciTech Connect

    Zaqarashvili, Teimuraz V.; Vörös, Zoltán; Narita, Yasuhito; Bruno, Roberto

    2014-03-01

    Magnetic flux tubes in the solar wind can be twisted as they are transported from the solar surface, where the tubes are twisted due to photospheric motions. It is suggested that the twisted magnetic tubes can be detected as the variation of total (thermal+magnetic) pressure during their passage through the observing satellite. We show that the total pressure of several observed twisted tubes resembles the theoretically expected profile. The twist of the isolated magnetic tube may explain the observed abrupt changes of magnetic field direction at tube walls. We have also found some evidence that the flux tube walls can be associated with local heating of the plasma and elevated proton and electron temperatures. For the tubes aligned with the Parker spiral, the twist angle can be estimated from the change of magnetic field direction. Stability analysis of twisted tubes shows that the critical twist angle of the tube with a homogeneous twist is 70°, but the angle can further decrease due to the motion of the tube with respect to the solar wind stream. The tubes with a stronger twist are unstable to the kink instability, therefore they probably cannot reach 1 AU.

  12. Transport of magnetic flux and the vertical structure of accretion discs - I. Uniform diffusion coefficients

    NASA Astrophysics Data System (ADS)

    Guilet, Jérôme; Ogilvie, Gordon I.

    2012-08-01

    Standard models of accretion discs study the transport of mass on a viscous time-scale but do not consider the transport of magnetic flux. The evolution of a large-scale poloidal magnetic field is, however, an important problem because of its role in the launching of jets and winds and in determining the intensity of turbulence. As a consequence, the transport of poloidal magnetic flux should be considered on an equal basis to the transport of mass. In this paper, we develop a formalism to study such a transport of mass and magnetic flux in a thin accretion disc. The governing equations are derived by performing an asymptotic expansion in the limit of a thin disc, in the regime where the magnetic field is dominated by its vertical component. Turbulent viscosity and resistivity are included, with an arbitrary vertical profile that can be adjusted to mimic the vertical structure of the turbulence. At a given radius and time, the rates of transport of mass and magnetic flux are determined by a one-dimensional problem in the vertical direction, in which the radial gradients of various quantities appear as source terms. We solve this problem to obtain the transport rates and the vertical structure of the disc. This paper is then restricted to the idealized case of uniform diffusion coefficients, while a companion paper will study more realistic vertical profiles of these coefficients. We show the advection of weak magnetic fields to be significantly faster than the advection of mass, contrary to what a crude vertical averaging might suggest. This results from the larger radial velocities away from the mid-plane, which barely affect the mass accretion owing to the low density in these regions but do affect the advection of magnetic flux. Possible consequences of this larger accretion velocity include a potentially interesting time dependence with the magnetic flux distribution evolving faster than the mass distribution. If the disc is not too thin, this fast advection

  13. MHD waves on solar magnetic flux tubes - Tutorial review

    NASA Technical Reports Server (NTRS)

    Hollweg, Joseph V.

    1990-01-01

    Some of the highly simplified models that have been developed for solar magnetic flux tubes, which are intense photospheric-level fields confined by external gas pressure but able to vary rapidly with height, are presently discussed with emphasis on the torsional Alfven mode's propagation, reflection, and non-WKB properties. The 'sausage' and 'kink' modes described by the thin flux-tube approximation are noted. Attention is also given to the surface waves and resonance absorption of X-ray-emitting loops, as well as to the results of recent work on the resonant instabilities that occur in the presence of bulk flows.

  14. Magnetic flux noise in dc SQUIDs: temperature and geometry dependence.

    PubMed

    Anton, S M; Birenbaum, J S; O'Kelley, S R; Bolkhovsky, V; Braje, D A; Fitch, G; Neeley, M; Hilton, G C; Cho, H-M; Irwin, K D; Wellstood, F C; Oliver, W D; Shnirman, A; Clarke, John

    2013-04-05

    The spectral density S(Φ)(f) = A(2)/(f/1 Hz)(α) of magnetic flux noise in ten dc superconducting quantum interference devices (SQUIDs) with systematically varied geometries shows that α increases as the temperature is lowered; in so doing, each spectrum pivots about a nearly constant frequency. The mean-square flux noise, inferred by integrating the power spectra, grows rapidly with temperature and at a given temperature is approximately independent of the outer dimension of a given SQUID. These results are incompatible with a model based on the random reversal of independent, surface spins.

  15. MHD waves on solar magnetic flux tubes - Tutorial review

    NASA Astrophysics Data System (ADS)

    Hollweg, Joseph V.

    Some of the highly simplified models that have been developed for solar magnetic flux tubes, which are intense photospheric-level fields confined by external gas pressure but able to vary rapidly with height, are presently discussed with emphasis on the torsional Alfven mode's propagation, reflection, and non-WKB properties. The 'sausage' and 'kink' modes described by the thin flux-tube approximation are noted. Attention is also given to the surface waves and resonance absorption of X-ray-emitting loops, as well as to the results of recent work on the resonant instabilities that occur in the presence of bulk flows.

  16. Magnetic helicity content in solar wind flux ropes

    NASA Astrophysics Data System (ADS)

    Dasso, Sergio

    2009-03-01

    Magnetic helicity (H) is an ideal magnetohydrodynamical (MHD) invariant that quantifies the twist and linkage of magnetic field lines. In magnetofluids with low resistivity, H decays much less than the energy, and it is almost conserved during times shorter than the global diffusion timescale. The extended solar corona (i.e., the heliosphere) is one of the physical scenarios where H is expected to be conserved. The amount of H injected through the photospheric level can be reorganized in the corona, and finally ejected in flux ropes to the interplanetary medium. Thus, coronal mass ejections can appear as magnetic clouds (MCs), which are huge twisted flux tubes that transport large amounts of H through the solar wind. The content of H depends on the global configuration of the structure, then, one of the main difficulties to estimate it from single spacecraft in situ observations (one point - multiple times) is that a single spacecraft can only observe a linear (one dimensional) cut of the MC global structure. Another serious difficulty is the intrinsic mixing between its spatial shape and its time evolution that occurs during the observation period. However, using some simple assumptions supported by observations, the global shape of some MCs can be unveiled, and the associated H and magnetic fluxes (F) can be estimated. Different methods to quantify H and F from the analysis of in situ observations in MCs are presented in this review. Some of these methods consider a MC in expansion and going through possible magnetic reconnections with its environment. We conclude that H seems to be a ‘robust’ MHD quantity in MCs, in the sense that variations of H for a given MC deduced using different methods, are typically lower than changes of H when a different cloud is considered. Quantification of H and F lets us constrain models of coronal formation and ejection of flux ropes to the interplanetary medium, as well as of the dynamical evolution of MCs in the solar wind.

  17. Automated Detection of Small-scale Magnetic Flux Ropes and Their Association with Shocks

    NASA Astrophysics Data System (ADS)

    Zheng, Jinlei; Hu, Qiang; Chen, Yu; le Roux, Jakobus

    2017-09-01

    We have quantitatively examined one type of fundamental space plasma structures in the solar wind, the magnetic flux ropes, especially those of relatively small scales. They usually are of durations ranging from a few minutes to a few hours. The main objectives are to reveal the existence in terms of their occurrence and distributions in the solar wind, to quantitatively examine their configurations and properties, and to relate to other relevant processes, involving particle energization and intermittent structures in the solar wind. The technical approach is a combination of time-series analysis methods with the Grad-Shafranov reconstruction technique. This modeling method is capable of characterizing two and a half dimensional cross section of space plasma structures, based on in-situ spacecraft measurements along a single path across. We present the automated detection of flux ropes, construction of an online magnetic flux rope database, and detailed case studies of such structures identified downstream of interplanetary shocks.

  18. MAGNETIC FLUX CONSERVATION IN THE HELIOSHEATH INCLUDING SOLAR CYCLE VARIATIONS OF MAGNETIC FIELD INTENSITY

    SciTech Connect

    Michael, A. T.; Opher, M.; Provornikova, E.; Richardson, J. D.; Tóth, G. E-mail: mopher@bu.edu E-mail: jdr@space.mit.edu

    2015-04-10

    In the heliosheath (HS), Voyager 2 has observed a flow with constant radial velocity and magnetic flux conservation. Voyager 1, however, has observed a decrease in the flow’s radial velocity and an order of magnitude decrease in magnetic flux. We investigate the role of the 11 yr solar cycle variation of the magnetic field strength on the magnetic flux within the HS using a global 3D magnetohydrodynamic model of the heliosphere. We use time and latitude-dependent solar wind velocity and density inferred from Solar and Heliospheric Observatory/SWAN and interplanetary scintillations data and implemented solar cycle variations of the magnetic field derived from 27 day averages of the field magnitude average of the magnetic field at 1 AU from the OMNI database. With the inclusion of the solar cycle time-dependent magnetic field intensity, the model matches the observed intensity of the magnetic field in the HS along both Voyager 1 and 2. This is a significant improvement from the same model without magnetic field solar cycle variations, which was over a factor of two larger. The model accurately predicts the radial velocity observed by Voyager 2; however, the model predicts a flow speed ∼100 km s{sup −1} larger than that derived from LECP measurements at Voyager 1. In the model, magnetic flux is conserved along both Voyager trajectories, contrary to observations. This implies that the solar cycle variations in solar wind magnetic field observed at 1 AU does not cause the order of magnitude decrease in magnetic flux observed in the Voyager 1 data.

  19. Catastrophe of coronal magnetic flux ropes in partially open magnetic fields

    NASA Astrophysics Data System (ADS)

    Hu, Y. Q.

    2001-05-01

    Using a 2.5-D, time-dependent ideal MHD model in Cartesian coordinates, a numerical study is carried out to find equilibrium solutions associated with a magnetic flux rope in the corona. The ambient magnetic field is partially open, consisting of a closed arcade in the center and an open field at the flank. The coronal magnetic flux rope is characterized by its magnetic properties, including the axial and annular magnetic fluxes and the magnetic helicity, and its geometrical features, including the height of the rope axis, the halfwidth of the rope and the length of the vertical current sheet below the rope. It is shown that for a given partially open ambient magnetic field, the dependence of the geometrical features on the magnetic properties displays a catastrophic behavior, namely, there exists a certain critical point, across which an infinitesimal enhancement of the magnetic parameters causes a finite jump of the geometrical parameters for the rope. The amplitude of the jump depends on the extent to which the ambient magnetic field in open, and approaches to zero when the ambient magnetic field becomes completely closed. The implication of such a catastrophe in solar active phenomena is briefly discussed.

  20. Tropical Gravity Wave Momentum Fluxes and Latent Heating Distributions

    NASA Technical Reports Server (NTRS)

    Geller, Marvin A.; Zhou, Tiehan; Love, Peter T.

    2015-01-01

    Recent satellite determinations of global distributions of absolute gravity wave (GW) momentum fluxes in the lower stratosphere show maxima over the summer subtropical continents and little evidence of GW momentum fluxes associated with the intertropical convergence zone (ITCZ). This seems to be at odds with parameterizations forGWmomentum fluxes, where the source is a function of latent heating rates, which are largest in the region of the ITCZ in terms of monthly averages. The authors have examined global distributions of atmospheric latent heating, cloud-top-pressure altitudes, and lower-stratosphere absolute GW momentum fluxes and have found that monthly averages of the lower-stratosphere GW momentum fluxes more closely resemble the monthly mean cloud-top altitudes rather than the monthly mean rates of latent heating. These regions of highest cloud-top altitudes occur when rates of latent heating are largest on the time scale of cloud growth. This, plus previously published studies, suggests that convective sources for stratospheric GW momentum fluxes, being a function of the rate of latent heating, will require either a climate model to correctly model this rate of latent heating or some ad hoc adjustments to account for shortcomings in a climate model's land-sea differences in convective latent heating.

  1. Tropical Gravity Wave Momentum Fluxes and Latent Heating Distributions

    NASA Technical Reports Server (NTRS)

    Geller, Marvin A.; Zhou, Tiehan; Love, Peter T.

    2015-01-01

    Recent satellite determinations of global distributions of absolute gravity wave (GW) momentum fluxes in the lower stratosphere show maxima over the summer subtropical continents and little evidence of GW momentum fluxes associated with the intertropical convergence zone (ITCZ). This seems to be at odds with parameterizations forGWmomentum fluxes, where the source is a function of latent heating rates, which are largest in the region of the ITCZ in terms of monthly averages. The authors have examined global distributions of atmospheric latent heating, cloud-top-pressure altitudes, and lower-stratosphere absolute GW momentum fluxes and have found that monthly averages of the lower-stratosphere GW momentum fluxes more closely resemble the monthly mean cloud-top altitudes rather than the monthly mean rates of latent heating. These regions of highest cloud-top altitudes occur when rates of latent heating are largest on the time scale of cloud growth. This, plus previously published studies, suggests that convective sources for stratospheric GW momentum fluxes, being a function of the rate of latent heating, will require either a climate model to correctly model this rate of latent heating or some ad hoc adjustments to account for shortcomings in a climate model's land-sea differences in convective latent heating.

  2. Space proton flux and the temporal distribution of cardiovascular deaths

    NASA Astrophysics Data System (ADS)

    Stoupel, E.; Abramson, J.; Domarkiene, S.; Shimshoni, M.; Sulkes, J.

    The influence of solar activity (SA) and geomagnetic activity (GMA) on human homeostasis has long been investigated. The aim of the present study was to analyse the relationship between monthly proton flux (>90 MeV) and other SA and GMA parameters and between proton flux and temporal (monthly) distribution of total and cardiovascular-related deaths. The data from 180 months (1974-1989) of distribution in the Beilinson Campus of the Rabin Medical Centre, Israel, and of 108 months (1983-1991) from the Kaunas Medical Academy, were analysed and compared with SA, GMA and space proton flux (>90 MeV). It was concluded: (1) monthly levels of SA, GMA and radiowave propagation (Fof2) are significantly and adversely correlated with monthly space proton flux (>90 MeV); (2) medical-biological phenomena that increase during periods of low solar and/or geomagnetic activity may be stimulated by physical processes provoked by the concomitant increase in proton flux; (3) the monthly number of deaths related (positively or negatively) to SA are significantly and adversely related to the space proton flux (>90 MeV).

  3. Magnetic Flux Compression Concept for Aerospace Propulsion and Power

    NASA Technical Reports Server (NTRS)

    Litchford, Ron J.; Robertson, Tony; Hawk, Clark W.; Turner, Matt; Koelfgen, Syri

    2000-01-01

    The objective of this research is to investigate system level performance and design issues associated with magnetic flux compression devices for aerospace power generation and propulsion. The proposed concept incorporates the principles of magnetic flux compression for direct conversion of nuclear/chemical detonation energy into electrical power. Specifically a magnetic field is compressed between an expanding detonation driven diamagnetic plasma and a stator structure formed from a high temperature superconductor (HTSC). The expanding plasma cloud is entirely confined by the compressed magnetic field at the expense of internal kinetic energy. Electrical power is inductively extracted, and the detonation products are collimated and expelled through a magnetic nozzle. The long-term development of this highly integrated generator/propulsion system opens up revolutionary NASA Mission scenarios for future interplanetary and interstellar spacecraft. The unique features of this concept with respect to future space travel opportunities are as follows: ability to implement high energy density chemical detonations or ICF microfusion bursts as the impulsive diamagnetic plasma source; high power density system characteristics constrain the size, weight, and cost of the vehicle architecture; provides inductive storage pulse power with a very short pulse rise time; multimegajoule energy bursts/terawatt power bursts; compact pulse power driver for low-impedance dense plasma devices; utilization of low cost HTSC material and casting technology to increase magnetic flux conservation and inductive energy storage; improvement in chemical/nuclear-to-electric energy conversion efficiency and the ability to generate significant levels of thrust with very high specific impulse; potential for developing a small, lightweight, low cost, self-excited integrated propulsion and power system suitable for space stations, planetary bases, and interplanetary and interstellar space travel

  4. Possible Properties of Kinetic Flux Ropes Generated by Magnetic Reconnection

    NASA Astrophysics Data System (ADS)

    Ng, C. S.

    2015-12-01

    We present latest results of numerical studies of a recently obtained analytic solution that can describe small-scale kinetic flux ropes. Such exact nonlinear solution of the Vlasov-Poisson-Ampere system of equations can be regarded as two-dimensional Bernstein-Greene-Kruskal (BGK) mode, generalizing from a solution in a magnetized plasma with finite magnetic field strength [Ng, Bhattacharjee, and Skiff, Phys. Plasmas 13, 055903 (2006)], with the additional effect of field-aligned current. Such solution might explain magnetic flux ropes observed to form within the diffusion region in 3D kinetic simulations of magnetic reconnection, and the 2D version of them (plasmoids, secondary islands). We will present properties of solutions based on a range of typical plasma parameters within regions of the magnetosphere where magnetic reconnection could happen. These solutions could potentially be used to compare with future Magnetospheric Multiscale Mission (MMS) observation. This work is supported by a National Science Foundation grant PHY-1004357 and the Alaska NASA EPSCoR Program (NNX13AB28A).

  5. A Quantitative Study of Magnetic Flux Transport on the Sun,

    DTIC Science & Technology

    1983-02-15

    the Sun . Using Kitt Peak magnetograms as input, as have determined a best-fit diffusion constant by comparing the computed and observed fields at later times. This paper presents the initial results of a project to simulate the transport of solar magnetic flux using diffusion, differential rotation, and meridional flow. The study concerns the evolution of large-scale fields on a time scale of weeks of years, and ignores the rapid changes that accompany the emergence of new magnetic regions and the day-to-day changes of the supergranular network

  6. Magnetic Bipoles in Emerging Flux Regions on the Sun

    NASA Astrophysics Data System (ADS)

    Barth, C. S.; Livi, S. H. B.

    1990-11-01

    ABSTRACT. We analyse magnetograms and H-alpha filtergrams of an Emerging Flux Region. Small bipoles have been observed on the magnetograms emerging between opposite polarities. Separation velocities of the opposite poles for 45 bipoles observed on June 9, 1985 have been measured and are in the range 0.5 < Vs < 3.5 km/s. A significant magnetic flux increase in the region was observed due to contributions from the emerging bipoles. RESUMEN. Se analizan magnetogramas y filtrogramas en H-alfa de una region de flujo emergente. Se observan pequenos dipolos en los magnetogramas emergiendo entre polaridades opuestas. Se midieron velocidades de separacion de polos opuestos para 45 bipolos observados en junio 9 de 1985 y estan en el intervalo 0.5 < Vs < 3.5 km/s. Se observo un aumento significativo del flujo magnetico en la region debido a contribuciones de los bipolos emergentes. Key words: SUN-CHROMOSPHERE - SUN-MAGNETIC FIELDS

  7. Magnetic flux assisted thermospin transport in a Rashba ring

    NASA Astrophysics Data System (ADS)

    Feng, Liang; Benling, Gao; Yu, Gu

    2016-10-01

    The electron transport through a Rashba ring with a magnetic flux and driven by a temperature difference is investigated. It is found that the spin interference effect induced by the Rashba spin-orbit interaction and by the magnetic flux can break the balance between the spin-up and spin-down component currents in the thermally driven charge current and thus result in a spin current. The analytical derivation and numerical calculations reveal that the magnitude, sign, peaks and spin-polarization of the generated spin current can be readily modulated by the system parameters. In particular, with some choices of the parameters, the spin polarization of the generated spin current can reach 100%, that is, a fully spin-polarized thermospin current can be produced. These results may help the use of the spin-dependent Seebeck effect to generate and manipulate a spin current. Project supported by the National Natural Science Foundation of China (No.11404142).

  8. The Near-Earth Meteoroid Flux, Speed Distribution, and Uncertainty

    NASA Technical Reports Server (NTRS)

    Moorhead, Althea; Cooke, William J.; Brown, Peter G.; Campbell-Brown, Margaret; Moser, Danielle E.

    2016-01-01

    Meteoroids are known to pose a threat to spacecraft; they can puncture components, disturb spacecraft attitude, and possibly create secondary electrical effects. Accurate environment models are therefore critical for mitigating meteoroid-related risks. While there are several meteoroid environment models available for assessing spacecraft risk, the uncertainties associated with these models are not well understood. Because meteoroid properties are derived from indirect observations such as meteors and impact craters, the uncertainty in the meteoroid flux is potentially quite large. We combine existing meteoroid flux measurements with new radar and optical meteor data to improve our characterization of the meteoroid flux onto the Earth and its velocity distribution. We use data extracted from the NASA all-sky network, the Canadian Automated Meteor Observatory, and the Canadian Meteor Orbit Radar. We improve our characterization of the observed meteoroid speed distribution by incorporating modern descriptions of the ionization efficiency (e.g., Thomas et al., 2016). We also present estimates of the uncertainties associated with our meteoroid flux distribution. Finally, we discuss the implications for spacecraft. Our model is constrained by the cratering rate on the space-facing surface of LDEF, and thus the risk posed to spacecraft by meteoroid-induced physical damage is the least uncertain component of our model. Other sources of risk, however, may vary. For instance, a lower average meteoroid speed would require a higher meteoroid mass flux in order to match the LDEF crater counts, leading to higher predicted rates of attitude disturbances.

  9. Steady-state distributions of probability fluxes on complex networks

    NASA Astrophysics Data System (ADS)

    Chełminiak, Przemysław; Kurzyński, Michał

    2017-02-01

    We consider a simple model of the Markovian stochastic dynamics on complex networks to examine the statistical properties of the probability fluxes. The additional transition, called hereafter a gate, powered by the external constant force breaks a detailed balance in the network. We argue, using a theoretical approach and numerical simulations, that the stationary distributions of the probability fluxes emergent under such conditions converge to the Gaussian distribution. By virtue of the stationary fluctuation theorem, its standard deviation depends directly on the square root of the mean flux. In turn, the nonlinear relation between the mean flux and the external force, which provides the key result of the present study, allows us to calculate the two parameters that entirely characterize the Gaussian distribution of the probability fluxes both close to as well as far from the equilibrium state. Also, the other effects that modify these parameters, such as the addition of shortcuts to the tree-like network, the extension and configuration of the gate and a change in the network size studied by means of computer simulations are widely discussed in terms of the rigorous theoretical predictions.

  10. Coronal Heating and the Magnetic Flux Content of the Network

    NASA Technical Reports Server (NTRS)

    Falconer, D. A.; Moore, R. L.; Porter, J. G.; Hathaway, D. H.; Whitaker, Ann F. (Technical Monitor)

    2001-01-01

    Previously, from analysis of SOHO/EIT coronal images in combination with Kitt Peak magnetograms (Falconer et al 1998, ApJ, 501, 386-396), we found that the quiet corona is the sum of two components: the e-scale corona and the coronal network. The large-scale corona consists of all coronal-temperature (T approx. 10(exp 6) K) structures larger than supergranules (>approx.30,000 km). The coronal network (1) consists of all coronal-temperature structures smaller than supergranules, (2) is rooted in and loosely traces the photospheric magnetic network, (3) has its brightest features seated on polarity dividing fines (neutral lines) in the network magnetic flux, and (4) produces only about 5% of the total coronal emission in quiet regions. The heating of the coronal network is apparently magnetic in origin. Here, from analysis of EIT coronal images of quiet regions in combination with magnetograms of the same quiet regions from SOHO/MDI and from Kitt Peak, we examine the other 95% of the quiet corona and its relation to the underlying magnetic network. We find: (1) Dividing the large-scale corona into its bright and dim halves divides the area into bright "continents" and dark "oceans" having spans of 2-4 supergranules. (2) These patterns are also present in the photospheric magnetograms: the network is stronger under the bright half and weaker under the dim half. (3) The radiation from the large-scale corona increases roughly as the cube root of the magnetic flux content of the underlying magnetic network. In contrast, Fisher et A (1998, ApJ, 508, 985-998) found that the coronal radiation from an active region increases roughly linearly with the magnetic flux content of the active region. We assume, as is widely held, that nearly all of the large-scale corona is magnetically rooted in the network. Our results, together with the result of Fisher et al (1999), suggest that either the coronal heating in quiet regions has a large non-magnetic component, or, if the heating

  11. Coronal Heating and the Magnetic Flux Content of the Network

    NASA Astrophysics Data System (ADS)

    Falconer, D. A.; Moore, R. L.; Porter, J. G.; Hathaway, D. H.

    2001-05-01

    Previously, from analysis of SOHO/EIT coronal images in combination with Kitt Peak magnetograms (Falconer et al 1998, ApJ, 501, 386-396), we found that the quiet corona is the sum of two components: the large-scale corona and the coronal network. The large-scale corona consists of all coronal-temperature ( million-degree) structures larger than the width of a chromospheric network lane (> 10,000 km). The coronal network (1) consists of all coronal-temperature structures of the scale of the network lanes and smaller (< 10,000 km), (2) is rooted in and loosely traces the photospheric magnetic network, (3) has its brightest features seated on polarity dividing lines (neutral lines) in the network magnetic flux, and (4) produces only about 5% of the total coronal emission in quiet regions. The heating of the coronal network is apparently magnetic in origin. Here, from analysis of EIT coronal images of quiet regions in combination with magnetograms of the same quiet regions from SOHO/MDI and from Kitt Peak, we examine the other 95% of the quiet corona and its relation to the underlying magnetic network. We find: (1) Dividing the large-scale corona into its bright and dim halves divides the area into bright "continents" and dark "oceans" having spans of 2-4 supergranules. (2) These patterns are also present in the photospheric magnetograms: the network is stronger under the bright half and weaker under the dim half. (3) The radiation from the large-scale corona increases roughly as the cube root of the magnetic flux content of the underlying magnetic network. In contrast, Fisher et al (1998, ApJ, 508, 985-998) found that the coronal radiation from an active region increases roughly linearly with the magnetic flux content of the active region. We assume, as is widely held, that nearly all of the large-scale corona is magnetically rooted in the network. Our results, together with the result of Fisher et al (1998), suggest that either the coronal heating in quiet regions

  12. Are heliospheric flows magnetic line- or flux-conserving?

    NASA Astrophysics Data System (ADS)

    Nickeler, D. H.; Karlický, M.

    2006-11-01

    This article discusses and tests the validity of the frozen in magnetic field paradigm (or 'ideal magnetohydrodynamics (MHD) constraint') which is usually adopted by many authors dealing with heliospheric physics. To show the problem of using ideal MHD in such a counterflow configuration like the heliosphere, we first recapitulate the basic concepts of freezing-in of magnetic fields, respectively magnetic topology conservation and its violation (= magnetic reconnection) in 3-D, already done by other authors with different methods with respect to derivations and interpretations. Then we analyse different heliospheric plasma environments. As a model of the stagnation region/stagnation point in front of the heliospheric nose, we present and discuss the general solution of the ideal MHD Ohm's law in the vicinity of a 2-D stagnation point, which was found by us. We show that ideal MHD either leads necessarily to a diverging magnetic field strength in the vicinity of such a stagnation point, or to a vanishing mass density on the heliopause boundaries. In the case that components of the electric field parallel to the magnetic field do not exist due to the chosen form of the non-ideal Ohm's law, it is always possible to formulate the transport equation of the magnetic field as a modified ideal Ohm's law. We find that the form of the Ohm's law which is often used in heliospheric physics (see e.g. Baranov and Fahr, 2003), is not able to change magnetic topology and thus cannot lead to magnetic reconnection, which necessarily has to occur at the stagnation point. The diverging magnetic field, for instance, implies the breakdown of the flux freezing paradigm for the heliosphere. Its application, especially at the heliospheric nose, is therefore rather doubtful. We conclude that it is necessary to search for an Ohm's law which is able to violate magnetic topology conservation.

  13. Alternative magnetic flux leakage modalities for pipeline inspection

    SciTech Connect

    Katragadda, G.; Lord, W.; Sun, Y.S.; Udpa, S.; Udpa, L.

    1996-05-01

    Increasing quality consciousness is placing higher demands on the accuracy and reliability of inspection systems used in defect detection and characterization. Nondestructive testing techniques often rely on using multi-transducer approaches to obtain greater defect sensitivity. This paper investigates the possibility of taking advantage of alternative modalities associated with the standard magnetic flux leakage tool to obtain additional defect information, while still using a single excitation source.

  14. Magnetic and Electric Flux Quanta: the Pion Mass

    SciTech Connect

    P Cameron

    2011-12-31

    The angular momentum of the magnetic flux quantum is balanced by that of the associated supercurrent, such that in condensed matter the resultant angular momentum is zero. The notion of a flux quantum in free space is not so simple, needing both magnetic and electric flux quanta to propagate the stable dynamic structure of the photon. Considering these flux quanta at the scale where quantum field theory becomes essential, at the scale defined by the reduced Compton wavelength of the electron, exposes variants of a paradox that apparently has not been addressed in the literature. Leaving the paradox unresolved in this note, reasonable electromagnetic rationales are presented that permit to calculate the masses of the electron, muon, pion, and nucleon with remarkable accuracy. The calculated mass of the electron is correct at the nine significant digit limit of experimental accuracy, the muon at a part in one thousand, the pion at two parts in ten thousand, and the nucleon at seven parts in one hundred thousand. The accuracy of the pion and nucleon mass calculations reinforces the unconventional common notion that the strong force is electromagnetic in origin.

  15. A method for embedding circular force-free flux ropes in potential magnetic fields

    SciTech Connect

    Titov, V. S.; Török, T.; Mikic, Z.; Linker, J. A.

    2014-08-01

    We propose a method for constructing approximate force-free equilibria in pre-eruptive configurations in which a thin force-free flux rope is embedded into a locally bipolar-type potential magnetic field. The flux rope is assumed to have a circular-arc axis, a circular cross-section, and electric current that is either concentrated in a thin layer at the boundary of the rope or smoothly distributed across it with a maximum of the current density at the center. The entire solution is described in terms of the magnetic vector potential in order to facilitate the implementation of the method in numerical magnetohydrodynamic (MHD) codes that evolve the vector potential rather than the magnetic field itself. The parameters of the flux rope can be chosen so that its subsequent MHD relaxation under photospheric line-tied boundary conditions leads to nearly exact numerical equilibria. To show the capabilities of our method, we apply it to several cases with different ambient magnetic fields and internal flux-rope structures. These examples demonstrate that the proposed method is a useful tool for initializing data-driven simulations of solar eruptions.

  16. Influence of Photospheric Magnetic Conditions on the Catastrophic Behaviors of Flux Ropes in Solar Active Regions

    NASA Astrophysics Data System (ADS)

    Zhang, Quanhao; Wang, Yuming; Hu, Youqiu; Liu, Rui; Liu, Jiajia

    2017-02-01

    Since only the magnetic conditions at the photosphere can be routinely observed in current observations, it is of great significance to determine the influences of photospheric magnetic conditions on solar eruptive activities. Previous studies about catastrophe indicated that the magnetic system consisting of a flux rope in a partially open bipolar field is subject to catastrophe, but not if the bipolar field is completely closed under the same specified photospheric conditions. In order to investigate the influence of the photospheric magnetic conditions on the catastrophic behavior of this system, we expand upon the 2.5-dimensional ideal magnetohydrodynamic model in Cartesian coordinates to simulate the evolution of the equilibrium states of the system under different photospheric flux distributions. Our simulation results reveal that a catastrophe occurs only when the photospheric flux is not concentrated too much toward the polarity inversion line and the source regions of the bipolar field are not too weak; otherwise no catastrophe occurs. As a result, under certain photospheric conditions, a catastrophe could take place in a completely closed configuration, whereas it ceases to exist in a partially open configuration. This indicates that whether the background field is completely closed or partially open is not the only necessary condition for the existence of catastrophe, and that the photospheric conditions also play a crucial role in the catastrophic behavior of the flux rope system.

  17. Stability of magnetic flux ropes with background flow

    NASA Astrophysics Data System (ADS)

    Goedbloed, Hans; Keppens, Rony

    2012-10-01

    MHD stability of magnetic flux ropes is usually studied from the view point of perturbing a static equilibrium background, whereas the significant background flow that is usually present completely modifies the stability of such systems. A new theory, based on energy conservation and self-adjoint operators, permits the computation of the full spectrum of waves and instabilities of stationary plasmas. It involves the construction of a network of curves (the spectral web) in the complex omega-plane associated with the complex complementary energy, which is the energy needed to maintain harmonic time dependence in an open system. Vanishing of that energy, at the intersections of the mentioned curves, yields the eigenvalues of the closed system. Thus, for the first time, knowledge of the full complex spectrum of modes together with a connecting structure is obtained. This theory is applied to compute the complete spectrum of waves and instabilities of flux ropes in a thin accretion disk and of the rotating magnetized jets emitted from those disks. It yields specific stability criteria in terms of the helicities of the magnetic field and of the flow velocity that may be compared with observable parameters of the flux ropes.

  18. Flux Rope Acceleration and Enhanced Magnetic Reconnection Rate

    SciTech Connect

    C.Z. Cheng; Y. Ren; G.S. Choe; Y.-J. Moon

    2003-03-25

    A physical mechanism of flares, in particular for the flare rise phase, has emerged from our 2-1/2-dimensional resistive MHD simulations. The dynamical evolution of current-sheet formation and magnetic reconnection and flux-rope acceleration subject to continuous, slow increase of magnetic shear in the arcade are studied by employing a non-uniform anomalous resistivity in the reconnecting current sheet under gravity. The simulation results directly relate the flux rope's accelerated rising motion with an enhanced magnetic reconnection rate and thus an enhanced reconnection electric field in the current sheet during the flare rise phase. The simulation results provide good quantitative agreements with observations of the acceleration of flux rope, which manifests in the form of SXR ejecta or erupting filament or CMEs, in the low corona. Moreover, for the X-class flare events studied in this paper the peak reconnection electric field is about O(10{sup 2} V/m) or larger, enough to accelerate p articles to over 100 keV in a field-aligned distance of 10 km. Nonthermal electrons thus generated can produce hard X-rays, consistent with impulsive HXR emission observed during the flare rise phase.

  19. Flux transfer events on the magnetopause - Spatial distribution and controlling factors

    NASA Technical Reports Server (NTRS)

    Berchem, J.; Russell, C. T.

    1984-01-01

    The spatial distribution of flux transfer events (FTE) of magnetic flux tubes pulled from the earth's magnetopause is analyzed using ISEE 1 and 2 data from 1977-82. Attention is given to interplanetary conditions influencing different observed FTE polarities. FTEs were observed on nearly 25 percent of the passes near the dayside magnetopause. Direct FTEs were located mainly in the northern dawn sector and reverse FTEs appeared in the southern dusk sector. The distribution indicated an origin in the equatorial sector, and data correlate the appearance of FTEs only when the interplanetary magnetic field (IMF) had southward or nearly horizontal orientation. The presence of a southward component in the IMF was coincident with the appearance of an FTE 45 percent of the events. E-W components in the IMF exhibited no connections with the occurrence of an FTE.

  20. Exact analytic flux distributions for two-dimensional solar concentrators.

    PubMed

    Fraidenraich, Naum; Henrique de Oliveira Pedrosa Filho, Manoel; Vilela, Olga C; Gordon, Jeffrey M

    2013-07-01

    A new approach for representing and evaluating the flux density distribution on the absorbers of two-dimensional imaging solar concentrators is presented. The formalism accommodates any realistic solar radiance and concentrator optical error distribution. The solutions obviate the need for raytracing, and are physically transparent. Examples illustrating the method's versatility are presented for parabolic trough mirrors with both planar and tubular absorbers, Fresnel reflectors with tubular absorbers, and V-trough mirrors with planar absorbers.

  1. Dilation of force-free magnetic flux tubes. [solar magnetic field profiles

    NASA Technical Reports Server (NTRS)

    Frankenthal, S.

    1977-01-01

    A general study is presented of the mapping functions which relate the magnetic-field profiles across a force-free rope in segments subjected to various external pressures. The results reveal that if the external pressure falls below a certain critical level (dependent on the flux-current relation which defines the tube), the magnetic profile consists of an invariant core sheathed in a layer permeated by an azimuthal magnetic field.

  2. Magnetic flux concentrations from dynamo-generated fields

    NASA Astrophysics Data System (ADS)

    Jabbari, S.; Brandenburg, A.; Losada, I. R.; Kleeorin, N.; Rogachevskii, I.

    2014-08-01

    Context. The mean-field theory of magnetized stellar convection gives rise to two distinct instabilities: the large-scale dynamo instability, operating in the bulk of the convection zone and a negative effective magnetic pressure instability (NEMPI) operating in the strongly stratified surface layers. The latter might be important in connection with magnetic spot formation. However, as follows from theoretical analysis, the growth rate of NEMPI is suppressed with increasing rotation rates. On the other hand, recent direct numerical simulations (DNS) have shown a subsequent increase in the growth rate. Aims: We examine quantitatively whether this increase in the growth rate of NEMPI can be explained by an α2 mean-field dynamo, and whether both NEMPI and the dynamo instability can operate at the same time. Methods: We use both DNS and mean-field simulations (MFS) to solve the underlying equations numerically either with or without an imposed horizontal field. We use the test-field method to compute relevant dynamo coefficients. Results: DNS show that magnetic flux concentrations are still possible up to rotation rates above which the large-scale dynamo effect produces mean magnetic fields. The resulting DNS growth rates are quantitatively reproduced with MFS. As expected for weak or vanishing rotation, the growth rate of NEMPI increases with increasing gravity, but there is a correction term for strong gravity and large turbulent magnetic diffusivity. Conclusions: Magnetic flux concentrations are still possible for rotation rates above which dynamo action takes over. For the solar rotation rate, the corresponding turbulent turnover time is about 5 h, with dynamo action commencing in the layers beneath.

  3. A magnetohydrodynamic simulation of the formation of magnetic flux tubes at the earth's dayside magnetopause

    NASA Technical Reports Server (NTRS)

    Ogino, Tatsuki; Walker, Raymond J.; Ashour-Abdalla, Maha

    1989-01-01

    Dayside magnetic reconnection was studied by using a three-dimensional global magnetohydrodynamic simulation of the interaction between the solar wind and the magnetosphere. Two different mechanisms were found for the formation of magnetic flux tubes at the dayside magnetopause, which depend on the orientation of the interplanetary magnetic field (IMF). The dayside magnetic flux tubes occur only when the IMF has a southward component. A strongly twisted and localized magnetic flux tube similar to magnetic flux ropes appears at the subsolar magnetopause when the IMF has a large B(y) component. When the B(y) component is small, twin flux tubes appear at the dayside magnetopause. Both types of magnetic flux tube are consistent with several observational features of flux transfer events and are generated by antiparallel magnetic reconnection.

  4. A magnetohydrodynamic simulation of the formation of magnetic flux tubes at the Earth's dayside magnetopause

    SciTech Connect

    Ogino, Tatsuki ); Walker, R.J.; Ashour-Abdalla, Maha )

    1989-02-01

    The authors have studied dayside magnetic reconnection by using a three-dimensional global magnetohydrodynamic simulation of the interaction between the solar wind and the magnetosphere. They found two different mechanisms for the formation of magnetic flux tubes at the dayside magnetopause which depend on the orientation of the interplanetary magnetic field (IMF). The dayside magnetic flux tubes occur only when the IMF has a southward component. A strongly twisted and localized magnetic flux tube similar to magnetic flux ropes appears at the subsolar magnetopause when the IMF has a large B{sub y} component. When the B{sub y} component is small, twin flux tubes appear at the dayside magnetopause. Both types of magnetic flux tube are consistent with several observational features of flux transfer events and are generated by antiparallel magnetic reconnection.

  5. Nonlinear evolution of magnetic flux ropes. 2: Finite beta plasma

    NASA Technical Reports Server (NTRS)

    Osherovich, V. A.; Farrugia, C. J.; Burlaga, L. F.

    1995-01-01

    In this second paper on the evolution of magnetic flux ropes we study the effects of gas pressure. We assume that the energy transport is described by a polytropic relationship and reduce the set of ideal MHD equations to a single, second-order, nonlinear, ordinary differential equation for the evolution function. For this conservative system we obtain a first integral of motion. To analyze the possible motions, we use a mechanical analogue -- a one-dimensional, nonlinear oscillator. We find that the effective potential for such an oscillator depends on two parameters: the polytropic index gamma and a dimensionless quantity kappa the latter being a function of the plasma beta, the strength of the azimuthal magnetic field relative to the axial field of the flux rope, and gamma. Through a study of this effective potential we classify all possible modes of evolution of the system. In the main body of the paper, we focus on magnetic flux ropes whose field and gas pressure increase steadily towards the symmetry axis. In this case, for gamma greater than 1 and all values of kappa, only oscillations are possible. For gamma less than 1, however, both oscillations and expansion are allowed. For gamma less than 1 and kappa below a critical value, the energy of the nonlinear oscillator determines whether the flux rope will oscillate or expand to infinity. For gamma less than 1 and kappa above critical, however, only expansion occurs. Thus by increasing kappa while keeping gamma fixed (less than 1), a phase transition occurs at kappa = kappa(sub critical) and the oscillatory mode disappears. We illustrate the above theoretical considerations by the example of a flux rope of constant field line twist evolving self-similarly. For this example, we present the full numerical MHD solution. In an appendix to the paper we catalogue all possible evolutions when (1) either the magnetic field or (2) the gas pressure decreases monotonically toward the axis. We find that in these cases

  6. Spatial distribution of Mercury's flux ropes and reconnection fronts: MESSENGER observations

    NASA Astrophysics Data System (ADS)

    Sun, W. J.; Fu, S. Y.; Slavin, J. A.; Raines, J. M.; Zong, Q. G.; Poh, G. K.; Zurbuchen, T. H.

    2016-08-01

    We perform a statistical study of flux ropes and reconnection fronts based on MErcury Surface, Space ENviroment, GEochemistry, and Ranging (MESSENGER) magnetic field and plasma observations to study the implications for the spatial distribution of reconnection sites in Mercury's near magnetotail. The results show important differences of temporal and spatial distributions as compared to Earth. We have surveyed the plasma sheet crossings between -2 RM and -3 RM downtail from the planet, i.e., the location of Near-Mercury Neutral Line (NMNL). Plasma sheets were defined to be regions with β ≥ 0.5. Using this definition, 39 flux ropes and 86 reconnection fronts were identified in the plasma sheet. At Mercury, the distributions of flux ropes and reconnection fronts show clear dawn-dusk asymmetry with much higher occurrence rate on the dawnside plasma sheet than on the duskside. This suggests that magnetic reconnection in Mercury's magnetotail occurs more frequently in the dawnside than in the duskside plasma sheet, which is different than the observations in Earth's magnetotail showing more reconnection signatures in the duskside plasma sheet. The distribution of plasma sheet thickness shows that plasma sheet near the midnight is the thinnest part and does not show obvious asymmetry. Thus, the reasons that cause magnetic reconnection to preferentially occur on the dawnside of the magnetotail at Mercury may not be the plasma sheet thickness and require further study. The peak occurrence rates of flux ropes and reconnection fronts in Mercury's plasma sheet are ~ 60 times higher than that of Earth's values, which we interpret to be due to the highly variable magnetospheric conditions at Mercury. Such higher occurrence rate of magnetic reconnection would generate more plasma flows in the dawnside plasma sheet than in the duskside. These plasma flows would mostly brake and initiate the substorm dipolarization on the postmidnight sector at Mercury rather than the

  7. Generation of a flare loop structure and ejection of magnetic flux from an erupting laboratory arched magnetic flux rope

    NASA Astrophysics Data System (ADS)

    Tripathi, S.; Gekelman, W. N.

    2011-12-01

    A laboratory plasma experiment has been built to generate an arched magnetic flux rope (AMFR) which is essentially an arch-shaped, current-carrying, magnetized plasma structure. Coronal loops and prominences are the main examples of solar AMFRs that frequently erupt and evolve into more energetic events such as flares and coronal mass ejections. Numerous small-scale AMFRs are also observed in the solar corona. In order to capture the important micro-physics of an erupting AMFR, the laboratory experiment has been designed by careful scaling of the solar plasma parameters. The laboratory AMFR (n ~ 1019 m-3, Te ~ 10 eV, L ~ 0.5 m) is produced using a LaB6 plasma source in presence of an arched vacuum magnetic field (B ~ 1 kG) and it evolves in a large magnetized plasma (1.0 m diameter, 4.5 m long, n ~ 1018 m-3, Te ~ 4 eV, B = 25-150 G). Two laser beams (1064 nm, ~0.5 J/pulse) strike movable carbon targets placed behind the electrodes to generate controlled plasma flows from the footpoints of the AMFR. The laser generated flows can mimic a variety of plasma flow conditions that exist on the sun and they can trigger the AMFR eruption by injecting dense plasma and magnetic flux in the AMFR. The experiment runs continuously with a 0.5 Hz repetition rate and is highly reproducible. Thus, several thousands of identical eruptions are routinely generated and evolution of the magnetic field, density, and plasma temperature is recorded in 3D with a high spatiotemporal resolution ( dx = 1 mm, dt= 20 ns) using movable diagnostic probes. Fast-camera images of the erupting AMFR demonstrate striking similarities between laboratory and solar plasma structures, most notably the observation of a flare-loop like structure following the eruption of the laboratory AMFR. The eruption of the AMFR can be initiated either by the laser generated intense flows or by the presence of a strong background magnetic field (B > 50 G ~ magnetic field at the leading edge of the AMFR). In both scenarios

  8. Prediction of metabolic flux distribution from gene expression data based on the flux minimization principle.

    PubMed

    Song, Hyun-Seob; Reifman, Jaques; Wallqvist, Anders

    2014-01-01

    Prediction of possible flux distributions in a metabolic network provides detailed phenotypic information that links metabolism to cellular physiology. To estimate metabolic steady-state fluxes, the most common approach is to solve a set of macroscopic mass balance equations subjected to stoichiometric constraints while attempting to optimize an assumed optimal objective function. This assumption is justifiable in specific cases but may be invalid when tested across different conditions, cell populations, or other organisms. With an aim to providing a more consistent and reliable prediction of flux distributions over a wide range of conditions, in this article we propose a framework that uses the flux minimization principle to predict active metabolic pathways from mRNA expression data. The proposed algorithm minimizes a weighted sum of flux magnitudes, while biomass production can be bounded to fit an ample range from very low to very high values according to the analyzed context. We have formulated the flux weights as a function of the corresponding enzyme reaction's gene expression value, enabling the creation of context-specific fluxes based on a generic metabolic network. In case studies of wild-type Saccharomyces cerevisiae, and wild-type and mutant Escherichia coli strains, our method achieved high prediction accuracy, as gauged by correlation coefficients and sums of squared error, with respect to the experimentally measured values. In contrast to other approaches, our method was able to provide quantitative predictions for both model organisms under a variety of conditions. Our approach requires no prior knowledge or assumption of a context-specific metabolic functionality and does not require trial-and-error parameter adjustments. Thus, our framework is of general applicability for modeling the transcription-dependent metabolism of bacteria and yeasts.

  9. Distributed Sensible Heat Flux Measurements for Wireless Sensor Networks

    NASA Astrophysics Data System (ADS)

    Huwald, H.; Brauchli, T.; Lehning, M.; Higgins, C. W.

    2015-12-01

    The sensible heat flux component of the surface energy balance is typically computed using eddy covariance or two point profile measurements while alternative approaches such as the flux variance method based on convective scaling has been much less explored and applied. Flux variance (FV) certainly has a few limitations and constraints but may be an interesting and competitive method in low-cost and power limited wireless sensor networks (WSN) with the advantage of providing spatio-temporal sensible heat flux over the domain of the network. In a first step, parameters such as sampling frequency, sensor response time, and averaging interval are investigated. Then we explore the applicability and the potential of the FV method for use in WSN in a field experiment. Low-cost sensor systems are tested and compared against reference instruments (3D sonic anemometers) to evaluate the performance and limitations of the sensors as well as the method with respect to the standard calculations. Comparison experiments were carried out at several sites to gauge the flux measurements over different surface types (gravel, grass, water) from the low-cost systems. This study should also serve as an example of spatially distributed sensible heat flux measurements.

  10. Magnetic Flux Compression Concept for Nuclear Pulse Propulsion and Power

    NASA Technical Reports Server (NTRS)

    Litchford, Ronald J.

    2000-01-01

    The desire for fast, efficient interplanetary transport requires propulsion systems having short acceleration times and very high specific impulse attributes. Unfortunately, most highly efficient propulsion systems which are within the capabilities of present day technologies are either very heavy or yield very low impulse such that the acceleration time to final velocity is too long to be of lasting interest, One exception, the nuclear thermal thruster, could achieve the desired acceleration but it would require inordinately large mass ratios to reach the range of desired final velocities. An alternative approach, among several competing concepts that are beyond our modern technical capabilities, is a pulsed thermonuclear device utilizing microfusion detonations. In this paper, we examine the feasibility of an innovative magnetic flux compression concept for utilizing microfusion detonations, assuming that such low yield nuclear bursts can be realized in practice. In this concept, a magnetic field is compressed between an expanding detonation driven diamagnetic plasma and a stationary structure formed from a high temperature superconductor (HTSC). In general, we are interested in accomplishing two important functions: (1) collimation of a hot diamagnetic plasma for direct thrust production; and (2) pulse power generation for dense plasma ignition. For the purposes of this research, it is assumed that rnicrofusion detonation technology may become available within a few decades, and that this approach could capitalize on recent advances in inertial confinement fusion ICF) technologies including magnetized target concepts and antimatter initiated nuclear detonations. The charged particle expansion velocity in these detonations can be on the order of 10 (exp 6)- 10 (exp 7) meters per second, and, if effectively collimated by a magnetic nozzle, can yield the Isp and the acceleration levels needed for practical interplanetary spaceflight. The ability to ignite pure

  11. Magnetic Flux Compression Concept for Nuclear Pulse Propulsion and Power

    NASA Technical Reports Server (NTRS)

    Litchford, Ronald J.

    2000-01-01

    The desire for fast, efficient interplanetary transport requires propulsion systems having short acceleration times and very high specific impulse attributes. Unfortunately, most highly efficient propulsion systems which are within the capabilities of present day technologies are either very heavy or yield very low impulse such that the acceleration time to final velocity is too long to be of lasting interest, One exception, the nuclear thermal thruster, could achieve the desired acceleration but it would require inordinately large mass ratios to reach the range of desired final velocities. An alternative approach, among several competing concepts that are beyond our modern technical capabilities, is a pulsed thermonuclear device utilizing microfusion detonations. In this paper, we examine the feasibility of an innovative magnetic flux compression concept for utilizing microfusion detonations, assuming that such low yield nuclear bursts can be realized in practice. In this concept, a magnetic field is compressed between an expanding detonation driven diamagnetic plasma and a stationary structure formed from a high temperature superconductor (HTSC). In general, we are interested in accomplishing two important functions: (1) collimation of a hot diamagnetic plasma for direct thrust production; and (2) pulse power generation for dense plasma ignition. For the purposes of this research, it is assumed that rnicrofusion detonation technology may become available within a few decades, and that this approach could capitalize on recent advances in inertial confinement fusion ICF) technologies including magnetized target concepts and antimatter initiated nuclear detonations. The charged particle expansion velocity in these detonations can be on the order of 10 (exp 6)- 10 (exp 7) meters per second, and, if effectively collimated by a magnetic nozzle, can yield the Isp and the acceleration levels needed for practical interplanetary spaceflight. The ability to ignite pure

  12. Electrostatic and electromagnetic fluctuations detected inside magnetic flux ropes during magnetic reconnection

    NASA Astrophysics Data System (ADS)

    Wang, Rongsheng; Lu, Quanming; Nakamura, Rumi; Huang, Can; Li, Xing; Wu, Mingyu; Du, Aimin; Gao, Xinliang; Wang, Shui

    2016-10-01

    A series of magnetic flux ropes embedded in the ion diffusion region of a magnetotail magnetic reconnection event were investigated in this paper. Waves near the lower hybrid frequency were measured within each of the flux ropes and can be associated with the enhancements of energetic electrons in some of the flux ropes. The waves in the largest flux ropes were further explored in more detail. The electrostatic lower hybrid frequency range waves are detected at the edge, while electromagnetic lower hybrid frequency range waves are observed at the center of the flux rope. The electromagnetic waves are right-hand polarized and propagated nearly perpendicular to magnetic field lines, with a wavelength of ion-electron hybrid scale. The observations are analogous to simulations in which the electrostatic lower hybrid waves are confined to the edge of current sheet but can directly penetrate into the current sheet center in the form of the electromagnetic mode. The observations indicate that the electromagnetic lower hybrid frequency range waves can be excited inside magnetic flux ropes.

  13. Measurements of Magnetic Helicity within Two Interacting Flux Ropes

    NASA Astrophysics Data System (ADS)

    Dehaas, Timothy; Gekelman, Walter

    2016-10-01

    Magnetic helicity (HM) has become a useful tool in the exploration of astrophysical plasmas. Its conservation in the MHD limit (and even some fluid approaches) constrains the global behavior of large plasma structures. One such astrophysical structure is a magnetic flux rope: a rope-like, current-carrying plasma embedded in an external magnetic field. Bundles of these ropes are commonly observed extending from the solar surface and can be found in the near-earth environment. In this well-diagnosed experiment (3D measurements of ne, Te, Vp, B, J, E, uflow) , two magnetic flux ropes were generated in the Large Plasma Device at UCLA. These ropes were driven kink-unstable, commencing complex motion. As they interact, helicity conservation is broken in regions of reconnection, turbulence, and instabilities. The changes in helicity can be visualized as 1) the transport of helicity (ϕB +E × A) and 2) the dissipation of the helicity (-2EB). Magnetic helicity is observed to have a negative sign and its counterpart, cross helicity, a positive one. These qualities oscillate 8% peak-to-peak. As the ropes move and the topology of the field lines change, a quasi-separatrix layer (QSL) is formed. The volume averaged HM and the largest value of Q both oscillate but not in phase. In addition to magnetic helicity, similar quantities such as self-helicity, mutual-helicity, vorticity, and canonical helicity are derived and will be presented. This work is supported by LANL-UC research Grant and done at the Basic Plasma Science Facility, which is funded by DOE and NSF.

  14. Distribution of the number of generations in flux compactifications

    NASA Astrophysics Data System (ADS)

    Braun, Andreas P.; Watari, Taizan

    2014-12-01

    Flux compactification of string theory generates an ensemble with a large number of vacua, called the landscape. By using the statistics of various properties of low-energy effective theories in the string landscape, one can therefore hope to provide a scientific foundation to the notion of naturalness. This article discusses how to answer such questions of practical interest by using flux compactification of F-theory. It is found that the distribution is approximately in a factorized form given by distribution on the choice of 7-brane gauge group, that on the number of generations Ngen and that on effective coupling constants. The distribution on Ngen is approximately Gaussian for the range |Ngen|≲10 . The statistical cost of higher-rank gauge group is also discussed.

  15. Laser switch for stroboscopic read-out of magnetic flux

    NASA Astrophysics Data System (ADS)

    Ferrara, Marco; Carelli, Pasquale; Chiarello, Fabio; Castellano, Maria Gabriella; Torrioli, Guido; Cosmelli, Carlo

    2004-06-01

    We have realized and tested a fast stroboscopic detector for magnetic flux measurements. The key element of our detector is a hysteretic dc superconducting quantum interference device (SQUID). Stroboscopic read-out of the magnetic flux coupled with the SQUID is accomplished by biasing the SQUID with fast current pulses. The shorter these pulses, the more stroboscopic and less invasive the measurement we are performing. In order to reduce the duration of the current pulses, we take advantage of the superconducting-normal transition induced by laser light in thin superconducting films. The interaction of laser light with superconducting thin films has been investigated thoroughly in the past and many applications have been proposed which rely on the fast typical times with which superconductivity is broken and a resistive behavior arises. We have measured a threshold resolution of 6.9mΦ0 at 4.2 K, and this value corresponds to the thermodynamic limit of the SQUID. The detector has been accurately characterized: An improved and more sensitive version might prove useful for quantum mechanics and quantum computation experiments, for example, in detecting the state of flux qubits.

  16. Polar-Region Distributions of Poynting Flux: Global Models Compared With Observations

    NASA Astrophysics Data System (ADS)

    Melanson, P. D.; Lotko, W.; Murr, D.; Gagne, J. R.; Wiltberger, M.; Lyon, J. G.

    2007-12-01

    Low-altitude distributions of electric potential, field-aligned current and Poynting flux derived from the Lyon- Fedder-Mobarry global simulation model of the magnetosphere are compared with distributions derived from SuperDARN, the Iridium satellite constellation, and the Weimer 2005 empirical model for a one-hour interval (1400-1500 UT) on 23 November 1999 during which the interplanetary magnetic field was steady and southward. Synthetic measurements along a pseudo-satellite track are also obtained from each distribution and compared with measurements from the DMSP F13 satellite. Previous studies of the event are supplemented here with updated simulation results for the electric potential and field-aligned currents, new simulation diagnostics for the Poynting flux incident on the ionosphere, and comparisons of observational and simulation results with the Weimer empirical model. The location and extent of the simulated Poynting fluxes that occur in the afternoon sector, between the Region-1 and 2 currents, are consistent with the observed and empirically modeled locations, but the magnitudes exhibit significant differences (locally up to ~100% both higher and lower). Elsewhere, the distribution of simulated fluxes more closely resembles the empirically modeled values than the observed ones and in general is greater in magnitude by about 100%. Additionally, the fraction of simulated Poynting flux that flow into the polar cap region (above 75 deg) is about one third of the total flowing into the ionosphere above 60 deg; a similar value is found for both the observed and the empirically modeled fluxes. The effect of including the parallel potential drop in the self-consistent mapping of electric potential between the ionosphere and inner boundary of the simulation domain is also examined. Globally the effect is small (< 5%); however, in regions where the field-aligned potential drop is appreciable, local changes of 100% or more are found in the magnitude of the

  17. Influence of magnetic domain landscape on the flux dynamics in superconductor/ferromagnet bilayers

    NASA Astrophysics Data System (ADS)

    Adamus, Z.; Cieplak, Marta Z.; Kończykowski, M.; Zhu, L. Y.; Chien, C. L.

    2016-02-01

    We use a line of miniature Hall sensors to study the influence of the magnetic domain distribution on the flux dynamics in superconductor/ferromagnet bilayers. Two bilayers are built of a ferromagnetic Co/Pt multilayer with perpendicular magnetic anisotropy and a superconducting Nb layer, with the insulating layer in-between to avoid proximity effect. The magnetic domain patterns of various geometries are reversibly predefined in the Co/Pt multilayers using the appropriate magnetization procedure. The Pt thickness is different in the two bilayers, resulting in different width and length of the domains, which profoundly affects vortex dynamics. We show that narrow short domains lead to strong confinement of vortices at the sample edge, while narrow elongated domains of uniform width induce smaller confinement and easy vortex entry. Large enhancement of flux pinning and critical current density, by a factor of more than 7, is observed in the last case, while the former results in smaller enhancement. When domains are wide, the disorder in the domain widths becomes beneficial for larger enhancement of pinning, while more uniform distribution of domain widths results in a precipitous drop of the enhancement. The analysis of these results suggests that with increasing domain width, a transition occurs from vortex chains pinned by narrow domains to disordered triangular vortex lattice pinned by a maze of multiply interconnected magnetic domains.

  18. Emergence of magnetic flux from the convection zone into the corona

    NASA Astrophysics Data System (ADS)

    Archontis, V.; Moreno-Insertis, F.; Galsgaard, K.; Hood, A.; O'Shea, E.

    2004-11-01

    Numerical experiments of the emergence of magnetic flux from the uppermost layers of the solar interior to the photosphere and its further eruption into the low atmosphere and corona are carried out. We use idealized models for the initial stratification and magnetic field distribution below the photosphere similar to those used for multidimensional flux emergence experiments in the literature. The energy equation is adiabatic except for the inclusion of ohmic and viscous dissipation terms, which, however, become important only at interfaces and reconnection sites. Three-dimensional experiments for the eruption of magnetic flux both into an unmagnetized corona and into a corona with a preexisting ambient horizontal field are presented. The shocks preceding the rising plasma present the classical structure of nonlinear Lamb waves. The expansion of the matter when rising into the atmosphere takes place preferentially in the horizontal directions: a flattened (or oval) low plasma-β ball ensues, in which the field lines describe loops in the corona with increasing inclination away from the vertical as one goes toward the sides of the structure. Magnetograms and velocity field distributions on horizontal planes are presented simultaneously for the solar interior and various levels in the atmosphere. Since the background pressure and density drop over many orders of magnitude with increasing height, the adiabatic expansion of the rising plasma yields very low temperatures. To avoid this, the entropy of the rising fluid elements should be increased to the high values of the original atmosphere via heating mechanisms not included in the present numerical experiments. The eruption of magnetic flux into a corona with a preexisting magnetic field pointing in the horizontal direction yields a clear case of essentially three-dimensional reconnection when the upcoming and ambient field systems come into contact. The coronal ambient field is chosen at time t=0 perpendicular to

  19. Plasma dynamics on current-carrying magnetic flux tubes. II - Low potential simulation

    NASA Technical Reports Server (NTRS)

    Swift, Daniel W.

    1992-01-01

    The evolution of plasma in a current-carrying magnetic flux tube of variable cross section is investigated using a one-dimensional numerical simulation. The flux tube is narrow at the two ends and broad in the middle. The middle part of the flux tube is loaded with a hot, magnetically trapped population, and the two ends have a more dense, gravitationally bound population. A potential difference larger than the gravitational potential but less than the energy of the hot population is applied across the domain. The general result is that the potential change becomes distributed along the anode half of the domain, with negligible potential change on the cathode half. The potential is supported by the mirror force of magnetically trapped particles. The simulations show a steady depletion of plasma on the anode side of the flux tube. The current steadily decreases on a time scale of an ion transit time. The results may provide an explanation for the observed plasma depletions on auroral field lines carrying upward currents.

  20. Metabolic Network Fluxes in Heterotrophic Arabidopsis Cells: Stability of the Flux Distribution under Different Oxygenation Conditions1[W][OA

    PubMed Central

    Williams, Thomas C.R.; Miguet, Laurent; Masakapalli, Shyam K.; Kruger, Nicholas J.; Sweetlove, Lee J.; Ratcliffe, R. George

    2008-01-01

    Steady-state labeling experiments with [1-13C]Glc were used to measure multiple metabolic fluxes through the pathways of central metabolism in a heterotrophic cell suspension culture of Arabidopsis (Arabidopsis thaliana). The protocol was based on in silico modeling to establish the optimal labeled precursor, validation of the isotopic and metabolic steady state, extensive nuclear magnetic resonance analysis of the redistribution of label into soluble metabolites, starch, and protein, and a comprehensive set of biomass measurements. Following a simple modification of the cell culture procedure, cells were grown at two oxygen concentrations, and flux maps of central metabolism were constructed on the basis of replicated experiments and rigorous statistical analysis. Increased growth rate at the higher O2 concentration was associated with an increase in fluxes throughout the network, and this was achieved without any significant change in relative fluxes despite differences in the metabolite profile of organic acids, amino acids, and carbohydrates. The balance between biosynthesis and respiration within the tricarboxylic acid cycle was unchanged, with 38% ± 5% of carbon entering used for biosynthesis under standard O2 conditions and 33% ± 2% under elevated O2. These results add to the emerging picture of the stability of the central metabolic network and its capacity to respond to physiological perturbations with the minimum of rearrangement. The lack of correlation between the change in metabolite profile, which implied significant disruption of the metabolic network following the alteration in the oxygen supply, and the unchanging flux distribution highlights a potential difficulty in the interpretation of metabolomic data. PMID:18667721

  1. Simulation of magnetic flux leakage: Application to tube inspection

    NASA Astrophysics Data System (ADS)

    Prémel, Denis; Fnaeich, E. A.; Djafa, S.; Pichon, L.; Trillon, A.; Bisiaux, B.

    2012-05-01

    The detection of flaws in steel pipes using Magnetic Flux Leakage (MFL) consists in detecting magnetic flux leaks outside the pipe, either with a magnetic sensor or with an induction coil, while the pipe is rotating. In the Vallourec group, many NDT units use MFL for testing ferromagnetic pipes. In order to improve the performances of flaw detection, CEA LIST and the Vallourec Research Aulnoye (VRA) group are collaborating on MFL modelling. The aim is to be able to perform parametric studies thanks to a fast 3D numerical model dedicated to MFL systems. A simplified 2D geometry has already been derived for the development of first simulation tools. When considering the B-H curve of ferromagnetic materials, the non-linear magnetostatic problem can be solved with the generalized boundary element method (BEMG), which comes to the evaluation of two equivalent scalar potentials: the surface charge density and the volume charge density. When applying the Galerkin method for the discretization of integral equations, the particularity of this numerical model lies in the implementation of high order basis functions for the interpolation of the scalar unknowns. This paper presents some first numerical results for the numerical validation of the semi-analytical model.

  2. Magnetic Reconnection During Flux Conversion in a Driven Spheromak

    SciTech Connect

    Hooper, E B; Kopriva, T A; Cohen, B I; Hill, D N; McLean, H S; Wood, R D; Woodruff, S; Sovinec, C R

    2005-06-07

    During buildup of a spheromak by helicity injection, magnetic reconnection converts toroidal flux into poloidal flux. This physics is explored in the resistive magnetohydrodynamic code, NIMROD [C.R. Sovinec, A.H. Glasser, T.A. Gianakon, D.C. Barnes, R.A. Nebel, S.E. Kruger, D.D. Schnack, S.J. Plimpton, A. Tarditi, and M.S. Chu, J. Comp. Phys., 195, 355-386 (2004)], which reveals negative current sheets with {lambda} = {mu}{sub 0}j {center_dot} B/B{sup 2}reversed relative to the applied current. The simulated event duration is consistent with magnetic diffusion on the sheet thickness and is accompanied by cathode voltage spikes and poloidal field increases similar to those seen in the Sustained Spheromak Physics Experiment, SSPX [E. B. Hooper, L. D. Pearlstein, and R. H. Bulmer, Nucl. Fusion 39, 863 (1999)]. All magnetic fieldlines are open during reconnection and their trajectories are very sensitive to their starting points, resulting in chaos. The current sheets are most intense inside the separatrix near the X-point of the mean-field spheromak, suggesting that the reconnection occurs near fieldlines which are closed in the azimuthal average.

  3. Magnetic flux pileup and plasma depletion in Mercury's subsolar magnetosheath

    NASA Astrophysics Data System (ADS)

    Gershman, Daniel J.; Slavin, James A.; Raines, Jim M.; Zurbuchen, Thomas H.; Anderson, Brian J.; Korth, Haje; Baker, Daniel N.; Solomon, Sean C.

    2013-11-01

    from the Fast Imaging Plasma Spectrometer (FIPS) and Magnetometer (MAG) on the MErcury Surface, Space ENvironment, GEochemistry, and Ranging spacecraft during 40 orbits about Mercury are used to characterize the plasma depletion layer just exterior to the planet's dayside magnetopause. A plasma depletion layer forms at Mercury as a result of piled-up magnetic flux that is draped around the magnetosphere. The low average upstream Alfvénic Mach number (MA ~3-5) in the solar wind at Mercury often results in large-scale plasma depletion in the magnetosheath between the subsolar magnetopause and the bow shock. Flux pileup is observed to occur downstream under both quasi-perpendicular and quasi-parallel shock geometries for all orientations of the interplanetary magnetic field (IMF). Furthermore, little to no plasma depletion is seen during some periods with stable northward IMF. The consistently low value of plasma β, the ratio of plasma pressure to magnetic pressure, at the magnetopause associated with the low average upstream MA is believed to be the cause for the high average reconnection rate at Mercury, reported to be nearly 3 times that observed at Earth. Finally, a characteristic depletion length outward from the subsolar magnetopause of ~300 km is found for Mercury. This value scales among planetary bodies as the average standoff distance of the magnetopause.

  4. Turbulence-Induced Magnetic Flux Asymmetry at Nanoscale Junctions

    NASA Astrophysics Data System (ADS)

    Bushong, Neil; Pershin, Yuriy; di Ventra, Massimiliano

    2007-11-01

    It was recently predicted [J. Phys. Condens. MatterJCOMEL0953-8984 18, 11059 (2006)10.1088/0953-8984/18/49/001] that turbulence of electron flow may develop at nonadiabatic nanoscale junctions under appropriate conditions. Here we show that such an effect leads to an asymmetric current-induced magnetic field on the two sides of an otherwise symmetric junction. We propose that measuring the fluxes ensuing from these fields across two surfaces placed at the two sides of the junction would provide direct and noninvasive evidence of the transition from laminar to turbulent electron flow. The flux asymmetry is predicted to first increase, reach a maximum, and then decrease with increasing current, i.e., with increasing amount of turbulence.

  5. Metabolic flux distributions: genetic information, computational predictions, and experimental validation.

    PubMed

    Blank, Lars M; Kuepfer, Lars

    2010-05-01

    Flux distributions in intracellular metabolic networks are of immense interest to fundamental and applied research, since they are quantitative descriptors of the phenotype and the operational mode of metabolism in the face of external growth conditions. In particular, fluxes are of relevance because they do not belong to the cellular inventory (e.g., transcriptome, proteome, metabolome), but are rather quantitative moieties, which link the phenotype of a cell to the specific metabolic mode of operation. A frequent application of measuring and redirecting intracellular fluxes is strain engineering, which ultimately aims at shifting metabolic activity toward a desired product to achieve a high yield and/or rate. In this article, we first review the assessment of intracellular flux distributions by either qualitative or rather quantitative computational methods and also discuss methods for experimental measurements. The tools at hand will then be exemplified on strain engineering projects from the literature. Finally, the achievements are discussed in the context of future developments in Metabolic Engineering and Synthetic Biology.

  6. Kinetic models of magnetic flux ropes observed in the Earth magnetosphere

    SciTech Connect

    Vinogradov, A. A.; Vasko, I. Y.; Petrukovich, A. A.; Zelenyi, L. M.; Artemyev, A. V.; Yushkov, E. V.

    2016-07-15

    Magnetic flux ropes (MFR) are universal magnetoplasma structures (similar to cylindrical screw pinches) formed in reconnecting current sheets. In particular, MFR with scales from about the ion inertial length to MHD range are widely observed in the Earth magnetosphere. Typical MFR have force-free configuration with the axial magnetic field peaking on the MFR axis, whereas bifurcated MFR with an off-axis peak of the axial magnetic field are observed as well. In the present paper, we develop kinetic models of force-free and bifurcated MFR and determine consistent ion and electron distribution functions. The magnetic field configuration of the force-free MFR represents well-known Gold-Hoyle MFR (uniformly twisted MFR). We show that bifurcated MFR are characterized by the presence of cold and hot current-carrying electrons. The developed models are capable to describe MFR observed in the Earth magnetotail as well as MFR recently observed by Magnetospheric Multiscale Mission at the Earth magnetopause.

  7. A copper-lined magnet coil with maximum field of 700 T for electromagnetic flux compression

    NASA Astrophysics Data System (ADS)

    Takeyama, Shojiro; Kojima, Eiji

    2011-10-01

    A copper-lined (CL) primary coil, which is a composite of steel and copper, was devised for the electromagnetic flux compression technique to generate ultrahigh magnetic fields. The newly developed coil was found to be highly efficient for electromagnetic energy transfer and provided stabilization of the liner implosive motion with less influence from the current feeding gap. Dynamical current density distribution of the materials used in a primary coil was evaluated and applied to the design of the CL coil. Fields of up to 730 T were achieved by employing the CL coil with an energy injected from a 4 MJ condenser bank. This value is the highest achieved thus far in an indoor setting. The peak magnetic fields were found to depend significantly on the initial seed magnetic field. The optimum seed fields for obtaining the highest peak magnetic field were determined.

  8. A flux-splitting method for hyperbolic-equation system of magnetized electron fluids in quasi-neutral plasmas

    SciTech Connect

    Kawashima, Rei Komurasaki, Kimiya Schönherr, Tony

    2016-04-01

    A flux-splitting method is proposed for the hyperbolic-equation system (HES) of magnetized electron fluids in quasi-neutral plasmas. The numerical fluxes are split into four categories, which are computed by using an upwind method which incorporates a flux-vector splitting (FVS) and advection upstream splitting method (AUSM). The method is applied to a test calculation condition of uniformly distributed and angled magnetic lines of force. All of the pseudo-time advancement terms converge monotonically and the conservation laws are strictly satisfied in the steady state. The calculation results are compared with those computed by using the elliptic–parabolic-equation system (EPES) approach using a magnetic-field-aligned mesh (MFAM). Both qualitative and quantitative comparisons yield good agreements of results, indicating that the HES approach with the flux-splitting method attains a high computational accuracy.

  9. Coronal and heliospheric magnetic flux circulation and its relation to open solar flux evolution

    NASA Astrophysics Data System (ADS)

    Lockwood, Mike; Owens, Mathew J.; Imber, Suzanne M.; James, Matthew K.; Bunce, Emma J.; Yeoman, Timothy K.

    2017-06-01

    Solar cycle 24 is notable for three features that can be found in previous cycles but which have been unusually prominent: (1) sunspot activity was considerably greater in the northern/southern hemisphere during the rising/declining phase; (2) accumulation of open solar flux (OSF) during the rising phase was modest, but rapid in the early declining phase; (3) the heliospheric current sheet (HCS) tilt showed large fluctuations. We show that these features had a major influence on the progression of the cycle. All flux emergence causes a rise then a fall in OSF, but only OSF with foot points in opposing hemispheres progresses the solar cycle via the evolution of the polar fields. Emergence in one hemisphere, or symmetric emergence without some form of foot point exchange across the heliographic equator, causes poleward migrating fields of both polarities in one or both (respectively) hemispheres which temporarily enhance OSF but do not advance the polar field cycle. The heliospheric field observed near Mercury and Earth reflects the asymmetries in emergence. Using magnetograms, we find evidence that the poleward magnetic flux transport (of both polarities) is modulated by the HCS tilt, revealing an effect on OSF loss rate. The declining phase rise in OSF was caused by strong emergence in the southern hemisphere with an anomalously low HCS tilt. This implies the recent fall in the southern polar field will be sustained and that the peak OSF has limited implications for the polar field at the next sunspot minimum and hence for the amplitude of cycle 25.Plain Language SummaryThere is growing interest in being able to predict the evolution in solar conditions on a better basis than past experience, which is necessarily limited. Two of the key features of the solar <span class="hlt">magnetic</span> cycle are that the polar fields reverse just after the peak of each sunspot cycle and that the polar field that has accumulated by the time of each sunspot</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015A%26A...583A..47P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015A%26A...583A..47P"><span>Supergranular-scale <span class="hlt">magnetic</span> <span class="hlt">flux</span> emergence beneath an unstable filament</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Palacios, J.; Cid, C.; Guerrero, A.; Saiz, E.; Cerrato, Y.</p> <p>2015-11-01</p> <p>Aims: Here we report evidence of a large solar filament eruption on 2013, September 29. This smooth eruption, which passed without any previous flare, formed after a two-ribbon flare and a coronal mass ejection towards Earth. The coronal mass ejection generated a moderate geomagnetic storm on 2013, October 2 with very serious localized effects. The whole event passed unnoticed to flare-warning systems. Methods: We have conducted multi-wavelength analyses of the Solar Dynamics Observatory through Atmospheric Imaging Assembly (AIA) and Helioseismic and <span class="hlt">Magnetic</span> Imager (HMI) data. The AIA data on 304, 193, 211, and 94 Å sample the transition region and the corona, respectively, while HMI provides photospheric magnetograms, continuum, and linear polarization data, in addition to the fully inverted data provided by HMI. Results: This <span class="hlt">flux</span> emergence happened very close to a filament barb that was very active in mass motion, as seen in 304 Å images. The observed <span class="hlt">flux</span> emergence exhibited hectogauss values. The <span class="hlt">flux</span> emergence extent appeared just beneath the filament, and the filament rose during the following hours. The emergence acquired a size of 33'' in ~12 h, about ~0.16 km s-1. The rate of signed <span class="hlt">magnetic</span> <span class="hlt">flux</span> is around 2 × 1017 Mx min-1 for each polarity. We have also studied the eruption speed, size, and dynamics. The mean velocity of the rising filament during the ~40 min previous to the flare is 115 ± 5 km s-1, and the subsequent acceleration in this period is 0.049 ± 0.001 km s-2. Conclusions: We have observed a supergranular-sized emergence close to a large filament in the boundary of the active region NOAA11850. Filament dynamics and magnetogram results suggest that the <span class="hlt">magnetic</span> <span class="hlt">flux</span> emergence takes place in the photospheric level below the filament. Reconnection occurs underneath the filament between the dipped lines that support the filament and the supergranular emergence. The very smooth ascent is probably caused by this emergence and torus instability</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/908279','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/908279"><span>System having unmodulated <span class="hlt">flux</span> locked loop for measuring <span class="hlt">magnetic</span> fields</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Ganther, Jr., Kenneth R.; Snapp, Lowell D.</p> <p>2006-08-15</p> <p>A system (10) for measuring <span class="hlt">magnetic</span> fields, wherein the system (10) comprises an unmodulated or direct-feedback <span class="hlt">flux</span> locked loop (12) connected by first and second unbalanced RF coaxial transmission lines (16a, 16b) to a superconducting quantum interference device (14). The FLL (12) operates for the most part in a room-temperature or non-cryogenic environment, while the SQUID (14) operates in a cryogenic environment, with the first and second lines (16a, 16b) extending between these two operating environments.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1201430','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1201430"><span>Dual-spacecraft reconstruction of a three-dimensional <span class="hlt">magnetic</span> <span class="hlt">flux</span> rope at the Earth's magnetopause</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Hasegawa, H.; Sonnerup, B. U. Ö.; Eriksson, S.; Nakamura, T. K. M.; Kawano, H.</p> <p>2015-02-03</p> <p>We present the first results of a data analysis method, developed by Sonnerup and Hasegawa (2011), for reconstructing three-dimensional (3-D), magnetohydrostatic structures from data taken as two closely spaced satellites traverse the structures. The method is applied to a <span class="hlt">magnetic</span> <span class="hlt">flux</span> transfer event (FTE), which was encountered on 27 June 2007 by at least three (TH-C, TH-D, and TH-E) of the five THEMIS probes near the subsolar magnetopause. The FTE was sandwiched between two oppositely directed reconnection jets under a southward interplanetary <span class="hlt">magnetic</span> field condition, consistent with its generation by multiple X-line reconnection. The recovered 3-D field indicates that a <span class="hlt">magnetic</span> <span class="hlt">flux</span> rope with a diameter of ~ 3000 km was embedded in the magnetopause. The FTE <span class="hlt">flux</span> rope had a significant 3-D structure, because the 3-D field reconstructed from the data from TH-C and TH-D (separated by ~ 390 km) better predicts <span class="hlt">magnetic</span> field variations actually measured along the TH-E path than does the 2-D Grad–Shafranov reconstruction using the data from TH-C (which was closer to TH-E than TH-D and was at ~ 1250 km from TH-E). Such a 3-D nature suggests that the field lines reconnected at the two X-lines on both sides of the <span class="hlt">flux</span> rope are entangled in a complicated way through their interaction with each other. The generation process of the observed 3-D <span class="hlt">flux</span> rope is discussed on the basis of the reconstruction results and the pitch-angle <span class="hlt">distribution</span> of electrons observed in and around the FTE.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1201430-dual-spacecraft-reconstruction-three-dimensional-magnetic-flux-rope-earth-magnetopause','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1201430-dual-spacecraft-reconstruction-three-dimensional-magnetic-flux-rope-earth-magnetopause"><span>Dual-spacecraft reconstruction of a three-dimensional <span class="hlt">magnetic</span> <span class="hlt">flux</span> rope at the Earth's magnetopause</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Hasegawa, H.; Sonnerup, B. U. Ö.; Eriksson, S.; ...</p> <p>2015-02-03</p> <p>We present the first results of a data analysis method, developed by Sonnerup and Hasegawa (2011), for reconstructing three-dimensional (3-D), magnetohydrostatic structures from data taken as two closely spaced satellites traverse the structures. The method is applied to a <span class="hlt">magnetic</span> <span class="hlt">flux</span> transfer event (FTE), which was encountered on 27 June 2007 by at least three (TH-C, TH-D, and TH-E) of the five THEMIS probes near the subsolar magnetopause. The FTE was sandwiched between two oppositely directed reconnection jets under a southward interplanetary <span class="hlt">magnetic</span> field condition, consistent with its generation by multiple X-line reconnection. The recovered 3-D field indicates that amore » <span class="hlt">magnetic</span> <span class="hlt">flux</span> rope with a diameter of ~ 3000 km was embedded in the magnetopause. The FTE <span class="hlt">flux</span> rope had a significant 3-D structure, because the 3-D field reconstructed from the data from TH-C and TH-D (separated by ~ 390 km) better predicts <span class="hlt">magnetic</span> field variations actually measured along the TH-E path than does the 2-D Grad–Shafranov reconstruction using the data from TH-C (which was closer to TH-E than TH-D and was at ~ 1250 km from TH-E). Such a 3-D nature suggests that the field lines reconnected at the two X-lines on both sides of the <span class="hlt">flux</span> rope are entangled in a complicated way through their interaction with each other. The generation process of the observed 3-D <span class="hlt">flux</span> rope is discussed on the basis of the reconstruction results and the pitch-angle <span class="hlt">distribution</span> of electrons observed in and around the FTE.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3693171','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3693171"><span>Decoupling Suspension Controller Based on <span class="hlt">Magnetic</span> <span class="hlt">Flux</span> Feedback</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Zhang, Wenqing; Li, Jie; Zhang, Kun; Cui, Peng</p> <p>2013-01-01</p> <p>The suspension module control system model has been established based on MIMO (multiple input and multiple output) state feedback linearization. We have completed decoupling between double suspension points, and the new decoupling method has been applied to CMS04 <span class="hlt">magnetic</span> suspension vehicle in national mid-low-speed maglev experiment field of Tangshan city in China. Double suspension system model is very accurate for investigating stability property of maglev control system. When <span class="hlt">magnetic</span> <span class="hlt">flux</span> signal is taken back to the suspension control system, the suspension module's antijamming capacity for resisting suspension load variety has been proved. Also, the external force interference has been enhanced. As a result, the robustness and stability properties of double-electromagnet suspension control system have been enhanced. PMID:23844415</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19920045456&hterms=plasma+explained&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dplasma%2Bexplained','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19920045456&hterms=plasma+explained&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dplasma%2Bexplained"><span>Plasma dynamics on current-carrying <span class="hlt">magnetic</span> <span class="hlt">flux</span> tubes</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Swift, Daniel W.</p> <p>1992-01-01</p> <p>A 1D numerical simulation is used to investigate the evolution of a plasma in a current-carrying <span class="hlt">magnetic</span> <span class="hlt">flux</span> tube of variable cross section. A large potential difference, parallel to the <span class="hlt">magnetic</span> field, is applied across the domain. The result is that density minimum tends to deepen, primarily in the cathode end, and the entire potential drop becomes concentrated across the region of density minimum. The evolution of the simulation shows some sensitivity to particle boundary conditions, but the simulations inevitably evolve into a final state with a nearly stationary double layer near the cathode end. The simulation results are at sufficient variance with observations that it appears unlikely that auroral electrons can be explained by a simple process of acceleration through a field-aligned potential drop.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23844415','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23844415"><span>Decoupling suspension controller based on <span class="hlt">magnetic</span> <span class="hlt">flux</span> feedback.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zhang, Wenqing; Li, Jie; Zhang, Kun; Cui, Peng</p> <p>2013-01-01</p> <p>The suspension module control system model has been established based on MIMO (multiple input and multiple output) state feedback linearization. We have completed decoupling between double suspension points, and the new decoupling method has been applied to CMS04 <span class="hlt">magnetic</span> suspension vehicle in national mid-low-speed maglev experiment field of Tangshan city in China. Double suspension system model is very accurate for investigating stability property of maglev control system. When <span class="hlt">magnetic</span> <span class="hlt">flux</span> signal is taken back to the suspension control system, the suspension module's antijamming capacity for resisting suspension load variety has been proved. Also, the external force interference has been enhanced. As a result, the robustness and stability properties of double-electromagnet suspension control system have been enhanced.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009Natur.457..167C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009Natur.457..167C"><span>Energy <span class="hlt">flux</span> determines <span class="hlt">magnetic</span> field strength of planets and stars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Christensen, Ulrich R.; Holzwarth, Volkmar; Reiners, Ansgar</p> <p>2009-01-01</p> <p>The <span class="hlt">magnetic</span> fields of Earth and Jupiter, along with those of rapidly rotating, low-mass stars, are generated by convection-driven dynamos that may operate similarly (the slowly rotating Sun generates its field through a different dynamo mechanism). The field strengths of planets and stars vary over three orders of magnitude, but the critical factor causing that variation has hitherto been unclear. Here we report an extension of a scaling law derived from geodynamo models to rapidly rotating stars that have strong density stratification. The unifying principle in the scaling law is that the energy <span class="hlt">flux</span> available for generating the <span class="hlt">magnetic</span> field sets the field strength. Our scaling law fits the observed field strengths of Earth, Jupiter, young contracting stars and rapidly rotating low-mass stars, despite vast differences in the physical conditions of the objects. We predict that the field strengths of rapidly rotating brown dwarfs and massive extrasolar planets are high enough to make them observable.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19129842','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19129842"><span>Energy <span class="hlt">flux</span> determines <span class="hlt">magnetic</span> field strength of planets and stars.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Christensen, Ulrich R; Holzwarth, Volkmar; Reiners, Ansgar</p> <p>2009-01-08</p> <p>The <span class="hlt">magnetic</span> fields of Earth and Jupiter, along with those of rapidly rotating, low-mass stars, are generated by convection-driven dynamos that may operate similarly (the slowly rotating Sun generates its field through a different dynamo mechanism). The field strengths of planets and stars vary over three orders of magnitude, but the critical factor causing that variation has hitherto been unclear. Here we report an extension of a scaling law derived from geodynamo models to rapidly rotating stars that have strong density stratification. The unifying principle in the scaling law is that the energy <span class="hlt">flux</span> available for generating the <span class="hlt">magnetic</span> field sets the field strength. Our scaling law fits the observed field strengths of Earth, Jupiter, young contracting stars and rapidly rotating low-mass stars, despite vast differences in the physical conditions of the objects. We predict that the field strengths of rapidly rotating brown dwarfs and massive extrasolar planets are high enough to make them observable.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014LTP....40..773L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014LTP....40..773L"><span><span class="hlt">Magnetic</span> <span class="hlt">flux</span> creep in HTSC and Anderson-Kim theory (Review Article)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lykov, A. N.</p> <p>2014-09-01</p> <p>Theoretical results and experimental data on <span class="hlt">flux</span> creep in high-temperature superconductors (HTSC) are analyzed in this review paper. When reviewing experimental work, the main attention is paid to the most striking experimental results which have had a major impact on the study of <span class="hlt">flux</span> creep in HTSC. On the other hand, the analysis of theoretical results is focused on the studies which explain the features of <span class="hlt">flux</span> creep by introducing modifications to the Anderson-Kim (AK) theory, i.e., on the studies that have not received sufficient attention earlier. However, it turned out that the modified AK theory could explain a number of features of <span class="hlt">flux</span> creep in HTSC: the scaling behavior of current-voltage curves in HTSC, the finite rate of <span class="hlt">flux</span> creep at ultralow temperatures, the logarithmic dependence of the effective pinning potential on the transport current and its decrease with temperature. The harmonic potential field which is used in this approach makes it possible to solve accurately both the problem of viscous vortex motion and the problem of thermally activated <span class="hlt">flux</span> creep in this <span class="hlt">magnetic</span> field. Moreover, the energy <span class="hlt">distribution</span> of pinning potential and the interaction of vortices with each other are also taken into account in the approach. Thus, the modification of the AK theory consists, essentially, in its refinement and achieving a more realistic approximation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012A%26A...542A..96K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012A%26A...542A..96K"><span>The continuum intensity as a function of <span class="hlt">magnetic</span> field. II. Local <span class="hlt">magnetic</span> <span class="hlt">flux</span> and convective flows</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kobel, P.; Solanki, S. K.; Borrero, J. M.</p> <p>2012-06-01</p> <p>Context. To deepen our understanding of the role of small-scale <span class="hlt">magnetic</span> fields in active regions (ARs) and in the quiet Sun (QS) on the solar irradiance, it is fundamental to investigate the physical processes underlying their continuum brightness. Previous results showed that <span class="hlt">magnetic</span> elements in the QS reach larger continuum intensities than in ARs at disk center, but left this difference unexplained. Aims: We use Hinode/SP disk center data to study the influence of the local amount of <span class="hlt">magnetic</span> <span class="hlt">flux</span> on the vigour of the convective flows and the continuum intensity contrasts. Methods: The apparent (i.e. averaged over a pixel) longitudinal field strength and line-of-sight (LOS) plasma velocity were retrieved by means of Milne-Eddington inversions (VFISV code). We analyzed a series of boxes taken over AR plages and the QS, to determine how the continuum intensity contrast of <span class="hlt">magnetic</span> elements, the amplitude of the vertical flows and the box-averaged contrast were affected by the mean longitudinal field strength in the box (which scales with the total unsigned <span class="hlt">flux</span> in the box). Results: Both the continuum brightness of the <span class="hlt">magnetic</span> elements and the dispersion of the LOS velocities anti-correlate with the mean longitudinal field strength. This can be attributed to the "<span class="hlt">magnetic</span> patches" (here defined as areas where the longitudinal field strength is above 100 G) carrying most of the <span class="hlt">flux</span> in the boxes. There the velocity amplitude and the spatial scale of convection are reduced. Due to this hampered convective transport, these patches appear darker than their surroundings. Consequently, the average brightness of a box decreases as the the patches occupy a larger fraction of it and the amount of embedded <span class="hlt">flux</span> thereby increases. Conclusions: Our results suggest that as the <span class="hlt">magnetic</span> <span class="hlt">flux</span> increases locally (e.g. from weak network to strong plage), the heating of the <span class="hlt">magnetic</span> elements is reduced by the intermediate of a more suppressed convective energy transport within</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_16 --> <div id="page_17" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="321"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011JMP....52k2103D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011JMP....52k2103D"><span>Exponentially localized Wannier functions in periodic zero <span class="hlt">flux</span> <span class="hlt">magnetic</span> fields</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>De Nittis, G.; Lein, M.</p> <p>2011-11-01</p> <p>In this work, we investigate conditions which ensure the existence of an exponentially localized Wannier basis for a given periodic hamiltonian. We extend previous results [Panati, G., Ann. Henri Poincare 8, 995-1011 (2007), 10.1007/s00023-007-0326-8] to include periodic zero <span class="hlt">flux</span> <span class="hlt">magnetic</span> fields which is the setting also investigated by Kuchment [J. Phys. A: Math. Theor. 42, 025203 (2009), 10.1088/1751-8113/42/2/025203]. The new notion of <span class="hlt">magnetic</span> symmetry plays a crucial rôle; to a large class of symmetries for a non-<span class="hlt">magnetic</span> system, one can associate "<span class="hlt">magnetic</span>" symmetries of the related <span class="hlt">magnetic</span> system. Observing that the existence of an exponentially localized Wannier basis is equivalent to the triviality of the so-called Bloch bundle, a rank m hermitian vector bundle over the Brillouin zone, we prove that <span class="hlt">magnetic</span> time-reversal symmetry is sufficient to ensure the triviality of the Bloch bundle in spatial dimension d = 1, 2, 3. For d = 4, an exponentially localized Wannier basis exists provided that the trace per unit volume of a suitable function of the Fermi projection vanishes. For d > 4 and d ⩽ 2m (stable rank regime) only the exponential localization of a subset of Wannier functions is shown; this improves part of the analysis of Kuchment [J. Phys. A: Math. Theor. 42, 025203 (2009), 10.1088/1751-8113/42/2/025203]. Finally, for d > 4 and d > 2m (unstable rank regime) we show that the mere analysis of Chern classes does not suffice in order to prove triviality and thus exponential localization.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19890004016','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19890004016"><span>C IV <span class="hlt">fluxes</span> from the Sun as a star, and the correlation with <span class="hlt">magnetic</span> <span class="hlt">flux</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Schrijver, C. J.; Linsky, J. L.; Bennett, J.; Brown, A.; Saar, S. H.</p> <p>1988-01-01</p> <p>A total of 144 C IV wavelength 1548 Solar Maximum Mission (SMM)-UVSP spectroheliograms of solar plages were analyzed, some of which are series of exposures of the same region on the same day. Also analyzed were the C IV wavelength 1551 rasters of plages and C IV wavelength 1548 rasters of the quiet sun. The sample contained data on 17 different plages, observed on 50 different days. The center-to-limb variations of the active regions show that the optical thickness effects in the C IV wavelength 1548 line can be neglected in the conversion from intensity to <span class="hlt">flux</span> density. As expected for the nearly optically thin situation, the C IV wavelength 1548 line is twice as bright as the C IV 1551 line. The average C IV wavelength 1548 <span class="hlt">flux</span> density for a quiet region is 2700 ergs/cm/s and, with surprisingly little scatter, 18,000 erg/cm/s for plages. The intensity histograms of rasters obtained at disk center can be separated into characteristic plage and quiet sun contributions with variable relative filling factors. The relationship between the C IV and <span class="hlt">magnetic</span> <span class="hlt">flux</span> densities for spatially resolved data is inferred to be almost the same, with only an additional factor of order unity in the constant of proportionality.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016SPD....4710203N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016SPD....4710203N"><span>Circular-cylindrical <span class="hlt">flux</span>-rope analytical model for <span class="hlt">Magnetic</span> Clouds</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nieves-Chinchilla, Teresa; Linton, Mark; Hidalgo, Miguel A.; Vourlidas, Angelos; Savani, Neel P.; Szabo, Adam; Farrugia, Charlie; Yu, Wenyuan</p> <p>2016-05-01</p> <p>We present an analytical model to describe <span class="hlt">magnetic</span> <span class="hlt">flux</span>-rope topologies. When these structures are observed embedded in Interplanetary Coronal Mass Ejections (ICMEs) with a depressed proton temperature, they are called <span class="hlt">Magnetic</span> Clouds ( MCs). The model extends the circular-cylindrical concept of Hidalgo et al. (2000) by introducing a general form for the radial dependence of the current density. This generalization provides information on the force <span class="hlt">distribution</span> inside the <span class="hlt">flux</span> rope in addition to the usual parameters of MC geometrical information and orientation.The generalized model provides flexibility for implementation in 3D MHD simulations. Here, we evaluate its performance in the reconstruction of MCs in in-situ observations. Four Earth directed ICME events, observed by the Wind spacecraft, are used to validate the technique. The events are selected from the ICME Wind list with the <span class="hlt">magnetic</span> obstacle boundaries chosen consistently with the <span class="hlt">magnetic</span> fi eld and plasma in situ observations and with a new parameter (EPP, Electron Pitch angle <span class="hlt">distribution</span> Parameter) which quantifies the bidirectionally of theplasma electrons. The goodness of the fit is evaluated with a single correlation parameter to enable comparative analysis of the events. In general, at first glance, the model fits the selected events very well. However, a detailed analysis of events with signatures of significant compression indicates the need to explore geometries other than the circular-cylindrical.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JGRA..12010175F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JGRA..12010175F"><span>Counterstreaming electrons in small interplanetary <span class="hlt">magnetic</span> <span class="hlt">flux</span> ropes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Feng, H. Q.; Zhao, G. Q.; Wang, J. M.</p> <p>2015-12-01</p> <p>Small interplanetary <span class="hlt">magnetic</span> <span class="hlt">flux</span> ropes (SIMFRs) are commonly observed by spacecraft at 1 AU, and their origin still remains disputed. We investigated the counterstreaming suprathermal electron (CSE) signatures of 106 SIMFRs measured by Wind during 1995-2005. We found that 79 (75%) of the 106 <span class="hlt">flux</span> ropes contain CSEs, and the percentages of counterstreaming vary from 8% to 98%, with a mean value of 51%. CSEs are often observed in <span class="hlt">magnetic</span> clouds (MCs), and this indicates these MCs are still attached to the Sun at both ends. CSEs are also related to heliospheric current sheets (HCSs) and the Earth's bow shock. We divided the SIMFRs into two categories: The first category is far from HCSs, and the second category is in the vicinity of HCSs. The first category has 57 SIMFRs, and only 7 of 57 ropes have no CSEs. This ratio is similar to that of MCs. The second category has 49 SIMFRs; however, 20 of the 49 events have no CSEs. This ratio is larger than that of MCs. These two categories have different origins. One category originates from the solar corona, and most ropes are still connected to the Sun at both ends. The other category is formed near HCSs in the interplanetary space.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017SPD....4810404G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017SPD....4810404G"><span>Chromospheric heating due to internetwork <span class="hlt">magnetic</span> <span class="hlt">flux</span> cancellations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gosic, Milan; de la Cruz Rodriguez, Jaime; De Pontieu, Bart; Bellot Rubio, Luis; Ortiz, Ada; Esteban Pozuelo, Sara</p> <p>2017-08-01</p> <p>The heating of the solar chromosphere is one of the most intriguing unanswered problems in solar physics. It is believed that this phenomenon may significantly be supported by small-scale internetwork (IN) <span class="hlt">magnetic</span> fields. Indeed, cancellations of IN <span class="hlt">magnetic</span> <span class="hlt">flux</span> patches might be an efficient way to transport <span class="hlt">flux</span> and energy from the photosphere to the chromosphere. Because of this, it is essential to determine where they occur, the rates at which they proceed, and understand their influence on the chromosphere. Here we study the spatial and temporal evolution of IN cancelling patches using high resolution, multiwavelength, coordinated observations obtained with the Interface Region Imaging Spectrograph (IRIS) and the Swedish 1-m Solar Telescope (SST). Employing multi-line inversions of the Mg II h&k lines we show that cancelling events, while occurring ubiquitously over IN regions, produce clear signatures of heating in the upper atmospheric layers. Using the RADYN code we determine the energy released due to cancellations of IN elements and discuss about their impact on the dynamics and energetics of the solar chromosphere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JTePh..62..553R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JTePh..62..553R"><span>Resistive states of the composite superconductors at <span class="hlt">magnetic</span> <span class="hlt">flux</span> creep</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Romanovskii, V. R.</p> <p>2017-04-01</p> <p>The effect of <span class="hlt">magnetic</span> <span class="hlt">flux</span> creep on the formation of resistive states of the composite superconductors has been studied taking into account their self-heating. The obtained results have been compared with the calculations carried out using the existing thermal stabilization theory, which is based on the model of a stepwise transition from the superconducting to normal state. It has been shown that, over a wide range of the superconductor temperature, this model leads to overrated effective electric resistances of the composite. As a result of its stable self-heating, the notions on the critical current, which determine the maximum transport current and on the resistive transition temperature, the higher of which in the transport current begins dividing between the superconductor and matrix, a loss a physical sense at <span class="hlt">magnetic</span> <span class="hlt">flux</span> creep, are used in the existing thermal stabilization theory. As a result, the limits of the theory of thermal stabilization of the composite superconductors can be extended if the theory has been used to describe stable sates at currents, which are higher than the conditionally defined critical current of the composite.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1992PhRvB..4612154F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1992PhRvB..4612154F"><span>Localized electrons on a lattice with incommensurate <span class="hlt">magnetic</span> <span class="hlt">flux</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fishman, Shmuel; Shapir, Yonathan; Wang, Xiang-Rong</p> <p>1992-11-01</p> <p>The <span class="hlt">magnetic</span>-field effects on lattice wave functions of Hofstadter electrons strongly localized at boundaries are studied analytically and numerically. The exponential decay of the wave function is modulated by a field-dependent amplitude J(t)=tprodt-1r=02 cos(παr), where α is the <span class="hlt">magnetic</span> <span class="hlt">flux</span> per plaquette (in units of a <span class="hlt">flux</span> quantum) and t is the distance from the boundary (in units of the lattice spacing). The behavior of ||J(t)|| is found to depend sensitively on the value of α. While for rational values α=p/q the envelope of J(t) increases as 2t/q, the behavior for α irrational (q-->∞) is erratic with an aperiodic structure which drastically changes with α. For algebraic α it is found that J(t) increases as a power law tβ(α) while it grows faster (presumably as tβ(α)lnt) for transcendental α. This is very different from the growth rate J(t)~e√t that is typical for cosines with random phases. The theoretical analysis is extended to products of the type Jν(t)=tprodt-1r=02 cos(παrν) with ν>0. Different behavior of Jν(t) is found in various regimes of ν. It changes from periodic for small ν to randomlike for large ν.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMSH51F2649S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMSH51F2649S"><span>Gravitational Steady States of Coronal Loops as <span class="hlt">Magnetic</span> <span class="hlt">Flux</span> Ropes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sugiyama, L.; Asgari-Targhi, M.</p> <p>2016-12-01</p> <p>Many coronal loops observed on the surface of the sun appear to bemagnetic <span class="hlt">flux</span> ropes containing plasma, with ends tied in the photosphere. Different types of loops contribute to important solar processes, but relatively little is known about their configuration.Like all toroidal confined, curved plasmas carrying current,they are intrinsically unstable to expansion in major radius.Consistent 3D MHD steady states are derived for the coronal partof the loop, including non-negligible effects due to the plasma pressure and solar gravity. Most loops have relativelyslender inverse aspect ratios ɛ =a/R≤ 1.For predominantly simple, non-helical loops, three gravitationally stabilized asymptotic solutions can be foundthat can be related to toroidal <span class="hlt">magnetically</span> confined plasams.Comparison to observations shows thattwo solutions bracket the observed heights R<108m of the common thin coronal loops (ɛ ˜ 0.02) in solar active regions.The third solution better describes the fatter loops (ɛ ˜ 0.1)that sometimes appear along the <span class="hlt">magnetic</span> neutral line in an active regionand grow to produce solar flares or coronal mass ejections.Since radial expansion is higher order than the basic <span class="hlt">flux</span> ropeconfinement, the states also approximately describe radially unstable loops over similar heights.The solutions can also be generalized to other stabilizing mechanismsand may provide a useful basis for studies of loop dynamics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21567635','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21567635"><span>INTERPLANETARY <span class="hlt">MAGNETIC</span> <span class="hlt">FLUX</span> DEPLETION DURING PROTRACTED SOLAR MINIMA</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Connick, David E.; Smith, Charles W.; Schwadron, Nathan A. E-mail: Charles.Smith@unh.edu</p> <p>2011-01-20</p> <p>We examine near-Earth solar wind observations as assembled within the Omni data set over the past 15 years that constitute the latest solar cycle. We show that the interplanetary <span class="hlt">magnetic</span> field continues to be depleted at low latitudes throughout the protracted solar minimum reaching levels below previously predicted minima. We obtain a rate of <span class="hlt">flux</span> removal resulting in <span class="hlt">magnetic</span> field reduction by 0.5 nT yr{sup -1} at 1 AU when averaged over the years 2005-2009 that reduces to 0.3 nT yr{sup -1} for 2007-2009. We show that the <span class="hlt">flux</span> removal operates on field lines that follow the nominal Parker spiral orientation predicted for open field lines and are largely unassociated with recent ejecta. We argue that the field line reduction can only be accomplished by ongoing reconnection of nominally open field lines or very old closed field lines and we contend that these two interpretations are observationally equivalent and indistinguishable.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMSH13B4099H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMSH13B4099H"><span>Forecasting the Solar Photosphere's <span class="hlt">Magnetic</span> <span class="hlt">Flux</span> with Local Data Assimilation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hickmann, K. S.; Godinez, H. C.; Henney, C. J.; Arge, C. N.</p> <p>2014-12-01</p> <p>Accurate forecasts of the photospheric <span class="hlt">magnetic</span> <span class="hlt">flux</span> are important since the photosphere provides the driving bound-ary conditions for the Corona and Solar wind which impact near Earth space weather. These space weather phenomenaeffect satellite trajectories and communication systems as well as safety on manned space missions. In this presen-tation we detail our recent improvements to the data assimilation mechanisms in the Air Force Data AssimilativePhotospheric <span class="hlt">flux</span> Transport (ADAPT) model. These include implementation of the local ensemble transform Kalmanfilter (LETKF) for the assimilation of satellite observations. In the past non-local ensemble methods have been usedto assimilate data into photosphere models. Due to the small ensemble sizes allowed for Solar forecasts spuriouscorrelations were introduced in the sample covariance, causing model divergence from observations. With our imple-mentation of the LETKF in ADAPT this ensemble divergence has been reduced. In addition multi-scale techniqueshave been implemented in ADAPT to deal with the lack of active region creation in the photosphere model. Lackof large scale active region creation in the ADAPT model caused ensemble bias when assimilating observations ofnewly created regions using ensemble Kalman methods. Separating the scales at which active regions occur allowsobservational noise for such regions to be controlled independently. We show that our consideration of the multi-scalenature of photosphere <span class="hlt">flux</span> transport has allowed more accurate assimilation of large active regions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFMIN41C..07M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFMIN41C..07M"><span>Development of Large-Scale Data Visualization System for <span class="hlt">Magnetic</span> <span class="hlt">Flux</span> Tracing in Global MHD Simulations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Murata, K. T.; Watari, S.; Kubota, Y.; Fukazawa, K.; Tsubouchi, K.; Fujita, S.; Tanaka, T.; Den, M.; Murayama, Y.</p> <p>2011-12-01</p> <p>At NICT (National Institute of Information and Communications Technology) we have been developing a new research environment named "OneSpaceNet". The OneSpaceNet is a cloud-computing environment to provide the researchers rich resources for research studies, such as super-computers, large-scale disk area, licensed applications, database and communication devices. The large-scale disk area is rovided via Gfarm, which is one of the <span class="hlt">distributed</span> file systems. This paper first proposes a <span class="hlt">distributed</span> data-type and/or data-intensive processing system that are provided via Gfarm as a solution to large-scale data processing in the context of <span class="hlt">distributed</span> data management and data processing environments in the field of solar-terrestrial physics. The usefulness of a system composed of many file system nodes was examined using large-scale computer simulation data. In the parallel 3D visualization of computer simulation data varying in terms of data processing granularity, optimized load balancing through FIFO scheduling or pipe-line scheduling yielded parallelization efficacy. Using the large-scale data processing system, we have developed a <span class="hlt">magnetic</span> <span class="hlt">flux</span> tracing system of global MHD simulations. Under the assumption of <span class="hlt">magnetic</span> field frozen-in theory of ideal MHD plasma, we trace an element (or elements) of plasma at all steps of global MHD simulation, and visualize <span class="hlt">magnetic</span> <span class="hlt">flux</span> (<span class="hlt">magnetic</span> field lines) penetrating the element(s). Since this system depends on the frozen-in theory, we need to examine when and where this assumption breaks before we apply it for physical data analyses. Figure (a) and Figure (b) show <span class="hlt">magnetic</span> field lines in the vicinity of the Earth's magnetopause visualized via present system. Both figures show that the <span class="hlt">magnetic</span> field lines are scattered as they advance downward. In the present talk we discuss the error in the tracings and the restrictions to apply for this technique.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFMSH11B1642T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFMSH11B1642T"><span>A laboratory study of arched <span class="hlt">magnetic</span> <span class="hlt">flux</span> rope eruptions*</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tripathi, S.; Gekelman, W. N.</p> <p>2010-12-01</p> <p>Arched <span class="hlt">magnetic</span> <span class="hlt">flux</span> ropes (AMFRs) are arch-shaped twisted <span class="hlt">magnetic</span>-structures that confine plasma and carry electrical current. Coronal loops and solar prominences are the main examples of AMFRs in the solar atmosphere. Solar AMFRs appear stable for long duration (several Alfven transit times) and then suddenly erupt due to occurrence of instabilities (e.g., kink instability). Solar AMFR eruptions have been frequently observed to evolve into more energetic events such as solar flares and coronal mass ejections. A laboratory plasma experiment has been constructed to simulate such eruptions in an ambient <span class="hlt">magnetized</span> plasma. The laboratory AMFR (n ~ 1019 m-3 , Te ~ 10 eV, B ~ 1 kG, L ~ 0.5 m) is produced using an annular LaB6 cathode and an annular anode mounted on two movable shafts in a vacuum chamber (1.0 m diameter, 4.5 m long). Each AMFR electrode has an electromagnet to produce a vacuum <span class="hlt">magnetic</span> field along the curved axis of the AMFR. The vacuum chamber has an additional plasma source and electromagnets to produce the ambient <span class="hlt">magnetized</span> plasma (n ~ 1018 m-3, Te ~ 4 eV, B ~ 25 G). Two laser beams (1064 nm, ~0.5 J/pulse) strike movable carbon targets placed behind the orifices of the electrodes to generate controlled plasma flows from the AMFR footpoints that drives the eruption. The experiment operates with a 0.5 Hz repetition rate and is highly reproducible. Thus, time evolution of the AMFR is recorded in three-dimensions with high spatio-temporal resolutions using movable diagnostic probes. Initial results on the dramatic eruption of an arched <span class="hlt">magnetic</span> <span class="hlt">flux</span> rope will be presented that demonstrate outward expansion of the AMFR, release of the AMFR plasma to the background, and excitation of magnetosonic waves in the ambient plasma. Reference: S. K. P. Tripathi and W. Gekelman, Phys. Rev. Lett. 105, 075005 *Work supported by US DOE and NSF Fast camera image of a laboratory AMFR. Laser generated flows can be seen emanating from the both footpoints of the AMFR.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PhRvB..95a4430H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PhRvB..95a4430H"><span>Observation of asymmetric <span class="hlt">distributions</span> of <span class="hlt">magnetic</span> singularities across <span class="hlt">magnetic</span> multilayers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hierro-Rodriguez, A.; Quirós, C.; Sorrentino, A.; Blanco-Roldán, C.; Alvarez-Prado, L. M.; Martín, J. I.; Alameda, J. M.; Pereiro, E.; Vélez, M.; Ferrer, S.</p> <p>2017-01-01</p> <p>Whereas a great deal of work is being devoted to <span class="hlt">magnetic</span> singularities in two-dimensional (2D) systems (surfaces, interfaces, films) due to their possible applications, much less is known about their properties along the perpendicular direction. Here, we report on a pronounced asymmetry of the in-depth <span class="hlt">distribution</span> of meronlike <span class="hlt">magnetic</span> textures, which are <span class="hlt">magnetic</span> singularities similar to ½ skyrmions, in <span class="hlt">magnetic</span> layers. Meron textures are observed to be <span class="hlt">distributed</span> in two groups defined by their topology. One of them resides almost exclusively at the top surface of the film and the other at the bottom one. This observation has been brought to light with element-specific <span class="hlt">magnetic</span> transmission soft x-ray microscopy. Micromagnetic simulations reveal that closure domains are at the origin of this asymmetry. The result might be of general interest for controlling <span class="hlt">magnetic</span> three-dimensional (3D) architectures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21451309','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21451309"><span><span class="hlt">Distribution</span> of thermal neutron <span class="hlt">flux</span> around a PET cyclotron.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ogata, Yoshimune; Ishigure, Nobuhito; Mochizuki, Shingo; Ito, Kengo; Hatano, Kentaro; Abe, Junichiro; Miyahara, Hiroshi; Masumoto, Kazuyoshi; Nakamura, Hajime</p> <p>2011-05-01</p> <p>The number of positron emission tomography (PET) examinations has greatly increased world-wide. Since positron emission nuclides for the PET examinations have short half-lives, they are mainly produced using on-site cyclotrons. During the production of the nuclides, significant quantities of neutrons are generated from the cyclotrons. Neutrons have potential to activate the materials around the cyclotrons and cause exposure to the staff. To investigate quantities and <span class="hlt">distribution</span> of the thermal neutrons, thermal neutron <span class="hlt">fluxes</span> were measured around a PET cyclotron in a laboratory associating with a hospital. The cyclotron accelerates protons up to 18 MeV, and the mean particle current is 20 μA. The neutron <span class="hlt">fluxes</span> were measured during both 18F production and C production. Gold foils and thermoluminescent dosimeter (TLD) badges were used to measure the neutron <span class="hlt">fluxes</span>. The neutron <span class="hlt">fluxes</span> in the target box averaged 9.3 × 10(6) cm(-2) s(-1) and 1.7 × 10(6) cm(-2) s(-1) during 18F and 11C production, respectively. Those in the cyclotron room averaged 4.1 × 10(5) cm(-2) s(-1) and 1.2 × 10(5) cm(-2) s(-1), respectively. Those outside the concrete wall shielding were estimated as being equal to or less than ∼3 cm s, which corresponded to 0.1 μSv h(-1) in effective dose. The neutron <span class="hlt">fluxes</span> outside the concrete shielding were confirmed to be quite low compared to the legal limit.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ApJ...843...93C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ApJ...843...93C"><span><span class="hlt">Magnetic</span> <span class="hlt">Flux</span> Rope Shredding By a Hyperbolic <span class="hlt">Flux</span> Tube: The Detrimental Effects of <span class="hlt">Magnetic</span> Topology on Solar Eruptions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chintzoglou, Georgios; Vourlidas, Angelos; Savcheva, Antonia; Tassev, Svetlin; Tun Beltran, Samuel; Stenborg, Guillermo</p> <p>2017-07-01</p> <p>We present the analysis of an unusual failed eruption captured in high cadence and in many wavelengths during the observing campaign in support of the Very high Angular resolution Ultraviolet Telescope (VAULT2.0) sounding rocket launch. The refurbished VAULT2.0 is a Lyα (λ 1216 Å) spectroheliograph launched on 2014 September 30. The campaign targeted active region NOAA AR 12172 and was closely coordinated with the Hinode and IRIS missions and several ground-based observatories (NSO/IBIS, SOLIS, and BBSO). A filament eruption accompanied by a low-level flaring event (at the GOES C-class level) occurred around the VAULT2.0 launch. No coronal mass ejection was observed. The eruption and its source region, however, were recorded by the campaign instruments in many atmospheric heights ranging from the photosphere to the corona in high cadence and spatial resolution. This is a rare occasion that enabled us to perform a comprehensive investigation on a failed eruption. We find that a rising <span class="hlt">Magnetic</span> <span class="hlt">Flux</span> Rope (MFR)-like structure was destroyed during its interaction with the ambient <span class="hlt">magnetic</span> field, creating downflows of cool plasma and diffuse hot coronal structures reminiscent of “cusps.” We employ magnetofrictional simulations to show that the <span class="hlt">magnetic</span> topology of the ambient field is responsible for the destruction of the MFR. Our unique observations suggest that the <span class="hlt">magnetic</span> topology of the corona is a key ingredient for a successful eruption.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008NucFu..48j5004S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008NucFu..48j5004S"><span>Beryllium <span class="hlt">flux</span> <span class="hlt">distribution</span> and layer deposition in the ITER divertor</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schmid, K.</p> <p>2008-10-01</p> <p>The deposition of Be eroded from the main chamber wall on the W surfaces in the ITER divertor could result in the formation of Be rich Be/W mixed layers with a low melting temperature compared with pure W. To predict whether or not these layers form the Be <span class="hlt">flux</span> <span class="hlt">distribution</span> in the ITER divertor is required. This paper presents the results of a combination of plasma transport with erosion/deposition simulations that allow one to calculate both the Be <span class="hlt">flux</span> <span class="hlt">distribution</span> and the Be layer deposition in the ITER divertor. This model includes the Be source due to Be erosion in the main chamber and the deposition, re-erosion and re-deposition of Be in the ITER divertor. The calculations show that the fraction of Be in the incident particle <span class="hlt">flux</span> in the divertor ranges from ≈10-3 to ≈5% with a pronounced inner-outer divertor asymmetry. The <span class="hlt">flux</span> fractions in the inner divertor are on average ten times higher than in the outer divertor. Thick Be layers only form at the inner strike point and the dome baffles. The highest Be layer growth rate is found to be 1.0 nm s-1. Despite the Be deposition the formation of Be rich Be/W mixed layers is not to be expected in ITER. The expected surface temperature at these locations during steady-state operation is too low as to result in Be diffusion into W and thus Be/W mixed layers cannot form. The paper also discusses the influence of off normal events such as ELMs or VDEs on the formation of Be/W mixed layers.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006JAP....99hP101W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006JAP....99hP101W"><span>Enhanced <span class="hlt">magnetic</span> particle transport by integration of a <span class="hlt">magnetic</span> <span class="hlt">flux</span> guide: Experimental verification of simulated behavior</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wirix-Speetjens, Roel; Fyen, Wim; Boeck, Jo De; Borghs, Gustaaf</p> <p>2006-04-01</p> <p>In the past, <span class="hlt">magnetic</span> biosensors have shown to be promising alternatives for classical fluorescence-based microarrays, replacing the fluorescent label by a superparamagnetic particle. While on-chip detection of <span class="hlt">magnetic</span> particles is firmly established, research groups continue to explore the unique ability of manipulating these particles by applying controlled <span class="hlt">magnetic</span> forces. One of the challenging tasks in designing <span class="hlt">magnetic</span> force generating structures remains the generation of large forces for a minimal current consumption. Previously, a simple transporting device for single <span class="hlt">magnetic</span> particles has been demonstrated using a <span class="hlt">magnetic</span> field that is generated by two tapered current carrying conductors [R. Wirix-Speetjens, W. Fyen, K. Xu, J. De Boeck, and G. Borghs, IEEE Trans. Magn. 41(10), 4128 (2005)]. We also developed a model to accurately predict the motion of a <span class="hlt">magnetic</span> particle moving in the vicinity of a solid wall. Using this model, we now present a technique that enhances the <span class="hlt">magnetic</span> force up to a factor of 3 using a <span class="hlt">magnetic</span> <span class="hlt">flux</span> guide. The larger <span class="hlt">magnetic</span> force results in an average speed of the particle which increases with a factor of 3. These simulations show good agreement with experimental results.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017SPIE10219E..0PK','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017SPIE10219E..0PK"><span>Real-time visualization of <span class="hlt">magnetic</span> <span class="hlt">flux</span> densities for transcranial <span class="hlt">magnetic</span> stimulation on commodity and fully immersive VR systems</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kalivarapu, Vijay K.; Serrate, Ciro; Hadimani, Ravi L.</p> <p>2017-05-01</p> <p>Transcranial <span class="hlt">Magnetic</span> Stimulation (TMS) is a non-invasive procedure that uses time varying short pulses of <span class="hlt">magnetic</span> fields to stimulate nerve cells in the brain. In this method, a <span class="hlt">magnetic</span> field generator ("TMS coil") produces small electric fields in the region of the brain via electromagnetic induction. This technique can be used to excite or inhibit firing of neurons, which can then be used for treatment of various neurological disorders such as Parkinson's disease, stroke, migraine, and depression. It is however challenging to focus the induced electric field from TMS coils to smaller regions of the brain. Since electric and <span class="hlt">magnetic</span> fields are governed by laws of electromagnetism, it is possible to numerically simulate and visualize these fields to accurately determine the site of maximum stimulation and also to develop TMS coils that can focus the fields on the targeted regions. However, current software to compute and visualize these fields are not real-time and can work for only one position/orientation of TMS coil, severely limiting their usage. This paper describes the development of an application that computes <span class="hlt">magnetic</span> <span class="hlt">flux</span> densities (h-fields) and visualizes their <span class="hlt">distribution</span> for different TMS coil position/orientations in real-time using GPU shaders. The application is developed for desktop, commodity VR (HTC Vive), and fully immersive VR CAVETM systems, for use by researchers, scientists, and medical professionals to quickly and effectively view the <span class="hlt">distribution</span> of h-fields from MRI brain scans.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JMMM..431...27Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JMMM..431...27Y"><span>Particles size <span class="hlt">distribution</span> in diluted <span class="hlt">magnetic</span> fluids</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yerin, Constantine V.</p> <p>2017-06-01</p> <p>Changes in particles and aggregates size <span class="hlt">distribution</span> in diluted kerosene based <span class="hlt">magnetic</span> fluids is studied by dynamic light scattering method. It has been found that immediately after dilution in <span class="hlt">magnetic</span> fluids the system of aggregates with sizes ranging from 100 to 250-1000 nm is formed. In 50-100 h after dilution large aggregates are peptized and in the sample stationary particles and aggregates size <span class="hlt">distribution</span> is fixed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19940011918','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19940011918"><span>Resolving LDEF's <span class="hlt">flux</span> <span class="hlt">distribution</span>: Orbital (debris?) and natural meteoroid populations</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mcdonnell, J. A. M.</p> <p>1993-01-01</p> <p>A consistent methodology for the collation of data from both penetration and perforation experiments and from data in the Meteoroid and Debris Special Investigator Group (M-D SIG) data-base has led to the derivation of the average impact <span class="hlt">flux</span> over LDEF's exposure history 1984-1990. Data are first presented for LDEF's N,S,E,W and Space faces ('offset' by 8 deg and 'tilted' by 1 deg respectively). A model fit is derived for ballistic limits of penetration from 1 micron to 1mm of aluminium target, corresponding to impactor masses from 10(exp -18) kg (for rho sub p = 2g/cu cm) to 10(exp -10) kg (for rho sub p = 1g/cu cm). A second order harmonic function is fitted to the N,S,E, and W <span class="hlt">fluxes</span> to establish the angular <span class="hlt">distribution</span> at regular size intervals; this fit is then used to provide 'corrected' data corresponding to <span class="hlt">fluxes</span> applicable to true N,S,E,W and Space directions for a LEO 28.5 degree inclination orbit at a mean altitude of 465 km.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_17 --> <div id="page_18" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="341"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/6363058','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/6363058"><span>Results of railgun experiments powered by <span class="hlt">magnetic</span> <span class="hlt">flux</span> compression generators</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Hawke, R.S.; Brooks, A.L.; Deadrick, J.; Scudder, J.K.; Fowler, C.M.; Caird, R.S.; Peterson, D.R.</p> <p>1981-03-16</p> <p>Researchers from the Lawrence Livermore National Laboratory and the Los Alamos National Laboratory initiated a joint railgun research and development program to explore the potential of electromagnetic railguns to accelerate projectiles to hypervelocities. The effort was intended to (1) determine experimentally the limits of railgun operation; (2) verify calculations of railgun performance; and (3) establish a data base at megampere currents. The program has led to the selection of a particular <span class="hlt">magnetic</span> <span class="hlt">flux</span> compression generator (MFCG) design for a set of initial experiments and the design of small- and large-square-bore railguns to match the expected MFCG power profile. The bore sizes are 12.7 and 50 mm, respectively. In this paper, the design of the railguns and the diagnostic and data reduction techniques, followed by the results of eight experiments with the two railgun types, are presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/6811182','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/6811182"><span>Results of railgun experiments powered by <span class="hlt">magnetic</span> <span class="hlt">flux</span> compression generators</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Hawke, R.S.; Brooks, A.L.; Deadrick, F.J.; Scudder, J.K.; Fowler, C.M.; Caird, R.S.; Peterson, D.R.</p> <p>1980-10-24</p> <p>Researchers from LLNL and LANSL initiated a joint railgun research and development program to explore the potential of electromagnetic railguns to accelerate projectiles to hypervelocities. The effort was intended to determine experimentally the limits of railgun operation, to verify calculations of railgun performance, and to establish a data base at megampere currents. The program has led to the selection of a particular <span class="hlt">magnetic</span> <span class="hlt">flux</span> compression generator (MFCG) design for a set of initial experiments and to the design of small- and large-square bore railguns to match the expected MFCG power profile. The bore sizes are 12.7 and 50 mm, respectively. The design of the railguns and the diagnostic and data reduction techniques, followed by the results of eight experiments with the two railgun types are presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5518764','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5518764"><span>Coronal and heliospheric <span class="hlt">magnetic</span> <span class="hlt">flux</span> circulation and its relation to open solar <span class="hlt">flux</span> evolution</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Owens, Mathew J.; Imber, Suzanne M.; James, Matthew K.; Bunce, Emma J.; Yeoman, Timothy K.</p> <p>2017-01-01</p> <p>Abstract Solar cycle 24 is notable for three features that can be found in previous cycles but which have been unusually prominent: (1) sunspot activity was considerably greater in the northern/southern hemisphere during the rising/declining phase; (2) accumulation of open solar <span class="hlt">flux</span> (OSF) during the rising phase was modest, but rapid in the early declining phase; (3) the heliospheric current sheet (HCS) tilt showed large fluctuations. We show that these features had a major influence on the progression of the cycle. All <span class="hlt">flux</span> emergence causes a rise then a fall in OSF, but only OSF with foot points in opposing hemispheres progresses the solar cycle via the evolution of the polar fields. Emergence in one hemisphere, or symmetric emergence without some form of foot point exchange across the heliographic equator, causes poleward migrating fields of both polarities in one or both (respectively) hemispheres which temporarily enhance OSF but do not advance the polar field cycle. The heliospheric field observed near Mercury and Earth reflects the asymmetries in emergence. Using magnetograms, we find evidence that the poleward <span class="hlt">magnetic</span> <span class="hlt">flux</span> transport (of both polarities) is modulated by the HCS tilt, revealing an effect on OSF loss rate. The declining phase rise in OSF was caused by strong emergence in the southern hemisphere with an anomalously low HCS tilt. This implies the recent fall in the southern polar field will be sustained and that the peak OSF has limited implications for the polar field at the next sunspot minimum and hence for the amplitude of cycle 25. PMID:28781930</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017A%26A...604A...8V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017A%26A...604A...8V"><span>Reconstructing solar <span class="hlt">magnetic</span> fields from historical observations. II. Testing the surface <span class="hlt">flux</span> transport model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Virtanen, I. O. I.; Virtanen, I. I.; Pevtsov, A. A.; Yeates, A.; Mursula, K.</p> <p>2017-07-01</p> <p>Aims: We aim to use the surface <span class="hlt">flux</span> transport model to simulate the long-term evolution of the photospheric <span class="hlt">magnetic</span> field from historical observations. In this work we study the accuracy of the model and its sensitivity to uncertainties in its main parameters and the input data. Methods: We tested the model by running simulations with different values of meridional circulation and supergranular diffusion parameters, and studied how the <span class="hlt">flux</span> <span class="hlt">distribution</span> inside active regions and the initial <span class="hlt">magnetic</span> field affected the simulation. We compared the results to assess how sensitive the simulation is to uncertainties in meridional circulation speed, supergranular diffusion, and input data. We also compared the simulated <span class="hlt">magnetic</span> field with observations. Results: We find that there is generally good agreement between simulations and observations. Although the model is not capable of replicating fine details of the <span class="hlt">magnetic</span> field, the long-term evolution of the polar field is very similar in simulations and observations. Simulations typically yield a smoother evolution of polar fields than observations, which often include artificial variations due to observational limitations. We also find that the simulated field is fairly insensitive to uncertainties in model parameters or the input data. Due to the decay term included in the model the effects of the uncertainties are somewhat minor or temporary, lasting typically one solar cycle.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1917124V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1917124V"><span>Reconstructing solar <span class="hlt">magnetic</span> fields from historical observations: Testing the surface <span class="hlt">flux</span> transport model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Virtanen, Iiro; Virtanen, Ilpo; Pevtsov, Alexei; Yeates, Anthony; Mursula, Kalevi</p> <p>2017-04-01</p> <p>We aim to use the surface <span class="hlt">flux</span> transport model to simulate the long-term evolution of the photospheric <span class="hlt">magnetic</span> field from historical observations. In this work we study the accuracy of the model and its sensitivity to uncertainties in its main parameters and the input data. We test the model by running simulations with different values of meridional circulation and supergranular diffusion parameters, and study how the <span class="hlt">flux</span> <span class="hlt">distribution</span> inside active regions and the initial <span class="hlt">magnetic</span> field affect the simulation. We compare the results to assess how sensitive the simulation is to uncertainties in meridional circulation speed, supergranular diffusion and input data. We also compare the simulated <span class="hlt">magnetic</span> field with observations. We find that there is generally good agreement between simulations and observations. While the model is not capable of replicating fine details of the <span class="hlt">magnetic</span> field, the long-term evolution of the polar field is very similar in simulations and observations. Simulations typically yield a smoother evolution of polar fields than observations, that often include artificial variations due to observational limitations. We also find that the simulated field is fairly insensitive to uncertainties in model parameters or the input data. Due to the decay term included in the model the effects of the uncertainties are rather minor or temporary, lasting typically one solar cycle.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22611602','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22611602"><span>Enhanced <span class="hlt">magnetic</span> <span class="hlt">flux</span> density mapping using coherent steady state equilibrium signal in MREIT</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Jeong, Woo Chul; Sajib, Saurav Z. K.; Kim, Hyung Joong; Woo, Eung Je; Lee, Mun Bae; Kwon, Oh In</p> <p>2016-03-15</p> <p>Measuring the z-component of <span class="hlt">magnetic</span> <span class="hlt">flux</span> density B = (B{sub x}, B{sub y}, B{sub z}) induced by transversally injected current, <span class="hlt">magnetic</span> resonance electrical impedance tomography (MREIT) aims to visualize electrical property (current density and/or conductivity <span class="hlt">distribution</span>) in a three-dimensional imaging object. For practical implementations of MREIT technique, it is critical to reduce injection of current pulse within safety requirements. With the goal of minimizing the noise level in measured B{sub z} data, we propose a new method to enhance the measure B{sub z} data using steady-state coherent gradient multi-echo (SSC-GME) MR pulse sequence combining with injection current nonlinear encoding (ICNE) method in MREIT, where the ICNE technique injects current during a readout gradient to maximize the signal intensity of phase signal including B{sub z}. The total phase offset in SSC-GME includes additional <span class="hlt">magnetic</span> <span class="hlt">flux</span> density due to the injected current, which is different from the phase signal for the conventional spoiled MR pulse sequence. We decompose the <span class="hlt">magnetization</span> precession phase from the total phase offset including B{sub z} and optimize B{sub z} data using the steady-state equilibrium signal. Results from a real phantom experiment including different kinds of anomalies demonstrated that the proposed method enhanced B{sub z} comparing to a conventional spoiled pulse sequence.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19800039288&hterms=Emergence&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DEmergence','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19800039288&hterms=Emergence&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DEmergence"><span>Evidence for globally coherent variability in solar <span class="hlt">magnetic</span> <span class="hlt">flux</span> emergence</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Golub, L.; Vaiana, G. S.</p> <p>1980-01-01</p> <p>We examine the large-scale spatial and temporal variations in the emergence of X-ray bright points on the sun, in order to study the global properties of <span class="hlt">magnetic</span> <span class="hlt">flux</span> emergence. Major variations in the rate of <span class="hlt">flux</span> emergence are observed at all solar latitudes, on a time scale of 3-5 months. The most economical explanation of the observations is that the full sun participated in a single large eruptive event during the available 8 month observing period from Skylab in 1973. The peak of this global event corresponds in time to the eruption of a major complex of activity. Moreover, it appears that the only portion of the solar surface which deviates from the above pattern of behavior is the low latitude region in the vicinity of the AR complex; this area shows a temporary depletion immediately following the AR outburst. The high-latitude regions in both hemispheres show the same variation and appear to lead the low-latitude emergence by approximately 1 month.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/20782501','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/20782501"><span>Riemannian geometry of twisted <span class="hlt">magnetic</span> <span class="hlt">flux</span> tubes in almost helical plasma flows</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Garcia de Andrade, L.C.</p> <p>2006-02-15</p> <p>Riemannian geometry of curves applied recently by Ricca [Fluid Dyn. Res 36, 319 (2005)] in the case of inflectional disequilibrium of twisted <span class="hlt">magnetic</span> <span class="hlt">flux</span> tubes is used here to compute the <span class="hlt">magnetic</span> helicity force-free field case. Here the application of Lorentz force-free to the <span class="hlt">magnetic</span> <span class="hlt">flux</span> tube in tokamaks allows one to obtain an equation that generalizes the cylindrical tokamak equation by a term that contains the curvature of the <span class="hlt">magnetic</span> <span class="hlt">flux</span> tube. Another example of the use of the <span class="hlt">magnetic</span> <span class="hlt">flux</span> tube is done by taking the electron magnetohydrodynamics (MHD) fluid model (EMHD) of plasma physics that allows one to compute the velocity of the fluid in helical and almost helical flows in terms of the Frenet torsion of thin <span class="hlt">magnetic</span> <span class="hlt">flux</span> tubes. The cases of straight and curved twisted tubes are examined. Second-order effects on the Frenet torsion arise on the poloidal component of the <span class="hlt">magnetic</span> field, while curvature effects appear in the toroidal component. The <span class="hlt">magnetic</span> fields are computed in terms of the penetration depth used in superconductors. The ratio between poloidal and toroidal components of the <span class="hlt">magnetic</span> field depends on the torsion and curvature of the <span class="hlt">magnetic</span> <span class="hlt">flux</span> tube. It is shown that the rotation of the almost helical plasma flow contributes to the twist of the <span class="hlt">magnetic</span> <span class="hlt">flux</span> tube through the total Frenet torsion along the tube.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21574685','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21574685"><span>ENERGY INJECTION VIA <span class="hlt">FLUX</span> EMERGENCE ON THE SUN DEPENDING ON THE GEOMETRIC SHAPE OF <span class="hlt">MAGNETIC</span> FIELD</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Magara, T.</p> <p>2011-04-20</p> <p><span class="hlt">Flux</span> emergence is a complicated process involving flow and <span class="hlt">magnetic</span> field, which provides a way of injecting <span class="hlt">magnetic</span> energy into the solar atmosphere. We show that energy injection via this complicated process is characterized by a physical quantity called the emergence velocity, which is determined by the spatial relationship between the flow velocity and <span class="hlt">magnetic</span> field vectors. By using this quantity, we demonstrate that the geometric shape of <span class="hlt">magnetic</span> field might play an important role in the energy injection via <span class="hlt">flux</span> emergence.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFMSM42A..01G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFMSM42A..01G"><span>Three-Dimensional <span class="hlt">Magnetic</span> Field Line Reconnection involving <span class="hlt">Magnetic</span> <span class="hlt">Flux</span> Ropes (Invited)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gekelman, W. N.; van Compernolle, B.; Lawrence, E.; Vincena, S. T.</p> <p>2010-12-01</p> <p>We report on two experiments in which three dimensional <span class="hlt">magnetic</span> field line reconnection plays a role. <span class="hlt">Magnetic</span> field line reconnection is a processes in which the <span class="hlt">magnetic</span> field energy is converted to particle energy and heating accompanied by changes in the <span class="hlt">magnetic</span> topology. In the first experiment two <span class="hlt">magnetic</span> <span class="hlt">flux</span> ropes are generated from initially adjacent pulsed current channels in a background magnetoplasma in the LAPD device at UCLA. The currents exert mutual jXB forces causing them to twist about each other and merge. The currents are not static but move towards or away from each other in time. In addition the currents are observed to filament after merging. Volumetric space-time data show multiple reconnection sites with time-dependent locations. The quasi-separatrix layer (QSL) is a narrow region between the <span class="hlt">flux</span> ropes. Two field lines on either side of the QSL will have closely spaced foot-points at on end of the <span class="hlt">flux</span> ropes, but a very different separation at the other end. Outside the QSL, neighboring field lines do not diverge. The QSL has been measured, for the first time in this experiment [1] and its three dimensional development will be shown in movies made from the data. A system involving the reconnection of three <span class="hlt">flux</span> ropes will also be presented. Three <span class="hlt">flux</span> ropes are generated by drawing currents through apertures in a carbon shield located in front of a 10 cm diameter cathode immersed in the background magnetoplasma. The currents are observed to twist about themselves, writhe about each other and thrash about due to kink the kink instability. Multiple reconnection regions (which are three dimensional) and a complex QSL are observed. The <span class="hlt">magnetic</span> helicity is evaluated from volumetric data in both cases and its rate of change is used to estimate the plasma resistivity. These measurements lead one to suspect that <span class="hlt">magnetic</span> field line reconnection is not an independent topic, which can be studied in isolation, but part of the phenomena associated</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013JPhCS.409a2193S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013JPhCS.409a2193S"><span>Long-term variations of muon <span class="hlt">flux</span> angular <span class="hlt">distribution</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shutenko, V. V.; Astapov, I. I.; Barbashina, N. S.; Dmitrieva, A. N.; Kokoulin, R. P.; Kompaniets, K. G.; Petrukhin, A. A.; Yashin, I. I.</p> <p>2013-02-01</p> <p>Intensity of the atmospheric muon <span class="hlt">flux</span> depends on a number of factors: energy spectrum of primary cosmic rays (PCR), heliospheric conditions, state of the magnetosphere and atmosphere of the Earth. The wide-aperture muon hodoscope URAGAN (Moscow, Russia, 55.7° N, 37.7° E, 173 m a.s.l.) makes it possible to investigate not only variations of the intensity of muon <span class="hlt">flux</span>, but also temporal changes of its angular <span class="hlt">distribution</span>. For the analysis of angular <span class="hlt">distribution</span> variations, the vector of local anisotropy is used. The vector of local anisotropy is the sum of individual vectors (directions of the reconstructed muon tracks) normalized to the total number of reconstructed tracks. The vector of local anisotropy and its projections show different sensitivities to parameters of the processes of modulation of PCR in the heliosphere and the Earth's magnetosphere, and the passage of secondary cosmic rays through the terrestrial atmosphere. In the work, results of the analysis of long-term variations of hourly average projections of the vector of local anisotropy obtained from the URAGAN data during experimental series of 2007-2011 are presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016RAA....16...15J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016RAA....16...15J"><span>Testing a solar coronal <span class="hlt">magnetic</span> field extrapolation code with the Titov-Démoulin <span class="hlt">magnetic</span> <span class="hlt">flux</span> rope model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jiang, Chao-Wei; Feng, Xue-Shang</p> <p>2016-01-01</p> <p>In the solar corona, the <span class="hlt">magnetic</span> <span class="hlt">flux</span> rope is believed to be a fundamental structure that accounts for <span class="hlt">magnetic</span> free energy storage and solar eruptions. Up to the present, the extrapolation of the <span class="hlt">magnetic</span> field from boundary data has been the primary way to obtain fully three-dimensional <span class="hlt">magnetic</span> information about the corona. As a result, the ability to reliably recover the coronal <span class="hlt">magnetic</span> <span class="hlt">flux</span> rope is important for coronal field extrapolation. In this paper, our coronal field extrapolation code is examined with an analytical <span class="hlt">magnetic</span> <span class="hlt">flux</span> rope model proposed by Titov & Démoulin, which consists of a bipolar <span class="hlt">magnetic</span> configuration holding a semi-circular line-tied <span class="hlt">flux</span> rope in force-free equilibrium. By only using the vector field at the bottom boundary as input, we test our code with the model in a representative range of parameter space and find that the model field can be reconstructed with high accuracy. In particular, the <span class="hlt">magnetic</span> topological interfaces formed between the <span class="hlt">flux</span> rope and the surrounding arcade, i.e., the “hyperbolic <span class="hlt">flux</span> tube” and “bald patch separatrix surface,” are also reliably reproduced. By this test, we demonstrate that our CESE-MHD-NLFFF code can be applied to recovering the <span class="hlt">magnetic</span> <span class="hlt">flux</span> rope in the solar corona as long as the vector magnetogram satisfies the force-free constraints.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002JAP....92.5532L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002JAP....92.5532L"><span>Analysis of an eddy-current brake considering finite radius and induced <span class="hlt">magnetic</span> <span class="hlt">flux</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lee, Kapjin; Park, Kyihwan</p> <p>2002-11-01</p> <p>Since the eddy-current problem usually depends on the geometry of the moving conductive sheet and the pole shape, there is no general method to find an analytical solution. The analysis of the eddy currents in a rotating disk with an electromagnet is performed in the case of time-invariant field with the consideration of the boundary conditions of the rotating disk and induced <span class="hlt">magnetic</span> <span class="hlt">flux</span>. First, the concept of Coulomb's law and the method of images are introduced with the consideration of the boundary conditions. Second, the induced <span class="hlt">magnetic</span> <span class="hlt">flux</span> density is calculated by using Ampere's law. Third, the net <span class="hlt">magnetic</span> <span class="hlt">flux</span> density is introduced by defining the <span class="hlt">magnetic</span> Reynolds number Rm as the ratio of the induced <span class="hlt">magnetic</span> <span class="hlt">flux</span> density to the applied <span class="hlt">magnetic</span> <span class="hlt">flux</span> density. Finally, the braking torque is calculated by applying the Lorentz force law and the computed results are compared with experimental ones.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22364515','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22364515"><span>RECONCILING MODELS OF LUMINOUS BLAZARS WITH <span class="hlt">MAGNETIC</span> <span class="hlt">FLUXES</span> DETERMINED BY RADIO CORE-SHIFT MEASUREMENTS</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Nalewajko, Krzysztof; Begelman, Mitchell C.; Sikora, Marek</p> <p>2014-11-20</p> <p>Estimates of <span class="hlt">magnetic</span> field strength in relativistic jets of active galactic nuclei, obtained by measuring the frequency-dependent radio core location, imply that the total <span class="hlt">magnetic</span> <span class="hlt">fluxes</span> in those jets are consistent with the predictions of the <span class="hlt">magnetically</span> arrested disk (MAD) scenario of jet formation. On the other hand, the <span class="hlt">magnetic</span> field strength determines the luminosity of the synchrotron radiation, which forms the low-energy bump of the observed blazar spectral energy <span class="hlt">distribution</span> (SED). The SEDs of the most powerful blazars are strongly dominated by the high-energy bump, which is most likely due to the external radiation Compton mechanism. This high Compton dominance may be difficult to reconcile with the MAD scenario, unless (1) the geometry of external radiation sources (broad-line region, hot-dust torus) is quasi-spherical rather than flat, or (2) most gamma-ray radiation is produced in jet regions of low <span class="hlt">magnetization</span>, e.g., in <span class="hlt">magnetic</span> reconnection layers or in fast jet spines.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMSM42A..03G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMSM42A..03G"><span><span class="hlt">Magnetic</span> reconnection in 3D magnetosphere models: <span class="hlt">magnetic</span> separators and open <span class="hlt">flux</span> production</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Glocer, A.; Dorelli, J.; Toth, G.; Komar, C. M.; Cassak, P.</p> <p>2014-12-01</p> <p>There are multiple competing definitions of <span class="hlt">magnetic</span> reconnection in 3D (e.g., Hesse and Schindler [1988], Lau and Finn [1990], and Boozer [2002]). In this work we focus on separator reconnection. A <span class="hlt">magnetic</span> separator can be understood as the 3D analogue of a 2D x line with a guide field, and is defined by the line corresponding to the intersection of the separatrix surfaces associated with the <span class="hlt">magnetic</span> nulls. A separator in the magnetosphere represents the intersection of four distinct <span class="hlt">magnetic</span> topologies: solar wind, closed, open connected to the northern hemisphere, and open connected to the southern hemisphere. The integral of the parallel electric field along the separator defines the rate of open <span class="hlt">flux</span> production, and is one measure of the reconnection rate. We present three methods for locating <span class="hlt">magnetic</span> separators and apply them to 3D resistive MHD simulations of the Earth's magnetosphere using the BATS-R-US code. The techniques for finding separators and determining the reconnection rate are insensitive to IMF clock angle and can in principle be applied to any magnetospheric model. The present work examines cases of high and low resistivity, for two clock angles. We also examine the separator during <span class="hlt">Flux</span> Transfer Events (FTEs) and Kelvin-Helmholtz instability.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19890062607&hterms=rotation+magnetic+flux&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Drotation%2Bmagnetic%2Bflux','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19890062607&hterms=rotation+magnetic+flux&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Drotation%2Bmagnetic%2Bflux"><span>Slow twists of solar <span class="hlt">magnetic</span> <span class="hlt">flux</span> tubes and the polar <span class="hlt">magnetic</span> field of the sun</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hollweg, Joseph V.; Lee, Martin A.</p> <p>1989-01-01</p> <p>The solar wind model of Weber and Davis (1967) is generalized to compute the heliospheric <span class="hlt">magnetic</span> field resulting from solar rotation or a steady axisymmetric twist including a geometrical expansion which is more rapid than spherical. The calculated increase in the ratio of the toroidal to poloidal field components with heliocentric radial distance r clarifies an expression derived recently by Jokipii and Kota (1989). <span class="hlt">Magnetic</span>-field components transverse to r do not in general grow to dominate the radial component at large r. The analysis also yields expressions for the Poynting <span class="hlt">flux</span> associated with the steady twists.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20150007699','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20150007699"><span>Simulations of Emerging <span class="hlt">Magnetic</span> <span class="hlt">Flux</span>. II. The Formation of Unstable Coronal <span class="hlt">Flux</span> Ropes and the Initiation of Coronal Mass Ejections</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Leake, James E.; Linton, Mark G.; Antiochos, Spiro K.</p> <p>2014-01-01</p> <p>We present results from three-dimensional magnetohydrodynamic simulations of the emergence of a twisted convection zone <span class="hlt">flux</span> tube into a pre-existing coronal dipole field. As in previous simulations, following the partial emergence of the sub-surface <span class="hlt">flux</span> into the corona, a combination of vortical motions and internal <span class="hlt">magnetic</span> reconnection forms a coronal <span class="hlt">flux</span> rope. Then, in the simulations presented here, external reconnection between the emerging field and the pre-existing dipole coronal field allows further expansion of the coronal <span class="hlt">flux</span> rope into the corona. After sufficient expansion, internal reconnection occurs beneath the coronal <span class="hlt">flux</span> rope axis, and the <span class="hlt">flux</span> rope erupts up to the top boundary of the simulation domain (approximately 36 Mm above the surface).We find that the presence of a pre-existing field, orientated in a direction to facilitate reconnection with the emerging field, is vital to the fast rise of the coronal <span class="hlt">flux</span> rope. The simulations shown in this paper are able to self-consistently create many of the surface and coronal signatures used by coronal mass ejection (CME) models. These signatures include surface shearing and rotational motions, quadrupolar geometry above the surface, central sheared arcades reconnecting with oppositely orientated overlying dipole fields, the formation of coronal <span class="hlt">flux</span> ropes underlying potential coronal field, and internal reconnection which resembles the classical flare reconnection scenario. This suggests that proposed mechanisms for the initiation of a CME, such as "<span class="hlt">magnetic</span> breakout," are operating during the emergence of new active regions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22356846','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22356846"><span>Simulations of emerging <span class="hlt">magnetic</span> <span class="hlt">flux</span>. II. The formation of unstable coronal <span class="hlt">flux</span> ropes and the initiation of coronal mass ejections</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Leake, James E.; Linton, Mark G.; Antiochos, Spiro K.</p> <p>2014-05-20</p> <p>We present results from three-dimensional magnetohydrodynamic simulations of the emergence of a twisted convection zone <span class="hlt">flux</span> tube into a pre-existing coronal dipole field. As in previous simulations, following the partial emergence of the sub-surface <span class="hlt">flux</span> into the corona, a combination of vortical motions and internal <span class="hlt">magnetic</span> reconnection forms a coronal <span class="hlt">flux</span> rope. Then, in the simulations presented here, external reconnection between the emerging field and the pre-existing dipole coronal field allows further expansion of the coronal <span class="hlt">flux</span> rope into the corona. After sufficient expansion, internal reconnection occurs beneath the coronal <span class="hlt">flux</span> rope axis, and the <span class="hlt">flux</span> rope erupts up to the top boundary of the simulation domain (∼36 Mm above the surface). We find that the presence of a pre-existing field, orientated in a direction to facilitate reconnection with the emerging field, is vital to the fast rise of the coronal <span class="hlt">flux</span> rope. The simulations shown in this paper are able to self-consistently create many of the surface and coronal signatures used by coronal mass ejection (CME) models. These signatures include surface shearing and rotational motions, quadrupolar geometry above the surface, central sheared arcades reconnecting with oppositely orientated overlying dipole fields, the formation of coronal <span class="hlt">flux</span> ropes underlying potential coronal field, and internal reconnection which resembles the classical flare reconnection scenario. This suggests that proposed mechanisms for the initiation of a CME, such as '<span class="hlt">magnetic</span> breakout', are operating during the emergence of new active regions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/20365784','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/20365784"><span>Theoretical analysis of <span class="hlt">flux</span> amplification by soft <span class="hlt">magnetic</span> material in a putative biological <span class="hlt">magnetic</span>-field receptor.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Shcherbakov, Valera P; Winklhofer, Michael</p> <p>2010-03-01</p> <p>Birds are endowed with a <span class="hlt">magnetic</span> sense that allows them to detect Earth's <span class="hlt">magnetic</span> field and to use it for orientation. Physiological and behavioral experiments have shown the upper beak to host a magnetoreceptor. Putative magnetoreceptive structures in the beak are nerve terminals that each contain a dozen or so of micrometer-sized clusters of superparamagnetic nanocrystals made of magnetite/maghemite and numerous electron-opaque platelets filled with a so far unidentified, amorphous ferric iron compound. The platelets typically form chainlike structures, which have been proposed to function as <span class="hlt">magnetic</span> <span class="hlt">flux</span> focusers for detecting the intensity of the geomagnetic field. Here, we test that proposition from first principles and develop an unconstrained model to determine the equilibrium <span class="hlt">distribution</span> of <span class="hlt">magnetization</span> along a linear chain of platelets which we assume to behave <span class="hlt">magnetically</span> soft and to have no <span class="hlt">magnetic</span> remanence. Our analysis, which is valid for arbitrary values of the intrinsic <span class="hlt">magnetic</span> susceptibility chi , shows that chi needs to be much greater than unity to amplify the external field by two orders of magnitude in a chain of platelets. However, the high amplification is confined to the central region of the chain and subsides quadratically toward the ends of the chain. For large values of chi , the possibility opens up of realizing magnetoreceptor mechanisms on the basis of attraction forces between adjacent platelets in a linear chain. The force in the central region of the chain may amount to several pN, which would be sufficient to convert <span class="hlt">magnetic</span> input energy into mechanical output energy. The striking feature of an ensemble of platelets is its ability to organize into tightly spaced chains under the action of an external field of given strength. We discuss how this property can be exploited for a magnetoreception mechanism.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JGRA..122.5965R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JGRA..122.5965R"><span>Characteristics of ion <span class="hlt">distribution</span> functions in dipolarizing <span class="hlt">flux</span> bundles: Event studies</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Runov, A.; Angelopoulos, V.; Artemyev, A.; Birn, J.; Pritchett, P. L.; Zhou, X.-Z.</p> <p>2017-06-01</p> <p>Taking advantage of multipoint observations from a repeating configuration of the five Time History of Events and Macroscale Interactions during Substorms (THEMIS) probes separated by 1 to 2 Earth radii (RE) along X, Y, and Z in the geocentric solar magnetospheric system (GSM), we study ion <span class="hlt">distribution</span> functions collected by the probes during three dipolarizing <span class="hlt">flux</span> bundle (DFB) events observed at geocentric distances 9 < R < 14 RE. By comparing these probes' observations, we characterize changes in the ion <span class="hlt">distribution</span> functions with respect to probe separation along the X and Y GSM directions and |Bx| levels, which characterize the distance from the neutral sheet. We found that the characteristics of the ion <span class="hlt">distribution</span> functions strongly depended on the |Bx| level, whereas changes with respect to X and Y were minor. In all three events, ion <span class="hlt">distribution</span> functions f(v) observed inside DFBs were organized by <span class="hlt">magnetic</span> and electric fields. The probes near the <span class="hlt">magnetic</span> equator observed perpendicular anisotropy of the phase space density in the range between thermal energy and twice the thermal energy, although the <span class="hlt">distribution</span> in the ambient plasma sheet was isotropic. The anisotropic ion <span class="hlt">distribution</span> in DFBs injected toward the inner magnetosphere may provide the free energy for waves and instabilities, which are important elements of particle energization.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_18 --> <div id="page_19" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="361"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22370207','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22370207"><span>On the area expansion of <span class="hlt">magnetic</span> <span class="hlt">flux</span> tubes in solar active regions</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Dudík, Jaroslav; Dzifčáková, Elena; Cirtain, Jonathan W. E-mail: elena@asu.cas.cz</p> <p>2014-11-20</p> <p>We calculated the three-dimensional (3D) <span class="hlt">distribution</span> of the area expansion factors in a potential <span class="hlt">magnetic</span> field, extrapolated from the high-resolution Hinode/SOT magnetogram of the quiescent active region NOAA 11482. Retaining only closed loops within the computational box, we show that the <span class="hlt">distribution</span> of area expansion factors show significant structure. Loop-like structures characterized by locally lower values of the expansion factor are embedded in a smooth background. These loop-like <span class="hlt">flux</span> tubes have squashed cross-sections and expand with height. The <span class="hlt">distribution</span> of the expansion factors show an overall increase with height, allowing an active region core characterized by low values of the expansion factor to be distinguished. The area expansion factors obtained from extrapolation of the Solar Optical Telescope magnetogram are compared to those obtained from an approximation of the observed magnetogram by a series of 134 submerged charges. This approximation retains the general <span class="hlt">flux</span> <span class="hlt">distribution</span> in the observed magnetogram, but removes the small-scale structure in both the approximated magnetogram and the 3D <span class="hlt">distribution</span> of the area expansion factors. We argue that the structuring of the expansion factor can be a significant ingredient in producing the observed structuring of the solar corona. However, due to the potential approximation used, these results may not be applicable to loops exhibiting twist or to active regions producing significant flares.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22256282','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22256282"><span><span class="hlt">Distributed</span> parameter statics of <span class="hlt">magnetic</span> catheters.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Tunay, Ilker</p> <p>2011-01-01</p> <p>We discuss how to use special Cosserat rod theory for deriving <span class="hlt">distributed</span>-parameter static equilibrium equations of <span class="hlt">magnetic</span> catheters. These medical devices are used for minimally-invasive diagnostic and therapeutic procedures and can be operated remotely or controlled by automated algorithms. The <span class="hlt">magnetic</span> material can be lumped in rigid segments or <span class="hlt">distributed</span> in flexible segments. The position vector of the cross-section centroid and quaternion representation of an orthonormal triad are selected as DOF. The strain energy for transversely isotropic, hyperelastic rods is augmented with the mechanical potential energy of the <span class="hlt">magnetic</span> field and a penalty term to enforce the quaternion unity constraint. Numerical solution is found by 1D finite elements. Material properties of polymer tubes in extension, bending and twist are determined by mechanical and <span class="hlt">magnetic</span> experiments. Software experiments with commercial FEM software indicate that the computational effort with the proposed method is at least one order of magnitude less than standard 3D FEM.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19930071260&hterms=Shibata&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DShibata%252C%2BM','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19930071260&hterms=Shibata&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DShibata%252C%2BM"><span>Three-dimensional magnetohydrodynamics of the emerging <span class="hlt">magnetic</span> <span class="hlt">flux</span> in the solar atmosphere</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Matsumoto, R.; Tajima, T.; Shibata, K.; Kaisig, M.</p> <p>1993-01-01</p> <p>The nonlinear evolution of an emerging <span class="hlt">magnetic</span> <span class="hlt">flux</span> tube or sheet in the solar atmosphere is studied through 3D MHD simulations. In the initial state, a horizontal <span class="hlt">magnetic</span> <span class="hlt">flux</span> sheet or tube is assumed to be embedded at the bottom of MHD two isothermal gas layers, which approximate the solar photosphere/chromosphere and the corona. The <span class="hlt">magnetic</span> <span class="hlt">flux</span> sheet or tube is unstable against the undular mode of the <span class="hlt">magnetic</span> buoyancy instability. The <span class="hlt">magnetic</span> loop rises due to the linear and then later nonlinear instabilities caused by the buoyancy enhanced by precipitating the gas along <span class="hlt">magnetic</span> field lines. We find by 3D simulation that during the ascendance of loops the bundle of <span class="hlt">flux</span> tubes or even the <span class="hlt">flux</span> sheet develops into dense gas filaments pinched between <span class="hlt">magnetic</span> loops. The interchange modes help produce a fine fiber <span class="hlt">flux</span> structure perpendicular to the <span class="hlt">magnetic</span> field direction in the linear stage, while the undular modes determine the overall buoyant loop structure. The expansion of such a bundle of <span class="hlt">magnetic</span> loops follows the self-similar behavior observed in 2D cases studied earlier. Our study finds the threshold <span class="hlt">flux</span> for arch filament system (AFS) formation to be about 0.3 x 10 exp 20 Mx.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22016166','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22016166"><span>HOW MUCH DOES A <span class="hlt">MAGNETIC</span> <span class="hlt">FLUX</span> TUBE EMERGE INTO THE SOLAR ATMOSPHERE?</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Magara, T.</p> <p>2012-03-20</p> <p>The emergence process of the <span class="hlt">magnetic</span> field into the solar atmosphere plays an essential role in determining the configuration of the <span class="hlt">magnetic</span> field and its activity on the Sun. This paper focuses on how much the <span class="hlt">magnetic</span> <span class="hlt">flux</span> contained by a <span class="hlt">flux</span> tube emerges into the solar atmosphere, which is the key to understanding the physical mechanism of solar eruptions. By comparing a kinematic model of an emerging <span class="hlt">flux</span> tube to a series of magnetohydrodynamic simulations, we derive the characteristics of the emergence process, showing how the process depends on the pre-emerged state of the <span class="hlt">magnetic</span> field such as the radius of a <span class="hlt">flux</span> tube, field strength, field-line twist, and wavelength of undulation assumed by the <span class="hlt">flux</span> tube. We also discuss the relationship between <span class="hlt">magnetic</span> configurations and their stability on the Sun.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015APS..DPPN12083G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015APS..DPPN12083G"><span>Pulsating Reconnection in the interaction of two <span class="hlt">magnetic</span> <span class="hlt">flux</span> ropes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gekelman, Walter; Dehaas, Tim; Daughton, William; van Compernolle, Bart</p> <p>2015-11-01</p> <p>Two <span class="hlt">flux</span> ropes (dia = 7 cm, ds = 3 cm, L = 10m, Irope = 300 A/rope) are generated by using a mask in front of a high emissivity cathode (n = 4X1012 cm3, Te-rope = 8.5 eV) in a background magnetoplasma (He, Boz = 330 G, n =1.0X1012cm3, Te = 4 eV) in the LAPD device at UCLA. The ropes are kink unstable (I >250 A) but not violently so. All three components of the <span class="hlt">magnetic</span> field were measured with small (1 mm dia) 3-axis probes sensitive to ∂/B-> ∂ t and the plasma potential measured with an emissive probe. These were measured at 42,075 locations in the volume containing the ropes and 7000 time steps (δτ = .33 μs). The total electric field E-> = - ∇ ϕ -∂/A-> ∂ t and parallel resistivity as well as the Quasi Seperatrix layer (QSL) were derived from the data. The <span class="hlt">flux</span> ropes periodically collide as they kink. Each time this happens a strong QSL (Q<400) forms and the resistivity jumps to over a hundred times the classical value at locations within the QSL and also on the gradient of the rope current. The reconnection rate is directly evaluated by integrating the electric field along field lines as well as the energy deposition J-> . E-> . The data indicate that there is more than one process causing the enhanced resistivity. The reconnection rate cannot be explained by conventional 2D theories. Work done at the BaPSF which is supported by NSF/DOE. project supported by DOE and a LANL research grant.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AIPC.1813f0001K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AIPC.1813f0001K"><span>Effect of air gap variation on the performance of single stator single rotor axial <span class="hlt">flux</span> permanent <span class="hlt">magnet</span> generator</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kasim, Muhammad; Irasari, Pudji; Hikmawan, M. Fathul; Widiyanto, Puji; Wirtayasa, Ketut</p> <p>2017-02-01</p> <p>The axial <span class="hlt">flux</span> permanent <span class="hlt">magnet</span> generator (AFPMG) has been widely used especially for electricity generation. The effect of the air gap variation on the characteristic and performances of single rotor - single stator AFPMG has been described in this paper. Effect of air gap length on the <span class="hlt">magnetic</span> <span class="hlt">flux</span> <span class="hlt">distribution</span>, starting torque and MMF has been investigated. The two dimensional finite element <span class="hlt">magnetic</span> method has been deployed to model and simulated the characteristics of the machine which is based on the Maxwell equation. The analysis has been done for two different air gap lengths which were 2 mm and 4 mm using 2D FEMM 4.2 software at no load condition. The increasing of air gap length reduces the air-gap <span class="hlt">flux</span> density. For air gap 2 mm, the maximum value of the <span class="hlt">flux</span> density was 1.04 T while 0.73 T occured for air gap 4 mm.. Based on the experiment result, the increasing air gap also reduced the starting torque of the machine with 39.2 Nm for air gap 2 mm and this value decreased into 34.2 Nm when the air gap increased to 4 mm. Meanwhile, the MMF that was generated by AFPMG decreased around 22% at 50 Hz due to the reduction of <span class="hlt">magnetic</span> <span class="hlt">flux</span> induced on stator windings. Overall, the research result showed that the variation of air gap has significant effect on the machine characteristics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JAP...121f5105L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JAP...121f5105L"><span>Enhancement of thermoelectric properties in benzene molecule junction by the <span class="hlt">magnetic</span> <span class="hlt">flux</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, Haidong; Wang, Yuan; kang, Xiubao; Liu, Shaohui; Li, Ruixue</p> <p>2017-02-01</p> <p>The thermoelectric properties through a benzene molecule with two metal leads are theoretically studied. The results reveal that the thermoelectric properties are strongly influenced by the <span class="hlt">magnetic</span> <span class="hlt">flux</span>. The reason for such a behavior is that the quantum interference caused by the <span class="hlt">magnetic</span> field leads to the anti-resonance effect, which results in obvious thermoelectric effects. The value of Z T with a period of 1 for the <span class="hlt">magnetic</span> <span class="hlt">flux</span> and the magnitude of Z T may exceed 2 under some specific <span class="hlt">magnetic</span> <span class="hlt">flux</span> and onsite Coulomb interaction.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010JAP...107iA736F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010JAP...107iA736F"><span>Prediction method of <span class="hlt">flux</span> loss in anisotropic NdFeB/SmFeN hybrid <span class="hlt">magnets</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fukunaga, Hirotoshi; Murata, Hiroki; Yanai, Takeshi; Nakano, Masaki; Yamashita, Fumitoshi</p> <p>2010-05-01</p> <p>We systematically evaluated the initial <span class="hlt">flux</span> loss of anisotropic HDDR-NdFeB/RD-SmFeN hybrid bonded <span class="hlt">magnets</span>. The measured <span class="hlt">flux</span> loss values were compared with those obtained by two prediction methods based on our previous proposal. Consequently, it was clarified that the initial <span class="hlt">flux</span> loss of anisotropic bonded <span class="hlt">magnets</span> can be predicted from demagnetization curves at room and exposure temperatures of the corresponding hybrid <span class="hlt">magnets</span>, which suggests that the method proposed previously for isotropic <span class="hlt">magnets</span> can be also applicable to anisotropic ones.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AIPA....7e6628Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AIPA....7e6628Y"><span>Design and analysis of a new <span class="hlt">flux</span>-intensifying permanent <span class="hlt">magnet</span> brushless motor with multilayer <span class="hlt">flux</span> barriers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yang, Shen; Zhu, Xiaoyong; Xiang, Zixuan; Fan, Deyang; Wu, Wenye; Yin, Jianing</p> <p>2017-05-01</p> <p>This paper proposes a new <span class="hlt">flux</span>-intensifying permanent <span class="hlt">magnet</span> brushless motor for potential application in electric vehicles. The key of the proposed motor is to adopt the concept of <span class="hlt">flux</span>-intensifying effect, thus the preferable <span class="hlt">flux</span>-weakening ability and extended speed range can be achieved. The usage of segmented and relatively thinner permanent <span class="hlt">magnet</span> (PM) in the proposed motor contributes to the increase of d-axis inductance Ld. In addition, the multilayer <span class="hlt">flux</span> barriers along q-axis <span class="hlt">flux</span> path will effectively decrease q-axis inductance Lq. As a result, the unique feature of Ld>Lq can be obtained, which is beneficial to extending the speed range of the proposed motor. Furthermore, the <span class="hlt">flux</span>-intensifying effect can reduce the risk of irreversible demagnetization in PMs. The electromagnetic performances of the proposed motor are analyzed and investigated in details by using the finite element methods, which demonstrate the excellent <span class="hlt">flux</span>-weakening capability and wide speed range can be achieved in the proposed FI-PMBL motor.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1346128-structure-magnetic-flux-annihilation-layer-formed-collision-supersonic-magnetized-plasma-flows','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1346128-structure-magnetic-flux-annihilation-layer-formed-collision-supersonic-magnetized-plasma-flows"><span>Structure of a <span class="hlt">magnetic</span> <span class="hlt">flux</span> annihilation layer formed by the collision of supersonic, <span class="hlt">magnetized</span> plasma flows</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Suttle, L. G.; Hare, J. D.; Lebedev, S. V.; ...</p> <p>2016-05-31</p> <p>We present experiments characterizing the detailed structure of a current layer, generated by the collision of two counter-streaming, supersonic and <span class="hlt">magnetized</span> aluminum plasma flows. The anti parallel <span class="hlt">magnetic</span> fields advected by the flows are found to be mutually annihilated inside the layer, giving rise to a bifurcated current structure—two narrow current sheets running along the outside surfaces of the layer. Measurements with Thomson scattering show a fast outflow of plasma along the layer and a high ion temperature (Ti~¯ZTe, with average ionization ¯Z=7). Lastly, analysis of the spatially resolved plasma parameters indicates that the advection and subsequent annihilation of themore » in-flowing <span class="hlt">magnetic</span> <span class="hlt">flux</span> determines the structure of the layer, while the ion heating could be due to the development of kinetic, current-driven instabilities.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27314720','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27314720"><span>Structure of a <span class="hlt">Magnetic</span> <span class="hlt">Flux</span> Annihilation Layer Formed by the Collision of Supersonic, <span class="hlt">Magnetized</span> Plasma Flows.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Suttle, L G; Hare, J D; Lebedev, S V; Swadling, G F; Burdiak, G C; Ciardi, A; Chittenden, J P; Loureiro, N F; Niasse, N; Suzuki-Vidal, F; Wu, J; Yang, Q; Clayson, T; Frank, A; Robinson, T S; Smith, R A; Stuart, N</p> <p>2016-06-03</p> <p>We present experiments characterizing the detailed structure of a current layer, generated by the collision of two counterstreaming, supersonic and <span class="hlt">magnetized</span> aluminum plasma flows. The antiparallel <span class="hlt">magnetic</span> fields advected by the flows are found to be mutually annihilated inside the layer, giving rise to a bifurcated current structure-two narrow current sheets running along the outside surfaces of the layer. Measurements with Thomson scattering show a fast outflow of plasma along the layer and a high ion temperature (T_{i}∼Z[over ¯]T_{e}, with average ionization Z[over ¯]=7). Analysis of the spatially resolved plasma parameters indicates that the advection and subsequent annihilation of the inflowing <span class="hlt">magnetic</span> <span class="hlt">flux</span> determines the structure of the layer, while the ion heating could be due to the development of kinetic, current-driven instabilities.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/1346128','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/1346128"><span>Structure of a <span class="hlt">magnetic</span> <span class="hlt">flux</span> annihilation layer formed by the collision of supersonic, <span class="hlt">magnetized</span> plasma flows</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Suttle, L. G.; Hare, J. D.; Lebedev, S. V.; Swadling, G. F.; Burdiak, G. C.; Ciardi, A.; Chittenden, J. P.; Loureiro, N. F.; Niasse, N.; Suzuki-Vidal, F.; Wu, J.; Yang, Q.; Clayson, T.; Frank, A.; Robinson, T. S.; Smith, R. A.; Stuart, N.</p> <p>2016-05-31</p> <p>We present experiments characterizing the detailed structure of a current layer, generated by the collision of two counter-streaming, supersonic and <span class="hlt">magnetized</span> aluminum plasma flows. The anti parallel <span class="hlt">magnetic</span> fields advected by the flows are found to be mutually annihilated inside the layer, giving rise to a bifurcated current structure—two narrow current sheets running along the outside surfaces of the layer. Measurements with Thomson scattering show a fast outflow of plasma along the layer and a high ion temperature (T<sub>i</sub>~¯ZT<sub>e</sub>, with average ionization ¯Z=7). Lastly, analysis of the spatially resolved plasma parameters indicates that the advection and subsequent annihilation of the in-flowing <span class="hlt">magnetic</span> <span class="hlt">flux</span> determines the structure of the layer, while the ion heating could be due to the development of kinetic, current-driven instabilities.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1346128','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1346128"><span>Structure of a <span class="hlt">magnetic</span> <span class="hlt">flux</span> annihilation layer formed by the collision of supersonic, <span class="hlt">magnetized</span> plasma flows</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Suttle, L. G.; Hare, J. D.; Lebedev, S. V.; Swadling, G. F.; Burdiak, G. C.; Ciardi, A.; Chittenden, J. P.; Loureiro, N. F.; Niasse, N.; Suzuki-Vidal, F.; Wu, J.; Yang, Q.; Clayson, T.; Frank, A.; Robinson, T. S.; Smith, R. A.; Stuart, N.</p> <p>2016-05-31</p> <p>We present experiments characterizing the detailed structure of a current layer, generated by the collision of two counter-streaming, supersonic and <span class="hlt">magnetized</span> aluminum plasma flows. The anti parallel <span class="hlt">magnetic</span> fields advected by the flows are found to be mutually annihilated inside the layer, giving rise to a bifurcated current structure—two narrow current sheets running along the outside surfaces of the layer. Measurements with Thomson scattering show a fast outflow of plasma along the layer and a high ion temperature (T<sub>i</sub>~¯ZT<sub>e</sub>, with average ionization ¯Z=7). Lastly, analysis of the spatially resolved plasma parameters indicates that the advection and subsequent annihilation of the in-flowing <span class="hlt">magnetic</span> <span class="hlt">flux</span> determines the structure of the layer, while the ion heating could be due to the development of kinetic, current-driven instabilities.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002SPIE.4935..454O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002SPIE.4935..454O"><span><span class="hlt">Magnetic</span> field <span class="hlt">distribution</span> of strong hybrid <span class="hlt">magnet</span> in high torque motor</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Oguri, Kazuya; Mizutani, Akihiro; Ogino, Sanshiroh; Ochiai, Yasuzumi; Kawahata, Masahiro; Nishi, Yoshitake</p> <p>2002-11-01</p> <p>A variable reluctance hybrid <span class="hlt">magnet</span> has been developed to apply new type of high torque motors. A permanent <span class="hlt">magnet</span>, electromagnet and yoke construct the variable reluctance hybrid <span class="hlt">magnet</span>. From an engineering point of view, it is important to know the <span class="hlt">magnetic</span> field around a variable reluctance hybrid <span class="hlt">magnet</span>. Based on the results of <span class="hlt">magnetic</span> <span class="hlt">flux</span> density measurement around the hybrid variable reluctance <span class="hlt">magnet</span>, the high <span class="hlt">magnetic</span> <span class="hlt">flux</span> density was found at edges and joints. The high <span class="hlt">magnetic</span> <span class="hlt">flux</span> density was also obtained with electrical current of 10 A at optimum setting form. Therefore, we concluded that the strong force of rotor of the hybrid motor was generated by high surface <span class="hlt">flux</span> density of the hybrid <span class="hlt">magnet</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012IJTFM.132..278Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012IJTFM.132..278Y"><span>Control of <span class="hlt">Magnetic</span> Field for Sustainment of Ion Production and Uniform Ion <span class="hlt">Flux</span> to Substrate in Neutral Loop Discharge Plasma</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yoshida, Takuhei; Sakurai, Yohei; Sugawara, Hirotake; Murayama, Akihiro</p> <p></p> <p>We simulated the electron and ion motions in a neutral loop discharge plasma under the control of the foot of separatrix sweeping over a substrate and the neutral loop moving within a short distance from the RF antenna by a Monte Carlo method. We analyzed the <span class="hlt">distributions</span> of ion production and ion <span class="hlt">flux</span> to the substrate. We revealed that ion production is sensitive to the gradient of <span class="hlt">magnetic</span> field rather than the electric field strength. Moreover, by superposing the <span class="hlt">flux</span> <span class="hlt">distributions</span> weighted by the passage time of the foot of separatrix on the substrate, we obtained a uniform time-averaged <span class="hlt">distribution</span> of ion <span class="hlt">flux</span> to the substrate in a radius range of r = 4.0-14.0 cm with σ/m = 0.25% (m: the average, σ: the standard deviation).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005PhDT........16B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005PhDT........16B"><span>Monte Carlo Study of the <span class="hlt">Magnetic</span> <span class="hlt">Flux</span> Lattice Fluctuations in High-Tc Superconductors</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Beny, Cedric</p> <p></p> <p>By allowing to measure the <span class="hlt">magnetic</span> field <span class="hlt">distribution</span> inside a material, muon spin rotation experiments have the potential to provide valuable information about microscopic properties of high-temperature superconductors. Nevertheless, information about the intrinsic superconducting properties of the material is masked by random thermal and static fluctuations of the <span class="hlt">magnetic</span> field which penetrates the material in the form of vortices of quantized <span class="hlt">magnetic</span> <span class="hlt">flux</span>. A good understanding of the fluctuations of those vortices is needed for the correct determination of intrinsic properties, notably the coherence length [xi], and the field penetration depth [lambda]. We develop a simulation based on the Metropolis algorithm in order to understand the effect, on the <span class="hlt">magnetic</span> field <span class="hlt">distribution</span>, of disorder- and thermally-induced fluctuations of the vortex lattice inside a layered superconductor. Our model correctly predicts the melting temperatures of the YBa2Cu3O6. 95 (YBCO) superconductor but largely underestimates the observed entropy jump. Also we failed to simulate the high field disordered phase, possibly because of a finite size limitation. In addition, we found our model unable to describe the first-order transition observed in the highly anisotropic Bi2Sr2CaCu2O8+y. Our model predicts that for YBCO, the effect of thermal fluctuations on the field <span class="hlt">distribution</span> is indistinguishable from a change in [xi]. It also confirms the usual assumption that the effect of static fluctuations at low temperature can be efficiently modeled by convolution of the field <span class="hlt">distribution</span> with a Gaussian function. However the extraction of [xi] at low fields requires a very high resolution of the field <span class="hlt">distribution</span> because of the low vortex density.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008A%26A...480L...9W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008A%26A...480L...9W"><span>Energy spectrum of interplanetary <span class="hlt">magnetic</span> <span class="hlt">flux</span> ropes and its connection with solar activity</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wu, D. J.; Feng, H. Q.; Chao, J. K.</p> <p>2008-03-01</p> <p>Context: Recent observations of the solar wind show that interplanetary <span class="hlt">magnetic</span> <span class="hlt">flux</span> ropes (IMFRs) have a continuous scale-<span class="hlt">distribution</span> from small-scale <span class="hlt">flux</span> ropes to large-scale <span class="hlt">magnetic</span> clouds. Aims: In this work, we investigate the energy spectrum of IMFRs and its possible connection with solar activity. Methods: In consideration of the detectable probability of an IMFR to be proportional to its diameter, the actual energy spectrum of IMFRs can be obtained from the observed spectrum based on spacecraft observations in the solar wind. Results: It is found that IMFRs have a negative power-law spectrum with an index α = 1.36±0.03, which is similar to that of solar flares, and is probably representative of interplanetary energy spectrum of coronal mass ejections (CMEs), that is, the energy spectrum of interplanetary CMEs (ICMEs). This indicates that the energy <span class="hlt">distribution</span> of CMEs has a similar negative power-law spectrum. In particular, there are numerous small-scale CMEs in the solar corona, and their interplanetary consequences may be directly detected in situ by spacecraft in the solar wind as small-scale IMFRs, although they are too weak to appear clearly in current coronagraph observations. Conclusions: The presence of small-scale CMEs, especially the energy spectrum of CMEs is potentially important for understanding both the solar magneto-atmosphere and CMEs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003AGUFMSH42B0518F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003AGUFMSH42B0518F"><span>Experimental Investigation of the Stability of a Single and Multiple <span class="hlt">Magnetic</span> <span class="hlt">Flux</span> Ropes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Furno, I.; Intrator, T.; Hemsing, E.</p> <p>2003-12-01</p> <p>Both the stability of a single <span class="hlt">magnetic</span> <span class="hlt">flux</span> rope and the interaction between multiple <span class="hlt">magnetic</span> <span class="hlt">flux</span> ropes are fundamental issues in the dynamics of the solar corona. Examples are in coronal mass ejections, in which highly twisted <span class="hlt">flux</span> ropes are believed to play a crucial role, and in solar flares and large-scale eruptions in which transport of twist through <span class="hlt">magnetic</span> reconnection is observed between distinct coronal <span class="hlt">flux</span> systems. To study the interaction of <span class="hlt">magnetic</span> <span class="hlt">flux</span> ropes in a controlled laboratory environment, we use the Reconnection Scaling eXperiment (RSX) device at Los Alamos National Laboratory, which was originally designed to study three-dimensional <span class="hlt">magnetic</span> reconnection during the coalescence of parallel current channels. Commercial plasma guns are used to inject <span class="hlt">magnetic</span> helicity into hydrogen plasma column (r = 2 cm radius, L = 0.2-3 m length). Multiple <span class="hlt">flux</span> ropes carrying currents up to 1 kA are created along the axial direction of a 4 m linear vacuum vessel. A set of 12 identical external coils surrounding the vessel provides an axial <span class="hlt">magnetic</span> field parallel to the current channels. The azimuthal (Bθ = 0-100 Gauss) and axial (Bz = 0-1000 Gauss) <span class="hlt">magnetic</span> field components as well as the plasma density (1012}-10{14 cm-3) can be varied independently. In particular, the twist of <span class="hlt">magnetic</span> field lines, defined by Φ = LBθ / rBz, can be scaled in the range 1 < Φ < 10 independently of the plasma collisionality. In the present work, the stability of single <span class="hlt">flux</span> rope and the interaction of two <span class="hlt">flux</span> ropes are studied in the RSX operational space. <span class="hlt">Magnetic</span> data and visible light emission from a fast CCD camera are presented showing twisting and braiding of <span class="hlt">magnetic</span> <span class="hlt">flux</span> ropes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22039327','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22039327"><span>BUILDUP OF <span class="hlt">MAGNETIC</span> SHEAR AND FREE ENERGY DURING <span class="hlt">FLUX</span> EMERGENCE AND CANCELLATION</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Fang Fang; Manchester, Ward IV; Van der Holst, Bart; Abbett, William P.</p> <p>2012-07-20</p> <p>We examine a simulation of <span class="hlt">flux</span> emergence and cancellation, which shows a complex sequence of processes that accumulate free <span class="hlt">magnetic</span> energy in the solar corona essential for the eruptive events such as coronal mass ejections, filament eruptions, and flares. The flow velocity at the surface and in the corona shows a consistent shearing pattern along the polarity inversion line (PIL), which together with the rotation of the <span class="hlt">magnetic</span> polarities, builds up the <span class="hlt">magnetic</span> shear. Tether-cutting reconnection above the PIL then produces longer sheared <span class="hlt">magnetic</span> field lines that extend higher into the corona, where a sigmoidal structure forms. Most significantly, reconnection and upward-energy-<span class="hlt">flux</span> transfer are found to occur even as <span class="hlt">magnetic</span> <span class="hlt">flux</span> is submerging and appears to cancel at the photosphere. A comparison of the simulated coronal field with the corresponding coronal potential field graphically shows the development of non-potential fields during the emergence of the <span class="hlt">magnetic</span> <span class="hlt">flux</span> and formation of sunspots.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/944333','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/944333"><span>Measurements and Phenomenological Modeling of <span class="hlt">Magnetic</span> <span class="hlt">Flux</span>Buildup in Spheromak Plasmas</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Romero-Talamas, C A; Hooper, E B; Jayakumar, R; McLean, H S; Wood, R D; Moller, J M</p> <p>2007-12-14</p> <p>Internal <span class="hlt">magnetic</span> field measurements and high-speed imaging at the Sustained Spheromak Physics Experiment (SSPX) [E. B. Hooper, L. D. Pearlstein, R. H. Bulmer, Nucl. Fusion 39, 863 (1999)] are used to study spheromak formation and field buildup. The measurements are analyzed in the context of a phenomenological model of <span class="hlt">magnetic</span> helicity based on the topological constraint of minimum helicity in the open <span class="hlt">flux</span> before reconnecting and linking closed <span class="hlt">flux</span>. Two stages are analyzed: (1) the initial spheromak formation, i. e. when all <span class="hlt">flux</span> surfaces are initially open and reconnect to form open and closed <span class="hlt">flux</span> surfaces, and (2) the stepwise increase of closed <span class="hlt">flux</span> when operating the gun on a new mode that can apply a train of high-current pulses to the plasma. In the first stage, large kinks in the open <span class="hlt">flux</span> surfaces are observed in the high-speed images taken shortly after plasma breakdown, and coincide with large <span class="hlt">magnetic</span> asymmetries recorded in a fixed insertable <span class="hlt">magnetic</span> probe that spans the <span class="hlt">flux</span> conserver radius. Closed <span class="hlt">flux</span> (in the toroidal average sense) appears shortly after this. This stage is also investigated using resistive magnetohydrodynamic simulations. In the second stage, a time lag in response between open and closed <span class="hlt">flux</span> surfaces after each current pulse is interpreted as the time for the open <span class="hlt">flux</span> to build helicity, before transferring it through reconnection to the closed <span class="hlt">flux</span>. Large asymmetries are seen during these events, which then relax to a slowly decaying spheromak before the next pulse.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_19 --> <div id="page_20" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="381"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JAP...122k5103Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JAP...122k5103Y"><span><span class="hlt">Flux</span>-pinning-induced stress and magnetostriction in a superconducting strip under combination of transport current and <span class="hlt">magnetic</span> field</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yang, Yumei; Wang, Xingzhe</p> <p>2017-09-01</p> <p>The magnetoelastic properties and behaviors arising from the <span class="hlt">flux</span>-pinning effect are investigated for a long rectangular superconducting strip subject to a combination of applied transport current and <span class="hlt">magnetic</span> field. Based on the Bean critical state model and linear elastic theory, the <span class="hlt">flux</span>-pinning-induced stress in the superconducting strip is analytically obtained under the zero-field cooling condition. In particular, the magnetostriction performance for the strip with a one-sided restraint condition is then investigated. The results show that the trapped <span class="hlt">magnetic</span> <span class="hlt">flux</span> is <span class="hlt">distributed</span> asymmetrically along the y-direction. A non-zero resultant force is consequently observed from the <span class="hlt">magnetization</span> arising from the applied transport current and <span class="hlt">magnetic</span> field. An obvious tension stress emerges around the constrained side of the strip along which the highest probability for cracking occurs and leads to a structural instability. The analytical results give insight into the <span class="hlt">flux</span>-pinning-induced stress and magnetostriction response of the superconducting strip under both complex carrying-current and applied <span class="hlt">magnetic</span> field conditions. These results may also provide helpful guidance in avoiding the breakdown of high-temperature superconductors.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23464209','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23464209"><span>2D divertor heat <span class="hlt">flux</span> <span class="hlt">distribution</span> using a 3D heat conduction solver in National Spherical Torus Experiment.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Gan, K F; Ahn, J-W; Park, J-W; Maingi, R; McLean, A G; Gray, T K; Gong, X; Zhang, X D</p> <p>2013-02-01</p> <p>The divertor heat <span class="hlt">flux</span> footprint in tokamaks is often observed to be non-axisymmetric due to intrinsic error fields, applied 3D <span class="hlt">magnetic</span> fields or during transients such as edge localized modes. Typically, only 1D radial heat <span class="hlt">flux</span> profiles are analyzed; however, analysis of the full 2D divertor measurements provides opportunities to study the asymmetric nature of the deposited heat <span class="hlt">flux</span>. To accomplish this an improved 3D Fourier analysis method has been successfully applied in a heat conduction solver (TACO) to determine the 2D heat <span class="hlt">flux</span> <span class="hlt">distribution</span> at the lower divertor surface in the National Spherical Torus Experiment (NSTX) tokamak. This advance enables study of helical heat deposition onto the divertor. In order to account for heat transmission through poorly adhered surface layers on the divertor plate, a heat transmission coefficient, defined as the surface layer thermal conductivity divided by the thickness of the layer, was introduced to the solution of heat conduction equation. This coefficient is denoted as α and a range of values were tested in the model to ensure a reliable heat <span class="hlt">flux</span> calculation until a specific value of α led to the constant total deposited energy in the numerical solution after the end of discharge. A comparison between 1D heat <span class="hlt">flux</span> profiles from TACO and from a 2D heat <span class="hlt">flux</span> calculation code, THEODOR, shows good agreement. Advantages of 2D heat <span class="hlt">flux</span> <span class="hlt">distribution</span> over the conventional 1D heat <span class="hlt">flux</span> profile are also discussed, and examples of 2D data analysis in the study of striated heat deposition pattern as well as the toroidal degree of asymmetry of peak heat <span class="hlt">flux</span> and heat <span class="hlt">flux</span> width are demonstrated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1911181D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1911181D"><span>Structure and evolution of <span class="hlt">flux</span> transfer events near <span class="hlt">magnetic</span> reconnection dissipation region</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dong, Xiangcheng; Dunlop, Malcolm; Trattner, Karlheinz; Phan, Tai; Fu, Huishan; Cao, Jinbin; Russell, Christopher; Giles, Barbara; Torbert, Roy; Le, Guan</p> <p>2017-04-01</p> <p>We investigate a series three small scale <span class="hlt">flux</span> transfer events (FTEs) associated with reconnected <span class="hlt">flux</span> ropes (FR) recently generated by a nearby, dayside <span class="hlt">magnetic</span> reconnection (MR) site. The data are provided by the Magnetospheric Multiscale (MMS) spacecraft near noon local time. Intense current density (>3 μA/m2), a thin current layer (44km˜0.5di), strong electron heating, a high-amplitude electric field (>100 mV/m), electron crescent-shaped <span class="hlt">distributions</span> and the absence of an ion jet at the magnetopause indicate that MMS crossed the <span class="hlt">magnetic</span> reconnection dissipation region [Burch and Phan, 2016]. Within one minute before MMS crossed this dissipation region, three evolving, small scale FTEs were observed one by one moving southward from the reconnection site located northward of MMS. The electric currents (calculated both using the curlometer technique and from particle moments) are mainly located in the center of the FTEs and parallel with the <span class="hlt">magnetic</span> field. The large current in the center can reach 600 nA/m-2 and shows a bifurcated feature. We find that the associated FTEs are created by secondary <span class="hlt">magnetic</span> reconnection and have different <span class="hlt">magnetic</span> field topologies, which is a similar condition to that expected in the Multiple X-line MR model. The size of the FTEs become larger with the time elapsed since MR and the reconnection jets at the FTEs are all located on the trailing and outer edges. The above features indicate that these FTEs are still in the evolution stage after they are ejected from reconnection region ('active' FTEs). Our observation may suggest that mesoscale or typical size FTEs can be created from secondary MR, initially, and subsequently can evolve to a typical size in the process of spreading.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMSH41B4131J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMSH41B4131J"><span><span class="hlt">Magnetic</span> <span class="hlt">Flux</span> Concentrations in Stratified Turbulent Plasma Due to Negative Effective <span class="hlt">Magnetic</span> Pressure Instability</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jabbari, S.; Brandenburg, A.</p> <p>2014-12-01</p> <p> al. 2013). When the field is vertical, the resulting <span class="hlt">magnetic</span> <span class="hlt">flux</span> concentrations lead to the <span class="hlt">magnetic</span> spots and can be of equipartition field strength. DNS, MFS, and implicit large eddy simulations (ILES) confirm that in a proper parameter regime, vertical imposed fields lead to the formation of circular <span class="hlt">magnetic</span> spots (Brandenburg et al. 2014).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010APS..MAR.V9012C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010APS..MAR.V9012C"><span><span class="hlt">Magnetic</span> <span class="hlt">flux</span> superperiods in fractional quantum Hall interferometers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Camino, F. E.; Lin, P. V.; Goldman, V. J.</p> <p>2010-03-01</p> <p>Superperiodic Aharonov-Bohm oscillations in conductance of e/3 quasiparticles have been reported in three Fabry-Perot interferometer devices. Superperiods are observed in the FQH regime, when filling 1/3 edge channel encircles an island of 2/5 FQH fluid. Etch trenches define the devices, which consist of a 2D electron island connected to the 2DES bulk via two wide constrictions. An oscillatory signal in the conductance is observed when tunneling occurs in the constrictions. The width of the 1/3 edge channel weakly depends on the size of the device, on the other hand, the enclosed 2/5 island area varies by a factor of 4. We compare the <span class="hlt">magnetic</span> field periods in the different size devices and review the evidence that the <span class="hlt">flux</span> period is 5h/e. [1] The FQH edge channel structure essentially depends on the 2D electron density profile. We discuss the self- consistent density profile in the device defined by the etch trenches. We also discuss electron depletion due to electric field of front gates, which is not screened efficiently by 2D electrons and thus leads to a smaller gradient of the confining potential than the mesa etch. [1] F. E. Camino et al., PRB 72, 075342 (2005); W. Zhou et al., PRB 73, 245322 (2006); P. V. Lin et al., PRB (in press, 2009).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19890054926&hterms=rotation+magnetic+flux&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Drotation%2Bmagnetic%2Bflux','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19890054926&hterms=rotation+magnetic+flux&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Drotation%2Bmagnetic%2Bflux"><span>The <span class="hlt">magnetic</span>, basal, and radiative-equilibrium components in Mount Wilson Ca II H + K <span class="hlt">fluxes</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Schrijver, C. J.; Dobson, Andrea K.; Radick, Richard R.</p> <p>1989-01-01</p> <p>Mount Wilson Ca II H + K <span class="hlt">flux</span> measurements of cool dwarf stars are analyzed and compared with stellar Mg II h + k <span class="hlt">fluxes</span>, variability amplitudes, rotation rates, and solar data. It is concluded that the Mount Wilson Ca II H + K <span class="hlt">fluxes</span> comprise three principal parts: (1) a photospheric contribution in the line wings, (2) a basal chromospheric component that appears to be unrelated to stellar <span class="hlt">magnetic</span> activity and is, therefore, possibly nonmagnetic in origin, and (3) a chromospheric component which is associated with <span class="hlt">magnetically</span> active regions and the (quiet and active) network. The basal chromosphere appears to cover the entire surface of <span class="hlt">magnetically</span> inactive stars. The basal Ca II H + K <span class="hlt">flux</span> density for solar-type stars equals the average emission observed in the centers of solar supergranulation cells, where the <span class="hlt">magnetic</span> <span class="hlt">flux</span> density is small.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19890054926&hterms=wilson+journal&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dwilson%2Bjournal','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19890054926&hterms=wilson+journal&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dwilson%2Bjournal"><span>The <span class="hlt">magnetic</span>, basal, and radiative-equilibrium components in Mount Wilson Ca II H + K <span class="hlt">fluxes</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Schrijver, C. J.; Dobson, Andrea K.; Radick, Richard R.</p> <p>1989-01-01</p> <p>Mount Wilson Ca II H + K <span class="hlt">flux</span> measurements of cool dwarf stars are analyzed and compared with stellar Mg II h + k <span class="hlt">fluxes</span>, variability amplitudes, rotation rates, and solar data. It is concluded that the Mount Wilson Ca II H + K <span class="hlt">fluxes</span> comprise three principal parts: (1) a photospheric contribution in the line wings, (2) a basal chromospheric component that appears to be unrelated to stellar <span class="hlt">magnetic</span> activity and is, therefore, possibly nonmagnetic in origin, and (3) a chromospheric component which is associated with <span class="hlt">magnetically</span> active regions and the (quiet and active) network. The basal chromosphere appears to cover the entire surface of <span class="hlt">magnetically</span> inactive stars. The basal Ca II H + K <span class="hlt">flux</span> density for solar-type stars equals the average emission observed in the centers of solar supergranulation cells, where the <span class="hlt">magnetic</span> <span class="hlt">flux</span> density is small.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017IAUS..328...85W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017IAUS..328...85W"><span>The Suppression and Promotion of <span class="hlt">Magnetic</span> <span class="hlt">Flux</span> Emergence in Fully Convective Stars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Weber, Maria A.; Browning, Matthew K.; Boardman, Suzannah; Clarke, Joshua; Pugsley, Samuel; Townsend, Edward</p> <p>2017-10-01</p> <p>Evidence of surface <span class="hlt">magnetism</span> is now observed on an increasing number of cool stars. The detailed manner by which dynamo-generated <span class="hlt">magnetic</span> fields giving rise to starspots traverse the convection zone still remains unclear. Some insight into this <span class="hlt">flux</span> emergence mechanism has been gained by assuming bundles of <span class="hlt">magnetic</span> field can be represented by idealized thin <span class="hlt">flux</span> tubes (TFTs). Weber & Browning (2016) have recently investigated how individual <span class="hlt">flux</span> tubes might evolve in a 0.3M⊙ M dwarf by effectively embedding TFTs in time-dependent flows representative of a fully convective star. We expand upon this work by initiating <span class="hlt">flux</span> tubes at various depths in the upper ~50-75% of the star in order to sample the differing convective flow pattern and differential rotation across this region. Specifically, we comment on the role of differential rotation and time-varying flows in both the suppression and promotion of the <span class="hlt">magnetic</span> <span class="hlt">flux</span> emergence process.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5509615','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5509615"><span>The <span class="hlt">magnetic</span>, basal, and radiative-equilibrium components in Mount Wilson Ca II H + K <span class="hlt">fluxes</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Schrijver, C.J.; Dobson, A.K.; Radick, R.R.; Joint Institute for Laboratory Astrophysics, Boulder, CO )</p> <p>1989-06-01</p> <p>Mount Wilson Ca II H + K <span class="hlt">flux</span> measurements of cool dwarf stars are analyzed and compared with stellar Mg II h + k <span class="hlt">fluxes</span>, variability amplitudes, rotation rates, and solar data. It is concluded that the Mount Wilson Ca II H + K <span class="hlt">fluxes</span> comprise three principal parts: (1) a photospheric contribution in the line wings, (2) a basal chromospheric component that appears to be unrelated to stellar <span class="hlt">magnetic</span> activity and is, therefore, possibly nonmagnetic in origin, and (3) a chromospheric component which is associated with <span class="hlt">magnetically</span> active regions and the (quiet and active) network. The basal chromosphere appears to cover the entire surface of <span class="hlt">magnetically</span> inactive stars. The basal Ca II H + K <span class="hlt">flux</span> density for solar-type stars equals the average emission observed in the centers of solar supergranulation cells, where the <span class="hlt">magnetic</span> <span class="hlt">flux</span> density is small. 27 refs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ApJS..229...15R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ApJS..229...15R"><span>Spectropolarimetric Evidence for a Siphon Flow along an Emerging <span class="hlt">Magnetic</span> <span class="hlt">Flux</span> Tube</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Requerey, Iker S.; Ruiz Cobo, B.; Del Toro Iniesta, J. C.; Orozco Suárez, D.; Blanco Rodríguez, J.; Solanki, S. K.; Barthol, P.; Gandorfer, A.; Gizon, L.; Hirzberger, J.; Riethmüller, T. L.; van Noort, M.; Schmidt, W.; Martínez Pillet, V.; Knölker, M.</p> <p>2017-03-01</p> <p>We study the dynamics and topology of an emerging <span class="hlt">magnetic</span> <span class="hlt">flux</span> concentration using high spatial resolution spectropolarimetric data acquired with the Imaging Magnetograph eXperiment on board the sunrise balloon-borne solar observatory. We obtain the full vector <span class="hlt">magnetic</span> field and the line of sight (LOS) velocity through inversions of the Fe i line at 525.02 nm with the SPINOR code. The derived vector <span class="hlt">magnetic</span> field is used to trace <span class="hlt">magnetic</span> field lines. Two <span class="hlt">magnetic</span> <span class="hlt">flux</span> concentrations with different polarities and LOS velocities are found to be connected by a group of arch-shaped <span class="hlt">magnetic</span> field lines. The positive polarity footpoint is weaker (1100 G) and displays an upflow, while the negative polarity footpoint is stronger (2200 G) and shows a downflow. This configuration is naturally interpreted as a siphon flow along an arched <span class="hlt">magnetic</span> <span class="hlt">flux</span> tube.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMSM12A..02W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMSM12A..02W"><span>The Solar Wind - Magnetosphere Energy Coupling Function and Open <span class="hlt">Magnetic</span> <span class="hlt">Flux</span> Estimation: Two Science Aspects of the SMILE Mission</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, C.; Dai, L.; Sun, T.; Han, J.</p> <p>2015-12-01</p> <p>The Solar wind Magnetosphere Ionosphere Link Explorer (SMILE) is a novel self-standing mission to observe solar wind - magnetosphere coupling via simultaneous in situ solar wind /magnetosheath plasma and <span class="hlt">magnetic</span> field measurements, X-ray images of the magnetosphere, and UV images of global auroral <span class="hlt">distribution</span> defining system - level consequences. The SMILE mission is jointly supported by ESA and CSA, and the launch date is expected to be in 2021. SMILE will address several key outstanding questions concerning how the solar wind interacts with the magnetospheres on a global level. Quantitatively estimating the energy input from the solar wind into the magnetosphere on a global scale is still an observational challenge. Using global MHD simulations, we derive a new solar wind - magnetosphere energy coupling function. The X-ray images of the magnetosphere from the SMILE mission will help estimate the energy transfer from the solar wind into the magnetosphere. A second aspect SMILE can address is the open <span class="hlt">magnetic</span> <span class="hlt">flux</span>, which is closely related to <span class="hlt">magnetic</span> reconnections in the dayside magnetopause and magnetotail. In a similar way, we find that the open <span class="hlt">magnetic</span> <span class="hlt">flux</span> can be estimated through a combined parameter f, which is a function of the solar wind velocity, number density, the southern interplanetary <span class="hlt">magnetic</span> field strength, and the ionospheric Pederson conductance. The UV auroral images from SMILE will be used to determine the open <span class="hlt">magnetic</span> <span class="hlt">flux</span>, which may serve as a key space weather forecast element in the future.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3843682','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3843682"><span>Analysis of the <span class="hlt">Distribution</span> of <span class="hlt">Magnetic</span> Fluid inside Tumors by a Giant Magnetoresistance Probe</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Gooneratne, Chinthaka P.; Kurnicki, Adam; Yamada, Sotoshi; Mukhopadhyay, Subhas C.; Kosel, Jürgen</p> <p>2013-01-01</p> <p><span class="hlt">Magnetic</span> fluid hyperthermia (MFH) therapy uses the <span class="hlt">magnetic</span> component of electromagnetic fields in the radiofrequency spectrum to couple energy to <span class="hlt">magnetic</span> nanoparticles inside tumors. In MFH therapy, <span class="hlt">magnetic</span> fluid is injected into tumors and an alternating current (AC) <span class="hlt">magnetic</span> <span class="hlt">flux</span> is applied to heat the <span class="hlt">magnetic</span> fluid- filled tumor. If the temperature can be maintained at the therapeutic threshold of 42°C for 30 minutes or more, the tumor cells can be destroyed. Analyzing the <span class="hlt">distribution</span> of the <span class="hlt">magnetic</span> fluid injected into tumors prior to the heating step in MFH therapy is an essential criterion for homogenous heating of tumors, since a decision can then be taken on the strength and localization of the applied external AC <span class="hlt">magnetic</span> <span class="hlt">flux</span> density needed to destroy the tumor without affecting healthy cells. This paper proposes a methodology for analyzing the <span class="hlt">distribution</span> of <span class="hlt">magnetic</span> fluid in a tumor by a specifically designed giant magnetoresistance (GMR) probe prior to MFH heat treatment. Experimental results analyzing the <span class="hlt">distribution</span> of <span class="hlt">magnetic</span> fluid suggest that different <span class="hlt">magnetic</span> fluid weight densities could be estimated inside a single tumor by the GMR probe. PMID:24312280</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24312280','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24312280"><span>Analysis of the <span class="hlt">distribution</span> of <span class="hlt">magnetic</span> fluid inside tumors by a giant magnetoresistance probe.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Gooneratne, Chinthaka P; Kurnicki, Adam; Yamada, Sotoshi; Mukhopadhyay, Subhas C; Kosel, Jürgen</p> <p>2013-01-01</p> <p><span class="hlt">Magnetic</span> fluid hyperthermia (MFH) therapy uses the <span class="hlt">magnetic</span> component of electromagnetic fields in the radiofrequency spectrum to couple energy to <span class="hlt">magnetic</span> nanoparticles inside tumors. In MFH therapy, <span class="hlt">magnetic</span> fluid is injected into tumors and an alternating current (AC) <span class="hlt">magnetic</span> <span class="hlt">flux</span> is applied to heat the <span class="hlt">magnetic</span> fluid- filled tumor. If the temperature can be maintained at the therapeutic threshold of 42 °C for 30 minutes or more, the tumor cells can be destroyed. Analyzing the <span class="hlt">distribution</span> of the <span class="hlt">magnetic</span> fluid injected into tumors prior to the heating step in MFH therapy is an essential criterion for homogenous heating of tumors, since a decision can then be taken on the strength and localization of the applied external AC <span class="hlt">magnetic</span> <span class="hlt">flux</span> density needed to destroy the tumor without affecting healthy cells. This paper proposes a methodology for analyzing the <span class="hlt">distribution</span> of <span class="hlt">magnetic</span> fluid in a tumor by a specifically designed giant magnetoresistance (GMR) probe prior to MFH heat treatment. Experimental results analyzing the <span class="hlt">distribution</span> of <span class="hlt">magnetic</span> fluid suggest that different <span class="hlt">magnetic</span> fluid weight densities could be estimated inside a single tumor by the GMR probe.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1367091-heat-flux-modeling-using-ion-drift-effects-diii-mode-plasmas-resonant-magnetic-perturbations','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1367091-heat-flux-modeling-using-ion-drift-effects-diii-mode-plasmas-resonant-magnetic-perturbations"><span>Heat <span class="hlt">flux</span> modeling using ion drift effects in DIII-D H-mode plasmas with resonant <span class="hlt">magnetic</span> perturbations</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Wingen, Andreas; Schmitz, Oliver; Evans, Todd E.; ...</p> <p>2014-01-01</p> <p>The heat <span class="hlt">flux</span> patterns measured in low-collisionality DIII-D H-mode plasmas strongly deviate from simultaneously measured CII emission patterns, used as indicator of particle <span class="hlt">flux</span>, during applied resonant <span class="hlt">magnetic</span> perturbations. While the CII emission clearly shows typical striations, which are similar to <span class="hlt">magnetic</span> footprint patterns obtained from vacuum field line tracing, the heat <span class="hlt">flux</span> is usually dominated by one large peak at the strike point position. The vacuum approximation, which only considers applied <span class="hlt">magnetic</span> fields and neglects plasma response and plasma effects, cannot explain the shape of the observed heat <span class="hlt">flux</span> pattern. One possible explanation is the effect of particle drifts.more » This is included in the field line equations and the results are discussed with reference to the measurement. Electrons and ions show di fferent drift motions at thermal energy levels in a guiding center approximation. While electrons hardly deviate from the field lines, ions can drift several centimetres away from field line <span class="hlt">flux</span> surfaces. A model is presented in which an ion heat <span class="hlt">flux</span>, based on the ion drift motion from various kinetic energies as they contribute to a thermal Maxwellian <span class="hlt">distribution</span>, is calculated. The simulated heat <span class="hlt">flux</span> is directly compared to measurements with a varying edge safety factor q95. This analysis provides evidence for the dominate e ect of high-energy ions in carrying heat from the plasma inside the separatrix to the target. High-energy ions are deposited close to the unperturbed strike line while low-energy ions can travel into the striated <span class="hlt">magnetic</span> topology.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1367091','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1367091"><span>Heat <span class="hlt">flux</span> modeling using ion drift effects in DIII-D H-mode plasmas with resonant <span class="hlt">magnetic</span> perturbations</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Wingen, Andreas; Schmitz, Oliver; Evans, Todd E.; Spatschek, K. H.</p> <p>2014-01-01</p> <p>The heat <span class="hlt">flux</span> patterns measured in low-collisionality DIII-D H-mode plasmas strongly deviate from simultaneously measured CII emission patterns, used as indicator of particle <span class="hlt">flux</span>, during applied resonant <span class="hlt">magnetic</span> perturbations. While the CII emission clearly shows typical striations, which are similar to <span class="hlt">magnetic</span> footprint patterns obtained from vacuum field line tracing, the heat <span class="hlt">flux</span> is usually dominated by one large peak at the strike point position. The vacuum approximation, which only considers applied <span class="hlt">magnetic</span> fields and neglects plasma response and plasma effects, cannot explain the shape of the observed heat <span class="hlt">flux</span> pattern. One possible explanation is the effect of particle drifts. This is included in the field line equations and the results are discussed with reference to the measurement. Electrons and ions show di fferent drift motions at thermal energy levels in a guiding center approximation. While electrons hardly deviate from the field lines, ions can drift several centimetres away from field line <span class="hlt">flux</span> surfaces. A model is presented in which an ion heat <span class="hlt">flux</span>, based on the ion drift motion from various kinetic energies as they contribute to a thermal Maxwellian <span class="hlt">distribution</span>, is calculated. The simulated heat <span class="hlt">flux</span> is directly compared to measurements with a varying edge safety factor q95. This analysis provides evidence for the dominate e ect of high-energy ions in carrying heat from the plasma inside the separatrix to the target. High-energy ions are deposited close to the unperturbed strike line while low-energy ions can travel into the striated <span class="hlt">magnetic</span> topology.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017GeoRL..44.4489M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017GeoRL..44.4489M"><span>Electron butterfly <span class="hlt">distributions</span> at particular <span class="hlt">magnetic</span> latitudes observed during Juno's perijove pass</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ma, Q.; Thorne, R. M.; Li, W.; Zhang, X.-J.; Mauk, B. H.; Paranicas, C.; Haggerty, D. K.; Kurth, W. S.; Connerney, J. E. P.; Bagenal, F.; Bolton, S. J.</p> <p>2017-05-01</p> <p>We report observations of energetic electron butterfly <span class="hlt">distributions</span> measured in a narrow range of Jupiter's <span class="hlt">magnetic</span> latitudes by Juno during perijove 1. The electron butterfly <span class="hlt">distributions</span> are characterized as clear electron <span class="hlt">flux</span> peaks at 30-80° pitch angles, compared with the 90°-peaked pitch angle <span class="hlt">distributions</span> of the trapped electrons. Jupiter Energetic Particle Detector Instrument measurements during the close approach to Jupiter indicate a specific electron population with butterfly <span class="hlt">distributions</span> formed between the main auroral oval and the radiation belt. The off-90° <span class="hlt">flux</span> peak is most clearly observed at tens of keV energies and gradually merges toward 90° pitch angle at higher energies. By projecting the observed electron pitch angle <span class="hlt">distributions</span> along the <span class="hlt">magnetic</span> field line, we found that the electron butterfly <span class="hlt">distributions</span> are observed close to their source region. The particular electron <span class="hlt">distribution</span> is possibly formed by parallel acceleration of electrons through Landau resonance with electrostatic waves.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/419495','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/419495"><span>Stator-<span class="hlt">flux</span>-based vector control of induction machines in <span class="hlt">magnetic</span> saturation</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Hofmann, H.; Sanders, S.R.; Sullivan, C.</p> <p>1995-12-31</p> <p>In many variable-torque applications of induction machines it is desirable to operate the machine in <span class="hlt">magnetic</span> saturation, thus allowing the machine to produce higher torques. Stator-<span class="hlt">flux</span>-based control schemes have been developed as a possible alternative method of control of induction machines. Stator-<span class="hlt">flux</span>-based control schemes need not depend on the <span class="hlt">magnetic</span> characteristics of the machine, and hence are potentially more robust and easier to implement in <span class="hlt">magnetic</span> saturation than rotor-<span class="hlt">flux</span>-based control. The authors analyze the induction machine in saturation using a nonlinear {pi}-model of the machine`s <span class="hlt">magnetics</span>, and develop a control scheme in the stator <span class="hlt">flux</span> reference frame that is independent of <span class="hlt">magnetics</span>. Experiments carried out on a 3 hp, 1,800 rpm wound rotor induction machine show smooth operation of the control scheme at torque levels up to at least 4 times rated torque.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMSM51A2536S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMSM51A2536S"><span>MMS observations of small <span class="hlt">magnetic</span> <span class="hlt">flux</span> ropes in the near-tail (X > -11 Re)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Slavin, J. A.; Poh, G.; Le, G.; Strangeway, R. J.; Russell, C. T.; Anderson, B. J.; Fischer, D.; Plaschke, F.; Bromund, K. R.; Leinweber, H. K.; Kepko, L.; Chutter, M.; Le Contel, O.; Torbert, R. B.; Nakamura, R.; Magnes, W.; Baumjohann, W.</p> <p>2015-12-01</p> <p><span class="hlt">Magnetic</span> reconnection is the most important energy conversion process in the Earth's magnetotail. <span class="hlt">Flux</span> ropes are helical <span class="hlt">magnetic</span> structures created by multiple X-line reconnection in the tail current sheet in the presence of a guide field in the east - west direction. Many numerical simulations predict that the formation of small <span class="hlt">flux</span> ropes, referred to as secondary islands, takes place as reconnection transitions from the slow Sweet-Parker mode to fast reconnection with inertial scale neutral points. High time resolution MMS <span class="hlt">magnetic</span> and electric fields measurements are near ideal for the investigation of secondary island - type <span class="hlt">flux</span> ropes carried Earthward from downstream reconnnection sites, as well as their interaction with the strong dipolar <span class="hlt">magnetic</span> fields of the inner magnetosphere. We present and analyze initial MMS <span class="hlt">magnetic</span> field measurements of small <span class="hlt">flux</span> ropes in the near-tail during the commissioning phase while the spacecraft were in a "string-­of-­pearls" configuration.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016SoPh..291.2145R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016SoPh..291.2145R"><span>Typical Profiles and <span class="hlt">Distributions</span> of Plasma and <span class="hlt">Magnetic</span> Field Parameters in <span class="hlt">Magnetic</span> Clouds at 1 AU</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rodriguez, L.; Masías-Meza, J. J.; Dasso, S.; Démoulin, P.; Zhukov, A. N.; Gulisano, A. M.; Mierla, M.; Kilpua, E.; West, M.; Lacatus, D.; Paraschiv, A.; Janvier, M.</p> <p>2016-08-01</p> <p><span class="hlt">Magnetic</span> clouds (MCs) are a subset of interplanetary coronal mass ejections (ICMEs). They are important because of their simple internal <span class="hlt">magnetic</span> field configuration, which resembles a <span class="hlt">magnetic</span> <span class="hlt">flux</span> rope, and because they represent one of the most geoeffective types of solar transients. In this study, we analyze their internal structure using a superposed epoch method on 63 events observed at L1 by the Advance Composition Explorer (ACE), between 1998 and 2006. In this way, we obtain an average profile for each plasma and <span class="hlt">magnetic</span> field parameter at each point of the cloud. Furthermore, we take a fixed time-window upstream and downstream from the MC to also sample the regions preceding the cloud and the wake trailing it. We then perform a detailed analysis of the internal characteristics of the clouds and their surrounding solar wind environments. We find that the parameters studied are compatible with log-normal <span class="hlt">distribution</span> functions. The plasma β and the level of fluctuations in the <span class="hlt">magnetic</span> field vector are the best parameters to define the boundaries of MCs. We find that one third of the events shows a peak in plasma density close to the trailing edge of the <span class="hlt">flux</span> ropes. We provide several possible explanations for this result and investigate if the density peak is of a solar origin ( e.g. erupting prominence material) or formed during the <span class="hlt">magnetic</span> cloud travel from the Sun to 1 AU. The most plausible explanation is the compression due to a fast overtaking flow, coming from a coronal hole located to the east of the solar source region of the <span class="hlt">magnetic</span> cloud.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21541537','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21541537"><span>Fermionic condensate in a conical space with a circular boundary and <span class="hlt">magnetic</span> <span class="hlt">flux</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Bellucci, S.; Bezerra de Mello, E. R.; Saharian, A. A.</p> <p>2011-04-15</p> <p>The fermionic condensate is investigated in a (2+1)-dimensional conical spacetime in the presence of a circular boundary and a <span class="hlt">magnetic</span> <span class="hlt">flux</span>. It is assumed that on the boundary the fermionic field obeys the MIT bag boundary condition. For irregular modes, we consider a special case of boundary conditions at the cone apex, when the MIT bag boundary condition is imposed at a finite radius, which is then taken to zero. The fermionic condensate is a periodic function of the <span class="hlt">magnetic</span> <span class="hlt">flux</span> with the period equal to the <span class="hlt">flux</span> quantum. For both exterior and interior regions, the fermionic condensate is decomposed into boundary-free and boundary-induced parts. Two integral representations are given for the boundary-free part for arbitrary values of the opening angle of the cone and <span class="hlt">magnetic</span> <span class="hlt">flux</span>. At distances from the boundary larger than the Compton wavelength of the fermion particle, the condensate decays exponentially, with the decay rate depending on the opening angle of the cone. If the ratio of the <span class="hlt">magnetic</span> <span class="hlt">flux</span> to the <span class="hlt">flux</span> quantum is not a half-integer number for a massless field the boundary-free part in the fermionic condensate vanishes, whereas the boundary-induced part is negative. For half-integer values of the ratio of the <span class="hlt">magnetic</span> <span class="hlt">flux</span> to the <span class="hlt">flux</span> quantum, the irregular mode gives a nonzero contribution to the fermionic condensate in the boundary-free conical space.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_20 --> <div id="page_21" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="401"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015APS..DPPN12081V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015APS..DPPN12081V"><span>Sausage Instabilities on top of Kinking Lengthening Current-Carrying <span class="hlt">Magnetic</span> <span class="hlt">Flux</span> Tubes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>von der Linden, Jens; You, Setthivoine</p> <p>2015-11-01</p> <p>Observations indicate that the dynamics of <span class="hlt">magnetic</span> <span class="hlt">flux</span> tubes in our cosmos and terrestrial experiments involve fast topological change beyond MHD reconnection. Recent experiments suggest that hierarchies of instabilities coupling disparate plasma scales could be responsible for this fast topological change by accessing two-fluid and kinetic scales. This study will explore the possibility of sausage instabilities developing on top of a kink instability in lengthening current-carrying <span class="hlt">magnetic</span> <span class="hlt">flux</span> tubes. Current driven <span class="hlt">flux</span> tubes evolve over a wide range of aspect ratios k and current to <span class="hlt">magnetic</span> <span class="hlt">flux</span> ratios λ . An analytical stability criterion and numerical investigations, based on applying Newcomb's variational approach to idealized <span class="hlt">magnetic</span> <span class="hlt">flux</span> tubes with core and skin currents, indicate a dependence of the stability boundaries on current profiles and overlapping kink and sausage unstable regions in the k - λ trajectory of the <span class="hlt">flux</span> tubes. A triple electrode planar plasma gun (Mochi.LabJet) is designed to generate <span class="hlt">flux</span> tubes with discrete core and skin currents. Measurements from a fast-framing camera and a high resolution <span class="hlt">magnetic</span> probe are being assembled into stability maps of the k - λ space of <span class="hlt">flux</span> tubes. This work was sponsored in part by the US DOE Grant DE-SC0010340.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013GeoRL..40..250M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013GeoRL..40..250M"><span>Plasmaspheric filament: an isolated <span class="hlt">magnetic</span> <span class="hlt">flux</span> tube filled with dense plasmas</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Murakami, Go; Yoshikawa, Ichiro; Yoshioka, Kazuo; Yamazaki, Atsushi; Kagitani, Masato; Taguchi, Makoto; Kikuchi, Masayuki; Kameda, Shingo; Nakamura, Masato</p> <p>2013-01-01</p> <p><title type="main">Abstract<p label="1">The Telescope of Extreme Ultraviolet (TEX) onboard Japan's lunar orbiter KAGUYA provided the first sequential images of the Earth's plasmasphere from the "side" (meridian) view. The TEX instrument obtained the global <span class="hlt">distribution</span> of the terrestrial helium ions (He+) by detecting resonantly scattered emission at 30.4 nm. One of the most striking features of the plasmasphere found by TEX is an arc-shaped structure of enhanced brightness, which we call a "plasmaspheric filament". In the TEX image on 2 June 2008, the filament structure was clearly aligned to the dipole <span class="hlt">magnetic</span> field line of L = 3.7 at 7.3 <span class="hlt">magnetic</span> local time. Our analysis suggests that the filament represents an isolated <span class="hlt">flux</span> tube filled with four times higher He+ density than its neighbors. We found four events of plasmaspheric filament in the images obtained between March and June 2008, and in all four events, the geomagnetic activity was quite low. The plasmaspheric filament in the TEX image is the first evidence that a "finger" structure seen in the IMAGE-EUV image is the projection of an isolated <span class="hlt">flux</span> tube.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950057092&hterms=feynman&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dfeynman','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950057092&hterms=feynman&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dfeynman"><span><span class="hlt">Distributions</span> of the interplanetary <span class="hlt">magnetic</span> field revisited</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Feynman, Joan; Ruzmaikin, Alexander</p> <p>1994-01-01</p> <p>The adequacy of the power spectrum to characterize the variations of a parameter depends on whether or not the parameter has a Gaussian <span class="hlt">distribution</span>. We here perform very simple tests of Gaussianity on the <span class="hlt">distribution</span>. We here perform very simple tests of Gaussianity on the <span class="hlt">distributions</span> of the magnitudes of the interplanetary <span class="hlt">magnetic</span> field, and on the <span class="hlt">distributions</span> of the components; that is, we find the first four cumulants of the <span class="hlt">distributions</span> (mean, variance, skewness, and kurtosis) and their solar cycle variations. We find, consistent with other recent analyses, that the traditional <span class="hlt">distributions</span> of the 1-hour averaged magnitude are not <span class="hlt">distributed</span> normally or lognomally as has often been assumed and the 1-hour averaged z component is found to have a nonzero kurtosis. Thus the power spectrum is insufficient to completely characterize these variations and polyspectra are needed. We have isolated variations in the 1/f frequency region of the spectrum and show that the <span class="hlt">distributions</span> of the magnitudes have nonzero skewness and kurtosis, the magnitudes are not <span class="hlt">distributed</span> lognormally, and the <span class="hlt">distributions</span> of the components have nonzero kurtosis. Thus higher-order spectra are again needed for a full characterization.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25129072','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25129072"><span>Freezing and thawing of artificial ice by thermal switching of geometric frustration in <span class="hlt">magnetic</span> <span class="hlt">flux</span> lattices.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Trastoy, J; Malnou, M; Ulysse, C; Bernard, R; Bergeal, N; Faini, G; Lesueur, J; Briatico, J; Villegas, Javier E</p> <p>2014-09-01</p> <p>The problem of an ensemble of repulsive particles on a potential-energy landscape is common to many physical systems and has been studied in multiple artificial playgrounds. However, the latter usually involve fixed energy landscapes, thereby impeding in situ investigations of the particles' collective response to controlled changes in the landscape geometry. Here, we experimentally realize a system in which the geometry of the potential-energy landscape can be switched using temperature as the control knob. This realization is based on a high-temperature superconductor in which we engineer a nanoscale spatial modulation of the superconducting condensate. Depending on the temperature, the <span class="hlt">flux</span> quanta induced by an applied <span class="hlt">magnetic</span> field see either a geometrically frustrated energy landscape that favours an ice-like <span class="hlt">flux</span> ordering, or an unfrustrated landscape that yields a periodic <span class="hlt">flux</span> <span class="hlt">distribution</span>. This effect is reflected in a dramatic change in the superconductor's magneto-transport. The thermal switching of the energy landscape geometry opens new opportunities for the study of ordering and reorganization in repulsive particle manifolds.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ApJ...837..159D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ApJ...837..159D"><span>The Formation of <span class="hlt">Magnetic</span> Depletions and <span class="hlt">Flux</span> Annihilation Due to Reconnection in the Heliosheath</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Drake, J. F.; Swisdak, M.; Opher, M.; Richardson, J. D.</p> <p>2017-03-01</p> <p>The misalignment of the solar rotation axis and the <span class="hlt">magnetic</span> axis of the Sun produces a periodic reversal of the Parker spiral <span class="hlt">magnetic</span> field and the sectored solar wind. The compression of the sectors is expected to lead to reconnection in the heliosheath (HS). We present particle-in-cell simulations of the sectored HS that reflect the plasma environment along the Voyager 1 and 2 trajectories, specifically including unequal positive and negative azimuthal <span class="hlt">magnetic</span> <span class="hlt">flux</span> as seen in the Voyager data. Reconnection proceeds on individual current sheets until islands on adjacent current layers merge. At late time, bands of the dominant <span class="hlt">flux</span> survive, separated by bands of deep <span class="hlt">magnetic</span> field depletion. The ambient plasma pressure supports the strong <span class="hlt">magnetic</span> pressure variation so that pressure is anticorrelated with <span class="hlt">magnetic</span> field strength. There is little variation in the <span class="hlt">magnetic</span> field direction across the boundaries of the <span class="hlt">magnetic</span> depressions. At irregular intervals within the <span class="hlt">magnetic</span> depressions are long-lived pairs of <span class="hlt">magnetic</span> islands where the <span class="hlt">magnetic</span> field direction reverses so that spacecraft data would reveal sharp <span class="hlt">magnetic</span> field depressions with only occasional crossings with jumps in <span class="hlt">magnetic</span> field direction. This is typical of the <span class="hlt">magnetic</span> field data from the Voyager spacecraft. Voyager 2 data reveal that fluctuations in the density and <span class="hlt">magnetic</span> field strength are anticorrelated in the sector zone, as expected from reconnection, but not in unipolar regions. The consequence of the annihilation of subdominant <span class="hlt">flux</span> is a sharp reduction in the number of sectors and a loss in <span class="hlt">magnetic</span> <span class="hlt">flux</span>, as documented from the Voyager 1 <span class="hlt">magnetic</span> field and flow data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017SoPh..292..129V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017SoPh..292..129V"><span>Toroidal <span class="hlt">Flux</span> Ropes with Elliptical Cross Sections and Their <span class="hlt">Magnetic</span> Helicity</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vandas, M.; Romashets, E.</p> <p>2017-09-01</p> <p>Axially symmetric constant-alpha force-free <span class="hlt">magnetic</span> fields in toroidal <span class="hlt">flux</span> ropes with elliptical cross sections are constructed in order to investigate how their alphas and <span class="hlt">magnetic</span> helicities depend on parameters of the <span class="hlt">flux</span> ropes. <span class="hlt">Magnetic</span> configurations are found numerically using a general solution of a constant-alpha force-free field with an axial symmetry in cylindrical coordinates for a wide range of oblatenesses and aspect ratios. Resulting alphas and <span class="hlt">magnetic</span> helicities are approximated by polynomial expansions in parameters related to oblateness and aspect ratio. These approximations hold for toroidal as well as cylindrical <span class="hlt">flux</span> ropes with an accuracy better than or of about 1%. Using these formulae, we calculate relative helicities per unit length of two (probably very oblate) <span class="hlt">magnetic</span> clouds and show that they are very sensitive to the assumed <span class="hlt">magnetic</span> cloud shapes (circular versus elliptical cross sections).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22399314','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22399314"><span>Controlling the <span class="hlt">magnetic</span> susceptibility in an artificial elliptical quantum ring by <span class="hlt">magnetic</span> <span class="hlt">flux</span> and external Rashba effect</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Omidi, Mahboubeh Faizabadi, Edris</p> <p>2015-03-21</p> <p><span class="hlt">Magnetic</span> susceptibility is investigated in a man-made elliptical quantum ring in the presence of Rashba spin-orbit interactions and the <span class="hlt">magnetic</span> <span class="hlt">flux</span>. It is shown that <span class="hlt">magnetic</span> susceptibility as a function of <span class="hlt">magnetic</span> <span class="hlt">flux</span> changes between negative and positive signs periodically. The periodicity of the Aharonov-Bohm oscillations depends on the geometry of the region where <span class="hlt">magnetic</span> field is applied, the eccentricity, and number of sites in each chain ring (the elliptical ring is composed of chain rings). The <span class="hlt">magnetic</span> susceptibility sign can be reversed by tuning the Rashba spin-orbit strength as well. Both the <span class="hlt">magnetic</span> susceptibility strength and sign can be controlled via external spin-orbit interactions, which can be exploited in spintronics and nanoelectronics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..16.4546D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..16.4546D"><span>Plasma signatures in large Martian <span class="hlt">magnetic</span> <span class="hlt">flux</span> ropes: MARSIS/ASPERA-3 observations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Diéval, Catherine; Morgan, David; Duru, Firdevs; Gurnett, Donald</p> <p>2014-05-01</p> <p>Cylindrical structures of highly twisted <span class="hlt">magnetic</span> field (<span class="hlt">flux</span> ropes) have been observed at Mars, using measurements by the MAG-ER magnetometer-electron reflectometer onboard Mars Global Surveyor (MGS) and by the MARSIS radar sounder onboard Mars Express (MEX). Signatures of <span class="hlt">flux</span> ropes are spikes of <span class="hlt">magnetic</span> field strength and <span class="hlt">magnetic</span> field rotations. Both small scale <span class="hlt">flux</span> ropes (diameters of a few tens of km) and large scale <span class="hlt">flux</span> ropes (diameters of around 100 km) have been found at Mars. We look at times of presumed <span class="hlt">flux</span> ropes on the dayside of Mars, detected in the local <span class="hlt">magnetic</span> field strength given by MARSIS. The signatures in MARSIS are <span class="hlt">magnetic</span> field strength increases (peak strength reaches several tens to hundred nT) for several minutes (size of hundreds of km along the spacecraft track), found outside but near crustal <span class="hlt">magnetic</span> field regions. Although we cannot determine the presence of a <span class="hlt">magnetic</span> field rotation because of the lack of a magnetometer onboard MEX, we assume that these <span class="hlt">magnetic</span> field increases are large <span class="hlt">flux</span> ropes. There are indeed large <span class="hlt">flux</span> ropes with similar characteristics which were established by the magnetometer data from MGS, and thought to form by stretching and reconnection of crustal <span class="hlt">magnetic</span> field by the solar wind. On the other hand, MEX possesses in situ ion measurements, unlike MGS. We will use the ion and electron data from the ASPERA-3 particle instrument onboard MEX in order to characterize the plasma (ionospheric only or mixing with shocked plasma?) inside the <span class="hlt">flux</span> ropes, which will give hints on their origin.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.1641P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.1641P"><span>Tracking the <span class="hlt">magnetic</span> structure of <span class="hlt">flux</span> ropes from eruption to in-situ detection</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Palmerio, Erika; Kilpua, Emilia; Green, Lucie; James, Alexander; Pomoell, Jens; Valori, Gherardo</p> <p>2016-04-01</p> <p>Coronal Mass Ejections (CMEs) are spectacular explosions from the Sun where huge amounts of plasma and <span class="hlt">magnetic</span> <span class="hlt">flux</span> are ejected into the heliosphere. CMEs are built at the Sun as a force-free (J ×B = 0) <span class="hlt">magnetic</span> <span class="hlt">flux</span> rope. It is well-established that CMEs are the main drivers of intense <span class="hlt">magnetic</span> storms and various space weather effects at the Earth. One of the most significant problems for improving the long lead-time space weather predictions is that there is no method to directly measure the structure of CME <span class="hlt">magnetic</span> fields, neither in the onset process nor during the subsequent propagation from the solar surface to the Earth. The <span class="hlt">magnetic</span> properties of the CME <span class="hlt">flux</span> rope (<span class="hlt">magnetic</span> helicity sign, the <span class="hlt">flux</span> rope tilt and the direction of the <span class="hlt">flux</span> rope axial field) can be estimated based on the properties of the source active region and characteristics of the related structures, such as filament details, coronal EUV arcades and X-ray sigmoids. We present here a study of two CME <span class="hlt">flux</span> ropes. We compare their <span class="hlt">magnetic</span> structure using the synthesis of these indirect proxies based on multi-wavelength remote sensing observations with the structure detected in-situ near the orbit of the Earth.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017SuScT..30a5011P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017SuScT..30a5011P"><span>Reduction of <span class="hlt">flux</span>-creep in <span class="hlt">magnetized</span> bulk HTS by use of permanent <span class="hlt">magnets</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Parks, D.; Weinstein, R.; Davey, K.; Sawh, R.-P.; Carpenter, K.</p> <p>2017-01-01</p> <p>We report the effect of permanent <span class="hlt">magnet</span> (PM) collars on the <span class="hlt">flux</span>-creep rate of <span class="hlt">magnetized</span> bulk HTS. The creep rates of single-grain, cylindrical samples are measured with attached collars activated to various fields, B PM, in the range 0 ≤ B PM ≤ B PM,max, where B PM,max is the fully saturated field of the PM. As B PM varies, the creep rate of the HTS is found to maintain its well-known form—a constant fractional loss λ, of original residual field, per decade of time. However, the magnitude of λ decreases as B PM increases. The decrease in λ is found to be linearly dependent on increasing B PM. The collar field for which <span class="hlt">flux</span>-creep extrapolates to zero is found to be comparable to the maximum trappable field of the HTS bulk, B T,max. The properties of the dependence of λ on the HTS peak field, B T,max, the PM field, B PM, and the creep rate λ 0 with B PM = 0 permit the reduced creep rate in these experiments to be predicted by a universal equation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19820038624&hterms=Energy+transformations&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DEnergy%2Btransformations','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19820038624&hterms=Energy+transformations&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DEnergy%2Btransformations"><span>Low-energy ion <span class="hlt">distribution</span> functions on a <span class="hlt">magnetically</span> quiet day at geostationary altitude /L = 7/</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Singh, N.; Raitt, W. J.; Yasuhara, F.</p> <p>1982-01-01</p> <p>Ion energy and pitch angle <span class="hlt">distribution</span> functions are examined for a <span class="hlt">magnetically</span> quiet day using averaged data from ATS 6. For both field-aligned and perpendicular <span class="hlt">fluxes</span>, the populations have a mixture of characteristic energies, and the <span class="hlt">distribution</span> functions can be fairly well approximated by Maxwellian <span class="hlt">distributions</span> over three different energy bands in the range 3-600 eV. Pitch angle <span class="hlt">distributions</span> varying with local time, and energy <span class="hlt">distributions</span> are used to compute total ion density. Pitch angle scattering mechanisms responsible for the observed transformation of pitch angle <span class="hlt">distribution</span> are examined, and it is found that a <span class="hlt">magnetic</span> noise of a certain power spectral density belonging to the electromagnetic ion cyclotron mode near the ion cyclotron frequency can be effective in trapping the field aligned <span class="hlt">fluxes</span> by pitch angle scattering.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/495658','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/495658"><span>BaBar technical design report: Chapter 9, <span class="hlt">Magnet</span> coil and <span class="hlt">flux</span> return</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>O`Connor, T.; The BaBar Collaboration</p> <p>1995-03-01</p> <p>The BaBar <span class="hlt">magnet</span> is a thin, 1.5 T superconducting solenoid with a hexagonal <span class="hlt">flux</span> return. This chapter discusses the physics requirements and performance goals for the <span class="hlt">magnet</span>, describes key interfaces, and summarizes the projected <span class="hlt">magnet</span> performance. It also presents the design of the superconducting solenoid, including <span class="hlt">magnetic</span> design, cold mass design, quench protection and stability, cold mass cooling, cryostat design, and coil assembly and transportation. The cryogenic supply system and instrumentation are described briefly, and the <span class="hlt">flux</span> return is described.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22348494','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22348494"><span>Squeezing of particle <span class="hlt">distributions</span> by expanding <span class="hlt">magnetic</span> turbulence and space weather variability</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Ruffolo, D.; Seripienlert, A.; Tooprakai, P.; Chuychai, P.; Matthaeus, W. H. E-mail: achara.ser@mahidol.ac.th E-mail: p.chuychai@sci.mfu.ac.th</p> <p>2013-12-10</p> <p>Among the space weather effects due to gradual solar storms, greatly enhanced high-energy ion <span class="hlt">fluxes</span> contribute to radiation damage to satellites, spacecraft, and astronauts and dominate the hazards to air travelers, which motivates examination of the transport of high-energy solar ions to Earth's orbit. Ions of low kinetic energy (up to ∼2 MeV nucleon{sup –1}) from impulsive solar events exhibit abrupt changes due to filamentation of the <span class="hlt">magnetic</span> connection from the Sun, indicating that anisotropic, field-aligned <span class="hlt">magnetic</span> <span class="hlt">flux</span> tubelike structures persist to Earth's orbit. By employing a corresponding spherical two-component model of Alfvénic (slab) and two-dimensional <span class="hlt">magnetic</span> fluctuations to trace simulated trajectories in the solar wind, we show that the <span class="hlt">distribution</span> of high-energy (E ≥ 1 GeV) protons from gradual solar events is squeezed toward <span class="hlt">magnetic</span> <span class="hlt">flux</span> structures with a specific polarity because of the conical shape of the <span class="hlt">flux</span> structures. Conical <span class="hlt">flux</span> structures and the squeezing of energetic particle <span class="hlt">distributions</span> should occur in any astrophysical wind or jet with expanding, <span class="hlt">magnetized</span>, turbulent plasma. This transport phenomenon contributes to event-to-event variability in ground level enhancements of GeV-range ions from solar storms, presenting a fundamental uncertainty in space weather prediction.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016A%26A...591A..16P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016A%26A...591A..16P"><span>Twisted versus braided <span class="hlt">magnetic</span> <span class="hlt">flux</span> ropes in coronal geometry. II. Comparative behaviour</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Prior, C.; Yeates, A. R.</p> <p>2016-06-01</p> <p>Aims: Sigmoidal structures in the solar corona are commonly associated with <span class="hlt">magnetic</span> <span class="hlt">flux</span> ropes whose <span class="hlt">magnetic</span> field lines are twisted about a mutual axis. Their dynamical evolution is well studied, with sufficient twisting leading to large-scale rotation (writhing) and vertical expansion, possibly leading to ejection. Here, we investigate the behaviour of <span class="hlt">flux</span> ropes whose field lines have more complex entangled/braided configurations. Our hypothesis is that this internal structure will inhibit the large-scale morphological changes. Additionally, we investigate the influence of the background field within which the rope is embedded. Methods: A technique for generating tubular <span class="hlt">magnetic</span> fields with arbitrary axial geometry and internal structure, introduced in part I of this study, provides the initial conditions for resistive-MHD simulations. The tubular fields are embedded in a linear force-free background, and we consider various internal structures for the tubular field, including both twisted and braided topologies. These embedded <span class="hlt">flux</span> ropes are then evolved using a 3D MHD code. Results: Firstly, in a background where twisted <span class="hlt">flux</span> ropes evolve through the expected non-linear writhing and vertical expansion, we find that <span class="hlt">flux</span> ropes with sufficiently braided/entangled interiors show no such large-scale changes. Secondly, embedding a twisted <span class="hlt">flux</span> rope in a background field with a sigmoidal inversion line leads to eventual reversal of the large-scale rotation. Thirdly, in some cases a braided <span class="hlt">flux</span> rope splits due to reconnection into two twisted <span class="hlt">flux</span> ropes of opposing chirality - a phenomenon previously observed in cylindrical configurations. Conclusions: Sufficiently complex entanglement of the <span class="hlt">magnetic</span> field lines within a <span class="hlt">flux</span> rope can suppress large-scale morphological changes of its axis, with <span class="hlt">magnetic</span> energy reduced instead through reconnection and expansion. The structure of the background <span class="hlt">magnetic</span> field can significantly affect the changing morphology of a</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20060009303&hterms=electric+current&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Delectric%2Bcurrent','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20060009303&hterms=electric+current&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Delectric%2Bcurrent"><span>Cluster electric current density measurements within a <span class="hlt">magnetic</span> <span class="hlt">flux</span> rope in the plasma sheet</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Slavin, J. A.; Lepping, R. P.; Gjerloev, J.; Goldstein, M. L.; Fairfield, D. H.; Acuna, M. H.; Balogh, A.; Dunlop, M.; Kivelson, M. G.; Khurana, K.</p> <p>2003-01-01</p> <p>On August 22, 2001 all 4 Cluster spacecraft nearly simultaneously penetrated a <span class="hlt">magnetic</span> <span class="hlt">flux</span> rope in the tail. The <span class="hlt">flux</span> rope encounter took place in the central plasma sheet, Beta(sub i) approx. 1-2, near the leading edge of a bursty bulk flow. The "time-of-flight" of the <span class="hlt">flux</span> rope across the 4 spacecraft yielded V(sub x) approx. 700 km/s and a diameter of approx.1 R(sub e). The speed at which the <span class="hlt">flux</span> rope moved over the spacecraft is in close agreement with the Cluster plasma measurements. The <span class="hlt">magnetic</span> field profiles measured at each spacecraft were first modeled separately using the Lepping-Burlaga force-free <span class="hlt">flux</span> rope model. The results indicated that the center of the <span class="hlt">flux</span> rope passed northward (above) s/c 3, but southward (below) of s/c 1, 2 and 4. The peak electric currents along the central axis of the <span class="hlt">flux</span> rope predicted by these single-s/c models were approx.15-19 nA/sq m. The 4-spacecraft Cluster <span class="hlt">magnetic</span> field measurements provide a second means to determine the electric current density without any assumption regarding <span class="hlt">flux</span> rope structure. The current profile determined using the curlometer technique was qualitatively similar to those determined by modeling the individual spacecraft <span class="hlt">magnetic</span> field observations and yielded a peak current density of 17 nA/m2 near the central axis of the rope. However, the curlometer results also showed that the <span class="hlt">flux</span> rope was not force-free with the component of the current density perpendicular to the <span class="hlt">magnetic</span> field exceeding the parallel component over the forward half of the rope, perhaps due to the pressure gradients generated by the collision of the BBF with the inner magnetosphere. Hence, while the single-spacecraft models are very successful in fitting <span class="hlt">flux</span> rope <span class="hlt">magnetic</span> field and current variations, they do not provide a stringent test of the force-free condition.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/10145105','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/10145105"><span>Computer model simulation of null-<span class="hlt">flux</span> <span class="hlt">magnetic</span> suspension and guidance</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>He, Jianliang; Rote, D.M.</p> <p>1992-06-01</p> <p>This paper discusses the <span class="hlt">magnetic</span> force computations in a null-<span class="hlt">flux</span> suspension system using dynamic circuit theory. A computer simulation model that can be used to compute <span class="hlt">magnetic</span> forces and predict the system performance is developed on the basis of dynamic circuit theory. Numerical examples are presented to demonstrate the application of the model. The performance of the null-<span class="hlt">flux</span> suspension system is simulated and discussed. 8 refs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ApJ...846..165U','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ApJ...846..165U"><span>Modeling Coronal Response in Decaying Active Regions with <span class="hlt">Magnetic</span> <span class="hlt">Flux</span> Transport and Steady Heating</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ugarte-Urra, Ignacio; Warren, Harry P.; Upton, Lisa A.; Young, Peter R.</p> <p>2017-09-01</p> <p>We present new measurements of the dependence of the extreme ultraviolet (EUV) radiance on the total <span class="hlt">magnetic</span> <span class="hlt">flux</span> in active regions as obtained from the Atmospheric Imaging Assembly (AIA) and the Helioseismic and <span class="hlt">Magnetic</span> Imager on board the Solar Dynamics Observatory. Using observations of nine active regions tracked along different stages of evolution, we extend the known radiance—<span class="hlt">magnetic</span> <span class="hlt">flux</span> power-law relationship (I\\propto {{{Φ }}}α ) to the AIA 335 Å passband, and the Fe xviii 93.93 Å spectral line in the 94 Å passband. We find that the total unsigned <span class="hlt">magnetic</span> <span class="hlt">flux</span> divided by the polarity separation ({{Φ }}/D) is a better indicator of radiance for the Fe xviii line with a slope of α =3.22+/- 0.03. We then use these results to test our current understanding of <span class="hlt">magnetic</span> <span class="hlt">flux</span> evolution and coronal heating. We use magnetograms from the simulated decay of these active regions produced by the Advective <span class="hlt">Flux</span> Transport model as boundary conditions for potential extrapolations of the <span class="hlt">magnetic</span> field in the corona. We then model the hydrodynamics of each individual field line with the Enthalpy-based Thermal Evolution of Loops model with steady heating scaled as the ratio of the average field strength and the length (\\bar{B}/L) and render the Fe xviii and 335 Å emission. We find that steady heating is able to partially reproduce the magnitudes and slopes of the EUV radiance—<span class="hlt">magnetic</span> <span class="hlt">flux</span> relationships and discuss how impulsive heating can help reconcile the discrepancies. This study demonstrates that combined models of <span class="hlt">magnetic</span> <span class="hlt">flux</span> transport, <span class="hlt">magnetic</span> topology, and heating can yield realistic estimates for the decay of active region radiances with time.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005EJPh...26..783S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005EJPh...26..783S"><span>Comparing a current-carrying circular wire with polygons of equal perimeter: <span class="hlt">magnetic</span> field versus <span class="hlt">magnetic</span> <span class="hlt">flux</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Silva, J. P.; Silvestre, A. J.</p> <p>2005-09-01</p> <p>We compare the <span class="hlt">magnetic</span> field at the centre and the self-<span class="hlt">magnetic</span> <span class="hlt">flux</span> through a current-carrying circular loop, with those obtained for current-carrying polygons with the same perimeter. As the <span class="hlt">magnetic</span> field diverges at the position of the wires, we compare the self-<span class="hlt">fluxes</span> utilizing several regularization procedures. The calculation is best performed utilizing the vector potential, thus highlighting its usefulness in practical applications. Our analysis answers some of the intuition challenges students face when they encounter a related simple textbook example. These results can be applied directly to the determination of mutual inductances in a variety of situations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/872981','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/872981"><span>Direct control of air gap <span class="hlt">flux</span> in permanent <span class="hlt">magnet</span> machines</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Hsu, John S.</p> <p>2000-01-01</p> <p>A method and apparatus for field weakening in PM machines uses field weakening coils (35, 44, 45, 71, 72) to produce <span class="hlt">flux</span> in one or more stators (34, 49, 63, 64), including a <span class="hlt">flux</span> which counters <span class="hlt">flux</span> normally produced in air gaps between the stator(s) (34, 49, 63, 64) and the rotor (20, 21, 41, 61) which carries the PM poles. Several modes of operation are introduced depending on the magnitude and polarity of current in the field weakening coils (35, 44, 45, 71, 72). The invention is particularly useful for, but not limited to, the electric vehicle drives and PM generators.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24218211','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24218211"><span>Isotopomer measurement techniques in metabolic <span class="hlt">flux</span> analysis I: nuclear <span class="hlt">magnetic</span> resonance.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Truong, Quyen X; Yoon, Jong Moon; Shanks, Jacqueline V</p> <p>2014-01-01</p> <p>Two-dimensional [(1)H, (13)C] heteronuclear single quantum correlation (HSQC) spectroscopy nuclear <span class="hlt">magnetic</span> resonance (NMR) is a comprehensive tool in metabolic <span class="hlt">flux</span> analysis using (13)C-labeling experiments. NMR is particularly relevant when extensive isotopomer measurements are required, such as for plant cells and tissues, which contain multiple cellular compartments. Several isotope isomers (isotopomers) can be detected and their <span class="hlt">distribution</span> extracted quantitatively from a single 2-D HSQC NMR spectrum. For example, 2-D HSQC detects the labeling patterns of adjacent carbon atoms and provides the enrichment of individual carbon atoms of the amino acids and glucosyl and mannosyl units present in hydrolysates of glycosylated protein. The HSQC analysis can quantitatively distinguish differences between the glucosyl units in the starch hydrolysate and a protein hydrolysate of plant biomass: this specifies crucial information about compartmentalization in the plant system. The peak structures obtained from the HSQC experiment show multiplet patterns that are directly related to the isotopomer abundances. These abundances have a nonlinear relationship to the <span class="hlt">fluxes</span> via isotopomer balancing. <span class="hlt">Fluxes</span> are obtained from the numerical solution of these balances and a stoichiometric model that includes biomass composition data as well as consumption rates of carbohydrate and nitrogen sources. Herein, we describe the methods for the experimental measurements for <span class="hlt">flux</span> analysis, i.e., determination of the biomass composition (lipid, protein, soluble sugar, and starch) as well as detailed procedures of acid hydrolysis of protein and starch samples and NMR sample preparation, using soybean embryo culture as the model plant system. Techniques to obtain the relative intensity of 16 amino acids and glucosyl units for protein hydrolysate and the glucosyl units of starch hydrolysate of soybean embryos in 2-D HSQC NMR spectra also are provided.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_21 --> <div id="page_22" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="421"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22434190','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22434190"><span>Observation of an evolving <span class="hlt">magnetic</span> <span class="hlt">flux</span> rope before and during a solar eruption.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zhang, Jie; Cheng, Xin; Ding, Ming-de</p> <p>2012-03-20</p> <p>Explosive energy release is a common phenomenon occurring in <span class="hlt">magnetized</span> plasma systems ranging from laboratories, Earth's magnetosphere, the solar corona and astrophysical environments. Its physical explanation is usually attributed to <span class="hlt">magnetic</span> reconnection in a thin current sheet. Here we report the important role of <span class="hlt">magnetic</span> <span class="hlt">flux</span> rope structure, a volumetric current channel, in producing explosive events. The <span class="hlt">flux</span> rope is observed as a hot channel before and during a solar eruption from the Atmospheric Imaging Assembly telescope on board the Solar Dynamic Observatory. It initially appears as a twisted and writhed sigmoidal structure with a temperature as high as 10 MK, and then transforms toward a semi-circular shape during a slow-rise phase, which is followed by fast acceleration and onset of a flare. The observations suggest that the instability of the <span class="hlt">magnetic</span> <span class="hlt">flux</span> rope triggers the eruption, thus making a major addition to the traditional <span class="hlt">magnetic</span>-reconnection paradigm.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014cosp...40E3507V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014cosp...40E3507V"><span>22 year cycle in the imbalance of the photospheric <span class="hlt">magnetic</span> <span class="hlt">fluxes</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vernova, Elena; Baranov, Dmitrii; Tyasto, Marta</p> <p></p> <p>The manifestation of the 22 year solar <span class="hlt">magnetic</span> cycle in the imbalance of positive and negative photospheric <span class="hlt">magnetic</span> <span class="hlt">fluxes</span> is studied. For the analysis we use synoptic maps of the photospheric <span class="hlt">magnetic</span> field of Kitt Peak Observatory (1976 - 2003) and John Wilcox Observatory in Stanford (1976 - 2012). We consider strong <span class="hlt">magnetic</span> fields for the heliolatitudes in the interval from +40° to -40°. It is shown that the sign of the imbalance between positive and negative <span class="hlt">fluxes</span> remains constant during 11 years from one inversion of the Sun’s global <span class="hlt">magnetic</span> field to the next one and always coincides with the sign of the polar field in the Northern hemisphere. Thus, the imbalance between the <span class="hlt">magnetic</span> <span class="hlt">fluxes</span> of different polarities changes according to the 22 year cycle. The sign of the imbalance is determined both by the phase of the solar cycle (before or after the inversion) and by the parity of the solar cycle. The imbalance of positive and negative <span class="hlt">magnetic</span> <span class="hlt">fluxes</span> can be observed not only for the strong fields in the sunspot zone. The mean <span class="hlt">magnetic</span> field of the Sun (Sun as a star), which is determined by the net <span class="hlt">flux</span> of the background fields, changes according to the same pattern as the imbalance of the strong fields. The regular changes of the imbalance of the photospheric <span class="hlt">magnetic</span> fields are reflected also in the parameters of heliosphere. We show the connection of the imbalance with the quadrupole component of the photospheric <span class="hlt">magnetic</span> field and with the imbalance of the interplanetary <span class="hlt">magnetic</span> field (the difference between the numbers of the days with positive and negative polarities of the interplanetary <span class="hlt">magnetic</span> field near Earth).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AIPC.1717e0004K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AIPC.1717e0004K"><span>Design, simulation and analysis of 3 kW low speed axial <span class="hlt">flux</span> permanent <span class="hlt">magnet</span> generator</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kasim, Muhammad; Irasari, Pudji; Hikmawan, Muhammad Fathul</p> <p>2016-03-01</p> <p>Design and simulation of an axial <span class="hlt">flux</span> permanent <span class="hlt">magnet</span> generator (AFPMG) have been described in this paper. It was designed using the single rotor - single stator construction. The analytical method was using in the design process. The design process also employed the simulation using Finite Element Method <span class="hlt">Magnetics</span> (FEMM) 4.2 software for identifying the <span class="hlt">magnetic</span> characteristic and heat transfer. The effect of fill factor (FF) variation on the generator performances also observed in this paper. The design result shows that using the selected FF, the conductor diameter, power output, efficiency and heat <span class="hlt">distribution</span> are affected but not for the Bg. The generator output can achieve up to 5.2 kW using the FF 0.4 which is more than assumed power output at the pre-design using FF 0.3. It also can be seen that the increasing FF will increase the power output and the efficiency. Despite a higher temperature compared with FF 0.3 and 0.35, the value of 0.4 is the most appropriate FF for designing the AFPMG.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ApJS..229...17S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ApJS..229...17S"><span>Estimation of the <span class="hlt">Magnetic</span> <span class="hlt">Flux</span> Emergence Rate in the Quiet Sun from Sunrise Data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Smitha, H. N.; Anusha, L. S.; Solanki, S. K.; Riethmüller, T. L.</p> <p>2017-03-01</p> <p>Small-scale internetwork (IN) features are thought to be the major source of fresh <span class="hlt">magnetic</span> <span class="hlt">flux</span> in the quiet Sun. During its first science flight in 2009, the balloon-borne observatory Sunrise captured images of the <span class="hlt">magnetic</span> fields in the quiet Sun at a high spatial resolution. Using these data we measure the rate at which the IN features bring <span class="hlt">magnetic</span> <span class="hlt">flux</span> to the solar surface. In a previous paper it was found that the lowest <span class="hlt">magnetic</span> <span class="hlt">flux</span> in small-scale features detected using the Sunrise observations is 9 × 1014 Mx. This is nearly an order of magnitude smaller than the smallest <span class="hlt">fluxes</span> of features detected in observations from the Hinode satellite. In this paper, we compute the <span class="hlt">flux</span> emergence rate (FER) by accounting for such small <span class="hlt">fluxes</span>, which was not possible before Sunrise. By tracking the features with <span class="hlt">fluxes</span> in the range {10}15{--}{10}18 Mx, we measure an FER of 1100 {Mx} {{cm}}-2 {{day}}-1. The smaller features with <span class="hlt">fluxes</span> ≤slant {10}16 Mx are found to be the dominant contributors to the solar <span class="hlt">magnetic</span> <span class="hlt">flux</span>. The FER found here is an order of magnitude higher than the rate from Hinode, obtained with a similar feature tracking technique. A wider comparison with the literature shows, however, that the exact technique of determining the rate of the appearance of new <span class="hlt">flux</span> can lead to results that differ by up to two orders of magnitude, even when applied to similar data. The causes of this discrepancy are discussed and first qualitative explanations proposed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017GeoRL..44.7653H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017GeoRL..44.7653H"><span>On the origins of <span class="hlt">magnetic</span> <span class="hlt">flux</span> ropes in near-Mars magnetotail current sheets</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hara, Takuya; Harada, Yuki; Mitchell, David L.; DiBraccio, Gina A.; Espley, Jared R.; Brain, David A.; Halekas, Jasper S.; Seki, Kanako; Luhmann, Janet G.; McFadden, James P.; Mazelle, Christian; Jakosky, Bruce M.</p> <p>2017-08-01</p> <p>We analyze Mars Atmosphere and Volatile EvolutioN (MAVEN) observations of <span class="hlt">magnetic</span> <span class="hlt">flux</span> ropes embedded in Martian magnetotail current sheets, in order to evaluate the role of magnetotail reconnection in their generations. We conduct a minimum variance analysis to infer the generation processes of magnetotail <span class="hlt">flux</span> ropes from the geometrical configuration of the individual <span class="hlt">flux</span> rope axial orientation with respect to the overall current sheet. Of 23 <span class="hlt">flux</span> ropes detected in current sheets in the near-Mars (˜1-3 Martian radii downstream) magnetotail, only 3 (possibly 4) can be explained by the magnetotail reconnection scenario, while the vast majority of the events (19 events) are more consistent with <span class="hlt">flux</span> ropes that are originally generated in the dayside ionosphere and subsequently transported into the nightside magnetotail. The mixed origins of the detected <span class="hlt">flux</span> ropes imply complex nature of generation and transport of Martian magnetotail <span class="hlt">flux</span> ropes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PhPl...24b2120L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PhPl...24b2120L"><span>Generation and evolution of <span class="hlt">magnetic</span> field in the relativistic plasma following q-nonextensive <span class="hlt">distribution</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lin, Fu-Jun; Chen, Zong-Hua; Li, Xiao-Qing; Liao, Jing-Jing; Zhu, Yun</p> <p>2017-02-01</p> <p>A GigaGauss quasi-steady <span class="hlt">magnetic</span> field can be generated in astrophysical plasmas and laser-produced plasmas with high-frequency electromagnetic radiation through wave-wave and wave-particle interactions. A set of governing equations for this field are obtained in the plasma consisting of ultra-relativistic electrons following q-nonextensive <span class="hlt">distribution</span>. The numerical results show that the initial field is unstable and can collapse to generate various spatially intermittent <span class="hlt">magnetic</span> <span class="hlt">flux</span> tubes. It can also be found that the behavior of the <span class="hlt">magnetic</span> field is greatly dependent on the nonextensive index q, which may be helpful in understanding the <span class="hlt">magnetic</span> turbulence.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://eric.ed.gov/?q=monitoring+AND+water&pg=5&id=EJ207057','ERIC'); return false;" href="https://eric.ed.gov/?q=monitoring+AND+water&pg=5&id=EJ207057"><span>Radial <span class="hlt">Flux</span> <span class="hlt">Distribution</span> of Low-Energy Neutrons.</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Higinbotham, J.</p> <p>1979-01-01</p> <p>Describes an experiment designed to illustrate the basic principle involved in the process of moderation of fast neutrons by water, and the monitoring of the low-energy neutron <span class="hlt">flux</span> using indium as a probe. (GA)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=Indium&id=EJ207057','ERIC'); return false;" href="http://eric.ed.gov/?q=Indium&id=EJ207057"><span>Radial <span class="hlt">Flux</span> <span class="hlt">Distribution</span> of Low-Energy Neutrons.</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Higinbotham, J.</p> <p>1979-01-01</p> <p>Describes an experiment designed to illustrate the basic principle involved in the process of moderation of fast neutrons by water, and the monitoring of the low-energy neutron <span class="hlt">flux</span> using indium as a probe. (GA)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JGRA..122..828H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JGRA..122..828H"><span>MAVEN observations of a giant ionospheric <span class="hlt">flux</span> rope near Mars resulting from interaction between the crustal and interplanetary draped <span class="hlt">magnetic</span> fields</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hara, Takuya; Brain, David A.; Mitchell, David L.; Luhmann, Janet G.; Seki, Kanako; Hasegawa, Hiroshi; Mcfadden, James P.; Halekas, Jasper S.; Espley, Jared R.; Harada, Yuki; Livi, Roberto; DiBraccio, Gina A.; Connerney, John E. P.; Mazelle, Christian; Andersson, Laila; Jakosky, Bruce M.</p> <p>2017-01-01</p> <p>We present Mars Atmosphere and Volatile EvolutioN (MAVEN) observations of a giant <span class="hlt">magnetic</span> <span class="hlt">flux</span> rope in the Martian dayside ionosphere. The <span class="hlt">flux</span> rope was observed at an altitude of <300 km, downstream from strong subsolar crustal <span class="hlt">magnetic</span> fields. The peak field amplitude was ˜200 nT, resulting in the largest difference between the observed <span class="hlt">magnetic</span> field strength and a model for crustal <span class="hlt">magnetic</span> fields of the entire MAVEN primary science phase. MAVEN detected planetary ions, including H+, O+, and O2+, across the structure. The axial orientation estimated for the <span class="hlt">flux</span> rope indicates that it likely formed as a result of interactions between the local crustal and overlaid draped interplanetary <span class="hlt">magnetic</span> fields. Pitch angle <span class="hlt">distributions</span> of ionospheric photoelectrons imply that this structure is connected to the Martian upper atmosphere. However, the <span class="hlt">flux</span> rope is not present in observations at the next commensurable orbit crossing (approximately two Martian days later), implying that it eventually detaches from the atmosphere and is carried downstream. The <span class="hlt">flux</span> rope observations occurred during an interplanetary coronal mass ejection event at Mars, suggesting that the disturbed upstream state played a role in allowing the interplanetary <span class="hlt">magnetic</span> field to penetrate deeper into the Martian ionosphere than is typical, allowing the formation of the <span class="hlt">flux</span> rope.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JGRA..121.7664S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JGRA..121.7664S"><span>Generalized magnetotail equilibria: Effects of the dipole field, thin current sheets, and <span class="hlt">magnetic</span> <span class="hlt">flux</span> accumulation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sitnov, M. I.; Merkin, V. G.</p> <p>2016-08-01</p> <p>Generalizations of the class of quasi-1-D solutions of the 2-D Grad-Shafranov equation, first considered by Schindler in 1972, are investigated. It is shown that the effect of the dipole field, treated as a perturbation, can be included into the original 1972 class solution by modification of the boundary conditions. Some of the solutions imply the formation of singularly thin current sheets. Equilibrium solutions for such sheets resolving their singular current structure on the scales comparable to the thermal ion gyroradius can be obtained assuming anisotropic and nongyrotropic plasma <span class="hlt">distributions</span>. It is shown that one class of such equilibria with the dipole-like boundary perturbation describes bifurcation of the near-Earth current sheet. Another class of weakly anisotropic equilibria with thin current sheets embedded into a thicker plasma sheet helps explain the formation of thin current sheets in a relatively distant tail, where such sheets can provide ion Landau dissipation for spontaneous <span class="hlt">magnetic</span> reconnection. The free energy for spontaneous reconnection can be provided due to accumulation of the <span class="hlt">magnetic</span> <span class="hlt">flux</span> at the tailward end of the closed field line region. The corresponding hump in the normal <span class="hlt">magnetic</span> field profile Bz(x,z = 0) creates a nonzero gradient along the tail. The resulting gradient of the equatorial <span class="hlt">magnetic</span> field pressure is shown to be balanced by the pressure gradient and the <span class="hlt">magnetic</span> tension force due to the higher-order correction of the latter in the asymptotic expansion of the tail equilibrium in the ratio of the characteristic tail current sheet variations across and along the tail.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006APS..DPPDI1001Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006APS..DPPDI1001Y"><span>Dynamic and Stagnating Plasma Flow Leading to <span class="hlt">Magnetic-Flux</span>-Tube Collimation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>You, Setthivoine</p> <p>2006-10-01</p> <p>This talk presents experimental observations, first reported by You, Yun, Bellan in PRL (art. 045002, 2005), strongly supporting the ``MHD pump-collimation'' model proposed by Bellan in Phys. Plasmas (vol. 10, p.1999, 2003). Collimated, plasma-filled, <span class="hlt">magnetic</span> <span class="hlt">flux</span> tubes are observed over a tremendous range of scales. In laboratory plasmas, on the surface of the Sun, or jetting out of galactic cores, these <span class="hlt">flux</span> tubes are extremely collimated, with cross-sections that do not vary much along the length of the tube even in the absence of external <span class="hlt">magnetic</span> fields or any significant ambient medium pressure. Furthermore, these <span class="hlt">flux</span> tubes are not in static equilibrium but exhibit strong plasma flows on a rapid time-scale compared to their overall motion within their surroundings. The Caltech experiment simulates <span class="hlt">magnetically</span>-driven astrophysical jets at the laboratory scale by imposing boundary conditions analogous to astrophysical jet boundary conditions and with plasma dimensionless numbers comparable to numerical MHD simulations. Observations show a distinct sequence of events. The initial <span class="hlt">flux</span> tubes flare out into the large vacuum, because the <span class="hlt">magnetic</span> field weakens away from the source. As electrical current flows, the <span class="hlt">flux</span> tubes become denser and more collimated while sucking plasma from gas sources at the system boundary, effectively acting like a magnetohydrodynamic pump. These <span class="hlt">flux</span> tubes then merge together into a single column which jets out into the vacuum. The jet continues the same pumping process, to become even denser and more collimated, until either the electrical current or the supply of particles stop. The strong plasma flow convects frozen-in <span class="hlt">magnetic</span> <span class="hlt">flux</span> to regions of weaker <span class="hlt">magnetic</span> field at the end of the tube, and as the flow stagnates there, <span class="hlt">magnetic</span> <span class="hlt">flux</span> piles up, pinching the tube into a collimated filament.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ApPhL.110f2601Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ApPhL.110f2601Z"><span>A portable <span class="hlt">magnetic</span> field of >3 T generated by the <span class="hlt">flux</span> jump assisted, pulsed field <span class="hlt">magnetization</span> of bulk superconductors</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhou, Difan; Ainslie, Mark D.; Shi, Yunhua; Dennis, Anthony R.; Huang, Kaiyuan; Hull, John R.; Cardwell, David A.; Durrell, John H.</p> <p>2017-02-01</p> <p>A trapped <span class="hlt">magnetic</span> field of greater than 3 T has been achieved in a single grain GdBa2Cu3O7-δ (GdBaCuO) bulk superconductor of diameter 30 mm by employing pulsed field <span class="hlt">magnetization</span>. The <span class="hlt">magnet</span> system is portable and operates at temperatures between 50 K and 60 K. <span class="hlt">Flux</span> jump behaviour was observed consistently during <span class="hlt">magnetization</span> when the applied pulsed field, Ba, exceeded a critical value (e.g., 3.78 T at 60 K). A sharp dBa/dt is essential to this phenomenon. This <span class="hlt">flux</span> jump behaviour enables the <span class="hlt">magnetic</span> <span class="hlt">flux</span> to penetrate fully to the centre of the bulk superconductor, resulting in full <span class="hlt">magnetization</span> of the sample without requiring an applied field as large as that predicted by the Bean model. We show that this <span class="hlt">flux</span> jump behaviour can occur over a wide range of fields and temperatures, and that it can be exploited in a practical quasi-permanent <span class="hlt">magnet</span> system.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhPl...22d2702V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhPl...22d2702V"><span><span class="hlt">Magnetic</span> <span class="hlt">flux</span> and heat losses by diffusive, advective, and Nernst effects in <span class="hlt">magnetized</span> liner inertial fusion-like plasma</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Velikovich, A. L.; Giuliani, J. L.; Zalesak, S. T.</p> <p>2015-04-01</p> <p>The <span class="hlt">magnetized</span> liner inertial fusion (MagLIF) approach to inertial confinement fusion [Slutz et al., Phys. Plasmas 17, 056303 (2010); Cuneo et al., IEEE Trans. Plasma Sci. 40, 3222 (2012)] involves subsonic/isobaric compression and heating of a deuterium-tritium plasma with frozen-in <span class="hlt">magnetic</span> <span class="hlt">flux</span> by a heavy cylindrical liner. The losses of heat and <span class="hlt">magnetic</span> <span class="hlt">flux</span> from the plasma to the liner are thereby determined by plasma advection and gradient-driven transport processes, such as thermal conductivity, <span class="hlt">magnetic</span> field diffusion, and thermomagnetic effects. Theoretical analysis based on obtaining exact self-similar solutions of the classical collisional Braginskii's plasma transport equations in one dimension demonstrates that the heat loss from the hot compressed <span class="hlt">magnetized</span> plasma to the cold liner is dominated by transverse heat conduction and advection, and the corresponding loss of <span class="hlt">magnetic</span> <span class="hlt">flux</span> is dominated by advection and the Nernst effect. For a large electron Hall parameter ( ωeτe≫1 ), the effective diffusion coefficients determining the losses of heat and <span class="hlt">magnetic</span> <span class="hlt">flux</span> to the liner wall are both shown to decrease with ωeτe as does the Bohm diffusion coefficient c T /(16 e B ) , which is commonly associated with low collisionality and two-dimensional transport. We demonstrate how this family of exact solutions can be used for verification of codes that model the MagLIF plasma dynamics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22408328','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22408328"><span><span class="hlt">Magnetic</span> <span class="hlt">flux</span> and heat losses by diffusive, advective, and Nernst effects in <span class="hlt">magnetized</span> liner inertial fusion-like plasma</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Velikovich, A. L.; Giuliani, J. L.; Zalesak, S. T.</p> <p>2015-04-15</p> <p>The <span class="hlt">magnetized</span> liner inertial fusion (MagLIF) approach to inertial confinement fusion [Slutz et al., Phys. Plasmas 17, 056303 (2010); Cuneo et al., IEEE Trans. Plasma Sci. 40, 3222 (2012)] involves subsonic/isobaric compression and heating of a deuterium-tritium plasma with frozen-in <span class="hlt">magnetic</span> <span class="hlt">flux</span> by a heavy cylindrical liner. The losses of heat and <span class="hlt">magnetic</span> <span class="hlt">flux</span> from the plasma to the liner are thereby determined by plasma advection and gradient-driven transport processes, such as thermal conductivity, <span class="hlt">magnetic</span> field diffusion, and thermomagnetic effects. Theoretical analysis based on obtaining exact self-similar solutions of the classical collisional Braginskii's plasma transport equations in one dimension demonstrates that the heat loss from the hot compressed <span class="hlt">magnetized</span> plasma to the cold liner is dominated by transverse heat conduction and advection, and the corresponding loss of <span class="hlt">magnetic</span> <span class="hlt">flux</span> is dominated by advection and the Nernst effect. For a large electron Hall parameter (ω{sub e}τ{sub e}≫1), the effective diffusion coefficients determining the losses of heat and <span class="hlt">magnetic</span> <span class="hlt">flux</span> to the liner wall are both shown to decrease with ω{sub e}τ{sub e} as does the Bohm diffusion coefficient cT/(16eB), which is commonly associated with low collisionality and two-dimensional transport. We demonstrate how this family of exact solutions can be used for verification of codes that model the MagLIF plasma dynamics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19890056315&hterms=dropout&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Ddropout','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19890056315&hterms=dropout&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Ddropout"><span>Electron heat <span class="hlt">flux</span> dropouts in the solar wind - Evidence for interplanetary <span class="hlt">magnetic</span> field reconnection?</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mccomas, D. J.; Gosling, J. T.; Phillips, J. L.; Bame, S. J.; Luhmann, J. G.; Smith, E. J.</p> <p>1989-01-01</p> <p>An examination of ISEE-3 data from 1978 reveal 25 electron heat <span class="hlt">flux</span> dropout events ranging in duration from 20 min to over 11 hours. The heat <span class="hlt">flux</span> dropouts are found to occur in association with high plasma densities, low plasma velocities, low ion and electron temperatures, and low <span class="hlt">magnetic</span> field magnitudes. It is suggested that the heat <span class="hlt">flux</span> dropout intervals may indicate that the spacecraft is sampling plasma regimes which are <span class="hlt">magnetically</span> disconnected from the sun and instead are connected to the outer heliosphere at both ends.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1996SoPh..166...17F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1996SoPh..166...17F"><span>Radiative Heating and the Buoyant Rise of <span class="hlt">Magnetic</span> <span class="hlt">Flux</span> Tubes in the Solar interior</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fan, Y.; Fisher, G. H.</p> <p>1996-06-01</p> <p>We study the effect of radiative heating on the evolution of thin <span class="hlt">magnetic</span> <span class="hlt">flux</span> tubes in the solar interior and on the eruption of <span class="hlt">magnetic</span> <span class="hlt">flux</span> loops to the surface. <span class="hlt">Magnetic</span> <span class="hlt">flux</span> tubes experience radiative heating because (1) the mean temperature gradient in the lower convection zone and the overshoot region deviates substantially from that of radiative equilibrium, and hence there is a non-zero divergence of radiative heat <span class="hlt">flux</span>; and (2) the <span class="hlt">magnetic</span> pressure of the <span class="hlt">flux</span> tube causes a small change of the thermodynamic properties within the tube relative to the surrounding field-free fluid, resulting in an additional divergence of radiative heat <span class="hlt">flux</span>. Our calculations show that the former constitutes the dominant source of radiative heating experienced by the <span class="hlt">flux</span> tube. In the overshoot region, the radiative heating is found to cause a quasi-static rising of the toroidal <span class="hlt">flux</span> tubes with an upward drift velocity ˜ 10-3|δ| cm s-1, where δ ≡ ∇e - ∇ad < 0 describes the subadiabaticity in the overshoot layer. The upward drift velocity does not depend sensitively on the field strength of the <span class="hlt">flux</span> tubes. Thus in order to store toroidal <span class="hlt">flux</span> tubes in the overshoot region for a period comparable to the length of the solar cycle, the magnitude of the subadiabaticity δ(< 0) in the overshoot region must be as large as ˜ 3 × 10-4. We discuss the possibilities for increasing the magnitude of δ and for reducing the rate of radiative heating of the <span class="hlt">flux</span> tubes in the overshoot region. Using numerical simulations we study the formation of ‘Ω’-shaped emerging loops from toroidal <span class="hlt">flux</span> tubes in the overshoot region as a result of radiative heating. The initial toroidal tube is assumed to be non-uniform in its thermodynamic properties along the tube and lies at varying depths beneath the base of the convection zone. The tube is initially in a state of neutral buoyancy with the internal density of the tube plasma equal to the local external density. We find from our</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMSH12B..02L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMSH12B..02L"><span><span class="hlt">Magnetic</span> and Energy Characteristics of Recurrent Homologous Jets from an Emerging <span class="hlt">Flux</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liu, J.; Wang, Y.; Erdelyi, R.; Liu, R.; Mcintosh, S. W.; Gou, T.; Chen, J.; Liu, K.; Liu, L.; Pan, Z.</p> <p>2016-12-01</p> <p>We present the detailed analysis of recurrent homologous jets originating from an emerging negative <span class="hlt">magnetic</span> <span class="hlt">flux</span> at the edge of an Active Region. Detailed investigation of the related Poynting <span class="hlt">flux</span> across the photosphere employing the HMI vector <span class="hlt">magnetic</span> field data confirms the vital role of the emerging <span class="hlt">flux</span> in accumulating the necessary free <span class="hlt">magnetic</span> energy for the associated reconnection to initiate jets. The observed jets show multi-thermal features. Their evolution shows high consistence with the characteristic parameters of the emerging <span class="hlt">flux</span>, suggesting that with more free <span class="hlt">magnetic</span> energy, the eruptions tend to be more violent, frequent and blowout-like. The average temperature, average electron number density and axial speed are found to be similar for different jets, indicating that they should have been formed by plasmas from similar origins. Statistical analysis of the jets and their footpoint region conditions reveals a strong positive relationship between the footpoint region total 131 Å intensity enhancement and jets' length/width. Stronger linearly positive relationships also exist between the total intensity enhancement/thermal energy of the footpoint regions and jets' mass/kinetic/thermal energy, with higher cross-correlation coefficients. All the above results, together, confirm the direct relationship between the <span class="hlt">magnetic</span> reconnection and the jets, and validate the important role of <span class="hlt">magnetic</span> reconnection in transporting large amount of free <span class="hlt">magnetic</span> energy into jets. It is also suggested that there should be more free energy released during the <span class="hlt">magnetic</span> reconnection of blowout than of standard jet events.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JPhCS.900a2011K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JPhCS.900a2011K"><span>Flare <span class="hlt">magnetic</span> reconnection <span class="hlt">fluxes</span> as possible signatures of flare contributions to gradual SEP events</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kahler, S. W.; Kazachenko, M.; Lynch, B. J.; Welsch, B. T.</p> <p>2017-09-01</p> <p>The primary sources of solar energetic (E > 20 MeV) particle (SEP) events are flares and CME-driven shocks. Some studies claim that even up to GeV energies solar flares are major contributors to SEP events. There are several candidate flare processes for producing SEPs, but acceleration in <span class="hlt">magnetic</span> reconnection regions is probably the most efficient. Previous studies have relied on flare radiation signatures to determine the times and locations of SEP injections. An alternative approach is to use the amount of <span class="hlt">magnetic</span> <span class="hlt">flux</span> that gets reconnected during solar flares. The photospheric <span class="hlt">magnetic</span> <span class="hlt">flux</span> swept out by flare ribbons is thought to be directly related to the amount of <span class="hlt">magnetic</span> reconnection in the corona and is therefore a key diagnostic tool for understanding the physical processes in flares and CMEs. We use the database of flare <span class="hlt">magnetic</span> reconnection <span class="hlt">fluxes</span> to compare these parameters with peak intensities of SEP events. We find that while sizes of 15 ∼25-MeV SEP events in the western hemisphere correlate with both CME speeds and reconnection <span class="hlt">fluxes</span>, there are many cases of large reconnection <span class="hlt">fluxes</span> with no observed SEP events. The occurrence of large reconnection <span class="hlt">fluxes</span> accompanied by slow CMEs but no SEP events suggests that the CME shocks are the primary, if not the only, sources of high energy (E > 100 MeV) SEP events.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005PhDT.......111S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005PhDT.......111S"><span><span class="hlt">Magnetic</span> <span class="hlt">flux</span> dynamics in superconducting films studied by scanning Hall probe microscopy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stan, Gheorghe</p> <p></p> <p>In this thesis we address two different issues in the field of <span class="hlt">flux</span> dynamics in superconductors with constricted geometry. In our experiments we used scanning Hall probe microscopy to investigate the <span class="hlt">magnetic</span> field profile above the samples' surface. In the first experiment, Vortex Nucleation in Narrow Thin-Film Strips, we studied the <span class="hlt">magnetic</span> <span class="hlt">flux</span> nucleation in type-II superconducting thin-film strips of mesoscopic width. The maximum <span class="hlt">magnetic</span> field below which vortices are completely expelled from niobium narrow thin-film strips was measured for different widths. Above this threshold field we examined the field dependence of the vortex density for the studied strips. In the second experiment, The Superconducting Dripping Faucet , we analyzed, in microbridge geometry, the dynamics of the <span class="hlt">magnetic</span> <span class="hlt">flux</span> nucleation in a one-dimensional type-I superconducting channel. For this experiment we have developed a novel high-bandwidth Hall probe to detect in real time the nucleation and subsequent motion of the <span class="hlt">magnetic</span> <span class="hlt">flux</span> tubes along a fabricated one-dimensional channel in a lead film. The complex dynamics exhibited by the <span class="hlt">flux</span> tubes nucleating from one end of the channel shares many characteristics of the well-known dripping faucet experiment. Nonlinear time series analysis was used to investigate the dynamics of the <span class="hlt">flux</span> tubes in our experiment.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22092185','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22092185"><span>SCATTERING OF THE f-MODE BY SMALL <span class="hlt">MAGNETIC</span> <span class="hlt">FLUX</span> ELEMENTS FROM OBSERVATIONS AND NUMERICAL SIMULATIONS</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Felipe, T.; Braun, D.; Crouch, A.; Birch, A.</p> <p>2012-10-01</p> <p>The scattering of f-modes by <span class="hlt">magnetic</span> tubes is analyzed using three-dimensional numerical simulations. An f-mode wave packet is propagated through a solar atmosphere embedded with three different <span class="hlt">flux</span> tube models that differ in radius and total <span class="hlt">magnetic</span> <span class="hlt">flux</span>. A quiet-Sun simulation without a tube present is also performed as a reference. Waves are excited inside the <span class="hlt">flux</span> tube and propagate along the field lines, and jacket modes are generated in the surroundings of the <span class="hlt">flux</span> tube, carrying 40% as much energy as the tube modes. The resulting scattered wave is mainly an f-mode composed of a mixture of m = 0 and m = {+-}1 modes. The amplitude of the scattered wave approximately scales with the <span class="hlt">magnetic</span> <span class="hlt">flux</span>. A small amount of power is scattered into the p{sub 1}-mode. We have evaluated the absorption and phase shift from a Fourier-Hankel decomposition of the photospheric vertical velocities. They are compared with the results obtained from the ensemble average of 3400 small <span class="hlt">magnetic</span> elements observed in high-resolution MDI Doppler datacubes. The comparison shows that the observed dependence of the phase shift with wavenumber can be matched reasonably well with the simulated <span class="hlt">flux</span> tube model. The observed variation of the phase shifts with the azimuthal order m appears to depend on details of the ensemble averaging, including possible motions of the <span class="hlt">magnetic</span> elements and asymmetrically shaped elements.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_22 --> <div id="page_23" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="441"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22092261','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22092261"><span>MAGNETAR GIANT FLARES-<span class="hlt">FLUX</span> ROPE ERUPTIONS IN MULTIPOLAR MAGNETOSPHERIC <span class="hlt">MAGNETIC</span> FIELDS</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Yu Cong</p> <p>2012-09-20</p> <p>We address a primary question regarding the physical mechanism that triggers the energy release and initiates the onset of eruptions in the magnetar magnetosphere. Self-consistent stationary, axisymmetric models of the magnetosphere are constructed based on force-free <span class="hlt">magnetic</span> field configurations that contain a helically twisted force-free <span class="hlt">flux</span> rope. Depending on the surface <span class="hlt">magnetic</span> field polarity, there exist two kinds of <span class="hlt">magnetic</span> field configurations, inverse and normal. For these two kinds of configurations, variations of the <span class="hlt">flux</span> rope equilibrium height in response to gradual surface physical processes, such as <span class="hlt">flux</span> injections and crust motions, are carefully examined. We find that equilibrium curves contain two branches: one represents a stable equilibrium branch, and the other an unstable equilibrium branch. As a result, the evolution of the system shows a catastrophic behavior: when the magnetar surface <span class="hlt">magnetic</span> field evolves slowly, the height of the <span class="hlt">flux</span> rope would gradually reach a critical value beyond which stable equilibriums can no longer be maintained. Subsequently, the <span class="hlt">flux</span> rope would lose equilibrium and the gradual quasi-static evolution of the magnetosphere will be replaced by a fast dynamical evolution. In addition to <span class="hlt">flux</span> injections, the relative motion of active regions would give rise to the catastrophic behavior and lead to <span class="hlt">magnetic</span> eruptions as well. We propose that a gradual process could lead to a sudden release of magnetosphere energy on a very short dynamical timescale, without being initiated by a sudden fracture in the crust of the magnetar. Some implications of our model are also discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22368483','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22368483"><span>A <span class="hlt">magnetic</span> <span class="hlt">flux</span> leakage and magnetostrictive guided wave hybrid transducer for detecting bridge cables.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Xu, Jiang; Wu, Xinjun; Cheng, Cheng; Ben, Anran</p> <p>2012-01-01</p> <p>Condition assessment of cables has gained considerable attention for the bridge safety. A <span class="hlt">magnetic</span> <span class="hlt">flux</span> leakage and magnetostrictive guided wave hybrid transducer is provided to inspect bridge cables. The similarities and differences between the two methods are investigated. The hybrid transducer for bridge cables consists of an aluminum framework, climbing modules, embedded <span class="hlt">magnetizers</span> and a ribbon coil. The static axial <span class="hlt">magnetic</span> field provided by the <span class="hlt">magnetizers</span> meets the needs of the <span class="hlt">magnetic</span> <span class="hlt">flux</span> leakage testing and the magnetostrictive guided wave testing. The <span class="hlt">magnetizers</span> also provide the attraction for the climbing modules. In the <span class="hlt">magnetic</span> <span class="hlt">flux</span> leakage testing for the free length of cable, the coil induces the axial leakage <span class="hlt">magnetic</span> field. In the magnetostrictive guided wave testing for the anchorage zone, the coil provides a pulse high power variational <span class="hlt">magnetic</span> field for generating guided waves; the coil induces the <span class="hlt">magnetic</span> field variation for receiving guided waves. The experimental results show that the transducer with the corresponding inspection system could be applied to detect the broken wires in the free length and in the anchorage zone of bridge cables.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3279227','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3279227"><span>A <span class="hlt">Magnetic</span> <span class="hlt">Flux</span> Leakage and Magnetostrictive Guided Wave Hybrid Transducer for Detecting Bridge Cables</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Xu, Jiang; Wu, Xinjun; Cheng, Cheng; Ben, Anran</p> <p>2012-01-01</p> <p>Condition assessment of cables has gained considerable attention for the bridge safety. A <span class="hlt">magnetic</span> <span class="hlt">flux</span> leakage and magnetostrictive guided wave hybrid transducer is provided to inspect bridge cables. The similarities and differences between the two methods are investigated. The hybrid transducer for bridge cables consists of an aluminum framework, climbing modules, embedded <span class="hlt">magnetizers</span> and a ribbon coil. The static axial <span class="hlt">magnetic</span> field provided by the <span class="hlt">magnetizers</span> meets the needs of the <span class="hlt">magnetic</span> <span class="hlt">flux</span> leakage testing and the magnetostrictive guided wave testing. The <span class="hlt">magnetizers</span> also provide the attraction for the climbing modules. In the <span class="hlt">magnetic</span> <span class="hlt">flux</span> leakage testing for the free length of cable, the coil induces the axial leakage <span class="hlt">magnetic</span> field. In the magnetostrictive guided wave testing for the anchorage zone, the coil provides a pulse high power variational <span class="hlt">magnetic</span> field for generating guided waves; the coil induces the <span class="hlt">magnetic</span> field variation for receiving guided waves. The experimental results show that the transducer with the corresponding inspection system could be applied to detect the broken wires in the free length and in the anchorage zone of bridge cables. PMID:22368483</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016IJMPA..3141021B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016IJMPA..3141021B"><span>Induced fermionic current by a <span class="hlt">magnetic</span> <span class="hlt">flux</span> in a cosmic string spacetime at finite temperature</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bezerra de Mello, Eugênio R.; Saharian, Aram A.; Mohammadi, Azadeh</p> <p>2016-01-01</p> <p>Here we analyze the finite temperature expectation values of the charge and current densities for a massive fermionic quantum field with nonzero chemical potential μ, induced by a <span class="hlt">magnetic</span> <span class="hlt">flux</span> running along the axis of an idealized cosmic string. These densities are decomposed into the vacuum expectation values and contributions coming from the particles and antiparticles. Specifically the charge density is an even periodic function of the <span class="hlt">magnetic</span> <span class="hlt">flux</span> with the period equal to the quantum <span class="hlt">flux</span> and an odd function of the chemical potential. The only nonzero component of the current density corresponds to the azimuthal current and it is an odd periodic function of the <span class="hlt">magnetic</span> <span class="hlt">flux</span> and an even function of the chemical potential. Both analyzed are developed for the cases where |μ| is smaller than the mass of the field quanta m.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JGRA..12110898Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JGRA..12110898Z"><span>Coalescence of <span class="hlt">magnetic</span> <span class="hlt">flux</span> ropes observed in the tailward high-speed flows</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhao, Yan; Wang, Rongsheng; Lu, Quanming; Du, Aimin; Yao, Zhonghua; Wu, Mingyu</p> <p>2016-11-01</p> <p>We report a tailward high-speed flow event observed by Cluster during 0203:00UT-0205:30UT on 20 September 2003. Within the flows, a series of three bipolar Bz signatures were observed. The first and third bipolar Bz signatures are identified as <span class="hlt">magnetic</span> <span class="hlt">flux</span> ropes, while the middle one is found to result from the collision of the two <span class="hlt">flux</span> ropes. A vertical thin current layer was embedded in the center of the middle bipolar Bz signature. Combining the plasma, electric field, and wave data around the thin current layer, we conclude that the two <span class="hlt">magnetic</span> <span class="hlt">flux</span> ropes were coalescing. The observations indicate that coalescence of <span class="hlt">magnetic</span> <span class="hlt">flux</span> ropes can happen in the regions away from reconnection site and can produce energetic electrons and waves. A basic criterion for identifying the coalescence in the magnetotail is proposed also.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012PhLB..718..620C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012PhLB..718..620C"><span><span class="hlt">Magnetic</span> <span class="hlt">flux</span> inversion in charged BPS vortices in a Lorentz-violating Maxwell-Higgs framework</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Casana, R.; Ferreira, M. M.; da Hora, E.; Miller, C.</p> <p>2012-12-01</p> <p>We demonstrate for the first time the existence of electrically charged BPS vortices in a Maxwell-Higgs model supplemented with a parity-odd Lorentz-violating (LV) structure belonging to the CPT-even gauge sector of the standard model extension and a fourth order potential (in the absence of the Chern-Simons term). The modified first order BPS equations provide charged vortex configurations endowed with some interesting features: localized and controllable spatial thickness, integer <span class="hlt">flux</span> quantization, electric field inversion and localized <span class="hlt">magnetic</span> <span class="hlt">flux</span> reversion. This model could possibly be applied on condensed matter systems which support charged vortices carrying integer quantized <span class="hlt">magnetic</span> <span class="hlt">flux</span>, endowed with localized flipping of the <span class="hlt">magnetic</span> <span class="hlt">flux</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950053605&hterms=spatial+statistics&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dspatial%2Bstatistics','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950053605&hterms=spatial+statistics&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dspatial%2Bstatistics"><span>On the spatial <span class="hlt">distribution</span> of <span class="hlt">magnetic</span> fields on the solar surface</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Tao, L.; Du, Y.; Rosner, R.; Cattaneo, F.</p> <p>1995-01-01</p> <p>Recent measurements of solar surface <span class="hlt">magnetic</span> fields suggest that the spatial <span class="hlt">distribution</span> of these fields is fractal. In order to understand the physical basis for such geometric complexity, we study here the advection of <span class="hlt">magnetic</span> <span class="hlt">flux</span> tubes relatively simple random motions on the surface of a fluid and investigate the spatial statistics of the resulting surface field. While this study does not directly address the question of why solar surface fields have the observed spatial structure, it is designed to build our intuition about how surface flows lead to complex spatial structuring of <span class="hlt">magnetic</span> fields. As part of our study, we discuss the various methods by which one can describe the spatial <span class="hlt">distribution</span> of the surface <span class="hlt">magnetic</span> <span class="hlt">flux</span> and relate them mathematically; this turns out to be a crucial point of our work since, as we show, a number of previous analyses have misinterpreted the analysis procedures for determining fractal dimensions. Our principal result is the explicit demonstration that simple random flows lead to <span class="hlt">magnetic</span> <span class="hlt">flux</span> spatial <span class="hlt">distributions</span> with a multifractal dimension spectrum. Furthermore, we demonstrate that this <span class="hlt">magnetic</span> spatial structure is generic, i.e., is characteristic of a very large class of random flows.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/12780185','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/12780185"><span>Effect of a <span class="hlt">magnetic</span> <span class="hlt">flux</span> line on the quantum beats in the Henon-Heiles level density.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Brack, M.; Bhaduri, R. K.; Law, J.; Maier, Ch.; Murthy, M. V. N.</p> <p>1995-03-01</p> <p>The quantum density of states of the Henon-Heiles potential displays a pronounced beating pattern. This has been explained by the interference of three isolated classical periodic orbits with nearby actions and periods. A singular <span class="hlt">magnetic</span> <span class="hlt">flux</span> line, passing through the origin, drastically alters the beats even though the classical Lagrangian equations of motion remain unchanged. Some of the changes can be easily understood in terms of the Aharonov-Bohm effect. However, we find that the standard periodic orbit theory does not reproduce the diffraction-like quantum effects on those classical orbits which intersect the singular <span class="hlt">flux</span> line, and argue that corrections of relative order variant Planck's over 2pi are necessary to describe these effects. We also discuss the changes in the <span class="hlt">distribution</span> of nearest-neighbor spacings in the eigenvalue spectrum, brought about by the <span class="hlt">flux</span> line. (c) 1995 American Institute of Physics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950047777&hterms=sequoia&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dsequoia','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950047777&hterms=sequoia&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dsequoia"><span><span class="hlt">Magnetic</span> <span class="hlt">flux</span> relaxation in YBa2Cu3)(7-x) thin film: Thermal or athermal</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Vitta, Satish; Stan, M. A.; Warner, J. D.; Alterovitz, S. A.</p> <p>1991-01-01</p> <p>The <span class="hlt">magnetic</span> <span class="hlt">flux</span> relaxation behavior of YBa2Cu3O(7-x) thin film on LaAlO3 for H is parallel to c was studied in the range 4.2 - 40 K and 0.2 - 1.0 T. Both the normalized <span class="hlt">flux</span> relaxation rate S and the net <span class="hlt">flux</span> pinning energy U increase continuously from 1.3 x 10(exp -2) to 3.0 x 10(exp -2) and from 70 to 240 meV respectively, as the temperature T increases from 10 to 40 K. This behavior is consistent with the thermally activated <span class="hlt">flux</span> motion model. At low temperatures, however, S is found to decrease much more slowly as compared with kT, in contradiction to the thermal activation model. This behavior is discussed in terms of the athermal quantum tunneling of <span class="hlt">flux</span> lines. The <span class="hlt">magnetic</span> field dependence of U, however, is not completely understood.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.5756T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.5756T"><span>Depression of the <span class="hlt">magnetic</span> field in an active small-scale <span class="hlt">flux</span> rope</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tang, Binbin; Li, Wenya; Wang, Chi; Dai, Lei; Burch, Jim; Ergun, Robert; Lindqvist, Per-Arne; Pollock, Craig; Russell, Christopher</p> <p>2017-04-01</p> <p>We report an active small-scale <span class="hlt">magnetic</span> <span class="hlt">flux</span> rope (˜9.8di) at the trailing edge of Kelvin-Helmholtz (KH) waves on September 27 2016 by the Magnetospheric Multiscale (MMS) mission, which is probably generated by multiple x-line reconnections. The <span class="hlt">magnetic</span> field inside this <span class="hlt">flux</span> rope is significantly depressed, resulting into a non-force-free structure. The currents of this <span class="hlt">flux</span> rope are filamentary but structured, and the current filaments at the edges induce an opposing field that causes observed |B| depressions in the central <span class="hlt">flux</span> rope. In addition, intense lower hybrid drift waves (LHDW) are found the magnetospheric edge of the <span class="hlt">flux</span> rope, whose wave potential reaches to ˜20% of the electron temperature, thus these waves could effectively scatter electrons by the wave electric field corresponding to a local density dip. We suggest LHDW may be stabilized by the electron resonance broadening.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110012806','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110012806"><span>Enthalpy <span class="hlt">Distributions</span> of Arc Jet Flow Based on Measured Laser Induced Fluorescence, Heat <span class="hlt">Flux</span> and Stagnation Pressure <span class="hlt">Distributions</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Suess, Leonard E.; Milhoan, James D.; Oelke, Lance; Godfrey, Dennis; Larin, Maksim Y.; Scott, Carl D.; Grinstead, Jay H.; DelPapa, Steven</p> <p>2011-01-01</p> <p>The centerline total enthalpy of arc jet flow is determined using laser induced fluorescence of oxygen and nitrogen atoms. Each component of the energy, kinetic, thermal, and chemical can be determined from LIF measurements. Additionally, enthalpy <span class="hlt">distributions</span> are inferred from heat <span class="hlt">flux</span> and pressure probe <span class="hlt">distribution</span> measurements using an engineering formula. Average enthalpies are determined by integration over the radius of the jet flow, assuming constant mass <span class="hlt">flux</span> and a mass <span class="hlt">flux</span> <span class="hlt">distribution</span> estimated from computational fluid dynamics calculations at similar arc jet conditions. The trends show favorable agreement, but there is an uncertainty that relates to the multiple individual measurements and assumptions inherent in LIF measurements.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014A%26A...562A..53B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014A%26A...562A..53B"><span>Mean-field and direct numerical simulations of <span class="hlt">magnetic</span> <span class="hlt">flux</span> concentrations from vertical field</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brandenburg, A.; Gressel, O.; Jabbari, S.; Kleeorin, N.; Rogachevskii, I.</p> <p>2014-02-01</p> <p>Context. Strongly stratified hydromagnetic turbulence has previously been found to produce <span class="hlt">magnetic</span> <span class="hlt">flux</span> concentrations if the domain is large enough compared with the size of turbulent eddies. Mean-field simulations (MFS) using parameterizations of the Reynolds and Maxwell stresses show a large-scale negative effective <span class="hlt">magnetic</span> pressure instability and have been able to reproduce many aspects of direct numerical simulations (DNS) regarding growth rate, shape of the resulting <span class="hlt">magnetic</span> structures, and their height as a function of <span class="hlt">magnetic</span> field strength. Unlike the case of an imposed horizontal field, for a vertical one, <span class="hlt">magnetic</span> <span class="hlt">flux</span> concentrations of equipartition strength with the turbulence can be reached, resulting in <span class="hlt">magnetic</span> spots that are reminiscent of sunspots. Aims: We determine under what conditions <span class="hlt">magnetic</span> <span class="hlt">flux</span> concentrations with vertical field occur and what their internal structure is. Methods: We use a combination of MFS, DNS, and implicit large-eddy simulations (ILES) to characterize the resulting <span class="hlt">magnetic</span> <span class="hlt">flux</span> concentrations in forced isothermal turbulence with an imposed vertical <span class="hlt">magnetic</span> field. Results: Using DNS, we confirm earlier results that in the kinematic stage of the large-scale instability the horizontal wavelength of structures is about 10 times the density scale height. At later times, even larger structures are being produced in a fashion similar to inverse spectral transfer in helically driven turbulence. Using ILES, we find that <span class="hlt">magnetic</span> <span class="hlt">flux</span> concentrations occur for Mach numbers between 0.1 and 0.7. They occur also for weaker stratification and larger turbulent eddies if the domain is wide enough. Using MFS, the size and aspect ratio of <span class="hlt">magnetic</span> structures are determined as functions of two input parameters characterizing the parameterization of the effective <span class="hlt">magnetic</span> pressure. DNS, ILES, and MFS show <span class="hlt">magnetic</span> <span class="hlt">flux</span> tubes with mean-field energies comparable to the turbulent kinetic energy. These tubes can reach a length of about</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4915706','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4915706"><span>E-<span class="hlt">Flux</span>2 and SPOT: Validated Methods for Inferring Intracellular Metabolic <span class="hlt">Flux</span> <span class="hlt">Distributions</span> from Transcriptomic Data</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Kim, Min Kyung; Lane, Anatoliy; Kelley, James J.; Lun, Desmond S.</p> <p>2016-01-01</p> <p>Background Several methods have been developed to predict system-wide and condition-specific intracellular metabolic <span class="hlt">fluxes</span> by integrating transcriptomic data with genome-scale metabolic models. While powerful in many settings, existing methods have several shortcomings, and it is unclear which method has the best accuracy in general because of limited validation against experimentally measured intracellular <span class="hlt">fluxes</span>. Results We present a general optimization strategy for inferring intracellular metabolic <span class="hlt">flux</span> <span class="hlt">distributions</span> from transcriptomic data coupled with genome-scale metabolic reconstructions. It consists of two different template models called DC (determined carbon source model) and AC (all possible carbon sources model) and two different new methods called E-<span class="hlt">Flux</span>2 (E-<span class="hlt">Flux</span> method combined with minimization of l2 norm) and SPOT (Simplified Pearson cOrrelation with Transcriptomic data), which can be chosen and combined depending on the availability of knowledge on carbon source or objective function. This enables us to simulate a broad range of experimental conditions. We examined E. coli and S. cerevisiae as representative prokaryotic and eukaryotic microorganisms respectively. The predictive accuracy of our algorithm was validated by calculating the uncentered Pearson correlation between predicted <span class="hlt">fluxes</span> and measured <span class="hlt">fluxes</span>. To this end, we compiled 20 experimental conditions (11 in E. coli and 9 in S. cerevisiae), of transcriptome measurements coupled with corresponding central carbon metabolism intracellular <span class="hlt">flux</span> measurements determined by 13C metabolic <span class="hlt">flux</span> analysis (13C-MFA), which is the largest dataset assembled to date for the purpose of validating inference methods for predicting intracellular <span class="hlt">fluxes</span>. In both organisms, our method achieves an average correlation coefficient ranging from 0.59 to 0.87, outperforming a representative sample of competing methods. Easy-to-use implementations of E-<span class="hlt">Flux</span>2 and SPOT are available as part of the open</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013SPD....4420301M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013SPD....4420301M"><span>Line-Tied <span class="hlt">Magnetic</span> <span class="hlt">Flux</span> Ropes in the Laboratory: Equilibrium Force Balance and Eruptive Instabilities</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Myers, Clayton E.; Yamada, M.; Belova, E. V.</p> <p>2013-07-01</p> <p><span class="hlt">Flux</span>-rope-based models of solar eruptions rely on the formation of a line-tied <span class="hlt">flux</span> rope equilibrium that persists until an ideal instability or a breakdown in force balance triggers an eruption. In this paper, we present a quantitative study of equilibrium force balance in solar-relevant <span class="hlt">flux</span> ropes, focusing primarily on the role of the potential <span class="hlt">magnetic</span> field in controlling the <span class="hlt">flux</span> rope behavior. This study was conducted using a newly constructed laboratory experiment in conjunction with supporting three-dimensional MHD simulations that directly model the experimental geometry. The <span class="hlt">flux</span> ropes studied here, which are produced in the <span class="hlt">Magnetic</span> Reconnection Experiment (MRX), evolve quasi-statically over many Alfvén times and have footpoints that are line-tied to two fixed electrodes [E. Oz, C. E. Myers, M. Yamada, et al., Phys. Plasmas 18, 102107 (2011)]. They are formed within a solar-relevant potential <span class="hlt">magnetic</span> field configuration that can be systematically modified between discharges. Detailed in situ <span class="hlt">magnetic</span> measurements from the experiments are compared directly to results from the simulations in order to quantitatively evaluate the various contributions to the equilibrium force balance. We find that forces derived from the applied toroidal guide field contribute significantly to the equilibrium—so much so that the <span class="hlt">flux</span> ropes are often well confined even in the absence of a "strapping" arcade. These observed guide field forces arise from changes in the toroidal <span class="hlt">magnetic</span> pressure and tension that result from a combination of effects within the expanding <span class="hlt">flux</span> rope. With regard to eruptions, the aforementioned guide field forces supplement the well-known strapping field forces to largely prevent the <span class="hlt">flux</span> ropes from erupting. In particular, many regimes were explored where the strapping field configuration is predicted to be "torus unstable" and yet the <span class="hlt">flux</span> ropes do not erupt. Eruptions are observed in some regimes, however, and we will discuss the physical</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017MS%26E..180a2040S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017MS%26E..180a2040S"><span>Neutron <span class="hlt">Distribution</span> in the Nuclear Fuel Cell using Collision Probability Method with Quadratic <span class="hlt">Flux</span> Approach</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shafii, M. A.; Fitriyani, D.; Tongkukut, S. H. J.; Abdullah, A. G.</p> <p>2017-03-01</p> <p>To solve the integral neutron transport equation using collision probability (CP) method usually requires flat <span class="hlt">flux</span> (FF) approach. In this research, it has been carried out in the cylindrical nuclear fuel cell with the spatial of mesh with quadratic <span class="hlt">flux</span> approach. This means that the neutron <span class="hlt">flux</span> at any region of the nuclear fuel cell is forced to follow the pattern of a quadratic function. The mechanism may be referred to as the process of non-flat <span class="hlt">flux</span> (NFF) approach. The parameters that calculated in this study are the k-eff and the <span class="hlt">distribution</span> of neutron <span class="hlt">flux</span>. The result shows that all parameters are in accordance with the result of SRAC.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20030062034&hterms=granules&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dgranules','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20030062034&hterms=granules&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dgranules"><span>Solar Coronal Heating and the <span class="hlt">Magnetic</span> <span class="hlt">Flux</span> Content of the Network</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Moore, R. L.; Falconer, D. A.; Porter, J. G.; Hathaway, D. H.</p> <p>2003-01-01</p> <p>We investigate the heating of the quiet corona by measuring the increase of coronal luminosity with the amount of <span class="hlt">magnetic</span> <span class="hlt">flux</span> in the underlying network at solar minimum when there were no active regions on the face of the Sun. The coronal luminosity is measured from Fe IX/X-Fe XII pairs of coronal images from SOHO/EIT. The network <span class="hlt">magnetic</span> <span class="hlt">flux</span> content is measured from SOHO/MDI magnetograms. We find that the luminosity of the corona in our quiet regions increases roughly in proportion to the square root of the <span class="hlt">magnetic</span> <span class="hlt">flux</span> content of the network and roughly in proportion to the length of the perimeter of the network <span class="hlt">magnetic</span> <span class="hlt">flux</span> clumps. From (1) this result, (2) other observations of many fine-scale explosive events at the edges of network <span class="hlt">flux</span> clumps, and (3) a demonstration that it is energetically feasible for the heating of the corona in quiet regions to be driven by explosions of granule-sized sheared-core <span class="hlt">magnetic</span> bipoles embedded in the edges of network <span class="hlt">flux</span> clumps, we infer that in quiet regions that are not influenced by active regions the corona is mainly heated by such <span class="hlt">magnetic</span> activity in the edges of the network <span class="hlt">flux</span> clumps. Our observational results together with our feasibility analysis allow us to predict that (1) at the edges of the network <span class="hlt">flux</span> clumps there are many transient sheared-core bipoles of the size and lifetime of granules and having transverse field strengths greater than approximately - 100 G, (2) approximately 30 of these bipoles are present per supergranule, and (3) most spicules are produced by explosions of these bipoles.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20030062133&hterms=granules&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dgranules','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20030062133&hterms=granules&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dgranules"><span>Solar Coronal Heating and the <span class="hlt">Magnetic</span> <span class="hlt">Flux</span> Content of the Network</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Falconer, D. A.; Moore, R. L.; Porter, J. G.; Hathaway, D. H.</p> <p>2003-01-01</p> <p>We investigate the heating of the quiet corona by measuring the increase of coronal luminosity with the amount of <span class="hlt">magnetic</span> <span class="hlt">flux</span> in the underlying network at solar minimum when there were no active regions on the face of the Sun. The coronal luminosity is measured from Fe IX/X-Fe XII pairs of coronal images from SOHO/EIT. The network <span class="hlt">magnetic</span> <span class="hlt">flux</span> content is measured from SOHO/MDI magnetograms. We find that the luminosity of the corona in our quiet regions increases roughly in proportion to the square root of the <span class="hlt">magnetic</span> <span class="hlt">flux</span> content of the network and roughly in proportion to the length of the perimeter of the network <span class="hlt">magnetic</span> <span class="hlt">flux</span> clumps. From (1) this result, (2) other observations of many fine-scale explosive events at the edges of network <span class="hlt">flux</span> clumps, and (3) a demonstration that it is energetically feasible for the heating of the corona in quiet regions to be driven by explosions of granule-sized sheared-core <span class="hlt">magnetic</span> bipoles embedded in the edges of network <span class="hlt">flux</span> clumps, we infer that in quiet regions that are not influenced by active regions the corona is mainly heated by such <span class="hlt">magnetic</span> activity in the edges of the network <span class="hlt">flux</span> clumps. Our observational results together with our feasibility analysis allow us to predict that (1) at the edges of the network <span class="hlt">flux</span> clumps there are many transient sheared-core bipoles of the size and lifetime of granules and having transverse field strengths > approx. 100 G, (2) approx. 30 of these bipoles are present per supergranule, and (3) most spicules are produced by explosions of these bipoles.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003ApJ...593..549F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003ApJ...593..549F"><span>Solar Coronal Heating and the <span class="hlt">Magnetic</span> <span class="hlt">Flux</span> Content of the Network</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Falconer, D. A.; Moore, R. L.; Porter, J. G.; Hathaway, D. H.</p> <p>2003-08-01</p> <p>We investigate the heating of the quiet corona by measuring the increase of coronal luminosity with the amount of <span class="hlt">magnetic</span> <span class="hlt">flux</span> in the underlying network at solar minimum when there were no active regions on the face of the Sun. The coronal luminosity is measured from Fe IX/X-Fe XII pairs of coronal images from SOHO/EIT, under the assumption that practically all of the coronal luminosity in our quiet regions comes from plasma in the temperature range 0.9×106K<=T<=1.3×106 K. The network <span class="hlt">magnetic</span> <span class="hlt">flux</span> content is measured from SOHO/MDI magnetograms. We find that the luminosity of the corona in our quiet regions increases roughly in proportion to the square root of the <span class="hlt">magnetic</span> <span class="hlt">flux</span> content of the network and roughly in proportion to the length of the perimeter of the network <span class="hlt">magnetic</span> <span class="hlt">flux</span> clumps. From (1) this result, (2) other observations of many fine-scale explosive events at the edges of network <span class="hlt">flux</span> clumps, and (3) a demonstration that it is energetically feasible for the heating of the corona in quiet regions to be driven by explosions of granule-sized sheared-core <span class="hlt">magnetic</span> bipoles embedded in the edges of network <span class="hlt">flux</span> clumps, we infer that in quiet regions that are not influenced by active regions the corona is mainly heated by such <span class="hlt">magnetic</span> activity in the edges of the network <span class="hlt">flux</span> clumps. Our observational results together with our feasibility analysis allow us to predict that (1) at the edges of the network <span class="hlt">flux</span> clumps there are many transient sheared-core bipoles of the size and lifetime of granules and having transverse field strengths greater than ~100 G, (2) ~30 of these bipoles are present per supergranule, and (3) most spicules are produced by explosions of these bipoles.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PhPl...24e2105V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PhPl...24e2105V"><span>Sausage instabilities on top of kinking lengthening current-carrying <span class="hlt">magnetic</span> <span class="hlt">flux</span> tubes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>von der Linden, Jens; You, Setthivoine</p> <p>2017-05-01</p> <p>We theoretically explore the possibility of sausage instabilities developing on top of a kink instability in lengthening current-carrying <span class="hlt">magnetic</span> <span class="hlt">flux</span> tubes. Observations indicate that the dynamics of <span class="hlt">magnetic</span> <span class="hlt">flux</span> tubes in our cosmos and terrestrial experiments can involve topological changes faster than time scales predicted by resistive magnetohydrodynamics. Recent laboratory experiments suggest that hierarchies of instabilities, such as kink and Rayleigh-Taylor, could be responsible for initiating fast topological changes by locally accessing two-fluid and kinetic regimes. Sausage instabilities can also provide this coupling mechanism between disparate scales. <span class="hlt">Flux</span> tube experiments can be classified by the <span class="hlt">flux</span> tube's evolution in a configuration space described by a normalized inverse aspect-ratio k ¯ and current-to-<span class="hlt">magnetic</span> <span class="hlt">flux</span> ratio λ ¯ . A lengthening current-carrying <span class="hlt">magnetic</span> <span class="hlt">flux</span> tube traverses this k ¯ - λ ¯ space and crosses stability boundaries. We derive a single general criterion for the onset of the sausage and kink instabilities in idealized <span class="hlt">magnetic</span> <span class="hlt">flux</span> tubes with core and skin currents. The criterion indicates a dependence of the stability boundaries on current profiles and shows overlapping kink and sausage unstable regions in the k ¯ - λ ¯ space with two free parameters. Numerical investigation of the stability criterion reduces the number of free parameters to a single one that describes the current profile and confirms the overlapping sausage and kink unstable regions in k ¯ - λ ¯ space. A lengthening, ideal current-carrying <span class="hlt">magnetic</span> <span class="hlt">flux</span> tube can therefore become sausage unstable after it becomes kink unstable.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMSH41E..04T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMSH41E..04T"><span>Embedding Circular Force-Free <span class="hlt">Flux</span> Ropes in Potential <span class="hlt">Magnetic</span> Fields</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Titov, V. S.; Torok, T.; Mikic, Z.; Linker, J.</p> <p>2013-12-01</p> <p>We propose a method for constructing approximate force-free equilibria in active regions that locally have a potential bipolar-type <span class="hlt">magnetic</span> field with a thin force-free <span class="hlt">flux</span> rope embedded inside it. The <span class="hlt">flux</span> rope has a circular-arc axis and circular cross-section in which the interior <span class="hlt">magnetic</span> field is predominantly toroidal (axial). Its <span class="hlt">magnetic</span> pressure is balanced outside by that of the poloidal (azimuthal) field created at the boundary by the electric current sheathing the <span class="hlt">flux</span> rope. To facilitate the implementation of the method in our numerical magnetohydrodynamic (MHD) code, the entire solution is described in terms of the vector potential of the <span class="hlt">magnetic</span> field. The parameters of the <span class="hlt">flux</span> rope can be chosen so that a subsequent MHD relaxation of the constructed configuration under line-tied conditions at the boundary provides a numerically exact equilibrium. Such equilibria are an approximation for the <span class="hlt">magnetic</span> configuration preceding solar eruptions, which can be triggered in our model by imposing suitable photospheric flows beneath the <span class="hlt">flux</span> rope. The proposed method is a useful tool for constructing pre-eruption <span class="hlt">magnetic</span> fields in data-driven simulations of solar active events. Research supported by NASA's Heliophysics Theory and LWS Programs, and NSF/SHINE and NSF/FESD.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_23 --> <div id="page_24" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="461"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/20868055','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/20868055"><span>Laboratory simulation of arched <span class="hlt">magnetic</span> <span class="hlt">flux</span> rope eruptions in the solar atmosphere.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Tripathi, S K P; Gekelman, W</p> <p>2010-08-13</p> <p>Dramatic eruption of an arched <span class="hlt">magnetic</span> <span class="hlt">flux</span> rope in a large ambient plasma has been studied in a laboratory experiment that simulates coronal loops. The eruption is initiated by laser generated plasma flows from the footpoints of the rope that significantly modify the <span class="hlt">magnetic</span>-field topology and link the <span class="hlt">magnetic</span>-field lines of the rope with the ambient plasma. Following this event, the <span class="hlt">flux</span> rope erupts by releasing its plasma into the background. The resulting impulse excites intense magnetosonic waves that transfer energy to the ambient plasma and subsequently decay.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21470961','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21470961"><span>Laboratory Simulation of Arched <span class="hlt">Magnetic</span> <span class="hlt">Flux</span> Rope Eruptions in the Solar Atmosphere</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Tripathi, S. K. P.; Gekelman, W.</p> <p>2010-08-13</p> <p>Dramatic eruption of an arched <span class="hlt">magnetic</span> <span class="hlt">flux</span> rope in a large ambient plasma has been studied in a laboratory experiment that simulates coronal loops. The eruption is initiated by laser generated plasma flows from the footpoints of the rope that significantly modify the <span class="hlt">magnetic</span>-field topology and link the <span class="hlt">magnetic</span>-field lines of the rope with the ambient plasma. Following this event, the <span class="hlt">flux</span> rope erupts by releasing its plasma into the background. The resulting impulse excites intense magnetosonic waves that transfer energy to the ambient plasma and subsequently decay.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19910059765&hterms=dipole+moment&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Ddipole%2Bmoment','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19910059765&hterms=dipole+moment&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Ddipole%2Bmoment"><span><span class="hlt">Magnetic</span> <span class="hlt">flux</span> transport and the sun's dipole moment - New twists to the Babcock-Leighton model</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wang, Y.-M.; Sheeley, N. R., Jr.</p> <p>1991-01-01</p> <p>The mechanisms that give rise to the sun's large-scale poloidal <span class="hlt">magnetic</span> field are explored in the framework of the Babcock-Leighton (BL) model. It is shown that there are in general two quite distinct contributions to the generation of the 'alpha effect': the first is associated with the axial tilts of the bipolar <span class="hlt">magnetic</span> regions as they erupt at the surface, while the second arises through the interaction between diffusion and flow as the <span class="hlt">magnetic</span> <span class="hlt">flux</span> is dispersed over the surface. The general relationship between <span class="hlt">flux</span> transport and the BL dynamo is discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016Ge%26Ae..56..393K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016Ge%26Ae..56..393K"><span>Skin-layer of the eruptive <span class="hlt">magnetic</span> <span class="hlt">flux</span> rope in large solar flares</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kichigin, G. N.; Miroshnichenko, L. I.; Sidorov, V. I.; Yazev, S. A.</p> <p>2016-07-01</p> <p>The analysis of observations of large solar flares made it possible to propose a hypothesis on existence of a skin-layer in <span class="hlt">magnetic</span> <span class="hlt">flux</span> ropes of coronal mass ejections. On the assumption that the Bohm coefficient determines the diffusion of <span class="hlt">magnetic</span> field, an estimate of the skin-layer thickness of ~106 cm is obtained. According to the hypothesis, the electric field of ~0.01-0.1 V/cm, having the nonzero component along the <span class="hlt">magnetic</span> field of <span class="hlt">flux</span> rope, arises for ~5 min in the surface layer of the eruptive <span class="hlt">flux</span> rope during its ejection into the upper corona. The particle acceleration by the electric field to the energies of ~100 MeV/nucleon in the skin-layer of the <span class="hlt">flux</span> rope leads to their precipitation along field lines to footpoints of the <span class="hlt">flux</span> rope. The skin-layer presence induces helical or oval chromospheric emission at the ends of flare ribbons. The emission may be accompanied by hard X-ray radiation and by the production of gamma-ray line at the energy of 2.223 MeV (neutron capture line in the photosphere). The <span class="hlt">magnetic</span> reconnection in the corona leads to a shift of the skin-layer of <span class="hlt">flux</span> rope across the <span class="hlt">magnetic</span> field. The area of precipitation of accelerated particles at the <span class="hlt">flux</span>-rope footpoints expands in this case from the inside outward. This effect is traced in the chromosphere and in the transient region as the expanding helical emission structures. If the emission extends to the spot, a certain fraction of accelerated particles may be reflected from the <span class="hlt">magnetic</span> barrier (in the <span class="hlt">magnetic</span> field of the spot). In the case of exit into the interplanetary space, these particles may be recorded in the Earth's orbit as solar proton events.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMSH14A..03P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMSH14A..03P"><span><p>Prediction of In-Situ <span class="hlt">Magnetic</span> Structure of <span class="hlt">Flux</span> Ropes from Coronal Observations.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Palmerio, E.; Kilpua, E.; James, A.; Green, L.; Pomoell, J.; Isavnin, A.; Valori, G.; Lumme, E.</p> <p>2016-12-01</p> <p>Coronal mass ejections (CMEs) are believed to be the main drivers of intense <span class="hlt">magnetic</span> storms and various space weather phenomena at Earth. The most important parameter that defines the ability of a CME to drive geomagnetic storms is the north-south <span class="hlt">magnetic</span> field component. One of the most significant problems in current long-term space weather forecasts is that there is no method to directly measure the <span class="hlt">magnetic</span> structure of CMEs before they are observed in situ. In recent years, CMEs have been successfully modeled as unstable expanding <span class="hlt">flux</span> ropes originating from low-corona, force-free <span class="hlt">flux</span> equilibria (either containing or forming a <span class="hlt">flux</span> rope in the wake of the instability). Due to their influence on the coronal plasma environment, the <span class="hlt">magnetic</span> structure of CME <span class="hlt">flux</span> ropes can be indirectly estimated based on the properties of the source active region and characteristics of the nearby structures, such as filament details, coronal EUV arcades and X-ray sigmoids. We present here a study of two CME <span class="hlt">flux</span> ropes, aiming at determining their <span class="hlt">magnetic</span> properties (<span class="hlt">magnetic</span> helicity sign, <span class="hlt">flux</span> rope tilt, and direction of the <span class="hlt">flux</span> rope axial field) when launched from the Sun by using a synthesis of indirect proxies based on multi-wavelength remote sensing observations. In addition, we employ a data-driven magnetofrictional method that models the CME initiation in the corona to determine the <span class="hlt">magnetic</span> structure in the two case studies. Finally, the predictions given by the observational synthesis and coronal modeling are compared with the structure detected in situ at Earth.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19900049894&hterms=temperature+thermal+infrared+laser&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dtemperature%2Bthermal%2Binfrared%2Blaser','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19900049894&hterms=temperature+thermal+infrared+laser&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dtemperature%2Bthermal%2Binfrared%2Blaser"><span>Infrared radiometric technique for rapid quantitative evaluation of heat <span class="hlt">flux</span> <span class="hlt">distribution</span> over large areas</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Glazer, Stuart; Siebes, Georg</p> <p>1989-01-01</p> <p>This paper describes a novel approach for rapid, quantitative measurement of spatially <span class="hlt">distributed</span> heat <span class="hlt">flux</span> incident on a plane. The technique utilizes the spatial temperature <span class="hlt">distribution</span> on an opaque thin film at the location of interest, as measured by an imaging infrared radiometer. Knowledge of film radiative properties, plus quantitative estimates of convection cooling permit the steady state energy balance at any location on the film sheet to be solved for the incident heat <span class="hlt">flux</span>. Absolute accuracies on the order of 10-15 percent have been obtained in tests performed in air. The method is particularly useful for evaluation of spatial heat <span class="hlt">flux</span> uniformity from <span class="hlt">distributed</span> heat sources over large areas. It has recently been used in several applications at the Jet Propulsion Laboratory, including <span class="hlt">flux</span> uniformity measurements from large <span class="hlt">distributed</span> quartz lamp arrays used during thermal vacuum testing of several spacecraft components, and <span class="hlt">flux</span> mapping of a low power NdYg laser beam.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014RAA....14..855C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014RAA....14..855C"><span>Numerical simulations of three-dimensional <span class="hlt">magnetic</span> swirls in a solar <span class="hlt">flux</span>-tube</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chmielewski, Piotr; Murawski, Krzysztof; Solov'ev, Alexandr A.</p> <p>2014-07-01</p> <p>We aim to numerically study evolution of Alfvén waves that accompany short-lasting swirl events in a solar <span class="hlt">magnetic</span> <span class="hlt">flux</span>-tube that can be a simple model of a <span class="hlt">magnetic</span> pore or a sunspot. With the use of the FLASH code we numerically solve three-dimensional ideal magnetohydrodynamic equations to simulate twists which are implemented at the top of the photosphere in <span class="hlt">magnetic</span> field lines of the <span class="hlt">flux</span>-tube. Our numerical results exhibit swirl events and Alfvén waves with associated clockwise and counterclockwise rotation of <span class="hlt">magnetic</span> lines, with the largest values of vorticity at the bottom of the chromosphere, and a certain amount of energy <span class="hlt">flux</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PhRvD..95a5005A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PhRvD..95a5005A"><span>Supersymmetric models on <span class="hlt">magnetized</span> orbifolds with <span class="hlt">flux</span>-induced Fayet-Iliopoulos terms</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Abe, Hiroyuki; Kobayashi, Tatsuo; Sumita, Keigo; Tatsuta, Yoshiyuki</p> <p>2017-01-01</p> <p>We study supersymmetric (SUSY) models derived from the ten-dimensional SUSY Yang-Mills theory compactified on <span class="hlt">magnetized</span> orbifolds, with nonvanishing Fayet-Iliopoulos (FI) terms induced by <span class="hlt">magnetic</span> <span class="hlt">fluxes</span> in extra dimensions. Allowing the presence of FI-terms relaxes a constraint on <span class="hlt">flux</span> configurations in SUSY model building based on <span class="hlt">magnetized</span> backgrounds. In this case, charged fields develop their vacuum expectation values to cancel the FI-terms in the D-flat directions of <span class="hlt">fluxed</span> gauge symmetries, which break the gauge symmetries and lead to a SUSY vacuum. Based on this idea, we propose a new class of SUSY <span class="hlt">magnetized</span> orbifold models with three generations of quarks and leptons. Especially, we construct a model where the right-handed sneutrinos develop their vacuum expectation values which restore the supersymmetry but yield lepton number violating terms below the compactification scale, and show their phenomenological consequences.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19820047461&hterms=Electron+Transfer&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DElectron%2BTransfer','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19820047461&hterms=Electron+Transfer&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DElectron%2BTransfer"><span>Energetic protons, alpha particles, and electrons in <span class="hlt">magnetic</span> <span class="hlt">flux</span> transfer events</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Scholer, M.; Hovestadt, D.; Ipavich, F. M.; Gloeckler, G.</p> <p>1982-01-01</p> <p>Energetic proton, alpha particle, and electron data are presented for two magnetopause crossings, which show <span class="hlt">magnetic</span> field signatures characteristic of <span class="hlt">flux</span> transfer events (FTEs). Energetic proton and alpha particles are observed streaming along the <span class="hlt">magnetic</span> field within the magnetosheath in all events showing <span class="hlt">magnetic</span> signatures characteristic of the FTEs. <span class="hlt">Flux</span> ratios as high as about 180 parallel and antiparallel to the <span class="hlt">magnetic</span> field are observed, which means that ions of about 30 keV per charge are at times streaming almost scatter-free from the magnetopause into the magnetosheath. Energetic ion bursts with signatures equal to those observed in FTEs are reduced by more than an order of magnitude as compared to the trapped particle <span class="hlt">flux</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JPhCS.767a2028Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JPhCS.767a2028Z"><span>Observations and analysis of small-scale <span class="hlt">magnetic</span> <span class="hlt">flux</span> ropes in the solar wind</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zheng, Jinlei; Hu, Qiang</p> <p>2016-11-01</p> <p>The small-scale <span class="hlt">magnetic</span> <span class="hlt">flux</span> ropes (of duration ranging from a few minutes to a few hours) in the solar wind have the typical topology of winding field lines around a central axis, which is similar to the large-scale <span class="hlt">flux</span> ropes, i.e., <span class="hlt">magnetic</span> clouds. However, accumulating evidence suggests that their plasma characteristics, origin, formation mechanism and evolution are different from those of large-scale <span class="hlt">flux</span> ropes. The small-scale <span class="hlt">flux</span> ropes are intensively studied in recent years, since they affect particle transport and energization, and are considered as the potential source of local acceleration. The Grad-Shafranov reconstruction technique is a tool to reconstruct the two and a half dimensional field structure based on in-situ measurements captured by an observing platform moving past it. In this study, we reconstruct the <span class="hlt">flux</span> rope structures in two events using the Grad-Shafranov reconstruction approach. In one event, a twin <span class="hlt">flux</span> rope structure at 1 AU occurring on 2002 February 1 and two following single <span class="hlt">flux</span> rope structures are identified behind an interplanetary shock. In the other event, we reconstruct the <span class="hlt">flux</span> rope structures occurring on 1998 March 25 and 26 at 1 AU in the ambient solar wind. The associated energetic particle signatures and the possible origin of these <span class="hlt">flux</span> rope structures are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22348434','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22348434"><span>Twist accumulation and topology structure of a solar <span class="hlt">magnetic</span> <span class="hlt">flux</span> rope</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Guo, Y.; Ding, M. D.; Cheng, X.; Zhao, J.; Pariat, E.</p> <p>2013-12-20</p> <p>To study the buildup of a <span class="hlt">magnetic</span> <span class="hlt">flux</span> rope before a major flare and coronal mass ejection (CME), we compute the <span class="hlt">magnetic</span> helicity injection, twist accumulation, and topology structure of the three-dimensional (3D) <span class="hlt">magnetic</span> field, which is derived by the nonlinear force-free field model. The Extreme-ultraviolet Imaging Telescope on board the Solar and Heliospheric Observatory observed a series of confined flares without any CME before a major flare with a CME at 23:02 UT on 2005 January 15 in active region NOAA 10720. We derive the vector velocity at eight time points from 18:27 UT to 22:20 UT with the differential affine velocity estimator for vector <span class="hlt">magnetic</span> fields, which were observed by the Digital Vector Magnetograph at Big Bear Solar Observatory. The injected <span class="hlt">magnetic</span> helicity is computed with the vector <span class="hlt">magnetic</span> and velocity fields. The helicity injection rate was (– 16.47 ± 3.52) × 10{sup 40} Mx{sup 2} hr{sup –1}. We find that only about 1.8% of the injected <span class="hlt">magnetic</span> helicity became the internal helicity of the <span class="hlt">magnetic</span> <span class="hlt">flux</span> rope, whose twist increasing rate was –0.18 ± 0.08 Turns hr{sup –1}. The quasi-separatrix layers (QSLs) of the 3D <span class="hlt">magnetic</span> field are computed by evaluating the squashing degree, Q. We find that the <span class="hlt">flux</span> rope was wrapped by QSLs with large Q values, where the <span class="hlt">magnetic</span> reconnection induced by the continuously injected <span class="hlt">magnetic</span> helicity further produced the confined flares. We suggest that the <span class="hlt">flux</span> rope was built up and heated by the <span class="hlt">magnetic</span> reconnection in the QSLs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/508130','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/508130"><span><span class="hlt">Magnetic</span> damping forces in figure-eight-shaped null-<span class="hlt">flux</span> coil suspension systems</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>He, Jianliang; Coffey, H.</p> <p>1997-08-01</p> <p>This paper discusses <span class="hlt">magnetic</span> damping forces in figure-eight-shaped null-<span class="hlt">flux</span> coil suspension systems, focusing on the Holloman maglev rocket system. The paper also discusses simulating the damping plate, which is attached to the superconducting <span class="hlt">magnet</span> by two short-circuited loop coils in the guideway. Closed-form formulas for the <span class="hlt">magnetic</span> damping coefficient as functions of heave-and-sway displacements are derived by using a dynamic circuit model. These formulas are useful for dynamic stability studies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFM.H41J..01S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFM.H41J..01S"><span>Nitrogen <span class="hlt">Flux</span> in Watersheds: The Role of Soil <span class="hlt">Distributions</span> and Climate in Nitrogen <span class="hlt">Flux</span> to the Coastal Ecosystems</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics D